Desempenho de um painel fotovoltaico de baixa tensão, acoplado ao protótipo de um conversor dc/dc topologia Booster

Low voltage solar panels increase the reliability of solar panels due to reduction of in series associations the configurations of photovoltaic cells. The low voltage generation requires DCDC converters devices with high efficiency, enabling raise and regulate the output voltage. This study analyzes the performance of a photovoltaic panel of Solarex, MSX model 77, configured to generate an open circuit voltage of 10.5 V, with load voltage of 8.5 V, with short circuit current of 9 A and a power of 77 W. The solar panel was assembled in the isolated photovoltaic system configuration, with and without energy storage as an interface with a DCDC converter, Booster topology. The converter was designed and fabricated using SMD (Surface Mounted Devices) technology IC (integrated circuit) that regulates its output voltage at 14.2 V, with an efficiency of 87% and providing the load a maximum power of 20.88 W. The system was installed and instrumented for measurement and acquisition of the following data: luminosities, average global radiation (data of INPE Instituto Nacional de Pesquisas Espaciais), solar panel and environment temperatures, solar panel and DC-DC converter output voltages, panel, inverter, and battery charge output currents. The photovoltaic system was initially tested in the laboratory (simulating its functioning in ideal conditions of operation) and then subjected to testing in real field conditions. The panel inclination angle was set at 5.5°, consistent with the latitude of Natal city. Factors such as climatic conditions (simultaneous variations of temperature, solar luminosities and ra diation on the panel), values of load resistance, lower limit of the maximum power required by the load (20.88 W) were predominant factors that panel does not operate with energy efficiency levels greater than 5 to 6%. The average converter efficiency designed in the field test reached 95%

Ocorrência de Dictyla monotropidia Stål (Hemiptera: Tingidae) em Cordia verbenacea Al. DC no Brasil

Recently, Dictyla monotropidia Stal was observed feeding on plants of black sage (Cordia verbenacea Al. DC). The colonies of this insect were observed on abaxial surface of leaves, with nymphs and adults sucking the phloem sieve, causing spot, yellow aspect and leaf fall. D. monotropidia was already related as pest in other Cordia species in countries of Central and South America. Although, this is the first report of this insect attacking plants of C. verbenacea in Brazil.

Produção de fitomassa, teor e produtividade do óleo essencial de Baccharis dracunculifolia DC. em função da adubação orgânica

Objetivou-se avaliar a produção de fitomassa, teor e produtividade do óleo essencial de Baccharis dracuculifolia DC., em função de doses de adubo orgânico, e foram utilizadas mudas produzidas por semente, e mantidas sob sombrite pelo período de 84 dias até serem transplantadas para o campo, no espaçamento de 1,0 x 1,0 m, com irrigação por gotejamento. O delineamento estatístico utilizado foi em blocos ao acaso, com quatro repetições, e as doses de composto orgânico foram: 0, 10, 20, 30, 40 e 50 t ha-1. Foi realizada uma colheita, aos 150 dias após o transplante das mudas. O óleo essencial foi extraído por hidrodestilação e analisado em cromatógrafo a gás acoplado a espectrômetro de massas (Shimadzu, QP-5000). Todos os resultados foram submetidos à análise de variância pelo teste F seguido da análise de regressão e o teste Tukey para os dados: massa seca útil da parte aérea, teor e produtividade do óleo essencial. Para as variáveis massa seca total e massa seca útil da parte aérea, as dosagens estudadas influenciaram as plantas, que apresentaram os melhores resultados na dose 50 t ha-1. Para teor de óleo não houve influência significativa para as dosagens estudadas, porém a dose 30 t ha-1 apresentou o melhor resultado. Entretanto para a produtividade do óleo essencial, as dosagens estudadas influenciaram as plantas, que na dosagem 30 t ha-1 obtiveram os melhores resultados.

Controle da ferrugem das folhas do capim-limão [Cymbopogon citratus (DC: ) Stapf] com produtos naturais

Cymbopogon citratus (DC.) Stapf é uma planta medicinal pertencente a família Poaceae, perene, importante para a indústria farmacêutica e alimentícia devido ao óleo essencial que produz. Um problema limitante para a produção comercial é a ferrugem, doença cujo agente etiológico é o fungo Puccinia nakanishikii Dietel. O presente trabalho objetivou avaliar a ação de produtos naturais no controle da doença in vitro e in vivo. Para os testes in vitro, empregaram-se os seguintes produtos sobre a germinação de esporos do patógeno: óleos essenciais de eucalipto, palma-rosa, cravo-da-índia, menta, limão, citronela e mil-folhas; extrato pirolenhoso de eucalipto e mentol cristalizado, em diferentes concentrações. Para os testes de campo foram selecionados quatro produtos, o óleo de citronela e de eucalipto, o extrato pirolenhoso, e o mentol. In vitro, todos os agentes mostraram-se promissores no controle do patógeno. Quando em condições in vivo, sob alta severidade da doença no ato da avaliação, os produtos testados foram capazes de reduzir a severidade da doença em comparação com a testemunha. O controle da doença com os agentes naturais variou de 38% (extrato pirolenhoso) a 61%(óleo essencial de eucalipto).

Secagem do resíduo de acerola (Malphigia emarginata D.C.): estudo do processo e avaliação do impacto sobre o produto final

Brazil, one of the largest agricultural producers in the world, has managed in recent years to significantly improve its production. However, in response to this advance in the agro-industrial sector, the generation of agro-industrial residues has also increased. New technological alternatives have to be implemented in order to bring economic and rational use of this material and drying is one of the possible choices. Considering the great importance that bioactive compounds present for food science and technology, this research aims to evaluate the air-drying process of acerola residue in a tray convective drier under controlled temperature (60, 70 e 80ºC), air velocity (4.0, 5.0 e 6.0 m/s) and material width (0.5, 0.62 e 0.75 cm) by applying an experimental planning 23 + 3. Based on that, the impact on physical-chemical characteristics, color, bioactive compounds concentration and antioxidant activity of dried acerola waste was evaluated, having the in natura and freeze dried waste as control groups. Dried acerola residue presented natural pigments, mainly carotenoids (143.68 - 68.29 mg/g) and anthocyanins (290.92 - 90.11 mg/100 g), which explain the red and yellow instrumental color parameters observed. The acerola residue powder is also rich in phenolic compounds (3261.11 -2692.60 mgGAEeq/100g), proanthocyanidins (61.33-58.46 eq/100g), ascorbic acid (389.44 739.29 mg/100 g) and DPPH antioxidant activity (20.91 24.72 μg Trolox eq/g). Results show decreased concentration of phenolic compounds, anthocyanins, carotenoids, proanthocyanidins and ascorbic acid caused by the air-drying process. However, even after the observed drying losses, the acerola residue powder can be considered a high value food ingredient, considering the high bioactive compounds concentration found in the final product, as well as the colorimetric characterization and microbiological stability of the dried powder

Atividade antibacteriana do óleo essencial de Melampodium divaricatum (Rich.) DC., Asteraceae

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Crescimento de filmes nanométricos monocristalinos de Fe/MgO(100) por "SPUTTERING" DC

The research behind this master dissertation started with the installation of a DC sputtering system, from its first stage, the adaptation of a refrigerating system, passing by the introduction of a heating system for the chamber using a thermal belt, until the deposition of a series of Fe/MgO(100) single crystal nanometric film samples. The deposition rates of some materials such as Fe, Py and Cu were investigated through an Atomic Force Microscope (AFM). For the single crystal samples, five of them have the same growth parameters and a thickness of 250Å, except for the temperature, which varies from fifty degrees from one to another, from 100ºC to 300ºC. Three other samples also have the same deposition parameters and a temperature of 300ºC, but with thickness of 62,5Å, 150Å, and 250Å. Magneto-optical Kerr Effect (MOKE) of the magnetic curves measurements and Ferromagnetic Resonance (FMR) were made to in order to study the influence of the temperature and thickness on the sample s magnetic properties. In the present dissertation we discuss such techniques, and the experimental results are interpreted using phenomenological models, by simulation, and discussed from a physical point of view, taking into account the system s free magnetic energy terms. The results show the growth of the cubic anisotropy field (Hac) as the sample s deposition temperature increases, presenting an asymptotic behavior, similar to the characteristic charging curve of a capacitor in a RC circuit. A similar behavior was also observed for the Hac due to the increase in the samples thicknesses. The 250˚A sample, growth at 300°C, presented a Hac field close to the Fe bulk value

Resolvendo problemas de fluxo de potência ótimo DC através de uma rede de hopfield modificada

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

Analysis of the E-J Curve of HTS Tapes Under DC and AC Magnetic Fields at 77 K

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

DC and AC side harmonics in CCC converters

The capacitor-commutated converter (CCC) has frequently been used in the conception of HVDC systems connected to busbars with low short circuit level. This alternative arrangement, in substitution to the conventional ones, guarantees less sensitive operational conditions to problems related with the commutation failure in the inverters besides supplying part of the reactive energy to be compensated. Studies related with its performance in steady and transient states have been presented in several works, however its behavior as harmonic source is still little explored. This work presents preliminary studies focusing the generation of characteristic harmonics by this type of converter. Subjects related with the amplification of the harmonic magnitudes are investigated and compared considering similar arrangements of conventional static converters (LCC) and CCC schemes. It is also analyzed the harmonic generation on the dc side of the installation and its influence on the ac side harmonics. The results are obtained from simulations in the time domain in PSpice environment and they clearly illustrate the operational differences between the L CC and the CCC schemes with regard to characteristic harmonic generation.

Variable-Structure Control Design of Switched Systems With an Application to a DC-DC Power Converter

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

DCM Boost interleaved converter for operation in AC and DC to trolleybus application

This paper is based on the development and experimental analysis of a DCM Boost interleaved converter suitable for application in traction systems of electrical vehicles pulled by electrical motors (Trolleybus), which are powered by urban DC or AC distribution networks. This front-end structure is capable of providing significant improvements in trolleybuses systems and in the urban distribution network costs, and efficiency. The architecture of proposed converter is composed by five boost power cells in interleaving connection, operating in discontinuous conduction mode. Furthermore, the converter can operate as AC-DC converter, or as DC-DC converter providing the proper DC output voltage range required by DC or AC adjustable speed drivers. Therefore, when supplied by single-phase AC distribution networks, and operating as AC-DC converter, it is capable to provide high power factor, reduced harmonic distortion in the input current, complying with the restrictions imposed by the IEC 61000-3-4 standards. The digital controller has been implemented using a low cost FPGA and developed totally using a hardware description language VHDL and fixed point arithmetic. Thus, two control strategies are evaluated considering the compliance with input current restrictions imposed by IEC 61000-3-4 standards, the regular PWM modulation and a current correction PWM modulation. In order to verify the feasibility and performance of the proposed system, experimental results from a 15 kW low power scale prototype are presented, operating in DC and AC conditions.

Simulation Tools of DC-DC Converters for Power Electronics Education

This paper presents interactive simulation tools to support the enhancement of power electronics education considering DC to DC converters. These interactive tools make use of the benefits of Java language to provide a dynamic and interactive visualization of simulations in steady-state for idealized non-isolated DC to DC converters. Additionally, this paper discusses the features and the usage of the interactive educational tools to serve as a first design tool for the laboratory experiments in the power electronics courses. In this way, some results were confronted with a well-known simulator package and with experimental results in order to validate the developed interactive simulation tools.

DC Electric Field Dependence of the Dielectric Constant of Pzt Thin Films Prepared by Polymeric Precursor Method

This work reports dielectric measurements performed on Pb(Zr0.53Ti0.47)O3 (PZT) thin films prepared by a polymeric precursor method. The -E curves obtained for the PZT film measured at 100 kHz, under a small ac 0.2 kV/cm signal-test and a dc scan featured a typical butterfly curve. However, the -E curves obtained for PZT film under a dc scan, with a scan rate of 0.003 V/s, shows a pronounced asymmetry. The absence of a symmetric secondary peak in -E curves could be an indication of essentially 180 domain switching.

Uso de reguladores vegetais na conservação refrigerada de acerolas (Malpighia glabra L.)

Com o objetivo de avaliar o uso do ácido giberélico (GA3) e da benzilaminopurina (BAP) na conservação de acerolas (Malpighia glabra L.) colhidas no estádio verde e armazenadas sob refrigeração, acerolas foram submetidas aos seguintes tratamentos, sob imersão por 30 minutos: controle (água), 50 mg L-1 e 100 mg L-1 de GA3, 50 mg L-1 e 100 mg L-1 de BAP. Após os tratamentos, os frutos foram deixados para secar ao ar em local fresco e, então, embalados em bandejas de isopor cobertas com filme de polietileno e armazenados em câmara B.O.D a 8±1ºC, por 14 dias. As avaliações foram realizadas em intervalos de 4 dias. Os frutos amostrados foram submetidos a avaliações de coloração, teor de sólidos solúveis, acidez titulável e teor de ácido ascórbico. A análise dos resultados mostrou que a aplicação dos reguladores não teve efeito no aumento da conservação refrigerada de acerolas e que somente a refrigeração foi suficiente para conservá-las durante 14 dias.