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BARROSO, VITOR BARATA RIBEIRO BLANCO. "EFFICIENT FLUID SIMULATION IN THE PARAMETRIC SPACE OF THREE-DIMENSIONAL STRUCTURED GRIDS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=28689@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO<br>BOLSA NOTA 10<br>Fluidos são extremamente comuns em nosso mundo e têm papel central em muitos fenômenos naturais. A compreensão de seu comportamento tem importância fundamental em uma vasta gama de aplicações e diversas áreas de pesquisa, da análise de fluxo sanguíneo até o transporte de petróleo, da exploração do fluxo de um rio até a previsão de maremotos, tempestades e furacões. Na simulação de fluidos, a abordagem conhecida como Euleriana é capaz de gerar resultados bastante corretos e precisos, mas as computações envolvidas podem se tornar excessivamente custosas quando há a necessidade de tratar fronteiras curvas e obstáculos com formas complexas. Este trabalho aborda esse problema e apresenta uma técnica Euleriana rápida e direta para simular o escoamento de fluidos em grades estruturadas parametrizadas tridimensionais. O principal objetivo do método é tratar de forma correta e eficiente as interações de fluidos com fronteiras curvas, incluindo paredes externas e obstáculos internos. Para isso, são utilizadas matrizes Jacobianas por célula para relacionar as derivadas de campos escalares e vetoriais nos espaços do mundo e paramétrico, o que permite a resolução das equações de Navier-Stokes diretamente no segundo, onde a discretização do domínio torna-se simplesmente uma grade uniforme. O trabalho parte de um simulador baseado em grades regulares e descreve como adaptá-lo com a aplicação das matrizes Jacobianas em cada passo, incluindo a resolução de equações de Poisson e dos sistemas lineares esparsos associados, utilizando tanto iterações de Jacobi quanto o método do Gradiente Biconjugado Estabilizado. A técnica é implementada na linguagem de programação CUDA e procura explorar ao máximo a arquitetura massivamente paralela das placas gráficas atuais.<br>Fluids are extremely common in our world and play a central role in many natural phenomena. Understanding their behavior is of great importance to a broad range of applications and several areas of research, from blood flow analysis to oil transportation, from the exploitation of river flows to the prediction of tidal waves, storms and hurricanes. When simulating fluids, the so-called Eulerian approach can generate quite correct and precise results, but the computations involved can become excessively expensive when curved boundaries and obstacles with complex shapes need to be taken into account. This work addresses this problem and presents a fast and straightforward Eulerian technique to simulate fluid flows in three-dimensional parameterized structured grids. The method s primary design goal is the correct and efficient handling of fluid interactions with curved boundary walls and internal obstacles. This is accomplished by the use of per-cell Jacobian matrices to relate field derivatives in the world and parameter spaces, which allows the Navier-Stokes equations to be solved directly in the latter, where the domain discretization becomes a simple uniform grid. The work builds on a regular-grid-based simulator and describes how to apply Jacobian matrices to each step, including the solution of Poisson equations and the related sparse linear systems using
both Jacobi iterations and a Biconjugate Gradient Stabilized solver. The technique is implemented efficiently in the CUDA programming language and strives to take full advantage of the massively parallel architecture of today s graphics cards.
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Gao, Haotian. "POD-Galerkin based ROM for fluid flow with moving boundaries and the model adaptation in parametric space." Diss., Kansas State University, 2018. http://hdl.handle.net/2097/38776.
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Doctor of Philosophy<br>Department of Mechanical and Nuclear Engineering<br>Mingjun Wei<br>In this study, a global Proper Orthogonal Decomposition (POD)-Galerkin based Reduced Order model (ROM) is proposed. It is extended from usual fixed-domain problems to more general fluid-solid systems with moving boundaries/interfaces. The idea of the extension is similar to the immersed boundary method in numerical simulations which uses embedded forcing terms to represent boundary motions and domain changes. This immersed boundary method allows a globally defined fixed domain including both fluid and solid, where POD-Galerkin projection can be directly applied. However, such a modified approach cannot get away with the unsteadiness of boundary terms which appear as time-dependent coefficients in the new Galerkin model. These coefficients need to be pre-computed for prescribed periodic motion, or worse, to be computed at each time step for non-prescribed (e.g. with fluid-structure interaction) or non-periodic situations. Though computational time for each unsteady coefficient is smaller than the coefficients in a typical Galerkin model, because the associated integration is only in the close neighborhood of moving boundaries. The time cost is still much higher than a typical Galerkin model with constant coefficients. This extra expense for moving-boundary treatment eventually undermines the value of using ROMs. An aggressive approach is to decompose the moving boundary/domain to orthogonal modes and derive another low-order model with fixed coefficients for boundary motion. With this domain decomposition, an approach including two coupled low-order models both with fixed coefficients is proposed. Therefore, the new global ROM with decomposed approach is more efficient. Though the model with the domain decomposition is less accurate at the boundary, it is a fair trade-off for the benefit on saving computational cost. The study further shows, however, that the most time-consuming integration in both approaches, which come from the unsteady motion, has almost negligible impact on the overall dynamics. Dropping these time-consuming terms reduces the computation cost by at least one order while having no obvious effect on model accuracy.
Based on this global POD-Galerkin based ROM with forcing term, an improved ROM which can handle the parametric variation of body motions in a certain range is also presented. This study shows that these forcing terms not only represent the moving of the boundary, but also decouple the moving parameters from the computation of model coefficients. The decoupling of control parameters provides the convenience to adapt the model for the prediction on states under variation of control parameters. An improved ROM including a shit mode seems promising in model adaptation for typical problems in a fixed domain. However, the benefit from adding a shit mode to model diminishes when the method is applied to moving-boundary problems. Instead, a combined model, which integrates data from a different set of parameters to generate the POD modes, provides a stable and accurate ROM in a certain range of parametric space for moving-boundary problems. By introducing more data from a different set of parameters, the error of the new model can be further reduced. This shows that the combined model can be trained by introducing more and more information. With the idea of the combined model, the improved global ROM with forcing terms shows impressive capability to predict problems with different unknown moving parameters, and can be used in future parametric control and optimization problems.
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Dubanchet, Vincent. "Modélisation et contrôle d’un robot spatial flexible pour la capture d’un débris en rotation." Thesis, Toulouse, ISAE, 2016. http://www.theses.fr/2016ESAE0022/document.
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Les débris en orbite sont actuellement une source de préoccupation majeure pour les acteurs du spatial et pour le reste de la population, comme en témoignent les articles de presse et les œuvres cinématographiques sur le sujet. En effet, la présence de ces objets menace directement les astronautes en mission et les satellites en opération. Parmi les nombreuses options déjà envisagées pour les traiter, cette thèse se concentre sur l’approche robotique, en proposant des outils et des méthodes de modélisation et de contrôle pour un satellite chasseur équipé d’un bras manipulateur. Des modèles dynamiques et des schémas de simulation optimisés sont ainsi développés pour tout système multi-corps constitué d’une base mobile supportant un nombre quelconque d’appendices rigides ou flexibles. Par la suite, les trajectoires de capture sont générées en conservant la continuité en accélération avec le mouvement naturel du point cible, dans le but de saisir aussi délicatement que possible le débris en rotation. Le suivi de cette trajectoire par l’effecteur du robot chasseur est alors assuré par une loi de contrôle à deux niveaux, dont le réglage repose sur la synthèse H1 structurée. Une étude de robustesse est également mise en place pour assurer la stabilité et les performances du système en boucle fermée, malgré les changements de configuration du bras. Enfin, la validation des travaux de thèse est réalisée par voie numérique avec un simulateur haute-fidélité, et par voie pratique avec un banc d’essais robotique incluant des composants physiques en temps réel<br>On-orbit debris are currently causing deep concern for space agencies, related companies, and also among the population. ¿is is evidenced by the numerous scientific articles and recent movies on the matter. Indeed, these objects pose a serious threat for the astronauts on mission and for operational satellites. Among the various technical concepts already designed to address these threats, this thesis focuses on space robotics. Tools and methods are thus introduced for the modeling and control of a chaser satellite equipped with a manipulator. Dynamic models and optimized simulation schemes are developed to handle any multi-body system made up of amoving base embedding various appendages, either rigid or flexible. ¿en, a trajectory planner is designed to ensure acceleration continuity with the natural motion of the debris in order to perform a soft capture. ¿is reference trajectory is tracked by the end-effector of the chaser using a two-level control law, which is tuned by the structured H1 synthesis. A robustness analysis is also presented to assess the stability and the performances of the closed-loop system with respect to the motion of the robotic arm. Finally, the outcome of the thesis is validated by a twofold approach: by numerical means with a highfidelity simulator, and by practical ones with a robotic test bench including physical components in real time
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Normann, James Brian. "Parametric identification of nonlinear structural dynamic systems." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/43294.
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The identification of linear structural dynamic systems has been dealt with extensively in past studies. Identification methods for nonlinear structures have also been introduced in previous articles, including procedures based on the method of multiple scales, iterative and noniterative direct methods, and state space mappings. Here, a procedure is introduced for the identification of nonlinear structural dynamic systems which is readily applicable to simple as well as more complex multiple degree of freedom systems. The procedure is based on multiple step integration methods for the solution of differential equations. The multiple step integration procedure and the iterative direct method are applied to a number of nonlinear single degree of freedom examples, and are applied to a simple two degrees of freedom example as well. RMS based noise is added to a simulated measured response in order to monitor the effects of measurement errors on the procedures. The input data is filtered before final processing in the identification algorithms. The multistep algorithm is compared to the iterative direct method on the basis of criteria such as accuracy, ease of use, and numerical efficiency.<br>Master of Science
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Danhaive, Renaud Aleis Pierre Emile. "Integrating interactive evolutionary exploration and parametric structural design." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99595.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2015.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 47-48).<br>Current modeling and analysis tools are extremely powerful and allow one to generate and analyze virtually any structural shape. However, most of them do not allow designers to integrate structural performance as an objective during conceptual design. As structural performance is highly linked to architectural geometry, there is a need for computational strategies allowing for performance-oriented structural design in architecture. In order to address these issues, this research combines interactive evolutionary optimization and parametric modeling to develop a new computational strategy for creative and high-performance conceptual structural design. Parametric modeling allows for quick exploration of complex geometries and can be combined with analysis and optimization algorithms for performance-driven design. However, this methodology often questions the designer's authorship as it is based on the use of black-box optimizers. On the other hand, interactive evolutionary optimization empowers the user by acknowledging his or her input as fundamental and includes it in the evolutionary optimization process. This approach aims at improving the structural performance of a concept without limiting the creative freedom of designers. Taking advantage of the two frameworks, this research implements an interactive evolutionary structural optimization framework in the widely used parametric modeling environment constituted by Rhinoceros and Grasshopper. Previous work has illustrated the benefits of combining parametric modeling and genetic algorithms for design space exploration. Comparatively, the implemented design tool capitalizes on Grasshopper's versatility for geometry generation but supplements the visual programming interface with a flexible portal increasing the designer's creative freedom through enhanced interactivity. The tool can accommodate a wide range of structural typologies and geometrical forms in an integrated environment. This research offers a versatile, performance- and user-oriented environment for creative and efficient conceptual structural design.<br>by Renaud Aleis Pierre Emile Danhaive.<br>M. Eng.
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Jones, Garrett P. (Garrett Pierce). "Interoperable software for parametric structural analysis and optimization." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82713.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2013.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis. "June 2013."<br>Includes bibliographical references (p. 62-64).<br>The advent of building information modeling in the structural engineering profession has brought forth new challenges to the traditional methods of design and analysis. The need for faster, more robust analyses to mitigate expenses and increase structural insight is a demand that stems from the implementation of BIM modeling. Current software interoperability now allows engineers limited opportunity to engage directly and immediately with the design process. The development of tools which can bring together the architectural and structural engineering professions are of paramount importance in the next phase of professional design. In response to this professional demand, a software framework for Rhino3D modeling software was created which explores the various methods of searching a design space and finding solutions. Both parametric design generation and genetic optimizations were employed, allowing architects and engineers to explore the design space of a structure using metrics important to each field. A case study is performed using the developed software framework to quantify results and validate the effectiveness of such a new design tool in the current engineering profession. The outcome is an improved design experience that is feasible in time and scope, allowing architects and engineers an opportunity to truly explore the design space. Keywords: Parametric modeling and analysis, Genetic optimization, Building information modeling<br>by Garrett P. Jones.<br>M.Eng.
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Stefan, Diana. "Structural and parametric identification of bacterial regulatory networks." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENM019/document.
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Les technologies expérimentales à haut débit produisent de grandes quantités de données sur les niveaux d'expression des gènes dans les bactéries à l'état d'équilibre ou lors des transitions de croissance.Un défi important dans l'interprétation biologique de ces données consiste à en déduire la topologie du réseau de régulation ainsi que les fonctions de régulation quantitatives des gènes.Un grand nombre de méthodes d'inférence a été proposé dans la littérature. Ces méthodes ont été utilisées avec succès dans une variété d'applications, bien que plusieurs problèmes persistent.Nous nous intéressons ici à l'amélioration de deux aspects des méthodes d'inférence.Premièrement, les données transcriptomiques reflètent l'abondance de l'ARNm, tandis que, le plus souvent, les composants régulateurs sont les protéines codées par les ARNm.Bien que les concentrations de l'ARNm et de protéines soient raisonnablement corrélées à l'état stationnaire, cette corrélation devient beaucoup moins évidente dans les données temporelles acquises lors des transitions de croissance à cause des demi-vies très différentes des protéines et des ARNm.Deuxièmement, la dynamique de l'expression génique n'est pas uniquement contrôlée par des facteurs de transcription et d'autres régulateurs spécifiques, mais aussi par des effets physiologiques globaux qui modifient l'activité de tous les gènes. Par exemple, les concentrations de l'ARN polymérase (libre) et les concentrations des ribosomes (libres) varient fortement avec le taux de croissance. Nous devons donc tenir compte de ces effets lors de la reconstruction d'un réseau de régulation à partir de données d'expression génique.Nous proposons ici une approche expérimentale et computationnelle combinée pour répondre à ces deux problèmes fondamentaux dans l'inférence de modèles quantitatifs de promoteurs bactériens à partir des données temporelles d'expression génique.Nous nous intéressons au cas où la dynamique de l'expression génique est mesurée in vivo et en temps réel par l'intermédiaire de gènes rapporteurs fluorescents. Notre approche d'inférence de réseaux de régulation tient compte des différences de demi-vie entre l'ARNm et les protéines et prend en compte les effets physiologiques globaux.Lorsque les demi-vies des protéines sont connues, les modèles expérimentaux utilisés pour dériver les activités des gènes à partir de données de fluorescence sont intégrés pour estimer les concentrations des protéines.L'état physiologique global de la cellule est estimé à partir de l'activité d'un promoteur de phage, dont l'expression n'est contrôlée par aucun des facteurs de transcription et ne dépend que de l'activité de la machinerie d'expression génique.Nous appliquons l'approche à un module central dans le réseau de régulation contrôlant la motilité et le système de chimiotactisme chez Escherichia coli.Ce module est composé des gènes FliA, FlgM et tar.FliA est un facteur sigma qui dirige l'ARN polymérase vers les opérons codant pour des composants de l'assemblage des flagelles.Le troisième composant du réseau, tar, code pour la protéine récepteur chimiotactique de l'aspartate, Tar, et est directement transcrit par FliA associé à l' holoenzyme ARN polymérase. Le module FliA-FlgM est particulièrement bien adapté pour l'étude des problèmes d'inférence considérés ici, puisque le réseau a été bien étudié et les démivies des protéines jouent un rôle important dans son fonctionnement.Nos résultats montrent que, pour la reconstruction fiable de réseaux de régulation transcriptionelle chez les bactéries, il est nécessaire d'inclure les effets globaux dans le modèle de réseau et d'en déduire de manière explicite les concentrations des protéines à partir des profils d'expression observés, car la demi-vie de l'ARNm et des protéines sont très différentes. Notre approche reste généralement applicable à une grande variété de problèmes d'inférence de réseaux et nous discutons les limites et les extensions possibles de la méthode<br>High-throughput technologies yield large amounts of data about the steady-state levels and the dynamical changes of gene expression in bacteria. An important challenge for the biological interpretation of these data consists in deducing the topology of the underlying regulatory network as well as quantitative gene regulation functions from such data. A large number of inference methods have been proposed in the literature and have been successful in a variety of applications, although several problems remain. We focus here on improving two aspects of the inference methods. First, transcriptome data reflect the abundance of mRNA, whereas the components that regulate are most often the proteins coded by the mRNAs. Although the concentrations of mRNA and protein correlate reasonably during steady-state growth, this correlation becomes much more tenuous in time-series data acquired during growth transitions in bacteria because of the very different half-lives of proteins and mRNA. Second, the dynamics of gene expression is not only controlled by transcription factors and other specific regulators, but also by global physiological effects that modify the activity of all genes. For example, the concentrations of (free) RNA polymerase and the concentration of ribosomes vary strongly with growth rate. We therefore have to take into account such effects when trying to reconstruct a regulatory network from gene expression data. We propose here a combined experimental and computational approach to address these two fundamental problems in the inference of quantitative models of the activity of bacterial promoters from time-series gene expression data. We focus on the case where the dynamics of gene expression is measured in vivo and in real time by means of fluorescent reporter genes. Our network reconstruction approach accounts for the differences between mRNA and protein half-lives and takes into account global physiological effects. When the half-lives of the proteins are available, the measurement models used for deriving the activities of genes from fluorescence data are integrated to yield estimates of protein concentrations. The global physiological state of the cell is estimated from the activity of a phage promoter, whose expression is not controlled by any transcription factor and depends only on the activity of the transcriptional and translational machinery. We apply the approach to a central module in the regulatory network controlling motility and the chemotaxis system in Escherichia coli. This module comprises the FliA, FlgM and tar genes. FliA is a sigma factor that directs RNA polymerase to operons coding for components of the flagellar assembly. The effect of FliA is counteracted by the antisigma factor FlgM, itself transcribed by FliA. The third component of the network, tar, codes for the aspartate chemoreceptor protein Tar and is directly transcribed by the FliA-containing RNA polymerase holoenzyme. The FliA-FlgM module is particularly well-suited for studying the inference problems considered here, since the network has been well-studied and protein half-lives play an important role in its functioning. We stimulated the FliA-FlgM module in a variety of wild-type and mutant strains and different growth media. The measured transcriptional response of the genes was used to systematically test the information required for the reliable inference of the regulatory interactions and quantitative predictive models of gene regulation. Our results show that for the reliable reconstruction of transcriptional regulatory networks in bacteria it is necessary to include global effects into the network model and explicitly deduce protein concentrations from the observed expression profiles. Our approach should be generally applicable to a large variety of network inference problems and we discuss limitations and possible extensions of the method
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Malladi, Sailaja. "Parametric modeling and analysis of structural bonded joints." Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=80.
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Thesis (M.S.)--West Virginia University, 2004.<br>Title from document title page. Document formatted into pages; contains x, 56 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 52-53).
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Masendeke, Rugare B. "Parametric study of stiffened steel containment shell structures." Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/19019.
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Includes bibliographical references. .<br>A FEM-based parametric study is undertaken to investigate the buckling behavior of meridionally and circumferentially stiffened steel cylindrical and conical shell frustum subjected to different load cases. This situation arises in different steel shell applications such as storage vessels (liquid, solid and gas) and in certain configurations of industrial process facilities. The stiffeners are flat strips of rectangular section welded on to the outer surface of the shell, either over the whole length of the shell meridian or around the circumference of the shell. It is required to establish how the elastic buckling load and mode shapes vary with respect to certain key parameters of the problem. The parameters of interest in the study include the number of stiffeners around the shell circumference and along the meridian, the stiffener-depth to shell-thickness ratio, and the stiffener depth-to-width ratio. This thesis reports the findings of the parametric study and also presents some results of experimental tests on laboratory small-scale models of stiffened cylindrical and conical frusta.
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Sareen, Samita. "Estimation and testing of structural parametric sealed-bid auctions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0026/NQ49879.pdf.
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Worden, Keith. "Parametric and nonparametric identification of nonlinearity in structural dynamics." Thesis, Heriot-Watt University, 1989. http://hdl.handle.net/10399/1033.
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The work described in this thesis is concerned with procedures for the identification of nonlinearity in structural dynamics. It begins with a diagnostic method which uses the Hubert transform for detecting nonlinearity and describes the neccessary conditions for obtaining a valid Hubert transform. The transform is shown to be incapable of producing a model with predictive power. A method based on the identification of nonlinear restoring forces is adopted for extracting a nonlinear model. The method is critically examined; various caveats, modifications and improvements are obtained. The method is demonstrated on time data obtained from computer simulations. It is shown that a parameter estimation approach to restoring force identification based on direct least—squares estimation theory is a fast and accurate procedure. In addition, this approach allows one to obtain the equations of motion for a multi—degree—of—freedom system even if the system is only excited at one point. The data processing methods for the restoring force identification including integration and differentiation of sampled time data are developed and discussed in some detail. A comparitive study is made of several of the most well—known least—squares estimation procedures and the direct least —squares approach is applied to data from several experiments where it is shown to correctly identify nonlinearity in both single— and multi—degree--of—freedom systems. Finally, using both simulated and experimental data, it is shown that the recursive least—squares algorithm modified by the inclusion of a data forgetting factor can be used to identify time—dependent structural parameters.
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Yanik, Yasar. "Quantification of parametric uncertainties effects in structural failure criteria /." Ilha Solteira, 2019. http://hdl.handle.net/11449/182040.
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Orientador: Samuel Silva<br>Resumo: Critérios de falhas realizam a predição de circunstâncias nas quais materiais sólidos estão sobre ação de carregamentos externos. As teorias de falhas são conhecidas como diferentes critérios de falhas, como von Mises e Tresca, os quais são os mais famosos para determinados materiais. Além disso, esta dissertação de mestrado pretende mostrar a comparação entre os critérios de falha de Tresca e von Mises, levando em conta incertezas subjacentes nas equações constitutivas e na análise de tensão. Para exemplificar acomparação,algumassimulaçõessãorealizadasusandoumaplacasimples,umproblema de deflexão simples,e a estrutura de um carro do formula SAE. Devido à complexidade deste sistema, diferentes tipos de etapas probabilísticas são utilizadas, como o método de superfície de resposta e a correlação de parâmetros. Os resultados mostram que várias variáveis aleatórias de entrada afetam em maneiras diferentes as variáveis aleatórias de saída e que não há uma diferença grande entre os critérios de falha de von Mises e Tresca quando incertezas são assumidas na formulação para a análise de tensão.<br>Abstract: Failure theory is the investigation of predicting circumstances under which solid materials under the processing of external loads. The theories of failure are known as different failure criteria such as von Mises and Tresca which are the most famous of these for certain materials. Additionally, this master dissertation intends to show a comparison between Tresca and von Mises failure criterions, taking into account the underlying uncertainties in the constitutive equations and stress analysis. In order to exemplify the comparison, some numerical simulations are performed using a simple plate, simple deflection problem and a frame of the formula car. Due to the complexity of frame of the formula car, different kind of probabilistic steps are used as a response surface method and parameters correlation. Results show that several random input variables effect the random output variables in various ways, and there is no such a big difference between the von Mises and Tresca failure criterions when uncertainties are assumed in the formulation for stress analysis.<br>Mestre
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Anderson, Matthew Francis. "Parametric investigation of strain gauges in structural damage detection." Thesis, University of Iowa, 2013. https://ir.uiowa.edu/etd/2436.
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Vibration-based damage detection (VBDD) methods are used to detect damage in structural members non-evasively. This investigation began with two objectives: to prove a VBDD method could detect damage using strain gauges both analytically and experimentally, and to then use that method to determine the distance from a damaged area that strain gauges could be effective. Work began simultaneously using finite element software and physical experiments. It was determined that a VBDD method could detect damage with strain gauges in both settings. A parametric study was then completed that used probabilistic methods to identify an effective range for strain gauges over the length of the structural member.
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Silva, Soto Daniel Alejandro. "Personalised finite-element models using image registration in parametric space." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/8584/.
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Heart failure (HF) is a chronic clinical condition in which the heart fails to pump enough blood to meet the metabolic needs of the body. Patients have reduced physical performance and can see their quality of life severely impaired; around 40-70% of patients diagnosed of HF die within the first year following diagnosis. It is underestimated that 900,000 people in the UK currently suffer from HF. HF has a big impact on the NHS, representing 1 million inpatient bed, 5% of all emergency medical admission to hospitals and costs 2% of the total NHS budget. The annual incidence of new diagnoses is reported as 93,000 people in England alone – and this figure is already increasing at a rate above that at which population is ageing [1]. Cardiac resynchronisation therapy (CRT) has become established as an effective solution to treat selected patients with HF. The research presented in this thesis has been conducted as part of a large EPSRC-Funded project on the theme of Grand Challenges in Heathcare, with co-investigators from King’s College London (KCL), Imperial College London, University College London (UCL) and the University of Sheffield. The aim is to develop and to apply modelling techniques to simulate ventricular mechanics and CRT therapy in patient cohorts from Guy’s Hospital (London) and from the Sheffield Teaching Hospitals Trust. This will lead to improved understanding of cardiac physiological behaviour and how diseases affect normal cardiac performance, and to improved therapy planning by allowing candidate interventions to be simulated before they are applied on patients. The clinical workflow within the hospital manages the patient through the processes of diagnosis, therapy planning and follow-up. The first part of this thesis focuses on the development of a formal process for the integration of a computational analysis workflow, including medical imaging, segmentation, model construction, model execution and analysis, into the clinical workflow. During the early stages of the project, as the analysis workflow was being compiled, a major bottle-neck was identified regarding the time required to build accurate, patient-specific geometrical meshes from the segmented images. The second part of this thesis focuses on the development of a novel approach based on the use of image registration to improve the process of construction of a high-quality personalised finite element mesh for an individual patient. Chapter 1 summarises the clinical context and introduces the tools and processes that are applied in this thesis. Chapter 2 describes the challenges and the implementation of a computational analysis workflow and its integration into a clinical environment. Chapter 3 describes the theoretical underpinnings of the image registration algorithm that has been developed to address the problem of construction of high-quality personalised meshes. The approach includes the use of regularisation terms that are designed to improve the mesh quality. The selection and implementation of the regularisation terms is discussed in detail in Chapter 4. Chapter 5 describes the application of the method to a series of test problems, whilst Chapter 6 describes the application to the patient cohort in the clinical study. Chapter 7 demonstrates that the method, developed for robust mesh construction, can readily be applied to determine boundary conditions for computational fluid dynamics (CFD) analysis. Chapter 8 provides a summary of the achievements of the thesis, together with suggestions for further work.
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Seckiner, Soner. "Parametric Analysis Of Inelastic Interaction In Frame-wall Structural Systems." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613654/index.pdf.
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The purpose of this thesis is to investigate the inelastic action in the reinforced concrete frame-wall structures analytically and with that analysis to follow the plastic formation of the structure. For this purpose, six mid-rise reinforced concrete buildings with frame-wall are modeled and analyzed to understand the effect of the height and base shear force ratio of the wall on the nonlinear interaction between reinforced concrete wall and frame members under static lateral loads and ground motion excitations. The parametric analysis is conducted by assuming planar response of the buildings under loadings.
The buildings are generated considering the limit design concept suggested by Turkish Earthquake Code 2007 and Turkish Standards TS500, and the frame-wall members are modeled by using spread plasticity elements and fiber discretization of sections. In the analysis stage, each element section is divided into confined and unconfined regions for detailed modeling of the building by using OpenSEES nonlinear finite element program. Two dimensional analyses are conducted under static and dynamic loadings. For static pushover analyses, three different lateral load cases (Triangular, Uniform and First-Mode Lateral Load Patterns) are considered. For dynamic analyses, eight different ground motions are used. These ground motions are scaled to the corresponding design response spectrum suggested by Turkish Earthquake Code 2007 by using RSPMATCH program. Using the result of the complex and simplified analyses, inter-story drift ratios, plastic rotations and internal force distributions of the buildings are investigated.
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Gentry, Jeanette J. "Nonlinear oscillations under multifrequency parametric excitation." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/43402.
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<p>A second-order system of differential equations containing a multifrequency
parametric excitation and weak quadratic and cubic nonlinearities is investigated.
The method of multiple scales is used to carry out a general analysis, and three
resonance conditions are considered in detail. First, the case in which the sum of
two excitation frequencies is near two times a natural frequency, λ<sub>s</sub> + λ<sub>t</sub> <u>~</u>2Ï <sub>q</sub>, is
examined. Second, the influence of an internal resonance, Ï <sub>q</sub =<u>~</u>3Ï r, on the previous
case is studied. Finally, the effect of the internal resonance w<sub>r</sub><u>~</u>3w<sub>q</sub> on the resonance
λ<sub>s</sub> + λ<sub>t</sub> <u>~</u>2Ï <sub>q</sub> is investigated. Results are presented as plots of response amplitudes
as functions of a detuning parameter, excitation amplitude, and, for the first case, a
measure of the relative values of λ<sub>s</sub> + λ<sub>t</sub>.</p><br>Master of Science
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Pentaris, Fragkiskos. "Digital signal processing for structural health monitoring of buildings." Thesis, Brunel University, 2014. http://bura.brunel.ac.uk/handle/2438/10560.
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Structural health monitoring (SHM) systems is a relatively new discipline, studying the structural condition of buildings and other constructions. Current SHM systems are either wired or wireless, with a relatively high cost and low accuracy. This thesis exploits a blend of digital signal processing methodologies, for structural health monitoring (SHM) and develops a wireless SHM system in order to provide a low cost implementation yet reliable and robust. Existing technologies of wired and wireless sensor network platforms with high sensitivity accelerometers are combined, in order to create a system for monitoring the structural characteristics of buildings very economically and functionally, so that it can be easily implemented at low cost in buildings. Well-known and established statistical time series methods are applied to SHM data collected from real concrete structures subjected to earthquake excitation and their strong and weak points are investigated. The necessity to combine parametric and non-parametric approaches is justified and to this direction novel and improved digital signal processing techniques and indexes are applied to vibration data recordings, in order to eliminate noise and reveal structural properties and characteristics of the buildings under study, that deteriorate due to environmental, seismic or anthropogenic impact. A characteristic and potential harming specific case study is presented, where consequences to structures due to a strong earthquake of magnitude 6.4 M are investigated. Furthermore, is introduced a seismic influence profile of the buildings under study related to the seismic sources that exist in the broad region of study.
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Nikpour, Mehdi. "Toeplitzness of Composition Operators and Parametric Toeplitzness." University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1346951238.
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Basile, Franklin C. "Parametric shape generation of aerodynamic and structural objects for aerodynamic, structural and radar cross-section analysis." Master's thesis, University of Central Florida, 1988. http://digital.library.ucf.edu/cdm/ref/collection/RTD/id/79106.
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University of Central Florida College of Engineering Thesis<br>This thesis describes the design and development of software to parametrically build three-dimensional aerodynamic objects or shapes for various engineering design and analysis activities. The software is designed to generate and display sufficient geometric output to completely define the object. Parameters are entered through a prompting sequence which determines the type of object and the amount of geometry needed to describe the object. Geometry created by this program will act as the baseline model for aerodynamic , structural, and radar cross-section analysis. An integral part of the program is the complete 3-D viewing capability. Interactive global display capability allows for visualization of the model from any direction. Input of a viewing direction or an eye-point position will automatically shift the viewer to the correct orientation in space while scaling and centering the model on teh display. Once the object geometry has been verified and accepted, it is converted to a surface model by a second program developed at the Martin Marietta Orlando Aerospace Company, and formatted for input into aerodynamic analysis programs such as S-HABP (Supersonic-Hypersonic Arbitary Body Program) for lift and drag calcuations at multiple angles of attack and trim conditions and/or CAMS (Computer Aided Missile Synthesis) for trajectory data calculations under various flight regimes. The geometry may also be formatted for input to the stress and dynamic mode analysis program NASTRAN or the physical optics scattering program POSCAT which is used to predict radar signal returns of an object at any desired frequency. Program design, geometry generation, and data manipulation techniques are presented in detail.<br>M.S.<br>Masters<br>Engineering<br>Engineering<br>182 p.<br>viii, 182 leaves, bound : ill. ; 28 cm.
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Lagergren, Maria. "Parametric model for structural stability computation of chassis in tipper trailers." Thesis, KTH, Hållfasthetslära (Inst.), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-92642.
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When a tipper trailer empties the load it carries, a torque occurs if the trailer stands on uneven ground. To withstand this torque, and prevent the trailer to roll over, the chassis‟ torsional stiffness must be high enough. The stiffness is highly dependent of the geometry of the chassis structure. When analysing different geometries the pre-processing of the finite element (FE)-model is time consuming. The first part in this master thesis was to assess what element type to use for this type of load case. It was necessary to simplify the FE-model as much as possible for the second part of the thesis. A comparison of modelling the chassis with beam elements instead of shell elements was performed. It was concluded that resultant beam elements should be used when analysing the torsional stiffness of the chassis. In the second part of this master thesis a program was developed to automate the FE-modelling of the chassis, this to be able to compare several chassis structures in a short amount of time. The program generates a FE-model of the desired chassis structure depending on parameters given from the user. The program produces a text file, containing information about the FE-model, which can be read and viewed in a LS-DYNA compatible pre-processor.
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Mueller, Caitlin T. "Computational exploration of the structural design space." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91293.
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Thesis: Ph. D. in Architecture: Building Technology, Massachusetts Institute of Technology, Department of Architecture, 2014.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (pages 199-206).<br>This dissertation focuses on computational strategies for incorporating structural considerations into the earliest stages of the architectural design process. Because structural behavior is most affected by geometric form, the greatest potential for structural efficiency and a harmony of design goals occurs when global formal design decisions are made, in conceptual design. However, most existing computational tools and approaches lack the features necessary to take advantage of this potential: architectural modeling tools address geometry in absence of performance, and structural analysis tools require an already determined geometrical form. There is a need for new computational approaches that allow designers to explore the structural design space, which links geometric variation and performance, in a free and interactive manner. The dissertation addresses this need by proposing three new design space strategies. The first strategy, an interactive evolutionary framework, balances creative navigation of the design space with a focus on performance. The original contributions of this strategy center on enhanced opportunities for designer interaction and control. The second strategy introduces structural grammars, which allow for the formulation of broad and diverse design spaces that span across typologies. This strategy extends existing work in geometry-based shape grammars by incorporating structural behavior in novel ways. Finally, the third strategy is a surrogate modeling approach that approximates the design space to enable fast and responsive design environments. This strategy contributes new ways for non-experts to use this machine-learning-based methodology in conceptual design. These three complementary strategies can be applied independently or in combination, and the dissertation includes a discussion about possibilities and techniques for integrating them. Finally, the dissertation concludes by reflecting on its potential impact on design in practice, and by outlining important areas for future work. Key words: conceptual structural design, design space exploration, structural optimization, interactive evolutionary algorithm, structural grammar, surrogate modeling, structural design tools<br>by Caitlin T. Mueller.<br>Ph. D. in Architecture: Building Technology
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Chau, Thi Tuyet Trang. "Non-parametric methodologies for reconstruction and estimation in nonlinear state-space models." Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S010/document.
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Le volume des données disponibles permettant de décrire l’environnement, en particulier l’atmosphère et les océans, s’est accru à un rythme exponentiel. Ces données regroupent des observations et des sorties de modèles numériques. Les observations (satellite, in situ, etc.) sont généralement précises mais sujettes à des erreurs de mesure et disponibles avec un échantillonnage spatio-temporel irrégulier qui rend leur exploitation directe difficile. L’amélioration de la compréhension des processus physiques associée à la plus grande capacité des ordinateurs ont permis des avancées importantes dans la qualité des modèles numériques. Les solutions obtenues ne sont cependant pas encore de qualité suffisante pour certaines applications et ces méthodes demeurent lourdes à mettre en œuvre. Filtrage et lissage (les méthodes d’assimilation de données séquentielles en pratique) sont développés pour abonder ces problèmes. Ils sont généralement formalisées sous la forme d’un modèle espace-état, dans lequel on distingue le modèle dynamique qui décrit l’évolution du processus physique (état), et le modèle d’observation qui décrit le lien entre le processus physique et les observations disponibles. Dans cette thèse, nous abordons trois problèmes liés à l’inférence statistique pour les modèles espace-états: reconstruction de l’état, estimation des paramètres et remplacement du modèle dynamique par un émulateur construit à partir de données. Pour le premier problème, nous introduirons tout d’abord un algorithme de lissage original qui combine les algorithmes Conditional Particle Filter (CPF) et Backward Simulation (BS). Cet algorithme CPF-BS permet une exploration efficace de l’état de la variable physique, en raffinant séquentiellement l’exploration autour des trajectoires qui respectent le mieux les contraintes du modèle dynamique et des observations. Nous montrerons sur plusieurs modèles jouets que, à temps de calcul égal, l’algorithme CPF-BS donne de meilleurs résultats que les autres CPF et l’algorithme EnKS stochastique qui est couramment utilisé dans les applications opérationnelles. Nous aborderons ensuite le problème de l’estimation des paramètres inconnus dans les modèles espace-état. L’algorithme le plus usuel en statistique pour estimer les paramètres d’un modèle espace-état est l’algorithme EM qui permet de calculer itérativement une approximation numérique des estimateurs du maximum de vraisemblance. Nous montrerons que les algorithmes EM et CPF-BS peuvent être combinés efficacement pour estimer les paramètres d’un modèle jouet. Pour certaines applications, le modèle dynamique est inconnu ou très coûteux à résoudre numériquement mais des observations ou des simulations sont disponibles. Il est alors possible de reconstruire l’état conditionnellement aux observations en utilisant des algorithmes de filtrage/lissage dans lesquels le modèle dynamique est remplacé par un émulateur statistique construit à partir des observations. Nous montrerons que les algorithmes EM et CPF-BS peuvent être adaptés dans ce cadre et permettent d’estimer de manière non-paramétrique le modèle dynamique de l’état à partir d'observations bruitées. Pour certaines applications, le modèle dynamique est inconnu ou très coûteux à résoudre numériquement mais des observations ou des simulations sont disponibles. Il est alors possible de reconstruire l’état conditionnellement aux observations en utilisant des algorithmes de filtrage/lissage dans lesquels le modèle dynamique est remplacé par un émulateur statistique construit à partir des observations. Nous montrerons que les algorithmes EM et CPF-BS peuvent être adaptés dans ce cadre et permettent d’estimer de manière non-paramétrique le modèle dynamique de l’état à partir d'observations bruitées. Enfin, les algorithmes proposés sont appliqués pour imputer les données de vent (produit par Météo France)<br>The amount of both observational and model-simulated data within the environmental, climate and ocean sciences has grown at an accelerating rate. Observational (e.g. satellite, in-situ...) data are generally accurate but still subject to observational errors and available with a complicated spatio-temporal sampling. Increasing computer power and understandings of physical processes have permitted to advance in models accuracy and resolution but purely model driven solutions may still not be accurate enough. Filtering and smoothing (or sequential data assimilation methods) have developed to tackle the issues. Their contexts are usually formalized under the form of a space-state model including the dynamical model which describes the evolution of the physical process (state), and the observation model which describes the link between the physical process and the available observations. In this thesis, we tackle three problems related to statistical inference for nonlinear state-space models: state reconstruction, parameter estimation and replacement of the dynamic model by an emulator constructed from data. For the first problem, we will introduce an original smoothing algorithm which combines the Conditional Particle Filter (CPF) and Backward Simulation (BS) algorithms. This CPF-BS algorithm allows for efficient exploration of the state of the physical variable, sequentially refining exploration around trajectories which best meet the constraints of the dynamic model and observations. We will show on several toy models that, at the same computation time, the CPF-BS algorithm gives better results than the other CPF algorithms and the stochastic EnKS algorithm which is commonly used in real applications. We will then discuss the problem of estimating unknown parameters in state-space models. The most common statistical algorithm for estimating the parameters of a space-state model is based on EM algorithm, which makes it possible to iteratively compute a numerical approximation of the maximum likelihood estimators. We will show that the EM and CPF-BS algorithms can be combined to effectively estimate the parameters in toy models. In some applications, the dynamical model is unknown or very expensive to solve numerically but observations or simulations are available. It is thence possible to reconstruct the state conditionally to the observations by using filtering/smoothing algorithms in which the dynamical model is replaced by a statistical emulator constructed from the observations. We will show that the EM and CPF-BS algorithms can be adapted in this framework and allow to provide non-parametric estimation of the dynamic model of the state from noisy observations. Finally the proposed algorithms are applied to impute wind data (produced by Méteo France)
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Govender, Nishalin. "A parametric investigation into the membrane stresses of hydrostatically loaded circular and elliptic toroidal shells." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25284.
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This study explores the membrane stresses of hydrostatically loaded elliptical and circular toroidal tanks. Equations are derived, using the membrane theory of shells, to obtain equations which can accurately describe the meridional and hoop stress behaviour at locations sufficiently far away from any bending disturbance occurring within the shell. The derived expressions are validated using the finite element software ADINA, indicating excellent agreement between the analytical and numerical solutions. A parametric study is undertaken, whereby the membrane profiles for prolate, oblate and circular toroidal shells is investigated. Parameters which are varied are the opening and aspect ratio of toroidal shells. Stress resultant profiles are shown for numerous cases in order to aid designers on suitable ratios to minimise membrane stresses for use when designing hydrostatically loaded toroidal shells. Lastly, numerical examples are investigated, keeping the volume constant and comparing the surface area due to a variation of opening and aspect ratios. It was found that when investigating toroidal shells, considerations are required when choosing the aspect ratio and opening ratios. Based on the results obtained, compromises between prolate and circular cross-sections with relatively small opening ratios are recommended in order to minimise the cost and maximise the structural efficiency, based on the membrane stresses occurring within the shell.
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Wallin, Daniel, and Martin Wasberg. "Parametric design of building structures in cooperation with architects : Usage and evaluation of structural plug-ins in 3D visualisation software." Thesis, KTH, Betongbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-188948.
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Architectural and structural design process are closely connected but traditionally done in twoseparate steps in the design process. This requires effective coordination between the two disciplinesand without the right tools problems often arise.The thesis was done by support from structural engineers at Tyréns and in collaboration with astudent from the department of architecture. The aim of the thesis was to investigate if the use ofparametric design tools from both architects and structural engineers could be a way of making thedesign process more effective. This thesis also include test the structural plug-ins of the parametricdesign tools and compare them with the outputs from traditional structural software and handcalculations.The comparison was made for different cases followed by a collaboration project. The cases wastargeting different structural features which in turn gave the knowledge needed to develop thecollaboration project.The case studies consists of five cases where the first two gives an introduction to parametricmodelling. The third case is a steel beam with fully restrained supports loaded by two pointloads. It will compare the displacement calculations between the different software. The next caseis a concrete slab with different supports along edges loaded by a uniformly load. The analysisincludes calculation and evaluation of section forces. The final case is a concrete dome. It is builtup by arches and five supports. The analysis of this case includes calculation and evaluation of thedisplacement.The collaboration project is a concrete structure built up by a curved surface lifted by curvedcolumns. The architect worked with the structure in parallel to this this thesis and targeted thedevelopment process whilst the authors targeted the structural parts and at the same time gavestructural insight to the architect.The results show a difference between the parametric structural tools and the traditional FEsoftware regarding deformation and moments. The hand calculations in the collaboration projectshow that the amount of reinforcement will not work with the given inputs and assumptions dueto practical reasons regarding spacing.The possibility to export models from the parametric environment to traditional engineering software’senables a faster analysis, since the modelling capabilities is limited and time-consumingin these. The structural capabilities of the parametric tools are good enough for deciding initialgeometry and properties but these will probably change when subjected to an more extensiveanalysis.
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Derar, Hind D. "Effect of Thermal Protection System on Vibration of Aerospace Structural Panels." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/DerarHD2008.pdf.
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Peters, A. D. "Structural urban space : a framework for the understanding of the physical city /." Thesis, Hong Kong : University of Hong Kong, 1995. http://sunzi.lib.hku.hk/hkuto/record.jsp?B25804042.
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Martinez-Sanchis, Elena. "Essays on identification and estimation of structural parametric and semiparametric models in microeconomics." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1444804/.
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This thesis focuses on identification and estimation of structural parametric and semi-parametric models in microeconometrics. The analysis of the conditions under which in the context of an econometric model-data can be informative about the parameters of interest of an economic process is essential and must be of high priority in any econometric work. When considering models with which to identify interesting features, emphasis should be placed on imposing the minimum set of restrictions in order to achieve identification, since inappropriate restrictions may lead to inconsistent estimates of the parameters of interest. For this reason in the literature one finds that some attention has been paid to relaxing parametric distributional assumptions on the unobservables or functional forms of the relationships between observables and unobservables. To begin with, I examine how the parameters of interest of a general class of models can be identified and then estimated when not all of the relevant variables are jointly observed in the same dataset. To do so, the existence of an additional data set with information on both the missing variables and on some common variables in the original data set is necessary. I then move on to an analysis of the identification of the preference parameters in a discrete choice demand model in which individuals only derive utility from the characteristics of the goods they consume. I discuss how this particular model makes the estimation of these parameters feasible without imposing distributional assumptions in the errors even if the number of goods in the choice set is very large. Finally, I consider the comparison of nonparametric regression curves between different samples. I propose to estimate the parameters that explain these differences between the conditional mean functions by using an estimator developed in the semiparametric literature which avoids the computational problems faced by the previously proposed estimators.
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Stinton, Graham William. "Structural studies into AM(_2)O(_7) framework materials and parametric Rietveld refinement." Thesis, Durham University, 2006. http://etheses.dur.ac.uk/2436/.
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This thesis investigates the structural properties of the AM2O7 family of materials, many of which show interesting thermal expansion properties and remarkably complex structures. It also develops Parametric Rietveld refinement, a method of extracting more information from multi-condition powder diffraction data. Chapter 1 reviews the relevant literature. Chapter 2 describes the equipment and analytic techniques used in the work. Chapter 3 describes Parametric Rietveld refinement, which aims to fit a single, evolving structural model to a series of diffraction data collected as a function of time, temperature, pressure or other external variable. This can lead to a number of benefits over conventional, sequential Rietveld refinement: it can increase the precision of refined parameters; allow physically realistic models to be applied during data analysis; and allow 'non-crystallographic’ quantities, such as temperature or rate constants, to be refined directly from diffraction data. Chapter 4 presents a full structure solution of ZrP(_2)O(_7) at room temperature from powder diffraction data. This involved developing a method for combining Rietveld refinement, restraints and simulated annealing. Despite 136 unique atoms and close-to metrically cubic symmetry, the true structure of this orthorhombic material can be refined to a high degree of precision. Chapter 5 is an investigation into the structures and thermal expansion of two AM(_2)O(_7) species, pseudo-cubic SnP(_2)O(_7) and GeP(_2)o(_7). A full structure solution of the room temperature phase of SnP(_2)O(_7) is presented. Two higher temperature phases of SnP(_2)O(_7) and the low temperature phase of GeP(_2)o(_7) are also analysed. Variable temperature data for both materials are presented. Chapter 6 describes the synthesis and characterisation via powder diffraction of solid-state solutions of the general formula Zr(_x)Sn(_1-x)P(_2)o(_7). The variation of properties across the series is investigated both at room temperature and upon heating.
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Wang, Lyang Suan. "Automating Parametric Redesign of Structural Thin-Walled Frames Based On Topology Optimized Structure." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu156618342438725.
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Eranki, Venkata Krishna Prashanth, and Gurudu Rishank Reddy. "Design and Structural Analysis of a Robotic Arm." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13834.
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Automation is creating revolution in the present industrial sector, as it reduces manpower and time of production. Our project mainly deals around the shearing operation, were the sheet is picked manually and placed on the belt for shearing which involves risk factor. Our challenge is designing of pick and place operator to carry the sheet from the stack and place it in the shearing machine for the feeding. We have gone through different research papers, articles and had observed the advanced technologies used in other industries for the similar operation. After related study we have achieved the design of a 3-jointed robotic arm were the base is fixed and the remaining joints move in vertical and horizontal directions. The end effector is also designed such that to lift the sheet we use suction cups were the sheet is uplifted with a certain pressure. Here we used Creo-Parametric for design and Autodesk-Inventor 2017 to simulate the designed model.
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Mokhuthu, Batho. "Parametric study on the buckling behaviour of singly and doubly curved concrete arch dams." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/11421.
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This study explores the buckling behaviour of thin walled and curved concrete arch dams investigated as a function of various parameters of interest, the focus being on the influence of dam thickness on the elastic buckling behaviour.
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Lim, Ryan S. (Ryan Seungwook). "Staged attitude-metrology pointing control and parametric integrated modeling for space-based optical systems." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35574.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006.<br>Includes bibliographical references (p. 155-158).<br>The quest for higher sensitivity and finer angular resolution in astronomy demands larger and more complex space imaging systems. This thesis presents the concepts developed for two different technologies that have the potential to contribute in improving the performance of space imaging systems. The first technology is precision pointing control technology, which can provide fine optical control operating in conjunction with coarse formation flying attitude control in order to meet the stringent optical requirements. This will potentially enable a long baseline Formation Flying Interferometer (FFI) such as NASA's Terrestrial Planet Finder (TPF). The concept for precision pointing control was realized by a testbed called the Precision Pointing Optical Payload (PPOP). The design and implementation of the PPOP are described, followed by an experimental demonstration of staged pointing control. The global metrology system of the Synchronized Position Hold Engage Reorient Experimental Satellites (SPHERES) provides coarse attitude control, whereas the PPOP provides fine pointing control using a set of fast steering mirrors. The second technology investigates parametric integrated modeling of space telescopes.<br>(cont.) This technology provides a design tool for examining alternative telescope architectures and identifying favorable architectures at an early stage of the design lifecycle. The MIT Space Systems Laboratory (MIT-SSL) is currently developing a parametric integrated model for a Modular Optical Space Telescope (MOST). This thesis provides an overview of the MOST model, with emphasis on the development of the optics sub-model. ZEMAX is used for calculating the wave front error based on the Zernike sensitivity analysis. A data interface between ZEMAX and MATLAB has been developed, which makes the process of performing the Zernike sensitivity analysis automated.<br>by Ryan S. Lim.<br>S.M.
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Zhou, Qing. "Combined linear/nonlinear stability analysis of plane and space frames." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-07112009-040327/.
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York, Darren M. "Structural analyses of a joint for deployable space systems." Thesis, University of Surrey, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332335.
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Mueller, Caitlin T. "High-dimensional design space visualization for conceptual structural design." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90083.
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Thesis: S.M., Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2014.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 63-66).<br>This thesis focuses on visualizing high-dimensional design spaces for early-stage design problems in structural engineering and related disciplines. The design space, which is defined as the n + 1-dimensional surface that relates n design variables to a performance metric, contains all possible solutions to a formulated design problem. Graphical views of the design space are highly useful for designers because they organize a wide range of design possibilities in a compact, intuitive, and logical manner, illuminating global patterns, variable behaviors and relationships, and the nature of paths taken during iterative design processes. Design problems with two or fewer variables can easily be visualized in Euclidian space, through a curve or surface, but high-dimensional problems are difficult to display graphically. This is the key challenge addressed in this thesis. The thesis includes a critical review of existing methods for high-dimensional design space visualization, highlighting the unmet needs across a range of approaches. In response to these needs, the thesis makes a key contribution in the form of a new design space visualization method, called isoperforming parallel coordinate clusters (IPC clusters), that overcomes the issues of previous techniques. The IPC cluster approach is demonstrated on several conceptual structural design problems, and its application in optimization, directed exploration, and related design strategies is illustrated. Finally, the thesis concludes with a discussion of applications, impact, and future research directions. Key words: design space visualization, conceptual design, structural design, structural optimization<br>by Caitlin T. Mueller.<br>S.M.
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Kim, Yool A. (Yool Ah). "Transient thermo-structural analysis of an insulated space structure." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/47384.
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Annandale, Robert William. "Thermal and structural analyses of large space antenna reflectors." Thesis, University of Surrey, 1986. http://epubs.surrey.ac.uk/843716/.
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This thesis is a theoretical investigation into the thermal and structural response of large reflector support trusses subject to the space environment. A review of the elements necessary in a successful spacecraft design is included. The determination of the temperature distributions within large orbiting tetrahedral trusses is described. The thermal environment is shown to be an important factor'' in determining the performance of spacecraft. High quality microwave performance of the communication system depends upon the magnitude of distortions within the reflector support truss, and the thermal expansion or contraction of members makes a significant contribution to this distortion. The possibility of flexural vibration of individual members of the truss arising during entry into, or exit from, the earth's shadow is considered. Individual slender members and the radio frequency reflecting mesh cast shadows within the truss. A method for calculating the duration and position of such shadowing events is discussed. The effect that shadows have upon shadowee temperatures is determined using computer programs written by the author. Situations in which temperature gradients between the truss faces exist are highlighted. Such gradients produce bending deflections of the truss. Classical theories are developed to predict the magnitude of thermally induced stresses in the adhesive layer of tubular lap joints having dissimilar adherends. Tubular joints which contain a transition layer are also examined. An appropriately chosen transition layer will reduce the adhesive shear stresses by a substantial amount. Finally, the development of thermally induced stresses and damage mechanisms in laminated composite tubes is discussed. The designer must be aware of the amount of damage that spacecraft materials will experience during the long life missions envisaged for the near future.
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Oueini, Shafic Sami. "Techniques for Controlling Structural Vibrations." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/27176.
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We tackle the problem of suppressing high-amplitude vibrations of cantilever beams when subjected to either primary external or principal parametric resonances. Guided by results of previous investigations into the nonlinear dynamics of single- and multi-degree-of-freedom structures, we design mechatronic systems of sensors, actuators, and electronic devices and implement nonlinear active feedback control.
In the case of external excitation, we devise two vibration absorbers based on either quadratic or cubic feedback. We conduct theoretical analyses and demonstrate that when a two-to-one (one-to-one) internal resonance condition is imposed between the plant and the quadratic (cubic) absorber, there exists a saturation phenomenon. When the plant is forced near its resonant frequency and the forcing amplitude exceeds a certain small threshold, the nonlinear coupling creates an energy-transfer mechanism that limits (saturates) the response of the plant.
Our theoretical studies reveal that the cubic absorber creates regimes of high-amplitude quasiperiodic and chaotic responses, thereby limiting its utility. However, we show that superior results can be achieved when the natural frequency of the quadratic absorber is set equal to one-half the excitation frequency. Consequently, we apply the quadratic technique through a variety of linear and nonlinear actuators, sensors, and electronic devices.
We design and build second-order analog circuits that emulate the quadratic absorber. Using a DC motor, piezoelectric ceramics, and Terfenol-D struts as actuators and potentiometers, strain gages, and accelerometers as sensors, we demonstrate successful single- and multi-mode vibration control.
In order to realize a more versatile implementation of the control strategy, we resort to a digital signal processing (DSP) board. We compose a code in C and design a digital absorber by developing algorithms that, in addition to replacing the analog circuit, automatically detect the amplitude and frequency of oscillation of the plant and fine-tune the absorber parameters.
We take advantage of the digital realization, implement a linear absorber, and compare the performance of the quadratic absorber with that of its linear counterpart.
In the case of parametric excitation, we investigate two techniques. First, we explore application of the quadratic absorber. We prove theoretically and demonstrate experimentally that this control scheme is not reliable. Then, we propose an alternate approach. We devise a control law based on cubic velocity feedback. We conduct theoretical and experimental investigations and show that the latter strategy leads to effective vibration suppression and bifurcation control.<br>Ph. D.
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Ruekberg, Jared Allen. "STRUCTURAL MICROMETEOROID AND RADIATION SHIELDING FOR INTERPLANETARY SPACECRAFT." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1401.
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This paper focused on two significant space forces that can affect the success of a spacecraft: the radiation and micrometeoroid environments. Both are looked at in the context of the region of space between Earth and Mars. The goal was create reference environments, to provide context to results of environmental modeling, and to provide recommendations to assist in early design decisions of interplanetary spacecraft. The radiation section of this report used NASA's OLTARIS program to generate data for analysis. The area of focus was on the radiation effects for crewed missions, therefore effective dose equivalent was the metric used to compare different models of radiation and shielding. Test spheres with one, two, or three different materials layers were compared, along with modifiers such as alloys or weight vs. thickness emphasis. Results were compared to limits set by the European and Russian Space Agencies to provide context. The results hinged heavily on the intensity of the Solar Particle Events (SPEs), with testing using additional temporary radiation shielding proving to be a requirement for feasible shielding masses. Differences in shield material effectiveness were found to be negligible for thin Galactic Cosmic Rays (GCRs) and thick SPEs. Thick shields were found to perform better when the more efficient shield was on the outside of the test sphere. The micrometeoroid section used equations and programs from multiple sources to generate state vectors, flux, and finally impact models for four different case studies. Impacts v were generated with mass, velocity, and impact angle/location statistics. The mass and velocity results were run through statistical software to generate information such as mean and standard deviation with confidence intervals. Also looked at were higher mass impacts, limited to above 10-3 grams as opposed to above 10-6 for the regular case. The results of this show that very thin monolithic shields (0.1 cm-0.25 cm) could protect against the average 10-6 impact. The Ram, Nadir, and Anti-sun faces received the highest quantity of impacts and Wake received the least. When looking at the worst cases average mass and velocity for the high mass impacts significantly higher shielding was required to prevent penetration (up to 5 cm for some cases). However, the test cases had probabilities of no high mass impacts greater than 46% of the time, with shorter mission having greater chances of no high mass impacts.
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Pridham, Brad A. Wilson John C. "State space modeling and identification of stochastic linear structural systems." *McMaster only, 2004.
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Lanzas, Lourdes Eneida 1962. "A parametric study on the behavior of slender reinforced concrete frames." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276945.
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By using a nonlinear computer analysis, a parametric study is developed in order to examine the accuracy of the Moment Magnifier Method of the American Concrete Institute Code (ACI 318-83). The variables used in the parametric study are: axial load intensity, P/Po; column reinforcement ratio, rho; slenderness ratio, klu; shape of column cross section, flexural stiffness ratio, and distribution of axial loads. In the parametric study, 216 cases of single bay fixed-base portal frames are examined. The higher moment for each one of these frames at failure are then compared with the design moment predicted by the Moment Magnifier Method of the American Concrete Institute Code (ACI 318-83). The Moment Magnifier Method proved to be very conservative when the columns are subjected to high level of axial loads and when the slenderness ratio is increased.
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Mantikas, Nikolaos. "Dynamics of large flexible multibody structures in space." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396146.
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Kaveh, Mohammad. "Topological optimization of rigidly jointed space frames." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238227.
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Kahn, Sergey. "Thinking Outside The Grid: Structural Design Through Multi-parametric Growth and Self-Adaptive Analysis." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491317566570458.
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Pugh, James Christopher. "A user friendly preprocessor for plane and space frames and space trusses." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/44655.
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<p>A user friendly preprocessor was developed and documented for
the plane and space frame and space truss structural analysis
programs that are based on the matrix displacements method.
This preprocessor is comprised of three programs. The main
program in the preprocessor is to allow the user to create
error free input data files. This program also allows
modifications of existing input data files. The two other
programs are the library manager and the graphics
presentation. The library manager is used to manage the
libraries of the element and material properties. The
graphics presentation is used to display a plane structure on
the graphics display. In Chapter 2, the development of a user
friendly preprocessor is discussed. After a short review of
the extension of the analysis program from plane frame to
space frame in Chapter 3, the preprocessor and its supporting
programs are described in detail in the user manual in Chapter
4. Possible extensions to the preprocessor are discussed in
Chapter 5. The appendix contains examples of input data files
for these structural analysis programs.</p><br>Master of Science
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Khalafalla, Eltayeb Elrayah. "Computer aided processing of geodesic structural forms." Thesis, University of Surrey, 1994. http://epubs.surrey.ac.uk/845/.
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Bondarchuk, M. S., and М. С. Бондарчук. "The use of parametric principles in the elements of park architecture." Thesis, Національний авіаційний університет, 2020. http://er.nau.edu.ua/handle/NAU/42093.
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1. Добрицына И.А. От постмодернизма – к нелинейной архитектуре: Архитектура в контексте современной философии и науки / И.А. Добрицына. – М.: Прогресс-Традиция, 2004. – 416 с.
2. Schumacher P. LECTURES & INTERVIEWS – theorizing architecture [Електронний ресурс] / Patrik Schumacher – Режим доступу: http://www.patrikschumacher.com/index.htm<br>The beginning of XXI century is marked by the emergence of research, experimentation and implementation in the direction of “paramentric”. Parametric principles have been applied in the design of architectural elements of the park. Based on the research, we can conclude that in the design of parks the direction of parametricism is a really new avant-garde style.
It largely relies on the structural, constructive and formative principles of nature, thereby continuing to develop the organic approach to a new level. The main feature of parametricism is the appeal to nonlinear forms, which brings it closer to bionic architecture. Thus, this new style is a natural step in the development of modern park architecture and integrates its achievement in the formation, relying on new design technologies and newest construction technologies.
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Howells, Hugh Alan. "Collapse behaviour of space trusses with thin-walled members." Thesis, University of Surrey, 1985. http://epubs.surrey.ac.uk/1038/.
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Rizzuto, J. P. "The structural behaviour of mutually supported elements in space structures." Thesis, Coventry University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420168.
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Alpert, David N. "Enriched Space-Time Finite Element Methods for Structural Dynamics Applications." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1377870451.
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