RCAAP Repository

This work describes the development of a muscular contraction originated signal (EMG) analysis system. Study and development of extraction and classification methods for these signals were made, so that they cold be recognized by an upper limb prosthesis with four degrees of freedom. To achieve such results, EMG signals from the biceps and triceps were classified in four distinctive patterns: elbow flexion, elbow extension, wrist pronation and wrist supination. Those patterns were classified by an artificial neural network, which received as inputs the characteristics of the EMG signals, extracted through detection of activation times and integral below the envelope. Analysis were made considering five pairs of electrodes, two located on the bíceps (long head (B1) and short head (B2)), and three on the tríceps ( long head (T1), short head (T3) and medium head (T2)). Dynamic and static contractions were evaluated during the experiments. As most of existing techiques rely on computationally demanding algorithms and complex mathematic analysis, the goal of this work was to find a simple and compact method to execute such tasks with the same performance, by use of simpler and more functional computational techniques, when compared with other well-known methods which achieve good results.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

There exists a growing concern among educators when it comes to the use of new information and communication technologies (ICT s) in the practical day-to-day contact with students. Through its low cost and public policy rules, the computer has shown itself to be a means by which this proposal could be realized. Therefore the objective has been the development, implementation and evaluation of educational software, which favors the integration of ICT s during the process of teaching and learning, and which can be used by the educator as an aid during the child s literacy process as an exercise-practice tool, thus allowing the individual student to interact in their own learning. The software was developed in Flash to combine optimization to the file size as well as speed to the loading of the drawings. The software presents exercises in different difficulty levels, with vibrant colors and sound applications as well as text being a predominant part of the whole environment, which themselves guaranty student motivation and involvement within the proposed framework of exercises. The architecture is made up of two main modules: Graphic Interface and Activities, which is divided into Modeling/Animation and Execution. To validate the proposal, aspects related to the ISO/IEC 9126-1 standard, as well as others which were defined exclusively for research were analyzed together with two groups of students in the 6 year old range, during the literacy phase, in the presence of educators, pedagogues and psychologists, with a total of 15 evaluation members and 24 students. The validation process was analyzed through the use of two methodological instruments: through the observational participation of the software s use by the students, as well as the filling in of a structured questionnaire, or checklist, by the evaluating members, who answer closed questions related to the software s characteristics and its didactic support on a satisfaction rating ranging from 0 to 10. The results showed there exists an effective contribution on behalf of the software as a game style tool with didactic potential, which can guaranty student motivation producing significant learning. There exists a concern on the part of the educational professionals in respect to quality and real efficiency of the computational recourses in the formation of critical thinking citizens, as well as their being reflexive in a knowledge based society. In terms of the computational-technical aspects, the different difficulty levels, the vibrant colors, sound applications and texts, all guaranty student motivation and involvement in respect to the activities provided. The checklist demonstrated satisfactorily, the technological quality when referring to the software s functionality and usability, once that the auxiliary needs of the educator were met and the students did not find any difficulties in its use.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

In the middle of the 20 20th th century the Brazilian electrical energy sector experienced a rapid growth, since that occasion the problem of voltage control in the transmission and distribution systems grabbed the attention of energy authorities, electrical sector offices and high voltage consumers. With the limitation of reactive power in transmission lines this started to be the reason of difficulties in the system operation at the same pace of the increase of loads and system voltage level along the system. The present work shows the theoretical study of the synchronous machines at the Pedreira pumping/generating station as synchronous compensators, the station is located at the heart of a huge consumer center (São Paulo and adjacencies). The use of these machines as synchronous compensators has the primary objective to improve the voltage levels in the station surroundings. Operative configurations were considered to allow the generation of reactive power at the Pedreira pumping/generating station for the system improvement. The research show the following factors of improvement in the area: increase in voltage levels; reduction of electrical losses; decrease in flux of reactive power in the system (transmission lines and transformers); decrease in active power generation for the supply of loads in the area; decrease in reactive power generated by other nearby synchronous compensators; and increase in system reliability during contingencies. Finally a comparison of system avoided costs is made, with the only change being the system operating philosophy, without investment costs in reactive power compensation equipment.

The objective of this study is to demonstrate the potentiality of Immersive Virtual Reality (IVR) techniques in computer based teaching/learning process, through the development of virtual educational environments. This research aimed at providing a human-machine form of interaction that would be more familiar and motivating for the user in the context where it took place. This work has as its main objectives: 1) to identify specific devices which better support the development of an educational and immersive virtual environment and 2) to investigate IVR techniques that allow a more natural and intuitive interaction between the user and his study objetc. To evaluate the proposed techniques, a prototype system was developed as a case study, which permitted the user to visualize and interact with the polyhedron surfaces inside a virtual environment making cuts in these surfaces through plans. To reach the interaction proposed in this system, this research identified the need to integrate VRML language and JavaScript in order to explore the positive aspects of both languages and reach the proposed level of interaction. After making the system available to potential users, they were able to do some experiments and confirmed that the techniques proposed are satisfactory and helpful in the learning process and in the visualization of surfaces from 3D cuts, thanks to the IVR proposed techniques.

Voice analysis is an important tool in the diagnosis of laryngeal disorders. Among distinct signal processing techniques employed for voice analysis, the spectrogram is commonly used, as it allows for a visualization of the variation of the energy of the signal as a function of the both time and frequency. In this context, this study investigates the use of the global energy of the voice signal, estimated through the spectrogram, as a tool for discrimination between signals obtained from healthy and pathological subjects. This research has also exploited the potential use of the global energy of the voice signal to discriminate distinct laryngeal disorders. In total, 94 subjets were involved in this study, from which 46 were dysphonic and 48 normal. The diagnosis of laryngeal disorders was confirmed by means of a videolaryngoscopic examination. Participants were also subjected to a clinical examination of vocal acoustic through the recording of the sustained vowel. The global energy allowed for the discrimination between normal and disphonic voice. Furthermore, this technique could discriminate the voice signal of patients suffering from left vocal fold paralysis from those suffering from other investigated disorders. The results suggest the global energy of the signal as an auxiliary and alternative tool for the diagnosis between normal and dysphonic voice.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Universidade Federal de Uberlândia

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Universidade Federal de Uberlândia

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

It is presented a study for the development and resolution of the equations of the coupling flow - deformation in porous media saturated with compressible fluid. The cases in analyses are transients, two-dimensional or three-dimensional systems, and are studied with the objective of get displacements on the surface, the field of stresses and deformations in the geotechnical medium, submitted to a static or cyclic superficial load. The process allows simulation of the ground behavior, soil or rock, consisting of different elastic and hydraulic properties when submitted a static, cyclical or harmonic superficial load. A field of pressure in the pores is generated in all medium as consequence of this load in the surface of the ground. A computer program simulates the pressure in the pores and all process of balance, deformation and the initial condition: neutral pressure in all points, express porous pressure numerically. The developed mathematical model simulates the field of stresses and displacements in the interior of the porous media, connected to the draining fluid in the pores, to the deformation fluid and the constituent porous structure. It can be observed that the biggest deformation occurs, mainly, due to reduction of the emptiness s, as consequence of a rearrangement internal structure of the ground, soil or the rock in analysis. The study it is made considering that the constituent solid particles of the geotechnical medium are incompressible. The equations that conduct the phenomenon are solved numerically through the technique of the spectral method, using a mesh of points of collocation in the analyzed domain and following evolution of the pressure with the time. The dissipation of the pressure connects to the displacements in the porous media, inducing the variation of stress in the interior of the medium.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais