Simulation Tools for Power Electronics Courses Based on Java Technologies

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Low-power laser irradiation improves histomorphometrical parameters and bone matrix organization during tibia wound healing in rats

The influence of daily energy doses of 0.03, 0.3 and 0.9 J of He-Ne laser irradiation on the repair of surgically produced tibia damage was investigated in Wistar rats. Laser treatment was initiated 24 h after the trauma and continued daily for 7 or 14 days in two groups of nine rats (n=3 per laser dose and period). Two control groups (n=9 each) with injured tibiae were used. The course of healing was monitored using morphometrical analysis of the trabecular area. The organization of collagen fibers in the bone matrix and the histology of the tissue were evaluated using Picrosirius-polarization method and Masson's trichrome. After 7 days, there was a significant increase in the area of neoformed trabeculae in tibiae irradiated with 0.3 and 0.9 J compared to the controls. At a daily dose of 0.9 J (15 min of irradiation per day) the 7-day group showed a significant increase in trabecular bone growth compared to the 14-day group. However, the laser irradiation at the daily dose of 0.3 J produced no significant decrease in the trabecular area of the 14-day group compared to the 7-day group, but there was significant increase in the trabecular area of the 15-day controls compared to the 8-day controls. Irradiation increased the number of hypertrophic osteoclasts compared to non-irradiated injured tibiae (controls) on days 8 and 15. The Picrosirius-polarization method revealed bands of parallel collagen fibers (parallel-fibered bone) at the repair site of 14-day-irradiated tibiae, regardless of the dose. This organization improved when compared to 7-day-irradiated tibiae and control tibiae. These results show that low-level laser therapy stimulated the growth of the trabecular area and the concomitant invasion of osteoclasts during the first week, and hastened the organization of matrix collagen (parallel alignment of the fibers) in a second phase not seen in control, non-irradiated tibiae at the same period. The active osteoclasts that invaded the regenerating site were probably responsible for the decrease in trabecular area by the fourteenth day of irradiation. (C) 2003 Elsevier B.V. All rights reserved.

Comparison of the photodynamic fungicidal efficacy of methylene blue, toluidine blue, malachite green and low-power laser irradiation alone against Candida albicans

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

SrBi2Nb2O9 thin films crystallized using a low power microwave oven

SrBi2Nb2O9 thin films were produced by the polymeric precursor method using an aqueous solution. The crystallization of the films was carried out using a domestic microwave oven by means of a SiC susceptor in order to absorb the microwave energy and rapidly transfer the heat to the film. Low microwave power and short time have been used. The films obtained are well-adhered, homogeneous and with good specularity, even when treated at 600 degreesC for 10 min. The microstructure and the structure of the films can be tuned by adjusting the crystallization conditions. Depending on the direction of the heat flux it is possible to obtain preferential oriented or polycrystalline films in the microwave oven for 10 min. The microstructure presented a polycrystalline nature with spheroid small mean grain size when the susceptor is placed above the substrate. When the susceptor is placed below the substrate, the films presented platelet grains with mean grain size around 250 nm and a 001 orientation. For comparison, films were also prepared by the conventional method at 700 degreesC for 2 h. (C) 2003 Elsevier Ltd. All rights reserved.

Low power laser radiation at 685 nm stimulates stem-cell proliferation rate in Dugesia tigrina during regeneration

Today's scientific interest in tissue engineering for organ transplantations and regeneration from stem cells, allied with recent observations on biostimulation of tissues and cells by laser radiation, stands as a strong motivation for the present work, in which we examine the effects of the low power laser radiation onto planarians under regenerative process. To investigate those effects, a number of 60 amputated worms were divided in three study groups: a control group and two other groups submitted to daily 1 and 3 min long laser treatment sections at similar to 910 W/m(2) power density. A 685 nm diode laser with 35 mW optical power was used. Samples were sent to histological analysis at the 4th, the 7th and the 15th (lays after amputation. A remarkable increase in stem cells counts for the fourth day of regeneration was observed when the regenerating worms was stimulated by the laser radiation. Our findings encourage further research works on the influence of optical radiation onto stem cells and tissue regeneration. (c) 2005 Elsevier B.V. All rights reserved.

Photosensitization of different Candida species by low power laser light

The aim of this study was to evaluate the effects of the laser radiation (685 nm) associated with photosensitizers on viability of different species of Candida genus. Suspensions of Candida albicans, Candida dubliniensis, Candida krusei and Candida tropicalis, containing 106 viable cells per milliliter were obtained with the aid of a Neubauer's chamber. From each species, 10 samples of the cell suspension were irradiated with diode laser (685 nm) with 28 J/cm(2) in the presence of methylene blue (0.1 mg/ml), 10 samples were only treated with methylene blue, 10 samples were irradiated with laser in the absence of the dye, 10 samples were treated with the dye and irradiated with laser light and 10 samples were exposed to neither the laser light nor to the methylene blue dye. From each sample, serial dilutions of 10(-2) and 10(-3) were obtained and aliquots of 0.1 ml of each dilution were plated in duplicate on Sabouraud dextrose agar. After incubation at 37 degrees C for 48 h, the number of colony-forming units (CFU/ml) was obtained and data were submitted to ANOVA and Tukey's test (p < 0.05). Laser radiation in the presence of methylene blue reduced the number of CFU/ml in 88.6% for C. albicans, 84.8% for C. dubliniensis, 91.6% for C krusei and 82.3% for C tropicalis. Despite of this, only laser radiation or methylene blue did not reduce significantly the number of CFU/ml of Candida samples, except for C tropicalis. It could be concluded that the photo activation of methylene blue by the red laser radiation at 685 nm presented fungicide effect on all Candida species studied. (c) 2006 Elsevier B.V. All rights reserved.

Java applets for a WWW-HTML-based course in power electronics

This paper introduces Java applet programs for a WWW (world wide web)-HTML (hypertext markup language)-based multimedia course in Power Electronics. The applet programs were developed with the purpose of providing an interactive visual simulation and analysis of idealized uncontrolled single-phase, and three-phase rectifiers. In addition, this paper discusses the development and utilization of JAVA applet programs to solve some design-oriented equations for rectifier applications. The major goal of these proposed JAVA applets was to provide more facilities for the students increase their pace in Power Electronics course, emphasizing waveforms analysis, and providing conditions for an on-line comparative analysis among different hands-on laboratory experiences, via a normal Internet TCP/IP connection. Therefore, using the proposed JAVA applets, which were embedded in a WWW-HTML-based course in Power Electronics, was observed an important improvement of the apprenticeship for the content of this course. Therefore, the course structure becomes fluid, allowing a true on-line course over the WWW, motivating students to learn its content, and apply it in some applications-oriented projects, and their home-works.

Histological study of hamster buccal mucosa following topical application of DMBA and exposition to low power 337 nm laser light

The aim of the present work is to analyze the histological changes on hamster buccal mucosa caused by the topical use of 7,12-dimethylbenzanthracene (DMBA) and exposition to a 220 μJ/pulse nitrogen laser light (@ 337 nm) at an average power of 2,3 mW. Twenty-one hamsters divided into two experimental groups were treated six times with DMBA. One hamster was kept as control. Group I was composed by ten hamsters and was submitted only to DMBA. Group II, also with ten hamsters, received the same treatment as group I and was exposed to the laser radiation. The time duration of each irradiation section was 10 seconds. All the treatment happened in alternated days. The histological analysis took place twice, after the end of the treatment and after sixty days. Both experimental groups presented dilatation of vessels, thickening of the epithelial tissue and the presence of inflammatory infiltrates. The preliminary results indicates that in group II the number of dilated vessels and its new area are much more significant than in group I.

Educational Java applets get in power electronics labs

This paper presents Java applet programs for a WWW (world wide web)-HTML (hypertext markup language)-based multimedia course in basic power electronics circuits. These tools make use of the benefits of Java language to provide a dynamic and interactive approach to simulate steady-state idealized rectifiers (uncontrolled and controlled; single-phase and three-phase). In addition, this paper discusses the development and the use of the Java applet programs to assist the teaching of basics rectifier power electronics circuits, and to serve as a first design tool for basics power electronics circuits in the experiments of the laboratories. In order to validate the developed simulation applets, the results were confronted with results obtained from a well-know simulator package PSPICE. © 2005 IEEE.

Permanent Magnet Hall Thruster for satellite orbit raising with low power energy consumption

Electric propulsion is now a succeful method for primary propulsion of deep space long duration missions and for geosyncronous satellite attitude control. Closed Drift Thruster, so called Hall Thruster or SPT (Stationary Plasma Thruster), was primarily conceived in USSR (the ancient Soviet Union) and, since then, it has been developed by space agencies, space research institutes and industries in several countries such as France, USA, Israel, Russian Federation and Brazil. In this work we present the main features of the Permanent Magnet Hall Thruster (PMHT) developed at the Plasma Laboratory of the University of Brasilia. The idea of using an array of permanent magnets, instead of an electromagnet, to produce a radial magnetic field inside the plasma channel of the thruster is very significant. It allows the development of a Hall Thruster with power consumption low enough to be used in small and medium size satellites. Description of a new vacuum chamber used to test the second prototype of the PMHT (PHALL II) will be given. PHALL II has an aluminum plasma chamber and is smaller with 15 cm diameter and will contain rare earth magnets. We will show plasma density and temperature space profiles inside and outside the thruster channel. Ion temperature measurements based on Doppler broadening of spectral lines and ion energy measurements are also shown. Based on the measured plasma parameters we constructed an aptitude figure of the PMHT. It contains the specific impulse, total thrust, propellant flow rate and power consumption necessary for orbit raising of satellites. Based on previous studies of geosyncronous satellite orbit positioning we perform numerical simulations of satellite orbit raising from an altitude of 700 km to 36000 km using a PMHT operating in the 100 mN - 500 mN thrust range. In order to perform these calculations integration techniques were used. The main simulation paraters were orbit raising time, fuel mass, total satellite mass, thrust and exaust velocity. We conclude comparing our results with results obtainned with known space missions performed with Hall Thrusters. © 2008 by the American Institute of Aeronautics and Astronautics, Inc.

Power electronics courses for the new paradigms of the electrical system

This paper presents a historical perspective of the Power Electronics education that has lead to the present situation in which such technology is indispensable for the exploitation of almost all type of clean energy primary sources. Some academic initiatives in Brazil are here discussed focusing the institutions grouped in a CAPES-Pró-Engenharia program. The curricula aspects and innovations are presented, emphasizing the multidisciplinary character of this field of Power Electronics application. © 2011 IEEE.

Power Electronics course: Analysis and evaluation of the educational software and the environment learning

This paper presents the analysis and evaluation of the Power Electronics course at So Paulo State University-UNESP-Campus of Ilha Solteira(SP)-Brazil, which includes the usage of interactive Java simulations tools and an educational software to aid the teaching of power electronic converters. This platform serves as an oriented course for the lectures and supplementary support for laboratory experiments in the power electronics courses. The simulation tools provide an interactive and dynamic way to visualize the power electronics converters behavior together with the educational software, which contemplates the theory and a list of subjects for circuit simulations. In order to verify the performance and the effectiveness of the proposed interactive educational platform, it is presented a statistical analysis considering the last three years. © 2011 IEEE.

A single-phase single-stage buck-boost inverter intended for low power alternative energy conversion systems: Analysis, design and experimentation

This paper presents the operational analysis of the single-phase integrated buck-boost inverter. This topology is able to convert the DC input voltage into AC voltage with a high static gain, low harmonic content and acceptable efficiency, all in one single-stage. Main functionality aspects are explained, design procedure, system modeling and control, and also component requirements are detailed. Main simulation results are included, and two prototypes were implemented and experimentally tested, where its results are compared with those corresponding to similar topologies available in literature. © 2012 IEEE.