bluuebunny/crossref_metadata_2025_split huggingface dataset:
Double noding technique for mixed mode crack propagation studies
Authors: Liaw B. M. , Kobayashi A. S. , Emery A. F. 
Published: August 2005

AbstractA simple dynamic finite element algorithm for analysing a propagating mixed mode crack tip is presented. A double noding technique, which can be easily incorporated into existing dynamic finite element codes, is used together with a corrected Ĵ integral to extract modes I and II dynamic stress intensity factors of a propagating crack. The utility of the procedure is demonstrated by analysing test problems involving a mode I central crack propagating in a plate subjected to uniaxial tension, a stationary slanted central crack in a plate subjected to uniaxial inpact loading and an extending slanted‐edge crack in plate subjected to uniaxial tension.
Partitioned rational Runge Kutta for parabolic systems
Authors: Liu Wing Kam , Belytschko Ted , Zhang Yi Fei 
Published: August 2005

AbstractA new family of coupled time integration operators of different orders is developed. It permits different time integration operators to be used simultaneously in various regions of the model. This approach has the advantage of applying a very accurate time integrator, such as Runge Kutta method of order two to four, to the local nonlinear region of interest and a simple time integrator, such as the implicit–explicit or mixed time implicit–explicit method of order one, for the remaining region. The computer implementation aspects, stability analysis as well as the numerical evaluations of these new methods are presented. This is another attractive addition to the repertoire of time integration methods.
FEM‐analysis of transverse vibrations of an axially moving membrane immersed in ideal fluid
Authors: Niemi J. , Pramila A. 
Published: August 2005

AbstractTransverse vibrations of an axially moving (travelling in its own plane) membrane submerged in ideal fluid are analysed using the FEM. The discrete equations differ from the equations of the common coupled problem in that there appear two additional inertia terms due to the convective acceleration. The effect of the density of the element mesh, the effect of the truncation distance and the effect of various lumping techniques on the accuracy of the results are studied. The FEM‐results are compared with available analytical and experimental results. The agreement seems to be rather good.
Remarks on computational magnetostatics
Authors: Sussman M. M. 
Published: August 2005

AbstractA two‐scalar‐potential formulation for magnetostatic computations has been recommended4 based on a comparative study of several different formulations in terms of their accuracy and efficiency. A different study3 challenged this recommendation. It is the purpose of this report to present results which confirm the practical necessity for the two‐potential formulation.The method used for the present study was to construct a simplified computer program designed to easily compare the alternative methods. This program uses the finite element method on a geometry suited for analysis of the ‘bifiliar conductor’ problem treated in both studies mentioned above. In this program, the alternative formulations are implemented with a great deal of common code. In particular, the input, stiffness matrix, matrix solution and editing routines are common to both formulations, with differences appearing only in the source terms for the stiffness matrix equation. The known analytic solution to this particular problem provides a reference with which the computed solutions is compared. The main conclusion of this study of the ‘bifiliar conductor’ problem is that for a given choice of mesh, the two‐potential formulation yields significantly more accuracy than the reduced‐potential formulation.
Numerical modelling of wave propagation using parabolic approximation with a boundary‐fitted co‐ordinate system
Authors: Tsay Ting‐Kuei , Ebersole Bruce A. , Liu Philip L.‐F. 
Published: August 2005

AbstractWith a boundary‐fitted curvilinear co‐ordinate system, the parabolic approximation is applied to the mildslope equation to describe the wave propagation. Both refraction and diffraction are included in the numerical model. Because the shoreline coincides with one of the curvilinear co‐ordinates, the numerical model can be used to compute wave propagations near an irregular shoreline.
Some acceleration methods for iterative computer of derivatives of eigenvalues and eigenvectors
Authors: Tan Roger C. E. 
Published: August 2005

AbstractThe performance of an iterative method for computing partial derivatives of eigenvalues and eigenvectors of parameter dependent matrices may be improved dramatically by various extrapolation methods proposed here. With exact computation, all these extrapolation methods yield the exact solution with a finite number of iterations. Two of these methods, which have not been used before for this problem, are compared with the ϵ‐algorithms. Numerical examples are given. The methods suggested may be used to obtain either highly accurate estimates or cheap estimates of modest accuracy.
Modelling liquid–solid phase changes with melt convection
Authors: Dantzig Jonathan A. 
Published: August 2005

AbstractMethods are described for modelling of phase change processes using the finite element method to simulate freezing and melting including convection in the melt. Evaluation of several enthalply/specific heat methods and time marching schemes is also included. Suppression of velocities in the solid region is described, and example problems are given. Comparison is made to simulations performed by other researchers using finite difference methods. Substantially different results were found for one of these problems, and this result is shown to be caused by numerical problems in the earlier work.
A general and effective way for evaluating the integrals with various orders of singularity in the direct boundary element method
Authors: Zhang Wu , Xu Huan‐Ran 
Published: August 2005

AbstractA general and efficient technique is developed for the evaluation of the integrals with various orders of singularity, such as occur in the three‐dimensional boundary element method (BEM). Generalized (extended) triangle, tetrahedron polar co‐ordinate mappings together with two conditions are used to remove the singularity of the integrals, and to evaluate the corresponding non‐singular ones in a new numerical space. Triangle and tetrahedron polar co‐ordinates in Reference 1 are proved to be a special case of the generalized ones in this paper. With the developed idea, boundary element results converge rapidly towards the analytical solutions for the strongly singular integrals evaluated directly, and the analytical solutions can be gained in principle, even when employing higher order, triangular boundary elements and tetrahedral cells. The generality and practicability of the method are demonstrated in the case of higher order elements, discontinuous elements and large engineering problems.
Improved hybrid solid element with a traction‐free cylindrical surface
Authors: Tian Zongshu , Tian Zheng 
Published: August 2005

AbstractNew 8‐node solid elements with two parallel faces and one traction‐free cylindrical surface are derived using the assumed stress hybrid model. Six new expressions of stress components are developed by using four stress functions and cylindrical co‐ordinates, so that the normal stress σz on the plane perpendicular to the two parallel faces varies as a parabola, and the assumed stress field satisfies the equilibrium equations as well as the traction‐free conditions over the cylindrical boundary. The assumed stress field also satisfies the compatibility conditions when the new element is degenerated into the 2‐dimensional case. Examples have clearly demonstrated that these present special elements are far superior in predicting the stress concentration factors, the distributions of circumferential stresses and the normal stress σz.
Some improvements of accuracy and efficiency in three dimensional direct boundary element method
Authors: Li Yin‐Sheng , Obata Tatsuo , Koguchi Hideo , Yada Toshio 
Published: August 2005

AbstractNumerical analysis with the Boundary Element Method (BEM) has been used more and more in various engineering fields in recent years. In numerical techniques, however, there are some problems which have not been fully solved even now. The most essential one is the drop in the accuracy of results for internal points near the boundary of the structure, where the singularity of integrands in the boundary integral equation is too strong to be evaluated with the normal numerical method. For the boundary integral equation of stress, this problem became more serious, and the accuracy can be improved only partly, even though very refined boundary elements are used.In this paper, the boundary integral equation is newly formulated using a relative quantity of displacement. In this way, the singularity of boundary integrals is reduced by the order of 1/r, and the accuracy of solution is improved significantly. Furthermore, in order to integrate it more accurately, two kinds of numerical integral methods are newly developed. By using these methods, both displacement and stress can be obtained with excellent accuracy at almost any point in the structure without any numerical difficulty, although the discretization may be comparatively coarse. The generality and practicability of the present formulation and integral methods are confirmed through some examples of three dimensional elastic problems.
Hygrothermomechanical evaluation of porous media under finite deformation. Part I ‐ finite element formulations
Authors: Advani S. H. , Lee T. S. , Lee J. K. , Kim C. S. 
Published: August 2005

AbstractThe coupled thermomechanical responses of fluid‐saturated porous continua subjected to finite deformation are investigated. Field equations governing the transient response of the media are derived from a continuum thermodynamics mixture theory based on mass balance, momentum balance and energy balance laws as well as the Clausius‐Duhem inequality. Finite element procedures for the two‐dimensional response, employing updated Lagrangian formulations for the solid skeleton deformation and the weak formulations for fluid and thermal transport equations, are implemented in a fully implicit form. Temperature‐dependent mechanical properties for the non‐linear solid matrix, characterized by Perzyna's viscoplastic model, are assumed. An iterative scheme based on the full Newton‐Raphson method is presented for simultaneously solving the coupled non‐linear equations.
Hybrid and mixed‐penalty finite elements for 3‐D analysis of soft hydrated tissue
Authors: Vermilyea M. E. , Spilker R. L. 
Published: August 2005

AbstractSolution of biomechanics problems involving three‐dimensional (3‐D) behaviour of soft tissue on geometries representative of such tissue in vivo will require the use of numerical methods. Toward this end, a pair of tetrahedral finite elements has been developed. The equations which are used to model the tissue behaviour for both elements are those commonly known as the linear biphasic equations. This model assumes that hydrated soft tissue is a mixture of two incompressible, immiscible phases, and employs mixture theory to derive governing equations for its mechanical behaviour. The finite element techniques applied to these equations for the two elements are the mixed‐penalty method and the hybrid method. Both elements are described here, and the special requirements for 3‐D analysis are discussed. Results obtained by solving canonical problems in two and three dimensions using both elements are presented and compared. Both elements are found to produce excellent results. The hybrid element is also noted to have advantages for non‐linear analyses involving finite deformation which will require solution in the future.
Optimization of large structures subjected to dynamic loads with the multiplier method
Authors: Chahande A. I. , Arora J. S. 
Published: August 2005

AbstractThe multiplier method for optimization of large‐scale mechanical and structural systems subjected to dynamic loads is investigated. A large‐scale dynamic response optimization problem is formulated and solved in several alternate ways using the first‐ and second‐order forms of the equations of motion. Results are compared with those obtained with the sequential quadratic programming algorithm—a primal method. In all the cases investigated, the multiplier algorithm is more efficient than the primal method. Therefore, it is concluded that the multiplier method is more appropriate for dynamic response optimization of large‐scale problems.
Preconditioned Krylov solvers for BEA
Authors: Prasad K. Guru , Kane J. H. , Keyes D. E. , Balakrishna C. 
Published: August 2005

AbstractThe performance of a number of preconditioned Krylov methods is analysed for a large variety of boundary element formulations. Low‐ and high‐order element, two‐dimensional (2‐D) and three‐dimensional 3‐D, regular, singular and hypersingular, collocation and symmetric Galerkin, single‐ and multi‐zone, thermal and elastic, continuous and discontinuous boundary formulations with and without condensation are considered. Preconditioned Conjugate Gradient (CG) solvers in standard form and a form effectively operating on the normal equations (CGN), Generalized Minimal Residual (GMRES), Conjugate Gradient Squared (CGS) and Stabilized Bi‐conjugate Gradient (Bi‐CGSTAB) Krylov solvers are employed in this study. Both the primitive and preconditioned matrix operators are depicted graphically to illustrate the relative amenability of the alternative formulations to solution via Kryiov methods, and to contrast and explain their computational performances. A notable difference between 2‐D and 3‐D BEA operators is readily visualized in this manner. Numerical examples are presented and the relative conditioning of the various discrete BEA operators is reflected in the performance of the Krylov equation solvers. A preconditioning scheme which was found to be uncompetitive in the collocation BEA context is shown to make iterative solution of symmetric Galerkin BEA problems more economical than employing direct solution techniques. We conclude that the preconditioned Krylov techniques are competitive with or superior to direct methods in a wide range of boundary formulated problems, and that their performance can be partially correlated with certain problem characteristics.
A third‐order triangular multilayered plate finite element with continuous interlaminar stresses
Authors: Di Sciuva Marco 
Published: August 2005

AbstractBased on a refined third‐order shear deformation plate theory recently proposed by the author, a three‐node, fully conforming, multilayered anisotropic plate element of arbitrary triangular shape is developed in this paper. The element incorporates 10 nodal d.o.f., namely the two in‐plane displacements, the two shear rotations, the transverse displacement and its first and second derivatives, thus giving a total of 30 d.o.f. The formulation includes extension, bending and transverse shear deformation states; moreover, it fulfils a priori the geometric and stress continuity conditions at the interfaces, and it requires only five generalized displacements to describe the kinematics of the plate deformation. The formulated plate element is assessed for its performance comparing its predictions either with exact solutions from the plate model or with other approximate two‐dimensional solutions.
An efficient dual boundary element technique for a two‐dimensional fracture problem with multiple cracks
Authors: Chen W. H. , Chen T. C. 
Published: August 2005

AbstractAn efficient dual boundary element technique for the analysis of a two‐dimensional finite body with multiple cracks is established. In addition to the displacement integral equation derived for the outer boundary, since the relative displacement of the crack surfaces is adopted in the formulation, only the traction integral equation is established on one of the crack surfaces. For each crack, a virtual boundary is devised and connected to one of the crack surfaces to construct a closed integral path. The rigid body translation for the domain enclosed by the closed integral path is then employed for evaluating the hypersingular integral. To solve the dual displacement/traction integral equations simultaneously, the constant and quadratic isoparametric elements are taken to discretize the closed integral paths/crack surfaces and the outer boundary, respectively. The present method has distinct computational advantages in solving a fracture problem which has arbitrary numbers, distributions, orientations and shapes of cracks by a few boundary elements. Several examples are analysed and the computed results are in excellent agreement with other analytical or numerical solutions.
Volume integral equations in non‐linear 3‐D magnetostatics
Authors: Kettunen Lauri , Forsman Kimmo , Levine David , Gropp William 
Published: August 2005

AbstractIn this paper a discussion of volume integral formulations in three‐dimensional non‐linear magnetostatics is presented. Integral formulations are examined in connection with Whitney's elements in order to find new approaches. A numerical algorithm based on a formulation implying properly the continuity conditions of magnetic field strength H, i.e. an h‐type formulation, is introduced. Results of demanding application problems are shown demonstrating the characteristics of this kind of volume integral approach. In addition, a discussion of the parallelized version of the numerical code based on the h‐type approach is presented appended with numerical results illustrating the advantages of combining integral formulations with concurrent computing.
Toxicity profile of delayed high dose sodium thiosulfate in children treated with carboplatin in conjunction with blood‐brain‐barrier disruption
Authors: Neuwelt Edward A. , Gilmer‐Knight Kristin , Lacy Cynthia , Nicholson H. Stacy , Kraemer Dale F. , Doolittle Nancy D. , Hornig Gregory W. , Muldoon Leslie L. 
Published: August 2005

AbstractPurposeTo assess the safety of delayed high dose intravenous (i.v.) sodium thiosulfate (STS) in a case series of 12 children with malignant brain tumors who were treated with intraarterial (i.a.) carboplatin in conjunction with blood‐brain‐barrier disruption (BBBD).MethodsTwelve children ages 17 months–12 years underwent a total of 132 BBBD chemotherapy treatments and also received delayed high dose STS (i.v.). Dose 1 of STS (10–16 g/m2) was administered 2 or 4 hr after carboplatin, and a second STS dose was administered 4 hr after dose 1 if the child had impaired baseline hearing. Toxicity data were graded in accordance with the National Cancer Institute Common Toxicity Criteria (Version 2). Audiologic monitoring to evaluate the otoprotective potential of STS was performed on 11 children. Ototoxicity was defined in accordance with the American Speech‐Language‐Hearing Association (ASHA) criteria. Baseline and end of treatment hearing status were graded using Brock's criteria.ResultsNausea and vomiting were well controlled with anti‐emetics administered approximately 30 min prior to STS infusion. Analogous to results in adult patients, there was mild transient hypernatremia and a trend for improved protection from ototoxicity in children who received STS delayed to 4 hr post‐treatment versus 2 hr. Tumor responses were seen in heavily pre‐treated patients with relatively chemo‐resistant tumors, suggesting that STS did not protect the tumor from platinum cytotoxicity.ConclusionHigh dose STS is well tolerated in children under 12 years of age. Further studies of STS in children are warranted to assess otoprotection and the impact of STS on platinum mediated efficacy. © 2005 Wiley‐Liss, Inc.
Initiation mechanism of ultrasonically irradiated emulsion polymerization
Authors: He Yuhui , Cao Ya , Liu Yan 
Published: August 2005

AbstractThe emulsion polymerization of some monomers can occur without the conventional free radical initiators under ultrasonic irradiation. However, the initiation mechanism is still under controversy. In this paper, the sources of free radicals arising from ultrasonically initiated emulsion polymerization were investigated. Experimental results show that ionic surfactants play a very important role in obtaining a high polymer yield. While monomer conversion is very low in the absence of surfactants or in the presence of nonionic surfactants, it increases significantly upon addition of a little amount of ionic surfactant. FTIR and a radical trapping experiment confirm that the free radicals involved in the irradiation process originate from the decomposition of the ionic surfactants. Under ultrasonic irradiation, ionic surfactants undergo bond scission between the alkyl and ionic group, where the bond is the weakest along the chain. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2617–2624, 2005
Ultrasound examination of the endometrium before and after Pipelle endometrial sampling
Authors: Van den Bosch T. , Van Schoubroeck D. , Ameye L. , Van Huffel S. , Timmerman D. 
Published: August 2005

AbstractObjectiveTo evaluate if, and to what extent, Pipelle de Cornier® endometrial sampling influences the ultrasonographic features of the endometrium.MethodsThis was a prospective descriptive study on 99 consecutive women in whom a Pipelle endometrial biopsy was performed. All patients first underwent a transvaginal ultrasound evaluation of the uterus. The endometrial thickness (ET) was measured and endometrial sonographic features were recorded. Thereafter, a Pipelle endometrial biopsy was taken. Finally, the ultrasound examination was repeated. The patients' characteristics, the sampling procedure, the endometrial histology and the sonographic findings before and after Pipelle biopsy were compared.ResultsNinety‐nine women, of whom 45% were postmenopausal, entered the study. The mean age was 59.0 years (SD, 9.9) for the postmenopausal women, and 41.6 years (SD, 8.7) for the rest. On histological examination, endometrial cancer was diagnosed in four patients and endometrial hyperplasia in eight patients. The average ET before Pipelle sampling was 9.0 mm (SD, 6.6) vs. 8.6 mm (SD, 7.0) after biopsy (P < 0.0001). After Pipelle sampling, the endometrium was less clearly delineated (P = 0.03) and more echogenic endometrial spots were seen (P < 0.0001). If an endometrial three‐layer pattern was noted before sampling, it was not observed in most women after Pipelle biopsy (P = 0.0003).ConclusionsET measurements are affected by Pipelle sampling and the quality of the ultrasound features tends to be altered by biopsy. Performing the ultrasound examination before proceeding with endometrial sampling may therefore improve diagnostic accuracy of ultrasound. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.