Teses em Engenharia Elétrica (Doutorado) - PPGEE/ITEC
URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2317
O Doutorado Acadêmico inicio-se em 1998 e pertence ao Programa de Pós-Graduação em Engenharia Elétrica (PPGEE) do Instituto de Tecnologia (ITEC) da Universidade Federal do Pará (UFPA).
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Item Acesso aberto (Open Access) Análise magnética e mecânica em transformadores sob correntes de energização e energização solidária(Universidade Federal do Pará, 2019-10-01) LIMA, Diorge de Souza; BEZERRA, Ubiratan Holanda; http://lattes.cnpq.br/6542769654042813The power transformer is one of the most important equipment in the electric power system, allowing the feasibility of connecting the generating centers to the consumer centers, even over long distances. Reliable and continuous operation is of fundamental importance for service maintenance and is subject to various types of disturbances that can lead to failures. In this perspective, studies of the dynamic behavior of transformer windings through computer simulations have been widely used to safely and accurately evaluate their operation. Therefore, this paper presents the methodology for research on a 50 MVA power transformer using the finite element method for static and time domain analysis. Thus, the study was performed by means of magnetic-mechanical couplings. In the first analysis (circuit study), the ATPDraw software was used to obtain the behavior of the inrush current and solidarity energization during the transformer bank energization. Therefore, in the ANSYS MAXWELL software magnetic studies were performed. For this, a real 3D model was used (taking into account the characteristics of the lamination core and windings, being in disc). Thus, the results of the behavior of magnetic induction and magnetic forces in the windings of the equipment are presented. Finally, in the ANSYS STRUCTURAL software, structural (mechanical) studies were performed. Also, as before, a close-to-real 3D model was used, presenting as results the behavior of the total deformation in the winding, the mechanical stress suffered and the degree of safety during the occurrence of energization. The static studies were considered three operating conditions: nominal condition, sympathetic inrush and inrush current. For the nominal condition, the equipment's plate data was used, for the energizing condition (sympathetic inrush and inrush current) the largest amplitude obtained during the simulation was used. It is noteworthy that for the time domain analysis, only the condition of the inrush current was analyzed, both for the high computational cost required and for being the worst condition in the static analysis.Item Acesso aberto (Open Access) Aprovisionamento dinâmico de recursos em redes ópticas elásticas multiplexadas por divisão de espaço considerando limitações de camada física(Universidade Federal do Pará, 2019-06-07) LOBATO, Fabricio Rossy de Lima; CARTAXO, Adolfo da Visitação Tregeira; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434In elastic optical networks (EONs) employing weakly-coupled single-mode multi-core fibers (MCF), inter-core crosstalk (XT) can affect significantly the network performance, particularly when the number of cores and the path length increase. Hence, from the network perspective, the impairment-aware (IA) routing, spectrum and core assignment (RSCA) problem is an important research challenge of MCF-EONs. In this thesis, we propose a dynamic provisioning methodology that solves independently the IA-RSCA problem taking impairments physical layer into account. To achieve the XT impact minimization, we decompose the IA-RSCA problem into two subproblems: the IA routing sub-problem and the IA spectrum and core assignment (IA-SCA) sub-problem. For the routing solution, a precomputation method based on the k-shortest path is used, and a physical layer impairment verification phase is performed taking the required optical signal to noise ratio into account. For the IA-SCA sub-problem, the novel XT-aware greedy algorithm is proposed to minimize the XT impact on the MCF-EONs performance as follows: for each new connection, the level of detected XT power of the new connection and interfering connections relative to the XT power threshold of each connection is minimized on the average over all those connections. This minimization is achieved by choosing the core and frequency slot of the new connection. In order to take the spectral overlapping extension of the new and interfering connections into account in the detected XT power, a novel frequency slot overlapping index is introduced. The performance of the proposed algorithm is evaluated through computer simulations. The results show that the total blocking probability and network average utilization achieved by the proposed algorithm are better than the ones obtained by core prioritization, random and first-fit strategies, for different scenarios of XT level and spectrum fragmentation.Item Acesso aberto (Open Access) Modelagem da perda de qualidade de videos H.264 em redes sem fio considerando perdas de PSNR e de frames(Universidade Federal do Pará, 2019-08-16) CARMONA, João Victor Costa; CAVALCANTE, Gervásio Protásio dos Santos; http://lattes.cnpq.br/2265948982068382; BARROS, Fabrício José Brito; http://lattes.cnpq.br/9758585938727609Multimedia applications have been growing in recent years; new consumptions like online games, video conference, video on demand and IP telephony are some of these. However, there is a greater prominence in the search related to videos and streaming, currently in high resolutions and mostly traffic over wireless networks, mainly due to the proliferation of mobile devices and significant increase of access networks, which make it more comfortable. Providing this information is easy. Thus, as an immediate consequence of this type of flow, there is a need for investments in techniques and mechanisms that provide the end user with the desired quality and satisfaction in the face of high definition content. This work aims to perform the modeling of video quality loss by analyzing their performance in various resolutions, specifically standards in HD and UHD, at 720p, 1080p and 2160p. In this sense, applying a correlation investigation between the metrics extracted from the videos, using Pearson’s correlation coefficient, and fundamentals of the area in question. Also proposing equations for quality loss modeling, based on analysis of metrics associated with packet loss, in which at the end of the study and according to notes made throughout the text, we used for the general modeling equation, the parameters of Loss of PSNR and Loss of Total Frames. The result obtained shows maximum values of RMSE and Standard Deviation of 0.793 dB and 0.810 dB, respectively, making the developed model very good for the tested video set and its resolutions.