Nano-scale machining, or Nanomachining is a hybrid process in which the total thermal energy necessary to remove atoms from a work-piece surface is applied from external sources. In the current study, the total thermal energy necessary to remove atoms from a work-piece surface is applied from two sources: (1) localized energy from a laser beam focused to a micron-scale spot to preheat the work-piece, and (2) a high-precision electron-beam emitted from the tips of carbon nano-tubes to remove material via evaporation/sublimation. Macro-to-nano scale heat transfer models are discussed for understanding their capability to capture and its application to predict the transient heat transfer mechanism required for nano-machining. In this case, thermal transport mechanism during nano-scale machining involves both phonons (lattice vibrations) and electrons; it is modeled using a parabolic two-step (PTS) model, which accounts for the time lag between these energy carriers. A numerical algorithm is developed for the solution of the PTS model based on explicit and implicit finite-difference methods. Since numerical solution for simulation of nanomachining involves high computational cost in terms of wall clock time consumed, performance comparison over a wide range of numerical techniques has been done to devise an efficient numerical solution procedure. Gauss-Seidel (GS), successive over relaxation (SOR), conjugate gradient (CG), d -form Douglas-Gunn time splitting, and other methods have been used to compare the computational cost involved in these methods. Use of the Douglas-Gunn time splitting in the solution of 3D time-dependent heat transport equations appears to be optimal especially as problem size (number of spatial grid points and/or required number of time steps) becomes large. Parallel computing is implemented to further reduce the wall clock time required for the complete simulation of nanomachining process. Domain decomposition with inter-processor communication using Message Passing Interface (MPI) libraries is adapted for parallel computing. Performance tuning has been implemented for efficient parallelization by overlapping communication with computation. Numerical solution for laser source and electron-beam source with different Gaussian distribution are presented. Performance of the parallel code is tested on four distinct computer cluster architecture. Results obtained for laser source agree well with available experimental data in the literature. The results for electron-beam source are self-consistent; nevertheless, they need to be validated experimentally.

This document describes radar propagation modelling using split step parabolic wave equation (PWE) method. A computer program using Fourier split-step (FSS) marching technique is developed for predicting the electromagnetic wave propagation in troposphere. The program allows specification of frequency, polarization, antenna radiation pattern, antenna altitude, elevation angle and terrain profile. Both staircase terrain modelling and conformal mapping are used to model the irregular terrain. Mixed Fourier transform is used to implement the impedance boundary conditions. The conditions and the limits of different approximations are stated. The propagation code, RPPT (Radar Propagation Prediction Tool) is developed in Matlab 6.0 with a user friendly GUI. Different PWE methods can be selected in RPPT for different applications. The results are presented as one-way propagation factor and path loss in decibels versus range.Comparisons are made between different PWE techniques and other propagation models to demonstrate the ability and accuracy of the present model to accommodate various situations. It is assumed that the reader is familiar with the tropospheric propagation.

Many problems in continuum mechanics, especially in the theory of elastic materials, lead to nonlinear partial differential equations. The nonconvexity of their underlying energy potential is a challenge for mathematical analysis, since convexity plays an important role in the classical theories of existence and regularity. In the last years one main point of interest was to develop techniques to circumvent these difficulties. One approach was to use different notions of convexity like quasi-- or polyconvexity, but most of the work was done only for static (time independent) equations. In this thesis we want to make some contributions concerning existence, regularity and numerical approximation of nonconvex dynamical problems.

Made available in DSpace on 2015-03-26T13:45:35Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1898009 bytes, checksum: 7ee3890dce9bee7dd59b31ebd52ed3a0 (MD5) Previous issue date: 2012-07-16 / Fundação de Amparo a Pesquisa do Estado de Minas Gerais / In this work, we study the graphs as invariants of stable Gauss maps from closed surfaces embedded in R3. We study the problem of realization of graphs by stable Gauss maps, emphasizing also cusp number of these maps. / Neste trabalho, estudamos os grafos como invariantes de aplicações de Gauss estáveis de superfícies fechadas mergulhadas em R3. Abordamos o problema de realização de grafos por aplicações de Gauss estáveis, enfatizando também o número de cúspides destas aplicações.

Dans cette thèse, on s'intéresse aux systèmes dynamiques holomorphes dépendants de paramètres. Notre objectif est de contribuer à une théorie de la stabilité et des bifurcations en plusieurs variables complexes, généralisant celle des applications rationnelles fondées sur les travaux de Mané, Sad, Sullivan et Lyubich. Pour une famille d'applications d'allure polynomiale, on prouve l'équivalence de plusieurs notions de stabilité, entre autres une version asymptotique du mouvement holomorphe des cycles répulsifs et d'un sous-ensemble de l'ensemble de Julia de mesure pleine. Cela peut etre considéré comme une généralisation mesurable à plusieurs variables du célèbre lambda-lemme et nous permet de dégager un concept cohérent de stabilité dans ce cadre. Après avoir compris les bifurcations holomorphes, on s'intéresse à la continuité Hausdorff des ensembles de Julia. Nous relions cette propriété à l'existence de disques de Siegel dans l'ensemble de Julia, et donnons un exemple de ce phénomène. Finalement, on étudie la continuité du point de vue de l'implosion parabolique. Nous établissons un théorème de Lavaurs deux-dimensionel, ce qui nous permet d'étudier des phénomènes de discontinuité pour des perturbations d'applications tangentes à l'identité. / In this thesis we study holomorphic dynamical systems depending on parameters. Our main goal is to contribute to the establishment of a theory of stability and bifurcation in several complex variables, generalizing the one for rational maps based on the seminal works of Mané, Sad, Sullivan and Lyubich. For a family of polynomial like maps, we prove the equivalence of several notions of stability, among the others an asymptotic version of the holomorphic motion of the repelling cycles and of a full-measure subset of the Julia set. This can be seen as a measurable several variables generalization of the celebrated lambda-lemma and allows us to give a coherent definition of stability in this setting. Once holomorphic bifurcations are understood, we turn our attention to the Hausdorff continuity of Julia sets. We relate this property to the existence of Siegel discs in the Julia set, and give an example of such phenomenon. Finally, we approach the continuity from the point of view of parabolic implosion and we prove a two-dimensional Lavaurs Theorem, which allows us to study discontinuities for perturbations of maps tangent to the identity.

In this thesis report for Dalarna University in Borlange and Absolicon company the study of a possibility to add an array of concentrating solar collectors to a Torsång district heating system was done. The whole idea of this work was to make a simulation of this kind of system, trying to get 15-20% of solar fraction, and make an economical evaluation. At the same time, another goal was to make two comparisons: between concentrating and flat-plate collector in the same system, and between two tools for collector analysis – Polysun and Absolicon tool, based on TRNSYS, which was designed to estimate the output of the collector for a certain temperature, without any load. During the study, the analysis of the simulating tools was made and the combination of those two tools was used. Using long iteration cycles, involving changing the field layout, number of collectors and distance between collector rows in flat-plate collector case, both types of collectors were analyzed. The method of the analysis was to get an equal output of the field and see the differences, which appear while using different collector types.

Neste trabalho estudamos problemas de evolução da forma \'d \' úpsilond\' SUP. \' úpsilon\' t\'\' + A (t,\'úpsilon\' )\' úpsilon\' = f(t,\'úpsilon\' ) \'úpsilon\'(0) = \' \' úpsilon\' IND. 0\' \', em um espaço de Banach X onde A(t, \'úpsilon\' ) : D \'está contido em\' X \'SETA \' X é um operador linear fechado e setorial para cada (t, \' úpsilon\' ). Quando o operador A(t, \' úpsilon\' ) é independente de \' úpsilon\' , isto é, A(t, \' úpsilon\') = A(t), mostramos um resultado de exitência, unicidade, continuidade relativamente a dados iniciais e continuação para o caso em que a não linearidade f tem crescimento crítico. Se A(t, \'úpsilon\' ) depende do tempo e do estado, então mostramos um resultado de existência, unicidade com f tendo crescimento sub-crítico semelhante aos resultados encontrados em [7, 33] / In this work we study initial value problems of the form \' d \'úpsilon\' SUP. dt + A (t, \'úpsilon\')\'úpsilon\' = f (t, \'úpsilon\' ) \' úpsilon\' (0) = \' úpsilon IND.0\', in a Banach space X where A(t,\' úpsilon\' ) : D \' this contained \' X \' ARROW\' X is an unbounded closed linear operator which is sectorial for each (t,\' úpsilon\' ). When the operator family A(t, \' úpsilon\' ) is independent of \' úpsilon\' , that is, A(t, \' úpsilon\' ) = A(t), we show a result on local well posedness and continuation with the nonlinearity f growing critically. If A(t,\' úpsilon\' ) depends on the time t and on the state \' úpsilon\' we show a local well posedness and continuation result that is similar to the result found in [7, 33]

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Esta tese trata do controle nulo local de um problema de fronteira-livre para a equaÃÃo do calor semilinear 1D com controles distribuÃdos (apoiado localmente no espaÃo) ou controles de fronteira (atuando em x = 0). provamos que, se o tempo final T à fixado e o estado inicial à suficientemente pequeno, existe controles que dirigem o estado exatamente para descansar no tempo t = T. AlÃm disso, analisamos a controlabilidade nulo de um sistema nÃo-linear 1D que modela a interaÃÃo de um fluido e sua fronteira. O fluido à governado pela equaÃÃo de Burgers viscosa e os controles distribuÃdos. Por Ãltimo, vamos lidar com o sistema de Navier-Stokes e Boussinesq 3D, definido em um cubo. Neste contexto, provamos um resultado sobre a sua controlabilidade aproximada global por meio de controles de fronteira que atuam em alguma parte da faces do cubo. / This Thesis deals with the local null control of a free-boundary problem for the 1D semilinear heat equation with distributed controls (locally supported in space) or boundary controls (acting at x = 0). we prove that, if the final time T is fixed and the initial state is sufficiently small, there exists controls that drive the state exactly to rest at time t = T. Furthermore, we analyze the null controllability of a 1D nonlinear system which models the interaction of a fluid and its boundary. The fluid is governed by the viscous Burgers equation and the distributed controls. Lastly, we deal with the 3D Navier-Stokes and Boussinesq system, posed in a cube. In this context, we prove a result concerning its global approximate controllability by means of boundary controls which act in some part of cube faces.

A presente dissertação tem como objetivo estudar o livro de estórias Luuanda, de José Luandino Vieira, mais especificamente a passagem denominada por muitos estudiosos como a parábola do cajueiro, situada na segunda estória, e por meio da identificação e análise de possíveis elementos parabólicos, buscaremos identificar a função dessa passagem para a compreensão da obra como um todo. Partindo da conceituação das parábolas neotestamentárias e de suas funções didática e confrontativa, nossa intenção é demonstrar que a passagem do cajueiro constitui-se como o elo entre as três estórias, pois promove a quebra de um comportamento passivo e conformista, descrito na primeira narrativa, além de estabelecer um princípio de reflexão e um ato de autoconfronto, na segunda narrativa, cujo resultado se materializará no comportamento das personagens da terceira estória. / The present dissertation aims to study the book of estórias Luuanda, written by José Luandino Vieira, more specifically, a passage named by many scholars as cashew parable, found out in the second narrative, and through identification and analysis of possible parabolic elements, we intend to identify the function of that passage to understand the whole book. Bearing in mind conceptions and functions of the New Testament parables, our intention is demonstrate that the cashew passage is the link between the three narratives of the book, for it promotes a break of a passive and conformist behavior, found out in the first narrative, moreover it also promotes a beginning of reflective and a self confrontation act, in the second narrative, which result will materialize itself as a new behavior in the characters in the third narrative.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-22T13:22:56Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese-Ricardo-Castillo.pdf: 814247 bytes, checksum: 0f3a9a10694a3324cae6464d5e29a2f6 (MD5) / Made available in DSpace on 2016-07-22T13:22:56Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese-Ricardo-Castillo.pdf: 814247 bytes, checksum: 0f3a9a10694a3324cae6464d5e29a2f6 (MD5) Previous issue date: 2016-02-17 / Estudamos condições de existência e não existência de soluções globais para um sistema acoplado de equações parabólicas não lineares e para um problema parabólico com expoente variável. Em ambos os casos, consideramos um domínio arbitrário de RN com fronteira regular e com condições de Dirichlet na fronteira. Como consequência destes resultados é possível determinar o coe ciente de Fujita destes problemas. / We study conditions for existence and non existence of global solutions for a nonlinear coupled parabolic systems and for parabolic problem with variable exponent. In both cases, we consider an arbitrary domain of RN with smooth boundary and Dirichlet condition on the boundary. As consequence of these results is possible to determinate the Fujita's exponent of ones.