The pulse bounces through a pair of gratings, which make it longer.
|
|
In my neighborhood in Brooklyn, there are so many different kinds of window gratings.
|
|
Others pulled up iron gratings and barricaded the middle of the road with them.
|
|
The gratings act like a prism, causing different colors to take paths of different lengths.
|
|
The scientists shined the beam through two gold-coated silicon nitride gratings, each with a different distance between the grates.
|
|
They concluded that positrons had hit the gratings, interacted with one another as matter waves, and produced the expected interference pattern on the film.
|
|
City workers removed more than 2,000 metal gratings, construction barriers and other items to prevent them from being used as weapons or as barricades.
|
|
I'd never given much thought to pickled broccoli stems before, but now I think their highest use is with darkly lush sheets of raw beef furred over with fine white horseradish gratings.
|
|
It was half-ruined, open to the air, and surrounded by metal gratings; one steel bar was loose, and the prince moved it aside with a great clank so that we could enter.
|
|
A tabletop with laser optics and a computer monitor showing the different wavelengths of light emitted by a frequency combPhoto: NISTThe researchers pass near-infrared laser pulses through a series of optics including special fibers, crystals, and gratings.
|
|
Now my eye constantly picks out elevated-train girders, footbridges, drawbridge houses, pipelines, fuel tanks, lampposts, window gratings, fence bars, guardrails, and I-beams holding up interstate overpasses, all in their own versions of Statue of Liberty green, and they fasten me to the city.
|
|
Midtown, the subway gratings puff out their hot breath, testament to a busy subterranean life; but you could not guess that millions of books are housed under Bryant Park, and that beneath the ground runs a system of train tracks, like toys for a studious giant.
|
|
And yet, the end-users, especially those inclined to wear skirts, are feeling even more on display than the 100,000 books arranged on floating shelves, due to the open sightlines afforded by slatted gratings that allow air and light to circulate between the levels of the open-concept library.
|
|
On Monday morning, as city work crews spent at least two hours finding and shutting off the broken main under the street, floodwaters cascaded into the apartment building's four-level garage through large metal gratings used for air ventilation, said Mr. Groll, as he walked past a snappy late-model Porsche.
|
|
Servings: 4Prep time: 20 minutesTotal time: 23 minutes Ingredients 8 ounces heavy creamseveral gratings of nutmegkosher salt and freshly ground black pepper, to taste6 ounces grated fontina cheese1/2 cup coarsely chopped fresh Italian parsley1/4 cup walnuts, roughly chopped2 tablespoons long thin orange and lemon zest1 pound firm sunchokes (Jerusalem artichokes), scrubbed2 tablespoons extra-virgin olive oilMaldon or other flaky sea saltPink peppercorns Directions 1.
|
|
Various gratings with complex structures have been designed: gratings combining several LPFGs, LPFGs with superstructures, chirped gratings, and gratings with apodization. Various LPFG-based devices have been developed: filters, sensors, fiber dispersion compensators, etc.
|
|
Blazed gratings can also be realized as transmission gratings. In this case the blaze angle is chosen such that the angle of the desired diffraction order coincides with the angle of the beam refracted at the grating material.Richardson Gratings, "Technical Note 4 - Transmission Gratings", section "Blazed Transmission Gratings" (30 September 2012).
|
|
Ruled gratings have imperfections that produce faint "ghost" diffraction orders that may raise the stray light level of a monochromator. A later photolithographic technique allows gratings to be created from a holographic interference pattern. Holographic gratings have sinusoidal grooves and so are not as bright, but have lower scattered light levels than blazed gratings. Almost all the gratings actually used in monochromators are carefully made replicas of ruled or holographic master gratings.
|
|
These gratings, called volume phase holography diffraction gratings (or VPH diffraction gratings) have no physical grooves, but instead a periodic modulation of the refractive index within the gel. This removes much of the surface scattering effects typically seen in other types of gratings. These gratings also tend to have higher efficiencies, and allow for the inclusion of complicated patterns into a single grating. In older versions of such gratings, environmental susceptibility was a trade-off, as the gel had to be contained at low temperature and humidity.
|
|
Gratings with such small periodicity are called subwavelength gratings and exhibit special optical properties. Made on an isotropic material the subwavelength gratings give rise to form birefringence, in which the material behaves as if it were birefringent.
|
|
Because of this, gratings are commonly used in monochromators and spectrometers. For practical applications, gratings generally have ridges or rulings on their surface rather than dark lines. Such gratings can be either transmissive or reflective. Gratings that modulate the phase rather than the amplitude of the incident light are also produced, frequently using holography.
|
|
Illusory contours are created at the boundary between two misaligned gratings. In these so-called abutting line gratings, the illusory contour is perpendicular to the inducing elements.
|
|
These are gratings that are reborn at higher temperatures after erasure of gratings, usually type I gratings and usually, though not always, in the presence of hydrogen. They have been interpreted in different ways including dopant diffusion (oxygen being the most popular current interpretation) and glass structural change. Recent work has shown that there exists a regeneration regime beyond diffusion where gratings can be made to operate at temperatures in excess of 1,295 °C, outperforming even type II femtosecond gratings. These are extremely attractive for ultra high temperature applications.
|
|
Holographic gratings have sinusoidal grooves and may not be as efficient as ruled gratings, but are often preferred in monochromators because they produce less stray light. A copying technique can make high quality replicas from master gratings of either type, thereby lowering fabrication costs. Another method for manufacturing diffraction gratings uses a photosensitive gel sandwiched between two substrates. A holographic interference pattern exposes the gel, which is later developed.
|
|
Phase-shifted fiber Bragg gratings (PS-FBGs) are an important class of gratings structures which have interesting applications in optical communications and sensing due to their special filtering characteristics. These types of gratings can be reconfigurable through special packaging and system design. Different coatings of diffractive structure are used for fiber Bragg gratings in order to reduce the mechanical impact on the Bragg wavelength shift for 1.1–15 times as compared to an uncoated waveguide.
|
|
Originally, high-resolution gratings were ruled by high-quality ruling engines whose construction was a large undertaking. Henry Joseph Grayson designed a machine to make diffraction gratings, succeeding with one of 120,000 lines to the inch (approx. 4,724 lines per mm) in 1899. Later, photolithographic techniques created gratings from a holographic interference pattern.
|
|
The corpuscular theory was weak on thin plates and silent on gratings;Newton (1730) observed feathers acting as reflection gratings and as a transmission gratings, but classified the former case under thin plates (p. 252), and the latter, more vaguely, under inflection (p. 322). In retrospect, the latter experiment (p. 322, end of Obs.
|
|
Typically, the photosensitive substances are sealed between two substrates that make them resistant to humidity, and thermal and mechanical stresses. VPH diffraction gratings are not destroyed by accidental touches and are more scratch resistant than typical relief gratings. Semiconductor technology today is also utilized to etch holographically patterned gratings into robust materials such as fused silica. In this way, low stray-light holography is combined with the high efficiency of deep, etched transmission gratings, and can be incorporated into high volume, low cost semiconductor manufacturing technology.
|
|
Optical gratings are less expensive, provide much higher resolution, and are easier to calibrate, due to their linear diffraction dependency. A prism's refraction angle varies nonlinearly with wavelength. On the other hand, gratings have significant intensity losses.
|
|
Point-by-point is also used in the fabrication of tilted gratings.
|
|
Optical axis gratings can be implemented in various materials, including liquid crystals, polymers, birefringent crystals, magnetic crystals and subwavelength gratings. This new type of grating has broad potential in imaging, liquid crystal display, communication, and numerous military applications.
|
|
Colours could be produced by various technologies like different light sources or gratings.
|
|
Source-mask optimization that is based on line-space gratings and tip-to-tip gratings only does not entail improvements for all parts of a logic pattern, e.g., a dense trench with a gap on one side.D. Rio et al., Proc.
|
|
Figure 5 shows the contrast sensitivity function for sine-wave gratings of equivalent subtense.
|
|
This wave pattern sets up a reflection pattern similar to the blazed gratings but utilizing Bragg diffraction, a process where the angle of reflection is dependent on the arrangement of the atoms in the gelatin. The holographic gratings can have up to 6000 lines/mm and can be up to twice as efficient in collecting light as blazed gratings. Because they are sealed between two sheets of glass, the holographic gratings are very versatile, potentially lasting decades before needing replacement. Light dispersed by the grating or prism in a spectrograph can be recorded by a detector.
|
|
The detailed structure for 20 and 50 slits gratings are illustrated in the second diagram.
|
|
Application of Fourier analysis to the visibility of gratings. Journal of Physiology, 197, 551-566.
|
|
Most monochromators use gratings, however. Some monochromators have several gratings that can be selected for use in different spectral regions. A double monochromator made by placing a prism and a grating monochromator in series typically does not need additional bandpass filters to isolate a single grating order.
|
|
External-cavity diode lasers are tunable lasers which use mainly double heterostructures diodes of the AlxGa(1-x)As type. The first external-cavity diode lasers used intracavity etalons and simple tuning Littrow gratings. Other designs include gratings in grazing-incidence configuration and multiple-prism grating configurations.
|
|
However, an exception exists when the ratio of the period to the wavelength is near one; in this case, a holographic grating has virtually the same efficiency as the ruled version. Holographic master gratings are replicated by a process identical to that used for ruled gratings.
|
|
A holographic grating is a type of diffraction grating formed by an interference-fringe field of two laser beams whose standing-wave pattern is exposed to a polished substrate coated with photoresist. Processing of the exposed medium results in a pattern of straight lines with a sinusoidal cross section. Holographic gratings may exhibit less scattered light than ruled gratings. Due to their sinusoidal groove profile, holographic gratings cannot be easily blazed and their efficiency is usually considerably less than a comparable ruled grating.
|
|
The writing lasers form a grating by modulating density of matter or by localizing matter (trapping) on the regions of maxima (or minima) of the writing interference fields. A thermal grating is an example. Matter gratings have slow dynamics (milliseconds) compared to population and phase gratings (potentially nanoseconds and faster).
|
|
Approximations to Bessel beams are made in practice either by focusing a Gaussian beam with an axicon lens to generate a Bessel–Gauss beam, by using axisymmetric diffraction gratings, or by placing a narrow annular aperture in the far field. High order Bessel beams can be generated by spiral diffraction gratings.
|
|
The branch of mathematics dealing with this part of optics is Fourier analysis. Gratings are also used extensively in research into visual perception. Campbell and Robson promoted using sine-wave gratings by arguing that the human visual performs a Fourier analysis on retinal images.Campbell, F. W., & Robson, J. G. (1968).
|
|
Soft X-rays have different optical properties than visible light and therefore experiments must take place in ultra high vacuum, where the photon beam is manipulated using special mirrors and diffraction gratings. Gratings diffract each energy or wavelength present in the incoming radiation in a different direction. Grating monochromators allow the user to select the specific photon energy they wish to use to excite the sample. Diffraction gratings are also used in the spectrometer to analyze the photon energy of the radiation emitted by the sample.
|
|
Typically, devices used to generate large amounts (>100 ps/nm) of chromatic dispersion are based on diffraction gratings, chirped fiber Bragg gratings, or dispersion compensating fiber. Unfortunately, these dispersive elements suffer from one or more of the following restrictions: # Limited operational bandwidth # Limited total dispersion # Low peak power handling # Large spatial footprint.
|
|
"Dispersive prisms and gratings" (pdf) in Michael Bass et al. (eds.) Handbook of Optics. Vol. 2, Ch. 5. McGraw Hill.
|
|
The valve diffracts laser light using an array of tiny movable ribbons mounted on a silicon base. The GLV uses six ribbons as the diffraction gratings for each pixel. The alignment of the gratings is altered by electronic signals, and this displacement controls the intensity of the diffracted light in a very smooth gradation.
|
|
Optical axis gratings (OAGs) are gratings of optical axis of a birefringent material. In OAGs, the birefringence of the material is constant, while the direction of optical axis is periodically modulated in a fixed direction. In this way they are different from the regular phase gratings, in which the refractive index is modulated and the direction of the optical axis is constant. The optical axis in OAGs can be modulated in either transverse or the longitudinal direction, which causes it to act as a diffractive or a reflective component.
|
|
In the study of visual perception, sinusoidal gratings are frequently used to probe the capabilities of the visual system. In these stimuli, spatial frequency is expressed as the number of cycles per degree of visual angle. Sine-wave gratings also differ from one another in amplitude (the magnitude of difference in intensity between light and dark stripes), and angle.
|
|
Figure 1. A figure similar to that of Figure 1 of Broerse, Vladusich, and O’Shea (1999), demonstrating what became known as the watercolor illusion. The vertical gratings are black and white with a thin line of red along each black bar. The horizontal gratings are black and white with a thin line of green along each black bar.
|
|
The chromo-modal dispersion device is constructed by combining the angular dispersion of diffraction gratings with the modal dispersion of a multimode waveguide.
|
|
A great advantage of the usage of polychromatic radiation is the shortening of the exposure times and this has recently been exploited by using white synchrotron radiation to realize the first dynamic (time-resolved) Phase contrast tomography. A technical barrier to overcome is the fabrication of gratings with high aspect ratio and small periods. The production of these gratings out of a silicon wafer involves microfabrication techniques like photolithography, anisotropic wet etching, electroplating and molding. A very common fabrication process for X-ray gratings is LIGA, which is based on deep X-ray lithography and electroplating.
|
|
The original high- resolution diffraction gratings were ruled. The construction of high-quality ruling engines was a large undertaking (as well as exceedingly difficult, in past decades), and good gratings were very expensive. The slope of the triangular groove in a ruled grating is typically adjusted to enhance the brightness of a particular diffraction order. This is called blazing a grating.
|
|
Diffraction gratings can also be used to produce dispersive effects; these are often used in high-power laser amplifier systems. Recently, an alternative to prisms and gratings has been developed: chirped mirrors. These dielectric mirrors are coated so that different wavelengths have different penetration lengths, and therefore different group delays. The coating layers can be tailored to achieve a net negative dispersion.
|
|
119,131–2; Darrigol, 2012, pp. 199–201; Kipnis, 1991, pp. 175–6. On 10 November, Fresnel sent a supplementary note dealing with Newton's rings and with gratings,Darrigol, 2012, p. 201. including, for the first time, transmission gratings – although in that case the interfering rays were still assumed to be "inflected", and the experimental verification was inadequate because it used only two threads.
|
|
Drawing of a grating Bonse-Hart interferometer. To have the superior sensitivity of crystal Bonse-Hart interferometry without some of the basic limitations, the monolithic crystals have been replaced with nanometric x-ray phase-shift gratings. The first such gratings have periods of 200 to 400 nanometers. They can split x-ray beams over the broad energy spectra of common x-ray tubes.
|
|
J. Canning, M. G. Sceats, "p-phase-shifted periodic distributed structures in germanosilicate fiber by UV post-processing", Electron. Lett., 30, (16), 1344-1345, (1994) This supported the development of the first distributed feedback (DFB) fiber lasers, and also laid the groundwork for most complex gratings that followed, including the sampled gratings first made by Peter Hill and colleagues in Australia.
|
|
The Phoenix Iron Works is a foundry in Oakland, California. Phoenix Iron Works has been a major supplier of manhole covers and street gutter gratings.
|
|
Echelle gratings are useful in planet-finding astronomy, and are used on the successful HARPS and PARAS (PRL Advanced Radial-velocity All-sky Search) spectrograph.
|
|
Most recently, a significant advance in grating-based imaging occurred due to the discovery of a phase moiré effect by Wen and colleagues. It led to interferometry beyond the Talbot self-imaging range, using only phase gratings and conventional sources and detectors. X-ray phase gratings can be made with very fine periods, thereby allowing imaging at low radiation doses to achieve high sensitivity.
|
|
ASPs are typically composed of two gratings (a diffraction grating and an analyzer grating) above a single photodiode. ASPs exploit the moire effect and the Talbot effect to gain their sinusoidal light sensitivity. According to the moire effect, if light acted as a particle, at certain incident angles the gaps in the diffraction and analyzer gratings line up, while at other incident angles light passed by the diffraction grating is blocked by the analyzer grating. The amount of light reaching the photodiode would be proportional to a sinusoidal function of incident angle, as the two gratings come in and out of phase with each other with shifting incident angle.
|
|
Phase gratings are easier to make when compared with the source and analyzer gratings mentioned above, since the grating depth required to cause phase shift is much less than what is needed to absorb x-rays. Phase gratings of 200 - 400 nanometer periods have been used to improve phase sensitivity in table- top PFI imagers. In PFI a phase grating is used to convert the fine interference fringes into a broad intensity pattern at a distal plane, based on the phase moiré effect. Besides higher sensitivity, another incentive for smaller grating periods is that the lateral coherence of the source needs to be at least one grating period.
|
|
Written in both hydrogenated and non-hydrogenated fiber of all types, type I gratings are usually known as standard gratings and are manufactured in fibers of all types under all hydrogenation conditions. Typically, the reflection spectra of a type I grating is equal to 1-T where T is the transmission spectra. This means that the reflection and transmission spectra are complementary and there is negligible loss of light by reflection into the cladding or by absorption. Type I gratings are the most commonly used of all grating types, and the only types of grating available off-the-shelf at the time of writing.
|
|
Henry Joseph Grayson - an Australian inventor who developed an engine (~1900) for making diffraction gratings that ruled 120,000 lines to the inch (approximately 4,700 per mm).
|
|
They are solidly built, and are remarkable for the thickness of their walls, and for the fewness of their windows, many of which are covered by gratings.
|
|
Merton handed these processes over to the National Physical Laboratory (NPL) for further development and they formed the basis of a considerable research programme. The ‘blazed’ gratings made by the Merton–NPL method were of great value in making available cheap infra-red spectrometers of high resolving power for research and industry, while long gratings ruled by this method came into use for engineering measurement and machine tool control.
|
|
A photomask having the intended grating features may also be used in the manufacture of fiber Bragg gratings. The photomask is placed between the UV light source and the photosensitive fiber. The shadow of the photomask then determines the grating structure based on the transmitted intensity of light striking the fiber. Photomasks are specifically used in the manufacture of chirped Fiber Bragg gratings, which cannot be manufactured using an interference pattern.
|
|
A new technology for grating insertion into integrated photonic lightwave circuits is digital planar holography (DPH). DPH gratings are generated in computer and fabricated on one or several interfaces of an optical waveguide planar with standard micro-lithography or nano-imprinting methods, compatible with mass-production. Light propagates inside the DPH gratings, confined by the refractive index gradient, which provides longer interaction path and greater flexibility in light steering.
|
|
In the late 19th century Henry Augustus Rowland found a need for very high precision screws in cutting diffraction gratings, so he developed a technique for making them.
|
|
Amsterdam: North-Holland. (11) (37) 1962 Tracing skew rays through concave diffraction gratings. Optica Acta 9, 389–394. Walter Thompson Welford 329 (12) (41) 1963 Bubble chamber optics. Appl.
|
|
Apodized gratings offer significant improvement in side-lobe suppression while maintaining reflectivity and a narrow bandwidth. The two functions typically used to apodize a FBG are Gaussian and raised-cosine.
|
|
The verticals will look green and horizontals pink in the example given. Therefore, the illusory color apparent on the test fields is contingent on the orientation of the lines in that test field. Furthermore, the orientation-color contingencies present in the illusion are the reverse of those present in the adapting stimulus (i.e., the magenta-vertical and green-horizontal adaptation gratings produced illusory magenta on the horizontal test gratings and illusory green on the vertical test grating).
|
|
It was developed in the 1980s for the fabrication of extreme high aspect ratio microstructures by scientists from the Karlsruhe Institute of Technology (KIT). Another technical requirement is the stability and precise alignment and movement of the gratings (typically in the range of some nm), but compared to other methods, e.g. the crystal interferometer the constraint is easy to fulfill. An x-ray far-field interferometer using only phase gratings is based on the phase moiré effect.
|
|
Although some monochromator designs do use focusing gratings that do not need separate collimators, most use collimating mirrors. Reflective optics are preferred because they do not introduce dispersive effects of their own.
|
|
Optics 2, 981–986. (13) (43) 1965 Aberration theory of gratings and grating mountings. Prog. Optics 4, 241–280. (14) (44) 1966 (With L. C. Martin) Technical optics, 2nd edn, vol. 1.
|
|
The efficiency of fiber Bragg grating based fiber-optic sensors can be provided by means of central wavelength adjustment of light emitting source in accordance with the current Bragg gratings reflection spectra.
|
|
Using new technologies, it offers a resolution improvement of ten times better than existing X-ray observatories.High-resolution X-ray gratings enable state-of-the-art spectrometer. Phys Org. 9 January 2018.
|
|
Coherent light must be split into two or more beams prior to being recombined in order to achieve interference. Typical methods for beam splitting are Lloyd´s mirrors, prisms and diffraction gratings.
|
|
In 2005, the street was thoroughly renovated and its cobblestone pavement replaced. The city ditch (Stadtbach) running through the middle of the street since medieval times is now visible again through metal gratings.
|
|
Sir Thomas Ralph Merton KBE, DSc, FRS (12 January 1888 – 10 October 1969) was an English physicist, inventor and art collector. He is particularly noted for his work on spectroscopy and diffraction gratings.
|
|
In quasitriangular Hopf algebra, the R-matrix is a solution of the Yang-Baxter equation. The numerical modeling of diffraction gratings in optical science can be performed using the R-matrix propagation algorithm.
|
|
Double folded-z-configuration monochromator. . Washington, DC: U.S. Patent and Trademark Office. Filed: 11 February 1959. The Cary 14 was one of the first instruments to incorporate high-quality gratings into its monochromators.
|
|
This is much more stable and accurate than in dispersive instruments where the scale depends on the mechanical movement of diffraction gratings. In practice, the accuracy is limited by the divergence of the beam in the interferometer which depends on the resolution. Another minor advantage is less sensitivity to stray light, that is radiation of one wavelength appearing at another wavelength in the spectrum. In dispersive instruments, this is the result of imperfections in the diffraction gratings and accidental reflections.
|
|
Depending on the symmetry of the perturbation that is used to write the LPFG, modes of different symmetries may be coupled. For instance, cylindrically symmetric gratings couple symmetric LP0m modes of the fiber. Microbend gratings, which are antisymmetric with respect to the fiber axis, create a resonance between the core mode and the asymmetric LP1m modes of the core and the cladding. Long period grating has a wide variety of applications, including band-rejection filters, gain flattening filter and sensors.
|
|
The main advantage of this technique is that it uses most of the incoming x-rays that would have been filtered by the crystals. Because only phase gratings are used, grating fabrication is less challenging than techniques that use absorption gratings. The first grating Bonse-Hart interferometer (gBH) operated at 22.5 keV photon energy and 1.5% spectral bandwidth. The incoming beam is shaped by slits of a few tens of micrometers such that the transverse coherence length is greater than the grating period.
|
|
The (super) lens stack here results in a computational result of a diffraction-limited resolution of 243 nm. Gratings with periods from 500 nm down to 170 nm are imaged, with the depth of the modulation in the resist reducing as the grating period reduces. All of the gratings with periods above the diffraction limit (243 nm) are well resolved. The key results of this experiment are super-imaging of the sub-diffraction limit for 200 nm and 170 nm periods.
|
|
Complex grating profiles can be manufactured by exposing a large number of small, partially overlapping gratings in sequence. Advanced properties such as phase shifts and varying modulation depth can be introduced by adjusting the corresponding properties of the subgratings.R. Stubbe, B. Sahlgren, S. Sandgren, and A. Asseh, "Novel technique for writing long superstructured fiber Bragg gratings," in Postdeadlin Papers, Photosensitivity and Quadratic Nonlinearity in Glass Waveguides: Fundamentals and Applications, Vol. 22of 1995 Technical Digest Series (Optical Society of America, Washington, D.C., 1995), p.
|
|
Originally, the manufacture of the photosensitive optical fiber and the 'writing' of the fiber Bragg grating were done separately. Today, production lines typically draw the fiber from the preform and 'write' the grating, all in a single stage. As well as reducing associated costs and time, this also enables the mass production of fiber Bragg gratings. Mass production is in particular facilitating applications in smart structures utilizing large numbers (3000) of embedded fiber Bragg gratings along a single length of fiber.
|
|
Occasionally, at transitions, one will briefly see irregular composites of the two gratings (such as the red and green gratings superimposed but with one or two bars of the green grating invisible). Monocular rivalry is easier to see when the component stimuli are of opposite colors, but it also occurs when the component stimuli have the same colors. As long as the two component stimuli differ spatiotemporally in some way, such as orientation (as shown), spatial frequency, or direction of movement, monocular rivalry can be seen.
|
|
For transmission gratings, Bragg planes are perpendicular to the entrance surface (=/2) while for reflection gratings, Bragg plans are parallel to the entrance surface (=0). If the beam does not meet the Bragg condition, it passes through the filter, undiffracted. In a Bragg filter, the incoming collimated light is first diffracted by a volume filter and only a small fraction of the spectrum is affected. Then, by using a second parallel filter with the same modulation period, light can be recombined and an image can be reconstructed.
|
|
While the term OADM applies to both types, it is often used interchangeably with ROADM. Physically, there are several ways to make an OADM. There are a variety of demultiplexer and multiplexer technologies including thin film filters, fiber Bragg gratings with optical circulators, free space grating devices and integrated planar arrayed waveguide gratings. The switching or reconfiguration functions range from the manual fiber patch panel to a variety of switching technologies including microelectromechanical systems (MEMS), liquid crystal and thermo-optic switches in planar waveguide circuits.
|
|
A basement that extends below a sidewalk or pavement is called an areaway, a sidewalk vault, or a hollow sidewalk. In some cities, these areaways were created by the raising of the street level to combat floods, and in some cases they form an (often now abandoned) tunnel network. To light these spaces, sidewalks incorporated gratings, which were a trip hazard and let water and street dirt as well as light into the basement. Replacing the open gratings with glass was an obvious improvement.
|
|
To obtain frequency dispersion over a wider frequency one must use a prism. In the optical regime, in which the use of gratings is most common, this corresponds to wavelengths between 100 nm and 10 µm. In that case, the groove density can vary from a few tens of grooves per millimeter, as in echelle gratings, to a few thousands of grooves per millimeter. When groove spacing is less than half the wavelength of light, the only present order is the m = 0 order.
|
|
There is a gap of nearly twenty years between Merton's scientific papers of 1928 and 1947. In this interval he was busy in the laboratory and was taking out patents for his inventions. Diffraction gratings were one of his lifelong interests and here his inventive genius best showed itself. The rarity and expense of good diffraction gratings led him to devise, in 1935, a method of copying them without loss of optical quality, by applying a thin layer of a cellulose ester solution to an original plane grating.
|
|
These new spectroscopes were more detailed than a prism, required less light, and could be focused on a specific region of the spectrum by tilting the grating. The limitation to a blazed grating is the width of the mirrors, which can only be ground a finite amount before focus is lost; the maximum is around 1000 lines/mm. In order to overcome this limitation holographic gratings were developed. Volume phase holographic gratings use a thin film of dichromated gelatin on a glass surface, which is subsequently exposed to a wave pattern created by an interferometer.
|
|
The ruler was developed by the National Institute of Standards and Technology, and unveiled in 2005. Nanoruler also is the name of a machine to produce large (greater than 300 mm x 300 mm) grating patterns with nanometer precision, based on the principle of Scanning Beam Interference Lithography. Instead of the traditional technique to produce gratings through mechanical ruling, this approach rules gratings through the interference of light beams. The Nanoruler was developed in the Space Nanotechnology Laboratory of the Kavli Institute for Astrophysics and Space Research at the Massachusetts Institute of Technology.
|
|
The most common other pulse compressor is based on gratings (see Chirped pulse amplification), which can easily create a much larger negative dispersion than a prism compressor (centimeters rather than tenths of millimeters). However, a grating compressor has losses of at least 30% due to higher-order diffraction and absorption losses in the metallic coating of the gratings. A prism compressor with an appropriate anti-reflection coating can have less than 2% loss, which makes it a feasible option inside a laser cavity. Moreover, a prism compressor is cheaper than a grating compressor.
|
|
In 2009, hollow-core waveguides using high contrast grating were proposed, followed by experimentally demonstration in 2012. This experiment is the first demonstration to show a high contrast grating reflecting optical beam propagating in the direction parallel to the gratings, which is a major distinction from photonic crystal or distributed Bragg reflector. In 2010, planar, single-layer lenses and focusing reflectors with high focusing power using a high contrast grating with spatially varying grating dimensions were proposed and demonstrated. Some literatures quote the high contrast gratings as photonic crystal slabs or photonic crystal membranes.
|
|
Reprinted in: (A reproduction of Rittenhouse's letter re his diffraction grating appears on pp. 369–374.) This was similar to notable German physicist Joseph von Fraunhofer's wire diffraction grating in 1821. Gratings with the lowest line- distance (d) were created, in the 1860s, by Friedrich Adolph Nobert (1806–1881) in Greifswald; then the two Americans Lewis Morris Rutherfurd (1816–1892) and William B. Rogers (1804–1882) took over the lead; and, by the end of the 19th century, the concave gratings of Henry Augustus Rowland (1848–1901) were the best available.
|
|
A number of other historic features would be preserved including, restoring and relaying the tracks of the old rail lines and restoring original features such as old gratings, paving and cobble stones, bollards, mooring posts, capstones and granite steps.
|
|
The higher the spatial frequency, which involves more complex objects within the visual field, the less likely there will be saccadic suppression.Wolf, W., Hauske, G., & Lupp, U. (1978). How presaccadic gratings modify postsaccadic modulation transfer function. Visual Research, 18, 1173-1179.
|
|
An echelle grating (from French échelle, meaning "ladder") is a type of diffraction grating characterised by a relatively low groove density, but a groove shape which is optimized for use at high incidence angles and therefore in high diffraction orders. Higher diffraction orders allow for increased dispersion (spacing) of spectral features at the detector, enabling increased differentiation of these features. Echelle gratings are, like other types of diffraction gratings, used in spectrometers and similar instruments. They are most useful in cross-dispersed high resolution spectrographs, such as HARPS, PRL Advanced Radial Velocity Abu Sky Search (PARAS), and numerous other astronomical instruments.
|
|
In physics, a high contrast grating is a single layer near-wavelength grating physical structure where the grating material has a large contrast in index of refraction with its surroundings. The term near-wavelength refers to the grating period, which has a value between one optical wavelength in the grating material and that in its surrounding materials. The high contrast gratings have many distinct attributes that are not found in conventional gratings. These features include broadband ultra-high reflectivity, broadband ultra-high transmission, and very high quality factor resonance, for optical beam surface-normal or in oblique incidence to the grating surface.
|
|
A disadvantage of the standard GBI setup is the sensitivity to only one component of the phase gradient, which is the direction parallel to the 1-D gratings. This problem has been solved either by recording differential phase contrast images of the sample in both direction x and y by turning the sample (or the gratings) by 90° or by the employment of two-dimensional gratings. Being a differential phase technique, GBI is not as sensitive as crystal interferometry to low spatial frequencies, but because of the high resistance of the method against mechanical instabilities, the possibility of using detectors with large pixels and a large field of view and, of crucial importance, the applicability to conventional laboratory X-ray tubes, grating-based imaging is a very promising technique for medical diagnostics and soft tissue imaging. First medical applications like a pre- clinical mammography study, show great potential for the future of this technique.
|
|
Their interest is about potential applications in building microfluidic channels, changing the color of materials, modifying local electrical properties, and building sub-diffraction-limit optical diffraction gratings. They also constitute the first stage of the Black Silicon formation process by femtosecond irradiation.
|
|
The term polychromatic means having several colors. It is used to describe light that exhibits more than one color, which also means that it contains radiation of more than one wavelength. The study of polychromatic is particularly useful in the production of diffraction gratings.
|
|
The term polychromatic means having several colors. It is used to describe light that exhibits more than one color, which also means that it contains radiation of more than one wavelength. The study of polychromatics is particularly useful in the production of diffraction gratings.
|
|
Gratings are usually specified by four parameters. Spatial frequency is the number of cycles occupying a particular distance (e.g., 10 lines [or cycles] per millimeter). Contrast is a measure of the difference in luminance between the light parts of the grating and the dark parts.
|
|
Fill an 'idiyappam' press or a sieve with the dough and press the noodles onto banana leaves or directly into an idli steamer. Add a little grated coconut if desired. Steam for 5–10 minutes. The idiyappam is served with coconut gratings and coconut milk.
|
|
Figure 5: Optical add-drop multiplexer. The primary application of fiber Bragg gratings is in optical communications systems. They are specifically used as notch filters. They are also used in optical multiplexers and demultiplexers with an optical circulator, or optical add- drop multiplexer (OADM).
|
|
Segal has helped engineer hybrid porous silicon materials for sensing purposes, including carbon dot-infused silicon transducers, hydrogel- confined silicon substrates, and polymer-silicon hybrids. Diffraction gratings Segal's research group engineered microstructured silicon optical sensors for the detection and monitoring of microorganisms, including bacteria and fungi, in both clinical samples and food. The microstructured substrates serve as reflective diffraction gratings for label-free measurements of refractive index. By tracking bacterial growth in response to antibiotics, Segal's group (in collaboration with the Department of Urology at the Bnai Zion hospital and Ha'Emek Medical Center) developed a means of rapid antimicrobial susceptibility testing for clinical samples.
|
|
The McCollough effect is a phenomenon of human visual perception in which colorless gratings appear colored contingent on the orientation of the gratings. It is an aftereffect requiring a period of induction to produce it. For example, if someone alternately looks at a red horizontal grating and a green vertical grating for a few minutes, a black-and-white horizontal grating will then look greenish and a black-and-white vertical grating will then look pinkish. The effect is remarkable because, although it diminishes rapidly with repeated testing, it has been reported to last up to 2.8 months when exposure to testing is limited.
|
|
It does this by reflecting a relatively multi-chromatic (as compared to most lasers) pulse off a series of two diffraction gratings, which splits them spatially into different frequencies, essentially the same thing a simple prism does with visible light. These individual frequencies have to travel different distances when reflected back into the beamline, resulting in the pulse being "stretched out" in time. This longer pulse is fed into the amplifiers as normal, which now have time to respond normally. After amplification the beams are sent into a second pair of gratings "in reverse" to recombine them into a single short pulse with high power.
|
|
The technologies include liquid polarisation gratings for airborne Doppler lidar systems. Shane came across a list of neural network cookbook recipes written by Tom Brewe. AI Weirdness, Shane's blog on Artificial Intelligence, features everyday neural networks and algorithms. Shane writes for Fast Company and O'Reilly Media.
|
|
Sailors Pourre, Kermoal, and Antonio descended into the Prométhée, closing the hatches behind them. They received citations in recognition of this act of courage. Couespel du Mesnil ordered buoys and gratings to be thrown overboard. The submarine's rate of sinking increased, water flooding into the diesel exhausts.
|
|
Photon etc. is a Canadian manufacturer of infrared cameras, widely tunable optical filters, hyperspectral imaging and spectroscopic scientific instruments for academic and industrial applications. Its main technology is based on volume Bragg gratings, which are used as filters either for swept lasers or for global imaging.
|
|
The light curve of the star in X-rays shows significant brightness variations within hours, however, the spectral distribution appears rather stable. The spectrum obtained by the High Energy Transmission Gratings on board Chandra X-ray Observatory seems to lack strong emission lines, including Fe Kα fluorescence.
|
|
Only recently, a neutron interferometer for cold and ultracold neutrons was designed and successfully run. Neutron-optical components in this case comprise three gratings. They are artificially holographically produced, i.e., by means of a light-optic two-wave interference setup illuminating a photo-neutron- refractive polymer.
|
|
If a frequency-selective element is included in the external cavity, it is possible to reduce the laser emission to a single wavelength, and even tune the radiation. For example, diffraction gratings have been used to create a tunable laser that can tune over 15% of its center wavelength.
|
|
Pongala is a harvest festival of Kerala and Tamil Nadu. The name 'Pongala' means 'to boil over' and refers to the ritualistic offering of porridge made of rice, sweet brown molasses, coconut gratings, nuts and raisins. Generally women devotees participate in this ritual. Tamil people celebrate as Pongal.
|
|
The Space Nanotechnology Laboratory performs research in interference lithography and diffraction grating fabrication. It has fabricated the high energy transmission gratings for one of NASA's Great Observatories, the Chandra X-Ray Observatory. It is also the home of the Nanoruler, a unique and high-precision grating patterning tool.
|
|
The church looks like a stronghold from outside. Its walls are made of stone and are 1-meter thick; the little windows have iron gratings, and the altar is like an embrasure. The door was made of thick oak boards studded with iron, with a unique heavy lock mechanism.
|
|
Rivington 1983, pp.5–9 The diagram above shows a punt without seats. The seats are usually just a simple board fitting against blocks on the sides, with cushions. The gaps between the treads are normally fitted with gratings to allow the passengers to keep their feet dry.
|
|
7x7 matrix using green laser and diff. beam splitter (Courtesy of Holo/Or) The diffractive beam splitterDiffraction Gratings and Applications, Loewen, Erwin C. and Popov, Evgeny. Marcel Dekker, Inc. 1997.Digital diffractive optics: an introduction to planar diffractive optics and related technology, Bernard C. Kress, Patrick Meyrueis , 2005.
|
|
The pulse is then sent into the amplifiers as normal. When it exits the beamlines it is recombined in a similar set of gratings to produce a single very short pulse, but because the pulse now has very high power, the gratings have to be large (approx 1 m) and sit in a vacuum. Additionally the individual beams must be lower in power overall; the compression side of the system uses 40 beamlines of about 5 kJ each to generate a total of 200 kJ, whereas the ignition side requires 24 beamlines of just under 3 kJ to generate a total of 70 kJ. The precise number and power of the beamlines are currently a subject of research.
|
|
The tangential cells showed modulations that matched the temporal frequency of the gratings, and the velocity of the moving gratings at which the neurons respond most strongly showed a close dependency on the pattern wavelength. This confirmed the accuracy of the model both at the cellular and the behavioral level. Although the details of the Hassenstein-Reichardt model have not been confirmed at an anatomical and physiological level, the site of subtraction in the model is now being localized to the tangential cells. When depolarizing current is injected into the tangential cell while presenting a visual stimulus, the response to the preferred direction of motion decreased, and the response to the null direction increased.
|
|
The efficiency of a grating may also depend on the polarization of the incident light. Gratings are usually designated by their groove density, the number of grooves per unit length, usually expressed in grooves per millimeter (g/mm), also equal to the inverse of the groove period. The groove period must be on the order of the wavelength of interest; the spectral range covered by a grating is dependent on groove spacing and is the same for ruled and holographic gratings with the same grating constant. The maximum wavelength that a grating can diffract is equal to twice the grating period, in which case the incident and diffracted light are at ninety degrees to the grating normal.
|
|
If the photons reside mainly in the higher index material, the confinement is due to total internal reflection. If the confinement is due many distributed Fresnel reflections, the device is termed a photonic crystal. There are many different types of geometries used in microphotonics including optical waveguides, optical microcavities, and Arrayed waveguide gratings.
|
|
The sea chest provides an intake reservoir from which piping systems draw raw water. Most sea chests are protected by removable gratings, and contain baffle plates to dampen the effects of vessel speed or sea state. The intake size of sea chests varies from less than 10 cm² to several square metres.
|
|
Usually X-ray diffraction in spectrometers is achieved on crystals, but in Grating spectrometers, the X-rays emerging from a sample must pass a source- defining slit, then optical elements (mirrors and/or gratings) disperse them by diffraction according to their wavelength and, finally, a detector is placed at their focal points.
|
|
A special form of a blazed grating is the echelle grating. It is characterized by particularly large blaze angle (>45°). Therefore, the light hits the short legs of the triangular grating lines instead of the long legs. Echelle gratings are mostly manufactured with larger line spacing but are optimized for higher diffraction orders.
|
|
Italy (Giuliano Toraldo di Francia) would survey diffraction theory; Great Britain (T. Smith) would survey aberration studies (without diffraction); and France (André Maréchal) and the Netherlands would report on the combined effect of aberrations and diffraction. Sweden (E. Ingelstam) would survey gratings; Great Britain, photographic objectives; and other groups were assigned other tasks.
|
|
With reflective gratings (where the holes are replaced by a highly reflective surface), the reflective portion can be tilted (blazed) to scatter a majority of the light into the preferred direction of interest (and into a specific diffraction order). For multiple wavelengths the same is true; however, in that case it is possible for longer wavelengths of a higher order to overlap with the next order(s) of a shorter wavelength, which is usually an unwanted side effect. In echelle gratings, however, this behavior is deliberately used and the blaze is optimized for multiple overlapping higher orders. Since this overlap is not directly useful, a second, perpendicularly mounted dispersive element (grating or prism) is inserted as an "order separator" or "cross disperser" into the beam path.
|
|
Recent studies have shown the ocelli of some insects (most notably the dragonfly, but also some wasps) are capable of form vision, as the ocellar lens forms an image within, or close to, the photoreceptor layer. In dragonflies it has been demonstrated that the receptive fields of both the photoreceptors and the second-order neurons can be quite restricted. Further research has demonstrated these eyes not only resolve spatial details of the world, but also perceive motion. Second-order neurons in the dragonfly median ocellus respond more strongly to upwards-moving bars and gratings than to downwards-moving bars and gratings, but this effect is only present when ultraviolet light is used in the stimulus; when ultraviolet light is absent, no directional response is observed.
|
|
Volume Bragg gratings (VBG) or volume holographic gratings (VHG) consist of a volume where there is a periodic change in the refractive index. Depending on the orientation of the modulation of the refractive index, VBG can be used either to transmit or reflect a small bandwidth of wavelengths. Bragg's law (adapted for volume hologram) dictates which wavelength will be diffracted: :2\Lambda\sin(\theta + \varphi)=m\lambda_B \,, where m is the Bragg order (a positive integer), λB the diffracted wavelength, Λ the fringe spacing of the grating, θ the angle between the incident beam and the normal (N) of the entrance surface and φ the angle between the normal and the grating vector (KG). Radiation that does not match Bragg's law will pass through the VBG undiffracted.
|
|
The Fourier transform method above can be used to find the form of the diffraction for any periodic structure where the Fourier transform of the structure is known. GoodmanGoodman, 2005, Sections 4.4.3 and 4.4.4, p 78 uses this method to derive expressions for the diffraction pattern obtained with sinusoidal amplitude and phase modulation gratings.
|
|
In they installed 130 new lights, 12 bankings, three modules of newspaper and 120 bolardos. BICENTENNIAL ARC Project presented by 24 young Mexican architects. Cesar Perez Becerril was the head of the Project. Monument that will be raised on Walk of the Reform, at a height of the gratings of The Lions, of Chapultepec's Forest.
|
|
A floor drain is a plumbing fixture that is installed in the floor of a structure, mainly designed to remove any standing water near it. They are usually round, but can also be square or rectangular. They usually range from ; most are in diameter. They have gratings that are made of metal or plastic.
|
|
The blaze angle is optimized to maximize efficiency for the wavelength of the used light. Descriptively, this means \theta_B is chosen such that the beam diffracted at the grating and the beam reflected at the steps are both deflected into the same direction. Commonly blazed gratings are manufactured in the so-called Littrow configuration.
|
|
Prof Henry Augustus Rowland FRS(For) HFRSE (November 27, 1848 – April 16, 1901) was an American physicist. Between 1899 and 1901 he served as the first president of the American Physical Society. He is remembered today particularly for the high quality of the diffraction gratings he made and for the work he did with them on the solar spectrum.
|
|
Schematic diagram of the chromo-modal dispersion device. Light is incident upon two parallel plane gratings, which disperse and collimate the optical spectrum. Angular dispersion is then applied to the spectrum using a lens. The input facet of a multimode fiber is placed at the lens focus such that the various spectral components are coupled into different fiber modes.
|
|
Fluorescence-based detection has been used in microarrays and PCR on a chip devices. Chemiluminescence is light generation by energy release from a chemical reaction. Bioluminescence and electrochemiluminescence are subtypes of chemiluminescence. Surface plasmon resonance sensors can be thin-film refractometers or gratings that measure the resonance behaviour of surface plasmon on metal or dielectric surfaces.
|
|
Influenced by the campuses of southern Europe, many of Rice's buildings are Mediterranean Revival in style, with sand and pink-colored bricks, large archways and columns acting as architectural motifs. Noteworthy exceptions include the glass-walled Brochstein Pavilion, Lovett College with its Brutalist-style concrete gratings, the eclectic-Mediterranean Duncan Hall, and the modern Moody Center for the Arts.
|
|
The beds had gratings underneath which admitted fresh air and the open style of the arched walkways exposed staff to fresh air. The, now demolished, Eastern ward block had a basement story of open piers and arches allowing a free circulation of the air beneath the ground floor. There was a basement tramway for trolleys to transport coal.
|
|
Sheng He (born 1964, China) is a Professor of Psychology in the Department of Psychology, University of Minnesota. He is broadly interested in the neural basis of human vision, visual attention, and visual awareness. His most influential works include the demonstration of adaptation to invisible visual patterns (such as gratings), and the depth of invisible processing during binocular suppression.
|
|
A typical test stimulus might show adjacent patches of black-and-white vertical and horizontal gratings (as above). The McCollough-effect colors are less saturated than the induction colors. The induction stimuli can have any different colors. The effect is strongest, however, when the colors are complementary, such as red and green, or blue and orange.
|
|
Cast metal storm drain grate with Neenah Foundry marking Neenah Foundry is a manufacturing company in the north central United States, based in Neenah, Wisconsin. The company manufactures cast iron manhole covers, gratings, and similar items for municipal and construction applications. Neenah Enterprises, Inc. manufactures iron castings for the heavy truck, agriculture, construction, and related markets.
|
|
The resolution of a grism is proportional to the tangent of the wedge angle of the prism in much the same way as the resolutions of gratings are proportional to the angle between the input and the normal to the grating. Grisms are being used in the NIRCam instrument on the James Webb Space Telescope for wavefront sensing.
|
|
The company began marketing optical position measuring equipment for machine tools in 1956. Moire fringes produced by diffraction gratings were the basis for the position measurement. In the late 1980s there were several sections of the company involved in non-military areas. These included microwave communications equipment (Ferranti Communications), and petrol (gas) station pumps (Ferranti Autocourt).
|
|
Young similarly explained the colors of "striated surfaces" (e.g., gratings) as the wavelength-dependent reinforcement or cancellation of reflections from adjacent lines. He described this reinforcement or cancellation as interference. Thomas Young (1773–1829) Neither Newton nor Huygens satisfactorily explained diffraction—the blurring and fringing of shadows where, according to rectilinear propagation, they ought to be sharp.
|
|
The interferometer consists of three parallel and equally spaced phase gratings, and an x-ray camera. The incident beam is diffracted by a first grating of period 2P into two beams. These are further diffracted by a second grating of period P into four beams. Two of the four merge at a third grating of period 2P.
|
|
Defective optical issues (such as uncorrected myopia) can render it worse, but suitable lenses can help. Images (such as gratings) can be sharpened by lateral inhibition, i.e., more highly excited cells inhibiting the less excited cells. A similar reaction is in the case of chromatic aberrations, in which the color fringes around black-and-white objects are inhibited similarly.
|
|
High contrast gratings have been employed in many optoelectronic devices. It has been incorporated as the mirrors for vertical-cavity surface-emitting lasers. The light-weight of high contrast grating enables fast microelectromechanical structure actuation for wavelength tuning. The reflection phase of the high contrast grating is engineered to control the emission wavelength of vertical-cavity surface-emitting lasers.
|
|
Koechner, §2.5, pp66–78. Titanium- doped sapphire is the most common tunable solid-state laser, capable of laser operation from 670 nm to nm wavelength. Typically these laser systems incorporate a Lyot filter into the laser cavity, which is rotated to tune the laser. Other tuning techniques involve diffraction gratings, prisms, etalons, and combinations of these.
|
|
At the time of De Valois' move to Berkeley, linear systems analysis was emerging as a tool for studying the early stages of visual processing. Although this technique had long been applied to problems in optics and engineering, vision scientists Fergus Campbell and John Robson Campbell, F. W., & Robson, J. G., "Application of Fourier analysis to the visibility of gratings", Journal of Physiology (London), 197, 551–556 (1967). measured human sensitivity to patterns of spatial sinusoidal gratings of varying periodicity and first proposed spatial frequency selective "channels" to explain a number of psychophysical phenomena in pattern perception. De Valois, consistent with his conviction that perception must be linked to neuronal responses, seized on these findings and began electrophysiological studies of the mechanisms of early visual processing of form.
|
|
As Bell's former associate, Thomas Watson, was fully occupied as the superintendent of manufacturing for the nascent Bell Telephone Company back in Boston, Massachusetts, Bell hired Charles Sumner Tainter, an instrument maker who had previously been assigned to the U.S. 1874 Transit of Venus Commission, for his new 'L' Street laboratory in Washington, at the rate of $15 per week.Mims 1982, p. 7. On February 19, 1880, the pair had managed to make a functional photophone in their new laboratory by attaching a set of metallic gratings to a diaphragm, with a beam of light being interrupted by the gratings movement in response to spoken sounds. When the modulated light beam fell upon their selenium receiver Bell, on his headphones, was able to clearly hear Tainter singing Auld Lang Syne.
|
|
Not less than 30 years later the Japanese scientists Atsushi Momose, Tohoru Takeda and co-workers adopted this idea and refined it for application in biological imaging, for instance by increasing the field of view with the assistance of new setup configurations and phase retrieval techniques. The Bonse–Hart interferometer provides several orders of magnitude higher sensitivity in biological samples than other phase-contrast techniques, but it cannot use conventional X-ray tubes because the crystals only accept a very narrow energy band of X-rays (ΔE/E ~ 10−4). In 2012, Han Wen and co-workers took a step forward by replacing the crystals with nanometric phase gratings. The gratings split and direct X-rays over a broad spectrum, thus lifting the restriction on the bandwidth of the X-ray source.
|
|
There exists several methods to extend the tuning range of quantum cascade lasers using only monolithically integrated elements. Integrated heaters can extend the tuning range at fixed operation temperature to 0.7% of the central wavelength and superstructure gratings operating through the Vernier effect can extend it to 4% of the central wavelength, compared to <0.1% for a standard DFB device.
|
|
It was designed to house both male and female prisoners from the beginning. The prison was built by Messrs. Sara and Dunstan, from local Gladstone stone. It was the first prison in South Australia to restrict prisoner contact with visitors, separating them "by iron gratings nine feet apart, with a warder between" so conversations could be overheard and contraband restricted.
|
|
Accuracy is limited due to the friction and hysteresis imposed by this mechanical arrangement. For the highest accuracy, lowest measurement hysteresis and lowest friction applications, open linear encoders are used. Linear encoders may use transmissive (glass) or reflective scales, employing Ronchi or phase gratings. Scale materials include chrome on glass, metal (stainless steel, gold plated steel, Invar), ceramics (Zerodur) and plastics.
|
|
Reflection can be reduced by texturing the surface with 3D pyramids or 2D grooves (gratings). These kind of textured coating can be created using for example the Langmuir-Blodgett method. If wavelength is greater than the texture size, the texture behaves like a gradient-index film with reduced reflection. To calculate reflection in this case, effective medium approximations can be used.
|
|
There will be two immersion gratings, one optimized for K band and one optimized for L band. Due to the silicon grating, iShell will not be sensitive to light shorter than 1 µm. Each pixel is 0.125" on the sky and the spectroscopic dispersion is 75,000 when used with a 0.375" slit. Five slits from 0.375" to 4.0" are available for use.
|
|
It lies about 1.5 km. to the west of Aderet as the crow flies, and about northeast of Beit Guvrin National Park. The site is quite extensive and contains tunnels believed to have been in use during the Bar Kokhba revolt. Tombs from the Second Temple period, agricultural features and cisterns (now covered with iron gratings) can be seen on the site.
|
|
Polymer optical fibers can be used for remote sensing and multiplexing due to their low cost and high resistance. It is possible to write fiber Bragg gratings in single and multimode POF. There are advantages in doing this over using silica fiber since the POF can be stretched further without breaking, some applications are described in the PHOSFOS project page.
|
|
Typically the grating period is the same size as the Bragg wavelength, as shown above. For a grating that reflects at 1,500 nm, the grating period is 500 nm, using a refractive index of 1.5. Longer periods can be used to achieve much broader responses than are possible with a standard FBG. These gratings are called long-period fiber grating.
|
|
Each of the three foundations cost 70,000 lei, the boardwalk cost 370,000 lei to extract from the sea, the furniture itself cost approximately 90,000 lei while the total costs railings, gratings, chandeliers, lighting fixtures, furniture, and all other decorations cost 547,616 lei – according to Romanian art critic and researcher Doina Păuleanu and historic documents in the City of Constanța archives. Historical documents also show that electricity was installed by the Sociertatea Anonimă de Gaz of Budapest and railings, gratings, and metalwork items were executed by the Wolf Factory in Bucharest. The asphalt on the outer sidewalk and the iron grating including three gates, were made by the M. Segal Company in Bucharest costing 19,000 lei. The city also purchased a piano from the Otto Harnisch Company in Bucharest and hired an orchestra of 18 people at a cost of 20,000 lei per season.
|
|
Such monolithic, all-fiber devices are produced by many companies worldwide and at power levels exceeding 1 kW. The major advantage of these all fiber systems, where the free space mirrors are replaced with a pair of fiber Bragg gratings (FBGs), is the elimination of realignment during the life of the system, since the FBG is spliced directly to the doped fiber and never needs adjusting. The challenge is to operate these monolithic cavities at the kW CW power level in large mode area (LMA) fibers such as 20/400 (20 μm diameter core and 400 μm diameter inner cladding) without premature failures at the intra-cavity splice points and the gratings. Once optimized, these monolithic cavities do not need realignment during the life of the device, removing any cleaning and degradation of fiber surface from the maintenance schedule of the laser.
|
|
When the solvent had evaporated he detached this pellicle and applied its grooved surface to a moist gelatine film on a glass plate. When dry, the gelatine bore a faithful record of the original rulings. In 1948 Merton made an important basic advance in the art of ruling diffraction gratings. Since 1880 these had been ruled groove by groove by the method used by Rowlands.
|
|
Besides trapping cold atoms, optical lattices have been widely used in creating gratings and photonic crystals. They are also useful for sorting microscopic particles, and may be useful for assembling cell arrays. Atoms in an optical lattice provide an ideal quantum system where all parameters can be controlled. Thus they can be used to study effects that are difficult to observe in real crystals.
|
|
The Debye-Sears method determines the wavelength of monochromatic light using an acoustic or ultrasonic gratings. This method utilises the concept of piezoelectricity to obtain a grating. The phenomenon of diffraction of light using an ultrasonic grating was first observed by Debye and Sears in 1932. When ultrasonic waves are propagated in a liquid, the density varies from layer to layer due to periodic variation of pressure.
|
|
Pelikansgränd viewed from Österlånggatan. Eastern end of Pelikansgränd viewed from Lilla Hoparegränd. Gratings. Pelikansgränd is an alley in Gamla stan, the old town of Stockholm, Sweden, connecting Gaffelgränd to Österlånggatan. It forms a parallel street to Ferkens Gränd, Lilla Hoparegränd, Gaffelgränd, and Johannesgränd. The alley appears in historical records as Lilla S:t Johannes gränd in 1664, Pilicans Gränden around 1700, and Pelekans gr[änd] in 1733.
|
|
This underground station has two side platforms with two tracks. The mosaic band on both platforms features greys along with aqua, orange, ochre, light blue and light green. Near the south end of the station, there are gratings near the ceiling, with the tile band cut out to fit around them. A historically correct section of replacement tile can also be seen in this area.
|
|
Robots built by Largo out of parts salvaged from dumpsters, as well as the TPCD's own stealthy wall-mounted phones and soda dispensers that he co-opted. They are used for protecting Megagamers and its surroundings, or guarding the "spawn points" (sewer gratings). These have now been left around the city, as seen in one filler art day later on in the series. Their effectiveness is minimal.
|
|
Many microwave metamaterials use split-ring resonators. Photonic metamaterials are structured on the nanometer scale and manipulate light at optical frequencies. Photonic crystals and frequency-selective surfaces such as diffraction gratings, dielectric mirrors and optical coatings exhibit similarities to subwavelength structured metamaterials. However, these are usually considered distinct from metamaterials, as their function arises from diffraction or interference and thus cannot be approximated as a homogeneous material.
|
|
Fiber Bragg grating based fiber-optic sensors significantly enhance performance, efficiency and safety in several industries. With FBG integrated technology, sensors can provide detailed analysis and comprehensive reports on insights with very high resolution. These type of sensors are used extensively in several industries like telecommunication, automotive, aerospace, energy, etc. Fiber Bragg gratings are sensitive to the static pressure, mechanical tension and compression and fiber temperature changes.
|
|
The outside walls of the bowl consist of gratings or perforated plates through which fine product can pass. Grinding is largely autogenous (i.e. it takes place by collision between lumps of raw material), and is very efficient, producing little waste heat, provided that the materials are soft. Typically two or three washmills are connected in series, these being provided with successively smaller outlet perforations.
|
|
The first continuous-wave Raman laser using an optical fiber as the gain medium was demonstrated in 1976. In fiber-based lasers, tight spatial confinement of the pump light is maintained over relatively large distances. This significantly lowers threshold pump powers down to practical levels and furthermore enables continuous-wave operation. In 1988, the first Raman fiber laser based on fiber Bragg gratings has been made.
|
|
Each is further diffracted by the third grating. The multiple diffracted beams are allowed to propagate for sufficient distance such that the different diffraction orders are separated at the camera. There exists a pair of diffracted beams that co-propagate from the third grating to the camera. They interfere with each other to produce intensity fringes if the gratings are slightly misaligned with each other.
|
|
Bishop Henry Codman Potter held an elaborate consecration service. Courts began assigning girls there, and families also brought their wayward daughters. The new structure, built to house 154 "fallen" women, had three divisions: the House of Mercy, St. Agnes’s House, and a division for penitents. Iron gratings barred the windows, and persons assigned to one division were not allowed to mingle with those in other divisions.
|
|
Examples include acousto-optic modulators for cavity dumping and vacuum spatial filters for transverse mode control. For some low power lasers, the laser gain medium itself may be positioned at a beam waist. Other elements, such as filters, prisms and diffraction gratings often need large quasi-collimated beams. These designs allow compensation of the cavity beam's astigmatism, which is produced by Brewster-cut elements in the cavity.
|
|
The core of the masonry is made of quarry stone, the pillars are based on wooden gratings Up to 3000 workers of different nationalities participated in the construction. For the first time steam lifting machines were used to a greater extent. Worldwide, it was a quite unique building, since in many places at that time similar bridges were built from wood and not from granite.
|
|
You can see the initial small window panes. One of the gratings protecting the balconies was preserved during the reconstruction. There is also a historical interior decoration. It is abundantly used the motif of pine branches: stucco friezes in the form of garlands of branches, bunches of branches with cones on consoles supporting the ladder, cones and bundles of needles in the decoration of the staircase.
|
|
Hence, special instruments are required to measure such a minute change. Describes the atom interferometer principle Atom interferometers work on the principle of diffraction. The diffraction gratings are nano fabricated materials with a separation of a quarter wavelength of light. When a beam of atoms pass through a diffraction grating, due to the inherent wave nature of atoms, they split and form interference fringes on the screen.
|
|
Microbend grating is a convenient method to couple light from one guided fiber mode into another. Due to its antisymmetric nature of perturbation, it can be used to couple only into antisymmetric modes. Microbend gratings are easily tunable for a wide range of wavelengths.J. N. Blake, B. Y. Kim, H. E. Engan, and H. J. Shaw, “Analysis of intermodal coupling in a two-mode fiber with periodic microbends”.
|
|
Spectrophotometry: Quantitative measurement of transmittance based on wavelength. It is important in a number of biomedical fields ranging from the measurement of a solute in a sample to determining enzyme kinetics for a given substrate-enzyme pair. Spectrophotometry requires multiple wavelengths for a wide variety of samples. Therefore, an arc lamp is used to generate multiple wavelengths for collimating mirrors and diffraction gratings to generate collimated light at narrow bandwidths.
|
|
The lower deck would have consisted of two plates of HTS. For the first time in a Japanese ship, the Tosas would have had the lower portion of the single funnel protected by 229 mm of armor. In addition, the funnel openings in the lower deck would have been protected by armor gratings. The ships would have had an internal torpedo bulge to provide protection against underwater explosions.
|
|
70% of the time the response cue matched the pre-cue and 30% of the time did not match the pre- cue. The participants were asked to report texture of the gratings that appeared in the response-cue and discriminate its visibility. This set-up allowed them to compare the perception of attended (cued) and non-attended stimuli (uncued). Higher visibility was reported for stimuli that was unattended.
|
|
Spectral flow cytometry uses prisms or diffraction gratings to disperse the emitted light of a marker across a detector array. This allows for the full spectra from each particle to be measured. The measured spectra from single cells are subsequently unmixed by using reference spectra of all used dyes and the autofluorescence spectrum. This may allow for a wider panel design and the application of new biological markers.
|
|
To solve this problem HiPER uses a technique known as chirped pulse amplification (CPA). CPA starts with a short pulse from a wide-bandwidth (multi-frequency) laser source, as opposed to the driver which uses a monochromatic (single-frequency) source. Light from this initial pulse is split into different colours using a pair of diffraction gratings and optical delays. This "stretches" the pulse into a chain several nanoseconds long.
|
|
Duane argued that the way that crystal scattering can be explained by quantization of momentum is not explicable by models based on diffraction by classical waves, as in Bragg's Law. Duane applied his hypothesis to derive the scattering angles of X-Rays by a crystal. Subsequently, the principles that Duane advanced were also seen to provide the correct relationships for optical scattering at gratings, and the diffraction of electrons.Bitsakis, E.(1997).
|
|
This feature allowed them to monolithically integrate gain blocks (active waveguides providing amplification) with different passive elements, such as couplers, arrayed waveguide gratings (AWG), optical taps, turning mirrors and so on. Some of advanced Inplane Photonics' photonic circuits containing EDWAs were used by Lockheed Martin in their development of new high-speed on-board communication systems for the US Air Force. Inplane Photonics and its technology was later acquired by CyOptics.
|
|
He was in charge of oriental books. Reay held the professorship until his death, and remained at the Bodleian until retiring with a pension in 1860. Colleagues at the library fondly remembered "his habits of pottering around the library in search of his spectacles and hovering over hot-air gratings in search of warmth". He was also curate for a time of the church of St Peter-le-Bailey, Oxford.
|
|
One period (or cycle) of such a grating consists of one black bar and one adjacent white bar. Gratings where the black bars have a different width from the white bars are rectangular and are described by the duty cycle. The duty cycle is the ratio of width of the black bar to period (or pitch, i.e. the sum of the widths of one black and one white bar).
|
|
Length measurement is implemented in practice in many ways. The most commonly used approaches are the transit-time methods and the interferometer methods based upon the speed of light. For objects such as crystals and diffraction gratings, diffraction is used with X-rays and electron beams. Measurement techniques for three-dimensional structures very small in every dimension use specialized instruments such as ion microscopy coupled with intensive computer modeling.
|
|
HR mode is the high resolution mode. This mode incorporates a 40 micrometre exit slit to achieve high spectral resolution of R = 75000. HE mode is the high efficiency mode. This mode is used when a higher throughput is desired particularly in the case of faint objects spectral resolution is set to R = 40000. The R2 échelle diffraction grating has 52.65 grooves per millimeter and was manufactured by Richardson Gratings.
|
|
Optical fibers can be made into interferometric sensors such as fiber-optic gyroscopes, which are used in the Boeing 767 and in some car models (for navigation purposes). They are also used to make hydrogen sensors. Fiber-optic sensors have been developed to measure co-located temperature and strain simultaneously with very high accuracy using fiber Bragg gratings. This is particularly useful when acquiring information from small or complex structures.
|
|
The finish of the sandstone is a combination of smooth ashlar battlement details and rock-faced finish on the main column faces. The original design incorporated drainage gratings in the floor of the upper battlements. Extending out from the base of each tower are sandstone parapet walls framing the approaches to the bridge. These are rubble filled, and topped with footpaths, kerbs and drainage grates on each side of the roadway.
|
|
Describes the atom interferometer principle Atom interferometers work on the principle of diffraction. The diffraction gratings are nano fabricated materials with a separation of a quarter wavelength of light. When a beam of atoms pass through a diffraction grating, due to the inherent wave nature of atoms, they split and form interference fringes on the screen. An atom interferometer is very sensitive to the changes in the positions of atoms.
|
|
A single UV laser beam may also be used to 'write' the grating into the fiber point-by-point. Here, the laser has a narrow beam that is equal to the grating period. The main difference of this method lies in the interaction mechanisms between infrared laser radiation and dielectric material - multiphoton absorption and tunnel ionization. This method is specifically applicable to the fabrication of long period fiber gratings.
|
|
In it, Cary and Beckman compared designs for a modified self- collimating quartz Fery prism, a mirror-collimated quartz Littrow prism, and various gratings. The Littrow prism was a half-prism, which had a mirrored face. Use of a tungsten light source with the quartz Littrow prism as a monochromator was reported to minimize light scattering within the instrument. The Model D was the first model to enter actual production.
|
|
Diffraction of a spotlight over a mobile phone Some everyday electronic components contain fine and regular patterns, and as a result readily serve as diffraction gratings. For example, CCD sensors from discarded mobile phones and cameras can be removed from the device. With a laser pointer, diffraction can reveal the spatial structure of the CCD sensors. This can be done for LCD or LED displays of smart phones as well.
|
|
The iridescence signal of flowers is thus only appreciable very locally and hence not visible to man and flower visiting insects. However, natural gratings do occur in some invertebrate animals, like the peacock spiders, the antennae of seed shrimp, and have even been discovered in Burgess Shale fossils. Diffraction grating effects are sometimes seen in meteorology. Diffraction coronas are colorful rings surrounding a source of light, such as the sun.
|
|
The principles of diffraction gratings were discovered by James Gregory, about a year after Isaac Newton's prism experiments, initially with items such as bird feathers.Letter from James Gregory to John Collins, dated 13 May 1673. Reprinted in: especially p. 254 The first man-made diffraction grating was made around 1785 by Philadelphia inventor David Rittenhouse, who strung hairs between two finely threaded screws.Thomas D. Cope (1932) "The Rittenhouse diffraction grating".
|
|
More formal testing using preferential looking techniques use Teller acuity cards (presented by a technician from behind a window in the wall) to check whether the child is more visually attentive to a random presentation of vertical or horizontal gratings on one side compared with a blank page on the other side – the bars become progressively finer or closer together, and the endpoint is noted when the child in its adult carer's lap equally prefers the two sides. Another popular technique is electro-physiologic testing using visual evoked (cortical) potentials (VEPs or VECPs), which can be used to estimate visual acuity in doubtful cases and expected severe vision loss cases like Leber's congenital amaurosis. VEP testing of acuity is somewhat similar to preferential looking in using a series of black and white stripes (sine wave gratings) or checkerboard patterns (which produce larger responses than stripes). Behavioral responses are not required and brain waves created by the presentation of the patterns are recorded instead.
|
|
Coded aperture mask for gamma camera (for SPECT) Coded apertures or coded- aperture masks are grids, gratings, or other patterns of materials opaque to various wavelengths of electromagnetic radiation. The wavelengths are usually high-energy radiation such as X-rays and gamma rays. By blocking radiation in a known pattern, a coded "shadow" is cast upon a plane. The properties of the original radiation sources can then be mathematically reconstructed from this shadow.
|
|
For the infrared region, gratings usually have 10–200 grooves/mm. When a diffraction grating is used, care must be taken in the design of broadband monochromators because the diffraction pattern has overlapping orders. Sometimes broadband preselector filters are inserted in the optical path to limit the width of the diffraction orders so they do not overlap. Sometimes this is done by using a prism as one of the monochromators of a dual monochromator design.
|
|
The 400 DO lens had a multilayer diffractive element containing concentric circular diffraction gratings to take advantage of diffraction's opposite color dispersion (compared to refraction) to correct chromatic and spherical aberrations with less low dispersion glass, fewer aspheric surfaces and less bulk.Herbert Keppler, "News: How Canon will cut the weight & size of tele lenses by about one-third." pp 62-63, 148. Popular Photography, Volume 65 Number 1; January 2001. ISSN 0032-4582.
|
|
Terrazzo flooring was in the > foyer and on the terrace. The walls in the hall and on the upper two > landings were panelled. This was a substantial house, with the roof fully > lined with wood beneath the tiles and the lofts boarded. There were several > immense cellars linked by hatches and one of them contained a huge boiler > which provided hot air to the ground floor via brass gratings in the parquet > flooring.
|
|
In order to produce narrow bandwidth tuning these lasers use many types of cavities and resonators which include gratings, prisms, multiple-prism grating arrangements, and etalons.F. J. Duarte and L. W. Hillman, Dye Laser Principles (Academic, New York, 1990) Chapter 4. The first narrow linewidth dye laser, introduced by Hänsch, used a Galilean telescope as beam expander to illuminate the diffraction grating.T. W. Hänsch, Repetitively Pulsed Tunable Dye Laser for High Resolution Spectroscopy, Appl. Opt.
|
|
The illusion is that the red and green appear to spread over the black and white regions of the vertical and horizontal gratings respectively. Figure 2. Figure 1 from Pinna (2008). Purple undulated contours adjacent to orange ones are perceived as a map of the Mediterranean Sea (picture a) and the Gulf of Mexico (picture b) evenly colored by a light veil of orange tint spreading from the orange contours (coloration effect).
|
|
On the sides of the mausoleum there are three small windows carved into solid slabs of limestone, and, like in the old days, they are through-through stone gratings, consisting of multi-beam stars. The archway in the northern part connects the mausoleum with an older mosque. According to Abbaskuli aga Bakikhanov, "the cell where he prayed [Bakuvi], the school and the grave that are under the mosque named after him, still exist today".
|
|
Grating - drain cover, ancient Roman architecture at Vindobona, Austria. A grating covering a drain (as illustrated) can be a collection of iron bars (the identical, elongated elements) held together (to ensure the bars are parallel and regularly spaced) by a lighter iron frame. Gratings over drains and air vents are used as filters, to block movement of large particles (such as leaves) and to allow movement of small particles (such as water or air).
|
|
Gamma oscillations are observed in the majority of seizures and may contribute to their onset in epilepsy. Visual stimuli such as large, high- contrast gratings that are known to trigger seizures in photosensitive epilepsy also drive gamma oscillations in visual cortex. During a focal seizure event, maximal gamma rhythm synchrony of interneurons is always observed in the seizure onset zone, and synchrony propagates from the onset zone over the whole epileptogenic zone.
|
|
It gives color either by colored pigments it contains, or through structural coloration with mechanisms that include photonic crystals and diffraction gratings. Scales function in insulation, thermoregulation, producing pheromones (in males only), and aiding gliding flight, but the most important is the large diversity of vivid or indistinct patterns they provide, which help the organism protect itself by camouflage or mimicry, and which act as signals to other animals including rivals and potential mates.
|
|
A diffraction grating or a dispersive prism may be used to selectively redirect selected wavelengths of light within an optical system. In the case of transmission gratings and prisms, polychromatic light that passes through the object will be redirected according to wavelength. A slit may then be used to select wavelengths that are desired. A reflective grating may also be utilized for the same purpose, though in this case light is reflected rather than transmitted.
|
|
Unlike most other types of lasers, the laser cavity in fiber lasers is constructed monolithically by fusion splicing different types of fiber; fiber Bragg gratings replace conventional dielectric mirrors to provide optical feedback. They may also be designed for single longitudinal mode operation of ultra narrow distributed feedback lasers (DFB) where a phase-shifted Bragg grating overlaps the gain medium. Fiber lasers are pumped by semiconductor laser diodes or by other fiber lasers.
|
|
The first in-fiber Bragg grating was demonstrated by Ken Hill in 1978. Initially, the gratings were fabricated using a visible laser propagating along the fiber core. In 1989, Gerald Meltz and colleagues demonstrated the much more flexible transverse holographic inscription technique where the laser illumination came from the side of the fiber. This technique uses the interference pattern of ultraviolet laser light to create the periodic structure of the fiber Bragg grating.
|
|
The interfering UV beams are focused onto the fiber, and as the fiber moves, the fringes move along the fiber by translating mirrors in an interferometer. As the mirrors have a limited range, they must be reset every period, and the fringes move in a sawtooth pattern. All grating parameters are accessible in the control software, and it is therefore possible to manufacture arbitrary gratings structures without any changes in the hardware.
|
|
The benefit of using interference lithography is the quick generation of dense features over a wide area without loss of focus. Seamless diffraction gratings on areas of more than one square meter have been originated by interference lithography. Hence, it is commonly used for the origination of master structures for subsequent micro or nano replication processes (e.g. nanoimprint lithography) or for testing photoresist processes for lithography techniques based on new wavelengths (e.g.
|
|
Fully rigorous electromagnetic solutions exist for gratings, which tends to involve heavy mathematical formulism. A simple analytical formulism to explain the various properties of high contrast grating has been developed. A computational program based on this analytical solution has also been developed to solve the electromagnetic properties of high contrast grating, named High Contrast Grating Solver."High Contrast Grating Solver" The following provides a brief overview of the operation principle of high contrast grating.
|
|
One fascinating field in which SMPs are impacting quite significantly nowadays is photonics. Due to the shape changing capability, SMPs enable the production of functional and responsive photonic gratings. In fact, by using modern soft lithography techniques such as replica molding, it is possible to imprint periodic nanostructures, with sizes of the order of magnitude of visible light, onto the surface of shape memory polymeric blocks. As a result of the refractive index periodicity, these systems diffract light.
|
|
The company commercializes hyperspectral imaging systems based on volume Bragg gratings. This technique combines spectroscopy and imaging: each image is acquired on a narrow band of wavelengths (as small as 0.3 nm). The monochromatic images acquired from a hyperspectral data cube, which contains both the spatial (x- and y-axes) and spectral (z-axis) information of a sample. In this technique, global imaging is used in order to acquire a large area of a sample without damaging it.
|
|
Dr. Kenneth O. Hill is a physicist who specializes in the field of photonics. In the late 1970s, he discovered the phenomena of photosensitivity in optical fiber and has worked extensively in its applications. He first demonstrated Fiber Bragg gratings and their applications in optical communication and optical sensor systems. Further areas of his discovery and innovation include the phase mask technique for grating fabrication, fiber grating dispersion compensators, and wavelength selective fiber filters, multiplexers and demultiplexers.
|
|
The above demonstration using the Arc de Triomphe photo is a simplified version of an earlier experiment. A photo of a clocktower was made into a video by adding noise with a particular variance a number of times to create successive frames. This was done for different levels of noise variance, and a particularly optimal level was found for discerning the appearance of the clocktower. Similar experiments also demonstrated an increased level of contrast sensitivity to sine wave gratings.
|
|
The great cabin was converted to house the potted breadfruit plants, and gratings were fitted to the upper deck. William Bligh was appointed Commanding Lieutenant of the Bounty on 16 August 1787 at the age of 33, after a career that included a tour as sailing master of James Cook's during Cook's third and final voyage (1776–80). The ship's complement was 46 men: a single commissioned officer (Bligh), 43 other Royal Navy personnel, and two civilian botanists.
|
|
The wave nature of light becomes important at small scales such as those in ASPs, meaning a pure-moire model of ASP function is insufficient. However, at half-integer multiples of the Talbot depth, the periodicity of the diffraction grating is recapitulated, and the moire effect is rescued. By building ASPs where the vertical separation between the gratings is approximately equal to a half-integer multiple of the Talbot depth, the sinusoidal sensitivity with incident angle is observed.
|
|
In traditional suit construction, haircloth is used to stiffen the front panels in men's suit jackets, and Savile Row tailors still make bespoke suits this way. However, in modern suits, haircloth is often replaced with synthetic fabrics. In the history of brewing, for drying the malt, haircloth was spread over the kiln floor to keep grain from dropping down into the furnace. Perforated metal or tile (gratings, meshes) were also used, but had a drawback of scorching the grain.
|
|
Arcus is an X-ray grating spectrometer space observatory that combines X-ray optics and gratings to disperse the X-rays, much like how a prism separates sunlight into the colors of the rainbow. It would observe astrophysical phenomena in X-ray band over a broad target size range. Its mission includes investigations on the composition of cosmic dust grains, stellar evolution, identify the launching mechanisms of supermassive black hole winds, and structure formation of galaxy clusters.
|
|
Moiré deflectometry produces result that appears similar to an interferometry technique,O. Kafri Optics letters 1980; 5,555 in which the object to be tested (either phase object or specular surface) is mounted in the course of a collimated beam followed by a pair of transmission gratings placed at a distance from each other. The resulting fringe pattern, i.e., the moiré deflectogram, is a map of ray deflections corresponding to the optical properties of the inspected object.
|
|
Bricks were to be laid in old English Bond with damp proof courses and hoop iron reinforcing. Air gratings were to be fixed for the sub floor spaces with slate steps to the outer doors set on brick risers. External cladding and carpentry were to be of hardwood the frame and roof timbers of Oregon or approved local pine. Architraves and mouldings were to be in redwood, floor boards tallow wood and lining boards in Kauri pine.
|
|
Demonstration of monocular rivalry between two component sine-wave gratings: a vertical green-and-black grating and a horizontal red-and-black grating. Monocular rivalry is a phenomenon of human visual perception that occurs when two different images are optically superimposed. During prolonged viewing, one image becomes clearer than the other for a few moments, then the other image becomes clearer than the first for a few moments. These alternations in clarity continue at random for as long as one looks.
|
|
Historically, Raman spectrometers used holographic gratings and multiple dispersion stages to achieve a high degree of laser rejection. In the past, photomultipliers were the detectors of choice for dispersive Raman setups, which resulted in long acquisition times. However, modern instrumentation almost universally employs notch or edge filters for laser rejection. Dispersive single-stage spectrographs (axial transmissive (AT) or Czerny–Turner (CT) monochromators) paired with CCD detectors are most common although Fourier transform (FT) spectrometers are also common for use with NIR lasers.
|
|
Lyman became an assistant professor in physics at Harvard, where he remained, becoming full professor in 1917, and where he was also director of the Jefferson Physical Laboratory (1908–17). He made important studies in phenomena connected with diffraction gratings, on the wavelengths of vacuum ultraviolet light discovered by Victor Schumann and also on the properties of light of extremely short wavelength, on all of which he contributed valuable papers to the literature of physics in the proceedings of scientific societies.
|
|
This results in a large loss of power. In contrast, increasing d in the Lloyd's mirror technique does not result in power loss, since the second "slit" is just the reflected virtual image of the source. Hence, Lloyd's mirror enables the generation of finely detailed interference patterns of sufficient brightness for applications such as photolithography. Typical uses of Lloyd's mirror photolithography would include fabrication of diffraction gratings for surface encoders and patterning the surfaces of medical implants for improved biofunctionality.
|
|
Complex cells can be found in the primary visual cortex (V1), the secondary visual cortex (V2), and Brodmann area 19 (V3). Like a simple cell, a complex cell will respond primarily to oriented edges and gratings, however it has a degree of spatial invariance. This means that its receptive field cannot be mapped into fixed excitatory and inhibitory zones. Rather, it will respond to patterns of light in a certain orientation within a large receptive field, regardless of the exact location.
|
|
An example of a visual contingent aftereffect is the McCollough effect. The McCollough effect is one of a family of contingent aftereffects related to the processing of color and orientation. One can induce the aftereffect by exposure to a magenta and black vertical grating alternating with a green and black horizontal grating. After a few minutes of induction (5 or more is best), followed by a break of a few minutes, black- and-white vertical and horizontal gratings will appear colored.
|
|
Electromagnetically induced grating (EIG) is an optical interference phenomenon where an interference pattern is used to build a dynamic spatial diffraction grating in matter. EIGs are dynamically created by light interference on optically resonant materials and rely on population inversion and/or optical coherence properties of the material. They were first demonstrated with population gratings on atoms. EIGs can be used for purposes of atomic/molecular velocimetry, to probe the material optical properties such as coherence and population life-times,.
|
|
The large dispersion and small footprint of the device make the chromo-modal dispersion device potentially useful for on-chip dispersion compensation using optical components such as integrated gratings and planar multimode waveguides. The advantage of physical compactness, combined with the magnitude and tunability of its dispersion suggest its potential use as a versatile tool for pulse stretching or compression in a variety of applications in which the capabilities of singlemode fiber or diffraction grating-based dispersive elements will not suffice.
|
|
This provides further evidence that cognitive processes converge in order to help construct the perceptual experience. Although attention can lead to enhanced perceptual processing, the lack of attention to stimuli can also lead to a perceived enhanced perception of the stimuli. Participants were pre-cued that indicated the diagonal to which they should be attending. They were then presented with stimuli (gratings with different textures) and then a response cue that indicated the diagonal for which the participants had to judge their perception.
|
|
Stacks Immediately inside the doorway is a circulation desk as well as a small reading room. The wall contains a vertically-ribbed wainscot wrapping around the south and north walls. The south wall contains a dumbwaiter shaft as well as bookshelves. In the rear of the library are double-height iron stacks with openwork gratings, manufactured by Hopkins & Co. There are glass floor panels on the second level of the stacks, which form a mezzanine level and contain iron railings.
|
|
The tunnel has lain derelict for over 40 years, but is in fair condition, with the Hitchin end back-filled to within 7 feet of the tunnel roof and the Bedford end bricked up with gratings for local bats. However, public access holes have been closed at both ends. Entrance to the tunnel is not recommended, due to bats and standing water accumulation. The Bedford Portal is still visible in its cutting, but the Hitchin Portal is entirely covered in undergrowth.
|
|
Curb, gutter, and grating covering a storm drain Grating at a power plant A grating is any regularly spaced collection of essentially identical, parallel, elongated elements. Gratings usually consist of a single set of elongated elements, but can consist of two sets, in which case the second set is usually perpendicular to the first (as illustrated)."" by sanorient, The frp Demonstrations Project. When the two sets are perpendicular, this is also known as a grid (as in grid paper) or a mesh.
|
|
363 A two-level hangar was built under the flight deck, in height per level. The lower hangar was long by wide and the upper was . Each hangar could be sectioned off by electrically operated steel shutters on rollers. Her boilers were ducted down the side of the ship to exhaust either out of gratings at the rear of the flight deck or, when landing operations were in progress, out of the side of the lower hangar at the rear of the ship.
|
|
At room temperature, ruby lasers emit only short pulses of light, but at cryogenic temperatures they can be made to emit a continuous train of pulses. Some solid-state lasers can also be tunable using several intracavity techniques, which employ etalons, prisms, and gratings, or a combination of these.N. P. Barnes, Transition metal solid-state lasers, in Tunable Lasers Handbook, F. J. Duarte (Ed.) (Academic, New York, 1995). Titanium-doped sapphire is widely used for its broad tuning range, 660 to 1080 nanometers.
|
|
If the two paths both pass through the object at two locations which are separated by a lateral distance d, then a phase difference image of Φ(r) - Φ(r-d) is detected. Phase stepping one of the gratings is performed to retrieve the phase images. The phase difference image Φ(r) - Φ(r-d) can be integrated to obtain a phase shift image of the object. This technique achieved substantially higher sensitivity than other techniques with the exception of the crystal interferometer.
|
|
Diffraction at a blazed grating. The general case is shown with red rays; the Littrow configuration is shown with blue rays The Littrow configuration is a special geometry in which the blaze angle is chosen such that diffraction angle and incidence angle are identical.Richardson Gratings, "Technical Note 11", section "Determination of the Blaze Wavelength" (30 September 2012). For a reflection grating, this means that the diffracted beam is back-reflected into the direction of the incident beam (blue beam in picture).
|
|
Earth's atmosphere partially or totally blocks some wavelengths of electromagnetic radiation, but in visible light it is mostly transparent Spectroscopy is the study of objects based on the spectrum of color they emit, absorb or reflect. Spectroscopy is an important investigative tool in astronomy, where scientists use it to analyze the properties of distant objects. Typically, astronomical spectroscopy uses high-dispersion diffraction gratings to observe spectra at very high spectral resolutions. Helium was first detected by analysis of the spectrum of the sun.
|
|
The core of the science hardware of the IUE. The telescope tube and sunshade extend above the pivot point of the support stand, the cameras are just below, and some of the mirrors and diffraction gratings are at the bottom. The box extending from the midpoint of the assembly covers the location of the spacecraft gyros. Simplified optical diagram of the telescope The telescope was constructed as a joint project between NASA, ESRO (which became ESA in 1975) and the UK Science and Engineering Research Council.
|
|
93–95 A two- storey hangar was built under the flight deck, each level being high. The lower hangar was long by wide and the upper was . Each hangar could be sectioned off by electrically operated steel shutters on rollers. Her boilers were ducted down the side of the ship to exhaust either out of gratings at the rear of the flight deck, or, when landing operations were in progress, out of the side of the lower hangar at the rear of the ship.
|
|
Above these are shell-shaped niches alternating with rectangular windows, and vaulted ceiling with lunettes. The main chapel with high altar vertically oriented includes a vaulted ceiling, with illumination coming from the high choir, nave and chancel windows. The cloister is preceded by a galilee formed by arch and portal with an interrupted triangular pediment in the interior, joined to two rectangular gratings. Comprising two floors with archivolts, with segments marked by Tuscan and Ionian capitals along the upper floor, including balconies with iron railings.
|
|
Typically, the part to be created is first described using a CAD model, then converted to G-code using a CAM program, and the G-code is then executed by the machine control computer to move the cutting tool. The final surface is achieved with a series of cutting passes of decreasing depth. Alternative methods of diamond machining in practice also include diamond fly cutting and diamond milling. Diamond fly cutting can be used to generate diffraction gratings and other linear patterns with appropriately contoured diamond shapes.
|
|
The heaviest F900 class manhole cover would typically be used in docks, airports and other extreme heavy-duty applications. EN 124 does not apply for gratings of prefabricated drainage channels (according to EN 1433) or floor and roof gullies in buildings (specified in EN 1253-1). The Fabricated Access Covers Trade Association (FACTA) provides its own specification which came into effect in 2013. It has a similar scope as the EN 124, focuses on wheel loadings and is based on the European standards for structural steelwork.
|
|
The father-and-son scientific team of William Lawrence Bragg and William Henry Bragg, who were 1915 Nobel Prize Winners, were the original pioneers in developing X-ray emission spectroscopy. Jointly they measured the X-ray wavelengths of many elements to high precision, using high-energy electrons as excitation source. The cathode ray tube or an x-ray tube was the method used to pass electrons through a crystal of numerous elements. They also painstakingly produced numerous diamond-ruled glass diffraction gratings for their spectrometers.
|
|
In contrast to the fiber Bragg gratings, LPFGs couple copropagating modes with close propagation constants; therefore, the period of such a grating can considerably exceed the wavelength of radiation propagating in the fiber. Because the period of an LPFG is much larger than the wavelength, LPFGs are relatively simple to manufacture. Since LPFGs couple copropagating modes, their resonances can only be observed in transmission spectra. The transmission spectrum has dips at the wavelengths corresponding to resonances with various cladding modes (in a single-mode fiber).
|
|
Noticing soldiers with olive-colored uniforms, Uzis and an IDF helmet, a radio technician came out and yelled "Golani, Golani, don't shoot!", before his eyes had adapted to the sunlight when he noticed they were Syrians. He and the others ran back in and the Syrians chased them, throwing smoke grenades. Not knowing where the other Israelis were hiding, the Syrians called on them to surrender through the generator gratings and pointed flashlights inside, saying that whoever did not come out would be killed.
|
|
In principle, any wave impinging on a regular array of scatterers produces diffraction, as predicted first by Francesco Maria Grimaldi in 1665. To produce significant diffraction, the spacing between the scatterers and the wavelength of the impinging wave should be similar in size. For illustration, the diffraction of sunlight through a bird's feather was first reported by James Gregory in the later 17th century. The first artificial diffraction gratings for visible light were constructed by David Rittenhouse in 1787, and Joseph von Fraunhofer in 1821.
|
|
The notion of developing a near-field optical device was first conceived by Edward Hutchinson Synge in 1928 but was not realized experimentally until the 1950s when several researchers demonstrated the feasibility of sub-wavelength resolution. Published images of sub-wavelength resolution appeared when Ash and Nichols examined gratings with line spacing less than one millimeter using microwaves of 3 cm wavelength. In 1982 Dieter Pohl at IBM in Zurich, Switzerland, first obtained sub-wavelength resolution at visible wavelengths using near-field optical techniques.
|
|
A biofilm on the surface of a fishtank produces diffraction grating effects when the bacteria are all evenly sized and spaced. Such phenomena are an example of Quetelet rings. Striated muscle is the most commonly found natural diffraction grating and, this has helped physiologists in determining the structure of such muscle. Aside from this, the chemical structure of crystals can be thought of as diffraction gratings for types of electromagnetic radiation other than visible light, this is the basis for techniques such as X-ray crystallography.
|
|
In extrastriate visual areas, cells can have very large receptive fields requiring very complex images to excite the cell. For example, in the inferotemporal cortex, receptive fields cross the midline of visual space and require images such as radial gratings or hands. It is also believed that in the fusiform face area, images of faces excite the cortex more than other images. This property was one of the earliest major results obtained through fMRI (Kanwisher, McDermott and Chun, 1997); the finding was confirmed later at the neuronal level (Tsao, Freiwald, Tootell and Livingstone, 2006).
|
|
When all of the visual cortex neurons that are influenced by a specific scene respond together, the perception of the scene is created by the summation of the various sine-wave gratings. (This procedure, however, does not address the problem of the organization of the products of the summation into figures, grounds, and so on. It effectively recovers the original (pre-Fourier analysis) distribution of photon intensity and wavelengths across the retinal projection, but does not add information to this original distribution. So the functional value of such a hypothesized procedure is unclear.
|
|
The dispersive mechanism is generally based on holographic or ruled diffraction gratings similar to those used commonly in spectrometers. It can be advantageous, for achieving resolution and coupling efficiency, to employ a combination of a reflective or transmissive grating and a prism – known as a GRISM. The operation of the WSS can be bidirectional so the wavelengths can be multiplexed together from different ports onto a single common port. To date, the majority of deployments have used a fixed channel bandwidth of 50 or 100 GHz and 9 output ports are typically used.
|
|
Grating monochromators disperse ultraviolet, visible, and infrared radiation typically using replica gratings, which are manufactured from a master grating. A master grating consists of a hard, optically flat, surface that has a large number of parallel and closely spaced grooves. The construction of a master grating is a long, expensive process because the grooves must be of identical size, exactly parallel, and equally spaced over the length of the grating (3–10 cm). A grating for the ultraviolet and visible region typically has 300–2000 grooves/mm, however 1200–1400 grooves/mm is most common.
|
|
Later instruments used potassium bromide prisms to extend the range to 25 μm (400 cm−1) and caesium iodide 50 μm (200 cm−1). The region beyond 50 μm (200 cm−1) became known as the far-infrared region; at very long wavelengths it merges into the microwave region. Measurements in the far infrared needed the development of accurately ruled diffraction gratings to replace the prisms as dispersing elements, since salt crystals are opaque in this region. More sensitive detectors than the bolometer were required because of the low energy of the radiation.
|
|
The research purposes include radiography, scattering imaging, differential phase contrast, and diffraction imaging. It is also possible to adjust and modify the experiment based on what information is of most importance. Almost every application that utilize this technique have the same approach, mathematics and science behind it such as the experimental setup,complementary information and Fourier analysis. Single-shot multi- contrast x-ray imaging gained its importance recently in contrast to Talbot–Lau interferometer because of the less optical element such as diffraction gratings being used under it and hence obtaining every information digitally.
|
|
Artificial dielectrics are fabricated composite materials, often consisting of arrays of conductive shapes or particles in a nonconductive support matrix, designed to have specific electromagnetic properties similar to dielectrics. As long as the lattice spacing is smaller than a wavelength, these substances can refract and diffract electromagnetic waves, and are used to make lenses, diffraction gratings, mirrors, and polarizers for microwaves. These were first conceptualized, constructed and deployed for interaction in the microwave frequency range in the 1940s and 1950s. The constructed medium, the artificial dielectric, has an effective permittivity and effective permeability, as intended.
|
|
LaRochelle's research activities focus on optical fiber components, fiber laser systems, integrated photonics, and optical networking. She has made significant contributions to the development of passive and active fiber devices and their application to optical signal processing. She is known for inventing fiber optic components including super-structured fiber Bragg gratings for chromatic dispersion equalizers, multi-wavelength fiber lasers and optical code division multiplexing. Her work has been published in more than 150 scientific articles and she has directed the research work of over 70 graduate students and post-doctoral fellows.
|
|
As light is incident upon the surface of the metal film, it excites surface plasmons. The surface plasmon frequency is specific for the material, but through the use of gratings on the surface of the film, different frequencies can be obtained. The surface plasmons are also preserved through the use of waveguides as they make the surface plasmons easier to travel on the surface and the losses due to resistance and radiation are minimized. The electric field generated by the surface plasmons influences the electrons to travel toward the collecting substrate.
|
|
Paullin, 1910 p.46 That evening, gale-force winds separated the two ships, leaving Rodgers, Porter, and the few American seamen aboard the now-renamed Insurgent to save the ship and to control the prisoners without support from the crew of Constellation nearby. To make matters worse, just before surrendering their ship, the French crew had thrown overboard the gratings to the hold along with handcuffs and other items used to secure prisoners. Greatly outnumbered, Rodgers had seized all weapons and ordered the prisoners to the lower hold,Allen, 1909 p.
|
|
Schouten interpreted beta stroboscopy, reversed rotation, as consistent with there being Reichardt detectors in the human visual system for encoding motion. Because the spoked wheel patterns he used (radial gratings) are regular, they can strongly stimulate detectors for the true rotation, but also weakly stimulate detectors for the reverse rotation. There are two broad theories for the wagon-wheel effect under truly continuous illumination. The first is that human visual perception takes a series of still frames of the visual scene and that movement is perceived much like a movie.
|
|
Although it is not a new technique, the use of slide molds allows more accurate reproduction of details than traditional two-piece molds. This is done by using injection molds with moving parts (known as "slides") that are inserted into the mold to form parts and then removed so the part can be extracted from the mold. It helps increase the authenticity of the model and reduce the number of parts by molding details onto larger parts. Weld patterns between plates, gratings, one-piece hull and turret interior are common features included in Dragon kits.
|
|
Henry Joseph Grayson (9 May 1856 – 21 March 1918) was a British-born Australian nurseryman and scientist, best known as the designer of a machine for ruling diffraction gratings. Grayson was born in Worrall, near Sheffield, Yorkshire, England, son of Joseph Grayson, a Master Cutler, and his wife Fanny, née Smith. Grayson came of a family of market gardeners, and travelled to New Zealand in the early 1880s. After he returned to England and married Elizabeth Clare on 11 August 1886, the couple soon migrated to Victoria (Australia) where Grayson worked as a nursery gardener.
|
|
These sorts of gratings are described by a graph (illustrated). On the y-axis of the graph is the luminance obtained by moving a light meter over the grating perpendicular to the orientation of the grating. On the x-axis of the graph is the distance the light meter moved. The example is a square-wave grating (see second panel of the illustration); the graph consists of flat, low lines (corresponding to the black bars), with abrupt corners leading to flat high lines (corresponding to the white bars).
|
|
Grating elements can have luminances other than that of sharp-edged bars. If the graph of a grating is sinusoidal (see top panel in the illustration), the grating looks like a set of blurry light and dark bars and it is called a sine-wave grating. Sine-wave gratings are used extensively in optics to determine the transfer functions of lenses. A lens will form an image of a sine-wave grating that is still sinusoidal, but with some reduction in its contrast depending on the spatial frequency and possibly some change in phase.
|
|
Two fluorescent lights extend out from near the top of the wall to the north and south, A slate damp course exists at the base of the facade. On both levels of the east facade, there are timber framed double goods doors in the centre with a double-hung four pane sash window either side. Both windows on the lower level are protected by galvanised steel sheeting and steel gratings. The central door opening is continuous between the floors and there is a vertically barred ventilation opening across the top of the lower door.
|
|
When the stimuli used to present phantom contours consist of adjacent dark and light achromatic horizontal stripes (squarewave gratings), variations in spatial and temporal frequency can be examined. An increase or decrease in stripe thickness adjusts spatial frequency, and temporal frequency is manipulated by increases and decreases in flicker rate. Findings show that as spatial frequency is increased, sensitivity to temporal frequency decreases. For example, with a temporal frequency of 7 Hz, the spatial frequency required in order for subjects to perceive the phantom contour was 8.96 cycles degree −1.
|
|
70–71 In the 1970s, the Police proceeded to adapt men, resources and resources. A gray-green suit and a beret were introduced as operational uniform for Celere units; helmets were equipped with an impact- resistant plastic visor; the Beretta M1934 pistols were replaced with the M51; the Beretta M12 submachine gun was introduced.p. 81 In terms of vehicles, in the "Celere" departments the new OM and FIAT "shielded" vans were introduced, with bulletproof glass, ventilation systems that prevent the inhalation of tear gas and equipped with movable metal gratings against the throwing of stones.
|
|
However, once news of the French defeats at Spicheren and Wörth reached Paris at the beginning of August, work commenced in earnest. Some 80,000 men were employed in clearing fields of fire in front of the fortifications, including felling many of the trees in the parkland of the Bois de Boulogne, the wood from which was used to build obstacles. Another 12,000 workers set about blocking or obstructing the gates to allow a minimum of traffic to pass.Fermer 2011, pp. 27-28 The openings for canals and aqueducts were blocked or closed with gratings.
|
|
Dandelion seeds (1858 or later) Talbot allowed free use of the calotype process for scientific applications, and he himself published the first known photomicrograph of a mineral crystal. Another photomicrograph shows insect wings as seen in the "solar microscope" he and others developed for projecting images onto a large screen of tiny objects using sunlight as a light source. The large projections could then be photographed by exposure to sensitized paper. He studied the diffraction of light using gratings and discovered a new phenomenon, now known as the Talbot effect.
|
|
The principle of phase-contrast imaging in general was developed by Frits Zernike during his work with diffraction gratings and visible light. The application of his knowledge to microscopy won him the Nobel Prize in Physics in 1953. Ever since, phase-contrast microscopy has been an important field of optical microscopy. The transfer of phase- contrast imaging from visible light to X-rays took a long time due to the slow progress in improving the quality of X-ray beams and the non-availability of X-ray optics (lenses).
|
|
As in ABI an additional signal coming from Ultra-small-angle scattering by sub-pixel microstructures of the sample, called dark-field contrast, can also be reconstructed. This method provides high spatial resolution, but also requires long exposure times. An alternative approach is the retrieval of the differential phase by using Moiré fringes. These are created as a superposition of the self-image of G1 and the pattern of G2 by using gratings with the same periodicity and inclining G2 against G1 regarding to the optical axis with a very small angle(<<1).
|
|
Other characteristic elements are decorative (and functional) wrought iron gratings and the tiles known as azulejos. Landscaping—both for common private homes and homes on a more lavish scale—also carries on older traditions, with plants, flowers, and fountains, pools, and streams of water. Beyond these general elements, there are also specific local architectural styles, such as the flat roofs, roofed chimneys, and radically extended balconies of the Alpujarra, the cave dwellings of Guadix and of Granada's Sacromonte, or the traditional architecture of the Marquisate of Zenete. Gran Teatro Falla in Cádiz.
|
|
In the inner garden of the Museum, he had a small observatory built in 1866/1867, where he set up several precision instruments to determine the latitude (zenith telescope) and time (clock). There he also kept an astronomical regulator, heliostat, spectroscope, diffraction gratings, microscope with micrometer, balance, thermometers and barometers. He also ordered the standards of length (glass) and weight (copper). Combining these instruments he tried to determine a standard of length by use of a seconds pendulum (initially a Foucault pendulum, later he ordered a Repsold reversible pendulum which arrived shortly after his death).
|
|
These basic components can be used for a variety of applications and all share a common production platform. In his comments upon the grant’s award, William Sargeant, the National Science Foundation program officer who oversaw Chiral Photonics' first SBIR award, noted the range of existing and incipient markets. "This technology could be one of the most significant recent advances in the field of polarization and wavelength control. There is an enormous host of applications for which chiral fiber gratings could find markets." Chiral Photonics’ components are all of the all- fiber variety.
|
|
Cadmium zinc telluride, (CdZnTe) or CZT, is a compound of cadmium, zinc and tellurium or, more strictly speaking, an alloy of cadmium telluride and zinc telluride. A direct bandgap semiconductor, it is used in a variety of applications, including semiconductor radiation detectors, photorefractive gratings, electro-optic modulators, solar cells, and terahertz generation and detection. The band gap varies from approximately 1.4 to 2.2 eV, depending on composition. Radiation detectors using CZT can operate in direct-conversion (or photoconductive) mode at room temperature, unlike some other materials (particularly germanium) which require liquid nitrogen cooling.
|
|
Case Western Reserve has dedicated a Michelson House to him, and Michelson Hall (an academic building of science classrooms, laboratories and offices) at the United States Naval Academy also bears his name. Michelson Laboratory at Naval Air Weapons Station China Lake in Ridgecrest, California is named for him. There is a display in the publicly accessible area of the Lab which includes facsimiles of Michelson's Nobel Prize medal, the prize document, and examples of his diffraction gratings. Numerous awards, lectures, and honors have been created in Albert A. Michelson's name.
|
|
The Obelisk was the first sewer ventshaft built to eliminate noxious gases from the sewer at levels that would not be detected by the residents of the city. The vent shaft was built to replace the street gratings that had been used to ventilate the sewer system. The place is important in demonstrating aesthetic characteristics and/or a high degree of creative or technical achievement in New South Wales. The Obelisk is a sandstone vent shaft which displays the classical architecture and technology of the late nineteenth century.
|
|
Other forms of excitation filters include the use of monochromators, wedge prisms coupled with a narrow slit (for selection of the excitation light) and the use of holographic diffraction gratings, etc. [for beam diffraction of white laser light into the required excitation wavelength (selected for by a narrow slit)]. An excitation filter is commonly packaged with an emission filter and a dichroic beam splitter in a cube so that the group is inserted together into the microscope. The dichroic beam splitter controls which wavelengths of light go to their respective filter.
|
|
The direction of selectivity or preferred direction is determined by whether the difference is positive or negative. The direction which produces a positive outcome is the preferred direction. In order to confirm that the Reichardt-Hassenstain model accurately describes the directional selectivity in the retina, the study was conducted using optical recordings of free cytosolic calcium levels after loading a fluorescent indicator dye into the fly tangential cells. The fly was presented uniformly moving gratings while the calcium concentration in the dendritic tips of the tangential cells was measured.
|
|
This was the first method used widely for the fabrication of fiber Bragg gratings and uses two-beam interference. Here the UV laser is split into two beams which interfere with each other creating a periodic intensity distribution along the interference pattern. The refractive index of the photosensitive fiber changes according to the intensity of light that it is exposed to. This method allows for quick and easy changes to the Bragg wavelength, which is directly related to the interference period and a function of the incident angle of the laser light.
|
|
Most commonly confused with diffraction gratings are the iridescent colors of peacock feathers, mother-of-pearl, and butterfly wings. Iridescence in birds, fish and insects is often caused by thin-film interference rather than a diffraction grating. Diffraction produces the entire spectrum of colors as the viewing angle changes, whereas thin-film interference usually produces a much narrower range. The surfaces of flowers can also create a diffraction, but the cell structures in plants are usually too irregular to produce the fine slit geometry necessary for a diffraction grating.
|
|
It is composed of a sequence of prisms, or gratings. When properly adjusted it can alter the spectral phase φ(ω) of the input pulse so that the output pulse is a bandwidth-limited pulse with the shortest possible duration. A pulse shaper can be used to make more complicated alterations on both the phase and the amplitude of ultrashort pulses. To accurately control the pulse, a full characterization of the pulse spectral phase is a must in order to get certain pulse spectral phase (such as transform-limited).
|
|
They extend for several hundred feet to Avenue H. Up until about 2006, you could see the cemented over gratings extending down Nostrand Avenue. When a new building went up, the grates were removed. Prior to the building of the exit at the south end of the station, there was only a temporary wooden ramp connecting the platforms and the tunnels were actually visible to passengers. Another factor limiting capacity on the line is the set up of the Rogers Avenue Junction, where trains can diverge from the IRT Eastern Parkway Line to the IRT Nostrand Avenue Line or continue on Eastern Parkway.
|
|
In August 1650, Father Manuel da Anunciação ordered the opening of five tombs, including his own, in the presbytery, between the lateral retables. The following year, on 17 February 1651, Father Manuel da Anunciação died, and a year later, his bones were moved to the credenza in the altar. In 1659, the clergyman João Roiz Vitória provided funding for a few public works, with the acquisition of bunks and gratings, a silver custodio and some ornaments. D. Manuel Luís Baltazar da Câmara, 1st Count of Riberia Grande, and 8th Donatary-Captain of São Miguel visited in September 1664, along with his wife.
|
|
Full view of a storm drain (Ontario, Canada) There are two main types of stormwater drain (highway drain or road gully in the UK) inlets: side inlets and grated inlets. Side inlets are located adjacent to the curb and rely on the ability of the opening under the back stone or lintel to capture flow. They are usually depressed at the invert of the channel to improve capture capacity.Kerb Inlet, Local Government & Municipal Knowledge Base, accessed February 6, 2010, Many inlets have gratings or grids to prevent people, vehicles, large objects or debris from falling into the storm drain.
|
|
As with other diffraction gratings, the echelle grating conceptually consists of a number of slits with widths close to the wavelength of the diffracted light. The light of a single wavelength in a standard grating at normal incidence is diffracted to the central zero order and successive higher orders at specific angles, defined by the grating density/wavelength ratio and the selected order. The angular spacing between higher orders monotonically decreases and higher orders can get very close to each other, while lower ones are well separated. The intensity of the diffraction pattern can be altered by tilting the grating.
|
|
It is surrounded by a thin white curtain which allows diners at the table to view out into the restaurant but prevents other diners from viewing in. The Grill restaurant, which serves British cuisine, is decorated in a Moorish theme, attributed to King Alfonso's influence during his time in London in exile in the 1930s. The cream-painted walls feature gilded gratings and mirrored arches and display a Flemish tapestry. The ceilings are ornate, featuring gold leaves and brass chandeliers, and the room also features deep red riveted leather chairs and deep red curtains, with a Middle Eastern-looking exotic carpet.
|
|
The use of trench drains in construction began with the commission by the British Airports Authority of a company called Gatic. Airports were in need of a form of trench drainage with fewer movable parts and less tendency to collapse under heavy traffic than the traditional drainage gratings. Gatic designed and engineered the first stainless steel slot drain, and it was installed first at Stansted Airport in the United Kingdom, following which it was specified at Britain’s most famous airport – Heathrow. These airports continue to use stainless steel slot drainage both airside and landside for surface water drainage requirements.
|
|
The Tomb was designed by the famous Polish sculptor, Stanisław Kazimierz Ostrowski. It was located within the arcade that linked the two symmetrical wings of the Saxon Palace, then the seat of the Polish Ministry of War. The central tablet was ringed by 5 eternal flames and 4 stone tablets bearing the names and dates of battles in which Polish soldiers had fought during World War I and the Polish–Soviet War (1919–21). Behind the Tomb were two steel gratings bearing emblems of Poland's two highest Polish military decorations — the Virtuti Militari and Cross of Valor.
|
|
English makers early took up this improvement, due to the obsession with resolving test objects such as diatoms and Nobert ruled gratings. By the late 1840s, English makers such as Ross, Powell and Smith; all could supply highly corrected condensers on their best stands, with proper centring and focus. It is erroneously stated that these developments were purely empirical - no-one can design a good achromatic, spherically corrected condenser relying only on empirics. On the Continent, in Germany, the corrected condenser was not considered either useful or essential, mainly due to a misunderstanding of the basic optical principles involved.
|
|
Discrete categories of objects such as faces, body parts, tools, animals and buildings have been associated with preferential activation in specialised areas of the cerebral cortex, leading to the suggestion that they may be produced separately in discrete neural regions. Several such regions have been identified within the visual cortex. The fusiform face area (FFA) was first described by Sergent et al.(1992) Sergent J, Ohta S, MacDonald B (1992) Functional neuroanatomy of face and object processing: a positron emission tomography study. Brain 115:15-36 who conducted a PET (positron emission tomography) study on subjects viewing gratings, faces, and objects.
|
|
The low frequency drop-off is due to lateral inhibition within the retinal ganglion cells. A typical retinal ganglion cell presents a centre region with either excitation or inhibition and a surround region with the opposite sign. By using coarse gratings, the bright bands fall on the inhibitory as well as the excitatory region of the ganglion cell resulting in lateral inhibition and account for the low-frequency drop-off of the human contrast sensitivity function. One experimental phenomenon is the inhibition of blue in the periphery if blue light is displayed against white, leading to a yellow surrounding.
|
|
In order to separate the phase information from other contributions to the signal, a technique called "phase-stepping" is used. One of the gratings is scanned along the transverse direction term over one period of the grating, and for different positions of the grating an image is taken. The intensity signal in each pixel in the detector plane oscillates as a function of . The recorded intensity oscillation can be represented by a Fourier series and by recording and comparing these intensity oscillations with or without the sample the separated differential phase shift and absorption signal relative to the reference image can be extracted.
|
|
A q-plate can convert a right-polarized beam into a beam with an OAM of -2ħ, and a left-polarized beam into a +2ħ state. A q-plate is an optical device which can generate light beams with orbital angular momentum of light (OAM) from a beam with well-defined Spin angular momentum of light (SAM). It is currently realized using liquid crystals, polymers or sub-wavelength gratings. A method for generating orbital angular momentum of light (OAM) is based on the SAM-OAM coupling that may occur in a medium which is both anisotropic and inhomogeneous.
|
|
More complicated models of diffraction require working with the mathematics of Fresnel or Fraunhofer diffraction. X-ray diffraction makes use of the fact that atoms in a crystal have regular spacing at distances that are on the order of one angstrom. To see diffraction patterns, x-rays with similar wavelengths to that spacing are passed through the crystal. Since crystals are three-dimensional objects rather than two- dimensional gratings, the associated diffraction pattern varies in two directions according to Bragg reflection, with the associated bright spots occurring in unique patterns and d being twice the spacing between atoms.
|
|
The frequency-doubling illusion is an apparent doubling of spatial frequency when a sinusoidal grating is modulated rapidly in temporal counterphase.Kelly, D.H. (1981) Nonlinear visual responses to flickering sinusoidal gratings. Journal of the Optical Society of America, 71, 1051-1055Sun, H., Lee, B. B., White, A. J. R., Swanson, W. H., (2002). Examination of mechanisms underlying the frequency-doubling illusion. Journal of Vision, Volume 2, Number 10, Abstract 9, Page 9a Recently, it has been proposed that the illusion arises from a spatially nonlinear ganglion cell class.Maddess, T., Goldberg, I., Dobinson, J., Wine, S., Welsh, A.H. & James, A.C. (1999).
|
|
Russell is a Fellow of the Optical Society of America and the founding chair of the OSA Topical Meeting Series on Bragg Gratings, Photosensitivity and Poling in Glass. In 2000 he won OSA's Joseph Fraunhofer Award/Robert M. Burley Prize for the invention of photonic crystal ("holey") fibre, which he first proposed in 1991. In 2002 he won the Applied Optics Division Prize of the UK Institute of Physics. In 2004 he won the Thomas Young Medal and Prize of the Institute of Physics, and in 2005 he was elected a Fellow of the Royal Society.
|
|
Young described iridescence as the result of interference between reflections from two or more surfaces of thin films, combined with refraction as light enters and leaves such films. The geometry then determines that at certain angles, the light reflected from both surfaces interferes constructively, while at other angles, the light interferes destructively. Different colours therefore appear at different angles. In animals such as on the feathers of birds and the scales of butterflies, interference is created by a range of photonic mechanisms, including diffraction gratings, selective mirrors, photonic crystals, crystal fibres, matrices of nanochannels and proteins that can vary their configuration.
|
|
The curved petals form a paraboloidal dish which directs the sun's heat to the reproductive parts at the centre of the flower, keeping it some degrees Celsius above the ambient temperature. Surface gratings, consisting of ordered surface features due to exposure of ordered muscle cells on cuts of meat. The structural coloration on meat cuts appears only after the ordered pattern of muscle fibrils is exposed and light is diffracted by the proteins in the fibrils. The coloration or wavelength of the diffracted light depends on the angle of observation and can be enhanced by covering the meat with translucent foils.
|
|
By locally changing each grating dimension while keeping its thickness the same, planar, single-layer lenses and focusing reflectors with high focusing power have been obtained. Besides its high reflectivity, the high contrast grating has been designed as a high quality factor resonator. Low-loss hollow-core waveguide are made with high contrast gratings with high reflectivity at oblique incident angle. Applications such as slow light and optical switch W. Yang and C. J. Chang-Hasnain, “Ultra-compact optical switch using high contrast grating hollow-core waveguide,” Conference on Lasers and Electro-Optics, OSA Technical Digest (CD) (Optical Society of America, 2013).
|
|
NASA conception of IXO, mirror view, artist's impression. IXO scientific goals require gathering many pieces of information using different techniques such as spectroscopy, timing, imaging, and polarimetry. Therefore, IXO will carry a range of detectors, which will provide complementary spectroscopy, imaging, timing, and polarimetry data on cosmic X-ray sources to help disentangle the physical processes occurring in them. Two high-resolution spectrometers, a microcalorimeter (XMS or cryogenic imaging spectrograph (CIS)) and a set of dispersive gratings (XGS) will provide high-quality spectra over the 0.1–10 keV bandpass where most astrophysically abundant ions have X-ray lines.
|
|
They present a strong characteristic of the façade, with protruding balconies, fine gratings, frame spans over worked masonry and the application of curved lines, especially in the design of courtyards and windows along street corners. At the same time, some buildings were constructed to house workers, organized into villages or in courtyards, such as the Pátio do Tijolo (literally, the Yard of Bricks). These were multi-family buildings, usually two to three storeys in height, with a high occupancy and little space. Architectural influences from the 20th century are limited, and restricted to a few points.
|
|
The ability of femtosecond lasers to efficiently fabricate complex structures and devices for a wide variety of applications has been extensively studied during the last decade. State-of-the-art laser processing techniques with ultrashort light pulses can be used to structure materials with a sub-micrometer resolution. Direct laser writing (DLW) of suitable photoresists and other transparent media can create intricate three-dimensional photonic crystals (PhC), micro-optical components, gratings, tissue engineering (TE) scaffolds and optical waveguides. Such structures are potentially useful for empowering next-generation applications in telecommunications and bioengineering that rely on the creation of increasingly sophisticated miniature parts.
|
|
Work had started on the project, which cost $1 million, several months earlier. The contract that the Mayor had requested approval for would have relocated vault lights, gratings, entrances and exits at 56th Street and 49th Street, and at the 45th Street, 53rd Street and 59th Street stations. Protected bike lanes, separated from vehicular traffic by a lane of parking, were proposed for Fourth Avenue in 2017 in an attempt to improve cycling infrastructure in New York City. The first bike lanes were added between 60th and 64th Streets within Sunset Park in 2018, followed by the section between 1st and 15th Streets in Park Slope in early 2019.
|
|
Stewart measured radiated power with a thermo-pile and sensitive galvanometer read with a microscope. He was concerned with selective thermal radiation, which he investigated with plates of substances that radiated and absorbed selectively for different qualities of radiation rather than maximally for all qualities of radiation. He discussed the experiments in terms of rays which could be reflected and refracted, and which obeyed the Stokes-Helmholtz reciprocity principle (though he did not use an eponym for it). He did not in this paper mention that the qualities of the rays might be described by their wavelengths, nor did he use spectrally resolving apparatus such as prisms or diffraction gratings.
|
|
He supplied the gates for the Verdun Memorial in 1928 and various parts for a number of buildings in Paris, including those designed by Robert Mallet-Stevens, for whom he produced the railings and gratings for the private mansions in Rue Mallet-Stevens in 1926.Jean Prouvé Museum of Modern Art, New York. In 1930 Prouvé helped establish the Union of Modern Artists whose manifesto read, "We like logic, balance and purity." Although he shaped his public image around the idea that he was not married to a specific aesthetic, the tenets of "l'École de Nancy" were certainly a powerful influence on his body of work.
|
|
These components allow nonlinear processing in the brain to be investigated. By frequency-tagging two superimposed gratings, spatial frequency and orientation tuning properties of the brain mechanisms that process spatial form can be isolated and studied. Stimuli of different sensory modalities can also be tagged. For example, a visual stimulus was flickered at Fv Hz and a simultaneously presented auditory tone was amplitude modulated at Fa Hz. The existence of a (2Fv + 2Fa) component in the evoked magnetic brain response demonstrated an audio-visual convergence area in the human brain, and the distribution of this response over the head allowed this brain area to be localized.
|
|
In 2008, a similar effect with different results was discovered, and has been termed the "anti-McCollough effect". This effect may be induced by alternating pairings of gratings in parallel alignment, one achromatic (black and white) and the other black and a single color (say black and red). If the color used was red, then after the induction phase the achromatic grating appeared slightly red. This effect is distinct from the classical effect in three important regards: the perceived color of the aftereffect is the same as the inducer's color, the perceived color of the aftereffect is weaker than the classical effect, and the aftereffect shows complete interocular transfer.
|
|
Metal gratings are sturdier and can have narrower strakes, and angling the trash rack properly can allow some self-cleaning from the action of the water. Modern trash racks as used by hydroelectric plants can incorporate such advanced features as wedge-wire screens, the Coanda effect, and cleaning robots. In waterways with large amounts of floating debris, various permanently installed "trash rakes" may be required to reduce the labor required for regular cleaning. rotating rake cylinders Trash racks are designed for water velocity of around 2 feet/second (0.6 metres/second) to prevent excessive energy loss due to the head loss across the trash rack.
|
|
Her PhD work combined theoretical coupled-wave analysis with lab work, in which she created large-scale, embossed surface-relief diffraction gratings with liquid crystal-filled grooves with high diffraction efficiency in un-polarized illumination. She has created some of the largest ambient displays ever. In Cologne, Germany she built a holographic replica of pre-existing buildings in the city's historic district and created a holographic display encompassing a city block. She also demonstrated that it was technically feasible – but agreed it was culturally unacceptable – to project TV images on the moon's surface. From 2003 until the end of 2004, she was the chief technology officer of Intel’s Display Division.
|
|
Electro-optical devices have combined aspects of both optical and electrical devices in the form of a modulator as well. Specifically, electro-optic modulators have been designed using evanescently coupled resonant metal gratings and nanowires that rely on long-range surface plasmons (LRSP). Likewise, thermo-optic devices, which contain a dielectric material whose refractive index changes with variation in temperature, have also been used as interferometric modulators of SPP signals in addition to directional-coupler switches. Some thermo-optic devices have been shown to utilize LRSP waveguiding along gold stripes that are embedded in a polymer and heated by electrical signals as a means for modulation and directional-coupler switches.
|
|
The statistical properties of the stimuli used to probe these neurons affect the properties of the surround as well. Because these areas are so highly interconnected, stimulation of one cell can affect the response properties of other cells, and therefore researchers have become increasingly aware of the choice of stimuli they use in these experiments. In addition to studies with simple stimuli (dots, bars, sinusoidal gratings), more recent studies have used more realistic stimuli (natural scenes) to study these effects. Stimuli that better represent natural scenes tend to induce higher levels of suppression, indicating this effect is tied closely to the properties of natural scenes such as textures and local context.
|
|
In conventional digital photography, lenses or mirrors map all of the light originating from a single point of an in-focus object to a single point at the sensor plane. Each pixel thus relates an independent piece of information about the far-away scene. In contrast, a PFCA does not have a lens or mirror, but each pixel has an idiosyncratic pair of diffraction gratings above it, allowing each pixel to likewise relate an independent piece of information (specifically, one component of the 2D Fourier transform) about the far-away scene. Together, complete scene information is captured and images can be reconstructed by computation.
|
|
Arrayed waveguide gratings (AWG) are commonly used as optical (de)multiplexers in wavelength division multiplexed (WDM) systems. These devices are capable of multiplexing many wavelengths into a single optical fiber, thereby increasing the transmission capacity of optical networks considerably. The devices are based on a fundamental principle of optics that light waves of different wavelengths do not interfere linearly with each other. This means that, if each channel in an optical communication network makes use of light of a slightly different wavelength, then the light from many of these channels can be carried by a single optical fiber with negligible crosstalk between the channels.
|
|
In April 1934, the old material was removed from the prison; holes were cut in the concrete and 269 cell fronts were installed, built using four carloads of steel ordered from the Stewart Iron Works. Two of four new stairways were built, as were 12 doors to the utility corridors and gratings at the top of the cells. On 26 April, an accidental small fire broke out on the roof and an electrician injured his foot by dropping a manhole cover on it. The Anchor Post Fence Company added fencing around Alcatraz and the Enterprise Electric Works added emergency lighting in the morgue and switchboard operations.
|
|
To that end, nearly every building on campus is noticeably Byzantine in style, with sand and pink-colored bricks, large archways and columns being a common theme among many campus buildings. Noteworthy exceptions include the glass-walled Brochstein Pavilion, Lovett College with its Brutalist-style concrete gratings, Moody Center for the Arts with its contemporary design, and the eclectic-Mediterranean Duncan Hall. In September 2011, Travel+Leisure listed Rice's campus as one of the most beautiful in the United States."America's most beautiful college campuses", Travel+Leisure (September 2011) Architectural Detail on Lovett Hall Columns Lovett Hall, named for Rice's first president, is the university's most iconic campus building.
|
|
The Bragg grating then transduces the strain to the change in wavelength. Specifically, fiber Bragg gratings are finding uses in instrumentation applications such as seismology, pressure sensors for extremely harsh environments, and as downhole sensors in oil and gas wells for measurement of the effects of external pressure, temperature, seismic vibrations and inline flow measurement. As such they offer a significant advantage over traditional electronic gauges used for these applications in that they are less sensitive to vibration or heat and consequently are far more reliable. In the 1990s, investigations were conducted for measuring strain and temperature in composite materials for aircraft and helicopter structures.
|
|
The replacement building was innovative, combining non-combustible brick, plaster and iron in a single foundry structure built in 1892 and other buildings completed in 1896-97. Throughout the main structure samples are found of the products made at Hecla. Staircases, fire escapes, manhole covers, street gratings, subway kiosks and the cast iron frameworks for elevators came from the Hecla Ironworks factory and were shipped by barge across the river from the Greenpoint Avenue piers. The 133 original subway entrance and exit shelters, built for the Interborough Rapid Transit Company prior to the New York City Subway's 1904 opening, were fashioned there and assembled in place on location.
|
|
Eggleton obtained the bachelor's degree (with honours) in Science in 1992 and PhD degree in Physics from the University of Sydney in 1996. In 1996, he joined Bell Laboratories, Lucent Technologies as a Postdoctoral Member of Staff in the Optical Physics Department under the supervision of Dr Richart E. Slusher. In 1998 he transferred to the Optical Fiber Research Department as a Member of Technical Staff and was promoted to Technical Manager of the Fiber Gratings Group in 2000. He was then promoted to Research Director within the Specialty Fiber Business Division of Bell Laboratories, where he was engaged in forward-looking research supporting Lucent Technologies business in optical fiber devices.
|
|
The sewer used brickwork sealed with Portland cement and caulked with rope, and was of an egg-shaped section, as pioneered by John Roe, which made them self-cleaning. Ventilators were constructed every or so, which were covered with metal gratings where the sewer ran beneath streets, and disguised by bushes where it ran through parks. This removed much of the threat of water-borne diseases such as cholera from the poorer areas of Edinburgh, and in 1889, a second, deeper interceptor sewer was constructed. It reached as far as Balerno, some to the south-west of the city centre, and resulted in the Water of Leith becoming relatively unpolluted again.
|
|
Station tilework U-shaped connection between the two sides of the station This station has two side platforms, which are connected at the south end just past the bumper blocks (forming a "U" shape), mitigating what is otherwise an inefficient terminal design, in which passengers must know which track a train is departing from before going to one of the two platforms. The IRT Nostrand Avenue Line tunnels continue beyond the bumper blocks at Flatbush Avenue and Nostrand Avenue. They extend for several hundred feet to Avenue H, but no tracks were ever laid in these tunnels. Up until about 2006, passengers could see the cemented-over gratings extending down Nostrand Avenue.
|
|
Photon etc.'s core technology is a continuously tunable filter based on volume Bragg gratings. It consists of a photo-thermo- refractive glass with a periodically varying index of refraction in which the modulation structure can be orientated to transmit or reflect incident light. In order to select a particular wavelength that will be filtered (diffracted), the angle of the filter is adjusted to meet Bragg condition: : \lambda_B = 2n\Lambda\sin(\theta + \varphi) \,, where is an integer, B is the wavelength that will be diffracted, is the step of the grating, is the angle between the incident beam and the normal of the entrance surface and is the angle between the normal and the grating vector.
|
|
Among them, there are the southern and eastern facades with bay windows that reveal the bay view. There are also rooms for the Shah and his family on the second floor. The smooth surface of the large stone planes of the palace is shaded by alternating rows of masonry, differing in color, width and texture, as well as the "shebeke" aura – stone gratings in small light apertures. There were daily-life objects, coins of the XII-XV centuries, copper utensils, weapons and decorations of the XIX century, musical instruments of the XV century found during the archaeological excavations both on the territory of the palace complex and in the territory of the historical center of Icheri-Sheher and Shirvan.
|
|
In the same year he had a presentation in the Astronomical Society in Paris about the idea of a telescope with a concave mirror – it was giving larger magnification than before. In recognition the Society invited him to participate in it. After arrival to Wrocław, Wolfke invented in 1908 a cathode tube with a glass window, and in 1909 with Karl Ritzmann he patented a cadmium-mercury lamp. He later sold his rights to it to the Carl-Zeiss Jena company, where he worked for a year after obtaining his doctorate. At University of Wrocław in the Otto Lummer’s team Wolfke worked at the generalization of the Abbe’s theory of optical imaging for non-linear gratings.
|
|
Two upper level windows that were cut in the western end-wall before 1916 have been replaced by a single window, while on the inward facing walls, one upper level window has been enlarged and another added since 1916. The windows cut in the lower level of the inward facing walls have instead been covered up. Electric power, security lights, fire alarm and a sprinkler system are more recent additions, as are the metal gratings over the loopholes. The building has also been restored with a black stain applied to the wood and has red corrugated iron roof, a colour scheme similar to how the building would have looked in the 1860s.
|
|
The BOA introduces a neutral density filter to the optical path that attenuates the light by approximately a factor of one hundred (five astronomical magnitudes). Both apertures are oversized (2.5 arc second clear aperture) permitting more than 95% of the light from a point source to enter the spectrograph. After passing through the PSA or BOA the light travels to one of the optics on the first of two optic select wheels, either one of the three FUV diffraction gratings or the first of the NUV collimation mirrors (table 1), depending on whether an FUV, NUV, or target acquisition channel is selected. All optics on the first wheel have an aspheric profile to correct for the Hubble spherical aberration.
|
|
At a residency at Yaddo artists’ retreat at Saratoga Springs in the spring of 1953, Dienes made a large number of monoprints by taking rubbings from textured surfaces using a printmaker’s brayer. Back in New York in the summer of 1953 she began taking rubbings of the sidewalks, subway gratings and other urban features on very large sheets of paper or Webril. As she told The Village Voice in 1956: ‘About 5 o’clock on Sunday mornings is the best time because there aren’t as many hecklers, and traffic is light. I take those big sheets of paper that photographers use but I have to keep a firm hold or they blow away.
|
|
In biology, this type of iridescence results from the formation of diffraction gratings on the surface, such as the long rows of cells in striated muscle, or the specialized abdominal scales of peacock spider Maratus robinsoni and M. chrysomelas. Some types of flower petals can also generate a diffraction grating, but the iridescence is not visible to humans and flower-visiting insects as the diffraction signal is masked by the coloration due to plant pigments. In biological (and biomimetic) uses, colours produced other than with pigments or dyes are called structural coloration. Microstructures, often multilayered, are used to produce bright but sometimes non-iridescent colours: quite elaborate arrangements are needed to avoid reflecting different colours in different directions.
|
|
The input and output ports of a plasmonic circuit will receive and send optical signals, respectively. To do this, coupling and decoupling of the optical signal to the surface plasmon is necessary. The dispersion relation for the surface plasmon lies entirely below the dispersion relation for light, which means that for coupling to occur additional momentum should be provided by the input coupler to achieve the momentum conservation between incoming light and surface plasmon polariton waves launched in the plasmonic circuit. There are several solutions to this, including using dielectric prisms, gratings, or localized scattering elements on the surface of the metal to help induce coupling by matching the momenta of the incident light and the surface plasmons.
|
|
Robert P. Madden (1928 – 1 April 2014) was an American spectroscopist who was president of the Optical Society of America in 1982. He studied as an undergraduate at Rochester University and as a postgraduate at Johns Hopkins University. After gaining his Ph.D. in 1956 (on diffraction gratings) he worked from 1958 to 1961 as a physicist with the U.S. Army Engineering Research and Development Laboratories (AERDL) at Fort Belvoir, Virginia on the optical properties of thin films in the ultraviolet. He then joined the National Bureau of Standards as head of the newly-created Far Ultraviolet Physics Section where he used the bureau's electron synchrotron to measure the effect of ultraviolet radiation on helium.
|
|
Drawing of Grating-based imaging Grating-based imaging (GBI) includes Shearing interferometry or X-ray Talbot interferometry (XTI), and polychromatic far-field interferometry (PFI). Since the first X-ray grating interferometer—consisting of two phase gratings and an analyzer crystal—was built, various slightly different setups for this method have been developed; in the following the focus lies on the nowadays standard method consisting of a phase grating and an analyzer grating. (See figure to the right). The XTI technique is based on the Talbot effect or "self-imaging phenomenon", which is a Fresnel diffraction effect and leads to repetition of a periodic wavefront after a certain propagation distance, called the "Talbot length".
|
|
The architecture of garages was ignored in the architectural journals despite famous architects such as Edwin Lutyens, Richard Barry Parker and Edgar Wood all designing garages for their wealthy clients. Charles Harrison Townsend was one of the few architects who put pen to paper (in The Builder in 1908) on the subject and recommended that the walls be glazed brick for ease of washing, air gratings to be low (petrol fumes are heavier than air), and drains half open to avoid build-up of gases. By 1910 corrugated iron and asbestos were being used instead of wood and garages became less imposing. From 1912 speculatively built houses in London were being built with motor houses.
|
|
Also, \scriptstyle C_T is the coefficient of temperature, which is made up of the thermal expansion coefficient of the optical fiber, \scriptstyle \alpha_\Lambda, and the thermo-optic coefficient, \scriptstyle \alpha_n. Fiber Bragg gratings can then be used as direct sensing elements for strain and temperature. They can also be used as transduction elements, converting the output of another sensor, which generates a strain or temperature change from the measurand, for example fiber Bragg grating gas sensors use an absorbent coating, which in the presence of a gas expands generating a strain, which is measurable by the grating. Technically, the absorbent material is the sensing element, converting the amount of gas to a strain.
|
|
There is a memorial plaque on the house, and it is designated as a historical and cultural monument of regional significance, so that the original exterior appearance is protected from alteration, including both the structural elements and decorations on the facade. The 2000 city registry indicates that the interior as well as the facade is protected. However, the appearance of the building has changed since Repin's day: originally a log house with a rustic plank roof, in the mid-20th-century it was trimmed with wood siding and iron window gratings and roofed with corrugated iron. Unlike the Repin house in Shiryaevo, this house is not a museum and is not open to the public.
|
|
The resolution of a prism is limited by its size; a larger prism will provide a more detailed spectrum, but the increase in mass makes it unsuitable for highly detailed work. This issue was resolved in the early 1900s with the development of high-quality reflection gratings by J.S. Plaskett at the Dominion Observatory in Ottawa, Canada. Light striking a mirror will reflect at the same angle, however a small portion of the light will be refracted at a different angle; this is dependent upon the indices of refraction of the materials and the wavelength of the light. By creating a "blazed" grating which utilizes a large number of parallel mirrors, the small portion of light can be focused and visualized.
|
|
Five of these were permanent metallic riveted spans, with novel console-arch-beam systems and gradually increasing span length from banks to the middle of the river. A three-arch granite viaduct linked the metallic central section to the right bank, and a two-winged bascule span joined it to the left bank. The design of the central spans, in which single uncut girders bridge more than one span, significantly relieves the stress on the central part of the arches, decreasing the support required in the river and giving the span structures a gentle arch shape. The bridge is decorated with cast iron gratings with artistic casting, granite pylons with lanterns and metallic three-colour lanterns in the Art Nouveau style.
|
|
Journal of Luminescence (ISSN 0022-2313) is a peer-reviewed scientific journal, published monthly. The journal covers topics related to the emission of light (luminescence): exciton and polariton dynamics, dynamics of localized excited states, energy transport in ordered and disordered systems, radiative and non-radiative recombination, relaxation processes, vibronic interactions in electronic excited states, photochemistry in condensed system, excited state resonance, double resonance, selective excitation spectroscopy, coherent processes in excited states, e.g. coherent optical transients, photon echos, transient gratings, multiphoton processes such as optical bistability, hole burning, photochromism, multiphoton spectroscopy, new techniques for the study of excited states. Articles in optical spectroscopy (absorption, MCD, luminescence, Raman scattering) and phosphors, scintillators, electro- and cathodo-luminescence, radiography, bioimaging, solar energy, energy conversion, etc.
|
|
Designed by the water sculptor William Pye, it is the largest working font in any British cathedral, and replaced an earlier portable neo-Gothic Victorian font. The font is cruciform in shape, and has a 10-foot-wide vessel filled to its brim with water, designed so that the water overflows in filaments through each corner into bronze gratings embedded in the cathedral's stone floor. The project cost £180,000 and was funded entirely by donations. Some parishioners reportedly objected to the new font, considering it 'change for change's sake', although Pye argued that the majority opinion was in favour: "I would say 90 per cent are in happy anticipation, five per cent are nervously expectant and five per cent are probably apoplectic".
|
|
A bandwidth well in excess of 1 GHz can be achieved with photodiode detectors. The main competitors of HgCdTe are less sensitive Si-based bolometers (see uncooled infrared camera), InSb and photon-counting superconducting tunnel junction (STJ) arrays. Quantum well infrared photodetectors (QWIP), manufactured from III-V semiconductor materials such as GaAs and AlGaAs, are another possible alternative, although their theoretical performance limits are inferior to HgCdTe arrays at comparable temperatures and they require the use of complicated reflection/diffraction gratings to overcome certain polarization exclusion effects which impact array responsivity. In the future, the primary competitor to HgCdTe detectors may emerge in the form of Quantum Dot Infrared Photodetectors (QDIP), based on either a colloidal or type-II superlattice structure.
|
|
This led to the convening of a Parliamentary Select Committee in 1825, to consider the salmon fisheries of the United Kingdom. Its remit was to report on the state of the fisheries, and the legislation that affected them. They produced two reports, the first of which contained 13 recommendations. These included a national close season, and weekly close times; making the taking or selling of salmon or trout during the close season an offence; a requirement that mill owners should erect and maintain gratings where water was taken from a river; guarding against the release of toxic substances into watercourses; a prohibition on the use of lights to catch salmon; and the regulation of the size of mesh that could be used in nets.
|
|
Imaging of sub-micrometre features has been greatly improved by using thinner silver and spacer layers, and by reducing the surface roughness of the lens stack. The ability of the silver lenses to image the gratings has been used as the ultimate resolution test, as there is a concrete limit for the ability of a conventional (far field) lens to image a periodic object – in this case the image is a diffraction grating. For normal-incidence illumination the minimum spatial period that can be resolved with wavelength λ through a medium with refractive index n is λ/n. Zero contrast would therefore be expected in any (conventional) far-field image below this limit, no matter how good the imaging resist might be.
|
|
Fig. 9: Holographic IDT designed to synthesize laterally (left) and 3D (right) focused acoustical vortices The individual selective manipulation of micro-objects requires to synthesize complex acoustic fields such as acoustic vortices (see previous section) at sufficiently high frequency to reach the necessary spatial resolution (typically the wavelength must be comparable to the size of the manipulated object to be selective). Many holographic methods have been developed to synthesize complex wavefields including transducer arrays, 3D printed holograms, metamaterials or diffraction gratings. Nevertheless all these methods are limited to relatively low frequencies with an insufficient resolution to address micrometric particles, cells or microorganisms individually. On the other hand, InterDigitated Transducers (IDTs) were known as a reliable technique to synthesize acoustic wavefields up to GHz frequency.
|
|
Recently the development of high power fiber lasers has generated a new set of applications for fiber Bragg gratings (FBGs), operating at power levels that were previously thought impossible. In the case of a simple fiber laser, the FBGs can be used as the high reflector (HR) and output coupler (OC) to form the laser cavity. The gain for the laser is provided by a length of rare earth doped optical fiber, with the most common form using Yb3+ ions as the active lasing ion in the silica fiber. These Yb-doped fiber lasers first operated at the 1 kW CW power level in 2004 based on free space cavities but were not shown to operate with fiber Bragg grating cavities until much later.
|
|
This emission is sent to a spectrometer (located in big purple box), where it is dispersed over a finite wavelength range — which is centered on the emission line of interest — by a pair of optical gratings. However, because the collected emission is dominated by radiation from along the beam path, the measurements are effectively localized to the intersection volume between the fiber view and the beam. On MST, this intersection volume is small (~ 2 cm3) compared to the plasma volume, allowing spatially resolved measurements of Ti and vi to be obtained. Data collected from a number of plasma discharges — for which the location of the fiber bundle system is varied — are used to construct radial profiles of the impurity ion temperature and velocity, providing important information for understanding the physics of plasmas in MST.
|
|
The central body, namely the interturrio, is about twenty metres long and is characterized by two orders of windows, the lower one composed of arch windows and the upper one made up of jack arch windows. The underlying portion features four entryways: the central ones are larger and taller and are vehicle accessible, while the two entryways to the sides are narrower and shorter and served as pedestrian passageways. The grooves along the entryways' inner walls suggest the original presence of the so-called cateractae, an alleged system of gate gratings operated from the upper floor. On the ground near the gate is still part of the guardhouse added in the Roman period, on which one can see the furrows on the stones caused by the transit of wagons.
|
|
In 1991, Hill was elected to Fellowship in the Optical Society of America (OSA) for his efforts pertaining to fused fiber optical couplers, photosensitivity in fibers, novel fiber-based devices and nonlinear effects in fibers. He was the 1995 recipient of the Manning Principal Award for the discovery of photosensitivity in optical fibers as well as the many commercial applications his work led to. At the 1996 Optical Fiber Communications Conference, Hill was awarded the John Tyndall Award sponsored by the Institute of Electrical and Electronics Engineers (IEEE), the Lasers and Electro-Optics Society (LEOS) and the Optical Society of America. The award was presented for the discovery of photosensitivity in optical fibers and its application to Bragg gratings used in device applications in optical communications and sensor systems.
|
|
Sari Dienes (8 October 1898 – 25 May 1992) was a Hungarian-born American artist. During a career spanning six decades she worked in a wide range of media, creating paintings, drawings, prints, sculptures, ceramics, textile designs, sets and costumes for theatre and dance, sound-art installations, mixed-media environments, music and performance art. Her large-scale 'Sidewalk Rubbings' of 1953–55 - bold, graphic, geometrical compositions, combining rubbings of manhole covers, subway gratings and other elements of the urban streetscape - signaled a move away from the gestural mark making of Abstract Expressionism towards the indexical appropriation of the environment that would be further developed in Pop art, and exerted a significant influence on Robert Rauschenberg and Jasper Johns.Johns cited in: Edward M. Plunkett, 'Send Letters, Postcards, Drawings, and Objects...', Art Journal, vol.
|
|
Grayson had by then succeeded in creating 120,000 diffractions lines to the inch (4,700 lines per mm). Grayson described his work on diffraction ruling in a report published for the Report of Meeting, Eighth Meeting of the Australasian Association for the Advancement of Science, held at Melbourne, Victoria in 1900: From this time onwards much of his time was given to the preparation of a dividing engine for ruling diffraction gratings. Grayson was transferred to the Natural Philosophy department of the university under Professor T. R. Lyle in 1913 and was allowed to give his full time to the machine. In July 1917 he read a paper before the Royal Society of Victoria giving a full description of the machine, which was published with several plates in the society's Proceedings for that year.
|
|
On January 28, 2010, the facility published a paper reporting the delivery of a 669 kJ pulse to a gold hohlraum, setting new records for power delivery by a laser, and leading to analysis suggesting that suspected interference by generated plasma would not be a problem in igniting a fusion reaction. Due to the size of the test hohlraums, laser/plasma interactions produced plasma-optics gratings, acting like tiny prisms, which produced symmetric X-ray drive on the capsule inside the hohlraum. After gradually altering the wavelength of the laser, scientists were able to compress a spherical capsule evenly and heat it up to 3.3 million kelvins (285 eV). The capsule contained cryogenically cooled gas, acting as a substitute for the deuterium and tritium fuel capsules that will be used later on.
|
|
In addition, the reflection gratings commonly used in the industry to alleviate this problem were made of very fine periodic posts and were difficult to produce in large formats. To address this problem, researchers at the Army Research Laboratory developed the corrugated quantum infrared photodetector (C-QWIP) in 2008, which used micromirrors on the photodetector to increase the effectiveness of redirecting the light onto the quantum well region at any wavelength. In essence, the 45-degree inclined detector sidewalls allowed light to be reflected parallel to the material layers to produce an electrical signal. Tests conducted by researchers at ARL and L-3 Communications Cincinnati Electronics determined that the C-QWIP demonstrated bandwidths exceeding 3 micrometers, which was 5 times wider than the commercial QWIP at the time.
|
|
An addressed fiber Bragg structure (AFBS) is a fiber Bragg grating, the optical frequency response of which includes two narrowband components with the frequency spacing between them (which is the address frequency of the AFBS) being in the radio frequency (RF) range. The frequency spacing (the address frequency) is unique for every AFBS in the interrogation circuit and does not change when the AFBS is subjected to strain or temperature variation. An addressed fiber Bragg structure can perform triple function in fiber-optic sensor systems: a sensor, a shaper of double-frequency probing radiation, and a multiplexor. The key feature of AFBS is that it enables the definition of its central wavelength without scanning its spectral response, as opposed to conventional fiber Bragg gratings (FBG), which are probed using optoelectronic interrogators.
|
|
The separation of matter wave packets from complete atoms was first observed by Esterman and Stern in 1930, when a Na beam was diffracted off a surface of NaCl. The first modern atom interferometer reported was a Young's-type double slit experiment with metastable helium atoms and a microfabricated double slit by Carnal and Mlynek in 1991, and an interferometer using three microfabricated diffraction gratings and Na atoms in the group around Pritchard at MIT. Shortly afterwards, an optical version of Ramsey spectrometer typically used in atomic clocks was recognized also as an atom interferometer at the PTB in Braunschweig, Germany. The largest physical separation between the partial wave packets of atoms was achieved using laser cooling techniques and stimulated Raman transitions by S. Chu and coworkers in Stanford.
|
|
The structure behaves optically as if it consisted of a stack of 88 diffraction gratings, making Aphrodita one of the most iridescent of marine organisms. Magnificent non-iridescent colours of blue-and-yellow macaw created by random nanochannels Deformed matrices, consisting of randomly oriented nanochannels in a spongelike keratin matrix, create the diffuse non-iridescent blue colour of Ara ararauna, the blue-and-yellow macaw. Since the reflections are not all arranged in the same direction, the colours, while still magnificent, do not vary much with angle, so they are not iridescent. The most intense blue known in nature: Pollia condensata berries Spiral coils, formed of helicoidally stacked cellulose microfibrils, create Bragg reflection in the "marble berries" of the African herb Pollia condensata, resulting in the most intense blue coloration known in nature.
|
|
In 1894 Righi (along with Indian physicist Jagadish Chandra Bose) was the first person to generate microwaves, producing 12 GHz microwaves with a metal ball spark oscillator, and detecting them with a dipole antenna and spark gap. He used his spark transmitter and detector at wavelengths of 20, 7.5 and 2.5 centimeters (frequencies of 1.5, 4 and 12 GHz) to perform classic optics experiments with microwaves, using quasioptical components, prisms and lenses made of paraffin wax and sulfur and wire diffraction gratings to demonstrate refraction, diffraction, and polarization of these short radio waves, providing experimental confirmation of James Clerk Maxwell's 1873 theory that radio waves and light were both electromagnetic waves, differing only in frequency. His work L'ottica delle oscillazioni elettriche (1897), which summarised his results, is considered a classic of experimental electromagnetism. In 1903 Righi wrote a book on wireless telegraphy.
|
|
September 2008, Bystrzyca Kłodzka: the exhibition "Jan Liwacz 1898-1980 – 110th anniversary of birth" Jan Liwacz (born 4 October 1898 in Dukla, died 22 April 1980 in Bystrzyca Kłodzka) was a master blacksmith and prisoner of Auschwitz concentration camp best known for the infamous "Arbeit macht frei" slogan over the camp's main entrance gate that he made. When the SS ordered him to make this sign, he placed a hidden message in the word ARBEIT: he turned the letter “B” upside down. He was detained and arrested on 16 October 1939 in Bukowsko, and kept in the prisons of Sanok, Krosno, Kraków, and Nowy Wiśnicz; he arrived at Auschwitz in its beginnings, on 20 June 1940, receiving the early camp number of 1010. As a metal worker he was assigned to a kommando manufacturing the camp's infrastructure elements (gratings, handrails, banisters, chandeliers, etc.).
|
|
University of California, Berkeley, 1999. However, the claim of frequency sensitivity is problematic given, for example, that changes of distance do not seem to affect the relevant perceptual patterns (as noted, for example, in the figure caption to Solomon and Pelli (1994) While the latter authors are referring specifically to letters, they make no objective distinction between these and other shapes. The relative insensitivity of contrast effects to distance (and thus spatial frequency) may also be observed by casual inspection of a paradigmantic sweep grating, as may be observed here The high-frequency cut-off represents the optical limitations of the visual system's ability to resolve detail and is typically about 60 cycles per degree. The high-frequency cut-off is related to the packing density of the retinal photoreceptor cells: a finer matrix can resolve finer gratings.
|
|
A. A. Kostenko, A. I. Nosich, P. F. Goldsmith, "Historical background and development of Soviet quasioptics at near-millimeter and sub-millimeter wavelengths" in With this apparatus he extended the work of Heinrich Hertz to higher frequencies, duplicating classical optics experiments using quasioptical components such as lenses, prisms and quarter-wave plates made of sulfur and wire diffraction gratings to demonstrate refraction, diffraction, double refraction, birefringence and polarization of millimeter waves. He was the first to measure the pressure of light on a solid body in 1899. The discovery was announced at the World Physics Congress in Paris in 1900, and became the first quantitative confirmation of Maxwell's theory of electromagnetism. In 1901 he became a professor of Moscow State University, however he quit the University in 1911, protesting against the politics of the Ministry of Education.
|
|
Many McPherson instrument and system designs have been awarded US patents. Some of these include: \- Monochromator Adapted for use in the Ultraviolet Region (US Patent No. 3,090,863)3 This Auto-focusing Normal Incidence instrument is designed for use in the extreme ultraviolet and vacuum ultraviolet region (30 to 200 nm.) It has been modernized and is still in production. \- Ultraviolet Monochromator (US Patent No. 3,211,049)3 This grazing incidence Rowland circle instrument is designed for use in the soft x-ray and extreme ultraviolet spectral region (1 to 30 nm.) It has been modernized and is still in production. \- Optical Grating Spectral Dispersion System (US Patent No. 3,409,3743 This criss-cross Czerny Turner optical system is capable of operation from about 105 nm to 10 micrometers in the infrared and features (patented) interchangeable gratings and a vacuum tight housing.
|
|
Saunders was born in London, Ontario, a son of William Saunders and Sarah Agnes Saunders, née Robinson, both of whom were born in England and emigrated to Canada at an early age. His father was renowned in the fields of orchard pests and fruit hybridization, was a founding member of the Entomological Society of Ontario and published books including Insects Injurious to Fruits (1883, J. B. Lippincott & Co.) and numerous scientific papers. He was recognized with honorary degrees from several universities and by honours from King George VI. Saunders studied Physics at Johns Hopkins University and worked under Henry A. Rowland, a pioneer in use of diffraction gratings for spectroscopy, graduating PhD in 1899. He tutored in Physics at Haverford College from 1899 to 1901, then at Syracuse University where he reached the status of Professor in 1914.
|
|
Fiber Bragg gratings are narrow-band reflectors and act as the mirrors of the laser cavity. They are inscribed directly into the core of the optical fiber used as the gain medium, which eliminates substantial losses that previously arose due to the coupling of the fiber to external bulk-optic cavity reflectors. Nowadays, commercially available fiber- based Raman lasers can deliver output powers in the range of a few tens of Watts in continuous-wave operation. A technique that is commonly employed in these devices is cascading, first proposed in 1994: The "first-order" laser light that is generated from the pump light in a single frequency-shifting step remains trapped in the laser resonator and is pushed to such high power levels that it acts itself as the pump for the generation of "second-order" laser light that is shifted by the same vibrational frequency again.
|
|
Recently, a lot of research was done to improve the grating-based technique: Han Wen and his team analyzed animal bones and found out that the intensity of the dark-field signal depends on the orientation of the grid and this is due to the anisotropy of the bone structure. They made significant progress towards biomedical applications by replacing mechanical scanning of the gratings with electronic scanning of the X-ray source. The grating-based phase-contrast CT field was extended by tomographic images of the dark-field signal and time-resolved phase-contrast CT. Furthermore, the first pre-clinical studies using grating-based phase-contrast X-ray imaging were published. Marco Stampanoni and his group examined native breast tissue with "differential phase-contrast mammography", and a team led by Dan Stutman investigated how to use grating-based imaging for the small joints of the hand.
|
|
Butterfly wing at different magnifications reveals microstructured chitin acting as a diffraction grating A number of fixed structures can create structural colours, by mechanisms including diffraction gratings, selective mirrors, photonic crystals, crystal fibres and deformed matrices. Structures can be far more elaborate than a single thin film: films can be stacked up to give strong iridescence, to combine two colours, or to balance out the inevitable change of colour with angle to give a more diffuse, less iridescent effect. Each mechanism offers a specific solution to the problem of creating a bright colour or combination of colours visible from different directions. Drawing of 'firtree' micro-structures in Morpho butterfly wing scale A diffraction grating constructed of layers of chitin and air gives rise to the iridescent colours of various butterfly wing scales as well as to the tail feathers of birds such as the peacock.
|
|
In electronics, Modulation is the process of varying one waveform in relation to another waveform. With a 'modulation collimator' the amplitude (intensity) of the incoming X-rays is reduced by the presence of two or more 'diffraction gratings' of parallel wires that block or greatly reduce that portion of the signal incident upon the wires. An X-ray collimator is a device that filters a stream of X-rays so that only those traveling parallel to a specified direction are allowed through. Minoru Oda, President of Tokyo University of Information Sciences, invented the modulation collimator, first used to identify the counterpart of Sco X-1 in 1966, which led to the most accurate positions for X-ray sources available, prior to the launch of X-ray imaging telescopes. SAS 3 carried modulation collimators (2-11 keV) and Slat and Tube collimators (1 up to 60keV).
|
|
Diode lasers can also be precisely modulated with a greater frequency than DPSSLs. Neodymium-doped solid state lasers continue to be the laser source of choice for industrial applications. Direct pumping of the upper Nd laser level at 885-nm (rather than at the more traditional broad 808-nm band) offers the potential of improved performance through a reduction in the lasing quantum defect, thereby improving system efficiency, reducing cooling requirements, and enabling further TEM00 power scaling. Because of the narrow 885-nm absorption feature in Nd:YAG, certain systems may benefit from the use of wavelength-locked diode pump sources, which serve to narrow and stabilize the pump emission spectrum to keep it closely aligned to this absorption feature. To date, high power diode laser locking schemes such as internal distributed feedback Bragg gratings and externally aligned volume holographic grating optics, VHG’s, have not been widely implemented due to the increased cost and assumed performance penalty of the technology.
|
|
From 1926 to 1927, Mannkopff was an assistant to Carl Runge at the University of Göttingen, working with Rowland gratings. From 1927 to 1930, he was a teaching assistant to James Franck there. In 1929, Mannkopff switched to mineralogy, and from 1930 to 1933 he was an assistant to Victor Moritz Goldschmidt at the Mineralogischen Institut of the University of Göttingen. At the institute, he applied his educational background to quantitative applications of spectroscopy to chemical analysis of the earth’s crust.Hentschel and Hentschell, 1996, Appendix F; see the entry for Mannkopff.II. Schlaglichter 1933-1945, Etudes des sciences aleph99.org In 1934, he became a Privatdozent at the University of Göttingen and in 1939 a nichtplanmäßiger Professor (supernumerary professor) there. In 1939, he also became a member of the short-lived, first Uranverein (Uranium Club), the abortive start of the German nuclear energy project.Hentschel and Hentschell, 1996, Appendix F; see the entry for Mannkopff.
|
|
In 1859, the Pilgrim Society began building a Victorian canopy designed by Hammett Billings at the wharf over the portion of the rock left there, which was completed in 1867. The Pilgrim Hall section of the rock was moved back to its original wharf location in 1880, rejoined to the remaining portion, and the date "1620" was carved into it. In 1920 the rock was temporarily relocated so that the old wharves could be removed and the waterfront re-landscaped to a design by landscape architect Arthur Shurcliff, with a waterfront promenade behind a low seawall in such a way that, when the rock was returned to its original site, it would be at water level. The care of the rock was turned over to the Commonwealth of Massachusetts, and a new Roman Doric portico was constructed, designed by McKim, Mead and White for viewing the tide-washed rock protected by gratings.
|
|
She lay slightly to port facing northeast in 86 metres of water, and during the next few months she slid a little more to port where she appears to have rested on a roughly 50 degree angle. Divers could find no evidence of collision or damage to the hull, casing or bridge and it was noted that the search periscope and ANF radar mast were extended, indicating she had been at periscope depth when she foundered. However, the snort mast had been broken and lay next to the sub, attached by only a thin shred of metal. The hatches and torpedo doors were all shut, and the two emergency buoys were still located within the casing, although the after one could not have been released as the hinged wooden gratings retaining it had been wired shut (sadly, it was later discovered that it had been wired shut because it often broke free whilst the sub was underway).
|
|
The spatial-frequency theory refers to the theory that the visual cortex operates on a code of spatial frequency, not on the code of straight edges and lines hypothesised by Hubel and Wiesel on the basis of early experiments on V1 neurons in the cat. In support of this theory is the experimental observation that the visual cortex neurons respond even more robustly to sine-wave gratings that are placed at specific angles in their receptive fields than they do to edges or bars. Most neurons in the primary visual cortex respond best when a sine-wave grating of a particular frequency is presented at a particular angle in a particular location in the visual field. (However, as noted by Teller (1984),Teller, D. "Linking Propositions" it is probably not wise to treat the highest firing rate of a particular neuron as having a special significance with respect to its role in the perception of a particular stimulus, given that the neural code is known to be linked to relative firing rates.
|
|
For example, in color coding by the three cones in the human retina, there is no special significance to the cone that is firing most strongly – what matters is the relative rate of firing of all three simultaneously. Teller (1984) similarly noted that a strong firing rate in response to a particular stimulus should not be interpreted as indicating that the neuron is somehow specialized for that stimulus, since there is an unlimited equivalence class of stimuli capable of producing similar firing rates.) The spatial-frequency theory of vision is based on two physical principles: # Any visual stimulus can be represented by plotting the intensity of the light along lines running through it. # Any curve can be broken down into constituent sine waves by Fourier analysis. The theory (for which empirical support has yet to be developed) states that in each functional module of the visual cortex, Fourier analysis is performed on the receptive field and the neurons in each module are thought to respond selectively to various orientations and frequencies of sine wave gratings.
|
|