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Parallel Plates (parallel + plate)
Terms modified by Parallel Plates Selected AbstractsDynamic viscoelasticity of hybrid kevlar and glass fiber reinforced LLDPE in the molten statePOLYMER COMPOSITES, Issue 4 2002S. A. R. Hashmi Kevlar and glass fibers were used to reinforce linear low density polyethylene (LLDPE), and composite sheets of 0.8, 1.5 and 2.5 mm thicknesses were obtained by using a compression molding technique. Dynamic viscoelastic properties of non-hybrid and hybrid composites of various compositions at 200°C are evaluated. Storage modulus (G,) and loss modulus (G,) increase with angular frequency (,) and reinforcement. Replacement of glass fiber by Kevlar at constant loading of fibers in LLDPE increases the value of G,, G, and ,,. The fractured surface of composite shows the gradient orientation of fibers particularly in 2.5 mm thick sheet. Top and bottom layers show relatively two-dimensional orientation as compared to the middle layer, which shows random orientation. The orientation of fibers decreases G, and ,, of Kevlar fiber and hybrid fiber hybrid fiber reinforced LLDPE composites. The effect of change in distance between parallel plate of rheometer (change in strain amplitude) on dynamic rheological properties is studied and reported here. [source] Viscoelasticity of Hyaluronan and Nonhyaluronan Based Vocal Fold Injectables: Implications for Mucosal Versus Muscle Use,THE LARYNGOSCOPE, Issue 3 2007Trace Caton BS Abstract Objectives: The purpose of this study was to measure and compare biomechanical properties of commonly used vocal fold injectates Cymetra, Radiesse, Restylane, Hylaform, and one investigational injectate, Carbylan-GSX 5%, to determine suitability for mucosal injection. Study Design: Rheologic investigation. Methods: Oscillatory shear stress was applied to five samples of each injectate using a parallel plate controlled stress rheometer. Shear stress, shear strain, and strain rate associated with the oscillatory shear deformation were computed from the prescribed torque and measured angular velocity; viscoelastic data were obtained on the basis of these functions. Values calculated included elastic shear moduli, viscous moduli, and dynamic viscosity as a function of oscillatory frequency (0.01,150 Hz). Results: Elastic moduli for all samples increased as the frequency increased. Hyaluronan based materials were all comparable with each other and at least an order of magnitude lower than the stiffer and more viscous Cymetra and Radiesse. Carbylan-GSX 5% was found to have almost identical values to Hylaform with the exception of its mean viscosity, which was noticeably lower. Conclusions: Hyaluronan based biomaterials offer less resistance to flow and stiffness and may be better suited for injections into the mucosa, whereas Cymetra and Radiesse appear to be appropriate for injections into muscle. Viscoelastic properties of Hylaform and Carbylan-GSX 5% were found to most resemble that of the human vocal fold mucosa. [source] The solution of fluid mechanics problems by probability methodsCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 2 2005Sergio E. Perez Abstract This study shows how fluid mechanics problems may be solved using probability methods. Problems solved include velocity distributions in steady and unsteady flow between parallel plates as well as steady flow through a constant diameter three-dimensional duct. We find that the results approach exact solutions as the number of random walks increases, and that the complexity of the flow equations precludes extension of the technique to three dimensions. We also find that these techniques are much easier for students to put into practice than others. © 2005 Wiley Periodicals, Inc. Comput Appl Eng Educ 13: 133,136, 2005; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20038 [source] Rheological characteristics of solid,fluid transition in dry granular dense flows: A thermodynamically consistent constitutive model with a pressure-ratio order parameterINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 9 2010Chung Fang Abstract Dry granular flows are characterized as quasi-static, dense and collisional states by the interactions among the grains, which is indexed macroscopically by an internal variable, called the order parameter defined as the square root of the static pressure to the total pressure. The solid,fluid state transition is regarded as a second-order phase transition process, and is described by a kinematic evolution of the order parameter. The thermodynamic analysis, based on the Müller,Liu entropy principle, is employed to deduce the equilibrium responses of the constitutive equations, while the dynamic responses are postulated on the basis of a quasi-linear and the second-order Ginzburg,Landau phase transition theories. The obtained model is applied to study the rheological characteristics of a dry granular dense flow between two infinite parallel plates, of which the results are compared with those from DEM simulations to estimate the model validity. The present study provides a general framework for the theoretical justifications on the thermodynamic consistencies of order-parameter-based constitutive models, and can be extended to flows in quasi-static or collisional states. Copyright © 2009 John Wiley & Sons, Ltd. [source] Linear stability analysis of flow in a periodically grooved channelINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2003T. Adachi1 Abstract We have conducted the linear stability analysis of flow in a channel with periodically grooved parts by using the spectral element method. The channel is composed of parallel plates with rectangular grooves on one side in a streamwise direction. The flow field is assumed to be two-dimensional and fully developed. At a relatively small Reynolds number, the flow is in a steady-state, whereas a self-sustained oscillatory flow occurs at a critical Reynolds number as a result of Hopf bifurcation due to an oscillatory instability mode. In order to evaluate the critical Reynolds number, the linear stability theory is applied to the complex laminar flow in the periodically grooved channel by constituting the generalized eigenvalue problem of matrix form using a penalty-function method. The critical Reynolds number can be determined by the sign of a linear growth rate of the eigenvalues. It is found that the bifurcation occurs due to the oscillatory instability mode which has a period two times as long as the channel period. Copyright © 2003 John Wiley & Sons, Ltd. [source] Simplified solution of developing laminar forced flow between parallel platesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2002Esmail M. A. Mokheimer Abstract A simplified simulation for developing laminar forced flow in the entrance region between two parallel plates is presented. This simulation is based on an implicit finite difference numerical representation of a boundary layer model describing the flow in the entry region. This boundary layer model comprises the two conservation equations of mass and momentum. A non-iterative implicit numerical scheme is developed to convert the partial differential form of these governing equations into algebraic equations. The resultant algebraic equations have been solved simultaneously via a simplified simulation using spreadsheet programs as well as a Fortran code for the sake of comparison. The numerically obtained developing axial velocity profile at large distance downstream of the entrance shows excellent agreement with the available fully developed analytical profile. Comparison between the abilities of the spreadsheet simulation with other high-level programming languages is outlined. Copyright © 2002 John Wiley & Sons, Ltd. [source] A numerical approach revealing the impact of rheological properties on mouthfeel caused by foodINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2007Katrin Mathmann Summary In contrast to the static chemoreceptor-related flavour perception, texture of food capable of flow is detected dynamically with oral mechanoreceptors while the food is manipulated in the mouth. The resulting sensation called mouthfeel strongly depends on the different physical properties of food. Aim of the current study is to determine numerically the occurring fluid mechanical forces in food suspensions using a simplified tongue-palate model system consisting of two parallel plates. For this purpose, the equations of fluid and particle motion are numerically solved by using structured overlapping grids. In the computational experiment, a density neutral fluid system between the plates is compressed by moving the upper plate with constant velocity down to the other one. It has been found that suspended particles move with the fluid flow but have only minor effect on the global flow field in the applied concentration. [source] TEXTURE PROFILE ANALYSIS , HOW IMPORTANT ARE THE PARAMETERS?JOURNAL OF TEXTURE STUDIES, Issue 5 2010ANDREW J. ROSENTHAL ABSTRACT A starch-glycerol gel was subjected to a two-bite compression test using two sample-instrument geometries, various speeds of compression and strain levels, both with lubrication or not. Results were interpreted using the primary characteristic terminology previously defined in Texture Profile Analysis. Compression speeds from 0.1 to 10 m/s showed a logarithmic relationship with hardness, cohesiveness, corrected cohesiveness and adhesiveness. Gels survived compression to strains of 0.90 without failing, strain levels from 0.25 to 0.90 resulted in an exponential rise in hardness with increasing strain and linear reduction in corrected cohesiveness. Lubrication had no significant influence on any of the measured parameters and an application of force with different sample-instrument geometry revealed that parallel plates and plungers only had an influence on gel hardness. Caution is urged when researchers modify the test protocol from 75% deformation with parallel plates. A minimum crosshead speed of 2 mm/s is recommended. PRACTICAL APPLICATIONS Texture Profile Analysis has been widely applied to test solid and semisolid foods; however, some researchers deviate from the original test protocol. This article attempts to show how modifying the parameters in the test protocol can influence the apparent properties of the sample. [source] OSCILLATING VANE GEOMETRY FOR SOFT SOLID GELS AND FOAMSJOURNAL OF TEXTURE STUDIES, Issue 6 2002C. SERVAIS ABSTRACT Several relationships between the torque and the stress exist for the vane geometry, but only a few equations have been proposed for the relationship between angular displacement and strain. In this study, an expression based on the infinite gap approximation for concentric cylinders is used and well-defined reference data are compared to oscillating vane data to validate the assumptions used. Gelatin gels are used for their property to stick to the wall and carrageenan gels are used to show that wall slip does not occur with oscillating vanes in serrated cup geometries. Shaving foams are used as a model low density, time and shear stable foam, which resists irreversible damage when loaded between serrated parallel plates. Results show that the assumptions used for the determination of stress and strain with the vane provide material viscoelastic properties that are not significantly different from reference values as obtained with concentric cylinders and parallel plates. [source] RHEOLOGY AND MICROSTRUCTURE OF WHEAT DOUGH DEVELOPED WITH CONTROLLED DEFORMATIONJOURNAL OF TEXTURE STUDIES, Issue 1 2000EMILY J. SCHLUENTZ ABSTRACT Undeveloped wheat dough samples were strained in shear and extensional flow between parallel plates to produce a controlled level of development. Dough made in a standard Farinograph, considered developed dough, was used for comparison. Scanning electron microscopy images of deformed dough were subjected to numerical image processing to characterize the protein matrix present. Results were compared to dynamic rheological properties to evaluate the influence of strain deformation on the formation of microstructure. Viscoelastic moduli of wheat dough showed that developed dough had the greatest amount of structure formation, followed by extensionally-strained and shear-strained samples, respectively. Undeveloped dough showed the lowest levels of structure development. Image analysis indicated statistically significant differences between protein matrices in developed and undeveloped samples; however, results were not significantly different between shear- and extension-ally-strained samples. [source] A simulation environment for diffusion weighted MR experiments in complex mediaMAGNETIC RESONANCE IN MEDICINE, Issue 3 2009Gregory T. Balls Abstract Simulations of diffusion in neural tissues have traditionally been limited to analytical solutions, to grid-based solvers, or to small-scale Monte Carlo simulations. None of these approaches has had the capability to simulate realistic complex neural tissues on the scale of even a single voxel of reasonable (i.e., clinical) size. An approach is described that combines a Monte Carlo Brownian dynamics simulator capable of simulating diffusion in arbitrarily complex polygonal geometries with a signal integrator flexible enough to handle a variety of pulse sequences. Taken together, this package provides a complete and general simulation environment for diffusion MRI experiments. The simulator is validated against analytical solutions for unbounded diffusion and diffusion between parallel plates. Further results are shown for aligned fibers, varying packing density and permeability, and for crossing straight fibers. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source] Identification of objects in an acoustic wave guide inversion II: Robin,Dirichlet conditionsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 4 2006Doo-Sung Lee Abstract In this paper we investigate the unknown body problem in a wave guide where one boundary has a pressure release condition and the other an impedance condition. The method used in the paper for solving the unknown body inverse problem is the intersection canonical body approximation (ICBA). The ICBA is based on the Rayleigh conjecture, which states that every point on an illuminated body radiates sound from that point as if the point lies on its tangent sphere. The ICBA method requires that an analytical solution be known exterior to a canonical body in the wave guide. We use the sphere of arbitrary centre and radius in the wave guide as our canonical body. We are lead then to analytically computing the exterior solution for a sphere between two parallel plates. We use the ICBA to construct solutions at points ranging over the suspected surface of the unknown object to reconstruct the unknown object using a least-squares matching of computed, acoustic field against the measured, scattered field. Copyright © 2005 John Wiley & Sons, Ltd. [source] A Wiener,Hopf approximation technique for a multiple plate diffraction problemMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 1 2004James R. Brannan Abstract An approximation method is derived for the computation of the acoustic field between a series of parallel plates, subject to a time periodic incident field. The method is based on the Wiener,Hopf method of factorization, with computations involving orthogonal bases of functions that are analytic in the complex half-plane. Copyright 2004 John Wiley & Sons, Ltd. [source] | ||||||||||||||||