bluuebunny/crossref_metadata_2025 huggingface dataset:
Solution of the advection–diffusion equation using the spline function and finite elements
Authors: Szymkiewicz R.
Published: August 2005

This paper deals with the solution of the one‐dimensional advection–diffusion equation. The method of solution is based on the process‐splitting technique. The transport equation is split up into the advection part and the diffusion part at every time step. The advection transport equation is solved by a method of characteristics using a spline function for interpolation. This solution approach proves to be very effective because it reduces numerical dispersion and wiggles. The diffusion equation is solved by the standard Galerkin finite‐element method. A comparison of calculations with the results of Holly and Preissmann and with analytical solutions demonstrates the great accuracy of the proposed method.
An element error indicator and a related stress‐improvement procedure
Authors: Cook Robert D.
Published: August 2005

A posteriori error indicators for strain energy error in finite‐element solutions have recently been shown to be effective. A popular error indicator, usually denoted by η, makes use of ‘error energy’, i.e. strain energy associated with the difference between the conventional element stresses σ and a smoothed stress field constructed from σ. It is intended that η be constructed by summing element contributions and that it be applied at the global level. The present study suggests that an error indicator applicable at the element level can be obtained by combining an element value of η with information about stress gradient and strain energy density. It is also shown how the stress gradient information can be used to obtain more accurate stresses at mesh boundaries.
Bandwidth reduction of rectangular matrices
Authors: Kaveh A.
Published: August 2005

Two graph‐theoretical algorithms are developed for bandwidth reduction of rectangular matrices. A K‐total graph is defined for a selected cycle basis, generalized cycle basis and cut set basis of a graph. This transforms a simultaneous ordering of the elements of a basis and members of a graph into that of a nodal numbering of its K‐total graph.

The first algorithm uses the K‐total graph and results in banded equilibrium and self‐stress matrices. The second employs a nodal ordering algorithm followed by a member ordering process. This algorithm can be used for optimizing the bandwidth of member‐cocycle incidence matrices, resulting in banded equilibrium matrices.
An efficient wave input procedure for infinite media
Authors: Zhao Chongbin , Valliappan S.
Published: August 2005

An efficient wave input procedure in the finite and infinite element coupled model is presented in this paper. Compared to the previous wave input method, the main advantage of the present wave input procedure lies in its computational efficiency because only a small region of the medium needs to be modelled by finite elements. The equivalence between the present wave input procedure and the previous one has been theoretically proven when a harmonic wave propagates vertically in an isotropic homogeneous elastic half‐space. In addition, the accuracy of the present wave input method has been evaluated based on the solutions obtained for SH‐wave, SV‐wave and P‐wave scattering problems in a semicircular canyon for which analytical solutions are already available.
Generalized conforming quadrilateral plate element by using semi‐loof constraints
Authors: Zhifei Long
Published: August 2005

A 12‐DOF quadrilateral element for plate bending is formulated based on the concept of generalized compatibility and semi‐Loof constraints. The element DOFs are defined with the conventional displacements at corner nodes and the semi‐Loof constraints are used in the formulation. This element is a generalized conforming one which passes Irons' patch test and can be used to solve problems with complicated boundaries. When overall considerations of simplicity, accuracy and reliability are taken into account, this new element is one of the best 12‐DOF quadrilateral plate‐bending elements currently available.
The Gauss–Laguerre quadrature rule for finite‐part integrals
Authors: Ioakimidis N. I.
Published: August 2005

The classical Gauss–Laguerre quadrature rule for the semi‐infinite integration interval [0,∞] is modified and applied to the case of the weight function exp(‐x)/x corresponding to finite‐part (or, equivalently, hypersingular) integrals. The new set of orthogonal polynomials is constructed and it is seen to consist of linear combinations of the classical Laguerre polynomials with appropriately determined coefficients. The zeros of these modified Laguerre polynomials are seen to be distinct, but one of these lies outside the integration interval. Formulae for the corresponding weights are also given and numerical values and results are presented. The present results generalize the corresponding results for the finite interval [0,1] to semi‐infinite intervals and they are applicable to a variety of applied mechanics and related problems, where finite‐part integrals appear in a natural way.
Iterative method of integral relations scheme for wake flows
Authors: Yang R.‐J. , Yeung W.‐S.
Published: August 2005

The orthonormal method of integral relations (MIR) is extended to calculate wake flow problems. Two previous difficulties are overcome: (1) the non‐constant integral domain is eliminated by introducing a linear transformation in the formulation; (2) the difficulty associated with determining unique orthonormal weighting functions is overcome by an iterative scheme. The new formulation is applied to calculate a wake flow. A high‐order solution for N up to 4 is obtained with relative ease.
The construction of nearly orthogonal multiblock grids for compressible flow simulation
Authors: Marchant M. J. , Weatherill N. P.
Published: August 2005

A method is described whereby structured multiblock meshes can be constructed from the solution of elliptic partial differential equations and which possess the property of orthogonality close to boundaries and near orthogonality within the domain. To construct grids for viscous flow simulations which have appropriate point distributions close to solid boundaries these grids are used with point redistribution formulations. The result is high‐quality grids for use with both inviscid and viscous flow simulation algorithms. Examples using the approach are given, and these include grids for single and multicomponent aerofoils and bluff bodies.
Numerical solution of regularized long‐wave equation
Authors: Jain P. C. , Shankar Rama , Singh T. V.
Published: August 2005

A combination of the splitting method and the cubic spline technique has been used to solve a non‐linear regularized long wave (RLW) equation. The accuracy and the stability of the proposed method are discussed. Then, two numerical examples are solved to illustrate the robustness of the algorithm. The results are in good agreement with the available results.
Iterative solution of the stream function–vorticity equations using a multigrid solver with finite elements
Authors: Davis M. B. , Carey G. F.
Published: August 2005

The solution of the stream function–vorticity equations is developed using a multigrid method to improve efficiency in a finite‐element p‐method. The equations are discretized using 2‐D Lagrange finite elements (linear, quadratic and cubic) and solved in iteratively decoupled form using successive approximation and continuation methods. The comparative performance of several multigrid and direct matrix solvers is investigated with respect to convergence characteristics and time performance on the Cray Y‐MP.
Stability of the multiple reciprocity method for transient heat conduction
Authors: Ramesh Palghat S. , Lean Meng H.
Published: August 2005

The multiple reciprocity method is based on using higher‐order fundamental solutions to eliminate domain integrals encountered in transient boundary integral formulations. The paper considers the numerical stability of this approach through an eigenvalue decomposition of the system matrix. We demonstrate that the multiple reciprocity method for transient heat conduction is stable only for appropriately chosen time steps.
Computation of outflow flux for convection‐dominated transport equations
Authors: Semper Bill
Published: August 2005

An a posteriori point‐wise outflow flux recovery scheme which capitalizes on the hyperbolic nature of convection‐dominated transport models is proposed. The scheme is seen to be robust in that it can be applied to any upwind finite‐difference or finite‐element approximation, and gives a superconvergent approximation to the outflow flux.
Multi‐level iterative technique and aggregation concept with semi‐analytical preconditioning for solving boundary‐value problems
Authors: Bulgakov V. E.
Published: August 2005

Some iterative multi‐level approaches for solving large‐scale finite‐element elliptic problems are proposed. It is suggested that these approaches be used in combination with an aggregation technique. On the basis of the aggregation concept a new efficient preconditioning procedure in the inner iterative scheme of the algorithm is developed. This procedure is derived from the fundamental solution of a corresponding elliptic problem. The efficiency of the approaches is demonstrated by numerical examples.
Explicit formulas for correcting finite‐element predictions of natural frequencies
Authors: Xie Y. M. , Steven G. P.
Published: August 2005

Explicit formulas for correcting finite‐element predictions of natural frequencies are presented for longitudinal, torsional and bending vibrations of beams. By employing these simple explicit formulas the finite‐element discretization error in the natural frequency predictions can be effectively reduced at almost no computational cost. For longitudinal and torsional vibrations the frequency correction always yields the exact solution, while for the bending vibration it gives a significant improvement over the uncorrected frequencies. This method is also applied to two‐ and three‐dimensional frames, and it is found that the errors in the original finite‐element predictions of natural frequencies are reduced by about 50 per cent after such a correction.
The effectivity of the Zienkiewicz–Zhu error estimate and two 2D adaptive mesh generators
Authors: Samuelsson A. , Wiberg N.‐E. , Zeng L. F.
Published: August 2005

The paper reports some numerical experiments on the effectivity of the Zienkiewicz–Zhu error estimate (1987) and comparisons of two adaptive mesh generators: ADMESH, developed by Jin and Wiberg (1990) and MAD2D by Peraire et al. (1987) and Zhu et al. (1990–91). From the experiments we observe that: (1) without any empirical correction, the effectivity of the error estimate for linear triangular elements is good if post‐processed continuous stresses are obtained by adequately using an iterative stress recovery procedure (Zienkiewicz et al., 1985), and is also acceptable by using a simple ‘averaging’ procedure; (2) these two mesh generators are basically comparable.
Iterative computation of second‐order derivatives of eigenvalues and eigenvectors
Authors: Tan Roger C. E. , Andrew Alan L. , Hong Felicia M. L.
Published: August 2005

An iterative method is introduced for computing second‐order partial derivatives (sensitivities) of eigenvalues and eigenvectors of matrices which depend on a number of real design parameters. Numerical tests confirm the viability of the method and support our theoretical analysis. Alternative methods are reviewed briefly and compared with the one proposed here.
Least‐squares T‐elments: Equivalent FE and BE forms of a substructure‐oriented boundary solution approach
Authors: Jirousek J. , Wróblewski A.
Published: August 2005

An efficient solution to boundary‐value problems may be based on the application of a suitably truncated T‐complete set of Trefftz functions over individual subdomains and on linking the fields by a least‐squares procedure. Although it yields a symmetric system of linear equations, this approach as originally presented by Zielinski and Zienkiewicz is not suited for implementation into FE codes. The present paper presents two equivalent formulations, which take respectively the form of the finite (FE) and non‐conventional boundary‐element (BE) approach. Both allow the resulting simultaneous equations to be assembled following the standard direct stiffness methods and can readily be implemented into existing FE codes.

As in the conventional p‐method, the accuracy may be controlled within large limits without increasing the number of elements. The present approach allows substantial saving in computer time in comparison with the so‐called hybrid‐Trefftz (HT) elements, though the assumed displacement fields are identical. The practical efficiency of the new T‐element approach is assessed on the problem of stress concentration in a symmetrically compressed perforated panel.
Numerical investigation of a method to reduce the reheating time of steel bars
Authors: Visser J. A. , van der Walt J. C.
Published: August 2005

Reduction of reheating time saves on energy input and increases the production rate in the steel‐making process. Reductions can be achieved by allowing the centre temperature of a steel bar to be lower than the surface temperature by a small margin, before starting with the hot rolling process. This can only be done if the temperature difference does not adversely affect the quality of the final product or the rolling equipment. The paper presents numerical simulations to investigate the savings that can be obtained for various temperature differences between surface and centre temperatures to evaluate the feasibility of the concept. The results presented include the cross‐sectional temperature distribution in a typical steel bar during reheating at hourly intervals as well as the effect of various differences between centre and surface temperatures on reheating time. The reheating time predicted for various steel bar sizes as well as for various differences between surface and centre temperatures are then compared against measured reheating times. To indicate the practical applicability of the concept to the hot rolling process the detailed temperature distribution in a typical steel bar, with an initial temperature difference between the surface and centre of the bar, was simulated numerically. This was compared to a similar simulation for a well soaked steel bar for which experimental measurements are also available. The numerical method used to obtain the simulations is also presented. Boundary conditions account for radiation, convection and conduction inside the steel bar. It is concluded that the concept of allowing differences between surface and centre temperatures of a steel bar during reheating holds great potential for energy savings in the steel‐making process.
BEM computation of DSIF in cracked viscoelastic plates
Authors: Polyzos D. , Stamos A. A. , Beskos D. E.
Published: August 2005

Dynamic stress intensity factors of cracked linear viscolastic solids under conditions of plane stress are computed by the boundary‐element method in conjunction with the numerical Laplace transform and the correspondence principle of linear viscoelasticity. Quadratic isoparametric conventional and quarter‐point boundary elements are employed. The multidomain approach is used in cases where symmetry cannot be invoked. Dynamic stress intensity factors are computed for cracked viscoelastic rectangular plates subjected to suddenly applied loads, and comparisons are made against results obtained by other numerical methods.
Numerical study of withdrawal and return of water following a volcanic eruption at sea
Authors: Rajamäki Markku , Saarinen Mika
Published: August 2005

A speculation is presented to explain in physical terms the biblical story in which the withdrawal and return of the sea saved the Hebrews but drowned the army of Pharaoh. The explosion of the volcano on the island of Thira (Santorini) is speculated to be connected with this biblical story.

To support our proposition concerning depression and flooding waves, we have made a numerical calculation with a highly accurate computer code and provided an outline of the PLIM method (piecewise linear interpolation method) used. This calculation is numerically very challenging because the volcano is located far from the shore and hence detailed discretization is not practical. In addition, we show that if a less accurate numerical method is used, the whole phenomenon is lost because of numerical errors.

Our simple approach provides a withdrawal and return of the water to the shore that is sufficiently large, but the duration of this occurence is only a few minutes. The opportunity for a much longer duration as a consequence of other phenomena has not been excluded, however.
Simplified heuristic Fourier analysis of iteration convergence rates
Authors: Ramshaw J. D. , Mesina G. L.
Published: August 2005

Chan and Elman (1989) have recently shown that heuristic Fourier analysis can be used to determine approximate convergence rates of iterative methods. Here we present a simple procedure and useful relations that facilitate the practical application of this method. The procedure is based on the fact that the mesh spacing h is typically small, so that attention may be restricted to the asymptotic behaviour of the convergence rate R for small h. We accordingly derive simple expressions for the first few coefficients in a Taylor series expansion of R in powers of h. These coefficients are expressed in terms of derivatives with respect to h of the complex Fourier growth factor ξ rather than its modulus |ξ|. The required derivatives can then be obtained by implicit differentiation without explicitly solving for ξ, which further simplifies the analysis. The overall procedure is illustrated by applying it to the Jacobi, Gauss‐Seidel and successive overrelaxation methods, for which we obtain results asymptotically equivalent to those of Chan and Elman. We also analyse the effect of second‐order Richardson acceleration on the Jacobi method, for which we obtain an asymptotic convergence rate in precise agreement with classical analysis.
Non‐linear analysis of plane elastic bodies with inclusions by a BEM‐FEM approach
Authors: Kokkinos F. T. , Reddy J. N.
Published: August 2005

In the present study a hybrid boundary‐element and finite‐element method is developed for the non‐linear analysis of two‐dimensional elastic media with inclusions, and it is utilized in defining the micro‐mechanical stress field in composite materials. The linear elastic, isotropic and homogeneous matrix is treated with the BEM, while the non‐linear elastic and orthotropic inclusions (fibres) are treated with the FEM.
Revised Greedy algorithm for formation of a minimal cycle basis of a graph
Authors: Kaveh A. , Roosta G. R.
Published: August 2005

An efficient algorithm is developed for the formation of a minimal cycle basis of a graph. This method reduces the number of cycles to be considered as candidates for being the elements of a minimal basis and makes practical use of the Greedy algorithm feasible. A comparison is made between the existing methods and the present algorithm. A counter‐example is presented for Kaveh's algorithm from planar graphs.
A self‐adaptive method for the GFDF solution of parabolic problems defined over 3D domains of general shape
Authors: Pennati V. , De Biase L. , Ratti G.
Published: August 2005

A self‐adaptive method for the solution of elliptic and parabolic problems defined over 3D general multiconnected regions by generalized finite‐difference formulae, with boundary approximation by means of polyhedra, is proposed. Different approaches to space refinements are studied and implemented. Numerical examples are given.
Explicit expressions of shape functions for the modified 8‐node serendipity element
Authors: Kikuchi Fumio
Published: August 2005

We derive explicit expressions of shape functions for the 8‐node serendipity element with bilinear element geometry, which is modified so that it can represent any quadratic fields in Cartesian co‐ordinates. The modification is similar to the one by MacNeal and Harder, but is slightly different and based on our own idea. We also show that the usual 6‐node triangular element can be obtained by applying the node degeneration technique to this modified element.
On understanding and teaching of the finite element method
Authors: Wiberg Nils–Erik
Published: August 2005

The success of the finite element method depends on the highly systematic way the analysis is built up, which means that the structure of the theoretical description and the code is transferable between different applications. It is advisable to teach the subject in such a way that this fact is fully exploited. It is a fact that most FE calculations today do not contain a check of the accuracy/quality of the solution. In the teaching of the FE method nothing is more important than the basic knowledge and understanding of the properties and behaviour of the obtained FE solution. The paper deals with the methodology in presenting the method, by use of conceptual diagrams. It also discusses the interpretation of the results from a classical FE analysis and the extraction of high quality information. Finally, error estimation and postprocessing are discussed. The detailed description of the boundary conditions is lost in the FE solution. In the postprocessing stage they should be taken into account once more.
Easy adaptation of a commercial FEM code for self‐similarity
Authors: Ståhle P.
Published: August 2005

Self‐similar situations are idealized states often referred to in continuum mechanics. Such a situation is generally expected when the formulated problem only involves one significant length parameter. The state at a stationary or at a steadily moving concentrated load may be self‐similar. In heat conductivity, the progressive phase transformation near a point‐shaped heat source results in a self‐similar situation. The problem may be non‐linear and history‐dependent. Thus, an incremental theory is needed, generally implying that the load has to be applied in small increments. However, at self‐similarity the solutions for different loads are similar. The final solution therefore includes its own history, which may be exploited.

This short communication demonstrates how an available FEM code (including many commercial codes) may be conveniently used for investigations of self‐similar situations in solid mechanics. Quasistatic elastic‐plastic problems are considered. The theory covers a general material behaviour including large strains and large deformations. The FEM code must allow for a user‐defined material. The technique is demonstrated on a problem for an edge crack growing while the scale of yielding is large. The result is compared with calculations using a node relaxation technique.
An automatic procedure for mixed‐mode crack growth analysis
Authors: Mi Y. , Aliabadi M. H.
Published: August 2005

In the paper the application of the dual boundary element method to three‐dimensional crack growth problems is presented. A procedure for remeshing of the free surfaces is presented to allow the simulation of surface breaking crack growth.
On boundary conditions for unbounded flows
Authors: Heinrich J. C. , Vionnet C. A.
Published: August 2005

We examine a method to impose boundary conditions on arbitrary boundaries, introduced to make domains of infinite extent finite for the purpose of numerical calculations, when a finite element discretization based on linear, bilinear or trilinear elements is used, in one, two or three dimensions, respectively. In particular, we look at the so‐called ‘free’ boundary condition, which consists in retaining the boundary integrals generated by the weighted‐residuals formulation along the open boundaries and adding them to the stiffness matrix. We show that this procedure is exactly equivalent to imposing on the boundary nodes a Sommerfeld radiation condition in one dimension, and a slightly modified form of the Sommerfeld boundary condition in two and three dimensions. We also show that the procedure is not applicable to the purely elliptic case.
Structural improvement of planar triangulations: Some constraints and practical issues
Authors: Field David A. , Frey William H.
Published: August 2005

Recent advances in planar mesh generation of arbitrary domains incorporate methods for placing points as well as connecting them into a triangulation. Postprocessing techniques such as Laplacian smoothing and mesh relaxation enhance the shape of triangles in these meshes but do not address the construction of meshes near boundaries or provide a criterion to determine the number of interior points of the initial triangulation. The paper addresses these issues by investigating the construction of degree‐6 triangulations, the primary goal of the mesh relaxation method.
Fluid flows around turbomachinery using an explicit pseudo‐temporal Euler FEM
Authors: Nigro N. , Storti M. , Idelsohn S.
Published: August 2005

This work is devoted to the simulation by finite elements of nearly incompressible inviscid flows in real 3D geometries, by means of an Euler code based on the SUPG (streamline upwind Petrov–Galerkin) method, explicit forward Euler pseudo‐temporal time integration and periodic and absorbing boundary conditions, among other features. The main goal is the application to flow around turbomachinery, with special emphasis on the performance analysis of a given machine, that involves several numerical computations at different operation points. Finally, these results are summarized in the form of characteristic curves.
A superposition method for the solution of crack problems
Authors: Smith R. N. L. , Della‐Ventura D.
Published: August 2005

We discuss a two‐step superposition method for calculating linear elastic stress intensity factors. The procedure requires the solution to the full cracked problem and the solution to a problem on the same mesh assuming the singularity due to a crack tip in an infinite region. We show that this is equivalent to the well known subtraction of singularity method if the two solutions are characterized by crack tip stress. The advantages of our procedure are that no modifications need to be made to a standard computer program and that once one singular solution is available on a given cracked mesh, solutions with different boundary conditions on the same mesh may be obtained in one step without including any singular crack effects. The mesh required to represent the singular crack tip field may also be studied independently of the complete problem. The additional computational cost of a two‐step procedure is minimal since the solution matrix from step one may be reused with a new right‐hand side. Numerical experiments using the boundary element method demonstrate the high accuracy and simplicity of the superposition approach.
A semi‐analytic method for dynamic response analysis based on Gurtin's variational principle
Authors: Peng J. S. , Lewis R. W. , Zhang J. Y.
Published: August 2005

In the paper a semi‐analytic approach for solving dynamic response problems is developed which is based on Gurtin's convolution‐type variational principle. A finite element discretization in the space domain and a series representation in the time domain are considered. This approach overcomes the shortcomings of existing methods yet utilizes their advantages for solving dynamic response problems. The example of a beam shows that this new approach is a very effective method in obtaining solutions for dynamic response problems. The paper also concentrates on utilizing time domain series for various boundary conditions, so that solutions calculated by this approach have a very high accuracy and efficiency.
Pseudoconsistent load vector and mass matrix for the discrete Kirchhoff triangle and the discrete shear triangle elements
Authors: Sydenstricker R. M. , Coutinho A. L. G. A. , Landau L. , Marques O. A.
Published: August 2005

Many finite elements based on Reissner‐Mindlin plate bending theory with discrete constraints have been developed in the past few years. This approach avoids the C1 continuity required by the classical Kirchhoff plate theory. However, in those elements the shape functions for deflections (or their derivatives) are not integrated. Particularly in DKT (discrete Kirchhoff triangle) and in DST (discrete shear triangle) elements, the lateral deflections are defined only on the boundaries. In the paper we briefly discuss the definition of the transverse displacement for these elements, and present a simple approach to define a pseudoconsistent load vector and mass matrix.
A more accurate FD solution for the 3D non‐linear heat equation
Authors: Zerroukat M. , Chatwin C. R.
Published: August 2005

The paper presents a new finite difference solution for the 3D non‐linear heat equation. This solution is based on the approach of making finite difference substitutions into the solution of the partial differential equation, rather than into the partial differential equation itself, which is the classical approach. Numerical results show that the new FD equation is approximately ten times more accurate than the classical solutions.
Combining arc‐length control and line searches in path following
Authors: Shi J. , Crisfield M. A.
Published: August 2005

When solving non‐linear algebraic equations resulting from a typical finite element discretization it is quite common that the popular Newton‐Raphson iteration fails to converge or requires an excessive number of iterations. To solve this problem, line searches have been proposed in conjunction with load control and quadratic arc‐length control, which has proved to be highly successful. In the paper we first review a number of the most popular arc‐length controls. Then we highlight the severe drawbacks associated with the coupling of the cylindrical arc‐length control and line searches. Next, various other forms of arc‐length controls are scrutinized in the light of this coupling. It is shown that for some of the arc‐length controls such a combination is extremely simple and straightforward, yet at the same time efficient and effective. For the rest the same complications incurred for the cylindrical arc‐length method remain.
Simple transformations by proper contracted forms: Can we change the usual practice?
Authors: Pedersen Pauli
Published: August 2005

In elasticity theory involving anisotropic materials, the rotational transformation of stress, strain and constitutive relations is of major importance. Also, when these problems are represented in matrix form there are several different contracted notations used to express the stress and strain tensors as column matrices. In general, the contracted notations used lead to unnecessary complications and may lead to errors. In the paper, contracted forms which yield orthonormal rotational transformations are advocated. These transformations are illustrated for stress, strain, modulus and compliance and are also applicable for strength transformation. The gains to be made are procedural and mathematically simple, leading to easier understanding.
Symmetrization of equations of motion for coupled systems subject to fluid–structural interactions
Authors: Liu Man , Gorman D. G.
Published: August 2005

System equations of motion for a fluid–structural coupled system are formulated and their symmetrization is presented. By using the state‐variable augmentation and degree of freedom reduction technique applicable to a damped mechanical system, a new approach is proposed to transform the asymmetrical equations of motion for a coupled system into some symmetrical ones. The significance of the transformation used is discussed. The relationship is established between the left and the right eigenvectors, based on which the modal superposition method can be used in predicting dynamic responses for a general asymmetrical fluid‐structural coupled system.
hp‐Version finite elements for geometrically non‐linear problems
Authors: Krause Roland , Mücke Roland , Rank Ernst
Published: August 2005

A p‐version of the finite element method and an hp‐extension is applied to a geometrically non‐linear model problem. Starting from a standard formulation in finite elasticity, some implementation details are outlined. The robustness and efficiency of this method, as already well known for linear problems, is demonstrated. In two numerical examples high accuracy and exponential rate of convergence in energy are shown. The method presented can be used effectively in problems where standard low‐order plane strain elements fail to give accurate results.
Notes on mesh optimal criteria in adaptive finite element computations
Authors: Li Long‐Yuan , Bettess Peter
Published: August 2005

In the paper the authors investigate the conditions of optimal mesh, and prove that the element errors in the optimal mesh should be identical for all existing elements. Also, it is shown that the correct mesh refinement formulations should be derived at an element level rather than the global level. Thus the element permissible errors need to be determined. The method to determine these permissible element errors is described.
Natural convection in a shallow laterally heated air‐filled cavity
Authors: Wright N. G. , Gaskell P. H. , Sleigh P. A.
Published: August 2005

The flow in a shallow, laterally heated air‐filled cavity is investigated numerically using a primitive variable formulation of the governing equations of motion. Solutions are obtained for the entire flow field using a coupled solver combined with an FAS non‐linear multigrid convergence accelerator. While care is taken to use a high‐order, bounded discretization scheme for convective transport, the overall stability and efficiency of the approach is enhanced through the use of defect correction. This combination of features enables solutions to be found on extremely fine grids. Results for the flow in the end region of such cavities are compared qualitatively with the predictions of asymptotic theory for large aspect ratio, A (length:height), up to values of A higher than previously reported (A= 100); the particular case of A = 20 is considered for Rayleigh numbers in the range 103 to 108. Finally it is demonstrated how such solutions can be further enhanced by using locally refined grids in the end regions.
Smooth modelling of the normal vector by using C0‐continuous lagrange elements in BEM
Authors: Sladek V. , Sladek J.
Published: August 2005

The paper reveals the conditions under which the approximations of the normal vector and global coordinates of interior points of two segments on a smooth contour can fail using the C1‐continuous Overhauser elements. A new continuous modelling of the normal vector is developed using the standard Lagrange elements. The derivation is consistent with the assumptions employed in the boundary element method formulations of potential problems. Test numerical examples are considered in order to analyse the accuracy of the approximations based on the use of standard C0‐continuous elements, Overhauser C1‐continuous elements and the proposed ‘smooth’ C0 elements.
A patch test for mesh alignment effects in localized failure
Authors: Pastor M. , Quecedo M.
Published: August 2005

Computation of failure mechanisms is of paramount importance for engineers assessing safety of structures. However, computation of failure loads and mechanisms presents numerical difficulties leading to wrong answers, especially in the case where failure consists in localization of plastic deformation or damage in localized zones. Here, the results depend on factors like mesh alignment and element distortion. The paper addresses the problem of designing a suitable patch test to assess element performance under localized failure. It will be shown how predictions of this test provide a reliable answer to the question of whether a particular element will or will not be suitable for such failure computations.
Line follower for finite element postprocessing and current imaging
Authors: Sepulveda N. G. , Wikswo J. P.
Published: August 2005

The display of isopotential contours is a standard technique in the interpretation of results generated by the finite element analysis of voltage distribution problems. The complementary display of the current flow or flux lines is in many ways more useful intuitively, but has not been used widely in finite element analyses. We describe a simple method for generating flux line distributions, and discuss the method as applied to the reconstruction of current distributions from magnetic field maps.
Numerical modeling and investigation of liquid phase epitaxy of Hg1–xCdxTe infrared detectors
Authors: Lin K. , Dold P. , Figgemeier H. , Benz K. W.
Published: August 2005

Numerical investigations have been performed for modeling the global temperature field of an industrial liquid phase epitaxy (LPE) facility and to estimate the temperature fluctuations in a Te‐rich solution during the LPE growth. The numerical results agreed well with experimental data and therefore provide reliable reference points for experimenters for further improvements of the growth conditions. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The influence of supersaturation on crystal morphology – experimental and theoretical study
Authors: Lu Jun Jun , Ulrich Joachim
Published: August 2005

The surface docking approach of molecular modeling for prediction of crystal morphology in the presence of additives is further developed in this work. It is modified in order to take into account the influence of supersaturation on the crystal habit. With the introduction of the BCF theory and the 2‐D growth mechanism in the above mentioned approach predictions have been carried out for paracetamol and caprolactam crystals, respectively. The verifications by crystals grown from solutions as simulated by the computer model give good agreements. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth and optical characterization of cerium and lead‐doped Bi12TiO20 sillenite single crystals
Authors: Carvalho J. F. , Hernandes A. C.
Published: August 2005

Bi12TiO20 (BTO) single crystals doped with PbO and CeO2 were grown by the Top Seeded Solution Growth (TSSG) technique from the liquid phase with nominal compositions of 10Bi2O3 : (1–x)TiO2 : x PbO and 10Bi2O3 : (1–x)TiO2 : xCeO2 with x = 0.25 and 0.10. No growth‐related difficulties were encountered other than those typical of sillenite crystals. Samples with good optical quality were obtained and were characterized by optical absorption, dark current, spectral photocurrent dependence, optical activity and electro‐optic coefficient measurements. A comparison is made of the results of the optical measurements of doped and undoped BTO crystals. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the void distribution and size in shaped sapphire crystals
Authors: Bunoiu O. M. , Nicoara I. , Santailler J. L. , Theodore F. , Duffar T.
Published: August 2005

Ribbon and rod sapphire pulling has been performed in three different crystal growth equipments in order to study the effect of the installation, of the atmosphere, of the die shape, of the feed material and of the pulling rate on the distribution, number and diameter of the characteristic voids (micro‐bubbles) in the crystals. The location of the bubbles in the crystals depends on the die geometry; however, in most cases they are essentially located close to the crystal periphery and then can be efficiently removed by lapping. After statistical analysis of the results, it is demonstrated that the number of gas moles incorporated in the crystals, inside the voids, is totally independent of any growth parameter. It is also shown that the bubble diameter depends only on the pulling rate. Consequently, for a given pulling rate, the number of bubbles auto‐adjusts in order to satisfy the constant molar gas incorporation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of cetyl pyridinium chloride additive on crystallization of gypsum in phosphoric and sulfuric acids medium
Authors: El‐Shall H. , Rashad M. M. , Abdel‐Aal E. A.
Published: August 2005

A basic study was carried out to understand effect of Cetyl Pyridinium Cloride (CPC) on calcium sulfate dihydrate (gypsum) crystallization. Induction time was measured under different supersaturation ratios ranging from 1.222 to 1.979. This is the time elapsed between the achievement of supersaturation and the appearance of a solid phase. The results show that, the induction time decreases exponentially with increasing the supersaturation ratio. In addition, the surface energy increases with CPC compared to the baseline (without CPC). Number of molecules required for formation of stable nucleus are calculated to be from 3 to 41 molecules depending on supersaturation ratios and presence of CPC. Interestingly, with addition of the CPC, the mean diameter of the crystals and the median increase. The growth rate was found dependent on the supersaturation with and without CPC. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermodynamic feasibility study for chemical vapour deposition of some ternary crystals using iodine and hydrogen iodide
Authors: Kunjachan S. , Korah I. , Ittyachen M. A.
Published: August 2005

Thermodynamic feasibility of transition metal dichalcogenide (TMDC) single crystals of Cu Al S2, Cu Al Se2, Cu Al Te2, Cu Ga S2, Cu Ga Se2, Cu Ga Te2, Cu In S2, Cu In Se2, Cu In Te2, Ag Ga S2, Ag Ga Se2, Ag Ga Te2, Ag In Se2, Ag In Te2, using iodine and hydrogen iodide as transporting agents has been reported in this paper. Results give range of temperature for the iodide transport and prevention of starting material formation (elemental transport) in the growth zone. From the range of temperature for the growth of crystals, selected source zone and growth zone temperatures with a differential of 100 °C are also listed. Referring the data listed in the tables can grow good quality crystals. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
HigHighly strained InGaAs/GaAs quantum wells emitting beyond 1.2 µm
Authors: Sharma T. K. , Zorn M. , Zeimer U. , Kissel H. , Bugge F. , Weyers M.
Published: August 2005

Highly strained InxGa1–xAs quantum wells (QWs) with GaAs barriers emitting around 1.2 µm are grown on GaAs substrates by metal organic vapour phase epitaxy (MOVPE) at low growth temperatures using conventional precursors. The effects of growth temperature, V/III ratio and growth rate on QW composition and luminescence properties are studied. The variation of indium incorporation with V/III ratio at a growth temperature of 510 °C is found to be opposite to the results reported for 700 °C. By an appropriate choice of the growth parameters, we could extend the room temperature photoluminescence (PL) wavelength of InGaAs/GaAs QWs up to about 1.24 µm which corresponds to an average indium content of 41% in the QW. The results of the growth study were applied to broad area laser diodes emitting at 1193 nm with low threshold current densities. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micromorphology of pure and PbI2‐doped CdI2 dendritic single crystals
Authors: Kumar Binay , Sinha Nidhi
Published: August 2005

Undoped and PbI2‐doped dendritic single crystals were grown by vapour growth technique. The basal surfaces of the as grown crystals were examined by optical and electron microscopy to observe wide variety of growth and defect features. Apart from typical features of dendritic growth, features of overgrowth, slip bands, growth steps and their bunching, etc. were observed. The basal surfaces of the crystals were then etched by controlled condensation of water vapour, after optimizing the etching condition, and the microscopic studies were repeated. Etch pits of hexagonal and triangular shape, both symmetric and asymmetric, and of different density, were observed in the case of undoped and doped crystals, respectively. In some cases, crystallographic hillocks were also observed. The crystals were also examined by X‐ray diffraction for their polytypism and related behaviour. The results are analyzed to elicit information on the correlation of structure, defects and surface features of the crystals. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical anisotropy in GaSe
Authors: Seyhan A. , Karabulut O. , Akįnoğlu B. G. , Aslan B. , Turan R.
Published: August 2005

Optical anisotropy of the layer semiconductor GaSe has been studied by photoluminescence (PL) and Fourier Transform Infrared Spectroscopy (FTIR). The PL spectra are dominated by two closely positioned emission bands resulting from the free exciton and the bound exciton connected direct band edge of GaSe. Photoluminescence and transmission spectra of GaSe crystals have been measured for two cases in which the propagation vector k is perpendicular (k ⟂ c) and parallel to the c‐axis (k // c). Peak position of the PL emission band and the onset of the transmission have been found to be significantly different for these two cases. This observed anisotropy is related to anisotropic band structure and the selection rules for the optical absorption in layered GaSe. FTIR transmission spectrum is in good agreement with PL results. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Flow cytogenetic studies in chromosomes and whole cells for the detection of clastogenic effects
Authors: Otto Friedrich J. , Oldiges Hubert
Published: August 2005

Flow cytometric measurements of the chromosomal DNA content have been used to develop a screening method for the detection of chemically‐ or physically‐induced cytogenetic damage. The reproducibility of this flow cytogenetic assay was shown in a series of subcultures of a Chinese hamster cell clone. The accuracy and sensitivity was tested in cultures treated with chemical mutagens and x‐rays. The clastogenic effectiveness was quantified and the dose‐effect relationship was established by the increase of the coefficient of variation of the peak of the largest chromosome type in the flow histograms. Since structural chromosome aberrations cause an unequal division of the DNA at mitosis, it is expected that clastogenic effects can be detected also in whole cells of growing populations as an increased dispersion of the cellular DNA content. In order to test this feature, high resolution flow cytometric measurements were performed in x‐irradiated hamster cells in vitro and mouse bone marrow cells in vivo.
Intracytoplasmic immunofluorescence in multiple myeloma
Authors: Zeile G.
Published: August 2005

A new intracytoplasmic immunofluorescence staining procedure has been investigated to detect and quantify myeloma cells by means of flow cytometry. Freshly harvested bone marrow aspirations from 12 patients with multiple myeloma were treated with collagenase and Triton X‐100, and incubated with different specimens of fluoroisothiocyanate‐marked antihuman immunoglobulins. DNA‐staining was then done with propidium iodide. Biparametric evaluation in a Cytofluorograf 6300 A/FC 200 showed a characteristic cluster distribution of normal and pathological immunoglobulin‐producing cells. This intracytoplasmic fluorochromic staining procedure may be significant for the specific identification of nonsecretive immunocytomas, which cannot be detected by serodiagnostic methods.