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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Agora exibindo 1 - 9 de 9

Acesso aberto (Open Access)
Algoritmos culturais com abordagem memética e multipopulacional aplicados a problemas de otimização
(Universidade Federal do Pará, 2012-04-20) SILVA, Deam James Azevedo da; OLIVEIRA, Roberto Célio Limão de; http://lattes.cnpq.br/4497607460894318
In many optimization problems is hard to reach a good result or a result close to the optimum value in a feasible time, especially when working on large scale. So, many of these problems are addressed by heuristics or metaheuristics running search for better solutions within the defined search space. Within the natural computing algorithms there are the cultural and genetic algorithms. These are evolutionary metaheuristics complement each other due to the dual mechanism of cultural heritage/genetic. The purpose of this paper is to study and use such mechanisms adding local search heuristics and multipopulation applied to combinatorial optimization problems (knapsack and travel salesman problems), constrained problems and multimodal functions. Some experiments have been conducted to assess the performance of the proposed combination of meta-heuristisc and heuristics mechanisms against approaches found in literature as applied to problem addressed here.
Acesso aberto (Open Access)
Alocação ótima de geração distribuída em redes de distribuição utilizando algoritmo híbrido baseado em cuckoo search e algoritmo genético
(Universidade Federal do Pará, 2018-09-02) OLIVEIRA, Victoria Yukie Matsunaga de; AFFONSO, Carolina de Mattos; http://lattes.cnpq.br/2228901515752720
This thesis presents a novel Cuckoo Search (CS) algorithm called Cuckoo-GRN (Cuckoo Search with Genetically Replaced Nests), which incorporates the benefits of genetic algorithm (GA) into the CS algorithm. The proposed method handles the abandoned nests from CS more efficiently by genetically replacing them, significantly improving the performance of the algorithm by establishing optimal balance between diversification and intensification. The algorithm is used for the optimal location and size of distributed generation units in a distribution system, in order to minimise active power losses while improving system voltage stability and voltage profile. The allocation of single and multiple distribution generation units is considered. The proposed algorithm is extensively tested in mathematical benchmark functions as well as in the 33-bus and 119-bus distribution systems. Simulation results show that Cuckoo-GRN can lead to a substantial performance improvement over the original CS algorithm and others techniques currently known in literature, regarding not only the convergence but also the solution accuracy.
Acesso aberto (Open Access)
Eletrônica molecular via método híbrido DFT/FGNE em anéis fenilas acoplados a eletrodos metálicos de nanotubos de carbono: a regra de conformação e quiralidade molecular
(Universidade Federal do Pará, 2011-11-11) SILVA JÚNIOR, Carlos Alberto Brito da; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In this thesis, we investigate in detail the electronic transport properties, conformation and symmetry of zz9 SWCN structures attached to phenyl rings (2, 3, 4 and 5) under the influence of external electric field (voltage) via hybrid method DFT type B3LYP 6-311G (d, p) combined with NEGF and Group Theory. We found a good relationship between: 1 - the chiral index () by Group Theory and the law of cos2 (, dihedral angle) for the geometry under the influence of external electric field because  only depends on the atomic positions () of conformations, and is also strongly correlated with current passing through the system; 2 - normalized conductance (G / Go) is proportional to cos2 in the region of the gap (EHOMO-ELUMO), ie, in regions where the resonance occurs negative differential resistance (NDR) and 3 - the Fowler-Northeim (FN) plot Vmin displays that occurs when the tail of a resonant transmission peak voltage enters the window, that is, when these structures is an NDR, NDR as the number of the IV plot is associated with the number Vmin of the FN plot and can be explained by the model of molecular transport line 4 - the barrier height (EF - EHOMO and ELUMO - EF) as a function of molecular length, 5 - Vmin as a function of barrier height (EF - EHOMO ) and the molecular length. Thus, one implies that the molecular conformation plays a major role in determining the transport properties of the junction, suggests that the second law of cos2 is a more general applicability regardless of the nature of the electrodes; 3 serves as a spectroscopic tool and also to identify the molecule at the junction, 4 and 5 as the molecular length reaches a certain value (1.3 nm) the Vmin remains virtually unchanged. The results showed that the structural properties (geometric) undergo significant changes with increasing external electric field that are in good agreement with the values found in literature. The behavior of I-V curves and G/Go-V lose their linear dependence to give rise to a nonlinear behavior with the appearance of NDR. This point reveals the structural modifications suffered by the system. The I-V plot confirmed the statements that were made through the structural analysis for the system considered and showed how it gives the load flow analysis systems.
Acesso aberto (Open Access)
Estratégia de projeto de atribuição de comprimento de onda com restrição de camada física em redes WDM
(Universidade Federal do Pará, 2014-03-28) MIRANDA, André Moacir Lage; SEGATTO, Marcelo Eduardo Vieira; http://lattes.cnpq.br/2379169013108798; COSTA, João Crisóstomo Weyl Albuquerque; http://lattes.cnpq.br/9622051867672434
The system based on Wavelength Division Multiplex (WDM) has been considered as a mature technology to be used in the backbone of optical networks. However, finding an optical solution for Routing and Wavelength Assignment (RWA) algorithm in the design and operation of the networks remains an open issue. The research conducted in this thesis, addresses the main issues regarding the process of Wavelength Assignment (RWA) in WDM systems, and as result a methodology that minimizes the degradation of the optical signal generated by Cross-Phase Modulation (XPM), has been proposed. This proposal consists of a hybrid methodology based on Graph-Coloring and Genetic Algorithm (GA), where the first has the function of reducing the number of necessary wavelengths to meet the traffic matrix (known a priori), and the latter will find the cannels activation order on the wavelengths grid with the aim of reducing the XPM effect. This proposal was compared with the First-Fit algorithm in different scenarios and network topologies, and has shown a significant reduction in blocking probability.
Acesso aberto (Open Access)
Estratégias baseadas em análise multicritério para seleção de tecnologia de acesso de primeira milha em padrão ISDB-T
(Universidade Federal do Pará, 2012-11-23) SERUFFO, Marcos César da Rocha; FRANCÊS, Carlos Renato Lisboa; http://lattes.cnpq.br/7458287841862567
This thesis proposes the development of a planning strategy that combines: load characterization of a typical Digital TV, extraction of a weight vector from belief networks, and multicriteria decision making with analytical methods (TOPSIS and ELECTRE III), providing decision support at the service providers; in order to enable the optimal choice for the return channel technology (ADSL2 +, PLC, WiMAX and 3G), considering the typical load of an interactive Digital TV scenario, standard ISDB-T. The proposed strategy has five steps: definition of return channels and performance metrics; performance measurements of access technologies in real scenarios; scenario simulation; apply correlation techniques to generate the weight vector; and application of analytical decision making for choosing the best technology to be implemented in a given scenario. As main result a generic and flexible model is presented, validated with a case study for ordering the preference of the evaluated technologies.
Acesso aberto (Open Access)
Estudo e desenvolvimento de um protótipo para redução da interferência de modo comum usando balanceamento dinâmico de impedância aplicado em biosensores e sensores eletroresistivos
(Universidade Federal do Pará, 2013-10-25) NEGRÃO, João Francisco Ribeiro; ARAÚJO, Guilherme Augusto Limeira; http://lattes.cnpq.br/8261564685433904; COSTA JÚNIOR, Carlos Tavares da; http://lattes.cnpq.br/6328549183075122
Electromagnetic interference caused by the electric power line adversely affects the signals of electronic instruments, especially those with low amplitude levels. This type of interference is known as common-mode interference. There are many methods and architectures used to minimize the influence of this kind of interference on electronic instruments, the most common of which is the use of band-reject filters. This paper presents the analysis, development, prototype and test of a new reconfigurable filter architecture for biomedical instruments and measuring data of high complexity fluid flow, such as two phase flows, interference in the measurement circuit may affect the measured data, aiming to reduce the common-mode interference and preserve the useful signal components in the same frequency range as that of the noise, using the technique of dynamic impedance balancing. . Also, any measurement system also suffers interference in the power line frequency (50/60 Hz in Brazil and France, 60Hz in United States of America). The circuit blocks were mathematically modeled and the overall closed-loop transfer function was derived. Then the project was described and simulated in the VHDL_AMS language and also in an electronics simulation software, using discrete component blocks, with and without feedback. After theoretical analysis and simulation results, a prototype circuit was built and tested using as input a signal obtained from ECG electrodes and Resistivity Needle Probes. The results from the experimental circuit matched those from simulation: a 97.6% noise reduction was obtained in simulations using a sinusoidal signal, and an 86.66% reduction was achieved using ECG electrodes in experimental tests. In both cases, the useful signal was preserved. The method and its architecture can be applied to attenuate interferences, which occur in the same frequency band as that of the useful signal components, while preserving these signals.
Acesso aberto (Open Access)
Exploring service relocation and differentiation to improve survivability on operation of resilient optical cloud networks
(Universidade Federal do Pará, 2016-03-17) SILVA, Carlos Natalino da; FRANCÊS, Carlos Renato Lisboa; http://lattes.cnpq.br/7458287841862567
Optical clouds are the combination of optical transport networks and cloud computing, which allows the integrated management of both infrastructures in one controller element. In this paradigm, cloud services can be provisioned in an anycast fashion, i.e., only the source node asking for a service and the amount of IT resources are specified, while it is up to the cloud control/management system to select the most suitable destination datacenter (DC) node. During the cloud service provisioning process resiliency is crucial in order to guarantee continuous network operations also in the presence of failures. On one hand, a survivability strategy needs to be able to meet the availability requirements of each specific cloud service, while on the other hand it must be efficient in using backup resources. Service relocation (i.e., the ability to live re-allocate one provisioned service to another DC) is one of the new features that can be used in this new paradigm, but needs to be applied carefully given its associated overhead may overload the network and DCs. Current works in the literature consider a single service model that lack representation of the heterogeneity expected for cloud services. In this context, some disrupted connection properties can be considered to improve the network survivability during the restoration process, e.g., priorities and service remaining holding time. This thesis proposes a restoration-based survivability strategy, which combines the benefits of both cloud service relocation and service differentiation concepts. The former is used to enhance the restorability performance (i.e., the percentage of successfully restored cloud services) offered by restoration, while the latter ensures that critical services are given the proper consideration while backup resources are assigned. An ILP and a heuristic are presented in order to solve the proposed survivability strategy. The proposed strategies are evaluated considering a variety of different simulation scenarios. Results show that performance achieved by the proposed ILP and heuristic are close to the ones achieved when using protection strategies, but with the inherent benefits in terms of efficient use of resources offered by restoration-based approaches.
Acesso aberto (Open Access)
Ferramentas e recursos livres para reconhecimento e síntese de voz em português brasileiro
(Universidade Federal do Pará, 2011-06-17) SAMPAIO NETO, Nelson Cruz; KLAUTAU JÚNIOR, Aldebaro Barreto da Rocha; http://lattes.cnpq.br/1596629769697284
Automatic speech recognition and text-to-speech systems have modules that depend on the language and, while there are many public resources for some languages (e.g. English and Japanese), the resources for Brazilian Portuguese (BP) are still limited. Another aspect is that for many tasks the current speech recognition system error rate is still high, when compared to that obtained by humans. Thus, despite the success of hidden Markov models (HMM), it is necessary to investigate new methods. This work has these two facts as motivation and is divided into two parts. The first part describes the resources and free tools developed for BP speech recognition and synthesis, consisting of text and audio databases, phonetic dictionary, grapheme-to-phone converter, syllabification module, language and acoustic models. All of them are publicly available and, together with a proposed application programming interface, have been used for the development of several new real-time applications, including a speech module for the OpenOffice suite. Performance tests are presented for evaluating the developed systems. The resources make easier the adoption of BP speech technologies by other academic groups, developers and industry. The second part of this work presents a new method for rescoring the recognition result obtained via HMMs, with the result being organized as a lattice. More specifically, the system uses discriminative classifiers that aim at reducing the confusability between pairs of phones. For each of these binary problems, automatic feature selection techniques are used to choose the proper parametric representation for the specific problem.
Acesso aberto (Open Access)
Metodologia para compressão de sinais de energia elétrica a partir de registros de forma de onda utilizando algorítmos genéticos e redes neurais artificiais
(Universidade Federal do Pará, 2016-12-16) BARROS, Fabíola Graziela Noronha; NUNES, Marcus Vinícius Alves; http://lattes.cnpq.br/9533143193581447; BEZERRA, Ubiratan Holanda; http://lattes.cnpq.br/6542769654042813
This thesis proposes a methodology for compression of electrical power signals from waveform records in electric systems, using genetic algorithm (GA) and artificial neural network (ANN).The genetic algorithm is used to select and preserve the points that better characterize the waveform contoursA and the artificial neural network is used in the compression of other points as well as on the signal reconstruction process. Thus, the data resulting are formed by a part of the original signal and by a compressed complementary part in the form of synaptic weights. The proposed methodology selects and preserves a percentage of the original signal samples, which are aspects not explored in the literature. The method was tested using field data obtained from an oscillographic recorder installed in a 230kV electrical power system. The results presented compression rates ranging from 88.36 to 95.86 for preservation rates ranging from 2.5 to 10 , respectively.

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