RCAAP Repository

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

In some circumstances, a person may be deprived of natural abilities, such as walking and speaking, perhaps due to limb amputation, spinal cord injuries (SCI), or degenerative diseases. Assistive technology devices allows motor-impaired people to overcome their limitations promoting greater independence. Particularly suitable in the case of people with severe motor impairment, electrical biosignals have been successfully utilised to operate alternative communication devices. For over half a century, information extracted from the electromyographic signal for the purpose of operating a given device has not considered the information provided by the basic unit of the muscle: the motor unit. The objective of this study is to investigate how accessing information at motor unit level would improve the operator's performance during a given task. The hypothesis is that the proposed methodology would allow generating more precise control commands, when compared to traditional approaches relying on global information obtained by conventional electromyographic signal acquisition and processing. A system to detect motor unit action potentials from the electromyographic signal was devised, including the electrode design, and the performance evaluated by measuring the time taken to perform several cursor control tasks. The specications of the cursor control task were extracted from a dierent study, which used the traditional electromyographic signal-processing approach. Comparing the results from both studies proved that the novel approach provides better control than the traditional one, being 27% faster in the most dificult task.

The use of single-phase medium-voltage grids with one or two wires represents a very widespread alternative in Brazilian electricity sector to supply rural loads, mainly because of the associated low investment when compared to the three-phase power distribution grids. Although such network topologies are capable to meet most of the needs of these facilities, specific features related to the need of using more expressive driving loads by some rural consumers recommend the employment of three-phase motors. Commonly, the solution for the problem has been the replacement of the single-phase branch of the rural consumer by a new branch with three-phase topology which is more expensive and often unfeasible for both the consumer and the distribution utilities. On some occasions, systems to convert the number of phases are also used, all based on power electronics. Given this scenario, this work aims to contribute to the expansion of the electricity market in rural areas, offering a distinct possibility for solving the problem by exploiting the physical topology of the single-phase branches existing in rural facilities to supply the same premises using a new concept to transform the number of phases, based solely on magnetic units. The proposed system of three-phase two-wire supply has its design physical and mathematically analyzed under different load conditions and the supply, and is patterned, computationally simulated and experimentally confirmed to have effectiveness. Based on these principles, the study shows that the proposal presents to be constructively simple, offers low maintenance and requires extremely attractive investments.

The majority of wind energy conversion systems (WECS) currently in operation in the world uses asynchronous generators for the transformation of the energy contained in the wind into electric energy. In Brazil, although small the amount of wind power stations, the existing units are mainly based on synchronous generation principles. This is in accordance with the technology named as German concept. Using this technology, the turbine operates with variable speed since the synchronization of the generation with the main grid is made through static frequency converters. Presently, the schemes using variable speed have not yet been followed by comprehensive computational simulation resources to provide means for assessment procedures and operating studies. This fact guided the subject of this thesis research topic, which directed to the development of a software destined to the modeling and studies of wind parks of variable speed taking into account aspects concerning to power quality. The technique here employed is based upon time domain representation. Therefore, a powerful tool to cope with both transient and steady state conditions is obtained. Within this context, distinct operational and real site situations of the electric utility grid at the point of common coupling are evaluated. The impacts on the power quality indexes emphasize the potentiality of the program as a tool to evaluate the connections of new wind parks to the interconnected power system.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Parallel computing is a powerful way to reduce the computation time and to improve the quality of solutions of evolutionary algorithms (EAs). At first, parallel evolutionary algorithms (PEAs) ran on very expensive and not easily available parallel machines. As multicore processors become ubiquitous, the improved performance available to parallel programs is a great motivation to computationally demanding EAs to turn into parallel programs and exploit the power of multicores. The parallel implementation brings more factors to influence performance, and consequently adds more complexity on PEAs evaluations. Statistics can help in this task and guarantee the significance and correct conclusions with minimum tests, provided that the correct design of experiments is applied. This work presents a methodology that guarantees the correct estimation of speedups and applies a factorial design on the analysis of PEAs performance. As a case study, the influence of migration related parameters on the performance of a parallel evolutionary algorithm solving two benchmark problems executed on a multicore processor is evaluated.

This study aimed at the identification and treatment of harmonic interference in the functioning of Salient Pole Synchronous Machines in order to make the techno-scientific community aware of such events. Mathematical models, computer simulations, laboratory tests and field measurements were developed as well as the creation and simulation of a new voltage waveform for the machine excitation system, which resulted in attenuation of electromagnetic torque oscillations even though this machine is operating under non-sinusoidal condition. To enable the precision and understanding of the rotating electric machine under non-sinusoidal load currents, the modeling and simulations took into account the harmonic components of the spatial distribution of magnetic flux density produced by machine windings, and the temporal harmonic components produced by non-linear loads. Comparisons were made between sinusoidal and non-sinusoidal steady-state synchronous machine operations, in order to give credibility for the developed mathematical models.

The Auditory Brainstem Respose signals are characteristic of the combination of neural activity responses in presence of sound stimuli, detected by the cortex and characterized by peaks and valleys. They are named by roman numerals (I, II, III, IV, V, VI and VII). The identification of these peaks is made by the classic manual process of analysis, which is based on the visualization of the signal generated by the sum of each sample. In the sum the morphological characteristics of the signal and the temporal aspects relevant waves made by Jewett are identified. However, in this visual process some difficulties may occur, regarding the recognition of patterns present, which may vary according to local, individual equipment and settings in the selected protocol. Making the analysis of ABR subject to the influence of many variables and a constant source of doubt about the reliability and agreement between examiners. In order to create a system to automatic detection of these peaks and self-learning, that takes into account the profile for evaluate from examiners this work was developed. The continuous wavelet transforms an innovative technique for the detection of peaks was used associate with a probabilistic model for classification based on the histograms with information provide by examiners. In evaluating of the system, based on the swat rate between the system and a manual technique an accuracy ranging for 74.3% to 99.7%, according to each waves. Thus the proposed technique is proved to be accurate especially in ABR that is a sign of low amplitude.

Operation of a switched reluctance machine (SRM) as a self-excited generator is focused in this work. The investigation is supported by a thorough literature review, and uses a mathematical model that accounts for the non linearity between flux linkages and currents, a requirement to correctly represent the generator operation in the proposed mode. The method chosen to start the process of self excitation is the use of a partially charged capacitor, placed in parallel with the generator phases and also with the electrical load. This capacitor is also used to smooth the steady state D.C. generated voltage, delivered to the load. Beyond generated voltage build up characteristics, a comprehensive investigation on the generator operation, considering different primary speeds, variable primary speeds, different electrical loads, load rejection, phase loss is carried out. Generated voltage and current control circuits to accommodate the generator operation are proposed. A bench test platform developed to verify the theoretical finds is used and all the results obtained in the work are experimentally checked and found to be in good accordance with theoretical expectations. As a whole, the investigation shows that the use of SRM as a self excited generator is rather feasible and does not require unattainable circuitry or control strategies.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

O uso de técnicas de restrições são empregadas em uma grande escala de aplicações de engenharia. De fato os desafios impostos para as restrições gráficas e matemáticas resultam em características extremamente eficientes para os softwares de CAD / CAE, permitindo a criação de ferramentas de apoio a tomada de decisão muito eficazes. As redes FTTx (PON) estão se tornando progressivamente uma realidade comercial, e as suas implementações são relatadas em todo o mundo. Todavia, o funcionamento destas redes exige meios adequados para o monitoramento de baixo custo, especialmente, a possibilidade para detectar as falhas remotamente, assim como diferenciar entre uma falha de equipamento e uma ruptura de fibra, e subsequentemente, localizá-la geograficamente é de grande importância para as empresas de telecomunicações. O uso de técnicas de reflectometria óptica no domínio do tempo (OTDR) é amplamente utilizado nas redes de ópticas ponto-a-ponto. Entretanto esta técnica tem limitações quando utilizada em redes de topologias distribuidas, pois o sinal é dividido nos ramos da rede e são somados no Terminal de Linha Óptica (OLT), difícultando a diferenciação do sinal de cada ramo da rede separadamente onde os sinais (OTDR) são sobrepostos entre si. Este trabalho propoe um algoritmo de Evolução Diferêncial que permite a simulação matemática de divisores ópticos e a separação do sinal sobreposto de redes com divisores, integrando estes com o projeto CAD de uma rede FTTH, empregando técnicas de restrições. O resultado é apresentado em uma solução de acoplamento do mundo \"optico\" de sinais de reflectometria (OTDR) em redes PON com o mundo \"fisico\" do projeto em CAD, considerando as ligações de fibra e os seus ramos (divididos ou splitados).

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

This study quantifies the mandibular movements of opening and close, laterotrusion and protrusion, obtained from 20 healthy subjects and 20 TMD subjects subdivided into 10 individuals with myopathy and 10 individuals with arthropaty, selected by Research Diagnostic Criteria (RDC) protocols. These movements of all subjects were captured and measured at maximum length, medium velocity and acceleration and deviation during your trajectories, were captured by three infrared cameras and measured by a computational system previously developed by the University Federal of Uberlândia, which, in this research was named Jaw Capture. This system receives images simultaneously from nine reflective markers and send and process this data to a computer using a firewire system through a mathematical approach to analyze and quantify in 3D (at X, Y and Z axis), the marker trajectories. The reflective markers were positioned by supporting systems fixed on vestibular face of lower incisives and skin surface of face. The movement ranges are similar among all individuals, meanwhile the deviation and the medium velocity and acceleration are very different between target and control group after statistical analysis. This system being proves reliable and efficient.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Cloud computing emerges as a new dominant paradigm in distributed systems, with a model that allows users to access, over demand, to a shared pool of computing configurable resources, such as networks, servers, storage, applications and services. These resources can be rapidly provided with minimal management effort or interaction from a supplier. In cloud computing, the infrastructure can be made available as a service through virtualization using hypervisors. Virtualization is a mechanism that presents the hardware and system resources of a given operating system. This technology is used in environments clouds through a large set of server using virtual machine monitors that are located between the hardware and the operating system. However, there is a wide spread of hypervisors, each with its own advantages and disadvantages. The specific characteristics of each virtual machine generates different performances. The aim of this work is to propose a methodology that seeks to discover how, when and as the increased performance of the algorithms in virtual environments is determined by the environment configuration and how the configuration parameters can influence each other, and finally, discover using statistical methods which settings of virtual environment achieve the best results on average. The tested algorithms (sudoku, pi, wordcount, testDFSIO read and write testDFSIO) belong to the benchmark Apache Hadoop. These experiments were planned and executed based on the experimental design theory. The experimental design is a pre-established set of tests using scientific and statistical criteria mainly, in order to determine the influence of various factors on the results (metric) of a system or process, identifying and observing the reasons that led to change in the expected value. The planning that was used is factorial planning 34, where each factor (core, memory, operating system and virtual machine) were varied in three levels. Tested operating systems were Ubuntu 14.04 64bit, CentOS 7.0 64bit and Windows 8.0 64bit; and virtual machines were tested KVM, Xen and VMware. Data were collected and analyzed using analysis of variance. The results show that the major analyzed factors changes the algorithm performance , but they can not be analyzed separately because there are also significant interactions belonging to these factors . At a 5% significance level, analysis of variance showed that the core interactions: memory, memory with OS, memory with VM and OS with VM, all these factors impact the runtime of the analyzed algorithms. According to the statistical method mean comparison was possible then make a comparison between the mean times of significant interaction between OS and VM, and based on results has been applied an adaptation of Pareto dominance theory called Pareto dominance. Also, with 5% significance level was possible to discover Pareto\'s borders. Considering the runtime algorithm, the Pareto Dominance introduced the virtual environment Xen with CentOS in the first border as the virtual environment that on average achieved the best performance for the analyzed computational algorithms. Virtual environments that occupied the second border were the environments Xen with Ubuntu and VMware with CentOS, ie they had on average lower times the first border and between them they were considered equivalent. The environments belonging to third border were KVM with Ubuntu, VMware with VMware and Ubuntu with Windows. The environments belonging to fourth border were Xen with Windows, KVM with CentOS and the environment that got on average lower than the other times was the KVM with Windows. It can be concluded that virtual machine Xen and CentOS operating system on average got the best performance. But if the user wants to use the Ubuntu operating system it is advisable to install it in Xen virtual machine. And if you want to use the Windows operating system recommends be installed on the VMware virtual machine.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The inability to navigate independently is one of the most significant handicaps due by blindness. Many difficulties can be faced when visually impaired people (VIP) need to visit new and unknown places. Our approach is to use locomotion simulation interface to allow a natural exploration way of virtual environment (VE) to assist VIP to create cognitive maps efficiently, and thereby to enhance their mobility skill. A computer system, called SACEC Assist System Spatial Cognition in the Blind, was developed using virtual reality techniques and natural interaction. The system allows the modeling of two-dimensional or three-dimensional virtual environments, and it is possible to reproduce actual environments such as schools, universities and others points of interest. The interaction with the virtual environment is based on the recognition of poses, which are interpreted as actions such as walking, turning, or front and side touch, and feedback sounds are sent to user. In order to review and validation of the developed system and the proposed interface tests are performed with actual VIPs, men and women aged from 18 to 60 years. A result shows the effectiveness of the SACEC in developing cognitive map of the simulated environment, as well the positive feedback shows that the system can be entertaining and pleasant to the participants. Therefore, SACEC has a great potential to be used in aid to Orientation and Mobility (OM) trainings, and thus contribute to greater social inclusion of those people.

People withmobilityandspeechrestrictionssimultaneoushaveverbalcommunicationandbody language impaired.Inthemostextremecasesthepatientsaredeprivedofalltheirmovements and speechcapabilities.ThissituationischaracterizedastheLocked-inSyndrome(LIS).The augmentativeandalternativecommunicationtechnologiesprovidemethodsandsoftwaresthat allowthesepatientstocommunicatewiththeexternalenvironmentandpeoplearoundthem. Among thevariousmethodsandexistingcommunicationprogramswecanhighlightthevirtual keyboard.However,datainputusingthiskindofkeyboardisconsiderablyslowerandmore tiresome forpeoplewithLIS.Thisworkaimstobuildanassistivevirtualkeyboardtoassist patients withseveremobilityrestrictionsandspeechtocommunicate.Toachievethisgoalit wasconductedtwosystematicreviewsandaliteraturereview.Fromtheknowledgegained from theseresearchswemodeledanddevelopedanassistivevirtualkeyboard.Moreover,we designed andimplementedanevolutionarymethodologythatallowsthekeyboardtoadaptitself to user svocabularyandwritingmode.Finally,anexperimentthatcomparesthetraditional method keyboardsoptimizationwiththemethodologyproposedinthisthesiswascarriedout.