http://www.bdtd.uerj.br/handle/1/3679 Mon, 20 Apr 2026 03:49:01 GMT 2026-04-20T03:49:01Z http://www.bdtd.uerj.br/handle/1/25406 Título: Optimizing truss structures with an augmented lagrangian cross-entropy approach Autor: Issa, Marcos Vinicius dos Santos Primeiro orientador: Cunha Junior, Americo Barbosa da Abstract: Otimização estrutural busca projetar estruturas eficientes, minimizando custos, peso ou impacto ambiental. Métodos tradicionais baseados em gradiente e metaheurísticas frequentemente lutam com problemas não convexos devido a ótimos locais e configurações complexas de parâmetros. Em alguns sistemas estruturais, métodos baseados em gradiente podem não ser possíveis de serem usados para otimização estrutural. Esta tese apresenta uma nova estrutura para lidar com o problema de otimização estrutural que emprega o Método de Entropia Cruzada (CE), uma técnica de Monte Carlo para simulação de eventos raros que pode lidar com problemas de otimização não convexos, com método Lagrangiano Aumentado nas restrições, usando o CEopt, um pacote MATLAB desenvolvido para aplicar o CE para desafios de otimização contínua não convexa. O CE é proposto para otimização de dimensão e forma de treliças estruturais que são usadas como testes de benchmark onde se busca minimizar a massa e conformidade. Os valores ótimos encontrados pelo CE são comparados com outros resultados obtidos por um programa quadrático sequencial (SQP), método baseado em gradiente, e um algoritmo genético (GA), uma metaheurística. Os resultados demonstram que o CE oferece uma solução para otimização estrutural que pode ser muito competitiva em termos de precisão e eficiência computacional em comparação com aquelas encontradas por outros métodos de otimização de metaheurísticas. Considerações práticas para implementação efetiva são discutidas. Os resultados mostram a eficiência e a facilidade de uso do método de entropia cruzada, defendendo sua adoção mais ampla para projeto estrutural ideal em cenários não convexos, onde o uso de métodos baseados em gradiente não é eficiente ou mesmo inviável porque pode ser altamente sensível ao chute inicial. Instituição: Universidade do Estado do Rio de Janeiro Tipo do documento: Tese Tue, 10 Dec 2024 00:00:00 GMT http://www.bdtd.uerj.br/handle/1/25406 2024-12-10T00:00:00Z http://www.bdtd.uerj.br/handle/1/24664 Título: Identificação de fases em ligas do sistema Fe-Al-Nb-C por técnicas de caracterização de materiais Autor: Santos, Kellen Venancio dos Primeiro orientador: Peripolli, Suzana Bottega Abstract: The increasing demand for materials with high mechanical strength, thermal stability, and low density has driven the development of advanced metallic alloys for sectors such as the automotive and aerospace industries. Microstructural control is essential, as the presence and distribution of intermetallic phases and precipitates directly influence the material's properties. Therefore, detailed microstructural characterization, using techniques such as Transmission Electron Microscopy (TEM), becomes fundamental, especially for complex alloys such as those in the Fe-Al-Nb-C system. In this work, initial analyses were carried out using Scanning Electron Microscopy (SEM) to evaluate the morphology of the phases and to obtain an overview of the microstructure of the as-received samples. Based on the results obtained, specific regions were selected for the preparation of ultrathin lamellae by Focused Ion Beam (FIB). These lamellae were then analyzed by TEM, with the acquisition of High-Resolution TEM (HRTEM) images, localized chemical analyses via Energy Dispersive X-ray Spectroscopy (EDS), allowing for the semi-quantitative identification of the chemical composition in regions of interest, and interplanar distance measurements aimed at the crystallographic identification of the phases present. This combined approach enabled a comprehensive microstructural investigation, integrating information on morphology, composition, and crystalline structure, allowing for the identification of phases such as kappa carbide (κ) and cementite (Fe₃C) among those present. Instituição: Universidade do Estado do Rio de Janeiro Tipo do documento: Dissertação Tue, 22 Jul 2025 00:00:00 GMT http://www.bdtd.uerj.br/handle/1/24664 2025-07-22T00:00:00Z http://www.bdtd.uerj.br/handle/1/24483 Título: Análise de convecção interna conjugada em microcanais utilizando a técnica da transformada integral Autor: Brito, Marcos Alejandro Primeiro orientador: Chalhub, Daniel José Nahid Mansur Abstract: The rise of electronic devices across sectors poses a thermal management challenge. Smaller, more potent devices highlight the need for better heat dissipation. Microchannel technology, with hydraulic diameters ranging from 1 micrometer to 1 milimeter, offers improved heat transfer, compactness, and integration without much space increase. Within this framework, the present work considers an extended Graetz problem with conjugated internal convection in a parallel plate microchannel, which is modeled as two-dimensional and steady-state across two distinct regions: the solid wall and the fluid, where the convection-diffusion equations are applied. The mentioned equations account for heat diffusion effects in both the wall and fluid domains, crucial for flows with small Péclet numbers. Thermal properties are assumed to be constant within each of the regions, while the flow is considered hydrodynamically developed but thermally developing. Moreover, slip flow and temperature jump conditions are also considered. A semi-analytical solution is presented based on the Generalized Integral Transform Technique (GITT) which offers a methodical approach for solving steady-state and time-dependent boundary value heat transfer problems. Therefore, using the matrix exponential method, the coupled ordinary differential equations system resulting from the GITT is analytically solved. Several previous research efforts on conjugated internal convection, have been developed employing a single-domain and single-region formulation. However, this work introduces a novel methodology for a single-domain, two-region formulation using piecewise-defined eigenfunctions and a preliminary parametric analysis to investigate the influence of various combined parameters on the performance of the system. The results of this investigation provided the temperature profile in both regions and characterized the behavior of the Nusselt number as a function of the Péclet and Knudsen numbers, the conjugate effect of the solid region, and the thermal conductivity ratio. Furthermore, these results were validated against previous studies. Instituição: Universidade do Estado do Rio de Janeiro Tipo do documento: Dissertação Tue, 10 Jun 2025 00:00:00 GMT http://www.bdtd.uerj.br/handle/1/24483 2025-06-10T00:00:00Z http://www.bdtd.uerj.br/handle/1/23917 Título: Pesquisa de técnica de revelação de adulteração de numeração estampada com carga hidráulica em chassis de veículos Autor: Simões, Danilo de Castro Primeiro orientador: Pimenta, André Rocha Abstract: Automotive vehicles are highly valuable assets, and for this reason, they are often targets of theft and robbery. To allow their traceability and location, they have a unique serial number engraved on their chassis, called the Vehicle Identification Number (VIN). In the "car cloning crime", this number is erased and a new number is engraved in place of the previous one. To identify the original serial number, forensic scientists use special chemical reagents, where the reagent is applied to the surface of the chassis. These reagents can identify the erased serial number, as they react more strongly with the steel region below the erased number marks. The FRY reagent is the most commonly applied for this procedure, but the results are usually unsatisfactory and need to be improved. In this work, two modifications to the FRY reagent were tested to improve its performance: replacing copper chloride with iron chloride and anhydrous barium chloride. To increase the safety of the police officer during forensic activity, this work also proposed the creation of a chemical FRY reagent in paste form. The FRY paste reagent will reduce the risk of accidents during transportation and use in situations where forensic procedures have to be performed in the field. 2 mm thick SAE 1010 steel sheets were engraved with the number 3 using a punch and a universal hydraulic testing machine. To simulate tampering, the sample was sanded until the marking was completely removed. The development test was performed with three reagents: FRY (copper chloride, hydrochloric acid and distilled water); FRY mod1 (iron chloride, hydrochloric acid and distilled water); FRY mod2 (anhydrous barium chloride, hydrochloric acid and distilled water). The FRY reagent made the number 3 visible again after 34 seconds of application. However, the tested variations, mod1 and mod2, failed to reveal the erased marking even after 15 minutes of application. The FRY paste was made using the FRY reagent and alumina particles. It was possible to create an efficient paste that revealed the erased marking in a time interval of 1 minute and 40 seconds. It was possible to identify that copper chloride played a fundamental role in identifying the hardening zone. The use of chemical paste reagents for field forensic activities shows promise, maintaining the efficiency of the reagent and reducing the dangerousness of the activity. Instituição: Universidade do Estado do Rio de Janeiro Tipo do documento: Dissertação Thu, 19 Dec 2024 00:00:00 GMT http://www.bdtd.uerj.br/handle/1/23917 2024-12-19T00:00:00Z