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Journal articles on the topic 'Wide Angle Reflection'

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Author: Grafiati

Published: 11 March 2023

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1

Shiraishi, Kazuya, Gou Fujie, Takeshi Sato, Susumu Abe, Eiichi Asakawa, and Shuichi Kodaira. "Interferometric OBS imaging for wide-angle seismic data." GEOPHYSICS 82, no. 5 (September 1, 2017): Q39—Q51. http://dx.doi.org/10.1190/geo2016-0482.1.

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Marine wide-angle seismic data obtained using air guns and ocean-bottom seismographs (OBSs) are effective for determining large-scale subseafloor seismic velocities, but they are ineffective for imaging details of shallow seismic reflection structures because of poor illumination. Surface-related multiple reflections offer the potential to enlarge the OBS data illumination area. We have developed a new seismic imaging method for OBS surveys applying seismic interferometry, a technique that uses surface-related multiples similarly to mirror imaging. Seismic interferometry can use higher order multiple reflections than mirror imaging, which mainly uses first-order multiple reflections. A salient advantage of interferometric OBS imaging over mirror imaging is that it requires only single-component data, whereas mirror imaging requires vertical geophone and hydrophone components to separate upgoing and downgoing wavefields. We applied interferometric OBS imaging to actual 175 km long wide-angle OBS data acquired in the Nankai Trough subduction zone. We obtained clear continuous reflection images in the deep and shallow parts including the seafloor from the OBS data acquired with large spacing. Deconvolution interferometry is more suitable than correlation interferometry to improve spatial resolution because of the effects of spectral division when applied to common receiver gathers. We examined the imaging result dependence on data acquisition and processing parameters considering the data quality and target depth. An air-gun-to-OBS distance of up to 50 km and a record length of 80 s were necessary for better imaging. In addition, our decimation tests confirmed that denser OBS spacing yielded better quality and higher resolution images. Understanding crosstalk effects due to the acquisition setting will be useful to optimize methods for eliminating them. Interferometric OBS imaging merged with conventional primary reflection imaging is a powerful method for revealing crustal structures.

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2

Zhu, Xinfa, and George A. McMechan. "Amplitude and phase versus angle for elastic wide-angle reflections in the τ‐p domain." GEOPHYSICS 80, no. 1 (January 1, 2015): N1—N9. http://dx.doi.org/10.1190/geo2013-0191.1.

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Near- and postcritical spherical-wave reflections contain amplitude and phase variations with incident angle that are not predicted by plane-wave solutions. However, if a spherical wavefield is decomposed into plane waves by a time-intercept-slowness ([Formula: see text]) transform, then plane-wave reflection coefficients (the Zoeppritz) can be used as the basis of amplitude/phase versus angle analysis. The spherical-wave effects on reflection coefficients near the critical angle (in the time-offset domain) were decomposed by [Formula: see text] transformation into plane waves. Kinematic ray tracing linked the reflection angle at the target reflector and the apparent slowness at the surface receiver, which enabled extracting the amplitude/phase versus angle data at the reflector from the surface [Formula: see text] data. The most reliable inversion results were obtained by combining the extracted amplitudes and phases in a composite inversion for the elastic parameters below the target reflector.

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3

Rendleman, C. A., and F. K. Levin. "Reflection maxima for reflections from single interfaces." GEOPHYSICS 53, no. 2 (February 1988): 271–75. http://dx.doi.org/10.1190/1.1442462.

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At a workshop on refraction and wide‐angle reflections, Hilterman (1985) pointed out that, in contrast to the plane‐wave case, when there is a point source, a P-wave reflected from a plane interface attains its maximum amplitude at an offset greater than that corresponding to the critical angle (Figure 1). The same conclusion had been drawn earlier by Červený (1967). However, neither Červený’s results, which were based on very complicated mathematical expressions derived by Brekhovskikh (1960), nor Hilterman’s computer‐generated data shed light on the physics implied by the shifted maximum.

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4

Chang, Ya-Chun, Wei-Feng Xu, Meng-Chieh Wu, Cyun-Tai Hong, and Chen-Kuan Kuo. "P‐29: Wide Visual Angle Anti‐Reflection Film." SID Symposium Digest of Technical Papers 51, no. 1 (August 2020): 1442–44. http://dx.doi.org/10.1002/sdtp.14159.

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5

Sava, Paul, and Ioan Vlad. "Wide-azimuth angle gathers for wave-equation migration." GEOPHYSICS 76, no. 3 (May 2011): S131—S141. http://dx.doi.org/10.1190/1.3560519.

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Extended common-image-point (CIP) gathers contain all of the necessary information for decomposition of reflectivity as a function of the reflection and azimuth angles at selected locations in the subsurface. This decomposition operates after the imaging condition applied to wavefields reconstructed by any type of wide-azimuth migration method, e.g., using downward continuation or time reversal. The reflection and azimuth angles are derived from the extended images using analytic relations between the space-lag and time-lag extensions. The transformation amounts to a linear Radon transform applied to the CIPs obtained after applying the extended imaging condition. If information about the reflector dip is available at the CIP locations, then only two components of the space-lag vectors are required, thus reducing computational cost and increasing the affordability of the method. Applications of this method include the study of subsurface illumination in areas of complex geology where ray-based methods are not usable and the study of amplitude variation with reflection and azimuth angles if the subsurface illumination is sufficiently dense. Migration velocity analysis could also be implemented in the angle domain, although an equivalent implementation in the extended domain is less costly and more effective.

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6

Khalaj-Amirhosseini, Mohammad, and Sayed Mohammad Javad Razavi. "WIDE-ANGLE REFLECTION WAVE POLARIZERS USING INHOMOGENEOUS PLANAR LAYERS." Progress In Electromagnetics Research M 9 (2009): 9–20. http://dx.doi.org/10.2528/pierm09070301.

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7

Estakhri, Nasim Mohammadi, Verena Neder, Mark W. Knight, Albert Polman, and Andrea Alù. "Visible Light, Wide-Angle Graded Metasurface for Back Reflection." ACS Photonics 4, no. 2 (February 3, 2017): 228–35. http://dx.doi.org/10.1021/acsphotonics.6b00965.

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8

Goldman, Ph.D., Laine. "Appreciative Reflection: A Wide-Angle Lens for Changing Perception." AI Practitioner 16, no. 3 (August 1, 2014): 53–58. http://dx.doi.org/10.12781/978-1-907549-20-5-8.

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9

Chartas, George, and Sarah Strickland. "Wide-Angle Quasar Feedback." Proceedings of the International Astronomical Union 11, S319 (August 2015): 58. http://dx.doi.org/10.1017/s1743921315010145.

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AbstractWe present results from the detection of relativistic winds launched near the innermost stable circular orbits of supermassive black holes. A recent detection of a powerful wind in the X-ray-bright narrow absorption line (NAL) z=1.51 quasar HS 0810+2554 strengthens the case that quasars play a significant role in feedback. In both deep Chandra and XMM-Newton observations of HS 0810 we detected blueshifted absorption lines implying outflowing velocities ranging from 0.1c and 0.4c. The presence of both an emission line at 6.8 keV and an absorption line at 7.8 keV in the spectral line profile of HS 0810 is a characteristic feature of a P-Cygni profile supporting the presence of an expanding outflowing highly ionized Fe absorber. A hard excess component is detected in the XMM-Newton observation of HS 0810 possibly originating from reflection off the disk. Modelling of the XMM-Newton spectrum constrains the inclination angle to be < 35° (68% confidence). The presence of relativistic winds in both low inclination angle NAL quasars as well as in high inclination angle BAL quasars implies that the solid angle of quasar winds may be quite large. The larger solid angle of quasar winds would also indicate that their contribution to the regulation of the host galaxy may be more important than previously thought.

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10

Fruehn, Juergen, Moritz M. Fliedner, and Robert S. White. "Integrated wide‐angle and near‐vertical subbasalt study using large‐aperture seismic data from the Faeroe—Shetland region." GEOPHYSICS 66, no. 5 (September 2001): 1340–48. http://dx.doi.org/10.1190/1.1487079.

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Acquiring large‐aperture seismic data (38 km maximum offset) along a profile crossing the Faeroe—Shetland basin in the North Atlantic enables us to use wide‐angle reflections and refractions, in addition to conventional streamer data (0–6 km), for subbasalt imaging. The wide‐angle results are complemented and confirmed by images obtained from the conventional near‐vertical‐offset range. Traveltime tomography applied to the wide‐angle data shows a low‐velocity layer (3.5–4.5 km/s) underneath southeastward‐thinning lava flows, suggesting a 2.5–3.0‐km‐thick sedimentary layer. The velocity model obtained from traveltime tomography is used to migrate wide‐angle reflections from large offsets that arrive ahead of the water‐wave cone. The migrated image shows base‐basalt and sub—basalt reflections that are locally coincident with the tomographic boundaries. Application of a new multiple suppression technique and controlled stacking of the conventional streamer data produces seismic sections consistent with the wide‐angle results. Prestack depth migration of the near‐vertical offsets shows a continuous base‐basalt reflection and a clearly defined termination of the basalt flows.

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11

Sain, Kalachand, and K. L. Kaila. "Inversion of wide‐angle seismic reflection times with damped least squares." GEOPHYSICS 59, no. 11 (November 1994): 1735–44. http://dx.doi.org/10.1190/1.1443560.

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The wide‐angle seismic reflection times appearing in the postcritical range are used extensively to image the crustal structure in deep seismic sounding investigations. The most commonly used method to calculate interval velocities and thicknesses of a stack of horizontal layers is based on Dix’s hyperbolic equation that requires traveltimes at zero offset and a prior estimate of root‐mean‐square (rms) velocity. Since the wide‐angle reflection times are represented by the nonhyperbolic Taner and Koehler series, a forced fit of such a data set by a hyperbolic equation causes large errors in the estimation of interval velocities. We propose a fast and simple method to determine the interval velocities from wide‐angle reflection times by minimizing the squared errors between the observed traveltimes and the forward response using a damped least‐squares technique. The forward response is calculated, including higher order terms of the reflection series, through Chebychev (orthogonal) polynomial approximations. Inversion of synthetic reflection times by this method, for a given velocity model contaminated by some random errors, and starting with various initial models, produces a final model that matches the true model. This modeling serves as a good indicator of the reliability of the estimated parameters. Besides, the method provides a measure of uncertainty and resolution of estimated parameters.

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12

Makris, Jannis, Knuth Lange, Leo Savostin, and Vladimir Sedov. "A wide-angle reflection profile across the Iceland-Faeroe Ridge." Geological Society, London, Special Publications 93, no. 1 (1995): 459–66. http://dx.doi.org/10.1144/gsl.sp.1995.093.01.36.

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13

de Franco, Roberto. "Interval velocity and thickness estimate from wide-angle reflection data." Geophysical Prospecting 49, no. 4 (July 2001): 395–404. http://dx.doi.org/10.1046/j.1365-2478.2001.00265.x.

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14

Osler, John C., and Charles W. Holland. "High‐resolution geoacoustic inversion from wide‐angle seismic reflection measurements." Journal of the Acoustical Society of America 104, no. 3 (September 1998): 1743. http://dx.doi.org/10.1121/1.423637.

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15

Liu, FuPing, XianJun Meng, JiaQi Xiao, AnLing Wang, and ChangChun Yang. "The Goos-Hänchen shift of wide-angle seismic reflection wave." Science China Earth Sciences 55, no. 5 (December 15, 2011): 852–57. http://dx.doi.org/10.1007/s11430-011-4344-5.

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16

Kemin, Dao, and G. M. Purdy. "High resolution velocity analysis of watergun wide angle reflection data." Chinese Journal of Oceanology and Limnology 4, no. 1 (March 1986): 41–55. http://dx.doi.org/10.1007/bf02850396.

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17

Majdański, M. "The uncertainty in layered models from wide-angle seismic data." GEOPHYSICS 78, no. 3 (May 1, 2013): WB31—WB36. http://dx.doi.org/10.1190/geo2012-0280.1.

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The analytical method of estimating the uncertainty in layered models is addressed to models obtained using a layer-stripping modeling strategy or forward modeling. It is based on a simple principle of small error propagation. There are two variants of the method: a simplified one that includes refraction and vertical reflections and one that also includes wide-angle reflections. Both give a quantitative estimation for the existing models. To allow for a simple analytical estimation, refracted waves are described using a head-wave approximation in constant velocity layers; wide angle reflection paths are also simplified. In the case of trial and error forward modeling, this method can help determine how well the used parameterization is reflected in the data and avoid over-fitting the structures. This is especially important because the forward modeling is very subjective and there is no method to assess the parameterization without generating alternative models. For inversion problems using the layer-stripping method, the analysis allows for a correct propagation of errors and will help to evaluate the effect of including a priori information with known uncertainty. As a result, the layer-stripping modeling strategy is worse than simultaneous inversion for layered models because it gives larger uncertainties.

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18

Oueity, Jounada, and Ron M. Clowes. "Paleoproterozoic subduction in northwestern Canada from near-vertical and wide-angle seismic reflection data." Canadian Journal of Earth Sciences 47, no. 1 (January 2010): 35–52. http://dx.doi.org/10.1139/e09-073.

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Near-vertical incidence and refraction – wide-angle reflection seismic data, recorded as part of Lithoprobe studies in the Paleoproterozoic–Archean domains of Canada’s Northwest Territories, show remarkable reflections from within the upper mantle. A parallel pair of reflectors imaged by the near-vertical data can be traced from Moho levels (∼33 km) down to ∼70 km depth. In a previous study, the reflectors were interpreted as the top and bottom of an ∼1.8 Ga subducted oceanic crust beneath the Hottah terrane. Further inboard, where the seismic line changes its direction from east–west to nearly north–south, another pair of reflectors extends subhorizontally for about 100 km at ∼70 km depth before dipping downward. The subhorizontal reflectors were not correlated with the dipping slab; instead they were interpreted as a separate feature. However, they roughly coincide with a horizontal interface modeled from wide-angle data by an earlier study. Considering the crooked line acquisition geometry, we re-examined both near-vertical incidence and wide-angle reflection data using 2-dimensional (2-D) and 3-D forward and inverse modeling algorithms. Our results demonstrate that the subhorizontal reflectors are the continuation of the relict subducted slab, which now extends laterally for 300 km. Its base is the source of the wide-angle data. The apparent flattening for the near-vertical data is most likely an artifact of projecting a 3-D geometry onto a 2-D cross section. The shallowly subducted slab probably contributed to the thickening and stabilization of the subcrustal lithosphere below the Wopmay orogen.

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19

Yin, Yunzhen, Yanyan Bu, and Xiangfu Wang. "PDMS-based subwavelength structures for broadband and wide-angle anti-reflection." Physica B: Condensed Matter 580 (March 2020): 411943. http://dx.doi.org/10.1016/j.physb.2019.411943.

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20

Mereu, R. F. "The complexity of the crust from refraction/wide-angle reflection data." Pure and Applied Geophysics PAGEOPH 132, no. 1-2 (1990): 269–88. http://dx.doi.org/10.1007/bf00874366.

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21

Zhao, Degang, Yangtao Ye, Shengjun Xu, Xuefeng Zhu, and Lin Yi. "Broadband and wide-angle negative reflection at a phononic crystal boundary." Applied Physics Letters 104, no. 4 (January 27, 2014): 043503. http://dx.doi.org/10.1063/1.4863691.

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22

Musacchio, G., R. De Franco, R. Cassinis, and G. Gosso. "Reinterpretation of a wide angle reflection “fan” across the Central Alps." Journal of Applied Geophysics 30, no. 1-2 (April 1993): 43–53. http://dx.doi.org/10.1016/0926-9851(93)90017-s.

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23

Thouvenot, F., S. N. Kashubin, G. Poupinet, V. V. Makovskiy, T. V. Kashubina, Ph Matte, and L. Jenatton. "The root of the Urals: evidence from wide-angle reflection seismics." Tectonophysics 250, no. 1-3 (November 1995): 1–13. http://dx.doi.org/10.1016/0040-1951(95)00058-8.

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24

Lerche, Ian. "Reflection of wide-angle acoustic waves from a high velocity interface." Pure and Applied Geophysics PAGEOPH 134, no. 1 (August 1990): 109–15. http://dx.doi.org/10.1007/bf00878083.

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25

Rance, Olivier, Anne Claire Lepage, Xavier Begaud, Kevin Elis, and Nicolas Capet. "Oblique Wide-Angle Multi-Sector Metamaterial Absorber for Space Applications." Applied Sciences 9, no. 16 (August 20, 2019): 3425. http://dx.doi.org/10.3390/app9163425.

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This article presents the design, realization and measurement of lightweight absorbing material for space applications. The electromagnetic absorber, operating on the [2 GHz, 2.3 GHz] frequency band, is designed for oblique incidence ranging from 35° to 65°. Wide-angle designs are demonstrated to be particularly challenging at oblique incidence and an approach consisting in dividing the surface in two different sectors with respect to the incoming angle is proposed. A specific measurement setup is presented in order to characterize this new kind of evolutive absorber. The measurement results show that the sectorial absorber achieves a reflection coefficient inferior to −11.5 dB, corresponding to an absorptivity above 0.965 on the frequency band [2 GHz, 2.3 GHz] for both TE and TM polarizations for angles of incidence varying from 35° to 65°.

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26

Kumar, Prakash, Kalachand Sain, and H. C. Tewari. "A direct method of estimating depth to a reflector from seismic wide-angle reflection times." Geophysical Journal International 152, no. 3 (March 2003): 740–48. http://dx.doi.org/10.1046/j.1365-246x.2003.01891.x.

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27

Jonah, Emmanuel O., Margit Härting, Eric Gullikson, Andrew Aquila, and David T. Britton. "Investigation of surface topology of printed nanoparticle layers using wide-angle low-Qscattering." Journal of Synchrotron Radiation 21, no. 3 (April 2, 2014): 547–53. http://dx.doi.org/10.1107/s160057751400410x.

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A new small-angle scattering technique in reflection geometry is described which enables a topological study of rough surfaces. This is achieved by using long-wavelength soft X-rays which are scattered at wide angles but in the low-Qrange normally associated with small-angle scattering. The use of nanometre-wavelength radiation restricts the penetration to a thin surface layer which follows the topology of the surface, while moving the scattered beam to wider angles preventing shadowing by the surface features. The technique is, however, only applicable to rough surfaces for which there is no specular reflection, so that only the scattered beam was detected by the detector. As an example, a study of the surfaces of rough layers of silicon produced by the deposition of nanoparticles by blade-coating is presented. The surfaces of the blade-coated layers have rough features of the order of several micrometers. Using 2 nm and 13 nm X-rays scattered at angular ranges of 5° ≤ θ ≤ 51° and 5° ≤ θ ≤ 45°, respectively, a combined range of scattering vector of 0.00842 Å−1≤Q≤ 0.4883 Å−1was obtained. Comparison with previous transmission SAXS and USAXS studies of the same materials indicates that the new method does probe the surface topology rather than the internal microstructure.

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28

Lan, Tian, Qiu-Cui Li, Yu-Shen Dou, and Xun-Ya Jiang. "A Study of a Wide-Angle Scanning Phased Array Based on a High-Impedance Surface Ground Plane." International Journal of Antennas and Propagation 2019 (January 20, 2019): 1–10. http://dx.doi.org/10.1155/2019/8143104.

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This paper presents a two-dimensional infinite dipole array system with a mushroom-like high-impedance surface (HIS) ground plane with wide-angle scanning capability in the E-plane. The unit cell of the proposed antenna array consists of a dipole antenna and a four-by-four HIS ground. The simulation results show that the proposed antenna array can achieve a wide scanning angle of up to 65° in the E-plane with an excellent impedance match and a small S11. Floquet mode analysis is utilized to analyze the active impedance and the reflection coefficient. Good agreement is obtained between the theoretical results and the simulations. Using numerical and theoretical analyses, we reveal the mechanism of such excellent wide scanning properties. For the range of small scanning angles, these excellent properties result mainly from the special reflection phase of the HIS ground, which can cause the mutual coupling between the elements of the real array to be compensated by the mutual coupling effect between the real array and the mirror array. For the range of large scanning angles, since the surface wave (SW) mode could be resonantly excited by a high-order Floquet mode TM−1,0 from the array and since the SW mode could be converted into a leaky wave (LW) mode by the scattering of the array, the radiation field from the LW mode is nearly in phase with the direct radiating field from the array. Therefore, with help from the special reflection phase of the HIS and the designed LW mode of the HIS ground, the antenna array with an HIS ground can achieve a wide-angle scanning performance.

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29

Filatova, Elena, and Andrey Sokolov. "Effect of reflection and refraction on NEXAFS spectra measured in TEY mode." Journal of Synchrotron Radiation 25, no. 1 (January 1, 2018): 232–40. http://dx.doi.org/10.1107/s1600577517016253.

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The evolution of near-edge X-ray absorption fine structure in the vicinity of theK-absorption edge of oxygen for HfO2over a wide range of incidence angles is analyzed by simultaneous implementation of the total-electron-yield (TEY) method and X-ray reflection spectroscopy. It is established that the effect of refraction on the TEY spectrum is greater than that of reflection and extends into the angular region up to angles 2θc. Within angles that are less than the critical angle, both the reflection and refraction strongly distort the shape of the TEY spectrum. Limitations of the technique for the calculation of optical constants from the reflection spectra using the Kramers–Kronig relation in the limited energy region in the vicinity of thresholds are discussed in detail.

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30

Begaud, Xavier, Anne Lepage, Stefan Varault, Michel Soiron, and André Barka. "Ultra-Wideband and Wide-Angle Microwave Metamaterial Absorber." Materials 11, no. 10 (October 20, 2018): 2045. http://dx.doi.org/10.3390/ma11102045.

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In order to extend the performance of radar absorbing materials, it is necessary to design new structures with wideband properties and large angles of incidence which are also as thin as possible. The objective of this work, realized within the framework of the SAFAS project (self-complementary surface with low signature) is, then, the development of an ultra-wideband microwave absorber of low thickness. The design of such material requires a multilayered structure composed with dielectric layers, metasurfaces, and wide-angle impedance matching layers. This solution has been realized with on-the-shelf materials, and measured to validate the concept. At normal incidence, the bandwidth ratio, defined for a magnitude of the reflection coefficient below −10 dB, is 4.7:1 for an absorber with a total thickness of 11.5 mm, which corresponds to λ/7 at the lowest operating frequency. For an incidence of 60°, this bandwidth ratio is reduced to 3.8:1, but the device remains ultra-wideband.

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31

Ma, Qing. "X-ray Scattering Studies of amorphous thin film materials." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C859. http://dx.doi.org/10.1107/s2053273314091402.

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In light of advances in detector technology, we revisit wide angle x-ray scattering techniques and their application to amorphous thin films that are of technological importance. For thin film materials the asymmetrical reflection geometry is employed to avoid the substrate signals. Incident x-ray angles are typically set close to the critical angles. There are various complications related to this geometry, in particular, raw scattering patterns being distorted. In addition, because these materials are typically weak scatterers due to disorder, increased data collection efficiency is always desired. Here, we report our activities using a 4-element vortex Si-drift detector for wide angle x-ray scattering experiments and present some experimental data collected on amorphous transparent conducting oxides.

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32

Fliedner, Moritz M., and Robert S. White. "Seismic structure of basalt flows from surface seismic data, borehole measurements, and synthetic seismogram modeling." GEOPHYSICS 66, no. 6 (November 2001): 1925–36. http://dx.doi.org/10.1190/1.1486760.

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We use the wide‐angle wavefield to constrain estimates of the seismic velocity and thickness of basalt flows overlying sediments. Wide angle means the seismic wavefield recorded at offsets beyond the emergence of the direct wave. This wide‐angle wavefield contains arrivals that are returned from within and below the basalt flows, including the diving wave through the basalts as the first arrival and P‐wave reflections from the base of the basalts and from subbasalt structures. The velocity structure of basalt flows can be determined to first order from traveltime information by ray tracing the basalt turning rays and the wide‐angle base‐basalt reflection. This can be refined by using the amplitude variation with offset (AVO) of the basalt diving wave. Synthetic seismogram models with varying flow thicknesses and velocity gradients demonstrate the sensitivity to the velocity structure of the basalt diving wave and of reflections from the base of the basalt layer and below. The diving‐wave amplitudes of the models containing velocity gradients show a local amplitude minimum followed by a maximum at a greater range if the basalt thickness exceeds one wavelength and beyond that an exponential amplitude decay. The offset at which the maximum occurs can be used to determine the basalt thickness. The velocity gradient within the basalt can be determined from the slope of the exponential amplitude decay. The amplitudes of subbasalt reflections can be used to determine seismic velocities of the overburden and the impedance contrast at the reflector. Combining wide‐angle traveltimes and amplitudes of the basalt diving wave and subbasalt reflections enables us to obtain a more detailed velocity profile than is possible with the NMO velocities of small‐offset reflections. This paper concentrates on the subbasalt problem, but the results are more generally applicable to situations where high‐velocity bodies overlie a low‐velocity target, such as subsalt structures.

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33

Liu, Chuanbao, Jingjin He, Ji Zhou, Jianchun Xu, Ke Bi, Junhong Chen, Lijie Qiao, and Yang Bai. "Broadband, High‐Efficiency and Wide‐Incident‐Angle Anomalous Reflection in Groove Metagratings." Annalen der Physik 533, no. 9 (June 28, 2021): 2100149. http://dx.doi.org/10.1002/andp.202100149.

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34

Luetgert, James, and Carol E. Mann. "Avalon terrane in eastern coastal Maine: Seismic refraction-wide-angle reflection data." Geology 18, no. 9 (1990): 878. http://dx.doi.org/10.1130/0091-7613(1990)018<0878:atiecm>2.3.co;2.

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35

Pawlik, G., K. Tarnowski, W. Walasik, A. C. Mitus, and I. C. Khoo. "Liquid crystal hyperbolic metamaterial for wide-angle negative–positive refraction and reflection." Optics Letters 39, no. 7 (March 19, 2014): 1744. http://dx.doi.org/10.1364/ol.39.001744.

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36

Hirm, A., S. Nadir, F. Thouvenot, R. Nicolich, G. Pellis, S. Scarascia, I. Tabacco, F. Castellano, and F. Merlanti. "Mapping the Moho of the Western Alps by wide-angle reflection seismics." Tectonophysics 162, no. 3-4 (May 1989): 193–202. http://dx.doi.org/10.1016/0040-1951(89)90243-6.

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37

ZHAO, Ai-Hua, and Zhi-Feng DING. "Double-Grid Algorithm for Calculating Travel Times of Wide-Angle Reflection Waves." Chinese Journal of Geophysics 48, no. 5 (September 2005): 1218–25. http://dx.doi.org/10.1002/cjg2.767.

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38

Zhu, Xinfa, and George A. McMechan. "Elastic inversion of near- and postcritical reflections using phase variation with angle." GEOPHYSICS 77, no. 4 (July 1, 2012): R149—R159. http://dx.doi.org/10.1190/geo2011-0230.1.

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Near- and postcritical (wide-angle) reflections provide the potential for velocity and density inversion because of their large amplitudes and phase-shifted waveforms. We tested using phase variation with angle (PVA) data in addition to, or instead of, amplitude variation with angle (AVA) data for elastic inversion. Accurate PVA test data were generated using the reflectivity method. Two other forward modeling methods were also investigated, including plane-wave and spherical-wave reflection coefficients. For a two half-space model, linearized least squares was used to invert PVA and AVA data for the P-wave velocity, S-wave velocity, and the density of the lower space and the S-wave velocity of the upper space. Inversion tests showed the feasibility and robustness of PVA inversion. A reverse-time migration test demonstrated better preservation of PVA information than AVA information during wavefield propagation through a layered overburden. Phases of deeper reflections were less affected than amplitudes by the transmission losses, which makes the results of PVA inversion more accurate than AVA inversion in multilayered media. PVA brings useful information to the elastic inversion of wide-angle reflections.

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Li, Jianfeng, Liangliang Mao, and Tianling Zhang. "FSS Sandwiched Dual-Frequency Reflectarray for Mobile Communication Applications." Electronics 12, no. 4 (February 10, 2023): 897. http://dx.doi.org/10.3390/electronics12040897.

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Sandwiched frequency selective surface (FSS) is proposed as an additional reflection surface for a dual-frequency reflectarray system. The range of reflection phase for a reflectarray depends on the substrate thickness sensitively. Usually, a tradeoff between the smooth linear level and the wide reflection phase range is needed, especially for a dual-frequency system. By inserting an FSS between the ground plane and the reflecting element layer, a selective plane for the dual-frequency band is provided. For the higher frequency band, the FSS layer is a reflection plane. For the lower frequency band, it is transparent and the reflection plane is changed into the metal ground plane. A dual-band reflectarray with a scattering angle of 30 degrees is simulated and measured to validate this concept.

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Xu, Sheng, Yu Zhang, and Bing Tang. "3D angle gathers from reverse time migration." GEOPHYSICS 76, no. 2 (March 2011): S77—S92. http://dx.doi.org/10.1190/1.3536527.

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Common-image gathers are an important output of prestack depth migration. They provide information needed for velocity model building and amplitude and phase information for subsurface attribute interpretation. Conventionally, common-image gathers are computed using Kirchhoff migration on common-offset/azimuth data volumes. When geologic structures are complex and strong contrasts exist in the velocity model, the complicated wave behaviors will create migration artifacts in the image gathers. As long as the gather output traces are indexed by any surface attribute, such as source location, receiver location, or surface plane-wave direction, they suffer from the migration artifacts caused by multiple raypaths. These problems have been addressed in a significant amount of work, resulting in common-image gathers computed in the reflection angle domain, whose traces are indexed by the subsurface reflection angle and/or the subsurface azimuth angle. Most of these efforts have concentrated on Kirchhoff and one-way wave-equation migration methods. For reverse time migration, subsurface angle gathers can be produced using the same approach as that used for one-way wave-equation migration. However, these approaches need to be revisited when producing high-quality subsurface angle gathers in three dimensions (reflection angle/azimuth angle), especially for wide-azimuth data. We have developed a method for obtaining 3D subsurface reflection angle/azimuth angle common-image gathers specifically for the amplitude-preserved reverse time migration. The method builds image gathers with a high-dimensional convolution of wavefields in the wavenumber domain. We have found a windowed antileakage Fourier transform method that leads to an efficient and practical implementation. This approach has generated high-resolution angle-domain gathers on synthetic 2.5D data and 3D wide-azimuth real data.

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Zhu, Xinfa, and George A. McMechan. "Stretch-free migration imaging condition." GEOPHYSICS 78, no. 4 (July 1, 2013): S203—S210. http://dx.doi.org/10.1190/geo2012-0519.1.

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Prestack migration has angle-dependent wavelet stretch effects, which lowers the image resolution at large reflection angles. Most current stretch correction methods operate on the migrated images. We develop a new stretch-free imaging condition, which does a shrink-and-shift operation on the extracted propagation wavelet after extrapolation, but before the imaging condition is applied. The algorithm is illustrated with the excitation amplitude imaging condition; the new images show successful stretch corrections over wide angle apertures, and preserve amplitude and phase.

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Lazaratos, Spyros K., James W. Rector, Jerry M. Harris, and Mark Van Schaack. "High‐resolution, cross‐well reflection imaging: Potential and technical difficulties." GEOPHYSICS 58, no. 9 (September 1993): 1270–80. http://dx.doi.org/10.1190/1.1443510.

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The case study presented in this paper demonstrates that reflections can be found in high‐frequency cross‐well data. These reflections can be enhanced by a processing sequence similar to the one applied to VSP data to produce very high‐resolution images. Vertical resolution of the order of 3–5 ft (1–1.5 m) for well distances of a few hundred feet is potentially feasible. Although this study produced a good tie between the cross‐well reflection image and the sonic log, our research also illustrated some of the technical difficulties associated with cross‐well reflection imaging. Specifically, we found that the signal‐to‐noise ratio of the image decreases as the distance between the imaged reflection points and the wells increases, and that aliased tube waves as well as shear and converted waves were the main components of the noise. We also observed that interpretation of wide‐angle reflections might be misleading, since these events are significantly stretched, both horizontally and vertically, during imaging. Improvements are required both in data acquisition (denser data collection, more fold, smaller angles of incidence) and processing/imaging (optimal use of fold) to make cross‐well reflection imaging useful. Still, the quality of these preliminary results, produced from a single gather of aliased data, indicates the promise of the approach.

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43

Mereu, R. F. "The complexity of the crust and Moho under the southeastern Superior and Grenville provinces of the Canadian Shield from seismic refraction - wide-angle reflection data." Canadian Journal of Earth Sciences 37, no. 2-3 (April 2, 2000): 439–58. http://dx.doi.org/10.1139/e99-122.

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The major features of the individual velocity models, Poisson's ratio values, and crustal complexity derived from the interpretation of seismic data sets from four long-range seismic refraction - wide-angle reflection experiments are summarized. The experiments were conducted from 1982-92 in the southeastern portion of the Canadian Shield. In the conventional analysis of seismic refraction - wide-angle reflection data, only the onset times and amplitudes of the major arrival phases are used to derive seismic velocity models of the region under study. These models are over smoothed, have a number of intermediate discontinuities, are unable to explain the Pg coda, and bear very little resemblance to the models derived from the analysis of near-vertical seismic reflection data. In this paper some of the differences between seismic models derived from near-vertical reflection analysis and those from refraction analysis are reconciled from an analysis of the wide-angle reflection fields of the crustal coda waves that follow the first arrivals. This was done using a migration technique that to a first approximation maps the amplitudes of the record sections into a two-dimensional (2-D) complexity section. These new sections show significant lateral variations in crustal and Moho reflectivity and may be used to complement the 2-D velocity anomaly sections and near-vertical reflection sections. The method was based on a numerical study that showed that the coda can be explained with a class of complex heterogeneous models in which sets of small-scale, high-contrast sloping seismic reflectors are "embedded" in a uniform seismic velocity gradient field.

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Chou, Ta-Hsin, Wen-Hsien Yang, Tzu-Yu Huang, and Hong Hocheng. "Roll-to-Roll Embossing of Sunlight Guide Film with Wide Outgoing Angle." International Journal of Automation Technology 5, no. 2 (March 5, 2011): 212–17. http://dx.doi.org/10.20965/ijat.2011.p0212.

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Artificial lighting consumes over 20% of the total energy used by commercial buildings. Sunlight guides used in windows guide sunlight to the ceilings of indoor rooms. Microstructure film designed and fabricated by roll-to-roll embossing improves solar energy use. A roller mold was fabricated with a diamond turning lathe and used for UltraViolet (UV) cured embossing. After embossing, sunlight guide film 400 mm wide was fabricated. The film microstructure prism and curved surfaces 21 µm high and spaced at 18 µm intervals. When sunlight illuminates the inclined or curved surface, incoming rays are reflected from the outgoing surface in total internal reflection. Specimen performance wasmeasured using measurement installation including a light source, photodetector, and a rotating table. These produced sunlight guide film able to adopt elevation angles of 40°-70°. The outgoing angle exceeded a 30° average above the transom’s outgoing horizontal 90° angle, which is defined by full width at half maximum of outgoing light intensity. Experimental results showed of the microstructure film had high energy efficiency and a broad range of outgoing angles, reducing energy consumption by 19% in artificial building lighting for an ideal room model.

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Neves, Fernando A., and Maarten V. de Hoop. "Some remarks on nonlinear amplitude versus scattering angle‐azimuth inversion in anisotropic media." GEOPHYSICS 65, no. 1 (January 2000): 158–66. http://dx.doi.org/10.1190/1.1444706.

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A feasibility study for inverting reflection coefficients for a single‐interface model consisting of a shale overlying a fractured sand is presented. To characterize the medium contact from amplitude versus scattering angles (AVA) behavior associated with the reflection from a particular interface, in view of the anisotropy, wide‐angle scattering data are required. However, wide‐angle scattering turns the inverse problem into an essentially nonlinear one. The inverse problem is hence analyzed with a global optimization procedure—a genetic algorithm with constraints. The key to making a genetic algorithm work for our AVA inverse problem appears to be a proper parameterization of the direct scattering problem and introducing a parameter hierarchy. These reduce the complexity of the misfit function occurring in the optimization procedure and let this function become convex over a relatively large range of medium parameter values. We illustrate how well our approach performs with a single‐interface example representing a shale/fractured‐sandstone contact. In this example, we assume the overburden, i.e., the shale, to be known; we allow the data to be contaminated with noise.

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Zelt, C. A., D. A. Forsyth, B. Milkereit, D. J. White, I. Asudeh, and R. M. Easton. "Seismic structure of the Central Metasedimentary Belt, southern Grenville Province." Canadian Journal of Earth Sciences 31, no. 2 (February 1, 1994): 243–54. http://dx.doi.org/10.1139/e94-024.

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Crust and upper-mantle structure interpreted from wide-angle seismic data along a 260 km profile across the Central Metasedimentary Belt of the southern Grenville Province in Ontario and New York State shows (i) relatively high average crustal and uppermost mantle velocities of 6.8 and 8.3 km/s, respectively; (ii) east-dipping reflectors extending to 24 km depth in the Central Metasedimentary Belt; (iii) weak lateral velocity variations beneath 5 km; (iv) a mid-crustal boundary at 27 km depth; and (v) a depth to Moho of 43–46 km. The wide-angle model is generally consistent with the vertical-incidence reflectivity of an intersecting Lithoprobe reflection line. The mid-crustal boundary correlates with a crustal detachment zone in the Lithoprobe data and the depth extent of east-dipping wide-angle reflectors. Regional structure and aeromagnetic anomaly trends support the southwest continuity of Grenville terranes and their boundaries from the wide-angle profile to two reflection lines in Lake Ontario. A zone of wide-angle reflectors with an average apparent eastward dip of 13° has a surface projection that correlates spatially with the boundary between the Elzevir and Frontenac terranes of the Central Metasedimentary Belt and resembles reflection images of a crustal-scale shear zone beneath Lake Ontario. A high-velocity upper-crustal anomaly beneath the Elzevir–Frontenac boundary zone is positioned in the hanging wall associated with the concentrated zone of wide-angle reflectors. The high-velocity anomaly is coincident with a gravity high and increased metamorphic grade, suggesting northwest transport of mid-crustal rocks by thrust faulting consistent with the mapped geology. The seismic data suggest (i) a reflective, crustal-scale structure has accommodated northwest-directed tectonic transport within the Central Metasedimentary Belt; (ii) this structure continues southwest from the exposed Central Metasedimentary Belt to at least southern Lake Ontario; and (iii) crustal reflectivity and complexity within the eastern Central Metasedimentary Belt is similar to that observed at the Grenville Front and the western Central Metasedimentary Belt boundary.

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Hawman, R. B., M. C. Chapman, C. A. Powell, J. E. Clippard, and H. O. Ahmed. "Wide-angle Reflection Profiling with Quarry Blasts in the Eastern Tennessee Seismic Zone." Seismological Research Letters 72, no. 1 (January 1, 2001): 108–22. http://dx.doi.org/10.1785/gssrl.72.1.108.

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Kim, Seunghwan, and Jaehoon Choi. "Optimal design of PML absorbing boundary condition for improving wide-angle reflection performance." Electronics Letters 40, no. 2 (2004): 104. http://dx.doi.org/10.1049/el:20040075.

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49

Dahl-Jensen, T., G. Lindsey, A. Law, and D. Snyder. "Processing of pre-critical wide-angle seismic reflection data from the BABEL project." Geophysical Journal International 122, no. 1 (July 1995): 1–15. http://dx.doi.org/10.1111/j.1365-246x.1995.tb03533.x.

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Klingelhoefer, Frauke, Chao-Shing Lee, Jing-Yi Lin, and Jean-Claude Sibuet. "Structure of the southernmost Okinawa Trough from reflection and wide-angle seismic data." Tectonophysics 466, no. 3-4 (March 2009): 281–88. http://dx.doi.org/10.1016/j.tecto.2007.11.031.

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