bluuebunny/crossref_metadata_2025 huggingface dataset:
Weighted Eigenvalue Problem Approach To The Critical Value Determination Of Screened Coulomb Potential Systems
Authors: Demiralp Metin
Published: March 2004

In this work, the radial time‐independent Schrödinger equation of a screened Coulomb potential system at the zero energy limit is first converted to a weighted eigenvalue problem of an ordinary differential operator. Then, by using an appropriate coordinate transformation, the differential equation is transformed into a form whose first and second order derivative related terms become same as the Extended Jacobi Polynomials' differential equation's corresponding terms. Only difference is the appearance of a multiplicative operator which can be considered as an effective potential. Work focuses on the point whether the solution is obtained easily depending on the structure of this potential. In this direction a screened Coulomb potential with a specific rational screening function is considered. The analytical solutions for the critical values of the screening parameter and the form of the wave function at the threshold of the continous spectrum are obtained. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal Control of One Dimensional Quantum Harmonic Oscillator Under an External Field With Quadratic Dipole Function and Penalty on Momentum: Construction of the Linearised Field Amplitude Integral Equation
Authors: Kurşunlu A. , Yaman İrem , Demiralp Metin
Published: March 2004

In this work, the optimal control of an harmonic oscillator is considered. The external field is assumed to be weak and hence is represented by only dipole interaction. The dipole function is taken as a second degree polynomial in spatial coordinate. The objective term is composed of the expectation value of algebraic position operator. Penalty term related operator is taken as momentum. Some specific structures for spatial dependence is assumed and temporal equations are obtained for unknowns. The equations represent forward and backward evolution. The connection is provided by an algebraic equation coming from field amplitude related equation. The key unknown is the field amplitude since its determination leads us to evaluate all unknowns without remarkable difficulty. The purpose is not to determine field amplitude at the most general case but to construct an equation which involves this unknown only. The equation obtained via the linearisation of the field amplitude dependence is shown to be a linear integral equation. We do not attempt to solve it but discuss how to use appropriate methods for the solution. The equation is analytically solved at the zero interaction time limit. The real comprehensive implementation is left for future work. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High Dimensional Model Representation Approximation of an Evolution Operator with a First Order Partial Differential Operator Argument
Authors: Yaman İrem , Demiralp Metin
Published: March 2004

In this work, a novel approximation scheme based on a recently developed representation, called the High Dimensional Model Representation (HDMR), is proposed to approximate evolution operators. The approximation is not developed at the operator level, instead the effect of the operator on an arbitrary function is approximated. The purpose of the work is to investigate how HDMR can be applied for the approximation of evolution operator and its efficiency. Although the approximation can be constructed for any order of multivariance, only the constant and univariate components of HDMR are considered in this work. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Comparison of the Model Order Reduction Techniques for Linear Systems Arising from VLSI Interconnection Simulation
Authors: Fatih Yetkin E. , DAĞ Hasan
Published: March 2004

In recent years, model order reduction scheme for reducing the dimension of linear systems has become very popular for computer aided design of the systems. In this paper, we analyze the existent methods of the model order reduction techniques used in Very Large Scale Integrated (VLSI) circuit interconnection modelling in terms of numerical stability, computational speed and accuracy. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spline Based Electronic Modelling
Authors: Senthilbalaji Girimurugan L.
Published: March 2004

“Without Mathematics almost everything is zilch”, a scientific maxim, is the kernel for this mathematical piece of research. The basic notion is to formulate mathematical models for devices and circuits deployed in state of the art electronic gadgets. The article searches for a tool to perform the aforementioned operation and finally accouters its models with well known mathematical approximation tools called Interpolators. The analysis of these models is carried out using MATLAB and the simulations are obtained for both frequency dependent and independent device characteristics. The scheme could result in some predicted merits when it allies with Very Large Scale and Ultra Large Scale Integration [VLSI,ULSI] techniques employed in the Electronic chip design industry and Artificial Intelligence. The quondam alliance could result in device miniaturization and the latter may result in the design of robots enabled in the control of electronic environments. However, the latter could be an application [for Robots] or an alliance where the principles of neural networks could be applied for the purpose of mathematical modelling. Thus, the article reveals a solution for how mathematics be applied to engineering and science. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stability conditions for the Leapfrog‐Euler scheme with central spatial discretization of any order
Authors: Shishkina Olga , Wagner Claus
Published: March 2004

In this paper a sufficient condition (Theorem 2.3) for the von Neumann stability of the Leapfrog‐Euler scheme, which uses central spatial discretization of any order for 3D convection‐diffusion equation, is derived in terms of the Courant and the diffusion numbers and the coefficients of approximation schemes. In the case of the second order differencing this condition becomes the necessary condition for the stability. Some particular sufficient conditions for the stability of the second and the fourth order schemes are also derived. A comparison of the results, which were obtained applying the derived stability conditions to compute the time step in the direct numerical simulations (DNS) of turbulent pipe flow with the help of the second and the fourth order schemes, is presented. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improving Rates of Convergence of Iterative Schemes for Implicit Runge‐Kutta Methods
Authors: Vigneswaran R.
Published: March 2004

Various iterative schemes have been proposed to solve the non‐linear equations arising in the implementation of implicit Runge‐Kutta methods. In one scheme, when applied to an s‐stage Runge‐Kutta method, each step of the iteration still requires s function evaluations but consists of r(>s) sub‐steps. Improved convergence rate was obtained for the case r = s + 1 only. This scheme is investigated here for the case r = ks, k = 2, 3, …, and superlinear convergence is obtained in the limit k→∞. Some results are obtained for Gauss methods and numerical results are given. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A compensation method based on recursive processing of nonlinear distortion for OFDM
Authors: Hosono Hiroyuki , Hosokawa Taisuke , Maeda Tsuyoshi , Maehara Fumiaki , Takahata Fumio
Published: March 2004

OFDM (orthogonal frequency division multiplexing) signal generates a very large signal amplitude. Consequently, distortion due to nonlinearity is produced when the signal is amplified through a nonlinear amplifier, which greatly degrades BER (bit‐error rate) performance. As a method of handling this problem, this paper proposes highly accurate compensation processing of nonlinear distortion by constructing a replica of the OFDM signal in the receiver. The proposed method is based on the hard decision result of demodulated received symbols containing nonlinear distortion, and the nonlinear distortion component is recursively estimated and compensated. The performance of the proposed method is evaluated by computer simulation assuming a thermal noise environment, and it is shown that the proposed method is better in both BER and the number of constructed replicas. The performance of the proposed method is also evaluated assuming a fading environment when the method is applied to land mobile communications. The problems of fading compensation when the distortion caused by nonlinear amplification is superposed are pointed out. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(7): 55–65, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10051
A dynamic server selection method using QoS statistics
Authors: Mase Kenichi , Kuribayashi Takayuki , Tsuno Akihiko
Published: March 2004

In this paper, we study server selection methods from the perspective of selecting the server having the shortest download time when a file is downloaded from a mirror Web site. Specifically, we focus on server selection methods on the client side and propose a dynamic server selection method based on Quality of Service (QoS) statistical data. This method features using past stored data in a more advanced manner than a conventional server selection method by collecting past QoS data according to the day of the week and the time period. We also study and evaluate the method based on experimental results using the Internet. First, we study the optimum values for the parameters of the proposed server selection method. Then we compare and evaluate this server selection method and an existing server selection method. As the evaluation metrics, in addition to objective evaluation indices such as the mean and maximum download time, we use the download give‐up rate and the stress level which reflect the user's feelings. Based on these results, we demonstrate the superiority of this server selection method. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(7): 43–54, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10168
Frequency efficiency by introducing adaptive array antenna in W‐CDMA system
Authors: Mikami Manabu , Fujii Teruya
Published: March 2004

The adaptive array antenna is an effective means of improving frequency efficiency in cellular mobile communication systems. In these systems, the frequency efficiency is generally improved by improving the CIR characteristic. This paper considers W‐CDMA systems from such a viewpoint, assuming that an adaptive array antenna is used in the wireless base station. The relation between the array antenna structure (the number and directivity of antenna elements) and the frequency efficiency is analyzed by examining the improvement of the CIR characteristic in a cellular environment containing multiple cells. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(7): 31–42, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10176
Planar array antenna using both‐sided MIC's feeder circuits
Authors: Egashira Kozo , Nishiyama Eisuke , Aikawa Masayoshi
Published: March 2004

In this paper, it is proposed that the “both‐sided” circuit technique, which consists of placing several types of transmission lines on both sides of the dielectric substrate, be used for array antenna feed systems. Microstrip lines are used on the front surface of the dielectric substrate, and slot lines are placed on the back side. By means of electromagnetic coupling, a new feed system is constructed. Further, trial fabrication and testing of a four‐element array antenna using this feed system were carried out. The measured radiation patterns indicate complementary effects caused by feeding of the radiating elements with mirror symmetry. Excellent characteristics substantially reducing unwanted cross‐polarization are confirmed. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(7): 23–30, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10179
FDTD analysis of the transmission/radiation characteristics of 90° bent transmission lines
Authors: Shiokawa Takayasu
Published: March 2004

Recently, with the advent of personal high‐performance electronic devices such as computers and with proliferation of mobile communications such as cellular phones, reduction of the size and weight of the systems, enhancement of processing speed, and voltage reduction of the electronic devices have been pursued. As a result, the problems of interference by unwanted electromagnetic waves between various devices and within individual devices have appeared. Various approaches are conceivable. The author has been performing research on these problems from the standpoint that the electromagnetic elucidation of the generation and propagation mechanisms of the unwanted waves is essential. In the present paper, the voltage and current distributions on a parallel two‐wire line with a bend, representing the basic configuration of a transmission line, are analyzed by the FDTD method. By using this analysis, the complex power near the bend is derived and the transmission/radiation characteristics at the bend are quantitatively elucidated. Next, the transmission/radiation characteristics of a microstrip line with a 90°bend are analyzed by the FDTD method in the case where an adjacent line exists. In this way, the effect of the adjacent line is elucidated. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(7): 11–22, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10190
Output equivalent circuit model of digital IC for estimating emissions radiated from signal trace
Authors: Miyazaki Chiharu , Oka Naoto , Uchida Takeshi , Tokuda Masamitsu , Nitta Shuichi
Published: March 2004

The output model of a digital IC for calculating normal‐mode emissions radiated from a signal trace was studied. It is confirmed that the difference of kinds and manufacturers of various digital ICs can be found by measuring normal‐mode radiations from a signal trace driven by a digital IC such as TTL or CMOS. In order to calculate the difference of normal‐mode emissions, it is proposed that the output equivalent circuit of the digital IC be modeled as a circuit consisting of a voltage source and an output resistor, and a method of obtaining them is presented. The validity of the output model of the digital IC is confirmed by the fact that the results of calculation using the output model of a digital IC agree very well with measured data. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(7): 1–10, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10199
Evaluation for a multicast extension of a label switching technology
Authors: Nagami Kenichi , Mitsuzawa Shigeo , Mogi Akiyoshi , Ise Kotaro , Katsube Yasuhiro , Esaki Hiroshi
Published: March 2004

The LSR (label switch router), which uses label switching technology, performs packet transmission by a label transmission module that uses fixed‐length labels, in addition to by an ordinary network transmission module. It realizes high‐speed and high‐performance packet transmission by making correspondence with IP packets and fixed‐length labels, and by transmitting them using the label transmission module. The basic part of unicast label distribution protocol used by LSR has been specified by IETF (Internet Engineering Task Force). As for multicast label switching technology, various protocols (FANP [5], TAG [7], IPSOFACT [11]) have been proposed, and they have been compared by Ooms and colleagues [13]. However, there has been no study that evaluated the effectiveness of multicast label switching technology by comparing two cases, one that uses label switching technology for multicast packet transmission and another that does not. In this article, we evaluate the effectiveness of multicast label switching technology by designing and implementing FANP, a protocol for multicast label switching, by measuring LSP setup time, which is overhead of LSR compared with ordinary routers, and by measuring throughput for the case with label switching technology and for the case without it. LSP setup time was about 40 ms per LSR, which shows that overhead of label switching technology is small. Also, we verified that the throughput is higher when we used the label switching technology than when we did not use it, and it is effective in routers that reproduce multicast packets, such as backbone routers with many multicast receivers. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(7): 66–74, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1189
A systematic comparison of coupled and distributive smoothing in multigrid for the poroelasticity system
Authors: Gaspar F. J. , Lisbona F. J. , Oosterlee C. W. , Wienands R.
Published: March 2004

In this paper, we present efficient multigrid methods for the system of poroelasticity equations discretized on a staggered grid. In particular, we compare two different smoothing approaches with respect to efficiency and robustness. One approach is based on the coupled relaxation philosophy. We introduce ‘cell‐wise’ and ‘line‐wise’ versions of the coupled smoothers. They are compared with a distributive relaxation, that gives us a decoupled system of equations. It can be smoothed equation‐wise with basic iterative methods. All smoothing methods are evaluated for the same poroelasticity test problems in which parameters, like the time step, or the Lamé coefficients are varied. Some highly efficient methods result, as is confirmed by the numerical experiments. Copyright © 2004 John Wiley & Sons, Ltd.
A robust multilevel approach for minimizing H(div)‐dominated functionals in an H1‐conforming finite element space
Authors: Austin Travis M. , Manteuffel Thomas A. , McCormick Steve
Published: March 2004

The standard multigrid algorithm is widely known to yield optimal convergence whenever all high‐frequency error components correspond to large relative eigenvalues. This property guarantees that smoothers like Gauss–Seidel and Jacobi will significantly dampen all the high‐frequency error components, and thus, produce a smooth error. This has been established for matrices generated from standard discretizations of most elliptic equations. In this paper, we address a system of equations that is generated from a perturbation of the non‐elliptic operator I‐grad div by a negative ε Δ. For εnear to one, this operator is elliptic, but as εapproaches zero, the operator becomes non‐elliptic as it is dominated by its non‐elliptic part. Previous research on the non‐elliptic part has revealed that discretizing I‐grad div with the proper finite element space allows one to define a robust geometric multigrid algorithm. The robustness of the multigrid algorithm depends on a relaxation operator that yields a smooth error. We use this research to assist in developing a robust discretization and solution method for the perturbed problem. To this end, we introduce a new finite element space for tensor product meshes that is used in the discretization, and a relaxation operator that succeeds in dampening all high‐frequency error components. The success of the corresponding multigrid algorithm is first demonstrated by numerical results that quantitatively imply convergence for any εis bounded by the convergence for εequal to zero. Then we prove that convergence of this multigrid algorithm for the case of ε equal to zero is independent of mesh size. Copyright © 2004 John Wiley & Sons, Ltd.
Algebraic multigrid methods for constrained linear systems with applications to contact problems in solid mechanics
Authors: Adams Mark F.
Published: March 2004

This paper develops a general framework for applying algebraic multigrid techniques to constrained systems of linear algebraic equations that arise in applications with discretized PDEs. We discuss constraint coarsening strategies for constructing multigrid coarse grid spaces and several classes of multigrid smoothers for these systems. The potential of these methods is investigated with their application to contact problems in solid mechanics. Published in 2004 by John Wiley & Sons, Ltd.
Cache aware multigrid for variable coefficient elliptic problems on adaptive mesh refinement hierarchies
Authors: Douglas C. C. , Hu J. , Ray J. , Thorne D. T. , Tuminaro R. S.
Published: March 2004

We derive a multilevel algorithm to solve variable coefficient elliptic boundary value problems on adaptively refined structured meshes, and we design a cache optimized version of this algorithm.The operations are optimized to exploit the cache memory subsystem. We present numerical results demonstrating the efficiency of the cache optimization. Copyright © 2004 John Wiley & Sons, Ltd.
Coarsening by compatible relaxation
Authors: Livne O. E.
Published: March 2004

A 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

Helmholtz 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

In 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

For 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

Meshfree 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

The 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

A 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

The 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

Hydroxyethyl 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

A 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

A 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

The 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

We 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

The 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

Some 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

A 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

Dynamic 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
Rotational vibration of poly(tetrafluoroethylene) chains by the electron spin resonance method
Authors: Hara Shigeo , Yamamoto Katsuhiro , Shimada Shigetaka , Nishi Hajime
Published: March 2004

Temperature‐dependent electron spin resonance spectra of main‐chain free radicals, CF2(β)C · F(α)CF2(β), in poly(tetrafluoroethylene) (PTFE) were analyzed by the change in the hyperfine splitting due to β‐fluorines, which was a decreasing function of the observation temperature. The results were interpreted in terms of the rotational vibration around the CαCβ bond. The amplitude of the vibration was estimated on the assumption of its harmonic oscillation. The vibration of the PTFE chain was found to have a large amplitude in comparison with that of a polyethylene chain in single crystals. The vibration of the large amplitude was caused by a weak interchain interaction in the PTFE matrices. The amplitude of the vibration in crosslinked PTFE was much larger than that in noncrosslinked PTFE. This result indicated that the free radicals in crosslinked PTFE were trapped in the amorphous region, which had the disordered sites of crosslinking, whereas the free radicals in noncrosslinked PTFE were mainly trapped in the paracrystalline region. The decay reaction of the free radicals in the PTFE matrices was also related to the heterogeneity in the structure and the rotational vibration. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1539–1547, 2004
Polyelectrolyte complexes of linear copolymers and hydrogels based on 2‐[(methacryloyloxy)ethyl]trimethylammonium chloride and N‐isopropylacrylamide
Authors: Mun Grigoriy A. , Khutoryanskiy Vitaliy V. , Nurkeeva Zauresh S. , Sergaziyev Aibek D. , Fefelova Natalia A. , Rosiak Janusz M.
Published: March 2004

The formation of polyelectrolyte complexes of linear copolymers and hydrogels based on copolymers of 2‐[(methacryloyloxy)ethyl]trimethylammonium chloride with N‐isopropylacrylamide (MADQUAT–NIPAAM) and poly(acrylic acid) (PAA) has been studied. The composition of the copolymer has been found to affect the composition of the polyelectrolyte complexes significantly, and the molecular weight of PAA influences their aggregation stability. Hydrogels of MADQUAT–NIPAAM immersed in solutions of PAA undergo contraction because of the formation of gel–polymer complexes. The rate of contraction and the final swelling degree of the gel–polymer complexes depend on the concentration of PAA in solution and its molecular weight. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1506–1513, 2004
Representations of the Schrödinger algebra and Appell systems
Authors: Feinsilver P. , Kocik J. , Schott R.
Published: March 2004

We investigate the structure of the Schrödinger algebra. Two constructions are given that yield the physical realization via general methods starting from the abstract Lie algebra. Representations are found on a Fock space with basis given by a canonical Appell system. Generalized coherent states are used in the construction of the Hilbert space of functions on which certain commuting elements act as self‐adjoint operators. This yields a probabilistic interpretation of these operators as random variables. An interesting feature is how the semidirect product structure of the Lie algebra is reflected in the probability density function. A Leibniz function and orthogonal basis for the Hilbert space are found. Then certain evolution equations connected with canonical Appell systems on this algebra are shown.