bluuebunny/crossref_metadata_2025 huggingface dataset:
Vital exhaustion and risk for cancer
Authors: Bergelt Corinna , Christensen Jane , Prescott Eva , Grønbæk Morten , Koch Uwe , Johansen Christoffer
Published: August 2005

BACKGROUND

Vital exhaustion, defined as feelings of depression and fatigue, has previously been investigated mainly as a risk factor for cardiovascular disease. The authors investigated the association between depressive feelings and fatigue as covered by the concept of vital exhaustion and the risk for cancer.

METHODS

The sample consisted of 8527 persons aged 21–94 who had been examined in 1991–1994 within the Copenhagen City Heart Study. For the analysis, the sample was divided into quartiles on the basis of vital exhaustion scores. Cancer cases were ascertained by linkage to the Danish Cancer Registry. The mean length of follow‐up was 8.6 years. Regression analyses for etiology‐based groups of cancer sites were conducted on the basis of the Cox proportional hazards model, with adjustment for a number of confounding variables.

RESULTS

Cancer was diagnosed in 976 persons (12%) during follow‐up. In comparison to those with the lowest scores, persons with the highest vital exhaustion scores had a significantly decreased risk for developing cancer at all sites (hazard ratio [HR], 0.80; 95% confidence interval [CI}, 0.66–0.96), smoking‐related cancers (HR, 0.64; 95% CI, 0.46–0.90), and virus and immune‐related cancers (HR, 0.51; 95% CI, 0.26–0.99). No significant change in risk was found for cancers related to alcohol consumption or hormones.

CONCLUSIONS

The results did not support the hypothesis that symptoms of fatigue and depression, as ascertained in the vital exhaustion index, increased the risk for cancer. Cancer 2005. © 2005 American Cancer Society.
Anorexia/cachexia‐related quality of life for children with cancer
Authors: Lai Jin‐Shei , Cella David , Peterman Amy , Barocas Joshua , Goldman Stewart
Published: August 2005

BACKGROUND

Anorexia is a common symptom in patients with cancer, which can lead to poor tolerance of treatment and can contribute to cachexia in extreme cases. Children with advanced‐stage cancer are especially vulnerable to malnutrition resulting from anorexia and cachexia. Currently, there are no instruments that measure common concerns specifically associated with anorexia and cachexia in children with cancer. The purpose of the current article was to test the psychometric properties of a newly developed pediatric Functional Assessment of Anorexia and Cachexia Therapy (peds‐FAACT) for children with cancer.

METHODS

Ninety‐six patients (ages 7–17 yrs) receiving cancer treatment and their parents were asked to complete the 12‐item peds‐FAACT. The authors implemented both classical test theory and item response theory to evaluate the agreement between parents and patients, internal consistency and unidimensionality of the scale, and stability of items across subgroups.

RESULTS

As a result, a patient‐reported six‐item scale was recommended as the core measure for all pediatric patients with cancer and four additional peripheral items were recommended for adolescent patients.

CONCLUSIONS

The peds‐FAACT demonstrated good psychometric properties, differentiated patients with different functional performance status, and was determined to be a useful tool for future clinical trials. Cancer 2005. © 2005 American Cancer Society.
Ritz finite element approach to nonlinear vibrations of a Timoshenko beam
Authors: Sarma B. S. , Varadan T. K.
Published: August 2005

The Ritz finite element approach is used to study the nonlinear free vibrations of a beam considering shear deformation and rotary inertia effects. The governing nonlinear equations are derived using Lagrange equations at the point of reversal of motion. The nonlinear strain‐displacement relations include the curvature terms based on three‐dimensional incremental deformations, as used in Trefftz theory. A simple and efficient beam element, with three independent degrees‐of‐freedom at each node, and with linear polynomial distributions within the element, is made use of. The reduced integration technique is adopted on the shear related matrix to eliminate spurious constraints occurring when exact integration is used for the same in the case of slender beams. The governing equations are solved using a direct iteration scheme. Numerical results are presented in the form of tables for hinged‐hinged immovable beam. When the present results are compared with the available ones wherever possible, good agreement is in general, found.
Cubic B‐spline product integration formulae which only require values of the product function at the spline knots
Authors: Lewis B. A.
Published: August 2005

This paper presents integration formulae for the product of a cubic spline with a non‐singular function, f(x). The formulae only employ the values of f(x) at the spline knots. A simple error analysis demonstrates the inefficiency of using all possible values of f(x) and alternative formulae are described.
An accurate explicit finite diference technique for solving the one‐dimensional wave equation
Authors: Noye B. J. , Rankovic M. J.
Published: August 2005

A highly accurate finite difference method is developed for the classical wave equation in one spatial dimension. The derivation uses the ‘modified equaiton’ approach, whereby the partial differential equation actually solved by the finite difference equation is determined. By investigating the largest error terms, the new method is compared with the standard explicit method and a method developed by Twizell.2 Theoretical conclusions have been verified by using the methods to solve a simple problem for which an exact solution is available.
MacCormack's scheme applied to plane wave propagation in a linear viscoelastic solid
Authors: Lorimer S. A. , Haddow J. B.
Published: August 2005

A modification of MacCormack's finite difference scheme is applied to a one‐dimensional problem of plane wave propagation resulting from the sudden application of stress to the surface of a linear viscoelastic solid half‐space. A further modification is proposed which uses results from a wavefront expansion. Numerical results are presented which indicate the effect of the Courant number on numerical instability and numerical dispersion with, and without, the modification based on the wavefront expansion results.
A relaxation technique for the parabolized Navier–Stokes (PNS) equations
Authors: Kaul Upender K.
Published: August 2005

A rapidly converging relaxation technique for the parabolized Navier–Stokes equation has been devised. The scheme is applicable in both supersonic and subsonic flows, but it is discussed here in the context of supersonic flows. The upstream propagating acoustic influence in the subsonic part of the flow is introduced semi‐implicitly through the streamwise momentum equation applied on the body, and through a forward‐differencing on the streamwise pressure gradient term in the interior. This procedure yields a new boundary condition on the energy in the total energy equation. The presser‐velocity system in the subsonic layer is coupled, but the positive time‐like marching characteristic of the governing equations is still maintained. The relaxation technique is demonstrated to work for a three‐dimensional flow over a cone‐flare in supersonic flight.
Curved beam element via penalty/mixed formulation for nonlinear in‐plane analysis
Authors: Akoussah Esenam , Beauliieu Denis , Dhatt Gouri
Published: August 2005

The problem of membrane locking for curved elements is discussed in detail. The penalty technique is used to develop a locking free curved beam element based on the Marguerre's relations. This formulation is then generalized to nonlinear analyses using updated Lagrangian description. Some examples are presented to assess the efficiency of the proposed model.
Numerical differentiation by the regularization method
Authors: Macleod Allan J.
Published: August 2005

A description is given of the regularization method of numerical differentiation. The method is compared with the recent method of McNamee, and is shown to perform well, especially with very noisy data. A FORTRAN program is also given.
A strain softening element to model fibre pull‐out
Authors: Steven Grant P.
Published: August 2005

In order to model, with finite elements, the process of fracture in a fibre reinforced composite material a rod type element with strain softening in the form of a negative extensional stiffness is proposed. The acceptability, in a structural context, of such negative stiffness is examined and the performance of the element in modelling the fracture of fibre reinforced cement compact tension specimens is compared with experimental results.
Deforming finite elements for the numerical solution of the nonlinear inverse heat conduction problem
Authors: Mehta R. C. , Jayachandran T.
Published: August 2005

A numerical solution of the nonlinear inverse heat conduction problem is obtained using an in‐line method in conjuction with the measured thermocouple temperature history. The deforming finite elements technique is used to treat initial time delay in temperature response due to thermocouple location. In the absence of elements deformation, the method reduces to the conventional Galerkin formulation. A three‐time level implicit scheme, which is unconditionally stable and convergent, is employed for the numerical solution. The temperature‐dependent thermophysical properties in the resulting matrices are evaluated at the intermediate level. The complication of solving a set of nonlinear algebraic equations at each step is avoided. Illustration of the technique is made on the one‐dimensional problem with a thermal radiation boundary condition. The results demonstrate that the method is remarkable in its stability to predict surface condition without debilitation.
A generalization of two‐dimensional theories of laminated composite plates
Authors: Reddy J. N.
Published: August 2005

A general two‐dimensional shear deformation theory of laminated composite plates is presented. The theory account for a desired degree of approximation of the displacements through the laminate thickness. As special cases, the classical, first‐order (Reissner–Mindlin) and other shear deformation theories available in the literature can be deduced from the present theory.
Tau method approximate solution of highorder differential eigenvalue problems defined in the complex plane, with an application to orr‐sommerfeld stability equation
Authors: Liu K. M. , Ortiz E. L.
Published: August 2005

Recent new formulations of the Tau method have made it possible to apply it to a variety of new problems. In this paper we consider the numerical estimation of complex eigenvalues of high‐order differential equations by using the Tau method. The example considered is Orr–Sommerfeld's stability equation, for which there is a considerable literature on high‐accuracy numerical estimations. Our numerical results compare favourably with the most accurate ones reported in the recent literature.
A sparse linear equations solver for 3D–regular domains
Authors: Lipitakis Elias A. , Evans David J.
Published: August 2005

The implementation of the Extended to Limit sparse LU factorization solution methods1 is given. Two FORTRAN subroutines for the approximate (or exact) factorization and the solution of resulting equations are supplied. The amount of fill‐in terms can be controlled by the user through parameters R1, R2, the limiting case being when the matrix is factorized exactly.
Further results on the accuracy of the SSpj algorithms
Authors: Wood W. L.
Published: August 2005

Intuitively, it may that the single‐step algorithm SSpj, which depends on approximating the function in a time‐step by a polynomial of degree p, should give the same order error whether it is applied to a first‐or second‐order equation. This paper exaplains by direct analysis why the error in the function produced by SS22 is only 0(Δt) in general, whereas for SS21 it is 0(Δt2). This leads to the further result that for SSpj the function and all its derivatives up to and including the (p – 1)th are approximated with same order of accuracy. Numerical results are given for SS22 and SS32.
Comparison of 3‐D finite elements for fluid flow
Authors: Robichaud Michel P. , Tanguy Philippe A.
Published: August 2005

Several new elements are compared to the standard trilinear velocity–constant pressure element (Q1 – P0) for the solution of the three‐dimensional Navier–Stokes equations by the finite element method. The test problem is the cubic wall‐driven cavity with solution sought at Reynolds numer of 400 and 3200. It is shown that the Q1 – P0 can be advantageously replaced by better elements and a choice among these elements is proposed.
Shallow shells under arbitrary loading: Analysis by the two‐surface truss model
Authors: Mbakogu F. C. , Pavlović M. N.
Published: August 2005

This paper is concerned with an extension of the two‐surface truss model—hitherto restricted to the analysis of shallow shells under normal loading—to the somewhat more general case of shallow shells under arbitrary loading. We begin with a brief review of the two‐surface truss model. Next, we show that our proposed extension is indeed quite straightforward once certain consequences of the two‐surface exposition of thinshell theory are fully appreciated. We then outline two alternative approaches to the incorporation of tangential surface into the truss model. Finally, we demonstrate the good working of the trussmodel scheme in the present context by means of a numerical example.
A simple error estimator in the finite element method
Authors: Rank E. , Zienkiewicz O. C.
Published: August 2005

Recently, a new class of error indicators and estimators for the finite element methods has been introduced which is particularly easy to implement into existing finite element codes. This paper proves that the new indicators are equivalent to those analysed earlier by Babuska, thus showing that the rigorous mathematical results for the well‐known jump indicator apply also for the new ones.
Similar solutions of the Stefan problem
Authors: Beckett P. M. , Poots G.
Published: August 2005

Similar solutions are constructed for the inward solidification of a semi‐inifinite region of ‘model’ phase change material (PCM). It is necessary for certai of the physical properties of the PCM to be proportional to xm, where x is the normal distance measured from the cold wall.
Knowledge engineering enhancement of finite element analysis
Authors: Breitkopf Piotr , Kleiber Michal
Published: August 2005

This paper describes concepts behind the IQFEM which is an experimental knowledge based system for algorithm selection in nonlinear finite element analysis. Problems demanding human expertise in the FEM field are identified. The need to emulate this expertise by means of an appropriate expert system is emphasized. Knowledge base organization and symbolic inference principles, as employed in the system, are reviewed. The IQFEM has been developed in PASCAL using the 16‐bit personal computer. The paper describes the work in progress and no definite conclusions are stated.
Simulation of industrial cold forming processes
Authors: Hussin A. A. M. , Hartley P. , Sturgess C. E. N. , Rowe G. W.
Published: August 2005

A microcomputer‐based system for the simulation of cold metalforming processes is described. The simulation uses a nonlinear elastic–plastic finite element method developed for use on a 16‐bit microcomputer. The suitability of such a system is demonstrated by reviewing its application to industrial forming processes such as heading and extrusion. The simulation system provides details of forming forces, metal flow, and stress and strain distributions which may be used as a guide to the structure and mechanical properties of the finished product.
Transport of solid materials within storage basins of river power plants: Software design and practical application
Authors: Heidinger R. , Baumhackl G.
Published: August 2005

Over 60 per cent of the demand for electrical energy in Austria is covered by hydroelectric power plants. Problems arise within backwater areas of river power plants, causing storage loss by sedimentation of solid particles. Higher costs in construction, loss of energy and danger of inundation cause energy companies to simulate characteristics of this phenomenon numerically. The following considerations show that particular programming techniques enable the user to predict changes in river geometry within a short time and even create an individual set of sediment transport formulae within the software.
High order finite difference schemes to solve Poisson's equation in cylindrical symmetry
Authors: Mittal R. C. , Gahlaut Sanjeev
Published: August 2005

In the present work, finite difference schemes of second and fourth order are derived for the solution of Poisson's equation in cylindrical symmetry. The resulting system of linear equations is solved by a direct solver with the help of Hockney's method. The schemes are tested on two test problems whose exact solutions are known. The numerical results obtained by the finite difference schemes show that they produce accurate results.
A note on applications of adaptive finite elements to elastohydrodynamic lubrication problems
Authors: Wu S. R. , Oden J. T.
Published: August 2005

Adaptive methods are applied to improve the finite element solutions for highly nonlinear elastohydrodynamic lubrication problem. A refinement scheme is developed which is based on the idea of equidistribution of local errors. Numerical experiments on the line contact problem show that the adaptive method is very effective in obtaining good approximations. Adaptive methods for point contact problems with light loads are also examined.
Geometric sensitivity analysis with isoparametric finite elements
Authors: Brockman R. A.
Published: August 2005

This paper presents the development of several analytical relationships for use in the gradient calculations common to sensitivity analysis and configuration optimization. The methods discussed are oriented toward two‐ and three‐dimensional continua modelled with isoparametric finite elements, and design parameters which control the geometric layout of the structure. The notable feature of these formulae is their simplicity, which leads to quick and systematic computational algorithms for most standard elements.
A numerical procedure for electrostatic problems in a variable conductivity medium
Authors: Beauquet G.
Published: August 2005

For a variable conductivity medium, a numerical procedure using a coupling of two‐ and three‐dimensional finite element methods is developed to find an approximate solution of the potential problem.
Optimum dynamic dampers for single‐degree‐of‐freedom systems
Authors: Ebrahimi Nader D.
Published: August 2005

Reducing the vibration amplitude of mechanical systems is an on‐going problem for engineers. This paper, which focuses on one aspect of the problem, discusses the design of optimum vibration absorbers for linear damped systems. After the optimum design problem is introduced, a numerical optimization strategy is implemented for the solution. The results are presented in the form of comprehensive design tables that can be readily used by designers since the parameters are given in terms of dimensionless variables. When the results of optimization are compared to the case of a system with no absorber, the comparison will show that the scheme presented in this paper significantly reduces the maximum vibration amplitude of the mechanical systems operating under the influence of harmonic excitation.
A note on invertible two‐dimensional quadratic finite element transformations
Authors: Baart M. L. , Mulder E. J.
Published: August 2005

This paper presents a simple algorithm for verifying the non‐singularity of parametric transformations with quadratic Jacobian determinants. The method is suitable for such transformations applied to all convex polygonal two‐dimensional master‐elements, but emphasis is placed on the triangle and the square. Geometric insight is used to curtail testing procedures where possible. The algorithm is compared for efficiency to a related procedure in which no use is made of the geometry of the implied curves. Results indicate that the geometric procedure, while slower in some cases owing to additional tests, is considerably more efficient for those cases where the geometry allows early termination of the algorithm.
A note on plasticity theory in matrix notation
Authors: Pedersen Pauli
Published: August 2005

In the matrix formulation of continuum mechanics, stress and strain tensors are contracted to vectors, and this lower order formulation has some advantages. However, due to an inconvenient contraction, the matrix formulation cannot be fully utilized in the theory of plasticity. The traditional contraction with engineering strains is rather artificial, and in the present note it is shown how the natural √2 contraction for both stresses and strains makes a very clean formulation possible. The importance of projection matrices is pointed out.
Modelling of thermal diffusion in three dimensions by the transmission line matrix method and the incorporation of nonlinear thermal properties
Authors: Pulko S. H. , Johns P. B.
Published: August 2005

Modelling of thermal diffusion in three dimensions by the TLM (transmission line matrix) method is described and the results compared with those obtained using finite element analysis. Two approaches to the incorporation of nonlinear properties in TLM routines are also described and compared.
A note on the optimum choice for penalty parameters
Authors: Nour‐Omid Bahram , Wriggers Peter
Published: August 2005

This paper looks at the numerical characteristics of penalty methods for evaluating the solution of symmetric systems of equations with imposed constraints. The sources of error resulting from this approach are identified and an estimate for the penalty parameter that minimizes this error is obtained. The results of the error analysis and the effect of penalty parameter on the accuracy and rates of convergence of the solution algorithm are demonstrated with the aid of some numerical examples.
On the use of deflation to improve the convergence of conjugate gradient iteration
Authors: Mansfield Lois
Published: August 2005

Experimental evidence is presented to show that the method of deflation introduced by Nicolaides can be quite effective in improving the rate of convergence in conjugate gradient iteration in certain types of problems.
Adaptive techniques in the finite element method
Authors: Zhu J. Z. , Zienkiewicz O. C.
Published: August 2005

An effective h‐version finite element adaptive strategy combined with mesh regeneration is presented. This is based on the error estimator developed in Reference 1. The rate of convergence of the adaptive procedure has been tested for some examples and very strong convergence observed. Unlike some existing h‐version adaptive procedures, a nearly optimal mesh of predicted accuracy can be obtained in one or two adaptive process steps.
Graphical representation of two‐dimensional fluid flow by stream vectors
Authors: Bertrand F. H. , Tanguy P. A.
Published: August 2005

A new graphical representation for fluid flow is explained. It combines the concepts of classical streamline plot and velocity vector display and enables a more adequate visualization of flow pattern, especially near solid boundaries.
Symbolic analysis of the reduced incompressible Navier‐Stokes equations
Authors: Fletcher C. A. J. , Armfield S. W.
Published: August 2005

Symbolic analysis is described and used to show that the reduced Navier‐Stokes equations are parabolic due to the convection‐diffusion interaction, but are elliptic due to the interaction between the pressure field and the continuity equation. It is demonstrated that the introduction of a transverse pressure gradient term into the streamwise momentum equation will render the complete system non‐elliptic and amenable to solution via a single spatial march in the streamwise direction.
Integrals over boundaries at infinity for the boundary integral method may be ignored
Authors: Sofianos A. I.
Published: August 2005

The boundary integral equation method sometimes requires the integration of kernel functions times displacement or traction fields over boundaries at infinity. The value of these integrals in the case of two‐dimensional elasticity and the action of non‐self‐equilibrating force densities, which is especially relevant in geotechnical engineering, is not obvious. It has been proven that these integrals sum to zero.
From Kirchhoff to Mindlin plate elements
Authors: Aalto J.
Published: August 2005

A procedure to generalize Kirchhoff thin plate finite elements so that they can be used for solving thick Mindlin plates is presented. Two typical discrete Kirchhoff elements, a triangular one and a quadrilateral one, are modified. Numerical results for a clamped circular plate show that the accuracy of the new Mindlin elements is the same as that of the original Kirchhoff elements and they can be used in the whole thickness range of Mindlin plate theory.
A simplified method for the dynamic analysis of shell structures
Authors: Gao Lin , Keming Sun , Menglin Lou
Published: August 2005

An efficient method suitable for the dynamic analysis of shell structures is introduced. The shell is partitioned into a series of strips, the vibration modes of which are taken as the basic vectors for co‐ordinate transformation. This approach highly reduces the degrees‐of‐freedom of the equation of motion and highly simplifies the computational effort, while good precision can still be ensured.
A finite element‐finite difference solution of three‐dimensional viscous‐inviscid interaction
Authors: Gülçat Ü. , Aslan A. R.
Published: August 2005

Based on the concept of viscous‐inviscid interaction, a hybrid solution technique in studying external flow past three‐dimensional bodies is developed. The finite element method is employed to solve the inviscid part of the flow and the finite difference technique is utilized in solving the viscous part of the flow. This hybrid technique is applied to study the flow past a swept bump on a circular cylinder. The 8‐noded trilinear brick elements are used for the finite element formulation of the problem where the flow is considered potential. In the viscous part, however, three‐dimensional boundary‐layer equations simplified with small cross‐flow assumption and expressed in the surface co‐ordinates are solved utilizing the finite difference method. Numerical studies are made for both the laminar and the turbulent flow cases using the boundary‐layer edge velocity distribution obtained through inviscid solution. The results are compared with the available experimental data. The boundary‐layer edge velocity distribution is in good agreement with the experimental data; the prediction of the separation point for the laminar case is the same. For the turbulent flow case, the velocity profiles in the flow direction when compared to the measurements are overall in reasonably good agreement, and the discrepancies are due to small cross‐flow assumption. However, the agreement concerning the wall shear stress component in the flow direction is more satisfactory.
Solution of full and deficient rank linear equations
Authors: Tewarson R. P. , Jen J. F.
Published: August 2005

An algorithm for computing the solution of a linear system of algebraic equations is described. If the system is rank deficient, then the minimum norm least‐squares solution is obtained. The method utilizes Gaussian elimination with scaled partial pivoting and (in rank deficient case) orthogonal triangularizations on the remaining coefficient matrix.
Element‐by‐element vector and parallel computations
Authors: Carey G. F. , Barragy E. , McLay R. , Sharma M.
Published: August 2005

Vector and parallel algorithms for finite‐element analysis using the element‐by‐element (EBE) data structure are developed. The algorithms are based on the EBE approach in conjunction with gradient‐type iterative solution. The essential idea is to exploit the independent dense local‐element matrix‐vector calculations and reconfigure them to take advantage of vector or parallel processing capabilities. The ideas also are well suited to finite‐element adaptive refinement computations. Specific algorithmic details related to the implementations are given, together with results of speed‐up performance studies conducted on the vector and parallel architectures. The basic vector and parallel versions of the matrix‐vector product for the EBE scheme are very straightforward modifications of the EBE algorithm, requiring little coding change.
On a modified streamline curvature method for the Euler equations
Authors: Cordova Jeffrey Q. , Pearson Carl E.
Published: August 2005

A modification of the streamline curvature method leads to a quasilinear second‐order partial differential equation for the streamline coordinate function. The existence of a stream function is not required. The method is applied to subsonic and supersonic nozzle flow, and to axially symmetric flow with swirl. For many situation, the associated numerical method is both fast and accurate.
Simulation techniques for multiphase and multicomponent flows
Authors: Ewing Richard E. , Espedal Magne S. , Puckett Jay A. , Schmidt Richard J.
Published: August 2005

The simulation of multiphase and multicomponent fluid flows often requires large coupled systems of nonlinear partial differential equations. These equations are convection‐dominated, with important local diffusive effects. An operator splitting technique is used to address these different phenomena. Adaptive local grid refinement methods are then presented to resolve the moving internal boundary layers which arise and often govern the mass transfer between the phases. Owing to the large size of many application, efficiency in computation is critical. Concepts of domain decomposition for dynamic adaptive grid refinement are presented. Techniques for dividing the problems into pieces for parallel computation on separate processors are also discussed.
A parallel algorithm for the general LU factorization
Authors: Kincaid David R. , Oppe Thomas C.
Published: August 2005

An algorithm for computing in parallel the general LU factorization of a matrix is presented. As special cases, one obtains the Doolittle, Crout and Cholesky methods. The algorithm was implemented and tested on a Cray X‐MP/48.
Effects of geometric nonlinearities on explicit time integrators
Authors: Neal Mark O. , Belytschko Ted
Published: August 2005

The effect of follower forces and initial stresses on the stability of the central difference method is studied. As a model, bar and beam elements are considered by means of the element eigenvalue inequality. It is shown that both follower‐force pressure loads and tensile initial stresses decrease the stable timestep but the decrease becomes significant only when the pressure or stress is greater than about a tenth of the tangent modulus.
On some recent evolutions in personal supercomputing and workstation graphics
Authors: Hajjar J. F. , Martha L. F. , O'Connor T. F. , Abel J. F.
Published: August 2005

Recent hardware advances for both enhanced computing and interactive graphics are used to improve the effectiveness of three‐dimensional engineering simulations. The two examples presented, drawn from structural engineering, deal with the fully nonlinear transient dynamic analysis of frames and boundary element stress analysis.
The versatility of automatic mesh generators based on tree structures and advanced geometric constructs
Authors: Shephard Mark S. , Baehmann Peggy L. , Grice Kurt R.
Published: August 2005

The ability of the finite octree and finite quadtree automatic mesh generators to satisfy effectively a wide variety of meshing capabilities is demonstrated. Areas considered include the ability to integrate easily with geometric modelling systems, versatile interactive mesh control functions, the ability to reorder unknowns directly from the finite element data structure and the ability to support automated finite element modelling.
Geometric idealizations in finite element computations
Authors: Szabó Barna A.
Published: August 2005

Commonly used geometric idealizations in finite element analyses introduce errors which require either a large number of degrees of freedom or the use of special procedures to correct. In this paper the effect of geometric idealizations on computed data is examined through the example of a spherical shell with an edge ring. This example demonstrates that in typical structural problems it is better to avoid the use of sharp reentrant corners than to compensate for them by mesh refinement. The effect of different mapping techniques is also examined.
Linear and nonlinear finite element analysis on multiprocessor computer systems
Authors: Wilson Edward L. , Farhat Charbel H.
Published: August 2005

Several general purpose computer systems with multiple processors operating concurrently are currently being commercially produced. Most of the present generation of finite element software was not designed to take advantage of this new technology. The purpose of this paper is to present the advantages of a new architecture for finite element programs which will operate efficiently on computer systems with any number of processors. Also, the basic approach is effective for multiprocessor computers with local or shared memory.

The new computer program architecture is based on an initial application of a simple algorithm which automatically subdivides the complete finite element domain into a number of subdomains equal to the number of available processors. The resulting data structure requires a minimum of communication between processors during the formation of basic element matrices, reduction of subdomain matrices and the postprocessing of element results. The assembly and solution of the global system of subdomains can be accomplished directly or iteratively, and new concurrent solution algorithms can be introduced.

Several of the ideas presented here have been tested on various types of computer. The new program architecture indicates that it is possible to obtain speed‐up times of over 90 per cent of the maximum theoretical values if appropriate numerical methods are employed.
Heat transfer analysis of structures containing phase‐change material
Authors: Loyd D. , Fröier M.
Published: August 2005

A method is presented for analysing industrial heat transfer problems in which there is a transition. The finite element method is used, and for the calculations the special‐purpose heat transfer program THAFEM is utilized. The latent heat of a region with phase‐change material (PCM) is concentrated at the nodes of the elements in the region. The method is rapid and gives the necessary agreement between calculations and experimental results.

As an example filling of explosives is considered. In order to avoid the formation of closed volumes of melted material surrounded by solidified explosive, it is necessary to control the cooling of the high‐explosive shell. The PCM is mainly trinitrotoluene with a melting point of 80.3°C. Another example that shows the applicability of the method is a fire‐proof floppy‐disk cabinet with walls made from layers of Glauber's salt, a PCM with a melting point of 32°C. The cabinet should withstand a fire, without the inside temperature exceeding the maximum allowed value of 52°C, for a prescribed time.
An isoparametric boundary solution for thermal radiation
Authors: Keavey M. A.
Published: August 2005

In order to solve problems of re‐radiation and reflection in finite element thermal analysis, a discretization consisting of flat isothermal surfaces is usually assumed. Such an approximation is clearly inconsistent if an isoparametric model is used for any surrounding solid. In addition, geometric view‐factors are often required explicitly, but their calculation is generally considered to be tedious and error prone. The representation of radiative exchange by a boundary integral equation is a standard analytical technique. The use of such a representation in conjunction with finite element analysis, however, appears to be quite recent. The present work describes a scheme whereby standard finite element/boundary element coupling theory may be applied to yield a method which is both simple and consistent. The use of isoparametric elements allows varying temperatures and curved surfaces to be modelled. For an empty enclosure the kernel of the integral equation is simply related to the differential geometric view‐factor. Re‐radiation and reflection are implicit.
An analysis of thermal effects of coupled thermo‐plasticity in metal forming processes
Authors: Slużalec Andrzej
Published: August 2005

In this paper, a solution procedure for nonlinear thermo‐mechanical problems appearing during plastic deformations of metals is presented. The finite element technique is used to achieve a coupled analysis of plastic deformations and heat transfer. Numerical results of ring forging demonstrate the presented method.
Comparative study for a new solution to the inverse heat conduction problem
Authors: Weiland E. , Babary J. P.
Published: August 2005

The solution we proposed for the inverse problem1 is evaluated. The study is based on Raynaud and Beck's paper,2 which provides test cases and simulation results for some common numerical inverse methods.
Tracking the transient phase‐change front using the temperature of the convectively cooled surface
Authors: Choi Heon‐Oh
Published: August 2005

The coupled conduction‐convection problems which results from the solidification of a convective liquid are transformed into an equivalent minimization problem using an additional boundary condition which can be obtained from experiments. This transformed problem eliminates the necessity of solving the dynamic and energy equations of the liquid phase. Numerical simulations are performed to examine the applicability of the present method. Comparisons are made between the transient positions of the phase‐change front obtained from the present method and the steady‐state solutions. Sensitivity analysis of 10 per cent variations of the cooling rate are made.
An improved time integrator for finite element analysis
Authors: Bixler Nathan E.
Published: August 2005

Several modifications to the widely used time integration scheme of Gresho et al.1 are suggested. The advantages of the modified time integrator are demonstrated by means of several simple example problems.
Parametrized multifield variational principles in elasticity: I. Mixed functionals
Authors: Felippa Carlos A.
Published: August 2005

A one‐parameter family of mixed variational principles for linear elasticity is constructed. This family includes the generalized Hellinger‐Reissner and total potential energy principles as special cases. The presence of the free parameter offers an opportunity for the systematic derivation of energy‐balanced finite elements that combine displacement and stress assumptions. It is shown that Fraeijs de Veubeke's stress‐assumption limitation principle takes a particulary elegant expression in terms of the parametrized discrete form. Other possible parametrizations are briefly discussed.
A single‐step algorithm for oscillatory problems
Authors: Thomas R. M. , Evans S. J.
Published: August 2005

We consider a class of multistage single‐step methods introduced by Zienkiewicz et al.1 and developed by Thomas and Gladwell.2 From this class, we derive methods which are particularly suitable for the numerical solution of oscillatory problems. We propose a particular pair of methods which permit local error estimation while retaining a ‘one‐step’ mode of operation. We discuss the implementation of this pair for both linear and nonlinear problems, and illustrate the discussion with numerical results.
Numerical analysis of transient states in one‐dimensional non‐linear systems
Authors: Jordan A. J. , Aniserowicz K.
Published: August 2005

An algorithm for the analysis of non‐linear partial differential equations describing transient states of one‐dimensional physical problems with boundary conditions given on the opposite ends of the analysed domain is presented. The algorithm makes use of the Runge‐Kutta and bisection methods used in space ℝ1 and the forward finite difference method for the time domain. The algorithm is illustrated by one‐dimensional analysis of a temperature field in a transient state.
A simulation of seasonal temperature and moisture content changes in the ground
Authors: Thomas H. R. , Owen R. C.
Published: August 2005

The paper describes the application of a numerical model to the prediction of seasonal temperature and moisture content changes in the ground. The results are compared with measured values taken over a two year period at the site of a monitored field experiment. Blind predications have been carried out on the basis of assumed material parameters. It is concluded that the analysis is largely capable of modelling the phenomena observed. Certain limitations are, however, exposed.
Numerical determination of the stress intensity factor KI in transient thermal state: Application to the cooling of a ‘penny shaped crack’
Authors: Berthomieu G. , Jouanna P. , De Langres E.
Published: August 2005

This study describes the evolution of the stress intensity factor KI for fissures in brittle elastic materials subjected to transient thermal actions. The case studied is a ‘penny shaped crack’ located in a rock mass and through which runs a fluid whose temperature falls in time.

Computation was carried out using the CASTEM finite element method and its subprograms. The four steps are described: mesh elaboration, calculation of temperature field, thermo‐mechanical computations and estimation of KI by displacements or the J integral method. The results are given for various transient thermal conditions and for a steady state case for reference. Cooling spreads very slowly in the rock mass and there are steep temperature gradients in the first few millimetres.
Local boundary integral equation analysis of 2‐dimensional potential problems using Fourier series
Authors: Askin S. , Fenner R. T.
Published: August 2005

Local boundary integral equation (boundary element) methods make it possible to determine the variables of interest in a small pre‐selected region of a solution domain, without the need to determine the unknowns over the rest of the boundary. A method of this type based on Fourier series is developed for two‐dimensional potential problems governed by Laplace's equation. Very accurate values of the function and its derivatives can be obtained.
A finite‐element technique for coupled reaction and heat transfer analysis with negligible mass diffusion
Authors: Lee Ching‐Chih
Published: August 2005

A technique is developed for solving a coupled reaction and heat transfer problem in which mass diffusion is negligible. The energy equation is solved by the conventional finite‐element method with temperature unknowns at the nodes, while the reaction kinetics is incorporated with reaction variables at the Gauss points in each element. As examples, cure of SMC (sheet moulding compound) in a cylinder and cure of rubber in an engine mount are analysed using a mechanistic and a phenomenological reaction model, respectively.
On the principle of cyclic symmetry in machine dynamics
Authors: Ramamurti V. , Seshu P.
Published: August 2005

Cyclic symmetric structures are those that posses a circumferentially periodic geometry, e.g. gear wheels, bladed discs, etc. Accurate prediction of their static and dynamic characteristics is essential to ensure optimum design. An analysis of the entire structure is often prohibitively costly. Through illustrative examples, the essential features of an analysis scheme exploiting the geometric periodicity are brought out. Avoiding much of the mathematics, the underlying principle (termed the‘eiψ relationship’) for both static and dynamic analysis is explained. The parallel to the special case of axisymmetric structures is drawn.
A new third‐order finite‐difference method for transient one‐dimensional advection—diffusion
Authors: Noye B. J.
Published: August 2005

The accuracy of some first and second‐order methods for solving the time‐dependent one‐dimensional constant‐coefficient advection‐diffusion equation are compared theoretically on the basis of the dominant error terms in their modified equivalent partial differential equations. A new very stable three‐point (in space) third‐order implicit method is then developed by combining two second‐order methods. The accuracies of the various methods are then compared by means of numerical tests.
On the box scheme for overland flow calculations
Authors: Wood W. L. , Arnold P. D.
Published: August 2005

This paper describes an example of a numerical solution of an overland flow problem where a box scheme which is unconditionally stable nevertheless has to have a limit on the time step.
Boundary‐element analysis of wave scattering from cracks
Authors: Jia Z. H. , Shippy D. J. , Rizzo F. J.
Published: August 2005

A multi region boundary‐element method is employed to study the scattering of time‐harmonic waves by cracks in a three‐dimensional elastic solid. Special shape functions are employed to model the near‐crack singularity. The multi region formulation enables removal of singularities from all boundary integral equations. The matter of fictitious eigenfrequencies is discussed and resolved. Values of dynamic stress intensity factors for three problems involving penny‐shaped cracks are compared with results of other investigators.
On buckling mode superposition in non‐linear analysis of shells
Authors: Flores Fernando G. , Godoy Luis A.
Published: August 2005

This paper is concerned with the numerical solution of kinematically non‐linear shell problems using approximate techniques. The interest is focused on shells of revolution, for which a technique proposed by Nagy and König has been implemented and assessed by means of numerical studies. The non‐linear path is approximated using a reduced basis of buckling modes. The results illustrate that reasonable estimates of moderately non‐linear paths can only be expected for cases in which the fundamental path is governed by membrane action.
On relaxation of jacobi iteration for consistent and generalized mass matrices
Authors: Wathen A. J.
Published: August 2005

In time‐dependent finite‐element calculations a ‘mass matrix’ arises. It is thus necessary to solve or approximate a matrix system at each step even for ‘explicit’ time integration methods. In this manuscript we analyse the efficiency of Jacobi‐like iteration for solving such matrix equations which arise when the Galerkin or Taylor‐Galerkin methods are used.
Free‐vibration analysis of cyclic symmetric structures
Authors: Balasubramanian P. , Jagadeesh J. G. , Suhas H. K. , Ramamurti V.
Published: August 2005

A subspace iteration scheme for the Hermitian eigenvalue problem arising from analysis of cyclic symmetric structures is presented. This operates in the semi‐complex domain and its computational efficiency is demonstrated. A modified convergence checking criterion which gives better error estimates, and a new trial vector selection scheme which accelerates convergence for the Hermitian eigenvalue problem based on the Ritz method, are presented.