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Dissertations / Theses on the topic 'The diffraction of waves on the reflectors'

Author: Grafiati
Published: 28 May 2022
Last updated: 31 July 2025

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1

Suedan, Gibreel A. "High frequency beam diffraction by apertures and reflectors." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27545.

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Most solutions for electromagnetic wave diffraction by obstacles and apertures assume plane wave incidence or omnidirectional local sources. Solutions to diffraction problems for local directive sources are needed. The complex source point representation of directive beams together with uniform solutions to high frequency diffraction problems is a powerful combination for this. Here the method is applied to beam diffraction by planar structures with edges, such as the half-plane, slit, strip, wedge and circular aperture. Previously used restrictions to very narrow beams and paraxial regions,
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2

Fozard, John Andrew. "Diffraction and scattering of high frequency waves." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433239.

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This thesis examines certain aspects of diffraction and scattering of high frequency waves, utilising and extending upon the Geometrical Theory of Diffraction (GTD). The first problem considered is that of scattering of electromagnetic plane waves by a perfectly conducting thin body, of aspect ratio O(k^1/2), where k is the dimensionless wavenumber. The edges of such a body have a radius of curvature which is comparable to the wavelength of the incident field, which lies inbetween the sharp and blunt cases traditionally treated by the GTD. The local problem of scattering by such an edge is tha
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3

Rogoff, Zigmund M. "Diffraction of acoustic waves at fluid-solid boundaries." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319952.

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4

Chen, Meng-Yi. "Nonlinear diffraction and refraction of regular and random waves." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/34378.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2006.<br>Includes bibliographical references (p. 302-306).<br>The mild-slope equation is an effective approximation for treating the combined effects of refraction and diffraction of infinitesimal water waves, for it reduces the spatial dimension of the linear boundary value problem from three to two. We extend this approximation to nonlinear waves up to the second order in wave steepness, in order to simplify the inherently three-dimensional task. Assuming that the geometrical complexity is r
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5

Cheung, Kwok Fa. "Time-domain solution for second-order wave diffraction." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/30987.

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A numerical method based on potential flow theory is developed for simulating transient, second-order interactions of ocean waves with large fixed bodies of arbitrary shape in two and three dimensions. The physical problem is represented by a mathematical model composed of a fluid domain bounded by the body surface, the still water surface, the seabed, and a control surface truncating the infinite fluid region. The nonlinear free surface boundary conditions defined on the instantaneous free surface are expanded about the still water level by a Stokes expansion procedure. The flow potential to
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6

Сайко, Ігор Миколайович, Игорь Николаевич Сайко та Ihor Mykolaiovych Sajko. "Математическое моделирование поведения систем отражателей при гармонических воздействиях на основе сингулярных интегральных уравнений". Thesis, Институт кибернетики имени В.М. Глушкова НАН Украины, 2016. http://essuir.sumdu.edu.ua/handle/123456789/44686.

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Мета дисертації – підвищення ефективності та точності визначення характеристик фізичних на локальних системах відбивачів, що знаходяться під впливом стаціонарних гармонічних антиплоских або плоских навантажень, якщо ці процеси моделюються СІР. Досягається завдяки двом типам досліджень: безпосередньому чисельному розв’язанню нових дифракційних задач, коли гармонічні впливи здійснюються на локальні системи відбивачів довільного поперечного перетину та довільної кількості (для яких в інтерпретації теорії пружності отримуються нові залежності), а також дослідженню обумовленості та стійкості викори
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7

Zhang, Qin. "Acoustic pulse diffraction by curved and planar structures with edges." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/32005.

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Efficient and accurate solutions of acoustic wave diffraction by a rigid step discontinuity and a curved half-plane are derived by the uniform geometrical theory of diffraction. These solutions can be used in seismic data processing to evaluate and, eventually, to improve the existing data processing procedures. They can also find applications in electromagnetics, microwave antenna design, acoustic design and sound engineering. The rigid step discontinuity solution given in this thesis is more accurate than the existing solutions which are based on Kirchhoff theory of diffraction. This solut
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8

Ohl, Clifford Owen Groome. "Free surface disturbances and nonlinear runup around offshore structures." Thesis, University of Oxford, 2000. http://ora.ox.ac.uk/objects/uuid:320ff8da-c225-40da-a7dd-d6cf55c97b51.

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Diffraction of regular waves, focused wave groups, and random seas by arrays of vertical bottom mounted circular cylinders is investigated using theoretical, computational, and experimental methods. Free surface elevation η is the defining variable used to test the potential theory developed. In addition, the nonlinearity of focused wave groups is investigated through the Creamer nonlinear transform and analysis of numerical wave tank data. Linear focused wave group theory is reviewed as a method for predicting the probable shape of extreme events from random wave spectra. The Creamer nonlinea
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9

Huang, Chi-Luen. "Effect of beam diffraction on nonlinear Rayleigh surface wave measurement." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47537.

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This research investigates the effects of beam diffraction from a source of finite width on nonlinear Rayleigh wave propagation in an elastic half space. Previous work has shown that nonlinear ultrasonic Rayleigh waves can be used to evaluate material damage due to plastic deformation and fatigue. In this measurement, a relatively small wedge transducer is employed to launch Rayleigh surface waves in the specimen and the first and second harmonic amplitudes are measured in the far field as a function of propagation distance. In order to obtain a reliable set of measurement data, one needs to m
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10

MENDES, LEONARDO DE SOUZA. "DIFFRACTION OF A ELECTROMAGNETIC WAVES BY A PARABOLIC SEMI-CYLINDER." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1987. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9491@1.

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É analisado o problema de difração de uma onda eletromagnética cilíndrica pela borda de um semi-cilindro parabólico. O problema é formulado em termos das funções de Weber do cilindro parabólico que são soluções da equação de onda em coordenadas cilindro-parabólicas. A solução é obtida com o auxílio da técnica de Wiener-Hopf que fornece, para os campos espalhados, um resultado em termos de uma equação integral. Obtém-se, então, as aproximações assintóticas destes resultados. Estas aproximações fornecem para regiões afastadas da fronteira de sombra uma solução em termos de ponto de sel
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11

Assier, Raphaël Charles. "On the diffraction of acoustic waves by a quarter-plane." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610447.

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12

Russell, Thomas A. "Predicting microwave diffraction in the shadows of buildings." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-10222009-125156/.

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13

Chase, Yun S. "Sound diffraction by an underwater ridge with finite impedance." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/17773.

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14

Kamel, Michel. "An investigation of the diffraction of detonation waves around single cylinders /." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68031.

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An experimental and theoretical investigation of detonation diffraction around single cylinders is performed. Four cylinder diameters: 1", 1.25", 2.35", and 4", along with three different mixtures: stoichiometric, equimolar, and 40% argon diluted oxyacetylene, are used interchangeably. The initial pressure is varied from 20 to 90 torr. Experiments are performed in a two dimensional rectangular channel with a test section 1085 mm long, 101 mm wide, and 25.4 mm thick. High speed framing Schlieren photographs of the diffraction phenomena are taken. Smoke foils are also used to provide a record of
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15

Carter, Mark. "Diffraction, interaction and core dynamics of reaction-diffusion waves : eikonal solutions." Thesis, Glasgow Caledonian University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267507.

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16

McCalmont, John Francis. "A vector Huygens-Fresnel model of the diffraction of electromagnetic waves." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/298811.

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The scalar Huygens-Fresnel Principle describing the propagation of light is reformulated to take into account the vector nature of light and the associated directed electric and magnetic fields. A vector Huygens secondary source is developed in terms of the fundamental radiating units of electromagnetism: the electric and magnetic dipoles. The vector Huygens wavelets are incorporated into a computer model that calculates the resulting vector fields after light passes through a diffracting system by a wavefront reconstruction process similar to that originally proposed by Huygens himself in 168
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17

Edvardsson, Elisabet. "Quasicrystals : Classification, diffraction and surface studies." Thesis, Karlstads universitet, Institutionen för ingenjörsvetenskap och fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-36299.

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Quasicrystal is the term used for a solid that possesses an essentially discrete diffraction pattern without having translational symmetry. Compared to periodic crystals, this difference in structure gives quasicrystals new properties that make them interesting to study -- both from a mathematical and from a physical point of view. In this thesis we review a mathematical description of quasicrystals that aims at generalizing the well-established theory of periodic crystals. We see how this theory can be connected to the cohomology of groups and how we can use this connection to classify quasic
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18

Chambers, James P. "Scale model experiments on the diffraction and scattering of sound by geometrical step discontinuities and curved rough surfaces." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/17858.

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19

Chehade, Samar. "Modelling of the 3D scattering of elastic waves by complex structures for specimen echoes calculation. Application to ultrasonic NDT simulation." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS273/document.

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Le sujet de la thèse s’inscrit dans le cadre du développement de modèles pour la simulation du contrôle non-destructif (CND) par ultrasons. L'objectif à long terme est la mise au point, par une méthode de rayons, d’un outil complet de simulation des échos issus de la géométrie (surfaces d’entrée, de fond…) ou des structures internes des pièces inspectées. La thèse vise plus précisément à intégrer le phénomène de diffraction par les dièdres à un modèle existant dérivant de l’acoustique géométrique et qui prend uniquement en compte les réflexions sur les faces.Pour cela, la méthode dite des fonc
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20

Skrynnikov, Yuri 1959. "Nonlinear coupled waves in stratified flows." Monash University, School of Mathematical Sciences, 2002. http://arrow.monash.edu.au/hdl/1959.1/7779.

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21

Chau, Fun Pang. "The second order velocity potential for diffraction of waves by fixed offshore structures." Thesis, University College London (University of London), 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296841.

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It is well known that second order effects may in many cases be important for the nonlinear hydrodynamic problems arising in ocean engineering. Despite considerable efforts having been made in the past in calculating second order unsteady forces, similar studies are rare for the actual second order velocity potential itself, which is important for the understanding of wave kinematics. A mathematical model has been developed for the calculation of the second order sum frequency diffraction potential for fixed bodies in waves. It is believed that a first step towards the solution of the second o
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22

Dalton, David Raymond. "Derivation and practical application of exact time domain solutions for diffraction of acoustic waves by a half plane." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27866.

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The history of diffraction theory, exact frequency domain solutions and selected past time domain solutions are briefly reviewed. Exact time domain solutions for scattering of plane, cylindrical and spherical acoustic waves by a half plane are derived by inverse Fourier transforming the frequency domain integral solutions. The solutions consist of two diffraction terms, a reflected term and a direct term. The diffracting edge induces step function discontinuities in the direct and reflected terms at two shadow boundaries. At each boundary, the associated diffraction term reaches a maximum ampl
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23

Kearns, James A. "An investigation of the diffraction of an acoustic plane wave by a curved surface of finite impedance." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/16749.

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24

Lawrow, Alexander. "Domain-inverted transducers for acousto-optic devices." Thesis, University of Kent, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267423.

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25

Bettess, Jacqueline Anne. "A software perspective on infinite elements for wave diffraction and wave forces on marine risers." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4289/.

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This thesis describes work on the problem of the scattering of water waves by fixed objects. The method used to solve this problem is that of finite and infinite elements. In particular the development of a new wave infinite element is described. Various aspects of the wave scattering problem are considered, but always from the perspective of the numerical methods, the algorithms and the computer implementations used. These deal not only with the modelling of the wave equations, but also the pre and post processing of the finite element algorithms. This encompasses the generation of suitable f
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26

Fuscaldo, Walter. "Advanced radiating systems based on leaky waves and nondiffracting waves." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S015/document.

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La focalisation du champ électromagnétique dans les zones de champ proche et lointain est un sujet de forte actualité pour l'imagerie médicale et la radiométrie des microondes jusqu'aux ondes millimétriques. Dans ce cadre, la théorie des ondes de fuite est un formalisme élégant qui permet de décrire d'une même façon les problèmes radiatifs en champ proche et en champ lointain des microondes aux fréquences optiques. Dans cette thèse, on utilise la polyvalence de la théorie des ondes de fuite pour développer des systèmes rayonnants complexes afin de contrôler les caractéristiques radiatives en c
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27

Wu, Meiyi. "Development of the x-ray standing waves methodology to probe the interfaces of periodic multilayers." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS175/document.

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La qualité des interfaces dans les multicouches périodiques est essentielle au développement de miroirs réfléchissant efficacement dans les domaines des rayons X et extrême ultraviolet (X-EUV). De manière générale, la structure des interfaces dépend des possibles interdiffusion et processus chimiques aux interfaces entre couches. L'idée principale de cette thèse est d'appliquer la technique des ondes stationnaires dans le domaine X à la caractérisation de matériaux, principalement mais non exclusivement aux multicouches périodiques. Cette méthode est basée sur l'interférence de deux faisceaux
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28

Suleiman, Aminat Oyiza. "Structural dynamics of 1T-TiSe2 using femtosecond electron diffraction." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95990.

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Thesis (MSc)--Stellenbosch University, 2014.<br>ENGLISH ABSTRACT: Trilayered transition metal dichalcogenides such as our sample (1T-TiSe2) have been studied for many years as systems with strong electron-electron and electron-phonon correlations. The main attraction to this family of compound is its potential to exhibit ground state phenomena known as charge density waves whose detailed physical origin has been controversially determined. In this study, we have used an ultrafast femtosecond laser based on a pump-probe technique, namely ultrafast electron diffraction, to investigate thes
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29

Shaw, Anurupa. "Ice thickness estimation using low frequencies, and an investigation of diffraction of sound in samples with micro structures using ultrasound." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54242.

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In the first section, the thickness of ice on the lakes and canals is estimated by analyzing the sound spectrum generated by dispersion of Lamb type waves propagating in ice. In winters when the lakes and canals freeze, it is important to know the thickness of the ice layer before setting foot on it. When a stone is thrown on the ice layer, a fluting sound can be heard. This is recorded for different thicknesses of ice, and the sound spectrum is compared with the results simulated using a parameterized model. This model is created using a combination of plane waves for different incident angle
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30

Herbison, Sarah. "Ultrasonic diffraction effects on periodic surfaces." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41180.

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Although the study of the interaction of acoustic and elastic waves with periodic surfaces and structures has a rich history dating back to Lord Rayleigh, it has recently been attracting new research efforts due to its value in the study of phononic crystals and in methods for ultrasonic non-destructive evaluation (NDE). The objective of the research described in this thesis is to provide new numerical and experimental tools capable of capturing important features that occur due to the diffraction of ultrasound on periodic solid surfaces. This thesis is divided into four main parts. First, the
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31

Willey, Carson Landis. "Ultrasonic Guided Wave Tomography for Wall Thickness Mapping in Pipes." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1460729589.

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32

Quinn, Mark Kenneth. "Shock diffraction phenomena and their measurement." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/shock-diffraction-phenomena-and-their-measurement(4c41f25a-2ba2-4a4b-aa9c-cdb8bb9ba921).html.

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The motion of shock waves is important in many fields of engineering and increasingly so with medical applications and applications to inertial confinement fusion technologies. The flow structures that moving shock waves create when they encounter a change in area is complex and can be difficult to understand. Previousresearchers have carried out experimental studies and many numerical studies looking at this problem in more detail. There has been a discrepancy between numerical and experimental work which had remained unanswered. One of the aims of this project is to try and resolve the discr
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33

Edmunds, James David. "Microwave transmissivity of sub-wavelength metallic structures." Thesis, University of Exeter, 2011. http://hdl.handle.net/10036/3214.

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The use of patterned metallic surfaces for the control of the transmission of microwave radiation has been reinvigorated in recent years due to the success and interest in metamaterial research. These metallic periodic structures, commonly referred to as frequency selective screens (FSSs), allow responses to be tailored according to the geometry of the metallic structure as opposed to the material composition. A consequence of the presence of a metallic corrugation is the possible excitation of surfaces waves (commonly referred to as surface plasmon polaritons at visible frequencies). Surface
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34

Matsouli, Ioanna. "Study of magneto-acoustic effects in FeBO←3 by synchrotron radiation diffraction imaging." Thesis, University of Warwick, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310013.

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35

Pile, David Fujio Pelleas. "Extremely asymmetrical scattering of waves in periodic Bragg arrays." Thesis, Queensland University of Technology, 2003. https://eprints.qut.edu.au/15794/1/David_Pile_Thesis.pdf.

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This thesis fills in the gaps in the existing theory of wave phenomena in thick diffraction gratings at extreme angles of scattering, i.e. when the scattered wave propagates parallel or almost parallel to the grating boundaries. A consistent theory of a new type of Bragg scattering of bulk and guided optical modes in thick uniform and non-uniform, dissipative and non-dissipative, slanted periodic gratings has been developed. This type of scattering is called extremely asymmetrical scattering (EAS). One of the main distinctive features of EAS is the strong resonant increase of the scatter
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Pile, David Fujio Pelleas. "Extremely asymmetrical scattering of waves in periodic Bragg arrays." Queensland University of Technology, 2003. http://eprints.qut.edu.au/15794/.

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This thesis fills in the gaps in the existing theory of wave phenomena in thick diffraction gratings at extreme angles of scattering, i.e. when the scattered wave propagates parallel or almost parallel to the grating boundaries. A consistent theory of a new type of Bragg scattering of bulk and guided optical modes in thick uniform and non-uniform, dissipative and non-dissipative, slanted periodic gratings has been developed. This type of scattering is called extremely asymmetrical scattering (EAS). One of the main distinctive features of EAS is the strong resonant increase of the scatter
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Tatsumi, Kazuyoshi, Shunsuke Muto, and Ján Rusz. "New algorithm for efficient Bloch-waves calculations of orientation-sensitive ELNES." Elsevier, 2013. http://hdl.handle.net/2237/20831.

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Popuzin, Vitaly. "Methods of fast Fourier transform in diffraction problems of elastic and acoustic waves with applications to crack mechanics." Doctoral thesis, Università di Catania, 2014. http://hdl.handle.net/10761/1548.

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The activity is connected with a development of modern fast computational methods applied to problems in wave dynamics, acoustics, and boundary-value problems of mechanics with mixed boundary conditions. This includes: 1) Development of fast methods for integral equations with convolution kernels arising in these fields of application. Such integral equations, after discretization, may be reduced to linear algebraic systems with matrix of Toepliz or circulant form. For both the types there can be applied fast iteration methods founded on Conjugate Gradient method with a preconditioning. Thi
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Haupt, Kerstin Anna. "Phase transitions in transition metal dichalcogenides studied by femtosecond electron diffraction." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/85608.

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Thesis (PhD)--Stellenbosch University, 2013.<br>ENGLISH ABSTRACT: Low-dimensional materials are known to undergo phase transitions to differently or- dered states, when cooled to lower temperatures. These phases often show a periodic modulation of the charge density (called a charge density wave – CDW) coupled with a periodic perturbation of the crystal lattice (called a periodic lattice distortion – PLD). Although many experiments have been performed and much has been learnt about CDW phases in low-dimensional materials, the reasons for their existence are still not fully understood yet
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40

Lord, Natacha Hajanirina. "Analysis of electromagnetic waves in a periodic diffraction grating using a priori error estimates and a dual weighted residual method." Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=16856.

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The problem of using the α,0 and the α, β-quasi periodic transformations within a finite element method in studying electromagnetic waves in a periodic space is addressed. We investigate an a priori error estimate for both transformations which allows us to solve our problem numerically on a uniform mesh. We also analyse the Dual Weighted Residual (DWR) method with the α,0-quasi periodic transformation to derive an a posteriori error estimate. This error estimate is later used to compute efficiently the numerical solution using an adaptive method. We then implement the above finite element met
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41

Marmorat, Simon. "Modèles asymptotiques et simulation numérique pour la diffraction d'ondes par des petites hétérogénéités." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLY001/document.

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Cette thèse est consacrée à l'étude du problème de la diffraction d'une onde acoustique par un ensemble de petites hétérogénéités pénétrables ainsi qu'au développement de méthodes de simulation numérique dédiées à la résolution efficace de ce type de problèmes. La principale nouveauté de ces travaux provient du fait que nous traitons ce problème dans le domaine temporel.La première partie de ce manuscrit est consacrée à l'analyse asymptotique du problème de diffraction, menée à bien grâce à la méthode des développements asymptotiques raccordés, le petit paramètre étant la taille caractéristiqu
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42

Uhrig, Matthias Pascal. "Numerical simulation of nonlinear Rayleigh wave beams evaluating diffraction, attenuation and reflection effects in non-contact measurements." Thesis, Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54368.

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Although several studies have proven the accuracy of using a non-contact, air-coupled receiver in nonlinear ultrasonic (NLU) Rayleigh wave measurements, inconsistent results have been observed when working with narrow specimens. The objectives of this research are first, to develop a 3D numerical finite element (FE) model which predicts nonlinear ultrasonic measurements and second, to apply the validated model on the narrow waveguide to determine causes of the previously observed experimental issues. The commercial FE-solver ABAQUS is used to perform these simulations. Constitutive law and e
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43

Kovalevich, Tatiana. "Tunable Bloch surface waves devices." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD022/document.

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Cette thèse est consacrée au développement de dispositifs accordables sur la base de cristaux photoniques unidimensionnels qui peuvent supporter des ondes de surface de Bloch (BSW). Tout d'abord, nous explorons les possibilités de contrôler la direction de propagation des BSW par le biais de la polarisation de la lumière incidente. Dans ce cas, nous gravons sur le dessus du cristal photonique 1D des structures passives de type réseau, qui permettent à la fois de coupler la lumière incidente aux BSWs et de se comporter comme une lame séparatrice ultracompacte contrôlée par la polarisation lumin
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Петровський, Михайло Васильович, Михаил Васильевич Петровский, Mykhailo Vasylovych Petrovskyi та ін. "К вопросу влияния геометрических размеров периодических металлодиэлектрических структур на пространственные и волноводные характеристики". Thesis, Сумский государственный университет, 2014. http://essuir.sumdu.edu.ua/handle/123456789/39670.

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В работе исследовались пространственые – диаграмма направленности излучения (ДН) и волноводные характеристики – коэффициент передачи и КСВ, при возбуждении систем на базе МДС диэлектрическим волноводом.
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Elzo, Aizarna Marta Ainhoa. "Diffraction résonnante des rayons X dans des systèmes multiferroïques." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00870407.

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Le but de cette thèse est d'explorer la faisabilité d'expériences de diffraction résonante sur des systèmes multiferroïques et en particulier avec un champ/courrant électrique appliqué. Un formalisme de matrices de propagation a été développé pour simuler la réflectivité résonante, en utilisant un ensemble d'ondes propres comme base arithmétique pour le calcul. Des expériences de diffraction résonante ont été menées sur trois oxides de métaux de transition. Cette technique combinant la selectivité chimique et la sensibité à l'espace réciproque, elle a été utilisée sur des films très minces de
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Pedersen, Helle Anette. "Étude de la diffraction tridimensionnelle des ondes sismiques dans des structures à géométrie bidimensionnelle : développement théorique et applications." Grenoble 1, 1994. http://www.theses.fr/1994GRE10212.

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La diffraction tridimensionnelle (3d) des ondes sismiques par des structures a geometrie bidimensionnelle (2d) est etudiee par la methode indirecte d'elements de frontiere (ibem, pour indirect boundary element method). Les ondes incidentes peuvent arriver en dehors du plan 2d et, en consequence, la diffraction est 3d avec couplage de tous les types d'onde. Ce travail est divise en trois parties. La theorie de ibem et son extension aux problemes de diffraction 3d par des structures 2d sont presentees dans la premiere partie. La deuxieme est consacree a l'application de la methode pour l'etude d
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Pinilla, Pachon Edwin German 1981. "Guiamento óptico de átomos através de feixes não difrativos do tipo "Frozen Waves" = Atom optical guiding along non-diffracting beams of type "Frozen Waves"." [s.n.], 2016. http://repositorio.unicamp.br/jspui/handle/REPOSIP/330786.

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Orientadores: Michel Zamboni Rached, Guillermo Gerardo Cabrera Oyarzún<br>Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin<br>Made available in DSpace on 2018-09-01T02:33:12Z (GMT). No. of bitstreams: 1 Pachon_EdwinGermanPinilla_D.pdf: 4993091 bytes, checksum: 788c9fb47dfe7b9fea6cc0935ad94d54 (MD5) Previous issue date: 2016<br>Resumo: Nesta tese, propõe-se um novo método para realizar guiamento de átomos neutros resfriados. Este método envolve o uso da pressão de radiação por ressonância para efetuar o guiamento dos átomos através de um campo óptico (fe
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Marmorat, Simon. "Modèles asymptotiques et simulation numérique pour la diffraction d'ondes par des petites hétérogénéités." Electronic Thesis or Diss., Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLY001.

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Cette thèse est consacrée à l'étude du problème de la diffraction d'une onde acoustique par un ensemble de petites hétérogénéités pénétrables ainsi qu'au développement de méthodes de simulation numérique dédiées à la résolution efficace de ce type de problèmes. La principale nouveauté de ces travaux provient du fait que nous traitons ce problème dans le domaine temporel.La première partie de ce manuscrit est consacrée à l'analyse asymptotique du problème de diffraction, menée à bien grâce à la méthode des développements asymptotiques raccordés, le petit paramètre étant la taille caractéristiqu
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Li, Boning. "Extending the scaled boundary finite-element method to wave diffraction problems." University of Western Australia. School of Civil and Resource Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0173.

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[Truncated abstract] The study reported in this thesis extends the scaled boundary finite-element method to firstorder and second-order wave diffraction problems. The scaled boundary finite-element method is a newly developed semi-analytical technique to solve systems of partial differential equations. It works by employing a special local coordinate system, called scaled boundary coordinate system, to define the computational field, and then weakening the partial differential equation in the circumferential direction with the standard finite elements whilst keeping the equation strong in the
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Janice, Brian A. "Differential Near Field Holography for Small Antenna Arrays." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-theses/999.

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"Near-field diagnosis of antenna arrays is often done using microwave holography; however, the technique of near-field to near-field back-propagation quickly loses its accuracy with measurements taken farther than one wavelength from the aperture. The loss of accuracy is partially due to windowing, but may also be attributed to the decay of evanescent modes responsible for the fine distribution of the fields close to the array. In an effort to achieve better resolution, the difference between these two phase-synchronized near-field measurements is used and propagated back. The performance of s
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