bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of Tricyclic Spiro Compounds on the Basis of Alloocimene.
Authors: Balbolov E. Kh. , Skumov M. Ya. , Mitkova M. S.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Bioactive Cyclic Peptides from the Psychrotolerant Fungus Penicillium algidum
Authors: Dalsgaard Petur W. , Larsen Thomas O. , Christophersen Carsten
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Stereoselective Synthesis of (7aS)‐1‐Methylenehexahydro‐1H‐pyrrolizine and (‐)‐Heliotridane from N‐Diphenylmethyl‐(S)‐proline Ethyl Ester.
Authors: Lysenko I. L. , Kulinkovich O. G.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Synthesis and Photophysics of a Porphyrin—Fullerene Dyad Assembled Through Watson—Crick Hydrogen Bonding.
Authors: Sessler Jonathan L. , Jayawickramarajah Janarthanan , Gouloumis Andreas , Torres Tomas , Guldi Dirk M. , Maldonado Stephen , Stevenson Keith J.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
First Century of Colloid Magneto‐Optics
Authors: Scholten P. C.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Al—Mn—Ti
Authors: Raghavan V.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Control of Magnetic Domain Structure and Electrical Spin Injection in Patterned Magnetic Nanostructures
Authors: Taniyama T. , Fujiwara N. , Yamazaki Y. , Nakatani I.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Peptide and Amide Bond Containing Dendrimers
Authors: Crespo Laia , Sanclimens Gloria , Pons Miquel , Giralt Ernest , Royo Miriam , Albericio Fernando
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
4,7‐Dihydro‐, 4,5,6,7‐Tetrahydro‐, and Octahydroisoindole (and Methanoisoindoles)
Authors: Marinicheva G. E. , Gubina T. I.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Chemistry of Diazosulfonates
Authors: Gafarova Yu. T. , Zlotskii S. S. , Marinozzi M. , Pellicciari R.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Recent Advances in Phosphorus—Carbon Bond Formation: Synthesis of H‐Phosphinic Acid Derivatives from Hypophosphorous Compounds
Authors: Montchamp Jean‐Luc
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Solid‐Supported Reagents and Catalysts for the Preparation of Large Ring Compounds
Authors: Gonthier Elisabeth , Breinbauer Rolf
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Myxobacterial Epothilones and Tubulysins as Promising Anticancer Agents
Authors: Doemling Alexander , Richter Wolfgang
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Chemistry of Pyramidalized Alkenes
Authors: Vazquez Santiago , Camps Pelayo
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
A Journey Across Recent Advances in Catalytic and Stereoselective Alkylation of Indoles
Authors: Bandini Marco , Melloni Alfonso , Tommasi Simona , Umani‐Ronchi Achille
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Towards the Synthesis of Ladder Oligo(p‐aniline)s
Authors: Wakin Salem , Leclerc Mario
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Synthesis of Unnatural Amino Acids
Authors: Ager David J. , Laneman Scott A.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Peptide Ligation
Authors: Klok Harm‐Anton
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Chemical Approaches for the Preparation of Biologically‐Inspired Supramolecular Architectures and Advanced Polymeric Materials
Authors: Klok Harm‐Anton
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Synthesis and Application of Proline and Pipecolic Acid Derivatives: Tools for Stabilization of Peptide Secondary Structures
Authors: Maison Wolfgang
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
α‐Helical Peptide Nucleic Acids (α‐PNAs)
Authors: Garner Philip , Dey Subhakar , Huang Yumei
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Enantiomeric Nucleic Acids—Spiegelmers
Authors: Klussmann Sven
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Palladium‐Catalyzed Cross‐Coupling in Aqueous Media: Recent Progress and Current Applications
Authors: Shaughnessy Kevin H. , DeVasher Rebecca B.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Carbon Dioxide, a Solvent and Synthon for Green Chemistry
Authors: Ballivet‐Tkatchenko D. , Camy S. , Condoret J. S.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Other Tetrahetero‐Substituted Methanes
Authors: Diaper C. M.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Thiocarbonic Acids and Derivatives
Authors: Sato S. , Furukawa N.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Cyanogen Halides, Cyanates and Their Sulfur, Selenium, and Tellurium Analogues, Sulfinyl and Sulfonyl Cyanides, Cyanamides, and Phosphaalkynes
Authors: Wu Y.‐Q.
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Recent Advances in Charge‐Accelerated aza‐Claisen Rearrangements
Authors: Nubbemeyer Udo
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Synthesis and Catalytic Applications of Dendrimer‐Templated Bimetallic Nanoparticles
Authors: Chung Young‐Min , Rhee Hyun‐Ku
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Adding New Tools to the Arsenal of Expressed Protein Ligation
Authors: Budisa Nediljko
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
Crown Ether Bearing Phosphazenes
Authors: Levalois‐Gruetzmacher Joelle
Published: August 2005

For Abstract see ChemInform Abstract in Full Text.
A condition for simplifying the forcing term in boundary element solutions of the diffusion equation
Authors: Sharp S.
Published: August 2005

This paper shows that if the forcing function in the diffusion equation satisfies Laplace's equation, with time considered as a parameter, then the associated volume integral in boundary element solutions can be transformed to a surface integral.
Dynamic plane stress computations for large plastic deformations
Authors: Johnson Gordon R.
Published: August 2005

There are many two‐dimensional computer codes available to compute wave propagation and plastic flow in solids. These codes are based on finite element or finite difference algorithms and are generally capable of analysing both axisymmetric and plane strain geometries. For the direct integration codes such as EPIC‐2,1,2 it is possible to perform plane stress computations by making only minor modifications to the plane strain algorithm. This note describes these modifications and presents an example.
Mass balance in shallow water simulation
Authors: Lynch Daniel R.
Published: August 2005

Mass balance relations are obtained for primitive and wave equation spectral models. The results prescribe a departure from conventional methods for boundary condition enforcement. Numerical results substantiate the theory.
A note on tangent stiffness for fully nonlinear contact problems
Authors: Wriggers P. , Simo J. C.
Published: August 2005

In the numerical solution of geometrically nonlinear contact problems by the finite element method, it is often assumed that the modification to the tangent stiffness takes the form of the single rank‐one‐update characteristic of the linear theory. It is shown that due to the kinematic nonlinearity such a simple structure no longer holds. Within the context of the discrete problem arising from a finite element formulation, explicit expressions for the residual and the tangent stiffness matrix are obtained for both penalty and Lagrangian parameter procedures.
A note on the numerical solution of the von karman small disturbance equation
Authors: Pilant M. S.
Published: August 2005

In this short note, we will derive the von Karman small disturbance equation from the full potential equation of gas dynamics through perturbation methods. Guderley1 and Germain2 have previously computed exact solutions, in similarity form, for the small disturbance equation. We show that these solutions can be computed efficiently by solving a single nonlinear second‐order differential equation. The shock and entropy conditions are automatically satisfied, and a one‐parameter family of solutions is recovered.
Penalty method constraints for mesh grading in two‐dimensional elasticity
Authors: Steven Grant P.
Published: August 2005

The application of the principle of virtual work in continuum mechanics is used to determine the equilibrium of a body in a compatible state of deformation. When there are constraints on the deformation then the minimization associated with the principle of virtual work has constraints imposed upon it. Constrained minimization is a much harder problem than unconstrained minimization. The penalty method effects a change from constrained to unconstrained minimization and has consequently become very useful to finite element modellers. This work examines the use of the penalty method to achieve finite element grid patterns where the same element type can be used and where significant changes in element size without associated element distortions are present. Several practical examples are presented and some theoretical aspects of the penalty method are discussed.
Finite element simulation of flows of fluids with integral constitutive equations
Authors: Malkus David S.
Published: August 2005

Finite element procedures to compute solutions to steady flow problems with ‘memory fluids’ have been developed. While many aspects of these methods are still under development, they have reached the stage at which they can be implemented in general‐purpose nonlinear fluid mechanics codes which use the penalty form of the ‘v‐p’ formulation. The key to the success of such methods is the use of a very special element which allows virtually exact determination of the streamlines, and large‐strain elastic deformation tensors of the motion implied by the velocity field, which are required by the constitutive theories in question. This paper describes the constitutive equations and the numerical treatment of them which can be used to compute steady, two‐dimensional flow solutions. Some new results concerning hole pressures in plane flows over transverse slots are presented.
The expressions of elasto‐plastic matrices based on the deformation theory of plasticity
Authors: He Ji‐Fan
Published: August 2005

When some elasto‐plastic problems are to be solved by finite element methods, e.g. when integral J in the elasto‐plastic fracture mechanics has to be calculated, the incremental method based on the deformation theory of plasticity is the most reasonable and effective. In this paper the expressions of elasto‐plastic matrices are derived from the Hencky equations. It is interesting that the expressions of matrices obtained in this paper are very similar in form to those derived from the Prandtl–Reuss equations in the flow theory of plasticity.
Defectiveness of weighting method in multicriterion optimization of structures
Authors: Koski Juhani
Published: August 2005

It is well known that the weighting method may fail in generating the Pareto optimal set of a multicriterion problem in non‐convex cases. In this paper, two simple truss examples, one static and one dynamic problem, are presented to show that this situation easily occurs in optimum structural design also.
Shock‐free transonic rotor design
Authors: Prince Timothy C. , Beauchamp Philip P.
Published: August 2005

An evaluation of Sobieczky's fictitious gas technique is presented as applied to the design of a transonic rotor. A representative transonic compressor rotor was redesigned using Sobieczky's technique in an ‘onion peel’ fashion. The design was followed by a full three‐dimensional inviscid analysis of the new rotor, to determine whether spanwise redistribution of the streamlines in the new flow would invalidate the technique by causing shocks to reappear. This analysis verified the suppression of shocks present in the initial flow field. This demonstrates that the technique can be used in practice to improve the design of transonic rotors and stators with subsonic flow at the inlet and exit.
Shock‐free redesign using finite elements
Authors: Carey G. F. , Pan T. T.
Published: August 2005

A finite element formulation and algorithm for calculation of shock‐free compressible flows and design of shockless airfoils is developed. The formulation is conceptually similar to current finite difference methods in that it combines the use of a fictitious gas for a regularized compressible potential flow calculation, together with the method of characteristics in the supersonic pocket. The redesigned shock‐free airfoil surface is determined from a subsidiary streamline calculation. In the present analysis, a variational finite element method is used and optimal control techniques are employed to compute the solution to the discrete problem. Numerical results and comparison studies with finite difference results for a representative case are given.
Element‐by‐element linear and nonlinear solution schemes
Authors: Carey Graham F. , Jiang Bo‐Nan
Published: August 2005

The preconditionded conjugate gradient method for solving a linear algebraic system of equations is recast to a form that permits sequential element‐by‐element calculations suitable for computations with finite element methods. This strategy has been implemented for solving the linear systems arising in a finite element approximation for the standard test example of Laplace's equation. The element‐by‐element strategy has also been applied to the sequence of linear systems obtained using a successive approximation scheme for a representative class of nonlinear problems. Little storage is needed for these schemes, and test computations have been made on microprocessor, minicomputer, main‐frame computers and special processors. The approach also appears appealing for calculations on parallel processors since individual element computations can be done in parallel.
A note on the comparison between bie and fd techniques for solving elliptic BVPs with boundary singularities
Authors: Ingham D. B. , Kelmanson M. A.
Published: August 2005

A quantative comparison between the boundary integral equation (BIE) method and the finite difference (FD) method is presented in which each technique is applied to an elliptic boundary‐value problem (BVP) containing a boundary singularity. Two types of singularity have previously been analysed theoretically, namely those due to a discontinuous boundary potential, which we shall refer to as S1, and those due to a sudden change from the specification of boundary potential flux, an S2 singularity. In this paper the analysis is presented for a third type of boundary singularity, namely an S3 singularity: that arising from a discontinuous boundary flux. Such a condition is frequently encountered in the field of heat transfer where, for example, a system or pipe has a change of lagging material.

In general, it is found that the BIE method is superior, with regards to the computational time required to achieve a certain degree of accuracy, over standard FD methods even when there is a boundary singularity. Further, the BIE method determines the solution near the singularity much more accurately than the FD method. The FD method does, however, have advantages for a very restrictive class of problems; for example, when the boundary conditions are of the Dirichlet type and the boundary geometry is rectangular. In this case an optimum relaxation parameter can easily be obtained. A soon as Neumann conditions are prescribed, the BIE is far more efficient than the FD, whatever the boundary geometry.

It is concluded that, for fast, accurate solutions of general Laplacian boundary‐value problems, the BIE is appreciably superior to the FD and this is even more pronounced when there is a boundary singularity.
Extension of the generalized benders' decomposition
Authors: Lazimy Rafael
Published: August 2005

Geoffrion6generalized the Benders' decomposition approach1to a general class of ‘complicated’ nonlinear optimization programs. The theoretical significance of the work in Reference 6 is significant, but its computational usefulness is rather limited, due to some serious computational difficulties inherent in the master problem. In this paper, we report on a simple technique to overcome and eliminate these difficulties.
Explicit basis functions of quadratic and improved quadratic finite element spaces for the Stokes problem
Authors: Caussignac Ph.
Published: August 2005

The basis functions of the quadratic and improved quadratic finite element spaces for the velocity of the two‐dimensional Stokes problem are explicitly given. A numerical example is produced to show the advantage of building the ridigity matrix directly from these bases.
Application of finite elements in heat exchangers
Authors: Ravikumaur S. G. , Seetharamu K. N. , Aswathanarayana P. A.
Published: August 2005

The application of finite elements in heat exchangers is illustrated, with the newly proposed element for two types of heat exchangers. It is found that the present model predicts the temperature distribution accurately.
A marching method for solving Poisson's equations in the ETA10
Authors: Follin Steven E. , Kascic Michael J.
Published: August 2005

A marching method for solving Poisson's equation in three dimensions is described and its suitability for a supercomputer is discussed. A more stable variant and its performance on a Cyber 205 supercomuter is then presented. Finally, a parallel vector processor under development, the ETA10, is described, implementation of the algorithm on this machine is discussed and estimated execution times are presented.
Reordering computations for parallel execution
Authors: Adams Loyce
Published: August 2005

In this paper, we show how to reorder the computations in the SOR algorithm to maintain the same asymptotic rate of convergence as the rowwise ordering and to obtain parallelism at different levels. A parallel program is written to illustrate these ideas and actual machines for implementation of this program are discussed.
Hourglassing control through boundary smoothing
Authors: Schulz J. C. , Heimdahl O. E. R.
Published: August 2005

A boundary smoothing technique for control of hourglassing deformation in quadrilateral and hexahedral finite elements is described. In this technique, supplemental forces are applied to lines of nodes along the boundary to eliminate length and angle changes associated with hourglassing. The main advantage of this technique is that it can be applied locally to a small number of nodes along the boundary rather than globally to all elements as is the case with other control techniques, thereby reducing the additional computational expense required for hourglassing control. This reduction can be especially significant in three‐dimensional problems. An example problem consisting of a square plate subjected to a step pressure is used to demonstrate the efficacy of the technique.
Pressure related instabilities of reduced Navier–Stokes equations for internal flows
Authors: Armfield S. W. , Fletcher C. A. J.
Published: August 2005

Order‐of‐magnitude deletion of the stream‐wise diffusion terms leads to a reduced form of the Navier–Stokes equations. Solving the reduced equations for internal flows with single‐sweep marching algorithms requires a severe minimum stream‐wise step‐size to avoid unstable solutions. This behaviour is shown to be predominantly due to a single term in the cross‐stream momentum equation, uvx, which introduces a strong elliptic character into the equations. An order‐of‐magnitude deletion of this term reduces the minimum stream‐wise step‐size sufficiently for accurate solutions to be obtained. Further reduction of the transverse momentum equation on an order‐of‐magnitude basis removes all cross‐stream velocity derivatives and completely eliminates the minimum stream‐wise step‐size condition for both swirling and non‐swirling flows.
A finite element model for tidal and residual circulation
Authors: Walters Roy A.
Published: August 2005

Harmonic decomposition is applied to the shallow water equations, thereby creating a system of equations for the amplitude of the various tidal constituents and for the residual motions. The resulting equations are elliptic in nature, are well posed and in practice are shown to be numerically well‐behaved. There are a number of strategies for choosing elements: the two extremes are to use a few high‐order elements with continous derivatives, or to use a large number of simpler linear elements. In this paper simple linear elements are used and prove effective.
Numerical calculation of the elastic field in a half‐space
Authors: Kalker J. J.
Published: August 2005

In this paper the title problem is solved by discretizing the region of application of the load as a finite union of rectangles with non‐overlapping interiors. The surface traction is discretized by taking it constant over each rectangle. Then the displacement and the displacement gradients at an arbitrary point of the half‐space, due to the discretized load, can be found exactly as a finite concatenation of elementary operations and of arctangents and logarithms. Although this representation is numerically appropriate near the rectangle which generates the (partial) elastic field, it is less suitable far away from it. An asymptotic expression for the elastic field in this region is provided. An algorithm for the calculation of the elastic field is given. The method is applied to two examples, viz. the sub‐surface stresses of the Hertz frictionless problem and the steady state frictional rolling problem, both with a ciruclar contact area.
A multi‐level block iterative method for mixed finite strip/finite element analysis
Authors: Smith T. R. Graves , Gierlinski J. T.
Published: August 2005

A block iterative procedure is described for use with a mixed finite strip/finite element method for solving prismatic structures containing non‐prisomatic elements. A multi‐level method incorporating the iteration is also discussed. The convergencies of the iterations and multi‐level solutions are considered with reference to a representative example.
Oscillatory integrals by Hermite interpolatory rules
Authors: Alaylioglu Ayse
Published: August 2005

This paper is concerned with the numerical construction of Hermite interpolatory product integration rules at arbitrarily prescribed nodes. The heart of the computational scheme is the efficient construction of Hermite functions of any order for any set of points. For the purpose of illustration, quadrature formulae based on the use of Basu. Clenshaw, Filippi, Filon and Polyá nodes are generated for oscillatory integrals. Of the nodes considered. Basu nodes yield the most accurate results in the interesting case of rapid oscillations, while Filippi nodes give rise to efficient common‐point quadrature rules when the integrand has slight oscillations. The results also demonstrate that Hermite rules compare well with the Lagrange quadrature for the same number of function evaluations.
Enhancing interactivity and automation through finite element neighbours
Authors: Hoole S. Ratnajeevan H.
Published: August 2005

In finite element analysis, each element is defined by a set of node numbers and stored. In this paper, it is shown that by storing the three neighbouring triangles of each triangular element, In addition to the three vertices, the interactivity and automation of the design station may be greatly enhanced. This enhancement results from the use of the data on neighbours in:

Identifying triangles pointed to on a graphics screen, through a digitizer. This is used for extracting potentials and field intensities at points, for refining meshes by adding points, and for imposing Neumann boundary conditions on the boundary edges and performing integrations, such as of force, over trianggles.

Following a path defined as a straight line for extracting graphs of potential and field intensity and performing contour integrations, like Maxwell stress, along such lines.

Checking the optimality of the mesh using the Delaunay criterion.

Determining discontinuities of field intensity at material interfaces.

Comparing the field intensities in adjacent triangles to measure error for adaptive refinement.

Alternatively, in an environment where memory for storing the neighbours is scarce, such as when using microcomputers, it is shown that the values may be computed when they are required, at the expense of speed.
On the use of a standard quadratic element in the analysis of consolidation following external loading
Authors: Thomas H. R. , Harb H. M.
Published: August 2005

The use of a standard quadratic element in the analysis of consolidation following external loading is explored. It is shown that such an element can produce satisfactory results for both instantaneous and ramp loading one‐dimensional problems. A double calculation procedure is proposed for the establishment of initial conditions under instantaneous loading. Simple refinement of the mesh, in the region of the free draining boundary, is shown to eliminate problems associated with ramp loading.
A method for infinite integrals of oscillating functions
Authors: Zhongjin Yang
Published: August 2005

Infinite integrals of oscillating functions are often used in scientific research. The general numerical methods can only provide infinite integrals of strictly monotonic functions, which cannot be used while the integrand is an oscillating function. In this paper, we utilize the zero point distribution of the integrand to give a useful method for infinite integrals of oscillating functions as well as its error estimate.
The performance of ITPACK on vector computers for solving large sparse linear systems arising in sample oil reseervoir simulation problems
Authors: Oppe Thomas C. , Kincaid David R.
Published: August 2005

Results are presented of the performance of two different versions of the ITPACK software package on large sparse linear systems arising in the solution of sample oil reservoir simulation problems using three different large vector computers (Cyber 205, Cray X‐MP48 and Amdahl VP1200). The main focus of this paper is on the necessary changes in the package that were made for efficiency when going from a memory‐to‐memory computer to a register‐to‐register computer. We feel that these are typical changes that must be considered when moving software of this type between vector computers. The execution times presented should not be considered to be representative of the overall performance of these computers.
A network method for nonlinear transient eddy current problems
Authors: Wong C. C.
Published: August 2005

Maxwell's curl equations for a conducting region are simulated by the impedance network. A set of simultaneous first‐order ordinary differential equations is developed for the network which can be used to solve linear or nonlinear, transient or static eddy current problems. The resulting set of equations is solved by the explicit fourth order Runge–Kutta method and in some cases by an implicit method based on the central difference scheme for time discretization. A number of examples, including eddy current losses in a saturated steel plate, are described to illustrate the applications of the method. It is found that the explicit method is more suitable for nonlinear problems, whereas the implicit method is more efficient for linear problems.
On the accuracy of a certain improved difference approximation of the heat equation
Authors: Bell Graham E.
Published: August 2005

The purpose of this paper is to identifiy the failings of a recently proposed ‘improved’ explicit finite difference replacement for the heat equation. It is shown that the time scale of the solutions obtained is not consistent with that of the equation of heat conduction.
Use of double nodes in the numerical simulation of multilayered flows of immiscible fluids
Authors: Mitsoulis Evan
Published: August 2005

The use of double nodes in side‐by‐side flows of immiscible fluids is introduced. The double nodes are required to satisfy the interface boundary conditions of continous velocities and stresses. The implementation of the technique in finite element simulations of two viscous immiscible fluids is illustrated through a typical example of co‐extrusion.
Patch test verification of a triangular thin‐shell element based on discrete Kirchhoff theory
Authors: Murthy S. Sridhara , Gallagher R. H.
Published: August 2005

A new curved triangular thin‐shell finite element, based on nonconforming displacement fields, has demonstrated its effectiveness in a variety of numerical examples.8 The patch test is applied to that element in the present paper. The element formulation is outlined, the special characteristics of the patch test for curved thin‐shell elements are described, and that test is performed for the conditions of the inextensional bending, membrane stretching and rigid body displacements. Excellent results are obtained for element subtending angles up to 16 degrees.
A general mixed finite element for Timoshenko beams
Authors: Kolberg U.
Published: August 2005

Starting from the principle of virtual work and applying the transformation of Legendre, a mixed finite element method is presented. This is done for the geometrically linear and nonlinear beam analysis including shear deformation. Lagrange polynomials of order six are chosen as element shape functions, and several examples are calculated, in order to show the efficiency of the numerical algorithm.
Exact singularity cancelling for the potential kernel in the boundary element method
Authors: Aliabadi M. H. , Hall W. S. , Hibbs T. T.
Published: August 2005

It is known that the transformation of a triangular curved element to a local plane square introduces a Jacobian which is effective in dealing with the numerical problems of evaluating the singular integrands arising from the presence of the inverse distance potential kernel in the boundary element method. It is shown that exact cancelling of the singularity occurs for triangular elements with linear, quadratic or cubic shape function representions.
A cost‐efficiency analysis of boundary flow calculations from a finite element solution to grounwater flow problems
Authors: Matthews R. S. , Wood W. L.
Published: August 2005

This paper uses examples with exact solutions to demonstrate that boundary flows with 8‐node finite elements are more cost effectively calculated by extrapolation from the Barlow points than by direct sampling at the boundary. The boundary flows are used to calculate the mass balance, and the use of the error in this as a measure of solution accuracy is discussed.
Isoparametric quadrilaterals and hexahedrons for mesh‐grading algorithms
Authors: McDill J. M. , Goldak J. A. , Oddy A. S. , Bibby M. J.
Published: August 2005

Two‐dimensional (2‐D) and three‐dimensional (3‐D) mesh‐grading finite elements for problems with localized phenomena are presented. These quadrilaterals and hexahedrons permit mesh grading without element distortion and, if desired, can be used in a convenient recursive form. They are particularly well suited to adaptive finite element methods. Constraints associated with mesh grading are embedded in the basis functions, making the elements computationally efficient and easy to implement in standard finite element programs. Dramatic computational savings have been achieved. The computational complexity for an implicit analysis of a point load on a 3‐D uniform mesh is O(n7). For the equivalent graded mesh it is O(log2n). The corresponding 2‐D analyses have computational complexities of O(n4) and O(log2n).
Dynamic response of structures loaded by a transverse wind force component
Authors: Causevic Mehmed S.
Published: August 2005

The paper first presents an analytical solution for the dynamic analysis of slender structures due to wind actions. The transverse lift force component of wind is assumed as external loading. The structure is then treated as a lumped parameter system. The normal mode method of analysis is used by means of Laplace transforms.
Computation of pressure from the finite element vorticity stream‐function approximation of the stokes problem
Authors: Caussignac Ph.
Published: August 2005

For the two‐dimensional steady‐state Stokes problem, the mixed velocity–pressure–vorticity formulation is used to compute the pressure from the known vorticity. By defining appropriate weighting functions in the finite element space for the velocity, the pressure is obtained on each element by solving a local variational problem. Numerical results are presented to compare this method with the usual one, which consists in solving a Poisson equation.
Three‐field mixed approximation and the plate bending problem
Authors: Zienkiewicz O. C. , Lefebvre D.
Published: August 2005

The three‐field mixed approximation is typical of Reissner–Mindlin plates, Hu–Washizu elasticity form, etc. A simple stability requirement is presented which, when used with a ‘conceptual’ patch test, shows why some of the currently used elements fail and how improved element forms can be generated.
A chemically enhanced oil recovery simulation benchmark
Authors: Sepehrnoori Kamy , Mamun Chowdhury K. , Pope Gary A.
Published: August 2005

The results of a benchmark on 15 computers for a chemical flooding simulator are reported in this paper. Comparisons between a single processor and multiprocessors are made.
Thickness effect on the spectral properties of thick plates
Authors: Hassan Kamal
Published: August 2005

In this paper is shown the effect of plate thickness on the spectral properties of the stiffness matrix which is obtained from finite element representation. The results confirm the very stiff properties associated with the strain energy based on Reissner and Mindlin theories in the case of thin plates. On the other hand, the Bergan and Wang approach converges to exactly the classical thin plate solution as the thickness decreases.
Numerical method for the resolution of nonlinear heat transfer problems
Authors: Jordan A. , Bouayed F. , Borucki A , Benmouna M.
Published: August 2005

We solve a nonlinear heat transfer problem using a general formalism based on the combination of the finite element and the optimal linearization methods. The results are compared with an ‘exact’ numerical iterative solution and the agreement is found to be good.
Contact mechanical algorithms
Authors: Kalker J. J.
Published: August 2005

An algorithm is given and proved for the solution of a strictly convex minimization problem with linear equality and inequality constraints, in a finite number of steps. It is used to solve frictionless and frictional problems in contact elastostatics, and it has the property that each step can be interpreted mechanically. It is believed that an adaptation of the algorithm will also work for large deformations, and in a non‐elastic setting.
Geometric sensitivity analysis with local coordinate transformations
Authors: Brockman R. A.
Published: August 2005

The dimensionality of truss, beam, membrane and shell finite elements is often less than that of the global co‐ordinate system, and element calculations must be performed in local co‐ordinates. Design parameters which affect the nodal co‐ordinates in such elements control both the element dimensions and orientation, and element design sensitivity calculations must account for both effects. The influence of geometric design variables may be separated into two distinct contributions, which must be applied at separate stages of the sensitivity calculation. The paper includes a description of the appropriate algorithms, examples for one‐ and two‐dimensional elements, and a sample Fortran routine.
A refined Hermitian isoparametric plate bending element
Authors: Virtanen S. , Pramila A.
Published: August 2005

A refined version of the Hermitian isoparametric element which avoids the difficulties with derivative parameters in the geometric mapping is presented. The accuracy of the element is compared with the DKT‐triangle, which is considered to be the most accurate 9 degrees‐of‐freedom plate bending element. The present element compares rather well with the DKT element. Moreover, comparisons are also made in some ‘non‐standard’ cases (circular plate with concentrated load off the centre and elliptical plate) which suggest that the accuracy of all the elements considered is slightly poorer in these than in the standard cases.
The stokes sieve problem
Authors: Conca Carlos
Published: August 2005

This paper presents a brief survey of some theoretical results concerning the motion of a viscous incompressible fluid in a domain containing a periodically perforated wall (or sieve). By studying a model problem, and using homogenization theory, the paper gives a complete description of the asymptotic behaviour of this kind of fluid flow as the sieve becomes finer and finer.
Some useful data structures for the generation of unstructured grids
Authors: Löhner Rainald
Published: August 2005

Several data structures for the generation of unstructured grids are described. Their usefulness stems from the fact that they enable the necessary search operations to be performed in an optimal way. In particular, we describe heap lists, quad‐ and octrees, and linked lists. Combining these data structures, the important problem of interpolating information between unstructured grids is also solved.
Adaptive and hierarchical weighted residual and least‐squares time integration of convection‐diffusion problems
Authors: Wiberg Nils‐Erik
Published: August 2005

In order to obtain an adaptive procedure for integration in time for convection‐diffusion problems we make the integration by use of hierarchical approximation of the variation in time. Different hierarchical functions can be used for different types of problem. Both weighted residual and least‐squares formulations are applied. A combination of those two gives a penalty method with a constraint equation corresponding to the least‐squares method. A whole class of different methods is obtained, suitable for an adaptive procedure due to the hierarchical approximation in time. A combination of Galerkin in space and least‐squares in time gives a number of higher order schemes in time. Some special cases of the general procedures can be identified. If a linear discontinuous hierarchical basis function is used in the Petrov‐Galerkin weak formulation, the method obtained corresponds to the discontinuous Petrov‐Galerkin method in time useful for convection‐dominated problems. The streamline‐diffusion method is found as the penalty method mentioned.
Some conjugate gradient methods for symmetric and nonsymmetric systems
Authors: Prakhya K. V. G.
Published: August 2005

The performance of Stiefel's conjugate gradient (CG) method and a reformulated three‐parameter CG are compared for structural analysis problems having varying condition numbers. It has been found that diagonal preconditioning in the three‐parameter CG method is efficient when high condition numbers are encountered.
Symmetrization of coupled eigenproblems by eigenvector augmentation
Authors: Felippa Carlos A.
Published: August 2005

The problem of elastoacoustic vibrations of a fluid enclosed in a flexible container leads to a generalized unsymmetric eigensystem of special form. This system can be symmetrized in eight different ways by eigenvector augmentation followed by static condensation.
A program for the explicit integration of a 4‐noded planar isoparametric hybrid stress element
Authors: Ledvinka Milan
Published: August 2005

The explicit matrices G and H for a 4‐noded plane hybrid element with assumed stresses in natural coordinates are presented. Savings in computation time and core storage are significant.
The convex hull problem for the selection of load cases in reinforced concrete cross‐section analysis
Authors: Recuero A. , Moran F.
Published: August 2005

Exact methods are presented for the problem of the convex hull in two and three dimensions. Given a set of points in the plane or in a three‐dimensional space, the convex hull problem consists in the determination of the points of the set which are vertices of the minimum convex polygon or polyhedron which contains all the points of the set.

Both algorithms have been implemented as subroutines in Microsoft BASIC for PC‐compatible microcomputers. Execution times for these subroutines vary almost linearly with the number of points of the set, for the plane, and with the product of the number of points of the set and the number of vertices of the polyhedron, for the space.

These methods can be used for the selection of load cases for the design or testing of reinforced concrete cross‐sections subjected to symmetrical bending and compression (plane) or to biaxial bending and compression (space). The load cases corresponding to internal points can be eliminated as a consequence of the convexity of the interaction diagram or surface.
A simple program for plotting streamlines and calculating residence times
Authors: Jan Yih‐Jena
Published: August 2005

In this paper, we give a rigorous and clear procedure for writing a program for plotting streamlines and calculating residence times. A program is given in the Appendix.
An integration algorithm and the corresponding consistent tangent operator for fully coupled elastoplastic and damage equations
Authors: Benallal Ahmed , Billardon René , Doghri Issam
Published: August 2005

This paper deals with the implementation in finite element calculations of complex elastoplastic constitutive equations exhibiting non‐linear kinematic and isotropic hardening, and fully coupled to a continuous ductile damage evolution model. The Newton method is used to solve the non‐linear global equilibrium equations as well as the non‐linear local equations obtained by fully implicit integration of the constitutive equations. The consistent local tangent modulus is obtained by exact linearization of the algorithm. The procedure described has been implemented in the general purpose code ABAQUS.
General form of the generalized variational principle in elasticity
Authors: Shikui Liu , Zhongxiang Jiang
Published: August 2005

A new method for establishing generalized variational principles, called the undetermined coefficient method, is presented. A more general form of functional for the generalized variational principles in elasticity and a concept of energy functional space are given. Based on the present functional, a general formulation for a hybrid/mixed element is established.
Analysis of unbounded field problems using dampers
Authors: Sharan Shailendra K.
Published: August 2005

A highly efficient damper technique, recently developed for the two‐dimensional finite element analysis of hydrodynamic pressures on structures vibrating in an incompressible fluid medium, is generalized and extended to three‐dimensional problems. Some numerical examples are presented to demonstrate the effectiveness and efficiency of the proposed damper. The damper technique has potential applications to a wide variety of other field problems.
A compact database scheme for the partitioned frontal solution algorithm
Authors: Lin Hong‐Tsung
Published: August 2005

A compact and effective data structure for memory management is introduced for front partitioning under relatively small memory capacity. The algorithm indexes frontal equations in a special database form and provides the frontal solver with the necessary coefficients for the Gaussian elimination process. If symmetry exists in frontal equations, only the upper/lower‐triangular part is accessed. An adjustable memory buffer is implemented to minimize data input/output operations in the database file. Ease of implementation is demonstrated (about 100 FORTRAN statements) in an existing coding. This development is advantageous for (but not restricted to) micro/minicomputer environments because of the compactness in coding and the efficiency in the access to the mass storage (requires at most the size of coefficients of the largest frontal). Results obtained on microcomputers using this scheme are given, together with comparisons. Other possible applications of the scheme are discussed.
A numerical comparison of conjugate gradient‐like methods
Authors: Langtangen Hans Petter , Tveito Aslak
Published: August 2005

Three second‐order, nonselfadjoint partial differential equations in two dimensions are discretized by the finite element method, leading to non‐symmetric systems of linear equations. The systems are solved by several conjugate gradient‐like methods, and compared for their computational cost. All methods are tested with and without preconditioning.
On the numerical instability of the smeared‐crack approach in the non‐linear modelling of concrete structures
Authors: González‐Vidosa F. , Kotsovos M. D. , Pavlović M. N.
Published: August 2005

This paper considers various possible problems that may be encountered in the course of structural‐concrete analyses by means of the brittle material model. Ways of dealing with such problems are suggested, and are illustrated by two examples which, in the past, have proved difficult to predict in a reliable manner.
Computation of electrostatic field distribution in a cable by least‐squares smoothing finite element method
Authors: Lakshmipathi R. , Rao Y. Narayana , Rao G. Sridhara
Published: August 2005

This paper presents a method for computing the electrostatic field distribution at the interface between two dissimilar dielectrics based on the least‐squares smoothing technique along with the potential‐based classical finite element method by suitably incorporating the interface nodal conditions. It is found to give accurate results when compared with the results obtained by classical finite element method, and also it gives the continuous field distribution at the nodes in the case of a homogeneous dielectric problem. By using this method, the electrostatic field distributions in a solid insulated single‐core cable with homogeneous dielectric and in a compressed sulphur hexafluoride (SF6) gas insulated disk‐type spacer cable are determined. Laboratory investigations have also been carried out on a disk‐type spacer cable by varying parameters like the spacer contact angle, the relative permittivity of the spacer material and the conductor diameter.
A computational procedure for automated flutter analysis
Authors: Murthy Durbha V. , Kaza Krishna Rao V.
Published: August 2005

A direct solution procedure for computing the flutter Mach number and the flutter frequency is applied to the aeroelastic analysis of propfans using a finite element structural model and an unsteady aerodynamic model based on a three‐dimensional subsonic compressible lifting surface theory. An approximation to the Jacobian matrix that improves the efficiency of the iterative process is presented. The Jacobian matrix is indirectly approximated from approximate derivatives of the flutter matrix, which are updated only in the direction of the last move. Examples are used to illustrate the convergence properties. The direct solution procedure facilitates the automated flutter analysis in addition to contributing to the efficient use of computer time as well as the analyst's time.
Direct cubic spline with application to quadrature
Authors: Anwar M. N. , El‐Tarazi M. N.
Published: August 2005

This paper presents a formulation of a cubic spline that fits the first derivatives of a function at mesh points and the function value and its second derivative at the beginning of the interval. Error bounds for the function and its first three derivatives are derived over the whole interval. This formulation can be applied, in particular, to quadratures.