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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Variations of Shape in Industrial Geometric Models

Veelo, Bastiaan Niels January 2004 (has links)
This thesis presents an approach to free-form surface manipulations, which conceptually improves an existing CAD system that constructs surfaces by smoothly interpolating a network of intersecting curves. There are no regularity requirements on the network, which already yields superior modelling capabilities compared to systems that are based on industry-standard NURBS surfaces. Originally, the shape of such a surface can be modified only locally by manipulating a curve in the network. In this process there is an inherent danger that the curve is being pulled away from intersections that it has with other curves. When this happens, the network is invalidated as a surface representation, and many curves may have to be adjusted to restore network consistency and surface quality. This thesis contributes a method that solves these problems by propagating changes that are made in one curve to curves in its vicinity. How and to what extent curves react to changes is controlled by two parameters that can be varied along the curve that is being manipulated. Any curve may be constrained in one or more degrees of freedom. The integrity of the curve network is implicitly conserved, as well as the geometric continuity of the surface. The result is a tool for the modification of curve-interpolating surfaces, which can easily be applied to large areas on models with any level of detail. This allows designers to concentrate on the creative process, rather than on planning chains of actions. They can explore different design variations, optimise shapes further, and generally be more productive. / Dette doktorgradsarbeidet presenterer en fremgangsmåte for formgivning og modifisering av datamaskinbaserte, skulpturerte flater. Metoden forbedrer et eksisterende system for data-assistert konstruksjon (DAK) som bygger dobbeltkrummede flater ved å interpolere et nettverk av skjærende kurver. Nettverket trenger ikke være regelmessig, noe som allerede gir bedre modelleringsmuligheter sammenliknet med systemer som er basert på standard NURBS flater. En slik flate kan opprinnelig bare endres lokalt ved å dra i en kurve. I denne prosessen er det fare for at kurven blir dratt fra skjæringspunkter den har med andre kurver. Hvis dette skjer, representerer ikke nettverket en flate lenger, og mange kurver må justeres for å få tilbake integriteten i nettverket og kvaliteten i formen. Denne avhandlingen bidrar med en metode som løser disse problemene ved å spre endringer som blir gjort i en kurve til andre kurver i nærheten. Hvordan og i hvilken utstrekning kurvene reagerer på endringen styres av to parametre som kan varieres langs kurven som blir endret. Enhver kurve kan låses i en eller flere frihetsgrader. Integriteten til nettverket samt glattheten i formen blir bevart automatisk. Resultatet er et redskap for modifikasjon av kurve-interpolerende flater som med letthet kan brukes på større områder av modeller med hvilken som helst grad av detalj. Dette gir designere muligheten til å konsentrere seg om det kreative, istedenfor å planlegge handlingsrekker. De kan utforske forskjellige designvariasjoner, optimalisere former ytterligere, og i det hele tatt være mer produktive.
92

Un método de elementos finitos para análisis hidrodinámico de estructuras navales

García Espinosa, Julio 20 December 1999 (has links)
La predicción precisa de los efectos producidos por el acoplamiento fluido estructura para cuerpos parcial o totalmente sumergidos, incluyendo superficies libres, es un problema de gran relevancia en la ingeniería naval así como en muchos otros campos del diseño de estructuras sometidas a la acción de fluidos.Las dificultades que se encuentran en la resolución de los problemas de interacción fluido estructura se deben principalmente a las siguientes causas:1. La dificultad de resolver numéricamente las ecuaciones de la dinámica de un fluido incompresible que, en general, si descartamos el caso más simple del modelo del flujo potencial, tienen un importante carácter no lineal. 2. Los obstáculos que se presentan al resolver la ecuación de la superficie libre, que constriñen el movimiento de las partículas a una superficie fluida de posición a priori desconocida.3. Las dificultades asociadas a la resolución del problema del movimiento de un cuerpo sumergido debido a las fuerzas de interacción, minimizando la deformación de los elementos de la malla y reduciendo, de esta manera, la necesidad del remallado.En la presente tesis se presenta un método estabilizado basado en el método de los elementos finitos que pretende solventar cada uno de los problemas anteriores. La metodología se basa en la modificación de las ecuaciones diferenciales de la dinámica de fluidos que gobiernan el flujo viscoso incompresible y el movimiento de la superficie libre, mediante la aplicación del método de cálculo finitesimal (FIC) propuesto en este trabajo.En el presente caso las ecuaciones modificadas son resueltas usando un esquema de pasos fraccionados semi-implícito y el método de los elementos finitos (FEM). El movimiento del cuerpo sumergido en el fluido debido a las fuerzas de interacción se calcula resolviendo un problema estructural dinámico, para el cual las fuerzas del fluido son las condiciones iniciales. Se incluye, además, un algoritmo para el movimiento de la malla debido a la deformación del dominio de cálculo. Este método minimiza la distorsión de la malla debida al movimiento del sólido rígido y al cambio de posición de la superficie libre. Este algoritmo se basa en la solución iterativa por el método de elementos finitos de un problema lineal, donde la malla de cálculo se considera un sólido elástico sometido a la deformación prescrita por el cambio en el dominio de cálculo. Las características de elasticidad del sólido, y en concreto su rigidez, se aplican de manera que los elementos que más se deforman tienen una rigidez mayor. Por último se presentan varios ejemplos de interés industrial, aplicación de la metodología propuesta en diferentes campos de la ingeniería naval.
93

A fully integrated SRAM-based CMOS arbitrary waveform generator for analog signal processing

Song, Tae Joong 23 June 2010 (has links)
This dissertation focuses on design and implementation of a fully-integrated SRAM-based arbitrary waveform generator for analog signal processing applications in a CMOS technology. The dissertation consists of two parts: Firstly, a fully-integrated arbitrary waveform generator for a multi-resolution spectrum sensing of a cognitive radio applications, and an analog matched-filter for a radar application and secondly, low-power techniques for an arbitrary waveform generator. The fully-integrated low-power AWG is implemented and measured in a 0.18-¥ìm CMOS technology. Theoretical analysis is performed, and the perspective implementation issues are mentioned comparing the measurement results. Moreover, the low-power techniques of SRAM are addressed for the analog signal processing: Self-deactivated data-transition bit scheme, diode-connected low-swing signaling scheme with a short-current reduction buffer, and charge-recycling with a push-pull level converter for power reduction of asynchronous design. Especially, the robust latch-type sense amplifier using an adaptive-latch resistance and fully-gated ground 10T-SRAM bitcell in a 45-nm SOI technology would be used as a technique to overcome the challenges in the upcoming deep-submicron technologies.
94

Abortion and the right to life: A case study of South Africa and Germany

Zimmer, Martina January 2016 (has links)
Magister Legum - LLM (Public Law and Jurisprudence) / The issue of abortion and the protection of the right to life have been discussed by many academics, yet remains an unresolved topic in many countries. The mere fact that abortion is the deliberate termination of a human pregnancy raises the question, whether or not such an act violates the right to life. Abortion has been legalised in South Africa and Germany. This study explores the area of abortion vis a viz the obligation of South Africa and German under the international and regional human rights instruments to protect the right to life. Notably, the right to life is protected under a plethora of international and regional human rights instruments. At international level, the right to life is protected under Article 3 of the Universal declaration of Human Rights and Article 6 of the International Covenant on Civil and Political Rights. At regional level of the right to life is protected by Article 2 of the European Convention on Human Rights and Article 4 of the African Charter on Human and Peoples� Rights. To give a broad understanding of the meaning, nature and content of the right to life, this mini-thesis shall critically analyse the words used under the above Articles which protect the right to life. Then the paper will endeavour on its main objective which is to determine whether or not the legalisation of Abortion in South Africa and Germany violates the right to life?
95

Métodos numéricos para escoamentos com linhas de contato dinâmicas / Numerical methods for flows with dynamic contact lines

Felipe Montefuscolo 28 May 2012 (has links)
O fenômeno de molhamento, estudo de como um líquido se deposita em um sólido, apresenta problemas ainda em aberto, dos pontos de vista da modelagem física e da simulação numérica. O maior interesse acadêmico neste tipo de escoamento é a linha tríplice (ou linha de contato) formada da interação sólido-líquido-gás. A condição de contorno clássica de não escorregamento na interface líquido-sólido leva a uma singularidade no tensor de tensões nesta linha. Além disso, ainda não está estabelecido qual o melhor modelo para descrever o ângulo de contato formado entre a superfície livre e o substrato (o sólido). Neste trabalho, são discutidos métodos numéricos para a simulação de linhas de contato dinâmicas. Os efeitos da tensão superficial são estudados com a abordagem do princípio do trabalho virtual, o qual leva o problema à equações na formulação variacional, linguagem natural para o tratamento numérico com o método dos elementos finitos (FEM). O domínio é discretizado por uma malha não-estruturada de forma que as interfaces separadoras são explicitamente representadas pela malha. As derivadas temporais são tratadas em uma abordagem Lagrangeana-Euleriana arbitrária (ALE). Finalmente, são apresentados os resultados numéricos obtidos com o método ALE-FEM, discutindo alguns aspectos da sua convergência temporal e espacial. / Wetting phenomena, study of how of a liquid spreads out on a solid substrate, presents challenges both in physical modeling and in numerical simulation. The triple line (or contact line) formed by the solid-liquid-gas interaction has increasingly attracted the attention of the fluid dynamic community. The classical no-slip boundary condition on the liquid-solid interface leads to a singularity in the stress tensor at contact lines. Furthermore, there is no consensus on what the best model to describe the dynamics of the contact angle formed by the solid substrate and free surface. In this work, numerical methods for simulating dynamic contact lines are considered. The capillarity effects are studied in the approach of the virtual-work principle, which describes the problem in the variational formulation, natural language for numerical treatment with the finite element method (FEM). The domain is discretized by a dynamic unstructured mesh, where the separating interfaces are explicit represented by the mesh. Time derivatives present in the governing equations are treated with the arbitrary Lagrangian-Eulerian (ALE) framework. Finally, we discuss some temporal and spatial convergence issues ofthe ALE-FEM method.
96

Patient-Specific Finite Element Modeling of the Blood Flow in the Left Ventricle of a Human Heart

Spühler, Jeannette Hiromi January 2017 (has links)
Heart disease is the leading cause of death in the world. Therefore, numerous studies are undertaken to identify indicators which can be applied to discover cardiac dysfunctions at an early age. Among others, the fluid dynamics of the blood flow (hemodymanics) is considered to contain relevant information related to abnormal performance of the heart.This thesis presents a robust framework for numerical simulation of the fluid dynamics of the blood flow in the left ventricle of a human heart and the fluid-structure interaction of the blood and the aortic leaflets.We first describe a patient-specific model for simulating the intraventricular blood flow. The motion of the endocardial wall is extracted from data acquired with medical imaging and we use the incompressible Navier-Stokes equations to model the hemodynamics within the chamber. We set boundary conditions to model the opening and closing of the mitral and aortic valves respectively, and we apply a stabilized Arbitrary Lagrangian-Eulerian (ALE) space-time finite element method to simulate the blood flow. Even though it is difficult to collect in-vivo data for validation, the available data and results from other simulation models indicate that our approach possesses the potential and capability to provide relevant information about the intraventricular blood flow.To further demonstrate the robustness and clinical feasibility of our model, a semi-automatic pathway from 4D cardiac ultrasound imaging to patient-specific simulation of the blood flow in the left ventricle is developed. The outcome is promising and further simulations and analysis of large data sets are planned.In order to enhance our solver by introducing additional features, the fluid solver is extended by embedding different geometrical prototypes of both a native and a mechanical aortic valve in the outflow area of the left ventricle.Both, the contact as well as the fluid-structure interaction, are modeled as a unified continuum problem using conservation laws for mass and momentum. To use this ansatz for simulating the valvular dynamics is unique and has the expedient properties that the whole problem can be described with partial different equations and the same numerical methods for discretization are applicable.All algorithms are implemented in the high performance computing branch of Unicorn, which is part of the open source software framework FEniCS-HPC. The strong advantage of implementing the solvers in an open source software is the accessibility and reproducibility of the results which enhance the prospects of developing a method with clinical relevance. / <p>QC 20171006</p>
97

L'inamovibilité des magistrats : un modèle ? / The irremovibility of judges

Pluen, Olivier 22 November 2011 (has links)
En droit français, l’inamovibilité est traditionnellement conçue comme une garantie d’indépendance statutaire attribuée au magistrat du siège de l’ordre judiciaire, afin de le protéger contre le risque d’éviction arbitraire par le Pouvoir politique. Elle est ainsi supposée faire bénéficier le magistrat d’une protection exorbitante par rapport au droit commun de la fonction publique. Déjà considérée comme un « antique et tutélaire principe » au milieu du XIXe siècle, cette garantie a traversé le temps et les régimes politiques, depuis l’époque médiévale jusqu’à aujourd’hui. Erigée en Loi fondamentale du royaume à la veille de la Révolution, elle a été reprise et consacrée par la presque totalité des Constitutions qui se sont succédées depuis 1791. Mais alors qu’elle semble offrir l’image d’un modèle de garantie susceptible d’inspirer le statut d’autres catégories d’agents publics, l’inamovibilité est de manière paradoxale, souvent décrite comme un « mythe ». La présente étude se donne dès lors pour objet de lever cette contradiction, en revenant de manière approfondie et comparative sur la condition et la finalité d’une garantie d’éviction, dont la particularité est d’être étroitement liée à la mission régalienne consistant à rendre la justice. / In French Law, irremovability is traditionally seen as a statutory guarantee of judicial judges’ independence that protects them from being arbitrary evicted by the Political power. Irremovability is then said to be a dispensatory status if compared to public servants normal one. Defined as an « ancient and tutelary principle » at the middle of the 19th Century, this guarantee ran through the ages and the political regimes from medieval times to today. Irremovability of judges was made a Kingdom’s fundamental Law just before the Revolution, and almost every constitution adopted since 1791 has made it a constitutionally sanctioned rule. In the meantime, whereas it could have been seen as a template for other civil servants legal status, irremovability of judges is, paradoxically enough, often described as a « myth ». This study’s aim is thus to solve this contradiction. It offers an in-depth and comparative analysis of the condition and goal of this legal guarantee against eviction – which distinctive feature is to be closely linked with one of the State’s main function: to administer Justice.
98

Actionneur linéaire rapide - Application aux soupapes électromagnétiques / Fast linear actuator - Application to electromagnetic valves

Raminosoa, Ando 11 September 2012 (has links)
Pour réduire les émissions de gaz polluants, les constructeurs automobiles cherchent à mieux contrôler le volume d'air introduit dans le moteur pour optimiser la combustion. Des dispositifs mécaniques ou hydrauliques couplés avec l'arbre à cames sont déjà en place dans certaines voitures et permettent des gains de 8 à 10% sur la consommation de carburant. L'utilisation d'un actionneur électromagnétique à la place de l'arbre à cames (application « camless ») pour commander les soupapes améliore nettement ce gain (15 à 20%). Les travaux de cette thèse consistent à modéliser une structure choisie, pour ensuite l'optimiser. Compte tenu des exigences de notre application et des contraintes d'environnement du moteur thermique, la modélisation doit être à la fois suffisamment précise et rapide pour estimer et améliorer les performances de l'actionneur. Pour la partie statique, nous avons opté pour un modèle réluctant 3D. Obtenu par extension de son homologue 2D, il reste rapide tout en donnant des résultats en accord avec les mesures. En régime transitoire, nous proposons une nouvelle approche analytique de la distribution des courants de Foucault, directement à partir de l'évolution du flux magnétique. L'équation de diffusion comporte alors des conditions aux limites de Neumann. Nous avons traité le cas d'un flux magnétique arbitraire grâce au théorème de Duhamel, ainsi que la saturation du matériau grâce à une approche semi-analytique. / Variable valve actuation is one of automotive constructors' strategies to fulfil environmental queries about emission of pollutant gases. It brings improvement to the thermal engine, and many constructors have their own devices associated to the camshaft, with a gain between 8 and 10% on fuel consumption. The use of camless actuator brings further more gain, from 15 to 20%. The established approach during this thesis consists in modelling a chosen topology of actuator, and next in optimization. However, camless specifications and constraints require fast models, but with correct accuracy. That's why we use 3D permeances network in steady state. That model is obtained from extension of its 2D version. It is still fast and gives results in good agreement with measurements. We proposed a new analytical approach of eddy currents distribution in transient state, directly from the evolution of magnetic flux. Thus we have Neumann's boundary conditions in the diffusion equation. Arbitrary magnetic flux excitation and saturated material (with semi-analytical approach) are considered.
99

What is “meta-” for? : a Peircean critique of the cognitive theory of metaphor

JIANG, Yicun 08 August 2017 (has links)
My thesis aims to anatomize the cognitive theory of metaphor and suggests a Peircean semiotic perspective on metaphor study. As metaphorical essentialists, Lakoff/Johnson tend to universalize a limited number of conceptual metaphors and, by doing this, they overlook the dynamic relation between metaphorical tenor and vehicle. Such notion of metaphor is not compatible with the polysemous nature of the sign. The diversity and multivalency of metaphorical vehicle, in particular, cast serious doubts on the hypothesis of “conceptual metaphors” which, being meta-metaphorical constructs, can tell us nothing but a dry and empty formula “A is B”. Consequently, Lakoff/Johnson’s notion of conceptual metaphor is very much a Chomskyan postulation. Also problematic is the expedient experientialism or embodied philosophy they have put forward as a middle course between objectivism and subjectivism. What is missing from their framework is a structural space for dynamic interpretation on the part of metaphor users. In contrast, cognitive linguists may find in Peirce’s theory of the sign a sound solution to their theoretical impasse. As a logician, Peirce sees metaphor as the realization of iconic reasoning at the language level. His exposition on iconicity and iconic reasoning has laid a solid foundation upon which may be erected a fresh epistemology of metaphor fit for the contemporary study of language and mind. Broadly speaking, metaphor in Peirce can be examined from roughly two perspectives. Macroscopically, metaphor is an icon in general as opposed to index and symbol, whereas, microscopically, it is a subdivided hypoicon on the third level as opposed to image and diagram. Besides, Peirce also emphasized the subjective nature of metaphor. Semioticians after Peirce have further developed his theory on metaphor. For example, through his concept of “arbitrary iconicity”, Ersu Ding stresses the arbitrary nature of metaphorization and tries to shift our attention away from Lakoff/Johnson’s abstract epistemological Gestalt to the specific cultural contexts in which metaphors occur. Umberto Eco, on the other hand, sees interpretation of signs as an open-ended process that involves knowledge of all kinds. Encyclopedic knowledge thus serves as unlimited source for metaphorical association. For Eco, the meaning of a metaphor should be interpreted in the cultural framework based on a specific cultural community. Both Ding’s and Eco’s ideas are in line with Peirce’s theoretical framework where the meaning of a metaphor depends on an interpreter in a particular socio-historical context. They all realize that we should go beyond the ontology of metaphorical expressions to acquire a dynamic perspective on metaphor interpretation. To overcome the need for presupposing an omnipotent subject capable of knowing the metaphor-in-itself, we turn to Habermas’s theory of communicative action in which the meaning of metaphor is intersubjectively established through negotiation and communication. Moreover, we should not overlook the dynamic tension between metaphor and ideology. Aphoristically, we can say that nothing is a metaphor unless it is interpreted as a metaphor, and we need to reconnect metaphors with the specific cultural and ideological contexts in which they appear.
100

Přesný funkční generátor / Precise function generator

Snopek, Petr January 2009 (has links)
The aim of the project is to design a concept of function generator with digital synthesis. The device will be controlled using microprocessor which allows synthesizing basic functions (sin, square, raw) as well as arbitrary functions stored in memory. User friendly graphical interface will be controlled by keyboard and rotary switch (IRC). The work emphasizes correct selection of DDS clock source, circuit elements and proper application of signal filtration method with attention to low distortion and low output phase noise.

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