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Interpolation Scheme (interpolation + scheme)
Selected AbstractsDynamics of unsaturated soils using various finite element formulationsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 5 2009Nadarajah Ravichandran Abstract Unsaturated soils are three-phase porous media consisting of a solid skeleton, pore liquid, and pore gas. The coupled mathematical equations representing the dynamics of unsaturated soils can be derived based on the theory of mixtures. Solution of these fully coupled governing equations for unsaturated soils requires tremendous computational resources because three individual phases and interactions between them have to be taken into account. The fully coupled equations governing the dynamics of unsaturated soils are first presented and then two finite element formulations of the governing equations are presented and implemented within a finite element framework. The finite element implementation of all the terms in the governing equations results in the complete formulation and is solved for the first time in this paper. A computationally efficient reduced formulation is obtained by neglecting the relative accelerations and velocities of liquid and gas in the governing equations to investigate the effects of fluid flow in the overall behavior. These two formulations are used to simulate the behavior of an unsaturated silty soil embankment subjected to base shaking and compared with the results from another commonly used partially reduced formulation that neglects the relative accelerations, but takes into account the relative velocities. The stress,strain response of the solid skeleton is modeled as both elastic and elastoplastic in all three analyses. In the elastic analyses no permanent deformations are predicted and the displacements of the partially reduced formulation are in between those of the reduced and complete formulations. The frequency of vibration of the complete formulation in the elastic analysis is closer to the predominant frequency of the base motion and smaller than the frequencies of vibration of the other two analyses. Proper consideration of damping due to fluid flows in the complete formulation is the likely reason for this difference. Permanent deformations are predicted by all three formulations for the elastoplastic analyses. The complete formulation, however, predicts reductions in pore fluid pressures following strong shaking resulting in somewhat smaller displacements than the reduced formulation. The results from complete and reduced formulations are otherwise comparable for elastoplastic analyses. For the elastoplastic analysis, the partially reduced formulation leads to stiffer response than the other two formulations. The likely reason for this stiffer response in the elastoplastic analysis is the interpolation scheme (linear displacement and linear pore fluid pressures) used in the finite element implementation of the partially reduced formulation. Copyright © 2008 John Wiley & Sons, Ltd. [source] On the residue calculus evaluation of the 3-D anisotropic elastic green's functionINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 5 2004A.-V. Phan Abstract An algorithm based upon the residue calculus for computing three-dimensional anisotropic elastic Green's function and its derivatives has been presented in Sales and Gray (Comput. Structures 1998; 69:247,254). It has been shown that the algorithm runs three to four times faster than the standard Wilson,Cruse interpolation scheme. However, the main concern of the Sales,Gray algorithm is its numerical instability that could lead to significant errors due to the existence of multiple poles of the residue. This paper proposes a remedy for the problem by adding the capability to evaluate the Green's function in case of multiple poles of the residue. Further, an improved numerical implementation based on the use of double-subscript-notation elastic constants in determining the Christoffel tensor is also at issue. Copyright © 2004 John Wiley & Sons, Ltd. [source] Integrated layout design of multi-component systemINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2009Jihong Zhu Abstract A new integrated layout optimization method is proposed here for the design of multi-component systems. By introducing movable components into the design domain, the components layout and the supporting structural topology are optimized simultaneously. The developed design procedure mainly consists of three parts: (i) Introduction of non-overlap constraints between components. The finite circle method (FCM) is used to avoid the components overlaps and also overlaps between components and the design domain boundaries. (ii) Layout optimization of the components and supporting structure. Locations and orientations of the components are assumed as geometrical design variables for the optimal placement while topology design variables of the supporting structure are defined by the density points. Meanwhile, embedded meshing techniques are developed to take into account the finite element mesh change caused by the component movements. (iii) Consistent material interpolation scheme between element stiffness and inertial load. The commonly used solid isotropic material with penalization model is improved to avoid the singularity of localized deformation in the presence of design dependent loading when the element stiffness and the involved inertial load are weakened by the element material removal. Finally, to validate the proposed design procedure, a variety of multi-component system layout design problems are tested and solved on account of inertia loads and gravity center position constraint. Solutions are compared with traditional topology designs without component. Copyright © 2008 John Wiley & Sons, Ltd. [source] Estimating temperature normals for USCRN stationsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 14 2005Bomin Sun Abstract Temperature normals have been estimated for stations of the newly developed US Climate Reference Network (USCRN) by using USCRN temperatures and temperature anomalies interpolated from neighboring stations of the National Weather Service Cooperative Station Network (COOP). To seek the best normal estimation approach, several variations on estimation techniques were considered: the sensitivity of error of estimated normals to COOP data quality; the number of neighboring COOP station used; a spatial interpolation scheme; and the number of years of data used in normal estimation. The best estimation method we found is the one in which temperature anomalies are spatially interpolated from COOP stations within approximately 117 km of the target station using a weighting scheme involving the inverse of square difference in temperature (between the neighboring and target station). Using this approach, normals of USCRN stations were generated. Spatial and temporal characteristics of errors are presented, and the applicability of estimated normals in climate monitoring is discussed. Copyright © 2005 Royal Meteorological Society [source] Efficient analysis of wireless communication antennas using an accurate [Z] matrix interpolation techniqueINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2010Yikai Chen Abstract An accurate impedance matrix interpolation technique based on the surface integral equation (SIE) is presented for the analysis of wireless communication antennas over wide frequency bands. The first-order derivative of the impedance matrix at the internal frequency is considered in the cubic polynomial-based interpolation scheme, thus the novel impedance matrix interpolation scheme will provide high accuracy and high efficiency over a frequency band. To demonstrate the efficiency and accuracy of the proposed method, numerical results for planar inverted F antennas (PIFA) and a wideband E-shaped patch antenna are presented. Good agreement among the interpolation results, exact MoM solutions, finite element method (FEM) solutions, and measured data is observed over the bandwidth. Besides, dimensions of the feeding probe are also studied to investigate their effect on the input impedance and radiation patterns. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010. [source] Background error covariance functions for vector wind analyses using Doppler-radar radial-velocity observationsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 621C 2006Qin Xu Abstract A two-dimensional form of cross-covariance function between the radar radial- and tangential-components (with respect to the direction of radar beam) of background wind errors is derived. Like the previously derived auto-covariance function for the radial component, this cross-covariance function is homogeneous but non-isotropic in the horizontal. The auto- and cross-covariance functions are used with the statistical interpolation technique to perform a vector wind analysis from Doppler radial-velocity observations on a conical surface of low-elevation radar-scans. The structures of the two covariance functions are compared and interpreted in terms of the influence of a single-point radial-velocity observation on the analysed vector wind field. The utility and value of these covariance functions are demonstrated through analysis experiments that use either simulated radial-velocity data from idealized flows or real radar observations. The results of the statistical interpolation scheme utilizing the proposed covariance functions are shown to be superior to the results of traditional VAD technique. The proposed technique can actually be considered a generalization of the traditional VAD technique. Copyright © 2006 Royal Meteorological Society [source] Temporal and spatial variation of annual rainfall on the island of Crete, GreeceHYDROLOGICAL PROCESSES, Issue 10 2003S. Naoum Abstract Annual rainfall records from the island of Crete in Greece were used with the aid of a geographical information system (GIS) to study the temporal and spatial rainfall characteristics. The GIS was used to produce a digital elevation model, delineate watersheds and estimate the areal rainfall from a network of raingauges by using different interpolation schemes. The rainfall,elevation correlation was significant, suggesting an orographic type of precipitation for the island. The rainfall records for the majority of the stations were found to fit the normal distribution. Deviation from normal for the rest of the records was attributed to the wettest year of 1977,1978. The year 1989,1990 was the driest, and most rainfall records showed a decrease in rainfall over 30 years with higher negative rainfall gradients at the higher elevations. Frequency analysis of the rainfall records was used to estimate areal rainfall for the island of Crete and its main watersheds for return periods of 2, 5 and 10 years. Copyright © 2003 John Wiley & Sons, Ltd. [source] High-order stable interpolations for immersed boundary methodsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2006Nikolaus Peller Abstract The analysis and improvement of an immersed boundary method (IBM) for simulating turbulent flows over complex geometries are presented. Direct forcing is employed. It consists in interpolating boundary conditions from the solid body to the Cartesian mesh on which the computation is performed. Lagrange and least squares high-order interpolations are considered. The direct forcing IBM is implemented in an incompressible finite volume Navier,Stokes solver for direct numerical simulations (DNS) and large eddy simulations (LES) on staggered grids. An algorithm to identify the body and construct the interpolation schemes for arbitrarily complex geometries consisting of triangular elements is presented. A matrix stability analysis of both interpolation schemes demonstrates the superiority of least squares interpolation over Lagrange interpolation in terms of stability. Preservation of time and space accuracy of the original solver is proven with the laminar two-dimensional Taylor,Couette flow. Finally, practicability of the method for simulating complex flows is demonstrated with the computation of the fully turbulent three-dimensional flow in an air-conditioning exhaust pipe. Copyright © 2006 John Wiley & Sons, Ltd. [source] ERROR SPACE MOTION CONTROL METHODOLOGY FOR COMPLEX CONTOURSASIAN JOURNAL OF CONTROL, Issue 1 2005Robert G. Landers ABSTRACT Motion control is a critical component of many engineering systems (e.g., manufacturing, robotics). Most systems have standard interpolation and control schemes for linear and circular contours; therefore, complex contours are often decomposed into a series of line segments and circular arcs. However, there are discontinuities where the line segments and arcs are joined together, and time to complete the contour is substantially increased when acceleration/deceleration interpolation schemes are employed. A motion control scheme known as the error space motion control methodology is proposed in this paper to design servomechanism motion control systems that may be utilized for complex contours. The error space motion control methodology is applied to a two-axis motion control system and simulation studies are conducted for linear, circular, elliptical, and limacon contours. The results demonstrate the excellent tracking ability of the proposed error space motion control methodology and its utility for complex contours. [source] | |||||||||||||