Showing papers on "Reflection (physics) published in 2011"

Light Propagation with Phase Discontinuities: Generalized Laws of Reflection and Refraction

Abstract: Conventional optical components rely on gradual phase shifts accumulated during light propagation to shape light beams. New degrees of freedom are attained by introducing abrupt phase changes over the scale of the wavelength. A two-dimensional array of optical resonators with spatially varying phase response and subwavelength separation can imprint such phase discontinuities on propagating light as it traverses the interface between two media. Anomalous reflection and refraction phenomena are observed in this regime in optically thin arrays of metallic antennas on silicon with a linear phase variation along the interface, which are in excellent agreement with generalized laws derived from Fermat’s principle. Phase discontinuities provide great flexibility in the design of light beams, as illustrated by the generation of optical vortices through use of planar designer metallic interfaces.

Reflection of normally incident light from silicon solar cells with pyramidal texture

Abstract: A surface texture enhances the capacity of a solar cell to absorb incident radiation. In high efficiency and industry standard designs alike, pyramidal surface textures play the key role of reducing the reflectance of the cell surface. This reduction is achieved by ensuring that incident light rays suffer at least a double reflection in the various facets of the structure. In this work, we define a general expression for the reflectance of a pyramidal texture by identifying discrete paths of reflection and the fraction of reflected light that follows each of these paths. We apply the expression to analyse the reflection of normally incident light at textured surfaces. We examine three common morphologies, finding that a regular array of inverted pyramids just outperforms a random array of upright pyramids, with a regular array of upright pyramids showing poorer capacity to reduce front surface reflection. We extend the analysis to determine the transmittance of the various structures, thus permitting the calculation of a figure of merit that can be used to optimise the thickness of antireflection coatings (ARCs). Finally, by examining the angles at which light is reflected by the pyramidal textures, we find that an encapsulant of refractive index greater than 1.59 gives between 79 and 92% of the initially reflected light a second chance to enter the solar cell.

Enhanced and switchable spin Hall effect of light near the Brewster angle on reflection

Abstract: We theorize an enhanced and switchable spin Hall effect (SHE) of light near the Brewster angle on reflection and demonstrate it experimentally. The obtained spin-dependent splitting reaches 3200 nm near the Brewster angle, which is 50 times larger than the previously reported values in refraction. We find that the amplifying factor in weak measurement is not a constant, which is significantly different from that in refraction. As an analogy of SHE in an electronic system, a switchable spin accumulation in SHE of light is detected. We were able to switch the direction of the spin accumulations by slightly adjusting the incident angle.

Propagating Waves Along Spicules

Abstract: Alfvenic waves are thought to play an important role in coronal heating and acceleration of solar wind. Here we investigate the statistical properties of Alfvenic waves along spicules (jets that protrude into the corona) in a polar coronal hole using high-cadence observations of the Solar Optical Telescope on board Hinode. We developed a technique for the automated detection of spicules and high-frequency waves. We detected 89 spicules and found (1) a mix of upward propagating, downward propagating, as well as standing waves (occurrence rates of 59%, 21%, and 20%, respectively); (2) the phase speed gradually increases with height; (3) upward waves dominant at lower altitudes, standing waves at higher altitudes; (4) standing waves dominant in the early and late phases of each spicule, while upward waves were dominant in the middle phase; (5) in some spicules, we find waves propagating upward (from the bottom) and downward (from the top) to form a standing wave in the middle of the spicule; and (6) the medians of the amplitude, period, and velocity amplitude were 55 km, 45 s, and 7.4 km s–1, respectively. We speculate that upward propagating waves are produced near the solar surface (below the spicule) and downward propagating waves are caused by reflection of (initially) upward propagating waves off the transition region at the spicule top. The mix of upward and downward propagating waves implies that exploiting these waves to perform seismology of the spicular environment requires careful analysis and may be problematic.

Three-dimensional continuous particle focusing in a microfluidic channel via standing surface acoustic waves (SSAW).

Abstract: Three-dimensional (3D) continuous microparticle focusing has been achieved in a single-layer polydimethylsiloxane (PDMS) microfluidic channel using a standing surface acoustic wave (SSAW). The SSAW was generated by the interference of two identical surface acoustic waves (SAWs) created by two parallel interdigital transducers (IDTs) on a piezoelectric substrate with a microchannel precisely bonded between them. To understand the working principle of the SSAW-based 3D focusing and investigate the position of the focal point, we computed longitudinal waves, generated by the SAWs and radiated into the fluid media from opposite sides of the microchannel, and the resultant pressure and velocity fields due to the interference and reflection of the longitudinal waves. Simulation results predict the existence of a focusing point which is in good agreement with our experimental observations. Compared with other 3D focusing techniques, this method is non-invasive, robust, energy-efficient, easy to implement, and applicable to nearly all types of microparticles.

Full-azimuth subsurface angle domain wavefield decomposition and imaging Part I: Directional and reflection image gathers

Abstract: We present a new subsurface angle-domain seismic imaging systemforgeneratingandextractinghigh-resolutioninformation about subsurface angle-dependent reflectivity. The system enables geophysicists to use all recorded seismic data in a continuousfashiondirectlyinthesubsurfacelocalangledomainLAD, resulting in two complementary, full-azimuth, common-imageangle gather systems: directional and reflection. The complete setofinformationfrombothtypesofanglegathersleadstoaccurate, high-resolution, reliable velocity model determination and reservoir characterization. The directional angle decomposition enables the implementation of specular and diffraction imaging in real 3D isotropic/anisotropic geological models, leading to simultaneous emphasis on continuous structural surfaces and discontinuous objects such as faults and small-scale fractures. Structural attributes at each subsurface point, e.g., dip, azimuth andcontinuity,canbederiveddirectlyfromthedirectionalangle gathers. The reflection-angle gathers display reflectivity as a function of the opening angle and opening azimuth. These gathers are most meaningful in the vicinity of actual local reflecting surfaces,wherethereflectionanglesaremeasuredwithrespectto the derived background specular direction. The reflection-angle gathers are used for automatic picking of full-azimuth angle-domainresidualmoveoutsRMOwhich,togetherwiththederived background orientations of the subsurface reflection horizons, provide a complete set of input data to isotropic/anisotropic tomography. The full-azimuth, angle-dependent amplitude variations are used for reliable and accurate amplitude versus angle andazimuthAVAZanalysisandreservoircharacterization.The proposed system is most effective for imaging and analysis below complex structures, such as subsalt and subbasalt, high-velocity carbonate rocks, shallow low-velocity gas pockets, and others. In addition, it enables accurate azimuthal anisotropic imaging and analysis, providing optimal solutions for fracture detectionandreservoircharacterization.

Finite-difference modeling experiments for seismic interferometry

Abstract: In passive seismic interferometry, new reflection data can be retrieved by crosscorrelating recorded noise data. The quality of the retrieved reflection data is, among others, dependent on the duration and number of passive sources present during the recording time, the source distribution, and the source strength. To investigate these relations we set up several numerical modeling studies. To carry out the modeling in a feasible time, we design a finite-difference algorithm for the simulation of long-duration passive seismic measurements of band-limited noise signatures in the subsurface. Novel features of the algorithm include the modeling of thousands of randomly placed sources during one modeling run. The modeling experiments explore the dependency relation between the retrieved reflections and source-signature length, source positions, number of sources, and source amplitude variations. From these experiments we observed that the positions of the passive sources and the length of the source signals are of direct influence on the quality of the retrieved reflections. Random amplitude variations among source signals do not seem to have a big impact on the retrieved reflections.

Interaction of highly nonlinear solitary waves with linear elastic media.

Abstract: We study the interaction of highly nonlinear solitary waves propagating in granular crystals with an adjacent linear elastic medium. We investigate the effects of interface dynamics on the reflection of incident waves and on the formation of primary and secondary reflected waves. Experimental tests are performed to correlate the linear medium geometry, materials, and mass with the formation and propagation of reflected waves. We compare the experimental results with theoretical analysis based on the long-wavelength approximation and with numerical predictions obtained from discrete particle models. Experimental results are found to be in agreement with theoretical analysis and numerical simulations. This preliminary study establishes the foundation for utilizing reflected solitary waves as novel information carriers in nondestructive evaluation of elastic material systems.

Dynamic three-dimensional sensing for specular surface with monoscopic fringe reflectometry.

Abstract: Dynamic full-field three-dimensional sensing of specular reflective surfaces can be conveniently implemented with fringe reflection technique. A monoscopic fringe reflectometric system can be adopted as a simple measuring setup. With the assistance of the windowed Fourier ridges method as an advanced fringe demodulation technique, only one cross grating is needed to reconstruct the three-dimensional surface shape changes. A suitable calibration enables determination of the actual three-dimensional surface profile. Experimental results of water wave variations are shown to demonstrate the feasibility of the proposed approach.

Millimeter-Wave Microstrip Comb-Line Antenna Using Reflection-Canceling Slit Structure

Abstract: A microstrip comb-line antenna is developed in the millimeter-wave band. When the element spacing is one guide wavelength for the broadside beam in the traveling-wave excitation, reflections from all the radiating elements are synthesized in phase. Therefore, the return loss increases significantly. Furthermore, re-radiation from elements due to the reflection wave degrades the design accuracy for the required radiation pattern. We propose the way to improve the reflection characteristic of the antenna with arbitrary beam directions including strictly a broadside direction. To suppress the reflection, we propose a reflection-canceling slit structure installed on the feeding line around each radiating element. A 27-element linear array antenna with a broadside beam is developed at 76.5 GHz. To confirm the feasibility of the simple design procedure, the performance is evaluated through the measurement in the millimeter-wave band.

RTM Angle Gathers Using Poynting Vectors

Abstract: Angle-domain common image gathers have been shown to provide several advantages for the analysis of migrated images. In this abstract we describe an efficient new method for creating angle gathers for reverse time migration (RTM). The method relies on the computation of the direction of energy flux (known in electromagnetics as the Poynting vector) in the space-time domain. Given the Poynting vectors for source and receiver wavefields, we may readily derive reflection angle and azimuth, and reflector dip and azimuth if desired. Unlike some previously considered angle-gather algorithms, the method depends only on local information at the reflection point, thereby avoiding the loss of resolution inherent in mixing quantities from different horizontal locations. In addition, we derive the weight function needed to produce correct relative amplitudes for these angle gathers.

Determination of the X-ray reflection emissivity profile of 1H 0707-495

Abstract: When considering the X-ray spectrum resulting from the reflection off the surface of accretion discs of AGN, it is necessary to account for the variation in reflected flux over the disc, i.e. the emissivity profile. This will depend on factors including the location and geometry of the X-ray source and the disc characteristics. We directly obtain the emissivity profile of the disc from the observed spectrum by considering the reflection component as the sum of contributions from successive radii in the disc and fitting to find the relative weightings of these components in a relativistically broadened emission line. This method has successfully recovered known emissivity profiles from synthetic spectra and is applied to XMM–Newton spectra of the Narrow Line Seyfert 1 galaxy 1H 0707-495. The data imply a twice-broken power-law form of the emissivity law with a steep profile in the inner regions of the disc (index 7.8) and then a flat region between 5.6 and 34.8rg before tending to a constant index of 3.3 over the outer regions of the disc. The form of the observed emissivity profile is consistent with theoretical predictions, thus reinforcing the reflection interpretation.

Three-Dimensional Near-Field Microwave Holography Using Reflected and Transmitted Signals

Abstract: A new 3-D holographic microwave imaging technique is proposed to reconstruct targets in the near-field range. It is based on the Fourier analysis of the wideband transmission and reflection signals recorded by two antennas scanning together along two rectangular parallel apertures on both sides of the inspected region. The complex scattering parameters of the two antennas are collected at several frequencies and then processed to obtain a representation of the 3-D target in terms of 2-D slice images at all desired range locations. No assumptions are made about the incident field and Green's function, which are derived either by simulation or by measurement. Furthermore, an approach is proposed to reduce the image artifacts along range. To validate the proposed technique, predetermined simulated targets are reconstructed. The effects of random noise, number of sampling frequencies, and dielectric contrast of the targets are also discussed.

Properties of Propagation of Electromagnetic Wave in a Multilayer Radar-Absorbing Structure With Plasma- and Radar-Absorbing Material

Abstract: A multilayer radar-absorbing structure with plasma- and radar-absorbing material (RAM) is established to investigate the stealth mechanisms of the multilayer absorber. The method of impedance transformation with multiple dielectrics is used to analyze the propagation of electromagnetic (EM) waves in the multilayer structure. The dependences of EM waves attenuation on the parameters of the plasma and RAMs are provided. The numerical results indicate that generally speaking, the joint attention effect of RAM and plasma is better than the effect of either RAM or plasma solely. The attenuation of an EM wave in the structure is strongly affected by: a) the characteristics of RAMs; b) the width of the plasma layer; c) the parameters of the outer layer material; d) the electron density of the plasma; and e) the collision frequency between electrons and neutrals. It is demonstrated that detailed numerical analyses are useful in practical applications pertaining to the control of the reflection of EM waves through a multilayer radar-absorbing structure with plasma and RAMs.

Numerical simulations of conversion to Alfven waves in sunspots

Abstract: We study the conversion of fast magneto-acoustic waves to Alfven waves by means of 2.5D numerical simulations in a sunspot-like magnetic configuration. A fast, essentially acoustic, wave of a given frequency and wave number is generated below the surface and propagates upward though the Alfven/acoustic equipartition layer where it splits into upgoing slow (acoustic) and fast (magnetic) waves. The fast wave quickly reflects off the steep Alfven speed gradient, but around and above this reflection height it partially converts to Alfven waves, depending on the local relative inclinations of the background magnetic field and the wavevector. To measure the efficiency of this conversion to Alfven waves we calculate acoustic and magnetic energy fluxes. The particular amplitude and phase relations between the magnetic field and velocity oscillations help us to demonstrate that the waves produced are indeed Alfven waves. We find that the conversion to Alfven waves is particularly important for strongly inclined fields like those existing in sunspot penumbrae. Equally important is the magnetic field orientation with respect to the vertical plane of wave propagation, which we refer to as "field azimuth". For field azimuth less than 90 degrees the generated Alfven waves continue upwards, but above 90 degrees downgoing Alfven waves are preferentially produced. This yields negative Alfven energy flux for azimuths between 90 and 180 degrees. Alfven energy fluxes may be comparable to or exceed acoustic fluxes, depending upon geometry, though computational exigencies limit their magnitude in our simulations.

3D RTM angle gathers from source wave propagation direction and dip of reflector

Abstract: Summary Creating an angle gather is a conceptually simple process of plotting reflection amplitudes along the angle. Reflection or opening angle can be directly calculated from source and receiver wave propagation directions or source propagation direction and dip of the reflector. We studied a cost effective approach to generate 3D Reverse Time Migration (RTM) angle gathers from source wave propagation direction and dip information. This is a mapping process of the shot image onto an angle and azimuth plane using the most energetic arrivals and their amplitudes and propagation directions.

Integrated Polarization Analyzing CMOS Image Sensor for Material Classification

Abstract: Material classification is an important application in computer vision. The inherent property of materials to partially polarize the reflected light can serve as a tool to classify them. In this paper, a real-time polarization sensing CMOS image sensor using a wire grid polarizer is proposed. The image sensor consist of an array of 128 × 128 pixels, occupies an area of 5 × 4 mm2 and it has been designed and fabricated in a 180-nm CMOS process. We show that this image sensor can be used to differentiate between metal and dielectric surfaces in real-time due to the different nature in partially polarizing the specular and diffuse reflection components of the reflected light. This is achieved by calculating the Fresnel reflection coefficients, the degree of polarization and the variations in the maximum and minimum transmitted intensities for varying specular angle of incidence. Differences in the physical parameters for various metal surfaces result in different surface reflection behavior, influencing the Fresnel reflection coefficients. It is also shown that the image sensor can differentiate among various metals by sensing the change in the polarization Fresnel ratio.

The reflection of the fundamental torsional guided wave from multiple circular holes in pipes

Abstract: Localised corrosion is a major concern in the petrochemical industry, and often occurs as clusters of pits. A study of the reflection from two and three small circular holes in pipes with the fundamental torsional guided wave incident is presented. FE analyses with both part and through thickness holes at different relative positions are presented, and are a step towards estimation of the scattering behaviour of multiple and random defects. The validity of employing the superposition technique in estimating reflection coefficients is assessed. Results show that the reflection coefficient for the T (0,1) mode is dependent on absolute frequency and axial separation, and independent of circumferential position. Employing superposition is found to be valid down to defect centre to centre separation distances of two diameters in the worst case, with improved validity with shallower defects. Results from the FE analyses are validated experimentally.

Asymptotic reflection of linear water waves by submerged horizontal porous plates

Abstract: On the basis of linear water-wave theory, an explicit expression is presented for the reflection coefficient R ∞ when a plane wave is obliquely incident upon a semi-infinite porous plate in water of finite depth The expression, which correctly models the singularity in velocity at the edge of the plate, does not rely on knowledge of any of the complex-valued eigenvalues or corresponding vertical eigenfunctions in the region occupied by the plate The solution R ∞ is the asymptotic limit of the reflection coefficient R as a → ∞, for a plate of finite length a bounded by a rigid vertical wall, and forms the basis of a rapidly convergent expansion for R over a wide range of values of a The special case of normal incidence is relevant to the design of submerged wave absorbers in a narrow wave tank Modifications necessary to account for a finite submerged porous plate in a fluid extending to infinity in both horizontal directions are discussed

Photonic band gaps in one-dimensionally ordered cold atomic vapors.

Abstract: We experimentally investigate the Bragg reflection of light at one-dimensionally ordered atomic structures by using cold atoms trapped in a laser standing wave. By a fine-tuning of the periodicity, we reach the regime of multiple reflection due to the refractive index contrast between layers, yielding an unprecedented high reflectance efficiency of 80%. This result is explained by the occurrence of a photonic band gap in such systems, in accordance with previous predictions.

Direct determination of the refractive index of natural multilayer systems.

Abstract: It is well known that the metal-like strong reflection observed in the elytra of some kinds of beetles is produced by multilayer thin-film interference. For the quantitative analyses of the structural colors in these elytra, it is necessary to know accurate values of the refractive indices of the materials that comprise the multilayer structure. However, index determination is not an easy task: The elytron surface is not flat but curved and usually contains many irregular bumps, which cause scattering loss. These structural characteristics prevent us from directly applying conventional optical techniques for index determination, such as ellipsometry, since these techniques require a perfectly specular surface. In this paper, we report a new experimental procedure that can directly determine the refractive indices of individual layers in natural multilayer systems. This procedure involves semi-frontal thin-sectioning of the sample and subsequent optical examinations using a microspectrophotometer. We demonstrate that the complex refractive index and its wavelength dependence can be successfully determined for one kind of beetle.

Boundary Effects on the Determination of Metamaterial Parameters From Normal Incidence Reflection and Transmission Measurements

Abstract: A method is described for the determination of the effective electromagnetic parameters of a metamaterial based only on external measurements or simulations, taking boundary effects at the interfaces between a conventional material and metamaterial into account. Plane-wave reflection and transmission coefficients at the interfaces are regarded as additional unknowns to be determined, rather than explicitly dependent on the material parameters. Our technique is thus analogous to the line-reflect-line (LRL) calibration method in microwave measurements. The refractive index can be determined from S-parameters for two samples of different thickness. The effective wave impedance requires the additional assumption that generalized sheet transition conditions (GSTCs) account for the boundary effects. Expressions for the bulk permittivity and permeability then follow easily. Our method is validated by comparison with the results using the Nicolson-Ross-Weir (NRW) for determining properties of an ordinary material measured in a coaxial line. Utilizing S-parameters obtained from 3-D full wave simulations, we test the method on magnetodielectric metamaterials. We compare the results from our method and the conventional one that does not consider boundary effects. Moreover, it is shown that results from our method are consistent under changes in reference plane location, whereas the results from other methods are not.

Encyclopedia of solid earth geophysics

Abstract: Absolute Age Determinations: Radiometric.-Archaeomagnetism.-Archaeoseismology.-Artificial Water Reservoir Triggered Earthquakes.-Biogeophysics.-Body Waves.-Characteristic Earthquakes and Seismic Gaps.-Continental Drift.-Continental Rifts.-Core Dynamo.-Core-Mantle Coupling.-Crustal Reflectivity (Oceanic) and Magma Chamber.-Curie Temperature.-Deep Scientific Drilling.-Deep Seismic Reflection and Refraction Profiling.-Differential Rotation of the Earth's Inner Core.-Earth Rotation.-Earth Tides.-Earth, Density Distribution.-Earth's Structure, Core.-Earth's Structure, Continental Crust.-Earth's Structure, Global.-Earth's Structure, Lower Mantle.-Earth's Structure, Upper Mantle.-Earthquake Lights.-Earthquake Precursors and Prediction.-Earthquake Prediction, M8 Algorithm.-Earthquake Rupture: Inverse Problem.-Earthquake Sounds.-Earthquake, Aftershocks.-Earthquake, Focal Mechanism.-Earthquake, Foreshocks.-Earthquake, Location Techniques.-Earthquake, Magnitude.-Earthquakes and Crustal Deformation.-Earthquakes, Early and Strong Motion Warning.-Earthquakes, Energy.-Earthquakes, Intensity.-Earthquakes, PAGER.-Earthquakes, Shake Map.-Earthquakes, Source Theory.-Earthquakes, Strong-Ground Motion.-Earthquakes, Volcanogenic.-Electrical Properties of Rocks.-Electrical Resistivity Surveys and Data Interpretation.-Electronic Geophysical Year.-Energy Budget of the Earth.-Energy Partitioning of Seismic Waves.-Equatorial Electrojet.-Fractals and Chaos.-Free Oscillations of the Earth.-Geodesy, Figure of the Earth.-Geodesy, Ground Positioning and Leveling.-Geodesy, Networks and Reference Systems.-Geodesy, Physical.-Geodetic Pendulums, Horizontal Ultra Broad Band.-Geodynamics.-Geoelectromagnetism.-Geoid.-Geoid Determination, Theory and Principles.-Geoid Undulation, Interpretation.-Geoid, Computational Method.-Geomagnetic Excursions.-Geomagnetic Field, Global Pattern.-Geomagnetic Field, IGRF.-Geomagnetic Field, Measurement Techniques.-Geomagnetic Field, Polarity Reversals.-Geomagnetic Field, Secular Variation.-Geomagnetic Field, Theory.-Geophysical Well Logging.-Geothermal Heat Pumps.-Geothermal Record of Climate Change.-GPS, Data Acquisition and Analysis.-GPS, Tectonic Geodesy.-Gravimeters.-Gravity Anomalies, Interpretation.-Gravity Data, Advanced Processing.-Gravity Data, Regional - Residual Separation.-Gravity Field of the Earth.-Gravity Field, Temporal Variations from Space Techniques.-Gravity Field, Time Variations from Surface Measurements.-Gravity Measurements, Absolute.-Gravity Method, Airborne.-Gravity Method, Principles.-Gravity Method, Satellite.-Gravity Method, Surface.-Gravity Modeling, Theory and Computation.-Gravity, Data to Anomalies.-Gravity, Global Models.-Gravity, Gradiometry.-Great Earthquakes.-Heat Flow Measurements, Continental.-Heat Flow, Continental.-Heat Flow, Seafloor: Methods and Observations.-Impact Craters on Earth.-Instrumentation, Electrical Resistivity.-Instrumentation, EM.-International Geophysical Year.-International Gravity Formula.-International Polar Year 2007-2008.-International Year of Planet Earth.-Inverse Theory, Artificial Neural Networks.-Inverse Theory, Global Optimization.-Inverse Theory, Linear.-Inverse Theory, Monte Carlo Method.-Inverse Theory, Singular Value Decomposition.-Isostasy.-Isostasy, Thermal.-Legal Continental Shelf.-Lithosphere, Continental.-Lithosphere, Continental: Thermal Structure.-Lithosphere, Mechanical Properties.-Lithosphere, Oceanic.-Lithosphere, Oceanic: Thermal Structure.-Magnetic Anisotropy.-Magnetic Anomalies, Interpretation.-Magnetic Data Enhancements and Depth Estimation.-Magnetic Domains.-Magnetic Gradiometry.-Magnetic Methods, Airborne.-Magnetic Methods, Principles.-Magnetic Methods, Satellite.-Magnetic Methods, Surface.-Magnetic Modeling, Theory and Computation.-Magnetic Storms and Electromagnetic Pulsations.-Magnetic, Global Anomaly Map.-Magnetometers.-Magnetotelluric Data Processing.-Magnetotelluric Interpretation.-Magnetovariation Studies.-Mantle Convection.-Mantle D'' Layer.-Mantle Plumes.-Mantle Viscosity.-Numerical Methods, Boundary Element.-Numerical Methods, Domain Decomposition.-Numerical Methods, Finite Difference.-Numerical Methods, Finite Element.-Numerical Methods, Multigrid.-Ocean Bottom Seismics.-Ocean, Spreading Centre.-Oceanic Intraplate Deformation: The Central Indian Ocean Basin.-Paleomagnetic Field Intensity.-Paleomagnetism, Magnetostratigraphy.-Paleomagnetism, Measurement Techniques and Instrumentation.-Paleomagnetism, Polar Wander.-Paleomagnetism, Principles.-Paleoseismology.-Plate Driving Forces.-Plate Motions in Time: Inferences on Driving and Resisting Forces.-Plate Tectonics, Precambrian.-Plates and Paleoreconstructions.-Poroelasticity.-Propagation of Elastic Waves: Fundamentals.-Radioactivity in Earth's Core.-Radiogenic Heat Production of Rocks.-Remanent Magnetism.-Remote Sensing and GIS Techniques for Tectonic Studies.-Remote Sensing, Applications to Geophysics.-SAR Interferometry.-Satellite Laser Ranging.-Seafloor Spreading.-Sedimentary Basins.-Seismic Anisotropy.-Seismic Data Acquisition and Processing.-Seismic Diffraction.-Seismic Discontinuities in the Transition Zone.-Seismic Hazard.-Seismic Imaging, Overview.-Seismic Instrumentation.-Seismic Microzonation.-Seismic Monitoring of Nuclear Explosions.-Seismic Noise.-Seismic Phase Names: IASPEI Standard.-Seismic Properties of Rocks.-Seismic Quiescence and Activation.-Seismic Seiches.-Seismic Signals in Well Observations: Pre, Co, Post.-Seismic Structure at Mid-Ocean Ridges.-Seismic Tomography.-Seismic Velocity-Density Relationships.-Seismic Velocity-Temperature Relationships.-Seismic Wave Propagation in Real Media: Numerical Modeling Approaches.-Seismic Waves, Scattering.-Seismic Zonation.-Seismic, Ambient Noise Correlation.-Seismic, Migration.-Seismic, Ray Theory.-Seismic, Receiver Function Technique.-Seismic, Reflectivity Method.-Seismic, Viscoelastic Attenuation.-Seismic, Waveform Modeling and Tomography.-Seismicity, Intraplate.-Seismicity, Subduction Zone.-Seismogram Interpretation.-Seismological Networks.-Seismology, Global Earthquake Model.-Seismology, Monitoring of CTBT.-Seismology, Rotational.-Shear-Wave Splitting: New Geophysics and Earthquake Stress-Forecasting.-Single and Multichannel Seismics.-Slow Earthquake.-Spherical Harmonic Analysis Applied to Potential Fields.-Statistical Seismology.-Subduction Zones.-Surface Waves.-T Waves.-Thermal Storage and Transport Properties of Rocks, I: Heat Capacity and Latent Heat.-Thermal Storage and Transport Properties of Rocks, II: Thermal Conductivity and Diffusivity.-Time Reversal in Seismology.-Traveltime Tomography Using Controlled-Source.-Seismic Data.-Tsunami.-Tsunami: Bay of Bengal.-Tsunami Watch and Warning Centers.-Vertical Seismic Profiling.-Very Long Baseline Interferometry.-Wavelet Analysis.

Light guide plate and virtual image display apparatus having the same

Abstract: Since a distance from an image extraction part to a light exiting surface is shorter downstream in an optical path than upstream in the optical path in relation to Z direction that is an arraying direction of reflection units, image light that propagates to pass between the image extraction part and the light exiting surface without becoming incident on the reflection units and therefore cannot be extracted to outside can be reduced. That is, since image light having a large total reflection angle in a light guide plate can be securely made incident on the image extraction part and efficiently extracted from the light exiting surface, light use efficiency in image formation can be enhanced. Thus, a virtual image display apparatus with brightness and high performance can be provided.

Runup of Tsunami Waves in U-Shaped Bays

Abstract: The problem of tsunami wave shoaling and runup in U-shaped bays (such as fjords) and underwater canyons is studied in the framework of 1D shallow water theory with the use of an assumption of the uniform current on the cross-section. The wave shoaling in bays, when the depth varies smoothly along the channel axis, is studied with the use of asymptotic approach. In this case a weak reflection provides significant shoaling effects. The existence of traveling (progressive) waves, propagating in bays, when the water depth changes significantly along the channel axis, is studied within rigorous solutions of the shallow water theory. It is shown that traveling waves do exist for certain bay bathymetry configurations and may propagate over large distances without reflection. The tsunami runup in such bays is significantly larger than for a plane beach.

Non-contact ultrasonic detection of angled surface defects

Abstract: Non-destructive testing is an important technique, and improvements are constantly needed. Surface defects in metals are not necessarily confined to orientations normal to the sample surface; however, much of the previous work investigating the interaction of ultrasonic surface waves with surface-breaking defects has assumed cracks inclined at 90° to the surface. This paper explores the interaction of Rayleigh waves with cracks which have a wide range of angles and depths relative to the surface, using a non-contact laser generation and detection system. Additional insight is acquired using a 3D model generated using finite element method software. A clear variation of the reflection and transmission coefficients with both crack angle and length is found, in both the out-of-plane and in-plane components. The 3D model is further used to understand the contributions of different wavemodes to B-Scans produced when scanning a sample, to enable understanding of the reflection and transmission behaviour, and help identify angled defects. Knowledge of these effects is essential to correctly gauge the severity of surface cracking.