Articles de revues : « Ray-tracing studies »

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AL-Behadili, Hasanain A. H., Mohsin Najim Sarayyih Almaliki et Saddam K. Alwan AlWane. « A Ray Tracing Model for Wireless Communications ». International Journal of Interactive Mobile Technologies (iJIM) 13, n^o 11 (15 novembre 2019) : 245. http://dx.doi.org/10.3991/ijim.v13i11.11730.

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<p>Recently, there has been an interest in modelling of the communication process. One of the most important reasons for developing such models is to forecast what will be happened. A number of modelling studies provide several assumptions and use different theories. up to now, there is still a lack of an optimum model which can be used for the purpose of future communications. This indicates a need to understand the aspects of communication modelling and the motivation behind improving our knowledge in this field. This paper details work done to design a propagation model of a wireless communication system to give a forecast of signal behavior. Data for this study were collected using a wireless communication system employed in the outdoor environment. The final part of this paper gives a summary and description of findings which include a comparison between the experimental and simulation results. The model finally shows a similar trend with the observation.</p>

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Edlabadkar, V. S., et Ashok Pimpale. « Ray tracing studies of a complete plane grating monochromator beam line ». Pramana 42, n^o 1 (janvier 1994) : 65–77. http://dx.doi.org/10.1007/bf02847334.

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Van Avendonk, Harm J. A., Alistair J. Harding, John A. Orcutt et W. Steven Holbrook. « Hybrid shortest path and ray bending method for traveltime and raypath calculations ». GEOPHYSICS 66, n^o 2 (mars 2001) : 648–53. http://dx.doi.org/10.1190/1.1444955.

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The shortest path method (SPM) is a robust ray‐tracing technique that is particularly useful in 3-D tomographic studies because the method is well suited for a strongly heterogeneous seismic velocity structure. We test the accuracy of its traveltime calculations with a seismic velocity structure for which the nearly exact solution is easily found by conventional ray shooting. The errors in the 3-D SPM solution are strongly dependent on the choice of search directions in the “forward star,” and these errors appear to accumulate with traveled distance. We investigate whether these traveltime errors can be removed most efficiently by an SPM calculation on a finer grid or by additional ray bending. Testing the hybrid scheme on a realistic ray‐tracing example, we find that in an efficient mix ray bending and SPM account for roughly equal amounts of computation time. The hybrid method proves to be an order of magnitude more efficient than SPM without ray bending in our example. We advocate the hybrid ray‐tracing technique, which offers an efficient approach to find raypaths and traveltimes for large seismic refraction studies with high accuracy.

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Gaelzer, R., L. F. Ziebell et R. S. Schneider. « Ray tracing studies on auroral kilometric radiation in finite width auroral cavities ». Journal of Geophysical Research 99, A5 (1994) : 8905. http://dx.doi.org/10.1029/93ja03566.

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Grekov, D. L., V. E. D'Yakov, R. C. Goldfinger et D. B. Batchelor. « Ray tracing studies of lower hybrid plasma heating in an ℓ = 2 torsatron ». Nuclear Fusion 30, n^o 10 (1 octobre 1990) : 2039–47. http://dx.doi.org/10.1088/0029-5515/30/10/006.

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Deresz, Krystyna A., Piotr Łaski, Radosław Kamiński et Katarzyna N. Jarzembska. « Advances in Diffraction Studies of Light-Induced Transient Species in Molecular Crystals and Selected Complementary Techniques ». Crystals 11, n^o 11 (3 novembre 2021) : 1345. http://dx.doi.org/10.3390/cryst11111345.

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The review provides a summary of the current methods of tracing photoexcitation processes and structural dynamics in the solid state, putting major emphasis on the X-ray diffraction techniques (time-resolved Laue diffraction on synchrotron sources and time-resolved serial femtosecond crystallography on X-ray free-electron lasers). The recent developments and nowadays experimental possibilities in the field are discussed along with the data processing and analysis approaches, and illustrated with some striking literature examples of the respective successful studies. Selected complementary methods, such as ultrafast electron diffraction or time-resolved X-ray absorption spectroscopy, are briefly presented.

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Pereira, José Carlos Garcia, José Rodríguez, Jorge Cruz Fernandes et Luís Guerra Rosa. « Homogeneous Flux Distribution in High-Flux Solar Furnaces ». Energies 13, n^o 2 (16 janvier 2020) : 433. http://dx.doi.org/10.3390/en13020433.

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Comparisons between experimental data and ray-tracing simulation results are presented for the high-flux SF60 solar furnace available at the Plataforma Solar de Almeria, Spain, which has an estimated thermal power of 60 kW. Since an important issue in many applications of solar concentrated radiation is to obtain a radiation distribution that is as homogeneous as possible over the central working area, so-called radiation homogenisers were also used but the degree of success achieved is just satisfactory, as the results show. Finally, further modelling studies using ray-tracing simulations aiming to attain a homogenous distribution of flux by means of double reflexion using two paraboloid surfaces are presented.

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ZABOTIN, NIKOLAY A., OLEG A. GODIN, PAUL C. SAVA et LIUDMILA Y. ZABOTINA. « ACOUSTIC WAVEFRONT TRACING IN INHOMOGENEOUS, MOVING MEDIA ». Journal of Computational Acoustics 20, n^o 03 (septembre 2012) : 1250009. http://dx.doi.org/10.1142/s0218396x12500099.

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We extend the Huygens wavefront tracing algorithm, which is a part of an open source Madagascar project, to sound propagation in inhomogeneous, moving media and apply it to a series of benchmark tasks. One set of tasks admits exact analytic solutions and serves the purpose of validation of the new algorithm. Another set of calculations demonstrates applicability of the algorithm to the studies of wavefront dynamics and stability in ocean and atmospheric acoustics. The method is based on a system of differential equations equivalent to the eikonal equation, but formulated in the ray coordinate system. In this paper, we present a first-order, two-dimensional discretization scheme that is interpreted very simply in terms of the Huygens' principle. The method has proved to be a convenient alternative to conventional ray tracing.

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Chen, Yi, Xian Rong Huang, Ning Zhang, Michael Dudley, Joshua D. Caldwell, Kendrick X. Liu et Robert E. Stahlbush. « Synchrotron X-Ray Topographic Studies of Recombination Activated Shockley Partial Dislocations in 4H-Silicon Carbide Epitaxial Layers ». Materials Science Forum 600-603 (septembre 2008) : 357–60. http://dx.doi.org/10.4028/www.scientific.net/msf.600-603.357.

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Electron-hole recombination activated Shockley partial dislocations bounding expanding stacking faults and their interactions with threading dislocations have been studied in 4H-SiC epitaxial layers using synchrotron x-ray topography. The bounding partials appear as white stripes or narrow dark lines in back-reflection X-ray topographs recorded using the basal plane reflections. Such contrast variations are attributable to the defocusing/focusing of the diffracted X-rays due to the edge component of the partial dislocations, which creates a convex/concave distortion of the basal planes. Simulation results based on the ray-tracing principle confirm our argument. The sign of the partial dislocations can be subsequently determined.

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Tadic, T., Y. Mokuno, Y. Horino et M. Jaksic. « GEOMETRICAL ABERRATIONS IN THE VON HAMOS AND THE PLANE BRAGG CRYSTAL SPECTROMETERS ». International Journal of PIXE 07, n^o 03n04 (janvier 1997) : 117–33. http://dx.doi.org/10.1142/s0129083597000151.

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Numerical calculations of the effect of the finite dimensions and orientations of source and crystal are presented for plane and von Hamos Bragg crystal spectrometers for PIXE analysis, combined with a position sensitive (X-ray) detector. Analytical studies of all effects are provided. It is shown that some parameters can produce line shifts and asymmetries. A numerical model for an X-ray diffraction ray-tracing procedure for a crystal Bragg spectrometer is described.

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Smith, Duncan E., Michael D. Hughes, Bhakti Patel et Diana-Andra Borca-Tasciuc. « An Open-Source Monte Carlo Ray-Tracing Simulation Tool for Luminescent Solar Concentrators with Validation Studies Employing Scattering Phosphor Films ». Energies 14, n^o 2 (15 janvier 2021) : 455. http://dx.doi.org/10.3390/en14020455.

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Luminescent solar concentrators enhance the power output of solar cells through wave-guided luminescent emission and have great potential as building-integrated photovoltaics. Luminescent solar concentrators with a variety of geometries and absorbing–emitting materials have been reported in the literature. As the breadth of available experimental configurations continues to grow, there is an increasing need for versatile Monte Carlo ray-tracing simulation tools to analyze the performance of these devices for specific applications. This paper presents the framework for a Monte Carlo ray-tracing simulation tool that can be used to analyze a host of three-dimensional geometries. It incorporates custom radiative transport models to consider the effects of scattering from luminescent media, while simultaneously modeling absorption and luminescent emission. The model is validated using experimental results for three-dimensional planar and wedge-shaped luminescent solar concentrators employing scattering phosphor films. Performance was studied as a function of length, wavelength, and the angle of incidence of incoming light. The data for the validation studies and the code (written using the Python programming language) associated with the described model are publically available.

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D’Andrea, Emmanuele, Maurizio Arena, Massimo Viscardi et Tommaso Coppola. « Bidimensional Ray Tracing Model for the Underwater Noise Propagation Prediction ». Fluids 6, n^o 1 (1 janvier 2021) : 19. http://dx.doi.org/10.3390/fluids6010019.

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An increasing attention has recently been paid to the effect of the underwater noise field generated by ship activities on the marine environment. Although this problem is widely discussed in international treaties and conventions, it has not yet found a consolidated technical-scientific treatment capable of quantifying the level of underwater noise emissions produced by naval systems. As part of a national research collaboration, a novel code has been developed to predict noise propagation according to the Ray Tracing approach. Such optical geometry-based technique allows for calculating the Transmission Loss (TL) trend in its respective contributions: geometrical loss (due to the distance between the source and receiver), dissipation loss (due to the characteristics of the propagation environment), and reflection loss (due to the surfaces that delimit the field). The simulation requires as input parameters the source info as spatial position, frequency, and sound pressure level (SPL) as well as the sea properties like seabed depth, the speed of sound profile, the layers thickness the water column is divided into, the sea salinity, temperature, and pH. The simulation code provides the SPL spatial distribution useful as a fast industrial tool in the future studies addressed to identify the emission limits for the protection of marine wildlife.

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Emmanoulopoulos, D. « Pinpointing the base of the AGN jets through general relativistic X-ray reverberation studies ». Proceedings of the International Astronomical Union 10, S313 (septembre 2014) : 346–51. http://dx.doi.org/10.1017/s1743921315002471.

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AbstractMany theoretical models of Active Galactic Nuclei (AGN) predict that the X-ray corona, lying above the black hole, constitutes the base of the X-ray jet. Thus, by studying the exact geometry of the close black hole environment, we can pinpoint the launching site of the jet. Detection of negative X-ray reverberation time delays (i.e. soft band X-ray variations lagging behind the corresponding hard band X-ray variations) can yield significant information about the geometrical properties of the AGN, such as the location of the X-ray source, as well as the physical properties of the the black hole, such as its mass and spin. In the frame-work of the lamp-post geometry, I present the first systematic X-ray time-lag modelling results of an ensemble of 12 AGN, using a fully general relativistic (GR) ray tracing approach for the estimation of the systems' response functions. By combing these state-of-the art GR response models with statistically innovative fitting routines, I derive the geometrical layout of the close BH environment for each source, unveiling the position of the AGN jet-base.

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Mulkerns, Niall M. C., William H. Hoffmann, Ian D. Lindsay et Henkjan Gersen. « An Analysis of Semicircular Channel Backscattering Interferometry through Ray Tracing Simulations ». Sensors 22, n^o 11 (6 juin 2022) : 4301. http://dx.doi.org/10.3390/s22114301.

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Recent backscattering interferometry studies utilise a single channel microfluidic system, typically approximately semicircular in cross-section. Here, we present a complete ray tracing model for on-chip backscattering interferometry with a semicircular cross-section, including the dependence upon polarisation and angle of incidence. The full model is validated and utilised to calculate the expected fringe patterns and sensitivities observed under both normal and oblique angles of incidence. Comparison with experimental data from approximately semicircular channels using the parameters stated shows that they cannot be explained using a semicircular geometry. The disagreement does not impact on the validity of the experimental data, but highlights that the optical mechanisms behind the various modalities of backscattering interferometry would benefit from clarification. From the analysis presented here, we conclude that for reasons of ease of analysis, data quality, and sensitivity for a given radius, capillary-based backscattering interferometry affords numerous benefits over on-chip backscattering interferometry.

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Firdaus, Firdaus, Noor Azurati Ahmad et Shamsul Sahibuddin. « Accurate Indoor-Positioning Model Based on People Effect and Ray-Tracing Propagation ». Sensors 19, n^o 24 (15 décembre 2019) : 5546. http://dx.doi.org/10.3390/s19245546.

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Wireless local area networks (WLAN)-fingerprinting has been highlighted as the preferred technology for indoor positioning due to its accurate positioning and minimal infrastructure cost. However, its accuracy is highly influenced by obstacles that cause fluctuation in the signal strength. Many researchers have modeled static obstacles such as walls and ceilings, but few studies have modeled the people’s presence effect (PPE), although the human body has a great impact on signal strength. Therefore, PPE must be addressed to obtain accurate positioning results. Previous research has proposed a model to address this issue, but these studies only considered the direct path signal between the transmitter and the receiver whereas multipath effects such as reflection also have a significant influence on indoor signal propagation. This research proposes an accurate indoor-positioning model by considering people’s presence and multipath using ray-tracing, we call it (AIRY). This study proposed two solutions to construct AIRY: an automatic radio map using ray tracing and a constant of people’s effect for the received signal strength indicator (RSSI) adaptation. The proposed model was simulated using MATLAB software and tested at Level 3, Menara Razak, Universiti Teknologi Malaysia. A K-nearest-neighbor (KNN) algorithm was used to define a position. The initial accuracy was 2.04 m, which then reduced to 0.57 m after people’s presence and multipath effects were considered.

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Ailihumaer, Tuerxun, Balaji Raghothamachar, Michael Dudley, Gilyong Chung, Ian Manning et Edward Sanchez. « Investigation of Dislocation Behavior at the Early Stage of PVT-Grown 4H-SiC Crystals ». Materials Science Forum 1004 (juillet 2020) : 44–50. http://dx.doi.org/10.4028/www.scientific.net/msf.1004.44.

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Dislocation behavior during the early stages of physical vapor transport (PVT) growth of 6-inch diameter 4H-SiC crystals has been investigated by synchrotron monochromatic beam X-ray topography (SMBXT) in conjunction with ray tracing simulations of dislocation images. Our studies reveal that most of the TSDs/TMDs are replicated into the newly grown layer while most TEDs are generated by either nucleation in pairs at the growth interface or by redirection of BPDs in the seed crystal. Most BPDs in the newly grown layer are of screw type with and this has been verified by comparison with ray tracing simulated images. TEDs with same and opposite sign of Burgers vector are found to be deflected on to the same basal plane by the overgrowth of macro-steps and they glide in the same and opposite directions respectively. TMDs deflected on to the basal plane by macro-steps get dissociated into c and a components, with the a segment undergoing glide to form V-shaped configurations.

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Uhlig, Steffen. « Ray-Tracing Studies on Optical Periscopes Suitable for Out-of-Plane Interconnects on Optical Backplanes ». IEEE Transactions on Electronics Packaging Manufacturing 33, n^o 1 (janvier 2010) : 55–64. http://dx.doi.org/10.1109/tepm.2009.2038062.

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Karimpour, Mohammadkarim, Evert Slob et Laura Valentina Socco. « Comparison of straight-ray and curved-ray surface wave tomography approaches in near-surface studies ». Solid Earth 13, n^o 10 (21 octobre 2022) : 1569–83. http://dx.doi.org/10.5194/se-13-1569-2022.

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Abstract. Surface waves are widely used to model shear-wave velocity of the subsurface. Surface wave tomography (SWT) has recently gained popularity for near-surface studies. Some researchers have used straight-ray SWT in which it is assumed that surface waves propagate along the straight line between receiver pairs. Alternatively, curved-ray SWT can be employed by computing the paths between the receiver pairs using a ray-tracing algorithm. The SWT is a well-established method in seismology and has been employed in numerous seismological studies. However, it is important to make a comparison between these two SWT approaches for near-surface applications since the amount of information and the level of complexity in near-surface applications are different from seismological studies. We apply straight-ray and curved-ray SWT to four near-surface examples and compare the results in terms of the quality of the final model and the computational cost. In three examples we optimise the shot positions to obtain an acquisition layout which can produce high coverage of dispersion curves. In the other example, the data have been acquired using a typical seismic exploration 3D acquisition scheme. We show that if the source positions are optimised, the straight-ray can produce S-wave velocity models similar to the curved-ray SWT but with lower computational cost than the curved-ray approach. Otherwise, the improvement of inversion results from curved-ray SWT can be significant.

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Dziarzhytski, Siarhei, Frank Siewert, Andrey Sokolov, Grzegorz Gwalt, Tino Seliger, Michael Rübhausen, Holger Weigelt et Günter Brenner. « Diffraction gratings metrology and ray-tracing results for an XUV Raman spectrometer at FLASH ». Journal of Synchrotron Radiation 25, n^o 1 (1 janvier 2018) : 138–44. http://dx.doi.org/10.1107/s1600577517013066.

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The extreme-ultraviolet double-stage imaging Raman spectrometer is a permanent experimental endstation at the plane-grating monochromator beamline branch PG1 at FLASH at DESY in Hamburg, Germany. This unique instrument covers the photon energy range from 20 to 200 eV with high energy resolution of about 2 to 20 meV (design values) featuring an efficient elastic line suppression as well as effective stray light rejection. Such a design enables studies of low-energy excitations like, for example, phonons in solids close to the vicinity of the elastic line. The Raman spectrometer effectively operates with four reflective off-axial parabolic mirrors and two plane-grating units. The optics quality and their precise alignment are crucial to guarantee best performance of the instrument. Here, results on a comprehensive investigation of the quality of the spectrometer diffraction gratings are presented. The gratings have been characterized byex situmetrology at the BESSY-II Optics Laboratory, employing slope measuring deflectometry and interferometry as well as atomic force microscopy studies. The efficiency of these key optical elements has been measured at the at-wavelength metrology laboratory using the reflectometer at the BESSY-II Optics beamline. Also, the metrology results are discussed with respect to the expected resolving power of the instrument by including them in ray-tracing studies of the instrument.

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Cao, Yiqing, Zhijuan Shen et Zhixia Zheng. « Method of calculating the aberrations of soft X-ray and vacuum ultraviolet optical systems ». Journal of Synchrotron Radiation 26, n^o 5 (1 août 2019) : 1558–64. http://dx.doi.org/10.1107/s1600577519007823.

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Based on the the third-order aberration theory of plane-symmetric optical systems, this paper studies the effect on aberrations of the second-order accuracy of aperture-ray coordinates and the extrinsic aberrations of this kind of optical system; their calculation expressions are derived. The resultant aberration expressions are then applied to calculate the aberrations of two design examples of soft X-ray and vacuum ultraviolet (XUV) optical systems; images are compared with ray-tracing results using SHADOW software to validate the aberration expressions. The study shows that the accuracy of the aberration expressions is satisfactory.

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Sassen, Kenneth, Nancy C. Knight, Yoshihide Takano et Andrew J. Heymsfield. « Effects of ice-crystal structure on halo formation : cirrus cloud experimental and ray-tracing modeling studies ». Applied Optics 33, n^o 21 (20 juillet 1994) : 4590. http://dx.doi.org/10.1364/ao.33.004590.

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Nakamura, Yoshikatsu. « Ray-tracing studies of the arrival direction and the ionospheric penetration of whistlers at low latitudes ». Journal of Geophysical Research 98, A9 (1993) : 15729. http://dx.doi.org/10.1029/93ja00729.

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Dance, S. M. « The Development of Computer Models for the Prediction of Factory Noise ». Building Acoustics 2, n^o 2 (juin 1995) : 437–54. http://dx.doi.org/10.1177/1351010x9500200203.

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The development of factory noise prediction models over the past thirty years has parallelled the development of computer technology. There are currently two main approaches to this problem both of which have been extensively investigated, they are the image-source method and the ray-tracing technique. Presented are brief details of the background to the specific problems of factory noise prediction together with the various approaches used to solve the problem. An outline of how the two types of mathematical models work, together with details of their representational development is presented. A comparison of the current potential of each type of model, enabling an insight into when and where each type of model may be effectively used, is given. Three independent studies comparing various prediction models were considered. All three reviews drew the conclusion that the Ondet and Barbry, and the Lindqvist models were the most accurate ray-tracing and image-source models, respectively. Finally, a review of barrier prediction models is presented.

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Wong, Basil T., M. Pinar Mengüç et R. Ryan Vallance. « Sequential Nano-Patterning Using Electron and Laser Beams : A Numerical Methodology ». Journal of Computational and Theoretical Nanoscience 3, n^o 2 (1 avril 2006) : 219–30. http://dx.doi.org/10.1166/jctn.2006.3001.

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A methodology is presented for nanometer-size patterning of a workpiece using both an electron-beam and a laser. A Monte Carlo/Ray Tracing technique is used in modeling the electron-beam propagation inside a thin gold film. This approach is identical to that of a typical Monte Carlo simulation in radiative transfer except that proper electron scattering properties are employed. The laser propagation within the one-dimensional, non-scattering film on top of a quartz substrate is modeled using a ray-tracing approach and reflections at the boundaries are accounted for with the Fresnel-expressions. The temperature distribution inside a gold film is then predicted using the Fourier law of heat conduction, after evaluating the accuracy of the model for the range considered. A sequential nano-pattern is created using these coupled numerical simulations. The procedure we present here is the first to outline the sequential nano-machining processes and likely to guide the experimental studies to success with less trial-and-error attempts.

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Panessa, Francesca, Paola Castangia, Andrea Tarchi, Loredana Bassani, Angela Malizia, Angela Bazzano et Pietro Ubertini. « Water maser emission in hard X-ray selected AGN ». Proceedings of the International Astronomical Union 13, S336 (septembre 2017) : 96–98. http://dx.doi.org/10.1017/s1743921317010614.

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AbstractWater megamaser emission is powerful in tracing the inner region of active nuclei, mapping accretion disks and providing important clues on their absorption properties. From the X-ray spectra of AGN it is possible to estimate the intrinsic power of the central engine and the obscuring column density. The synergy between X-ray and water maser studies allows us to tackle the AGN inner physics from different perspectives. For a complete sample of AGN selected in the 20-40 keV energy range, we have investigated the presence of water maser emission and its connection to the X-ray emission, absorption and accretion rate. The hard X-ray selection of the sample results in a water maser detection rate much higher than those obtained from optically-selected samples.

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Тясто, Марта, Marta Tyasto, Ольга Данилова, Olga Danilova, Наталия Птицына, Natalia Ptitsyna, Валерий Сдобнов et Valeriy Sdobnov. « Variations in cosmic ray cutoff rigidities during the greatgeomagnetic storm of November 2004 ». Solnechno-Zemnaya Fizika 1, n^o 2 (17 juin 2015) : 97–105. http://dx.doi.org/10.12737/7890.

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Very strong interplanetary and magnetospheric disturbance observed on 7–13 November 2004 can be regarded as one of the strongest events during the entire period of space observations. In this paper, we report on the studies of cosmic ray cutoff rigidity variations during 7–13 November 2004 showing how storm conditions can affect the direct cosmic ray access to the inner magnetosphere. Effective cutoff rigidities have been calculated for selected points on the ground by tracing trajectories of cosmic ray particles through the magnetospheric magnetic field of the “storm-oriented” Tsyganenko 2003 model [Tsyganenko, 2002a, b; Tsyganenko et al., 2003]. Cutoff rigidity variations have also been determined by the spectrographic global survey method on the basis of experimental data of the neutron monitor network. Correlations between the calculated and experimental cutoff rigidities, as well as between geomagnetic Dst index and interplanetary parameters have been investigated. Correlation coefficients between the cutoff rigidities obtained by the trajectory tracing method and the spectrographic global survey method have been found to be in the limits of 0.76–0.89 for all stations except the low-latitude station Tokyo (0.35). The most pronounced correlation has been revealed between the cutoff rigidities that exhibited a very large variation of 1–1.5 GV during the magnetic storm, and the Dst index.

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Lin, Psang Dain, et Chia-Hung Lu. « Modeling and Sensitivity Analysis of Laser Tracking Systems by Skew-Ray Tracing Method ». Journal of Manufacturing Science and Engineering 127, n^o 3 (29 septembre 2004) : 654–62. http://dx.doi.org/10.1115/1.1954790.

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Laser tracking systems, such as the Leica LTD 500, are used for precision position measurement of large or distant objects, for example, the alignment of aircraft wings or bridge girders during assembly. A laser tracker’s performance is theoretically better than other common metrology equipment, such as coordinate measuring machines (CMMs). It is desirable that a flexible laser tracking system replaces the standard CMM, but measurement accuracy is highly dependent on the accuracy of its rotating mirror mechanism and its link dimension variance during tracker manufacture and assembly. Therefore this study presents a skew-ray tracing method for modeling and sensitivity analysis of laser tracking systems. First, the geometric relations of position-detector and interferometer readings are derived in terms of the laser tracker’s parameters using skew-ray tracing method. Effects of corner-cube alignment errors on sensor readings are also investigated theoretically, and it is found that misalignment of the corner-cube causes errors in path length and, therefore, misestimation of distance. Effects of mirror mechanism dimension errors are also investigated by sensitivity analysis. This study will be of use to theoretical and practical studies involving the modeling, design, and use of laser tracking systems and similar devices.

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Katch, Lauren, et Andrea P. Arguelles. « A ray tracing approach to focusing ultrasonic beams in isotropic and anisotropic solids ». Journal of the Acoustical Society of America 152, n^o 4 (octobre 2022) : A227. http://dx.doi.org/10.1121/10.0016093.

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Focal depths in solid materials are generally calculated using analytical expressions that rely on the paraxial approximation (i.e., small angles related to shallow focusing). However, with increasing use of highly focused probes for acoustic microscopy and backscattering studies, these assumptions are often challenged. Additional challenges are posed by the presence of material anisotropy within the solid. In this presentation, we present a ray tracing based approach to characterize ultrasonic beam focusing when using highly focused ultrasonic transducers. The results are compared to traditional methods to calculate focal regions to evaluate the range of applicability for isotropic and anisotropic materials. For isotropic solids, a non-paraxial focusing equation is derived and compared to the conventional focusing equation for both normal incidence and oblique incidence immersion setups. Both focusing equations are compared through ray diagrams where the proximity to the true geometric focus is explored. The proposed focusing equation results in a closer approximation to the geometric focus, a smaller beam cross-section, and a greater time convergence compared to the conventional focusing equation. Lastly, the results are expanded to anisotropic media where potential for multiple foci and complex beam behavior arise.

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Watanabe, Takeo, Tsuneyuki Haga, Masahito Niibe et Hiroo Kinoshita. « Design of beamline optics for EUVL ». Journal of Synchrotron Radiation 5, n^o 3 (1 mai 1998) : 1149–52. http://dx.doi.org/10.1107/s0909049597017536.

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The design of front-end collimating optics for extreme-ultraviolet lithography (EUVL) is reported. For EUVL, collimating optics consisting of a concave toroidal mirror and a convex toroidal mirror can achieve shorter optical path lengths than collimating optics consisting of two concave toroidal mirrors. Collimating optics consisting of a concave toroidal mirror and a convex toroidal mirror are discussed. The design of collimating optics for EUVL beamlines based on ray-tracing studies is described.

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Jovanovic, Predrag, et Luka Popovic. « Supermassive binary black holes - possible observational effects in the x-ray emission ». Facta universitatis - series : Physics, Chemistry and Technology 12, n^o 2 (2014) : 159–66. http://dx.doi.org/10.2298/fupct1402159j.

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Here we discuss the possible observational effects in the X-ray emission from two relativistic accretion disks in a supermassive binary black hole system. For that purpose we developed a model and performed numerical simulations of the X-ray radiation from a relativistic accretion disk around a supermassive black hole, based on the ray-tracing method in the Kerr metric, and applied it to the case of the close binary supermassive black holes. Our results indicate that the broad Fe K? line is a powerful tool for detecting such systems and studying their properties. The most favorable candidates for observational studies are the supermassive binary black holes in the galactic mergers during the phase when the orbital velocities of their components are very large and exceed several thousand kms -1.

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Othman, Shah Farez, Nizam Tamchek, Farah Diana Muhammad et Mohd Hafidz Ithnin. « Modulation Transfer Function Analysis in Myopic Model Eye ». ASM Science Journal 16 (15 juillet 2021) : 1–8. http://dx.doi.org/10.32802/asmscj.2021.688.

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Hitherto, the eye modelling is based on the emmetropic eye taken its ocular optical components value from the population-based studies. However, no studies have been done to study the effect of aberration of myopic refractive error by modelling the eye using the parameters from ocular biometrics and ray tracing method. This study aimed to determine the modulation transfer function (MTF) of myopic refractive error using eye modelling and ray tracing technique. Three eye models had been successfully modelled in Zemax software, namely, emmetropic Liou and Brennan, myopic Liou and Brennan, corrected myopic Liou and Brennan. The optical performance of the eye models were tested using the MTF. From the MTF analysis at 100 cycles/mm, the MTF value of both tangential and sagittal rays for myopic Liou and Brennan eye was the lowest compared to its emmetropic model. Also, the MTF value of the corrected myopic Liou and Brennan model was higher compared to the uncorrected myopic model. However, the corrected myopic model produced lower MTF values for both tangential and sagittal MTF compared with the emmetropic model of Liou and Brennan. In this study, the accuracy of the MTF for myopia correction and emmetropia were calculated. It was found that the accuracy of the MTF value for corrected myopia at tangential and sagittal rays was lower.

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Galanis, O. C., C. B. Papazachos, P. M. Hatzidimitriou et E. M. Scordilis. « APPLICATION OF 3-D VELOCITY MODELS AND RAY TRACING IN DOUBLE DIFFERENCE EARTHQUAKE LOCATION ALGORITHMS : APPLICATION TO THE MYGDONIA BASIN (NORTHERN GREECE) ». Bulletin of the Geological Society of Greece 36, n^o 3 (1 janvier 2004) : 1396. http://dx.doi.org/10.12681/bgsg.16508.

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In the past years there has been a growing demand for precise earthquake locations for seismotectonic and seismic hazard studies. Recently this has become possible because of the development of sophisticated location algorithms, as well as hardware resources. This is expected to lead to a better insight of seismicity in the near future. A well-known technique, which has been recently used for relocating earthquake data sets is the double difference algorithm. In its original implementation it makes use of a one-dimensional ray tracing routine to calculate seismic wave travel times. We have modified the implementation of the algorithm by incorporating a three-dimensional velocity model and ray tracing in order to relocate a set of earthquakes in the area of the Mygdonia Basin (Northern Greece). This area is covered by a permanent regional network and occasionally by temporary local networks. The velocity structure is very well known, as the Mygdonia Basin has been used as an international test site for seismological studies since 1993, which makes it an appropriate location for evaluating earthquake location algorithms, with the quality of the results depending only on the quality of the data and the algorithm itself. The new earthquake locations reveal details of the area's seismotectonic structure, which are blurred, if not misleading, when resolved by standard (routine) location algorithms.

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Chaudhury, Bhaskar, et Shashank Chaturvedi. « Comparison of wave propagation studies in plasmas using three-dimensional finite-difference time-domain and ray-tracing methods ». Physics of Plasmas 13, n^o 12 (décembre 2006) : 123302. http://dx.doi.org/10.1063/1.2397582.

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Li, Qingfeng, Zeyun Li et Hanxian Fang. « Using 3D Ray Tracing Technology to Study the Disturbance Effect of Rocket Plume on Ionosphere ». Atmosphere 13, n^o 7 (20 juillet 2022) : 1150. http://dx.doi.org/10.3390/atmos13071150.

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In this paper, the initial neutral atmospheric parameters, background ionospheric parameters and geomagnetic field parameters of the ionosphere are obtained by NRLMSISE-00 model, IRI-2016 model and IGRF-13 model, respectively. Considering the neutral gas diffusion process, ion chemical reaction and plasma diffusion process, a three-dimensional dynamic model of chemical substances released by rocket plume disturbing the ionosphere is constructed. The influence of the disturbance on the echo path of high frequency radio waves with different incident frequencies is simulated by using three-dimensional digital ray-tracing technology. Using this model, the process of ionospheric disturbance caused by the main chemical substances H2 and H2O in the rocket plume under three different release conditions: fixed-point release at 300 km, vertical path at 250–350 km and parabolic path at 250–350 km, and the influence of the ionospheric cavity on the radio wave propagation of high frequency radio waves at different frequencies are simulated. The main purpose of the article is to focus on the effect of the cavity generated by the rocket exhaust on the propagation of radio waves. It mainly studies the perturbation effect on the ionosphere under different release conditions, considers the neutral gas diffusion process, ion chemical reaction and plasma diffusion process, and establishes the three-dimensional dynamics of the ionospheric electron density and the spatiotemporal distribution of the plume plasma learning model. Finally, the three-dimensional ray-tracing algorithm is used to simulate the propagation path of the radio wave through the disturbance area. We considered three different release conditions, including fixed-point release, vertical path and parabolic path. The ionospheric disturbances produced by these different releases are compared and analyzed, and their effects on the propagation path of radio waves are studied.

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Vanwelde, M., C. Hernalsteens, R. Tesse, E. Gnacadja, E. Ramoisiaux et N. Pauly. « The Zgoubidoo python framework for ray-tracing simulations with Zgoubi : applications to fixed-field accelerators ». Journal of Physics : Conference Series 2420, n^o 1 (1 janvier 2023) : 012039. http://dx.doi.org/10.1088/1742-6596/2420/1/012039.

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Abstract The study of beam dynamics in accelerators featuring main magnets with complex geometries such as Fixed Field Accelerators (FFAs) requires simulation codes allowing step-by-step particle tracking in complex magnetic fields, such as the Zgoubi ray-tracing code. To facilitate the use of Zgoubi and to allow readily processing the resulting tracking data, we developed a modern Python 3 interface, Zgoubidoo, using Zgoubi in the backend. In this work, the key features of Zgoubidoo are illustrated by detailing the main steps to obtain a non-scaling FFA accelerator from a scaling design. The results obtained are in excellent agreement with prior results, including the tune computation and orbit shifts. These results are enhanced by Zgoubidoo beam dynamics analysis and visualization tools, including the placement of lattice elements in a global coordinate system and the computation of linear step-by-step optics. The validation of Zgoubidoo on conventional scaling and non-scaling FFA designs paves the way for future uses in innovative FFA design studies.

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Wang, Shuguang, Fuqing Zhang et Chris Snyder. « Generation and Propagation of Inertia–Gravity Waves from Vortex Dipoles and Jets ». Journal of the Atmospheric Sciences 66, n^o 5 (1 mai 2009) : 1294–314. http://dx.doi.org/10.1175/2008jas2830.1.

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Abstract This study investigates gravity wave generation and propagation from jets within idealized vortex dipoles using a nonhydrostatic mesoscale model. Two types of initially balanced and localized jets induced by vortex dipoles are examined here. These jets have their maximum strength either at the surface or in the middle levels of a uniformly stratified atmosphere. Within these dipoles, inertia–gravity waves with intrinsic frequencies 1–2 times the Coriolis parameter are simulated in the jet exit region. These gravity waves are nearly phase locked with the jets as shown in previous studies, suggesting spontaneous emission of the waves by the localized jets. A ray tracing technique is further employed to investigate the propagation effects of gravity waves. The ray tracing analysis reveals strong variation of wave characteristics along ray paths due to variations (particularly horizontal variations) in the propagating environment. The dependence of wave amplitude on the jet strength (and thus on the Rossby number of the flow) is examined through experiments in which the two vortices are initially separated by a large distance but subsequently approach each other and form a vortex dipole with an associated amplifying localized jet. The amplitude of the stationary gravity waves in the simulations with 90-km grid spacing increases as the square of the Rossby number (Ro), when Ro falls in a small range of 0.05–0.15, but does so significantly more rapidly when a smaller grid spacing is used.

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Savchenko, V. V., et M. A. Savchenko. « Вычислительный эксперимент по моделированию распространения света в волокнистой профилированной структуре ». Успехи кибернетики / Russian Journal of Cybernetics, n^o 1(1) (31 mars 2020) : 50–57. http://dx.doi.org/10.51790/2712-9942-2020-1-1-7.

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Many studies show that profiled structures are the source of attaining desired system characteristics in industrial or other applications. In this short note, we continue considering proposed recently by us the profiled structure such as a beach umbrella based on the principles of origami design. To demonstrate the optical properties of the given model, a developed recursive ray tracing algorithm is used to simulate the propagation of light rays through the modelled paper fiber sample. In this paper, modeling light propagation through a porous structure using ray tracing technique is presented and results of modeling light propagation in a profiled structure with respect to simulated light propagation in fiber structure are discussed. Во многих работах указывается, что использование профилированных структур позволяет получить характеристики материала, необходимые для его применения в промышленности и других областях. В этой небольшой статье мы продолжаем рассматривать предложенную нами недавно профилированную структуру в виде пляжного зонта, основанную на принципах дизайна оригами. Для демонстрации оптических свойств данной модели используется разработанный алгоритм рекурсивной трассировки лучей для моделирования распространения световых лучей через смоделированный образец бумажного волокна. В этой статье представлено моделирование распространения света через пористую структуру с использованием техники трассировки лучей, а также обсуждаются результаты моделирования распространения света в профилированной структуре в сравнении с моделированным распространением света в волокнистой структуре.

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Stock, S. R., M. K. Stock et J. D. Almer. « Combined computed tomography and position-resolved X-ray diffraction of an intact Roman-era Egyptian portrait mummy ». Journal of The Royal Society Interface 17, n^o 172 (novembre 2020) : 20200686. http://dx.doi.org/10.1098/rsif.2020.0686.

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Hawara Portrait Mummy 4, a Roman-era Egyptian portrait mummy, was studied with computed tomography (CT) and with CT-guided synchrotron X-ray diffraction mapping. These are the first X-ray diffraction results obtained non-invasively from objects within a mummy. The CT data showed human remains of a 5-year-old child, consistent with the female (but not the age) depicted on the portrait. Physical trauma was not evident in the skeleton. Diffraction at two different mummy-to-detector separations allowed volumetric mapping of features including wires and inclusions within the wrappings and the skull and femora. The largest uncertainty in origin determination was approximately 1.5 mm along the X-ray beam direction, and diffraction- and CT-determined positions matched. Diffraction showed that the wires were a modern dual-phase steel and showed that the 7 × 5 × 3 mm inclusion ventral of the abdomen was calcite. Tracing the 00.2 and 00.4 carbonated apatite (bone's crystalline phase) reflections back to their origins produced cross-sectional maps of the skull and of femora; these maps agreed with transverse CT slices within approximately 1 mm. Coupling CT and position-resolved X-ray diffraction, therefore, offers considerable promise for non-invasive studies of mummies.

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Santana, Bernardo, El Khalil Cherif, Alexandre Bernardino et Ricardo Ribeiro. « Real-Time Georeferencing of Fire Front Aerial Images Using Iterative Ray-Tracing and the Bearings-Range Extended Kalman Filter ». Sensors 22, n^o 3 (2 février 2022) : 1150. http://dx.doi.org/10.3390/s22031150.

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Although Aerial Vehicle images are a viable tool for observing large-scale patterns of fires and their impacts, its application is limited by the complex optical georeferencing procedure due to the lack of distinctive visual features in forest environments. For this reason, an exploratory study on rough and flat terrains was conducted to use and validate the Iterative Ray-Tracing method in combination with a Bearings-Range Extended Kalman Filter as a real-time forest fire georeferencing and filtering algorithm on images captured by an aerial vehicle. The Iterative Ray-Tracing method requires a vehicle equipped with a Global Positioning System (GPS), an Inertial Measurement Unit (IMU), a calibrated camera, and a Digital Elevation Map (DEM). The proposed method receives the real-time input of the GPS, IMU, and the image coordinates of the pixels to georeference (computed by a companion algorithm of fire front detection) and outputs the geographical coordinates corresponding to those pixels. The Unscented Transform B is proposed to characterize the Iterative Ray-Tracing uncertainty. A Bearings-Range filter measurement model is introduced in a sequential filtering architecture to reduce the noise in the measurements, assuming static targets. A performance comparison is done between the Bearings-Only and the Bearings-Range observation models, and between the Extended and Cubature Kalman Filters. In simulation studies with ground truth, without filtering we obtained a georeferencing Root Mean Squared Errors (RMSE) of 30.7 and 43.4 m for the rough and flat terrains respectively, while filtering with the proposed Bearings-Range Extended Kalman Filter showed the best results by reducing the previous RMSE to 11.7 and 19.8 m, respectively. In addition, the comparison of both filter algorithms showed a good performance of Bearings-Range filter which was slightly faster. Indeed, these experiments based on the real data conducted to results demonstrated the applicability of the proposed methodology for the real-time georeferencing forest fires.

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Nyassor, Prosper K., Cristiano M. Wrasse, Igo Paulino, Eliah F. M. T. São Sabbas, José V. Bageston, Kleber P. Naccarato, Delano Gobbi et al. « Sources of concentric gravity waves generated by a moving mesoscale convective system in southern Brazil ». Atmospheric Chemistry and Physics 22, n^o 23 (29 novembre 2022) : 15153–77. http://dx.doi.org/10.5194/acp-22-15153-2022.

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Abstract. The studies on the sources of three concentric gravity waves (CGWs) excited by a moving mesoscale convective system (MCS) on the night of 1–2 October 2019 are investigated. These CGWs were observed using a hydroxyl (OH) all-sky imager, whereas the MCS was observed by the Geostationary Operational Environmental Satellite (GOES). Using 2D spectral analysis, we observed that the three CGWs have horizontal wavelength λH between ∼30–55 km, phase speed cH∼70–90 m s−1, and period τ∼7–12 min. Using backward ray tracing, we found that two of the CGWs were excited from convective cores within the MCS. We also found that the epicenters of the two waves were close to the tropopause positions of the ray-traced paths and nearby convective cores. Regarding the source, we verified that on this night the tropopause was ∼-80 ∘C, which was ∼10 ∘C colder than the days preceding and after the MCS and also colder than usually observed. Since the tropopause height and temperature are fundamental parameters underlying the analysis of the overshooting extent, we developed our own methodology to establish a reference tropopause that would enable a quantitative estimate of this parameter. Since the MCS (CGWs source) was moving, the overshooting convective cores were tracked in space and time. Using the tracking of the overshooting tops (OTs) in space and time with the aid of reverse ray tracing, we found that two out of the three CGWs were excited by the MCS, whereas the source of the remaining one was not directly associated with the MCS.

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Operto, M. Stéphane, Sheng Xu et Gilles Lambaré. « Can we quantitatively image complex structures with rays ? » GEOPHYSICS 65, n^o 4 (juillet 2000) : 1223–38. http://dx.doi.org/10.1190/1.1444814.

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Ray‐based prestack depth migration fails to image quantitatively complex structures when a single arrival—for example, the first or the strongest one—is taken into account. In this paper, we investigate whether accounting for multiple arrivals in ray‐based preserved amplitude prestack depth migration allows one to improve quantitative imaging of complex media. The asymptotic ray‐Born migration/inversion, originally designed to process one single arrival, is extended to the case of multiple arrivals by accounting for the cross‐contributions of all the source and receiver raypaths. Multiple arrivals in the folded ray fields are computed by a dynamic ray tracing based on a wavefront construction technique. With an application to the complex Marmousi model, we demonstrate that ray‐Born inversion can provide a reliable quantitative estimation of the relative impedance perturbation even in the complex deep part of the model, for which the amplitudes were underestimated drastically when only a single arrival was used, either the first or the strongest one. This 2-D case study shows that complex structures can be imaged quantitatively with rays. Future studies will require the optimizing of the implementation of ray‐Born migration/inversion with multiple arrivals before considering 3-D applications.

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Fregly, Benjamin J., Haseeb A. Rahman et Scott A. Banks. « Theoretical Accuracy of Model-Based Shape Matching for Measuring Natural Knee Kinematics with Single-Plane Fluoroscopy ». Journal of Biomechanical Engineering 127, n^o 4 (27 janvier 2005) : 692–99. http://dx.doi.org/10.1115/1.1933949.

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Quantification of knee motion under dynamic, in vivo loaded conditions is necessary to understand how knee kinematics influence joint injury, disease, and rehabilitation. Though recent studies have measured three-dimensional knee kinematics by matching geometric bone models to single-plane fluoroscopic images, factors limiting the accuracy of this approach have not been thoroughly investigated. This study used a three-step computational approach to evaluate theoretical accuracy limitations due to the shape matching process alone. First, cortical bone models of the femur, tibia/fibula, and patella were created from CT data. Next, synthetic (i.e., computer generated) fluoroscopic images were created by ray tracing the bone models in known poses. Finally, an automated matching algorithm utilizing edge detection methods was developed to align flat-shaded bone models to the synthetic images. Accuracy of the recovered pose parameters was assessed in terms of measurement bias and precision. Under these ideal conditions where other sources of error were eliminated, tibiofemoral poses were within 2mm for sagittal plane translations and 1.5deg for all rotations while patellofemoral poses were within 2mm and 3deg. However, statistically significant bias was found in most relative pose parameters. Bias disappeared and precision improved by a factor of two when the synthetic images were regenerated using flat shading (i.e., sharp bone edges) instead of ray tracing (i.e., attenuated bone edges). Analysis of absolute pose parameter errors revealed that the automated matching algorithm systematically pushed the flat-shaded bone models too far into the image plane to match the attenuated edges of the synthetic ray-traced images. These results suggest that biased edge detection is the primary factor limiting the theoretical accuracy of this single-plane shape matching procedure.

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Bhattacharyya, A., et B. Mitra. « Changes in cosmic ray cut-off rigidities due to secular variations of the geomagnetic field ». Annales Geophysicae 15, n^o 6 (30 juin 1997) : 734–39. http://dx.doi.org/10.1007/s00585-997-0734-6.

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Abstract. An analytical expression is derived for the cutoff rigidity of cosmic rays arriving at a point in an arbitrary direction, when the main geomagnetic field is approximated by that of an eccentric dipole. This expression is used to determine changes in geomagnetic cutoffs due to secular variation of the geomagnetic field since 1835. Effects of westward drift of the quadrupole field and decrease in the effective dipole moment are seen in the isorigidity contours. On account of the immense computer time required to determine the cutoff rigidities more accurately using the particle trajectory tracing technique, the present formulation may be useful in estimating the transmission factor of the geomagnetic field in cosmic ray studies, modulation of cosmogenic isotope production by geomagnetic secular variation, and the contribution of geomagnetic field variation to long term changes in climate through cosmic ray related modulation of the current flow in the global electric circuit.

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Willingale, Richard, Charlotte Feldman, Alan Michette, Tim Button, Camelia Dunare, Melvyn Folkard, David Hart et al. « Active Microstructured Optical Arrays of Grazing Incidence Reflectors ». X-Ray Optics and Instrumentation 2010 (5 août 2010) : 1–15. http://dx.doi.org/10.1155/2010/856836.

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The UK Smart X-Ray Optics (SXO) programme is developing active/adaptive optics for terrestrial applications. One of the technologies proposed is microstructured optical arrays (MOAs), which focus X-rays using grazing incidence reflection through consecutive aligned arrays of microscopic channels. Although such arrays are similar in concept to polycapillary and microchannel plate optics, they can be bent and adjusted using piezoelectric actuators providing control over the focusing and inherent aberrations. Custom configurations can be designed, using ray tracing and finite element analysis, for applications from sub-keV to several-keV X-rays, and the channels of appropriate aspect ratios can be made using deep silicon etching. An exemplar application will be in the microprobing of biological cells and tissue samples using Ti Kα radiation (4.5 keV) in studies related to radiation-induced cancers. This paper discusses the optical design, modelling, and manufacture of such optics.

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Poli, Emanuele, Maximilian Müller, Hartmut Zohm et Michael Kovari. « Fast evaluation of the current drive efﬁciency by electron cyclotron waves for reactor studies ». EPJ Web of Conferences 203 (2019) : 01008. http://dx.doi.org/10.1051/epjconf/201920301008.

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The determination of the current driven by electron cyclotron waves is usually performed employing ray/beam tracing codes, which require as an input the magnetic equilibrium, the electron density and the electron temperature profiles on one side and the beam injection parameters on the other. In the frame of systems-code applications, however, a different approach is needed, as some of the required input quantities are not available. Here, a procedure to evaluate the achievable ECCD efficiency for given global reactor parameters is proposed. It relies on a single numerical evaluation of the current drive efficiency (based on the adjoint method and including momentum-conserving corrections) for suitably chosen input values. The results are shown to be in good agreement with the full numerical optimization of the ECCD efficiency for a number of reactor-relevant scenarios. As described in this paper, this approach does not include the effect of parasitic absorption from higher cyclotron harmonics, which becomes important starting from electron temperatures of the order of 30 keV.

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Moscibrodzka, Monika A., et Aristomenis I. Yfantis. « Prospects for Ray-tracing Light Intensity and Polarization in Models of Accreting Compact Objects Using a GPU ». Astrophysical Journal Supplement Series 265, n^o 1 (1 mars 2023) : 22. http://dx.doi.org/10.3847/1538-4365/acb6f9.

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Abstract The Event Horizon Telescope (EHT) has recently released high-resolution images of accretion flows onto two supermassive black holes. Our physical understanding of these images depends on the accuracy and precision of numerical models of plasma and radiation around compact objects. The goal of this work is to speed up radiative-transfer simulations used to create mock images of black holes for comparison with the EHT observations. A ray-tracing code for general relativistic and fully polarized radiative transfer through plasma in strong gravity is ported onto a graphics processing unit (GPU). We describe our GPU implementation and carry out speedup tests using models of optically thin advection-dominated accretion flow onto a black hole realized semianalytically and in 3D general relativistic magnetohydrodynamic simulations, low and very high image pixel resolutions, and two different sets of CPU+GPUs. We show that a GPU with high double precision computing capability can significantly reduce the image production computational time, with a speedup factor of up to approximately 1200. The significant speedup facilitates, e.g., dynamic model fitting to the EHT data, including polarimetric data. The method extension may enable studies of emission from plasma with nonthermal particle distribution functions for which accurate approximate synchrotron emissivities are not available. The significant speedup reduces the carbon footprint of the generation of the EHT image libraries by at least an order of magnitude.

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Bergmann, R. B., T. J. Rinke, R. M. Hausner, M. Grauvogl, M. Vetter et J. H. Werner. « Thin film solar cells on glass by transfer of monocrystalline Si films ». International Journal of Photoenergy 1, n^o 2 (1999) : 89–93. http://dx.doi.org/10.1155/s1110662x99000173.

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Thin film solar cells based on monocrystalline Si films are transferred to a glass superstrate. Chemical vapor deposition serves to epitaxially deposit Si on quasi-monocrystalline Si films obtained from thermal crystallization of a double layer porous Si film on a Si wafer. A separation layer that forms during this crystallization process allows one to separate the epitaxial layer on top of the quasi-monocrystalline film from the starting Si wafer. We presently achieve an independently confirmed solar cell conversion efficiency of 9:26%. Ray tracing studies in combination with electrical device simulation indicate an efficiency potential of around 17% using simple device processing and moderate assumptions on minority carrier lifetime and surface recombination.

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Wawrzyniak, Natalia, et Andrzej Stateczny. « MSIS Image Postioning in Port Areas with the Aid of Comparative Navigation Methods ». Polish Maritime Research 24, n^o 1 (1 mars 2017) : 32–41. http://dx.doi.org/10.1515/pomr-2017-0004.

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Abstract The article presents a method to determine the position of mechanically scanned sonar images by comparing them with the database of simulated synthetic images. The synthetic images are generated from high-density bathymetric data coming from the same fragment of water region, using the ray tracing method. The article discusses the issues related to the choice of the probability function as the method of image comparing which allows to find the correct georeference of the real image. For the correlation method and the logical conjunction method, which are believed to give the best results, detailed studies were performed, including boundary cases. The obtained results of matching are presented in tabular and graphic form.

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Cheng, Qianyu, Hongyu Peng, Shanshan Hu, Yafei Liu, Zeyu Chen, Balaji Raghothamachar et Michael Dudley. « Effective Penetration Depths Investigation on Synchrotron X-Ray Topographic Images of Basal Plane Dislocations in 4H-SiC Crystals through Ray-Tracing Simulation ». ECS Meeting Abstracts MA2022-02, n^o 37 (9 octobre 2022) : 1355. http://dx.doi.org/10.1149/ma2022-02371355mtgabs.

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The demand for power electronic devices fabricated from silicon carbide (SiC) has increased rapidly in recent years for a diverse range of existing and emerging applications. The development of device technology highly depends on the quality of substrate and epitaxial material and the number of deleterious defects within, as those are critical factors that impact the device performance and long-term reliability [1, 2]. Therefore, understanding the nature of defects is of great importance for preventing the degradation or premature breakdown of devices. Synchrotron X-ray topography (XRT) is a dominant analytical method for the imaging and characterization of crystallographic defects. For 4° off-axis (0001) 4H-SiC wafers, the grazing-incidence geometry topographic technique is commonly employed to focus on the defect investigation near surface region. In this geometry, a small incidence angles (~1-2°) is used for allowing X-ray to only penetrate the sample with a shallow depth below the surface, therefore, it is essential to establish a procedure to define the effective penetration depth for detailed analysis of dislocation structures and density calculations. In earlier studies, Dudley in 1989 concluded that the observed penetration depths are limited by photoelectric absorption rather than extinction [3]. Ishiji in 2017 estimated the penetration depth based on the photoelectric absorption experienced by the diffracted X-rays [4]. However, only basal plane dislocations (BPDs) with screw segments parallel to the off-cut [11-20]-direction were evaluated in that study, which is insufficient for evaluating other types of BPDs. Therefore, a universal method to determine the effective penetration depth for all dislocation types would be of more practical importance. In this study, a procedure to define this effective penetration depth is demonstrated by investigating physical vapor transport (PVT) grown 4° off-axis 4H-SiC crystals through preforming systematic analysis of topographic and ray-tracing simulated contrast of BPDs with different Burgers vector and line direction combinations. The topographic images are recorded through synchrotron monochromatic beam in grazing incidence geometry. The simulation model is based on the principle of orientation contrast mechanism [5, 6] and developed by considering both the effects of surface relaxation [7] and X-ray absorption [8, 9] for evaluating the contributed factors of dislocation contrast formation. Analysis of the results indicates the observable dislocation contrast depends on the effective misorientation associated with the dislocation modulated by the photoelectric absorption effect. The dislocations with larger effective misorientation are associated with longer projected lengths and corresponding deeper effective penetration depths. A more simplified factor based on an approximate expression for the misorientation is also introduced in this study as an alternative to the full ray-tracing simulation approach. The effective penetration depth determination method presented in this study enables three-dimensional dislocation configuration analysis and accurate density calculations. Reference: Das, H., et al., Materials Science Forum, 2019. 963: p. 284-287. Kimoto, T., et al. 2017 IEEE International Reliability Physics Symposium (IRPS). 2017. Dudley, M., J. Wu, and G.D. Yao, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1989. 40-41: p. 388-392. Ishiji, K., et al., Japanese Journal of Applied Physics, 2017. 56(10): p. 106601. Dudley, M., X.R. Huang, and W. Huang, Journal of Physics D: Applied Physics, 1999. 32(10A): p. A139-A144. Huang, X.R., et al., Journal of Applied Crystallography, 1999. 32(3): p. 516-524. Peng, H., et al., Journal of Applied Crystallography, 2021. 54(2): p. 439-443. Fujie, F., et al., Acta Materialia, 2021. 208: p. 116746. Ailihumaer, T., et al., Materials Science and Engineering: B, 2021. 271: p. 115281. Figure 1

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Blom, Philip S. « Modeling regional propagation of infrasonic Mach cone energy from a supersonic source ». Journal of the Acoustical Society of America 152, n^o 4 (octobre 2022) : A191. http://dx.doi.org/10.1121/10.0015987.

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Supersonic sources such as bolides, aircraft, and rocket launches are known to produce a wide range of acoustic and infrasonic signals. The lower frequency infrasonic component of these signals can propagate large distances through the atmosphere due to the decreased thermo-viscous losses at low frequency and presence of temperature and wind induced infrasonic waveguides so that signals are often detected at regional distances of hundreds of kilometers. The dominant radiator of energy from such sources is the Mach cone signal that emanates from the source with very specific geometry. Ray tracing analysis using a Mach cone source model to predict infrasonic signals at regional distances will be presented and several parametric studies and comparisons with observed signals from several representative supersonic sources will be presented.

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