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Dissertations / Theses on the topic 'Wave refraction'
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Peak, Scott Douglas. "Wave refraction over complex nearshore bathymetry." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FPeak.pdf.
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Ray, Timothy Allen. "Wave propagation over complex bathymetry." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Jun%5FRay.pdf.
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Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, June 2003.Thesis advisor(s): Thomas H.C. Herbers, Edward B. Thornton. Includes bibliographical references (p. 37). Also available online.
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Carrie, A. L. S. "Wave refraction modelling and longshore sediment transport." Thesis, University of East Anglia, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372553.
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Mansfeld, Sebastian [Verfasser]. "Spin-Wave Optics: Refraction and Imaging / Sebastian Mansfeld." München : Verlag Dr. Hut, 2012. http://d-nb.info/1028785607/34.
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Dodd, N. "Parabolic approximations in water wave refraction and diffraction." Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384404.
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Au, L. B. "Wave propagation and grating formation in photorefractive materials." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235016.
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Khalid, Mohammad Asmatullah. "Comparison of measured and transformed directional wave spectra using linear refraction model." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/25752.
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Li, Changqing. "Wave Diffraction and Refraction Problem and a Block-Wise Band Matrix Solver." W&M ScholarWorks, 1995. https://scholarworks.wm.edu/etd/1539617698.
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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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Liu, James Cheng. "Comparison of measured and transformed directional wave spectra using a linear refraction model." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA247157.
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Thesis (M.S. in Meteorology)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Thornton, Edward B. Second Reader: Williams, Roger T. "December 1990." Description based on title screen as viewed on March 31, 2010. DTIC Identifier(s): Linear Refraction Model. Author(s) subject terms: Ocean Waves, Directional Spectra, Wave Refraction. Includes bibliographical references (p. 82-83). Also available in print.
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Laskar, Tasnim. "Determining shallow P-wave velocity and its engineering implication in Adama City, Ethiopia." Thesis, Uppsala universitet, Geofysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-385893.
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A great number of the urban areas in Ethiopia are situated within the Great Rift Valley of Ethiopia, a system consisting of depressions and large faults. As a region with significant seismic activities, it is vital that careful planning is implemented to avoid constructing buildings on flat surfaces as they can amplify ground motion in the case of an earthquake. This study was conducted in Adama, a city located within the rift system, to map and characterize the subsurface of a construction site with seismic refraction and investigate whether this is an optimal area to construct a building should an earthquake occur. Seismic refraction is based on Snell’s law, specifically the case of the critical angle, which is when the refracted angle is at 90 degrees and a number of the energy from the wave is rebounded back to the surface in accordance with Huygen’s Principle. Seismic waves were generated with a sledgehammer and recorded with 24 vertical geophones. The acquired data was then analysed with SeisImager and produced a 2D-tomography of the site with the corresponding velocity layers for a P-wave. Comparing the P-wave velocities to a table of Seismic Velocities of Rocks and Various Materials, one could determine that the subsurface layers consisted of rock soils, sand and silt. These are incredibly loose materials that will amplify ground motion during earthquake crisis and are therefore not optimal or ideal for constructing buildings.
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Kokorowski, David Anthony 1973. "Measuring decoherence and the matter-wave index of refraction with an improved atom interferometer." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8648.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2001.Includes bibliographical references (leaves 142-153).
This thesis describes experiments performed using the MIT atom interferometer, which has recently been upgraded to provide increased experimental precision and flexibility. The three-gratings comprising our Mach-Zehnder interferometer have been installed on a vibration isolated platform which has reduced rms motion of the gratings by a factor of two. The arrangement of gratings on the platform can be reconfigured at will, and the entire platform removed from the vacuum chamber for purposes of alignment. We have performed a series of experiments related to decoherence in an atom interferometer. We have explored decoherence due to photon scattering, in particular the transition from single- to multiple-photon decoherence, and have quantitatively verified the decoherence rate constant in the many-photon regime. We have also examined decoherence due to background gas scattering. Finally, we have investigated the distinction between decoherence and classical dephasing by comparing experiments which illustrate each of these phenomena. We have made new measurements of the index of refraction of argon for sodium matter-waves. Our results are twice as precise previous measurements but suffer from significant systematic error. A detailed study of systematics is presented along with concrete proposals for minimizing their effect in future matter-wave index of refraction measurements.
by David Anthonk Kokorowski.
Ph.D.
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Byman, Michael William. "An application of ocean wave-current refraction to the Gulf Stream using SEASAT SAR data." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/25693.
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Sen, Saffet Gokcen. "Investigation Of Electromagnetic Wave Propagation In Double Negative Materials." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609748/index.pdf.
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This thesis analyzes some aspects of electromagnetic wave propagation in double negative materials. Double negative materials have negative refractive indices. They are backward-wave materials. Plane waves undergo negative refraction at interfaces between double positive and double negative media. Causality principle implies these properties. High frequency plane wave scattering from a double negative infinitely long cylinder has been analyzed by using modified Watson transform, geometrical optics and Mie series. Mie series results and the modified Watson transform results have been found to be in good agreement. Hence, the physical mechanism of the scattering has been revealed.
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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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Foteinopoulou, Stavroula. "Electromagnetic Wave Propagation in Two-Dimensional Photonic Crystals." Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2003. http://www.osti.gov/servlets/purl/822058-9BqHHS/native/.
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Thesis (Ph.D.); Submitted to Iowa State Univ., Ames, IA (US); 12 Dec 2003.Published through the Information Bridge: DOE Scientific and Technical Information. "IS-T 2048" Stavroula Foteinopoulou. 12/12/2003. Report is also available in paper and microfiche from NTIS.
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Bell, Maria Jose Valenzuela. "Determinação da fase do índice de refração não linear do rubi e GdAlO3: Cr+3." Universidade de São Paulo, 1992. http://www.teses.usp.br/teses/disponiveis/54/54131/tde-21022014-102511/.
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Estudamos os efeitos não lineares em cristais dopados com Cr+3 como o Rubi (Al2O3: Cr+3) e o Aluminato de Gadolínio (GdAlO3: Cr+3), acrescentados através de um índice de refração dependente da intensidade de luz incidente, que caracteriza os meios tipo Kerr (n= n0+n2I, com n2= n2´+in2´). As propriedades não lineares desses cristais se devem à diferença de susceptibilidades do estado excitado e do estado fundamental dos íons de Cr+3. Este modelo é amplamente conhecido, e explica muito bem os efeitos não lineares do Rubi. Porém, para o GdAl O3: Cr+3 há um efeito que não pode ser explicado por esse modelo simplificado: a dependência da razão r= n2\"/n2\' com a intensidade, cuia observação experimental foi feita utilizando a técnica de Mistura de Duas Ondas (MDO). A explicação para esse efeito foi apresentada recentemente e propõe que seja devido à interação de pares de Cr, presente quando a concentração de íons de Cr no material é alta. Neste trabalho verificamos a dependência de r com a intensidade por MDO e utilizando uma nova técnica, a MDO transiente. Esta última possui a grande vantagem de fornecer a razão r de forma direta, enquanto que na MDO, r é obtido pelo ajuste de uma curva de ganho. Como resultado, observamos que a MDO transiente fornece uma dependência de r com a intensidade que está de acordo com a prevista pela interação de pares de Cr e é superior à obtida por MDO. Também apresentamos os parâmetros determinados via MDO (n2\', a intensidade de saturação do meio, r e o tempo de resposta do meio) para 488 nm no GdAlO3: Cr+3, cujos valores ainda não são conhecidos na literaturaWe have studied the nonlinear properties of Chromium doped crystals such as ruby (Al2O3: Cr+3) and Gadolinium aluminate (GdAlO3: Cr+3), given by the intensity dependent refractive index characteristic of Kerr media, where n= n0+n2I and n2= n2´+in2´. The nonlinear properties of these crystals are due to the difference between the excited and the ground state susceptibilities. This model is widely used and explains the nonlinearity of ruby. However, GdAlO3: Cr+3 presents an effect that cannot be explained by that simplified approach: the intensity dependence of the parameter r=n2\"/n2\'. The experimental observation of such dependence was achieved using the Two Wave Mixing technique. An explanation for this effect was recently proposed using the interaction between Chromium ions that occurs when their concentration is high enough. In this work we observed the intensity dependence of r via two wave mixing and using a new technique, transient Two wave mixing. The last one gives the parameter r in a direct way, while the two waves mixing gives r by the fitting of a gain curve. As a result, we observed that transient two wave mixing shows greater intensity dependence than two wave mixing and agree with the interaction of Chromium ions. Also, we present the Two wave mixing parameters (n2\', the saturation intensity and response time of the medium) at 488nm, that were never reported before
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Gonsiewski, James P. "Bedrock Mapping Using Shear Wave Velocity Characterization and H/V Analysis." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1453247272.
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Taouk, Habib B. "Optical wave propagation in active media." Ohio : Ohio University, 1991. http://www.ohiolink.edu/etd/view.cgi?ohiou1173729381.
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Ruan, Zhichao. "Dispersion Engineering : Negative Refraction and Designed Surface Plasmons in Periodic Structures." Doctoral thesis, Stockholm : Informations- och kommunikationsteknik, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4542.
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Varing, Audrey. "Wave characterization for coastal and nearshore marine renewable energy applications : focus on wave breaking and spatial varaibility of the wave field." Thesis, Brest, 2019. http://www.theses.fr/2019BRES0105.
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Les énergies marines renouvelables (EMR) sont soumises aux vagues générées par le vent. Une caractérisation précise de ces vagues est nécessaire dans les zones côtières et littorales où les vagues interagissent fortement avec le fond, générant de la réfraction et du déferlement parmi d’autres processus.Une étude approfondie sur l’initiation du déferlement est développée. La validité du critère de déferlement conventionnel uc/c (rapport entre la vitesse orbitale horizontale à la crête et la vitesse de phase) est examinée numériquement. Cette étude nous mène à définir un nouveau critère cinématique basé sur le rapport entre la vitesse orbitale maximale ||um|| et c. Ce nouveau critère améliore la détection de l’initiation du déferlement, car la position d’où s’initie l’instabilité conduisant au déferlement est mieux capturée à partir de ||um||. La variabilité spatiale du champ de vagues en zone côtière est majoritairement étudiée à partir de modèles spectraux. La capacité d’un modèle à phase-résolue (type Boussinesq BT) à fournir des informations complémentaires pour les EMR est étudiée. Les modèles spectraux et BT produisent des résultats très différents en termes de hauteur de vagues et de puissance en présence d’une forte réfraction causée par la variabilité de la bathymétrie. On définit une méthode innovante pour extraire des informations liées aux vagues à partir d’images satellites, issues d’un radar à synthèse d’ouverture (SAR), et les comparer aux sorties des modèles. Nos résultats montrent des similitudes encourageantes entre le modèle BT et les données SARSince Marine Renewable Energy (MRE) systems are submitted to wind generated waves. Accurate wave characterization is required in the coastal and nearshore environment where the waves are strongly modified by their interaction with the sea bottom, inducing refraction and wave breaking among other processes.A comprehensive study regarding the wave breaking initiation process is developed. The conventional kinematic criterion uc/c (ratio between the horizontal orbital velocity at the crest and the phase velocity) validity is numerically investigated. Our study leads us to a new kinematic wave breaking criterion based on the ratio between the maximum fluid velocity ||um|| near the wave crest and c. This new criterion improves the detection of the breaking initiation, since ||um|| accurately captures the location of the fluid instability leading to breaking.The wave field spatial variability in coastal areas is mostly studied with spectral wave models. We explore the ability of a phase-resolving model (Boussinesq-type, BT) to provide additional wave information for MRE applications.Spectral and BT models lead to significantly different spatial wave height and power patterns in the presence of strong bottom-induced refraction. We define an innovative methodology to extract wave information from satellite Synthetic Aperture Radar (SAR) images for comparison with models’ outputs. Our results highlight encouraging similarities between the BT model and SAR data
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Fiorin, Rodrigo. "Controle para protótipos registrados com laser de femtosegundos." Universidade Tecnológica Federal do Paraná, 2013. http://repositorio.utfpr.edu.br/jspui/handle/1/640.
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Um dos problemas da fabricação de protótipos de dispositivos fotônicos esta no controle dos vários parâmetros de construção. A utilização do laser de femtosegundo para a fabricação de dispositivos óticos esta cada vez mais comum devido as suas qualidades e propriedades. Com a utilizaçãao das instruções de programação e do laser de femtosegundo foi possível a alteração do índice de refração dos substratos de sodocálcico e de sílica fundida, tornando viável o guiamento em estruturas planas. Com estas estruturas de guiamento devidamente produzidas e caracterizadas, permitiu construir um acoplador direcional, mostrando a possibilidade de controle para fabricação de diversos dispositivos.One of the problems of manufacturing prototypes of photonic devices that control the various parameters of construction. The utilization of the femtosecond laser for the fabrication of optical devices is increasingly common due to their qualities and properties. With the utilization of the instructions for programming and femtosecond laser was possible alteration of the index of refraction of the substrates of soda-lime and fused silica, making viable guiding in planar structures. With these guiding structures properly produced and characterized, it was possible to build a directional coupler, showing the possibility of control for the manufacture of various devices.
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Wu, Jiedi. "New Constraints on Fault-Zone Structure from Seismic Guided Waves." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/28873.
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The structure of fault zones (FZs) plays an important role in understanding fault mechanics, earthquake rupture and seismic hazards. Fault zone seismic guided waves (GW) carry important information about internal structure of the low-velocity fault damage zone. Numerical modeling of observed FZGWs has been used to construct models of FZ structure. However, the depth extent of the waveguide and the uniqueness of deep structure in the models have been debated. Elastic finite-difference synthetic seismograms were generated for FZ models that include an increase in seismic velocity with depth both inside and outside the FZ. Strong GWs were created from sources both in and out of the waveguide, in contrast with previous homogenous-FZ studies that required an in-fault source to create GW. This is because the frequency-dependent trapping efficiency of the waveguide changes with depth. The near-surface fault structure efficiently guides waves at lower frequencies than the deeper fault. Fault structure at seismogenic depth requires the analysis of data at higher frequencies than the GWs that dominate at the surface. Adapting a two-station technique from surface wave studies, dispersive differential group arrival times between two earthquakes can be used to solve for FZ structures between the earthquakes. This method was tested with synthetic data and shallow events recorded in the SAFOD borehole in the San Andreas Fault. A pair of deep earthquakes recorded in the SAFOD borehole indicate a ~150 m wide San Andreas Fault waveguide with >20% velocity contrast at 10-12 km depth. With additional earthquakes, the full FZ structure at seismogenic depth could be imaged. Subsurface FZ structure can also be derived from a surface source and receiver array analogous to a body-wave refraction survey. Synthetic seismograms for such source-receiver geometry were generated and verified that FZGWs are refracted by the increase in velocity with depth. Synthetic data from a surface array were successfully inverted to derive FZ structure in the subsurface. The new methods presented in this dissertation extend the potential of FZGWs to image deeper FZ structure than has been uniquely constrained in the past.Ph. D.
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Bordiga, Giovanni. "Homogenization of periodic lattice materials for wave propagation, localization, and bifurcation." Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/259019.
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The static and dynamic response of lattice materials is investigated to disclose and control the connection between microstructure and effective behavior. The analytical methods developed in the thesis aim at providing a new understanding of material instabilities and strain localizations as well as effective tools for controlling wave propagation in lattice structures.
The time-harmonic dynamics of arbitrary beam lattices, deforming flexurally and axially in a plane, is formulated analytically to analyze the influence of the mechanical parameters on the dispersion properties of the spectrum of Floquet-Bloch waves. Several forms of dynamic localizations are shown to occur for in-plane wave propagation of grid-like elastic lattices. It is demonstrated that lattices of rods, despite being `simple' structures, can exhibit a completely different channeled response depending on the characteristics of the forcing source (i.e. frequency and direction) as well as on the slenderness of the elastic links. It is also shown how the lattice parameters can be tuned to attain specific dispersion properties, such as flat bands and sharp Dirac cones.
In the research field of material instabilities, a key result proposed in this thesis is the development of both static and dynamic homogenization methods capable of accounting for second-order effects in the macroscopic response of prestressed lattices. These methods, the former based on an incremental strain-energy equivalence and the latter based on the asymptotic analysis of lattice waves, allow the identification of the incremental constitutive operator capturing the macroscopic incremental response of arbitrary lattice configurations. The homogenization framework has allowed the systematic analysis of prestress-induced phenomena on the incremental response of both the lattice structure and its `effective' elastic solid, which in turn has enabled the identification of the complex interplay between microstructure, prestress, loss of ellipticity (shear band formation) and short-wavelength bifurcations.
Potential new applications for the control of wave propagation are also shown to be possible by leveraging the inclusion of second-order terms in the incremental dynamics. In particular, the tunability of the prestress state in a square lattice structure has been exploited to obtain dynamic interfaces with designable transmission properties. The interface can be introduced in a material domain by selectively prestressing the desired set of ligaments and the prestress level can be tuned to achieve total reflection, negative refraction, and wave channeling.
The obtained results open new possibilities for the realization of engineered materials endowed with a desired constitutive response, as well as to enable the identification of novel dynamic material instabilities.
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Cassiano, Gabriela Freire. "Migração lateral da desembocadura do Rio Itapocú, Santa Catarina - Brasil: evolução morfológica e condicionantes físicas." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/21/21133/tde-23092009-102909/.
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Desembocaduras são ambientes bastante dinâmicos e sujeitos à complexa interação entre fatores estabilizadores e desestabilizadores. Dependendo dessa interação, desembocaduras podem apresentar a tendência de migração ao longo de barreiras arenosas. Um dos mecanismos mais eficientes de transporte de sedimento paralelo à costa, e conseqüentemente migração de canais, são as correntes longitudinais geradas pelas ondas se aproximando obliquamente a costa. A motivação do presente trabalho é entender o comportamento morfodinâmico do sistema de desembocadura do rio Itapocú, localizado no centro-norte de Santa Catarina, frente aos processos forçantes que atuam na sua migração ao longo da linha de costa. A morfologia dos pontais arenosos foi obtida a partir de levantamentos morfológicos com o uso de DGPS. Para analisar a refração de ondas foi utilizado o modelo numérico MIKE 21 - SW, sendo considerados como condições de contorno dados de ondas referentes ao ano de 2002 e dados de ondas previstos referentes ao período de coleta. Os dados de saída do modelo foram utilizados para estimar a deriva litorânea potencial na região. Os resultados morfológicos obtidos demonstraram uma migração da desembocadura para o norte durante o período analisado, sendo mais intenso durante o inverno e o verão. A refração de ondas incidentes do quadrante sul sofreram mais o fenômeno da refração e as ondas de leste apresentaram menor variação angular ao se aproximarem da costa. A deriva litorânea potencial anual para os dados de ondas de 2002 apresentou sentido norte-sul, com inversão de sentido durante o outono, sul-norte. A deriva litorânea potencial para os dados referentes ao período estudado apresentou sentido sul-norte, concordando com a migração observada. A deriva potencial em frente aos pontais apresentou direção para o norte durante todas as estações. Os dados de descarga fluvial não apresentaram influência na migração do canal, porém apresentaram uma relação com a largura do mesmo sazonalmente. Os dados de morfologia juntamente com os dados de deriva litorânea referentes às ondas de 2004/2005 mostraram claramente a migração do canal para o norte sendo a deriva a principal contribuinte para a migração da desembocadura.Inlets are highly dynamic environments subjected to the complex interaction between stabilizing and destabilizing factors. Depending on this interaction, inlets have a tendency to migrate along sandy barriers. One of the most effective mechanisms for transporting sediment alongshore and consequently controlling the migration of inlets, are currents generated by waves approaching the coast at an angle. The motivation of this study is to better understand the morphodynamic behavior of the Itapocú inlet, at the northern Santa Catarina coast. The morphology of the sandy spits that enclose the inlet was obtained from morphological surveys conducted with the use of DGPS. To analyze the wave refraction the numerical model MIKE 21 SW has been applied to the region. Boundary conditions have been set based on a one-year long database (2002) and predicted waves for the studied period. The model output has been used to estimate the potential longshore drift in the region. Results show the migration of the inlet to the north during the analyzed period, with higher migration rates during winter and summer. Waves inciding from the south are the most influenced by the refraction process, while the less refracted waves are those coming from the east The net longshore drift obtained when using the 2002 database is southwards, presenting slight inversions during the year. When using the predicted wave data for the studied period, the potential longshore drift is dominated by northward direction, in agreement with the observed inlet migration. The Itapocú river discharge does not present any relation with the observed inlet migration rates, although there seems to be a relation with the seasonal channel width variability. The surveyed morphological evolution is well related to the potential longshore drift, indicating that during the monitored period, the northwards inlet migration is being controlled by the wave generated longshore drift.
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Ahammod, Shamim. "Determination of Vp, Vs, Glacial Drift Thickness and Poisson’s Ratio at a Site in Jay County, Indiana, Using Seismic Refraction and Multichannel Analysis of Surface Wave (MASW) Analysis on a Common Data Set." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1451337593.
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Groters, Douglas J. "The temporal and spatial variability of the marine atmospheric boundary layer and its effect on electromagnetic propagation in and around the Greenland Sea marginal ice zone." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23422.
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Approved for public release; distribution is unlimitedVariability of the MABL and its effect on the electromagnetic (EM) refractive structure around the Greenland Sea marginal ice zone were examined. Rawinsonde profiles and surface observations collected from 3 ships during MIZEX-87(20 March-11 April) served as the data set. A program, developed to calculate the refractivity at each vertical level of the rawinsonde profiles, also identified the levels at which trapping, superrefraction and subrefraction occurred. Temporal studies showed that a higher incidence of anomalous refractive layers occurred during periods when the region was under the influence of high pressure. More than 50% of the time, trapping and super-refractive layers were attributed to development of a capping inversion just above the MABL during these periods. Spatial studies showed that the refractive structure varied relative to distance from the ice edge as did the depth of the MABL. An upward slope in refractive layer heights was observed from the ice toward the open water. Significant spatial inhomogeneity was observed over horizontal ranges of less than 100 km. This was attributed to both the large-scale synoptic forcing affecting the region and to variations in the surface fluxes of heat and moisture over the ice and over the water. A range-dependent ray trace model developed at the Naval Ocean Systems Center was used to show how the ray paths of EM waves vary with a changing refractive structures. Keywords: Air water interactions, Greenland Sea, Atmospheric refraction, Electromagnetic wave propagation, Heat flux, Sea ice. Theses. (EDC)
http://archive.org/details/temporalspatialv00grot
Lieutenant, United States Navy
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Brodie, Katherine L. "Observations of storm morphodynamics using Coastal Lidar and Radar Imaging System (CLARIS): Importance of wave refraction and dissipation over complex surf-zone morphology at a shoreline erosional hotspot." W&M ScholarWorks, 2010. https://scholarworks.wm.edu/etd/1539616582.
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Elevated water levels and large waves during storms cause beach erosion, overwash, and coastal flooding, particularly along barrier island coastlines. While predictions of storm tracks have greatly improved over the last decade, predictions of maximum water levels and variations in the extent of damage along a coastline need improvement. In particular, physics based models still cannot explain why some regions along a relatively straight coastline may experience significant erosion and overwash during a storm, while nearby locations remain seemingly unchanged. Correct predictions of both the timing of erosion and variations in the magnitude of erosion along the coast will be useful to both emergency managers and homeowners preparing for an approaching storm. Unfortunately, research on the impact of a storm to the beach has mainly been derived from "pre" and "post" storm surveys of beach topography and nearshore bathymetry during calm conditions. This has created a lack of data during storms from which to ground-truth model predictions and test hypotheses that explain variations in erosion along a coastline. We have developed Coastal Lidar and Radar Imaging System (CLARIS), a mobile system that combines a terrestrial scanning laser and an X-band marine radar system using precise motion and location information. CLARIS can operate during storms, measuring beach topography, nearshore bathymetry (from radar-derived wave speed measurements), surf-zone wave parameters, and maximum water levels remotely. In this dissertation, we present details on the development, design, and testing of CLARIS and then use CLARIS to observe a 10 km section of coastline in Kitty Hawk and Kill Devil Hills on the Outer Banks of North Carolina every 12 hours during a Nor'Easter (peak wave height in 8 m of water depth = 3.4 m). High decadal rates of shoreline change as well as heightened erosion during storms have previously been documented to occur within the field site. In addition, complex bathymetric features that traverse the surf-zone into the nearshore are present along the southern six kilometers of the field site. In addition to the CLARIS observations, we model wave propagation over the complex nearshore bathymetry for the same storm event. Data reveal that the complex nearshore bathymetry is mirrored by kilometer scale undulations in the shoreline, and that both morphologies persist during storms, contrary to common observations of shoreline and surf-zone linearization by large storm waves. We hypothesize that wave refraction over the complex nearshore bathymetry forces flow patterns which may enhance or stabilize the shoreline and surf-zone morphology during storms. In addition, our semi-daily surveys of the beach indicate that spatial and temporal patterns of erosion are strongly correlated to the steepness of the waves. Along more than half the study site, fifty percent or more of the erosion that occurred during the first 12 hours of the storm was recovered within 24 hours of the peak of the storm as waves remained large (>2.5 m), but transitioned to long period swell. In addition, spatial variations in the amount of beach volume change during the building portion of the storm were strongly correlated with observed wave dissipation within the inner surf zone, as opposed to predicted inundation elevations or alongshore variations in wave height.
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Cajko, Frantisek. "Nano-Focusing of Light: Electromagnetic Analysis and Simulation." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1249331504.
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Wang, Qiang. "Atmospheric refraction and propagation over curved surfaces." n.p, 1997. http://ethos.bl.uk/.
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Lee, Jong-Ha. "Study on shallow subsurface imaging using refraction waves." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/145349.
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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
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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.Includes bibliographical references (p. 302-306).
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 restricted to a finite, though large, horizontal domain, the hybrid-element method designed earlier for linearized problems is modified for the two-dimensional elliptic boundary-value problems at the second order. This thesis consists of two parts. In Part I, the incident waves are monochromatic. Application is first made to the special case of a a semi-circular peninsula (or a vertical cylinder on a cliff). Effects of the angle of incidence are examined for the free surface height along the cylinder. Numerical results for three examples involving radially varying depth are discussed. In Part II the second-order mild-slope approximation will be further extended for random waves with a broad frequency spectrum. A stochastic approach of Sclavounos is generalized for the prediction of spectral response in harbors. Focuss is on the low-frequency harbor resonance, so the third-order solution is unnecessary. Numerical examples are given for a simple square harbor of constant depth. Effects of harbor entrance are examined. Possible extensions and other applications are discussed.
by Meng-Yi Chen.
Ph.D.
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Xiradakis, Pavlos. "The refractive effects of laser propagation through the ocean and within the ocean." Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Dec/09Dec%5FXiradakis.pdf.
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Thesis (M.S. in Physics)--Naval Postgraduate School, December 2009.Thesis Advisor(s): Walters, Donald. Second Reader: Borden, Brett. "December 2009." Description based on title screen as viewed on January 27, 2010. Author(s) subject terms: Ocean waves, Laser Scattering, Absorption, Refraction. Includes bibliographical references (p. 55). Also available in print.
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Ozturk, Fahri. "Modelling and experimental study of millimetre wave refractive systems." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/modelling-and-experimentalstudy-of-millimetre-waverefractive-systems(0fd069b3-27bd-437b-ae09-0811972ff23c).html.
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Astronomical instruments dedicated to the study of Cosmic Microwave Background polarization are in need of optics with very low systematic effects such as beam shape and cross-polarization in an optical configuration. With the demand for millimetre wave larger focal planes comprising thousands of pixels, these systematic effects have to be minimal across the whole focal surface. In order to reach the instrument requirements such as resolution, cross-polarization and beam ellipticity, new optical configurations with well-understood components have to be studied. Refractive configurations are of great importance amongst the potential candidates. The aim is to bring the required technology to the same level of maturity that has been achieved with well-understood existing ones. This thesis is focused on the study of such optical components for the W-band spectral domain. Using optical modelling with various software packages, combined with the manufacture and accurate experimental characterization of some prototype components, a better understanding of their performance has been reached. To do so, several test set-ups have been developed. Thanks to these new results, full Radio-Frequency refractive systems can be more reliably conceived.
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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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Shu, Kun-Tien. "Multidimensional reflection and refraction of infinite amplitude stress waves in elastic solids." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/17680.
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Darbyshire, Paul Mark. "The analytical structure of wave mixing problems in nonlinear optical media." Thesis, King's College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244080.
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Stigloher, Johannes [Verfasser], and Christian [Akademischer Betreuer] Back. "Reflection and Refraction of Spin Waves / Johannes Stigloher ; Betreuer: Christian Back." Regensburg : Universitätsbibliothek Regensburg, 2018. http://d-nb.info/1173974873/34.
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Climente, Alarcón Alfonso. "Refractive devices for acoustical and flexural waves." Doctoral thesis, Editorial Universitat Politècnica de València, 2015. http://hdl.handle.net/10251/48536.
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The aim of this work has been the design and demonstration of refractive
devices, not only for acoustic waves, but also for flexural waves in thin plates.
Mathematically these problems have been treated by means of the multiple
scattering theory, because the geometries of the problems were mainly
circular and such theory is the best one in these cases. The multiple scattering
theory, previously stated, is here explained. Additionally, a multilayer
scattering theory for flexural waves is here introduced and successfully used
to numerically simulate their behavior. Therefore, this PhD thesis is divided
in two parts.
The first part is devoted to describe two acoustic refractive devices: a
gradient index lens and an omnidirectional broadband acoustic absorber, or
“acoustic black hole”. Both are based on sonic crystals consisting of of rigid
cylinders immersed in a fluid background. As the homogenization method
states, the desired refractive index can be obtained by tailoring the radii
of the cylinders. Thereafter, numerical simulations and measurements were
conducted to test the behavior of each device. For this purpose, two specific
measuring systems were developed: the two-dimensional chamber and the
impedance chamber. Both are here explained in detail.
The second part describes the design of refractive devices for flexural
waves. Instead of using “platonic crystals”, we made use of the peculiar dispersion
relationship of flexural waves. As the equation states, the wave speed
is modified not only by the elastic properties of the plate, but also from its
thickness. Using the latest approach a set of numerical simulations of known
circularly symmetrical gradient index lenses have been performed. Additionally, an omnidirectional broadband insulating device for flexural waves has
been designed. It consist of a well-like thickness profile in an annular region
of the plate, that mimics the combination of an attractive and repulsive potentials.
The waves are focused at its bottom and dissipated by means of
an absorptive layer placed on top. Numerical simulations are here presented
and discussed.
Finally, we present an in-plane flexural resonator, consisting of a hole in
a thin plate traversed by a beam. Here, a closed form of the transfer matrix
is obtained by coupling the Kirchhoff-Love and the Euler-Bernoulli motion
equations. Numerical simulations, tested against a commercial finite element
simulator, prove its efficiencyClimente Alarcón, A. (2015). Refractive devices for acoustical and flexural waves [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48536
TESIS
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Azadeh, Mohammad. "Reflection and Refraction of Light from Nonlinear Boundaries." PDXScholar, 1994. https://pdxscholar.library.pdx.edu/open_access_etds/4715.
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This thesis deals with the topic of reflection and refraction of light from the boundary of nonlinear materials in general, and saturating amplifiers in particular. We first study some of the basic properties of the light waves in nonlinear materials. We then develop a general formalism to model the reflection and refraction of light with an arbitrary angle of incidence from the boundary of a nonlinear medium. This general formalism is then applied to the case of reflection and refraction from the boundary of linear dielectrics. It will be shown that in this limit, it reduces to the well known Fresnel and Snell's formulas. We also study the interface of a saturating amplifier. The wave equation we use for this purpose is approximate, in the sense that it assumes the amplitude of the wave does not vary significantly in a distance of a wave length. The limits and implications of this approximation are also investigated. We derive expressions for electric field and intensity reflection and transmission coefficients for such materials. In doing so, we make sure that the above mentioned approximation is not violated. These results are compared with the case of reflection and refraction from the interface of a linear dielectric.
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Harutyunyan, Satenik. "Magnetic and Elastic Interactions at Cracks and Interfaces in Ferromagnetic Materials." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/29209.
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In addition to being useful for some nondestructive evaluation techniques, interactions between magnetic fields and defects in solids may also alter material properties. To explore this possibility, Maxwellâ s equations were coupled with a continuum mechanics model for elastic strain to formulate analytical expressions for the interaction of a magnetic field with several crack geometries. The influence of crack velocity and a realistic (nonlinear) magnetic susceptibility were included into a model of this type for the first time and shown to introduce unexpected trends in the magneto-elastic stress intensity. Singularities magneto-elastic stresses appear at different combinations of magnetic field strength and crack velocity, and the stresses at the crack tip switch sign.
In a related study, the interaction of an alternating magnetic field with elastic stress through was explored through a coupling effect known as magneto-acoustic resonance. A model for the phenomena, in which magnetic waves excite elastic waves and vice versa, was formulated and used to explore the spin (magnon) and anti-plane elastic (phonon) interactions in piecewise homogeneous ferromagnetic spaces with two different sets of properties. The model suggests some combinations of magnetic field and frequency can produce a new kind of wave to appear. These new waves, which we call Accompanying Surface Magnetoelastic (ASM) waves, are localized at the interface between the two ferromagnetic media and they accompany reflection and transmission waves. It is shown that the amplitudes of the reflected, transmitted, and ASM waves depend strongly on magnetic field strength, frequency, and the angle of the incident wave, as well as on the physical properties of ferromagnetic media.Ph. D.
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Dougherty, Sara L. "Development of a 3-D upper crustal velocity model for the Goldstream Valley, central Alaska." Thesis, Boston College, 2008. http://hdl.handle.net/2345/352.
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The uppermost crustal velocity structure of the Goldstream Valley, central Alaska is investigated using a series of five explosions that were detonated in schist bedrock and recorded at >120 local stations to develop 1-D and 3-D models of the upper crust. Simple refraction analyses reveal that both P- and S-wave arrival times are azimuth dependent, with the fastest velocities in the southeast and northeast directions. The Swave velocity structure of the upper crust is also determined through multiple filter analysis and a damped, least squares inversion of 0.2-2 sec period Rg waves. The shear wave velocity model from the surface-wave analysis is combined with the refraction analysis results to develop 1-D P- and S-wave models to a depth of 2 km. In order to better constrain P- and S-wave velocity variations both laterally and with depth throughout the Goldstream Valley, 3-D velocity models are produced using a numerical simulation modelThesis (MS) — Boston College, 2008
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Geology and Geophysics
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Korampally, Venumadhav. "A novel ultra-low refractive index nanoporous dielectric based aqueous core waveguide system." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4878.
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Thesis (Ph.D.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 10, 2009) Includes bibliographical references.
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Hammond, Troy Douglas. "Atom interferometry--dispersive index of refraction and rotation induced phase shifts for matter-waves." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/46044.
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Rose, Alec Daniel. "All-angle negative refraction of photonic and polaritonic waves in three-dimensionally periodic structures." Thesis, Boston College, 2009. http://hdl.handle.net/2345/685.
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Thesis advisor: Krzysztof KempaThough nature provides a plethora of materials to work with, their properties are very much restricted, forcing severe limitations on the devices that are built from them. A huge portion of current technology stands to be significantly advanced and even revolutionized by the emergence of a new class of “configurable” materials. This class, generally referred to as metamaterials, has become more feasible than ever due to advancements in nanotechnology and fabrication techniques. Notable among nature’s limitations is an ever-positive index of refraction. This barrier has only recently been broken, and the known paths to negative refraction are few and limited. This paper introduces two distinct three-dimensional crystals capable of all-angle negative refraction. One uses the familiar photonic band, while the other is the first of its kind to rely on polaritonic waves. Their mode structures are examined and a set of parameters are chosen at which a negative effective index of refraction can be harnessed for unrestricted sub-wavelength lensing, demonstrated via numerical simulation. This work is expected to enable experimental observation of polaritonic negative refraction and sub-wavelength lensing at microwave frequencies
Thesis (BS) — Boston College, 2009
Submitted to: Boston College. College of Arts and Sciences
Discipline: College Honors Program
Discipline: Physics
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Small, Richard Justin Orford. "The refraction, shoaling and structure of non-linear internal waves at a continental shelf margin." Thesis, University of Southampton, 2000. https://eprints.soton.ac.uk/42171/.
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Observations of internal waves near the Continental shelf-edge are generally ascribed to generation by oscillating tidal flow over the local bathymetry, in the presence of a stratified water column, giving rise to the internal tide. In this thesis observations are presented which demonstrate that internal waves at the Malin shelf-edge comprise of both the locally generated internal tide, and waves from a distant source. This thesis focuses on processes affecting the latter phenomenon at the continental slope. A comprehensive collection of in-situ and satellite data from the Shelf Edge Study (SES) and the Shelf Edge Study Acoustic Measurement Experiment (SESAME) from August-September 1995 and August 1996 is used to describe the internal wave characteristics. During a period of neap tides a set of internal solitary waves was tracked across the continental slope every tidal cycle for three days. The measurements indicate that the waves evolved from an initial drop in the thermocline, and were not significantly refracted as they crossed the slope, due to the small change in phase speed across the slope, from around 0.8 to 0.6 ms"1. The internal waves depressed the thermocline by between 30 and 50 m and had particle speeds of 0.4 to 0.8 ms"1. The structure of the internal waves is examined and compared to weakly non-linear theory, and it is found that first order theory adequately describes the waves over the slope but that a second order theory is required to model the internal waves on the shelf. A non-linear refraction model is developed to simulate the internal wave propagation and evolution. Initial tests of the model for the refraction and shoaling of interfacial solitary waves propagating in simple environments show agreement with analytical results. The model is then extended to simulate the refraction and transformation of the internal waves observed during SES, using realistic density stratification and bathymetry. When realistic initial conditions derived from measurements are used, it is found that the model reproduces the phase speeds and refraction characteristics very well, but overestimates wave amplitudes at the shelf-edge and the shelf. Analysis of the simulated internal waves suggests that the waves would become unstable at these amplitudes and would in reality be damped. In fact it is shown from the observations that instabilities in the wave are likely to occur due to the high shear and high particle speed relative to the phase speed, and an example of possible breaking internal waves is illustrated. The likely regions of non-linear internal wave dissipation are considered in the Discussion, together with the local generation of internal tides, and possible source regions for the distant internal waves.
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Kadlec, Radim. "Analýza elektromagnetické vlny na rozhraní heterogenního prostředí." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-233658.
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The proposed dissertation thesis contains an analysis of conditions on the boundary between layers having varied electromagnetic properties. The research is performed using consistent theoretical derivation of analytical formulas, and the underlying problem is considered also in view of multiple boundaries including the effect of the propagation of electromagnetic waves having different instantaneous speed. The author presents a survey and formulation of the basic characteristics of methods used for electromagnetic wave propagation analysis; in this respect, special emphasis is placed on radial models. The processing of the topic involved the designing and verification (using a set of different, layered planar materials) of algorithms to analyze the electromagnetic field components. The algorithm was assembled to enable simple evaluation of all components of the electromagnetic field in relation to the speed of the wave propagation in a heterogeneous environment. The proposed algorithms are compared by means of different numerical methods for the modelling of electromagnetic waves on the boundary between materials; moreover, electromagnetic field components in common points of the model were also subject to comparison. When in conjunction with tools facilitating the analysis of material response to the source of a continuous signal, the algorithms constitute a supplementary instrument for the design of a layered material. Such design enables the realization of, for example, recoilless plane, recoilless transition between different types of environment, and filters for both optical and radio frequencies.
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Hwang, Chan Joo 1963. "Transmission of quartz capillary optical fibers as a function of diameter and refractive index fluid." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276943.
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Recent experiments with optical fibers have reached a remarkable development for optical communication spectroscopy as well as a medical technology. Hollow optical fibers are required for optical communications. The measurement of the transmission of light through fibers can provide information about the fiber quality and about the far-field energy which radiates from the fiber end. We used five flexible hollow fused quartz fibers to study laser beam propagation down the fiber axis. Five different refractive index fluids were prepared and inserted into the fiber core to measure the transmitted intensity as a function of core property. The plots of the normalized, relative transmitted intensity measured as a function of the beam insertion point show the dependence of the transmitted intensity as a function of fiber diameter and refractive index fluid.
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Silva, Sinhara Rishi Malinda. "Manipulating Electromagnetic waves with enhanced functionalities using Nonlinear and Chiral Metamaterials." Scholar Commons, 2017. https://scholarcommons.usf.edu/etd/7443.
Full textAbstract:
Metamaterials are artificial structures, which periodically arranged to exhibit fascinating electromagnetic properties, not existing in nature. A great deal of research in the field of metamaterial was conducted in a linear regime, where the electromagnetic responses are independent of the external electric or magnetic fields. Unfortunately, in linear regime the desired properties of metamaterials have only been achieved within a narrow bandwidth, around a fixed frequency. Therefore, nonlinearity is introduced into metamaterials by merging meta-atoms with well-known nonlinear materials. Nonlinear metamaterials are exploited in this dissertation to introduce and develop applications in microwave frequency with broadband responses. The nonlinearity was achieved via embedding varactor diode on to split ring resonator (SRR) design, which demonstrates tunability in resonance frequency and phase of the transmission signal. SRR exhibits power and frequency dependent broadband tunability and it is realized for external electro-magnetic signals. More importantly, the nonlinear SRR shows bi-stability with distinct transmission levels, where the transition between bi-states is controlled by the impulses of pump signal and it can be used as a switching device in microwave regime. In order to increase its functionality in other frequencies, a new design, double split ring resonator (DSRR) is introduced with two rings, which has two distinct resonance frequencies. The double split ring resonator also demonstrate similar behavior as the SRR but it is broadband. Furthermore, by designing the structure such that the inner ring has a frequency twice as outer ring resonance frequency; we observed the enhancement of harmonic generation. We exhibit enhancement in second harmonic generation and methods that can use to increase the harmonic signal power. Arranging the unit cells in an array and particular orientation further increases the harmonic power. In addition, we show that using a back plate to create a cavity will help to increase harmonic power. Furthermore, we have demonstrated that applying an external DC voltage can be used to tune resonance frequency as well as phase of the signal. Exploring these ideas in THz frequency regime is also important. So simulation results were obtained with advanced designs to achieve non-linearity in terahertz frequency regime to realize tunability, hysteresis and bi-stable states.
A negative refractive index can be realized in metamaterials consisting of strong magnetic and electric resonators with responses at the same frequency band. However, high loss and narrow bandwidth resulting from strong resonances have impeded negative index optical components and devices from reaching expected functionalities (e.g. perfect lens). Here, we demonstrate experimentally and numerically that a 2D helical chiral metamaterial exhibits broadband negative refractive index with extremely low loss. With Drude-like dispersion, its permittivity leads to zero-index, and broadband chirality further brings the index to negative values for left-handed circularly polarized light in the entire range below the plasma frequency. Non-resonant architecture results in very low loss (<2% per layer) and an extremely high Figure-of-merit (>90).
Tunable THz metamaterials has shown great potential to solve the material challenge due to the so-called “THz gap”. However, the tunable mechanism of current designs relies on using semiconductors insertions, which inevitably results in high Ohmic loss, and thereby significantly degrades the performance of metamaterials. In this work, we demonstrate a novel tunable mechanism based on polymeric microactuators. Our metamaterials are fabricated on the surface of patterned pillar array of flexible polymers embedded with magnetic nanoparticles. The transmission spectrum of the metamaterial can be tuned as the pillars are mechanically deformed though applied magnetic field. We observed and measured several type of deformation including bending, twisting and compressing when the applied magnetic field is polarized along different direction with respected to the axis of the magnetic particles. Compared to previous semiconductor based tunable mechanism, our structure has shown much lower loss. We demonstrate using simulations and experimentally that with an external magnetic field, we can achieve phase modulation using magnetic polymeric micro-actuators.