Journal articles: 'Non-isotropic scattering'

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Anim-Appiah, K. "Complex envelope correlations for non-isotropic scattering." Electronics Letters 34, no. 9 (1998): 918. http://dx.doi.org/10.1049/el:19980602.

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Sharma, P. "Time-series model for wireless fading channels in isotropic and non-isotropic scattering environments." IEEE Communications Letters 9, no. 1 (January 2005): 46–48. http://dx.doi.org/10.1109/lcomm.2005.1375237.

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Lian, Zhuxian, Lingge Jiang, and Chen He. "A 3-D GBSM Based on Isotropic and Non-Isotropic Scattering for HAP-MIMO Channel." IEEE Communications Letters 22, no. 5 (May 2018): 1090–93. http://dx.doi.org/10.1109/lcomm.2017.2784448.

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SALISBURY, JOHN W., N. M. MILTON, and P. A. WALSH. "Significance of non-isotropic scattering from vegetation for geobotanical remote sensing." International Journal of Remote Sensing 8, no. 7 (July 1987): 997–1009. http://dx.doi.org/10.1080/01431168708954743.

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Sergeev, V. A., G. R. Bikkuzina, and P. T. Newell. "Dayside isotropic precipitation of energetic protons." Annales Geophysicae 15, no. 10 (October 31, 1997): 1233–45. http://dx.doi.org/10.1007/s00585-997-1233-5.

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Abstract. Recently it has been shown that isotropic precipitation of energetic protons on the nightside is caused by a non-adiabatic effect, namely pitch-angle scattering of protons in curved magnetic field lines of the tail current sheet. Here we address the origin of isotropic proton precipitation on the dayside. Computations of proton scattering regions in the magnetopheric models T87, T89 and T95 reveal two regions which contribute to the isotropic precipitation. The first is the region of weak magnetic field in the outer cusp which provides the 1–2° wide isotropic precipitation on closed field lines in a ~2–3 hour wide MLT sector centered on noon. A second zone is formed by the scattering on the closed field lines which cross the nightside equatorial region near the magnetopause which provides isotropic precipitation starting ≈ 1.5–2 h MLT from noon and which joins smoothly the precipitation coming from the tail current sheet. We also analyzed the isotropic proton precipitation using observations of NOAA low altitude polar spacecraft. We find that isotropic precipitation of >30 to >80 keV protons continues around noon forming the continuous oval-shaped region of isotropic precipitation. Part of this region lies on open field lines in the region of cusp-like or mantle precipitation, its equatorward part is observed on closed field lines. Near noon it extends ~1–2° below the sharp boundary of solar electron fluxes (proxy of the open/closed field line boundary) and equatorward of the cusp-like auroral precipitation. The observed energy dispersion of its equatorward boundary (isotropic boundary) agrees with model predictions of expected particle scattering in the regions of weak and highly curved magnetic field. We also found some disagreement with model computations. We did not observe the predicted split of the isotropic precipitation region into separate nightside and dayside isotropic zones. Also, the oval-like shape of the isotropic boundary has a symmetry line in 10–12 MLT sector, which with increasing activity rotates toward dawn while the latitude of isotropic boundary is decreasing. Our conclusion is that for both dayside and nightside the isotropic boundary location is basically controlled by the magnetospheric magnetic field, and therefore the isotropic boundaries can be used as a tool to probe the magnetospheric configuration in different external conditions and at different activity levels.

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Vela-Garcia, L., J. Vázquez Castillo, R. Parra-Michel, and Matthias Pätzold. "An Accurate Hardware Sum-of-Cisoids Fading Channel Simulator for Isotropic and Non-Isotropic Mobile Radio Environments." Modelling and Simulation in Engineering 2012 (2012): 1–12. http://dx.doi.org/10.1155/2012/542198.

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The rapid technological development in the field of wireless communications calls for devices capable of reproducing and simulating the behavior of the channel under realistic propagation conditions. This paper presents a hardware fading channel simulator that is able to generate stochastic processes characterized by symmetrical and asymmetrical Doppler power spectral densities (PSDs) depending on the assumption of isotropic or non-isotropic scattering. The concept of the proposed hardware simulator is based on an implementation of the sum-of-cisoids (SOC) method. The hardware simulator is capable of handling any configuration of the cisoid's amplitudes, frequencies, and phases. Each of the cisoids that constitutes the SOC model is implemented using a piecewise polynomial approximation technique. The investigation of the higher-order statistics of the generated fading processes, like the level-crossing rate (LCR) and the average duration of fades (ADF), shows that our design is able to reproduce accurately the key features of realistic channel models that are considered as candidates for the latest wireless communication standards.

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Kanschat, Guido, and José Pablo Lucero Lorca. "A Weakly Penalized Discontinuous Galerkin Method for Radiation in Dense, Scattering Media." Computational Methods in Applied Mathematics 16, no. 4 (October 1, 2016): 563–77. http://dx.doi.org/10.1515/cmam-2016-0023.

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AbstractWe review the derivation of weakly penalized discontinuous Galerkin methods for scattering dominated radiation transport and extend the asymptotic analysis to non-isotropic scattering. We focus on the influence of the penalty parameter on the edges and derive a new penalty for interior edges and boundary fluxes. We study how the choice of the penalty parameters influences discretization accuracy and solver speed.

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Gayley, Kenneth G., and Stanley P. Owocki. "The non-isotropic diffusion approximation in Wolf-Rayet winds." Symposium - International Astronomical Union 163 (1995): 158–59. http://dx.doi.org/10.1017/s0074180900201848.

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We derive the dynamics of a steady-state Wolf-Rayet wind using a non-isotropic diffusion approximation applied to the transfer between strongly overlapping spectral lines. Following the approach of Friend and Castor (1983), the line list is assumed to approximate a statistically parametrized Poisson distribution in frequency, so that photon transport is controlled by an angle-dependent, effectively gray opacity. We find that multiple radiative momentum deposition is greatest when photons undergo a nearly local diffusion, e.g. through scattering between many lines closely spaced in frequency. Our results reiterate the view that the so-called “momentum problem” of WR winds is better characterized as an “opacity problem” of simply identifying enough driving lines. One way of increasing the number of thick lines in WR winds is to transfer opacity from saturated to unsaturated lines, yielding a steeper opacity distribution than that found in OB winds. We also consider the growth of instabilities, and find that WR winds are up to an order of magnitude less unstable than OB winds if both are driven radiatively. However, initially small perturbations can still be multiplied by many orders of magnitude as they advect through WR winds.

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Panchenko, O. F., and L. K. Panchenko. "Relaxation of Highly Non Equilibrium Charge Carriers in Crystals by Low-Energy Electron Influence." Solid State Phenomena 115 (August 2006): 261–66. http://dx.doi.org/10.4028/www.scientific.net/ssp.115.261.

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The cascade process describing the energy loss and relaxation or multiplication of highly non-equilibrium secondary electrons and holes in crystalline platinum irradiated by lowenergy electrons is studied. The pair-creation scattering rates are evaluated in the framework of the statistical model taking into account the electron band structure of platinum. Kinetic equations for the excited electron and hole energy distributions are solved numerically in the isotropic scattering approximation for some primary (excitation) energies Ep which do not exceed the plasma energy.

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SANGAWA, U. "Non-resonant Electromagnetic Scattering Properties of Menger's Sponge Composed of Isotropic Paraelectric Material." IEICE Transactions on Electronics E90-C, no. 2 (February 1, 2007): 484–91. http://dx.doi.org/10.1093/ietele/e90-c.2.484.

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De Giorgio, Vittorio, Mario Corti, and Laura Cantú. "Neutron scattering investigation of isotropic solutions of non-ionic amphiphiles at high concentration." Chemical Physics Letters 151, no. 4-5 (October 1988): 349–53. http://dx.doi.org/10.1016/0009-2614(88)85148-0.

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Jaime-Rodríguez, José Jimmy, Carlos Antonio Gómez-Vega, Carlos A. Gutiérrez, José Martín Luna-Rivera, Daniel Ulises Campos-Delgado, and Ramiro Velázquez. "A Non-WSSUS Channel Simulator for V2X Communication Systems." Electronics 9, no. 8 (July 24, 2020): 1190. http://dx.doi.org/10.3390/electronics9081190.

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This paper presents a simulator of non-wide sense stationary uncorrelated scattering (non-WSSUS) multipath fading channels for the performance analysis of vehicle-to-everything (V2X) communication systems. The proposed simulator is constructed with the combination of the Monte Carlo and sum-of-cisoids (SOC) principles, and it is suitable for multicarrier transmission schemes such as those defined for dedicated short-range communications (DSRC) and cellular-based V2X (C-V2X) communications. The channel simulator provides an accurate and flexible solution to reproduce the time and frequency (TF) correlation properties of non-WSSUS vehicular channels under arbitrary isotropic and non-isotropic scattering conditions. Furthermore, the proposed simulator allows velocity variations and non-linear trajectories of the mobile stations (MSs). To demonstrate the practical value of the presented simulator, we evaluate the bit error rate (BER) performance of two channel estimation techniques that are considered for IEEE 802.11p transceivers, namely the least squares (LS) estimator and the spectral temporal averaging (STA) technique. The BER performance of both channel estimators was analyzed by considering three propagating scenarios for road safety applications. Our results show that the non-stationary characteristics of the vehicular multipath fading channel have nearly no effects on the LS estimator’s BER performance. In contrast, the performance of the STA estimator is significantly affected by the channel’s non-stationary characteristics. A variation of the original STA technique that applies only a temporal averaging is introduced in this work to improve the system’s BER in non-WSSUS channels.

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Kostic, Milos, Nebojsa Doncov, Zoran Stankovic, and John Paul. "Numerical compact modeling approach of dispersive magnetoelectric media based on scattering parameters." Facta universitatis - series: Electronics and Energetics 33, no. 1 (2020): 73–82. http://dx.doi.org/10.2298/fuee2001073k.

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Z-TLM based compact modeling approach for dispersive media exhibiting magnetoelectric coupling is presented in this paper. Scattering parameters based representation of considered medium is created in a form of compact model by extracting effective electromagnetic parameters using a retrieval method, and implementing them into a non-uniform TLM grid. Proposed approach is illustrated here on the example of dispersive isotropic chiral medium modeling.

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Mahey, Rachna. "To investigate the Temporal and Spatial correlation behavioral characteristics of MIMO fading channels." INTERNATIONAL JOURNAL OF COMPUTERS & TECHNOLOGY 14, no. 7 (May 15, 2015): 5895–910. http://dx.doi.org/10.24297/ijct.v14i7.1906.

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This paper deals with the analysis of performance bounds of narrowband multiple-input multiple-output (MIMO) fading channels considering the transmission links from the mobile station (MS) to the base station (BS) through non-line-of-sight (NLOS) propagation conditions. It is assumed that an infinite number of local scatterers surround the MS and the BS. The Temporal as well as Spatial correlation properties of channel models are explored along with their capacity. The effect of number of scatterers; Doppler frequency; and isotropic/non-isotropic scattering conditions, on MIMO channel models is investigated in terms of statistical properties of one ring and two ring models, i.e. Time Autocorrelation Function (ACF) and two-dimensional (2D) Space Cross-correlation Function (CCF).Â

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Kacira, Kadir, Huseyin Bilgic, and Faruk Yasa. "The anisotropic approximations of the Henyey-Greenstein phase function for neutron transport equation." Nuclear Technology and Radiation Protection 29, no. 2 (2014): 102–7. http://dx.doi.org/10.2298/ntrp1402102k.

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The effect of anisotropic scattering on the eigenvalues of a multiplying (c >1) and non-multi-plying (c < 1) slab in one-speed neutron transport equation is studied. We have made some calculations, not only for the cases c<1 and 0 < g < 1, but also the cases of c >1 and -1<g<0 by using the linear and quadratic approximations of the Henyey-Greenstein scattering kernel. The asymmetry parameter g consists of isotropic, backward and forward bias. An extensive numerical survey is carried out for the eigenvalues in order to provide an accurate evaluation. The numerical results indicate that the discrete eigenvalue increases with forward scattering and decreases with backward scattering in expansions of linear and quadratic anisotropic scattering.

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She, Chiao-Yao (Joe). "The Relevance of Hanle Effect on Na and Fe Lidars." EPJ Web of Conferences 237 (2020): 04008. http://dx.doi.org/10.1051/epjconf/202023704008.

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A laser resonant scattering process involves two steps, excitation and emission. That emission occurs spontaneously is well accepted. That the atoms involved in the emission are excited coherently by a laser beam leading to a non-isotropic angular distribution of emission (an antenna pattern) is not well known. The difference between coherent and incoherent excitation leads to the Hanle effect. In this paper, I discuss the physics of Hanle effect, and its influences on the backward scattering intensity of Na, K, and Fe atomic transitions and the associated Na and Fe resonant fluorescence lidar systems.

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Appel, Christian, Björn Kuttich, Tobias Kraus, and Bernd Stühn. "In situ investigation of temperature induced agglomeration in non-polar magnetic nanoparticle dispersions by small angle X-ray scattering." Nanoscale 13, no. 14 (2021): 6916–20. http://dx.doi.org/10.1039/d0nr08434d.

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Non-polar magnetic nanoparticles agglomerate upon cooling. The agglomeration is driven by either directed magnetic dipole interactions or isotropic van der Waals interactions depending on the size of the nanoparticle.

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Baur, W. H., and R. X. Fischer. "Recognition and Treatment of Background Problems in Neutron Powder Diffraction Refinements." Advances in X-ray Analysis 29 (1985): 131–42. http://dx.doi.org/10.1154/s037603080001020x.

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AbstractIrregular backgrounds in time-of-flight neutron powder diffraction data and nonlinear backgrounds in angle dependent neutron powder diffraction data. were corrected by fitting fifth degree polynomials to those portions of the data most affected. The anomalous background intensities were in both cases due to non Bragg scattering. The polynomial fitting was carried out over a sufficiently widerange of the profile to avoid interfering with the Bragg peaks. The corrected data gave internally consistent results for the crystallographically nonequivalent (Si,Al) -0 (1) and(Si, Al) -0 (2) bond lengths in zeolite rho and compare favorably with previous refinements of this Zeolite in space group Im3m. Internal and external in consistencies of bond lengths are just as diagnostic of refinement difficulties as negative isotropic temperature factors or non positive definite an isotropic temperature factors are.

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Luk'yanchuk, Boris, Ramón Paniagua-Domínguez, Arseniy I. Kuznetsov, Andrey E. Miroshnichenko, and Yuri S. Kivshar. "Suppression of scattering for small dielectric particles: anapole mode and invisibility." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 375, no. 2090 (March 28, 2017): 20160069. http://dx.doi.org/10.1098/rsta.2016.0069.

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We reveal that an isotropic, homogeneous, subwavelength particle with high refractive index can produce ultra-small total scattering. This effect, which follows from the inhibition of the electric dipole radiation, can be identified as a Fano resonance in the scattering efficiency and is associated with the excitation of an anapole mode in the particle. This anapole mode is non-radiative and emerges from the destructive interference of electric and toroidal dipoles. The invisibility effect could be useful for the design of highly transparent optical materials. This article is part of the themed issue ‘New horizons for nanophotonics’.

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Feng, Jianglin. "Initial elemental analysis by X-ray crystallography." Journal of Applied Crystallography 44, no. 3 (April 22, 2011): 625–27. http://dx.doi.org/10.1107/s0021889811012404.

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A method is proposed for the initial identification of non-hydrogen atomic species in a crystal from X-ray diffraction intensities when the chemical composition is not available. When atom positions are determined, a portion of the scattering factor curve for each atom can be obtained by Fourier synthesis with reflections from concentric shells. From these curves, the atomic number and the isotropic displacement parameter for all non-H atoms, and the scaling constant of the structure factors, can be approximately determined.

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Rad, H. S., and S. Gazor. "The Impact of Non-Isotropic Scattering and Directional Antennas on MIMO Multicarrier Mobile Communication Channels." IEEE Transactions on Communications 56, no. 4 (April 2008): 642–52. http://dx.doi.org/10.1109/tcomm.2008.060121.

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Gutierrez, Carlos, and Matthias Patzold. "The design of sum-of-cisoids rayleigh fading channel simulators assuming non-isotropic scattering conditions." IEEE Transactions on Wireless Communications 9, no. 4 (April 2010): 1308–14. http://dx.doi.org/10.1109/twc.2010.04.091198.

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Cakoni, Fioralba, Peter Monk, and Jiguang Sun. "Error Analysis for the Finite Element Approximation of Transmission Eigenvalues." Computational Methods in Applied Mathematics 14, no. 4 (October 1, 2014): 419–27. http://dx.doi.org/10.1515/cmam-2014-0021.

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AbstractIn this paper we consider the transmission eigenvalue problem corresponding to acoustic scattering by a bounded isotropic inhomogeneous object in two dimensions. This is a non-self-adjoint eigenvalue problem for a quadratic pencil of operators. In particular we are concerned with theoretical error analysis of a finite element method for computing the eigenvalues and corresponding eigenfunctions. Our analysis of convergence makes use of Osborn's perturbation theory for eigenvalues of non-self-adjoint compact operators. Some numerical examples are presented to confirm our theoretical error analysis.

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GNANAPRAGASAM, G., and M. P. DAS. "COLLECTIVE MODES OF TRAPPED INTERACTING BOSONS." International Journal of Modern Physics B 22, no. 25n26 (October 20, 2008): 4349–57. http://dx.doi.org/10.1142/s0217979208050103.

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The derivation for collective modes of an interacting Bose gas trapped by an isotropic harmonic oscillator potential is presented using field-theoretic method. The presence of the two-body scattering term beyond the mean-field is seen to appear inevitably in the calculations, even in the simplest approximation. As a result we see the occurrence of a small number of non-condensate atoms in the ground state density fluctuations.

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Jia, Xiang Dong, and Yu Hua Ouyang. "Study on the Statistical Performance of Relay Cooperation Over Non-Isotropic Mobile-to-Mobile Nakagami-m Fading Channels." Applied Mechanics and Materials 347-350 (August 2013): 1611–15. http://dx.doi.org/10.4028/www.scientific.net/amm.347-350.1611.

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This work focuses on the investigation of the second-order statistical descriptions for full mobile wireless networks over non-isotropic Nakagami-mfading environment. The system consists of a source, a relay, and K destination users, all of which are mobile. For the full mobile system model, we first extend the Akki and Habers mobile-to-mobile (M2M) model to non-isotropic scattering fading channels by adopting the von Mises PDF for both the angle of arrival (AnOA) and the angle of departure (AnOD). With appropriate mathematical proof, we obtain the approximate solution to the correlation function of M2M Nakagami-mfading channel envelop, and the variance of the first derivative. Secondly, using the obtained correlation, we study the average outage rate (AOR) and the average outage duration (AOD) of the multi-user single relay cooperation system in detail, and obtain the closed-form analytical expressions to AOR and AOD.

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Yang, Qingdong, Weijin Chen, Yuntian Chen, and Wei Liu. "Ideal Kerker scattering by homogeneous spheres: the role of gain or loss." Beilstein Journal of Nanotechnology 13 (August 24, 2022): 828–35. http://dx.doi.org/10.3762/bjnano.13.73.

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We investigate how the optical gain or loss (characterized by isotropic complex refractive indexes) influence the ideal Kerker scattering of exactly zero backward scattering. It was previously shown that, for non-magnetic homogeneous spheres with incident plane waves, either gain or loss prohibit ideal Kerker scattering, provided that only electric and magnetic multipoles of a specific order are present and contributions from other multipoles can all be made precisely zero. Here we reveal that, when two multipoles of a fixed order are perfectly matched in terms of both phase and magnitude, multipoles of at least the next two orders cannot possibly be tuned to be all precisely zero or even perfectly matched, and consequently cannot directly produce ideal Kerker scattering. Moreover, we further demonstrate that, when multipoles of different orders are simultaneously taken into consideration, loss or gain can serve as helpful rather than harmful contributing factors, for the elimination of backward scattering.

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Konarev, Petr V., Maxim V. Petoukhov, Vladimir V. Volkov, and Dmitri I. Svergun. "ATSAS2.1, a program package for small-angle scattering data analysis." Journal of Applied Crystallography 39, no. 2 (March 12, 2006): 277–86. http://dx.doi.org/10.1107/s0021889806004699.

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The program packageATSAS2.1 for small-angle X-ray and neutron scattering data analysis is presented. The programs included in the package cover the major processing and interpretation steps from primary data reduction to three-dimensional modelling. This system is primarily oriented towards the analysis of biological macromolecules, but could also be used for non-biological isotropic and partially ordered objects (nanoparticle systems, colloidal solutions, polymers in solution and bulk). Recent developments in the programs included inATSAS2.1 are highlighted. The main programs run on multiple hardware platforms, including Windows PC, Linux RedHat and Suse, DEC Alpha, SGI IRIX and Mac OSX.

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de Prunelé, E. "Two-dimensional quantum scattering by non-isotropic interactions localized on a circle, applications to open billiards." Journal of Mathematical Physics 59, no. 10 (October 2018): 102102. http://dx.doi.org/10.1063/1.5004638.

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Cheng, Xiang, Cheng-Xiang Wang, David I. Laurenson, Sana Salous, and Athanasios V. Vasilakos. "New deterministic and stochastic simulation models for non-isotropic scattering mobile-to-mobile Rayleigh fading channels." Wireless Communications and Mobile Computing 11, no. 7 (October 30, 2009): 829–42. http://dx.doi.org/10.1002/wcm.864.

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Valagiannopoulos, Constantinos, S. Ali Hassani Gangaraj, and Francesco Monticone. "Zeeman gyrotropic scatterers." Nanomaterials and Nanotechnology 8 (January 1, 2018): 184798041880808. http://dx.doi.org/10.1177/1847980418808087.

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Anomalous scattering effects (invisibility, superscattering, Fano resonances, etc) enabled by complex media and metamaterials have been the subject of intense efforts in the past couple of decades. In this article, we present a full analysis of the unusual and extreme scattering properties of an important class of complex scatterers, namely, gyrotropic cylindrical bodies, including both homogeneous and core–shell configurations. Our study unveils a number of interesting effects, including Zeeman splitting of plasmonic scattering resonances, tunable gyrotropy-induced rotation of dipolar radiation patterns as well as extreme Fano resonances and non-radiating eigenmodes (embedded eigenstates) of the gyrotropic scatterer. We believe that these theoretical findings may enable new opportunities to control and tailor scattered fields beyond what is achievable with isotropic reciprocal objects, being of large significance for different applications, from tunable directive nano-antennas to selective chiral sensors and scattering switches, as well as in the context of nonreciprocal and topological metamaterials.

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Kaiafa, Angeliki, and Vassilios Sevroglou. "Interior Elastic Scattering by a Non-Penetrable Partially Coated Obstacle and Its Shape Recovering." Mathematics 9, no. 19 (October 4, 2021): 2485. http://dx.doi.org/10.3390/math9192485.

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In this paper, the interior elastic direct and inverse scattering problem of time-harmonic waves for a non-penetrable partially coated obstacle placed in a homogeneous and isotropic medium is studied. The scattering problem is formulated via the Navier equation, considering incident circular waves due to point-source fields, where the corresponding scattered data are measured on a closed curve inside the obstacle. Our model, from the mathematical point of view, is described by a mixed boundary value problem in which the scattered field satisfies mixed Dirichlet-Robin boundary conditions on the Lipschitz boundary of the obstacle. Using a variational equation method in an appropriate Sobolev space setting, uniqueness and existence results as well as stability ones are established. The corresponding inverse problem is also studied, and using some specific auxiliary integral operators an appropriate modified factorisation method is given. In addition, an inversion algorithm for shape recovering of the partially coated obstacle is presented and proved. Last but not least, useful remarks and conclusions concerning the direct scattering problem and its linchpin with the corresponding inverse one are given.

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Schiel, D., W. Richter, and G. Döge. "Notizen: Non-coincidence of Isotropic and Anisotropic Raman Spectra of the v3 Mode of the CH3F/CD3F System." Zeitschrift für Naturforschung A 45, no. 11-12 (December 1, 1990): 1381–82. http://dx.doi.org/10.1515/zna-1990-11-1228.

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AbstractIt has been proved with the aid of CH3F/CD3F mixtures that the remarkably large non-coincidence effect in the Raman scattering spectrum of the v3 mode of liquid methyl fluoride is due to intermolecular vibrational coupling mediated mainly by transition dipole interaction. The amount of the effect and its temperature and mole fraction dependence are - at least qualitatively - in agreement with Logan's theoretical concept. The rather different behaviour of the isotopic species and the asymmetry and narrow width of the isotropic band, however, raise new questions which require further investigations.

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Feng, Zhe Chuan, Dishu Zhao, Lingyu Wan, Weijie Lu, Jeffrey Yiin, Benjamin Klein, and Ian T. Ferguson. "Angle-Dependent Raman Scattering Studies on Anisotropic Properties of Crystalline Hexagonal 4H-SiC." Materials 15, no. 24 (December 8, 2022): 8751. http://dx.doi.org/10.3390/ma15248751.

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Raman scattering spectroscopy (RSS) has the merits of non-destructiveness, fast analysis, and identification of SiC polytype materials. By way of angle-dependent Raman scattering (ADRS), the isotropic characteristics are confirmed for c-face 4H-SiC, while the anisotropic properties of a-face 4H-SiC are revealed and studied in detail via combined experiments and theoretical calculation. The variation functional relationship of the angle between the incident laser polarization direction and the parallel (perpendicular) polarization direction was well established. The selection rules of wurtzite 4H-SiC are deduced, and the intensity variations of the A1, E2, and E1 Raman phonon modes dependent on the incident angle are calculated, and well-matched with experimental data. Raman tensor elements of various modes are determined.

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Ganushkina, N. Yu, T. I. Pulkkinen, M. V. Kubyshkina, V. A. Sergeev, E. A. Lvova, T. A. Yahnina, A. G. Yahnin, and T. Fritz. "Proton isotropy boundaries as measured on mid- and low-altitude satellites." Annales Geophysicae 23, no. 5 (July 28, 2005): 1839–47. http://dx.doi.org/10.5194/angeo-23-1839-2005.

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Abstract. Polar CAMMICE MICS proton pitch angle distributions with energies of 31-80 keV were analyzed to determine the locations where anisotropic pitch angle distributions (perpendicular flux dominating) change to isotropic distributions. We compared the positions of these mid-altitude isotropic distribution boundaries (IDB) for different activity conditions with low-altitude isotropic boundaries (IB) observed by NOAA 12. Although the obtained statistical properties of IDBs were quite similar to those of IBs, a small difference in latitudes, most pronounced on the nightside and dayside, was found. We selected several events during which simultaneous observations in the same local time sector were available from Polar at mid-altitudes, and NOAA or DMSP at low-altitudes. Magnetic field mapping using the Tsyganenko T01 model with the observed solar wind input parameters showed that the low- and mid-altitude isotropization boundaries were closely located, which leads us to suggest that the Polar IDB and low-altitude IBs are related. Furthermore, we introduced a procedure to control the difference between the observed and model magnetic field to reduce the large scatter in the mapping. We showed that the isotropic distribution boundary (IDB) lies in the region where Rc/ρ~6, that is at the boundary of the region where the non-adiabatic pitch angle scattering is strong enough. We therefore conclude that the scattering in the large field line curvature regions in the nightside current sheet is the main mechanism producing isotropization for the main portion of proton population in the tail current sheet. This mechanism controls the observed positions of both IB and IDB boundaries. Thus, this tail region can be probed, in its turn, with observations of these isotropy boundaries. Keywords. Magnetospheric physics (Energetic particles, Precipitating; Magnetospheric configuration and dynamics; Magnetotail)

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Vukanic, Jovan, Dusan Arsenovic, and Dragomir Davidovic. "A new way of obtaining analytic approximations of Chandrasekhar’s H function." Nuclear Technology and Radiation Protection 22, no. 2 (2007): 38–43. http://dx.doi.org/10.2298/ntrp0702038v.

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Applying the mean value theorem for definite integrals in the non-linear integral equation for Chandrasekhar?s H function describing conservative isotropic scattering, we have derived a new, simple analytic approximation for it, with a maximal relative error below 2.5%. With this new function as a starting-point, after a single iteration in the corresponding integral equation, we have obtained a new, highly accurate analytic approximation for the H function. As its maximal relative error is below 0.07%, it significantly surpasses the accuracy of other analytic approximations.

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Litvinenko, Yuri E. "EFFECTS OF NON-ISOTROPIC SCATTERING, MAGNETIC HELICITY, AND ADIABATIC FOCUSING ON DIFFUSIVE TRANSPORT OF SOLAR ENERGETIC PARTICLES." Astrophysical Journal 752, no. 1 (May 22, 2012): 16. http://dx.doi.org/10.1088/0004-637x/752/1/16.

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37

de Kok, R. J., Ch Helling, D. M. Stam, P. Woitke, and S. Witte. "The influence of non-isotropic scattering of thermal radiation on spectra of brown dwarfs and hot exoplanets." Astronomy & Astrophysics 531 (June 13, 2011): A67. http://dx.doi.org/10.1051/0004-6361/201117015.

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Sinha, S., E. Pop, R. W. Dutton, and K. E. Goodson. "Non-Equilibrium Phonon Distributions in Sub-100nm Silicon Transistors." Journal of Heat Transfer 128, no. 7 (December 21, 2005): 638–47. http://dx.doi.org/10.1115/1.2194041.

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Intense electron-phonon scattering near the peak electric field in a semiconductor device results in nanometer-scale phonon hotspots. Past studies have argued that ballistic phonon transport near such hotspots serves to restrict heat conduction. We reexamine this assertion by developing a new phonon transport model. In a departure from previous studies, we treat isotropic dispersion in all phonon branches and include a phonon emission spectrum from independent Monte Carlo simulations of electron-phonon scattering. We cast the model in terms of a non-equilibrium phonon distribution function and compare predictions from this model with data for ballistic transport in silicon. The solution to the steady-state transport equations for bulk silicon transistors shows that energy stagnation at the hotspot results in an excess equivalent temperature rise of about 13% in a 90nm gate-length device. Longitudinal optical phonons with non-zero group velocities dominate transport. We find that the resistance associated with ballistic transport does not overwhelm that from the package unless the peak power density approaches 50W∕μm3. A transient calculation shows negligible phonon accumulation and retardation between successive logic states. This work highlights and reduces the knowledge gaps in the electro-thermal simulation of transistors.

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JI, XIA, and HONGYU LIU. "On isotropic cloaking and interior transmission eigenvalue problems." European Journal of Applied Mathematics 29, no. 2 (May 22, 2017): 253–80. http://dx.doi.org/10.1017/s0956792517000110.

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This paper is concerned with the invisibility cloaking in acoustic wave scattering from a new perspective. We are especially interested in achieving the invisibility cloaking by completely regular and isotropic mediums. It is shown that an interior transmission eigenvalue problem arises in our study, which is the one considered theoretically in Cakoni et al. (Transmission eigenvalues for inhomogeneous media containing obstacles, Inverse Problems and Imaging, 6 (2012), 373–398). Based on such an observation, we propose a cloaking scheme that takes a three-layer structure including a cloaked region, a lossy layer and a cloaking shell. The target medium in the cloaked region can be arbitrary but regular, whereas the mediums in the lossy layer and the cloaking shell are both regular and isotropic. We establish that if a certain non-transparency condition is satisfied, then there exists an infinite set of incident waves such that the cloaking device is nearly invisible under the corresponding wave interrogation. The set of waves is generated from the Herglotz approximation of the associated interior transmission eigenfunctions. We provide both theoretical and numerical justifications.

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Akram, Muhammad Imran, and Asrar U. H. Sheikh. "On the Statistical Properties of Nakagami-Hoyt Vehicle-to-Vehicle Fading Channel under Nonisotropic Scattering." International Journal of Antennas and Propagation 2012 (2012): 1–12. http://dx.doi.org/10.1155/2012/179378.

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This paper presents the statistical properties of the vehicle-to-vehicle Nakagami-Hoyt (Nakagami-q) channel model under non-isotropic condition. The spatial time correlation function (STCF), the power spectral density (PSD), squared time autocorrelation function (SQCF), level crossing rate (LCR), and the average duration of Fade (ADF) of the Nakagami-Hoyt channel have been derived under the assumption that both the transmitter and receiver are nonstationary having nonomnidirectional antennas. A simulator that uses the inverse-fast-fourier-transform- (IFFT-) based computation method is designed for this model. The simulator and analytical results are compared.

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Browaeys, Thomas J., and Sergey Fomel. "Fractal heterogeneities in sonic logs and low-frequency scattering attenuation." GEOPHYSICS 74, no. 2 (March 2009): WA77—WA92. http://dx.doi.org/10.1190/1.3062859.

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Cycles in sedimentary strata exist at different scales and can be described by fractal statistics. We use von Kármán’s autocorrelation function to model heterogeneities in sonic logs from a clastic reservoir and propose a nonlinear parameter estimation. Our method is validated using synthetic signals. When applied to real sonic logs, it extracts the fractal properties of high spatial frequencies and one dominant cycle between 2.5 and [Formula: see text]. Results demonstrate non-Gaussian and antipersistent statistics of sedimentary layers. We have derived an analytical formula for the scattering attenuation of scalar waves by 3D isotropic fractal heterogeneities using the mean field theory. Penetration of waves exhibits a high-frequency cutoff sensitive to heterogeneity size. Therefore, shear waves can be attenuated more than compressional waves because of their shorter wavelength.

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Saranathan, Vinodkumar, Jason D. Forster, Heeso Noh, Seng-Fatt Liew, Simon G. J. Mochrie, Hui Cao, Eric R. Dufresne, and Richard O. Prum. "Structure and optical function of amorphous photonic nanostructures from avian feather barbs: a comparative small angle X-ray scattering (SAXS) analysis of 230 bird species." Journal of The Royal Society Interface 9, no. 75 (May 9, 2012): 2563–80. http://dx.doi.org/10.1098/rsif.2012.0191.

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Non-iridescent structural colours of feathers are a diverse and an important part of the phenotype of many birds. These colours are generally produced by three-dimensional, amorphous (or quasi-ordered) spongy β-keratin and air nanostructures found in the medullary cells of feather barbs. Two main classes of three-dimensional barb nanostructures are known, characterized by a tortuous network of air channels or a close packing of spheroidal air cavities. Using synchrotron small angle X-ray scattering (SAXS) and optical spectrophotometry, we characterized the nanostructure and optical function of 297 distinctly coloured feathers from 230 species belonging to 163 genera in 51 avian families. The SAXS data provided quantitative diagnoses of the channel- and sphere-type nanostructures, and confirmed the presence of a predominant, isotropic length scale of variation in refractive index that produces strong reinforcement of a narrow band of scattered wavelengths. The SAXS structural data identified a new class of rudimentary or weakly nanostructured feathers responsible for slate-grey, and blue-grey structural colours . SAXS structural data provided good predictions of the single-scattering peak of the optical reflectance of the feathers. The SAXS structural measurements of channel- and sphere-type nanostructures are also similar to experimental scattering data from synthetic soft matter systems that self-assemble by phase separation. These results further support the hypothesis that colour-producing protein and air nanostructures in feather barbs are probably self-assembled by arrested phase separation of polymerizing β-keratin from the cytoplasm of medullary cells. Such avian amorphous photonic nanostructures with isotropic optical properties may provide biomimetic inspiration for photonic technology.

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Wongthongsiri, Supawat, and Sohichi Hirose. "Scattering Analysis and Detection of Layered Plate Debonding Using Guided SH Waves with Boundary Element Method." Shock and Vibration 2022 (July 16, 2022): 1–10. http://dx.doi.org/10.1155/2022/8799555.

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This paper investigates the scattering behavior of guided shear horizontal (SH) waves in a two-dimensional, isotropic, and linear elastic layered plate with partially debonded interface by analyzing the reflection and transmission coefficients of scattered waves. The partial wave technique is established to form the displacement and stress of guided wave functions, and the boundary element method (BEM) is utilized to handle the numerical calculation with elastodynamic fundamental solutions in the frequency domain. After applying proper boundary conditions including continuity condition on the interface with traction-free debonding, the scattering coefficients can be obtained in terms of boundary element solutions. Two different materials (steel and aluminum) with various debonding lengths and locations in a 1 mm double-layered plate are considered. With several modes of the incident wave over a frequency range up to 4.5 MHz, the variations of scattering coefficients and scattering phenomena are numerically investigated as several parameters such as mode of the incident wave, materials, locations, and length of debonding are changed. The numerical results also suggest the potential of the suitable wave mode for the debonding detection, which can be useful for non-destructive inspection.

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Cheng, Xiang, Qi Yao, Cheng-Xiang Wang, Bo Ai, Gordon L. Stuber, Dongfeng Yuan, and Bing-Li Jiao. "An Improved Parameter Computation Method for a MIMO V2V Rayleigh Fading Channel Simulator Under Non-Isotropic Scattering Environments." IEEE Communications Letters 17, no. 2 (February 2013): 265–68. http://dx.doi.org/10.1109/lcomm.2013.011113.121535.

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FUKUOKA, DAISUKE, KOUSHIRO ARAHARA, TAKAAKI KOYAMA, NAOKI TANAKA, KENICHI OTO, KIYOFUMI MURO, SHOJIRO TAKEYAMA, GREGOSZ KARCZEWSKI, THOMASZ WOJTOWICZ, and JACEK KOSSUT. "COMPREHENSIVE STUDY OF SPIN-FLIP EXCITATIONS IN CdZnTe/CdZnMnTe QUANTUM WELLS." International Journal of Modern Physics B 21, no. 08n09 (April 10, 2007): 1610–14. http://dx.doi.org/10.1142/s0217979207043294.

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Spin-flip excitations in non-doped Cd 0.93 Zn 0.07 Te/Cd 0.48 Zn 0.04 Mn 0.48 Te quantum wells have been comprehensively studied by spin-flip Raman scattering (SFRS) spectroscopy and time-resolved Kerr rotation (TRKR) spectroscopy. In 4 nm quantum well, two spin-flip Raman peaks were observed in addition to the multiple Mn 2+ spin-flip scatterings. The spin-flip energies are isotropic against the magnetic field direction and well described by modified Brillouin functions. Based on the circumstantial analysis, they are assigned to the spin-flip of residual electrons and the electron spin-flip in the localized exciton, respectively, even though the large energy difference between the two electron spin-flip processes is a puzzle. While, in 9 nm quantum well a strange spin-flip excitation was observed together with a very weak Mn 2+ spin-flip scattering. The spin-flip energy changed strangely up to the magnetic field 4T, and then linearly increased with field (| g *|=1.15). A high-resolution TRKR spectroscopy revealed an unusual temperature dependence, which resembled "softening mode" of spin resonance observed in p-doped ferromagnetic CdMnTe quantum wells. However, these behaviors are well understood by an "inverted spin configuration", which results from a negative g*-factor and a very weak s-d interaction between the electrons and the manganese ions in the barrier.

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Orlenko, Elena V., and Fedor E. Orlenko. "Permutation Symmetry in Coherent Electrons Scattering by Disordered Media." Symmetry 12, no. 12 (November 28, 2020): 1971. http://dx.doi.org/10.3390/sym12121971.

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A non-Anderson weak localization of an electron beam scattered from disordered matter is considered with respect to the principle of electron indistinguishability. A weak localization of electrons of a new type is essentially associated with inelastic processing. The origin of inelasticity is not essential. We take into account the identity principle for electron beam and electrons of the atom of the scatterer with an open shell. In spite of isotropic scattering by each individual scatterer, the electron exchange contribution has a hidden parameters effect on the resulting angular dependence of the scattering cross-section. In this case, the electrons of the open shell of an atomic scatterer can be in the s-state, that is, the atomic shell remains spherically symmetric. The methods of an invariant time-dependent exchange perturbation theory and a Green functions with exchange were applied. An additional angular dependence of the scattering cross-section appears during the coherent scattering process. It is shown exactly for the helium scatterer that the role of exchange effects in the case of a singlet is negligible, while for the triplet state, it is decisive, especially for those values of the energy of incident electrons when de Broglie’s waves are commensurate with the atomic.

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Wu, Xuerui, Wenxiao Ma, Junming Xia, Weihua Bai, Shuanggen Jin, and Andrés Calabia. "Spaceborne GNSS-R Soil Moisture Retrieval: Status, Development Opportunities, and Challenges." Remote Sensing 13, no. 1 (December 24, 2020): 45. http://dx.doi.org/10.3390/rs13010045.

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Soil moisture is the most active part of the terrestrial water cycle, and it is a key variable that affects hydrological, bio-ecological, and bio-geochemical processes. Microwave remote sensing is an effective means of monitoring soil moisture, but the existing conventional radiometers and single-station radars cannot meet the scientific needs in terms of temporal and spatial resolution. The emergence of GNSS-R (Global Navigation Satellite Systems Reflectometry) technology provides an alternative method with high temporal and spatial resolution. An important application field of GNSS-R is soil moisture monitoring, but it is still in the initial stage of research, and there are many uncertainties and open issues. Based on a review of the current state-of-the-art of soil moisture retrieval using GNSS-R, this paper points out the limitations of existing research in observation geometry, polarization, and coherent and non-coherent scattering. The smooth surface reflectivity model, the random rough surface scattering model, and the first-order radiation transfer equation model of the vegetation, which are in the form of bistatic and full polarization, are employed. Simulations and analyses of polarization, observation geometry (scattering zenith angle and scattering azimuth angle), Brewster angle, coherent and non-coherent component, surface roughness, and vegetation effects are carried out. The influence of the EIRP (Effective Isotropic Radiated Power) and the RFI (Radio Frequency Interference) on soil moisture retrieval is briefly discussed. Several important development directions for space-borne GNSS-R soil moisture retrieval are pointed out in detail based on the microwave scattering model.

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Dong, Guan-Ting, Chun-Ta Wang, and Yu-Ju Hung. "Spatially Broadband Coupled-Surface Plasmon Wave Assisted Transmission Effect in Azo-Dye-Doped Liquid Crystal Cell." Nanomaterials 10, no. 7 (July 11, 2020): 1357. http://dx.doi.org/10.3390/nano10071357.

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Active tuning on a plasmonic structure is discussed in this report. We examined the transient transmission effects of an azo-dye-doped liquid crystal cell on a metallic surface grating. The transition between isotropic and nematic phases in liquid crystal generated micro-domains was shown to induce the dynamic scattering of light from a He-Ne laser, thereby allowing transmission through a non-transparent aluminum film overlaying a dielectric grating. Various grating pitches were tested in terms of transmission effects. The patterned gratings include stripe ones and circular forms. Our results indicate that surface plasmon polariton waves are involved in the transmission process. We also demonstrated how momentum diagrams of gratings and Surface Plasmon Polariton (SPP) modes combined with Mie scattering effects could explain the broadband coupling phenomenon. This noteworthy transition process could be applied to the development of spatially broadband surface plasmon polariton coupling devices.

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Wirawan, Rahadi, M. Djamal, A. Waris, Gunawan Handayani, and Hong Joo Kim. "Response Function of Collimated Detector for Non Axial Detector-Source Geometry." Advanced Materials Research 772 (September 2013): 571–78. http://dx.doi.org/10.4028/www.scientific.net/amr.772.571.

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Response function is a fundamental parameter for all detectors in order to analyze the energy distribution of gamma ray which undergoes scattering interaction with the material. The response functions of a 3 in. x 3 in. NaI(Tl) collimated detector for non axis detector-source geometry has been calculated using a Monte Carlo approach from GEANT4 simulation code with 0.662 MeV of mono-energetic of photon gamma ray. Collimated Pb with 4 cm thickness and 2 cm of holes diameter were employed for shielding. The source was assumed as an isotropic point source and it is placed at various positions to the detector axis. The comparison between the measured energy response functions and the simulated energy response functions after normalization were also performed in order to validate the modeling results.

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Chukov, Vitalii N. "The Rayleigh wave scattering on a rectangular lattice of the solid roughness discontinuities." Journal of Physics: Conference Series 2103, no. 1 (November 1, 2021): 012157. http://dx.doi.org/10.1088/1742-6596/2103/1/012157.

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Abstract The problem of the surface acoustic Rayleigh wave scattering on a deterministic three-dimensional roughness, occupying a finite size rectangular region of an isotropic solid free surface, is solved in the Rayleigh-Born approximation of the perturbation theory in a roughness amplitude. Formula for the displacement field in the scattered Rayleigh wave at a big distance from the roughness, as compared to rough region sizes L1,2 along the x1,2- axes respectively, and asymptotic formulas for this displacement field in the Bragg, i.e. short-wavelength λ≪ L1,2 limit, where λ is the wavelength, are derived. The new laws of scattering are obtained. They are caused by a strong modulation of scattering by the roughness form. They exceed the fundamental physical conception, that a wave scattering in the short-wavelength limit takes place on a medium discontinuities, by the statement, that a wave strongly senses the structure of a medium in the near vicinity of discontinuities as well as the form-factor of the discontinuities lattice. This form-factor is a dependence of the discontinuity amplitude, i.e. of a difference of the left and right limit values of a roughness non-zero derivative, including one of zero order, in coordinate at a point of discontinuity, on a number of this discontinuity in a lattice. This exceeded physical conception violates the classical Laue-Bragg-Wulff laws of scattering.

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Journal articles on the topic 'Non-isotropic scattering'

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