Conversor CA-CA de elevado fator de potência para aplicações com geradores de Ímã permanente

This paper proposes and describes a high power factor AC-AC converter for naval applications using Permanent Magnet Generator (PMG). The three-phase output voltages of the PMG vary from 260 Vrms (220 Hz) to 380 Vrms (360 Hz), depending on load conditions. The proposed converter consists of a Y-/ΔY power transformer, which provides electrical isolation between the PMG and remaining stages, and a twelve-pulse uncontrolled rectifier stage directly connected to a single-phase inverter stage, without the use of an intermediary DC-DC topology. This proposal results in more simplicity for the overall circuitry, assuring robustness, reliability and reduced costs. Furthermore, the multipulse rectifier stage is capable to provide high power factor and low total harmonic distortion for the input currents of the converter. The single-phase inverter stage was designed to operate with wide range of DC bus voltage, maintaining 120 Vrms, 60 Hz output. The control philosophy, implemented in a digital signal processor (DSP) which also contains protection routines, alows series connections between two identical converters, achieving 240 Vrms, 60 Hz total output voltage. Measured total harmonic distortion for the AC output voltage is lower than 2% and the input power factor is 0.93 at 3.6kW nominal load. © 2010 IEEE.

Inversor CS Boost monofásico em aplicações com fontes renováveis

This paper presents a new methodology for the operation and control of a single-phase current-source (CS) Boost Inverter, considering that the conventional current-source inverter (CSI) has a right-half-plane (RHP) zero in its control-to-output transfer function, and this RHP zero causes the known non-minimum-phase effects. In this context, a special design with low boost inductance and a multi-loop control is developed in order to assure stable and very fast dynamics. Furthermore, the Inverter presents output voltage with very low total harmonic distortion (THD), reduced components and high power density. Therefore, this paper presents the inverter operation, the proposed control technique, and main simulation and experimental results in order to demonstrate the feasibility of the proposal. © 2010 IEEE.

Charged particle transverse momentum spectra in pp collisions at √s = 0:9 and 7 TeV

The charged particle transverse momentum (pT) spectra are presented for pp collisions at √s = 0:9 and 7TeV. The data samples were collected with the CMS detector at the LHC and correspond to integrated luminosities of 231 μb-1 and 2.96 pb-1, respectively. Calorimeter-based high-transverse-energy triggers are employed to enhance the statistical reach of the high-pT measurements. The results are compared with leading and next-toleading order QCD and with an empirical scaling of measurements at different collision energies using the scaling variable xT - 2pT=ps over the pT range up to 136 GeV/c. Using a combination of xT scaling and direct interpolation at fixed pT, a reference transverse momentum spectrum at √s = 2:76TeV is constructed, which can be used for studying high-pT particle suppression in the dense QCD medium produced in heavy-ion collisions at that centre-of-mass energy. Copyright CERN.

3-D Space Vector PWM implementation for Four-Leg Voltage Source Inverter

The Space Vector PWM implementation and operation for a Four-leg Voltage Source Inverter (VSI) is detailed and discussed in this paper. Although less common, four-leg VSIs are a viable solution for situations where neutral connection is necessary, including Active Power Filter applications. This topology presents advantages regarding the VSI DC link and capacitance, which make it useful for high power devices. Theory, implementation and simulations are also discussed in this paper. © 2011 IEEE.

Bridgeless interleaved boost PFC converter with variable duty cycle control

This paper proposes a bridgeless boost interleaved PFC (power factor correction) converter with variable duty cycle control. The application of bridgeless technique causes reduction of conduction losses, while the interleaving technique of converters cells allows division of efforts in semiconductor devices and reduction of weight and volume of the input EMI filter. The use of variable duty cycle control has the functions of regulating the output voltage and eliminating the low order harmonic components that appears in the input current of the common interleaved power factor converters working in Discontinuous Conduction Mode (DCM). The simulation results of the proposed converter presented high power factor and a good transient response in relation to the output voltage regulation in presence of high load variations and supply voltage variations. © 2011 IEEE.

Coeficiente de operación de un sistema formado por un refrigerador doméstico acoplado a un acumulador de agua caliente para la recuperación de energía

An experimental apparatus containing a domestic refrigerator coupled to a vertical hot water storage tank was used for energy recovery. The original condenser of the refrigerator was maintained, but modified with a concentric tubes heat exchanger with countercurrent water and refrigerating gas flows. The coefficient of performance for the heat pump is calculated by the ratio of energy in the heat storage and the electric power consumed by the domestic refrigerator compressor. The results show that the increasing of hydrostatic pressure in the storage tank increases the water flow rate and the coefficient of performance. The proposed device also reduces the heat dissipation to the surroundings. This is more important in small confinements found in low-cost houses.

A new design methodology for multipulse rectifiers with Delta auto-connected transformers and a retrofit application in Adjustable Speed Drives (ASDs)

Multipulse rectifiers can replace a conventional six pulse three-phase rectifier (diode bridge) providing a DC voltage with low ripple, low Total Harmonic Distortion of current (THDi) and a high Power Factor (PF). In this context is presented a multipulse rectifier with generalized Delta-differential autotransformer topology, which can provide any level of DC output voltage for any level of three-phase AC input voltage. This paper presents all the possible configurations for Delta topology in order to choose, through graphics, one configuration that presents reduced weight and volume. The average voltage on the DC bus must be compatible with the DC voltage in the six pulse rectifier used in commercial ASDs. Therefore, it is possible to apply the retrofit technique to replace the conventional bridge rectifier by the proposed multipulse rectifier. Based on mathematic models and simulation results, an 18-pulse rectifier with Delta topology, 220 V of line voltage, 315 V of DC output, and rating 2.5 kW of power was designed, implemented and applied for three different commercial ASDs. Experimental results as voltage and current waveforms and results about PF and THDi will be presented. © 2012 IEEE.

A 12-month follow-up of hypopigmentation after laser hair removal

Introduction: Laser hair removal is becoming an increasingly popular alternative to traditional methods such as shaving, waxing, among other methods. Semiconductor diode lasers are considered the most efficient light sources available and are especially well suited for clinical applications including hair reduction. The effectiveness of laser hair reduction depends on many variables, including the skin type of the patient. Material and Methods: A patient with Fitzpatrick Skin Type IV was submitted to laser hair removal of the arms with a high-power diode laser system with long pulses with a wavelength of 800 nm, a fluence of 40 J/cm2 and a pulse width of 20 ms. A 12-month follow-up assessment was performed and included photography and questionnaire. Results: Hypopigmentation was observed after a single laser hair removal section. After 6 months with the area totally covered, a gradual suntan with a sun screen lotion with an SPF of 15 was prescribed by the dermatologist. After 12 months of the initial treatment, a complete recovery of the hypopigmentation was achieved. Conclusion: Although a safe procedure, lasers for hair removal may be associated with adverse side effects including undesired pigment alterations. Before starting a laser hair removal treatment, patients seeking the eradication of hair should be informed that temporary, and possibly permanent, pigmentary changes may occur. © 2013 Informa UK, Ltd.

Macrophage migration inhibitory factor and oral cancer

Background: Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine with pro-inflammatory functions and involved in tumorigenesis. The aim of this study was to evaluate the expression and localization of the macrophage MIF in oral squamous carcinoma (OSC). In addition, the relationship between MIF expression and clinicopathological parameters such as survival data, tobacco use, alcohol habits, TNM stage, tumor graduation, and peritumoral inflammatory infiltrate were evaluated. Methods: Using immunohistochemistry, expression and localization of MIF was detected in 44 specimens of OSC. The absolute number and relative proportions of MIF-positive cells detected were also determined separately for tumor parenchyma vs. stroma. All counts were determined from 10 consecutive high-power fields using an integration graticule. Moreover, some parameters were analyzed separately for lip and intra-oral cancers. Results: Migration inhibitory factor-positive cells were observed in both the tumor parenchyma and in inflammatory cells of all specimens. In contrast, MIF expression was not detected in tumoral nests associated with poorly differentiated tumors. In specimens of lip cancer, a greater number of MIF-positive stromal immune cells were detected than in intra-oral cancer specimens (Mann-Whitney test, P = 0.049). Conclusions: Oral squamous carcinoma cells consistently express MIF independent of their location. Lip tumors presented more MIF-positive peritumoral inflammatory cells, similar to control, suggesting that immunological differences in leukocyte activation exist between in lip and intra-oral cancers. © 2012 John Wiley & Sons A/S.

Mononuclear inflammatory infiltrate and microcirculation injury in acute rejection: Role in renal allograft survival

This study aimed at investigating associations between monocytes/ macrophages (Mo) infiltration and three important criteria associated with acute antibody-mediated rejection: C4d staining, microcirculation injury, and graft survival time. By quantitative analysis, Mo were counted in peritubular capillaries and in the interstitial compartment (peritubular/interstitial Mo), and they were also identified in glomeruli (glomerular Mo). The study included 47 patients who received renal allograft between 1991 and 2009. Capillaritis and glomerulitis were classified by the Banff scoring system, and C4d and Mo were analyzed by immunohistochemistry. In the quantitative analysis, the mean values of 50 Mo per 10 high-power fields (HPF) and 4 Mo per glomerulus were used as cut-off points for the peritubular/interstitial and glomerular compartments, respectively. Positive C4d cases were associated with the groups of biopsies with a mean value ≥50 Mo per 10 HPF (p = 0.01) and ≥4 Mo per glomerulus (p = 0.02). The group with a mean value ≥4 Mo per glomerulus also showed association with the presence of glomerulitis (p = 0.02). Peritubular/ interstitial Mo did not associate with glomerulitis. Capillaritis did not show association with peritubular/interstitial or glomerular Mo. As regards graft survival, the infiltration of Mo in glomeruli interfered with allograft survival (p = 0.01). The group with a mean value of ≥4 glomerular Mo presented worse survival at the time of the 1-year follow-up. According to the literature, our data showed that infiltration of mononuclear cells was associated with C4d staining, microcirculation injury, and glomerulitis, in particular, and that glomerular macrophages could influence renal allograft survival. Copyright © 2013 Informa Healthcare USA, Inc.

Retificador trifásico de 18 pulsos com estágio CC controlado por histerese constante

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Propriedades geomecânicas de um solo compactado com vermiculita para fins de cobertura em aterro de resíduos

Pós-graduação em Engenharia Civil e Ambiental - FEB

Controle da variação do arqueamento de um aerofólio utilizando atuadores de memória de forma

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação dos diferentes métodos de análise do dismorfismo eritrocitário, assim como a quantificação da proteinúria e a albuminúria na determinação da origem de hematúria

Pós-graduação em Fisiopatologia em Clínica Médica - FMB

Pesquisa da fração do sistema complemento C4d, capilarite e infiltração por macrófagos em biópsias de transplante renal: papel na rejeição aguda mediada por anticorpos e na sobrevida do enxerto

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)