bluuebunny/crossref_metadata_2025_split huggingface dataset:
Finite element methods for an acoustic well‐logging problem associated with a porous medium saturated by a two‐phase immiscible fluid
Authors: Sheen Dongwoo 
Published: August 2005

AbstractA mathematical model is presented concerning wave propagation in a domain that arises in geophysical well‐logging problems. The domain consists of a borehole Ωf surrounded by a porous medium Ωp. Ωf is filled with a compressible inviscid fluid, and Ωp is saturated by a two‐phase immiscible fluid. Absorbing boundary conditions for artificial boundaries and boundary conditions on the interface between Ωf and Ωp are used. The existence and uniqueness theorems are stated for the resulting initial‐boundary value problem. Stability and convergence estimates for a finite element method are also studied. © 1993 John Wiley & Sons, Inc.
Analysis of alternating direction collocation methods for parabolic and hyperbolic problems in two space variables
Authors: Fernandes Ryan I. , Fairweather Graeme 
Published: August 2005

AbstractWhile alternating direction implicit (ADI) collocation methods have been used for several years to solve parabolic problems in several space variables, no convergence analysis has been derived for any of these methods. We formulate and rigorously analyze ADI collocation schemes applied to the inhomogeneous heat and wave equations on the unit square subject to homogeneous Dirichlet boundary conditions and appropriate initial conditions. We prove that each method is second‐order accurate in time and of optimal accuracy in space in the L2 and H01 norms. Numerical experiments confirm the predicted rates of convergence. © 1993 John Wiley & Sons, Inc.
A computationally efficient modification of mixed finite element methods for flow problems with full transmissivity tensors
Authors: Koebbe Joe 
Published: August 2005

AbstractThe mixed finite element method for approximately solving flow equations in porous media has received a good deal of attention in the literature. The main idea is to solve for the head/pressure and fluid velocity (Darcy velocity) simultaneously to obtain a higher order approximation of the fluid velocity. In the case of a diagonal transmissivity tensor the algebraic equations resulting from the discretization can be reduced to a system of algebraic equations for the head/pressure variable alone. This reduction results in a smaller number of unknows to be solved for in an iterative method such as preconditioned conjugate gradient method. The fluid velocity is then obtained from an algebraic relationship. In the case of full transmissivity tensor, the algebraic reduction is more difficult. This paper investigates some algorithms resulting from the modification of the mixed finite element that take advantage of the mixed finite element method for the diagonal tensor case. The resulting schemes are more efficient implementations that maintain the same order of accuracy as the original schemes. © 1993 John Wiley & Sons, Inc.
Decoupled smooth interfaces for spectral‐element approximations of parabolic or elliptic type
Authors: Black Kelly 
Published: August 2005

AbstractA method is examined to approximate the interface conditions for Chebyshev polynomial approximations to the solutions of parabolic problems, and a smoothing technique is used to calculate the interface conditions for a domain decomposition method. The methods uses a polynomial of one less degree then the full approximation to calculate the first derivative so that interface values can be calculated by using only the adjacent subdomains. Theoretical results are given for the consistency of the scheme and practical results are presented. Computational results are given for both a fourth‐order Runga‐Kutta methods and an explicit/implicit scheme. © 1993 John Wiley & Sons, Inc.
Eulerian‐Lagrangian localized adjoint method: The theoretical framework
Authors: Herrera Ismael , Ewing Richard E. , Celia Michael A. , Russell Thomas F. 
Published: August 2005

AbstractThis is the second of a sequence of papers devoted to applying the localized adjoint method (LAM), in space‐time, to problems of advective‐diffusive transport. We refer to the resulting methodology as the Eulerian‐Lagrangian localized adjoint method (ELLAM). The ELLAM approach yields a general formulation that subsumes many specific methods based on combined Lagrangian and Eulerian approaches, so‐called characteristic methods (CM). In the first paper of this series the emphasis was placed in the numerical implementation and a careful treatment of implementation of boundary conditions was presented for one‐dimensional problems. The final ELLAM approximation was shown to possess the conservation of mass property, unlike typical characteristic methods. The emphasis of the present paper is on the theoretical aspects of the method. The theory, based on Herrera's algebraic theory of boundary value problems, is presented for advection‐diffusion equations in both one‐dimensional and multidimensional systems. This provides a generalized ELLAM formulation. The generality of the method is also demonstrated by a treatment of systems of equations as well as a derivation of mixed methods. © 1993 John Wiley & Sons, Inc.
On the p version of the finite element method in the presence of numerical integration
Authors: Kim Chang Geun , Suri Manil 
Published: August 2005

AbstractWe analyze the error in the p version of the finite element method when the effect of the quadrature error is taken into account. We extend some results by Banerjee and Suri [Math. Comput. 59, 1–20 (1992)] on the H1‐norm error to the case of the error in the L2 norm. We investigate three sources of quadrature error that can occur: the error due to the numerical integration of the right‐hand side, that due to nonconstant coefficients, and that due to the presence of mapped elements. Presented are various theoretical and computational examples regarding the sharpness of our results. In addition, we make a note on the use of numerical quadrature in conjunction with p‐adaptive procedures and on the necessity of overintegration in the h version with linear elements, when the L2 norm is of interest. © 1993 John Wiley & Sons, Inc.
Optimal m‐stage Runge‐Kutta schemes for steady‐state solutions of hyperbolic equations
Authors: Chen Mei‐Qin , Chiu Chichia 
Published: August 2005

AbstractA numerical scheme is developed to find optimal parameters and time step of m‐stage Runge‐Kutta (RK) schemes for accelerating the convergence to ‐steady‐state solutions of hyperbolic equations. These optimal RK schemes can be applied to a spatial discretization over nonuniform grids such as Chebyshev spectral discretization. For each m given either a set of all eigenvalues or a geometric closure of all eigenvalues of the discretization matrix, a specially structured nonlinear minimax problem is formulated to find the optimal parameters and time step. It will be shown that each local solution of the minimax problem is also a global solution and therefore the obtained m‐stage RK scheme is optimal. A numerical scheme based on a modified version of the projected Lagrangian method is designed to solve the nonlinear minimax problem. The scheme is generally applicable to any stage number m. Applications in solving nonsymmetric systems of linear equations are also discussed. © 1993 John Wiley & Sons, Inc.
Pseudospectral method for transient viscoelastic flow in an axisymmetric channel
Authors: Xu S. , Davies A. R. , Phillips T. N. 
Published: August 2005

AbstractA new pseudospectral method for simulating transient viscoelastic flows is presented. The governing equations are a system of seven first‐order equations of mixed type. The essential features of the method are (i) all seven independent flow variables are represented on a common Chebyshev‐Gauss‐Lobatto grid; (ii) the pressure is treated in such a way as to give a globally divergence‐free velocity field, i.e., the divergence of the velocity field vanishes globally within the region, and (iii) different time scales pertaining within the hyperbolic constitutive equations are treated using the splitting technique of LeVeque and Yee originally proposed in a finite‐difference context. The method is applied to transient axisymmetric flow of an Oldroyd B fluid in a channel formulated in two ways: (I) as an initial boundary‐value problem, and (II) as a body‐force problem. © 1993 John Wiley & Sons, Inc.
Numerical method for a class of parabolic problems in composite media
Authors: Kačur J. , Van Keer R. 
Published: August 2005

AbstractThis paper deals with a numerical method, viz. a Rothe Galerkin finite element method, for a class of parabolic problems in composite media with jump conditions for the unknown at the interfaces of the subdomains, retaining the continuity of its conormal derivative. Crucial to our approach is a nonstandard variational formulation in a product Sobolev space setting. We begin with the discretization in time by the Rothe method, which, in essence, involves a backward finite difference scheme and which provides a constructive method for proving existence of a (unique) variational exact solution under weak conditions for the data. We are left with a recurrent system of elliptic problems at each subsequent time point which are solved numerically by a Galerkin finite element method. The resulting algorithm may be implemented by adapting standard codes for parabolic problems in one‐component domains, when suitably taking into account the specific transmission conditions at the internal boundaries. The emphasis of the paper is on convergence results and error estimates for both the fully discrete and the semi‐discrete approximation of the exact solution. The effectiveness of the approach is illustrated by means of a 1D and a 2D example, the analytical solution of which is known. © 1993 John Wiley & Sons, Inc.
Solution of the Navier‐Stokes equations by the spectral‐difference method
Authors: Cortes Arturo B. , Miller J. D. 
Published: August 2005

AbstractThe Jacobi polynomial collocation method is extended to two and three dimensions by superimposing the individual one‐dimensional expansions. Two innovative ideas are introduced in this article. The first is the cornerless/edgeless computational grid, and the second is the modified compressibility method, which is an iterative pressure solver. To evaluate the new method's applicability in solving the Navier‐Stokes equation, the lid‐driven cavity flow problem was solved. Two configurations were considered, the square cavity and the rectangular cavity with an aspect ratio of 2. A comparison of the center‐line velocity profiles from two‐ and three‐dimensional simulations at a Reynolds number of 1000 is provided for each of the configurations. The center‐line velocity comparisons showed good quantitative agreement with previous studies. © 1994 John Wiley & Sons, Inc.
Thermally coupled, stationary, incompressible MHD flow; existence, uniqueness, and finite element approximation
Authors: Meir A. J. 
Published: August 2005

AbstractThis article addresses the questions of existence, uniqueness, and finite element approximation (including some computational aspects) of solutions to the equations of steady‐state magnetohy‐drodynamic (MHD) when buoyancy effects due to temperature differences in the flow cannot be neglected. We couple the MHD equations to the heat equation and employ the well‐known Boussinesq approximation. We consider the equations posed on a bounded three‐dimensional domain. The boundary conditions for the velocity are of Dirichlet type; the boundary conditions for the temperature are mixed (of Dirichlet type and of Neumann type); we also specify the normal component of the magnetic field and tangential component of the electric field on the boundary. We point out that these problems are relevant to many physical phenomena such as the cooling of nuclear reactors by electrically conducting fluids, continuous metal casting, crystal growth, and semi‐conductor manufacture. © 1995 John Wiley & Sons, Inc.
Alternative T‐complete systems of shape functions applied in analytical Trefftz finite elements
Authors: Szybiński B. , Zieliński A. P. 
Published: August 2005

AbstractThe authors compare the behavior of hybrid Trefftz p‐elements with two different types of shape functions identically fulfilling governing differential equations. Numerical examples include several boundary problems for Laplace, Poisson, and plane elasticity equations. Accuracy of the solutions, convergence properties, numerical stability and sensitivity for mesh distortion are investigated. It is shown that both systems of the functions can be efficiently applied, although they have different properties. © 1995 John Wiley & Sons, Inc.
Advection‐diffusion equations: Temporal sinc methods
Authors: Bowers Kenneth L. , Carlson Timothy S. , Lund John 
Published: August 2005

AbstractA fully Sinc–Galerkin method for solving advection–diffusion equations subject to arbitrary radiation boundary conditions is presented. This procedure gives rise to a discretization, which has its most natural representation in the form of a Sylvester system where the coefficient matrix for the temporal discretization is full. The word “full” often implies a computationally more complex method compared to, for example, temporal marching. In a comparison of time‐marching versus this sinc‐temporal procedure, the Sylvester formulation defines a common framework within which these procedures can be evaluated. This framework has been included in the introduction to illustrate an efficiency measure for either method. Similar remarks with regard to fullness versus sparseness in the Sylvester formulation apply when the spatial discretization is spectral or, for example, differencing. Although it is indicated how this sinc‐temporal method can be combined with alternative spatial discretizations, the natural affinity between sinc methods for space and time discretizations motivate carrying out the numerical illustrations using the sinc basis in each. © 1995 John Wiley & Sons, Inc.
A general approach for using a stiff equation solver to integrate a system of partial differential equations
Authors: Zimmerman W. R. 
Published: August 2005

AbstractA general approach for using a stiff ordinary differential equation solver to integrate a system of time‐dependent partial differential equations in one spacial dimension is described. A computer program based upon the algorithm was written and used to solve nonlinear problems in shock hydrodynamics and hydrology as well as a nonlinear system of ordinary differential equations. The approach is global‐implicit and provides an option to the development of specialized computer programs for specific problems of interest. © 1995 John Wiley & Sons, Inc.
Recovery of the optimal mesh density function and near‐optimal meshes with rectangular elements in the mapped domain
Authors: Hugger Jens 
Published: August 2005

AbstractA method is developed for the recovery and representation of near‐optimal finite‐element meshes of rectangular elements in the mapped domain. The method extends a previously known method, which was restricted to square elements in the mapped domain. The method was developed to obtain a simple, cost‐effective representation of computational meshes for adaptive finite‐element methods solving parametrized problems. © 1995 John Wiley & Sons, Inc.
A Petrov‐Galerkin mixed finite element method with exponential fitting
Authors: Van Nooyen R. R. P. 
Published: August 2005

AbstractWe discuss a Petrov‐Galerkin mixed finite element formulation of the semiconductor continuity equations on a rectangular domain. We give error estimates for equations that are in principle degenerate in the singularly perturbed case. We give arguments that indicate that the method is also effective in the singularly perturbed case. We develop a discretization that gives a higher‐order accurate solution for use in an a posteriori error estimator. © 1995 John Wiley & Sons, Inc.
An adaptive boundary collocation method for linear PDEs
Authors: Golik W. L. , Kolodziej J. A. 
Published: August 2005

AbstractThe article proposes an adaptive algorithm based on a boundary collocation method for linear PDEs satisfying the maximal principle with possibly nonlinear boundary conditions. Given the error tolerance and an initial number of terms in the solution expansion, the algorithm computes expansion coefficients by collocation of boundary conditions and evaluates the maximum absolute error on the boundary. If error exceeds the error tolerance, additional expansion terms and boundary collocation points are added and the process repeated until the tolerance is satisfied. The performance of the algorithm is illustrated by an example of the potential flow past a cylinder placed between parallel walls. © 1995 John Wiley & Sons, Inc.
Array comparative genomic hybridization profiling of first‐trimester spontaneous abortions that fail to grow in vitro
Authors: Benkhalifa M. , Kasakyan S. , Clement P. , Baldi M. , Tachdjian G. , Demirol A. , Gurgan T. , Fiorentino F. , Mohammed M. , Qumsiyeh M. B. 
Published: August 2005

AbstractObjectivesCytogenetic analysis of spontaneous abortion samples can be limited by culture failure. Failure to grow in vitro has traditionally been suspected to be due to in vivo death of tissue associated with spontaneous abortion (SAB) or simply technical factors of growth in culture.MethodWe used array comparative genomic hybridization (array CGH) to investigate chromosomal imbalances in products of conception that failed to grow in vitro.ResultsOur data on 26 cases of SABs that failed to grow in culture are compared and contrasted with published data on cytogenetic findings following in vitro culture. The results revealed abnormalities uncommonly seen by classic cytogenetic methods. These abnormalities include high rates of double aneuploidy and autosomal monosomy. The data taken together suggest that classic cytogenetics of spontaneous abortion may yield normal karyotypes or selected abnormal karyotypes that permit cell proliferation in vitro while Array CGH detects other abnormalities.ConclusionArray CGH is becoming an important clinical assay for unbalanced chromosome abnormalities whether cells grow in culture or not and in cases of analysis on one or few cells. Copyright © 2005 John Wiley & Sons, Ltd.
Prediction of pregnancy complications by first‐trimester maternal serum PAPP‐A and free β‐hCG and with second‐trimester uterine artery Doppler
Authors: Spencer Kevin , Yu Christina K. H. , Cowans Nicholas J. , Otigbah Chineze , Nicolaides Kypros H. 
Published: August 2005

AbstractBackgroundPrevious studies have shown an association between low first trimester maternal serum free β‐hCG and PAPP‐A and subsequent development of pregnancy complications. Similarly, uterine artery Doppler in the late second trimester has shown that high impedance to flow is associated with increased risk for preeclampsia and fetal growth restriction. The objective of this study is to determine whether there is an association between the maternal serum concentration of PAPP‐A and free β‐hCG at 11–13+6 weeks with the uterine artery pulsatility index (PI) at 22–24 weeks, and secondly, to compare the screening characteristics of the two methods in the prediction of adverse pregnancy outcome.MethodsMaternal serum PAPP‐A and free β‐hCG at 11–13+6 weeks and uterine artery PI at 22–24 weeks were measured in 4390 women with singleton pregnancies. Pregnancies with chromosomal defects or fetal anomalies were excluded. The biochemical and Doppler measurements were compared between those with normal outcome and those resulting in spontaneous preterm delivery, pre‐eclampsia and fetal growth restriction (FGR). Detection rates using a combination of the biochemical and Doppler measurements were investigated.ResultsIn the pregnancies resulting in pre‐eclampsia (n = 64) and FGR (n = 172), the median PAPP‐A was lower (0.844 and 0.813 MoM), the median uterine artery mean PI was higher (1.56 and 1.18) but the median free βhCG was not significantly different (0.923 and 0.933 MoM) than in the normal outcome group. In the preterm delivery group (n = 159), the median free β‐hCG (0.944 MoM) and uterine artery mean PI (1.06) were not significantly different from normal but the median PAPP‐A (0.928 MoM) was significantly lower than normal. In screening for pre‐eclampsia, the detection rate, for a 5% false‐positive rate, was 14.1% for PAPP‐A, 54.7% for uterine artery mean PI and 62.1% for a combination of PAPP‐A and uterine artery mean PI.ConclusionMaternal serum PAPP‐A at 11–13+6 of gestation is significantly lower in adverse pregnancy outcomes. The combination of first trimester serum PAPP‐A and uterine artery mean PI at 22‐24 weeks improves the screening efficacy for the prediction of pre‐eclampsia. Copyright © 2005 John Wiley & Sons, Ltd.
Interstitial deletion del(10)(q25.2q25.3 ∼ 26.11)—case report and review of the literature
Authors: Kehrer‐Sawatzki Hildegard , Daumiller Eva , Müller‐Navia Jutta , Kendziorra Heidemarie , Rossier Eva , du Bois Gabriele , Barbi Gotthold 
Published: August 2005

AbstractObjectivesTo present the clinical, cytogenetic, and molecular cytogenetic findings of prenatally diagnosed interstitial deletion 10q25.2‐q26.1. The majority of distal 10q deletions are pure terminal deletions with breakpoints in 10q25 and 10q26. Only four patients have been described so far with interstitial deletions involving bands 10q25.2‐q26.1.MethodsPostmortem physical examination and autopsy of the foetus after medically terminated pregnancy. GTG‐banding, reverse painting, and FISH analysis with BAC clones on amniocyte metaphases were performed to determine the extent of the deletion.ResultsAt 20 weeks the eutrophic female foetus showed pronounced microretrogeny and hypertelorism, clubfeet as well as minor internal anomalies like pancreas anulare, atypically lobed liver, and missing choleocystis. Cardiac anomalies were not observed and the genitalia were of a normal female. The deletion encompasses 6‐Mb and is associated with hemizygosity for 30 genes, including the genes for beta‐tectorin, the beta‐1 adrenergic receptor, and the alpha‐2A adrenergic receptor.ConclusionAn interstitial deletion del(10)(q25.2q25.3 ∼ 26.11) was confirmed by FISH with mapped BAC clones. Clinical and molecular cytogenetic analyses of further interstitial 10q deletions are necessary to assess whether the phenotypic manifestations differ between deletions that are interstitial compared to those that include also the terminal region of chromosome 10. Copyright © 2005 John Wiley & Sons, Ltd.
Synthesis and characterization of a new poly(butadiene(g) acrylamide(g) acrylic acid)
Authors: Spila G. , Bertorello H. 
Published: August 2005

AbstractSynthetic crosslinked polymers were obtained by reacting oligomers of polybutadiene (av. mol. wt. ∼6000) with acrylamide and acrylic acid. Characterization of these new block‐crosslinked polymers was carried out by FTIR, 1H‐NMR, 13C‐NMR, SEM analyses, DTA, and DTG. The polymers were washed with benzene, ethanol, water, and acetone and then dried at high vacuum. Determinations of the swelling ratio Vs/Vo for the poly (BuAAAm)H, acid form, and poly (BuAAAm)Na, sodium form, were carried out in distilled water, at different pH values and concentrations of electrolytes. Kinetic studies with diffusion of solvents were related to the network structures of the poly (BuAAAm) in acid and sodium forms.