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1
Jeong, Jeeyoon, Dasom Kim, Hyeong-Ryeol Park, Taehee Kang, Dukhyung Lee, Sunghwan Kim, Young-Mi Bahk e Dai-Sik Kim. "Anomalous extinction in index-matched terahertz nanogaps". Nanophotonics 7, n.º 1 (1 de janeiro de 2018): 347–54. http://dx.doi.org/10.1515/nanoph-2017-0058.
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AbstractSlot-type nanogaps have been widely utilized in transmission geometry because of their advantages of exclusive light funneling and exact quantification of near-field enhancement at the gap. For further application of the nanogaps in electromagnetic interactions with various target materials, complementary studies on both transmission and reflection properties of the nanogaps are necessary. Here, we observe an anomalous extinction of terahertz waves interacting with rectangular ring-shaped sub-30 nm wide gaps. Substrate works as an index matching layer for the nanogaps, leading to a stronger field enhancement and increased nonlinearity at the gap under substrate-side illumination. This effect is expressed in reflection as a larger dip at the resonance, caused by destructive interference of the diffracted field from the gap with the reflected beam from the metal. The resulting extinction at the resonance is larger than 60% of the incident power, even without any absorbing material in the whole nanogap structure. The extinction even decreases in the presence of an absorbing medium on top of the nanogaps, suggesting that transmission and reflection from nanogaps might not necessarily represent the absorption of the whole structure.
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Chen, Yingying, Qinghua Liang, Haozhe Sun, Xiaochen Zhang, Weikang Dong, Meihua Niu, Yanji Zheng et al. "Kissing-loop nano-kirigami structures with asymmetric transmission and anomalous reflection". Light: Advanced Manufacturing 5 (2024): 1. http://dx.doi.org/10.37188/lam.2024.042.
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Yu, Guanxia, Yihang Lv, Xiaomeng Zhang e Ruoyu Cao. "Electromagnetic propagation characteristics of one-dimensional photonic crystals with metal layers in quasi-parity-time (PT)-symmetric system". Zeitschrift für Naturforschung A 75, n.º 7 (28 de julho de 2020): 665–70. http://dx.doi.org/10.1515/zna-2020-0104.
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AbstractIn this study, the propagation characteristics of electromagnetic waves in a parity-time (PT)-symmetrical 1D photonic crystal comprising dispersed silver layers are investigated. Based on the transmission matrix theory, the total reflection and transmission coefficients of the structure are obtained. It was found that, due to the PT-symmetrical structure, the reflections of the left and right incident waves are nonreciprocal. Numerical simulations indicated that the width of the band gap decreases with the increase in the gain and loss factor ρ in the PT medium, and the band gap ultimately disappears when ρ reaches a critical value, i. e., ${\rho }_{PT}$. With the increase in $\rho { >}{\rho }_{PT}$, anomalous transmittance and reflection occur within the original bang gap. As the gain and loss factor ρ continue to increase, the abnormal transmittance and reflectivity exhibit a trend of oscillatory decline, and perfect transmission can be achieved at larger values of ρ.
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Fan, Zihang, Zhaoyun Zong e Fubin Chen. "Accurate P-wave reflection and transmission coefficients for non-welded interface incorporating elasto-plastic deformation". Annals of Geophysics 66, n.º 3-4 (6 de novembro de 2023): PE322. http://dx.doi.org/10.4401/ag-8909.
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P-wave reflection and transmission coefficients for non-welded interface play crucial roles in broad practical engineering productions, involving fracture properties prediction and seismic inversion. However, the existing reflection coefficient equations for non-welded interface in elasto-plastic media are seldom studied, although the elasto-plastic deformation is frequently encountered in the Earth’s subsurface due to artificial and tectonic activities. In this study, we proposed the accurate reflection and transmission coefficients equation for a non-welded interface embedded in an elasto-plastic deformed medium based on the elasto-plastic acoustoelastic and linear-slip theory. In detail, this paper uses elasto-plastic acoustoelastic theory to derive the reflection and transmission coefficients equation. The reflection and transmission coefficients matrix are solved using the linear-slip theory as the boundary condition. Moreover, we use the hardening parameter and plastic deformation to represent the plastic properties of the rock, which is a function of stress and plastic deformation. Through Numerical analysis, the deformation caused by static stress has significantly changed the amplitude and the slope of the reflection and transmission coefficients amplitude. As the stress increases, the rock’s velocity becomes higher, and all reflection and transmission coefficients (i.e., RPP, RPS, TPP, TPS) abruptly change at the critical angle. Furthermore, with the increase in plastic deformation, the critical angle of the incident P-wave and the hardening parameter becomes larger than the unstressed state. The non-welded interface exhibits a low-pass frequency filter for reflected SV-waves and a high-pass frequency filter for reflected P-waves and transmitted P and SV waves. In addition, we can observe that static vertical stress can weaken the anomalous reflections caused by non-welded formations, but the effect is insignificant. On the other hand, the effect of fracture normal compliance to reflection and transmission is detailly investigated. When N<2.5*10-10(MPa-1), The non-welded interface is close to the welded interface, while N>2.5*10-5(MPa-1), the non-welded interface is close to the solid-air interface.
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Hatchell, Paul J. "Fault whispers: Transmission distortions on prestack seismic reflection data". GEOPHYSICS 65, n.º 2 (março de 2000): 377–89. http://dx.doi.org/10.1190/1.1444733.
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Transmission distortions are observed on prestack seismic data at two locations in the Gulf of Mexico. These distortions produce anomalous amplitude versus offset (AVO) signatures. The locations of the distortion zones are determined using acquisition geometry and ray tracing. No obvious reflection events, such as shallow gas zones, are observed at the predicted locations of the distortion zones. Instead, the distortion zones correlate with buried faults and unconformities. It is postulated that the distortions are produced by velocity changes across buried faults and unconformities. The distortions result from an interference pattern resulting from seismic waves arriving from different sides of the faults. A simple model is developed to explain many of the characteristics of the distortion pattern.
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Spall, Michael A., e Joseph Pedlosky. "Reflection and Transmission of Equatorial Rossby Waves*". Journal of Physical Oceanography 35, n.º 3 (1 de março de 2005): 363–73. http://dx.doi.org/10.1175/jpo-2691.1.
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Abstract The interaction of equatorial Rossby waves with a western boundary perforated with one or more narrow gaps is investigated using a shallow-water numerical model and supporting theory. It is found that very little of the incident energy flux is reflected into eastward-propagating equatorial Kelvin waves provided that at least one gap is located within approximately a deformation radius of the equator. Because of the circulation theorem around an island, the existence of a second gap off the equator reduces the reflection of short Rossby waves and enhances the transmission of the incident energy into the western basin. The westward energy transmitted past the easternmost island is further reduced upon encountering islands to the west, even if these islands are located entirely within the “shadow” of the easternmost island. A localized patch of wind forcing was also used to generate low-frequency Rossby waves for cases with island configurations representative of the western equatorial Pacific. For both idealized islands and a coastline based on the 200-m isobath, the amount of incident energy reflected into Kelvin waves depends on both the duration of the wind event and the meridional decay scale of the anomalous winds. For wind events of 2-yr duration with a meridional decay scale of 700 km, the reflected energy is 37% of the incident flux, and the energy transmitted into the Indian Ocean is approximately 10% of the incident flux, very close to that predicted by previous theories. For shorter wind events or winds confined more closely to the equator the reflected energy is significantly less.
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He, Mengyun, Yu Huang, Huimin Sun, Yu Fu, Peng Zhang, Chenbo Zhao, Kang L. Wang, Guoqiang Yu e Qing Lin He. "Quantum anomalous Hall interferometer". Journal of Applied Physics 133, n.º 8 (28 de fevereiro de 2023): 084401. http://dx.doi.org/10.1063/5.0140086.
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Electronic interferometries in integer and fractional quantum Hall regimes have unfolded the coherence, correlation, and statistical properties of interfering constituents. This is addressed by investigating the roles played by the Aharonov–Bohm effect and Coulomb interactions on the oscillations of transmission/reflection. Here, we construct magnetic interferometers using Cr-doped (Bi,Sb)2Te3 films and demonstrate the electronic interferometry using chiral edge states in the quantum anomalous Hall regime. By controlling the extent of edge coupling and the amount of threading magnetic flux, distinct interfering patterns were observed, which highlight the interplay between the Coulomb interactions and Aharonov–Bohm interference by edge states. The observed interference is likely to exhibit a long-range coherence and robustness against thermal smearing probably owing to the long-range magnetic order. Our interferometer establishes a platform for (quasi)particle interference and topological qubits.
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XU ZHANG-CHENG, GUO CHANG-LIN, ZHAO ZONG-YAN, T.FUKAMACHI e R.NEGISHI. "ANOMALOUS TRANSMISSION OF X-RAYS UNDER ASYMMETRICAL REFLECTION CONDITION NEAR THE ABSORPTION EDGE". Acta Physica Sinica 47, n.º 11 (1998): 1818. http://dx.doi.org/10.7498/aps.47.1818.
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Falsi, Ludovica, Salvatore Macis, Yehonatan Gelkop, Luca Tartara, Eleonora Bonaventura, Paola Di Pietro, Andrea Perucchi et al. "Anomalous Optical Properties of KTN:Li Ferroelectric Supercrystals". Nanomaterials 13, n.º 5 (27 de fevereiro de 2023): 899. http://dx.doi.org/10.3390/nano13050899.
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We report a spectroscopic investigation of potassium–lithium–tantalate–niobate (KTN:Li) across its room-temperature ferroelectric phase transition, when the sample manifests a supercrystal phase. Reflection and transmission results indicate an unexpected temperature-dependent enhancement of average index of refraction from 450 nm to 1100 nm, with no appreciable accompanying increase in absorption. Second-harmonic generation and phase-contrast imaging indicate that the enhancement is correlated to ferroelectric domains and highly localized at the supercrystal lattice sites. Implementing a two-component effective medium model, the response of each lattice site is found to be compatible with giant broadband refraction.
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Papathanasiou, T. K., A. B. Movchan e D. Bigoni. "Wave reflection and transmission in multiply stented blood vessels". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 473, n.º 2202 (junho de 2017): 20170015. http://dx.doi.org/10.1098/rspa.2017.0015.
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Closed circulatory systems display an exquisite balance between vascular elasticity and viscous fluid effects, to induce pulse-smoothing and avoid resonance during the cardiac cycle. Stents in the arterial tree alter this balance through stiffening and because a periodic structure is introduced, capable of interacting with the fluid in a complex way. While the former feature has been investigated, the latter received no attention so far. But periodic structures are the building blocks of metamaterials, known for their ‘non-natural’ behaviour. Thus, the investigation of a stent's periodic microstructure dynamical interactions is crucial to assess possible pathological responses. A one-dimensional fluid–structure interaction model, simple enough to allow an analytical solution for situations of interest involving one or two interacting stents, is introduced. It is determined: (i) whether or not frequency bands exist in which reflected blood pulses are highly increased and (ii) if these bands are close to the characteristic frequencies of arteries and finally, (iii) if the internal structure of the stent can sensibly affect arterial blood dynamics. It is shown that, while the periodic structure of an isolated stent can induce anomalous reflection only in pathological conditions, the presence of two interacting stents is more critical, and high reflection can occur at frequencies not far from the physiological values.
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Dash, Sasmita, Christos Liaskos, Ian F. Akyildiz e Andreas Pitsillides. "Graphene Hypersurface for Manipulation of THz Waves". Materials Science Forum 1009 (agosto de 2020): 63–68. http://dx.doi.org/10.4028/www.scientific.net/msf.1009.63.
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In this work, we investigated graphene hypersurface (HSF) for the manipulation of THz waves. The graphene HSF structure is consists of a periodic array of graphene unit cells deposited on silicon substrate and terminated by a metallic ground plane. The performance of the proposed HSF is numerically analyzed. Electromagnetic parameters of HSF such as permeability, permittivity, and impedance are studied. The proposed graphene HSF has active control over absorption, reflection, and transmission of THz waves. The graphene HSF provides perfect absorption, zero reflection and zero transmission at resonance. Moreover, the graphene HSF structure has the advantage of anomalous reflection and frequency reconfiguration. Incident waves can be reflected in the desired direction, depending on the phase gradient of the HSF and the perfect absorption is maintained at all reconfigurable frequencies upon reconfiguration. The results reveal the effectiveness of the graphene HSF for the manipulation of THz waves.
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Feng, Yijun, Xiaohua Teng, Junming Zhao, Yan Chen e Tian Jiang. "Anomalous reflection and refraction in anisotropic metamaterial realized by periodically loaded transmission line network". Journal of Applied Physics 100, n.º 11 (2006): 114901. http://dx.doi.org/10.1063/1.2369540.
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Yepes, Cristina, Stefano Maci, Sergei A. Tretyakov e Enrica Martini. "On the role of spatial dispersion in boundary conditions for perfect non-specular reflection". EPJ Applied Metamaterials 9 (2022): 17. http://dx.doi.org/10.1051/epjam/2022015.
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Exact solutions for perfect anomalous reflection through metasurfaces have been recently developed in terms of both ideal nondispersive impenetrable boundary conditions (BCs) and penetrable BCs on top of a grounded slab. The second model is more accurate for the description of metasurfaces realized in PCB technology. Focusing on this particular class of metasurfaces, this paper investigates the connection between the two solutions, with the aim to clarify the role of spatial dispersion. It is shown that the two solutions can be related through an equivalent transmission network where transmission lines with different wavenumbers are associated to the incident and reflected waves. Finally, numerical analyses are carried out to assess the impact of neglecting spatial dispersion, as it is done in designs based on a linear phase gradient of the local reflection coefficient.
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Mei, Jun, Lijuan Fan e Xiaobin Hong. "Elastic Metagratings with Simultaneous Modulation of Reflected and Transmitted Waves". Crystals 12, n.º 7 (24 de junho de 2022): 901. http://dx.doi.org/10.3390/cryst12070901.
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Elastic metagratings enabling independent and complete control of both reflection and transmission of bulk longitudinal and transverse waves are highly desired in application scenarios such as non-destructive assessment and structural health monitoring. In this work, we propose a kind of simply structured metagrating composed only of elliptical hollow cylinders carved periodically in a steel background. By utilizing the grating diffraction theory and genetic algorithm, we endow these metagratings with the attractive functionality of simultaneous and high-efficiency modulation of every reflection and transmission channel of both longitudinal and transverse waves. Interesting wave-front manipulation effects including pure mode conversion and anomalous deflection along the desired direction are clearly demonstrated through full-wave numerical simulations. Due to its subwavelength thickness and high manipulation efficiency, the proposed metagrating is expected to be useful in the design of multifunctional elastic planar devices.
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Alshits, V. I., A. N. Darinskii e A. L. Shuvalov. "Anomalous reflection and transmission of acoustic beam on the interface between two 180°-ferroelectric domains". Ferroelectrics 126, n.º 1 (fevereiro de 1992): 323–28. http://dx.doi.org/10.1080/00150199208227080.
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Mao, Weijian, e Graham W. Stuart. "Transmission‐reflection tomography: Application to reverse VSP data". GEOPHYSICS 62, n.º 3 (maio de 1997): 884–94. http://dx.doi.org/10.1190/1.1444196.
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A multiphase tomographic algorithm is presented that allows 2-D and 3-D slowness (inverse of velocity) and variable reflector depth to be reconstructed simultaneously from both transmission and reflection traveltimes. We analyze the ambiguity in the determination of velocity and depth in transmission and reflection data and realize that depth perturbation is more sensitive to reflection traveltime anomalies than slowness perturbation, whereas the reverse is true of transmission traveltime anomalies. Because of the constraints on velocity and depth provided by the different wave types, this algorithm reduces the ambiguity substantially between velocity and depth prevalent in reflection tomography and also avoids the undetermined problem in transmission tomography. The linearized inversion was undertaken iteratively by decoupling velocity parameters from reflector depths. A rapid 2-D and 3-D ray‐tracing algorithm is used to compute transmission and reflection traveltimes and partial derivatives with respect to slowness and reflector depth. Both depth and velocity are parameterized in terms of cubic B‐spline functions. Synthetic examples indicate the improvement in tomographic results when both transmission and reflection times are included. The method has been applied to a reverse vertical seismic profile (VSP) data set recorded on the British coal measures along a crossed‐linear array. Traveltimes were picked automatically by the simultaneous determination of time delays and stacking weights using a waveform matching technique. The tomographic inversion of the observed reverse VSP images two fault‐zones of lower velocity than the surrounding media. The location of the faults was confirmed by near‐by reflection lines. The technique can be applied to offset VSPs or reverse VSPs and coincident VSP and surface reflection data.
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Soares, J., I. Wainer e N. C. Wells. "Reflection of equatorial Kelvin waves at eastern ocean boundaries Part I: hypothetical boundaries". Annales Geophysicae 17, n.º 6 (30 de junho de 1999): 812–26. http://dx.doi.org/10.1007/s00585-999-0812-z.
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Abstract. A baroclinic shallow-water model is developed to investigate the effect of the orientation of the eastern ocean boundary on the behavior of equatorial Kelvin waves. The model is formulated in a spherical polar coordinate system and includes dissipation and non-linear terms, effects which have not been previously included in analytical approaches to the problem. Both equatorial and middle latitude response are considered given the large latitudinal extent used in the model. Baroclinic equatorial Kelvin waves of intraseasonal, seasonal and annual periods are introduced into the domain as pulses of finite width. Their subsequent reflection, transmission and dissipation are investigated. It is found that dissipation is very important for the transmission of wave energy along the boundary and for reflections from the boundary. The dissipation was found to be dependent not only on the presence of the coastal Kelvin waves in the domain, but also on the period of these coastal waves. In particular the dissipation increases with wave period. It is also shown that the equatorial β-plane approximation can allow an anomalous generation of Rossby waves at higher latitudes. Nonlinearities generally have a small effect on the solutions, within the confines of this model.Key words. Oceanography: general (equatorial oceanography; numerical modeling) · Oceanography: physical (eastern boundary currents)
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Khanin, S. D., A. I. Vanin, Yu A. Kumzerov, V. G. Solovyev, A. V. Cvetkov e M. V. Yanikov. "PECULIAR PROPERTIES OF ELECTROMAGNETIC RADIATION PROPAGATION IN PHOTONIC CRYSTALLINE METAL-DIELECTRIC SYSTEMS BASED ON OPALS". RADIO COMMUNICATION TECHNOLOGY, n.º 51 (30 de dezembro de 2021): 89–99. http://dx.doi.org/10.33286/2075-8693-2021-51-89-99.
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The article studies the propagation of electromagnetic waves in metal-dielectric systems based on opals. We revealed anomalous transmission and absorption of light by hybrid plasmon- photonic layered heterostructures associated with the excitation of surface plasmon polaritons propagating along the metal-dielectric interface. The position of maxima in the reflection spectra of nanocomposites, obtained by filling the opal matrix with metal by the electrothermodiffusion method, is explained by the Bragg diffraction, and the asymmetric form of the spectral curves is attributed to the Fano resonance.
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Entin, I. R., V. I. Khrupa e L. I. Datsenko. "Bragg and diffuse components of X-ray reflection measured using acoustic excitation of an Si crystal with oxide precipitates". Journal of Applied Crystallography 23, n.º 5 (1 de outubro de 1990): 355–58. http://dx.doi.org/10.1107/s0021889890004320.
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Bragg and diffuse scattering contributions to a reflection can be separated using the intensity dependence on the amplitude of transverse ultrasound excited in the crystal. The method is based on the fact that a weak ultrasound with wavelength equal to the extinction length suppresses almost completely the anomalous transmission of the coherent (Bragg) beam in a sufficiently thick absorbing crystal and does not affect diffuse scattering. Both parameters characterizing diffraction in a slightly imperfect crystal, the static Debye–Waller factor and the coefficient of additional absorption due to diffuse scattering, have been determined for a silicon crystal containing oxide precipitates after heat treatment.
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Hu, Hongjun. "Analysis of the Transmission Spectrum of Flat Glass from Near-infrared to the Ultraviolet". Highlights in Science, Engineering and Technology 48 (16 de maio de 2023): 230–36. http://dx.doi.org/10.54097/hset.v48i.8352.
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Contemporarily, glass windows have a great impact on human beings’ daily life. It is crucial to design a glass with a reasonable thickness with a high transmission of visible light as well as a high reflection of near infrared light. In general, reflection from the glass surface and absorption of light waves by the glass material are important features for transmission. Therefore, for UV-visible near-infrared light waves, the greater the thickness of the glass, the greater the light absorption loss and the lower the transmission rate. However, it is believed that there are multiple reflections of light waves in flat glass and that the losses caused by reflections should also be related to the refractive index of the glass and the wavelength of the incident light. On this basis, this study has developed theoretical models of transmittance versus incident light wavelength and glass thickness, refractive index and absorption coefficient. According to the theoretical analysis, the thickness of the glass has a significant effect on the transmission spectrum of sunlight. To experimentally verify this theoretically predicted anomaly, this paper designed the experimental and measurement route and built the experimental test rig. A variety of glass samples in the thickness range of 1mm-10mm were designed and prepared for this project, and the UV-Vis-NIR transmission of the glass was scanned and measured, while the final measurement results observed anomalies in the variation of transmission with thickness. The experimental results, therefore, provide valid support for the theoretical model of this paper.
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Pupyrev, P. D., A. M. Lomonosov, I. A. Nedospasov e A. P. Mayer. "Anomalous reflection and transmission of surface acoustic waves at a crystal edge via coupling to leaky wedge waves". Applied Physics Letters 119, n.º 2 (12 de julho de 2021): 021902. http://dx.doi.org/10.1063/5.0051060.
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Yao, Yongzhao, Keiichi Hirano, Yoshihiro Sugawara, Kohei Sasaki, Akito Kuramata e Yukari Ishikawa. "Observation of dislocations in thick β-Ga2O3 single-crystal substrates using Borrmann effect synchrotron x-ray topography". APL Materials 10, n.º 5 (1 de maio de 2022): 051101. http://dx.doi.org/10.1063/5.0088701.
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We performed Borrmann effect x-ray topography (XRT) to observe dislocations and other structural defects in a thick β-Ga2O3 (001) substrate. The Borrmann effect was realized by working in a symmetrical Laue geometry ( g = 020). Anomalous transmission occurred under the exact Bragg condition, producing a strong diffraction beam that allowed us to image defects across the entire thickness of the substrate. The analysis clearly revealed straight b-axis screw-type and curved dislocations and allowed assessing the corresponding behaviors. Other structural defects, including pipe-shaped voids and dislocation loops produced by mechanical damage, were also observed. Finally, we compared Borrmann effect transmission topography and conventional reflection topography and explained the appearance of some characteristic defects in the two modes. Our results show that Borrmann effect XRT is a powerful and effective technique to study the spatial distribution and structural properties of defects in highly absorbing β-Ga2O3.
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Ross, Gerald M. "Evolution of Precambrian continental lithosphere in Western Canada: results from Lithoprobe studies in Alberta and beyond". Canadian Journal of Earth Sciences 39, n.º 3 (1 de março de 2002): 413–37. http://dx.doi.org/10.1139/e02-012.
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The Precambrian lithosphere of western Canada was assembled into the present crustal configuration between ca. 2.01.78 Ga by plate collisions, sometimes accompanied by arc magmatism, with subsequent cooling of the lithosphere since ca. 1.7 Ga. Collisional processes inferred along preserved plate sutures include (1) subduction of oceanic lithosphere and accretion of Proterozoic arc crust to the western Rae Province; (2) marginal basin consumption and tectonic entrapment of the Hearne Province between coeval subductioncollision zones; and (3) amagmatic marginal basin closure, perhaps analogous to the roots of small collisional orogens, such as the Pyrenees. Seismic reflection profiles acquired during the Lithoprobe Alberta Basement Transect have captured images of syn- to post-collisional structures along these sutures and evidence for crustal-scale thrust imbrication and rigid body accretion of Archean crust with preservation of precollisional tectonic fabric. The degree to which lithospheric mantle beneath Archean crustal blocks was preserved during these collisions is unknown, although tectonic geometries imply significant thermal and (or) mechanical interaction. Post-collisional, intrusive mafic magmatism is imaged widely in both seismic reflection and refraction surveys. These magmatic events are demonstrably Proterozoic, based on crosscutting relationships seen on seismic reflection profiles and geochronology of lower crustal xenoliths, and are comparable in scale to Phanerozoic igneous provinces (e.g., large igneous provinces) but have little preserved surface manifestation. Reactivation of Precambrian basement structures is limited or very subtle, reflecting strength control by the mantle on stress transmission and crustal failure. Long-wavelength elastic deformation of the crust during the Phanerozoic occurred in regions associated with, or adjacent to, Proterozoic mafic magmatism, suggesting local rheologic control of anomalous Phanerozoic paleotopography.
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Zanotto, Simone, Giacomo Mazzamuto, Francesco Riboli, Giorgio Biasiol, Giuseppe C. La Rocca, Alessandro Tredicucci e Alessandro Pitanti. "Photonic bands, superchirality, and inverse design of a chiral minimal metasurface". Nanophotonics 8, n.º 12 (13 de novembro de 2019): 2291–301. http://dx.doi.org/10.1515/nanoph-2019-0321.
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AbstractPhotonic band structures are a typical fingerprint of periodic optical structures, and are usually observed in spectroscopic quantities such as transmission, reflection, and absorption. Here we show that the chiro-optical response of a metasurface constituted by a lattice of non-centrosymmetric, L-shaped holes in a dielectric slab shows a band structure, where intrinsic and extrinsic chirality effects are clearly recognized and connected to localized and delocalized resonances. Superchiral near-fields can be excited in correspondence to these resonances, and anomalous behaviors as a function of the incidence polarization occur. Moreover, we have introduced a singular value decomposition (SVD) approach to show that the above mentioned effects are connected to specific fingerprints of the SVD spectra. Finally, by means of an inverse design technique we have demonstrated that the metasurface based on an L-shaped hole array is a minimal one. Indeed, its unit cell geometry depends on the smallest number of parameters needed to implement arbitrary transmission matrices compliant with the general symmetries for 2d-chiral structures. These observations enable more powerful wave operations in a lossless photonic environment.
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Honnicke, Marcelo Goncalves, e Cesar Cusatis. "Detection of the standing X-ray wavefield intensity inside a thin crystal using back-diffraction topography and imaging". Journal of Applied Crystallography 42, n.º 6 (30 de outubro de 2009): 999–1003. http://dx.doi.org/10.1107/s0021889809040199.
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The standing X-ray wavefield into a single-crystal bulk is characterized by a combination of the diffracted–reflected h-beams and the diffracted–transmitted o-beam. For different angular positions on the total reflection region, the standing X-ray wavefield has its maximum from the region between the atomic planes (low photoelectric absorption) to the region on the atomic planes (high photoelectric absorption). Historically, the evidence for such a characteristic has come from experiments such as anomalous transmission (Borrmann effect, originally detected in Laue geometry) and fluorescent measurements with a single crystal under diffraction conditions. In the present work, such a characteristic is demonstrated by the direct measurement of the standing X-ray wavefield intensity into a 50 µm-thick single-crystal CCD detector (Si 800) set in back-diffraction geometry.
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Chen, Fubin, Zhaoyun Zong, Xingyao Yin e Yanwen Feng. "Accurate formulae for P-wave reflectivity and transmissivity for a non-welded contact interface with the effect of in situ vertical stress". Geophysical Journal International 229, n.º 1 (24 de novembro de 2021): 311–27. http://dx.doi.org/10.1093/gji/ggab475.
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SUMMARY A detailed knowledge of wave reflectivity parametrization for non-welded interface plays an important role in fracture characterization and reservoir prediction. However, the effect of in situ stress on reflectivity formulae for non-welded contact interface remains unclear. Here based on the linear-slip theory and acoustoelasticity theory, we propose the accurate P-wave reflectivity and transmissivity formulae for planar P wave incident upon the non-welded interface between two elastic half-spaces under the in situ vertical stress. The discontinuous boundary conditions coupled with vertical stress is used to represent the non-welded contact interface for the elastic and viscous cases. Then accurate formulae are derived by solving the boundary conditions. Numerical results show that the proposed formulae are frequency-dependent and the non-welded interface performs as high- and low-pass filters for reflected and transmittedP wave at low stress, respectively. Moreover, initial vertical stress can change the maximum amplitudes of reflection and transmission coefficients and the corresponding critical angles. Particularly, vertical stress weakens the fracture-induced anomalous seismic reflections in zones lack of significant impedance contrasts at low incidence angles. The sensitivity analysis suggests a non-welded interface transforms into a welded interface at normal compliance ${\Delta _N} \le 5 \times {10^{ - 11}}$ m Pa−1. The phases and amplitudes of the four coefficients reach the maximum values at the specific viscosity $\eta \approx {10^6}$ Pa·s m−1 for the case of P wave obliquely incident upon the viscous interface at incidence angle 30°. Finally, we describe a method for simulating seismic reflection at the interface of two elastic media with experimental measurement.
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KOURCHI, Hasna, Simon BERNARD, Farid CHATI e Fernand LéON. "Metagratings for underwater acoustic wavefront manipulation". INTER-NOISE and NOISE-CON Congress and Conference Proceedings 270, n.º 9 (4 de outubro de 2024): 2231–39. http://dx.doi.org/10.3397/in_2024_3153.
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Metagratings are flat periodic assemblies of small scatterers, engineered to achieve effects such as steering, beamforming, or absorption. They have recently received attention in both electromagnetism and acoustic fields. In this work, we report the design, modeling, and experimental characterization of metagratings to steer underwater acoustic wavefronts towards anomalous directions (i.e. not classically allowed by Snell-Decartes relationships) with high efficiency (close to 100%). They are build from simple assemblies of small brass cylinders, hold by 3D-printed plastic supports, and can redirect ultrasonic wavefronts either in reflection mode (when placed in front of a reflective surface like e.g. the water / air interface) or in transmission mode. Furthermore, we demonstrate how metagratings build from an asymmetrical pattern of multiple basic elements can achieve near perfect asymmetrical transmission: a wavefront incident from side of the structure is fully transmitted, while a similar wavefront incoming from the other side is fully reflected, achieving an acoustic one-way mirror effect. This work combine theoretical analysis, finite element modeling, and experimentation in water tanks to explore and demonstrate the potential of such metagratings for various applications in underwater acoustics, like communication, noise mitigation, and stealth.
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RAVAZZOLI, CLAUDIA L. "ANALYSIS OF THE REFLECTION AND TRANSMISSION COEFFICIENTS IN THREE-PHASE SANDSTONE RESERVOIRS". Journal of Computational Acoustics 09, n.º 04 (dezembro de 2001): 1437–54. http://dx.doi.org/10.1142/s0218396x0100084x.
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As it is well-known, seismic and acoustic data play a very important role in the characterization of hydrocarbon reservoirs. The correct interpretation of the anomalies observed in seismic wave velocities, quality factors and reflection coefficients in such environments makes necessary to use accurate models taking into account the main petrophysical features of the rocks. This also brings into play the importance of adequately describing the in situ properties of the reservoir fluids. This work investigates the influence of gas saturation and excess pore fluid pressure on wave energy splitting at plane interfaces within a Biot-type porous medium saturated by a liquid–gas mixture. Using laboratory measurements made on a wide variety of sandstones, we incorporate in the model the effective pressure dependence of rock matrix properties such as bulk and shear modulus, porosity and pore space compressibility. Also, using empirical laws, we estimate the properties of real hydrocarbon gases, oils and brines of different compositions under variable pressure and temperature conditions. We present analytical computations of the amplitude reflection and transmission coefficients to study the combined effect of the forementioned variables, aiming at a further AVA trend analysis.
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Monzon, Cesar. "Venturi effect on slotted metamaterial interfaces: broadband tunnelling". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 465, n.º 2110 (8 de julho de 2009): 2977–90. http://dx.doi.org/10.1098/rspa.2009.0092.
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We demonstrate the existence of broadband anomalous transmission of electromagnetic (EM) waves through an electrically very narrow aperture in a thin metal plate backed by left-handed media (LHM). It is shown that the incoming energy is simply squeezed through the aperture, without any reflection, regardless of how small the physical aperture is. Analogous to the Venturi effect in fluids, the EM energy behaves as an incompressible fluid, flowing through the constriction (aperture), as if the wave character of EM was lost. This counterintuitive tunnelling effect is not related to resonances and is impossible to achieve with naturally occurring materials. Analysis indicates that a cascaded waveguide implementation, in the form of a slotted metallized LHM wall, retains the exotic broadband transparency character. Applications for a device with these properties abound in the RF/microwave/THz/optical ranges, to which the analysis can be scaled. To complement this analysis, a proposal for achieving broadband LHM is also included.
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Смирнова, И. А., Е. В. Шулаков e Э. В. Суворов. "Формирование изображения краевой дислокации при аномальном прохождении рентгеновского излучения". Физика твердого тела 61, n.º 8 (2019): 1499. http://dx.doi.org/10.21883/ftt.2019.08.47977.453.
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The image formation features of section and projection topograms of an edge dislocation normal to a crystal surface are considered for the case of X-ray anomalous transmission. Experimental images are analyzed using the numerical simulation of diffraction experiment. The new mechanism of an image formation of defects arranged near an output crystal surface is proposed. The distinctions of dislocation topographic images from local disorientation rosettes of reflecting planes are noted.
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Oliveira, Luna R. N., e Marcos G. E. da Luz. "Basic Cells Special Features and Their Influence on Global Transport Properties of Long Periodic Structures". Entropy 26, n.º 11 (3 de novembro de 2024): 942. http://dx.doi.org/10.3390/e26110942.
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In this contribution, we address quantum transport in long periodic arrays whose basic cells, localized potentials U(x), display certain particular features. We investigate under which conditions these “local” special characteristics can influence the tunneling behavior through the full structure. As the building blocks, we consider two types of U(x)s: combinations of either Pöschl–Teller, U0/cosh2[αx], potentials (for which the reflection and transmission coefficients are known analytically) or Gaussian-shaped potentials. For the latter, we employ an improved potential slicing procedure using basic barriers, like rectangular, triangular and trapezoidal, to approximate U(x) and thus obtain its scattering amplitudes. By means of a recently derived method, we discuss scattering along lattices composed of a number, N, of these U(x)s. We find that near-resonance energies of an isolated U(x) do impact the corresponding energy bands in the limit of very large Ns, but only when the cell is spatially asymmetric. Then, there is a very narrow opening (defect or rip) in the system conduction quasi-band, corresponding to the energy of the U(x) quasi-state. Also, for specific U0’s of a single Pöschl–Teller well, one has 100% transmission for any incident E>0. For the U(x) parameters rather close to such a condition, the associated array leads to a kind of “reflection comb” for large Ns; |TN(k)|2 is not close to one only at very specific values of k, when |TN|2≈0. Finally, the examples here—illustrating how the anomalous transport comportment in finite but long lattices can be inherited from certain singular aspects of the U(x)s—are briefly discussed in the context of known effects in the literature, notably for lattices with asymmetric cells.
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Luo, Mu, Norio Arihara, Shangxu Wang, Bangrang Di e Jianxin Wei. "Abnormal transmission attenuation and its impact on seismic-fracture prediction — A physical modeling study". GEOPHYSICS 71, n.º 1 (janeiro de 2006): D15—D22. http://dx.doi.org/10.1190/1.2159048.
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Fracture-induced anisotropy can lead to observable azimuthal variations of seismic attributes that then can be used for characterizing a fracture system. Unfortunately, abnormal transmission losses along raypaths also can result in similar azimuthal variations leading to uncertainty in such fracture determination. Using a physical model containing gas-filled fractures, we investigate the impact of abnormal transmission loss on fracture detection from ultrasonic data in a laboratory setting. Recorded reflection amplitudes and traveltimes are used to study ultrasonic responses to the presence of the gas-filled fractures and to understand observed azimuthal attribute anomalies. Experimental results from this study highlight the pitfalls in using azimuthal attribute variations as indicators of the presence of fractures when abnormal transmission attenuation is significant.
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Müller, Martin. "The Anomalous Influence of Polyelectrolyte Concentration on the Deposition and Nanostructure of Poly(ethyleneimine)/Poly(acrylic acid) Multilayers". Molecules 24, n.º 11 (6 de junho de 2019): 2141. http://dx.doi.org/10.3390/molecules24112141.
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The deposition and nanostructure of polyelectrolyte (PEL) multilayers (PEMs) of branched poly(ethyleneimine)/poly(acrylic acid) (PEI/PAA) onto silicon substrates was studied in terms of the dependence of pH and the PEL concentration (cPEL) in the individual adsorption steps z. Both a commercial automatic dipping device and a homebuilt automatic stream coating device (flow cell) were used. Gravimetry, SFM, transmission (TRANS) and in situ attenuated total reflection (ATR) FTIR spectroscopy were used for the quantitative determination of the adsorbed amount, thickness, chemical composition and morphology of deposited PEMs, respectively. Firstly, the combination of pH = 10 for PEI and pH = 4 for PAA, where both PEL were predominantly in the neutral state, resulted in an extraordinarily high PEM deposition, while pH combinations, where one PEL component was charged, resulted in a significantly lower PEM deposition. This was attributed to both PEL conformation effects and acid/base interactions between basic PEI and acidic PAA. Secondly, for that pH combination an exponential relationship between PEM thickness and adsorption step z was found. Thirdly, based on the results of three independent methods, the course of the deposited amount of a PEM-10 (z = 10) versus cPEL in the range 0.001 to 0.015 M at pH = 10/4 was non-monotonous showing a pronounced maximum at cPEL = 0.005 M. Analogously, for cPEL = 0.005 M a maximum of roughness and structure size was found. Fourthly, related to that finding, in situ ATR-FTIR measurements gave evidence for the release of outermost located PEI upon PAA immersion (even step) and of outermost PAA upon PEI immersion (odd step) under formation of PEL complexes in solution. These studies help us to prepare PEL-based films with a defined thickness and morphology for interaction with biofluids in the biomedical and food fields.
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Mukhutdinova, M. A., e A. N. Yurasov. "Modeling of the magnetorefractive effect in Co-Al<sub>2</sub>O<sub>3</sub> nanocomposites in the framework of the Bruggeman approximation". Russian Technological Journal 12, n.º 3 (31 de maio de 2024): 55–64. http://dx.doi.org/10.32362/2500-316x-2024-12-3-55-64.
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Objectives. To investigate the magnetorefractive effect (MRE) in nanocomposites, which consists in changing the reflection, transmittance and light absorption coefficients of samples with large magnetoresistance (MR) upon their magnetization. Materials offering high magneto-optical activity and significant MR include magnetic nanocomposites. These materials are based on a polymer matrix, which includes inorganic magnetic particles, fibers or layered particles, whose nanometer sizes range from 1 to 100 nm in at least one dimension. The main purpose of creating such nanocomposites is to combine the special properties of several components in one material. The presence in such materials of gigantic, colossal and tunneling MR, as well as the giant anomalous Hall effect, is of practical interest. Uses range from magnetic recording, light modulation, and receivers for thermal radiation, while the MRE itself is a promising method for the non-destructive testing of any nanostructures, e.g., measuring MR.Methods. The use of effective medium theory to describe the optics and magneto-optics of dispersed media provides a means to determine the complex permittivity of a medium through the permittivity of its constituent components or vice versa. The present work considers the example of a Co-Al2O3 nanocomposite with a concentration of ferromagnetic metal Co 0.4 near the percolation threshold. This particular case was considered for study, since all the properties of nanocomposites change dramatically near the percolation threshold.Results. Using the Bruggeman effective medium approximation (EMA) to describe the optical and magneto-optical properties of nanocomposites on the example of Co-Al2O3, the characteristics of MRE are obtained, namely, the change in MRE for reflection and transmission of light at normal incidence and at the angle of incidence near the Brewster angle (below the percolation threshold) or the main angle of incidence for metals (above the percolation threshold), which enhances MRE. The advantage of the EMA is the ability to study magneto-optical spectra in the range of average volume concentrations of the metal component.Conclusions. The obtained values correspond well to the known experimental data. Moreover, the described approach can be used to study any nanostructures.
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Chen, Tao, Hejing Wang, Roger Mason e Li Chen. "HRTEM investigation of intralayer and interlayer stacking defects and pyrophyllite interlayers in illite". Mineralogical Magazine 74, n.º 3 (junho de 2010): 451–61. http://dx.doi.org/10.1180/minmag.2010.074.3.451.
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AbstractMetastable authigenic 1M illite from shale of diagenetic grade has been studied using a high-resolution transmission electron microscope (HRTEM) equipped with energy-dispersive spectrometer, X-ray diffraction, and scanning electron microscope. The illite occurs as deformed flakes deficient in interlayer K+ cations with 0.6 per half cell, and with abnormally high Al in both octahedral and tetrahedral sites. Complex structural adjustments reflecting the unusual chemical composition are observed in images of illite at near-atomic resolution. Different distances and directions of intralayer shift between the upper tetrahedral sheet and the lower tetrahedral sheet within 2:1 layers are found in this sample. Intralayer undershift structure coupled with interlayer displacement is found in a 1M illite crystal, and intralayer overshift structure coupled with no interlayer displacement is found in a 1M domain of a larger crystal. Two tetrahedral sheets across the interlayer region sometimes deviate from ideal positions causing interlayer displacement. Two pyrophyllite layers are found overlying a stack of ordered 1M illite layers, and are overlain by illite layers with anomalous interlayer offsets. This offset is considered to result from an increase in the lateral dimensions of the tetrahedral sheet due to anomalous high Al content. Our observation of intralayer and interlayer deficiencies indicate that authigenic illite that crystallized in the early stage of diagenesis at low temperatures tends to give rise to heterogeneous, disordered, and metastable structures.
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Fukamachi, Tomoe, Sukswat Jongsukswat, Dongying Ju, Riichirou Negishi, Keiichi Hirano e Takaaki Kawamura. "X-ray interference fringes from a weakly bent plane-parallel crystal with negative strain gradient". Acta Crystallographica Section A Foundations and Advances 75, n.º 6 (7 de outubro de 2019): 842–50. http://dx.doi.org/10.1107/s2053273319011859.
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Under the anomalous transmission condition in the Bragg mode, X-ray interference fringes were observed between two beams with different hyperbolic trajectories in a very weakly bent plane-parallel perfect crystal with negative strain gradient. The origin of the fringes was analysed based on the dynamical theory of diffraction for a distorted crystal. In the reflected beam from the entrance surface, the interference fringes were observed between once- and twice-reflected beams from the back surface. In the transmitted beam from the back surface, the interference fringes were observed between the direct beam and once-reflected beam from the entrance surface. In the emitted beam from the lateral surface, the interference fringes were observed between the beams after different numbers of reflections in the crystal. The multiply reflected beams were formed by a combined result of long propagation length along the beam direction with large divergence of the refracted beams when the strain gradient was negative. The period of these interference fringes was sensitive to very weak strain, of the order of 10−7.
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Aliev, I. N., M. M. Yashin, A. A. Loboiko, O. O. Gorbatova e R. E. Lyatifov. "Spectroscopic Properties Study of Photonic Crystals and Nanostructures". Herald of the Bauman Moscow State Technical University. Series Natural Sciences, n.º 2 (107) (abril de 2023): 35–49. http://dx.doi.org/10.18698/1812-3368-2023-2-35-49.
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The paper proposes substantiation of dependence of dielectric permittivity, polariton dispersion and light group velocity in the sodium uranyl acetate on the wavelength. Many bands were found in the uranyl compounds transmission and absorption spectra. It was indicated that the polariton waves group velocity was decreasing anomalously in vicinity of the resonant absorption frequencies, i.e., the light was effectively stopped. This led to abnormal increase in the efficiency between the light interaction processes and the matter. Optical properties of the one-dimensional photonic crystal film formed by electrochemical etching of aluminum foil were studied. Experimental data on the transmission and reflection spectra in the region of first, second and third stop bands of the anode photonic aluminum oxide crystal were compared with theoretical dependence obtained from the known dispersion relation. Refractive indices of the first and second layers of various thin photonic crystal films, structure period and effective refractive index of the structures were theoretically calculated. Possibility of controlling position of the stop bands of one-dimensional photonic crystals in accordance with the Wulff --- Bragg’s relation was established. The studied photonic crystals could be used in experimental setups to register the light combined scattering spectra of dielectric media in the low-frequencies region
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Alalade, Muyiwa, Ina Reichert, Daniel Köhn, Frank Wuttke e Tom Lahmer. "A Cyclic Multi-Stage Implementation of the Full-Waveform Inversion for the Identification of Anomalies in Dams". Infrastructures 7, n.º 12 (27 de novembro de 2022): 161. http://dx.doi.org/10.3390/infrastructures7120161.
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For the safe and efficient operation of dams, frequent monitoring and maintenance are required. These are usually expensive, time consuming, and cumbersome. To alleviate these issues, we propose applying a wave-based scheme for the location and quantification of damages in dams. To obtain high-resolution “interpretable” images of the damaged regions, we drew inspiration from non-linear full-multigrid methods for inverse problems and applied a new cyclic multi-stage full-waveform inversion (FWI) scheme. Our approach is less susceptible to the stability issues faced by the standard FWI scheme when dealing with ill-posed problems. In this paper, we first selected an optimal acquisition setup and then applied synthetic data to demonstrate the capability of our approach in identifying a series of anomalies in dams by a mixture of reflection and transmission tomography. The results had sufficient robustness, showing the prospects of application in the field of non-destructive testing of dams.
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Ji, Yanju, Li Han, Xingguo Huang, Xuejiao Zhao, Kristian Jensen e Yibing Yu. "A high-order finite-difference scheme for time-domain modeling of time-varying seismoelectric waves". GEOPHYSICS 87, n.º 2 (31 de janeiro de 2022): T135—T146. http://dx.doi.org/10.1190/geo2021-0235.1.
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Simulation of the seismoelectric effect serves as a useful tool to capture the observed seismoelectric conversion phenomenon in porous media, thus offering promising potential in underground exploration activities to detect pore fluids such as water, oil, and gas. The static electromagnetic (EM) approximation is among the most widely used methods for numerical simulation of the seismoelectric responses. However, the static approximation ignores the accompanying electric field generated by the shear wave, resulting in considerable errors when compared to analytical results, particularly under high-salinity conditions. To mitigate this problem, we have adopted a spatial high-order finite-difference time-domain method based on Maxwell’s full equations of time-varying EM fields to simulate the seismoelectric response in 2D mode. To improve the computational efficiency influenced by the velocity differences between seismic and EM waves, different time steps are set according to the stability conditions, and the seismic feedback values of EM time nodes are obtained by linear approximation within the seismic unit time step. To improve the simulation accuracy of the seismoelectric response with the time-varying EM calculation method, finite-difference coefficients are obtained by solving the spatial high-order difference approximation based on the Taylor expansion. Our method yields consistent simulation results compared to those obtained from the analytical method under different salinity conditions, thus indicating its validity for simulating seismoelectric responses in porous media. We further apply our method to layered and anomalous body models and extend our algorithm to three dimensions. Results indicate that the time-varying EM calculation method can effectively capture the reflection and transmission phenomena of the seismic and EM wavefields at the interfaces of contrasting media. This may allow for the identification of abnormal locations, thus highlighting the capability of seismoelectric response simulation to detect subsurface properties.
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Morita, Kenji, e Bun Tsuchiya. "Dynamic Behavior of Li in Solid-State Li-Ion Batteries Studied using MeV Ion Beam Analysis Techniques". Journal of Energy and Power Technology 03, n.º 02 (26 de março de 2021): 1. http://dx.doi.org/10.21926/jept.2102029.
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In this review, various studies on the Li depth profiles of metal/electrolyte/metal capacitors and batteries of Au/LCO/LATP/Pt, LCO/LiPON/Si, and LMO/LiPON/NbO with different metal electrodes at both sides (by bias; LCO =LiCoO2, LATP =Li3.1Al0.86Ti1.14Ge1.27P1.73O12, LMO =LiMn2O4, NbO = Nb2O5) using the in-situ reflection ERD (ERD) technique with 9MeV O+4 ion beam and transmission ERD (TERD) technique with 5MeV He+2 ion beam, respectively, are described. For capacitors, the transport fraction of Li-ion in the electrolyte is less than unity. The Li atoms diffuse in the direction opposite to the ion. It has been shown that the batteries are rechargeable. On the other hand, it is observed that an anomalous over-charging takes place when the batteries are over-biased (Si/LiPON/LCO and LMO/LiPON/NbO), and strong reactions of Li with the metal electrodes take place under these conditions. The anomaly observed is explained in terms of the imbalance in the capacities of Li in anode and cathode, which can be attributed to the sizeable amounts of hydrogen present as an impurity during the fabrication of the battery. This is because hydrogen can potentially reduce the capacity of Li in both anode and cathode. The reactions of Li with metal electrodes are discussed in terms of the transport fraction of Li ions (less than unity) and the difference in the work functions of metal electrodes at both sides. Finally, it is noted that the removal of hydrogen in batteries can potentially improve safety, efficiency, and lifetime. These can be achieved by reducing the reaction of Li with metal electrodes. The recoil-scatter method in the TERD technique can measure the Li depth profile in the absence of background yields.
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Kim, Min-Gwan, Siheon Jeong, Seok-Tae Kim e Ki-Yong Oh. "Anomaly Detection of Underground Transmission-Line through Multiscale Mask DCNN and Image Strengthening". Mathematics 11, n.º 14 (17 de julho de 2023): 3143. http://dx.doi.org/10.3390/math11143143.
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This study proposes an integrated framework to automatically detect anomalies and faults in underground transmission-line connectors (UTLCs) with thermal images because anomaly detection of underground transmission-line connectors (UTLCs) plays a critical role in power line risk management. The proposed framework features three key characteristics. First, the measured thermal images were preprocessed through z-score normalization and image strengthening. Z-score normalization improves the robustness of feature extraction for UTLCs even though noise exists in a thermal image, and image strengthening improves the accuracy of segmentation for UTLCs. Second, a preprocessed thermal image is segmented to detect UTLCs by addressing a multiscale mask deep convolutional neural network (MS mask DCNN). The MS mask DCNN effectively detects UTLCs, enabling anomaly detection only for pixels of UTLCs. Specifically, the multiscale feature extraction module enables the extraction of distinct features of UTLCs and environments, and the skip-layer fusion module concatenates distinct features from the feature extraction module. Furthermore, a half tensor is used to reduce computational resources but maintain the same segmentation accuracy, enhancing the feasibility of the proposed framework in field applications. Third, anomaly detection is performed by addressing the contour method and unsupervised clustering method of DBSCAN. The contour method compensates for the limits of the MS mask DCNN for real-world applications because the neural networks cannot secure perfect accuracy of 100% owing to a lack of sufficient training images and low computational resources. DBSCAN improves the accuracy of diagnosis and ensures robustness to eliminate noise from thermal reflection caused by low-emissivity objects. Field experiments with high-voltage UTLCs demonstrated the effectiveness of the proposed framework. Ablation studies also confirmed that the methods addressed in this study outperform other methods. The proposed framework with a novel automatic non-destructive patrol inspection system would decrease the risks of human casualties during the periodic operation and maintenance of UTLCs, which are currently the most critical concerns.
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Gultom, Pangihutan, Chia-Chieh Hsu, Min Kai Lee, Shu Hsuan Su e Jung-Chung-Andrew Huang. "Epitaxial Growth and Characterization of Nanoscale Magnetic Topological Insulators: Cr-Doped (Bi0.4Sb0.6)2Te3". Nanomaterials 14, n.º 2 (11 de janeiro de 2024): 157. http://dx.doi.org/10.3390/nano14020157.
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The exploration initiated by the discovery of the topological insulator (BixSb1−x)2Te3 has extended to unlock the potential of quantum anomalous Hall effects (QAHEs), marking a revolutionary era for topological quantum devices, low-power electronics, and spintronic applications. In this study, we present the epitaxial growth of Cr-doped (Bi0.4Sb0.6)2Te3 (Cr:BST) thin films via molecular beam epitaxy, incorporating various Cr doping concentrations with varying Cr/Sb ratios (0.025, 0.05, 0.075, and 0.1). High-quality crystalline of the Cr:BST thin films deposited on a c-plane sapphire substrate has been rigorously confirmed through reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM) analyses. The existence of a Cr dopant has been identified with a reduction in the lattice parameter of BST from 30.53 ± 0.05 to 30.06 ± 0.04 Å confirmed by X-ray diffraction, and the valence state of Cr verified by X-ray photoemission (XPS) at binding energies of ~573.1 and ~583.5 eV. Additionally, the influence of Cr doping on lattice vibration was qualitatively examined by Raman spectroscopy, revealing a blue shift in peaks with increased Cr concentration. Surface characteristics, crucial for the functionality of topological insulators, were explored via Atomic Force Microscopy (AFM), illustrating a sevenfold reduction in surface roughness as the Cr concentration increased from 0 to 0.1. The ferromagnetic properties of Cr:BST were examined by a superconducting quantum interference device (SQUID) with a magnetic field applied in out-of-plane and in-plane directions. The Cr:BST samples exhibited a Curie temperature (Tc) above 50 K, accompanied by increased magnetization and coercivity with increasing Cr doping levels. The introduction of the Cr dopant induces a transition from n-type ((Bi0.4Sb0.6)2Te3) to p-type (Cr:(Bi0.4Sb0.6)2Te3) carriers, demonstrating a remarkable suppression of carrier density up to one order of magnitude, concurrently enhancing carrier mobility up to a factor of 5. This pivotal outcome is poised to significantly influence the development of QAHE studies and spintronic applications.
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Pile, David. "Anomalous reflection". Nature Photonics 9, n.º 4 (31 de março de 2015): 210. http://dx.doi.org/10.1038/nphoton.2015.48.
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Fan, Shaoqin, Yanzhao Chen, Li Wang, Xiaopan Liu e Jiangfeng Chen. "Application of Seismic Channel Wave Technology on Small Structure Exploration in Coal Mine". International Journal of Energy 3, n.º 3 (12 de dezembro de 2023): 14–18. http://dx.doi.org/10.54097/ije.v3i3.004.
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At lane 20207 and lane 50207 of the 80207 working face of Sitai Mine, many small faults are exposed, and their extension is unknown, which causes great interference to safe and efficient mining and even normal production of the working face. In order to guide the rational transformation and safe and efficient production of the working face with science, Sitai Coal Mine commissioned Henan Polytechnic University to find out the extension of the exposed fault on the face and other geological anomalies by using geophysical exploration methods. According to the purpose of geophysical exploration in Sitai coal mine, combined with the geological conditions of the working face, the SUMMIT II EX type seismic channel wave exploration produced by DMT company of Germany is selected to explore the 80207 working face with the combined detection method of transmission and reflection. According to the detection results, combined with the existing hydrogeological data of Sitai mine, the relative channel wave anomaly area is delineated. The results show that the seismic channel wave exploration can provide a basis for the prevention and control of mine water disaster conveniently and effectively.
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Abramova, E. S., S. F. Balandin, V. A. Donchenko, V. F. Myshkin, V. A. Khan e M. S. Pavlova. "PHYSICAL PROCESSES IN THE ATMOSPHERE IONIZED BY LASER RADIATION DURING THE CREATION OF A RADIO COMMUNICATION LINE". T-Comm 16, n.º 8 (2022): 4–11. http://dx.doi.org/10.36724/2072-8735-2022-16-8-4-11.
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The results of studies of ionization processes in the atmosphere that occur under the action of laser radiation make it possible to consider the possibility of using directed laser beams for location or formation of a communication channel. To do this, with the help of laser radiation in the atmosphere, a channel with a weakly ionized wall is formed, into which radio emission is introduced. The mini mum electron concentration Ne in the ionized channel, which ensures the reflection of the transmitted electromagnetic wave, depends on its frequency. If the frequency of electromagnetic radiation propagating in the channel is less than the frequency of plasma oscillations in the medium, then the waves are completely reflected from the ionized layer. In the range of long waves (1000-3000 m), the effect of self-radiation of plasma centers can be used to transmit information. By changing the dimensions of the plasma source in space, by modulating the laser radiation, it is possible to vary the frequency and amplitude of the emitted electromagnetic waves in a given range. The main mechanisms of creation of weak ionization channels in the atmosphere by laser radiation are considered. A scheme for the transmission of electromagnetic energy is proposed and its parameters are calculated. A variant of electromagnetic energy transfer by creating a plasma mirror in the atmosphere is considered. The frequency, duration, and energy of laser pulses necessary to create weak ionization channels in the atmosphere and ionosphere are estimated. The calculations and experiments carried out showed that an IR laser sub nanosecond radiation source with a pulse repetition rate of 108 Hz and providing a breakdown or pre-breakdown ionization mode can be used to transfer electromagnetic microwave energy in the atmosphere. It has been established that in the atmosphere it is possible to use both the breakdown mode and the pre-breakdown mode for generating and transmitting long-wave and microwave electromagnetic radiation. It is shown that in the pre-breakdown mode of aerosol ionization, anomalous scattering on plasma particle halos may occur due to the formation of plasmons, which increase the scattering intensity by 2-3 orders of magnitude.
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Lewis, R., M. B. Marshall e R. S. Dwyer-Joyce. "Measurement of interface pressure in interference fits". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 219, n.º 2 (1 de fevereiro de 2005): 127–39. http://dx.doi.org/10.1243/095440605x8432.
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When components such as bearings or gears are pressed onto a shaft, the resulting interference induces a pressure at the interface. The size of this pressure is important as many components fail because fatigue initiates from press-fit stress concentrations. The aim of the present work was to develop ultrasound as a tool for non-destructive determination of press-fit contact pressures. An interference fit interface behaves like a spring. If the pressure is high, there are few air gaps, so it is very stiff and allows transmission of an ultrasonic wave. If the pressure is low, then interface stiffness is lower and most ultrasound is reflected. A spring model was used to determine maps of contact stiffness from interference-fit ultrasonic reflection data. A calibration procedure was then used to determine the pressure. The interface contact pressure has been determined for a number of different press- and shrink-fit cases. The results show a central region of approximately uniform pressure with edge stress at the contact sides. The magnitude of the pressure in the central region agrees well with the elastic Lamé analysis. In the more severe press-fit cases, the surfaces scuffed which led to anomalies in the reflected ultrasound. These anomalies were associated with regions of surface damage at the interface. The average contact pressure in a shrink-fit and press-fit joint were similar. However, in the shrink-fit joint more uneven contact pressure was observed with regions of poor conformity. This could be because the action of pressing on a sleeve plastically smooths out long wavelength roughness, leading to a more conforming surface.
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Krakow, William. "The Structure of Thin Gold Films at the Early Stage of Continuous Film Growth". Proceedings, annual meeting, Electron Microscopy Society of America 48, n.º 1 (12 de agosto de 1990): 18–19. http://dx.doi.org/10.1017/s0424820100178847.
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The use of a transmission electron microscope to observe surface structure of thin films has been demonstrated in recent years by diffraction contrast imaging to ∼ 10Å resolution using the forbidden reflections of [111] Au and at atomic resolution using bright-field phase contrast on both [001] and [111] oriented Au films. It has also been possible to demonstrate that beyond a minimum thickness, these films can be free standing and viewed in the microscope without significant modification due to the incident electron beam generating sputtering events at high beam currents. It is therefore now possible to obtain free standing [001] Au films which exhibit various types of surface topography. These films were obtained by varying the growth parameters with a microprocessor controller attached to a UHV deposition system. The deposition of Au was precisely controlled onto a thick Ag substrate which was initially deposited upon NaCl single crystals.Fig. 1 shows a low magnification image ∼ 40Å thick [001] Au film grown at a vacuum level of 5 × 10-9 Torr, 50° substrate temperature and a deposition rate of ∼ 1/20 ML/sec. Clearly defined atomic step regions are visible as demonstrated by the terrace-like contrast variations over extended regions i.e. a step-ledge growth regime. Regions between these terrace areas represent coalescence of individual grains which were not attached at an earlier stage of growth. These regions exhibit finer scale terraces and ledges which follow either <100> or <110> directions as evidenced by comparing their directions to stacking faults and twins occasionally observed in the field of view. Small holes are also present which have crystallographic edge facets and anomalous contrast bands also occur which represent the lack of tracking of the upper surface layer growth to steps which exist at the lower surface. Fig. 1 was obtained by diffraction contrast from the direct beam alone. It was not necessary to use the forbidden reflections here since they produced too drastic a contrast change.
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Tang, Mengtao, Daniel P. Stark, Jacopo Chevallard, Stéphane Charlot, Ryan Endsley e Enrico Congiu. "Lyman-alpha spectroscopy of extreme [O iii] emitting galaxies at z ≃ 2-3: implications for Lyα visibility and LyC leakage at z > 6". Monthly Notices of the Royal Astronomical Society 503, n.º 3 (10 de março de 2021): 4105–17. http://dx.doi.org/10.1093/mnras/stab705.
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ABSTRACT Spectroscopic observations of massive z > 7 galaxies selected to have extremely large [O iii] + H β equivalent width (EW ∼1500 Å) have recently revealed large Ly α detection rates, in contrast to the weak emission seen in the general population. Why these systems are uniquely visible in Ly α at redshifts where the intergalactic medium (IGM) is likely significantly neutral is not clear. With the goal of better understanding these results, we have begun a campaign with MMT and Magellan to measure Ly α in galaxies with similar [O iii] + H β EWs at z ≃ 2–3. At these redshifts, the IGM is highly ionized, allowing us to clearly disentangle how the Ly α properties depend on the [O iii] + H β EW. Here, we present Ly α EWs of 49 galaxies at z = 2.2–3.7 with intense [O iii] + H β line emission (EW = 300–3000 Å). Our results demonstrate that strong Ly α emission (EW >20 Å) becomes more common in galaxies with larger [O iii] + H β EW, reflecting a combination of increasingly efficient ionizing photon production and enhanced transmission of Ly α. Among the galaxies with the most extreme [O iii] + H β emission (EW ∼1500 Å), we find that strong Ly α emission is not ubiquitous, with only 50 per cent of our population showing Ly α EW >20 Å. Our data suggest that the range of Ly α strengths is related to the observed ellipticity, with those systems that appear edge-on or elongated having weaker Ly α emission. We use these results to interpret the anomalous Ly α properties seen in z > 7 galaxies with extreme [O iii] + H β emission and discuss implications for the escape of ionizing radiation from these extreme line emitting galaxies.
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Mintchev, M., E. Ragoucy e P. Sorba. "Reflection–transmission algebras". Journal of Physics A: Mathematical and General 36, n.º 41 (1 de outubro de 2003): 10407–29. http://dx.doi.org/10.1088/0305-4470/36/41/012.
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Wei, Zeyong, Hongqiang Li, Chao Wu, Yang Cao, Jinzhi Ren, Zhihong Hang, Hong Chen, Daozhong Zhang e C. T. Chan. "Anomalous reflection from hybrid metamaterial slab". Optics Express 18, n.º 12 (24 de maio de 2010): 12119. http://dx.doi.org/10.1364/oe.18.012119.
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