Littérature scientifique sur le sujet « OPTICALLY THIN MEDIA »
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Articles de revues sur le sujet "OPTICALLY THIN MEDIA"
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Chen, L. H., A. Garo, K. Cen et G. Grehan. « Numerical simulation of soot optical diagnostics in non-optically thin media ». Applied Physics B 87, no 4 (17 mai 2007) : 739–47. http://dx.doi.org/10.1007/s00340-007-2646-2.
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McGarragh, Greg, et Philip Gabriel. « Efficient computation of radiances for optically thin media by Padé approximants ». Journal of Quantitative Spectroscopy and Radiative Transfer 111, no 12-13 (août 2010) : 1885–99. http://dx.doi.org/10.1016/j.jqsrt.2010.03.011.
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Boardman, A., et P. Egan. « S-polarized waves in a thin dielectric film asymmetrically bounded by optically nonlinear media ». IEEE Journal of Quantum Electronics 21, no 10 (octobre 1985) : 1701–13. http://dx.doi.org/10.1109/jqe.1985.1072568.
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Azad, F. H. « Differential Approximation to Radiative Transfer in Semitransparent Media ». Journal of Heat Transfer 107, no 2 (1 mai 1985) : 478–81. http://dx.doi.org/10.1115/1.3247443.
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Radiative transfer in a semitransparent medium is treated using the differential approximation. Boundary conditions are formulated to accommodate direction-dependent reflection and refraction at a dielectric interfaces. The approximate results are compared to numerical solution of the exact integral equation. Also, a modification based on the exact formulation of the integrated intensity at the interface is presented that significantly improves the accuracy of the differential approximation in the optically thin regimes.
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Brown, D. C. « Rigrod laser-pumped-laser resonator model : II. Application to thin and optically-dilute laser media ». Laser Physics 24, no 8 (15 juillet 2014) : 085003. http://dx.doi.org/10.1088/1054-660x/24/8/085003.
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Matousek, P., N. Everall, M. Towrie et A. W. Parker. « Depth Profiling in Diffusely Scattering Media Using Raman Spectroscopy and Picosecond Kerr Gating ». Applied Spectroscopy 59, no 2 (février 2005) : 200–205. http://dx.doi.org/10.1366/0003702053085115.
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We demonstrate how pulsed laser Raman excitation (∼1 ps) followed by fast optical Kerr gating (∼4 ps) can be used to effectively separate Raman signals originating from different depths in heterogeneous diffusely scattering media. The diffuse scattering slows down photon propagation through turbid samples enabling higher depth resolution than would be obtained for a given instrumental time resolution in an optically transparent medium. Two types of experiments on two-layer systems demonstrate the ability to differentiate between surface and sub-surface Raman signals. A Raman spectrum was obtained of stilbene powder buried beneath a 1 mm over-layer of PMMA (poly(methyl methacrylate)) powder. The signal contrasts of the lower stilbene layer and upper PMMA layer were improved by factors ≥5 and ≥180, respectively, by rejecting the Raman component of the counterpart layer. The ability to select the Raman signal of a thin top surface layer in preference to those from an underlying diffusely scattering substrate was demonstrated using a 100 μm thick optically transparent film of PET (poly(ethylene terephthalate)) on top of stilbene powder. The gating resulted in the suppression of the underlying stilbene Raman signal by a factor of 1200. The experiments were performed in back-scattering geometry using 400 nm excitation wavelength. The experimental technique should be well suited to biomedical applications such as disease diagnosis.
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Yang, Bo, Jian-Fu Zhang, Alex Lazarian et José Renan de Medeiros. « Statistical tracing of turbulent magnetic fields in the optically thick interstellar medium ». Monthly Notices of the Royal Astronomical Society 503, no 1 (1 février 2021) : 768–76. http://dx.doi.org/10.1093/mnras/stab236.
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ABSTRACT Based on high-resolution 3D data cubes from a magnetohydrodynamic (MHD) turbulence simulation, we study how to reveal the direction of the magnetic field within the optically thick interstellar medium by using the velocity gradient technique (VGT), correlation function anisotropy (CFA), and principal component analysis of anisotropies (PCAA). Considering the CO molecular tracers as a tracing method for radiative transfer processes, we find that the VGT and CFA can successfully trace the orientation of mean magnetic fields, which is in good agreement with the low-resolution numerical results obtained in the case of an optically thin medium. Similar to the simulation of an optically thin ISM, our simulations show that PCCA is still unusable in optically thick media. The synergetic application of the VGT and CFA to high-resolution spectroscopic observations is expected to yield valuable information on the interstellar magnetic field.
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Badjin, Dmitry A., et Semyon I. Glazyrin. « Physical and numerical instabilities of radiatively cooling shocks in turbulent magnetized media ». Monthly Notices of the Royal Astronomical Society 507, no 1 (11 août 2021) : 1492–512. http://dx.doi.org/10.1093/mnras/stab2318.
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ABSTRACT We consider the influence of a fluctuating magnetic field on to the structure formation and instabilities of radiatively cooling blast waves. The study is based on an example of optically thin post-adiabatic supernova remnants (SNRs) in the homogeneous interstellar medium. By means of analytic estimations and full-scale multidimensional simulations, we investigate the roles of thermal, hydrodynamic (corrugation, pulsational, convective, Rayleigh–Taylor, linear and non-linear Vishniac) and numerical instabilities (‘carbuncle’ and grid-forced effects). It is found that of primary importance is the interplay of the thermal instability with quasi-regular and random components of the interstellar field. Bending fluctuations caused by the latter can be strongly amplified by non-linear Vishniac instability in the SNR regions where the regular component is almost normal to the shock. The instabilities driven by counter-directional pressure and density gradients are limited mostly to very narrow post-shock cooling layers, transient perturbations of the same short scales, and rather weakly magnetized environments. Some of these results can also be applied to radiative shocks separating optically thick media from thin or semitransparent ones. Several recommendations and requirements on numerical simulation techniques are formulated.
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Zheng, Cheng, Jong Kang Park, Murat Yildirim, Josiah R. Boivin, Yi Xue, Mriganka Sur, Peter T. C. So et Dushan N. Wadduwage. « De-scattering with Excitation Patterning enables rapid wide-field imaging through scattering media ». Science Advances 7, no 28 (juillet 2021) : eaay5496. http://dx.doi.org/10.1126/sciadv.aay5496.
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Nonlinear optical microscopy has enabled in vivo deep tissue imaging on the millimeter scale. A key unmet challenge is its limited throughput especially compared to rapid wide-field modalities that are used ubiquitously in thin specimens. Wide-field imaging methods in tissue specimens have found successes in optically cleared tissues and at shallower depths, but the scattering of emission photons in thick turbid samples severely degrades image quality at the camera. To address this challenge, we introduce a novel technique called De-scattering with Excitation Patterning or “DEEP,” which uses patterned nonlinear excitation followed by computational imaging–assisted wide-field detection. Multiphoton temporal focusing allows high-resolution excitation patterns to be projected deep inside specimen at multiple scattering lengths due to the use of long wavelength light. Computational reconstruction allows high-resolution structural features to be reconstructed from tens to hundreds of DEEP images instead of millions of point-scanning measurements.
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Kabashnikov, V. P., V. M. Popov et A. I. Bril'. « Use of the Approximation of Optically Thin Pulsations in the Problems of Radiative Heat Transfer in Turbulent Media ». Heat Transfer Research 34, no 1-2 (2003) : 10. http://dx.doi.org/10.1615/heattransres.v34.i1-2.130.
Texte intégralThèses sur le sujet "OPTICALLY THIN MEDIA"
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Yang, Fuzi. « Optically excited surface polaritons using strongly absorbing media ». Thesis, University of Exeter, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279743.
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McHugh, D. « Second harmonic optical and magneto-optical effects in thin film media ». Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411066.
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Balasubramanian, Kunjithapatham. « Structural inhomogeneity and anisotropy in optical filters and thin films ; applications to optical storage media ». Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184564.
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Optical filters and thin film optical devices play an important role in Science and Industry. Several significant applications have emerged in optics, microelectronics and computer technology. In this work, we study some aspects of their design and applications. One class of optical fibers, known as Christiansen filters, are based on scattering phenomena in suspensions of solid particles in a liquid medium. Some new scattering filters in the visible and the near UV regions and their performance characteristics are reported here. Feasibility to fabricate such optical filters in solid matrix form is established. Some applications of these scattering filters are discussed. After an introduction to the optics of homogeneous and isotropic thin films, I discuss the general design of anisotropic thin film media and a scheme implemented to calculate their performance. Optical anisotropy, produced by the growth-induced columnar microstructure in thin films and its effects on the performance of optical filters are studied. Large shifts in the peak wavelength of a typical narrow band filter are predicted. Magneto-optical (MO) thin film media of great importance to erasable optical data storage technology are studied. An approximate technique based on a 2 x 2 matrix formalism is developed to calculate the normal incidence performance of these media. To investigate anisotropic effects, to incorporate more than one magnetic film with arbitrary orientations of magnetization, and to study oblique incidence performance, a completely general 4 x 4 matrix technique is implemented in a computer program. Effects of substrate/superstrate birefringence in the read-out signal of MO media are investigated. Several optimizing design criteria, particularly, the effectiveness in employing appropriate metal or dielectric reflector layers are studied. The influence of the plasma edge of metals in enhancing the polar Kerr rotation of MO media is discussed with illustrations. A contour plot of the Kerr rotation and reflectance is developed to help in the design of these media. An explanation is given for the observation of Kerr rotation enhancement near the plasma reflection edge of the reflector layer adjacent to the active MO layer and in general, where the reflectance spectrum shows a steep gradient.
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Wu, Te-ho. « Magnetic, magneto-optic, and magneto-transport studies of thin film media of magneto-optical recording ». Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186291.
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This dissertation contains a fairly comprehensive study on the characteristics of magneto-optical (MO) recording media. The primary aspects which are investigated consist of magnetic, magneto-optic, magneto-transport properties, and observations of domains. The main materials which have been examined are amorphous rare earth-transition metal (RE-TM) Tbₓ(FeCo)₁₋ₓ and multilayered Co/Pt and Co/Pd thin films. The samples were fabricated in several industrial and academic laboratories under different deposition conditions and deposited on different underlayers and substrates. The instrumentation used in this study include: a Vibrating Sample Magnetometer (VSM), a polar Kerr effect and extraordinary Hall effect loop tracer, an optical magnetic domain analyzer, and the magnetoresistance/resistivity probes. The magneto-optical property studied here is polar Kerr rotation. The magnetic properties investigated include saturation magnetization, coercivity, anisotropy energy constant, anisotropy field, and exchange coupling constant. The magneto-transport properties include resistivity, magnetoresistance and extraordinary Hall effect with four different geometries. In the domain observations, the domain nucleation, growth and collapse phenomena were investigated. In addition, the degree of jaggedness of various domain structures has been characterized by measuring the fractal dimension. Moreover, the domain distribution is analyzed in the demagnetized state both for the sample demagnetized by an in-plane magnetic field and the sample demagnetized by a perpendicular field. At the same time, both states were also studied in light of the initial magnetization curves obtained by measurements of polar Kerr effect, extraordinary Hall effect, and magnetoresistance. The domain density as a function of domain size as well as the minimum domain size can be inferred from the initial magnetization curves.
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PATTELLI, LORENZO. « Imaging light transport at the femtosecond scale : a walk on the wild side of diffusion ». Doctoral thesis, 2017. http://hdl.handle.net/2158/1087854.
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In this thesis work we investigated light transport in scattering media from a spatio-temporal perspective. To this purpose, we have designed and developed an experimental optical-gating setup and a new Monte Carlo software library focused on the measurement and simulation of spatio-temporal evolution of light transport down to a sub-picosecond resolution. The unique properties of both these tools allowed us to unveil an array of unexplored aspects of light propagation occurring in the extremely general plane-parallel slab geometry, which are of relevance both for application and fundamental purposes due to their asymptotic nature.
Indeed, time-domain techniques are commonly considered to offer the most straightforward and powerful characterization capabilities, in that they allow to selectively address different transport regimes and directly observe their evolution. However, as we extensively demonstrate, combining the temporal information with wide-field spatial imaging capabilities offers a significant improvement, unveiling a set of irreducible information that could not be accessed from separate spatial and temporal characterizations.
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Pattelli, Lorenzo. « Imaging light transport at the femtosecond scale ». Doctoral thesis, 2018. http://hdl.handle.net/2158/1157248.
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In this thesis work we investigated light transport in scattering media from a spatio-temporal perspective. To this purpose, we have designed and developed an experimental optical-gating setup and a new Monte Carlo software library focused on the measurement and simulation of spatio-temporal evolution of light transport down to a sub-picosecond resolution. The unique properties of both these tools allowed us to unveil an array of unexplored aspects of light propagation occurring in the extremely general plane-parallel slab geometry, which are of relevance both for application and fundamental purposes due to their asymptotic nature.
Indeed, time-domain techniques are commonly considered to offer the most straightforward and powerful characterization capabilities, in that they allow to selectively address different transport regimes and directly observe their evolution. However, as we extensively demonstrate, combining the temporal information with wide-field spatial imaging capabilities offers a significant improvement, unveiling a set of irreducible information that could not be accessed from separate spatial and temporal characterizations.
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Lin, Yen-Cheng, et 林彥成. « NiSi and NiGe Thin Films For Optical Recording Media ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/02184446834660008851.
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碩士明志科技大學
材料工程研究所
101
In this study, metal induced crystallization (MIC) mechanism was investigated. The NiSi / Si blayered and NiGe / Ge thin films were prepared by four guns magnetron sputtering system. Thermal analysis shows that the NiSi / Si bilayer films have two phase transition steps, one step is at 130℃~ 270℃ and the other one is in the range of 300℃~ 375℃. The NiGe / Ge film has two phase transition steps, which temperature is occurred at 270℃ and 400℃. The TEM images show that all as-deposited NiSi / Si bilayered thin films display amorphous Si and NiSi2 structures. After annealing at 270℃ for 30 mins, the as-deposited NiSi / Si bilayered films transform to two crystal phases of cubic Si and NiSi2.Upon further increasing the annealing temperature to 500℃, the many crystal cubic Si and NiSi2 phases coexist in the NiSi / Si films. The as-deposited NiGe / Ge film has a-Ge and NiGe phase, and it would transform to the cubic Ge and NiGe coexisting phase after annealing at 270℃ for 20 mins, After annealing at 400℃ for 20 mins, it would transform to the cubic Ge and NiGe coexisting phase. The TEM images show that all as-deposited NiGe / Ge layered thin films display amorphous Ge and NiGe structures. After annealing at 270℃ for 20 mins, the as-deposited NiGe / Ge bilayered films transform to two crystal phases of cubic Ge and NiGe.Upon further increasing the annealing temperature to 400℃, the many crystal cubic Ge and NiGe phases coexist in the NiGe / Ge films. The optical contrast of NiSi / Si blayer thin films annealed at 500℃ is 40.1% and NiGe / Ge bilayer thin films annealed at 400℃is 87.2%, which is higher than the Blu-ray Disc specification of 15%. It indicates that the NiSi / Si and NiGe / Ge films can be application for the blu-ray disc.
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Guemmache, Karim. « Étude électrique et spectroscopique des décharges à barrière diélectrique à la pression atmosphérique en milieux réactifs ». Thèse, 2019. http://hdl.handle.net/1866/23813.
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Le travail présenté dans le cadre de ce mémoire s’intéresse à l’étude des plasmas à la pression atmosphérique en configuration décharge à barrière diélectrique (DBD), pertinents pour le traitement de surface. Plus spécifiquement, les DBDs à l’étude sont en milieux réactifs pour le dépôt de couches minces (multi)fonctionnelles, soit en présence d’un précurseur organosilicié (HMDSO) et/ou d’un agent oxydant (N₂O). L’étude est centrée sur l’analyse de deux propriétés fondamentales du plasma : la température électronique (Tₑ) et la densité des atomes d’hélium dans un état métastable (n_He(2³S)). La première est étudiée en ayant recours à des mesures des populations des niveaux n=3 de l’hélium par spectroscopie optique d’émission, alors que la seconde l’est à partir de ces mêmes mesures couplées à des mesures électriques. La particularité de cette étude est la mise au point de nouveaux diagnostics électriques et spectroscopiques pour réaliser des mesures résolues spatialement, c'est-à-dire en fonction du temps de résidence (t_res) du mélange gazeux injecté en continu. Dans les milieux réactifs étudiés, ces nouveaux diagnostics montraient des changements dans les caractéristiques courant-tension entre l’entrée et la sortie de la décharge. Cependant, Tₑ conservait un profil homogène spatialement alors que la n_He(2³S) se montrait relativement plus faible en entrée, de par leurs interactions avec les précurseurs et les impuretés présents dans ces milieux. L’analyse des signatures optiques du HMDSO dans le volume de la décharge a aussi permis de faire des liens avec les propriétés de surface des couches réalisées en conditions similaires. Notamment, les mesures de vitesse de dépôt observées sur les couches, étant plus faibles avec l’augmentation du t_res, ont pu être liées aux émissions des fragments carbonés, plus fortes en entrée, ainsi qu’à la n_He(2³S), plus faible à cet endroit, sachant que ces derniers jouent un rôle important dans la fragmentation du précurseur HMDSO. De plus, l’analyse de rapport d’intensités d’émissions de ces fragments semble montrée une tendance similaire aux rapports atomiques O/C obtenus par mesures de spectroscopie à rayon X (XPS) sur les couches produites, mais l’interprétation de ces évolutions se veut plus complexe.The work presented in this master’s thesis focuses on the study of atmospheric pressure plasmas in a dielectric barrier discharge (DBD) configuration, which are relevant for surface treatment. More specifically, the DBDs under study are in reactive media for the deposition of (multi)functional coatings, either in the presence of an organosilicon precursor (HMDSO) and/or an oxidizing agent (N₂O). The study focuses on the analysis of two fundamental plasma properties: the electron temperature (Tₑ) and the density of helium atoms in a metastable state (n_He(2³S)). The first is studied using measurements of the n = 3 level helium populations by optical emission spectroscopy, while the second is based on these same measurements coupled with electrical measurements. The peculiarity of this study is the development of new electrical and spectroscopic diagnoses to carry out spatially resolved measurements, that is depending on the residence time (t_res) of the gas mixture injected continuously. In the reactive media studied, these new diagnoses showed changes in the current-voltage characteristics between the entrance and the exit of the discharge. However, the Tₑ maintained a spatially homogeneous profile while the n_He(2³S) was relatively lower at entry, because of their interactions with the precursors and the impurities present in these media. The analysis of the HMDSO optical signatures in the discharge volume also made it possible to establish links with the surface properties of the coatings produced under similar conditions. In particular, the measurements of deposition rate observed on the coatings, being lower with the increase of the t_res, could be linked to the emissions of the carbonaceous fragments, stronger at the entrance, as well as to the n_He(2³S), weaker here, knowing that they play an important role in the fragmentation of the HMDSO precursor. Moreover, the analysis of emission intensity ratios of these fragments seems to show a similar trend to the O/C atomic ratios obtained by X-ray spectroscopy (XPS) measurements on the coatings produced, but the interpretation of these evolutions is more complex.
Livres sur le sujet "OPTICALLY THIN MEDIA"
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P, Shibaev V., dir. Polymers as electrooptical and photooptical active media. Berlin : Springer, 1996.
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Graeme, Dewar, et Society of Photo-optical Instrumentation Engineers., dir. Complex photonic media : 13-16 August, 2006, San Diego, California, USA. Bellingham, Wash : SPIE, 2006.
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Hannouch, Hanin. Gabriel Lippmann's Colour Photography. Nieuwe Prinsengracht 89 1018 VR Amsterdam Nederland : Amsterdam University Press, 2022. http://dx.doi.org/10.5117/9789463728553.
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Physicist Gabriel Lippmann’s (1845–1921) photographic process is one of the oldest methods for producing colour photographs. So why do the achievements of this 1908 Nobel laureate remain mostly unknown outside niche circles? Using the centenary of Lippmann’s death as an opportunity to reflect upon his scientific, photographic, and cultural legacy, this book is the first to explore his interferential colour photography. Initially disclosed in 1891, the emergence of this medium is considered here through three shaping forces: science, media, and museums. A group of international scholars reassess Lippmann’s reception in the history of science, where he is most recognised, by going well beyond his endeavours in France and delving into the complexity of his colour photography as a challenge to various historiographies. Moreover, they analyse colour photographs as optical media, thus pluralising Lippmann photography’s ties to art, cultural and imperial history, as well as media archaeology. The contributors also focus on the interferential plate as a material object in need of both preservation and exhibition, one that continues to fascinate contemporary analogue photographers. This volume allows readers to get to know Lippmann, grasp the interdisciplinary complexity of his colourful work, and ultimately expand his place in the history of photography.
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ZnO bao mo zhi bei ji qi guang, dian xing neng yan jiu. Shanghai Shi : Shanghai da xue chu ban she, 2010.
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Shibaev, Valery P. Polymers as Electrooptical and Photooptical Active Media. Springer, 2011.
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Thomas, Michael E. Optical Propagation in Linear Media. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780195091618.001.0001.
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A typical optical system is composed of three basic components: a source, a detector, and a medium in which the optical energy propagates. Many textbooks cover sources and detectors, but very few cover propagation in a comprehensive way, incorporating the latest progress in theory and experiment concerning the propagating medium. This book fulfills that need. It is the first comprehensive and self-contained book on this topic. It is useful reference book for researchers, and a textbook for courses like Laser Light Propagation, Solid State Optics, and Optical Propagation in the Atmosphere.
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Williams, Keith. James Joyce and Cinematicity. Edinburgh University Press, 2020. http://dx.doi.org/10.3366/edinburgh/9781474402484.001.0001.
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This book investigates how the cinematic tendency of Joyce’s writing developed from popular media predating film. It explores Victorian culture’s emergent 'cinematicity' as a key creative driver of Joyce’s experimental fiction, showing how his style and themes share the cinematograph’s roots in Victorian optical entertainment and science. The book’s scope reveals and elucidates Joyce's references to optical toys, shadowgraphs, magic lanterns, panoramas, photographic analysis and film peepshows; while abundant close analysis shows how his techniques elaborated and critiqued their effects on modernity’s ‘media-cultural imaginary’, making Joyce’s writing appear in advance of the narrative forms of early film itself. The introduction historicises the visual culture during Joyce’s youth, as well as optical science, Dublin’s first screenings and the context of his Volta Cinematograph. Chapter 1 focuses on the key role of magic lantern themes and techniques in Dubliners’ breakthrough into Modernist style and form. Chapter 2 how experiments in photographic analysis and reanimation of movement furnished a model for Joyce’s representation of the dynamic development of consciousness through the three versions of A Portrait of the Artist. Chapter 3 demonstrates how Joyce created a literary equivalent to the moving panorama in Ulysses, providing an influential template for immersive representations of the city in both Modernist fiction and film. Finally, a Coda qualifies ‘radiophonic’ readings of Finnegans Wake arguing instead that it extends Joyce’s interest in the history and future of cinematicity, through ‘verbal dissolves’ and engaging with the emergent medium of television.
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Cameron, Allan. Visceral Screens. Edinburgh University Press, 2020. http://dx.doi.org/10.3366/edinburgh/9781474419192.001.0001.
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Horror cinema grants bodies and images a precarious hold on sense and order: from the zombie’s gory disintegration to the vampire’s absent reflection and from the shaky camerawork of ‘found footage’ horror to the spectacle of shattering glass in the Italian giallo. Addressing classic horror movies alongside popular and innovative contemporary works, Visceral Screens shows how they have rendered the human form as a type of ‘image-body’, mediated by optical effects, chromatic shifts, glitches and audiovisual fragmentation. The question of signification is central to this metaphorical exchange, since horror frequently pushes both bodies and media to the limits of their expressive capacity. Conducting their own anatomies of the screen, cutting across bodies and media alike, horror films revel in the breakdown of frames, patterns and figures, exposing the seams between matter and meaning.
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Fojas, Camilla. Border Optics. NYU Press, 2021. http://dx.doi.org/10.18574/nyu/9781479806980.001.0001.
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The US-Mexico border zone is one of the most visualized and imagined spaces in the United States, not just for the mythology of the Southwest as the cornerstone of US identity but as a place under continual crisis, permanent visibility, and territorial defense. Border Optics argues that the border is both a laboratory and an archive that indexes an optical regime and a way of seeing drawn from maps, geographical surveys, military strategic plans, illustrations, photographs, postcards, novels, film, and television—all of which combine fascination with the region with the visual codes of surveillance and survey. Optics signals a complete visual apparatus, from recording and representation to the infrastructure and institutions that support the visual regime. The border optic refers to the expanded vision of the border as a consequence of the interface of militarism, technology, and the media archive of the region. The primary aim of this complex of industry, state, and private endeavors is not simply enforcement but control, particularly of the movement of goods and people in accordance with the split codes of the border-security imaginary. This book explores several related cultural media and apparatuses that have shaped a dominant way of seeing informed by the history of the region. This includes a countervision apparent in revisionist border historical accounts, art, media, architectural design, and activist movements, along with the strains of subversion within the dominant view.
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Koivisto, Ida. The Transparency Paradox. Oxford University PressOxford, 2022. http://dx.doi.org/10.1093/oso/9780192855466.001.0001.
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Abstract The book provides a compact theoretical account of the hidden functioning logic of the ideal of transparency. Transparency as a concept has become hugely popular in legal discourse and beyond. The book argues that there are underlying optical, conceptual, and social reasons why transparency makes sense to us: it promises immediate seeing and understanding. That is why it can form a powerful metaphor of controllability: in the state, for example, the governed are able to monitor the inner workings of the governor through transparency practices. The modern push for transparency is premised on the notion that the truth about governance is key to its legitimacy, and transparency can provide legitimacy through access to truth. The book argues that this premise is false. Instead of accessing legitimacy by providing truth, transparency is labelled by either or logic, which is referred to as ‘the truth-legitimacy trade-off’ in the book: transparency can provide either truth or legitimacy. Through this argument, the book questions the neutrality promise vested in transparency and claims that transparency is primarily a tool for creating appearances. The book consists of nine chapters divided into three parts: The Opacity of Transparency, The Promise of Transparency, and The Reality of Transparency. It combines legal and policy themes and research with interdisciplinary inputs, such as social philosophy and cultural and media studies, contributing to the growing literature on critical transparency studies.
Chapitres de livres sur le sujet "OPTICALLY THIN MEDIA"
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Kaymakanova, N. I., L. I. Pavlov, L. M. Ivanov et P. P. Paskov. « Optical Processes and χ(2) Susceptibility Dispersion of LBO for Storage Media and Tunable Frequency Oscillator ». Dans Nano-Crystalline and Thin Film Magnetic Oxides, 333–40. Dordrecht : Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4493-3_30.
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Goncharova, O. V. « Quasi-Zero-Dimensional Media Formed by Thin-Film Technique : Microstructure, Subpicosecond Optical Nonlinearities, Applications ». Dans Springer Series in Chemical Physics, 441–42. Berlin, Heidelberg : Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-642-80314-7_193.
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Ozvaldic, Maja. « Virtualities of the Visible ». Dans Architekturen, 213–30. Bielefeld, Germany : transcript Verlag, 2022. http://dx.doi.org/10.14361/9783839461112-012.
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In Virtualities of the Visible: The architecture of mixed realities, Maja Ozvaldic, an architectural designer and educator, explores early modern European visual culture and its techniques for altering reality to frame a contemporary notion of mixed realities. Furthermore, in attempting to trace its development within the genealogy of optical media and its entanglement with cultural production in general, this essay briefly outlines the cultural and technological context for the unfolding paradigm of the human-computer-vision and sketches its impact on architecture in particular.
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Garrett, Steven L. « Radiation and Scattering ». Dans Understanding Acoustics, 543–620. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44787-8_12.
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Abstract At this point, we have made a rather extensive investigation into the sounds that excite Helmholtz resonators as well as the departures from equilibrium that propagate as plane waves through uniform or inhomogeneous media. We have not, as yet, dealt with how those sounds are actually produced in fluids. Our experience tells us that sound can be generated by vibrating objects (e.g., loudspeaker cones, stringed musical instruments, drums, bells), by modulated or unstable flows (e.g., jet engine exhaust, whistles, fog horns, speech), by electrical discharges in the atmosphere (i.e., thunder), or by optical absorption (e.g., modulated laser beams). In this chapter, we will develop the perspective and tools that will be used for the calculation of the radiation efficiency of various sources and combinations of sources, like the sound reinforcement system shown in Fig. 12.1.
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« 1Chapter 2 Optically Thin and Thick Limits for Radiative Transfer in Participating Media ». Dans Thermal Radiation Heat Transfer, 611–48. CRC Press, 2010. http://dx.doi.org/10.1201/9781439894552-19.
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« Magnetostatics of Thin-film Magneto-optical Media ». Dans The Physical Principles of Magneto-optical Recording, 469–514. Cambridge University Press, 1995. http://dx.doi.org/10.1017/cbo9780511622472.014.
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Thomas, Michael E. « Optical Propagation in Solids ». Dans Optical Propagation in Linear Media. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780195091618.003.0013.
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This chapter emphasizes the linear optical properties of solids as a function of frequency and temperature. Such information is basic to understanding the performance of optical fibers, lenses, dielectric and metallic mirrors, window materials, thin films, and solid-state photonic devices in general. Optical properties are comprehensively covered in terms of mathematical models of the complex index of refraction based on those discussed in Chapters 4 and 5. Parameters for these models are listed in Appendix 4. A general review of solid-state properties precedes this development because the choice of an optical material requires consideration of thermal, mechanical, chemical, and physical properties as well. This section introduces the classification of optical materials and surveys other material properties that must be considered as part of total optical system design involving solidstate optics. Solid-state materials can be classified in several ways. The following are relevant to optical materials. Three general classes of solids are insulators, semiconductors, and metals. Insulators and semiconductors are used in a variety of ways, such as lenses, windows materials, fibers, and thin films. Semiconductors are used in electrooptic devices and optical detectors. Metals are used as reflectors and high-pass filters in the ultraviolet. This type of classification is a function of the material’s electronic bandgap. Materials with a large room-temperature bandgap (Eg > 3eV) are insulators. Materials with bandgaps between 0 and 3 eV are semiconductors. Metals have no observable bandgap because the conduction and valence bands overlap. Optical properties change drastically from below the bandgap, where the medium is transparent, to above the bandgap, where the medium is highly reflective and opaque. Thus, knowledge of its location is important. Appendix 4 lists the bandgaps of a wide variety of optical materials. To characterize a medium within the region of transparency requires an understanding of the mechanisms of low-level absorption and scattering. These mechanisms are classified as intrinsic or extrinsic. Intrinsic properties are the fundamental properties of a perfect material, caused by lattice vibrations, electronic transitions, and so on, of the atoms composing the material.
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Petrov, V. V., A. A. Kryuchyn, V. M. Rubish et M. L. Trunov. « Recording of Micro/Nanosized Elements on Thin Films of Glassy Chalcogenide Semiconductors by Optical Radiation ». Dans Chalcogens [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.102886.
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Inorganic resists based on chalcogenide glassy semiconductor (CGS) films can be effectively used in the creation of micro- and nanoelements of optoelectronic devices, micro- and nanoelectromechanical systems, and diffractive optical elements. The use of these materials is based mainly on their sensitivity to different types of radiation, which causes phase and structural changes in CGS films, and transparency in the infrared range. A number of photoinduced changes are observed in CGS, which are associated with structural transformations, phase transitions, defect formation, and atomic diffusion. It is important to determine technologies for the formation of micro- and nanoscale structures on CGS films, which can be used in the creation of diffractive optical elements for optoelectronic devices. Increasing the resolution of recording media based on vitreous chalcogenide semiconductors can be achieved by choosing the recording modes and composition of glasses, in which the strongest nonlinearity of the exposure characteristics of photosensitive material, as well as the introduction into the structure of recording media nanoparticles of noble metals for excitation of plasmonic resonance.
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Thomas, Michael E. « Optical Electromagnetics II ». Dans Optical Propagation in Linear Media. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780195091618.003.0006.
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In this chapter the same basic topics are addressed as in the previous chapter, but now in the presence of matter. This greatly complicates the description of optical propagation and continues to be the primary topic of the remaining chapters. A formal structure is developed to handle absorption and scattering phenomena in general. The modeling of optical propagation is reduced to having to know the complex index of refraction of the medium. A macroscopic description represents the large-scale observable character of optical propagation. At this level, many models are phenomenological, but lead to important general properties, definitions, formulas, and the establishment of basic concepts. Because microscopic models to be presented in future chapters contain considerable detail, this section is an important prerequisite to the remaining text. Again, plane waves are a useful tool for the description of optical propagation. The Poynting vector, causality, and Poynting’s theorem are used to develop and derive quantities and relationships concerning radiometry and the flow of electromagnetic power at optical frequencies. Consider Maxwell’s equations again, but in the presence of linear isotropic matter. Now the constitutive relations will play a more important role and are the foundation of classical dispersion theory.
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Fojas, Camilla. « Borderveillant Media ». Dans Border Optics, 29–61. NYU Press, 2021. http://dx.doi.org/10.18574/nyu/9781479806980.003.0002.
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This chapter explores “borderveillant media” as the popular cultural front line of border security that emerged contemporaneously with the failures of Customs and Border Protection’s Secure Border Initiative (SBI). The Secure Border Initiative meant to increase surveillance at the border through an integrated system called SBInet, Secure Border Initiative Network. The SBI program failed to deliver on its promise of complete technological governmentality at the border but succeeded in expanding its surveillant infrastructure. The program was terminated in 2011 and replaced by mediated forms of entertainment and wiki surveillance, wikiveillance. These media glorify surveillance cultures, project control of the borderlands through optical advantage, and recruit the public into enacting the principles of borderveillance: screening, collecting data, and sorting migrants into split categories broadly aligned with criminal alien and domestic innocent. This chapter details various migrant strategies of resistance to borderveillant cultures.
Actes de conférences sur le sujet "OPTICALLY THIN MEDIA"
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Johnson, R. V., et A. R. Tanguay. « Optical beam propagation in anisotropic media ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1985. http://dx.doi.org/10.1364/oam.1985.fs1.
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Optical diffraction in media with arbitrary inhomogeneous anisotropies (including linear birefringence and/or optical activity) is characterized by pronounced polarization effects. These effects have typically been analyzed by the coupled wave formalism. An alternative analytical technique is the anisotropic optical beam propagation method (BPM) first proposed by Thylen and Yevick.1 The BPM is a highly intuitive approach to solving the light propagation equation in an optically inhomogeneous medium. The coupled wave approach is preferred for spectrally pure inhomogeneities (simple gratings), whereas the BPM is the preferred algorithm for spectrally rich inhomogeneities (image modulated gratings). The BPM replaces the distributed diffraction problem with an equivalent lumped element approximation consisting of infinitesimally thin phase and polarization modulation planes separated by optically homogeneous layers. The evolution of the light profile both in the near field and in the plane wave spectrum can be monitored as the light beam propagates through the anisotropic medium. In this paper we extend the analysis to include optical activity for modeling volume grating in materials such as bismuth silicon oxide. We also perform detailed numerical experiments to assess which classes of problem are better suited for the coupled wave formalism and which for the BPM formalism.
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Ravishankar, Mahesh, et Sandip Mazumder. « Application of the Modified Differential Approximation (MDA) for Radiation Transport to Arbitrary Three-Dimensional Geometry ». Dans ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12844.
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The first-order spherical harmonics method (or P1 approximation) has found prolific usage for approximate solution of the radiative transfer equation (RTE) in participating media. However, the accuracy of the P1 approximation deteriorates as the optical thickness of the medium is decreased. The Modified Differential Approximation (MDA) was originally proposed to remove the shortcomings of the P1 approximation in optically thin situations. This article presents algorithms to apply the MDA to arbitrary geometry—in particular, three-dimensional (3D) geometry with obstructions, and inhomogeneous media. The wall-emitted component of the intensity was computed using a combined view-factor and ray-tracing approach. The Helmholtz equation, arising out of the medium-emitted component, was solved using an unstructured finite-volume procedure. The general procedure was validated against benchmark Monte Carlo results. The accuracy of MDA was found to be far superior to the standard P1 approximation in optically thin situations, and comparable to the P1 approximation in optically thick situations. Calculation and storage of the view-factor matrix was found to be a major shortcoming of the MDA, and several strategies to reduce both memory and computational time are discussed and demonstrated. In addition, for inhomogeneous media, calculation of optical distances requires a ray-tracing procedure, which was found to be a bottleneck from a computational efficiency standpoint.
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Tyan, Y. S., T. K. Hatwar, G. Farruggia, R. H. Victora, M. W. Culver et C. F. Brucker. « Co/Pt Disks with a Simplified Structure ». Dans Symposium on Optical Memory. Washington, D.C. : Optica Publishing Group, 1996. http://dx.doi.org/10.1364/isom.1996.owd.7.
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MO technology is now widely used for erasable optical storage. Almost all MO media products to date are based on rare-earth/transition metal alloys (RE-TM), such as TbFeCo. Although these alloys provide excellent recording performance, their intrinsic corrosion sensitivity necessitates the use of protective layers, typically thin nitride films, on both sides of the recording layer, to protect them from the environment. Frequently, to further enhance the recording performance, an additional reflector layer is used to form an optically tuned quadri-layer structure. The nitride type protective layers are slow and difficult to fabricate. The multilayer, optically tuned structure necessitates tight manufacturing tolerance. The compatibility between layers in terms of adhesion and stress often is difficult to control. These factors, and the fact that the RE-TM alloys are sensitive to oxidation and need to be coated in an excellent vacuum environment, all contribute to the cost of the media.
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Sakami, M., K. Mitra et P. F. Hsu. « Transient Radiative Transfer in Anisotropically Scattering Media Using Monotonicity-Preserving Schemes ». Dans ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-1376.
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Abstract This research work deals with the analysis of transient radiative transfer in one-dimensional scattering medium. The time-dependant discrete ordinates method was used with an upwind monotonic scheme: the piecewise parabolic scheme. This scheme was chosen over a total variation diminishing version of the Lax-Wendroff scheme. These schemes were originally developed to solve Eulerian advection problem in hydrodynamics. The capability of these schemes to handle sharp discontinuity in a propagating electromagnetic wave front was compared. The accuracy and the efficiency of the discrete ordinates method associated with the piecewise parabolic advection scheme were studied. Comparisons with Monte Carlo and integral formulation methods show the accuracy and the efficiency of this proposed method. Parametric study for optically thin and thick medium, different albedos and phase functions is then made in the unsteady state zone.
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Duff, Joseph D., Stuart J. Williams et Balaji Panchapakesan. « Microfluidic Pumping With Optically Induced Actuation of a Carbon Nanotube Membrane ». Dans ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30097.
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We present the design; fabrication and testing of a Polydimethylsiloxane (PDMS)-based microfluidic pump with optically induced membrane actuation. The thin membrane consists of a layer of PDMS (100 μm) and a layer of carbon nanotubes (190 nm). An applied infrared laser opto-mechanically activates the film of carbon nanotubes (CNT), leading to membrane deformation and subsequent fluid motion. Photomechanical actuation offers an alternative way to drive microfluidic devices and provides distinct advantages over alternative methods. The advantages include simplistic, low-cost device fabrication, Wireless actuation, remote controllability electrical–mechanical decoupling, low noise and the elimination of electrical circuits. The performance of this pump in terms of pressure head and flow rate is substantially high. In addition, the micro pump is self-priming and insensitive to particles and bubbles in the pumped media.
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Verbiest, Thierry, Sven Van Elshocht, Gunter Beelen, Carlo Boutton, Martti Kauranen et André Persoons. « Nonlinear Optics of Chiral Media ». Dans Organic Thin Films for Photonic Applications. Washington, D.C. : Optica Publishing Group, 1997. http://dx.doi.org/10.1364/otfa.1997.thd.1.
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Chiral media interact differently with left- and right-hand circularly-polarized light. In linear optics this gives rise to optical activity effects like circular dichroism, optical rotation and optical rotatory dispersion. Optical activity effects also occur in nonlinear optics. For example, second-harmonic generation from chiral surfaces is different for left- and right-hand circularly-polarized fundamental excitation.[1,2]
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Boulanger, Joan, Olivier Balima et Andre´ Charette. « A Reconstruction Scheme Based on the Radiative Transfer Equation for Graded Index Semi-Transparent Media ». Dans 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22818.
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Graded refractive index media appear in numerous industrial applications such as non-isothermal flows, optics material processing, biological imaging. Refractive index gradient has been an early help for combusting flow visualisation. The numerical treatment of radiative transport is difficult in such media due to the curvature of rays, especially when the media are not optically thick. Computer-aided remote probing (inversion) is done today with the help of the diffusion approximation adapted to varying refractive index media but is unsuitable for thin media. Therefore, it is important to develop an approach allowing the use of the radiative transport equation which is the most complete formalism for radiative transfer to date and to couple it to reconstruction schemes. The aim of this study is to demonstrate the reconstruction of an arbitrary refractive index distribution from a least-squares gradient-based iterative inversion algorithm taking advantage of the full transient Radiative Transfer Equation (tRTE). The finite-difference discrete-ordinates method for the tRTE and its adjoint has been implemented, accounting for spatial changes in the distribution of the refractive index in a semi-transparent medium. A least-squares gradient-based iterative algorithm has been designed and elementary tests have been carried to demonstrate reconstruction possibilities.
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Sankar, Maathangi, et Sandip Mazumder. « Hybrid SN-PN Solution of the Radiative Transfer Equation in Multi-Dimensional Media ». Dans ASME/JSME 2011 8th Thermal Engineering Joint Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajtec2011-44131.
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The Modified Differential Approximation (MDA) was originally proposed for solution of the radiative transfer equation (RTE) in order to remove the shortcomings of the P1 approximation in scenarios where the radiation intensity is strongly directionally dependent. In the original MDA approach, the wall-emitted component of the intensity is determined using a surface-to-surface exchange formulation that makes use of geometric viewfactors. Such an approach is computationally very expensive for complex geometry and/or inhomogeneous media. This article presents a new formulation in which the wall-emitted component is solved using the Discrete Ordinates Method (SN approximation), while the medium-emitted component is solved using the P1 approximation, resulting in a hybrid SN-PN RTE solver. Results show that the hybrid Discrete Ordinates-P1 method (DOM-P1) is computationally very efficient, but its accuracy is poor in optically thin situations where ray effects, inherent in the Discrete Ordinates Method, are pronounced. To circumvent this problem, the control-angle Discrete Ordinates Method (CADOM) is finally employed, and the accuracy of the hybrid CADOM-P1 method is found to be far superior to the hybrid DOM-P1 method.
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Irie, Masahiro. « Photochromic Diarylethenes for Erasable Optical Memory. » Dans Organic Thin Films for Photonic Applications. Washington, D.C. : Optica Publishing Group, 1995. http://dx.doi.org/10.1364/otfa.1995.wtt.2.
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Photon-mode optical recording offers advantages over magnet-optic or phase change recording, which utilizes light as a heat source for recording, with regard to resolution, speed of writing, and multiplex recording capability. One of the candidates for the photon-mode recording media is organic photochromic media(1). Although much effort has been made in this field in the past, the photochromic materials still await practical application. The limitation is due to the lack of suitable materials which fulfill the requirements for the reversible recording media(2). The requirements for the use are: 1. Archival storage capability. 2. Low fatigue (write/erase cycles can be repeated many times). 3. High sensitivity at diode laser wavelengths and rapid response. 4. Non-destructive readout capability. 5. High contrast even if the thin film thickness is thin.
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Shirk, James S., Steven R. Flom, J. R. Lindle, F. J. Bartoli, Michael E. Boyle, James D. Adkins et Arthur W. Snow. « Nonlinear Optical Properties of Phthalocyanine Copolymers ». Dans Organic Thin Films for Photonic Applications. Washington, D.C. : Optica Publishing Group, 1993. http://dx.doi.org/10.1364/otfa.1993.wd21.1.
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