RCAAP Repository

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Currently, access to information is increasingly easy because of the advancement of Information and Communication Technology (TIC), reflecting the popularization of computers and the Internet, both in schools as at home. In the same context research projects are being developed toward new teaching methodologies. These projects facilitate new educational methods compared with traditional methods. Today is possible to simulate several laboratories (physics, chemistry, mathematics) by a single computer lab. There are several technologies that support the creation of these systems, included Virtual Reality that lets you create Virtual models and environments and simulate them as if they were real. Another technology is Augmented Reality, where you can insert elements of virtual learning in real environments, which increases the number of alternative educational tools. However distributed systems Virtual Reality and Augmented Reality developed today are limited in the amount of virtual objects belonging to the environment used, another issue is that these systems use either Virtual or Augmented Reality to solve their problems independently, not completing the two technologies. Thus, this dissertation came with the proposal to develop a distribution architecture for Virtual and Augmented Reality, where any model or virtual environment may be distributed, which allows greater flexibility of the proposed architecture

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Nowadays, even more, the access to the use of Informatics as a support to human actions and tasks is extremely spread in schools, homes, industry and several other applications. Specifically in Education, the use of Informatics as a supporting tool to the teacher and students has been the focus of many research undertaken in this area. Several technologies can be used in the educational process. In this dissertation special highlight is given to Virtual Reality, as a tool which is able to present to students new ways of exploring knowledge when compared to traditional approaches (black board, solid objects, chalk). This dissertation presents Virtual Reality techniques as additional tools to the teaching of General Chemistry, specifically, molecular geometry. In order to understand Organic Chemistry, a great level of abstraction is required by the students, since a large number of visualization alternatives is possible, when dealing with molecular geometry. These must be understood and visualized. Thus, this dissertation intends to contribute by presenting a Virtual Reality based environment, where Hydrocarbon molecules can be visualized and explored in three dimensions, providing a better way to help students to learn this specific subject.

Although it seems plausible to consider the importance of the Internet as an educational and/or professional tool for people with special needs, several studies support the idea that the increasing web page complexity renders access to information ever so much more difficult for the visually impaired. Based on the analysis of the resources available in some of the most popular commercial and free products, and on some of the major difficulties this group of users faces, this dissertation proposes an experimental computational tool to support screen reader software aiming to improve the browsing experience for the visually impaired by implementing a set of mechanisms designed to simplify the way such users can reach the textual information itself. Presented and submitted to the assessment of a group of volunteer users, it was possible to observe that the proposed application, despite its limitations, helped to enhance the browsing experience by visually impaired users, reducing the effort required to get to the content that was being searched for. Additional notes provided by the participants by means of evaluation forms, in addition to other observations derived from the monitoring of the browsing sessions, allow us to conclude that improvements, corrections and further implementations can draw the tool even closer to the expectations of its potential users.

This work is an experimental quantitative research and it investigated how much the eciency of the CoSaMP algorithm modied according to the theory that advocates the changes of the QuadTree model{based Compressive Sensing (CS) when applied to images with quantization and sparsity approximation noise. The aim of this study was to evaluate the impact of quantization and sparsity approximation noise to the eciency of image reconstruction and to compare the eciency between the Quadtree model{ based CoSaMP and the traditional CoSaMP. For this, a thorough literature review of the state of the art in image compression, theory of conventional CS and theory of model{based CS was done. After the review stage, MatlabTM routines were built and several tests varying values of M measurements, S sparsity levels and Q quantization steps were applied to four images with different sparsity levels and resolutions. Results showed that the quantization errors are not perceived when the sparsity approximation error level is high. On the other hand, when the sparsity approximation error level is low we observed better performance for steps 1, 2, 4 and 8. The results also showed that the ratio between the number of measurements and the sparsity approximation level meets the following criteria: 3:00 ≤ M=S ≤ 3:75. In this case, the values of M=S ranged from the lowest to highest, as the images varied from less to more sparsely scattered. It was observed that the eciency of the algorithm does not depend on the N stacked image size, but rather the S sparsity approximation level. Furthermore, we observed that the Quadtree CoSaMP outperforms the CoSaMP for all M measurements and performances better than the conventional CS when we take less measurements.

Renewable energy sources has been attracting great interest due to well known environment issues and, hence, the development of power electronics converters to deal with the transformation of these sources into conventional energy forms has been the main challenge faced by many researches working in this area of expertise. Within this subject, this paper focuses the establishment of a new control strategy applied to a step-down/step-up single-stage inverter with imposed waveforms of CSI inductor current and output voltage. The proposed control strategy provides high voltage gain without using high frequency transformer, which contributes to weigh and size reduction of the proposed DC-AC converter structure. Theoretical and simulation analysis are presented and corroborated by experimental results of a 180W laboratory prototype.

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The author of this work presents a solution to transpose MIDI musical sequences codified in SMF (Standard MIDI File) in format 0 or format 1. This transposition is accomplished automatically, being applied in all the tracks and music MIDI channels. This computational tool preserves the format and contents registered in the original files. This transposition is based on the singer vocal range (comfort zone) and by the choice of the melody MIDI channel that he wants to sing. As a result of this research, an application named BestVocal was created, by incorporate the transposition tool based in the comfort vocal range of the singer and incorporate a tool to eliminate pauses of the MIDI file too. Another inclusion is given by a tool that allows it to visualize, save and print the existent lyric of the present file. The Best Vocal allows the user to modify the MIDI instruments of any channel too. Using these computational tools, the singer will avoid having nodules, polyps and other diseases originating from the inadequate effort of his vocal fold. Another earning obtained by the singer, with such system, resides in the fact that singing only in the vocal range where your voice sounds good, will avoid, to him, sing out of tune, avoiding, too, muting notes out of your vocal range. So, he will maintain his credibility as a good professional to his audience.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The IEEE 802.16 standard denes the specications for the medium access control layer (MAC) and the parameters for the physical layer (PHY), which allow to structure an architecture for providing Quality of Service (QoS) in the broadband wireless access networks [1, 2]. However, it leaves open how to implement policies to meet the QoS requirements of user applications, so as to enable manufacturers to dierentiate their products to this standard. This work, aim a more realistic analysis of the uplink scheduling mechanism, based on discipline Priority Queue (PQ), taking into account the parameters of the OFDM (Orthogonal Frequency Division Modulation) physical layer specied in IEEE 802.16. To do so, it extends the WiMAX module for the uplink scheduling mechanism that considers the value of the signal-to-noise ratio (SNR) shown in the subscriber station (SS) and allow selection of a modulation and coding scheme (MCS) according with the characteristics of wireless communication channel. Thus, an MCS which produces an OFDM symbol more resistant to interference of the physical environment, the transmitted signal will achieve greater distance between the SS (Subscriber Station) and BS (Base Station), while the eficient MCS will allow for more eective data rate for the communication channel, encoded more data bits per OFDM symbol. This work has been evaluated using the simulation tool NS-2 (Network Simulator, version 2) with the simulation module for WiMAX networks extended this work to allow more realistic results.

This dissertation presents an architecture to the Argumented Reality environment distribution , using the Web as a mechanism of distribution and execution. Considering the works related with the referred topic, realizing the works use the web as a mechanism of distribution, and the environment is installed and configured in its works station. Facing this, there is the aim of a development in the distribution of the Argumented Reality environment which executes directly on the web, throughout the browser. To prove the architecture, it was created a software prototype. The Argumented Reality interface from this software is based on a case study which represents a specific area of knowledge, in this case, a continuous current motor. This way the Argumented Reality interface makes the interaction by the menu and marker. The architecture uses the model client/server , and it was divided in three layers in the server and four layers on the customers. The prototype was submitted by shocked tests and scalability to prove his performance with multiple users. The tests were conducted by 35 students from the high school (technological) and teachers from the information technology area. All of them used the system and answered a questionnaire based on the ISONORM. The results obtained permits to conclude the software is effective and applied.

The study of refunding requests by damage on consumers appliances has attracted attention in both scientific community and power companies. In view of its relevance in the power distribution utility, the topic has stimulated scientific research aimed at developing reliable tools to assist decisions towards the analysis of the relationship between equipment damage and system disturbances. In this sense, the main works in progress related to the subject point out on the evaluation the use of computational resources. It s noted that there are no sufficient studies concerning the prevention of possible conflicts arising from damage caused by faults in the distribution system have been conducted so far. In this context, this dissertation focuses its efforts on perfecting previous publications developed in this research area. The main issues addressed in this work relate to knowledge of the characteristics of refunding requests made to the power distribution utility, study and computational implementation of mitigation devices, as well as assessing the consistency of the proposed model through a study of real cases.

The objective of this document is to provide a method of analysis and verification of energy efficiency and power quality in industrial ventilation systems. Firstly, the motivation, procedures, methodologies used and a description of the work bench are presented. Analyses are directed specifically to the centrifugal fan installed in the Faculty of Electrical Engineering - UFU. The analysis consists of the substitution of inefficient and obsolete equipment by other modern and efficient, especially standard motors for motors of high efficiency and modernizing the control of air flow with the introduction of frequency inverter. The energy efficiency study examines the consumption of the system for these situations. The power quality study checks disturbances caused by the ventilation system when it is driven by frequency inverter. It also examines its behavior when subjected to non-ideal source and the influence of this event in total system efficiency. Finally, methods for economic analysis of investments will be presented, and a case study.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

A very controversial issue that assumes increasing importance in the national scenario is related to the well area known as Refunding Request for Damages. This subject, amongst other aspects, aims at providing means to support the necessary answer to the consumers when a equipment damage is claimed due to a occurrence in the electrical network. With this in mind, the main idea consists in establishing a correct relationship between power system distribution or transmission phenomena with a given required demand for refunding. In this way, the conventional procedures actually in practice are quite empirical and the search for computational means to provide the required answer appears as an attractive scientific and technique base approach. Using this approach it is believed that a more consistent and impartial method would be of great help to accomplish the focused matter. Within this context, this dissertation aims to contribute in two specific topics: the first is associated to a methodology to cope with the equipment time of use and its insertion in the so called APR software. The second target goes towards the investigation of 25 cases of real refunding requests occurred at the Centrais Eletricas Matogrossenses CEMAT so as to provide a first step towards the validation procedure of the overall procedures.