RCAAP Repository

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Conselho Nacional de Desenvolvimento Científico e Tecnológico

The need to make access and manipulation of digital information has made more intuitive with which new technologies emerge. In this respect we can highlight the growth of applications of Virtual and Augmented Reality, which began to demand improvements in methods of interaction used. Thus, this study aims to investigate methods of interaction and develop an augmented reality application that makes use of a more intuitive way of manipulating virtual objects. With the study of the state of the art, it was noted that the use of hands, by positioning and gestures, consists of an intuitive interface and cognitively advantageous for use. Using this information, it was determined that the application to be developed as resources should provide the possibility to interact with virtual objects using their hands without using any apparatus attached to the body, taking into account needs to be compatible with different skin colors skin to ensure use in environments with complex backgrounds (containing various objects and people) with little dependence on illumination. For this, we used the Kinect device together with the OpenNI framework and NITE middleware, which consist of software modules for specific applications with interaction via gestures. The display of the augmented image was carried through the implementation of a module event handling, and rendering operations, which used as a rendering engine the Ogre3D library. Finally, we discussed the development of the application with the proposed requirements, which is to allow interaction in a simplified environment of AR, which allows the creation of virtual objects and their manipulation (rotation, scaling, translation and deletion) via pre-defined gestures and menus.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The IEEE 802.16 standard, also known as WiMAX (Worldwide Interoperability for Microwave Access), defines a broadband wireless access network (BWA) with metropolitan coverage, capable of achieving high data rates transmission, with easy deployment and maintenance. Its main advantage is the presence of an inherent QoS (Quality of Service) architecture. Two layers are specified, the Medium Access Control (MAC) layer and Physical Layer (PHY) [1] [2]. The MAC layer is connection-oriented. The heterogeneous traffic, nRT (non Real Time) and RT (Real Time), which is generated by network applications is managed as service flows. Each flow is defined by a direction, downlink (DL) or uplink (UL), and a set of parameters to standardize operations among stations. The flows are mapped into classes of service for QoS provisioning, according to your requirements. The main QoS mechanism is the scheduler, which is responsible for defining the order delivery of packets stored in the queues of the stations, but the standard does not define its policy of operation. As the bandwidth in WiMAX networks is a limited resource, and the traffic classes, RT and nRT, has different requirements such as the maximum latency, the purpose of this work is an extension of the scheduling mechanism for UL traffic presented in [3], based on Priority Queuing (PQ), to provide differentiated treatment with traffic prioritization. Aiming to increase the protection and isolation between traffic classes, RT and nRT, was created a new queue separating the requests of these classes. Aiming to increase the efficiency of resource utilization has been proposed a new scheme that pre-allocates the remaining resources in the UL, before receiving the bandwidth request, ie, in advance, straightly to the data transmission of the user stations. The assessment of this proposal was made by means of modeling and simulation, and the results showed that its performance was superior to the proposal presented in [3], reducing the average delay of rtPS (Real Time Polling Service) class and increasing the average throughput and resource utilization of nRT classes.

Purpose: to present a method, based in finite elements technique, to estimate leakage capacitances on induction motors for common mode studies. Material and Method: It was used the software FEMM (Finite Element Method Magnetics) to do the leakage capacitances computation through its geometric representation. In consequence, it was used some WEG induction motors to take the capacitances and to present a methodology of motor representation in FEMM. Moreover, it was necessary to analyze how the input parameters on FEMM affect the final results and how they interfere on the common-mode studies. Due to the impossibility of taking some leakage capacitances, it was used analytical formulations to calculate the capacitances and validate the methodology developed in this work. Results: after comparing the obtained values in FEMM with the measurements and analytical calculations, it was possible to verify the method effectiveness, being also highlighted with a study of the common-mode currents behavior. Conclusions: the finite elements method is a powerful tool to predict induction motor parameters to the common-mode study, being a valid alternative and sometimes more effective than the traditional method of measurements and calculation.

If compared with other areas of research Augmented Reality shows are fairly recent, and as such subject to new scientific research and technological innovations. According to Kirner and Siscoutto [2007] Augmented Reality environments makes easier the action of the user in three-dimensional space by increasing the system performance and allowing for better interaction techniques. In these environments it is common to use only one camera to capture the real scene and to allow interaction with the system. Therefore, in applications where it is presented a large number of virtual information, at the time of interaction with these data is a great risk of instability in the scene caused by the occlusion of markers, and confusion in data visualization. In addition, the area of interaction with virtual objects is limited to around the user, making the action on the virtual objects located further away. This study proposes the use of more than one camera on the development of these systems and thereby causes an increased interaction area with virtual objects in the scene, making easier the use of markers and enabling a better "cleaning" of environment displayed. The user has the option of presenting the fiducial markers not only the main camera, but the other cameras available. The verification will occur which marker was used by analyzing the camera image which was presented but the corresponding actions will be performed on objects in the scene presented the main camera, allowing the interaction to occur without interference in the environment. In implementing the prototype was used GoblinXNA platform, an open-source platform written in C # on the Microsoft XNA Game Studio and the library ALVAR. To support this context, was used a questionnaire to the participants of the experiments. Through analysis of these could infer that the proposed strategy is feasible and enables an expansion of the area of interaction with virtual objects in augmented reality systems.

The comparative study of electric machines has been in vogue due to the growing demand for electromechanical converters with maximum possible efficiency. In this scene, the switched reluctance machines have proven to be competitive. Comparative studies between these machines and the already established induction machines can be easily found in the scientific literature, but studies on various configurations of the switched reluctance machines are not as widespread. This work shows the modeling, simulation and presents a comparative study of two Switched Reluctance Machines to a single phase (6x6) and three-phase (6x4). Aspects of construction, drive and efficiency are discussed in order to find advantages and disadvantages to each of these machines.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

This work presents the development and the experimental analysis of a new single-phase hybrid rectifier with high power factor (PF) and low harmonic distortion of current (THDI), suitable for high power application. The proposed structure is composed by an ordinary single-phase diode rectifier with parallel connection of a switched converter. It is outlined that the switched converter is capable of composing the input line current waveform assuring high PF and low THDI. However, the power rating of the switched converter is lesser than 50% of the total output power, assuring robustness and reliability for the proposed hybrid rectifier. Two prototypes rated at 1 kW and 10 kW were developed and analyzed in laboratory, using digital control technique. A PWM control strategy was implemented imposing quasi-sinusoidal line input current waveform and limiting the switched converter power contribution. It was found that the line input current harmonic spectrum is in accordance with the harmonic limits imposed by IEC61000-3-2 and IEC61000-3-4. The principle of operation, the mathematical analysis, and experimental results from a 1 kW and 10 kW prototypes are also presented in this work.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The study of lightning and the resulting induced voltages is very important in the process of designing of transmission lines. In this work it will be presented problems that can be caused by such phenomenon in electrical systems, as a consequence of these voltages peaks. A analysis of the characterization of atmospheric discharge is performed in order to understand causes of induced overvoltages in transmission lines. Will be presented the classical methodology and a new proposal to estimate the tower surge impedance. In the new developed technique was used the finite element method, to obtain a computational model of the transmission tower, so as to simplify the studies. For the calculation of induced overvoltages, it was used the classic methodology developed by Sune Rusck, which is highly regarded and used for such propose. Based on the Rusck s theory, a computational model of induced voltages in transmission lines was implemented in EMTP/ ATPDraw environment, which it is a software developed by Hermann W. Dommel, with great application in evaluation of electromagnetic transients in power systems. From the model developed, results were obtained of induced voltages which are compared with measurements made by P. P. Barker, for checking and adjustment. Furthermore, propagation analysis of induced voltages on transmission lines were made, as well as the influence of some parameters in its amplitude and waveform.

We have developed and created a simulator for calculations and indicatios of maximum permissible values for the electric and magnetic fields as well as the power density in Rádio Base Station, with the use of CDMA technology, in the range of 800 MHz, being the values allowable were referenced and based on the International Commission on Non-ionizing radiation protection. The simulator developed allows to calculate the interference field radiated by rádio base station, with input data such as channel power rádio; Gain Antenna; Number of Rádio Channels, Frequency Operation; Losses in Cable, Attenuation of Direction; Minimum distance; Reflections. To get quickly without the need for the implementation of instruments for measurements, calculations only in that simulator, we calculated values such as: Effective Radiated Power; Density Power Sector; electric field in the Sector; Magnetic Field in the sector; Flux Density Magnetic; point of maximum permissible exposure to electric field and the power density. As results presented in graphs for clarity of visualization of power density in the industry, as well as defining the coverage area. Is also present in the simulator, folders with specifications of antennas, towers and cables used in mobile phones, whose manufacturers are: World RFS, Andrew, and Karthein Brasilsat. They are presented several "links" network access "internet" to complement the specifications of cables, antennas, etc. .. Moreover also part of the simulator to perform calculations quickly and safely assisting in obtaining results of loss of rádio signal generated by rádio base station. Where the simulator has paintings depicting the spreads, where we define propagation "A" and "B".By spreading the "A" we can get the calculations of rádio signal attenuation models in areas of urban, dense urban, suburban, and rural open. Are added in the calculations of reflection coefficients of reflection, the standing wave ratio, return loss, the ratio of reflected power, as well as losses of the signal by impedance mismatch. As for the spread "B" as we can get results in the loss calculations in the rádio signal line in sight and no sight, the effective area, the power density, the power received, the range, the level conversion and the conversion gain in radiant systems.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Although the Bandwidth Broker has been proposed with the objective to give more intelligence to DiffServ networks, allowing the allocation of resources in a dynamic way for applications, once the resources are granted they remain statically allocated along the requested period. In this article, we propose an enhanced resource allocation mechanism, based on the fact that the instantaneous traffic load of the applications are generally dynamic in nature, and consequently, the required bandwidth is less than the allocated bandwidth during some periods. Simulation results demonstrated that the proposed mechanism yields better resource utilization while respecting limits of drop of packets and end-to-end delay.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

This dissertation presents the development of a system of authority in Augmented Reality, to aid the development of teaching materials aimed at vocational education, focusing on a dedicated interface for users not experienced in programming. Considering related work, it was found that the authorship related systems have the interface built on heterogeneous groups of users, which often hampers its use as it is first necessary to understand the technology and only after the development of tasks. Therefore, we propose an authoring system built with the effective participation of users, regarding the interface and the tasks that should enable. To validate this research, we chose a case study that represents a specific area of professional education, in this case, motor mechanics. Once developed, the material is applied to the evaluation of a group of ten students, by means of objective and subjective issues related to the component. Another class, the same course, studied the same component, but with conventional teaching materials. Subsequently, we applied this group the same questions, in order to distinguish possible contributions of the strategy developed using Augmented Reality. For validation of the user interface was based on a questionnaire ISONORM 9126 - NBR 13596, which provides a model of six characteristics and software quality sub characteristics after tabulated it was found that most users were very satisfied with the developed interface.