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Dissertations / Theses on the topic 'Geometrical configuration'
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1
Ullah, Muhammad Arshad [Verfasser]. "Forage production in Panicum grass-legumes intercropping by combining geometrical configuration, inoculation and fertilizer under rainfed conditions / Muhammad Arshad Ullah." Kassel : Kassel University Press, 2010. http://d-nb.info/1016846126/34.
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Oksuz, Nevin. "Quantum-chemical Study Of Geometrical And Electronic Structures Of Aromatic Five-membered Heterocyclic Oligomers In The Ground And Lowest Singlet Excited States." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605397/index.pdf.
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The nature of the ground state and the first (lowest) singlet excited state geometrical conformations and electronic transitions in the aromatic five-membered heterocyclic oligomers &ndasholigothiophenes (nT), oligofurans (nF), and oligopyrroles (nP)- containing up to six monomer units (total of 18 molecules) were explored using several computational methodologies. Geometry optimizations were carried out at Austin Model 1 (AM1), Restricted Hartree-Fock (RHF/6-31G*), and Density Functional Theory (DFT, B3LYP/6-31G*) levels for the ground-state conformations of these structurally well-defined heterocyclic oligomers. The Configuration Interaction Singles (CIS) method with the 6-31G* basis set was chosen in computation of the optimal geometry of the lowest singlet excited state. Lowest singlet excitation S1ß
S0 energies were calculated using the Zerner&rsquo
s Intermediate Neglect of Differential Overlap for Spectroscopy (ZINDO/S), CIS (CIS/6-31G*), and Time-Dependent DFT (TDDFT/6-31G* and TDDFT/6-31+G*) methods. In computation of the emission S1à
S0 energies, we have employed all methods above except ZINDO/S. In investigation of geometries of the ground and lowest singlet excited state, we compared the bond length alternation (BLA) parameters, Dri in the conjugated backbone of the oligomers. Saturation of the geometrical parameters at the center of oligomers was observed after a certain chain length. Among all methodologies used in computation of excitation (S1ß
S0) and emission (S1à
S0) energies, TDDFT results showed the best agreement with experimental data. Fits of computed and experimental excitation energies to an exponential function using the least squares method enabled us to predict Effective Conjugation Length (ECL) values. We obtained the ECLs of 17 (17), 16 (15), and 14 (13) monomer units for polythiophene (PTh), polyfuran (PFu), and polypyrrole (PPr), which have very good agreement with the results obtained from the fits of experimental data (the values in parentheses).
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Béreiziat, Daniel. "Structure locale de l'écoulement de fluides newtoniens et non newtoniens en canaux ondules." Vandoeuvre-les-Nancy, INPL, 1993. http://www.theses.fr/1993INPL036N.
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L'objectif de ce travail expérimental consiste en la reconnaissance approfondie de la structure locale de l'écoulement le long de parois ondulées de grande amplitude, représentatives des échangeurs de chaleur adaptés au traitement des produits alimentaires. Les expériences sont menées à partir de deux techniques de mesure: la vélocimétrie à laser et la méthode polarographique. La gamme expérimentale d'écoulement va d'un nombre de Reynolds égal à 7 jusqu'à 17000. Les paramètres géométriques des plaques ondulées sont: le pas de l'ondulation vaut 11 mm ou 65 mm, le diamètre hydraulique varie de 7 mm à 33 mm et l'angle entre la direction principale de l'écoulement et l'ondulation est de 90 (géométrie 2d) ou de 60 (géométrie 3d). L'ensemble des mesures en canal bidimensionnel 2d montre la présence d'un tourbillon de recirculation qui nait dans la zone de sillage pour un nombre de Reynolds généralise reg de 30 et disparait pour reg=530. La fin du régime laminaire ou le gradient pariétal de vitesse varie linéairement avec reg est détectée pour un nombre de Reynolds généralisé de 2000 qui constitue le seuil d'apparition d'une turbulence pleinement développée. Nous avons montre également l'influence du caractère rheofluidifiant des solutions sur la forme, la taille et le développement du tourbillon de recirculation en régime laminaire
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Lallemand, Christine. "Optimisation de forme des structures axisymetriques." Lyon, INSA, 1985. http://www.theses.fr/1985ISAL0058.
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L'étude porte sur la détermination des formes optimales de structures axisymétriques soumises à des charg~nts dissymétriques, (développements en séries de Fourier). L'objectif est de rendre la pius uniforme possible la contrainte tangentielle. Le programme utilise une méthode dite de Lagrangien étendu pour l'optimisation mathématique d'une fonction soumise à des limitations. Plusieurs améliorations ont été apportées au calcul des gradients. Le programme présente les résultats obtenus sur un exemple emprunté à l'aéronautique, (boîte de vitesse d'hélicoptères).
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Mignon, Hervé. "Anémométrie phase Doppler et particules non sphériques : cas des cylindres et des ellipsoïdes." Rouen, 1997. http://www.theses.fr/1997ROUES004.
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L'anémométrie phase Doppler est une technique de mesure optique utilisée pour évaluer la taille et la vitesse de particules sphériques et homogènes en mouvement. Ce mémoire est dédié à l'extension de cette technique aux particules non sphériques. En raison de leurs importances tant fondamentales qu'appliquées, ce manuscrit se focalise sur les cylindres infiniment longs et les particules ellipsoïdes. La géométrie dite plane est employée pour déterminer la taille d'une particule cylindrique arbitrairement orientée. La réponse des géométries dites planes et standard est étudiée pour des particules ellipsoïdes, déformées ou en cours de déformation. L'influence d'un écart à la sphéricité sur une mesure phase Doppler est quantifiée. Ces configurations sont évaluées numériquement par l'optique géométrique puis validées expérimentalement.
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Khalid, Jawed Mohammad. "Geometrically nonlinear configurations in rod-like structures." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/106703.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 203-216).
Rod-like structures are ubiquitous in both nature (e.g. bacterial flagella) and engineering (ropes, cables, pipelines, and Carbon nanotubes), from nanometer to kilometer scale, and often undergo geometrically nonlinear deformation. Due to the slender geometry of the structures, the material strain usually remains in linear elastic limit even though the deformed geometry deviates significantly from the original geometry. The geometric nonlinearities that result from the deformation process pose enormous challenges to traditional analytical and numerical tools. Moreover, it is often unfeasible to perform experiments at the original length-scale of these systems. We overcome these challenges by combining model experiments with cutting-edge computational tools ported from computer graphics, and theoretical analysis towards developing predictive physical understanding of these systems. The prominence of geometry in this class of systems enables the scaling (up or down) of the problem to the desktop scale, which allows for systematic experimental exploration of parameter space. In parallel, we conduct numerical simulations using the Discrete Elastic Rods (DER) method, which was originally developed for the animation industry for special effects of the visually dramatic dynamics of hair, fur, and other rod-like structures. We port DER into engineering as a predictive computational tool and test ride it against our own model experiments. A collection of problems from three a priori unrelated scenarios, at disparate length-scales, are explored. First, as a model for laying of submarine cables onto the seabed (kilometer scale), we consider deployment of elastic rods onto a moving substrate (conveyor belt) and quantify the resulting nonlinear coiling patterns. The DER method is employed to identify the phase boundaries between different patterns and characterize the morphology. Our results are interpreted using a reduced geometric model for the evolution of the position of the contact point with the belt and the curvature of the rod in its neighborhood. This geometric model reproduces all of the coiling patterns, which allows us to establish a universal link between our elastic problem and the analogous patterns obtained when depositing a viscous thread onto a moving surface; a well-known system referred to as the fluid mechanical sewing machine. Secondly, we consider a macroscopic analog model for the locomotion of uni-flagellar bacteria (micron scale) in a viscous fluid. Our precision experiments are compared against numerical simulations that employ the Lighthill's slender body theory (a non-local description of fluid force) and DER, with excellent quantitative agreement without any fitting parameter. A novel mechanical instability is uncovered, whereby the filament buckles above a critical rotation frequency. We then augment our experiments and simulations to include the effect of a no-slip rigid boundary on the locomotion of uni-flagellar bacteria. We find that the propulsive force is strongly affected by the presence of a nearby boundary. Thirdly, we perform precision desktop experiments with overhand knots (centimeter scale) with increasing values for the crossing number (our measure of topology) and characterize their mechanical response through tension-displacement tests. The tensile force required to tighten the knot is governed by an intricate balance between topology, bending, and friction. A reduced theory is developed, which predictively rationalizes the process.
by Mohammad Khalid Jawed.
Ph. D.
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Cho, Sung Nae. "Casimir Force in Non-Planar Geometric Configurations." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11156.
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The Casimir force for charge-neutral, perfect conductors of non-planar geometric configurations have been investigated. The configurations were: (1) the plate-hemisphere, (2) the hemisphere-hemisphere and (3) the spherical shell. The resulting Casimir forces for these physical arrangements have been found to be attractive. The repulsive Casimir force found by Boyer for a spherical shell is a special case requiring stringent material property of the sphere, as well as the specific boundary conditions for the wave modes inside and outside of the sphere. The necessary criteria in detecting Boyer's repulsive Casimir force for a sphere are discussed at the end of this thesis.Ph. D.
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Cai, Li. "Dexel-based geometric reasoning and visualization for die configuration /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486402288260244.
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Rain, Pascal. "Étude des phénomènes prédisruptifs et disruptifs à grande distance dans l'huile minérale de transformateur sous tension alternative." Grenoble INPG, 1992. http://www.theses.fr/1992INPG0076.
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Ce travail se rapporte a l'étude des phénomènes predisruptifs et disruptifs des grands intervalles d'huile minérale (jusqu'a 25 cm) soumis a de hautes tensions alternatives 50 Hz (jusqu'a 250 kvcr). L'objectif est d'obtenir une compréhension plus approfondie des mécanismes de génération et de propagation des streamers, canaux conducteurs lumineux plus ou moins ramifies qui précèdent le claquage des liquides diélectriques, et d'identifier les facteurs d'atténuation de la tenue des grands volumes d'huile soumis a des hautes tensions. Le comportement des streamers a été caractérise en géométrie divergente grâce a un dispositif de visualisation approprie. L'influence de la configuration des électrodes a été soulignée. Les résultats ont permis de proposer un schéma général du claquage a grande distance. Parmi les causes les plus plausibles de rupture d'isolation en champ quasi-uniforme, l'action de particules conductrices peu nombreuses mais de grande taille a été retenue. Le comportement d'une particule métallique millimétrique unique a été étudie et son influence sur la tenue diélectrique a été caractérisée
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Herterich, Emmi. "Sequential Holonomic Quantum Gates : Open Path Holonomy in Λ-configuration." Thesis, Uppsala universitet, Materialteori, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-296137.
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In the Λ-system, non-adiabatic holonomic quantum phases are used to construct holonomic quantum gates. An interesting approach would be to implement open path holonomies in the Λ-system. By dividing the loop into two curve segments with a unitary transformation between them, universality can be reached. In doing so the exibility of the scheme has been increased by the fact that one single full pulse is now enough for universality, and we have achieved a clearer proof of the geometric property of the Λ system.I ett Λ-system så används icke-adiabatiska holonoma kvantfaser för att bygga holonoma kvantgrindar. I detta arbete undersöker vi om holonomier för öppna kurvor kan implementeras i Λsystemet. Genom att dela upp en loop i Λ-systemet i två sekvenser med en unitär transformation emellan så kan vi konstruera en universell holonom kvantgrind. Med detta så har vi ökat exibiliteten för systemet genom att vi nu bara behöver ta en loop för att nå universalitet, och vi har även erhållit en klarare bild över den geometriska egenskapen hos Λ-systemet.
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Chang, Teng-Wen. "Geometric typed feature structures : toward design space exploration /." Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phc4569.pdf.
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Zein, Waël. "Etude d'un capteur absorbant l'energie solaire par le fluide caloporteur : application au chauffage des piscines de plein-air." Poitiers, 1986. http://www.theses.fr/1986POIT2289.
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Modelisation des transferts radiatifs pour les differents composants du capteur. Resolution numerique des equations permettant d'obtenir les lois d'evolution des performances du capteur en fonction de ces caracteristiques geometriques, des conditions radiatives et meteorologiques d'un site. Verification experimentale a l'aide d'un simulateur de rayonnement. Application envisagee, au chauffage d'une piscine en plein-air. Optimisation des conditions de fonctionnement et analyse economique du systeme de chauffage
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Chakraborty, Debanond. "Configuration interaction (singles) study of geometric and electronic properties of conducting polymers." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ54869.pdf.
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Lee, Kyung Eun. "The effect of geometrical configurations on physiological pulsatile flow in ideal and realistic vessel geometries." Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485736.
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Newman, James Charles III. "Integrated Multidisciplinary Design Optimization Using Discrete Sensitivity Analysis for Geometrically Complex Aeroelastic Configurations." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30711.
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The first two steps in the development of an integrated multidisciplinary design optimization procedure capable of analyzing the nonlinear fluid flow about geometrically complex aeroelastic configurations have been accomplished in the present work. For the first step, a three-dimenstional unstructured grid approach to earodynamic shape sensitivity analysis and design optimization has been developed. The advantage of unstructured grids, when compared with a structured-grid approach, is their inherent ability to discretize irregularly shaped domains with greater efficiency and less effort. Hence, this approach is ideally suited fro geometrically complex configurations of practical interest. In this work the time-dependent, nonlinear Euler equations are solved using an upwind, cell-centered, finite-volume scheme. The descrete, linearized systems which result from this scheme are solved iteratively by a preconditioned conjugate-gradient-like algorithm known as GMRES for the two-dimensional cases and a Gauss-Seidel algorithm for the three-dimensional; at steady-state, similar procedures are used to solve the accompanying linear aerodynamic sensitivitiy equations in incremental iterative form. As shown, this particular form of the sensitivity equation makes large-scale gradient-based aerodynamic optimization possible bytaking advantage of memory efficient methods to construct exact Jacobian matrix-vector products. Various surface parameterization techniques have been employed in the current study to control the shape of the design surface. Once this surface has been deformed, the interior volume of the unstructured grid is adapted by considering the mesh as a system of interconnected tension springs. Grid sensitivities are obtained by differentiating the surface parameterization and the grid adaptiation algorithms with ADIFOR, an advanced automatic-differentiation software tool. To demonstrate the ability of this procedure to analyze and design complex configurations of practical interest, the sensitivity analysis and shape optimization has been performaed for several two- and three-dimensional cases. In two-dimensions, an initially symmetric NACA-0012 airfoil and a high-lift multielement airfoil were examined. For the three-dimensional configurations, an initially rectangular wing with uniform NACA-0012 cross-scetions was optimized; in additions, a complete Boeing 747-200 aircraft was studied. Furthermore, the current study also examines the effect of inconsistency in the order of spatial accuracy between the nonlinear fluid and linear shape sensitivity equations.
The second step was to develop a computationally efficient, high-fidelity, integrated static aeroelastic analysis procedure. To accomplish this, a structural analysis code was coupled with the aforementioned unstructured grid aerodynamic analysis solver. The use of an unstructured grid scheme for the aerodynamic analysis enhances the interactions compatibility with the wing structure. The structural analysis utilizes finite elements to model the wing so that accurate structural deflections may be obtained. In the current work, paramenters have been introduced to control the interaction of the computational fluid dynamics and structural analyses; these control parameters permit extremely efficient static aeroelastic computations. To demonstrate and evaluate this procedure, static aeroelastic analysis results for a flexible wing in low subsonic, high subsonic (subcritical), transonic (supercritical), and supersonic flow conditions are presented.
Ph. D.
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Rice, Michael, Adam Davis, and Christian Bettwieser. "A WIDEBAND CHANNEL MODEL FOR AERONAUTICAL TELEMETRY — PART 1: GEOMETRIC CONSIDERATIONS AND EXPERIMENTAL CONFIGURATION." International Foundation for Telemetering, 2002. http://hdl.handle.net/10150/606288.
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International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, CaliforniaThis paper is the first of two papers that present a multipath channel model for wideband aeronautical telemetry. Channel sounding data, collected at Edwards AFB, California at both L-Band and lower S-Band, were used to generate channel model. In Part 1, analytic and geometric considerations are discussed and the frequency domain modeling technique is introduced. In Part 2, the experimental results are summarized and a channel model composed of three propagation paths is proposed.
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Kotera, Mitsuharu. "Synthèse de composés azaspiranniques via régression d'énamines hétérocycliques fonctionnelles : synthèse formelle de la ( + ou - )-perhydrohistrionicotoxine." Rouen, 1987. http://www.theses.fr/1987ROUES018.
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Stéréochimie de la contraction de cycle d'énaminoesters, énaminoaldéhydes (et -acétals) hétérocycliques (7 chaînons en 6 chaînons et 6 chaînons en 5 chaînons): préparation de pipéridines et pyrrolidines difonctionnalisées précurseurs d'aza-1 spiro (5. 5) undécanes et d'aza-1 spiro (4. 5) décanes. Configurations
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Yadav, Mohan Singh Kim Seungjin. "Geometric effects of flow restrictions and configurations on interfacial structures in two-phase flow." [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4069/index.html.
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Amarouche, Mohand. "Modelisation des agregats de gaz rares et dynamique d'ar : :(3)**(+)." Toulouse 3, 1988. http://www.theses.fr/1988TOU30135.
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Calcul de la structure d'equilibre et de l'energie d'agregats ioniques positifs de xe et ar a l'aide d'un hamiltonien de type excitonique, extrait des courbes de potentiel des diatomiques correspondants, en incluant le couplage spin-orbite et les interactions a 3 corps entre dipoles induits instantanement. Emploi de ce modele pour calculer les barrieres de potentiel entre divers isomeres, les diverses possibilites de fragmentation apres photoionisation verticale et les echanges de masse lors de collisions entre agregats; observation d'une stabilite remarquable des agregats a 13 et 19 atomes, formes de couronnes pleines autour de coeurs ionises a 3 ou 4 atomes. Couplage du modele excitonique a la methode de dynamique "hemiquantique" pour etudier la photodissociation de ar::(3)**(+), dont on calcule la section efficace a partir du moment de transition de l'espece diatomique obtenu par des calculs ab initio
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NARAYANAN, VIJAY. "STRUCTURAL ANALYSIS OF REINFORCED SHELL WING MODEL FOR JOINED-WING CONFIGURATION." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1116214221.
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Higashiyama, Kazumi. "The semi-absolute anabelian geometry of geometrically pro-p arithmetic fundamental groups of associated low-dimensional configuration spaces." Kyoto University, 2019. http://hdl.handle.net/2433/242582.
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Mochel, Loïc. "Etude des effets technologiques par des méthodes numériques innovantes sur des configurations de lanceur." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066059/document.
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Aujourd’hui, l’accès à l’espace constitue un enjeu scientifique, technologique et politique d’importance. Il est primordial de pouvoir garantir le succès de la mise sur orbite des satellites pour un coût de transport minimal. Les lanceurs tels qu’Ariane 5 sont soumis à des fluctuations de pression pouvant induire des efforts instationnaires repris par les vérins du moteur Vulcain. Ces efforts s’exercent notamment dans la zone décollée du culot du lanceur normalement à l’axe de la poussée et sont qualifiés de charges latérales. Du point de vue de la simulation numérique, l’étape de discrétisation des éléments technologiques du lanceur rend la génération de maillages structurés particulièrement complexe. Cette constatation conduit à la présente étude. Dans le but d’évaluer l’influence des effets technologiques sur la prévision des charges latérales pour des configurations réalistes de lanceur, la thématique des frontières immergées est étudiée. L’objectif est de développer une stratégie numérique permettant d’accroître le niveau de complexité de la géométrie considérée tout en conservant la précision des résultats des études antérieures sur des configurations simplifiées. Cette stratégie s’inscrit dans le cadre de simulations numériques ZDES d’écoulements massivement décollés d’arrière-corps, à haut nombre de Reynolds et en régime compressible. Les capacités de la méthodologie développée sont évaluées sur des cas tests numériques canoniques avant d’être éprouvées sur des configurations simplifiées de lanceur. Enfin, l’effet de cette stratégie sur la prévision des charges latérales est étudiéNowadays, access to space has become a great issue in scientific, technological and political framework. It is essential to ensure the success of the placing of orbiting satellites with a minimal flight cost. Launchers, as the Ariane 5 space launcher, are subject to pressure fluctuations which can lead to unsteady loads on the actuators of the Vulcain engine. These loads occur especially in the separated zone of the launcher base flow and act normally to the thrust axis. They are referred to as side loads. From the numerical simulation perspective, the launcher technological elements discretization process makes the generation of structured mesh particularly difficult. The present study lies within such a framework. In order to assess the influence of the technological effects on the side loads prediction for realistic launcher configurations, immersed boundaries are studied. The aim is to develop a numerical strategy able to increase the level of geometrical complexity of the geometry at stake while maintaining the accuracy of the results of previous studies on simplified configurations. This strategy fits into numerical simulations of ZDES type of separating/reattaching flows at high Reynolds number and compressible regime. The abilities of the methodology are first assessed on canonical numerical test cases. Then, the strategy is applied on simplified launcher configurations. Finally, the effect of this strategy on the side loads prediction is assessed
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Ambrozková, Anna. "Geometrické struktury a objekty z hlediska aplikací v mechanice." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417093.
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This Master's thesis relates to continuum mechanics and its connection with selected directions of modern differential geometry, which deal with geometric structures and objects. These are mainly tensors, bundles, varieties and jets. The first part is devoted to the mechanics of the continuum itself and its description in several areas, others deal with mathematical concepts and their possible application in mechanics.
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Zhou, Dong Huang Wei-Ping. "Advanced finite-difference time-domain techniques for simulation of optical devices with complex material properties and geometric configurations /." *McMaster only, 2005.
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Brachmi, Rhizlane. "Congestion Mitigation Strategy:Modeling the Effect of Different Geometric Configurations of a Two-Lane On-Ramp on Capacity Using VISSIM." Cleveland State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=csu1560189783503486.
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Hu, Hao. "Detection and treatment of inconsistent or locally over-constrained configurations during the manipulation of 3D geometric models made of free-form surfaces." Thesis, Paris, ENSAM, 2018. http://www.theses.fr/2018ENAM0002/document.
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Trois modules seront développés: Le module de détection a produit une analyse des problématiques figurations con, à savoir un ensemble de domaines où soit quelques nouveaux DDL ou des changements locaux dans les contraintes sont obligatoires. Le module de traitement permettra à la défi nition des mécanismes pour aider la décision sur modi cations. Le module de prédiction dire le degré de déformation en pré-analyser les caractéristiques des configurations de NURBSThree modules will be developed: The detection module has produced an analysis of problematic con figurations, i.e. a set of areas where either some new DOFs or some local changes in the constraints are mandatory. The treatment module will enable the defi nition of mechanisms to help the decision on modi cations. The prediction module will tell the degree of deformation by pre-analyzing the features of NURBS configurations
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Olakoyejo, O. T. (Olabode Thomas). "Geometric optimisation of conjugate heat transfer in cooling channels with different cross-sectional shapes." Thesis, University of Pretoria, 2012. http://hdl.handle.net/2263/25484.
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In modern heat transfer, shape and geometric optimisation are new considerations in the evaluation of thermal performance. In this research, we employed constructal theory and design to present three-dimensional theoretical and numerical solutions of conjugate forced convection heat transfer in heat generating devices with cooling channels of different cross-sectional shapes. In recent times, geometric configurations of cooling channel have been found to play an important role in thermal performance. Therefore, an efficient ways of optimally designing these cooling channels shapes is required. Experimentation has been extensively used in the past to understand the behaviour of heat removals from devices. In this research, the shapes of the cooling channels and the configurations of heat-generating devices were analytically and numerically studied to minimise thermal resistance and thus illustrate cooling performance under various design conditions. The cooling channels of five different cross-sectional shapes were studied: Circular, square, rectangular, isosceles right triangular and equilateral triangular. They were uniformly packed and arranged to form larger constructs. The theoretical analysis is presented and developed using the intersection of asymptotes method. This proves the existence of an optimal geometry of parallel channels of different cross-sectional shapes that penetrate and cool a volume with uniformly distributed internal heat generation and heat flux, thus minimising the global thermal resistance. A three-dimensional finite volume-based numerical model was used to analyse the heat transfer characteristics of the cross-sectional shapes of various cooling channels. The numerical computational fluid dynamics (CFD) package recently provided a more cost-effective and less time-consuming means of achieving the same objective. However, in order to achieve optimal design solutions using CFD, the thermal designers have to be well experienced and carry out a number of trial-and-error simulations. Unfortunately, this can not always guarantee an accurate optimal design solution. In this thesis a mathematical optimisation algorithm (a leapfrog optimisation program and DYNAMIC-Q algorithm) coupled with numerical CFD was employed and incorporated into the finite volume solver, –FLUENT, and grid (geometry and mesh) generation package, – GAMBIT to search and identify the optimal design variables at which the system would perform optimally for greater efficiency and better accuracy. The algorithm was also specifically designed to handle constraint problems where the objective and constraint functions were expensive to evaluate. The automated process was applied to different design cases of cooling channels shapes. These cooling channels were embedded in a highly conductive solid and the peak temperature was minimised. The trend and performance of all the cooling channel shapes cases studied were compared analytically and numerically. It was concluded that an optimal design can be achieved with a combination of CFD and mathematical optimisation. Furthermore, a geometric optimisation of cooling channels in the forced convection of a vascularised material (with a localised self-cooling property subjected to a heat flux) was also considered. A square configuration was studied with different porosities. Analytical and numerical solutions were provided. This gradient-based optimisation algorithm coupled with CFD was used to determine numerically the optimal geometry that gave the lowest thermal resistance. This optimiser adequately handled the numerical objective function obtained from numerical simulations of the fluid flow and heat transfer. The numerical results obtained were in good agreement with results obtained in the approximate solutions based on scale analyses at optimal geometry dimensions. The approximate dimensionless global thermal resistance predicted the trend obtained in the numerical results. This shows that there were unique optimal design variables (geometries) for a given applied dimensionless pressure number for fixed porosity. The results also showed that the material property had a significant influence on the performance of the cooling channel. Therefore, when designing the cooling structure of vascularised material, the internal and external geometries of the structure, material properties and pump power requirements would be very important parameters to be considered in achieving efficient and optimal designs for the best performance. Finally, this research investigated a three-dimensional geometric optimisation of conjugate cooling channels in forced convection with an internal heat generation within the solid for an array of cooling channels. Three different flow orientations based on constructal theory were studied numerically- firstly, an array of channels with parallel flow; secondly, an array of channels in which flow of every second row was in a counter direction and finally, an array of channels in which the flow direction in every channel was opposite to that of previous channel. The geometric configurations and flow orientations were optimised in such a way that the peak temperature was minimised subject to the constraint of fixed global volume of solid material. The optimisation algorithm coupled with CFD was also used to determine numerically the optimal geometry that gave the lowest thermal resistance. The use of the optimisation algorithm coupled with the computational fluid dynamics package; render the numerical results more robust with respect to the selection of optimal structure geometries, internal configurations of the flow channels and dimensionless pressure difference.Thesis (PhD(Eng))--University of Pretoria, 2012.
Mechanical and Aeronautical Engineering
unrestricted
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Gasti, Wahida. "Etude et realisation d'un processeur rapide de transformations geometriques d'images numeriques." Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13131.
Full textAbstract:
Les transformations geometriques d'images sont essentiellement utilisees pour: corriger les erreurs de parallaxe dues aux conditions de prise de vues, comparer des images provenant de capteurs differents, superposer des images reelles et des images conceptuelles, realiser des effets speciaux
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Arrouk, Khaled. "Techniques de conception assistée par ordinateur (CAO) pour la caractérisation de l'espace de travail de robots manipulateurs parallèles." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2012. http://tel.archives-ouvertes.fr/tel-00766814.
Full textAbstract:
Les environnements CAO fournissent des outils puissants pour la programmation graphique et la manipulation d'entités géométriques complexes. Dans cette thèse, nous proposons d'exploiter ce potentiel dans le domaine de la conception de robots parallèles. Ces robots sont considérés comme une alternative intéressante vis-à-vis de leurs homologues sériels dans différentes applications comme le " pick and place " et l'usinage. Cependant, leur utilisation industrielle est encore restreinte en raison d'un espace de travail limité, de modèles géométriques difficiles à résoudre et l'existence de configurations singulières délimitant leur domaine d'exploitation. L'analyse et la caractérisation de l'espace de travail jouent alors un rôle fondamental dans la phase de conception de robots manipulateurs parallèles. Dans ce travail de thèse, nous proposons des approches géométriques originales donnant lieu à un ensemble de méthodes et techniques basées CAO pour l'analyse et la caractérisation de l'espace de travail de robots parallèles plans et spatiaux. L'espace de travail est généré comme un solide dans l'environnement CAO à partir d'un paramétrage géométrique, d'esquisses et d'opérations élémentaires telles que le balayage hélicoïdal et l'intersection. Nous avons montré que ces méthodes constituent des outils pertinents et efficaces d'aide à la conception des mécanismes parallèles. Ils permettent également la résolution du problème géométrique direct et la génération de trajectoires libres de singularités. Plusieurs types de manipulateurs ont été considérés dans ce travail pour mettre en avant et illustrer les techniques CAO / Géométriques proposées : robots parallèles plans à 3 degrés de mobilité de type 3-RPR, 3-RRR, 3-PPR et 3-PRR, robots parallèles spatiaux à 6 degrés de mobilité de type ou 3-CRS ou 3-PRRS.
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Aristidou, Andreas. "Tracking and modelling motion for biomechanical analysis." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/237554.
Full textAbstract:
This thesis focuses on the problem of determining appropriate skeletal configurations for which a virtual animated character moves to desired positions as smoothly, rapidly, and as accurately as possible. During the last decades, several methods and techniques, sophisticated or heuristic, have been presented to produce smooth and natural solutions to the Inverse Kinematics (IK) problem. However, many of the currently available methods suffer from high computational cost and production of unrealistic poses. In this study, a novel heuristic method, called Forward And Backward Reaching Inverse Kinematics (FABRIK), is proposed, which returnsvisually natural poses in real-time, equally comparable with highly sophisticated approaches. It is capable of supporting constraints for most of the known joint types and it can be extended to solve problems with multiple end effectors, multiple targets and closed loops. FABRIK wascompared against the most popular IK approaches and evaluated in terms of its robustness and performance limitations. This thesis also includes a robust methodology for marker prediction under multiple marker occlusion for extended time periods, in order to drive real-time centre of rotation (CoR) estimations. Inferred information from neighbouring markers has been utilised, assuming that the inter-marker distances remain constant over time. This is the firsttime where the useful information about the missing markers positions which are partially visible to a single camera is deployed. Experiments demonstrate that the proposed methodology can effectively track the occluded markers with high accuracy, even if the occlusion persists for extended periods of time, recovering in real-time good estimates of the true joint positions. In addition, the predicted positions of the joints were further improved by employing FABRIK to relocate their positions and ensure a fixed bone length over time. Our methodology is tested against some of the most popular methods for marker prediction and the results confirm that our approach outperforms these methods in estimating both marker and CoR positions. Finally, an efficient model for real-time hand tracking and reconstruction that requires a minimumnumber of available markers, one on each finger, is presented. The proposed hand modelis highly constrained with joint rotational and orientational constraints, restricting the fingers and palm movements to an appropriate feasible set. FABRIK is then incorporated to estimate the remaining joint positions and to fit them to the hand model. Physiological constraints, such as inertia, abduction, flexion etc, are also incorporated to correct the final hand posture. A mesh deformation algorithm is then applied to visualise the movements of the underlying hand skeleton for comparison with the true hand poses. The mathematical framework used for describing and implementing the techniques discussed within this thesis is Conformal GeometricAlgebra (CGA).
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BELLOSTA, DECHAVANNE VERONIQUE. "Contribution a l'etude de la reactivite de derives glucidiques vis-a-vis d'organometalliques : nouvelles syntheses stereospecifiques de c-glycosides." Paris 6, 1987. http://www.theses.fr/1987PA066256.
Full textAbstract:
Deux nouvelles methodes de syntheses stereospecifiques de desoxy-2 c-glucosides possedant une fonction ester d'enol sont presentees : - l'addition conjuguee d'organocuprates cyanes sur des hexeno-1 pyrannuloses-3 peracetyles (l'anhydride acetique piegeant l'enolate intermediaire) permet d'obtenir des aryl-alpha -d-c-glycosides. Cette methode est detendue avec succes en serie furannose; - l'arylation de glycals catalysee par des sels de palladium fournit les composes voulus en une seule etape a partir de derives glucidiques commerciaux. L'etude de la configuration des c-glycosides obtenus est effectuee et de nombreuses donnees structurales sont exposees
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Maríngolo, Fernanda Palhares. "Grupo de tranças e espaços de configurações." Universidade Federal de São Carlos, 2007. https://repositorio.ufscar.br/handle/ufscar/5847.
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Previous issue date: 2007-06-27Universidade Federal de Sao Carlos
In this work, we study the Artin braid group, B(n), and the confguration spaces (ordered and unordered) of a path connected manifold of dimension ¸ 2. The fundamental group of confguration space (unordered) of IR2 is identifed with the Artin braid group. This identifcation is used to conclude that the confguration space of IR2 is an Eilenberg-MacLane space of type K(B(n), 1). Therefore, it can be proved that the braid group B(n) contains no nontrivial element of the finite order. We use this fact to prove a generalization of a 2−dimensional version of the Borsuk-Ulam theorem presented by Connett [3].
Neste trabalho, apresentamos o grupo de tranças de Artin, B(n), e os espaços de configurações (ordenado e não ordenado) de uma variedade conexa por caminhos de dimensão ¸ 2, a fim de identificar o grupo fundamental do espaço de configurações (não ordenado) de IR2 com o grupo de tranças de Artin. Usamos este fato para concluir que o espaço de configurações de IR2 é um espaço de Eilenberg-MacLane do tipo K(B(n), 1). Deste modo pode ser provado que o grupo de tranças B(n) não possui elementos não triviais de ordem finita, e usamos este fato na demonstração de uma generalização da versão bi-dimensional do teorema de Borsuk-Ulam apresentado por Connett [3].
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Escobar, Alvarez Hector Domingo. "Geometrical configuration comparison of redundant inertial measurement units." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-12-2623.
Full textAbstract:
Inertial measurement units (IMUs) are used in a wide range of applications to estimate position, velocity, and attitude of vehicles. The high cost of tactical grade IMUs makes the low-cost microelectromechanical systems (MEMS) based IMUs appealing. These types of IMUs are less accurate, so to counteract this effect, multiple and different configurations should be used. The work presented here provides efficient and low cost solutions using different configurations of redundant (multiple) MEMS-IMU swarms, which increase the level of accuracy to potentially the order of that of a tactical IMU. Several configurations are presented and compared through different methods.text
34
HE, YAO-DONG, and 何耀東. "The influence of plane geometrical configuration of structure on the R-curve." Thesis, 1986. http://ndltd.ncl.edu.tw/handle/32286887828105145669.
Full text
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(8770007), Andres M. Bejarano Posada. "Generation of Topological Interlocking Configurations from a Geometric Approach." Thesis, 2020.
Find full textAbstract:
A Topological Interlocking Configuration (TIC) is an assembly where the shape and alignment of the blocks define the kinematic constraints. Conventional TICs are single-layered structures made of convex blocks. The interface between the blocks in an assembly is face-to-face contact. The traditional convention disregards the use of joinery, adhesive, or other mechanisms that keep two pieces next to each other. However, TICs require a support structure that prevents the lateral strain of the blocks.The generation process of a TIC starts with a surface tessellation that describes a geometric domain. Each tile in the tessellation represents a traversal section of a block. For regular tessellations and uniform generation parameters, such sections lie in the middle of their respective blocks. Additionally, such conditions guarantee the blocks align adequately with each other. If one of such conditions does not hold, then the resultant blocks may not be aligned. Furthermore, there could be overlapping between the blocks, which makes a TIC invalid.
Traditionally, the generation parameters are angle values set at the edges of the tiles. The angles must match between tiles such that each block in the assembly has a geometry that imposes kinematic constraints to its neighboring blocks. Using the same angle values on regular and semi-regular tessellation produces feasible blocks. That is not the case for non-regular tessellations, curvilinear surfaces, and free-form 3D meshes. In such cases, the generation method must find specific angle values to design the blocks and reduce overlapping.
In this thesis, we propose a TIC generation framework focused on the generation of valid interlocking assemblies based on multiple types of surface tessellations. We start with the Height-Bisection method, a TIC generation approach that uses the distances from a tile to its respective evolution sections as the generation parameters. The method considers the bisector vectors between two tiles to define the parameters that generate aligned blocks to each other. We expand the generation model to a complete pipeline process that finds feasible generation parameters. The pipeline includes clipping parameters and methods in case that overlapping between blocks cannot be avoided.
Additionally, we describe a generalization of the mid-section evolution concept to include multiple evolution steps during the generation process. Our approach considers the angles and distances required to generate infinitely many TICs, including shapes that are not possible using the traditional generation method and the Height-Bisection method. Finally, we consider the interlocking assemblies that cannot maintain static equilibrium due to the shape of the surface tessellation. We consider the Structure Feasibility Analysis method to find the location and magnitude of the minimum tension forces that guarantee a TIC will reach a static equilibrium state. We describe how to update the generation parameters according to the results of the feasibility analysis. Our results show that the proposed pipeline generates valid TICs based on different surface tessellations, including closed and free-form shapes.
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Nziu, P. K. "Optimal geometric configuration of a cross bore in high pressure vessels." Thesis, 2018. http://hdl.handle.net/10352/414.
Full textAbstract:
M.Tech (Department of Mechanical Engineering, Faculty of Engineering and Technology), Vaal University of Technology.The purpose of this study was to develop analytical and numerical solutions to be used in the design of thick walled high pressure vessels for optimal location of a cross bore. In addition, the effects of internally applied combined thermo-mechanical loading on Stress Concentration Factor (SCF) on these vessels, was also evaluated. An analytical solution, to predict principal stresses on radial circular cross bore, was developed. The developed analytical solution was verified using finite element analysis methods. An optimisation process, using finite element analysis, was further done to determine the optimal combination of the major cross bore geometry that affect stress concentration. The cross bore geometries that were studied included the size, shape, location, obliquity and thickness ratio. The geometrically optimised cross bore was then subjected to combined thermo-mechanical loading to determine the resulting stress concentration effects. A total of 169 finite element part models were created and analysed. Seven thick walled cylinders having either circular or elliptical shaped cross bore positioned at radial, offset or and inclined were investigated. The analytical solution developed correctly predicted all the radial stresses at the intersection of the cross bore and main bore. However, out of 35 studied models, this analytical solution predicted the magnitude of hoop stresses in 9 models and that of axial stresses in 15 models correctly. The lowest SCF given by the radial circular cross bore was 2.84. Whereas, the SCF due to offsetting of the same cross bore size reduced to 2.31. Radial elliptical shaped cross bore gave the overall lowest SCF at 1.73. In contrast, offsetting of the same elliptical shaped cross bore resulted in tremendous increase in SCF magnitude exceeding 1.971. Additionally, the magnitudes of SCF were observed to increase whenever the circular offset cross bores were inclined along the RZ axis of the cylinder. The hoop stress due to internally applied combined thermo-mechanical loading increased gradually with increase in temperature until it reached a maximum value after which it began to fall sharply. In contrast, the corresponding SCF reduced gradually with increase in temperature until it reached a uniform steady state. After which, any further increase in temperature had insignificant change in stress concentration factor. The optimal SCF magnitude due to combined thermo-mechanical loading was 1.43. This SCF magnitude was slightly lower than that due to the pressure load acting alone.
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Meyer, Carsten. "Elektronische und geometrische Struktur von oxidischen Mikroclustern am Beispiel von MgO." Doctoral thesis, 2000. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2000091119.
Full textAbstract:
Im Rahmen der vorliegenden Arbeit ist ein selbstkonsistentes, ab-initio Verfahren (SCTBLMTO) entwickelt worden,
das die Berechnung elektronischer und geometrischer Strukturen von heterogenen Mikroclustern im Rahmen der
Tight-Binding Linear-Muffin-Tin-Orbital Näherung gestattet. Mittels der sogenannten
Atomic-Sphere-Approximation (ASA) ist hierbei eine kompakte Formulierung des Hamiltonoperators möglich. Durch
die Bestimmung der totalen Energie der Cluster in der Ein-Zentren-Näherung kann die numerisch aufwendige
Berechnung der über den ganzen Cluster ausgedehnten Wellenfunktion und damit der dreidimensionalen
Elektronendichte umgangen werden. Die angewendeten Approximationen erlauben es, selbst auf vergleichsweise
langsamen Rechnern, Cluster mit bis zu einigen hundert Atomen ohne Symmetrieeinschränkungen selbstkonsistent zu
berechnen. Gegenüber anderen ab-initio Verfahren bedeutet dies eine Steigerung der berechenbaren Clustergröße um
einen Faktor sechs. Im weiteren wurde gezeigt, daß die Parallelisierung des Algorithmus, d.h. die Verteilung von
Rechenschritten auf mehrere parallel arbeitende Rechner die Laufzeit des Programms drastisch reduziert.
Um die Implementation des SCTBLMTO-Verfahrens zu überprüfen, wurden zunächst Vergleichsrechnungen an
kleinen MgON-Clustern mit einem kommerziell verfügbaren DFT-Verfahren (DMol) durchgeführt. Hier traten
deutliche Relaxationseffekte bei der geometrischen Struktur der Cluster mit der Herausbildung typischer
Bindungswinkel in den kubischen Strukturen zutage. Eine Analyse der Clustergeometrien ergab zudem eine
ausgeprägte Abhängigkeit der Bindungsabstände der Atome von deren jeweiligen Koordinationszahlen. MgO18, mit 36
Atomen der größte mit DMol berechenbare Cluster, besitzt trotz der Tatsache, daß etwa 94% seiner Atome an der
Clusteroberfläche positioniert sind, bereits 96% der Bindungsenergie des Festkörpers. Dies läßt den Schluß zu, daß die
spezifische Kohäsionsenergie von Oberflächenatomen des Clusters sich nicht sehr stark vom Bulkwert unterscheidet.
Ein einfaches Modell, welches die Beiträge zur Kohäsionsenergie anhand der Atompositionen in den kubischen und
den ringförmigen Clustern festlegt, bestätigt diese Vermutung. Anhand des Modells kann ferner geschlossen werden,
daß ein stabiles Wachstum einer kubischen, dem Festkörper ähnlichen Phase ab einer Clustergröße von N=15
Molekülen an beginnt. Die Erklärung der gemessenen Abundance Spektren von MgON-Clustern ist allein auf Basis
der totalen Energien der Cluster nicht möglich. Erst die Betrachtung des Zerfalls von neutralen und ionisierten
Clustern in Fragmente unterschiedlicher Größe kann die Messungen erklären. Insgesamt ist die Stabilität der Cluster
durch das Zusammenspiel elektronischer Effekte, wie z.B. hoher oder niedriger Ionisationsenergien und geometrischer
Effekte begründet. Ferner wurde gezeigt, daß auf Basis der ermittelten Daten gemessene
Collision-Induced-Fragmentation (CIF) Muster quantitativ interpretierbar sind.
Die SCTBLMTO-Rechnungen für sehr kleine MgON-Cluster ergeben im Vergleich mit den Referenzrechnungen
einerseits und den experimentellen Befunden andererseits keine zufriedenstellenden Resultate für die
Kohäsionsenergien. Der Grund hierfür liegt eindeutig darin, daß diese Geometrien Grenzfälle der Muffin-Tin- (MT)
Näherung darstellen. Durch die Einführung von Leerkugeln verbessern sich die Resultate deutlich. Im Gegensatz
hierzu stimmen die Gleichgewichtsabstände der Cluster, d.h. im Endeffekt die Minima in der totalen Energie als
Funktion der Atomabstände, überraschend gut mit den Referenzdaten im Rahmen der lokalen Dichteapproximation
(LDA) überein. Auch hier bewirkt die MT-Näherung einen Teil des Fehlers, der jedoch mit zunehmender Clustergröße
geringer wird. Im Vergleich der Hypergeometrieflächen, die mit unterschiedlichen Rechenverfahren ermittelt wurden,
zeigt die SCTBLMTO-Methode zwar recht große Isomerunterschiede, beurteilt die lokalen Minima relativ zueinander
und damit die geometrischen Grundzustände jedoch meist richtig. Die Untersuchungen zeigten weiter, daß
Korrelationseffekte einen starken Einfluß auf die Gleichgewichtsgeometrien der Cluster haben und daher unbedingt
berücksichtigt werden müssen. Die totalen sowie die lokalen Zustandsdichten der kleinen Cluster werden von dem hier
entwickelten Verfahren in guter Übereinstimmung mit den DMol-Referenzdaten wiedergegeben. Einzig die Zustände
im unbesetzten Teil der DOS werden durch die Muffin-Tin-Näherung verzerrt.
Schließlich läßt sich zumindest bei kleinen MgON-Clustern ein deutlicher Zusammenhang zwischen der Position der
Atome und deren elektronischer Struktur herstellen. Eine detaillierte Analyse der lokalen Zustandsdichte ergibt:
Atome an den Ecken der Cluster bilden den höchsten besetzten Zustand, wogegen Atome, die sich innerhalb der
Cluster befinden, tieferliegende Zustände besetzen. In allen Strukturen bilden die Sauerstoffatome das höchste
besetzte Orbital und die Magnesiumatome das niedrigste unbesetzte. Insgesamt können die Bindungsverhältnisse in
den MgO-Clustern als lokalisiert charakterisiert werden.
Gegenüber der schnellen Annäherung der geometrischen Eigenschaften an die Festkörperstruktur konvergieren die
lokalen Zustandsdichten der Zentralatome langsamer gegen die DOS des Festkörpers. Erst ab MgO147, bei dem die
Zentralatome von drei Schichten von oberflächennahen Atomen umgeben sind, können auch Details der
Bulkzustandsdichte in der LDOS zugeordnet werden.
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Lin, Fung-Chaung, and 林芳全. "Applications of Geometric Configuration Variation of Product Components on Computer-aided Idea Development." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/55100199374732290256.
Full textAbstract:
碩士國立交通大學
工業工程研究所
81
Computer-aided design(CAD) is one major trend in the area of industrial design. However, there are few researches about computer-aided idea development. We''ve already agreed that computer is one of the best tools for development. Thus it is worth investigating how to manipulate CAD tools for helping idea development. This paper intends to find the effective possible ways of computer aided idea development by investigating the essence of design development process. We concentrate on how to apply the variation of the geometric configuration of product components to computer-aided idea development. In this paper, there are the studies of design thinking activity, relating form development methods, and the computer geometric transformation methods. Then we submit the possible process of computer-aided idea development, and finally show an example.
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蔡明修. "Influence of the luminescence property of phosphorescent by changing geometric configuration of 2-phenylpyridine." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/19059681857044555711.
Full text
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Wang, Hung Hsun, and 王鴻勳. "Flow and heat transfer of non-Newtonian and nanofluids under various geometric configurations." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/61411659251106106796.
Full textAbstract:
博士國立暨南國際大學
土木工程學系
100
Chap. 1 introduces the general applications in nanofluid and useful general mathematic formulae onto geometric configurations. In Chaps. 2 and 3, by taking the balance of the flow rate in a vertical double-passage channel, the effect of inertia, buoyancy, porous medium, micropolar fluid and viscous dissipation have been investigated via the control of flow rate. Chap. 4 studies the effect of magnetic field, viscous dissipation, non-uniform heat source and/or sink and thermal radiation on flow and heat transfer in a hydromagnetic liquid film over an unsteady stretching surface with prescribed heat flux condition. Taking into account of the Brownian diffusion and thermophoresis of slip mechanisms in the concentration equation, Chapter 5 investigates the flow, heat and mass transfer in two geometric configurations: I. Near a Rotating Disk and II. Over a Bi-directional Stretching Surface and the results illustrate that the correlations of physical parameters for the heat and mass transfer rates have been developed on a regression analysis. With the nanoparticle volume fraction being specified, different types of nanoparticles, namely, silver Ag, copper Cu, alumina Al2O3, and titanium TiO2 with water as the base fluid are considered in Chapter 6 under two geometric configurations which are III. Near a Rotating Disk and IV. Over a Bi-directional Stretching Surface. The velocity, temperature and concentration profiles, the hydrodynamic and thermal boundary layer thickness, the surface friction coefficients, heat and mass transfer rate are demonstrated and discovered with the effect of parameters. Chap. 7 concludes the results of the present studies and gives suggestion for the future works.
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Yeh, Hsin-Fan, and 葉信汎. "Seismic Nonlinear Analysis of Transmission Towers under Various Geometric Configurations─Considering Soil-Structure Interaction." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/89884455979008535626.
Full textAbstract:
碩士淡江大學
土木工程學系
90
It is well known that many of power plants are constructed in the mountainous region or by the side of the river, therefore the conveying route of electric power beginning from such a plant to some residential and industrial areas is often changeable both in its elevation and its orientation, due to the ruggedness of topography which transmission towers march across. This makes that the tensile force acting at transmission towers from cables might have diverse horizontal or vertical angles with ground surface. Accordingly, each transmission tower would exhibit its unique seismic behaviors. By the use of 3-D beam elements and efficient cable elements for the modeling of towers and cables respectively, the effect due to topography variation upon the stress distribution across over the composed elements of the tower would be investigated in detail in this research. Furthermore, to enhance the value in practice, an effective spatial soil-structure interaction model and an effective parameter called “failure index” will be utilized in the analyses. It is shown in the results that the seismic behaviors of transmission towers would be affected significantly by either the magnitude of the force transmitted by cables or by the route orientation that the tower group goes along.
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Zhu, Shuqiang. "Central configurations of the curved N-body problem." Thesis, 2017. https://dspace.library.uvic.ca//handle/1828/8334.
Full textAbstract:
We extend the concept of central configurations to the N-body problem in spaces of nonzero constant curvature. Based on the work of Florin Diacu on relative equilib- ria of the curved N-body problem and the work of Smale on general relative equilibria, we find a natural way to define the concept of central configurations with the effective potentials. We characterize the ordinary central configurations as constrained critical points of the cotangent potential, which helps us to establish the existence of ordi- nary central configurations for any given masses. After these fundamental results, we study central configurations on H2, ordinary central configurations in S3, and special central configurations in S3 in three separate chapters. For central configurations on H2, we generalize the theorem of Moulton on geodesic central configurations, the theorem of Shub on the compactness of central configurations, the theorem of Conley on the index of geodesic central configurations, and the theorem of Palmore on the lower bound for the number of central configurations. We show that all three-body central configurations that form equilateral triangles must have three equal masses. For ordinary central configurations in S3, we construct a class of S3 ordinary central configurations. We study the geodesic central configurations of two and three bodies. Three-body non-geodesic ordinary central configurations that form equilateral trian- gles must have three equal masses. We also put into the evidence some other classes of central configurations. For special central configurations, we show that for any N ≥ 3, there are masses that admit at least one special central configuration. We then consider the Dziobek special central configurations and obtain the central con- figuration equation in terms of mutual distances and volumes formed by the position vectors. We end the thesis with results concerning the stability of relative equilibria associated with 3-body special central configurations. We find that these relative equilibria are Lyapunov stable when confined to S1, and that they are linearly stable on S2 if and only if the angular momentum is bigger than a certain value determined by the configuration.Graduate
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Leite, Rafaela Pereira. "Influência da geometria dos parafusos da extrusora na dispersão de nanocompósitos." Master's thesis, 2020. http://hdl.handle.net/1822/69516.
Full textAbstract:
Dissertação de mestrado em Engenharia de PolímerosA preparação de sistemas poliméricos bem dispersos, especialmente a produção de nanocompósitos de polímero-argila, tornou-se um tópico de pesquisa intenso devido ao seu elevado potencial de aplicação. Atualmente, assume-se que um elevado grau de dispersão da argila, particularmente elevada esfoliação, aprimora o desempenho do nanocompósito. Apesar de se conhecerem os parâmetros que influenciam a dispersão da argila na matriz do polímero - adesão interfacial, coesão dos tactoides e condições operatórias - o efeito de cada um no início e na extensão da dispersão das argilas ainda é tópico de discussão. As extrusoras de duplo fuso são frequentemente utilizadas na preparação de nanocompósitos de matriz polimérica, dadas as suas excelentes capacidades de mistura, produção contínua e elevada e flexibilidade geométrica, uma vez que é possível adaptar a configuração dos parafusos aos requisitos do processo. Assim, o presente estudo teve como foco principal a análise do efeito da geometria de diversos tipos de elementos de parafuso no grau de dispersão dos nanocompósitos processados. Para tal, foram avaliados diferentes parâmetros, nomeadamente o efeito da concentração da carga, a velocidade de rotação do fuso e a configuração do fuso através de caracterização reológica em linha, utilizando uma um novo reómetro em linha de fenda dupla, desenvolvido no IPC/UMinho, denominado fieira reométrica.
The preparation of well dispersed polymer systems, especially the production of polymer clay nanocomposites has become a widely recognized research topic due to their high potential. It is now assumed that a high degree of dispersion, particularly high exfoliation, improves the nanocomposite performance. And although we know the parameters that influence the dispersion of clay in the polymer matrix, such as interfacial adhesion, chemical affinity and operative conditions, the effect of each one on the beginning and extent of clay dispersion is still a topic of discussion. Twin-screw extruders are often used in the preparation of polymer matrix nanocomposites, given their excellent blending capabilities, continuous and high throughput, and geometric flexibility. Thus, the present study focused on the analysis of the effect of geometry of various types of screw elements on the degree of dispersion of the processed nanocomposites. For this, different parameters were evaluated, namely the load effect, the screw speed and the screw configuration through in-line characterization using a new double slit in-line rheometer, developed at IPC/UMinho, called rheometric slit die.
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(7847843), Rahul Deshmukh. "Influence of geometry and placement configuration on side forces in compression springs." Thesis, 2019.
Find full textAbstract:
A leading cause of premature failure and excessive wear and tear in mechanical components that rely on compression springs for their operation is the development of unwanted side forces when the spring is compressed.
These side forces are usually around 10% - 20% of the magnitude of the axial load and point in different directions in the plane perpendicular to the axis of the spring.
The magnitude and direction of the resultant of side forces varies very non-linearly and unpredictably even though the axial force behavior of the spring is very consistent and predictable.
Since these side forces have to be resisted by the housing components that hold the spring in place, it is difficult to design these components for optimal operation.
The hypothesis of this study is that side forces are highly sensitive to small changes in spring geometry and its placement configuration in the housing.
Several experiments are conducted to measure the axial and side forces in barrel springs and two different types of finite element models are developed and calibrated to model the spring behavior.
Spring geometry and placement are parameterized using several control variables and an approach based on design of experiments is used to identify the critical parameters that control the behavior of side-forces.
The models resulted in deeper insight into the development of side forces as the spring is progressively loaded and how its contact interactions with the housing lead to changes in the side force.
It was found that side-forces are indeed sensitive to variations in spring geometry and placement.
These sensitivities are quantified to enable designers to and manufacturers of such springs to gain more control of side force variations between different spring specimens.
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Jen-WeiWu and 吳振瑋. "Measurements of geometric parameters of pseudo-steady Mach reflections wave configurations and their comparisons with predictions from the three-shock theory." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/84243473497532778904.
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Ighalo, Fervent U. "Optimisation of microchannels and micropin-fin heat sinks with computational fluid dynamics in combination with a mathematical optimisation algorithm." Diss., 2011. http://hdl.handle.net/2263/26207.
Full textAbstract:
In recent times, high power density trends and temperature constraints in integrated circuits have led to conventional cooling techniques not being sufficient to meet the thermal requirements. The ever-increasing desire to overcome this problem has led to worldwide interest in micro heat sink design of electronic components. It has been found that geometric configurations of micro heat sinks play a vital role in heat transfer performance. Therefore, an effective means of optimally designing these heat sinks is required. Experimentation has extensively been used in the past to understand the behaviour of these heat extraction devices. Computational fluid dynamics (CFD) has more recently provided a more cost-effective and less time-consuming means of achieving the same objective. However, in order to achieve optimal designs of micro heat sinks using CFD, the designer has to be well experienced and carry out a number of trial-and-error simulations. Unfortunately, this will still not always guarantee an accurate optimal design. In this dissertation, a design methodology which combines CFD with a mathematical optimisation algorithm (a leapfrog optimisation program and DYNAMIC-Q algorithm) is proposed. This automated process is applied to three design cases. In the first design case, the peak wall temperature of a microchannel embedded in a highly conductive solid is minimised. The second case involves the optimisation of a double row micropin-fin heat sink. In this case, the objective is to maximise the total rate of heat transfer with the effect of the thermal conductivity also being investigated. The third case extends the micropin-fin optimisation to a heat sink with three rows. In all three cases, fixed volume constraint and manufacturing restraints are enforced to ensure industrial applicability. Lastly, the trends of the three cases are compared. It is concluded that optimal design can be achieved with a combination of CFD and mathematical optimisation.Dissertation (MEng)--University of Pretoria, 2011.
Mechanical and Aeronautical Engineering
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