Power Factor Correction Boost Converter Based on the Three-State Switching Cell

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação nutricional, em tilápias-do-nilo, de farinhas de sangue bovino obtidas por três métodos de processamento

Avaliaram-se farinhas de sangue obtidas pelos métodos de processamento em tambor, convencional e atomização. As farinhas foram submetidas ao processo de extração e fracionamento da proteína para determinação do perfil do tamanho molecular, que foi comparado ao do sangue bovino in natura. Nas amostras, submetidas ou não ao processo de desengorduramento, foram realizadas análises da digestibilidade in vitro da proteína. Para determinação dos coeficientes de digestibilidade dos nutrientes in vivo, foram confeccionadas quatros rações, sendo uma sem farinha de sangue, denominada ração-referência purificada. Para essa etapa, juvenis de tilápia-do-nilo com peso médio inicial de 100,0±5,0 g foram estocados em aquários de 250 L, em delineamento de blocos casualizados, com quatro repetições e dez peixes/unidade experimental. As rações-teste foram obtidas com a introdução de 30% das farinhas de sangue em estudo. O processamento afetou a estrutura proteica original do sangue in natura em condições de alta temperatura e tempo prolongado, efeito traduzido pela alta proporção de peptídeos de baixo peso molecular e aminoácidos livres, correspondendo a baixos valores de digestibilidade da proteína da farinha de sangue nos testes in vivo e in vitro. A farinha de sangue atomizada e a de tambor são eficientemente utilizadas por tilápias-do-nilo. Na farinha de sangue convencional, a proteína teve valor biológico inferior ao das outras duas farinhas. Na formulação de rações contendo farinha de sangue para tilápias-do-nilo, a isoleucina deve ser considerada o primeiro aminoácido limitante, seguida pela metionina+cistina, arginina e treonina, que foram encontradas em níveis críticos para essa espécie, principalmente na farinha de sangue convencional.

Aspects of classical and quantum motion on a flux cone

Motion of a nonrelativistic particle on a cone with a magnetic flux running through the cone axis (a flux cone) is studied. It is expressed as the motion of a particle moving on the Euclidean plane under the action of a velocity-dependent force. The probability fluid (quantum flow) associated with a particular stationary state is studied close to the singularity, demonstrating nontrivial Aharonov-Bohm effects. For example, it is shown that, near the singularity, quantum flow departs from classical flow. In the context of the hydrodynamical approach to quantum mechanics, quantum potential due to the conical singularity is determined, and the way it affects quantum flow is analyzed. It is shown that the winding number of classical orbits plays a role in the description of the quantum Bow. The connectivity of the configuration space is also discussed.

Serpentine leafminer (Liriomyza trifolii) on potato (Solanum tuberosum): field observations and plant photosynthetic responses to injury

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Proposta de avanço para o método Tambor-Pulmão-Corda Simplificado aplicado em ambientes de produção sob encomenda

Recentes aplicações da Teoria das Restrições em Gestão de Operações têm adotado o chamado método Tambor-Pulmão-Corda Simplificado (S-DBR - Simplified Drum-Buffer-Rope) como padrão para planejamento e controle da produção. Contudo, poucas são as referências bibliográficas, especialmente em periódicos nacionais e internacionais, que relatam seus principais conceitos e premissas. Este artigo se propõe a apresentar o método S-DBR para planejamento da produção e sua correspondente abordagem de controle da produção denominado Gerenciamento do Pulmão, aqui abordados em ambientes de produção sob encomenda (MTO - make to order), suas principais características, pressupostos e diferenças em relação ao método DBR clássico. É também apresentada uma proposta complementar ao método S-DBR para estabelecer promessas de entregas urgentes mantendo elevada probabilidade de entrega no prazo.

Generalization of the delta-differential autotransformer for 12 and 18-pulse converters

This work proposes a methodology to generalize the A-connections for 12 and 18-pulse autotransformers. A single mathematical expression, obtained through simple trigonometric operations, represents all the connections. The proposed methodology allows choosing any ratio between the input and the output voltages. The converters can operate either as step-up or as step-down voltage. To simplify the design of the windings, graphics are generated to calculate the turn-ratio and the polarity of each secondary winding, with respect to the primary winding. A design example, followed by digital simulations, and experimental results illustrate the presented steps. The results also show that high power factor is an inherent characteristic of multi-pulse converters, without any active or passive power factor pre-regulators needs.

A 12 kW three-phase low THD rectifier with high-frequency isolation and regulated DC output

A robust 12 kW rectifier with low THD in the line currents, based on an 18-pulse transformer arrangement with reduced kVA capacities followed by a high-frequency isolation stage is presented in this work. Three full-bridge (buck-based) converters are used to allow galvanic isolation and to balance the dc-link currents, without current sensing or current controller. The topology provides a regulated dc output with a very simple and well-known control strategy and natural three-phase power factor correction. The phase-shift PWM technique, with zero-voltage switching is used for the high-frequency dc-dc stage. Analytical results from Fourier analysis of winding currents and the vector diagram of winding voltages are presented. Experimental results from a 12 kW prototype are shown in the paper to verify the efficiency, robustness and simplicity of the command circuitry to the proposed concept.

Effect of mechanical loading on the I-c degradation behavior of Bi-2223 tapes

During the winding process of HTS coils the tapes of Bi-2223 are subjected to the influence of bending strain, axial strain, compressive force and torsional deformation resulting in I-c degradation. In the literature the effects of the individual strain components are separately analyzed in spite of during coil winding and energizing the strain-stress effects are combined. In this work using commercial tapes of Bi-2223 Ag/AgMg with and without stainless steel reinforcement several samples were wound on cylindrical FRP G-10 holder in which different combined strains are applied. Measurements of I - V characteristic curves are done to determine the degree of critical current degradation and the operational limits. The results are compared with the I, values of short samples and other specimens subjected to deformation generated by loading types such as tensile and bending strain.

New 12kW three-phase 18-pulse high power factor AC-DC converter with regulated output voltage for rectifier units

This work presents a new high power factor three-phase rectifier based on a Y-connected differential autotransformer with reduced kVA and 18-pulse input current followed by three DC-DC boost converters. The topology provides a regulated output voltage and natural three-phase input power factor correction. The lowest input current harmonic components are the 17th and the 19th. Three boost converters, with constant input currents and regulated parallel connected output voltages are used to process 4kW each one. Analytical results from Fourier analyses of winding currents and the vector diagram of winding voltages are presented. Simulation results to verify the proposed concept and experimental results are shown in the paper.

Morphological aspects of the liver of the Podocnemis expansa (Testudines, podocnemididae)

The liver of P. expansa was characterized morphohistologically. To this end, twenty livers from clinically healthy male and female Podocnemis expansa, weighing from 2.0 to 4,5 kg, supplied by the commercial breeder Fazenda Moenda da Serra, in Araguapaz, state of Goiás, Brazil, were analyzed macro-and microscopically. The coelomatic cavity was opened and the topography of the fresh organs was examined visually. After the histological preparation, the slides were stained with Hematoxylin and Eosin (HE), Periodic Acid-Schiff (PAS), Gomori Trichrome, Reticulin and Picrosirius. The liver of P. expansa is a voluminous organ with an approximately rectangular shape and brown coloration, varying from light to dark shades, and is divided into a right lobe, left lobe, and a central portion. The right lobe is the largest of the three portions. The gall bladder is located in a depression in the caudal portion of the right lobe, where the gall duct begins and empties into the duodenum. Histologically, the hepatocytes are arranged in the form of double cords surrounded by winding sinusoidal capillaries. In cross section, they resemble acini containing approximately two to five hepatocytes surrounding a probable central biliary canaliculus. The hepatocytes are polyhedral or pyramidal in shape, of uniform size, with a few central nuclei and others displaced peripherally, and the cytoplasm is little eosinophilic when analyzed by the HE staining technique. The parenchyma is supported by delicate reticular fibers surrounding hepatocytes and sinusoids. The parenchyma and perisinusoidal spaces contain large quantities of melanomacrophages, mainly close to the portal spaces.

Fault current limiter using transformer and modular device of YBCO coated conductor

In this work, we report on the evaluation of a superconducting fault current limiter (SFCL). It is consisted of a modular superconducting device combined with a short-circuited transformer with a primary copper winding connected in series to the power line and the secondary side short-circuited by the superconducting device. The basic idea is adding a magnetic component to contribute to the current limitation by the impedance reflected to the line after transition of the superconducting device. The evaluation tests were performed with a prospective current up to 2 kA, with the short-circuited transformer of 2.5 kVA, 220 V/660 V connected to a test facility of 100 kVA power capacity. The resistive SFCL using a modular superconducting device was tested without degradation for a prospective fault current of 1.8 kA, achieving the limiting factor 2.78; the voltage achieved 282 V corresponding to an electric field of 11 V/m. The test performed with the combined SFCL (xsuperconducting device + transformer) using series and toroidal transformers showed current limiting factor of 3.1 and 2 times, respectively. The test results of the combined SFCL with short-circuited transformer showed undesirable influence of the transformer impedance, resulting in reduction of the fault current level. © 2002-2011 IEEE.

A influência da dança na percepção de estruturas rítmicas monotônicas em adolescentes surdos

Dance activities were administered to a group of deaf adolescents via visual and auditory stimuli in order to improve their perceptions of monotonic rhythmic structures. Status of psychomotor development was also assessed before and after participation in the program. Twenty deaf adolescents (ages between 12 and 13 years) were divided into two groups, experimental (EG) and control (CG). Before and after participating in the program for 26 weeks, participants were evaluated in rhythmical tasks adapted from the classical test of M. Stambak. The tasks included the perception of drum beats, actually viewed hit movements, or heard via a sound amplifier. Psychomotor tests were administered only to the EG. The period of practice with dance activities changed the individuals' performance in the monotonic rhythmic test. Also, the success rate improved in both, visual and auditory input tasks. Individuals in the CG showed no changes in performance. For the EG, in the post-test, the status of psychomotor development was six months below the target age of the tests (i.e., 11 years). Findings suggested that dance activities can change deaf individuals' auditory perception of rhythmic structures. Participation in such a program can also positively affect psychomotor development. © FTCD/FIP-MOC.

Projeto e simulação de um sistema de controle via LMIs da produção de vapor de uma caldeira aquatubular

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação de um biorreator rotativo para fermentação em estado sólido

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dinâmica caótica e sincronização de fase em mapas acoplados

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)