bluuebunny/crossref_metadata_2025_split huggingface dataset:
The extended finite element method (XFEM) for solidification problems
Authors: Chessa Jack , Smolinski Patrick , Belytschko Ted 
Published: October 2002

AbstractAn enriched finite element method for the multi‐dimensional Stefan problems is presented. In this method the standard finite element basis is enriched with a discontinuity in the derivative of the temperature normal to the interface. The approximation can then represent the phase interface and the associated discontinuity in the temperature gradient within an element. The phase interface can be evolved without re‐meshing or the use of artificial heat capacity techniques. The interface is described by a level set function that is updated by a stabilized finite element scheme. Several examples are solved by the proposed method to demonstrate the accuracy and robustness of the method. Copyright © 2001 John Wiley & Sons, Ltd.
A BEM‐based genetic algorithm for identification of polarization curves in cathodic protection systems
Authors: Miltiadou Panayiotis , Wrobel Luiz C. 
Published: October 2002

AbstractThe purpose of this work is to apply an inverse boundary element formulation in order to develop efficient algorithms for identification of polarization curves in a cathodic protection system. The problem is to minimize an objective function measuring the difference between observed and BEM‐predicted surface potentials. The numerical formulation is based on the application of genetic algorithms, which are robust search techniques emulating the natural process of evolution as a means of progressing towards an optimum solution.Examples of application are included in the paper for different types of polarization curves in finite and infinite electrolytes. The accuracy and efficiency of the numerical results are verified by comparison with standard conjugate gradient techniques. As a result of this research, the genetic algorithm approach is shown to be more robust, independent of the position of the sensors and of initial guesses, and will be further developed for three‐dimensional applications. Copyright © 2002 John Wiley & Sons, Ltd.
Flexible multibody dynamics based on a non‐linear Euler–Bernoulli kinematics
Authors: Boyer F. , Glandais N. , Khalil W. 
Published: October 2002

AbstractThis paper presents a new dynamic model of a multi‐beam system in the floating‐frame approach. The proposed solution can be used to model light flexible manipulators in fast dynamic conditions or large space structures undergoing moderate but finite deformations. The model is based on the non‐linear Euler–Bernoulli kinematics proposed in J. Mech. Mach. Theory 1999; 34:205. From this ‘exact’ kinematics we develop two approximate models. The first one is a linear model with respect to the deformation parameters, the second is a quadratic one. These two models capture the dynamic stiffening, and are consistent in the sense that they contain all the terms up to their maximal order with respect to the energy conservation. These two models are tested by simulation and compared with the standard floating frame model based on linear elastic kinematics and with the finite element codes of Reference [23] (Module d'analyse de mécanismes flexibles MECANO: Manuel d'utilisation. LTAS report, University of Liege, Belgium, 1988). Copyright © 2002 John Wiley & Sons, Ltd.
The partition of unity quadrature in meshless methods
Authors: Carpinteri A. , Ferro G. , Ventura G. 
Published: October 2002

AbstractIn dealing with mesh‐free formulations a major problem is connected to the computation of the quadratures appearing in the variational principle related to the differential boundary value problem. These integrals require, in the standard approach, the introduction of background quadrature subcells which somehow make these methods not ‘truly meshless’. In this paper a new general method for computing definite integrals over arbitrary bounded domains is proposed, and it is applied in particular to the evaluation of the discrete weak form of the equilibrium equations in the framework of an augmented Lagrangian element‐free formulation. The approach is based on splitting the integrals over the entire domain into the sum of integrals over weight function supports without modifying in any way the variational principle or requiring background quadrature cells. The accuracy and computational cost of the technique compared to standard Gauss subcells quadrature are discussed. Copyright © 2002 John Wiley & Sons, Ltd.
A consistent geometrically non‐linear approach for delamination
Authors: Wells G. N. , de Borst R. , Sluys L. J. 
Published: October 2002

AbstractA new model is presented for the simulation of delamination in laminated composite materials. A key feature is that the material structure and the finite element mesh are uncoupled. The displacement discontinuities that arise during the delamination process are described mathematically using discontinuous functions. This leads naturally to a set of coupled equations for the continuous and the discontinuous parts of the response. Discontinuities can pass through solid finite elements arbitrarily, with the displacement jump continuous across element boundaries. The performance of the model is demonstrated for several problems of delamination and geometric instability. Copyright © 2002 John Wiley & Sons, Ltd.
High‐order artificial boundary conditions for ideal axisymmetric irrotational flow around 3D obstacles
Authors: Zheng Chunxiong , Han Houde 
Published: October 2002

AbstractIn this paper the numerical solution for ideal irrotational incompressible flow around axisymmetric 3D obstacles is discussed with the artificial boundary method. By introducing an artificial boundary, we divide the exterior unbounded domain into a bounded part and an unbounded part. After setting up a proper artificial boundary condition, we get an approximate reduced problem defined on the bounded part. Both non‐local and local artificial boundary conditions are designed. Numerical experiment is also presented, and its result demonstrates the effectiveness of these artificial boundary conditions. Copyright © 2002 John Wiley & Sons, Ltd.
A hybrid extended finite element/level set method for modeling phase transformations
Authors: Ji H. , Chopp D. , Dolbow J. E. 
Published: October 2002

AbstractA hybrid numerical method for modelling the evolution of sharp phase interfaces on fixed grids is presented. We focus attention on two‐dimensional solidification problems, where the temperature field evolves according to classical heat conduction in two subdomains separated by a moving freezing front. The enrichment strategies of the eXtended Finite Element Method (X‐FEM) are employed to represent the jump in the temperature gradient that governs the velocity of the phase boundary. A new approach with the X‐FEM is suggested for this class of problems whereby the partition of unity is constructed with C1(Ω) polynomials and enriched with a C0(Ω) function. This approach leads to jumps in temperature gradient occurring only at the phase boundary, and is shown to significantly improve estimates for the front velocity. Temporal derivatives of the temperature field in the vicinity of the phase front are obtained with a projection that employs discontinuous enrichment. In conjunction with a finer finite difference grid, the Level Set method is used to represent the evolution of the phase interface. An iterative procedure is adopted to satisfy the constraints on the temperature field on the phase boundary. The robustness and utility of the method is demonstrated with several benchmark problems of phase transformation. Copyright © 2002 John Wiley & Sons, Ltd.
Numerical solution of thermal convection problems using the multidomain boundary element method
Authors: Florez W. F. , Power H. , Chejne F. 
Published: October 2002

AbstractThe multidomain dual reciprocity method (MD‐DRM) has been effectively applied to the solution of two‐dimensional thermal convection problems where the momentum and energy equations govern the motion of a viscous fluid. In the proposed boundary integral method the domain integrals are transformed into equivalent boundary integrals by the dual reciprocity approach applied in a subdomain basis. On each subregion or domain element the integral representation formulas for the velocity and temperature are applied and discretised using linear continuous boundary elements, and the equations from adjacent subregions are matched by additional continuity conditions. Some examples showing the accuracy, the efficiency and flexibility of the proposed method are presented. © 2002 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 18: 469–489, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/num.10016
Robust hyperplane synthesis for sliding mode control systems via sensitivity minimization
Authors: Tam Hei Ka , Ho Daniel W.C. , Lam James 
Published: October 2002

AbstractA robust hyperplane computation scheme for sliding mode control systems is proposed in this paper. A novel sensitivity index for the sliding eigenvalues with respect to perturbations in the system matrix, the input matrix and the hyperplane matrix is derived in the first instance. The robust hyperplane design problem is then formulated as an optimization task in which the proposed sensitivity index is accordingly minimized. Gradient information of the objective function is established which permits optimization to be proceeded effectively. A numerical example with statistical testing is employed to illustrate the design technique. Copyright © 2002 John Wiley & Sons, Ltd.
Review of polystyrene diffusion studies in latex particles by small‐angle neutron scattering
Authors: Kim S. D. , Klein A. , Sperling L. H. 
Published: October 2002

AbstractThis paper reviews small‐angle neutron scattering (SANS) and some results from direct nonradiative energy transfer (DET), for the observation of the diffusion coefficients of polystyrene chains at latex interfaces. To compare SANS with DET, doubly labeled polystyrene with deuterium and fluorescence groups were synthesized, showing that while SANS and DET produce comparable data in terms of diffusion coefficients, both results differ in detail, each having their own advantages. Chain confinement, ionic end groups, and short branch effects on interdiffusion were studied. Large polymer chains confined in small particles have non‐Gaussian shapes that store rubber elastic energy. Rapid, non‐diffusion relaxation is inhibited because the density would be required to become less than normal. Hence confinement effects on the diffusion rate are not significant. Using the DET method, ionic end‐groups were found to increase the early‐time apparent interdiffusion coefficients during film formation. The early‐time apparent diffusion coefficients of polystyrene with varying end‐groups were found to increase as follows:

The higher apparent diffusion coefficients of the chains with ionic groups are presumably due to a surface segregation of the end‐groups caused by the polar, aqueous environment during latex synthesis.The interdiffusion behavior of sulfite‐ended polystyrene (Mn ≅ 300 000 g/mol) with H‐ends, one sulfite end, and two sulfite ends were compared via SANS and DET. The diffusion coefficients of polystyrene with one or two sulfite end groups were five times and ten times lower than that of polystyrene, respectively. The ionic end group effects on the reduced diffusion coefficients are interpreted as the competition between enhancement by the surface segregation of end groups and reduction by end group aggregation. Noting that sulfate end groups diffused faster, while sulfite end groups diffused slower, the effect is complex, and not yet fully resolved.Diffusion coefficients of polystyrene with branches were studied by DET. Short branches work to decrease the Tg and hence increase the diffusion coefficients. However, after the experimental temperature, T, is converted to a normalized temperature, T‐Tg, the diffusion coefficients are found to be almost independent upon the number of branches and the length of branches. The branch length ranged from one‐carbon to 40 carbons. Side chains of entanglement molecular weight or longer may be required to significantly reduce the diffusion coefficient. Copyright © 2002 John Wiley & Sons, Ltd.
Investigation into the surface relief grating mechanism via XPS in new azobenzene based optical material
Authors: Sharma Lakshmi , Matsuoka Toshio , Kimura Tatsumi , Matsuda Hiro 
Published: October 2002

AbstractResearch into azobenzene and its compounds focuses on the molecules ability to cis‐trans isomerize, this photoisomerization enables surface relief gratings (SRGs) to be formed on the azobenzene functionalized polymer films. SRG allows information to be written and then erased, an essential requirement of most modern electrical products. The interest into SRG photofabrication is thus rapidly increasing and is emerging at the forefront of photonic and nanotechnology research. The surface relief grating mechanism, however, is not fully understood, a photoplasticization process is postulated, which is thought to occur via the azo‐chromophores photoisomerization, so encouraging polymer chain migration to the surface. In comparison, suggestions have shown the SRG process does not involve a change in the film surface profile but in the local refractive index. Currently, no research has yet established the surface relief grating mechanism, this paper sets out to determine the mechanism and investigate those theories already postulated by observing the thin film surfaces prior to and after SRG using X‐ray photoelectron spectroscopy (XPS). By identifying the surface components, greater insight and understanding of the SRG mechanism can be achieved.In this paper, poly(4‐(N‐(2‐methacryloyloxyethyl)‐N‐ethylamino)‐4′‐nitroazobenzene)90‐co‐(methylmethacrylate)10 50 : 50 PMMA blend was exposed to SRGs. Using XPS the surface composition was determined prior to and after SRG. Following SRG, the spectra for O 1s, N 1s and C 1s using XPS expressed a change in the components at the surface. This is most evident in the N 1s spectra, with PMMA not containing nitrogen, the N 1s becomes the determining factor. The nitrogen absence combined with a significant increase in the carbon and oxygen peak intensity concludes the azobenzene lies not on the surface but, in fact, within the bulk after SRG. The initial light irradiation process must be a consideration. However, on X‐ray analysis the sample showed the same spectra as the one prior to SRG. Copyright © 2002 John Wiley & Sons, Ltd.
Expression of synaptic vesicle protein 2 (SV2) in neuroendocrine tumours of the gastrointestinal tract and pancreas
Authors: Jakobsen Anne‐Marie , Ahlman Håkan , Wängberg Bo , Kölby Lars , Bengtsson Malin , Nilsson Ola 
Published: October 2002

AbstractIdentification of neuroendocrine differentiation in tumours has important implications for prognosis and therapy. The aim of the present study was to evaluate monoclonal antibodies against synaptic vesicle protein 2 (SV2) as histopathological markers for neuroendocrine differentiation intumours of the gastroinestinal tract and pancreas. Paraffin blocks from 211 gastrointestinal tumours were examined by immunocytochemistry, using a monoclonal antibody against SV2. Virtually all endocrine tumours of the gastrointestinal tract (11/11 gastric, 53/53 ileal, 16/21 appendiceal, and 22/22 rectal) and pancreas (24/24) were positively labelled. SV2 labelling was also demonstrated in gastrointestinal pacemaker cell tumours (8/8), while adenocarcinomas of the gastrointestinal tract and pancreas were negative, with the exception of occasional adenocarcinomas demonstrating weak SV2 labelling (stomach 1/22, rectum 1/29, and pancreas 0/21). Western blotting of tumour biopsies confirmed expression of SV2 in endocrine tumours of the gastrointestinal tract and pancreas. No relationship was observed between SV2 expression in tumours and hormone production or malignant potential. In conclusion, SV2 is expressed in neuroendocrine tumours of the gastrointestinal tract and pancreas, but not in non‐endocrine tumours. The SV2 monoclonal antibody can therefore be used as a general marker for neuroendocrine differentiation in gastrointestinal and pancreatic tumours. Copyright © 2001 John Wiley & Sons, Ltd.
Cyclooxygenase‐2 expression during carcinogenesis in the human stomach
Authors: van Rees Bastiaan P. , Saukkonen Kirsi , Ristimäki Ari , Polkowski Wojciech , Tytgat Guido N. J. , Drillenburg Paul , Johan A. Offerhaus G. 
Published: October 2002

AbstractThe prolonged use of non‐steroidal anti‐inflammatory drugs (NSAIDs) has been associated with a reduced risk of gastric cancer. The best‐known target of these drugs is cyclooxygenase (COX); the COX‐2 isoform is frequently up‐regulated in gastric adenocarcinomas. Using the post‐gastrectomy stomach as a model, the expression of COX‐2 mRNA and protein has been investigated during tumour progression in the human stomach. COX‐2 expression was comparable in gastric stump carcinomas and conventional gastric carcinomas and localized primarily to the cytoplasm of the neoplastic cells. COX‐2 mRNA was elevated in biopsies containing intestinal metaplasia, as determined by reverse transcriptase polymerase chain reaction (RT‐PCR). COX‐2 immunopositivity became more frequent during progression from reactive epithelium to high‐grade dysplasia, both in the epithelial and in the stromal cell compartment. Co‐localization of COX‐2‐positive stromal cells was seen with CD68, α‐smooth muscle actin (α‐SMA), vimentin, and HLA‐DR, but an as yet unidentified subpopulation of stromal cells remained. Co‐localization with the macrophage marker CD68 was only observed in a minority of COX‐2‐positive cells. These data show that COX‐2 expression is a relatively early event during carcinogenesis in the stomach. COX‐2 expression increases during tumour progression in the stomach, suggesting a role for COX‐2 expression in gastric tumourigenesis. Copyright © 2001 John Wiley & Sons, Ltd.
VEGF and bFGF are highly expressed in intraluminal fibromyxoid lesions in bronchiolitis obliterans organizing pneumonia
Authors: Lappi‐Blanco Elisa , Soini Ylermi , Kinnula Vuokko , Pääkkö Paavo 
Published: October 2002

AbstractBronchiolitis obliterans organizing pneumonia (BOOP) and usual interstitial pneumonia (UIP) are fibrous pulmonary disorders in which new fibromyxoid connective tissue is formed in distal air spaces. In BOOP this tissue is susceptible to even complete reversal, but in UIP it participates in the remodelling of the interstitium. Our previous study showed that in BOOP this newly formed intraluminal tissue is more capillarized than in UIP. This paper studies the immunohistochemical expression of vascular endothelial growth factor (VEGF) and its receptors Flt‐1 and Flk‐1, and basic fibroblast growth factor (bFGF) in BOOP and UIP. It was hypothesized that there would be a difference in the expression of these angiogenic growth factors paralleling the difference in their capillarization. The results show that both VEGF and bFGF are widely expressed in BOOP and in UIP. It was shown with two different VEGF antibodies that its expression was more pronounced in the intraluminal fibromyxoid lesions in BOOP than in UIP (p<0.001 and 0.004, respectively). Similarly, bFGF also showed stronger espression in BOOP than in UIP (p<0.02) in these areas. The expression of Flt‐1 and Flk‐1 was in agreement with the expression of VEGF. It is concluded that the growth factors VEGF and bFGF may have an important role in the pathogenesis of BOOP and UIP; furthermore, their expression correlates with the angiogenic activity of the newly formed intraluminal fibromyxoid connective tissue in BOOP. Angiogenesis mediated by these growth factors may be one reason for the reversal of intraluminal fibromyxoid connective tissue in BOOP and for its good clinical outcome. Copyright © 2001 John Wiley & Sons, Ltd.
Multiple molecular alterations of FHIT in betel‐associated oral carcinoma
Authors: Chang Kuo‐Wei , Kao Shou‐Yen , Tzeng Reuo‐Jar , Liu Chung‐Ji , Cheng Ann‐Joy , Yang Shun‐Chun , Wong Yong‐Kie , Lin Shu‐Chun 
Published: October 2002

AbstractTo determine the alterations of the FHIT (fragile histidine triad) gene in oral squamous cell carcinoma (OSCC), this study examined mutation, promoter methylation, mRNA transcription, and protein expression of FHIT in OSCC associated mostly with the use of betel and/or tobacco. Analyses of the coding exons (exons 5–9) identified a deletion of one base in intron 4 in one tumour and a deletion of exon 7 in two tumours. Using bisulphite genomic sequencing, 28% of theinformative subjects exhibited promoter methylation. An aberrant FHIT transcript spanning from exon 3 to exon 10, which was verified by RT‐PCR analysis, was identified in 36% of the OSCC subjects, 50% of the oral pre‐invasive lesions, and 5% of the non‐cancerous match tissue.An abnormal immunohistochemical level of Fhit was detected in 41% of OSCC subjects. Astatistically significant association was found between aberrant transcription of the FHIT geneand an abnormal level of Fhit immunoreactivity. The results indicated that alteration ofFHIT is a frequent occurrence in OSCC and thus suggests that the aberrance in FHIT transcription could be an early event of oral carcinogenesis. Copyright © 2002 John Wiley & Sons, Ltd.
Does MSI‐low exist?
Authors: Tomlinson Ian , Halford Sarah , Aaltonen Lauri , Hawkins Nicholas , Ward Robyn 
Published: October 2002

AbstractMicrosatellite instability is a well‐recognised phenomenon. Ten to 15% of sporadic colorectal cancers with a high level of MSI form a well defined group with distinct clinicopathological features. The set of tumours with low level of microsatellite instability (MSI‐low), though widely referred to, is not a clearly defined group. The definitions of MSI‐low have varied among groups and between different studies from the same group. Some studies have found associations between the MSI‐L phenotype and molecular features, notably a higher frequency of K‐ras mutations, and, possibly, methylation of methylguanine methyltransferase. Two recent independent studies, however, showed respectively that 68% and 79%, non‐MSI‐H cancers showed some MSI and could therefore be classed nominally as MSI‐L. There was no evidence for a qualitatively discrete MSI‐L group, but quantitative differences in the level of MSI were found. Copyright © 2002 John Wiley & Sons, Ltd.