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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Limts Of Beach And Dune Erosion In Response To Wave Runup From Large-Scale Laboratroy Data

Roberts, Tiffany M 30 April 2008 (has links)
The SUPERTANK dataset is analyzed to examine the upper limit of beach change in response to elevated water level induced by wave runup. Thirty SUPERTANK runs are investigated, including both erosional and accretionary wave conditions under random and monochromatic waves. Two experiments, one under a spilling and one under a plunging breaker-type, from the Large-Scale Sediment Transport Facility (LSTF) are also analyzed. The upper limit of beach change approximately equals the maximum vertical excursion of swash runup. Exceptions to this direct relationship are those with beach or dune scarps when gravity-driven changes, i.e., avalanching, become significant. The vertical extent of wave runup, Rmax, above mean water level on a beach without a scarp is found to approximately equal the significant breaking wave height, Hbs. Therefore, a simple formula Rmax = Hbs is proposed. The linear relationship between maximum runup and breaking wave height is supported by a conceptual derivation. This predictive formula reproduced the measured runup from a large-scale 3-dimensional movable bed physical model. Beach and dune scarps substantially limit the uprush of swash motion, resulting in a much reduced maximum runup. Predictions of wave runup are not improved by including a slope-dependent surf-similarity parameter. The limit of wave runup is substantially less for monochromatic waves than for random waves, attributed to absence of low-frequency motion for monochromatic waves.
22

Computational Real-Time Sound Synthesis of Rain

Zita, Andreas January 2003 (has links)
<p>Real-time sound synthesis in computer games using physical modeling is an area with great potential. To date, most sounds are pre-recorded to match a certain event. Instead by using a model to describe the sound producing event, a number of problems encountered when using pre-recorded sounds can be avoided. This thesis will introduce these problems and present a solution. The thesis will also evaluate one such physical model, for rain sound, and implement a real- time simulation to demonstrate the advantages of the method.</p>
23

Ground Movements in the Zagros Fold-Thrust Belt of SW Iran Measured by GPS and InSAR Compared to Physical Models

Nilfouroushan, Faramarz January 2007 (has links)
<p>This thesis uses geodetic satellite data to measure present-day crustal deformation in the Zagros fold-thrust belt (SW Iran). Geodetic-type measurements are also used in down-scaled models that simulate the surface deformations seen in convergent settings like the Zagros fold-thrust belt.</p><p>Global Positioning System (GPS) measurements of three surveys between 1998 and 2001 indicate 9 ± 3 mm/yr and 5 ± 3 mm/yr shortening across the SE and NW Zagros respectively. GPS results show that in addition to the different rates and directions of shortening on either side of the NS trending Kazerun fault, local along-belt extension occurs to the east. </p><p>Differential SAR interferograms of ERS1 & 2 images between 1992 and 1999 detect 8 ± 4 mm/yr uplift rate across a newly recognized fault in SW Qeshm Island. This can be attributed to a steep imbricate thrust that may still represent the local Zagros deformation front.</p><p>The salt diapirs in the Zagros rise from a source layer that acts as a low-frictional decollement that decouples the deformation of the cover sediments from their basement in the eastern Zagros whereas the cover to the west deforms above a high-friction decollement. Physical models were prepared to simulate cover deformation in the Zagros by shortening a sand pack above adjacent high- and low-frictional decollements (represented by a ductile layer). The strain distributions differed above the two types of decollements; it was more heterogeneous above the salt where local extension in the shortening direction was dominant. A separate work also investigated systematically the role of basal friction on cover deformation in convergent settings. Accurate height measurements of the model surface by laser-scanner indicated a deformation front more distal than usual, particularly in the low-basal frictional models. The volume reduction in our shortened sand models correlated directly with their basal friction.</p>
24

Ground Movements in the Zagros Fold-Thrust Belt of SW Iran Measured by GPS and InSAR Compared to Physical Models

Nilfouroushan, Faramarz January 2007 (has links)
This thesis uses geodetic satellite data to measure present-day crustal deformation in the Zagros fold-thrust belt (SW Iran). Geodetic-type measurements are also used in down-scaled models that simulate the surface deformations seen in convergent settings like the Zagros fold-thrust belt. Global Positioning System (GPS) measurements of three surveys between 1998 and 2001 indicate 9 ± 3 mm/yr and 5 ± 3 mm/yr shortening across the SE and NW Zagros respectively. GPS results show that in addition to the different rates and directions of shortening on either side of the NS trending Kazerun fault, local along-belt extension occurs to the east. Differential SAR interferograms of ERS1 &amp; 2 images between 1992 and 1999 detect 8 ± 4 mm/yr uplift rate across a newly recognized fault in SW Qeshm Island. This can be attributed to a steep imbricate thrust that may still represent the local Zagros deformation front. The salt diapirs in the Zagros rise from a source layer that acts as a low-frictional decollement that decouples the deformation of the cover sediments from their basement in the eastern Zagros whereas the cover to the west deforms above a high-friction decollement. Physical models were prepared to simulate cover deformation in the Zagros by shortening a sand pack above adjacent high- and low-frictional decollements (represented by a ductile layer). The strain distributions differed above the two types of decollements; it was more heterogeneous above the salt where local extension in the shortening direction was dominant. A separate work also investigated systematically the role of basal friction on cover deformation in convergent settings. Accurate height measurements of the model surface by laser-scanner indicated a deformation front more distal than usual, particularly in the low-basal frictional models. The volume reduction in our shortened sand models correlated directly with their basal friction.
25

Modeling and Simulation of Physical Systems in a Mechatronic Context

Sjöstedt, Carl-Johan January 2009 (has links)
This thesis gives different views on the modeling and simulation of physical systems, especially together with embedded systems, forming mechatronic systems. The main considered application domain is automotive. One motivation behind the work is to find suitable representations of physical systems to be used in an architectural description language for automotive embedded systems, EAST-ADL2, which is implemented as a UML2 profile, and uses concepts from both UML and SysML. As a part of the thesis, several languages and tools are investigated, including bond graphs, MATLAB/Simulink, Ptolemy II, Modelica, MATLAB/Simscape and SysML. For SysML, the modeling of continuous-time systems and how it relates to MATLAB/Simulink and Modelica is evaluated. A case study of an electric power assisted steering is modeled to show the differences, the similarities and the usage of the above mentioned languages and tools. To be able to classify the tools and languages, five realization levels were developed: Physical modeling models Constraint models Continuous causal models Discretized models Discretized models with solver and platform implementation By using these realization levels, models, tools and modeling languages can be classified, and transformations between them can be set up and analyzed. As a result, a method to describe the simulation behavior of a MATLAB/Simulink model has been developed using SysML activity diagrams as an approach to achieve integrated system models. Another result is an evaluation of the parametric diagrams of SysML for continuous-time modeling, which shows that they do not enable “physical modeling”, i.e. modeling the topology of the system and getting the underlying equations out of this topology. By including physical ports and physical connectors to SysML internal block diagrams, this could be solved. The comparison also shows many similarities between the languages. The results led to a more detailed investigation on conjugate variables, such as force and velocity, and electric current and voltage, and how these are treated in various languages. The thesis also includes two industrial case studies: one of a twin-screw compressor, and one of a simulation environment for automotive fuel-cell systems. Conclusions are drawn from these models, referring to the realization levels. / QC 20100810
26

Síntese por modelagem física da clarineta = modelo por guia de ondas com escoamento / Synthesis by physical modeling of the clarinet : model using waveguides with flow

Oliveira, Luís Carlos de 08 December 2011 (has links)
Orientadores: Rafael Santos Mendes, Ricardo Goldemberg / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-18T23:37:16Z (GMT). No. of bitstreams: 1 Oliveira_LuisCarlosde_D.pdf: 5521873 bytes, checksum: 20aeecff279d6a276f652e26512c7903 (MD5) Previous issue date: 2011 / Resumo: Este trabalho aplica a técnica do guia de ondas digital ("Digital Waveguide") na síntese de instrumentos de sopro da família das madeiras, em particular, da clarineta. Esta técnica foi desenvolvida na década de 1980 e, desde então, tem sido utilizada em síntese de instrumentosmusicais por modelagem física. A técnica consiste, grosso modo, no processo de discretização da solução por ondas viajantes da Equação da Onda. Este procedimento permite obter uma estrutura de filtros digitais que simula a propagação da onda sonora para a direita e para a esquerda com velocidade de propagação equivalente à velocidade do som, c. No entanto, nos resultados de modelagem física publicados, constatou-se a ausência da velocidade de escoamento do ar, u. A contribuição deste trabalho consiste em reelaborar a estrutura de filtros digitais de modo a contemplar a velocidade de escoamento do fluido. A fundamentação teórica estabelece que para um meio de propagação sonora em movimento as velocidades de propagação para a direita é c + u e para a esquerda é c ? u. Propõe-se então, uma estratificação do tubo da clarineta em camadas divididas por mesma área ou mesma largura de modo a verificar a influência do perfil de velocidades na síntese sonora. Foi observado que a inclusão do escoamento implica uma "distorção" na curva da pressão interna do tubo, o que aproxima essa forma dos resultados experimentais / Abstract: This study aims to apply the technique of Digital Waveguide in synthesis of woodwind instruments, particularly the clarinet. This technique was developed in the mid-80 and since then, has application in the synthesis of musical instruments by physical modeling. It consists, roughly, in the process of discretization of the traveling wave solution of the Wave Equation. This leads to a digital filter structure that simulates the propagation of sound waves to the right and left with the speed of sound propagation, c. However, in the published results of physical modeling, the air flow velocity, u, was not included. The contribution of this work is to redesign the structure of digital filters in order to contemplate the velocity of the fluid. The theoretical framework provides that in a medium in motion the velocities of propagation to the right is c + u and to the left is c ? u. It is proposed then a stratification of the tube of the clarinet in layers divided by the same area or same width in order to verify the influence of velocity profile in the synthesized sound. It was observed that the inclusion of flow provides a "distortion" in the internal pressure of the tube. It sets resemblance to experimental results / Doutorado / Engenharia de Computação / Doutor em Engenharia Elétrica
27

Modelagem física de meios fraturados anisotrópicos e estudo da birrefringência sísmica em função dos parâmetros anisotrópicos / Physical modeling of anisotropic fractured media and study of seismic splitting as a function of the anisotropic parameters

Figueiredo, José Jadsom Sampaio de 03 May 2012 (has links)
Orientador: Joerg Dietrich Wilhelm Schleicher / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências / Made available in DSpace on 2018-08-20T00:32:10Z (GMT). No. of bitstreams: 1 Figueiredo_JoseJadsomSampaiode_D.pdf: 25764128 bytes, checksum: 358c6580d480aca067e19d0095ab844b (MD5) Previous issue date: 2012 / Resumo: Meios anisotrópicos fissurados ou fraturados têm sido amplamente investigados em muitos estudos teóricos e experimentais. Neste trabalho, realizamos uma série de medidas ultrassônicas objetivando investigar o comportamento de diferentes meios artificialmente anisotrópicos. Três questões foram abordadas: (1) estudo da birrefringência da onda S em função da frequência da fonte, (2) estimativa das direções de fraturas através de ondas elásticas e (3) o estudo do excesso de complacência em meio transversalmente isotrópico com a inclusão de fissuras. No primeiro caso, o efeito da frequência da fonte na estimativa dos parâmetros elásticos (o parâmetro de Thomsen e a atenuação de ondas cisalhantes) foi estudado em três modelos anisotrópicos contendo inclusões (pequenos discos de borrachas) em uma matriz sólida de resina epóxi e densidade de fissuras variando de 0 para 6,2 %. Dois dos três modelos fissurados tem 10 camadas enquanto o outro tem 17. Medidas de birrefringência das onda S têm mostrado que efeitos de dispersão são mais proeminentes em modelos em que a razão entre o comprimento de onda sísmica e a abertura da fissura é 1,6 - 1,64 do que para outros modelos em que essa razão está variando entre 2,72 - 2,85. O modelo com grandes fissuras deu uma magnitude de atenuação três vezes maior em comparação com outro modelo que tinha pequenas inclusões. Os resultados para estes modelos indicam que o espalhamento elástico, as atenuações intrínseca e de espalhamento ...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital / Abstract: Anisotropic cracked media have been widely investigated in many theoretical and experimental studies. In this work, we have performed ultrasonic surveys to investigate the behavior of different artificially anisotropic media. Three questions were addressed here: (1) study of the S-wave splitting as a function of source frequency, (2) estimation of the fracture directions using elastic waves and (3) investigation of compliance excess in transversally isotropic media with crack inclusions. Firstly, we studied the effect of source frequency on the estimation of elastic parameters (the Thomsen parameter and shear-wave attenuation) in four anisotropic models containing cracks simulated by penny-shaped rubber inclusions in a solid epoxy resin matrix with crack density that ranges from 0 to 6.2 %. Two of the three cracked models have 10 layers and the last one has 17 layers. Our S-wave splitting measurements have shown that scattering e_ects are more prominent in models where the ratio of seismic wavelength to crack aperture ranges from 1.6 to 1.64 than in other models where this ratio varies from 2.72 to 2.85. The model with large cracks gave a magnitude of attenuation three times higher as compared with another model that had small inclusions. The results for these models indicate that elastic scattering, intrinsic and scattering attenuation ...Note: The complete abstract is available with the full electronic document / Doutorado / Reservatórios e Gestão / Doutor em Ciências e Engenharia de Petróleo
28

Computational Real-Time Sound Synthesis of Rain

Zita, Andreas January 2003 (has links)
Real-time sound synthesis in computer games using physical modeling is an area with great potential. To date, most sounds are pre-recorded to match a certain event. Instead by using a model to describe the sound producing event, a number of problems encountered when using pre-recorded sounds can be avoided. This thesis will introduce these problems and present a solution. The thesis will also evaluate one such physical model, for rain sound, and implement a real- time simulation to demonstrate the advantages of the method.
29

Diagnostic du colmatage des générateurs de vapeur à l'aide de modèles physiques et statistiques / Steam generators clogging diagnosis through physical and statistical modelling

Girard, Sylvain 17 December 2012 (has links)
Les générateurs de vapeur sont d'imposants échangeurs de chaleur qui alimentent les turbines des centrales nucléaires à eau pressurisée. Au cours de leur exploitation, des dépôts d'oxydes s'y accumulent et obstruent progressivement des trous prévus pour le passage du fluide. Ce phénomène, appelé colmatage, pose des problèmes de sûreté. Une méthode de diagnostic est nécessaire pour optimiser la stratégie de maintenance permettant de s'en prémunir. La piste explorée dans cette thèse est l'analyse de la réponse dynamique des générateurs de vapeur lors de transitoire de puissance, à l'aide d'un modèle physique monodimensionnel. Deux améliorations ont été apportées au modèle existant au cours de la thèse : la prise en compte des débits perpendiculaires à l'axe du générateur de vapeur et la modélisation du déséquilibre cinématique entre la phase liquide et la phase vapeur. Ces éléments ont ajouté des degrés de liberté permettant de mieux reproduire le comportement réel des générateurs de vapeur. Une nouvelle méthodologie de calage et de validation a alors été proposée afin de garantir la robustesse du modèle.Le problème inverse initial était mal posé car plusieurs configurations spatiales de colmatage peuvent donner des réponses identiques. La magnitude relative de l'effet des dépôts suivant leur localisation a été évaluée par analyse de sensibilité avec la méthode de Sobol'. La dimension de la sortie fonctionnelle du modèle a au préalable été réduite par une analyse en composantes principales.Enfin, une méthode de réduction de dimension appelée régression inverse par tranches a été mise en œuvre pour déterminer dessous-espaces de projection optimaux pour le diagnostic. Une méthode de diagnostic plus robuste et mieux maitrisée que celle existante a pu être proposée grâce à cette nouvelle formulation. / Steam generators are massive heat exchangers feeding the turbines of pressurised water nuclear power plants. Internal parts of steam generators foul up with iron oxides which gradually close some holes aimed for the passing of the fluid. This phenomenon called clogging causes safety issues and means to assess it are needed to optimise the maintenance strategy. The approach investigated in this thesis is the analysis of steam generators dynamic behaviour during power transients with a monodimensional physical model. Two improvements to the model have been implemented. One was taking into account flows orthogonal to the modelling axis, the other was introducing a slip between phases accounting for velocity difference between liquid water and steam. These two elements increased the model's degrees of freedom and improved the adequacy of the simulati onto plant data. A new calibration and validation methodology has been proposed to assess the robustness of the model. The initial inverse problem was ill posed: different clogging spatial configurations can produce identical responses. The relative importance of clogging, depending on its localisation, has been estimated by sensitivity analysis with the Sobol' method. The dimension of the model functional output had been previously reduced by principal components analysis. Finally, the input dimension has been reduced by a technique called sliced inverse regression. Based on this new framework, a new diagnosis methodology, more robust and better understood than the existing one, has been proposed.
30

Nature-Based Solutions for Coastal Protection: A Multi-Scale Investigation of Wave-Vegetation Interactions

Markov, Acacia 12 January 2023 (has links)
Nature-based solutions (NBS) are promising strategies for protecting vulnerable coasts in the context of climate change, utilizing the coastal protection capabilities of natural ecosystems for engineering applications. The ability of coastal marsh vegetation to attenuate wave energy and prevent coastal erosion has been acknowledged for decades, however, consideration for their use in coastal protection strategies is presently limited, particularly in Canada due to a lack of engineering guidelines and limited available research considering region-specific variables. Physical modelling presents a useful tool for investigating the coastal protection function provided by marsh vegetation in a controlled, repeatable environment, which can ultimately inform the design of nature-based coastal protection strategies. To date, such studies have investigated the influence of plant biophysical parameters (stem flexibility, width, and height) and hydrodynamic conditions (wave height, wave period, and plant submergence) on wave attenuation. These studies have used either live vegetation, requiring full-scale wave testing, or surrogate vegetation, which allows simplified testing at either full- or reduced-scale. Overall, live vegetation studies have been limited in the variety of saltmarsh plants considered, with few studies considering plant species native to the Canadian coastline. Several physical modelling studies have been performed using surrogate plants, however, methods of surrogate development for flexible vegetation or reduced-scale testing are not yet well developed. This thesis aims to address knowledge gaps pertaining to the use of marsh vegetation in coastal protection strategies, particularly through the development of experimental methods with both live and surrogate plants. A full-scale flume study with live vegetation was performed to develop fundamental knowledge of wave-vegetation interactions for Spartina alterniflora and Spartina patens, two salt marsh species native to Canada’s Atlantic coast. S. alterniflora was observed to demonstrate a resistance strategy in response to hydrodynamic forcing, versus the avoidance strategy of S. patens, supporting complementary functioning of the two species if utilized together in coastal protection schemes. Observations of plant properties and stem bending from live plant tests were subsequently applied in the development of a small-scale flume study, which examined wave attenuation associated with a downscaled S. alterniflora meadow in the configuration of a “living dyke” structure. Wave damping induced by surrogate vegetation was observed to be minimal for the tested wave conditions (0.073 m < Hm0 < 0.225 m, 2.0 < Tp < 3.2 s, 1:4 scale) and beach slope (1V:20H), with wave height evolution dominated by wave shoaling and breaking. Several methods were considered for modelling the S. alterniflora meadow at reduced scale, and results demonstrated a sensitivity to surrogate diameter but not flexibility. The development of robust experimental methods for investigating the performance of nature-based coastal infrastructure is essential for the establishment of appropriate design conditions. The scale series approach of this thesis supports such methodological advancements and is expected to make preliminary contributions to design guidance on coastal marsh-based NBS and provide critical direction for future studies.

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