Made available in DSpace on 2014-06-12T15:54:54Z (GMT). No. of bitstreams: 2 arquivo9423_1.pdf: 6736856 bytes, checksum: 7f03b32b2fa913297725321598c5ecee (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2012 / Nos últimos 40 anos a Internet se tornou um componente central para o comércio eletrônico internacional, comunicações, e para o desenvolvimento técnico e científico. Inicialmente as pesquisas relacionadas à Internet se focavam em melhoramentos na velocidade de transmissão de dados, capacidade e cobertura geográfica. Atualmente medição, modelagem e análise em redes de computadores, particularmente classificação de tráfego, tornaram-se um ponto crucial para manutenção do funcionamento da rede. Isto se deve principalmente ao crescimento exponencial das redes de computares em termos de tamanho, complexidade e diversidade de serviços. Neste contexto, sistemas de Deep Packet Inspection (DPI) se tornaram um elemento importante para medição de tráfego, já que classificação de aplicações baseada em portas caiu em desuso devido ao tunelamento de protocolos e uso indevido de portas padrões, por exemplo, softwares P2P que usam portas não bloqueadas para burlar regras de firewalls. Tradicionalmente, sistemas de DPI classificavam tráfego usando técnicas de string matching, i.e., as assinaturas de aplicações eram representadas por strings (cadeias de caracteres). Dessa maneira o procedimento de busca de padrões se dava através da inspeção da carga útil dos pacotes a procura dessas strings. String matching funciona bem para padrões simples, porém falha ao descrever padrões mais complexos, e.g., padrões com tamanho variável. Para solucionar este problema, sistemas de DPI têm substituído assinaturas representadas com strings por padrões descritos através de expressões regulares. Embora mais precisos, sistemas de DPI demandam maior poder computacional e geralmente não escalam bem conforme as velocidades dos enlaces aumentam. Este fato abriu espaço para várias pesquisas relacionadas à otimização de tais sistemas. Aproveitando este espaço, esta tese propõe um novo modelo de Deterministic Finite Automata (DFA) para casamento de padrões em sistemas DPI, o Ranged Compressed DFA (RCDFA). O RCDFA, junto com três otimizações propostas, atingem níveis de compressão de até 98% em bases de assinaturas bem conhecidas. Além do mais, o RCDFA codificado com um novo layout de memória (ALE) proposto neste trabalho é até 46 vezes mais rápido que os motores de DPI baseados em DFAs tradicionais

This work is a numerical study of Burgers' equation with Robin's boundary conditions. The goal is to determine the behavior of the solutions in the limiting cases of Dirichlet and Neumann boundary conditions. We develop and test two separate finite element and Galerkin schemes. The Galerkin/Conservation method is shown to give better results and is then used to compute the response as the Robin's Boundary conditions approach both the Dirichlet and Neumann boundary conditions. Burgers' equation is treated as a perturbation of the linear heat equation with the appropriate realistic constants. The goal is to determine if the use of the Robin's boundary conditions to approximate Dirichlet and Neumann boundary conditions affords any advantage over schemes that employ only "exact" Dirichlet or Neumann boundary conditions. Our finite element results indicate that solutions using appropriate Robin's boundary conditions approach the same solutions obtained by "exact" Dirichlet or Neumann boundary conditions. This allows us to obtain realistic solutions in some cases where the other schemes had previously failed. / Master of Science

No description available.

This project investigates the heat flow from the rock into ventilating airways by studying various parameters. Two approaches have been used: laboratory measurement of thermal properties to study their variation, and analytic and numerical models to study the effect of these variations on the heat flow. Access to a heat-flux system and special treatment of contact resistance has provided the opportunity to study thermal conductivity as a function of moisture contained in rock specimens. For porous sandstone, tuff, and concretes, thermal conductivity can double when the specimens are soaked; the functional dependence of conductivity on moisture for the first two cases is definitely non-linear. Five previous models for conductivity as a function of porosity are shown not to explain this new phenomenon. A preliminary finite element model is proposed which explains the key features. Other variations of conductivity with applied pressure, location, constituents, weathering or other damage, and anisotropy have been measured. In the second phase of the research, analytical and numerical methods have been employed to consider the effects of the variation in the thermal properties plus the use of insulation on the heat flow from the rock into the ventilated and cooled airways. Temperature measurements taken in drill holes at a local mine provide confirmation for some of the models. Results have been provided in a sensitivity analysis mode so that engineers working on other projects can see which parameters would require more detailed consideration. The thermal conductivity of the rock close to the airways is a key factor in affecting heat loads. Dewatering and the use of insulation, such as lightweight foamed shotcretes, are recommended.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. December 2014. / Let G be a finite group and let r ∈ N. A coloring of G is any mapping : G −→ {1, 2, 3, ..., r}. Colorings of G, and are equivalent if there exists an element g in G such that (xg−1) = (x) for all x in G. A coloring of a finite group G is called symmetric with respect to an element g in G if (gx−1g) = (x) for all x ∈ G. We derive formulae for computing the number of symmetric colorings and the number of equivalence classes of symmetric colorings for some classes of finite groups

2 v. : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (D.E.)--Dept. of Electrical Engineering, University of Adelaide

Thesis (D.E.) - Dept. of Electrical Engineering, University of Adelaide.

In this dissertation, we study four methods for constructing codes and designs from finite groups. The first method was developed by Carmichael and Ernst in the nineteen thirty's. The second method is a generalization of the first one by D.R. Hughes in the nineteen sixty's. These first two methods use t-transitive groups to construct t-designs. The last methods arc two recent techniques developed by J .D. Key and J. Moori (2002). they use primitive finite groups to build l-designs. We will apply these methods to simple groups, and use the incidence matrix of the constructed designs to generate codes. / Thesis (Msc. in Mathematics) North-West University, Mafikeng Campus, 2013

published_or_final_version / Civil and Structural Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Civil and Structural Engineering / Master / Master of Philosophy