bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coarsening by compatible relaxation
Authors: Livne O. E. 
Published: March 2004

AbstractA proper coarse variable set for algebraic multigrid (AMG) solvers can be constructed using compatible relaxation (CR). For a given coarse set, CR is a modified relaxation scheme that keeps the values of the coarse variables intact. Its convergence factor is a predictor of the potential AMG efficiency, similarly to the smoothing factor in geometric multigrid. A practical, CR‐based coarse set construction algorithm is presented. Numerical results for model problems are demonstrated. Copyright © 2004 John Wiley & Sons, Ltd.
An algebraic multigrid wave–ray algorithm to solve eigenvalue problems for the helmholtz operator
Authors: Livshits Irene 
Published: March 2004

AbstractHelmholtz equations with variable coefficients are known to be hard to solve both analytically and numerically. In this paper, we introduce a numerical multigrid solver for one‐dimensional Helmholtz eigenvalue problems with periodic potentials and solutions. The solvers employ wave–ray methodology suggested by Brandt, Livshits for Helmholtz equations with constant coefficients. The paper concludes with numerical experiments and the discussion of future efforts for solving two‐dimensional problems. Copyright © 2004 John Wiley & Sons, Ltd.
A fully implicit parallel algorithm for simulating the non‐linear electrical activity of the heart
Authors: Murillo Maria , Cai Xiao‐Chuan 
Published: March 2004

AbstractIn this paper, we study a fully implicit parallel Newton–Krylov–Schwarz method (NKS) for solving the bidomain equations describing the electrical excitation process of the heart. NKS has been used successfully for many non‐linear problems, but this is the first attempt to use this method for the bidomain model which consists of a system of time dependent partial differential equations of mixed type. Our experiments on parallel computers show that the method is scalable and robust with respect to many of the parameters in the bidomain model. In the outer layer of the algorithm, we use a non‐linearly implicit backward Euler method to discretize the time derivative, and the resulting systems of large sparse non‐linear equations are solved using an inexact Newton method. The Jacobian system required to solve in each Newton iteration is solved with a GMRES method preconditioned by a new component‐wise restricted additive Schwarz preconditioner. The efficiency and robustness of the overall method depend heavily on what preconditioner we use. By comparing several preconditioners, we found our new restricted additive Schwarz method offers the best performance. Our parallel software is developed using the PETSc package of Argonne National Laboratory. Numerical results obtained on an IBM SP will be reported. Copyright © 2004 John Wiley & Sons, Ltd.
Hierarchical hybrid grids: data structures and core algorithms for multigrid
Authors: Bergen Benjamin Karl , Hülsemann Frank 
Published: March 2004

AbstractFor many scientific and engineering applications, it is often desirable to use unstructured grids to represent complex geometries. Unfortunately, the data structures required to represent discretizations on such grids typically result in extremely inefficient performance on current high‐performance architectures. Here, we introduce a grid framework using patch‐wise, regular refinement that retains the flexibility of unstructured grids, while achieving performance comparable to that seen with purely structured grids. This approach leads to a grid hierarchy suitable for use with geometric multigrid methods, thus combining asymptotically optimal algorithms with extremely efficient data structures to obtain a powerful technique for large scale simulations. Copyright © 2004 John Wiley & Sons, Ltd.
Algebraic multigrid (AMG) for saddle point systems from meshfree discretizations
Authors: Leem K. H. , Oliveira S. , Stewart D. E. 
Published: March 2004

AbstractMeshfree discretizations construct approximate solutions to partial differential equation based on particles, not on meshes, so that it is well suited to solve the problems on irregular domains. Since the nodal basis property is not satisfied in meshfree discretizations, it is difficult to handle essential boundary conditions. In this paper, we employ the Lagrange multiplier approach to solve this problem, but this will result in an indefinite linear system of a saddle point type. We adapt a variation of the smoothed aggregation AMG method of Vaněk et al. to this saddle point system. We give numerical results showing that this method is practical and competitive with other methods with convergence rates that are ∼c/logN. Copyright © 2004 John Wiley & Sons, Ltd.
Viscoelastic behavior of polypropylene/nitrile rubber thermoplastic elastomer blends: Application of Kerner's models for reactively compatibilized and dynamically vulcanized systems
Authors: Bandyopadhyay G. G. , Bhagawan S. S. , Ninan K. N. , Thomas Sabu 
Published: March 2004

AbstractThe viscoelastic properties of binary blends of nitrile rubber (NBR) and isotactic polypropylene (PP) of different compositions have been calculated with mean‐field theories developed by Kerner. The phase morphology and geometry have been assumed, and experimental data for the component polymers over a wide temperature range have been used. Hashin's elastic–viscoelastic analogy principle is used in applying Kerner's theory of elastic systems for viscoelastic materials, namely, polymer blends. The two theoretical models used are the discrete particle model (which assumes one component as dispersed inclusions in the matrix of the other) and the polyaggregate model (in which no matrix phase but a cocontinuous structure of the two is postulated). A solution method for the coupled equations of the polyaggregate model, considering Poisson's ratio as a complex parameter, is deduced. The viscoelastic properties are determined in terms of the small‐strain dynamic storage modulus and loss tangent with a Rheovibron DDV viscoelastometer for the blends and the component polymers. Theoretical calculations are compared with the experimental small‐strain dynamic mechanical properties of the blends and their morphological characterizations. Predictions are also compared with the experimental mechanical properties of compatibilized and dynamically cured 70/30 PP/NBR blends. The results computed with the discrete particle model with PP as the matrix compare well with the experimental results for 30/70, 70/30, and 50/50 PP/NBR blends. For 70/30 and 50/50 blends, these predictions are supported by scanning electron microscopy (SEM) investigations. However, for 30/70 blends, the predictions are not in agreement with SEM results, which reveal a cocontinuous blend of the two. Predictions of the discrete particle model are poor with NBR as the matrix for all three volume fractions. A closer agreement of the predicted results for a 70/30 PP/NBR blend and the properties of a 1% maleic anhydride modified PP or 3% phenolic‐modified PP compatibilized 70/30 PP/NBR blend in the lower temperature zone has been observed. This may be explained by improved interfacial adhesion and stable phase morphology. A mixed‐cure dynamically vulcanized system gave a better agreement with the predictions with PP as the matrix than the peroxide, sulfur, and unvulcanized systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1417–1432, 2004
Thermodynamic analysis of the phase separation during the polymerization of a thermoset system into a thermoplastic matrix. II. Prediction of the phase composition and the volume fraction of the dispersed phase
Authors: Riccardi Carmen Cristina , Borrajo Julio , Meynie Laure , Fenouillot Françoise , Pascault Jean‐Pierre 
Published: March 2004

AbstractA thermodynamic simulation of the phase‐separation process of an off‐critical blend, based on a thermoplastic matrix with a reactive epoxy system undergoing polycondensation at a constant temperature, was performed. The model considered the composition dependence of the interaction parameter, χ(T,Φ2) (where T is the temperature and Φ2 is the volume fraction of polystyrene), along with the polydispersity of both polymers. For every level of conversion, the simulation provided the amount, composition, stoichiometric ratio, and conversion of each phase present. The accuracy of the model was proved by the good agreement between the experimental and predicted glass‐transition temperatures and heat capacity changes at the glass‐transition temperatures for both phases. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1361–1368, 2004
Thermodynamic analysis of the phase separation during the polymerization of a thermoset system into a thermoplastic matrix. I. Effect of the composition on the cloud‐point curves
Authors: Riccardi Carmen Cristina , Borrajo Julio , Meynie Laure , Fenouillot Françoise , Pascault Jean‐Pierre 
Published: March 2004

AbstractThe cloud‐point curves of polystyrene (PS) mixed with reactive epoxy monomers based on diglycidyl ether of bisphenol A with stoichiometric amounts of 4,4′‐methylenebis(2,6‐diethylaniline) were experimentally studied. A thermodynamic analysis of the phase‐separation process in these epoxy‐modified polymers was performed that considered the composition dependence of the interaction parameter, χ(T,Φ2) (where T is the temperature and Φ2 is the volume fraction of polystyrene), and the polydispersity of both polymers. In this analysis, χ(T,Φ2) was considered the product of two functions: one depending on the temperature [D(T)] and the other depending on the composition [B(Φ2)]. For mixtures without a reaction, the cloud‐point curves showed upper critical solution temperature behavior, and the dependence of χ(T,Φ2) on the composition was determined from the threshold point, that is, the maximum cloud‐point temperature. During the isothermal reactions of mixtures with different initial PS concentrations, the dependence of χ(T,Φ2) on the composition was determined under the assumption that, at each conversion level, the D(T) contribution to the χ(T,Φ2) value had to be constant independently of the composition. For these mixtures, it was demonstrated that the changes in the chemical structure produced by the epoxy–amine reaction reduced χ(T,Φ2). This effect was more important at lower volume fractions of PS. Nevertheless, the decrease in the absolute value of the entropic contribution to the free energy of mixing was the principal driving force behind the phase‐separation process. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1351–1360, 2004
Ionic conductivity and tensile properties of hydroxyethyl and hydroxypropyl chitosan membranes
Authors: Wan Ying , Creber Katherine A. M. , Peppley Brant , Tam Bui V. 
Published: March 2004

AbstractHydroxyethyl chitosan and hydroxypropyl chitosan were prepared through the reaction of alkali‐chitosan with 2‐chloroethanol and propylene epoxide, respectively. Fourier transform infrared and 13C NMR measurements were made to examine the substitution on the chitosan unit. According to a comparison of the peak areas between the modified chitosan and unmodified chitosan and the integration of peak areas of 1H NMR spectra, for both modified chitosans, the maximum degree of substitution was less than 25%. The ionic conductivity and mechanical properties of modified chitosan membranes were investigated. In comparison with the unmodified chitosan membrane, hydrated hydroxyethyl and hydroxypropyl chitosan membranes with a higher degree of substitution showed an increase in ionic conductivity of about one order of magnitude; moreover, the crystallinity of hydroxyethyl and hydroxypropyl chitosan membranes was remarkably reduced, and their swelling indices increased significantly. However, these modified membranes did not exhibit significant changes in their tensile strength and breaking elongation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1379–1397, 2004
Modeling of displacement damage in an ion‐beam‐modified perfluorosulfonate ionomer
Authors: Fekete Zoltan A. , Wilusz Eugene , Karasz Frank E. 
Published: March 2004

AbstractA Monte Carlo simulation has been used to model the effects of medium‐energy ion‐beam modification of Nafion. With typical ion energies of 100–200 keV, the treatment affects the outer 0.5–2‐μm surface layer. An equation has been developed for predicting the expected range of implantation as a function of the ion energy and atomic number. The expected range of displacement damage due to the ion beam can similarly be described over the whole parameter range of interest with a double logarithmic fit. A full characterization of the distributions with their first four statistical moments is also presented. The quantitative description of the profiles obtained is useful for the rational design of an ion‐beam treatment for the preparation of integrally skinned membranes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1343–1350, 2004
X‐ray photoelectron spectroscopy of miscible poly(methyl methacrylate)/poly(styrene‐co‐acrylonitrile) and immiscible poly(methyl methacrylate)/polyacrylonitrile polymer surfaces metallized by nickel
Authors: Bébin Philippe , Prud'homme Robert E. 
Published: March 2004

AbstractA miscible blend of poly(methyl methacrylate) and poly(styrene‐co‐acrylonitrile) and an immiscible blend of poly(methyl methacrylate) and polyacrylonitrile were metallized by nickel, and their surfaces were analyzed by X‐ray photoelectron spectroscopy. Before metallization, the heteroatom distribution at the polymer surface was very different in the miscible and immiscible blends. However, this distribution was modified during metallization, which was only possible via polymer‐bond breaking, leading to similar compositions at the two interfaces. Oxygen exhibited a better affinity with nickel than nitrogen, but nickel oxide and nickel nitride were both formed at the interface. Nickel nitride prevented the metal from diffusing into the substrate, playing the role of a barrier, thus driving the oxygen to the metal layer. Amorphous carbon was also detected at the interface as a new carbon species, but it did not have any significant influence on the changes induced in the distribution of heteroatoms at the polymer surfaces. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1408–1416, 2004
Rheological properties of solutions of general‐purpose poly(vinyl alcohol) in dimethyl sulfoxide
Authors: Lee Eun Jeoung , Kim Nam Hee , Dan Kyung Sik , Kim Byoung Chul 
Published: March 2004

AbstractThe characteristic rheological responses of solutions of atactic poly(vinyl alcohol) (PVA) in dimethyl sulfoxide were investigated in terms of the concentration and molecular weight. The syndiotactic dyad content and weight‐average molecular weight of PVA were 52% and 85,000–186,000, respectively. On a modified Cole–Cole plot, the solutions did not give a single master curve with a slope of 2 but gave various curves with slopes of less than 2. Furthermore, the slope slightly decreased with increasing concentration. The deviation from the master curve indicated that the solutions were rheologically heterogeneous, despite optical transparency. Among the PVA solutions, the 14 wt % solutions exhibited very unusual rheological behavior. The loss tangent changed with the shear rate and produced three distinct regions, which indicated a shear‐induced phase transition. With respect to Winter's view on gelation, the 14 wt % solutions underwent a double sol–gel transition as the shear rate increased over the frequency range of 0.05–500 rad/s. However, the molecular weight did not have such noticeable effects on the rheological behavior over the concentration range of 10–14 wt %. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1451–1456, 2004
Partial miscibility in a nylon‐6/nylon‐66 blend coalesced from their common α‐cyclodextrin inclusion complex
Authors: Wei Min , Shin I. Daniel , Urban Brad , Tonelli Alan E. 
Published: March 2004

AbstractWe successfully formed a series of inclusion complexes (ICs) between an α‐cyclodextrin (α‐CD) host and two kinds of guest polymers, nylon‐6 and nylon‐66. An attempt to achieve an intimate blend between nylon‐6 and nylon‐66 through the formation and dissociation of their common α‐CD IC was made. The formation of all nylon ICs was verified with wide‐angle X‐ray diffraction, differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) and cross‐polarized/magic‐angle‐spinning 13C NMR spectroscopy. The experimental results demonstrated that α‐CD could only host single nylon polymer chains in the IC channels, either nylon‐6 or nylon‐66 in their own complexes, and presumably either nylon in neighboring channels of their common IC. The IC‐coalesced blend of nylon‐6 and nylon‐66 was obtained after the removal of the host cyclodextrin from their common IC with dimethyl sulfoxide. The spectroscopic results (FTIR and 13C NMR) illustrated that there was a degree of intimate miscibility existing in the IC‐coalesced blend, but not in the solution‐cast physical blend, although X‐ray diffraction patterns showed that the crystal structure of the IC‐coalesced blend was similar to that of the physical blend. DSC thermal profiles suggested that nylon‐66 first formed crystals during coalescence and that the subsequent crystallization of nylon‐6 was greatly affected by the nylon‐66 crystallites because of the close proximity of the two components in portions of the coalesced blend. DSC observations also demonstrated that the melting of the coalesced blend did not lead to complete phase separation of the nylon‐6 and nylon‐66 components. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1369–1378, 2004
Scattering function for wormlike chains with finite thickness
Authors: Nakamura Yo , Norisuye Takashi 
Published: March 2004

AbstractThe particle scattering function P(k) is approximately evaluated for the Kratky–Porod wormlike chain with a circular cross section to examine the effect of chain diameter d on the scattering curve of k2P(k) versus k, the magnitude of the scattering vector, for stiff chains and also the applicability of the cross‐section plot of ln[kP(k)] versus k2 to them. In the evaluation, series expansions from the rod and coil limits up to the fifth‐order and third‐order deviations, respectively, are combined together. The major results or conclusions derived are as follows. First, the conventional equation, P(k) = P0(k) exp(−k2d2/16), for straight cylinders overestimates k2P(k) at relatively large values of k, whereas its alternative, P(k) = P0(k)[2J1(kd/2)/(kd/2)]2, is a good approximation to exact P(k) unless contour length L is shorter than 10d. Here, P0(k) denotes the scattering function for the chain contour, and J1(x) is the Bessel function of the first order. Second, as d is increased for a fixed value of L (relative to the Kuhn segment length), the k2P(k)–k curve lowers with a pronounced maximum, and the peak position shifts to a lower scattering angle. Third, if the chain is somewhat flexible, the cross‐section plot has an approximately linear region, with a slope fairly close to −d2/16 expected from the aforementioned conventional equation. This plot for rods appreciably bends down, and thus the experimental observation of an approximately linear relation (over a wide k range) implies that, in contrast to the prevailing notion, the polymer examined is not completely rigid but instead is somewhat flexible. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1398–1407, 2004
Bio‐based nanocomposites from functionalized plant oils and layered silicate
Authors: Lu Jue , Hong Chang K. , Wool Richard P. 
Published: March 2004

AbstractSome discovery work was done on the synthesis of clay nanocomposites based on renewable plant oils. Functionalized triglycerides, such as acrylated epoxidized soybean oil, maleinized acrylated epoxidized soybean oil, and soybean oil pentaerythritol maleates, combined with styrene were used as the polymer matrix. The miscibility of these monomers and clay organomodifier was assessed by solubility parameters. The formation of nanocomposites was confirmed by both X‐ray data and transmission electron microscopy. The morphology showed a mix of intercalated and partially exfoliated sheets. The flexural modulus increased 30% at only 4 vol % clay content, but there was no significant effect on flexural strength, glass‐transition temperature, and thermal stability. Property enhancement was related to the degree of exfoliation that depends on both the polarity and flexibility of the monomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1441–1450, 2004
Thermal behavior of metallodendrimers possessing bis(terpyridinyl)Ru(II) connectivity and different surface functionality
Authors: Hwang Seok‐Ho , Soo Yoo Kyung , Moorefield Charles N. , Lee Sang‐Won , Newkome George R. 
Published: March 2004

AbstractA series of metallodendrimers, assembled by means of bis(terpyridinyl)Ru(II) connectivity on poly(propylene imine) dendrimer scaffolds, with homogeneous or heterogeneous surfaces, were prepared. Differential scanning calorimetry and thermogravimetric analysis were used to determine their thermal behavior, glass‐transition temperatures, and the decomposition kinetics and temperatures; no synergy effects for these properties were observed for the heterogeneously surfaced constructs in contrast to the corresponding homogeneously coated materials, which exhibited different values depending on their surface functionalities. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1487–1495, 2004
Poly(ether ether ketone)/poly(aryl ether sulfone) blends: Melt rheological behavior
Authors: Nandan Bhanu , Kandpal L. D. , Mathur G. N. 
Published: March 2004

AbstractDynamic rheological measurements were carried out on blends of poly(ether ether ketone) (PEEK)/poly(aryl ether sulfone) (PES) in the melt state in the oscillatory shear mode. The data were analyzed for the fundamental rheological behavior to yield insight into the microstructure of PEEK/PES blends. A variation of complex viscosity with composition exhibited positive–negative deviations from the log‐additivity rule and was typical for a continuous‐discrete type of morphology with weak interaction among droplets. The point of transition showed that phase inversion takes place at composition with a 0.6 weight fraction of PEEK, which agreed with the actual morphology of these blends observed by scanning electron microscopy. Activation energy for flow, for blend compositions followed additive behavior, which indicated that PEEK/PES blends may have had some compatibility in the melt. Variation of the elastic modulus (G′) with composition showed a trend similar to that observed for complex viscosity. A three‐zone model used for understanding the dynamic moduli behavior of polymers demonstrated that PEEK follows plateau‐zone behavior, whereas PES exhibits only terminal‐zone behavior in the frequency range studied. The blends of these two polymers showed an intermediate behavior, and the crossover frequency shifted to the low‐frequency region as the PEEK content in PES increased. This revealed the shift of terminal‐zone behavior to low frequency with an increased PEEK percentage in the blend. Variation of relaxation time with composition suggested that slow relaxation of PEEK retards the relaxation process of PES as the PEEK concentration in the blend is increased because of the partial miscibility of the blend, which affects the constraint release process of pure components in the blend. A temperature‐independent correlation observed in the log–log plots of G′ versus loss modulus (G″) for different blend systems fulfilled the necessary condition for their rheological simplicity. Further, the composition‐dependent correlations of PEEK/PES blends observed in a log–log plot of G′ versus G″ showed that the blends are either partially miscible or immiscible and form a discrete‐continuous phase morphology. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1548–1563, 2004