Showing papers on "Reflection (physics) published in 2006"
TL;DR: In this article, it was shown that the acoustic Green's function between any two points in the medium can be represented by an integral of crosscorrelations of wavefield observations at those two points.
Abstract: The term seismic interferometry refers to the principle of generating new seismic responses by crosscorrelating seismic observations at different receiver locations. The first version of this principle was derived by Claerbout (1968), who showed that the reflection response of a horizontally layered medium can be synthesized from the autocorrelation of its transmission response. For an arbitrary 3D inhomogeneous lossless medium it follows from Rayleigh's reciprocity theorem and the principle of time-reversal invariance that the acoustic Green's function between any two points in the medium can be represented by an integral of crosscorrelations of wavefield observations at those two points. The integral is along sources on an arbitrarily shaped surface enclosing these points. No assumptions are made with respect to the diffusivity of the wavefield. The Rayleigh-Betti reciprocity theorem leads to a similar representation of the elastodynamic Green's function. When a part of the enclosing surface is the earth's free surface, the integral needs only to be evaluated over the remaining part of the closed surface. In practice, not all sources are equally important: The main contributions to the reconstructed Green's function come from sources at stationary points. When the sources emit transient signals, a shaping filter can be applied to correct for the differences in source wavelets. When the sources are uncorrelated noise sources, the representation simplifies to a direct crosscorrelation of wavefield observations at two points, similar as in methods that retrieve Green's functions from diffuse wavefields in disordered media or in finite media with an irregular bounding surface.
700 citations
TL;DR: By combining the Dirac equation of relativistic quantum mechanics with the Bogoliubov-de Gennes equation of superconductivity, the electron-hole conversion at a normal-metal-superconductor interface in graphene is investigated and the Andreev reflection of Dirac fermions has several unusual features.
Abstract: By combining the Dirac equation of relativistic quantum mechanics with the Bogoliubov-de Gennes equation of superconductivity we investigate the electron-hole conversion at a normal-metal-superconductor interface in graphene. We find that the Andreev reflection of Dirac fermions has several unusual features: (1) the electron and hole occupy different valleys of the band structure; (2) at normal incidence the electron-hole conversion happens with unit efficiency in spite of the large mismatch in Fermi wavelengths at the two sides of the interface; and, most fundamentally: (3) away from normal incidence the reflection angle may be the same as the angle of incidence (retroreflection) or it may be inverted (specular reflection). Specular Andreev reflection dominates in weakly doped graphene, when the Fermi wavelength in the normal region is large compared to the superconducting coherence length.
562 citations
TL;DR: This investigation demonstrates that THz technique is capable of detecting and identifying hidden RDX-related explosives in a diffuse reflection mode, which is crucial for the standoff detection in the real world applications.
Abstract: The reflection spectrum of the explosive RDX was acquired from a diffuse reflection measurement using a THz time-domain spectroscopy system in combination with a diffuse reflectance accessory. By applying the Kramers-Kronig transform to the reflection spectrum, the absorption spectrum (0.2-1.8 THz) was obtained. It agrees with the result from a transmission measurement and distinguishes RDX from other materials. The effect of the reference spectrum was examined by using both a Teflon pellet and a copper plate as references. The strong absorption of RDX at 0.82 THz allowed it to be identified by the diffuse reflection measurement even when the RDX sample was covered with certain optically opaque materials. Our investigation demonstrates that THz technique is capable of detecting and identifying hidden RDX-related explosives in a diffuse reflection mode, which is crucial for the standoff detection in the real world applications.
328 citations
TL;DR: In this article, the authors present several tactics to avoid artefacts in shot-domain reverse-time migration, such as muting of a shot gather before migration, or wavefront migration which performs correlation only within a time window following first arriving travel times, are useful in suppressing artefacts.
Abstract: Recently, rapid developments in computer hardware have enabled reverse-time migration to be applied to various production imaging problems. As a wave-equation technique using the two-way wave equation, reverse-time migration can handle not only multi-path arrivals but also steep dips and overturned reflections. However, reverse-time migration causes unwanted artefacts, which arise from the two-way characteristics of the hyperbolic wave equation. Zero-lag cross correlation with diving waves, head waves and back-scattered waves result in spurious artefacts. These strong artefacts have the common feature that the correlating forward and backward wavefields propagate in almost the opposite direction to each other at each correlation point. This is because the ray paths of the forward and backward wavefields are almost identical. In this paper, we present several tactics to avoid artefacts in shot-domain reverse-time migration. Simple muting of a shot gather before migration, or wavefront migration which performs correlation only within a time window following first arriving travel times, are useful in suppressing artefacts. Calculating the wave propagation direction from the Poynting vector gives rise to a new imaging condition, which can eliminate strong artefacts and can produce common image gathers in the reflection angle domain.
305 citations
TL;DR: Experimental results are presented that illustrate that the technique is accurate near object limbs, as the theory predicts, with less precise, but still useful, results elsewhere.
Abstract: When unpolarized light is reflected from a smooth dielectric surface, it becomes partially polarized. This is due to the orientation of dipoles induced in the reflecting medium and applies to both specular and diffuse reflection. This paper is concerned with exploiting polarization by surface reflection, using images of smooth dielectric objects, to recover surface normals and, hence, height. This paper presents the underlying physics of polarization by reflection, starting with the Fresnel equations. These equations are used to interpret images taken with a linear polarizer and digital camera, revealing the shape of the objects. Experimental results are presented that illustrate that the technique is accurate near object limbs, as the theory predicts, with less precise, but still useful, results elsewhere. A detailed analysis of the accuracy of the technique for a variety of materials is presented. A method for estimating refractive indices using a laser and linear polarizer is also given.
242 citations
TL;DR: In this article, a computational analysis of laser keyhole welding is achieved, where multiple reflection and Fresnel absorption are implemented simultaneously with the proposed ray tracing technique in a discrete grid cell system during the simulation for every single time step.
Abstract: A computational analysis of laser keyhole welding is achieved. The main driving force to make the molten pool as a narrow and deep keyhole is the recoil pressure induced by evaporation of the material. Also, the multiple reflection effect on the keyhole wall plays an important role in making the keyhole deeper and raising its total energy absorption rate. Multiple reflection and Fresnel absorption are implemented simultaneously with the proposed ray tracing technique in a discrete grid cell system during the simulation for every single time step. In particular, the Fresnel absorption model is chosen as an energy transfer mechanism from laser beam to workpiece. With all the governing equations including continuity, momentum and energy equation, the VOF method is adopted to trace the free surface of the molten pool. Simulation results are compared with the experimental ones to verify its validity. A pulsed Nd : YAG laser was used for keyhole welding experiments on mild steel plates of 7 mm thickness. It was observed that the generated keyhole maintains its solidified shape without any closing phenomenon both in the experiments and in the simulations.
234 citations
TL;DR: In this article, the authors studied the X-ray spectral variability of the narrow line Seyfert 1 galaxy NGC 4051 as observed during two XMM-Newton observations.
Abstract: We study the X-ray spectral variability of the narrow line Seyfert 1 galaxy NGC 4051 as observed during two XMM-Newton observations. To gain insight on the general behaviour, we first apply model-independent techniques such as rms spectra and flux-flux plots. We then perform time-resolved spectral analysis by splitting the observations into 68 spectra (2 ks each). The data show evidence for a neutral and constant-reflection component and for constant emission from photoionized gas, which are included in all spectral models. The nuclear emission can be modelled both in terms of a 'standard model' [pivoting power-law plus a blackbody (BB) component for the soft excess] and of a two-component one (power law plus ionized reflection from the accretion disc). Both the models reproduce the source spectral variability and cannot be distinguished on a statistical ground. The distinction has thus to be made on a physical basis. The standard model results indicate that the soft excess does not follow the standard BB law (L BB oc T 4 ), despite a variation in luminosity by about one order of magnitude. The resulting temperature is consistent with being constant and has the same value as observed in the PG quasars. Moreover, although the spectral slope is correlated with flux, which is consistent with spectral pivoting, the hardest photon indices are so flat (Γ ∼ 1.3-1.4) as to require rather unusual scenarios. Furthermore, the very low flux states exhibit an inverted r-flux behaviour which disagrees with a simple pivoting interpretation. These problems can be solved in terms of the two-component model in which the soft excess is not thermal, but due to the ionized reflection component. In this context, the power law has a constant slope (about 2.2) and the slope-flux correlation is explained in terms of the relative contribution of the power-law and reflection components which also explains the shape of the flux-flux plot relationship. The variability of the reflection component from the inner disc closely follows the predictions of the light-bending model, suggesting that most of the primary nuclear emission is produced in the very innermost regions, only a few gravitational radii (rg) from the central black hole.
156 citations
TL;DR: In this paper, a 3D finite-difference modeling of reflected and scattered seismic energy over discrete systems of vertical fractures is used to identify subsurface areas with high fracturing and to determine the strike of those fractures.
Abstract: Wepresentthedetailsofanewmethodfordeterminingthereflection and scattering characteristics of seismic energy from subsurface fractured formations. The method is based upon observations we have made from 3D finite-difference modeling of the reflected and scattered seismic energy over discrete systems of vertical fractures. Regularly spaced, discrete vertical fracture corridors impart a coda signature, which is a ringing tail of scatteredenergy,toanyseismicwaveswhicharetransmittedthrough or reflected off of them. This signature varies in amplitude and coherence as a function of several parameters including: 1 the difference in angle between the orientation of the fractures and the acquisition direction, 2 the fracture spacing, 3 the wavelength of the illuminating seismic energy, and 4 the compliance, or stiffness, of the fractures. This coda energy is most coherent when the acquisition direction is parallel to the strike of thefractures.Ithasthelargestamplitudewhentheseismicwavelengths are tuned to the fracture spacing, and when the fractures have low stiffness. Our method uses surface seismic reflection tracestoderiveatransferfunctionthatquantifiesthechangeinan apparent source wavelet before and after propagating through a fracturedinterval.Thetransferfunctionforanintervalwithnoor low amounts of scattering will be more spikelike and temporally compact. The transfer function for an interval with high scattering will ring and be less temporally compact. When a 3D survey is acquired with a full range of azimuths, the variation in the derived transfer functions allows us to identify subsurface areas with high fracturing and to determine the strike of those fractures.Wecalibratedthemethodwithmodeldataandthenapplied ittotheEmiliofieldwithafracturedreservoir.Themethodyielded results which agree with known field measurements and previously published fracture orientations derived from PS anisotropy.
155 citations
TL;DR: In this article, the authors adopt the finite-difference time-domain (FDTD) method to analyze surface acoustic waves propagating in two-dimensional phononic waveguides.
Abstract: In this paper, we adopt the finite-difference time-domain (FDTD) method to analyze surface acoustic waves propagating in two-dimensional phononic waveguides. To implement the FDTD program for dealing with surface acoustic waves, the Bloch theorem and absorbing boundary conditions are employed to deal with the periodic boundary condition and reflection from a numerical boundary. A phononic crystal consisting of circular steel cylinders that form a square lattice in an epoxy matrix is considered as an example to study phononic crystal waveguides. The dispersion relation and displacement fields are calculated to identify the band gaps and eigenmodes. The result shows the existence of a complete band gap of surface waves and thus an acoustic waveguide is created accordingly. Eigenmodes of surface waves inside the waveguide are indicated and pseudo surface acoustic waves propagating inside the straight waveguide are demonstrated. Further, waveguides with a sharp bend are reported and an improved design is suggested to enhance energy transmission.
154 citations
TL;DR: In this paper, a series expansion from a rapidly spatially varying expansion level and the resulting general velocity formulation is given as a triple-summation of terms involving high derivatives of this expansion level.
153 citations
TL;DR: In this article, the authors show that the so-called frozen mode regime offers a unique solution to the above problem, where the incident light enters the photonic crystal with little reflection and, subsequently, is completely converted into the frozen mode with huge amplitude and almost zero group velocity.
Abstract: The problem of slowing down light by orders of magnitude has been extensively discussed in the literature. Such a possibility can be useful in a variety of optical and microwave applications. Many qualitatively different approaches have been explored. Here we discuss how this goal can be achieved in linear dispersive media, such as photonic crystals. The existence of slowly propagating electromagnetic waves in photonic crystals is quite obvious and well known. The main problem, though, has been how to convert the input radiation into the slow mode without losing a significant portion of the incident light energy to absorption, reflection, etc. We show that the so-called frozen mode regime offers a unique solution to the above problem. Under the frozen mode regime, the incident light enters the photonic crystal with little reflection and, subsequently, is completely converted into the frozen mode with huge amplitude and almost zero group velocity. The linearity of the above effect allows the slowing of lig...
TL;DR: In this article, a Lamb wave-based crack identification technique for aluminium plates was developed with an integrated active piezoelectric sensor network, and a correlation function was further established, which helped identify the crack position based on a triangulation approach with the aid of a nonlinear least-squares optimization algorithm.
Abstract: With an integrated active piezoelectric sensor network, a Lamb wave-based crack identification technique for aluminium plates was developed. Experimental results showed that the propagation of Lamb waves in aluminium plate-like structures is considerably complicated due to wave dispersion, material attenuation, boundary reflection, etc. In order to eliminate the diverse interference, a wavelet transform technique was applied to purify the acquired Lamb wave signals, and the characteristics of Lamb wave signals were extracted from the wave energy spectrum. A correlation function was further established, which helped identify the crack position based on a triangulation approach with the aid of a nonlinear least-squares optimization algorithm. Such an approach provides satisfactory results in locating the crack position in aluminium plates with cracks of 5 and 20 mm in length.
TL;DR: In this paper, it was proved that the continuity of the tangential components of the average electric and magnetic fields is insufficient to describe the reflection of plane waves by a set of thin parallel wires embedded in a dielectric host using a homogenization approach.
Abstract: In this paper, it is proved that the continuity of the tangential components of the average electric and magnetic fields is insufficient to describe the reflection of plane waves by a set of thin parallel wires embedded in a dielectric host using a homogenization approach. Based on physical arguments a new boundary condition is proposed to characterize the scattering of waves by the homogenized wire medium. In order to further support the proposed theory, the problem of reflection of a plane wave by a set of semi-infinite parallel wires is solved analytically within the thin-wire approximation. Extensive numerical simulations demonstrate that when the additional boundary condition is considered the agreement between full wave results and homogenization theory is very good even for wavelengths comparable with the lattice constant.
TL;DR: In this article, the reflection and transmission coefficients of a thin vertical porous wall with different porous shapes with different shapes have been analyzed, and the porous effect parameter G has been obtained.
Abstract: The present paper aims at getting the porous effect parameter G of a thin permeable wall. The reflection and transmission coefficients of a thin vertical porous wall with different porous shapes an...
TL;DR: The theory of quantum reflection is extended to account for the mean-field interactions of a condensate which suppresses quantum reflection at low velocity and the reflected condensates show collective excitations as recently predicted.
Abstract: We study how interactions affect the quantum reflection of Bose-Einstein condensates. A patterned silicon surface with a square array of pillars resulted in high reflection probabilities. For incident velocities greater than 2.5 mm/s, our observations agreed with single-particle theory. At velocities below 2.5 mm/s, the measured reflection probability saturated near 60% rather than increasing towards unity as predicted by the accepted theoretical model. We extend the theory of quantum reflection to account for the mean-field interactions of a condensate which suppresses quantum reflection at low velocity. The reflected condensates show collective excitations as recently predicted.
TL;DR: New closed-form expressions for analysis of Teng-Man measurements of the electro-optic coefficients of poled polymer thin films account for multiple reflection effects using a rigorous analysis of the multilayered structure for varying angles of incidence.
Abstract: We present new closed-form expressions for analysis of Teng-Man measurements of the electro-optic coefficients of poled polymer thin films. These expressions account for multiple reflection effects using a rigorous analysis of the multilayered structure for varying angles of incidence. The analysis based on plane waves is applicable to both transparent and absorptive films and takes into account the properties of the transparent conducting electrode layer. Methods for fitting data are presented and the error introduced by ignoring the transparent conducting layer and multiple reflections is discussed.
Patent•
21 Nov 2006
TL;DR: A backlight unit has a light source, a reflection sheet, a light guide plate, an air space, and a diffuser, where the reflection sheet is configured to arrange individual light sources having different spectra or different light emission quantities near an incident plane of the light guide and scatter dots are disposed which take light propagating through the light guides out of the reflection sheets side.
Abstract: A backlight unit has a light source, a reflection sheet, a light guide plate, an air space, and a diffuser, wherein the reflection sheet, the light guide plate, the air space, and the diffuser are overlaid in this order. The light source is configured to arrange individual light sources having different spectra or different light emission quantities near an incident plane of the light guide plate, and on a plane facing the reflection sheet of the light guide plate, scatter dots are disposed which take light propagating through the light guide plate out of the reflection sheet side. The backlight unit and a liquid crystal display device including the same have excellent display quality.
TL;DR: In this article, the non-classical reflection of solitons from a purely attractive potential was investigated and the effect of nonlinear mean-field interactions was found to be due to the nonlinear Schrodinger equation.
Abstract: Matter-wave bright solitons are predicted to reflect from a purely attractive potential well although they are macroscopic objects with classical particle-like properties. The non-classical reflection occurs at small velocities and a pronounced switching to almost perfect transmission above a critical velocity is found, caused by nonlinear mean-field interactions. Full numerical results from the nonlinear Schrodinger equation are complimented by a two-mode variational calculation to explain the predicted effect, which can be used for velocity filtering of solitons. The experimental realization with laser-induced potentials or two-component Bose-Einstein condensates is suggested.
17 Oct 2006
TL;DR: The Transmissive Mirror Device (TMD) as discussed by the authors is a micro-mirror array, which consists of numerous micromirrors placed perpendicular to the surface of a flat, thin metal plate.
Abstract: We propose a new imaging optics called the Transmissive Mirror Device (TMD). It consists of numerous micromirrors
placed perpendicular to the surface of a flat, thin metal plate. The micro-mirror array is implemented
by the inner walls of minute square holes, which are densely pitted on the device. The basic mode of operation
is based on two reflections by a pair of adjacent mutually perpendicular mirrors, i.e., a dihedral corner reflector.
Although the principal of operation is based on reflection by mirrors, the device is also transmissive and deflects
light. Since this imaging system forms a real image at a plane symmetric point, the depth of the 3D image is
inverted. Its optical defects are low optical transmittance and stray light caused by non-reflected light and that
reflected once. We manufactured the device experimentally with nano-precision machining technology and also
evaluated it.
TL;DR: In this paper, the anechoic effect is studied theoretically and numerically by adapting techniques used in electron scattering and band-gap computations for photonic and phononic crystals, and a method to locate zeroes of analytical functions is applied to prove the existence of, and to specify, thin coatings with vanishing reflectance at isolated frequencies.
Abstract: Thin rubber layers with air-filled cavities can be used as anechoic submarine coatings. Normally incident sonar energy is redistributed in the lateral direction and absorbed. In this paper, the anechoic effect is studied theoretically and numerically by adapting techniques used in electron scattering and band-gap computations for photonic and phononic crystals. Reflection and transmission matrices are computed recursively, from basic ones for layers containing periodic arrays of spherical cavities. A method to locate zeroes of analytical functions is applied to prove the existence of, and to specify, thin coatings with vanishing reflectance at isolated frequencies. Coatings much thinner than quarter-wavelength ones are found. Most of the absorption loss takes place close to the cavities and scattering of compressional spherically symmetric waves is important. The viscoelastic shear-wave properties of the rubber are crucial for generating this loss. The requirements for vanishing reflectance are specified using a simplified model with normal plane waves and spherically symmetric waves, that includes effects of multiple scattering among the cavities. An energy relation is derived, relating the anelastic loss in the rubber coating to loss by monopole resonance scattering from isolated cavities. The noticeable effects of multiple scattering are incorporated by a modulating factor.
TL;DR: A modified two-flux approximation is suggested for calculating the hemispherical transmittance and reflectance of a refracting, absorbing, and scattering medium in the case of collimated irradiation of the sample along the normal to the interface.
Abstract: A modified two-flux approximation is suggested for calculating the hemispherical transmittance and reflectance of a refracting, absorbing, and scattering medium in the case of collimated irradiation of the sample along the normal to the interface. The Fresnel reflection is taken into account in this approach. It is shown that the new approximation is rather accurate for the model transport scattering function. For an arbitrary scattering medium, the error of the modified two-flux approximation is estimated by comparison with the exact numerical calculations for the Henyey-Greenstein scattering function in a wide range of albedos and optical thicknesses. Possible applications of the derived analytical solution to identification problems are discussed.
TL;DR: In this article, the authors established the existence of a global solution to a regular reflection of a shock hitting a ramp for the pressure gradient system of equations, which is a subsystem, and an approximation, of the full Euler system, and offered a couple of derivations.
Abstract: We establish the existence of a global solution to a regular reflection of a shock hitting a ramp for the pressure gradient system of equations. The set-up of the reflection is the same as that of Mach’s experiment for the compressible Euler system, i. e., a straight shock hitting a ramp. We assume that the angle of the ramp is close to 90 degrees. The solution has a reflected bow shock wave, called the diffraction of the planar shock at the compressive corner, which is mathematically regarded as a free boundary in the self-similar variable plane. The pressure gradient system of three equations is a subsystem, and an approximation, of the full Euler system, and we offer a couple of derivations.
TL;DR: Effects of the ocean surface reflection for solar irradiance on the normalized water-leaving radiance in the visible wavelengths are evaluated and discussed for various conditions of the atmosphere, solar-zenith angles, and wind speeds.
Abstract: Effects of the ocean surface reflection for solar irradiance on the normalized water-leaving radiance in the visible wavelengths are evaluated and discussed for various conditions of the atmosphere, solar-zenith angles, and wind speeds. The surface reflection effects on water-leaving radiance are simply due to the fact that the radiance that is backscattered out of the water is directly proportional to the downward solar irradiance just beneath the ocean surface. The larger the solar-zenith angle, the less the downward solar irradiance just beneath the ocean surface (i.e., more photons are reflected by the ocean surface), leading to a reduced value of the radiance that is backscattered out of the ocean. For cases of large solar-zenith angles, the effects of surface irradiance reflection need to be accounted for in both the satellite-derived and in situ measured water-leaving radiances.
TL;DR: A robot-based gonioreflectometer for measuring radiance factor and bidirectional reflectance distribution function has been developed at the Physikalisch-Technische Bundesanstalt as mentioned in this paper.
Abstract: At the Physikalisch-Technische Bundesanstalt a new robot-based gonioreflectometer for measuring radiance factor and bidirectional reflectance-distribution function has been developed. The facility enables measurements of the directed reflection characteristics of materials with arbitrary angles of irradiation and detection relative to the surface normal.
TL;DR: The reported reflection and refraction phenomena arise within a few wavelengths at the interface and thereby suggest a new approach to polarimetry that can be used in microfluidic volumes.
Abstract: A light beam changes direction as it enters a liquid at an angle from another medium, such as air. Should the liquid contain molecules that lack mirror symmetry, then it has been predicted by Fresnel that the light beam will not only change direction, but will actually split into two separate beams with a small difference in the respective angles of refraction. Here we report the observation of this phenomenon. We also demonstrate that the angle of reflection does not equal the angle of incidence in a chiral medium. Unlike conventional optical rotation, which depends on the path-length through the sample, the reported reflection and refraction phenomena arise within a few wavelengths at the interface and thereby suggest a new approach to polarimetry that can be used in microfluidic volumes.
TL;DR: In this article, the potential of the direct wave of radar ground-coupled antennas for the on-site physical characterization of concrete is evaluated by systematic comparison of direct and reflected wave attenuations.
Abstract: The research work presented in this paper aims at evaluating the potential of the direct wave of radar ground-coupled antennas for the on site physical characterization of concrete. According to studies highlighting the ability of radar reflected waves to characterize concrete, the potential of the direct wave is studied by systematic comparison of direct and reflected wave attenuations. Among the various features of electromagnetic waves propagating through concrete, attenuation is the most sensitive to moisture and chloride contents. In order to study the sensitivity of the direct wave to the physical condition of the concrete, laboratory experiments were conducted on concrete slabs with various porosities, water contents and chloride contamination levels. The results of this study show very satisfactory correlations between attenuations of direct and reflected waves, indicating that both waves provide similar information regarding the physical state of concrete. This correlation was confirmed on two bridges by comparison of direct wave attenuation maps with reflection attenuation maps. Therefore, radar interpretation method based on the direct wave attenuation should be able to detect, in a very fast way, physical contrasts in concrete structures and, consequently, identify probable pathological areas.
TL;DR: In this paper, the authors reported that electromagnetic wave reflected from a flat metallic mirror superimposed with a planar wavy metallic structure with subwavelength features that resemble "fish scales" reflects like a conventional mirror without diffraction, but shows no phase change with respect to the incident wave.
Abstract: We report that electromagnetic wave reflected from a flat metallic mirror superimposed with a planar wavy metallic structure with subwavelength features that resemble “fish scales” reflects like a conventional mirror without diffraction, but shows no phase change with respect to the incident wave. Such unusual behavior resembles a reflection from a hypothetical zero refractive index material, or “magnetic wall”. We also discovered that the structure acts as a local field concentrator and a resonant “amplifier” of losses in the underlying dielectric.
TL;DR: In this article, the governing equations for two-dimensional generalized thermoelastic diffusion in an elastic solid are solved and the closed-form expressions for the reflection coefficients for various reflected waves are obtained.
TL;DR: What is believed to be a new class of solutions of the three-flat problem for circular flats is described in terms of functions that are symmetric or antisymmetric with respect to reflections at a single line passing through the center of the flat surfaces.
Abstract: In interferometric surface and wavefront metrology, three-flat tests are the archetypes of measurement procedures to separate errors in the interferometer reference wavefront from errors due to the test part surface, so-called absolute tests. What is believed to be a new class of solutions of the three-flat problem for circular flats is described in terms of functions that are symmetric or antisymmetric with respect to reflections at a single line passing through the center of the flat surfaces. The new solutions are simpler and easier to calculate than the known solutions based on twofold mirror symmetry or rotation symmetry. Strategies for effective azimuthal averaging and a method for determining the averaging error are also discussed.
TL;DR: In this paper, the reflection and transmission of incident waves interacting with a long rectangular breakwater with two thin side-boards protruding vertically downward, was investigated, in which the structure is assumed to be placed in water of uniform constant depth, and an eigenfunction expansion method was used to obtain the solution.