We consider fast computation methods for simulation of dynamics of a collection of particles dispersed in an unbounded Stokesian suspension. Stokesian suspensions are of great practical interest in the manufacturing and processing of various commercial products. The most popular dynamic simulation method for these kind of suspensions was developed by Brady and Bossis (Brady and Bossis [1988]). This method uses a truncated multipole expansion to represent the fluid traction on particle surfaces. The hydrodynamic interactions in Stoke-sian suspension are long ranged in nature, resulting in strong coupled motion of all particles. For an N particle system, this method imposes an O(N3) computational cost, thus posing limitations to the number of particles that may be simulated. More recent methods (Sierou and Brady [2001], Scintilla, Darve and Shaqfeh [2005]) have attempted to solve this problem using Particle Mesh Ewald summation techniques by distributing the moments on a grid and using Fast Fourier Transform algorithms, resulting in an O(N log N) computational cost. We review these methods and propose a version that we believe is some-what superior. In the course of this study, we have identified and corrected errors in previous studies that maybe of some importance in determining the bulk properties of suspensions. Finally, we show the utility of our method in determining certain properties of suspensions and compare them to existing analytical results for the same.

Made available in DSpace on 2017-06-01T18:18:09Z (GMT). No. of bitstreams: 1 dissertacao_jose_adelmy.pdf: 831223 bytes, checksum: 7694339884ad14bc6bf49eeeed5452b9 (MD5) Previous issue date: 2011-09-19 / It aims to demonstrate that the prision s civilian judicial depositary infidel remains possible in Brazil, even with the ratification of the American Convention on Human Rights 1969. The aim is to study the legal nature of each type of deposit and, from this theoretical framework, to assess the hypothesis that the depositary has no legal contractual nature, but of public law, not getting involved with running the debt, nor with no other element of private law, the burden may fall on the lender itself or on the third. In this sense, the prison's legal depository for debt would not be unfaithful, but as a result of contempt revealed the breach of the procedural costs of public law respectively taken before the judge of performance and are not covered by the ban established by that international standard . On the other hand, analyzes the conflict between fundamental rights involving individual liberty and the guarantees of access to justice and effective judicial protection, concluding that the old criteria of hermeneutic solution of antinomies are insufficient to examine the question, but be given a proper constitutional interpretation in each case with footstool on the principle of proportionality. Be seen, too, hermeneutics and linguistically, the legislative reference and each of the judicial precedent of stare decisis n. 25 of the Brazilian Supreme Court, verifying that the conflict was apparent only in the jurisprudential core of the confrontation between the rights of liberty and property, muddying up the investigative eye on the tension that decision scoresheet, as drafted, gives rise to comes to guaranteeing access to justice and effective judicial protection. Thus, we conclude that no binding precedent n. 25 needs to be reviewed by the Supreme Court, and until that happens, it is necessary that an interpretation suited to its constitutional drafting in order to restrict their destination only to depository contract, not reaching the legal custodians / Objetiva-se demonstrar que a prisão civil do depositário judicial infiel continua sendo possível no Brasil, mesmo em face da ratificação da Convenção Americana de Direitos Humanos de 1969. Busca-se estudar a natureza jurídica de cada espécie de depósito e, a partir desse referencial teórico, aferir-se que a hipótese do depositário judicial não possui índole contratual, mas de direito público, não se envolvendo com a dívida em execução, nem com nenhum outro elemento de direito privado, podendo o encargo recair sobre o próprio credor ou sobre terceiro. Nesse sentido, a prisão do depositário judicial infiel não seria por dívida, mas como decorrência do desacato (contempt) revelado pelo descumprimento dos encargos processuais de direito público por si assumidos perante o juiz da execução, não estando abrangida pela proscrição estabelecida por aquela norma internacional. Por outro lado, analisa-se o conflito de direitos fundamentais envolvendo a liberdade individual e as garantias de acesso à justiça e da efetividade da tutela jurisdicional, concluindo-se que os velhos critérios hermenêuticos de solução de antinomias são insuficientes ao exame da questão, devendo ser dada uma interpretação constitucional adequada em cada caso concreto com supedâneo no princípio da proporcionalidade. Analisa-se, também, hermenêutica e linguisticamente, a referência legislativa e cada um dos precedentes judiciais da súmula vinculante n. 25 do Supremo Tribunal Federal, verificando-se que o conflito foi apreciado jurisprudencialmente apenas sob o âmago do confronto entre os direitos de liberdade e de propriedade, turvando-se o olhar investigativo sobre a tensão que aquela decisão sumular, tal como redigida, enseja em relação às garantias de acesso à justiça e de efetividade da tutela jurisdicional. Desse modo, conclui-se que a súmula vinculante n. 25 precisa ser revisada pelo STF, e, até que isso aconteça, impõe-se que seja dada uma interpretação constitucional adequada à sua redação, a fim de se restringir sua destinação apenas aos depositários contratuais, não alcançando os depositários judiciais

Made available in DSpace on 2017-06-01T18:18:11Z (GMT). No. of bitstreams: 1 dissertacao_saulo_medeiros.pdf: 8392995 bytes, checksum: 7ebb27c6fb8c324a022b70e074f30cc3 (MD5) Previous issue date: 2011-10-26 / This dissertation presents an analysis of the jurisprudence of the Brazilian s Supreme Court inserted in the binding precedent number four as a legal and economic perspective of the labor relations. That binding precedent declared that, except in cases provided for in the Constitution, the minimum salary couldn't be used as the index base for calculating benefit of a public servant or employee, or be replaced by judicial decision. From this perspective, is forbidden to use the minimum salary as a basis for calculating the additional by unhealthy labor against the labor law and the labor jurisprudence hitherto existing. This study aims to remake the building process of constitutional jurisprudence binding about labor questions and brought to the center of legal debate elements of the economic situation. For this purpose, it was made the historical evolution of the minimum salary in Brazil for the employers to enable to identify its influence on investment decisions in a neoliberal and globalized economic environment. With the result obtained this study pretend to verify how much the jurisprudence can be utilized as collateral instrument in the businesses and find out the negative effects over the social rights of the workmen / Esta dissertação apresenta uma análise da jurisprudência do Supremo Tribunal Federal consubstanciada na súmula vinculante n.º 4 sob uma perspectiva jurídico-econômica das relações de trabalho. A súmula vinculante n.º 4 do Supremo Tribunal Federal declarou que, salvo casos previstos na Constituição, o salário mínimo não pode ser usado como indexador de base de cálculo de vantagem de servidor público ou de empregado, nem ser substituído por decisão judicial. Sob tal perspectiva, foi proibida a utilização do salário mínimo como base de cálculo do adicional de insalubridade, em confronto com a legislação trabalhista e com a jurisprudência até então sedimentada. Este estudo pretende refazer o processo de construção da jurisprudência constitucional vinculante em matéria trabalhista trazendo para o centro da discussão jurídica elementos de conjuntura econômica. Para tanto, fez-se a evolução do custo real do valor do salário mínimo brasileiro, a fim de possibilitar a identificação da sua influência nas decisões de investimento num cenário econômico neoliberal e globalizado. A partir deste dado, buscou-se apreender em que grau a jurisprudência tem sido utilizada como instrumento de segurança às relações econômicas e a eventual consequência frente à necessidade de garantir-se a melhoria da condição social dos trabalhadores

This project studied two different ways of imposing boundary conditions weakly with the finite difference summation-by-parts (SBP) operators. These operators were combined with the boundary handling methods of simultaneous-approximation-terms (SAT) and the Projection to impose homogeneous Neumann and Dirichlet boundary conditions. The convergence rate of both methods was analyzed for different boundary conditions for the one-dimensional (1D) Schrödinger equation, without potential, which resulted in both methods performing similarly. A multi-block discretization was then implemented and different combinations of SBP-SAT and SBP-Projection were applied to impose inner boundary conditions of continuity between the blocks. A convergence study of the different methods of imposing the inner BC:s was conducted for the 1D Schrödinger equation without potential. The resulting convergence was the same for all methods and it was concluded that they performed similarly. Methods involving SBP-Projection had the slight advantage of faster computation time. Finally, the 1D Gross-Pitaevskii equation (GPE) and the 1D Schrödinger equation were analyzed with a step potential. The waves propagating towards the potential barrier were in both cases partially transmitted and partially reflected. The waves simulated with the Schrödinger equation dispersed, while the solitons simulated with the GPE kept their shape due to the equations reinforcing non-linear term. The bright soliton was partly transmitted and partly reflected. The dark soliton was either totally reflected or totally transmitted.

In order to understand how the brain functions, under normal as well as pathological conditions, it is important to study the mechanisms underlying information integration. Depending on the nature of an input arriving at a synapse, different strategies may be used by the neuron to integrate and respond to the input. Naturally, if a short train of high-frequency synaptic input arrives, it may be beneficial for the neuron to be equipped with a fast mechanism that is highly sensitive to inputs on a short time scale. If, on the contrary, inputs arriving with low frequency are to be processed, it may be necessary for the neuron to possess slow mechanisms of integration. For example, in certain working memory tasks (e. g. delay-match-to-sample), sensory inputs may arrive separated by silent intervals in the range of seconds, and the subject should respond if the current input is identical to the preceeding input. It has been suggested that single neurons, due to intrinsic mechanisms outlasting the duration of input, may be able to perform such calculations. In this work, I have studied a mechanism thought to be particularly important in supporting the integration of low-frequency synaptic inputs. It is mediated by a cascade of events that starts with activation of group I metabotropic glutamate receptors (mGlu1/5), and ends with a membrane depolarization caused by a current that is mediated by canonical transient receptor potential (TRPC) ion channels. This current, denoted ITRPC, is the focus of this thesis. A specific objective of this thesis is to study the role of ITRPC in the integration of synaptic inputs arriving at a low frequency, < 10 Hz. Our hypothesis is that, in contrast to the well-studied, rapidly decaying AMPA and NMDA currents, ITRPC is well-suited for supporting temporal summation of such synaptic input. The reason for choosing this range of frequencies is that neurons often communicate with signals (spikes) around 8 Hz, as shown by single-unit recordings in behaving animals. This is true for several regions of the brain, including the entorhinal cortex (EC) which is known to play a key role in producing working memory function and enabling long-term memory formation in the hippocampus. Although there is strong evidence suggesting that ITRPC is important for neuronal communication, I have not encountered a systematic study of how this current contributes to synaptic integration. Since it is difficult to directly measure the electrical activity in dendritic branches using experimental techniques, I use computational modeling for this purpose. I implemented the components necessary for studying ITRPC, including a detailed model of extrasynaptic glutamate concentration, mGlu1/5 dynamics and the TRPC channel itself. I tuned the model to replicate electrophysiological in vitro data from pyramidal neurons of the rodent EC, provided by our experimental collaborator. Since we were interested in the role of ITRPC in temporal summation, a specific aim was to study how its decay time constant (τdecay) is affected by synaptic stimulus parameters. The hypothesis described above is supported by our simulation results, as we show that synaptic inputs arriving at frequencies as low as 3 - 4 Hz can be effectively summed. We also show that τdecay increases with increasing stimulus duration and frequency, and that it is linearly dependent on the maximal glutamate concentration. Under some circumstances it was problematic to directly measure τdecay, and we then used a pair-pulse paradigm to get an indirect estimate of τdecay. I am not aware of any computational model work taking into account the synaptically evoked ITRPC current, prior to the current study, and believe that it is the first of its kind. We suggest that ITRPC is important for slow synaptic integration, not only in the EC, but in several cortical and subcortical regions that contain mGlu1/5 and TRPC subunits, such as the prefrontal cortex. I will argue that this is further supported by studies using pharmacological blockers as well as studies on genetically modified animals. / QC 20101005

This paper describes simulations of the generalized modified Benjamin-Bona-Mahony (BBM) equation, using finite difference methods (FDM). Well-posed boundary conditions (BCs) as well as stable semi-discrete approximations are derived using summations-by-parts (SBP) operators combined with the projection method. For time integration, explicit Runge-Kutta 4 (RK4) is used, as well as SBP-SAT, which discretizes the temporal domain using SBP operators and imposes initial conditions using simultaneous approximation term (SAT). These time-marching methods are evaluated and compared in terms of accuracy and computing times, and soliton-boundary interaction is studied. It is shown that SBP-SAT time-marching perform well and is more suitable than RK4 for this type of non-linear, dispersive problem. Generalized summation-by-parts (GSBP) time-marching perform particularly well, due to high accuracy with few solution points.

The computation of the Coulomb potentials and forces in charged particle systems under 3d-periodic boundary conditions is possible in an efficient way by utilizing the Ewald summation formulas and applying the fast Fourier transform (FFT). In this paper we consider the particle-particle NFFT (P2NFFT) approach, which is based on the fast Fourier transform for nonequispaced data (NFFT) and compare the error behaviors regarding different window functions, which are used in order to approximate the given continuous charge distribution by a mesh based charge density. Typically B-splines are applied in the scope of particle mesh methods, as for instance within the well-known particle-particle particle-mesh (P3M) algorithm. The publicly available P2NFFT algorithm allows the application of an oversampled FFT as well as the usage of different window functions. We consider for the first time also an approximation by Bessel functions and show how the resulting root mean square errors in the forces can be predicted precisely and efficiently. The results show that, if the parameters are tuned appropriately, the Bessel window function is in many cases even the better choice in terms of computational costs. Moreover, the results indicate that it is often advantageous in terms of efficiency to spend some oversampling within the NFFT while using a window function with a smaller support.

In this paper we describe a parallel algorithm for calculating nonequispaced fast Fourier transforms on massively parallel distributed memory architectures. These algorithms are implemented in an open source software library called PNFFT. Furthermore, we derive a parallel fast algorithm for the computation of the Coulomb potentials and forces in a charged particle system, which is based on the parallel nonequispaced fast Fourier transform. To prove the high scalability of our algorithms we provide performance results on a BlueGene/P system using up to 65536 cores.

In this report, we study how finite differences can be used to simulate acoustic wave propagation originating from a point source in the ocean using the Helmholtz equation. How to model sediment layers and the vast size of the ocean is studied in particular. The finite differences are implemented with summation by parts operators with boundary conditions enforced with simultaneous approximation terms and projection. The numerical solver is combined with the WaveHoltz method to improve the performance. Sediment layers are handled with interface conditions and the domain is artificially expanded using absorbing layers. The absorbing layer is implemented with an alternative approach to the super-grid method where the domain expansion is accomplished by altering the wave speed rather than with coordinate transformations. To isolate these issues, other parameters such as variations in the ocean floor are neglected. With this simplification, cylindrical coordinates are used and the angular variation is assumed to be zero. This reduces the problem to a quasi-three-dimensional system. We study how the parameters of the alternative absorbing layer approach affect its quality. The numerical solver is verified on several test cases and appears to work according to theory. Finally, a semi-realistic simulation is carried out and the solution seems correct in this setting.

The computation of the Coulomb potentials and forces in charged particle systems under 3d-periodic boundary conditions is possible in an efficient way by utilizing the Ewald summation formulas and applying the fast Fourier transform (FFT). In this paper we consider the particle-particle NFFT (P2NFFT) approach, which is based on the fast Fourier transform for nonequispaced data (NFFT) and compare the error behaviors regarding different window functions, which are used in order to approximate the given continuous charge distribution by a mesh based charge density. Typically B-splines are applied in the scope of particle mesh methods, as for instance within the well-known particle-particle particle-mesh (P3M) algorithm. The publicly available P2NFFT algorithm allows the application of an oversampled FFT as well as the usage of different window functions. We consider for the first time also an approximation by Bessel functions and show how the resulting root mean square errors in the forces can be predicted precisely and efficiently. The results show that, if the parameters are tuned appropriately, the Bessel window function is in many cases even the better choice in terms of computational costs. Moreover, the results indicate that it is often advantageous in terms of efficiency to spend some oversampling within the NFFT while using a window function with a smaller support.