739 resultados para drag


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

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

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The Cu-Au mine of Chapada is located in the municipality of Alto Horizonte, in the northwestern portion of Goiás state and is inserted in the geological context of the Brasilia Belt, specifically the Mara Rosa Magmatic Arc, which hosts important deposits of Au and Cu-Au. The rocks found in the study area belong mainly to the Volcano-Sedimentary Sequence of Mara Rosa and are composed of basic to acidic metavolcanic rocks, psammiticpellitic metasedimentary rocks, chemical rocks and also hydrothermal products. Late intrusions occur and are represented by pegmatitic dikes and tonalitic bodies. The ore deposit of the Chapada mine is formed predominantly by the chalcopyrite-pyritemagnetite association, where pyrite is the most abundant mineral. Through the structural mapping of the mining fronts, it was able to recognize three deformational phases (Dn, Dn +1, Dn +2). During the Dn phase, isoclinal recumbent folds were formed, in association with amphibolites facies metamorphism. Later, in phase Dn +1, there was formation of drag folds and intrafolial folds in association with retrograde metamorphism in the greenschist facies. The deformational phase Dn +2, in its turn, was responsible for late symmetrical folding of the foliation, with NS and EW axes, resulting in an interference pattern of the dome-and-basin type

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Fluidization consists in a bed of solid particles acquire fluid behavior by using a fluid (in this case air) flowing through the solid particles. Because of this, it can be a good mix of these materials, as well as to show increased rates of heat and mass transport. The fluid flowing through the spaces between the particles gives an interstitial velocity, that if is too low does not cause movement of the particulates. The gradual increase in speed will generate small vibrations between the particles promotes its fluidization. Our study focus in the fluid state of solid bed , when the fluid velocity reaches a state where the drag forces are sufficient to support the weight of the solid particles making these solids behave like fluids . Knowledge of the minimum velocity required to fluidize that particles is of great importance since below this speed there is no fluidization, and far above it, the solids are carried out of the bed. The fluidized bed reactor is widely used in physics and engineering, particularly in gas-solid fluidization, with emphasis on thermochemical processes

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In our experiments, we studied the classical dynamic of a particle in vertical motion subject to a constant gravitational field and the partial shock with an elastic wall with oscillatory motion located below the particle. The motion of the particle was confined to the vertical direction by a glass guide tube, which was initially evacuated, allowing viscous drag forces to be disregarded. The time between impacts, as well as the time between the reference phase of the movement of the base and the moment of impact and the period of oscillation of the base will be acquired by a hardware and software to obtain the phases space to be compared later with the description of the system through mapping discrete variables via the 'particle velocity immediately after shock 'and' phase of the movement of the base at the instant of shock 'obtained by computer simulation. This requires developing an electronic analog system followed by Digital implemented in reconfigurable logic, more specifically a sequential machine able to discriminate the impact with the metal base from the impacts of the glass guide tube, based on the frequency spectrum of the response of the microphone to these different impacts

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Essential oils are products from plants and can be located in parts or in its entirety. There are several methods for its extraction, where the most suitable depends on the plant or the use of the essence. The main species cultivated in Brazil are the Corymbia citriodora, Eucalyptus globulus and Eucalyptus staigeriana. The Corymbia citriodora is a species that was introduced in Brazil along with other species, with the initial objective of timber production. The yield of oil can range from 0.5 % to 3.0% according to the literature and this can be optimized by reducing the moisture content of the leaves. Studies show that the lower water content in the leaves allows the vapor stream generated in the extractor can drag, more efficiently, the volatiles stored in the cells as compared with the green material. The drying of the sheets is important for companies, so that there is transport of water, increasing the volume of the sheets to distillation and hence a greater volume of oil. The objective of this study was to compare the drying methods, analyzing the income of the essence and determine the best method to optimize the yield of essential oil. Experimental tests were performed natural drying 10, 15 and 20 days and fluidized with times of 60, 90 and 120 minutes and after drying were extractions of the oil. The results obtained for fresh leave yield was 1.20 % and the drying time which showed the highest yield was 15 and 20 days with 2.90 % and 2.70 % yield, respectively, with the lowest level humidity of 16%. The yields obtained in fluidized bed drying did not change as the natural drying to between 1.64% and 1.7%. It is concluded that the decreased level of the sheets increases the yield of oil and the temperature in the fluidized bed is essential for the removal of water from the leaves necessary to increase the yield

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Through measurements of basic parameters for determining the fluidization regime, as particle size, minimum fluidization velocity, bed porosity, etc., This paper analyze the mass distribution of the phases of the bed to be discussed in relation to: the flow gas physical properties of the solid particles and the forces acting on the solid particles circulating within the bed, as the weight force, buoyancy and drag forces (Stokes' Law). Due to the weight force is constant, open up the discussion about which of the other two forces, buoyancy and drag force, influencing the behavior of the bed. We used the photographic method to realize the statistical analyzes. Therefore, we can conclude what changes can be made more convenient in fluidizing the bed to obtain the highest efficiency for a good mixing used in industrial processes

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

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The identification of Salmonella spp. in food samples by microbiological diagnosis is time consuming, with approximately five different stages, requiring about 120 hours until the final result. The utilization of the polymerase chain reaction technique (PCR) can reduce this time, but substances present in samples may affect the reaction. The present work aimed to compare DNA extraction by thermic treatment and by the use of cetyltrimethil ammonium bromide (CTAB), in products originated from poultry houses corresponding to raw material (meat meal) and experimentally contaminated drag swabs. Materials obtained from the extractions were submitted to PCR, utilizing a pair of initiator oligonucleotides for amplification of Sdf 1 gene fragments. Comparing the methods of extraction, it was observed that when CTAB was employed, SE was detected in 70% of meat meal and in 80% of drag swabs, while the thermic treatment method yielded positive results in 20% of meat meal and in 40% of drag swabs. SE was detected under both methods utilized for DNA extraction, but the use of CTAB detected a greater number of positive samples, compared with thermal treatment.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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The determination of hydrodynamic coefficients of full scale underwater vehicles using system identification (SI) is an extremely powerful technique. The procedure is based on experimental runs and on the analysis of on-board sensors and thrusters signals. The technique is cost effective and it has high repeatability; however, for open-frame underwater vehicles, it lacks accuracy due to the sensors' noise and the poor modeling of thruster-hull and thruster-thruster interaction effects. In this work, forced oscillation tests were undertaken with a full scale open-frame underwater vehicle. These conducted tests are unique in the sense that there are not many examples in the literature taking advantage of a PMM installation for testing a prototype and; consequently, allowing the comparison between the experimental results and the ones estimated by parameter identification. The Morison's equation inertia and drag coefficients were estimated with two parameter identification methods, that is, the weighted and the ordinary least-squares procedures. It was verified that the in-line force estimated from Morison's equation agrees well with the measured one except in the region around the motion inversion points. On the other hand, the error analysis showed that the ordinary least-squares provided better accuracy and, therefore, was used to evaluate the ratio between inertia and drag forces for a range of Keulegan-Carpenter and Reynolds numbers. It was concluded that, although both experimental and estimation techniques proved to be powerful tools for evaluation of an open-frame underwater vehicle's hydrodynamic coefficients, the research provided a rich amount of reference data for comparison with reduced models as well as for dynamic motion simulation of ROVs. [DOI: 10.1115/1.4004952]

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Membranes of Poly(2,5-benzimidazole) (ABPBI), prepared by polycondensation in polyphosphoric acid, were characterized from the fuel cell application point of view: mechanical properties of the membranes for different acid doping levels, thermal stability, permeability for the different gases/vapors susceptible of use in the cell (hydrogen, oxygen, methanol and ethanol), electro-osmotic water drag coefficient, oxidation stability to hydroxyl radicals, phosphoric acid leaching rate and, finally, in-plane membrane conductivity. ABPBI membranes presented an excellent thermal stability, above 500 degrees C in oxygen, suitable mechanical properties for high phosphoric acid doping levels, a low methanol and ethanol limiting permeation currents, and oxygen permeability compared to Nafion membranes, and a low phosphoric acid leaching rate when exposed to water vapor. On the contrary, hydrogen permeation current was higher than that of Nafion, and the chemical stability was very limited. Membrane conductivity achieved 0.07 S cm(-1) after equilibration with a humid environment. Fuel cell tests showed reasonable good performances, with a maximum power peak of 170 mW cm(-2) for H-2/air at 170 degrees C operating under a humidified hydrogen stream, 39.9 mW cm(-2) for CH3OH/O-2 at 200 degrees C for a methanol/water weight ratio of 1: 2, and 31.5 mW cm(-2) for CH3CH2OH/O-2 at the same conditions than for methanol. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.014207jes] All rights reserved.

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Experimental results of flow around a circular cylinder with moving surface boundary-layer control (MSBC) are presented. Two small rotating cylinders strategically located inject momentum in the boundary layer of the cylinder, which delays the separation of the boundary layer. As a consequence, the wake becomes narrower and the fluctuating transverse velocity is reduced, resulting in a recirculation free region that prevents the vortex formation. The control parameter is the ratio between the tangential velocity of the moving surface and the flow velocity (U-c/U). The main advantage of the MSBC is the possibility of combining the suppression of vortex-induced vibration (VIV) and drag reduction. The experimental tests are preformed at a circulating water channel facility and the circular cylinders are mounted on a low-damping air bearing base with one degree-of-freedom in the transverse direction of the channel flow. The mass ratio is 1.8. The Reynolds number ranges from 1600 to 7500, the reduced velocity varies up to 17, and the control parameter interval is U-c/U = 5-10. A significant decreasing in the maximum amplitude of oscillation for the cylinder with MSBC is observed. Drag measurements are obtained for statically mounted cylinders with and without MSBC. The use of the flow control results in a mean drag reduction at U-c/U = 5 of almost 60% compared to the plain cylinder. PIV velocity fields of the wake of static cylinders are measured at Re = 3000. The results show that the wake is highly organized and narrower compared to the one observed in cylinders without control. The calculation of the total variance of the fluctuating transverse velocity in the wake region allows the introduction of an active closed-loop control. The experimental results are in good agreement with the numerical simulation studies conducted by other researchers for cylinders with MSBC. (C) 2012 Elsevier Ltd. All rights reserved.

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The flow around circular smooth fixed cylinder in a large range of Reynolds numbers is considered in this paper. In order to investigate this canonical case, we perform CFD calculations and apply verification & validation (V&V) procedures to draw conclusions regarding numerical error and, afterwards, assess the modeling errors and capabilities of this (U)RANS method to solve the problem. Eight Reynolds numbers between Re = 10 and Re 5 x 10(5) will be presented with, at least, four geometrically similar grids and five discretization in time for each case (when unsteady), together with strict control of iterative and round-off errors, allowing a consistent verification analysis with uncertainty estimation. Two-dimensional RANS, steady or unsteady, laminar or turbulent calculations are performed. The original 1994 k - omega SST turbulence model by Menter is used to model turbulence. The validation procedure is performed by comparing the numerical results with an extensive set of experimental results compiled from the literature. [DOI: 10.1115/1.4007571]