互易律对有机光导体感光特性影响的研究

互易律对有机光导体的感光性能有何影响，通过对制备的以Y－TiOPc为电荷产生材料的有机光导体所作的测试实验，证明有机光导体并不遵守互易律，其感光度随光强的增加而降低，由于在光谱780－840nm波长范围内具有很高的感光度，故特别适合半导体激光扫描的要求。     

Numerical simulation of non‐isothermal phase change problem using ADRBEM with augmented items

In this paper, the phase change moving interface problem along the axial direction of the cylinder in the lead alloys containing tin is simulated by the axisymmetric dual reciprocity boundary element method (ADRBEM) with augmented items. The numerical method is verified by comparing with the analytical solution under a certain condition. The calculating results show that the ADRBEM with augmented items is an effective numerical method to solve the analogous problem of non‐isothermal phase change, which occurs in the crystal growth process. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(7): 408– 416, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20173     

Signalling boosts the evolution of cooperation in repeated group interactions

Many biological and social systems show significant levels of collective action. Several cooperation mechanisms have been proposed, yet they have been mostly studied independently. Among these, direct reciprocity supports cooperation on the basis of repeated interactions among individuals. Signals and quorum dynamics may also drive cooperation. Here, we resort to an evolutionary game-theoretical model to jointly analyse these two mechanisms and study the conditions in which evolution selects for direct reciprocity, signalling, or their combination. We show that signalling alone leads to higher levels of cooperation than when combined with reciprocity, while offering additional robustness against errors. Specifically, successful strategies in the realm of direct reciprocity are often not selected in the presence of signalling, and memory of past interactions is only exploited opportunistically in the case of earlier coordination failure. Differently, signalling always evolves, even when costly. In the light of these results, it may be easier to understand why direct reciprocity has been observed only in a limited number of cases among non-humans, whereas signalling is widespread at all levels of complexity.     

Fostering the determinants of knowledge sharing in professional virtual communities

Professional virtual communities (PVCs), which are formed on the Internet, are expected to serve the needs of members for communication, information, and knowledge sharing. The executives of organizations should consider PVCs as a new innovation or knowledge pool since members share knowledge. However, many PVCs have failed due to members’ low willingness to share knowledge with other members. Thus, there is a need to understand and foster the determinants of members’ knowledge sharing behavior in PVCs. This study develops an integrated model designed to investigate and explain the relationships between contextual factors, personal perceptions of knowledge sharing, knowledge sharing behavior, and community loyalty. Empirical data was collected from three PVCs and tested using structural equation modeling (SEM) to verify the fit of the hypothetical model. The results show that trust significantly influences knowledge sharing self-efficacy, perceived relative advantage and perceived compatibility, which in turn positively affect knowledge sharing behavior. Furthermore, the study finds that the norm of reciprocity does not significantly affect knowledge sharing behavior. The results of the study can be used to identify the motivation underlying individuals’ knowledge sharing behavior in PVCs. By investigating the impacts of contextual factors and personal perceptions on knowledge sharing behavior, the integrated model better explains behavior than other proposed models. This study might help executives of virtual communities and organizations to manage and promote these determinants of knowledge sharing to stimulate members’ willingness to share knowledge and enhance their virtual community loyalty. As only little empirical research has been conducted on the impact of knowledge sharing self-efficacy, perceived relative advantage, and perceived compatibility on the individual’s knowledge sharing behavior in PVCs, the empirical evidence reported here makes a valuable contribution in this highly important area.     

A Galerkin formulation for shear deformable plate bending dynamics

A Galerkin boundary element formulation for shear deformable plate bending dynamics is developed. The formulation makes use of the static fundamental solutions for the weighted residual integral equations. The domain integrals carrying the inertia terms and generic static loads are considered as body forces and approximated with boundary values using the dual reciprocity method. The load is modelled as a series of impact loads of time varying intensity and moving in space in a predetermined path. The formulation was implemented and tested solving a benchmark problem. The results are compared with finite element solutions. Copyright © 2004 John Wiley & Sons, Ltd.     

Boundary element—dual reciprocity formulation for bound electron states in semiconductor quantum wires

Using the boundary element dual reciprocity method-multi-domain (DRM-MD) a bound electron states and corresponding wave functions in semiconductor quantum wires embedded in a matrix were considered. The single circular and rectangular as well as the two near circular quantum wires were analyzed. In the case of two coupled quantum wires the dependence of the resulting wave function and eigenenergies as a function of the distance between wires was calculated. The DRM-MD gave a linear electron state model and developed numerical approach accurately captured the symmetry breaking and splitting of the degenerated energy states due to presence of additional wire. According to the symmetry of the structures a suitable mesh reduction was employed and different modes were considered separately. For a case of hetero-structures domain decomposition was used.     

Transient non‐linear heat conduction–radiation problems—a boundary element formulation

A novel boundary‐only formulation for transient temperature fields in bodies of non‐linear material properties and arbitrary non‐linear boundary conditions has been developed. The option for self‐irradiating boundaries has been included in the formulation. Heat conduction equation has been partially linearized by Kirchhoff's transformation. The result has been discretized by the dual reciprocity boundary element method. The integral equation of heat radiation has been discretized by the standard boundary element method. The coupling of the resulting two sets of equations has been accomplished by static condensation of the radiative heat fluxes arising in both sets. The final set of ordinary differential equations has been solved using the Runge–Kutta solver with automatic time step adjustment. The algorithm proved to be robust and stable. Numerical examples are included. Copyright © 1999 John Wiley & Sons, Ltd.     

非线性流体晃动时域双协边界元法分析

利用双协边界元法在时域内对流体晃动进行分析,推导出边界积分方程及相应的边界条件。分析过程中考虑流体粘性,利用时间迭代,逐步追踪流体自由面,因而在流体不断变动的边界上考虑其边界条件。数值结果表明本文的双协边界元法是可行的。     

基于利他激励的群体演化合作模型

为探究个体与系统状态的演化,构建了个体行为策略与网络结构的演化模型,探讨个体在利他激励机制下对合作演化的影响。在该模型中,个体首先通过对其他个体的帮助获得一定的额外互惠收益,并通过个体混合收益累计个体收益与帮助其他个体获得额外收益的加权,以此来激励个体合作。然后在博弈过程中,通过个体混合收益取代费米函数中的个体累计收益用于促进个体选择利他合作策略,从而促进整个群体的总收益与合作水平。蒙特卡罗仿真实验结果表明,个体在利他激励机制下更愿意帮助其他个体。在不同网络结构中,小世界网络最能扩散利他激励机制,其系统合作者密度最高。     

IMPLEMENTATION OF THE BOUNDARY ELEMENT METHOD IN THE DYNAMICS OF FLEXIBLE BODIES

This paper presents the implementation of the Boundary Element Method in the dynamics of flexible multibody systems. Kane's equations are used to formulate the governing boundary initial value problem for an arbitrary three-dimensional elastic body subjected to large overall base motion. Using continuum mechanics principles, direct boundary element incremental formulations are derived. The Galerkin approach was employed to generate the weighted residual statement which serves as a transitory point between continuum mechanics and boundary integral equations. By adapting the updated Langrangian formulation for large displacements analysis and using the Maxwell–Betti reciprocal theorem, integral representations for geometric stiffening were also derived. The non-linear terms were found to be functions of the time-variant stresses associated with the inertial forces at the reference configuration. The domain integrals arising from body forces (such as gravitational loads, inertia loads and thermal loads, etc.) are presented as DRM integrals (Dual-Reciprocity Method). Using the substructuring technique the elastic body is divided into several regions leading to a system of equations whose matrices are sparse (block-banded). The linearized equations of motion were discretized along the boundary of the body, and an algorithm for the integration involving the Houbolt method was used to establish an algebraic system of pseudo-static equilibrium equations. A Newton–Raphson-type iteration scheme was used to solve these discretized balance equations. To take advantage of the sparsity of the matrices, special routines were used to decompose and solve the resulting linear system of equations. An illustrative example is presented to demonstrate the validity of the method as well as how the effects of geometric stiffening effects are captured. The example consists of spin-up manoeuvre of a tapered beam attached to a moving base. The beam was modelled as two-dimensional plane strain problem divided into a number of substructures. Numerical simulation results show how the phenomenon of dynamic stiffening is captured by the present approach.