bluuebunny/crossref_metadata_2025_split huggingface dataset:
Automated refinement of conformal quadrilateral and hexahedral meshes
Authors: Tchon Ko‐Foa , Dompierre Julien , sCamarero Ricardo 
Published: March 2004

AbstractConformal refinement using a shrink and connect strategy, known as pillowing or buffer insertion, contracts and reconnects contiguous elements of an all‐quadrilateral or an all‐hexahedral mesh in order to locally increase vertex density without introducing hanging nodes or non‐cubical elements. Using layers as shrink sets, the present method automates the anisotropic refinement of such meshes according to a prescribed size map expressed as a Riemannian metric field. An anisotropic smoother further enhances vertex clustering to capture the features of the metric. Both two‐ and three‐dimensional test cases with analytic control metrics confirm the feasibility of the present approach and explore strategies to minimize the trade‐off between element shape quality and size conformity. Additional examples using discrete metric maps illustrate possible practical applications. Although local vertex removal and reconnection capabilities have yet to be developed, the present refinement method is a step towards an automated tool for conformal adaptation of all‐quadrilateral and all‐hexahedral meshes. Copyright © 2004 John Wiley & Sons, Ltd.
A fast collocation method for an inverse boundary value problem
Authors: Fang Weifu , Lu Mingying 
Published: March 2004

AbstractIn this paper, we present an implementation of a fast multiscale collocation method for boundary integral equations of the second kind, and its application to solving an inverse boundary value problem of recovering a coefficient function from a boundary measurement. We illustrate by numerical examples the insensitive nature of the map from the coefficient to measurement, and design and test a Gauss–Newton iteration algorithm for obtaining the best estimate of the unknown coefficient from the given measurement based on a least‐squares formulation. Copyright © 2004 John Wiley & Sons, Ltd.
Modelling error estimation and adaptive modelling of perforated materials
Authors: Vemaganti Kumar 
Published: March 2004

AbstractTraditional computational analyses of perforated materials, much like traditional computational analyses of heterogeneous materials, involve the use of homogenization, using either the assumption of periodicity or the assumption of statistical homogeneity. Recently, Oden and Vemaganti (Journal of Computational Physics 2000; 164:22–47) have proposed a goal‐oriented approach to the modelling of heterogeneous multi‐phase linearly elastic materials that does not rely on such idealized situations. In this approach, the mathematical model is adaptively selected based on estimates of the modelling error: the error resulting from the smearing out of rapidly varying material moduli. The approach is said to be goal‐oriented because the adaptive process is driven by local estimates of modelling error in quantities of interest to the analyst, instead of global estimates. We extend this goal‐oriented adaptive approach to the case of perforated domains composed of linearly elastic materials. Toward this end, new global and local bounds on modelling errors resulting from homogenization of perforated materials are developed. A representative numerical experiment is presented. Copyright © 2004 John Wiley & Sons, Ltd.
On a method for vibration analysis of viscous compressible fluid–structure systems
Authors: Mokeyev Vladimir V. 
Published: March 2004

AbstractA fluid–structure interaction formulation for viscous compressible fluid is under consideration. The formulation involves finite element approximation of linearized Navier–Stokes equations and response determination made by means of modal superposition analysis. Standard and simplified schemes of the viscous compressible fluid–structure interaction problem solution are developed. The schemes are based on the frequency condensation method of a complex eigenvalue problem solving. Free and forced oscillations of several fluid–structure systems are studied by the standard and simplified schemes. The analysis of the results obtained shows that the simplified scheme provides a saving of 90% of the computational time required to define oscillation of the structure with viscous compressible fluid in the lowest frequency range. A certain influence of the fluid viscosity on the transient response of the fluid–structure system is also demonstrated. Copyright © 2004 John Wiley & Sons, Ltd.
Non‐linear analysis of the thermo‐electro‐mechanical behaviour of shear deformable FGM plates with piezoelectric actuators
Authors: Yang J. , Kitipornchai S. , Liew K. M. 
Published: March 2004

AbstractThis paper investigates the non‐linear bending behaviour of functionally graded plates that are bonded with piezoelectric actuator layers and subjected to transverse loads and a temperature gradient based on Reddy's higher‐order shear deformation plate theory.The von Karman‐type geometric non‐linearity, piezoelectric and thermal effects are included in mathematical formulations. The temperature change is due to a steady‐state heat conduction through the plate thickness. The material properties are assumed to be graded in the thickness direction according to a power‐law distribution in terms of the volume fractions of the constituents. The plate is clamped at opposite edges, while the remaining edges can be free, simply supported or clamped. Differential quadrature approximation in the X‐axis is employed to convert the partial differential governing equations and the associated boundary conditions into a set of ordinary differential equations. By choosing the appropriate functions as the displacement and stress functions on each nodal line and then applying the Galerkin procedure, a system of non‐linear algebraic equations is obtained, from which the non‐linear bending response of the plate is determined through a Picard iteration scheme. Numerical results for zirconia/aluminium rectangular plates are given in dimensionless graphical form. The effects of the applied actuator voltage, the volume fraction exponent, the temperature gradient, as well as the characteristics of the boundary conditions are also studied in detail. Copyright © 2004 John Wiley & Sons, Ltd.
A numerical methodology to assess the quality of the design velocity field computation methods in shape sensitivity analysis
Authors: Ródenas J. J. , Fuenmayor F. J. , Tarancón J.E. 
Published: March 2004

AbstractThe velocity field in shape sensitivity analysis is not uniquely defined although it must meet numerous theoretical and practical criteria. These practical criteria can be used to compare the existing velocity field computation methods which meet the theoretical criteria, but only in qualitative terms.When the FEM is used in design sensitivity analysis (DSA), due to the FE discretization error, the DSA errors will depend on the design velocity field considered. This paper presents a numerical methodology for quality evaluation of design velocity field computation methods in quantitative terms based on the analysis of the DSA discretization error.The sensitivity of the squared energy norm (χm = ∂∥u∥2/∂am, am being a design variable) has been taken as the magnitude to measure the error of the DSA. For h‐refinements, the squared error in energy norm (∥e(u) ∥2) and the error in χm(e(χm)) are theoretically related by a constant which is independent of the refinement degree of the FE model. The quality of the design velocity field computation methods can therefore be assessed in terms of the stability of e(χm) /∥e(u) ∥2 in sequences of meshes. An example of the use of this methodology, where six design velocity field computation methods are compared, is presented. Copyright © 2004 John Wiley & Sons, Ltd.
Numerical modelling of impulse wave generated by fast landslides
Authors: Quecedo M. , Pastor M. , Herreros M. I. 
Published: March 2004

AbstractThe damage caused by impulse waves generated in water bodies by fast landslides can be very high in terms of human lives and economic losses. The complex phenomena taking place in this highly unsteady process are difficult to model because three interacting phases: air, water and soil are involved. Solutions currently available are based on either closed form equations supported experimentally or the depth integrated Navier–Stokes equations. The latter, although of more general applicability, requires knowledge of the evolution of the bathimetry and slide drag forces and their applicability may be restricted by the steep slopes existing in most real cases.To avoid these limitations, the authors propose the solution of the full Navier–Stokes equations, using indicator functions to assign the material properties to each spatial point in the domain. The method performance is illustrated by comparison against the experimental results obtained in a physical model of an actual case. Copyright © 2004 John Wiley & Sons, Ltd.
Which are the important modes of a subsystem?
Authors: Givoli Dan , Barbone Paul E. , Patlashenko Igor 
Published: March 2004

AbstractA linearly behaving vibrational substructure (or more generally a linear dynamic subsystem) attached to a main structure (or a main dynamic system) is considered. After discretization, the substructure is represented by a finite, typically large, number of degrees of freedom,Nsand hence also byNSeigenmodes. In order to reduce the computational effort, it is common to apply ‘modal reduction’ to the subsystem such that onlyNrmodes out of the total number ofNSmodes are retained, whereNr≪Ns. The following question then arises: ‘WhichNrmodes should be retained?’ In structural dynamics, it is traditional to retain those modes associated with the lowest frequencies. In this paper, the question is answered by solving an appropriate optimization problem. The most important modes of the subsystem are shown to be those whose coupling matrices, which are defined in a particular way, have the highest norm. This leads to a simple and effective algorithm for optimal modal reduction. The new criterion for ‘modal importance’ is explained both mathematically and physically, and is demonstrated by numerical examples. Copyright © 2004 John Wiley & Sons, Ltd.
Shear loaded interface crack under the influence of friction: a finite difference solution
Authors: Dorogoy Avraham , Banks‐Sills Leslie 
Published: March 2004

AbstractFormulation of the elastic two‐dimensional problem of contact with friction is presented. Two‐dimensional equilibrium equations and boundary conditions in an orthogonal curvilinear co‐ordinate system are written explicitly. The above formulation is solved with the aid of the finite difference technique. An iterative algorithm which does not require load increments is employed for solving interface fracture problems with contact and friction subjected to a monotonically increasing load. The J‐integral is extended for problems in which there is friction along the crack faces. Stress intensity factors are calculated by means of the J‐integral, as well as an asymptotic expansion of the tangential shift. Two problems are analysed: (1) a crack in homogeneous material in the presence of friction involving stationary contact; and (2) an interface crack in the presence of friction involving receding contact. Results are compared to those found by analytical and semi‐analytical methods which are presented in the literature, as well as to those obtained by means of the finite element method. The accuracy of the results establishes the reliability of the finite difference analysis, as well as the post‐processors. In addition, a problem involving stick conditions is considered. It is observed that with increasing friction, the normal gaps and tangential shifts decrease. The size of the contact zone increases and values of the stress intensity factor decrease. Copyright © 2004 John Wiley & Sons, Ltd.
Finite element response sensitivity analysis using force‐based frame models
Authors: Conte J. P. , Barbato M. , Spacone E. 
Published: March 2004

AbstractThis paper presents a method to compute consistent response sensitivities of force‐based finite element models of structural frame systems to both material constitutive and discrete loading parameters. It has been shown that force‐based frame elements are superior to classical displacement‐based elements in the sense that they enable, at no significant additional costs, a drastic reduction in the number of elements required for a given level of accuracy in the computed response of the finite element model. This advantage of force‐based elements is of even more interest in structural reliability analysis, which requires accurate and efficient computation of structural response and structural response sensitivities. This paper focuses on material non‐linearities in the context of both static and dynamic response analysis. The formulation presented herein assumes the use of a general‐purpose non‐linear finite element analysis program based on the direct stiffness method. It is based on the general so‐called direct differentiation method (DDM) for computing response sensitivities. The complete analytical formulation is presented at the element level and details are provided about its implementation in a general‐purpose finite element analysis program. The new formulation and its implementation are validated through some application examples, in which analytical response sensitivities are compared with their counterparts obtained using forward finite difference (FFD) analysis. The force‐based finite element methodology augmented with the developed procedure for analytical response sensitivity computation offers a powerful general tool for structural response sensitivity analysis. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis, UV photo‐polymerization and degradation study of PEG containing polyester polyol acrylates
Authors: Nivasu Venkata M. , Yarapathi Reddy V. , Tammishetti Shekharam 
Published: March 2004

AbstractSuccinic acid‐co‐polyethylene glycol polyester polyol acrylates, capable of in situ polymerization with UV radiation, were synthesized and characterized. Effect of structural changes such as internal branching, external crosslinking on their polymerization and degradation properties were investigated. Use of external crosslinkers reduced the polymerizability of the polymer. Lipases of different origins expedited the degradation to different extents and lipase isolated from porcine pancreas appeared to be more efficient than lipases from other sources. Copyright © 2004 John Wiley & Sons, Ltd.
Cellulose acetate and polyethersulfone blend ultrafiltration membranes. Part I: Preparation and characterizations
Authors: Mahendran Rajagopalan , Malaisamy Ramamoorthy , Mohan Doraiswamy Raju 
Published: March 2004

AbstractThe overall objective of this investigation is to achieve high‐performance membranes with respect to flux and rejection characteristics, with an interplay of blending polymers having desired qualities. Thus, cellulose diacetate and polyethersulfone as candidate materials, in the presence of polyethylene glycol 600 as a pore forming agent, were blended in 100/0, 95/5, 90/10, 85/15, 80,20 and 75/25% compositions using N,N′‐dimethylformamide as solvent and membranes were prepared by the phase inversion technique. Polymer blend composition, additive concentration, and casting and gelation conditions were standardized for the preparation of asymmetric membranes with various pore statistics and morphology. These blend membranes were characterized for compaction in ultrafiltration experiments at 414 kPa pressure in order to attain steady state flux and is reached within 4–5 hr. The pure water flux was measured at 345 kPa pressure and is determined largely by the composition of polyethersulfone and additive concentration. The flux was found to reach the highest values of 66.5 and 275 1/(cm2 hr) at 0 and 10 wt% additive concentrations respectively, at 25% SPS content of the blend. Membrane hydraulic resistance derived by measuring water flux at various transmembrane pressure and by using an algorithm was found to be inversely proportional to pure water flux. Water content is estimated by simple drying and weighing procedures and found proportional to pure water flux for all the membranes. The molecular weight cut‐offs (MWCOs) of different membranes were determined with proteins of different molecular weights and found to vary from 20–69 kDa (globular proteins) depending on the PEG and SPS content in the casting dope. Skin surface porosity of the membranes were analyzed by scanning the frozen membrane samples using scanning electron microscopy (SEM) at different magnifications. The surface porosity is in direct correlation to the MWCO derived from solute retention experiments. Copyright © 2004 John Wiley & Sons, Ltd.
Controlled/‘living’ radical polymerization of methyl methacrylate with p‐TsCl/CuBr/BPY initiating system under microwave irradiation
Authors: Chen Gaojian , Zhu Xiulin , Cheng Zhenping , Lu Jianmei , Chen Jianying 
Published: March 2004

AbstractAtom‐transfer radical polymerization of methyl methacrylate under microwave irradiation (MI) using p‐TsCl/CuBr/BPY as the initiating system was successfully carried out. The polymerization of methyl methacrylate under MI shows linear first‐order rate plots, a linear increase in the number‐average molecular weight with conversion and low polydispersities, 1.1 < Mw/Mn < 1.3. The influence of polymerization time, temperature and monomer/initiator ratio on the conversion, molecular weight and polymer distribution were studied using the MI process, and compared with that obtained by the corresponding conventional heating (CH) process. The MI process not only increases the rate of polymerization, but also narrows the polydispersity index of polymers. The apparent rate constant, $k_{\rm p}^{\rm app}$, under MI is 6–8 times higher than that under CH with an identical initiating system and polymerization temperature. The effect of MI on the stereoregularity and Tg of PMMA were investigated by 13C NMR spectroscopy and DSC, respectively. Copyright © 2004 Society of Chemical Industry
Synthesis and polymerization of a novel oxirane bearing a cyclic acetal of salicylaldehyde chain moiety
Authors: Maślińska‐Solich Jolanta , Sowa Mirosław , Neugebauer Dorota 
Published: March 2004

AbstractThe novel compound 2(1,3‐dioxolan‐2‐yl)phenoxymethyloxirane was synthesized and anionically polymerized with potassium hydroxide, potassium hydride and potassium tert‐butoxide. Polymers were characterized by 1H and 13C NMR spectroscopy, size exclusion chromatography and electrospray mass spectrometry. Copyright © 2004 Society of Chemical Industry
Physical properties and β‐phase increment of AgNO3‐filled poly(vinylidene fluoride) films
Authors: Tawansi A , Oraby AH , Badr SI , Elashmawi IS 
Published: March 2004

AbstractX‐ray diffraction (XRD), infrared (IR) transmition and optical absorption (OA) spectra, differential thermal analysis (DTA), dc electrical resistivity (ρ), magnetic susceptibility (χ) and electron spin resonance (ESR) of AgNO3‐filled poly(vinylidene fluoride) (PVDF) films, were measured over the filler mass fraction range 0.001 ≤ W ≤ 15%. XRD and IR analysis evidenced the increase of α‐ and β‐PVDF crystalline phases due to the AgNO3 filler. The maximum crystallinity increment was found at W = 0.5%. Three endothermic peaks were detected by DTA, and were attributed subsequently to: the first order para–para‐electric phase transition, the first‐order ferro‐para‐electric phase transition and the melting. The melting peak was used to calculate the order of reaction and the activation energy of melting. The observed OA peaks and/or plateau were attributed to the charge‐transfer complex formed mainly by the AgNO3 filler. This assumption was supported by the diamagnetic susceptibility detected for the present system. The temperature dependence of ρ was explored according to a previously proposed one‐dimensional interpolaron‐hopping model. The hopping distance was formulated numerically as a function of temperature and filling level. The ESR findings were attributed to the roles of AgNO3 and dimethylformamide solvent in complex formation. Copyright © 2004 Society of Chemical Industry
Synthesis and physico‐chemical characterization of networks based on methacryloxypropyl‐grafted nano‐silica and methyl methacrylate
Authors: Mauger M , Dubault A , Halary JL 
Published: March 2004

AbstractModel hybrid materials were prepared by using a well‐known four‐step procedure, including (a) preparation of spherical silica particles of nanometre size and narrow size‐distribution, (b) grafting of 3‐methacryloxypropyl units (MOPGS) at the surface of the particles, (c) formation of stable dispersions of the grafted particles in methyl methacrylate (MMA), and (d) copolymerization of MMA and MOPGS, initiated by UV irradiation, and then completed by thermal reaction. Progressive changes in network architecture were obtained by changing the particle diameter, d, the volume fraction of filler, ϕ, the number of MOP units grafted per surface unit of silica particle, n, and the nature of the grafting agent bearing the MOP unit. Materials of good transparency were obtained, even at high volume fractions of filler. This feature is the result of an excellent dispersion of the particles within the polymer matrix, as confirmed by transmission electron microscopy and atomic force microscopy. Swelling experiments were carried out to define the conditions, and function of d, ϕ, and n for preparing networks, in which the sol phase is almost lacking. The results were rationalized by defining a new parameter: ξD = 6ϕn/(1–ϕ)d. DSC plots were used as a first characterization of the materials. The presence of filler was accompanied by a slight increase in the glass transition onset temperature, T, and a marked broadening of the transition range, ΔTg. Both T and ΔTg were shown to increase linearly as a function of ξD. Copyright © 2004 Society of Chemical Industry
In situ formed processable polypyrrole nanoparticle/amphiphilic elastomer composites and their properties
Authors: Lee Eun Seong , Park Jae Hyung , Wallace Gordon G , Bae You Han 
Published: March 2004

AbstractA lack of processability is one of the major problems associated with practical applications of conductive and electroactive polypyrrole. Polypyrrole nanoparticles that were sterically stabilized in a solution and supported by an amphiphilic elastomer of poly(ethylene glycol) (Mn 2000 g mol−1)/poly(tetramethylene ether glycol) (Mn 2000 g mol−1) multiblock copolymer, were investigated in terms of conductivity, processability and mechanical properties. The hydrogel, amphiphilic elastomer was soluble in various organic solvents such as methanol, acetone and ethanol, but only swellable in water. The synthetic conditions of polypyrrole nanoparticles in the presence of the multiblock copolymer were optimized. The conductivity of polypyrrole film formed from the nanoparticle suspension was measured with the van der Pauw four‐probe method and reached as high as 3.0 ± 0.2 S cm−1. The film also showed elastomeric properties, which were influenced by the amount of multiblock copolymer added during nanoparticle synthesis. Copyright © 2004 Society of Chemical Industry