http://www.bdtd.uerj.br/handle/1/3521 2026-03-05T16:44:58Z 2026-03-05T16:44:58Z Issa, Marcos Vinicius dos Santos http://www.bdtd.uerj.br/handle/1/25406 2026-03-05T15:14:34Z 2024-12-10T00:00:00Z

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

2024-12-10T00:00:00Z Feitosa, Isabelle Ramos http://www.bdtd.uerj.br/handle/1/25405 2026-03-05T12:41:05Z 2025-09-19T00:00:00Z

Título: Preparação de resinas magnéticas à base de poli(acrilonitrila-co-divinilbenzeno) contendo grupos amidoxima para remoção de azul de metileno de meio aquoso Autor: Feitosa, Isabelle Ramos Primeiro orientador: Costa, Marcos Antônio da Silva Abstract: This Dissertation describes the synthesis, characterization and adsorptive evaluation of magnetic poly(acrylonitrile-co-divinylbenzene) resins functionalized with amidoxime groups, aiming at the removal of methylene blue from aqueous media. The resins were obtained by polymerization in aqueous suspension, using toluene or methyl benzoate as porogenic agents and magnetite previously stabilized with oleic acid as the magnetic phase. The functionalization of the resins by amidoximation was confirmed by FTIR spectroscopy, accompanied by morphological and textural changes evaluated by scanning electron mi- croscopy (SEM), thermogravimetry (TGA), Vibrating Sample Magnetometry (VSM) and mercury porosimetry. The results showed that the type of diluent plays a determining role in the porous structure of the material, with the resins synthesized with toluene and higher magnetite content (20%) being those that presented the largest surface area and pore volume, compared to those prepared with methyl benzoate. The presence of amidoxime groups in the polymeric structure resulted in a significant increase in the adsorption capacity of the dye. Among all the samples, the resin prepared using toluene as diluent and 20% magnetic material (TOL20MA) showed the best performance, removing more than 99% of methylene blue under the conditions evaluated, with kinetics adjusted to the pseudo-second order model. These results demonstrate the potential of amidoximated magnetic resins as efficient adsorbents for cationic dyes, highlighting the relevance of pore engineering and selective functionalization for optimizing performance in effluent treatment processes. Instituição: Universidade do Estado do Rio de Janeiro Tipo do documento: Dissertação

2025-09-19T00:00:00Z Campos, Kaio Aguiar http://www.bdtd.uerj.br/handle/1/25401 2026-03-04T19:08:31Z 2025-02-27T00:00:00Z

Título: Análise do comportamento mecânico e durabilidade de chapa cimentícia reforçada com fibra de sisal Autor: Campos, Kaio Aguiar Primeiro orientador: Goliath, Kíssila Botelho Abstract: The construction industry faces significant environmental challenges, such as high carbon emissions and the consumption of non-renewable resources. In this context, vegetable fibers emerge as promising alternatives as reinforcements in cementitious materials, providing greater sustainability and good mechanical properties. This study evaluates the mechanical behavior and durability of cementitious plates reinforced with 5% long aligned sisal fibers, following the guidelines of the NBR 15498 (2021) standard. To improve the durability of the composite, 50% of the cement consumption in the matrix was replaced by 40% metakaolin and 10% fly ash, to avoid fiber degradation by alkaline attack. Experimental tests were carried out to analyze mechanical behavior, permeability, apparent density, water absorption, accelerated aging, and dimensional variation. The results showed that the plates exhibited a tensile strength in flexion of 22.31 ± 4.56 MPa under ambient conditions and 19.07 ± 2.68 MPa under saturated conditions, meeting the normative requirements for internal and external applications. The apparent density of the plates was 1.72 g/cm³, and the water absorption index was 13.81%. Accelerated aging revealed a moderate increase in mechanical strength due to the use of supplementary cementitious materials, which reduced the alkaline degradation of the fibers. Meanwhile, the dimensional variation due to humidity remained within acceptable limits for applications in humid environments. No droplet formation was observed on the lower surface of the plate during the permeability test, meeting the requirements established by the standard. It is concluded that the use of sisal fibers in cementitious plates is a competitive alternative to commercially available plates, standing out as a solution to reduce environmental impacts and expand the use of more sustainable materials in construction. Future studies should explore life cycle analyses to quantify environmental impacts and conduct field tests to evaluate the per-formance and durability of cementitious plates under real-world conditions. Instituição: Universidade do Estado do Rio de Janeiro Tipo do documento: Dissertação

2025-02-27T00:00:00Z Borges, Juliano de Santana http://www.bdtd.uerj.br/handle/1/25400 2026-03-04T18:52:40Z 2025-09-12T00:00:00Z

Título: Correção de variações momentâneas de tensão em microrredes de corrente contínua em navios militares contendo cargas pulsadas Autor: Borges, Juliano de Santana Primeiro orientador: Freitas, Cleiton Magalhães Abstract: Shipboard Direct Current Microgrids (dc-SMGs) offer advantages in efficiency, weight, and load integration. However, high-power pulsed loads, such as directed-energy weapons, cause voltage sags on the DC bus, compromising power quality. This dissertation investigates two decentralized control strategies to mitigate these variations: the conventional droop method and the Virtual DC Machine (VDCM) technique. A complete dc-SMG model was developed, including a gas turbine generator (Rowen model), rectifier with LC filter, conventional loads, a pulsed load, and a supercapacitor-based Energy Storage System (ESS), connected via a double interleaved boost converter. The droop and VDCM techniques were implemented and compared, both complemented by feedforward control and a hysteresis-based management algorithm. The results showed that both techniques performed equivalently, maintaining the bus voltage within the normative limit. Although VDCM offers greater flexibility and inertia emulation, it did not demonstrate practical superiority over droop in the studied scenario. It is concluded that the simplicity and robustness of droop, when integrated with dynamic compensation mechanisms, constitutes a suitable solution for naval dc-SMGs with pulsed loads. The main contribution of this work lies in the comparative and contextualized validation of these strategies, providing technical support for the selection of control architectures where reliability and simplicity are critical. Instituição: Universidade do Estado do Rio de Janeiro Tipo do documento: Dissertação

2025-09-12T00:00:00Z