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Showing papers on "Reflection (physics) published in 2013"


Book
14 Jun 2013
TL;DR: In this article, the Fourier Transform and Dirac Delta Function are used to measure the properties of an ultrasonic NDE with models, and the Stationary Phase Method (SPM) is used to scale the model-based defect sizing.
Abstract: 1. An Ultrasonic System. 2. Linear Systems and the Fourier Transform. 3. Fundamentals. 4. Propagation of Bulk Waves. 5. Reciprocal Theorem and Other Integral Relations. 6. Reflection and Refraction of Bulk Waves. 7. Propagation of Surface and Plate Waves. 8. Ultrasonic Transducer Radiation. 9. Materials Attenuation and Efficiency Factors. 10. Flaw Scattering. 11. Transducer Reception Process. 12. Ultrasonic Measurement Models. 13. Near-Field Measurement Models. 14. Quantitative Ultrasonic NDE with Models. 15. Model-Based Flaw Sizing. Appendixes: A. Fourier Transform. B. Dirac Delta Function. C. Basic Notations and Concepts. D. Hilbert Transform. E. Stationary Phase Method. F. Properties of Ellipsoids. Index.

314 citations


Proceedings ArticleDOI
01 Dec 2013
TL;DR: This paper introduces an automatic method for removing reflection interference when imaging a scene behind a glass surface using the use of SIFT-flow to align the images such that a pixel-wise comparison can be made across the input set.
Abstract: This paper introduces an automatic method for removing reflection interference when imaging a scene behind a glass surface. Our approach exploits the subtle changes in the reflection with respect to the background in a small set of images taken at slightly different view points. Key to this idea is the use of SIFT-flow to align the images such that a pixel-wise comparison can be made across the input set. Gradients with variation across the image set are assumed to belong to the reflected scenes while constant gradients are assumed to belong to the desired background scene. By correctly labelling gradients belonging to reflection or background, the background scene can be separated from the reflection interference. Unlike previous approaches that exploit motion, our approach does not make any assumptions regarding the background or reflected scenes' geometry, nor requires the reflection to be static. This makes our approach practical for use in casual imaging scenarios. Our approach is straight forward and produces good results compared with existing methods.

177 citations


Journal ArticleDOI
TL;DR: An active impedance metasurface with full 360° reflection phase control is presented to remove the phase tuning deficiency in conventional approach and can be applied to many cases where fine and full phase tuning is needed, such as beam steering in reflectarray antennas.
Abstract: Impedance metasurface is composed of electrical small scatters in two dimensional plane, of which the surface impedance can be designed to produce desired reflection phase. Tunable reflection phase can be achieved by incorporating active element into the scatters, but the tuning range of the reflection phase is limited. In this paper, an active impedance metasurface with full 360° reflection phase control is presented to remove the phase tuning deficiency in conventional approach. The unit cell of the metasurface is a multiple resonance structure with two resonance poles and one resonance zero, capable of providing 360° reflection phase variation and active tuning within a finite frequency band. Linear reflection phase tuning can also be obtained. Theoretical analysis and simulation are presented and validated by experiment at microwave frequency. The proposed approach can be applied to many cases where fine and full phase tuning is needed, such as beam steering in reflectarray antennas.

170 citations


Journal ArticleDOI
TL;DR: The controlled formation of a bright solitary matter-wave from a Bose–Einstein condensate of 85Rb, which is observed to propagate over a distance of ∼1.1 mm in 150 ms with no observable dispersion is reported.
Abstract: Bright solitary waves in Bose–Einstein condensates are analogues of solitons in conventional wave systems, and may enable interesting tests of many-body quantum systems. Using 85Rb, Marchant et al. show the controlled formation of bright solitary matter-waves, and their reflection from a repulsive barrier.

158 citations


Journal ArticleDOI
TL;DR: Remarkably, via the adjustment of the designed specific acoustic impedance, extraordinary reflection can be steered for unprecedented acoustic wavefront while that ordinary reflection could be surprisingly switched on or off.
Abstract: We unveil the connection between the acoustic impedance along a flat surface and the reflected acoustic wavefront, in order to empower a wide wariety of novel applications in acoustic community. Our designed flat surface can generate double reflections: the ordinary reflection and the extraordinary one whose wavefront is manipulated by the proposed impedance-governed generalized Snell's law of reflection (IGSL). IGSL is based on Green's function and integral equation, instead of Fermat's principle for optical wavefront manipulation. Remarkably, via the adjustment of the designed specific acoustic impedance, extraordinary reflection can be steered for unprecedented acoustic wavefront while that ordinary reflection can be surprisingly switched on or off. The realization of the complex discontinuity of the impedance surface has been proposed using Helmholtz resonators.

143 citations


Book ChapterDOI
18 Mar 2013
TL;DR: In this article, collisionless plasmas are discussed and it is shown that ion reflection is the dominant ion dissipation mechanism at nearly perpendicular, supercritical shocks and that an increasing fraction of the ions incident on a supercritical shock is reflected as the Mach number increases.
Abstract: Topics on collisionless plasmas are discussed and include: (1) Ion reflection is the dominant ion dissipation mechanism at nearly perpendicular, supercritical shocks. (2) An increasing fraction of the ions incident on a supercritical shock is reflected as the Mach number increases. The actual fraction reflected can be predicted using the Rankine Hugoniot conservation relations. (3) The effective temperature associated with the dispersion in velocity space associated with ion reflection accounts for a large fraction of the temperature rise observed across supercritical, quasi perpendicular shocks.

137 citations


Journal ArticleDOI
TL;DR: In this article, a flat acoustic metasurface that generates an extraordinary reflection is demonstrated, and the arbitrary direction of the extraordinary reflection can be predicted by a Green's function formulation.
Abstract: When acoustic waves are impinged on an impedance surface in fluids, it is challenging to alter the vibration of fluid particles since the vibrational direction of reflected waves shares the same plane of the incidence and the normal direction of the surface. We demonstrate a flat acoustic metasurface that generates an extraordinary reflection, and such metasurface can steer the vibration of the reflection out of the incident plane. Remarkably, the arbitrary direction of the extraordinary reflection can be predicted by a Green's function formulation, and our approach can completely convert the incident waves into the extraordinary reflection without parasitic ordinary reflection.

131 citations


Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate that 100% light absorption can be achieved in a graphene-based hyperbolic metamaterial, consisting of periodically arranged graphene layers which are tilted with respect to the interface.
Abstract: We demonstrate that 100% light absorption can be achieved in a graphene-based hyperbolic metamaterial, consisting of periodically arranged graphene layers which are tilted with respect to the interface. The geometrical parameters of the multilayered structure and the chemical potential of graphene are chosen in such a way that the in-plane relative effective permittivity is close to 1. Under this condition, the graphene multilayer exhibits asymmetry which appears as a very large difference between waves propagating upward and downward with respect to multilayer boundaries. One of them has a very high attenuation constant and neither of the waves undergo reflection at slab interfaces, resulting in total absorption even for an optically ultra-thin slab.

124 citations



Journal ArticleDOI
TL;DR: In this paper, a relativistic flying mirror in plasmas is used to accelerate a high-intensity electromagnetic wave to velocities close to the speed of light in the vacuum, where refractive index modulations are induced by a strong electromagnetic wave.
Abstract: Relativistic flying mirrors in plasmas are thin, dense electron or electron-ion layers accelerated by high-intensity electromagnetic waves to velocities close to the speed of light in the vacuum; in nonlinear media, refractive index modulations are induced by a strong electromagnetic wave. The reflection of the electromagnetic wave from the relativistic mirror results in its energy and frequency changing. In the counter-propagation configuration, the frequency of the reflected wave is multiplied by the factor proportional to the gamma-factor squared. This scientific area promises the development of sources of ultrashort X-ray pulses in the attosecond range. The expected intensity will reach the level at which the effects predicted by nonlinear quantum electrodynamics start to play a key role. In the co-propagating configuration, the energy of the electromagnetic wave is transferred to the ion energy, providing a highly efficient acceleration mechanism.

121 citations


Journal ArticleDOI
TL;DR: In this article, the authors consider single-layer arrays of electrically small lossy particles that completely absorb electromagnetic waves at normal incidence and consider the design possibilities of all four fundamental classes of bi-anisotropic inclusions: reciprocal chiral and omega particles, non-reciprocal Tellegen and moving particles.
Abstract: We consider single-layer arrays of electrically small lossy particles that completely absorb electromagnetic waves at normal incidence. Required conditions for electromagnetic properties of bi-anisotropic particles have been identified in the most general case of uniaxial reciprocal and nonreciprocal particles. We consider the design possibilities offered by the particles of all four fundamental classes of bi-anisotropic inclusions: reciprocal chiral and omega particles and nonreciprocal Tellegen and moving particles. We also study the reflection/transmission properties of asymmetric structures with different properties when illuminated from the opposite sides of the sheet. It has been found that it is possible to realize single-layer grids which exhibit the total absorption property when illuminated from one side but are totally transparent when illuminated from the other side (an ultimately thin isolator). Other possible properties are co-polarized or twist polarized reflection from the side opposite to the absorbing one. Finally, we discuss possible approaches to practical realization of particles with the properties required for single-layer perfect absorbers and other proposed devices.

Journal ArticleDOI
TL;DR: An efficient method to separate the diffuse and specular reflection components from a single image, built on the observation that the intensity ratios between the maximum values and range values are independent of surface geometry.
Abstract: In this paper, we propose an efficient method to separate the diffuse and specular reflection components from a single image. The method is built on the observation that, for diffuse pixels, the intensity ratios between the maximum values and range values (maximums minus minimums) are independent of surface geometry. The specular fractions of the image pixels can then be computed by using the intensity ratio. For textured surfaces, image pixels are classified into clusters by constructing a pseudo-chromaticity space, and the intensity ratio of each cluster is robustly estimated. Unlike existing techniques, the proposed method works in a pixel-wise manner, without specular pixel identification and any local interaction. Experimental results show that the proposed method runs 4× faster than the state of the art and produces improved accuracy in specular highlight removal.

Patent
11 Nov 2013
TL;DR: In this article, the problem of providing a panel-type building material with a dielectric antenna in which a beautiful color tone is provided or a pattern is drawn on a surface is addressed.
Abstract: PROBLEM TO BE SOLVED: To provide a panel-type building material with a dielectric antenna in which a beautiful color tone is provided or a pattern is drawn apparently on a surface.SOLUTION: The panel-type building material with the dielectric antenna includes a semiconductor power generation layer 2 in which a number of rod antennas 3 are disposed. A height of the rod antenna 3 in a vertical direction with respect to a surface of the semiconductor power generation layer 2 is 0.01 to 40 times as high as a maximum sensitivity wavelength of the semiconductor power generation layer. A radius of the rod antenna 3 is 0.005 to 1.5 times as large as the height. Between the rod antennas 3, a reflection layer 6 is provided that reflects a part of electromagnetic waves from the sun. The reflection layer 6 may be formed from a material of which the specific dielectric constant is lower than that of the rod antenna 3 and since materials of various color tones are selectable, the surface of the panel-type building material with the dielectric antenna can be colored or patterns can be drawn thereon.

Posted Content
TL;DR: In this article, a tabletop coherent high harmonic light source at 29 nm illuminates a nanopatterned surface at 45 degree angle of incidence, and the reconstructed image contains quantitative amplitude and phase information, comparing favorably with both scanning electron microscope and atomic force microscopy images.
Abstract: We demonstrate high resolution extreme ultraviolet (EUV) coherent diffractive imaging in the most general reflection geometry by combining ptychography with tilted plane correction. This method makes it possible to image extended surfaces at any angle of incidence. Refocused light from a tabletop coherent high harmonic light source at 29 nm illuminates a nanopatterned surface at 45 degree angle of incidence. The reconstructed image contains quantitative amplitude and phase (in this case pattern height) information, comparing favorably with both scanning electron microscope and atomic force microscopy images. In the future, this approach will enable imaging of complex surfaces and nanostructures with sub-10 nm-spatial resolution and fs-temporal resolution, which will impact a broad range of nanoscience and nanotechnology including for direct application in actinic inspection in support of EUV lithography.

Journal ArticleDOI
TL;DR: In this article, a type of light absorber made of continuous layers of metal and dielectric films is studied, where the metal films can have thicknesses close to their skin depths in the wavelength range concerned, which allows for both light transmission and reflection.
Abstract: A type of light absorber made of continuous layers of metal and dielectric films is studied. The metal films can have thicknesses close to their skin depths in the wavelength range concerned, which allows for both light transmission and reflection. Resonances induced by multiple reflections in the structure, when combined with the inherent lossy nature of metals, result in strong absorption spectral features. An eigen-mode analysis is carried out for the plasmonic multilayer nanostructures which provides a generic understanding of the absorption features. Experimentally, the calculation is verified by a reflection measurement with a representative structure. Such an absorber is simple to fabricate. The highly efficient absorption characteristics can be potentially deployed for optical filter designs, sensors, accurate photothermal temperature control in a micro-environment and even for backscattering reduction of small particles, etc.

Journal ArticleDOI
TL;DR: In this paper, the ground motion at a seismic station contains information about the structure in the vicinity of the site, and this can be exploited by applying an autocorrelation procedure to the continuous records.
Abstract: S U M M A R Y Stations on the Australian continent receive a rich mixture of continuous ground motion with ambient seismic noise from the surrounding oceans, and numerous small earthquakes in the earthquake belts to the north in Indonesia, and east in Tonga-Kermadec, as well as more distant source zones. The ground motion at a seismic station contains information about the structure in the vicinity of the site, and this can be exploited by applying an autocorrelation procedure to the continuous records. By creating stacked autocorrelograms of the ground motion at a single station, information on crust properties can be extracted in the form of a signal that includes the crustal reflection response convolved with the autocorrelation of the combined effect of source excitation and the instrument response. After applying suitable high-pass filtering, the reflection component can be extracted to reveal the most prominent reflectors in the lower crust, which often correspond to the reflection at the Moho. Because the reflection signal is stacked from arrivals from a wide range of slownesses, the reflection response is somewhat diffuse, but still sufficient to provide useful constraints on the local crust beneath a seismic station. Continuous vertical component records from 223 stations (permanent and temporary) across the continent have been processed using autocorrelograms of running windows 6 hr long with subsequent stacking.A distinctive pulsewith a time offset between 8 and 30 s fromzero is found in the autocorrelation results, with frequency content between 1.5 and 4 Hz, suggestingP-wave multiples trapped in the crust. Synthetic modelling, with control of multiple phases, shows that a local pmp phase can be recovered with the autocorrelation approach. This identification enables us to make out the depth to the most prominent crustal reflector across the continent. We obtain results that largely conform to those from previous studies using a combination of data from refraction, reflection profiles and receiver functions. This approach can be used for crustal property extraction using just vertical component records, and effective results can be obtained with temporary deployments of just a few months.

Journal ArticleDOI
TL;DR: In this article, the interaction of electromagnetic (EM) radiation with single-layer graphene and a stack of parallel graphene sheets at arbitrary angles of incidence was studied, and it was shown that the behavior is qualitatively different for transverse magnetic (or p-polarized) and transverse electric (or spolarised) waves, and that the absorbance of single layer graphene attains a minimum (maximum) for the p (s)-polarization at the angle of total internal reflection when the light comes from a medium with a higher dielectric constant.
Abstract: We study the interaction of electromagnetic (EM) radiation with single-layer graphene and a stack of parallel graphene sheets at arbitrary angles of incidence. It is found that the behavior is qualitatively different for transverse magnetic (or p-polarized) and transverse electric (or s-polarized) waves. In particular, the absorbance of single-layer graphene attains a minimum (maximum) for the p (s)-polarization at the angle of total internal reflection when the light comes from a medium with a higher dielectric constant. In the case of equal dielectric constants of the media above and beneath graphene, for grazing incidence graphene is almost 100% transparent to p-polarized waves and acts as a tunable mirror for the s-polarization. These effects are enhanced for a stack of graphene sheets, so the system can work as a broad band polarizer. It is shown further that a periodic stack of graphene layers has the properties of a one-dimensional photonic crystal, with gaps (or stop bands) at certain frequencies. When an incident EM wave is reflected from this photonic crystal, the tunability of the graphene conductivity renders the possibility of controlling the gaps, and the structure can operate as a tunable spectral-selective mirror.

Journal ArticleDOI
TL;DR: In this article, the authors extracted global body wave propagation (of P, PP, PKP, S, SS, ScS, P′P′, etc. waves) using seismic hum with frequency-wave number filtering in the range of 5 to 40 µmHz.
Abstract: [1] Seismic interferometry has now been applied to the exploration of the Earth's interior at scales ranging from local to global. Most studies have used surface-wave propagation. Recently, some studies have focused on body wave propagation on local and regional scales but not on a global scale. In this study, we succeed in extracting global body wave propagation(of P, PP, PKP, S, SS, ScS, P′P′, etc. waves) using seismic hum with frequency-wave number filtering in the range of 5 to 40 mHz. Although the observed body wave propagation is similar to that of the corresponding components of Green's functions, there are two differences between them: the lack of reflection phases in the observation and the dominance of shear-coupled PL waves in the observation. These differences originate from the dominance of shear-traction sources on the Earth's surface, which causes the breakdown of equipartition among modes with different radial orders. For further studies of body wave exploration by seismic interferometry, these differences should be considered.

Journal ArticleDOI
TL;DR: It is demonstrated for the first time that dense relativistic electron mirrors can be created from the interaction of a high-intensity laser pulse with a freestanding, nanometre-scale thin foil.
Abstract: Reflecting light from a mirror moving close to the speed of light has been envisioned as a route towards producing bright X-ray pulses since Einstein’s seminal work on special relativity For an ideal relativistic mirror, the peak power of the reflected radiation can substantially exceed that of the incident radiation due to the increase in photon energy and accompanying temporal compression Here we demonstrate for the first time that dense relativistic electron mirrors can be created from the interaction of a high-intensity laser pulse with a freestanding, nanometre-scale thin foil The mirror structures are shown to shift the frequency of a counter-propagating laser pulse coherently from the infrared to the extreme ultraviolet with an efficiency 410 4 times higher than in the case of incoherent scattering Our results elucidate the reflection process of laser-generated electron mirrors and give clear guidance for future developments of a relativistic mirror structure

Journal ArticleDOI
TL;DR: Reflection mid-infrared spectroscopy is proved to be a reliable and sensitive spectro-analytical method for identifying and mapping different metal-oxalate alteration compounds on the surface of artworks, thus providing conservation scientists with a non-invasive tool to obtain information on the state of conservation and causes of alteration of artwork.

Journal ArticleDOI
TL;DR: In this paper, a hybrid approach combining a finite element and a wave and finite element (WFE) model is presented for calculating the reflection and transmission coefficients of a joint, which allows for developing a model of the structure where the basis functions are the waves travelling through the structure's various waveguides.



Journal ArticleDOI
TL;DR: In this paper, a matched eigenfunction expansion method is applied to obtain the analytic solution for the interaction of oblique monochromatic incident waves with a submerged horizontal porous plate in the context of two-dimensional linear potential theory.


Journal ArticleDOI
TL;DR: In this article, the authors observed the diffraction, refraction, and reflection of a global extreme-ultraviolet (EUV) wave propagating in the solar corona, and they concluded that the EUV wave should be a nonlinear magnetosonic wave or shock driven by the associated coronal mass ejection (CME).
Abstract: We present observations of the diffraction, refraction, and reflection of a global extreme-ultraviolet (EUV) wave propagating in the solar corona. These intriguing phenomena are observed when the wave interacts with two remote active regions, and together they exhibit properties of an EUV wave. When the wave approached AR11465, it became weaker and finally disappeared in the active region, but a few minutes later a new wavefront appeared behind the active region, and it was not concentric with the incoming wave. In addition, a reflected wave was also simultaneously observed on the wave incoming side. When the wave approached AR11459, it transmitted through the active region directly and without reflection. The formation of the new wavefront and the transmission could be explained with diffraction and refraction effects, respectively. We propose that the different behaviors observed during the interactions may be caused by different speed gradients at the boundaries of the two active regions. We find that the EUV wave formed ahead of a group of expanding loops a few minutes after the start of the loops' expansion, which represents the initiation of the associated coronal mass ejection (CME). Based on these results, we conclude that the EUV wave should be a nonlinear magnetosonic wave or shock driven by the associated CME, which propagated faster than the ambient fast mode speed and gradually slowed down to an ordinary linear wave. Our observations support the hybrid model that includes both fast wave and slow non-wave components.

Journal ArticleDOI
TL;DR: In this paper, the anomalous amplitude distribution of the acoustic waves at Stromboli is not necessarily due to the source radiation pattern but it is strongly influenced by the topography of the ground-atmosphere interface.

01 Jul 2013
Abstract: The effects of micro-ramp height and location on a shock induced separation bubble were quantified using planar particle image velocimetry measurements. Conditional averaging was used to show that the amount of separation is related to the momentum flux in the near-wall region (< 0.5?) of the incoming boundary layer. The momentum flux added to this region scales linearly with micro-ramp height and larger microramps are shown to be more effective in stabilizing the interaction. Full boundary layer mixing is attained 5.? downstream of the micro-ramp and this forms a lower limit on the required distance between microramp and reflected shock foot.

Journal ArticleDOI
TL;DR: In this article, the authors analyzed spectra for all active galactic nuclei (AGNs) in the Rossi X-ray Timing Explorer archive, and calculated fluxes and luminosities in the 2-10 keV band for 100 AGNs with sufficient brightness and overall observation time.
Abstract: We have analyzed spectra for all active galactic nuclei (AGNs) in the Rossi X-ray Timing Explorer archive. We present long-term average values of absorption, Fe line equivalent width (EW), Compton reflection, and photon index, and calculate fluxes and luminosities in the 2-10 keV band for 100 AGN with sufficient brightness and overall observation time to yield high-quality spectral results. We compare these parameters across the different classifications of Seyferts and blazars. Our distributions of photon indices for Seyfert 1s and 2s are consistent with the idea that Seyferts share a common central engine; however, our distributions of Compton reflection hump strengths do not support the classical picture of absorption by a torus and reflection off a Compton-thick disk with type depending only on inclination angle. We conclude that a more complex reflecting geometry such as a combined disk and torus or clumpy torus is likely a more accurate picture of the Compton-thick material. We find that Compton reflection is present in ~85% of Seyferts and by comparing Fe line EW's to Compton reflection hump strengths we have found that on average 40% of the Fe line arises in Compton thick material; however, this ratio was not consistent from object to object and did not seem to be dependent on optical classification.