Harmonic content identification based on neural method for single phase power systems

An alternative method is presented in this paper to identify the harmonic components of non-linear loads in single phase power systems based on artificial neural networks. The components are identified by analyzing the single phase current waveform in time domain in half-cycle of the ac voltage source. The proposed method is compared to the fast Fourier transform. Simulation and experimental results are presented to validate the proposed approach.

Isolation and identification of black yeasts by enrichment on atmospheres of monoaromatic hydrocarbons

Black yeast members of the Herpotrichiellaceae present a complex ecological behavior: They are often isolated from rather extreme environments polluted with aromatic hydrocarbons, while they are also regularly involved in human opportunistic infections. A selective technique to promote the in vitro growth of herpotrichiellaceous fungi was applied to investigate their ecophysiology. Samples from natural ecological niches and man-made environments that might contain black yeasts were enriched on an inert solid support at low humidity and under a controlled atmosphere rich in volatile aromatic hydrocarbons. Benzene, toluene, and xylene were provided separately as the sole carbon and energy source via the gas phase. The assayed isolation protocol was highly specific toward mesophilic Exophiala species (70 strains of this genus out of 71 isolates). Those were obtained predominantly from creosote-treated railway ties (53 strains), but isolates were also found on wild berries (11 strains) and in guano-rich soil samples (six strains). Most of the isolates were obtained on toluene (43 strains), but enrichments on xylene and benzene also yielded herpotrichiellaceous fungi (17 and 10 isolates, respectively). Based upon morphological characterizations and DNA sequences of the full internal transcriber spacers (ITS) and the 8.5S rRNA genes, the majority of the obtained isolates were affiliated to the recently described species Exophiala xenobiotica (32 strains) and Exophiala bergeri (nine strains). Members of two other phylogenetic groups (24 and two strains, respectively) somewhat related to E. bergeri were also found, and a last group (three strains) corresponded to an undescribed Exophiala species. © 2010 The Author(s).

Contribution of distributed generators to the harmonic distortion in low voltage power network

In the last 20 years immense efforts have been made to utilize renewable energy sources for electric power generation. This paper investigates some aspects of integration of the distributed generators into the low voltage distribution network. An assessment of impact of the distributed generators on the voltage and current harmonic distortion in the low voltage network is performed. Results obtained from a case study, using real-life low voltage network, are presented and discussed.

Biochemical biomarkers in Nile tilapia (Oreochromis niloticus) after short-term exposure to diesel oil, pure biodiesel and biodiesel blends

Fossil fuels such as diesel are being gradually replaced by biodiesel, a renewable energy source, cheaper and less polluting. However, little is known about the toxic effects of this new energy source on aquatic organisms. Thus, we evaluated biochemical biomarkers related to oxidative stress in Nile tilapia (Oreochromis niloticus) after two and seven exposure days to diesel and pure biodiesel (B100) and blends B5 and B20 at concentrations of 0.01 and 0.1mLL -1. The hepatic ethoxyresorufin-O-deethylase activity was highly induced in all groups, except for those animals exposed to B100. There was an increase in lipid peroxidation in liver and gills in the group exposed to the higher concentration of B5. All treatments caused a significant increase in the levels of 1-hydroxypyrene excreted in the bile after 2 and 7d, except for those fish exposed to B100. The hepatic glutathione-S-transferase increased after 7d in animals exposed to the higher concentration of diesel and in the gill of fish exposed to the higher concentration of pure diesel and B5, but decreased for the two tested concentrations of B100. Superoxide dismutase, catalase and glutathione peroxidase also presented significant changes according to the treatments for all groups, including B100. Biodiesel B20 in the conditions tested had fewer adverse effects than diesel and B5 for the Nile tilapia, and can be suggested as a less harmful fuel in substitution to diesel. However, even B100 could activate biochemical responses in fish, at the experimental conditions tested, indicating that this fuel can also represent a risk to the aquatic biota. © 2011 Elsevier Ltd.

Computer tools to aid the learning and design steps for photovoltaic systems

This paper presents novel simulation tools to assist the lecturers about learning processes on renewable energy sources, considering photovoltaic (PV) systems. The PV behavior, functionality and its interaction with power electronic converters are investigated in the simulation tools. The main PV output characteristics, I (current) versus V (voltage) and P (power) versus V (voltage), were implemented in the tools, in order to aid the users for the design steps. In order to verify the effectiveness of the developed tools the simulation results were compared with Matlab. Finally, a prototype was implemented with the purpose to compare the experimental results with the results from the proposed tools, validating its operational feasibility. © 2011 IEEE.

Research on photovoltaics: Review, trends and perspectives

This paper presents a briefly review, some trends and perspectives in the field of Photovoltaic energy conversion, which is considered to be the most important renewable energy source in few years, in the coming decades. The power electronics plays a fundamental role in this process, developing systems each times more competitive, efficient, reliable, and also reducing costs and reducing the payback time. Some trends are visible, which are the use of Silicon Carbide devices in PV inverters, the use of integrated inverter structures, the integration of power converters into the PV module or the use of few PV series connection, the development of thinner and more efficient solar cells. Moreover, the discussion about the necessity of MPPT and anti-island schemes are presented, mainly considering the expected growth of grid-tied applications. © 2011 IEEE.

Fontes energéticas associadas ao farelo de girassol ou à ureia em dietas para novilhos

The objective of this study was to evaluate the performance and carcass traits of steers fed corn or citrus pulp associated with sunflower meal or urea. Diets were composed of two energy sources (corn grain and citrus pulp) associated with two protein sources (soybean meal and urea), resulting in four treatments in forage:concentrate ratio of 40:60. It were used 24 steers, 1/2 Angus × 1/2 Nellore (18 months old and 329 kg BW) distributed in a completely randomized design which were finished in feedlot for 80 days. It were evaluated the intake, average daily gain and carcass traits of the animals. Intake of dry matter (DMI), crude protein (CPI) and neutral detergent fiber (NDFI) were affected (p<0.05) by diets. The diet with citrus pulp and urea (PU) showed the lowest (p<0.05) DMI (8.30 kg), CPI (1.03 kg) and NDFI (3.31 kg). The average daily weight gain (ADG) followed the behavior of DMI, NDFI and CPI and the lowest value (p<0.05) was observed for animals fed diet PU. Regarding carcass traits, diets containing corn associated with urea (MU) or sunflower meal (MFG) and citrus pulp associated with sunflower meal (PFG), provided the highest (p<0.05) carcass cold weights (238.37, 247.26 and 237.14 kg, respectively). However, the lowest cold carcass dressing percentage (p<0.05) was obtained in diet MU (50.57%). The association of citrus pulp with urea should not be performed when citrus pulp partially or totally replace corn as energy source in diets, because possibly this association promote an energy deficit resulting in lower performance and worse carcass traits of animals finished in feedlot.

Tri-state single-phase integrated inverters with input to output power decoupling control

Researches on control for power electronics have looked for original solutions in order to advance renewable resources feasibility, specially the photovoltaic (PV). In this context, for PV renewable energy source the usage of compact, high efficiency, low cost and reliable converters are very attractive. In this context, two improved simplified converters, namely Tri-state Boost and Tri-state Buck-Boost integrated single-phase inverters, are achieved with the presented Tri-state modulation and control schemes, which guarantees the input to output power decoupling control. This feature enhances the field of single-phase PV inverters once the energy storage is mainly inductive. The main features of the proposal are confirmed with some simulations and experimental results. © 2012 IEEE.

Quenching in a non-ideal mechanical system and the Averaging Method

In this paper, for the first time, a quenching result in a non-ideal system is rigorously obtained. In order to do this a new mechanical hypothesis is assumed, it means that the moment of inertia of the rotating parts of the energy source is big. From this is possible to use the Averaging Method. © 2012 American Institute of Physics.

Efficiency analysis of an isolated high voltage gain converter operating in resonant and non-resonant mode

This paper presents an efficiency investigation of an isolated high step-up ratio dc-dc converter aimed to be used for energy processing from low-voltage high-current energy sources, like batteries, photovoltaic modules or fuel-cells. The considered converter consists of an interleaved active clamp flyback topology combined with a voltage multiplier at the transformer secondary side capable of two different operating modes, i.e. resonant and non-resonant according to the design of the output capacitors. The main goal of this paper is to compare these two operating modes from the component losses point of view with the aim of maximize the overall converter efficiency. The approach is based on losses prediction using steady-state theoretical models (designed in Mathcad environment), taking into account both conduction and switching losses. The models are compared with steady-state simulations and experimental results considering different operating modes to validate the approach. © 2012 IEEE.

Macroinvertebrados aquáticos associados à Eichhornia azurea (Swartz) Kunth e suas relações com as variáveis abióticas em ecossistemas lênticos marginais (São Paulo, Brasil)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Quantificação de ácidos graxos de alevinos de tilápia do Nilo (Oreochromis niloticus) alimentados com diferentes fontes de óleos vegetais

The present work aimed to quantify the fatty acids in total lipids of Nile tilapia fingerlings (Oreochromis niloticus) fed with different sources of vegetable oils mechanically extracted. Were used 320 tilapias (O. niloticus) with average initial weight and average total initial length of 2.55±0.57 g and 5.59±0.43 cm, respectively, fed for a period of 60 days, in a randomized block design with eight treatments and four replications. The diets were prepared with 320 g/kg crude protein and 3.500 kcal of digestible energy per kg of feed enriched with eight different oils: sunflower, canola, sesame, linseed, peanut, Para's nut soy and macadamia, with an addition of 4%. Among the major fatty acids the oleic, palmitic, linolenic and linoleic were obtained in higher concentration (mg/g of LT) in fish from all treatments. The sums of polyunsaturated fatty acids after 60 days of cultivation had increased in all treatments compared to the 30 days of the experiment. This is due to the addition of oils with high contents of n-6 and n-3 fatty acids. The fatty acids in the carcass are a reflection of the energy source of oil used. As a conclusion it is recommended the use of linseed oil in the diet of tilapia fingerlings due to great improvement in the relationship between n-6/n-3.

The application of a surface response methodology in the solar/UV-induced degradation of dairy wastewater using immobilized ZnO as a semiconductor

An Advanced Oxidation Process (AOPs) was carried out in this study with the use of immobilized ZnO and solar/UV as an energy source to degrade dairy wastewater. The semibatch reactor system consisted of metal plate of 800 × 250 mm and a glass tank. The reaction time was of 3 h for 3 L of dairy wastewater. Experiments were performed based on a surface response methodology in order to optimize the photocatalytic process. Degradation was measured in percentage terms by total organic carbon (TOC). The entry variables were ZnO coating thickness and pH, using three levels of each variable. The optimized results showed a TOC degradation of 31.7%. Optimal parameters were metal-plate coating of 100 m of ZnO and pH of 8.0. Since solar/UV is a constant and free energy source in most tropical countries, this process tends to suggest an interesting contribution in dairy wastewater treatment, especially as a pretreatment and the optimal conditions to guarantee a better efficiency of the process. © 2013 Gisella R. Lamas Samanamud et al.

Produção de etanol a partir de mosto hidrolisado hemicelulósico de ponta e palha de cana-de-açúcar

Pós-graduação em Microbiologia Agropecuária - FCAV

Estudo comparativo do estresse oxidativo entre tilápias (Oreochromis niloticus) e cascudos (Pterygoplichthys anisitsi) expostos a óleo diesel e a biodiesel

Pós-graduação em Biologia Animal - IBILCE