In numerical simulations, problems stemming from aerodynamics pose many challenges for the method used. Some of these are addressed in this thesis, such as the fluid interacting with objects, the presence of shocks, and various types of boundary conditions. Scenarios of the kind mentioned above are described mathematically by initial boundary value problems (IBVPs). We discretize the IBVPs using high order accurate finite difference schemes on summation by parts form (SBP), combined with weakly imposed boundary conditions, a technique called simultaneous approximation term (SAT). By using the energy method, stability can be shown. The weak implementation is compared to the more commonly used strong implementation, and it is shown that the weak technique enhances the rate of convergence to steady state for problems with solid wall boundary conditions. The analysis is carried out for a linear problem and supported numerically by simulations of the fully non-linear Navier–Stokes equations. Another aspect of the boundary treatment is observed for fluid structure interaction problems. When exposed to eigenfrequencies, the coupled system starts oscillating, a phenomenon called flutter. We show that the strong implementation sometimes cause instabilities that can be mistaken for flutter. Most numerical schemes dealing with flows including shocks are first order accurate to avoid spurious oscillations in the solution. By modifying the SBP-SAT technique, a conservative and energy stable scheme is derived where the order of accuracy can be lowered locally. The new scheme is coupled to a shock-capturing scheme and it retains the high accuracy in smooth regions. For problems with complicated geometry, one strategy is to couple the finite difference method to the finite volume method. We analyze the accuracy of the latter on unstructured grids. For grids of bad quality the truncation error can be of zeroth order, indicating that the method is inconsistent, but we show that some of the accuracy is recovered. We also consider artificial boundary closures on unbounded domains. Non-reflecting boundary conditions for an incompletely parabolic problem are derived, and it is shown that they yield well-posedness. The SBP-SAT methodology is employed, and we prove that the discretized problem is stable.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2004. / Härtill 4 uppsatser.

Thesis (M.Ed.)--Memorial University of Newfoundland. / Typescript. Restricted until November 1995. Bibliography: leaves 107-109. Also available online.

Thesis (M.S.)--Brigham Young University. Dept. of Statistics, 2006. / Includes bibliographical references (p. 45-46).

Thesis (Ph. D.)--University of Chicago, Department of Philosophy, December 2000. / Includes bibliographical references. Also available on the Internet.

Dissertation (Ph.D.) -- Worcester Polytechnic Institute. / Keywords: Computer aided manufacturing planning; Object-oriented systems analysis (OSA); Feature; manufacturing resource capability; setup planning; multi-part fixture Includes bibliographical references (p.146-154).

No description available.

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[pt] O dinamismo dos mercados vem se intensificando, em face da globalização, dos avanços tecnológicos e das mudanças sociais. Consequentemente, as empresas necessitam se adaptar tempestivamente para se manter competitivas, ou podem vir a desaparecer. Neste contexto, inovações disruptivas são cada vez mais frequentes. Assim é o caso da manufatura aditiva, conhecida popularmente por impressão 3D. Tratam-se de tecnologias com potencial disruptivo que vai além do paradigma de produção, influenciando a logística, a sociedade, os mercados e múltiplos setores, tais quais o de saúde, o de defesa, o automotivo, o de construção civil e até mesmo o de alimentos. Nesta vertente, o presente trabalho busca verificar o potencial disruptivo das tecnologias de manufatura aditiva, iniciando pelo aprofundamento no conhecimento sobre estas tecnologias. Em seguida, é feita análise sobre a gestão das cadeias de suprimentos atual e as implicações das tecnologias de manufatura aditiva sobre a gestão das cadeias de suprimentos. Por fim, o estudo confronta o potencial disruptivo da manufatura aditiva com a cadeia de suprimentos de sobressalentes da Marinha do Brasil, no intuito de aprimorar aquela cadeia de suprimentos, buscando, naquelas tecnologias, solução para as dificuldades enfrentadas pela Esquadra do Brasil. / [en] The dynamism of markets has been intensifying by the globalization, the technological advances and the social changes. Consequently, companies need to adapt timely to remain competitive, or may disappear. In this context, disruptive innovations are becoming more frequent. This is the case of additive manufacturing, popularly known as 3D printing. These are technologies with disruptive potential that goes beyond the production paradigm, influencing logistics, society, markets and multiple sectors, such as health, defense, automotive, civil construction and even food. From this point, this work seeks to verify the disruptive potential of additive manufacturing technologies, starting with the deepening of the knowledge about these technologies. Next, it is analyzed the management of current supply chains and the implications of additive manufacturing technologies on supply chain management. Finally, the study confronts the disruptive potential of additive manufacturing with the Brazilian Navy s supply chain of spare parts, in order to improve that supply chain, searching solutions to the difficulties faced by the Brazilian Fleet in those technologies.

Este trabalho objetiva o estudo da avaliação de desempenho de partes de controle de circuitos integrados, em relação ao consumo de área em silício e atraso de propagação de sinais. Para a implementação são adotados dois diferentes estilos de leiaute (PLA e gate matrix). Para ambos os casos foi utilizado um conjunto único de regras de projeto. A análise dos circuitos visando implementação com PLA 6 é feita com base em estimativas de área e atraso deste, sendo definidas as suas células básicas. Para gate matrix, é feita a síntese de leiaute com um gerador automático de leiaute para circuitos em lógica aleatória e o atraso é estimado por modelo simplificado. A avaliação elétrica para calcular o atraso dos sinais é baseada em modelos simplificados de timing, previamente estudados, que levam em conta elementos parasitas das redes de transistores. São analisadas partes de controle de sistemas reais e máquinas de estados finitos hipotéticas. O trabalho visa propor a melhor estratégia de implementação, através da previsão do desempenho dos circuitos, em função do tamanho e complexidade (em número de portas e sinais de interface) do circuito. / The subject of this work is the performance analysis of control parts of integrated circuits, as a function of silicon area and signals propagation delay. Two different layout styles are used for implementation (PLA and gate matrix). Both of them use the same design rules. The analysis of the circuits implemented with PLA is based on area and delay estimation, with the basic cells already defined. For gate matrix, the layout synthesis is made with an automatic layout generator for random logic circuits and the delay is estimated by simplified models. The electrical evaluation to compute the delay signal is based on simplified timing models, previously studied, taking into account parasitic elements of the transistor networks. Control parts of real systems and finite state machines are analysed. This work aims to select the best implementation strategy, based on performance estimation, as a function of the size and complexity (gates and interface signals) of the circuit.