材料期刊网

Effective Medium Approximation for Nonlinear Composite Media

Guoqing GU+ , International Centre for Materials Physics , Academia Sinica , 110015 , Shenyang , ChinaGe CHEN , College of Systems Science and Systems Engineering , Shanghai Institute of Mechanical Engineering , 200093 , ShanghaiK.W.Yu , Department of Physics , Chin

材料科学技术（英文）

We build the perturbation expansion method for nonlinear composite media and extend the EMA for nonlinear effective conductivity. Using the solutions of boundary-value problems of a cylindrical in- clusion, we derive formulae for nonlinear effective conductivity.

关键词: effective medium approximation , null

Stabilizing unstable discrete systems

Physical Review E

A general method for stabilizing unstable discrete systems to a fixed point or high-period orbit is developed analytically and numerically in this paper. It is shown that the method can be equally applied to the systems with one or more positive Lyapunov exponents. Moreover, the method does not require a prior analytical knowledge of the system under investigation, nor any additional control parameters.

关键词: adaptive adjustment mechanism;high-dimensional systems;controlling;chaos;periodic-orbits;dynamical-systems;attractors

Formation energy of ternary alloy systems calculated by an extended Miedema model

Physica B-Condensed Matter

It is important to know the formation energy of a ternary alloy system in many fields of materials science and engineering. It requires a significant effort to measure it experimentally. Theoretical calculations of formation energy having the flexibility to deal with complexity are very useful and have scientific meaning. Apparently there are no such theories existing even though in principle one could calculate the energy of any alloy system. In this paper calculations of the formation energies for ternary alloy systems consisting of combinations of structural metals with all constituents being transition and/or simple metals are presented using an extended Miedema model. The calculations for 12 alloy systems show good agreement with experimental data. It is concluded that this is a simple and convenient method for calculating the formation energy for a ternary alloy system. (C) 2002 Elsevier Science B.V. All rights reserved.

关键词: formation energy;ternary alloys;extended Miedema model;transition-metal alloys;formation enthalpies;thermodynamic properties;intermetallic compounds;mixing enthalpy;rare-earth;aluminum;binary;cu;phase

HOPPING CONDUCTION IN SOME FRACTAL SYSTEMS

Journal of Physics-Condensed Matter

The DC and AC hopping conduction in some fractal systems are studied. The DC conductivity is analysed in some partial fractal systems where both localized and superlocalized states exist. The AC conductivity sigma(omega) is shown to scale as omega[ln(nu(ph)/omega)]((D+2-zeta))/(zeta) and is proportional approximately to omega(s) with s = 0.88 for three-dimensional percolation. The ambiguities in the analysis of conductivity data are discussed and it is pointed out that the measurement of some characteristic length scales is very important in analysing the hopping mechanism and the origin of localization from experimental results.

关键词: black polymer composites;disordered-systems;coulomb gap;superlocalization;media

Application of Substitutional Model in Oxide Systems

Lin LI , O.Van Der Biest , Peiling WANG

材料科学技术（英文）

The application of substitutional model in oxide systems, in comparison with that of sublattice model, is discussed. The results show that in the case of crystalline phases and liquid phases without molecular-like associates or the shortage of element in sublattice, these two models get consistent in the description of the formalism of Gibbs free energies of phases and obtain the same result of phase diagram calculation when the valence of the cations keep the same.

关键词: Oxide systems , null , null

An algorithm based on variable feedback to synchronize chaotic and hyperchaotic systems

Physica D

In recent years, the subject of how to synchronize chaotic and hyperchaotic systems has attracted much attention due to its theoretic interest and potential applications to secure communications. Various approaches have been proposed and pursued. In this work, an algorithm based on variable feedback is developed analytically and applied to a nine-dimensional Lorenz system numerically. One finds that the proposed method can be applied to chaotic systems with one or more Lyapunov exponents. It is also demonstrated that the given method can be further simplified for concrete systems. (C) 2002 Elsevier Science B.V. All rights reserved.

关键词: chaos synchronization;hyperchaos;Lyapunov exponent;variable feedback;proportional feedback;coupled oscillators;communication

Study on the thermal stability of Cu-P based amorphous alloy systems

Journal of Materials Processing Technology

The crystallization temperatures and other thermal properties have been measured systematically for two ternary Cu-Ni-P and two quaternary Cu-Ni-Sn-P amorphous systems. The dependence of crystallization temperature on the composition for the four alloy systems can not be described basically by the usual used Naka rule. The Gibbs free energy of crystallization can be calculated for the alloy systems with the model proposed by Shu et al. Using the calculated free energy of crystallization, it is still not possible to properly describe all of the crystallization temperatures of the alloy systems. However, it has been found that the correlation between the crystallization temperature and the content of the alloy systems can be reasonably explained by the nucleation and growth rates of a new phase for the classical theory of phase transformation. It has been established that the classical theory of phase transformation can be used to describe the thermal stability of the Cu-based amorphous alloys during their crystallization process. (C) 1999 Published by Elsevier Science S.A. All rights reserved.

关键词: thermal stability;amorphous alloys;Cu-P based alloy systems;classical;theory of phase transformation;solid-liquid interface;structural model;glasses

THE FACTORS AFFECTING ENTROPY OF MIXING OF LIQUID ALLOY SYSTEMS

Z. Wu , C.H. Li , P. Qin , H.L. Liu and N. Y. Chen(Shanghai Institute of Metallurgy , Chinese Academy of Sciences , Shanghai 200050 , China)

金属学报(英文版)

A modified Miedema model using four atomic parameters and pattern recognition or artificial neural network has been used to study the factors that affect the entropy of mixing of liquid binary alloy systems. It has been found that the systems with larger electronegativity difference (△Φ) usuallg have negative △Sxs of mixing, while the systems with larger valence electron density difference(denoted by △n) and small △Φ usually have positive △Sxs of mixing. The artificial neural network-atomic parameter method can be used to predict the △Sxs of binary alloy systems consisting of non-transition elements.

关键词: entropy of mixing , null , null

Synchronizing the parameter non-matching chaotic systems

材料科学技术（英文）

It is shown that synchronization, in a weak sense, can be achieved between two-parameter non-matching systems by using the adaptive control method. In essence, this requires just a scalar signal transmitted from the drive to the response system. Two typical chaotic systems, i.e., Lorenz and Rossler system, are taken as examples of applications in this paper.

关键词: chaotic systems;synchronization;adaptive control;hyperchaos

THERMODYNAMIC TREATMENT OF MULTICOMPONENT SYSTEMS USING INTERACTION PARAMETERS

Z. T. Ma , J Ohser and D. Janke(Institute of Iron and Steel Technology , Freiberg University of Mining and Technology , Germany )

金属学报(英文版)

The partial thermodynamic functions of solvent and solutes in multicomponent systems have been expressed in terms of the interaction parameters. The corresponding analytical expressions of the activity coefficients of solvent and solutes enable to de scribe the thermodynamic properties of multicomponent systems. The advantages of this treatment are found in its thermodynamic consistency and a rather small influ ence of the higher order interaction parameters on the properties of the systetms.

关键词: thermodynamics; activity; model