Academic literature on the topic 'Refraction onde'
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Journal articles on the topic "Refraction onde"
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Hao, Zhichao, and Yuankun Liu. "Transparent Object Shape Measurement Based on Deflectometry." Proceedings 2, no. 8 (July 9, 2018): 548. http://dx.doi.org/10.3390/icem18-05428.
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This paper proposes a method for obtaining surface normal orientation and 3-D shape of plano-convex lens using refraction stereo. We show that two viewpoints are sufficient to solve this problem under the condition that the refractive index of the object is known. What we need to know is that (1) an accurate function that maps each pixel to the refraction point caused by the refraction of the object. (2) light is refracted only once. In the simulation, the actual measurement process is simplified: light is refracted only once; and the accurate one-to-one correspondence between incident ray and refractive ray is realized by known object points. The deformed grating caused by refraction point is also constructed in the process of simulation. A plano-convex lens with a focal length of 242.8571 mm is used for stereo data acquisition, normal direction acquisition, and the judgment of normal direction consistency. Finally, restoring the three-dimensional information of the plano-convex lens by computer simulation. Simulation results suggest that our method is feasibility. In the actual experiment, considering the case of light is refracted more than once, combining the calibration data acquisition based on phase measurement, phase-shifting and temporal phase-unwrapping techniques to complete (1) calibrating the corresponding position relationship between the monitor and the camera (2) matching incident ray and refractive ray.
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Qiao, Xiaorui, Atsushi Yamashita, and Hajime Asama. "Underwater Structure from Motion for Cameras Under Refractive Surfaces." Journal of Robotics and Mechatronics 31, no. 4 (August 20, 2019): 603–11. http://dx.doi.org/10.20965/jrm.2019.p0603.
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Structure from Motion (SfM), as a three-dimensional (3D) reconstruction technique, can estimate the structure of an object by using a single moving camera. Cameras deployed in underwater environments are generally confined to waterproof housings. Thus, the light rays entering the camera are refracted twice; once at the interface between the water and the camera housing, and again at the interface between the camera housing and air. Images captured from scenes in underwater environments are prone to, and deteriorate, from distortion caused by this refraction. Severe distortions in geometric reconstruction would be caused if the refractive distortion is not properly addressed. Here, we propose a SfM approach to deal with the refraction in a camera system including a refractive surface. The impact of light refraction is precisely modeled in the refractive model. Based on the model, a new calibration and camera pose estimation method is proposed. This proposed method assists in accurate 3D reconstruction using the refractive camera system. Experiments, including simulations and real images, show that the proposed method can achieve accurate reconstruction, and effectively reduce the refractive distortion compared to conventional SfM.
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Zhi Chen, Zhi Chen, Honglan Xie Honglan Xie, Biao Deng Biao Deng, Guohao Du Guohao Du, Huaidong Jiang Huaidong Jiang, and Tiqiao Xiao Tiqiao Xiao. "Toward one nanometer X-ray focusing: a complex refractive lens design." Chinese Optics Letters 12, no. 12 (2014): 123401–4. http://dx.doi.org/10.3788/col201412.123401.
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Ding, Xiaohu, Wei Wang, Jane Scheetz, and Mingguang He. "The Guangzhou Twin Eye Study: 2019 Update." Twin Research and Human Genetics 22, no. 6 (December 2019): 492–98. http://dx.doi.org/10.1017/thg.2019.118.
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AbstractThe primary aim of the Guangzhou Twin Eye Study (GTES) is to explore the impact that genes and environmental influences have on common eye diseases. Since 2006, approximately 1300 pairs of twins, aged 7–15 years, were enrolled at baseline. Progressive phenotypes, such as cycloplegic refraction, axial length, height and weight, have been collected annually. Nonprogressive phenotypes such as parental refraction, corneal thickness, fundus photo, intraocular pressure and DNA were collected once at baseline. We are collaborating with fellow international twin researchers and psychologists to further explore links with general medical conditions. In this article, we review the history, major findings and future research directions for the GTES.
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Liu, Bin, Quan Yong Shen, Jian Mei Ye, Zi Qing Xie, and Min Yan Xu. "Characteristics of the Lateral Shift at the Surface of the Metamaterial." Applied Mechanics and Materials 201-202 (October 2012): 238–41. http://dx.doi.org/10.4028/www.scientific.net/amm.201-202.238.
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In some metamaterial such as the chiral negative refraction medium, the lateral shift is analyzed in theory. When total internal reflection occurs, the lateral shift curves as the incident angle have been figured out for a linearly polarized incident wave. The shift directions of the TM and TE components in the reflected wave are opposite when the incident angle is between the two critical angles of the eigen-waves. Both TM and TE waves will have positive lateral shift once the incident angle is larger than the total internal reflection angle. By contrast with the common medium and normal chiral medium, we have found that the lateral shift character in the chiral negative refraction medium is distinctive.
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Sivak, Jacob G., and Jeremy M. Sivak. "Conserved characteristics of ocular refractive development – Did the eye evolve once?" Experimental Eye Research 183 (June 2019): 84–87. http://dx.doi.org/10.1016/j.exer.2018.05.007.
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Marshall, Robert E., and Katherine L. Horgan. "Multi-wavelength radar target detection in an extreme advection duct event." International Journal of Microwave and Wireless Technologies 3, no. 3 (April 4, 2011): 373–81. http://dx.doi.org/10.1017/s1759078711000225.
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Near sea surface radio frequency (RF) refraction is four dimensional (4D) and can significantly impact the performance of radar systems. The refractivity field is dictated by the vertical thermodynamic structure of the constantly evolving marine atmospheric boundary layer (MABL). Logistical and budgetary restraints on meteorological measurements over water to capture the spatio-temporal structure of refractivity fields influencing radar performance have limited the knowledge of how and why radar performance is azimuth, range, and time dependent. Rapidly increasing computer processing speeds and decreasing memory capacity costs have supported the horizontal and vertical resolution requirements for mesoscale numerical weather prediction (NWP) models to resolve the thermodynamic structure in the MABL. Once modeled, refractivity structure is easily calculated from the thermodynamic structure. Mesoscale NWP models coupled with modern parabolic equation radar performance models can support the prediction of 4D radar performance in challenging non-homogeneous, near surface refractivity fields at the time and location of the modeler's choice. The NWP modeling presented in this paper demonstrates how large-scale offshore flow of warm and dry air over colder seas produces strong near surface RF trapping. Large land-sea temperature differences can produce near shore sea breezes and surface-based ducts. This paper describes modeled radar performance in such a complex ducting structure over the Persian Gulf during large-scale northwest atmospheric flow. The refractivity field was resolved by the Coupled Ocean/ Atmosphere Mesoscale Prediction System (COAMPS® is a registered trademark of the Naval Research Laboratory) and the notional radar performance was modeled by the advanced refractive effects prediction system (AREPS). The results indicate strong spatial and wavelength-dependent enhancements and degradations in radar performance relative to a standard atmosphere.
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Wade, Nicholas J. "Light and Sight since Antiquity." Perception 27, no. 6 (June 1998): 637–70. http://dx.doi.org/10.1068/p270637.
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Light and sight were not distinguished from one another until the dioptrics and the anatomy of the eye had been adequately described in the seventeenth century. A survey of early theories of light is presented, together with descriptions of developing knowledge of ocular anatomy Once the analogy between the eye and a camera had been made, the problem of accommodation was exposed, and corrections for errors of refraction could be given theoretical support. Theories of accommodation in the seventeenth and eighteenth centuries are briefly reviewed, as is the early history of eye glasses.
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Ganapathy, Boopalan, and Subramaniam Chittur Krishnaswamy. "Energy Transfer Using Gradient Index Metamaterial." International Journal of Antennas and Propagation 2018 (2018): 1–6. http://dx.doi.org/10.1155/2018/7946168.
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The gradient refractive index structure in this paper is used to increase the quantum of energy transfer. This is done by improving the directive gain of the pyramidal horn antenna at a frequency of 10 GHz. A three-dimensional array of closed square rings is placed in front of the horn antenna aperture to form a gradient refractive index structure. This structure increases the directive gain by 1.6 dB as compared to that of the conventional horn antenna. The structure nearly doubles the wireless power transfer quantum between the transmitter and the receiver when placed at both ends. The increase in the directivity is achieved by converting the spherical wave emanating from the horn to a plane wave once it passes through the structure. This transformation is realized by the gradient refractive index structure being placed perpendicular to the direction of propagation. The gradient refractive index is constructed by changing the dimensions of a closed square ring placed in the unit cell of the array. The change in the refractive index gives rise to an improvement of the half power beam width and side lobe level compared to that of the normal horn. The design and simulation were done using CST Studio software.
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Mineeva, L. A., L. I. Balashevich, A. A. Kozhukhov, A. A. Baranov, L. B. Shubin, and A. V. Kabanov. "Blood glucose level impact on biometric parameters, refraction and intraocular pressure in patients with subcompensated insulin-requiring type II diabetes." Russian Ophthalmological Journal 12, no. 1 (March 16, 2019): 35–42. http://dx.doi.org/10.21516/2072-0076-2019-12-1-35-42.
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Purpose. To study the relationship of biometric parameters, visual acuity, eye refraction and intraocular pressure (IOP) with blood glucose levels and glycated hemoglobin (HbA1c) in patients with subcompensated insulin-requiring type II diabetes mellitus. Material and methods. Ophthalmic monitoring lasted 3 years, the experience of insulin therapy — 6 years. 32 patients (27 women and 5 men) with insulin-requiring diabetes mellitus and no severe general diabetic complications or concomitant eye pathology were monitored for 3 years. The patients’ average age was 60.4 ± 5.3 years; average weight 94.3 ± 16.5 kg; average height 163.4 cm; average BMI (body mass index) was 29.93 kg/m2, all received insulin treatment for 6 years. Patients determined the level of blood glucose themselves on a daily basis using individual “Accu-Check” and/or “OneTouch select” glucometers, supplemented by endocrinologist checks on scheduled examinations once a month. The level of glycated hemoglobin (HbA1c) was determined once every 3–6 months. The 3-year ophthalmic monitoring involved both eyes and included biomicroscopy, autorefractometry, pneumotonometry, measurement of the anterior-posterior axis, the depth of the anterior chamber and lens thickness; pachymetry of the cornea in the central optical zone, and ophthalmoscopy. Visometry was performed according to ETDRS (Early Treatment Diabetic Retinopathy Study Research Group) requirements. Results. The impact of blood glucose level on visual acuity (Spearman R = 0.18/-0.23, t (N-2) = 1.07/-1.34, p = 0.1) is higher than that of HbA1c (Spearman R = 0.07/-0.15, t (N-2) = 0.4/-0.8, p = 0.65) The higher the glucose level, the lower the depth of the anterior chamber and the shorter the APA. In contrast, the higher the level of HbA1c, the thicker the cornea in the central optical zone. Both the glucose and the HbA1c levels reveal a similar positive correlations with IOP. A refraction shift toward myopia from 42 % to 55 % was shown to correlate to HbA1c, and a corresponding reduction of hyperopia share was revealed. Conclusions. In patients with subcompensated insulin-requiring diabetes mellitus type II, biometric parameters, refraction and intraocular pressure are determined by changes in the level of blood glycemia.
Dissertations / Theses on the topic "Refraction onde"
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Ould, Ahmed Khalifa Mohamed Abderahmane. "Calcul automatique des deformations de la houle, refraction, diffraction, friction : application a l'etude d'un chenal d'acces portuaire." Nantes, 1987. http://www.theses.fr/1987NANT2055.
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Pour amenager un site cotier quelconque, l'ingenieur de genie civil a besoin de connaitre les differents facteurs physiques susceptibles de le solliciter. Dans cette recherche, nous nous limitons a l'etude des deformations de la houle car elle est le principal facteur de ces sollicitations. Dans ce cadre, nous avons developpe un code de calcul, resol, base sur la modelisation de l'agitation de la houle, quand elle se propage sur des fonds variables. Cet outil permet d'etablir des plans de houle donnant les deformations des cretes dans l'espace. Cependant, quand les fonds deviennent tourmentes, les plans de houle qu'il fournit presentent des croisements d'orthogonales ou theoriquement les hauteurs de houle y sont infinies. C'est pour cette raison que nous avons concu un code de calcul complementaire, red, base sur un modele mathematique combinant la refraction a la diffraction (modele de radder). Afin d'avoir des resultats realistes, il est indispensable de tenir compte des phenomenes dissipatifs qui se produisent a l'interface eau-sol. Dans ce but, une ebauche d'analyse de l'influence de la friction est integree a resol, en supposant que les fonds restent fixes. Les differents modeles, issus d'etudes bibliographiques, sont d'abord traites avant d'en presenter les analyses algorithmiques. Diverses applications a des configurations theoriques simples ont ete le support d'une validation theorique systematique des codes. L'une des principales originalites de ce travail demeure, d'une part l'analyse de l'agitation de la houle dans des sites concrets (baie de saint brieuc et estuaire de la loire) grace a ces deux codes et, d'autre part la validation experimentale du modele de refraction diffraction par une serie de mesures en nature
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Ghorbel, Nabil. "Etude sismique et magneto-tellurique du socle et de la couverture sedimentaire dans la partie sud de l'anomalie magnetique du bassin de paris , le val de loire et le nivernais." Paris 6, 1987. http://www.theses.fr/1987PA066395.
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Cette etude permet de distinguer deux types de socle. A l'est de la loire, un type granitique, un profil transversal entre villequiers et beffes montre qu'au passage de l'anomalie le socle forme un horst dont le toit est situe a 1000 m de profondeur environ. A l'ouest de la loire, un socle probablement metamorphique
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Boyer, Laurent. "Etude des phenomenes de reflexion-refraction des ondes planes acoustiques dans les milieux piezoelectriques." Paris 7, 1994. http://www.theses.fr/1994PA077126.
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Le probleme de la diffraction des ondes acoustiques par un dioptre plan dans les milieux piezoelectriques est traite dans le cas general, pour des configurations (materiaux, coupes) ne presentant pas de symetrie particuliere. La methode de resolution fait appel au concept de la matrice mixte d'un milieu semi-infini. Cette matrice regroupe quatre sous-matrices de couplages: volume-volume, surface-volume, volume-surface et surface-surface. Le calcul de la matrice mixte donne acces aux coefficients de diffraction des ondes de volumes sur un dioptre plan (utile pour la conception de dispositifs tels que des lignes a retard a ondes de volume). Mais aussi il permet de modeliser la transduction (en emission et en reception) des ondes de volume par des perturbations de surface (electriques ou mecaniques) et la propagation des ondes de surface. Inclue dans des programmes d'analyse de dispositifs utilisant des transducteurs a peignes interdigites, la matrice mixte permet d'analyser et de concevoir des dispositifs tels que des lignes a retard ou des analyseurs de spectre a ondes de volume et aussi de modeliser correctement la propagation des ondes de surface sous un reseau d'electrodes
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Leszczyszyn, Antin M. "Resonant generation and refraction of dispersive shock waves in one-dimensional nonlinear Schrödinger flows." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/9233.
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In the Thesis, two important theoretical problems arising in the theory of one-dimensional defocusing nonlinear Schrödinger (NLS) flows are investigated analytically and numerically: (i) the resonant generation of dispersive shock waves (DSWs) in one-dimensional NLS flow past a broad repulsive penetrable barrier; and (ii) the interaction of counter-propagating DSW and a simple rarefaction wave (RW), which is referred to as the DSW refraction problem. The first problem is motivated by the recent experimental observations of dark soliton radiation in a cigar-shaped BEC by sweeping through it a localised repulsive potential; the second problem represents a dispersive-hydrodynamic counterpart of the classical gas-dynamics problem of the shock wave refraction on a RW, and, apart from its theoretical significance could also find applications in superfluid dynamics. Both problems also naturally arise in nonlinear optics, where the NLS equation is a standard mathematical model and the `superfluid dynamics of light' can be used for an all-optical modelling of BEC flows. The main results of the Thesis are as follows: (i) In the problem of the transcritical flow of a BEC through a wide repulsive penetrable barrier an asymptotic analytical description of the arising wave pattern is developed using the combination of the localised ``hydraulic'' solution of the 1D Gross-Pitaevskii (GP) equation with repulsion (the defocusing NLS equation with an added external potential) and the appropriate exact solutions of the Whitham-NLS modulation equations describing the resolution of the upstream and downstream discontinuities through DSWs. We show that the downstream DSW effectively represents the train of dark solitons, which can be associated with the excitations observed experimentally by Engels and Atherton (2008). (ii) The refraction of a DSW due to its head-on collision with the centred RW is considered in the frameworks of two one-dimensional defocusing NLS models: the standard cubic NLS equation and the NLS equation with saturable nonlinearity, the latter being a standard model for the light propagation through photorefractive optical crystals. For the cubic nonlinearity case we present a full asymptotic description of the DSW refraction by constructing appropriate exact solutions of the Whitham modulation equations in Riemann invariants. For the NLS equation with saturable nonlinearity, whose modulation system does not possess Riemann invariants, we take advantage of the recently developed method for the DSW description in non-integrable dispersive systems to obtain key parameters of the DSW refraction. In both problems, we undertake a detailed analysis of the flow structure for different parametric regimes and calculate physical quantities characterising the output flows in terms of relevant input parameters. Our modulation theory analytical results are supported by direct numerical simulations of the corresponding full dispersive initial value problems (IVP).
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Gérardin, Benoit. "Manipulation et contrôle d'ondes élastiques guidées en milieux complexes." Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC230/document.
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Quelle que soit la nature des ondes utilisées et des milieux traversés, le contrôle de la propagation ondes est d'un intérêt majeur pour de nombreuses applications. D'une part, la complexité du milieu peut être exploitée en exerçant un contrôle cohérent du front d’onde incident. D'autre part, on peut forcer une onde à se propager suivant un chemin désiré en concevant soi-même le milieu de propagation. Dans cette thèse, nous étudions ces deux aspects à partir d'expériences ultrasons-laser mettant en jeu la propagation d'ondes de Lamb dans des plaques.La propagation des ondes à travers un milieu diffusant est tout d’abord étudiée à partir de sa matrice de diffusion. Une prédiction théorique importante est l’existence de canaux de propagation totalement ouverts ou fermés. Une première partie de ces travaux consiste à démontrer expérimentalement ce résultat en mettant en évidence la possibilité de transmettre totalement une onde à travers un milieu désordonné. Dans un second temps, la mesure d’une matrice des temps de vol nous permet d’étudier ces canaux dans le domaine temporel. Ceux-ci donnent lieu à des paquets d’onde dont la cohérence spatiale et temporelle est conservée tout au long de leur propagation dans le milieu.Le second volet de cette thèse consiste à tirer profit des phénomènes de réflexion et réfraction négative afin de contrôler la propagation des ondes de Lamb. D’une part, la réflexion négative est mise à profit pour réaliser une conjugaison de phase passive des ondes de Lamb. D’autre part, le concept des milieux complémentaires est exploré afin d’annuler la diffraction des ondes et ainsi camoufler certaines zones du milieu de propagationWhatever their nature or the propagation medium, controlling the propagation of waves is of fundamental interest for many applications. On the one hand, one can tame wave-fields in order to take advantage of the complexity of the medium. On the other hand, one can force waves along desired paths through a careful design of manmade materials. In this thesis, we study those two aspects on the basis of laser-ultrasonic experiments involving the propagation of Lamb waves in elastic plates.The control of wave propagation through complex systems is first investigated by means of the scattering matrix approach. In diffusive media, theorists have demonstrated the existence of propagation channels either closed or open through which the wave can travel. The first part of this work present a direct experimental evidence of this result as well as the ability to fully transmit a wave through a disordered medium. In a second part, the measurement of the time-delay matrix allows the study of such channels in the time domain. They are shown to give rise to particle-like wave packets that remain focused in time and space throughout their trajectory in the medium.The second part of this thesis consists in studying the concepts of negative reflection and refraction for the manipulation of Lamb wave propagation. On the one hand, negative reflection is taken advantage of to perform a passive phase conjugation of Lamb waves. On the other hand, the notion of complementary media is investigated in order to cancel the diffraction of waves and cloak some areas of the plate
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PELENC, DENIS. "Elaboration par epitaxie en phase liquide et caracterisation de couches monocristallines de yag dope : realisation de lasers guide d'onde neodyme et ytterbium a faibles seuils." Grenoble 1, 1993. http://www.theses.fr/1993GRE10171.
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Dans le cadre des recherches sur des dispositifs laser compacts pouvant etre pompes par diodes, ce memoire decrit le developpement d'une nouvelle technique d'elaboration de lasers guides d'onde, l'epitaxie en phase liquide. Cette technique a ete appliquee a la croissance de couches minces monocristallines de yag dope neodyme et ytterbium sur des substrats de yag non dope. Afin d'obtenir des guides de bonne qualite, nous avons defini les conditions de croissance des couches et montre l'interet de la croissance d'une surcouche de confinement. Deux co-dopages ont ete etudies en supplement a l'ion actif: gallium pour controler l'indice optique des couches, lutetium pour controler leur parametre cristallin. La determination du coefficient de segregation des divers dopants a requis le developpement d'un modele qui prend en compte l'evolution des bains au cours du temps. Nous avons mesure l'augmentation d'indice due a chaque dopant et propose un mecanisme expliquant cette augmentation. La caracterisation spectroscopique des couches a indique que les ions actifs ont les memes proprietes que le materiau massif de meme composition. La caracterisation laser a montre des pertes par propagation tres faibles (environ 0,1 db/cm), comparables a celles du materiau massif. Pour la transition laser a 1064 nm du neodyme, nous avons demontre l'effet laser pour une puissance absorbee au seuil de 700 w et mesure un rendement differentiel de 40% en pompage par diode, pour un seuil de 14 mw. Pour des transitions laser quasi-3 niveaux, une diminution significative du seuil par rapport a une configuration non guidee a ete obtenue: a 946 nm dans un guide dope neodyme, a 1029 nm dans un guide dope ytterbium en pompage par barrette de diode 1w. Un rendement differentiel de 80% a egalement ete mesure dans un guide dope ytterbium emettant a 1048 nm
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Diaz, Cusi Jordi. "Anisotropie sismique et deformation dans le manteau superieur : sismique refraction et ondes s telesismiques en iberie. methodes et resultats d'analyses sks au tibet." Paris 7, 1994. http://www.theses.fr/1994PA077321.
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Dans l'experience iliha on realise des profils de refraction sismique montrant la stratification de la lithosphere subcrustale sous le sud-ouest de l'iberie. Les profils dans plusieurs azimuts et avec un point milieu commun permettent d'etablir une anisotropie azimutale dans les couches a forte vitesse, de direction n-ne. Une tentative de mise en evidence de la birefringence d'ondes s telesismiques au meme endroit permet de discuter les causes et les modeles de l'anisotropie. Sa direction n'est incompatible ni avec le mouvement absolu de plaques, ni avec la direction d'etirement cadomienne. Sa distribution heterogene en profondeur mise en evidence par la refraction apporte un nouvel element a la discussion de sa location lithospherique ou asthenospherique. La birefringence des ondes sks est alors etudiee en detail au tibet ou les effets sont plus evidents. Un enregistrement en reseau avec une densite exceptionnelle permet de discuter la signification de mesures isolees et les limitations des methodes d'analyse habituelles. On etablit que la direction d'anisotropie change notablement, de 90 et brutalement, en peu de dizaines de kilometres au passage du haut himalaya et de la suture de l'indus-tsangpo. Elle reste stable et est associee avec un retard des ondes, au nord, suggerant un flux impliquant de la fusion partielle
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Campagne, Benjamin. "Non linéarités optiques dans les matériaux xérogels et polymères dopés. Application a la protection passive de senseurs contre les impulsions laser." Phd thesis, Université Paris Sud - Paris XI, 1999. http://pastel.archives-ouvertes.fr/pastel-00713905.
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Ce memoire est consacre a l'etude de certaines proprietes optiques non lineaires de nouvelles molecules organiques piegees dans des matrices solides xerogels et polymeres. Ces travaux concernent divers processus non lineaires presents dans ces materiaux solides dans le but de preserver les detecteurs photoniques tels que l'il ou les capteurs ccd contre l'agression laser. Ces materiaux fonctionnent comme des limiteurs optiques passifs : ils reagissent a la presence d'un rayonnement laser impulsionnel suffisamment intense en affaiblissant la luminance transmise. Parmi les differents mecanismes non lineaires, nous avons etudie les processus : d'absorption saturable inverse (asi) avec des chromophores de la famille des phtalocyanines et des porphyrines, de refraction non lineaire (rnl) et d'absorption a deux photons (adp). L'utilisation de lasers impulsionnels de duree nanoseconde, picoseconde et sub-picoseconde nous a permis d'evaluer la contribution des differents processus mis en jeu grace a un grand nombre d'experiences. Nous avons mis en evidence par des experiences de z-scan que des matrices solides dopees avec des chromophores asi presentent egalement de la rnl. Des molecules organiques du type quadripolaire exhibant le mecanisme adp semblent posseder une forte absorption des etats excites, comme pour les asi. Enfin, nous avons aborde l'etude du processus de diffusion induite dans un milieu inhomogene compose d'une matrice xerogel poreuse adaptee en indice avec un melange de solvants aux proprietes non lineaires. Afin d'expliquer de maniere satisfaisante la plupart des mesures experimentales, nous proposons des simulations numeriques basees sur la technique de la bpm. L'exploitation d'un seul mecanisme n'est pas toujours suffisante pour assurer une protection ideale. On peut alors envisager utiliser une combinaison de plusieurs mecanismes pour accroitre l'efficacite du systeme limiteur optique et pour beneficier d'une protection large bande spectrale.
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Almeida, Juliana Mara Pinto de. "Nanoparticles in oxide and chalcogenide glasses: optical nonlinearities and waveguide fabrication by femtosecond laser pulses." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-10112015-102237/.
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Femtosecond laser has been an essential tool for nonlinear optics and materials processing at micrometer scale, in which chalcogenide and heavy metal oxide glasses have received special attention not only for their high third-order optical nonlinearities but also due to their transparency up to the infrared regions. Although metallic nanoparticles are expected to improve the optical properties of glasses, there are no enough experimental researches about their influence on the nonlinear refractive index (n2) and nonlinear absorption coefficient (β), moreover at femtosecond regime. Based on the scientific and technological interests on highly nonlinear glasses, the goal of this thesis was to apply femtosecond laser pulses in two main domains: (i) at the basis of fundamental science, to study the effect of metallic nanoparticles in the third-order nonlinear optical properties of glasses; and (ii) at the field of applied science, aiming the development of photonic devices, performed by the fabrication of 3D optical waveguides containing metallic nanoparticles. This aim was achieved through the techniques of z-scan and femtosecond laser micromachining, which provided the nonlinear optical characterization and waveguides development, respectively. First, we analyzed the third-order nonlinear optical properties of the GeO2-Bi2O3 glass containing gold nanoparticles, which promoted saturation of the absorption in the region of the surface plasmon resonance band. On the other hand, these gold nanoparticles did not affect the n2 that kept constant in the wavelength range of 480 - 1500 nm. The same features were investigated for a Pb2P2O7-WO3 matrix doped with copper nanoparticles. In contrast to the gold doped ones, these samples showed a slight enhancement of the nonlinear refractive index when the energy of the excitation approaches the surface plasmon band. We also found out that the Pb2P2O7-WO3 matrix is a good host to grow silver nanoparticles by fs-laser micromachining. Similarly, copper nanoparticles were produced in a borosilicate glass using single-step laser processing. The explanation for metallic nanoparticle formation is addressed in this thesis, as well as, its application in waveguides. Thus, we demonstrated the functionality of optical waveguides containing Cu0 or Ag0 nanoparticles. Still based on the technological interests on glasses doped with nanoparticles, we showed a single-step synthesis of silver sulfide nanoparticles in chalcogenide glass, which was carried in partnership with researches at Princeton University. The materials investigated in this PhD work are of great importance for photonics, in which the synthesis of nanoparticles, fabrication of waveguides and nonlinear optical characterization have been performed.O laser de femtossegundos tem sido uma ferramenta essencial tanto para a óptica não-linear quanto para o processamento de materiais na escala micrométrica, na qual os vidros calcogenetos e óxidos de metais pesados têm recebido atenção especial, não apenas pelas suas elevadas não-linearidades ópticas de terceira ordem, mas também devido à sua transparência até o infravermelho. Embora seja esperado que nanopartículas metálicas melhorem as propriedades ópticas dos vidros, não existe investigações experimentais suficientes sobre a sua influência no índice de refração não linear (n2) e no coeficiente de absorção linear (β), sobretudo no regime de femtossegundos. Com base nos interesses científicos e tecnológicos de vidros altamente não-lineares, o objetivo deste trabalho foi aplicar pulsos laser de femtossegundos em dois domínios principais: (i) na campo da ciência fundamental, para estudar o efeito de nanopartículas metálicas nas propriedades ópticas não lineares de terceira ordem destes materiais; e (ii) no domínio da ciência aplicada, visando o desenvolvimento de dispositivos fotônicos, realizado pelo fabricação de guias de onda tridimensionais contendo nanopartículas metálicas. Este objetivo foi alcançado através das técnicas de varredura-z e microfabricação com laser de femtossegundos, que proporcionaram a caracterização óptica não-linear e o desenvolvimento de guias de onda, respectivamente. Primeiramente, foram investigadas as propriedades ópticas não-lineares de terceira ordem do vidro GeO2-Bi2O3 contendo nanopartículas de ouro, as quais promoveram saturação da absorção na região da banda de ressonância de plásmon. Por outro lado, essas nanopartículas não afetaram o n2, que se manteve constante no intervalo de comprimento de onda 480 - 1500 nm. As mesmas características foram investigadas para uma matriz Pb2P2O7-WO3 dopada com nanopartículas de cobre. Em contraste com os vidros dopados com ouro, estas amostras apresentaram um ligeiro aumento do índice de refração não linear quando a energia de excitação está próxima da banda de ressonância de plásmon. Observou-se ainda que a matriz Pb2P2O7-WO3 é ideal para a obtenção de nanopartículas de prata através da microfabricação com laser de femtossegundos. Similarmente, nanopartículas de cobre foram produzidas em vidro de borosilicato usando somente uma varredura a laser. A explicação para a formação de nanopartículas metálicas é abordada nesta tese, bem como sua aplicação em guias de onda. Deste modo, demonstrou-se a funcionalidade de guias de onda ópticos compostos por nanopartículas de Cu0 e Ag0. Ainda com base nos interesses tecnológicos em vidros dopados com nanopartículas, demonstrou-se uma síntese de nanopartículas de sulfeto de prata em vidro calcogeneto usando o processamento de única etapa, realizada em parceria com pesquisadores da Universidade de Princeton. Os materiais investigados neste trabalho de doutorado são de grande importância para aplicações em fotônica, em que a síntese de nanopartículas, a fabricação de guias de onda e a caracterização óptica não-linear foram realizadas.
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Zhou, Hang. "Modélisation de la propagation atmosphérique d'ondes électromagnétiques en 2D et 3D à partir de transformées de Fourier et en ondelettes." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30018/document.
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La propagation à longue distance est un problème majeur dans les télécommunications, la navigation et la surveillance. L'objectif de cette thèse est de développer une méthode rapide pour simuler la propagation des ondes dans une atmosphère en 2D et 3D. Dans ce travail, deux contributions principales vers cet objectif sont obtenues. Tout d'abord, des méthodes auto-cohérentes,c'est-à-dire basées sur une théorie discrète de l'électromagnétisme, sont développées en 2D et 3D. Ensuite, une méthode rapide 2D basée sur les ondelettes est proposée. Pour simuler la propagation d'ondes électromagnétiques dans une atmosphère 2D, la méthode split-step Fourier (SSF) est largement utilisée. Le calcul est effectué itérativement en distances en tenant compte d'une réfractivité variable, du relief et des caractéristiques du sol. À chaque pas, le signal est transformé du domaine spatial au domaine spectral. La méthode des écrans de phase est appliquée pour modéliser les effets de réfraction. D'autre part, pour modéliser un sol impédant, la transformée mixte de Fourier discrète (SSF-DMFT) est utilisée. Le concept de la théorie électromagnétique auto-cohérente implique que l'utilisation d'équations de Maxwell discrètes pour la simulation numérique évite les solutions parasites. Dans la méthode couramment utilisée SSF-DMFT, la transformée spectrale est basée sur la condition aux limites d'impédance discrète, alors que le propagateur provient de l'équation continue. Pour pallier cette incohérence, une méthode auto-cohérente est proposée, notée la DSSF-DMFT. La formulation est dérivée des équations discrètes pour obtenir l'auto-cohérence. Des tests numériques montrent que SSF-DMFT présente des oscillations parasites dans certaines conditions de simulation, tandis que DSSF-DMFT reste précis. En effet, l'auto-cohérence empêche certaines instabilités numériques. Pour simuler la propagation dans des environnements en 3D, les méthodes précédentes doivent être étendues en 3D. Tout d'abord, la 3D-SSF est présentée comme une extension naturelle de la SSF. Ensuite, la 3D-DSSF est dérivée d'équations discrètes. Pour considérer un sol impédant, la 3D-DSSF-DMFT est développée conduisant à de nouvelles expressions pour les propagateurs. Ces méthodes sont testées dans plusieurs configurations incluant un profil de réfractivité extrait de mesures. Les résultats montrent une grande précision et une capacité à prendre en compte les effets latéraux. Cependant, pour la propagation dans de grand domaines, les ressources nécessaires en temps et en mémoire deviennent la préoccupation principale. Pour alléger la charge de calcul, une méthode split-step en ondelettes (SSW) est proposée en 2D comme une méthode alternative à SSF. Elle est basée sur la transformée rapide en ondelettes dont la complexité est faible et qui permet de compresser les champs. La propagation est réalisée à partir d'une combinaison linéaire d'ondelettes propagées individuellement. La compression est appliquée pour augmenter l'efficacité. Afin de considérer la réflexion sur le sol, une nouvelle méthode de source image locale dédiée à la propagation des ondelettes est proposée. Les tests numériques montrent que la SSW a une efficacité de calcul plus élevée que la SSF tout en gardant une bonne précisionThe long-range propagation of electromagnetic waves is a major issue in telecommunication, navigation, and surveillance. The objective of this Ph.D. thesis is to develop fast and accurate modeling methods for the tropospheric propagation in 2D and 3D. In this work, two main contributions towards this objective are achieved. Firstly, self-consistent methods, i.e. based on the discrete electromagnetic theory, are developed in 2D and 3D. Secondly, a fast wavelet-based 2D method is proposed. For simulating the electromagnetic wave propagation in a 2D atmosphere, the split-step Fourier method (SSF) is widely used. The computation is performed marching on in distances taking into account a variable refractivity, an irregular relief, and the electric characteristics of the ground. At each step, the signal is transformed from the spatial to the spectral domains. The phase screens method is applied to model refraction. Besides, to model an impedance ground, the discrete mixed Fourier transform (SSF-DMFT) is used. The concept of the self-consistent electromagnetic theory implies that the use of discrete Maxwell equations for numerical simulations does not lead to spurious solutions. In the widely used SSF-DMFT, the spectral transform is based on the discrete impedance boundary condition, while the propagator is derived from the continuous equation. To overcome this inconsistency, a discrete formulation of SSF-DMFT is proposed, denoted as DSSF-DMFT. The spectral transform and propagator are both derived from the discrete equations to achieve self-consistency. Numerical tests show that SSF-DMFT has spurious oscillations in certain simulation conditions, whereas DSSF-DMFT remains accurate. Indeed, the self-consistency prevents from numerical instabilities. To simulate the propagation in 3D environments, the previous methods are extended to 3D. First, 3D-SSF is presented as a natural extension of SSF. Then, 3D-DSSF is derived from discrete equations. To consider an impedance ground, 3D-DSSF-DMFT is developed leading to new expressions for the propagators. These methods are tested for several configurations, including a refractivity profile extracted from measurements. Results show that they have a high accuracy. They notably consider lateral effects. However, for the propagation in a large computation domain, time and memory occupations become the main concern. To improve the computation burden, a split-step wavelet method (SSW) is proposed in 2D as an alternative to SSF. It is based on the fast wavelet transform, which complexity is weak and which allows for data compression. The propagation is performed by means of a linear combination of wavelets that are individually propagated. Data compression is applied to increase the efficiency. A new local image source method dedicated to wavelet propagation is proposed to consider the ground reflection. Numerical tests show that this method has a higher computational efficiency than SSF while keeping a good accuracy
Books on the topic "Refraction onde"
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Ozbay, E., G. Ozkan, and K. Aydin. Left-handed metamaterials—A review. Edited by A. V. Narlikar and Y. Y. Fu. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780199533046.013.20.
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This article focuses on left-handed metamaterials (LHMs). It begins with a discussion of negative-permeability metamaterials, with particular emphasis on split-ring resonators (SRRs) and SRRr arrays and how magnetic permeability influences the response of materials to the incident magnetic field. It then considers the transmission spectra of SRR, LHM and a composite metamaterial as well as the reflection characteristics of a one-dimensional double-negative material. It also examines the effect of disorder on the transmission and reflection properties of ordered left-handed materials, along with the negative refraction, negative phase velocity, and subwavelength imaging and resolution of LHMs. The article concludes with an analysis of planar negative-index metamaterials.
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Spiegel, Avi Max. Coevolution. Princeton University Press, 2017. http://dx.doi.org/10.23943/princeton/9780691159843.003.0003.
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This chapter seeks to understand how Islamist movements have evolved over time, and, in the process, provide important background on the political and religious contexts of the movements in question. In particular, it shows that Islamist movements coevolve. Focusing on the histories of Morocco's two main Islamist movements—the Justice and Spirituality Organization, or Al Adl wal Ihsan (Al Adl) and the Party of Justice and Development (PJD)—it suggests that their evolutions can only be fully appreciated if they are relayed in unison. These movements mirror one another depending on the competitive context, sometimes reflecting, sometimes refracting, sometimes borrowing, sometimes adapting or even reorganizing in order to keep up with the other.
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Guenther, B. D. Modern Optics Simplified. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198842859.001.0001.
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This textbook is designed for use in a standard physics course on optics at the sophomore level. The book is an attempt to reduce the complexity of coverage found in Modem Optics to allow a student with only elementary calculus to learn the principles of optics and the modern Fourier theory of diffraction and imaging. Examples based on real optics engineering problems are contained in each chapter. Topics covered include aberrations with experimental examples, correction of chromatic aberration, explanation of coherence and the use of interference theory to design an antireflection coating, Fourier transform optics and its application to diffraction and imaging, use of gaussian wave theory, and fiber optics will make the text of interest as a textbook in Electrical and bioengineering as well as Physics. Students who take this course should have completed an introductory physics course and math courses through calculus Need for experience with differential equations is avoided and extensive use of vector theory is avoided by using a one dimensional theory of optics as often as possible. Maxwell’s equations are introduced to determine the properties of a light wave and the boundary conditions are introduced to characterize reflection and refraction. Most discussion is limited to reflection. The book provides an introduction to Fourier transforms. Many pictures, figures, diagrams are used to provide readers a good physical insight of Optics. There are some more difficult topics that could be skipped and they are indicated by boundaries in the text.
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Ogden, Daniel. The Werewolf in the Ancient World. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198854319.001.0001.
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The ancient world already cherished a rich folklore of werewolfism that broadly resembled the one copiously attested for the central medieval period in Europe. Our best access to the sort of narrative that underpinned such folklore comes in the well-known werewolf tale of the Neronian Petronius’ Satyricon, which shares some striking motifs with the equally famous AD 1160-78 Anglo-Norman tale of Bisclavret by Marie de France. It was, accordingly, folklore that determined the ancients’ conception of what a werewolf actually was. Almost all the evidence for werewolfism in antiquity should be regarded either as folkloric in nature or as secondary to and refractive of a folkloric core. The ancients re-deployed, finessed and parlayed this focal conception in distinct ways in diverse cultural contexts. Notions, themes and images were borrowed from this folkloric home and transferred, in as it were a metaphorical fashion, to other realms of human experience and endeavour, be this: aetiological myth, in the case of the material bearing upon Lykaon; rites of passage or of maturation, in the case of the material bearing upon the Lykaia rite; or medicine, in the case of the medical writers’ identification of the disease of ‘lycanthropy.’ It is this that accounts for what initially appears to be the incoherent, chaotic and centrifugal nature of the evidence-field for werewolves that the ancients have bequeathed to us.
Book chapters on the topic "Refraction onde"
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Wohlfarth, Ch. "Refractive index of pentan-2-one." In Refractive Indices of Pure Liquids and Binary Liquid Mixtures (Supplement to III/38), 263. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-75291-2_146.
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Wohlfarth, Ch. "Refractive index of heptan-2-one." In Refractive Indices of Pure Liquids and Binary Liquid Mixtures (Supplement to III/38), 407. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-75291-2_246.
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Wohlfarth, Ch. "Refractive index of butan-2-one." In Refractive Indices of Pure Liquids and Binary Liquid Mixtures (Supplement to III/38), 183. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-75291-2_91.
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Wohlfarth, Ch. "Refractive index of propan-2-one." In Refractive Indices of Pure Liquids and Binary Liquid Mixtures (Supplement to III/38), 132–34. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-75291-2_60.
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Wohlfarth, Christian. "Refractive index of pyrrolidin-2-one." In Optical Constants, 135. Berlin, Heidelberg: Springer Berlin Heidelberg, 2017. http://dx.doi.org/10.1007/978-3-662-49236-9_125.
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Wohlfarth, Christian. "Refractive index of butan-2-one." In Optical Constants, 137. Berlin, Heidelberg: Springer Berlin Heidelberg, 2017. http://dx.doi.org/10.1007/978-3-662-49236-9_127.
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Wohlfarth, Christian. "Refractive index of pentan-2-one." In Optical Constants, 195. Berlin, Heidelberg: Springer Berlin Heidelberg, 2017. http://dx.doi.org/10.1007/978-3-662-49236-9_182.
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Wohlfarth, Christian. "Refractive index of pentan-3-one." In Optical Constants, 196. Berlin, Heidelberg: Springer Berlin Heidelberg, 2017. http://dx.doi.org/10.1007/978-3-662-49236-9_183.
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Wohlfarth, Christian. "Refractive index of hexan-2-one." In Optical Constants, 250. Berlin, Heidelberg: Springer Berlin Heidelberg, 2017. http://dx.doi.org/10.1007/978-3-662-49236-9_235.
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Wohlfarth, Christian. "Refractive index of propan-2-one." In Optical Constants, 102. Berlin, Heidelberg: Springer Berlin Heidelberg, 2017. http://dx.doi.org/10.1007/978-3-662-49236-9_95.
Full textConference papers on the topic "Refraction onde"
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Miessner, Ulrich, Ralph Lindken, and Jerry Westerweel. "Velocity Measurements in Microscopic Two-Phase Flows by Means of Micro PIV." In ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2008. http://dx.doi.org/10.1115/icnmm2008-62093.
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This article examines the velocity distributions of microscopic liquid-liquid two-phase flows by means of micro particle image velocimetry (micro-PIV). Aqueous droplets are dispersed into an oil bulk at the T-junction of a micro fluidic Polydimethylsiloxane (PDMS) device. The channel geometry is rectangular (H: 100μm, W: 100μm). The flow is pressure driven. Tracer particles (D: 0.5–1.2μm) are added to either phase, enabling simultaneous measurements in both phases. However, the use of immiscible liquids causes optical disturbances due to a difference in refractive indices of the two liquids and due to a curved interface geometry. Particle images are thus imaged in a distorted field of view. The results of a PIV analysis will be inaccurate in scaling as well as in location of the velocity vectors — depending on the mismatch of the refractive index. We present a basic analysis on the effect of mismatched refractive indices on the precision of the velocity measurements. The estimation is based on Snell’s law and the simplified geometry of a spherical droplet. Furthermore, we propose a method to match not only the index of refraction accurately but also to leave one additional degree of freedom to set an additional property of the liquid-liquid system, e.g. viscosity ratio or density ratio. The latter ensures that properties of the modified liquid-liquid system are close to those of the non-modified two-phase system. The findings of this study are part of the design of a Lab-on-a-Chip device. It performs a DNA analysis in an online quality control application. The miniaturization of a two-phase flow combines the benefits of confined sample compartments (i.e. droplets) with the easy-to-control process parameters of a miniaturized device (e.g. temperature, pressure). Thus band broadening of the sample by Taylor-Aris dispersion is avoided and the processes can be set accurately.
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Song, Zhenfei, Chen Zhao, and Lixin Ren. "One method on refraction star-map simulation." In Optical Sensing and Imaging Technology, edited by HaiMei Gong, John E. Greivenkamp, Jun Tanida, Yadong Jiang, Jin Lu, and Dong Liu. SPIE, 2019. http://dx.doi.org/10.1117/12.2540973.
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Lugo, J. E., Rafael Doti, and J. Faubert. "Negative refraction in one-dimensional photonic crystals." In Photonics North 2012, edited by Jean-Claude Kieffer. SPIE, 2012. http://dx.doi.org/10.1117/12.2001446.
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Doti, R., J. E. Lugo, and J. Faubert. "Negative refraction characterization in one-dimensional photonic crystals." In Photonics North 2012, edited by Jean-Claude Kieffer. SPIE, 2012. http://dx.doi.org/10.1117/12.2001448.
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Uhlmann, Gunther, and So¨nke Hansen. "Recovering Acoustic and Elastic Parameters From Travel Times." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32149.
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The relation between travel times and waves in anisotropic media is explained using the geometrical optics method in a phase space setting. This approach also covers caustics and multiple arrivals. We than consider the question of whether one can determine an anisotropic index of refraction by measuring travel times. We show that this is indeed the case if the index of refraction satisfies some additional assumptions.
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Hou, Peng, Yuanyuan Chen, Jielong Shi, Ming Shen, and Qi Wang. "The analyses of negative refraction in finite one-dimensional photonic crystals." In 2006 International Symposium on Biophotonics, Nanophotonics and Metamaterials. IEEE, 2006. http://dx.doi.org/10.1109/metamat.2006.334969.
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Gu, Zu-Han, and Anting Wang. "Nonstandard refraction of light from one-dimensional dielectric quasi-periodic surfaces." In SPIE NanoScience + Engineering, edited by Michael T. Postek and John A. Allgair. SPIE, 2009. http://dx.doi.org/10.1117/12.824626.
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Hu, Changbao, Yiping Xu, and Huosheng He. "Comment on properties of one-dimensional photonic crystals containing negative refraction materials." In Photonics Asia 2007, edited by Xing Zhu, Stephen Y. Chou, and Yasuhiko Arakawa. SPIE, 2007. http://dx.doi.org/10.1117/12.757203.
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Strickler, James H., and Watt W. Webb. "Signal measurements of multilayer refractive write-once data storage media." In Optical Data Storage Topical Meeting, edited by Donald B. Carlin, David B. Kay, and Alfred A. Franken. SPIE, 1992. http://dx.doi.org/10.1117/12.137569.
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Gu, Zu-Han, and Anting Wang. "Nonstandard refraction of light from one- and two-dimensional dielectric quasi-periodic surfaces." In SPIE Optical Engineering + Applications, edited by Zu-Han Gu and Leonard M. Hanssen. SPIE, 2010. http://dx.doi.org/10.1117/12.859143.
Full textReports on the topic "Refraction onde"
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Ostashev, Vladimir, Michael Muhlestein, and D. Wilson. Extra-wide-angle parabolic equations in motionless and moving media. Engineer Research and Development Center (U.S.), September 2021. http://dx.doi.org/10.21079/11681/42043.
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Wide-angle parabolic equations (WAPEs) play an important role in physics. They are derived by an expansion of a square-root pseudo-differential operator in one-way wave equations, and then solved by finite-difference techniques. In the present paper, a different approach is suggested. The starting point is an extra-wide-angle parabolic equation (EWAPE) valid for small variations of the refractive index of a medium. This equation is written in an integral form, solved by a perturbation technique, and transformed to the spectral domain. The resulting split-step spectral algorithm for the EWAPE accounts for the propagation angles up to 90° with respect to the nominal direction. This EWAPE is also generalized to large variations in the refractive index. It is shown that WAPEs known in the literature are particular cases of the two EWAPEs. This provides an alternative derivation of the WAPEs, enables a better understanding of the underlying physics and ranges of their applicability, and opens an opportunity for innovative algorithms. Sound propagation in both motionless and moving media is considered. The split-step spectral algorithm is particularly useful in the latter case since complicated partial derivatives of the sound pressure and medium velocity reduce to wave vectors (essentially, propagation angles) in the spectral domain.