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1
Sharif, Ahmadian A. "Wave field around submerged breakwaters." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1414995/.
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Shoreline response to submerged breakwaters is particularly influenced by the wave field behind the structure driven by coastal processes. The 2D aspects of wave transmission behind submerged breakwaters have been extensively studied by researchers. However, available 2D engineering design tools are inefficient in breakwater design due to not being able to provide any information on the spatial distribution of the nearshore wave field around the breakwater. There are very few studies considering 3D effects in the literature and consequently no reliable guidance for engineers. This encouraged the author to investigate this subject experimentally and numeri¬cally, with the aim of contributing to this important research topic. A comprehensive set of 2D and 3D experiments has been conducted in three wave tanks with different scales. A method has been prepared for predicting the waves transmitted behind the breakwaters based on the data-driven algorithms called Artificial Neural Networks (ANN) and using some of the experimental data collected. Multi-layer perceptron (MLP) and Radial basis function (RBF) models were designed and trained by the Levenberg-Marquardt learning algorithm (LM) and a derivative- based algorithm of gradient descent (GD) respectively. To verify the numerical model, wave simulation was also carried out using DHI MIKE 21 BW (2DH Boussinesq Wave module) based on the numerical solution of the time domain formulations of Boussinesq type equations. The spatial variations of wave energy and wave pattern around the breakwater were generally found to depend on incident wave climate and whether or not wave breaking occurred over the breakwater as well as degree of breaking, with different wave patterns observed for different wave conditions. In cases with waves breaking over the breakwater the lower wave heights were observed behind the breakwater crown on the shorewardside; for nonbreaking wave conditions passing over the submerged breakwater lower wave heights were observed in the gap between the end of the breakwater and the flume wall. Investigations illustrated that the dimensionless Cartesian coordinates x/L₀ and y/L₀ were the most significant parameter in the 3D wave field around the breakwater, with wave height and energy varying spatially around the structure. This confirms the importance of 3D effects on wave height prediction and highlights the inadequacy of 2D models that are unable to deal with spatial variation of wave height behind the breakwater. The RBF model trained by non-dimensional parameters was determined as the most appropriate tool and was proven to be more capable of handling wave transmission prediction comparing with other ANN models. Predictions from the proposed ANN model were found to be in very good agreement with new laboratory data never seen by the model before. The ANN model predictions have also been compared with results from the MIKE 21 BW model. The proposed ANN model was validated in three distinct cases of interpolation, extrapolation and larger scale tests. The model gave the most reliable and convincing predictions within a specific range of input parameters (interpolation) while outside this range (extrapolation) to some extent, reasonable results were still achieved. The proposed model was assessed under larger scale conditions with data collected in another wave tank with different laboratory facilities. Outputs under these conditions also showed good agreement. This shows that the performance of the model is not affected significantly by scale changes and the model has the potential to be used in real applications. The Boussinesq wave model was found to overestimate wave-induced breaking dissipation over the crest of the submerged breakwater leading to underprediction of wave transmission. The evaluations showed more consistency between the measured experimental data and predictions from the ANN model in comparison to those from the Boussinesq wave model. These demonstrate the accuracy and reliability of the model and its capability in predicting the wave field around submerged breakwaters. A simplified version of the numerical model and wave prediction scheme is provided in this thesis for practical applications. The proposed ANN model is a significant advance in that it can be used to predict 3D wave pattern around submerged breakwaters in the range of dimensionless Cartesian coordinate -0.26
2
Wu, Cheng Y. (Cheng Yi) 1938. "Wave-wave interactions and the infrasonic pressure field in the ocean." Thesis, University of Auckland, 1988. http://hdl.handle.net/2292/2469.
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Building on Kibblewhite's long term investigations of the nonlinear wave-wave interactions and the infrasonic ocean noise and the microseisms these induce, this thesis further explores the physical nature of these processes. The classical description of this interaction, which takes into account only the homogeneous component of the induced field, has been extended to include the inhomogeneous component. A complete expression for the wave induced noise spectrum is established following a geometrical analysis of the dispersion relations among interacting waves. The relative importance of these two components and their directivity properties are also calculated and discussed. It is shown that while at observation points deeper than 500 meters the effects of the inhomogeneous component can be regarded as negligible, it can cause an increase of noise level of up to 40 dB in the region near the surface of the sea. Furthermore, in contrast to the nearly omni-directional distribution of the homogeneous component of the induced acoustic field, there is a tendency for the energy associated with the inhomogeneous component to focus in the wind direction. Based upon a multilayer analysis of a visco-elastic geoacoustic model, Green's functions and the spectral transfer functions relating the surface source pressure field to the underwater noise and microseism fields are derived for both near and far field cases. A 3-dimensional presentation defined on the dispersion plane (frequency and horizontal wave number) is introduced to describe the sea bottom reflection-loss and, Green's functions, and is extended to include the inhomogeneous region for the first time. The characteristics of this 3-D presentation are explained in terms of the geoacoustic parameters. The influence of the interaction of multiple seas (and swell) on the induced acoustic field are also discussed in this thesis. All these effects are considered in the calculation of the synthetic spectra of both the noise and microseism field. When compared with measured data excellent agreement is found between the theoretical and experimental results, which provides further confirmation that the nonlinear interaction is the most important source of the infrasonic ocean noise, as well as confirming the basic validity of the procedure introduced by Kibblewhite and Ewans to derive the ocean noise spectra from microseism records.
3
Rogers, Jonathan Robert. "Wave-current interaction in the presence of a reflective wave field." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397386.
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4
Inch, Kris William. "Field observations of infragravity wave response to variable sea-swell wave forcing." Thesis, University of Plymouth, 2017. http://hdl.handle.net/10026.1/10164.
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Infragravity waves are low frequency (0.005-0.04 Hz) waves that can dominate the spectrum of water motions and sediment transport processes within the inner surf zone. Despite the established importance of infragravity waves in shaping our coasts and numerous studies dating back to the 1950s, several aspects of infragravity wave analysis, generation and dissipation remain poorly understood. As much of the recent infragravity research has focussed on fetch-limited coasts, less is known about the climatology of these waves on energetic coastlines subject to both swell and fetch-limited waves. It has been postulated that bed friction only plays a significant role in the dissipation of infragravity waves where the bed is exceptionally rough, but the precise impact of bed roughness is not fully understood, particularly on extremely rough rock platforms. Finally, although there have been many methodologies proposed for the decomposition of reflective wave fields (an essential tool for studying infragravity wave dynamics), very little attention has been given to evaluating their accuracy, particularly the impact of uncorrelated noise. This study aims, primarily through the collection of an extensive field dataset and the establishment of accurate analysis tools, to provide new insight into the propagation, dissipation and reflection of infragravity waves on energetic coastlines of varied roughness, subject to both swell and fetch-limited waves. To ensure the accurate decomposition of infragravity wave signals into their incident and reflected components, a sensitivity analysis into the effect of uncorrelated noise on an array separation method is performed. Results show that signal noise, often prevalent in field data, introduces a significant bias to estimates of incident and reflected wave spectra, and corresponding reflection coefficients. This bias can exceed 100% for signal-to-noise ratios of < 1. Utilising the systematic change in coherence with noise, a correction function is developed which is effective at reducing bias by up to 90%. When applied to field data, results imply that infragravity reflection coefficients can be overestimated by > 50% if signal noise is unaccounted for. Consequently, noise reduction should form an integral part of future infragravity wave studies. New research from a dissipative, fetch-unlimited sandy beach (Perranporth, Cornwall, UK) and a macrotidal, rocky shore platform (Freshwater West, Pembrokeshire, UK) uniquely demonstrates that the level of infragravity wave energy close to shore is linearly dependent on the offshore short wave energy flux H_o^2 T_p (r^2 = 0.93and 0.79, respectively). Infragravity waves approach the coast as bound waves lagging slightly (~4 s) behind the wave group envelope and are released in the surf zone where their heights can exceed 1 m. Considerable infragravity dissipation is observed in the surf zone and is a function of both frequency and H_o^2 T_p. Complex Empirical Orthogonal Function (EOF) analysis reveals (quasi-)standing waves at low infragravity frequencies < 0.017 Hz. Conversely, at higher frequencies (>0.017 Hz), infragravity waves demonstrated progressively more dissipation (up to 90%) and progressive wave characteristics, with increasing frequency. Much of the observed dissipation occurs very close to shore (h < 0.8 m) and the dependence of the reflection coefficient on a normalised bed slope parameter implies a mild sloping bed regime at these high infragravity frequencies, suggesting that the observed dissipation is dominated by wave breaking processes. This is supported by the results of bispectral analysis which show predominantly infragravity-infragravity interactions in shallow water and the development of infragravity harmonics indicative of steepening and eventual breaking of the infragravity waves. This study presents the first simultaneous field observations of infragravity waves on a macrotidal, rocky shore platform and adjacent sandy beach. Infragravity wave dissipation is observed on both the platform and beach and occurs at statistically similar rates, demonstrating that frictional dissipation due to bed roughness is not the dominant dissipation mechanism, even in this extreme case. Sea-swell waves are also unaffected by the extreme roughness of the platform, with relative wave heights on the beach and platform (γ = 0.38 and 0.43, respectively) scaling well with their respective gradients and are in very close agreement with formulations derived from sandy beaches. Overall, bed roughness is shown to have no significant impact on infragravity or sea-swell wave transformation, with offshore forcing and bed slope being the main controlling factors, particularly under moderate to high energy offshore forcing.
5
Kilby, Charles F. "Development of the shear wave magnetometer." Thesis, University of Bath, 1992. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306852.
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Melo, Jose Luis Branco Seabra de. "Nonlinear parametric wave model compared with field data." Monterey, Calif. : Naval Postgraduate School, 1985. http://catalog.hathitrust.org/api/volumes/oclc/57738811.html.
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Haase, Heiko. "Full-wave field interactions of nonuniform transmission lines." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975448641.
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Pinkham, Wade A. "A Lateral Field Excited Acoustic Wave Pesticide Sensor." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/PinkhamWA2007.pdf.
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9
Galicia, Felicisimo. "Plasma wave induced chaos in a magnetic field." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38863.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and, (B.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1996.Includes bibliographical references (leaf 125).
by Felicisimo Galicia.
B.S.
M.Eng.
10
Kuntz, Achim. "Wave field analysis using virtual circular microphone arrays." München Verl. Dr. Hut, 2008. http://d-nb.info/993260292/04.
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Xie, Zhongqiang. "Fourth-order finite difference methods for the time-domain Maxwell equations with applications to scattering by rough surfaces and interfaces." Thesis, Coventry University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369842.
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McAllister, Mark Laing. "Analysis of laboratory and field measurements of directionally spread nonlinear ocean waves." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28762.
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Surface gravity waves exist in the oceans as multi-directional nonlinear phenomena. Understanding how these two properties interact is intrinsically important in itself. Furthermore, an understanding of this relationship may be used to gain insight into other oceanic phenomena. This thesis first describes an experimental investigation into the relationship between directionality and non-linearity (Part I). This relationship was then used as a tool to estimate the directional spreading of field data (Part II). Experiments have been conducted in which directionally spread focused wave groups were created in a wave tank. The relationship between the degree of directional spreading and the second-order bound harmonics of the wave groups was examined, in particular the formation of a `set-up'. These measurements were then compared to predictions from second-order theories, finding good agreement. The two-dimensional structure of the bound waves was explored giving new insight into the underlying physics. Experiments were then carried out for directionally spread crossing wave groups. It is believed that the crossing of two sufficiently separated wave groups may be the cause of an anomalous set-up in the second-order bound waves observed for some extreme and potentially freak waves. This set-up is reproduced experimentally. Again, the results of these test agreed very well when compared to second-order theory. The insight gained from the foregoing experiments was then utilised in the analysis of field data. A method, which requires only a single measurement to estimate the observed degree of directional spreading, was applied to a large dataset of field measurements from the North Alwyn platform in the North Sea. This method was then compared to conventional approaches, which require multiple concurrent measurements. The method that requires only a single measurement was shown to be effective, and presents a promising approach to gaining additional insight about the directional spreading of point observations.
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Armstrong, Jonathan. "Design of a Free Field Blast Simulating Shock Tube." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32241.
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A 30.5 cm diameter, detonation driven shock tube facility has been designed, constructed and tested. The design goals of the shock tube were to reproduce free field blast wave profiles on a laboratory scale using atmospheric gaseous detonation as the energy source. Numerical simulations were utilized to explore the gas dynamic evolution inside detonation driven shock tubes and to select the optimal design parameters for the shock tube.The Friedlander profile was used to evaluate the generated pressure profiles as an approximation of free field blast waves. It has been found that the detonation driver length should be kept below 20% of the total length of the tube in order to produce Friedlander waves. Additionally, it has been found that an annular vent can be added to the shock tube to enhance the negative phase of the blast profile, more accurately reproducing real free field blast waves. The shock tube has been constructed in a modular fashion from 2.54 cm thick steel tubing. An adjustable bag type diaphragm has been employed to allow for a variable driver size and a high voltage ignition system is used to initiate detonation in the driver section. Due to the available location for the shock tube, tests using the vented configuration could not be accomplished for safety reasons. Conducted experiments produced results that agree well with corresponding numerical simulations. Overall, the shock tube design was successful in creating Friedlander blast waves. At the time of writing, a manufacturer error in correctly reporting the specifications of the clamps used on the shock tube resulted in a lower maximum pressure of operation.
14
Valle, A. N. "Causality of regular wave equations in an external field." Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/27655.
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Jönsson, Anette. "The Baltic Sea Wave Field : Impacts on the Sediment and Biogeochemistry." Licentiate thesis, Linköping University, Linköping University, Department of Water and Environmental Studies, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5565.
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The wave field in the Baltic Sea has been modelled for a two-year period with the spectral wave model HYPAS. There is a large seasonal variation in the field and a minor annual one, both reflect the wind variation in the area. Since the Baltic Sea is fetch limited, the dominant wind direction is important for the maximum wave heights.
By studying the modelled wave energy density in combination with bottom type maps, the effect of the wave field on the sediment surface is examined. Up to half the bottoms in the Baltic Sea are affected ~25% of the time. A statistical relation between wave energy density and bottom types is found for the Gulf of Riga, but in the rest of the area the sediment maps were to coarse. It is, due to this, not possible to say if the result is valid for the whole area or if it is site specific.
During resuspension events the remineralisation is increased since deposited organic material is reintroduced into the watermass and there exposed to higher levels of oxygen. This process could act as an increased regional source of nitrogen in nutrient budgets and thus influence the conditions for nitrogen fixation and perhaps explain some of the geographical differences in the nitrogen fixation rates.
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Colbert, David B. "Field evaluation of ocean wave measurements with GPS buoys." Thesis, Monterey, California. Naval Postgraduate School, 2010. http://hdl.handle.net/10945/5117.
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Approved for public release; distribution is unlimitedAn intercomparison of Datawell accelerometer buoys, Datawell GPS buoys, and prototype GPS buoys was conducted to determine the viability of using off-the-shelf GPS receivers to measure ocean surface waves. In the experiment, conducted off the coast of California near Bodega Bay, clusters off Datawell and prototype GPS buoys were deployed to collect ocean surface wave measurements. The first phase of the research was an intercomparison of wave measurements from a Datawell accelerometer sensor, the Magellan MMCX GPS receiver and the GlobalSat MR-350 GPS receiver. The Datawell accelerometer and the Magellan MMCX receiver measurements of both vertical and horizontal wave orbital excursions are in good agreement. The GlobalSat MR-350 receiver also accurately resolved horizontal wave orbital displacements but failed to reproduce the vertical wave excursion measurement by the accelerometer sensors. The second phase of the project was an independent intercomparison between the Datawell MK-II accelerometer buoys, Datawell Waverider GPS buoys, and the prototype GPS buoys built by the NPS team using the Magellan MMCX receiver. The intercomparison showed good agreement between the off-the-shelf GPS buoys, the newer Datawell GPS buoys as well as the traditional Datawell accelerometer buoys in the energetic part of the wave spectrum.
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Narayana, Merugu Lakshmi. "Concurrent algorithms for microwave and millimetre wave field problems." Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334591.
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Bleda, Pérez Sergio. "Contribuciones a la implementación de sistemas Wave Field Synthesis." Doctoral thesis, Universitat Politècnica de València, 2009. http://hdl.handle.net/10251/6685.
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De entre los sistemas de reproducción de sonido 3D,
Wavefield Synthesis (WFS) presenta una serie de
ventajas sobre el resto, principalmente en lo que respecta al gran
realismo y sensación de inmersión acústica que proporciona. Otra
gran ventaja adicional, es que la zona útil de escucha es muy
amplia, superando al resto de sistemas disponibles en la
actualidad. La teoría de WFS fue propuesta a finales de los 80 y
principios de los 90, no siendo hasta el siglo XXI cuando se han
puesto en marcha los primeros prototipos de estos sistemas, aunque
muchos aspectos no contemplados en la teoría inicial siguen siendo
en la actualidad retos importantes. La presente tesis aborda el
estudio de la implementación de los sistemas de WFS aportando
soluciones prácticas a las limitaciones tecnológicas que presentan
estos sistemas, así como otra serie de problemas de implementación
y funcionamiento en tiempo real que, aunque en una primera
instancia no se describen como limitaciones físicas, suponen un
problema a superar cuando se busca un sistema que funcione
eficientemente.
El objetivo final de esta tesis es aportar soluciones que
contribuyan al desarrollo de un sistema de WFS totalmente
funcional, por lo que durante su desarrollo ha sido necesario
encontrar soluciones particulares y originales a multitud de
problemas de diferente índole. Esta serie de problemas proviene
por un lado de las limitaciones físicas de WFS y por otro de la
implementación práctica del sistema. Por otro lado también se ha
trabajo en los aspectos computacionales relacionados con la
implementación en tiempo real de sistemas de WFS, los cuales
necesitan una gran potencia de cálculo para dicho funcionamiento
en tiempo real sin cortes ni grandes latencias. Este último se ha
tratado de forma rigurosa dedicando un capítulo completo para su
análisis y propuesta de soluciones eficientes y efectivas en
coste.Bleda Pérez, S. (2009). Contribuciones a la implementación de sistemas Wave Field Synthesis [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/6685
Palancia
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Samluk, Jesse Paul. "Millimeter wave far-field imaging via optical upconversion techniques." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 106 p, 2008. http://proquest.umi.com/pqdweb?did=1597632791&sid=10&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Farnsworth, Katherine L. "Response Modes of the Lower Chesapeake Bay Wave Field." W&M ScholarWorks, 1997. http://web.vims.edu/library/Theses/Farnsworth97.PDF.
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Schumacher, Erik. "Diffraction of atoms by a standing-wave light field." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/185757.
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We study theoretically the diffraction of atoms by a standing-wave light field. Conceptually the text is divided into two parts. In the first part we deal with the coherent interaction only. We use a band theoretical approach to describe the laser-atom interaction, and to characterize two-beam resonances (Dopplerons and Bragg resonances). These two-beam resonances are major candidates to develop effective atom beam splitters. We study the interaction with classical light fields as well as with quantum fields. In the second part we take incoherent processes, i.e. spontaneous emission, into account and present a numerical scheme for the solution of the generalized optical Bloch equations. This scheme is based on the split-operator technique, and we use it to study numerically the influence of spontaneous emission on the diffraction process. We compare our results with recent experimental data, and investigate the impact of spontaneous emission on the performance of two-beam resonances.
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Hoq, Qazi Enamul. "Quantization Of Spin Direction For Solitary Waves in a Uniform Magnetic Field." Thesis, University of North Texas, 2003. https://digital.library.unt.edu/ark:/67531/metadc4210/.
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It is known that there are nonlinear wave equations with localized solitary wave solutions. Some of these solitary waves are stable (with respect to a small perturbation of initial data)and have nonzero spin (nonzero intrinsic angular momentum in the centre of momentum frame). In this paper we consider vector-valued solitary wave solutions to a nonlinear Klein-Gordon equation and investigate the behavior of these spinning solitary waves under the influence of an externally imposed uniform magnetic field. We find that the only stationary spinning solitary wave solutions have spin
parallel or antiparallel to the magnetic field direction.
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Kosleck, Sascha [Verfasser], and Günther F. [Akademischer Betreuer] Clauss. "Prediction of Wave-Structure Interaction by Advanced Wave Field Forecast / Sascha Kosleck. Betreuer: Günther F. Clauss." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2013. http://d-nb.info/103231303X/34.
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Henry, Legena Albertha. "A study of ocean wave statistical properties using nonlinear, directional, phase-resolved ocean wave-field simulations." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1912/3230.
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Thesis (S.M.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), February 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 327-334).
In the present work, we study the statistics of wavefields obtained from non-linear phase-resolved simulations. The numerical model used to generate the waves models wave-wave interactions based on the fully non-linear Zakharov equations. We vary the simulated wavefield's input spectral properties: directional spreading function, Phillips parameter and peak shape parameter. We then investigate the relationships between a wavefield's input spectral properties and its output physical properties via statistical analysis. We investigate surface elevation distribution, wave definition methods in a nonlinear wavefield with a two-dimensional wavenumber, defined waves' distributions, and the occurrence and spacing of large wave events.
by Legena Albertha Henry.
S.M.
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Kosleck, Sascha Verfasser], and Günther [Akademischer Betreuer] [Clauss. "Prediction of Wave-Structure Interaction by Advanced Wave Field Forecast / Sascha Kosleck. Betreuer: Günther F. Clauss." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2013. http://d-nb.info/103231303X/34.
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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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Marty, Pierre Noel. "Modeling of ultrasonic guided wave field generated by piezoelectric transducers." Thesis, Imperial College London, 2002. http://hdl.handle.net/10044/1/7222.
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So, Poman Pok-Man. "Field-theory based CAD procedure for millimeter wave integrated circuits." Thesis, University of Ottawa (Canada), 1989. http://hdl.handle.net/10393/5884.
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Barksdale, Harry. "Millimeter wave scattering by rain in an antenna's near field." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53906.
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One of the important considerations in radio link analysis is the signal degradation that accompanies rainfall in a link’s path. Random scattering by rain can adversely affect a propagating wave in two ways. First, it results in attenuation and depolarization of the coherent field which is associated with the forward propagating wave. ln addition to this, random scattering gives rise to an incoherent field component that can further degrade the signal in a manner similar to multipath.
This dissertation presents an analysis of the coherent and incoherent effects of rain scatter at millimeter-wave frequencies. Within it, the scattering properties of individual spherical and non-spherical are quantified. Spherical raindrops are treated using the Mie theory and non-spherical ones analyzed with Waterman’s Extended Boundary Condition Method. Computed values of forward scattering amplitudes and scattering cross-sections for both spherical and non-spherical raindrops at 80, 45, 70 and 90 GHz are presented; the computer programs used to obtain the scattering data are also provided. Following the analysis of individual raindrops scatterers, the Foldy·Lax Twersky integral equations for coherent field and incoherent intensity are used to derive the coherent and incoherent outputs of a generic radio receiver. In doing so, the effects of scattering in an antenna’s far-field and radiating near field (Fresnel Region) are analyzed. Through this analysis, it is shown that the expected system outputs are essentially the same in either case.
Using the computed raindrop scattering parameters and models developed for the coherent and Incoherent system outputs, specific cases are Iooked at for 30, 45, 70 and 90 GHz operation and theoretical data presented. The data consists of the predicted attenuation and Isolation of the coherent signal and the ratio of coherent to Incoherent power In the presence of rain. From the latter it Is found that during heavy rainfall, the Incoherent effects can be appreciable and should be taken into account.Ph. D.
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Pham, Mai-Quyen. "Seismic wave field restoration using spare representations and quantitative analysis." Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1028/document.
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Cette thèse porte sur la restauration de champs d'ondes sismiques perturbés par trois sources de dégradation. Ces sources sont dues à des trajets de propagation complexes, au dispositif d'acquisition, à des sources liées ou non à l'acquisition, et potentiellement présentes simultanément : des réflexions multiples (ou échos), une dégradation de la réponse impulsionnelle attendue (ou flou) et des perturbations plus aléatoires (ou bruits).Nous avons considéré dans un premier temps le problème des réflexions multiples, réflexions qui se sont réfléchies plusieurs fois sur au moins une interface. Nous nous intéressons ici au filtrage adaptatif de ces réflexions sismiques multiples à partir de modèles approximatifs issus de modélisation sismique. Ce filtrage est réalisé dans un domaine de trames d'ondelettes discrètes, mono- et bidimensionnelles, sous contraintes de parcimonie et de variation lente des filtres adaptatifs. Ceci est intéressant en réflexion sismique, car les méthodes standard peuvent produire des filtres très mal conditionnés, du fait notamment du caractère passe-bande des données sismiques. Dans ce travail, une formulation variationnelle des problèmes de réflexions multiples est proposée. Nous utilisons des algorithmes proximaux, dont la convergence est garantie lorsqu'il s'agit d'optimiser dans un cadre convexe. L'avantage de ces approches est l'utilisation d'une régularisation sophistiquée, permettant de considérer la parcimonie à la fois a) dans le domaine d'ondelettes, b) via des a priori sur les filtres pour lesquels nous avons utilisé différentes fonctions de régularisation (norme l1, l2, mixte l1-2 et nucléaire). Notre méthode vise à étendre et améliorer certains aspects de la méthode proposée par S. Ventosa en collaboration avec CGG en 2012, et testée avec succès sur plusieurs campagnes sismiques. Les résultats que nous avons obtenus démontrent la performance de notre méthode non seulement sur des données synthétiques bruitées mais également sur des données réelles. Nous nous intéressons ensuite au problème de déconvolution aveugle. En géophysique, un modèle simplifié de la Terre souvent utilisé fait l'hypothèse d'un nombre de couches localement parallèles, chacune avec des propriétés constantes. Mais la vitesse, la densité ou les deux peuvent varier d'une couche à l'autre. L'impédance acoustique est calculée pour chaque couche ; puis les coefficients de réflexion pour une incidence normale sont calculés aux endroits où il y a des changements d'impédance acoustique. Chaque changement d'impédance acoustique opère une modification d'amplitude et de polarisation liée aux coefficients de réflexion. Ainsi, la séquence de réflectivité (réponse impulsionnelle) est convoluée avec la forme d'onde descendante pour donner une trace sismique. Ce problème constitue un contexte de déconvolution aveugle où l'on recherche un signal inconnu, convolué avec une forme d'onde elle aussi inconnue en présence de bruit additif. La déconvolution requiert souvent d'introduire des hypothèses complémentaires sous forme de pénalisation, notamment non convexe. L'ambiguïté d'échelle en déconvolution aveugle suggère l'usage de fonctions de contraste invariantes en échelle. Dans cette thèse, nous proposons un algorithme de minimisation alternée, de type explicite-implicite à métrique variable. Il traite une approximation lisse du rapport l1/l2 (SOOT pour "Smoothed One-Over-Two penalty") pour des données réelles signées. Nous étudions les propriétés de convergence de la méthode proposée, basées sur l'inégalité de Kurdyka-Lojasiewicz. Les performances de cette nouvelle approche sont illustrées à travers un exemple en déconvolution aveugle de données sismiques, mais aussi sur des imagesThis thesis deals with two different problems within the framework of convex and non convex optimization. The first one is an application to multiple removal in seismic data with adaptive filters and the second one is an application to blind deconvolution problem that produces characteristics closest to the Earth layers. More precisely : unveiling meaningful geophysical information from seismic data requires to deal with both random and structured “noises”. As their amplitude may be greater than signals of interest (primaries), additional prior information is especially important in performing efficient signal separation. We address here the problem of multiple reflections, caused by wave-field bouncing between layers. Since only approximate models of these phenomena are available, we propose a flexible framework for time-varying adaptive filtering of seismic signals, using sparse representations, based on inaccurate templates. We recast the joint estimation of adaptive filters and primaries in a new convex variational formulation. This approach allows us to incorporate plausible knowledge about noise statistics, datas parsity and slow filter variation in parsimony-promoting wavelet transforms. The designed primal-dual algorithm solves a constrained minimization problem that alleviates standard regularization issues in finding hyper parameters. The approach demonstrates significantly good performance in low signal-to-noise ratio conditions, both for simulatedand real field seismic data. In seismic exploration, a seismic signal (e.g. primary signal) is often represented as the results of a convolution between the “seismic wavelet” and the reflectivity series. The second goal of this thesis is to deconvolve them from the seismic signal which is presented in Chapter 6. The main idea of this work is to use an additional premise that the reflections occur as sparsely restricted, for which a study on the “sparsity measure”is considered. Some well known methods that fall in this category are proposed such as[Sacchi et al., 1994; Sacchi, 1997]. We propose a new penalty based on a smooth approximation of the l1/l2 function that makes a difficult non convex minimization problem. We develop a proximal-based algorithm to solve variational problems involving this function and we derive theoretical convergence results. We demonstrate the effectiveness of our method through a comparison with a recent alternating optimization strategy dealing with the exact l1/l2 term
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Earlie, Claire Siobhan. "Field observations of wave induced coastal cliff erosion, Cornwall, UK." Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/3526.
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Coastal cliff erosion is a widespread problem that threatens property and infrastructure along many of the world’s coastlines. The management of this risk calls for robust quantification of cliff erosion rates, which are often difficult to obtain along rocky coasts. Quantification of sea-cliff rates of retreat on annual to decadal time scales has typically been limited to rapidly eroding soft rock coastlines. Rates of erosion used for shoreline management in the UK are generally based on analysis of historic maps and aerial photographs which, in rocky coast environments, does not wholly capture the detail and timing at which the processes operate and the failures occur across the cliff face. The first stage of this study uses airborne LiDAR (Light Detection and Ranging) data at nine sites around a rocky coastline (Cornwall, UK) to gain a quantitative understanding of cliff erosion where average recession rates are relatively low (c. 0.1 m yr-1). It was found that three-dimensional volumetric changes on the cliff face and linear rates of retreat can be reliably calculated from consecutive digital elevation models (DEMs) several years apart. Rates of erosion ranged between 0.03–0.3 m yr-1. The spatial variability in recession rates was considered in terms of the relationship with the varying boundary conditions (rock mass characteristics, cliff geometries, beach morphology) and forcing parameters (wave climate and wave exposure). Recession rates were statistically correlated with significant wave height (Hs), rock mass characteristics (GSI) and the ratio between the two (GSI/Hs). Although the rates derived using airborne LiDAR are comparable to the longer term rates of retreat, the detail of erosion to the cliff-face provides additional insight into the processes occurring in slowly eroding environments, which are vital for understanding the failure of harder rock coastlines. In addition to this, the importance of the wave climate and rainfall needs further attention on a more localised scale. Monthly cliff face volume changes, at two particularly vulnerable sites (Porthleven and Godrevy, Cornwall, UK), were detected using a Terrestrial Laser Scanner (TLS). Using these volumes alongside information on beach profile, beach- cliff junction elevation changes and nearshore hydrodynamics have allowed an insight into how the cliffs respond to seasonal fluctuations in wave climate and beach morphology. Monthly variability in beach morphology between the two sites over a one-year survey period i  indicated the influence that beach slope and the elevation of the beach-cliff junction have on the frequency of inundation and the power of wave-cliff impacts. Failure mechanisms between the two sites ranged from rotational sliding of superficial material to quarrying and block removal over the entire cliff elevation, according to the extent of wave-cliff interaction. This particular survey period highlighted the sensitivity of cliff erosion to the variability in wave climate and beach morphology at two different locations in the south-west of the UK, where the vast majority (over 85% of the annual value) of cliff face erosion occurs during the winter when extreme storm waves prevail. Coastal cliff erosion from storm waves is observed worldwide but the processes are notoriously difficult to measure during extreme storm wave conditions when most erosion normally occurs, limiting our understanding of cliff processes. Over January-March 2014, during the largest Atlantic storms in at least 60 years with deep water significant wave heights of 6 – 8 m, cliff-top ground motions of a rocky cliff in the south-west of the UK (Porthleven, Cornwall) showed vertical ground displacements in excess of 50–100 μm; an order of magnitude larger than observations made previously. Repeat terrestrial laser scanner surveys, over a 2-week period encompassing the extreme storms, gave a cliff face volume loss 2 orders of magnitude larger than the long-term erosion rate. Cliff-top ground motions and erosion volumes were compared at two different locations, one a reflective beach with steeply shelving bathymetry (Porthleven, Cornwall) and the other an intermediate, low tide bar-rip beach with a wide coastal slope (Godrevy, Cornwall). Under similar wave conditions (6–8 m Hs and 15–20 s. Tp) the vertical ground motions were an order of magnitude greater at the cliffs fronted by steeply shelving bathymetry, where the breaking waves plunge right at the shoreline, with little prior dissipation, leading to large energetic runup impacting the cliff. These storm results imply that erosion of coastal cliffs exposed to extreme storm waves is highly episodic and that long-term rates of cliff erosion will depend on the frequency and severity of extreme storm wave impacts as well as the wave dissipation that occurs as a function of the nearshore bathymetry. Having recorded microseismic cliff-top motion on this scale for the first time and determined an effective method of monitoring the energetic wave impacts, this study emphasises how investigations of cliff behaviour during storms is not only obtainable, but paramount to understanding coastal evolution under extreme conditions.
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Balaji, Uma. "Field theory analysis and design of circular waveguide components." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ32732.pdf.
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Wlodarczyk, A. J. "The application of spectral synthesis in electromagnetic field problems." Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381100.
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Jönsson, Anette. "The Baltic Sea wave field : impacts on the sediment and biogeochemistry /." Linköping : Tema, Univ, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5565.
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Li, Fei 1959. "Flow field modifications and wave development in a plane Poiseuille flow." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/42483.
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Silva, Marcio José da. "Modelagem de um sistema para auralização musical utilizando Wave Field Synthesis." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/27/27158/tde-18052015-163521/.
Full textAbstract:
Buscando-se a aplicação prática da teoria de Wave Field Synthesis (WFS) na música, foi feita uma pesquisa visando à modelagem de um sistema de sonorização capaz de criar imagens sonoras espaciais com a utilização desta técnica. Diferentemente da maioria das outras técnicas de sonorização, que trabalham com uma região de escuta pequena e localizada, WFS permite projetar os sons de cada fonte sonora - como instrumentos musicais e vozes - em diferentes pontos do espaço de audição, em uma região de escuta que pode abranger quase toda a área compreendida por este espaço, dependendo da quantidade de alto-falantes instalados. O desenvolvimento de um código de estrutura modular para WFS foi baseado na plataforma orientada a patches Pure Data (Pd), e no sistema de auralização AUDIENCE, desenvolvido na USP, sendo integrável como ferramenta para espacialização sonora interativa. A solução emprega patches dinâmicos e uma arquitetura modular, permitindo flexibilidade e manutenabilidade do código, com vantagens frente a outros software existentes, particularmente na instalação, operação e para lidar com um número elevado de fontes sonoras e alto-falantes. Para este sistema também foram desenvolvidos alto-falantes especiais com características que facilitam seu uso em aplicações musicais.Seeking the practical application of the theory of Wave Field Synthesis (WFS) in music, a research aimed at modeling a sound system capable of creating spatial sound images with the use of this technique was made. Unlike most other techniques for sound projection that work with a small, localized listening area, WFS allows projecting the sounds of each sound source - such as musical instruments and voices - at different points within the hearing space, in a region that can cover almost the entire area comprised by this space, depending on the amount of installed speakers. The development of a modular structured code for WFS was based on the patch-oriented platform Pure Data (Pd), and on the AUDIENCE auralization system developed at USP, and it is integrable as a tool for interactive sound spatialization. The solution employs dynamic patches and a modular architecture, allowing code flexibility and maintainability, with advantages compared to other existing software, particularly in the installation, operation and to handle a large number of sound sources and speakers. For this system special speakers with features that facilitate its use in musical applications were also developed.
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Corteel, Etienne. "Caractérisation et extensions de la wave field synthesis en conditions réelles." Paris 6, 2004. http://www.theses.fr/2004PA066410.
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Odarenko, E. N., Y. V. Sashkova, and A. A. Shmat’ko. "Localized field enhancement in slow-wave modes of modified Bragg waveguide." Thesis, IEEE, 2017. https://openarchive.nure.ua/handle/document/18123.
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Modified scheme of Bragg reflection waveguide
with additional layers between the hollow core and cladding is
considered. Dispersion diagrams are calculated on the base of
dispersion equations solutions for ordinary and modified Bragg
waveguides. Slow-wave regimes are considered for both kinds of
structure. Electric field spatial distributions for localized slowwave
modes of Bragg reflection waveguide are obtained. It is
shown that modified scheme of Bragg waveguide provides the
enhanced localization of the surface modes field in the hollow
core. Therefore modified Bragg waveguide is the promising
electrodynamic system not only for laser-driven accelerators but
also for the vacuum electron devices where usual slow-wave
structures are unconvenient.
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PUEO, ORTEGA BASILIO JAVIER. "Analysis and enhancement of multiactuator panels for wave field synthesis reproduction." Doctoral thesis, Universitat Politècnica de València, 2008. http://hdl.handle.net/10251/3347.
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Esta tesis aborda el desarrollo y mejora de los altavoces de panel multiexcitados (MAPs) con particular importancia en su aplicación para la reproducción de síntesis de campo (WFS). Los altavoces MAPs pueden usarse como alternativa a las agrupaciones de altavoces dinámicos para WFS con ventajas adicionales. Sin embargo, puesto que los altavoces MAPs son paneles finitos que se excitan en varios puntos de su superficie, existen cuestiones estructurales y geométricas que deben ser tratadas para garantizar que todos los excitadores actúan uniformemente para crear una agrupación de altavoces válida para WFS. Este objetivo se acomete a través de un método para el análisis de la radiación del campo sonoro en el dominio espacio-temporal que ha sido propuesto y validado en esta tesis. De la presente investigación se desprenden diversas conclusiones. El método propuesto analiza las imperfecciones del campo sonoro por el submuestreo espacial en una representación gráfica que muestra la distribución de energía radiada en el espacio. Mediante un estudio comparativo entre altavoces MAPs de diferentes tamaños y agrupaciones de altavoces dinámicos, la principal conclusión que se desprende, con implicaciones prácticas, es que el campo creado por paneles de grandes dimensiones presenta menos imperfecciones que el de paneles pequeños equivalentes. El efecto del contorno del panel en la calidad del campo creado también se ha considerado al comparar varias condiciones de contorno con diversos materiales elásticos. La conclusión principal es la conveniencia de usar condiciones elásticas que pueden crear una tecnología viable de sujeción de paneles y que presentan una radiación acústica adecuada. Los bordes también afectan a la respuesta de los excitadores cercanos, que debe ser convenientemente ecualizada para obtener una respuesta similar a la de los excitadores centrales.Pueo Ortega, BJ. (2008). Analysis and enhancement of multiactuator panels for wave field synthesis reproduction [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/3347
Palancia
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Bharadwaj, Sripoorna Paniyadi Krishna. "Theoretical Study of Spin-wave Effects in Quantum Ferromagnets." Thesis, University of Oregon, 2017. http://hdl.handle.net/1794/22640.
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In this dissertation, we examine quantum ferromagnets and determine various effects of the magnetic Goldstone modes or "magnons'' in these systems.
Firstly, we calculate the magnon contribution to the transport relaxation rate of conduction electrons in metallic ferromagnets and find that at asymptotically low temperatures, the contribution behaves as T^2 exp(-T_0/T) and not as T^2 predicted previously. To perform these calculations, we derive and use a very general effective theory for metallic ferromagnets. This activation barrier-like behavior is due to the fact that spin waves only couple electrons from different Stoner subbands that arise from the splitting of the conduction band in presence of a nonzero magnetization. The T^2 behavior is found to be valid only in a pre-asymptotic temperature window. The temperature scale T_0 is the energy of the least energetic ferromagnon that couples electrons of different spins.
Second, we discuss magnon-induced long-range correlation functions in quantum magnets. In the ordered phases of both classical ferromagnets and antiferromagnets, the long-range correlations induced by the magnons lead to a singular wavenumber dependence of the longitudinal order-parameter susceptibility in spatial dimensions 2
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Banfi, Davide. "A field and laboratory study on the dynamic response of the Eddystone lighthouse to wave loading." Thesis, University of Plymouth, 2018. http://hdl.handle.net/10026.1/11607.
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Because little was known about how the masonry lighthouses constructed during the 19th century at exposed locations around the British Isles were responding to wave action, the dynamic response of the Eddystone lighthouse under wave impacts was investigated. Like other so called 'rock lighthouses', the Eddystone lighthouse was built on top of a steep reef at a site that is fully submerged at most states of the tide. Consequently, the structure is exposed to loading by unbroken, breaking and broken waves. When the breaking occurs, wave loading leads to complex phenomena that cannot be described theoretically due to the unknown mixture of air and water involved during the wave-structure interaction. In addition, breaking waves are generally distinguished from unbroken and broken wave due to the fact that they cause impulsive loads. As a consequence, the load effects on the structural response require a dynamic analysis. In this investigation the dynamic response of the Eddystone lighthouse is investigated both in the field and by means of a small-scale model mounted in a laboratory wave channel. In particular, field data obtained by the use of geophones, cameras and a wave buoy are presented together with wave loading information obtained during the laboratory tests under controlled conditions. More than 3000 structural events were recorded during the exceptional sequence of winter storms that hit the South-West of England in 2013/2014. The geophone signals, which provide the structural response in terms of velocity data, are differentiated and integrated in order to obtain accelerations and displacements respectively. Dynamic responses show different behaviours and higher structural frequencies, which are related to more impulsive loads, tend to exhibit a predominant sharp peak in velocity time histories. As a consequence, the structural responses have been classified into four types depending on differences of ratio peaks in the time histories and spectra. Field video images indicate that higher structural frequencies are usually associated with loads caused by plunging waves that break on or just in front of the structure. However, higher structural velocities and accelerations do not necessarily lead to the largest displacements of around a tenth of mm. Thus, while the impulsive nature of the structural response depends on the type of wave impact, the magnitude of the structural deflections is strongly affected by both elevation of the wave force on the structure and impact duration, as suggested by structural numerical simulations and laboratory tests respectively. The latter demonstrate how the limited water depth strongly affects the wave loading. In particular, only small plunging waves are able to break on or near the structure and larger waves that break further away can impose a greater overall impulse due to the longer duration of the load. As a consequence of the depth limited conditions, broken waves can generate significant deflections in the case of the Eddystone lighthouse. However, maximum accelerations of about 0.1g are related to larger plunging waves that are still able to hit the lighthouse with a plunging jet. When compared to the Iribarren number, the dimensionless irregular momentum flux proposed by Hughes is found to be a better indicator concerning the occurrence of the structural response types. This is explained by the fact that the Iribarren number does not to take into account the effects of the wide tidal range at the Eddystone reef, which has a strong influence on the location of the breaking point with respect to the lighthouse. Finally, maximum run up were not able to rise up to the top of the lighthouse model during the laboratory tests, despite this having been observed in the field. As a consequence, the particular configuration of the Eddystone reef and the wind could have a considerable bearing and exceptional values of the run up, greater than 40 m, cannot be excluded in the field.
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Chen, Shuoqi. "Characterization of semiconductor-based guided wave structures using field theoretical analysis techniques." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21927.pdf.
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Hirisave, Shivaram Niranjan. "Attosecond Resolved Electron Wave Packet Dynamics in Helium." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/293618.
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Electron dynamics in atoms and molecules occurs on a time-scale of attoseconds (10⁻¹⁸s). With the availability of strong field (∼ 10¹²- 10¹³ W cm⁻²) femtosecond (10⁻¹⁵s) laser pulses with electric fields that can reach and exceed the Coulomb field strength experienced by an electron in the ground state of an atom, it is now possible to generate even shorter pulses with durations on the order of attoseconds by the process of high-harmonic generation (HHG). In this dissertation, experiments to study electron dynamics on attosecond time-scales in a helium atom using attosecond pulses generated by HHG will be described. We use extreme-ultraviolet (XUV) attosecond pulse trains and strong femtosecond near-infrared (IR) laser pulses to excite and ionize helium atoms. We first discuss an experimental technique that allows us to quantify and reduce the detrimental effects of Gouy phase slip on attosecond XUV-IR experiments. We then discuss our experiments to study the dynamic behavior of electronic states in a strong field modified helium atom where we use attosecond pulses to explore the strong-field modified atomic landscape. Using the Floquet theory to interpret our experimental observations we measure the variation in quantum phase of interferences between different fourier components of Floquet states as the IR intensity is varied and as different ionization channels dominate, in real-time. Next, we briefly discuss quantum interferences between photo-electrons ionized from XUV excited states in helium using an IR field which is polarized orthogonal to the XUV polarization. We observe variation in angular distribution of photo-electrons as a function of XUV-IR time-delay. We then discuss a new technique to measure the time-of-birth of attosecond pulses using XUV+IR photo-ionization in helium as a measurement probe. Finally, experiments to study the evolution of XUV excited wave-packets in helium on a time-scale of 100's of femtoseconds with attosecond resolution will be described.
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Crawford, Anna M. "Field observations of linear transition ripple migration and wave orbital velocity skewness." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ54833.pdf.
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Izadian, Kaykhosro. "Blast wave from the explosion of finite pressurized sphere - far field experience." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107882.
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In the present research, the far field behaviour of the non-ideal blast waves generated by the explosion of a pressurized sphere is investigated. Roe's method is used to solve conservation laws for propagation of the non-ideal blasts. Two cases of bursting spheres are investigated: the hot sphere and the cold sphere. Far field equivalency between ideal and non-ideal blast waves is examined based on matching shock overpressure curves, shock trajectories and flow properties. The numerical solution indicates that the hot sphere blast and the ideal point blast of the same initial energy are equivalent in the far field. In contrary with the hot sphere blast, the present study showed that the cold sphere blast is not equivalent with the ideal point blast of the same initial energy. Moreover, the overpressure curves for hot spheres with different initial pressure at the same initial energy coalesce in the far field. However, the overpressure curves for cold spheres with different initial pressure at the same initial energy do not merge in the far field. The shock overpressure of strong explosion of cold sphere is superior compared to that of ideal point source with the same initial energy in the far field. On the other hand, the shock overpressure of weak explosion of cold sphere is inferior compared to that of corresponding ideal point source at the same initial energy. The present study also elaborates on the definition of the energy of a pressurized sphere. It is concluded that the energy calculated from Brode's formula is the true explosion energy. This is the energy which is given to the environment by the propagation of the blast resulted from bursting of the sphere. In addition, it is shown that flow properties of hot sphere and ideal point blast match in the far field, only in the part of the gas near the shock front. The energy of this part was computed and it is called self-similar energy. This energy was used to determine the hot sphere shock trajectory in the far field. The other parts of the gas near the center of the hot sphere retain the non-ideal initial conditions. The flow properties of cold sphere and ideal point blast do not match in the far field.Dans la présente recherche, le comportement en champ lointain des vagues de non-idéal souffle engendré par l'explosion d'une sphère pressurisée est étudié. Méthode de Roe est utilisée pour résoudre des lois de conservation pour la propagation du non-idéal explosions. Deux cas d'éclatement des sphères sont étudiés: la sphère chaude et froide de la sphère. L'équivalence entre le champ lointain ondes de souffle idéal et non idéal est examinée sur la base des courbes correspondant surpression de choc, les trajectoires de choc et propriétés d'écoulement. La solution numérique indique que l'explosion de sphère chaude et point idéal explosion de la même énergie initiale est équivalente dans le champ lointain. Au contraire avec l'explosion de sphère chaude, la présente étude a montré que l'explosion de sphère froide n'est pas équivalente à l'explosion point idéale de la même énergie initiale. De plus, les courbes de surpression pour les sphères chaudes avec pression initiale différente à la même énergie initiale fusionner dans le champ lointain. Toutefois, les courbes de surpression pour les sphères froide avec pression initiale différente à la même d'énergie initiale ne pas fusionner dans le champ lointain. choc de surpression de la forte explosion de la sphère froide est supérieure par rapport à la surpression de choc de source ponctuelle idéale avec la même énergie initiale dans le champ lointain d'ailleure que la surpression d'explosion de choc faibles de la sphère froide est inférieure par rapport à la surpression de choc de point idéal correspondant source à la même énergie initiale.La présente étude expose également sur la définition de l'énergie d'une sphère pressurisée et conclut que l'énergie de la formule de Brode est l'énergie véritable explosion, qui est l'énergie donnée à l'environnement par la propagation de l'explosion résulte de l'éclatement de la sphère. Cette énergie est appelée auto-similaire de l'énergie. Cette énergie a été utilisée pour déterminer la trajectoire choc de la sphère chaude dans le champ lointain. Les autres parties du gaz près du centre de la sphère conserver les non-idéales conditions initiale.
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Oldfield, R. G. "The analysis and improvement of focused source reproduction with wave field synthesis." Thesis, University of Salford, 2013. http://usir.salford.ac.uk/29510/.
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This thesis presents a treatise on the rendering of focused sources using wave field synthesis (WFS). The thesis describes the fundamental theory of WFS and presents a thorough derivation of focused source driving functions including, monopoles, dipoles and pistonic sources. The principle characteristics of focused sources including, array truncation, spatial aliasing, pre-echo artefacts, colouration and amplitude errors are analysed in depth and a new spatial aliasing criterion is presented for focused sources. Additionally a new secondary source selection protocol is presented allowing for directed and symmetrically rendered sources. This thesis also describes how the low frequency rendering of focused sources is limited by the focusing ability of the loudspeaker array and thus derives a formula to predict the focusing limits and the corresponding focal shift that occurs at low frequencies and with short arrays. Subsequently a frequency dependent position correction is derived which increases the positional accuracy of the source. Other characteristics and issues with the rendering of focused sources are also described including the use of large arrays, rendering of moving focused sources, issues with multiple focused sources in the scene, the phase response, and the focal point size of focused sound field. The perceptual characteristics are also covered, with a review of the literature and a series of subjective tests into the localisation of focused sources. It is shown that an improvement in the localisation can be achieved by including the virtual first order images as point sources into the WFS rendering. Practical rendering of focused sources is generally done in compromised scenarios such as in non-anechoic, reverberant rooms which contain various scattering objects. These issues are also covered in this thesis with the aid of finite difference time domain models which allow the characterisation of room effects on the reproduced field, it is shown that room effects can actually even out spatial aliasing artefacts and therefore reduce the perception of colouration. Scattering objects can also be included in the model, thus the effects of scattering are also shown and a method of correcting for the scattering is suggested. Also covered is the rendering of focused sources using elevated arrays which can introduce position errors in the rendering.
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McNatt, J. Cameron. "Wave field patterns generated by wave energy converters." Thesis, 2012. http://hdl.handle.net/1957/33939.
Full textAbstract:
The eventual deployment of wave energy converters (WECs) on a commercial scale will necessitate the grouping of devices into arrays or "wave farms," in order to minimize overhead costs of mooring, maintenance, installation, and electrical cabling for shoreward power delivery. Closely spaced WECs will interact hydrodynamically through diffracted and radiated waves. Recent research has focused on the WEC wave field and used its structures to design constructive WEC arrays as well as to describe the means of WEC energy absorption. In this study, the WEC wave field is investigated for a single WEC and a five WEC array with linear wave theory and experimental results. Both regular waves and spectral seas are considered. Computational results are produced with the linear boundary-element-method (BEM) hydrodynamic software WAMIT for a simple WEC geometry. Experimental data comes from WEC array tests that took place at Oregon State University over the winter of 2010-11 [1]. The experimental measurements help validate the computational modeling, and the computational models serve as an aid to interpreting the experimental data.
Results reveal two universal WEC wave field features - partially standing waves and a wave shadow, both of which are the result of the coherent interaction of the planar incident wave with the circular generated wave, composed of
the diffracted and radiated waves. The partial standing waves in the offshore are seen qualitatively in experimental data but could not be exactly reproduced computationally, because the computational model is only a simple representation of the physical model. In the lee of the WEC, the measured longshore structure of the wave shadow is in good agreement with theoretical expectations as well as computational results. It is believed that the agreement is
because the formation of the wave shadow is dominated by energy extraction, which was approximately the same for both the computational and physical models.
A study of the linear WEC wave field in regular waves and spectral seas reveals patterns such as the wave shadow that have also been found in experimental data. The positions and magnitudes of the offshore partially standing
waves are very sensitive to wavelength, and WEC geometry, motions and location, and in spectral seas, they are smoothed when considering significant wave height. All of which suggest that it may be difficult to use them advantageously in the design of WEC arrays. The wave shadow is a dominant feature of the WEC wave field for both regular waves and spectral seas. It appears to be fairly generic and to be based on power absorption. In the
design of WEC arrays, rather than attempting constructive interference by using standing wave crests, perhaps the best one can do is to avoid destructive interference of the wave shadow.Graduation date: 2013
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Leng-HsuanTseng and 曾薐璇. "Freak Wave Occurrence Probability in a Nonlinear Wave Field." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/69490452906039016641.
Full textAbstract:
碩士國立成功大學
水利及海洋工程學系碩博士班
101
Freak wave will cause huge risks to ships or people doing costal activities. Prediction of freak wave can provide information for early warning and then decrease risk of hazards. Since the mechanism of freak wave is still unclear so far, deterministic prediction is not possible. Therefore stochastic method is used by this study for research of occurrence probability prediction of freak wave. In this study, nonlinear wave theory is applied for formula to estimate freak wave occurrence probability. Result demonstrates that occurrence probability of freak wave is related to two parameters: number of waves and kurtosis of water elevation. Analysis of the formula shows the maximum occurrence probability can become four times larger than the probability estimared under linear condition. Moreover, validated by the continuous measured data at Bisa Harbor, the average root-mean-square-error of assessment of occurrence probability is 22.4%. The possible reason to this difference is the ratio of significant wave height and root-mean-square of water elevation, which is assumed to be 4 under linear condition. Modified the formula by our field measurement data, the accuracy of estimation of occurrence probability improved. The modified formula is also validated by other in-situ data and can be used for future works with better assessments.
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SHI, YOU-CHENG, and 石有成. "Millimeter-wave image line field analyses." Thesis, 1988. http://ndltd.ncl.edu.tw/handle/79569624495422770246.
Full text
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Dai, Ting-Yu, and 戴廷育. "Field study of wave run-up." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/ub3qh9.
Full textAbstract:
碩士國立中山大學
海洋環境及工程學系研究所
97
It is important to estimate the quantity of wave run-up and overtopping in seawall design. Previous study on the investigations of run-up is carried out mostly in the laboratories, it seldom perform in field measurements. About previous wave run-up equation can’t accurately estimate run-up elevation. According to run-up data, this study hope that it can make the formula to meet the actual local situation. It can have a better reference by designing coastal structures. This paper study wave run-up during five typhoons by Kalmaegi ,Fung-Wong,Nuri, Hagupit,and Jangmi. It measuring wave height , water level,and topography. These data show that the run-up elevation in bay higher than in breakwater. It shows that wave pass through a submerged breakwater can decay wave height. Analysis of measured data and found that when the wave height is about 1~4 meter with 1/(H0/L0)0.5 has a good correlation. It similar to some past researchers. Experience equations close to measured value when wave height smaller than 4 meter. When wave height more than 4 meter, the empirical prediction value is larger than measured value. Wave run-up doesn’t have good theory, and experience equations different about every field. The empirical equations depends on the scene to investigate the effects of various parameter.