998 resultados para Newtonian behavior


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This work is an application of the second order gauge theory for the Lorentz group, where a description of the gravitational interaction is obtained that includes derivatives of the curvature. We analyze the form of the second field strength, G=partial derivative F+fAF, in terms of geometrical variables. All possible independent Lagrangians constructed with quadratic contractions of F and quadratic contractions of G are analyzed. The equations of motion for a particular Lagrangian, which is analogous to Podolsky's term of his generalized electrodynamics, are calculated. The static isotropic solution in the linear approximation was found, exhibiting the regular Newtonian behavior at short distances as well as a meso-large distance modification.

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The physicochemical (pH, fat and total solids content), sensory (appearance, consistency and taste), and rheological characteristics of five different commercial brands of lactic beverages were determined. Rheological measurements were obtained at 5 degreesC and 25 degreesC using a Brookfield rheometer. The experimental data were described by the power law and Herschel-Bulkley models. The ANOVA of the results were conducted using an incomplete block design, and using Tukey test. Samples showed a significant difference (P less than or equal to 0.05%) for fat content and pH. There was a significant difference in total solids content only among Nestle (A), Batavo (C), and Parmalat (D) samples. Sensory evaluation showed more global acceptability for Nestle; however, Nestle and Vigor (E) lactic beverages obtained better results for appearance than for consistency and taste. Batavo obtained the best score for taste. All test samples exhibited non-Newtonian behavior, with thixotropy. Upward curves showed pseudoplastic behavior, while downward curves showed dilatant behavior with the exception of the Nestle sample, at 25 degreesC. Lactic beverages from all brands analyzed showed similar rheological behavior. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

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The rheological behavior of coffee extract with different water contents (49 to 90%) was studied at a wide range of temperatures (274 to 365 K) using a concentric cylinder rheometer. The flow curves followed different models depending on the concentration and temperature level. Newtonian behavior was observed at high values of water content and temperature, changing to power law as these values were decreased. The Newtonian viscosity as well as the consistency and behavior index could be well correlated by functions simultaneously dependent on temperature and water content. The rheological parameters, together with experimental values of pressure loss in tube flow, were used to calculate friction factors. These showed to be in good agreement with those resulting from classical theoretical and empirical equations, thus confirming the reliability of the rheological measurements.

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Glasses of composition 40InF3-20SrF2-16BaF2-20ZnF 2-2GdF3-2NaF (mol%) have been prepared under controlled atmosphere. The time response of the stresses under the application of a constant strain was determined by microellipsometer technique, performed in ambient atmosphere at T < Tg = 294°C. The glasses show a Newtonian behavior at small stress level. During the relaxation process, very small grooves perpendicular to the applied strain appeared on the glass surface and affected its behavior after a time. The formation of these grooves is associated with the ambient atmosphere. Measurements in dry atmosphere showed that humidity was an important parameter in the relaxation process.

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The sugarcane juice is a relatively low-cost agricultural resource, abundant in South Asia, Central America and Brazil, with vast applications in producing ethanol biofuel. In that way, a good knowledge of the rheological properties of this raw material is of crucial importance when designing and optimizing unit operations involved in its processing. In this work, the rheological behavior of untreated (USCJ, 17.9 °Brix), clarified (CSCJ, 18.2 °Brix) and mixed (MSCJ, 18.0 °Brix) sugarcane juices was studied at the temperature range from 277K to 373K, using a cone-and-plate viscometer. These fluids were found to present a Newtonian behavior and their flow curves were well-fitted by the viscosity Newtonian model. Viscosity values lied within the range 5.0×10 -3Pas to 0.04×10 -3Pas in the considered temperature interval. The dependence of the viscosity on the temperature was also successfully modeled through an Arrhenius-type equation. In addition to the dynamic viscosity, experimental values of pressure loss in tube flow were used to calculate friction factors. The good agreement between predicted and measured values confirmed the reliability of the proposed equations for describing the flow behavior of the clarified and untreated sugarcane juices. © 2010 Elsevier B.V.

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Pós-graduação em Engenharia e Ciência de Alimentos - IBILCE

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Pós-graduação em Engenharia e Ciência de Alimentos - IBILCE

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)