Thèses : « Experimental and numerical results »

1

Yalamanchili, Seshu R. « Response of multiple fastener composite joints : numerical and experimental results / ». Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-11242009-020154/.

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Hein, Torsten, et Marcus Meyer. « Identification of material parameters in linear elasticity - some numerical results ». Universitätsbibliothek Chemnitz, 2007. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200702040.

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In this paper we present some numerical results concerning the identification of material parameters in linear elasticity by dealing with small deformations. On the basis of a precise example different aspects of the parameter estimation problem are considered. We deal with practical questions such as the experimental design for obtaining sufficient data for recovering the unknown parameters as well as questions of treating the corresponding inverse problems numerically. Two algorithms for solving these problems can be introduced and extensive numerical case studies are presented and discussed.

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Perazzini, Matteo. « Evaluation of FBG strain sensor reliability through analytical, numerical and experimental results ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22947/.

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The fiber Bragg grating (FBG) sensor is one of the most suitable sensors for structural health monitoring (SHM) of aircraft structures. In principle, the FBG, with adequate sampling and signal processing techniques, is usually more accurate than classical electrical resistive strain gauge. However, since the most common installation method is surface bonding, some significative differences between the strain in the host structure and the one experienced by the fiber may be observed. The aim of this work is the evaluation of the fiber Bragg grating optical fiber sensor reliability for strain detection in non-uniform strain conditions. A FBG sensor is surface bonded on a rectangular specimen with a centered hole under tensile loading. A multi device method for the strain detection is created with the use of optical fiber, strain gauge and DIC technologies at the same time. In addition, based on microscopic observations, a 3D finite element model of the bonded optical fiber is created to simulate the behavior of the test specimen and to have an insight into the strain transfer between the host material and the optical fiber core. Lastly, being the test specimen a well-known case in literature, the strain is also computed with closed-form expressions. All the experimental, numerical, and analytical results are then compared. Taking into account the possible sources of error, the comparison shows coherence between the different results. The optical fiber strain sensor reliability is verified through the multiple device method which represents the starting point for future research activities.

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Marcel, Sébastien. « Numerical thermal investigation of a space probe heat shield - Comparison with experimental results ». Thesis, KTH, Rymd- och plasmafysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-91471.

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The objective of this internship was to study the physical properties of a thermal protection used for a space probe to be launched for a mission to Mars. The protection is composed of two main components. The topmost part is a cork derivative that deteriorates via ablation and pyrolysis in order to reduce the amount of heat transferred to the vehicle's main body. The junction between the ablative layer and the spaceship is ensured by a sandwich material composed of two carbon skins separated by a grid of Aluminium honeycomb cells. In a first part, numerical models of variable complexity were created to simulate the properties of the sandwich material (thermal conductivity, specific thermal capacity). The models' results were then compared to experimental measurements to upgrade Astrium's databases concerning similar products with new values for the physical properties of the studied materials. The results obtained by both the model and the experiments were found to be in accordance, which justies the validity of the simulation, and the choices made for the values of physical properties. In addition, a thorough consideration of the in　uence of phenomena neglected was performed to justify the stability of the numerical computations. In a second time, a staggered coupled simulation was developed to study the physical behaviour of the ablative protection. A thermal simulation considered the ablation, pyrolysis and thermal conduction. A mechanical simulation considered the swelling induced by the heating of the cork material. The results (temperature, swelling, density) from infra-red experiments and plasma jet testing were compared to the prediction of the coupled simulation. Although a substantial discrepancy remained between experimental and numerical results, the mere fact that a working program emulating at the same time ablation and swelling gave results physically coherent was already a positive advance in this domain.

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Novick, Jaison Allen. « Chaotic scattering in an open vase-shaped cavity : Topological, numerical, and experimental results ». W&M ScholarWorks, 2009. https://scholarworks.wm.edu/etd/1539623550.

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We present a study of trajectories in a two-dimensional, open, vase-shaped cavity in the absence of forces The classical trajectories freely propagate between elastic collisions. Bound trajectories, regular scattering trajectories, and chaotic scattering trajectories are present in the vase. Most importantly, we find that classical trajectories passing through the vase's mouth escape without return. In our simulations, we propagate bursts of trajectories from point sources located along the vase walls. We record the time for escaping trajectories to pass through the vase's neck. Constructing a plot of escape time versus the initial launch angle for the chaotic trajectories reveals a vastly complicated recursive structure or a fractal. This fractal structure can be understood by a suitable coordinate transform. Reducing the dynamics to two dimensions reveals that the chaotic dynamics are organized by a homoclinic tangle, which is formed by the union of infinitely long, intersecting stable and unstable manifolds.;This study is broken down into three major components. We first present a topological theory that extracts the essential topological information from a finite subset of the tangle and encodes this information in a set of symbolic dynamical equations. These equations can be used to predict a topologically forced minimal subset of the recursive structure seen in numerically computed escape time plots. We present three applications of the theory and compare these predictions to our simulations. The second component is a presentation of an experiment in which the vase was constructed from Teflon walls using an ultrasound transducer as a point source. We compare the escaping signal to a classical simulation and find agreement between the two. Finally, we present an approximate solution to the time independent Schrodinger Equation for escaping waves. We choose a set of points at which to evaluate the wave function and interpolate trajectories connecting the source point to each "detector point". We then construct the wave function directly from these classical trajectories using the two-dimensional WKB approximation. The wave function is Fourier Transformed using a Fast Fourier Transform algorithm resulting in a spectrum in which each peak corresponds to an interpolated trajectory. Our predictions are based on an imagined experiment that uses microwave propagation within an electromagnetic waveguide. Such an experiment exploits the fact that under suitable conditions both Maxwell's Equations and the Schrodinger Equation can be reduced to the Helmholtz Equation. Therefore, our predictions, while compared to the electromagnetic experiment, contain information about the quantum system. Identifying peaks in the transmission spectrum with chaotic trajectories will allow for an additional experimental verification of the intermediate recursive structure. Finally, we summarize our results and discuss possible extensions of this project.

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Huang, Jun. « A study on fatigue of welded structures : predictive modeling based on automatic learning, numerical analysis, and experimental results / ». Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3071054.

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Wegman, Kevin R. « Numerical Modeling of a Printed Circuit Heat Exchanger Based on Experimental Results from the High-Temperature Helium Test Facility ». The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461266010.

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Sierra-Espinosa, Fernando Zenaido. « The turbulence structure of the flow in a 90#deg C# pipe junction : a comparison of numerical predictions to experimental laser doppler and particle image velocimetry results ». Thesis, Cardiff University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286901.

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Benezech, Jean. « Modélisation aux échelles méso- et macroscopique du comportement mécanique de zones singulières de pièces de structure en CMC ». Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0309.

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Les composites à matrice céramique (CMC) présentent une architecture multi-échelle complexe. Pour être utilisé en tant que composant de moteur aéronautique qui nécessitent des géométries complexes, ces matériaux doivent être tissés sous forme d'architectures textiles spécifiques. Mon travail s’est concentré sur l’étude d’une pièce de type raidisseur, et plus particulièrement sur le détail d’une jonction composite tissée. La taille caractéristique de cette pièce se situe entre les échelles méso- et macroscopique, ce qui rend impossible l’utilisation des hypothèses de séparabilité des échelles. Nous avons tout d’abord développé un montage expérimentale de flexion/cisaillement adapté à la jonction tissée. Ces essais ont non seulement permis d’identifier et de caractériser le comportement mécanique de cette pièce, mais aussi, de mettre en lumière l’interdépendance entre le chargement, l’architecture textile et les mécanismes d’endommagement, qui est particulièrement importante dans le cas de la jonction tissée. C’est pourquoi, la modélisation de ce détail de structure doit inclure une connaissance approfondie de l’architecture interne du matériau. Nous avons donc développé une approche originale de segmentation variationnelle à partir de µCT, afin de construire des modèles numériques réalistes du matériau à l’échelle mésoscopique. Cette approche repose sur une heuristique globale-locale qui améliore itérativement la ressemblance d’un modèle géométrique initial. Cette démarche a permis de construire le jumeau numérique de la jonction tissée. Le modèle final ne comportant pas d’interpénétration entre fils, un maillage tétraédrique conforme peut ensuite être généré directement à partir de l’image ainsi labellisée. Des simulations EF à l’échelle mésoscopique ont été menées en prenant en compte le comportement non-linéaire des constituants des CMC. Elles permettent de prévoir le niveau de chargement menant aux premiers endommagements. De plus, la localisation des endommagements ainsi que leurs interactions avec l’architecture méso ont également ont été reproduites de manière satisfaisante.Cependant, ces modèles incluent une description très détaillée du matériau et nécessitent donc des ressources de calcul importantes. Une description approchée de ces détails pourrait être suffisante pour obtenir une prédiction correcte des propriétés élastiques, voir de l’amorçage de l’endommagement. Nous avons donc proposé un pont méso-macro permettant de construire le comportement apparent des éléments macroscopiques à partir de l’information méso sous-jacente. Les propriétés des éléments macroscopiques sont obtenues en assimilant localement le matériau à un stratifié équivalent construit à partir des fractions volumiques et des orientations locales des constituants. Cette approche permet de réduire drastiquement la taille des problèmes EF, tout en conservant une description approchée de la méso-structure. Le modèle macroscopique enrichi permet de reproduire fidèlement les résultats obtenus à l’échelle mésoscopique, tant que la taille de filtrage reste comparable à celle des fils.Les modèles proposés ont été utilisés pour reproduire les résultats expérimentaux et approfondir leur analyse. Nous avons étudié en particulier la sensibilité aux conditions aux limites de l’essai, ainsi que l’influence des variabilités liées au procédé de fabrication des éprouvettes. Enfin, la chaine d’outils développée dans le cadre de la thèse pourra être utilisée pour étudier différentes définitions textiles de la jonction, permettant in fine de définir l’architecture optimale de la pièce
Woven ceramic matrix composites (CMC) exhibit an intricate multi-scale architecture. To be used as components of aircraft engines, the weaving of such parts could also incorporate specific features compared to « classical » woven CMC as they need to comply with complex geometries. My work focused on a stiffener-like fully woven junction that is made of a complex 3D woven fabric, and whose characteristic size lies at the frontier between the mesoscopic and the macroscopic scales, i.e. where scale separation hypothesis is not applicable.I have first developed an experimental device to perform shear/bending tests on the woven junction. These tests not only allowed to gain significant knowledge about the mechanical behavior of such part, but also to highlight the interplay between the load, material architecture and damage mechanisms that is particularly significant in the case of the woven junction. Therefore, numerical prediction of the mechanical behavior of the woven junction necessitates a sound knowledge of its inner structure.With this aim, I have developed an original segmentation method to build realistic numerical models of textile composites, using X-ray micro-computed tomography and a prior geometric model. The procedure includes a global-local heuristic to iteratively improve the resemblance of the initial model. This approach allowed to build “digital twins” of the woven junction. A conformal tetrahedral image-based mesh could then be obtained as the resulting models are free of interpenetration. Mesoscale FE simulations, including non-linear behavior laws of the yarns and matrix, allowed to predict the maximal load leading to the first damage events, and to reproduce accurately the damage localization and its interaction with the architecture.However, with such level of details incorporated in the model, the simulations necessitate significant computational resources. An approximate macro-scale description may be sufficient to evaluate the elastic properties, or even to simulate damage initiation. Therefore, we have proposed a meso-informed macroscopic modelling framework where the behaviour of the macro-elements is derived from the knowledge of the local direction and volume fraction of constituents, thanks to the digital twin. The effective behaviour of the macro-elements is obtained through an equivalent lamina. This method drastically reduces the size of the model while preserving an approximate description of the underlying local anisotropy and heterogeneities. With respect to the damage initiation, the meso-informed macroscopic model accurately reproduced the results obtained using the reference mesoscale model, as long as the filtering size remains comparable to the yarn size. This allowed to propose an optimal modelling framework with an adequate level of description of meso-details and acceptable computational requirements.Finally, I have used these models to thoroughly compare the numerical simulations with the experimental results: variabilities of experimental boundary conditions have been analyzed, as well as the influence of specific heterogeneities related to the fabrication process. We have also used this framework to explore different weaving patterns in order to obtain an optimal design of the woven junction

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Carvalho, Marco Aurélio. « IPCM Telemetry System : Experimental Results ». International Foundation for Telemetering, 2015. http://hdl.handle.net/10150/596440.

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ITC/USA 2015 Conference Proceedings / The Fifty-First Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2015 / Bally's Hotel & Convention Center, Las Vegas, NV
The aeronautical industries have been suffering financial cutbacks and the market has to face new challenges associated with new companies. Telemetry community has been facing the increase of the electromagnetic spectrum usage for a variety of applications (e.g. 4G), after all telemetry is everywhere. In view of these issues and focused on the inherent requirements of the Flight Test application, the IPEV R&D group proposes the iPCM Telemetry architecture as solution for the existing reliability and bandwidth issues associated with the telemetry link. In this article, as a proof-of-concept of the iPCM architecture, it has been performed an experimental assembly. The results demonstrate the iPCM's ability to regenerate corrupted data providing the required data integrity and reliability, besides the capability to dynamically select the FTI transmitted parameter list to optimize the bandwidth link.

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Diening, Lars. « Theoretical and numerical results for electrorheological fluids ». [S.l. : s.n.], 2002. http://www.freidok.uni-freiburg.de/volltexte/458.

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Nyqvist, Robert. « Algebraic Dynamical Systems, Analytical Results and Numerical Simulations ». Doctoral thesis, Växjö : Växjö University Press, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:vxu:diva-1142.

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Muir, John P. « Experimental results for inductive strips in inhomogeneous finline ». Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/26535.

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Louvet, Anne-Claire Alice. « The bounded rationality constraint : experimental and analytical results ». Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14755.

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Sullivan, Patrick J. « Analysis and experimental results of RF CMOS mixers / ». Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9835390.

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Pahmer, Sueda Carmen M. « Contribution à l'étude de filtres actifs de puissance de type shunt : commande-simulation ». Grenoble INPG, 1996. http://www.theses.fr/1996INPG0080.

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Le travail presente consiste a etudier de maniere detaillee les algorithmes de commande d'un filtre actif de puissance de type shunt realise a partir d'un onduleur de tension connecte sur un reseau triphase de puissance finie. Ces algorithmes ont ete testes en simulation a l'aide du logiciel a usage general electro-magnetic transients program (emtp). A ce propos, cinq methodes distantes pour obtenir les courants de reference pour chaque phase de l'onduleur de tension ont ete formalises. De la meme maniere, la regulation de tension aux bornes du condensateur de cet onduleur a egalement ete abordee. Dans certains cas de figure la numerisation controle-commande a ete developpe de maniere a simuler des structures les plus proches possibles de la realite. Quelques resultats experimentaux obtenus a l'aide d'un filtre actif de commande numerique permettent de valider notre methodologie

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Koray, Erge. « Numerical And Experimental Analysis Of Indentation ». Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/2/12605953/index.pdf.

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Indentation tests are widely used with simultaneous measurements of indentation depth and force especially for determining material properties. In this study
numerical and experimental investigation of the force-indentation measurements is presented. For indentation tests on anisotropic metals, a novel indenter which is not self similar is used with three transducers to measure the displacements. It is seen that in order to have high repeatability and accuracy at the tests, workpiece and indenter parameters have crucial importance. These parameters in the indentations are analyzed by finite element methods. Ideal dimensions of the workpiece are determined. It is shown that plane strain conditions can only be achieved by embedded indentations. Effect of surface quality and clamping on repeatability are investigated. It is shown that surface treatments have significant effects on the results. Also it is seen that clamping increases the repeatability drastically. Moreover, indentation tests are conducted to verify the results of numerical simulations. Effect of anisotropy on the force-displacement curves is clearly observed.

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Duris, Joseph Gerald. « Experimental and numerical characterization of softballs ». Online access for everyone, 2004. http://www.dissertations.wsu.edu/Thesis/Fall2004/J%5FDuris%5F121504.pdf.

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Svensson, Olle. « Experimental results from the Lysekil Wave Power Research Site ». Doctoral thesis, Uppsala universitet, Elektricitetslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-179098.

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This thesis presents how experimental results, from wave power research performed offshore at the Lysekil research site, were obtained. The data were used to verify theoretical models as well as evaluate the feasibility of wave power as a future sustainable energy source. The first experiments carried out at the research site was the measurement of the force in a line where one end was connected to a buoy with a diameter of 3 m and the other end to a set of springs with limited stroke length. The system is exposed to high peak forces compared to average forces. The maximum measured force in the line, when the buoy motion is limited by a stiff stopper rope is ten times the average force in that particular sea state. The experiment performed on the first wave energy converter tested at the Lysekil Research Site is described. The infrastructure of the site is presented where the central connection point is the measuring station. The key finding is that it is possible to transform the motions of ocean waves into electrical energy and distribute it to land. Many wave energy converters must be interconnected if large amounts of energy are to be harvested from the waves. The first submerged substation intended for aggregation of energy from wave power converters is described, with focus on the measurement and control system placed inside the substation. During this experiment period the generators were equipped with many different sensors; these measurements are explained in the thesis. The system that aggregates power from the studied wave energy converter is regularly exposed to peak power of up to 20 times the maximum average output from the converter. Vertical and horizontal movement of the buoy has been measured in different ways. The result is that the vertical displacement of the buoy can be measured with a simple accelerometer circuit but it is much more complicated to measure the horizontal displacement. A special method for measuring the horizontal displacement has been implemented by measuring the strain in the enclosure and the force in the line.
Den här avhandlingen berättar om hur experimenten vid Lysekils forskningsområde för vågkraft har utförts. Insamlade mätdata har använts för att verifiera teoretiska samband som modulerats vid Elektricitetslära, Uppsala universitet. De teoretiska och praktiska resultaten har visat på att vågkraft har förutsättningarna att implementeras som en hållbar framtida energikälla. Intressanta mätmetoder har utvecklas och påfrestningarna på utrustningin och dess samband med medel effekten har studerats.
Lysekils projektet

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Kjellin, Jon. « Vertical Axis Wind Turbines : Electrical System and Experimental Results ». Doctoral thesis, Uppsala universitet, Elektricitetslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-182438.

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The wind power research at the division of Electricity at Uppsala University is aimed towards increased understanding of vertical axis wind turbines. The considered type of wind turbine is an H-rotor with a directly driven synchronous generator operating at variable speed. The experimental work presented in this thesis comprises investigation of three vertical axis wind turbines of different design and size. The electrical, control and measurement systems for the first 12 kW wind turbine have been designed and implemented. The second was a 10 kW wind turbine adapted to a telecom application. Both the 12 kW and the 10 kW were operated against dump loads. The third turbine was a 200 kW grid-connected wind turbine, where control and measurement systems have been implemented. Experimental results have shown that an all-electric control, substituting mechanical systems such as blade-pitch, is possible for this type of turbine. By controlling the rectified generator voltage, the rotational speed of the turbine is also controlled. An electrical start-up system has been built and verified. The power coefficient has been measured and the stall behaviour of this type of turbine has been examined. An optimum tip speed ratio control has been implemented and tested, with promising results. Use of the turbine to estimate the wind speed has been demonstrated. This has been used to get a faster regulation of the turbine compared to if an anemometer had been used.

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Camara, Enrique. « Validation of Time Domain Flutter PredictionTool with Experimental Results ». Thesis, KTH, Kraft- och värmeteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160541.

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In turbomachinery applications as propulsion and power generation, there is a continuous endeavour to design engines with higher efficiency, driving the compressor and turbine blades towards slimmer and more aerodynamically loaded configurations that frequently operate with fluids at higher temperatures and speeds. This combination of reduced design space and adverse operating environment makes the blades more susceptible to flutter and challenges the designer to predict its occurrence. Nowadays there are different CFD solvers that allow the prediction of flutter in turbomachinery; some of them are more efficient than others and provide considerable computational power savings when compared with traditional CFD methods that sometimes require the simulation of several or all the blades in a given row. The present thesis work is aimed at investigating the strengths and potential limitations of a novel time marching method for Flutter prediction in the Travelling Wave Mode (TWM) domain available in ANSYS CFX 14.5. The results are compared with experimental measurements obtained at the KTH test rig and CFD simulations in the Influence Coefficient Domain (INFC) performed in a previous MSc. Thesis in 2013. An approach in CFX to solve flutter is the Fourier Transformation method that uses only two passages with phase lagged periodic boundary conditions. In the previous thesis only one operating point was calculated using this method. This project focuses on the extension of the calculations to various operating points and expanding the solver validation.

Thesis work done at Siemens Industrial Turbomachinery, Finspang, Sweden.

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CALAND, VERONICA DE SOUZA. « EXPERIMENTAL RESULTS OF FRACTURE PARAMETERS FOR HIGH PERFORMANCE CONCRETE ». PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2001. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1995@1.

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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
A utilização mais freqüente dos concretos de alto desempenho na Construção Civil exige um melhor conhecimento sobre o comportamento deste material e a verificação de possíveis modificações no dimensionamento de elementos estruturais, como a consideração do efeito de escala. Recentemente, os conceitos da teoria da mecânica da fratura para a análise do comportamento das estruturas começaram a ser utilizados. A energia de fraturamento passa a ser uma propriedade intrínseca do material, fundamental no controle da resistência à flexão e ao cisalhamento Os principais objetivos desta dissertação são: obter experimentalmente os parâmetros de fraturamento para concretos de alto desempenho através da realização de ensaios estáveis e comparar estes resultados com resultados numéricos e experimentais encontrados na literatura. A metodologia utilizada para a determinação destes parâmetros é apresentada no trabalho. Foram executados ensaios estáveis à flexão em três pontos em vigas de concreto simples com entalhe, de acordo com as especificações elaboradas pela recomendação do comitê RILEM 50-FMC. As vigas foram moldadas no Laboratório de Estruturas da PUC- Rio e os ensaios realizados no Instituto de Tecnologia (ITUC) desta Universidade. Os ensaios foram realizados com controle de deslocamento da abertura do entalhe em uma máquina servo-hidráulica Instron modelo 8502. Foram ensaiadas 75 vigas, em quatro tamanhos diferentes, com alturas variando de 38 mm a 304 mm. A espessura das vigas foi mantida constante e igual a 38 mm. Os concretos utilizados apresentaram fator água/cimento entre 0,25 e 0,37 e resistência à compressão entre 70 MPa e 90 MPa.
The increasing use of high performance concrete in civil construction demands better knowledge of the behavior of this material and the review of possible changes in the design of structural elements, like the size effect. The concepts of the theory of fracture mechanics for the analysis of structures started to be used in recent days. The fracture energy became an inherent property of the material, and it is basic for the control of the nominal flexural strength and the modulus of rupture. The main purposes of this dissertation are to achieve experimentally the fracture parameters for high performance concrete by performing stable tests, and to carry out a comparison with numerical and experimental results found in literature. The methodology used for determining of these parameters is introduced in the work.Stable three-point bend tests were conducted in notched beams made with unreinforced concrete. These tests comply with the specifications given by the RILEM 50- FMC committee. The beams were cast at PUC-Rio Structural Laboratory and the tests were conducted at the Technology Institute (ITUC) of this University. The tests were performed using crack mouth opening displacement control in a closed-loop servohydraulic Instron machine model 8502. The experiments involved the testing of 75 singlenotched beams with four different sizes with depths varying from 38 mm to 304 mm. The thickness of the beams was kept constant and equal to 38 mm. The concrete had a watercement ratio varying from 0.37 to 0.25 and compressive strength between 70 MPa and 90 MPa.
La utilización más frecuente de los concretos de alto desempeño en la Construción Civil exige un mejor conocimiento sobre el comportamiento de este material y la verificación de posibles modificaciones en el dimensionamiento de elementos extructurales, como la consideración de la escala. Recientemente, los conceptos de la teoría de la mecánica de la fractura para el análisis del comportamiento de las extructuras comezaron a ser utilizados. La energía de fractura pasa a ser una propriedad intrínseca del material, fundamental en el control de la resistencia a la flexión y al cisallamento Los principales objetivos de esta disertación son: obtener experimentalmente los parámetros de fractura para concretos de alto desempeño a través de la realización de ensayos estables y comparar estos resultados con los resultados numéricos y experimentales encontrados en la literatura. LA metodología utilizada para la determinación de estos parámetros se presenta en el trabajo. Se ejecutaron ensayos estables a la flexión en tres puntos en vigas de concreto simple con entalle, de acuerdo con las especificaciones elaboradas por la recomendación del comité RILEM 50 FMC. Las vigas fueron moldadas en el Laboratorio de Extructuras de la PUC Rio y los ensayos realizados en el Instituto de Tecnología (ITUC) de esta Universidad. Los ensayos fueron realizados con control de desplazamiento de la abertura del entalle en una máquina servo hidráulica Instron modelo 8502. Fueron utilizadas 75 vigas, en cuatro tamaños diferentes, con alturas variando de 38 mm la 304 mm. Se mantuvo la espesura de las vigas constante e igual la 38 mm. Los concretos utilizados presentaran factor agua/cemento entre 0,25 y 0,37 y resistencia a la compresión entre 70 MPa y 90 MPa.

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Geoghegan, Mark. « EXPERIMENTAL RESULTS FOR MULTI-SYMBOL DETECTION OF PCM/FM ». International Foundation for Telemetering, 2001. http://hdl.handle.net/10150/607605.

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International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada
It has been previously shown, through computer simulations, that a multiple symbol detector can provide substantial gains in detection efficiency (nearly 3 dB) over traditional PCM/FM detectors. This is accomplished by performing correlations over multiple symbol intervals to take advantage of the memory inherent in the continuous phase PCM/FM signal. This paper presents measured hardware results, from a prototype developed for the Advanced Range Telemetry (ARTM) Project, that substantiate the previously published performance and sensitivity predictions. Furthermore, this work confirms the feasibility of applying this technology to high-speed commercial and military telemetry applications.

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24

Kothari, Rajiv D. « Experimental results on aliasing errors in circular BIST design ». Thesis, Virginia Tech, 1991. http://hdl.handle.net/10919/42137.

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The circular BIST design is a technique in which the existing circuit is modified, so that the processes of test generation and response compaction are carried out by the circuit being tested itself. Most response compaction techniques suffer from loss of information, known as aliasing. Aliasing is said to occur in a response compaction technique when the response generated by the circuit, under the presence of a fault, is different from its fault-free response, but this information is later lost during compaction, and the faulty compacted response at the end of the test session is identical to the fault-free compacted response.

A program to synthesize circular BIST hardware on general sequential circuits has been developed. A parallel fault simulator has been developed to detect aliasing errors in circular BIST design. Experimental results on aliasing probability in circular BIST design are reported for twenty-three sequential benchmark circuits.

Master of Science

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25

Stewart, Kevin Matthew. « MECHANICAL SIMULATION OF ARTICULAR CARTILAGE BASED ON EXPERIMENTAL RESULTS ». DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/93.

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Recently, a constituent based cartilage growth finite element model (CGFEM) was developed in order to predict articular cartilage (AC) biomechanical properties before and after growth. Previous research has noted limitations in the CGFEM such as model convergence with growth periods greater than 12 days. The main aims of this work were to address these limitations through (1) implementation of an exact material Jacobian matrix definition using the Jaumann-Kirchhoff (J-K) method and (2) quantification of elastic material parameters based upon research findings of the Cal Poly Cartilage Biomechanics Group (CPGBG). The J-K method was successfully implemented into the CGFEM and exceeded the maximum convergence strains for both the “pushed forward, then differentiated” (PFD) and “differentiated, then pushed forward” (DPF) methods, while maintaining correct material stress responses. Elastic parameters were optimized for confined compression (CC), unconfined compression (UCC), and uniaxial tension (UT) protocols. This work increases the robustness of the CGFEM through the J-K method, as well as defines an accurate starting point for AC growth based on the optimized material parameters.

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Garza, Jared W. « Tip Rub Induced Blade Vibrations : Experimental and Computational Results ». The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1391593189.

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27

Bondarchuk, Alexander. « Rock mass behavior under hydropower embankment dams : results from numerical analyses ». Licentiate thesis, Luleå : Luleå University of Technology, 2008. http://epubl.ltu.se/1402-1757/2008/03/.

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Li, Chi-kwong, et 李志光. « Some results on generalized spectral radii, numerical radii and spectral norms ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1986. http://hub.hku.hk/bib/B31230684.

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29

Austin, Anthony P. « Some new results on, and applications of, interpolation in numerical computation ». Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:11c16937-4a59-494d-a06f-6d27b634e2f3.

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This thesis discusses several topics related to interpolation and how it is used in numerical analysis. It begins with an overview of the aspects of interpolation theory that are relevant to the discussion at hand before presenting three new contributions to the field. The first new result is a detailed error analysis of the barycentric formula for trigonometric interpolation in equally-spaced points. We show that, unlike the barycentric formula for polynomial interpolation in Chebyshev points (and contrary to the main view in the literature), this formula is not always stable. We demonstrate how to correct this instability via a rewriting of the formula and establish the forward stability of the resulting algorithm. Second, we consider the problem of trigonometric interpolation in grids that are perturbations of equally-spaced grids in which each point is allowed to move by at most a fixed fraction of the grid spacing. We prove that the Lebesgue constant for these grids grows at a rate that is at most algebraic in the number of points, thus answering questions put forth by Trefethen and Weideman about the robustness of numerical methods based on trigonometric interpolation in points that are uniformly distributed but not equally-spaced. We use this bound to derive theorems about the convergence rate of trigonometric interpolation in these grids and also discuss the related question of quadrature. Specifically, we prove that if a function has V ≥ 1 derivatives, the Vth of which is Hölder continuous (with a Hölder exponent that depends on the size of the maximum allowable perturbation), then the interpolants converge uniformly to the function at an algebraic rate; larger values of V lead to more rapid convergence. A similar statement holds for the corresponding quadrature rule. We also consider what analogue, if any, there is for trigonometric interpolation of the famous 1/4 theorem of Kadec from sampling theory that restricts the size of the perturbations one can make to the integers and still be guaranteed to have a set of stable sampling for the Paley-Wiener space. We present numerical evidence suggesting that in the discrete case, the 1/4 threshold takes the form of a threshold for the boundedness of a "2-norm Lebesgue constant" and does not appear to have much significance in practice. We believe that these are the first results regarding this problem to appear in the literature. While we do not believe the results we establish are the best possible quantitatively, they do (rigorously) capture the main features of trigonometric interpolation in perturbations of equally-spaced grids. We make several conjectures as to what the optimal results may be, backed by extensive numerical results. Finally, we consider a new application of interpolation to numerical linear algebra. We show that recently developed methods for computing the eigenvalues of a matrix by dis- cretizing contour integrals of its resolvent are equivalent to computing a rational interpolant to the resolvent and finding its poles. Using this observation as the foundation, we develop a method for computing the eigenvalues of real symmetric matrices that enjoys the same advantages as contour integral methods with respect to parallelism but employs only real arithmetic, thereby cutting the computational cost and storage requirements in half.

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Li, Chi-kwong. « Some results on generalized spectral radii, numerical radii and spectral norms / ». [Hong Kong] : University of Hong Kong, 1986. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12321825.

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31

Nakauchi, Gene. « Analytical and numerical results for a curvature-driven geometric flow rule ». Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/127335/1/Gene_Nakauchi_Thesis.pdf.

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This research studies a particular curvature-driven geometric flow rule in the plane using techniques from differential geometry, computational mathematics, and formal asymptotics. The flow rule is a combination of the well-studied curve shortening flow, which is governed by a parabolic system of partial differential equations, and the Eikonal equation, which is governed by a hyperbolic system. The physical motivations for considering our model include propagating fire fronts and phase separation. The focus is on a variety of mathematical problems related to the flow rule, such as the explicit form of travelling wave solutions, linear stability, self-intersection, singularity formation, and the extinction problem for convex curves.

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32

Le, Thi Thien Thuy. « Results on controllability and numerical approximation of the minimum time function ». Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424319.

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This thesis focuses on the unconstrained and constrained minimum time problems, in particular on regularity, numerical approximation, feedback and synthesis aspects. We first consider the problem of This thesis focuses on the unconstrained and constrained minimum time problems, in particular on regularity, numerical approximation, feedback and synthesis aspects. We first consider the problem of small-time local controllability for nonlinear finite-dimensional time-continuous control systems in presence of state constraints. More precisely, given a nonlinear control system subject to state constraints and a closed set S, we provide sufficient conditions to steer to S every point of a suitable neighborhood of S along admissible trajectories of the system, respecting the constraints, and giving also an upper estimate of the minimum time needed for each point to reach the target. Then in framework of control affine nonlinear systems, sufficient conditions to reach a target for a suitable discretization of a given dynamics are provided. We make use of an approach based on Hamilton-Jacobi theory to prove the convergence of the solution of a fully discrete scheme to the (true) minimum time function, together with error estimates. We also design an approximate suboptimal discrete feedback and provide an error estimate for the time to reach the target through the discrete dynamics generated by this feedback. We next propose a new formulation of the minimum time problem in which we employ the signed minimum time function positive outside of the target, negative in its interior and zero on its boundary. Under some standard assumptions, we prove the so called Bridge Dynamic Programming Principle (BDPP) which is a relation between the value functions defined on the complement of the target and in its interior. Then owing to BDPP, we obtain the error estimates of a semi-Lagrangian discretization of the resulting Hamilton-Jacobi-Bellman equation. The remainder of this thesis is devoted to introducing an approach to compute the approximate minimum time function of control problems which is based on reachable set approximation. In particular, the theoretical justification of the proposed approach is restricted to a class of linear control systems and uses arithmetic operations for convex sets. The error estimate of the fully discrete reachable set is provided by employing Hausdorff distance. The detailed procedure solving the corresponding discrete problem is described. Under standard assumptions, by means of convex analysis and knowledge of regularity of the true minimum time function, we estimate the error of its approximation. Finally, we reconstruct discrete suboptimal trajectories which reach a set of supporting points from a given target for a class of linear control problems and also proving the convergence of discrete optimal controls by the use of nonsmooth and variational analysis. small-time local controllability for nonlinear finite-dimensional time-continuous control systems in presence of state constraints. More precisely, given a nonlinear control system subject to state constraints and a closed set S, we provide sufficient conditions to steer to S every point of a suitable neighborhood of S along admissible trajectories of the system, respecting the constraints, and giving also an upper estimate of the minimum time needed for each point to reach the target. Then in framework of control affine nonlinear systems, sufficient conditions to reach a target for a suitable discretization of a given dynamics are provided. We make use of an approach based on Hamilton-Jacobi theory to prove the convergence of the solution of a fully discrete scheme to the (true) minimum time function, together with error estimates. We also design an approximate suboptimal discrete feedback and provide an error estimate for the time to reach the target through the discrete dynamics generated by this feedback. We next propose a new formulation of the minimum time problem in which we employ the signed minimum time function positive outside of the target, negative in its interior and zero on its boundary. Under some standard assumptions, we prove the so called Bridge Dynamic Programming Principle (BDPP) which is a relation between the value functions defined on the complement of the target and in its interior. Then owing to BDPP, we obtain the error estimates of a semi-Lagrangian discretization of the resulting Hamilton-Jacobi-Bellman equation. The remainder of this thesis is devoted to introducing an approach to compute the approximate minimum time function of control problems which is based on reachable set approximation. In particular, the theoretical justification of the proposed approach is restricted to a class of linear control systems and uses arithmetic operations for convex sets. The error estimate of the fully discrete reachable set is provided by employing Hausdorff distance. The detailed procedure solving the corresponding discrete problem is described. Under standard assumptions, by means of convex analysis and knowledge of regularity of the true minimum time function, we estimate the error of its approximation. Finally, we reconstruct discrete suboptimal trajectories which reach a set of supporting points from a given target for a class of linear control problems and also proving the convergence of discrete optimal controls by the use of nonsmooth and variational analysis
La tesi è dedicata a problemi di tempo minimo finito dimensionali, sia con vincoli di stato che senza, con particolare riguardo alla regolarità all’approssimazione numerica e ad asp etti collegati di sintesi. Si considera in primo luogo il problema della controllabilità locale per tempi piccoli con vincoli di stato: si forniscono condizioni sufficienti per portare ad un bersaglio in tempo finito una traiettoria del sistema dato, senza violare i vincoli, e si dà una stima del tempo necessario. Nell’ambito di problemi affini rispetto al controllo, si danno condizioni sufficienti per la controllabilità a rispetto ad una particolare discretizzazione della dinamica. Tale risultato è motivato da un approccio all’approssimazione del tempo minimo T basato sulla sua caratterizzazione mediante un’equazione di Hamilton-Jacobi. Il contributo di questa parte della tesi consiste in un risultato teorico che estende la teoria esistente al caso in cui T non sia Lipschitz (cioè sotto ipotesi deboli di controllabilità) e nella costruzione di un feedback approssimato con la relativa stima dell’errore. Si propone inoltre una nuova formulazione del problema del tempo minimo, nella quale si fa uso di un tempo negativo quando la traiettoria è penetrata all’interno del bersaglio, allo scopo di ridurre l’errore di approssimazione vicino alla frontiera. Si dimostra una nuova versione del principio della programmazione dinamica (il “Principio Ponte”), che stabilisce una relazione tra il tempo minimo all’interno e all’esterno del bersaglio. Si studia poi una discretizzazione della corrispondente equazione di Hamilton-Jacobi e si forniscono stime dell’errore. La parte finale della tesi è dedicata all’introduzione di un nuovo approccio per il calcolo approssimato di T basato sull’approssimazione degli insiemi raggiungibili mediante l’aritmetica degli insiemi convessi, valido per sistemi lineari. Si fornisce una stima dell’errore mediante la distanza di Hausdorff per gli insiemi raggiungibili e per il tempo minimo. Si costruiscono inoltre traiettorie subottimali discrete e si prova la convergenza dei corrispondenti controlli al controllo ottimo

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Fällman, Monika Carina. « Turbulence measurements in fiber suspension flows : experimental methods and results ». Stockholm : Skolan för teknikvetenskap, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11460.

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34

Fällman, Monika Carina. « Turbulence measurements in fiber suspension flows : experimental methods and results ». Licentiate thesis, KTH, Mechanics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11460.

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Turbulent mixing is present in many pulp and paper processes. It is a particularly important factor in the design and improvements of the paper machine headbox, influencing the final paper structure. During this project, experimental methods to quantify the effect of fibers on turbulent suspension flows have been developed, and then used for studying turbulent mixing in fiber suspensions. A technique that uses microprobes to measure passive scalar mixing of salt for the characterization of turbulent fluctuations in a fiber suspension flow has been developed: Conductivity micro-probes have been built and turbulence measurements have been performed in simple jet and wake flows, studying turbulent mixing between the two streams of pulp suspension, of which one has been doped with salt. A relatively new technique to measure fluid velocity non-intrusively in opaque fluids has also been tested. The technique makes use of ultrasonic pulses to obtain velocity information through the Doppler-shift of reflected pulses. The main efforts reported on in the thesis are focused on method design and development as well as method evaluation.

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35

Mattozzi, Alessandro. « Small Molecule Diffusion in Spherulitic Polyethylene : Experimental Results and Simulations ». Doctoral thesis, Stockholm : Chemical Science and Engineering, KTH, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4196.

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36

Mattozzi, Alessandro. « Small molecule diffusion in spherulitic polyethylene : experimental results and simulations / ». Stockholm, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-355.

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37

Rice, Michael, et Kip Temple. « Space-Time Coding for Aeronautical Telemetry : Part II - Experimental Results ». International Foundation for Telemetering, 2011. http://hdl.handle.net/10150/595778.

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ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada
Experiments involving side-by-side comparisons of traditional two-antenna transmissions and space-time coded (STC) transmissions involving two transmit antennas confirm theoretical predictions that space time coding is effective in removing signal dropouts caused by the "twoantenna problem." The experiments involved real transmitters on an airborne platform and a prototype demodulator operating at the Air Force Flight Test Center. The theory is confirmed both by the behaviors of the received signal powers from the two signaling approaches as well as the improved link availability based on the bit error rate performance.

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38

Cheraghi, Seyed Hossein 1957. « MULTIPLE CHOICE MODULAR DESIGN PROBLEM EXPERIMENTAL RESULTS AND SENSITIVITY ANALYSIS ». Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276429.

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39

Breger, Lisa. « Trading in exogenous networks : a theoretical application and experimental results ». OpenSIUC, 2016. https://opensiuc.lib.siu.edu/dissertations/1299.

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The Federal Communications Commission (FCC) allocates bands of radio frequency on the electromagnetic spectrum to agents call primary users (PUs), typically through standard auctions. However, with an increased demand for the use of radio spectrum, it is valuable to devise ways for unused channels to be sold in a secondary market to secondary users (SUs) who do not have licensing rights to access the spectrum. We first propose a model in which PUs can set prices and offer unused channels to SUs. We consider a small network of primary and secondary users in which the network is defined exogenously by their respective locations. In this framework, equilibrium prices depend on the structure of the network. We find that a SUs can potentially face two prices in equilibrium and that SUs with only one potential seller receive offers first but face high prices. We extend this model to consider cases of uncertainty between sellers to find a range of relative prices for which two prices arise in equilibrium. The implications of the results are twofold. First, with specially defined networks, PUs will extract all market surplus if given complete price-setting power. Secondly, uncertain competition in the market can benefit buyers since PUs may set prices more conservatively. While the first chapter focuses on the application toward spectrum sharing, it is worthwhile to note that the properties of this model can be extended to many applications. In the second and third chapters, we aim to test these price-setting predictions in an experimental study. The study was conducted using the software z-Tree (Zurich Toolbox for ii Readymade Economic Experiments) developed by Fischbacher (2007), and took place in a campus computer lab. Participants in the study made take-it-or-leave-it offers to potential buyers with whom they are linked in a repeated measures study. Across a number of sessions, we varied the network structure and price possibilities, as well as information on the network, to gain insight on how uncertainty of competition affected price offers. With this data, we tracked the convergence of price offers in each group and examined if and when equilibrium predictions were reached.

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MEDDA, TIZIANA. « Three Essays on the generalizability of experimental results in economics ». Doctoral thesis, Università degli Studi di Cagliari, 2016. http://hdl.handle.net/11584/266707.

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Although few economists today dismiss the use of the laboratory experiments, it would be a mistake to think that experimental methodology no longer represents a controversial issue in economics. One of the major criticisms is represented by the external validity of experimental data and concerns the transferability of results obtained in laboratory to the real world. The aim of this thesis is to tackle the issue of external validity focusing in particular on one aspect: the possible lack of representativeness of standard subjects pools usually used in economic research. The first experimental study compares the choices of undergraduates and subjects representative of population in different treatments and with different reward dimensions by exploiting the experimental design used by Pelligra and Stanca (2013) to investigate social preferences in a field experiment. Our results show that two samples follow a common behavioral pattern with the only exception of a significant difference in choices where self-interest may play a prominent role. In the second study we use a between-subjects design to compare the behavior of experienced and inexperienced subjects. We investigate whether the laboratory experience, built through repeated participation in experimental sessions, biases subjects’ behavior in a set of representative simple games used to study social preferences. Our main finding shows how subjects having a high level of experience in lab experiments do not behave in a significantly different way from novices.

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Ertunç, Özgür. « Experimental and numerical investigations of axisymmetric turbulence ». [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=983289212.

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42

Zakrisson, Björn. « Numerical and experimental studies of blast loading / ». Luleå : Luleå University of Technology, 2010. http://pure.ltu.se/ws/fbspretrieve/4485391.

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43

Topcu, Nagihan. « Numerical, Analytical And Experimental Analysis Of Indentation ». Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605942/index.pdf.

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Indentation is a practical and easy method, therefore, is a preferred method of material characterization. Main aim of this thesis study is to determine anisotropic properties of metals by indentation tests. The basic property of the indenter used in the finite element analyses and experiments is that it is specific to this process. Thesis includes studies on optimization of the indenter geometry, analyses of effects of friction coefficient, multiple indentations, tilting of the indenter and clamping of the specimen on force-displacements curves during indentation by finite element analyses. This study also includes finite element analyses of compression tests where these experiments have been necessary to prove anisotropic behavior of the specimen material. In addition to compression, tension tests are done to have a reference for indentation tests. On the other hand, the upper bound method which is an analytical solution is applied on the assumption of plane strain indentation.

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Isik, Nihat Sinan. « Experimental And Numerical Assessment Of Pressuremeter Testing ». Phd thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607065/index.pdf.

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The purposes of this study are to investigate the possible effects of variables like testing depth, length to diameter ratio of the probe, presence of disturbed annulus around the borehole etc. on the derived parameters from the pressuremeter test, and to develop possible alternative methods for the determination of undrained shear strength of cohesive soils, and cohesion and internal friction angle of intermediate geomaterials. For this purpose numerical simulations of pressuremeter test were performed. In the study, it is also aimed to investigate the effect of rock quality designation (RQD) or some other rock mass parameters such as geological strength index (GSI) and rock mass rating (RMR) and intact rock strength on the deformation modulus determined from the pressuremeter test. To accomplish this task, Dikmen greywackes, weathered andesites and mudrocks exposed around Ankara - Sincan region were selected for field and laboratory studies. Empirical relationships using GSI, RMR, RQD were developed for the estimation of deformation modulus of greywackes and mudrocks cropping out around Ankara. Numerical simulations revealed the presence of disturbed annulus around the borehole causes underestimation of deformation modulus and overestimation of undrained shear strength. Test depth has no effect on the deformation modulus and undrained shear strength
the effect of length to diameter ratio of the probe on the deformation modulus is minor where as it causes overestimations of undrained shear strength. Pore pressure dissipation in low permeability soils around the pressuremeter was studied using numerical simulations. These analyses suggest that for permeabilities lower that 10-10 m/sec there is no pore pressure dissipation around the pressuremeter probe. It was determined that the inverse analysis yielded successful results for the determination of shear strength parameters of intermediate geomaterials.

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Dibben, David. « Numerical and experimental modelling of microwave applicators ». Thesis, University of Cambridge, 1995. https://www.repository.cam.ac.uk/handle/1810/237037.

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This thesis presents a time domain finite element method for the solution of microwave heating problems. This is the first time that this particular technique has been applied to microwave heating. It is found that the standard frequency domain finite element method is unsuitable for analysing multimode applicators containing food-like materials due to a severe ill-conditioning of the matrix equations. The field distribution in multimode applicators loaded with low loss materials is found to be very sensitive to small frequency changes. Several solutions at different frequencies are therefore required to characterise the behaviour of the loaded applicator. The time domain finite element method is capable of producing multiple solutions at different frequencies when used with Gaussian pulse excitation; it is therefore ideally suited to the analysis of multimode applicators. A brief survey of the methods available for the solution of the linear equations is provided. The performance of these techniques with both the frequency domain and time domain finite element methods is then studied. Single mode applicators are also analysed and it is found that the frequency domain method is superior in these cases. Comparisons are given between the calculated results and experimental data for both single mode and multimode systems. The importance of experimental verification being stressed. The choice of element type is an important consideration for the finite element method. Three basic types of element are considered; nodal, Whitney edge elements and linear edge elements. Comparisons of the errors with these elements show that Whitney elements produce a consistently lower error when post-processing is used to smooth the solution. The coupled thermal-electromagnetic problem is investigated with many difficulties being identified for the application to multimode cavity problems.

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Pulicherla, Yashpal Surendhar Goud, et Ramkiran Kesana. « Experimental and Numerical Study of Orthotropic Materials ». Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-15710.

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In current enterprises, simulations are being utilized to lessen the cost of product advancement. Along this line, there is an awesome enthusiasm for enhancing precision and accuracy of simulations. For an accurate and reliable simulation, it is essential to use an accurate material model and provide it with accurate material information. In exhibit industries, orthotropic materials are being simulated utilizing isotropic material model, as orthotropic material model requires more material data which is not promptly accessible. This proposal intends to test and identify orthotropic materials and simulate them using orthotropic material model in ABAQUS. Materials utilized as a part of this proposal are Aluminium, LDPE, PET. Required material data was gotten by performing Uni-directional tensile tests, DIC, and an algorithm we developed in light of Inverses method. To get highly accurate material data from DIC, a few kinds of patterns were examined, and a superior pattern was resolved for camera configuration being utilized.

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Vaziri, Mohsen. « Screw plate testing : experimental and numerical investigations ». Thesis, University of Surrey, 1988. http://epubs.surrey.ac.uk/843439/.

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The estimation of the compressibility of normally and overconsolidated granular soils was the main aim of the research. A model screw plate instrument was designed and developed and various plate geometries and plate advancement mechanisms were studied with a view to assessing soil disturbance during installation. Screw plate loading tests were conducted by means of a plate 50 mm in diameter 3 mm thick and 5 mm pitch. All the tests were conducted in a calibration chamber under stress controlled conditions on normally and overconsolidated saturated Leighton Buzzard sand along Ko and isotropic stress paths. Stress path triaxial tests were performed on normally and overconsolidated sand specimens. The stress-strain responses observed from such tests were compared with the pressure-settlement curves obtained from screw plate tests. The CRISP Finite Element Program was utilised to model the embedded plate and the chamber. Stress distributions and induced settlements beneath the plate were studied. Finally the effect of plate rigidity on the distribution of stresses was investigated and the validity of dimensions of the calibration chamber for the purpose of screw plate testing was proven.

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Shimoi, Koji. « Numerical and experimental investigation of ice shedding ». Thesis, Wichita State University, 2010. http://hdl.handle.net/10057/3639.

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The shedding of ice accreted on aircraft surfaces poses a serious threat to flight safety as it can cause severe damage to downstream aircraft components such as aft-mounted engines. While there is strong need for ice shedding simulation tools to support aircraft icing analysis and certification, currently available ice shedding analysis methods may not predict ice fragment trajectory accurately due to the inability to simulate the random nature of ice shedding events and the lack of experimental aerodynamic data for ice fragments. In addition, most of the simulation tools have not been validated with experimental trajectory data. Both experimental and numerical investigations of shed ice trajectory were conducted as part of the continuing development of an ice trajectory simulation tool at Wichita State University. The research discussed in this thesis involved wind tunnel experiments conducted to obtain experimental aerodynamic coefficients for simulated ice fragments, numerical ice trajectory analyses, Monte Carlo simulations to evaluate the risk of ice fragment impact on critical aircraft components, and trajectory experiments performed to validate the ice trajectory simulation tool. Wind tunnel experiments were performed in the WSU 7-ft x 10-ft wind tunnel facility to obtain an aerodynamic database of force and moment coefficients for a 12-inch square flat plate with 0.4-inch thickness, a 10-inch diameter disk with 1-inch thickness and a 18-inch span glaze ice fragment with symmetric horns computed with the LEWICE ice accretion code. The experiments were conducted at airspeed of 160 mph with varying Euler angles (yaw, pitch and roll). The aerodynamic coefficients of the three fragments tested demonstrated considerable sensitivity to fragment shape and orientation. The experimental data were incorporated into the WSU trajectory analysis code developed. The ice shedding analyses were conducted with two simulated ice fragments for a business jet aircraft using the WSU trajectory code. The two simulated ice fragments include a disk and a glaze ice fragment with symmetric horns released from the aircraft nose and from the antenna on the top of the fuselage, respectively. Monte Carlo simulations were performed to compute probability maps of trajectory footprints at the engine inlet plane. The analysis demonstrated the effect of the shed location, initial fragment orientation and aircraft angle of attack on ice fragment trajectories. The results for Monte Carlo simulations performed with the disk fragment showed that the fragment would have less than a 0.15% chance of impacting the engine. For the glaze ice fragment, it was found that the probability of a collision between the fragment and the engine was as high as 24.2%, depending on the aircraft’s pitch and yaw angles. Next, an experimental methodology was developed to obtain the trajectories of simulated ice fragments released in a tunnel airstream for the validation of the ice fragment trajectory code. The tested fragments were a 6-inch square flat plate with 0.4-inch thickness, a rectangular flat plate measuring 12- inch long by 6-inch wide by 0.4-inch thick, a 12-inch span single horn glaze ice fragment and a 12-inch span double horn symmetric glaze ice fragment. Experiments were performed at airspeed of 160 mph in the WSU 7-ft x 10-ft wind tunnel facility. High-speed video cameras were employed to record the fragment’s trajectories at 500 to 1,000 frames per second. The coordinates of a fragment’s trajectories were determined from high speed images with the help of gridded vinyl sheets attached to one of the wind tunnel side-walls and to the ceiling. The fragment trajectories showed considerable sensitivity to the ice fragment shapes and their initial pitch angles at the moment of release. The flat plates with initial pitch angle of 0° experienced considerable rotation as they moved downstream, while the flat plate with initial pitch angle of 90° traveled downstream in a nearly straight path without rotation. Two cases of the single horn glaze ice fragment were sensitive to initial orientation and exhibited oscillatory rotations with respect to their spanwise axis. Two cases of the double horn symmetric glaze ice fragment resulted in similar trajectories, however experienced considerably different speed. Finally, the experimental trajectories were compared with analytical trajectories computed with the WSU trajectory code. Good agreement was demonstrated between the experimental and computed trajectories in most cases. However, the analytical results for the flat plate cases with significant rotations were more than 10% different compared to the experimental data due to the effect of the plate large rotation speed on the aerodynamic forces and moments acting on the plates.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering.

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Chen, Lihong. « Numerical and experimental modelling of brush seals ». Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268200.

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Rahmad, Rohani. « Numerical and experimental studies of metal machining ». Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445843.

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Thèses sur le sujet « Experimental and numerical results »

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