bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adaptive analysis of thin shells using facet elements
Authors: Hinton E. , Özakça M. , Rao N. V. R. 
Published: November 2005

AbstractAn adaptive mesh refinement (AMR) procedure is used in static thin shell analysis using triangular facet shell elements. The procedure described herein uses the h‐version of adaptive refinement based on an error estimate determined by using the best guess values of bending moments and membrane forces obtained from a previous solution. It includes the use of a relaxation factor to achieve better convergence. Some examples are presented to illustrate this method. The results obtained are compared with those of uniform mesh refinement (UMR).
Conjugate progector preconditioning for the solution of contact problems
Authors: Dostál Zdeněk 
Published: November 2005

AbstractWe present a new algorithm for numerical solution of contactproblems without friction. The method is based on enhancing conjugate projector preconditioning into the standard conjugate gradient method for the solution of quadratic programming problems with inequality constraints. We show that the algorithm is correct and discuss the efficiency of the algorithm. The relation of the algorithm to the domain decomposition methods is also explained. The paper is supplied with numerical experiment.
Grapplings with the simulation of non‐Newtonian flows in polymer processing
Authors: Shen Shan‐Fu 
Published: November 2005

AbstractIn computational mechanics, flow simulation of polymer processing not only must deal with exotic constitutive behaviour and complex geometry, but often faces the presence of moving free boundaries. The cavity‐filling of injection moulding, treated as a Stefan problem, could be better attacked, computationally, by a fixed‐domain approach after a Baiocchi transformation. For thermosetting materials, modelling the rheology and the chemical reaction needs the kinematics in the meniscus region behind the moving front. The fluid mechanics, however, touches on the unresolved question of the moving contact point, fundamental to wetting phenomena. Aspects of particular interest to polymer processing are reviewed. In spite of the imperfections, the simulation of the ASTM standard ‘spiral‐mould test’ for thermosets has recently proved promising as an inverse problem to characterize the rheology of a commercial fast‐reacting thermosetting material. The key was to match the simulation only to portions of the data that were least influenced by the uncertainties.
Numerical simulation of unsteady multiphase pipeline flow with virtual mass effect
Authors: Bournaski E. 
Published: November 2005

AbstractMultiphase solid–liquid pipeline flow with small quantities of free gas is treated in the paper. A 1‐D separated unsteady flow model with liquid and gas virtual mass effect is described. A stable numerical method for the model equations based on the characteristics method is developed. Some accurate iteration procedures at every grid point for the solution of the algebraic equations are shown. The wave speed for flow in a pipeline worked out on the basis of this theoretical model shows a good correspondence with experimental results for two‐ and three‐phase mixtures.
Fracture mechanics weight functions in three dimensions: Subtraction of fundamental fields
Authors: Bains R. , Aliabadi M. H. , Rooke D. P. 
Published: November 2005

AbstractA new procedure is presented for the determination of the fracture mechanics weight functions that are required for the evaluation of stress intensity factors in cracked solids. The procedure can be used with a standard three‐dimensional boundary element code. The weight functions are proportional to the displacements on the boundary of the solid when the only loading is a pair of self‐equilibrated point forces at the crack front. In previous work, the highly singular crack‐tip fields that this loading produces have been modelled by replacing the crack front by a cylindrical cavity with appropriate displacement boundary conditions on the cavity walls. It is shown here that results are dependent on the cavity radius and that convergence of the results cannot be guaranteed.An alternative procedure, based on the substraction of fundamental fields (SFF), is demonstrated herein. The high‐order singularities are removed from the field before the reduced problem is solved numerically using a standard boundary element method. Since the reduced problem is equivalent to an unloaded crack in a solìd subjected to boundary tractions, the usual quarter‐point displacement elements and quarter‐point traction singular elements can be used to improve the accuracy. Weight functions, so obtained, are used to evaluate stress intensity factors as a function of position on the crack front for a straight‐fronted crack in a rectangular bar subjected to various loadings. Both edge and central cracks are considered and the validity of the technique is demonstrated by comparing the results with previously published values.
Shear deformability of thin‐walled beams with arbitrary cross sections
Authors: Romano Giovanni , Rosati Luciano , Ferro Giuseppe 
Published: November 2005

AbstractFormulas for the computation of the shear deformability of thin‐walled prismatic beams can be found in the technical literature only in the special case of symmetric cross sections. In order to fill this gap a formulation of the flexural behaviour of thin‐walled beams taking into account transverse shear deflections is developed in the present paper. On this basis, the general expression of the shear centre location and the shear deformability tensor for open and closed sections of arbitrary shape are given and their properties discussed. In the case of polygonal, circular and arc‐shaped cross sections explicit formulas, which can be suitably implemented for automatic computations, are provided. For the sake of completeness, the expression of the stiffness tensor for prismatic beams, previously obtained by the first two authors in a co‐ordinate‐free version, is reported. Finally, a numerical example is carried out and comparisons with the results given by Cowper1 for symmetric cross sections are presented.
A method for direct evaluation of singular integral in direct boundary element method
Authors: Liao Heshan , Xu Zhixin 
Published: November 2005

AbstractA new method is presented for evaluating the Cauchy principal value integral and the free term in the three‐dimensional elastic boundary element method. This method expresses the singular integral as the sum of a weakly singular integral and an integrable Cauchy principal value integral. The former can be computed by means of the usual standard Gaussian quadrature after a transformation suggested by Lachat and Watson,10 who correctly limited its use only to weakly singular integral. The latter can be calculated by direct integration in the Cauchy principal value sense. This paper also points out some limitations in the use of triangle polar co‐ordinate suggested by Li et al.11 and later extended by Zhang and Xu.16 The general expression of the free term for a boundary point with arbitrary characteristic surface is also presented. Simple numerical examples which verify the efficiency and accuracy of the present method are given.
Seismic crack propagation analysis of concrete structures using boundary elements
Authors: Pekau O. A. , Batta V. 
Published: November 2005

AbstractThe time‐domain boundary element method is applied to study the propagation of discrete cracks under dynamic loadings. The principles of linear elastic fracture mechanics are employed to accurately represent the stress singularity in front of the crack tip. A fracture criterion suitable for brittle materials is employed to determine the time and direction of the propagating crack. Discrete crack closure under dynamic loadings is modelled and the response of a 2‐D cracked body is obtained by direct integration of the equations of motion. Results are presented for three test problems wherein the accuracy and usefulness of the proposed formulation is established through comparisons with available data. 'It is expected that this formulation can be used to study the seismic cracking of mass concrete structures such as gravity dams.
On a simple triangular reissner/mindlin plate element based on incompatible modes and discrete constraints
Authors: Batoz Jean‐Louis , Katili Irwan 
Published: November 2005

AbstractIn this paper the formulation of a new triangular element based on the Reissner/Mindlin plate theory is presented. The element has three nodes and three d.o.f. per node only. It is based on constant bending modes plus incompatible energy orthogonal higher order bending modes. The transverse shear effects are represented using the moment equilibrium and the constitutive equations. Discrete (collocation) shear constraints are considered on each side to relate the kinematical and the independent shear strains. The element has a proper rank, is completely locking free, passes all constant patch‐tests exactly. The detailed numerical evaluation shows that the element, called DST‐BK, is a robust and high‐performance element for thick and thin plates.
Projection methods in flexible multibody dynamics. Part I: Kinematics
Authors: Shabana A. A. , Hwang Y. L. , Wehage R. A. 
Published: November 2005

AbstractIn this paper a recursive projection method for the dynamic analysis of open‐loop mechanical systems that consist of a set of interconnected deformable bodies is presented. The configuration of each body in the system is identified using a coupled set of reference and elastic co‐ordinates. The absolute velocities and accelerations of leaf or child bodies in the open‐loop system are expressed in terms of the absolute velocities and accelerations of the parent bodies and the time derivatives of the relative co‐ordinates of the joints between the bodies. The dynamic differential equations of motion are developed for each link using the generalized Newton‐Euler equations. The relationship between the actual joint reactions and the generalized forces combined with the kinematic relationships and the generalized Newton‐Euler equations are used to develop a system of loosely coupled equations which has a sparse matrix structure. Using matrix partitioning and recursive projection techniques based on optimal block factorization an efficient solution for the system accelerations and joint reaction forces is obtained. This solution technique yields a much smaller operations count and can more effectively exploit vectorization and parallel processing. It also allows a systematic procedure for decoupling the joint and elastic accelerations.
Coupling finite elements and magnetic networks in magnetostatics
Authors: Philips Dirk Alexander 
Published: November 2005

AbstractIn this paper a new method for computing non‐linear magnetostatic fields is introduced, which allows the simultaneous coupling of a finite element structure with a magnetic network. Combining the advantages of both methods while avoiding their drawbacks, this coupling yields both an accurate and time‐efficient computation.The traditional method of the unknown mesh fluxes is applied for the solution of the magnetic network. The finite element solution, on the other hand, is based on a classical first‐order interpolation of the unknown vector potential. The coupling is established by a proper organization of the unknowns on the boundary common to the finite element and network regions. In this way, a single system of non‐linear equations is obtained.Moreover, it is shown that the coupled system of equations is equivalent to a single finite element system if generalized base functions are allowed. Consequently, various results from finite element theory may be applied. For instance, the matrix governing the iteratively linearized system of equations can directly be shown symmetrical and positive definite.Finally, the field inside a permanent magnet motor is calculated with the coupled method. Although the number of unknowns is dramatically reduced compared to a full FE calculation, the same level of accuracy is achieved. Hereby, the benefit of the coupled method is clearly proved.
Direct evaluation of singular boundary integrals in two‐dimensional biharmonic analysis
Authors: Camp Charles V. 
Published: November 2005

AbstractDevelopment of techniques to provide rapid and accurate evaluation of the integrations required in boundary element method (BEM) formulations are receiving more attention in the literature. In this work, a series of direct expressions for surface integrals, required for a boundary element solution of the non‐homogeneous biharmonic over a general two‐dimensional curvilinear surface, are presented. The concept of an isoparametric representation, usually applied to the variation of the field variables and the geometry, is extended to the parametric mapping of the curvilinear geometry. The result renders the typically complicated Jacobian function into a series of polynomial expressions based on the shape function set and several discrete Jacobian values. An application of the isoparametric approximation of the Jacobian for a quadratic element representation is developed. Implementation of this approximation significantly improves the accuracy of the boundary integral solution by eliminating error associated with numerical quadrature. Overall computational efficiency is improved by reducing the time necessary to calculate individual surface integrals and evaluate field variables at internal points. A numerical solution of the boundary integral equations of phenomena governed by the biharmonic equation is presented and compared with an exact analysis.
Tissue factor pathway inhibitor: structure, biology and involvement in disease
Authors: Lwaleed Bashir A , Bass Paul S 
Published: November 2005

AbstractTissue factor (TF)‐initiated coagulation plays a significant role in the pathophysiology of many diseases, including cancer and inflammation. Tissue factor pathway inhibitor (TFPI) is a plasma Kunitz‐type serine protease inhibitor, which modulates initiations of coagulation induced by TF. In a factor (F) Xa‐dependent feedback system, TFPI binds directly and inhibits the TF–FVII/FVIIa complex. Normally, TFPI exists in plasma both as a full‐length molecule and as variably carboxy‐terminal truncated forms. TFPI also circulates in complex with plasma lipoproteins. The levels and the dual inhibitor effect of TFPI on FXa and TF–FVII/FVIIa complex offers insight into the mechanisms of various pathological conditions triggered by TF. The use of selective pharmacological inhibitors has become an indispensable tool in experimental haemostasis and thrombosis research. In vivo administration of recombinant TFPI (rTFPI) in an experimental animal model prevents thrombosis (and re‐thrombosis after thrombolysis), reduces mortality from E. coli‐induced‐septic shock, prevents fibrin deposition on subendothelial human matrix and protects against disseminated intravascular coagulation (DIC). Thus, TFPI may play an important role in modulating TF‐induced thrombogenesis and it may also provide a unique therapeutic approach for prophylaxis and/or treatment of various diseases. In this review, we consider structural and biochemical aspects of the TFPI molecule and detail its inhibitory mechanisms and therapeutic implications in various disease conditions. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Synthesis and properties of sulfonated poly(arylene ether) containing tetraphenylmethane moieties for proton‐exchange membrane
Authors: Wang L. , Meng Y. Z. , Wang S. J. , Li X. H. , Xiao M. 
Published: November 2005

AbstractA novel sulfonated poly(arylene ether) containing tetraphenylmethane moieties was successfully synthesized by the sulfonation of a designed parent polymer using chlorosulfonic acid as sulfonation agent. The sulfonation took place only at the para position on the pendant phenyl rings because of the specially designed parent polymer. The sulfonation degree can be easily controlled by using different ratios of sulfonation agent to polymer repeating unit. The position and degree of sulfonation were characterized by 1H NMR and elemental analysis. The sulfonated polymers are highly soluble in common organic solvents, such as dimethylsulfoxide, N,N′‐dimethylacetamide, dimethylformamide, ethylene glycol monomethyl ether, and can be readily cast into tough and smooth films from solutions. The films showed good thermal and hydrolysis stabilities. Moreover, Fenton's reagent test revealed that the membrane exhibited superior stability to oxidation. The proton conductivities of the films were determined to be equivalent with Nafion® 117 under same conditions. The new polymer with sulfonic acid function on pendent phenyl rings can be potentially used as a proton‐exchange membrane for polymer electrolyte membrane fuel cell. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6411–6418, 2005
Synthesis and properties of poly(heteroaryleneethynylene)s consisting of electron‐accepting benzothiadiazole/quinoxaline units and electron‐donating alkyl thiophene units
Authors: Ashraf Raja Shahid , Klemm Elisabeth 
Published: November 2005

AbstractLow‐band‐gap π‐conjugated polymers composed of π‐excessive thiophene and π‐deficient benzothiadiazole and quinoxaline units were prepared in high yields by a polycondensation method using palladium cross‐coupling reactions of alkylthiophene diacetylenes, 4,7‐dibromo‐2,1,3‐benzothiadiazole, and 5,8‐dibromo‐2,3‐dipyridine‐2‐ylquinoxaline. The copolymers were characterized by NMR, IR, UV, gel permeation chromatography, and elemental analysis. High‐molecular‐weight (weight‐average molecular weight up to 82,600 g/mol), thermostable, soluble, and film‐forming materials were obtained. The polymers were photoluminescent in chloroform and showed metallic luster in the solid state. The absorption and emission in solution and in the solid state of the polymers revealed that the polymers generated a π‐stacked structure in the solid state, and the polymer molecules in the film were ordered. Thin films of poly[3‐dodecylthiophen‐2,5‐diylethynylene‐(benzo[1,2,5]thiadiazole‐4,7‐diyl)ethynylene] (P‐1), poly[3,4‐di dodecylthiophen‐2,5‐diylethynylene‐(benzo[1,2,5]thiadiazole‐4,7‐diyl)ethynylene] (P‐2), poly[3‐dodecylthiophene‐2,5‐diylethynylene‐(2,3‐dipyridine‐2‐ylquinoxaline‐5,8‐diyl)ethynylene] (P‐3), and poly[3,4‐didodecylthiophene‐2,5‐diylethynylene‐(2,3‐dipyridine‐2‐ylquinoxaline‐5,8‐diyl)‐ethynylene] (P‐4) exhibited an optical band gap of ∼1.85–2.08 eV. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels of the polymers were determined from electrochemical measurements. In the absorption and emission spectra of these polymers in chloroform/methanol mixtures, all the polymers revealed solvatochromic effects, which were related to the formation of aggregates, as confirmed by temperature‐dependence absorption investigations. The absorption spectra of P‐2 and P‐4 at different temperatures also revealed significant effects of the structure on the molecular interactions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6445–6454, 2005
Decohesion of a rigid punch from an elastic layer: Transition from “flaw sensitive” to “flaw insensitive” regime
Authors: Tang Tian , Hui Chung‐Yuen 
Published: November 2005

AbstractA cohesive zone model is used to study the pull‐off of a rigid flat cylindrical punch of radius c from an elastic layer of thickness h. The adhesion between the punch and the elastic layer is assumed to be sufficiently weak so that pull‐off occurs by the growth of a crack from the edge of contact. Our result shows that the pull‐off stress, when normalized by the interfacial strength σo, depends on a single dimensionless parameter χf = σc(1−v2) g(ξ)/2πEWad, where E and v are the Young's modulus and Poisson's ratio of the elastic layer, respectively, Wad is the work of adhesion, and g(ξ) is a known dimensionless function of ξ ≡ c/h. χf can be viewed as a generalized Tabor parameter. It characterizes the transition from a “brittle” or flaw sensitive failure regime to a “ductile” or flaw insensitive regime. The result in this work is used to generalize Maugis' theory of adhesive contact to the case where the elastic substrate is of finite thickness. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3628–3637, 2005
Studies on polyimide imidization in far‐infrared radiation
Authors: Lu Yun‐Hua , Zhan Mao‐Sheng 
Published: November 2005

AbstractIn this paper, the monomers 4,4′‐oxydiphthalic anhydride (ODPA), 3,3′,4,4′‐biphenyl dianhydride (BPDA), 3,4′‐oxidianiline (3,4′‐ODA), and 4,4′‐oxidianiline (4,4′‐ODA) were selected to synthesize polyimides (PI) or copolyimides (co‐PI) in N,N‐dimethyl acetamide (DMAc) by two‐step method. To control the PI molecular weight (MW), phthalic anhydride (PA) was used as the end‐capping reagent. The effect of far‐infrared radiation (FIR) on PI imidization was investigated by Fourier transform infrared spectroscopy (FTIR). Some factors affecting imidization process in FIR were discussed, including PI imidization time and temperature, molecular structure, designed number average molecular weight, crystalline, imidization procedure, film thickness, polyamide acid (PAA) solid content, and so forth. The PI imidization process in FIR will be affected by all these factors. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3621–3627, 2005
Identification of flavonoids using liquid chromatography with electrospray ionization and ion trap tandem mass spectrometry with an MS/MS library
Authors: Lee Jong Suk , Kim Dong Hyun , Liu Kwang‐Hyeon , Oh Tae Kwang , Lee Choong Hwan 
Published: November 2005

AbstractSearchable MS/MS spectra libraries, constructed using the results of liquid chromatography coupled with electrospray ionization (ESI) tandem mass spectrometry (LC/MS/MS) with data‐dependent acquisition on an ion trap mass spectrometer, are presented with regard to the identification and confirmation of a variety of closely related flavonoids in a set of biological samples. Flavonoids were found to exhibit a maximum amount of structurally specific MS/MS spectra at 45% of normalized collision energy on the instrument used, without wideband activation. These MS/MS spectra were then searched automatically against a 297‐substance MS/MS library that contains many previously acquired spectra of standard flavonoids. The possible applications of this powerful technique to biological samples are also discussed. Daidzein and genistein were identified through the MS/MS spectra library while searching through LC/MS/MS data for plant and microbial extracts. Moreover, these compounds proved completely distinguishable from other flavonoids of closely related structures in the MS/MS spectra library, using the NIST MS search program. The applicability of the library‐searchable spectra at low concentrations was demonstrated by successful identification of daidzein and genistein at 0.05 and 0.5 µg/mL, respectively. Copyright © 2005 John Wiley & Sons, Ltd.