Two level homogenization of flows in deforming double porosity media: biot-darcy-brinkman model

We present the two-level homogenization of the flow in a deformable double-porous structure described at two characteristic scales: the higher level porosity associated with the mesoscopic structure is constituted by channels in an elastic skeleton which is made of a microporous material. The macroscopic model is derived by the asymptotic analysis of the viscous flow in the heterogeneous structure characterized by two small parameters. The first level upscaling yields a Biot continuum model coupled with the Stokes flow. The second step of the homogenization leads to a macroscopic flow model which attains the form of the Darcy-Brinkman flow model coupled with the deformation of the poroelastic continuum involving the effective parameters given by the microscopic and the mesoscopic porosity features

Computer modelling as a basis for forestry and wood processing equipment design

Today, the problem of finding and using computer-aided design systems as a modelling tool is acute. The aim of the study is to review computer modelling tools for the design of forestry and wood processing equipment. To achieve this objective, the possibilities of using different software packages have been described, examples of experiments with computer models and their results have been considered, and conclusions about the possibility of using utilities to solve design problems in the timber industry have been drawn. Based on the results of the study, it can be concluded that computer modelling provides certain capabilities and can be used as a tool for design in the forest industry

Structural dynamics within the open-source package SfePy

Diplomska naloga obravnava modalno analizo po metodi končnih elementov struktur s pomočjo odprtokodnega paketa SfePy. Najprej so predstavljene teoretične osnove in splošen postopek reševanja po metodi končnih elementov. V nadaljevanju je predstavljena uporaba paketa SfePy. Skozi nalogo so rezultati pridobljeni s SfePy primerjani z rezultati komercialnega orodja Abaqus. Naloga prikaže, da je odprtokodni paket SfePy pri modalni analizi po metodi končnih elementov učinkovit in se lahko primerja s komercialnimi orodji.This diploma thesis discusses modal analysis of structures using finite element method within the open-source package SfePy. Initially, the theorethical background and general principles of finite element method are given. The work is continued with the instructions on how to use the package SfePy. Through the thesis, the comparison between the open-source package SfePy and the commercial software Abaqus is made. Thesis shows that open-source package SfePy could be powerful at solving modal analysis problems and also comparable to the commercial software

Estudio comparativo de diferentes solvers en un software de elementos finitos

El presente Trabajo Fin de Grado es un estudio comparativo entre distintos solvers aplicables en un software de Elementos Finitos, HOFEM (High Order Finite Element Method) desarrollado en la Universidad Carlos III de Madrid. A través del encapsulamiento de código FORTRAN disponible, se espera, mediante una interfaz del lenguaje de programación Python obtener la solución de un sistema de ecuaciones proporcionado por las matrices obtenidas a partir de HOFEM, para, posteriormente, entregar esa solución al software de HOFEM para la obtención de la solución del problema en la fase de post-proceso. Debido a diferentes problemas obtenidos durante el proceso del encapsulado del código FORTRAN, y dado el tiempo limitado de ejecución del proyecto, se optó por otra vía de acción, implementando una interfaz basada en el paso de mensajes entre lenguajes, consistente en escribir las matrices a disco, para finalmente realizar un Estudio Comparativo entre los diferentes solvers utilizados.This Final Project is a comparative study between different solvers applicable to a Finite Element software, HOFEM (High Order Finite Element Method) developed at the Carlos III University of Madrid. Through the encapsulation of available FORTRAN code, it is expected, through an interface of the programming language Python to obtain the solution of a system of equations provided by the matrix obtained from HOFEM to, then deliver that solution to HOFEM software to obtain the solution of the problem in the step of post-processing. Due to various problems obtained during the encapsulation of FORTRAN code, and given the limited Project execution time, we chose another course of action, implementing an interface based on message passing between languages, consisting in writing matrices to disk, to finally make a comparative study between the different solvers used.Ingeniería de Sistemas de Comunicacione

Spin Transport in Lateral Spin Valves

This thesis outlines the construction of an ultra-high-vacuum angle-deposition system, developed specifically for the fabrication of lateral spin valves (LSVs). The thesis then proceeds to answer two important questions: what causes the loss of spin accumulation at low temperatures seen in LSVs? and how do spin currents interact in multi-terminal circuits? Through a double-dose electron beam lithography and angle-deposition technique, Cu/Py LSVs are fabricated and shown to have transparent contacts. By means of a DC injection method, the nonlocal voltage is measured as a function of injection current, magnetic field and temperature, enabling contributions from heat and spin currents to be isolated. The spin diffusion length is obtained from LSVs fabricated with Cu containing magnetic impurities $<$1 ppm and $\sim$4 ppm. Temperature dependent charge and spin transport measurements provide evidence linking the presence of the Kondo effect in Cu to the suppression of the spin diffusion length below 30 K. The spin-flip probability for magnetic impurities is found to be 34\%, orders of magnitude larger than other scattering mechanisms. This is extended to explain similar observations in the spin accumulation. These measurements establish the dominant role of Kondo scattering in spin-relaxation, even in low concentrations of order 1 ppm. Finally, a new multi-terminal LSV (MTLSV) is fabricated and the interaction between two spin currents is investigated. Fan-out and fan-in measurements are performed, demonstrating that spin currents separate and combine at junctions in a circuit with magnitudes dictated by the spin resistance of the conduction channels. It is also shown that two spin currents of opposite polarity will cancel out. Whether Kirchhoff's law holds for spin currents is discussed and this chapter helps lay the ground work for spin current based circuits and computation

Implementação computacional da solução de problemas térmicos e mecânicos pelo Método dos Elementos Finitos em Python

Trabalho de conclusão de curso (graduação)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2016.Esse trabalho tem como objetivo a apresentação da metodologia de solução computacional utilizando o método dos elementos finitos para problemas em engenharia relacionados à transferência de calor e à mecânica. As soluções computacionais, ou aproximadas, são obtidas por ferramentas de discretização sendo o Método dos Elementos Finitos e o Método das Diferenças Finitas alguns exemplos destes. O Método dos Elementos Finitos atualmente representa o padrão na indústria padrão solução de modelos em mecânica e em outros ramos da engenharia, isso devido à sua simplicidade de implementação e versatilidade. O modelo matemático para descrever o comportamento elástico de sólidos, teoria de estruturas linear e transferência de calor são apresentados juntamente com os respectivos tratamentos para o procedimento numérico e posterior implementação computacional utilizando a linguagem de programação Python. Resultados dos programas implementados, elastopy, sapy e diffuspy, utilizando elementos planos de quatro nós são verificados pela solução de problemas simples com solução analítica. Alguns exemplos são mostrados para demonstrar as capacidades dos programas desenvolvidos. As rotinas de cálculo e o pós processamento são efetuados na linguagem de programação Python que é uma linguagem de alto nível, de simples sintaxe e de fácil utilização.This work aims to present a well known methodology for computational solutions using the Finite Element Method in engineering problems. Computational solutions, or approximations, are obtained by means of discretization which includes the Finite Element Method and the Finite Differences Method. The Finite Element Method represents the standard tool for solving problems in mechanics and other engineering fields, mainly due its simplicity approach and versatility. The mathematical model for linear elastic solids, linear elastic structures and heat transfer problems are presented together with their treatment for a numerical solution and also computational implementation using Python programming language. Results from the solvers implemented, elastopy, sapy and diffuspy, using plane quadrilateral and two dimensional frame elements are verified through comparisons with analytical solution for simple problems. Examples are presented to demonstrated the libraries capabilities. The computer programs and post processing of results are all made with the Python programming language which is a high level scripting language with a simple syntax and is easy to use