bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of the tangent derivative boundary integral equations for the efficient computation of stresses and error indicators
Authors: Muci‐Küchler K. H. , Miranda‐Valenzuela J. C. , Soriano‐Soriano S. 
Published: October 2002

AbstractIn this work, a new global reanalysis technique for the efficient computation of stresses and error indicators in two‐dimensional elastostatic problems is presented. In the context of the boundary element method, the global reanalysis technique can be viewed as a post‐processing activity that is carried out once an analysis using Lagrangian elements has been performed. To do the reanalysis, the functional representation for the displacements is changed from Lagrangian to Hermite, introducing the nodal values of the tangential derivatives of those quantities as additional degrees of freedom. Next, assuming that the nodal values of the displacements and the tractions remain practically unchanged from the ones obtained in the analysis using Lagrangian elements, the tangent derivative boundary integral equations are collocated at each functional node in order to determine the additional degrees of freedom that were introduced. Under this scheme, a second system of equations is generated and, once it is solved, the nodal values of the tangential derivatives of the displacements are obtained. This approach gives more accurate results for the stresses at the nodes since it avoids the need to differentiate the shape functions in order to obtain the normal strain in the tangential direction. When compared with the use of Hermite elements, the global reanalysis technique has the attraction that the user does not have to give as input data the additional information required by this type of elements. Another important feature of the proposed approach is that an efficient error indicator for the values of the stresses can also be obtained comparing the values for the stresses obtained through the use of Lagrangian elements and the global reanalysis technique. Copyright © 2001 John Wiley & Sons, Ltd.
Non‐weak/strong solutions in gas dynamics: a C11p‐version STLSFEF in Lagrangian frame of reference using ρ, u, p primitive variables
Authors: Surana K. S. , Van Dyne David G. 
Published: October 2002

AbstractIn this paper, we present computations of the non‐weak solutions of class C11 of transient Navier–Stokes equations for compressible flow in Lagrangian frame of reference using space‐time least squares finite element formulation with primitive variables ρ, u, p. For high speed compressible flows the solutions reported here possess the same orders of continuity as the governing differential equations. The role of diffusion i.e. viscosity (physical or artificial) and thermal conductivity on shock structure is demonstrated. Compression of air in a rigid cylinder by a rigid, massless and frictionless piston is used as a model problem. True time evolutions of class C11 are reported beginning with the first time step until steady shock conditions are achieved. Comparisons with analytical solutions are presented when possible. Copyright © 2001 John Wiley & Sons, Ltd.
A GA‐based technique for layout optimization of truss with stress and displacement constraints
Authors: Azid I. A. , Kwan A. S. K. , Seetharamu K. N. 
Published: October 2002

AbstractVarious developments of increasing complexity involved in layout optimization are discussed. The use of conventional GA in layout optimization is briefly mentioned with emphasis on its limitations and conditions imposed in finding the optimal design. The proposed new technique is applied to the benchmark example of Michell's truss for verification. The approach has also been applied to new examples of bridge truss and crane truss problems in order to demonstrate the generality and robustness for topology optimization. The approach is extended to include dual stress‐displacements constraints since many practical problems involve these two constraints simultaneously. Two‐bar and 10‐bar trusses are solved as examples for layout optimization with both stress and displacement constraints with satisfactory results. The effect of mutation on the final topology is also discussed. The major drawbacks of the ground structure approach are overcome in this proposed new method. The optimal designs obtained demonstrate the ability, robustness and generality of using the proposed new technique in layout optimization problems. Copyright © 2001 John Wiley & Sons, Ltd.
A simplified approach for incorporating thickness stress in the analysis of sheet metal forming using shell elements
Authors: Cho J. W. , Yang D. Y. , Chung W. J. 
Published: October 2002

AbstractA simplified scheme for considering the thickness stress of shell elements induced by contact is presented which improves the accuracy of sheet metal forming analysis. The yield function formulated on the basis of plane stress conditions is modified to incorporate the effect of transverse normal stress induced by contact forces acting on shell elements and return mapping routine is used to update in‐plane stresses at each time step. The transverse normal stress distributions in the thickness direction are determined using the analytic solution of the cylindrical tube under the internal pressure. As numerical examples, uni‐axial compression, bi‐axial tension and bending tests are treated. The problem of cylindrical cup drawing is also calculated. Each result is compared with the results obtained by the analysis using ABAQUS continuum elements. Copyright © 2002 John Wiley & Sons, Ltd.
A p‐version finite element approach for two‐ and three‐dimensional problems of the J2 flow theory with non‐linear isotropic hardening
Authors: Düster A. , Rank E. 
Published: October 2002

AbstractIn this paper an implementation of a two‐ and three‐dimensional p‐version approach to the J2 flow theory with non‐linear isotropic hardening for small displacements and small strains is presented. Based on higher‐order quadrilateral and hexahedral element formulations, a Newton–Raphson iteration scheme combined with a radial return algorithm is applied to find approximate solutions for the underlying physically non‐linear model problem. Curved boundaries are taken care of with the blending function method, allowing an accurate representation of geometry with only a few p‐elements. Numerical examples demonstrate, that the p‐version supplies efficient and accurate approximations to this class of physically non‐linear problems. Copyright © 2001 John Wiley & Sons, Ltd.
Studies of multi‐start clustering for global optimization
Authors: Tu W. , Mayne R. W. 
Published: October 2002

AbstractGlobal/multi‐modal optimization problems arise in many engineering applications. Owing to the existence of multiple minima, it is a challenge to solve the multi‐modal optimization problem and to identify the global minimum especially if efficiency is a concern. In this paper, variants of the multi‐start with clustering strategy are developed and studied for identifying multiple local minima in nonlinear global optimization problems. The study considers the sampling procedure, the use of Hessian information in forming clusters, the technique for cluster analysis and the local search procedure. Variations of multi‐start with clustering are applied to 15 multi‐modal problems. A comparative study focuses on the overall search effectiveness in terms of the number of local searches performed, local minima found and required function evaluations. The performance of these multi‐start clustering algorithms ranges from very efficient to very robust. Copyright © 2002 John Wiley & Sons, Ltd.
A comprehensive catastrophe theory for non‐linear buckling of simple systems exhibiting fold and cusp catastrophes
Authors: Lignos X. A. , Parke G. A. R. , Harding J. E. , Kounadis A. N. 
Published: October 2002

AbstractNon‐linear static buckling of simple systems associated with typical discrete critical points is comprehensively presented using elementary Catastrophe Theory. Attention is focused on the Fold and Cusp Catastrophe, all local properties of which are assessed in detail. Hence, in dealing with stability problems of potential systems there is no need to seek any of these properties since all of these are known a priori. Then, one has only to classify, after reduction, the total potential energy of a system into one of the universal unfoldings of the above types of catastrophe. Two illustrative numerical examples show the methodology of the proposed technique. Copyright © 2002 John Wiley & Sons, Ltd.
On boundary conditions of the characteristic based split (CBS) algorithm for fluid dynamics
Authors: Nithiarasu P. 
Published: October 2002

AbstractThis paper discusses alternative procedures which can be used in the application of boundary conditions for the CBS algorithm. Attention is focused on the problem of application of prescribed velocity and traction conditions. The paper is illustrated with some incompressible flow problems. Although previously logical and correct boundary condition specifications were introduced, the procedures outlined in this paper simplify calculations and generally make it more accurate. Copyright © 2002 John Wiley & Sons, Ltd.
Stress intensity factors for three‐dimensional surface cracks using enriched finite elements
Authors: Ayhan A. O. , Nied H. F. 
Published: October 2002

AbstractThe analysis of three‐dimensional crack problems using enriched crack tip elements is examined in this paper. It is demonstrated that the enriched finite element approach is a very effective technique for obtaining stress intensity factors for general three‐dimensional crack problems. The influence of compatibility, integration, element shape function order, and mesh refinement on solution convergence is investigated to ascertain the accuracy of the numerical results. It is shown that integration order has the greatest impact on solution accuracy. Sample results are presented for semi‐circular surface cracks and compared with previously obtained solutions available in the literature. Good agreement is obtained between the different numerical solutions, except in the small zone near the free surface where previously published results have often neglected the change in the stress singularity at the free surface. The enriched crack tip element appears to be particularly effective in this region, since boundary conditions can be easily imposed on the stress intensity factors to accurately represent the correct free surface condition. Copyright © 2002 John Wiley & Sons, Ltd.
An augmented spatial digital tree algorithm for contact detection in computational mechanics
Authors: Feng Y. T. , Owen D. R. J. 
Published: October 2002

AbstractBased on the understanding of existing spatial digital tree‐based contact detection approaches, and the alternating digital tree (ADT) algorithm in particular, a more efficient algorithm, termed the augmented spatial digital tree (ASDT) algorithm, is proposed in the present work. The ASDT algorithm adopts a different point representation scheme that uses only the lower corner vertex to represent a (hyper‐)rectangle, with the upper corner vertex serving as the augmented information. Consequently, the ASDT algorithm can keep the working space the same as the original n‐dimensional space and, in general, a much better balanced tree can be expected. This, together with the introduction of an additional bounding subregion for the rectangles associated with each tree node, makes it possible to significantly reduce the number of node visits in the region search, although each node visit may be slightly more expensive. Three examples arising in computational mechanics are presented to provide an assessment of the performance of the ASDT. The numerical results indicate that the ASDT is, at least, over 3.9 times faster than the ADT. Copyright © 2002 John Wiley & Sons, Ltd.
The effect of zeolite on the curing of epoxy resin by polyaniline: a kinetic study
Authors: Sreedhar B. , Palaniappan S. , Narayanan S. 
Published: October 2002

AbstractPolyaniline sulfate‐zeolite composite was prepared by emulsion polymerization. Epoxy resin was cured using polyaniline‐sulfate salt and various amounts of polyaniline sulfate‐zeolite composite. The kinetics of the cure reaction for an epoxy resin based on the diglycidyl ether of bisphenol A (DGEBA) with polyaniline‐sulfate and polyaniline sulfate‐zeolite composite have been studied using differential scanning calorimetry (DSC) under isothermal and dynamic conditions. Isothermal kinetics analysis was performed using the phenomenological model of Kamal. Dynamic kinetic analysis was performed using Kissinger's method. Copyright © 2002 John Wiley & Sons, Ltd.
p27/kip1 expression in normal epithelium, benign and neoplastic breast lesions
Authors: De Paola Franca , Maria Vecci Anna , Maria Granato Anna , Liverani Marilena , Monti Franco , Maria Innoceta Anna , Gianni Lorenzo , Saragoni Luca , Ricci Monica , Falcini Fabio , Amadori Dino , Volpi Annalisa 
Published: October 2002

AbstractThe development of cancer in the breast and in other sites is a complex process requiring a number of different genetic and epigenetic alterations. The accumulation of the genetic changes is thought to underlie the progression from precancerous lesions to carcinomas. The expression of p27/kip1 protein, a cyclin‐dependent kinase inhibitor, was investigated by immunohistochemistry in normal epithelial specimens, benign alterations, and malignant lesions of the breast. The number of p27/kip1‐positive cells ranged from none to more than 98% in the overall series. Wide ranges of p27/kip1‐positive cells were consistently observed within each histological category, but the median value progressively decreased in typical hyperplasia and fibroadenoma, with an even more marked reduction in malignant lesions, compared with normal epithelium. Moreover, the percentage of cells expressing p27/kip1 in tumours was about three times lower in invasive than in in situ lesions and was inversely related to tumour size, but not to lymph node involvement. In conclusion, the degree to which p27 expression is altered in typical hyperplastic lesions and fibroadenomas indicates that the deregulation of p27 may occur very early on during breast cell transformation, but the usefulness of its determination to categorize subgroups of lesions at different risk of evolution remains somewhat doubtful. Copyright © 2001 John Wiley & Sons, Ltd.
Abnormal immunoreactivity of the E‐cadherin/catenin (α‐, β‐, and γ‐) complex in premalignant and malignant non‐melanocytic skin tumours
Authors: Papadavid Evangelia , Pignatelli Massimo , Zakynthinos Spyridon , Krausz Thomas , Chu Anthony C. 
Published: October 2002

AbstractE‐cadherin/catenin (α‐, β‐, and γ‐) complex plays a critical role in the control of epithelial differentiation. The aim of this study was to examine the immunoreactivity of E‐cadherin and α‐, β‐, and γ‐catenins in premalignant and malignant non‐melanocytic skin tumours (NMST) and to correlate their expression with the grade of tumour differentiation, as assessed by the established histopathological criteria and by the Ki‐67 index. Benign NMSTs were also studied. To investigate any possible influence of immunosuppression in the expression of E‐cadherin and catenins, the study compared tumours obtained from renal transplant recipients (RTRs) and immunocompetent patients. Immunoperoxidase staining of E‐cadherin and α‐, β‐, and γ‐catenins was performed in 42 squamous cell carcinomas (SCCs) (26 from RTRs and 16 from non‐RTRs), 30 lesions of Bowen's disease (11 from RTRs and 19 from non‐RTRs), 11 atypical squamoproliferative lesions from RTRs, 19 actinic keratoses (9 from RTRs and 10 from non‐RTRs), and 20 viral warts from RTRs. The findings of this study were as follows. Firstly, the probability of abnormal expression of E‐cadherin and α‐, β‐, and γ‐catenins increased from benign to premalignant and malignant NMSTs (p<0.001 for all). Secondly, there was agreement in abnormal expression between most of the molecules measured in malignant and premalignant NMSTs (p<0.05). Thirdly, in SCC, abnormal expression of E‐cadherin and catenins was more frequent in lesions with a high (>40%) Ki‐67 index than in those with a low Ki‐67 index (<40%) (p=0.003). However, only the abnormal expression of γ‐catenin increased with the grade of SCC differentiation (p=0.008). Fourthly, abnormal expression of γ‐catenin predicted a high proliferation index (Ki‐67 index 40%) in NMSTs (p<0.01, OR=6.19). Finally, there was no difference in the abnormal expression of E‐cadherin and catenins between NMSTs from immunosuppressed and immunocompetent patients. Thus, abnormal expression of the E‐cadherin/catenin complex was quite common in SCC and Bowen's disease and also in a proportion of intraepithelial dysplastic lesions, such as atypical squamoproliferative lesions and actinic keratosis, suggesting that these changes may be early indicators of the neoplastic process. Abnormal expression of γ‐catenin was the sole predictor of high proliferation in NMST and was also correlated with the tumour grade, suggesting a possible important role for γ‐catenin in tumourigenesis. Copyright © 2001 John Wiley & Sons, Ltd.
Glomerulo‐tubular junction stenosis as a factor contributing to glomerular obsolescence in IgA nephropathy
Authors: Sato Mitsuhiro , Hotta Osamu , Taguma Yoshio 
Published: October 2002

AbstractPeriglomerular fibrosis (PF) is an interstitial injury observed in various renal diseases. It is speculated that this lesion, by occluding the glomerulo‐tubular junction (GTJ) and causing atubular glomeruli, may result functionally in a reduction of the glomerular filtration rate (GFR) and may be a factor contributing to the progression of renal disease. In the present study, 340 renal biopsy specimens were analysed to determine whether or not there was nephron injury derived from such a mechanism, as well as direct glomerular injury, in IgA nephropathy (IgAN). The patients were divided into five groups according to the degree of glomerular sclerosis. The average age was lower in groups with milder sclerosis and serum creatinine (Cr) was elevated in groups with more severe sclerosis. Because the GTJ was assumed to disappear when an atubular glomerulus was formed, the ratio of the number of glomeruli with discernible GTJ to the total number of glomeruli was evaluated. As glomerular sclerosis progressed, discernible GTJ reduced significantly (p<0.001) and the degree of PF increased significantly (p<0.05). By serial section study in cases with pronounced PF, transitions between the stages of stenosis of the GTJ and atubular glomeruli were observed. It is speculated that the occlusion of the GTJ eventually hyalinizes the glomerulus; in such cases, glomerular obsolescence of the collapse type might be formed. On the other hand, obsolescence of the mesangial proliferative type might be formed in the hyalinization derived from direct glomerular injury. In this context, glomerular obsolescence of the collapse type was observed more frequently and was accompanied by more increased PF than obsolescence of the mesangial proliferative type (p<0.001). These results suggest that in addition to direct glomerular injury, nephron injury derived from interstitial damage of this type plays an important contributory role in the progression of IgAN. Copyright © 2002 John Wiley & Sons, Ltd.
Expression of 4C8 antigen, a novel transendothelial migration‐associated molecule on activated T lymphocytes, in inflammatory bowel disease
Authors: Oshitani Nobuhide , Hato Fumihiko , Kitagawa Seiichi , Masuyama Junichi , Higuchi Kazuhide , Matsumoto Takayuki , Arakawa Tetsuo 
Published: October 2002

AbstractRecruitment of peripheral leukocytes to intestine is an essential process for intestinal inflammation. This study examined the localization of a novel molecule, 4C8 antigen, in inflammatory bowel disease; this molecule is involved in the transendothelial migration of T lymphocytes. Surgical specimens of human intestine were obtained from nine patients with ulcerative colitis, 13 with Crohn's disease, and eight controls. Immunohistological staining was performed using antibodies against 4C8 antigen, and CD3, CD4, CD8, CD20, CD68, CD45RA, CD45RO, CD11a, and CD62 (E‐ and P‐selectin) by the peroxidase method. Immunological double staining was subsequently performed for the same specimens stained with anti‐4C8 antibody using the alkaline phosphatase method. In normal controls, 4C8‐positive cells were mainly found in lamina propria. 4C8‐positive cells were increased in lamina propria and submucosa of specimens with Crohn's disease. Accumulation of 4C8‐positive cells surrounding CD62‐positive vessels was found in the submucosa of specimens with inflammatory bowel disease, but not in controls. Immunohistological double staining revealed that the major subsets of 4C8‐positive cells were positive for CD3, CD4, CD45RO, and CD11a. 4C8‐positive cells in human intestine belong to the subset of helper/inducer memory T cells newly recruited from the peripheral pool. Inhibition of the 4C8‐ligand system could have potentially uses in the treatment of inflammatory bowel disease. Copyright © 2002 John Wiley & Sons, Ltd.
An increase in cost‐effectiveness of first trimester maternal screening programmes for fetal chromosome anomalies is obtained by contingent testing
Authors: Christiansen Michael , Olesen Larsen Severin 
Published: October 2002

AbstractWe assessed the discriminatory efficiency and cost‐effectiveness of a novel way of organising first trimester screening for Down syndrome (DS), contingent testing, where a serological test (PAPP‐A and β‐hCG: the double test) is made in early first trimester and followed by nuchal translucency testing (NT) only in women with an intermediate risk, e.g. <1:65 and >1:1000, and not in all women as in normal first trimester screening (NFTS). Using Monte Carlo simulation contingent testing had a detection rate (DR) of 78.9% and a false‐positive rate (FPR) of 4.0% for DS with 19.4% of women offered NT testing. The DR of NFTS was 85.5% and the FPR 4.4%. The decrease in NT screening was associated with an increase from 23% to 29% in the proportion of DS cases born. The cost of the contingent testing programme was £53 000 per DS case not born and £91 000 in NFTS. The number of aborted fetuses per DS case were 0.35 and 0.36, respectively. Thus, contingent testing is an organisation of first trimester screening where costs can be reduced with a marginal decrease in performance. Contingent testing is attractive in areas where NT screening is the bottleneck preventing the introduction of first trimester screening. Copyright © 2002 John Wiley & Sons, Ltd.