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Li, Tsan Hang. "Theoretical study of negative refractive electromagnetic and acoustic media /". View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202004%20LIT.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 124-126). Also available in electronic version. Access restricted to campus users.
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Lehman, Joseph Christian. "Sphero-cylindrical Refraction with Spherical Lenses". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587510615809807.
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Beaman, Heather. "Reflection-Refraction". VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1888.
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I find my inspiration by looking at the world around me. I take snapshots, compose photographs, and collect physical objects from my surroundings. I interpret these materials by layering printmaking, mixed media, and alternative photographic processes. I use the simplification of the human form when developing the composition. As my work takes shape, I present a universal person placed in a situational narrative. Layering the human figure with my travels and experiences creates a pause or an intimate moment that the viewer shares with the art work.
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Hartwig, Andreas. "The influence of optics, peripheral refraction and posture on refractive error development". Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/the-influence-of-optics-peripheral-refraction-and-posture-on-refractive-error-development(f0382767-3194-4631-8cab-d473d64900bd).html.
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The aim of the present project was to analyse the link between peripheral posture, optics, optics and refractive error progression. Preliminary studies were conducted to ensure that peripheral aberrometry is valid for further analysis. The repeatability of the IRX-3 for peripheral aberrometry was asgood as for central measurements and the recalculation of elliptical pupils did not seem to be necessary for measurements up to 20 degrees eccentricity. Higher order aberration measurements werecomparable to other studies. Eye and head movements as well as working distance did not differ significantly between myopes and non-myopes. However, there was some evidence, that forward bending of the head during reading increases in association with higher refractive error progression rates. The link between central higher order aberrations and refractive error development was analysed by comparing higher order aberrations between isometropes and anisometropes. This analysisdid not show any significant association of higher order aberrations on the development, as no major differences were found between the two groups. For central vision, changes in biometric parameters during accommodation were analysed. It was found that biometric parameters change similarly in myopes and non-myopes. Peripheral accommodation was found to differ between myopes and emmetropes indicating that there might be an influence of peripheral refraction on myopisation. However, associationbetween peripheral refraction or peripheral aberrations and refractive error progression were not significant. The reason for this observation might be the low refractive error progression (0.04± 0.29 D in myopes and -0.12 ± 0.38 D in emmetropes) during one year in the study population.
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Rodgman, D. N. "Refraction in volume graphics". Thesis, Swansea University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638701.
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In this study, we have proposed several methods for sampling field-based representations of refraction attributes, and analysed these methods in terms of the quality and accuracy of the results produced. We have identified two types of anomalies that affect the correctness of some methods, and found that the best of these methods is capable of producing images of equal quality to surface-graphics techniques. Our approach produces good results with functionally defined models, and discrete volumetric data, in the absence of noise. We have also established that this approach allows the modelling and rendering of types of objects that cannot be represented in surface graphics (e.g. objects with a continuous, non-uniform refractive index). Where noise is present in volumetric data, it significantly affects the correctness of rendering refraction, usually resulting in images of poor quality. A number of methods for smoothing have been examined, including low-pass filtering and various types of nonlinear diffusion. We have shown that regularised anisotropic nonlinear diffusion is a powerful and effective method for processing noisy volumetric data sets in order to improve the quality of images featuring refraction. High quality images featuring refraction often take a long time to render. We have presented the design and implementation of a parallel, open source volume graphics rendered which supports refraction and multi-volume scenes. A large number of issues related to a efficient operation of a parallel renderer have been examined, and a high-performance, scaleable parallel renderer has been developed, which performs efficiently on both networked clusters, and shared memory multi-processor machines.
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Turpin, Avilés Alejandro. "Conical refraction: fundamentals and applications". Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/322801.
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El fenomen de la refracció cònica en cristalls biaxials és conegut des del 1832, quan William Hamilton va predir matemàticament que un feix de llum idealment col·limat travessant un cristall biaxial paral·lelament a un dels eixos òptics del cristall, es refracta com un conus asimètric i emergeix del cristall com un cilindre de llum, la secció transversal del qual forma un anell de llum. La posterior observació del fenomen només uns mesos després per part de Humphrey Lloyd, va convertir la refracció cònica en un dels primers fenòmens observats després de la seva predicció, així com va donar el triomf de la teoria ondulatòria de la llum sobre la teoria corpuscular. A finals dels anys 70 del segle passat, Belsky i Khapalyuk van presentar la formulació difractiva del fenomen per a feixos amb simetria cil·líndrica, la qual va estar re-formulada per Berry durant la passada dècada.
En aquesta tesi, explorem la refracció cònica d’una manera àmplia, alhora que profunda. Primerament, demostrem que, després d’un cert desenvolupament, la teoria de Berry pot ser utilitzada per estudiar la propagació de qualsevol feix, independentment del seu estat de polarització o perfil transversal, tant al llarg de l’eix òptic com a fora del mateix i per a qualsevol nombre de cristalls biaxials en cascada. Aquesta teoria difractiva també és utilitzada per a demostrar que, només ajustant la raó entre el radi de l’anell de refracció cònica i l’amplada del feix d’entrada, es poden aconseguir feixos molt dispars i que donen lloc a singularitats òptiques i vector beams molt interessants. Seguidament, demostrem que la refracció cònica pot ser entesa com la transformació de les ones incidents en dues ones còniques, la interferència de les quals dóna lloc als típics anells dobles al pla focal. A més a més, proposem una teoria alternativa que permet calcular el patró final després del cristall de qualsevol tipus de feix d’entrada, només tenint en compte refracció de vectors d’ona incidents i ho apliquem al cas particular de tenir múltiples cristalls en cascada. En particular, demostrem un sistema de multiplexació i de-multiplexació de senyals monocromàtiques per a aplicacions en les comunicacions òptiques en espai lliure basat en tres cristalls biaxials en cascada.
Tot l’estudi anterior serveix per a la realització de noves propostes per a trampes òptiques per a àtoms neutres i partícules absorbents. En aquest sentit, demostrem tant teòricament com experimental que les estructures fosques que es generen amb refracció cònica són de gran utilitat per a atrapar àtoms ultra-freds, en col·laboració amb el grup del Prof. Gerhard Birkl a la Technische Universität Darmstadt. Tanmateix, utilitzem la particular distribució de polarització dels anells de refracció cònica per a construir una ampolla òptica re-configurable en temps real i que permet carregar i descarregar partícules macroscòpiques absorbents.
També ens endinsem en el món de l’òptica quàntica a través de l’estudi de la generació de segon harmònic tant de tipus I com de tipus II a partir d’un feix de refracció cònica i demostrem que les propietats del feix de segon harmònic són pràcticament iguals a les del feix fonamental. Finalment, fem una proposta teòrica per a dissenyar un dispositiu capaç de detectar entrellaçament quàntic en moment lineal entre fotons bessons on l’element clau és un cristall biaxial.The conical refraction phenomenon in biaxial crystals is known since 1832 when William Hamilton predicted mathematically that and ideally collimated light beam passing through a biaxial crystal parallel to one of the crystal optic axes would refract as an slanted cone within the crystal and emerge as a hollow light cylinder, whose transverse profiles forms a light ring. The afterwards observation of the phenomenon by Humphrey Lloyd made the conical refraction phenomenon to become one of the first phenomenon that were observed after their prediction, as well as the one who tip the scales towards the wave theory of light against the corpuscular theory. In the late 70s, Belsky and Khapalyuk presented the diffractive formulation of the phenomenon for cylindrically symmetric beams, this formalism being reformulated by Berry during the last decade. In this thesis, we explore conical refraction in deep and present some applications of this phenomenon. Firstly, we show that, after some theoretical development, Berry’s formalism can be used to predict the transformation of beams along any propagation direction, no matter the state of polarization or transverse profile they posses and the number of crystals in cascade used. The diffractive theory is also used to demonstrate that, by simply tuning the ratio between the conical refraction ring radius and the waist radius of the input beam, a rich variety of light beams and optical singularities can be generated. Then, we show that conical refraction can be understood as the transformation of the input plane waves into a pair of conical waves whose interference leads to the characteristic concentric bright rings at the focal plane. Additionally, we propose an alternative theory that allows calculating the resulting pattern beyond the biaxial crystal for any input light beam by considering splitting of input wave-vectors and we apply this simple formalism to predict the resulting pattern for a cascade of crystals. In particular, we demonstrate a multiplexing and de-multiplexing system for monochromatic signals for free space optical communications applications based on three biaxial crystals in cascade. The latter results are used to propose and realize different optical architectures for optical trapping of both ultra-cold atoms and absorbing particles. In this sense, show both theoretically and experimentally that dark optical geometries generated with conical refraction are of complete usefulness to trap Bose–Einstein condensates, in collaboration with the group of Prof. Gerhard Birkl at the Technische Universität Darmstadt. Additionally, we use the particular polarization distribution along the conical refraction rings to build a reconfigurable optical bottle capable to load and unload macroscopic absorbing particles at wish, in collaboration with the group of Prof. Wieslaw Krolikowski at the Australian National University. We also explore the world of quantum optics throughout the analysis of both type I and type II second harmonic generation of a conically refracted beam and we demonstrate that the second harmonic beam keeps most of the properties of the fundamental harmonic beam. Finally, we present a theoretical proposal to design an optical device able to detect linear momentum entanglement between twin photons, a biaxial crystal being the key element of the device.
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Trendall, Chris. "Ray tracing refraction in hardware". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0016/MQ49742.pdf.
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Valle, G. Raul del. "Model parameterization in refraction seismology". Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66057.
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Wu, Qi. "Negative refraction by photonic nanostructures". Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3337163.
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Martos, Justin Riley. "Fault Mapping with the Refraction Microtremor and Seismic Refraction Methods along the Los Osos Fault Zone". DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/873.
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The presence of active fault traces in proximity to any new infrastructure project is a major concern for the design process. The relative displacements that can be experienced in surface fault rupture during a seismic event must be either entirely avoided or mitigated in some way. Blind faults present a significant challenge to engineers attempting to identify these hazards. Current standards of practice employed to locate these features are time consuming and costly. This work investigates the geophysical methods of refraction microtremor (ReMi) and seismic refraction with regard to their applicability in this task. By imaging a distinct lateral variation in the shear wave velocity (Vs) profile across a short horizontal distance, these methods may provide a means of constraining traditional investigation techniques to a more focused area. The ReMi method is still very new, but holds key advantages over other geophysical methods in its ease of application and ability to achieve good results in highly urban settings. It is one of the few geophysical techniques that does not suffer in the presence of high amplitude ambient vibrations. The seismic refraction method is here applied in an attempt to corroborate data obtained through the ReMi analysis procedure. Sensitivity, precision parametric studies are carried out in order to learn how to best apply the ReMi method. Both tests are then applied at a previously trenched fault trace to determine whether the data can be matched to the subsurface information. Finally, the methods are deployed at a location with an inferred fault trace where little to nothing is known about the subsurface. The precision study indicates a coefficient of variation for the ReMi method on the order of 7%. At the known fault trace both methods generally agree qualitatively with available subsurface data and each other. Using the ReMi method, a marked shift is observed in the Vs profile laterally across the fault trace. In the case of the inferred fault trace, the same type of lateral variation in the Vs profile is observed using the ReMi method. The seismic refraction at this site does not agree with the ReMi data, but seems reasonable given the visible geomorphology. Receiver arrays placed in close proximity to the inferred fault trace recorded erratic signals during seismic refraction testing, and displayed abnormal response modes after transforming the ReMi data to frequency-slowness space. These anomalies may possibly be attributed to the presence of abnormal subsurface structural geometry indicative of faulting.
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Oxburgh, Stephen B. "Transforming transformation optics via generalised refraction". Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7539/.
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Generalised refraction is a topic which has, thus far, garnered far less attention than it deserves. The purpose of this thesis is to highlight the potential that generalised refraction has to offer with regards to imaging and its application to designing new passive optical devices. Specifically in this thesis we will explore two types of gener- alised refraction which takes place across a planar interface: refraction by generalised confocal lenslet arrays (gCLAs), and refraction by ray-rotation sheets. We will show that the corresponding laws of refraction for these interfaces produce, in general, light-ray fields with non-zero curl, and as such do not have a corresponding outgoing waveform. We will then show that gCLAs perform integral, geometrical imaging, and that this enables them to be considered as approximate realisations of metric tensor interfaces. The concept of piecewise transformation optics will be introduced and we will show that it is possible to use gCLAs along with other optical elements such as lenses to design simple piecewise transformation-optics devices such as invisibility cloaks and insulation windows. Finally, we shall show that ray-rotation sheets can be interpreted as performing geometrical imaging into complex space, and that as a consequence, ray-rotation sheets and gCLAs may in fact be more closely related than first realised. We conclude with a summary of potential future projects which lead naturally from the results of this thesis.
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Dirdal, Christopher Andrew. "Negative Refraction in Non-Magnetic Metamaterials". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19337.
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The discoveries and subsequent developments within the field of metamaterials have opened up for novel light-matter interactions towards the engineering of light behavior. The astonishing phenomenon of negative refraction remains challenging to realize for visible frequencies, and non-magnetic gain metamaterials have been proposed towards this end. This thesis pursues this idea by presenting a conceptual framework for which to understand the requirements and possibilities emerging from the causal behavior of the dielectric response. This results in clear and concrete instructions on how the dielectric response must be designed towards negative refraction. These are offered in terms of a novel perspective employing zero- and pole placements in rational functions and analysis of the dielectric function in its complex plane. A number of negative index systems are evaluated including two component media and low gain negative index media. Negative index concepts are introduced to the Electromagnetically Induced Transparency system. A strategy towards design and realization of arbitrary dielectric responses in terms of Krein and Nudel'man causal extrapolation is also presented.
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Cary, Peter William. "Waveform inversion of marine refraction data". Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330175.
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Davison, M. "Refraction effects in precise surveying measurements". Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378767.
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Sozou, Peter Demetris. "Studies in optical flow and refraction". Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320423.
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Zhang, Jie. "Nonlinear refraction and reflection traveltime tomography". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10717.
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Buriak, I. A. "Microware applications of negative-refraction metamaterials". Thesis, Sumy State University, 2016. http://essuir.sumdu.edu.ua/handle/123456789/46869.
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Metamaterials make a wide class of artificial composites,
characterized by features that are hardly achievable technologically and
unattainable in nature materials. These features, such as negative group
velocity of EM wave and thus refraction index, are obtained due to
simultaneously negative effective permittivity and permeability. The major
classes of these composites are single negative materials (SNG), double
negative materials (DNG), and electronic bandgap materials (EBG) or
photonic crystals [1]. Permittivity and permeability depend on frequency,
so there are RF MTMs (including microwave), terahertz, optical etc.
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Salomon, Felix. "Refraction index modification by synchrotron radiation". [S.l. : s.n.], 2007. http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-44255.
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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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Dube, Zack. "Computational Reconstruction of the Physical Eye Using a New Gradient Index of Refraction Model". Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34791.
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This thesis proposes and tests an individually customizable model of the human crystalline lens. This model will be crucial in developing both research on the human eye and driving diagnostic tools to help plan and treat optical issues, such as those requiring refractive surgery.
This thesis attempts to meet two goals: first, it will determine whether this new lens model can reproduce the major aberrations of real human eyes using a computational framework. Second, it will use clinical information to measure how well this model is able to predict post-operation results in refractive surgery, attempting to meet clinical standards of error.
The model of the crystalline lens proposed within this thesis is shown to be valid, as it is able to both reproduce individual patient's optical information, and correctly predicts the optical results of a refractive surgery of an individual human eye within clinical standards of error.
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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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Wang, Qiang. "Atmospheric refraction and propagation over curved surfaces". Thesis, Open University, 1998. http://oro.open.ac.uk/44453/.
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This thesis presents theoretical and experimental investigations of atmospheric refraction and diffraction of sound over curved surfaces. The main contributions of this work are as follows: The development of an alternative method for calculating the influence of wind on sound propagation in the presence of a ground of finite impedance. The development of numerical models to calculate sound propagation due to monopole and dipole sources over cylindrical or spherical convex and concave surfaces of finite impedance. Laboratory measurements of sound propagation over curved surfaces and comparisons with the proposed theoretical and numerical models. The exploration of the theory for surface wave contributions in an upward refracting atmosphere in the light of obtained experimental data and observation of the surface waves above a convex surface. Experimental and theoretical investigations of the effectiveness of a barrier in the presence of sound speed gradients.
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Etminan, Arvin. "Index of Refraction : Transparent Medium in 3D". Thesis, Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-79111.
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Denna uppsats är en beskrivning på utvecklingen av detta projekt, där fokuset handlar om teorier och fakta på ljus i samband med transparanta medium. Målet med projektet var att testa och experimentera inom det nämna området fast i 3D grafik, där resultatet är renderade bilder med analys, diskussioner och slutsatser.This essay describes the development of this project, where the focus is on theories and facts about light and transparent mediums. The aim of the project was to test and experiment the mentioned area in 3D graphics, where the results are single rendered images with analysis, discussions and conclusions.
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Wang, Qiang. "Atmospheric refraction and propagation over curved surfaces". n.p, 1997. http://ethos.bl.uk/.
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Otero, Molins Carles. "Lens-based technologies to study accommodation and refraction". Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/461452.
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A visual stimulus can be presented in free space or through lens-based systems. Interestingly, it has been reported many times in the past that some subjects have poorer accommodative responses when optically stimulated, with no aparent reason. However, this limitation has not precluded the use of lens-based systems in ophthalmic devices, virtual reality displays or research setups, probably because it is outweighed by some advantages such as the computer-control of the focal plane of the stimuli. Under this general context, the objective of this thesis is to apply lens-based technologies (from computer-controlled electró-optical lenses to Badal Systems) to study accommodation and refraction.
The methodology of this thesis is structured in 6 studies. The first three studies investigate the response of the accommodative system when optically-stimulated with a Badal optometer. The remaining 3 studies take advantage of electro-optical varifocal systems to investigate new methodologies related to the automated subjective refraction and the accommodative facility test. Concretely, the fourth study is a clinical validation of a new automated refraction algorithm and is the only study thatworks specifically on eye¿s refraction. The fifth and sixth studies use an electro-optical liquid lens to present a repeated step-like stimulus at different accommodative distances. The fifth study validates a new accommodative facility test that integrates both the far and near accommodative facility testwith random changes of accommodative stimulus and, the sixth study explores how the predictability of a stimulus affects the accommodation dynamics.
The results of the first three studies show that previously reported differences in accommodative response when using lens-based methods compared to free space viewing may be explained by the effect of other factors such as the refractive error or field of view rather than the method to stimulate accommodation. It is also shown that the most accurate accommodative responses are obtained for fields between 8º and 10º which suggests that there may be an optimum peripheral retinal image size for accommodation stimulation. Also, it is shown that the only factor that in isolation significantly affects the accuracy of the accommodative responses is the type of refractive error. And finally, it is also shown that the accuracy of the accommodation response generally improves with a 2-dimensional stimulus with apparent depth cues and simulated out-of-focus blur in a relatively large field of view. Even though these conditions may not be adequate for all individuals, they can be used to improve the overall visual comfort in those virtual reality systems that use a varifocal optical system to change the focal plane of a 2-dimensional surface or visual simulators.
The results of the study 4 show the first implementation of a potential novel method of performing non1cycloplegic subjective refraction in adults without clinician suport. Although this method has some limitations thatwarrant further research and it should be tested in a wider population in terms of age4 refraction and different ocular conditions4 it is precise and more accurate than objective refraction methods and it has the potential to be incorporated in novel lens1based technologies to improve primary eye care services in developing countries.
And finally, the last two studies showed also the first implementation of a new accommodative facility test that integrates both the far and near accommodative facility testwith random changes of accommodative stimulus. This new methodology is a faster test than performing both the near and far accommodative tests and it provides more information than conventional accommodative facility tests. Additionally these two studies showed that the prediction operator does not exist in accommodation and the unpredictability of the stimulus does not affect the accommodation dynamics.Un estímul visual es pot presentar a l'espai lliure o a través de sistemes basats en lents. Curiosament, en el passat s'ha reportat moltes vegades que alguns subjectes acomoden de forma més pobre quan aquesta és estimulada per mitjans òptics. Tanmateix, aquesta limitació no ha impedit l'ús de sistemes basats en lents en dispositius oftàlmics, sistemes de realitat virtual o muntatges òptics de recerca, probablement perquè es compensen les limitacions amb alguns avantatges com el control per ordinador del pla focal del estímul. En aquest context general, l'objectiu d'aquesta tesi és aplicar tecnologies basades en lents (des de lents electró-òptiques controlades per ordinador fins a sistemes Badal) per estudiar l'acomodació i refracció. La metodologia d'aquesta tesi està estructurada en 6 estudis. Els primers tres estudis investiguen la resposta del sistema acomodatiu quan està estimulat òpticament amb un optòmetre Badal. Els 3 estudis restants aprofiten els sistemes varifocals electró-òptics per investigar noves metodologies relacionades amb la refracció subjectiva automàtica i la prova de flexibilitat acomodativa. Concretament, el quart estudi és una validació clínica d'un nou algorisme de refracció automatitzat i és l'únic estudi que treballa específicament en la refracció ocular. Els estudis cinquè i sisè utilitzen una lent òptica electró-òptica per presentar un estímul repetit a diferents distàncies acomodatives. El cinquè estudi valida una nova prova híbrida acomodativa que integra la prova de flexibilitat acomodativa llunyana i propera amb canvis aleatoris d'estímul acomodatiu i, el sisè estudi explora com la predictibilitat d'un estímul afecta la dinàmica acomodativa. Els resultats dels tres primers estudis mostren que les diferències reportades anteriorment en la resposta acomodativa quan s'utilitzen mètodes basats en lents en comparació amb la visualització d'estímuls en l'espai lliure es pot explicar per l'efecte de factors com l'error refractiu o el camp de visió més que en el mètode d'estimulació d'acomodació. També es demostra que l'acomodació és més precisa per a camps visuals entre 8 i 10º, el que suggereix que hi pot haver una mida d'imatge retiniana òptima per a l'estimulació de l'acomodació. A més, es demostra que l'únic factor que afecta aïlladament l'exactitud de la resposta acomodativa és el tipus d'error refractiu. També, es demostra que la precisió de la resposta acomodativa generalment millora amb un estímul bidimensional amb pistes de profunditat perifèriques i desenfoc simulat per a un camp de visió relativament gran. Aquestes condicions es poden utilitzar per millorar el confort visual en aquells sistemes de realitat virtual o simuladors visuals que utilitzen un sistema òptic varifocal per canviar el pla focal d'una superfície bidimensional. Els resultats de l'estudi 4 mostren la primera implementació d'un nou mètode potencial per a la realització de refracció subjectiva no cicloplègica en adults sense suport clínic. Encara que aquest mètode requereix encara una investigació addicional en una població més àmplia en termes d'edat, refracció i condicions oculars diferents, és més precís que els mètodes de refracció objectius i té el potencial d'incorporar-se a noves tecnologies basades en lents per millorar els serveis d'atenció primària en països en vies de desenvolupament. Finalment, els dos últims estudis mostren la primera implementació d'una nova prova de flexibilitat acomodativa que integra tant la prova llunyana i propera, amb canvis aleatoris d'estímul acomodatiu. Aquesta nova metodologia és una prova més ràpida que l'execució de les proves d'acomodació pròxima i llunyana i proporciona més informació que les proves de flexibilitat acomodativa per separat. Addicionalment, aquests dos estudis mostren que la capacitat predictiva en l'acomodació es insignificant i que la imprevisibilitat de l'estímul no afecta la dinàmica acomodativa
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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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Azzeer, A. M. A. "Some nonlinear laser induced reflection and refraction phenomena". Thesis, Swansea University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635819.
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This thesis is primarily concerned with some laser-induced nonlinear reflection and refraction phenomena in lithium niobate (LiNbO3) crystals. These are photorefraction and phase conjugation. These phenomena are caused by nonlinear optical processes and the underlying basic theory is presented. A critical review of the theory of phase conjugation by Degenerate Four-Wave Mixing (DFWM) of coherent laser beams is given and an analysis and a simple mathematical description of photorefraction, i.e. light-induced refractive index changes, are presented. Laser beam coupling by two-wave mixing and phase conjugation by four-wave mixing in photorefractive media are discussed in detail. Relevant physical properties of LiNbO3 crystals were measured and are described. An account of the design of experiments and the apparatus used in the present study to investigate photorefraction and phase conjugation in LiNbO3 are presented. The characteristics of the He-Cd laser used in the experimental investigation were measured and are described. Experiments were conducted using two-wave mixing to yield the photorefractive parameters of LiNbO3 which were then used in the interpretation of the experiments in which phase conjugation was observed in DFWM studies. Details of the procedures and the results are given together with estimates obtained for diffusion and photovoltaic field strengths in the conditions used in the present investigation. Photographic evidence of the corrective removal of optical distortion from laser beam propagating through LiNbO3 cyrstal is given.
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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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Blanchette, Damon Arthur. "Adaptive Spectral Mapping for Real-Time Dispersive Refraction". Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-theses/110.
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Spectral rendering, or the synthesis of images by taking into account the wavelengths of light, allows effects otherwise impossible with other methods. One of these effects is dispersion, the phenomenon that creates a rainbow when white light shines through a prism. Spectral rendering has previously remained in the realm of off-line rendering (with a few exceptions) due to the extensive computation required to keep track of individual light wavelengths. Caustics, the focusing and de-focusing of light through a refractive medium, can be interpreted as a special case of dispersion where all the wavelengths travel together. This thesis extends Adaptive Caustic Mapping, a previously proposed caustics mapping algorithm, to handle spectral dispersion. Because ACM can display caustics in real-time, it is quite amenable to be extended to handle the more general case of dispersion. A method is presented that runs in screen-space and is fast enough to display plausible dispersion phenomena in real-time at interactive frame rates.
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Christiaans, Johan. "Investigation of refraction effects for small GPS networks". Master's thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/18308.
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Using observations from the Global Positioning System (GPS) satellites to determine a three dimensional (3-D) geodetic control network are considered. The repeatability of individual baselines and 3-D vector closures are examined, in order to investigate refraction effects on GPS networks. The effect on GPS baselines of a height bias in the reference point's coordinates is also investigated. A least squares adjustment program is developed and used to obtain a single consistent set of 3-D coordinates for the Tygerberg Test Network (TTN). The results of two GPS processing packages are compared by means of a conformal transformation. It is concluded that single frequency measurements produce better results than the ionospheric free observable on short baselines. Furthermore, a standard atmospheric model shows an improvement over the Marini model to account for tropospheric refraction.
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DERROUGH, SAMIR. "Reseaux polymeres interpenetres a gradient d'indice de refraction". Université Louis Pasteur (Strasbourg) (1971-2008), 1993. http://www.theses.fr/1993STR13028.
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L'elaboration d'un materiau a gradient d'indice de refraction (grin), transparent et thermodur, a ete rendue possible par le biais de reseaux polymeres interpenetres (rpi). Un reseau polyurethanne spherique d'indice de refraction 1,5, a ete gonfle par les precurseurs d'un reseau styrenique d'indice de refraction 1,6, que l'on polymerise in situ avant d'avoir atteint l'equilibre de gonflement. La polymerisation des precurseurs du second reseau etant rapide par rapport a leur vitesse de diffusion dans le premier reseau, un gradient d'indice de refraction est obtenu a travers l'echantillon. Au cours de notre etude, nous avons examine les differents parametres susceptibles d'influencer chacune des etapes de la formation du rpi a grin (formation du reseau 1, diffusion des precurseurs du reseau 2, elaboration du reseau 2) pour pouvoir apprehender ses caracteristiques finales. Pour ce qui est de la connaissance de l'evolution de l'indice de refraction au sein de notre materiau, la mise au point de techniques adequates a ete necessaire. Parallelement a cet aspect experimental, nous avons modelise l'augmentation du rayon d'une sphere polyurethanne (pur) en gonflement, ce qui conduit au profil du diffusant a chaque instant. Pour cela, nous avons utilise la theorie de candau qui permet de modeliser les phenomenes de diffusion-gonflement dans un gel. Une bonne concordance entre l'experience et la theorie a ete observee lorsque le pur est synthetise en milieu solvant
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Wee, Wei Hsiung. "The physics of negative refraction and transformation optics". Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/8996.
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Whilst optics is one of the oldest field in science, there are still aspects of electromagnetism that we are only beginning to uncover. For instance, it was demonstrated that materials with simultaneously negative permittivity and permeability exhibit certain exotic behavior; where familiar physical phenomena, such as refraction, are reversed. As such, these materials came to be known as negative refractive index materials (NRIM) and their collective properties as negative refraction. One of the most important and remarkable property of NRIM is perfect lensing - the ability to transport both supra and sub-wavelength optical information from one surface (object plane) to another (image plane), forming images with unprecedented resolution, beyond the diffraction limit. Perfect lensing itself is a consequence of deeper symmetries in electromagnetism, encapsulated in the language of transformation optics - with which we have both a descriptive tool to unify diverse electromagnetic configuarations, as well as a prescriptive tool to design media which bends light at will. While, such transformation medium and NRIM have been demonstrably realised using metamaterials, several challenges remain, of which loss is the major challenge. It is therefore under this trinity of concepts: metamaterials, negative refraction and transformation optics that this thesis is presented. In particular, this thesis illustrates the convergence of the later two concepts, giving rise to a novel class of perfect lens - the compact perfect lens. Here, we shall investigate, their unique properties, construction, challenges, and the dynamics of these lenses. In particular the formulation to study dynamics and effects of losses, is universal; applicable to lenses of any geometry. Finally we shall also propose an alternative universal, top-down approach to overcome losses in perfect lenses using phase conjugation, and demonstrate the capacity of such lenses to see through lossy, translucent obstacles.
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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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Goodwin, Eric Peter. "Dual Interferometer System for Measuring Index of Refraction". Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/195904.
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The optical power of a lens is determined by the surface curvature and the refractive index, n. Knowledge of the index is required for accurate lens design models and for examining material variations from sample to sample. The refractive index of glass can be accurately measured using a prism spectrometer, but measuring the index of soft contact lens materials presents many challenges. These materials are non-rigid, thin, and must remain hydrated in a saline solution during testing. Clearly an alternative to a prism spectrometer must be used to accurately measure index.A Dual Interferometer System has been designed, built and characterized as a novel method for measuring the refractive index of transparent optical materials, including soft contact lens materials. The first interferometer is a Low Coherence Interferometer in a Twyman-Green configuration with a scanning reference mirror. The contact lens material sample is placed in a measurement cuvette, where it remains hydrated. By measuring the locations of the multiple optical interfaces, the physical thickness t of the material is measured. A new algorithm has been developed for processing the low coherence signals obtained from the reflection at each optical interface.The second interferometer is a Mach-Zehnder interferometer with a tunable HeNe laser light source. This interferometer measures the optical path length (OPL) of the test sample in the cuvette in transmission as a function of five wavelengths in the visible spectrum. This is done using phase-shifting interferometry. Multiple thickness regions are used to solve 2π phase ambiguities in the OPL.The outputs of the two interferometers are combined to determine the refractive index as a function of wavelength: n(λ) = OPL(λ)/t. Since both t and OPL are measured using a detector array, n is measured at hundreds of thousands of data points. A measurement accuracy of 0.0001 in refractive index is achieved with this new instrument, which is verified using custom glass calibration samples.
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Ward, Dale Michael 1963. "Atmospheric sounding from satellite solar occultation refraction measurements". Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282495.
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Measurements of the refractive bending of solar radiation passing through the limb of the Earth's atmosphere can be utilized to recover vertical profiles of density and temperature. These parameters obtained using the technique of solar refractive sounding could be used to improve satellite solar occultation trace species retrievals and to monitor potential trends in upper atmospheric temperatures. The solar refractive sounding method is described in detail and applied to data available from the Stratospheric Aerosol and Gas Experiment (SAGE II). The meteorological profiles derived from the SAGE II data are not consistently accurate enough for general use due to poor vertical sampling and measurement uncertainties. However, the qualitatively decent results provide optimism for future development and implementation of solar occultation refractive sounders. Better techniques for measuring solar refraction and the potential improvements in the retrievals are also discussed.
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Constantinides, Antonios. "Refraction interference elimination employing smart arrays at VHF". Thesis, Middlesex University, 2017. http://eprints.mdx.ac.uk/22243/.
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Radio interference from the Middle East is one of the most significant problems plaguing the local radio services in Cyprus today. The issue is particularly noticeable on the highway, where it affects in-car tuners in all coastal areas of the island when the weather is hot and humid. In this work, the problem of interference from the Middle East was explored in the context of field strength variations versus the type of propagation mechanism favouring the radio waves in Band II, allowing them to travel from the Middle East to beyond the horizon in Cyprus. This problem was significant, since no line of sight exists between the two regions. After in-depth analysis adhering to the ITU (International Telecommunications Union) Recommendations, it was demonstrated that interference is caused by “Tropospheric Ducting”, i.e., trapping of the overseas transmitted signals between two layers of the troposphere at different heights. The upper air data were obtained using the Weather Research Forecasting (WRF-ARW version 3.4) model. The results yielded by the present study confirm that this model provides accurate prediction of interference for up to five days in advance. The interference problem is widely recognized, and therefore many attempts have been made to explicate its causes and provide solutions. The aim of the present study was to present a robust solution based on an innovative receiving antenna design. The antenna is a receiver’s component that collects electromagnetic waves from various directions. The rationale behind focusing on a circular array topology is that its tuning ensures that the receiver processes the desired signal only, while rejecting the unwanted interference. This can presently only be achieved by a large directional external antenna that must be steered mechanically in the desired direction. As this arrangement is not practical, an innovative smart antenna was proposed as an alternative. A circular phased array is a very compact antenna that produces a predicted radiation pattern, whereby it receives maximum energy from the desired direction without the need for mechanical control. Circular arrays exhibit high gain as well as immunity to interference, making them ideal for use in high interference environments. This combination allows the antenna to be incorporated into a commercial deck receiver or installed on vehicles.
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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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Schmutz, Myriam. "Apport des methodes geophysiques a la connaissance des glissements-coulees developpes dans les marnes noires. Application a super sauze (alpes de haute provence, france)". Université Louis Pasteur (Strasbourg) (1971-2008), 2000. http://www.theses.fr/2000STR1GE07.
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La recherche s'insere dans le cadre de l'etude des risques naturels et plus specifiquement dans celui de la connaissance precise de la structure de la masse en mouvement. Dans des cas complexes, cette structure n'est pas aisee a definir avec les precisions souhaitees a l'aide des methodes et outils classiquement employes. L'objectif de ce travail est d'etablir un bilan quant a l'apport des methodes geophysiques pour la connaissance de la structure des glissements-coulees developpes dans les manies noires fossilisant un bassin torrentiel constitue d'echines et de ravines, a partir du site de super sauze dans la vallee de barcelonnette (alpes de haute-provence, france). La paleo- topographie ravinee influe fortement sur la direction, l'epaisseur et les caracteristiques hydro- mecaniques desmateriaux de cette coulee,. . . Et donc sur son evolution, dans le temps et dans l'espace, au gre des conditions hydro-climatiques. Les methodes geophysiques employees dans le cadre de cette etude sont l'electrique a courant continu, l'electromagnetisme dans les domaines frequentiel et temporel, ainsi que la sismique refraction, car elles permettent de mettre en evidence des differences de compaction et de resistivite qui sont caracteristiques des parametres pouvant differencier une coulee du substratum. Le principal resultat commun aux diverses methodes geophysiques employees est la validite d'une interpretation 1d lorsque le terrain peut etre considere comme <
40
Wei, Tai-Huei. "Nonlinear Optical Absorption and Refraction Study of Metallophthalocyanine Dyes". Thesis, University of North Texas, 1992. https://digital.library.unt.edu/ark:/67531/metadc278287/.
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This dissertation deals with the characterization of the nonlinear absorption and refraction of two representative metallophthalocyanine dyes: chloro aluminum phthalocyanine dissolved in methanol, referred to as CAP, and a silicon naphthalocyanine derivative dissolved in toluene, referred to as SiNc. Using the Z-scan technique, the experiments are performed on both the picosecond and nanosecond timescales at a wavelength of 0.532 μm.
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Byers, David John. "Synoptic and mesoscale influences on refraction during SHAREM 110". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA303233.
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Thesis (M.S. in Meteorology and Physical Oceanography) Naval Postgraduate School, December 1995."December 1995." Thesis advisor(s): Kenneth L. Davidson, Carlyle H. Wash. Bibliography: p. 123. Also available online.
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Erck, Eric Stephenson. "Subsurface conductive isolation of refraction correlative magnetic signals (SCIRCMS)". Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/1072.
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Isolation of terrestrially-observed magnetic signals by restoring their diffusive loss due to subsurface electrical conductivity sufficiently correlates these signals with those derived from the Alfven ionospheric electron movement of refraction variation. Temporary magnetic observatories were established on a conductive sedimentary basin (with a sampling interval of 5 s) and on a resistive large igneous intrusion (with a sampling interval of 10 s). Conventional modeling techniques estimate and remove the effects of the magnetometer, geomagnetic diurnal changes, whorls (solar quiet current vortices), and some bays from the acquired signals. Conventional one-dimensional skin depth modeling estimates the diffusive attenuation. The residual magnetic signal and the diffusive filter (as applied to the topography) become quantities in the linear system estimation of the geoelectric subsurface. Angular frequency domain least squares solution of the equations yields an isolated magnetic anomaly spectrum. Interpretive refinement, by selection of the zero or near zero curvature onset of either the spectrum's real or imaginary component, critically prepares the signal solution for correlation to a pseudomagnetic anomaly signal. This is an independently-derived sequence of anomalous values derived from Global Positioning System (GPS) refracted ranges. Detailed application of the Biot-Savart law provides independent anomaly signals to which the magnetic anomalies correlations show great correlation improvement by the isolation. These correlation improvements are from 2% to 83% and 9% to 91% for the sedimentary basin and from 2% to 96% and 24% to 78% for the igneous intrusion.
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Robinson, Tyler D., Jonathan J. Fortney i William B. Hubbard. "Analytic Scattering and Refraction Models for Exoplanet Transit Spectra". IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/627105.
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Observations of exoplanet transit spectra are essential to understanding the physics and chemistry of distant worlds. The effects of opacity sources and many physical processes combine to set the shape of a transit spectrum. Two such key processes-refraction and cloud and/or haze forward-scattering-have seen substantial recent study. However, models of these processes are typically complex, which prevents their incorporation into observational analyses and standard transit spectrum tools. In this work, we develop analytic expressions that allow for the efficient parameterization of forward-scattering and refraction effects in transit spectra. We derive an effective slant optical depth that includes a correction for forward-scattered light, and present an analytic form of this correction. We validate our correction against a full-physics transit spectrum model that includes scattering, and we explore the extent to which the omission of forward-scattering effects may bias models. Also, we verify a common analytic expression for the location of a refractive boundary, which we express in terms of the maximum pressure probed in a transit spectrum. This expression is designed to be easily incorporated into existing tools, and we discuss how the detection of a refractive boundary could help indicate the background atmospheric composition by constraining the bulk refractivity of the atmosphere. Finally, we show that opacity from Rayleigh scattering and collision-induced absorption will outweigh the effects of refraction for Jupiter-like atmospheres whose equilibrium temperatures are above 400-500 K.
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Schonbrun, Ethan. "Negative refraction and anomalous propagation in silicon photonic crystals". Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3256376.
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Sudhakaran, Sunil. "Negative refraction from electromagnetic periodic structures and its applications". Thesis, Queen Mary, University of London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430074.
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Xia, Wenjun. "Refraction of nonlinear light beams in nematic liquid crystals". Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7726.
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Optical spatial solitons in nematic liquid crystals, termed nematicons, have become an excellent test bed for nonlinear optics, ranging from fundamental effects to potential uses, such as designing and demonstrating all-optical switching and routing circuits in reconfigurable settings and guided-wave formats. Following their demonstration in planar voltage-assisted nematic liquid crystal cells, the spatial routing of nematicons and associated waveguides have been successfully pursued by exploiting birefringent walkoff, interactions between solitons, electro-optic controlling, lensing effects, boundary effects, solitons in twisted arrangements, refraction and total internal reflection and dark solitons. Refraction and total internal reflection, relying on an interface between two dielectric regions in nematic liquid crystals, provides the most striking results in terms of angular steering. In this thesis, the refraction and total internal reflection of self-trapped optical beams in nematic liquid crystals in the case of a planar cell with two separate regions defined by independently applied bias voltages have been investigated with the aim of achieving a broader understanding of the nematicons and their control. The study of the refraction of nematicons is then extended to the equivalent refraction of optical vortices. The equations governing nonlinear optical beam propagation in nematic liquid crystals are a system consisting of a nonlinear Schr¨odinger-type equation for the optical beam and an elliptic Poisson equation for the medium response. This system of equations has no exact solitary wave solution or any other exact solutions. Although numerical solutions of the governing equations can be found, it has been found that modulation theories give insight into the mechanisms behind nonlinear optical beam evolution, while giving approximate solutions in good to excellent agreement with full numerical solutions and experimental results. The modulation theory reduces the infinite-dimensional partial differential equation problem to a finite dynamical system of comparatively simple ordinary differential equations which are, then easily solved numerically. The modulation theory results on the refraction and total internal reflection of nematicons are in excellent agreement with experimental data and numerical simulations, even when accounting for the birefringent walkoff. The modulation theory also gives excellent results for the refraction of optical vortices of +1 topological charge. The modulation theory predicts that the vortices can become unstable on interaction with the nematic interface, which is verified in quantitative detail by full numerical solutions. This prediction of their azimuthal instability and their break-up into bright beams still awaits an experimental demonstration, but the previously obtained agreement of modulation theory models with the behaviour of actual nematicons leads us to expect the forthcoming observation of the predicted effects with vortices as well.
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El-Aassar, Ahmed. "MODELING OF ATMOSPHERIC REFRACTION EFFECTS ON TRAFFIC NOISE PROPAGATION". Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3804.
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Traffic noise has been shown to have negative effects on exposed persons in the communities along highways. Noise from transportation systems is considered a nuisance in the U.S. and the government agencies require a determination of noise impacts for federally funded projects. There are several models available for assessing noise levels impacts. These models vary from simple charts to computer design models. Some computer models, i.e. Standard Method In Noise Analysis (STAMINA), the Traffic Noise Model (TNM) and the UCF Community Noise Model (CNM), have been used to predict geometric spreading, atmospheric absorption, diffraction, and ground impedance. However, they have largely neglected the atmospheric effects on noise propagation in their algorithms. The purpose of this research was to better understand and predict the meteorological effects on traffic noise propagation though measurements and comparison to acoustic theory. It should be noted that this represents an approach to incorporate refraction algorithms affecting outdoor noise propagation that must also work with algorithms for geometric spreading, ground effects, diffraction, and turbulence. The new empirical model for predicting atmospheric refraction shows that wind direction is a significant parameter and should be included in future modeling for atmospheric refraction. To accomplish this, the model includes a "wind shear" and "lapse rate" terms instead of wind speed and temperature as previously needed for input of the most used models. The model is an attempt to explain atmospheric refraction by including the parameters of wind direction, wind shear, and lapse rate that directly affect atmospheric refraction.Ph.D.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Environmental Engineering
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Hutchings, David Crichton. "Theory of nonlinear refraction and optical bistability in semiconductors". Thesis, Heriot-Watt University, 1988. http://hdl.handle.net/10399/1008.
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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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Andriatsitohaina, Johnny Eric Fernand Rastefano. "Accurate refraction modelling in 3-D complex isotropic media". Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614796.
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