Capacity Constrained Transit Assignment with Common Lines

This paper proposes the use of absorbing Markov chains to solve the capacity constrained transit network loading problem taking common lines into account. The approach handles congested transit networks, where some passengers will not be able to board because of the absence of sufficient space. The model also handles the common lines problem, where choice of route depends on frequency of arrivals. The mathematical formulation of the problem is presented together with a numerical example. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reprint of : Measuring the Luttinger liquid parameter with shot noise

We explore the low-frequency noise of interacting electrons in a one-dimensional structure (quantum wire or interaction-coupled edge states) with counterpropagating modes, assuming a single channel in each direction. The system is driven out of equilibrium by a quantum point contact (QPC) with an applied voltage, which induces a double-step energy distribution of incoming electrons on one side of the device. A second QPC serves to explore the statistics of outgoing electrons. We show that measurement of a low-frequency noise in such a setup allows one to extract the Luttinger liquid constant K which is the key parameter characterizing an interacting 1D system. We evaluate the dependence of the zero-frequency noise on K and on parameters of both QPCs (transparencies and voltages).     

The product of the restrained domination numbers of a graph and its complement

Let G=(V,E) be a graph.A set S■V is a restrained dominating set if every vertex in V-S is adjacent to a vertex in S and to a vertex in V-S.The restrained domination number of G,denoted γr(G),is the smallest cardinality of a restrained dominating set of G.In this paper,we show that if G is a graph of order n≥4,then γr(G)γr(G)≤2n.We also characterize the graphs achieving the upper bound.     

Localization-delocalization transition in chains with long-range correlated disorder

We investigated numerically localization properties of electron eigenstates in a chain with long-range correlated diagonal disorder. A tight-binding one-dimensional model with on-site energies exhibiting long-range correlated disorder (LCD) was used with various disorder strength W. LCD was defined so that it gave a power-law spectral density of the form S(k)αk^-p, where p determines the roughness of the potential landscape. Numerical results on the correlation length ξ of eigenstates shows the existence of the localization-delocalization transition at p=2. It is found that the critical values for disorder strength W_c and also the critical exponent ν for localization length change with the values of p.     

图的k-单圈划分中的优化问题

图的划分问题曾引起图论界的广泛关注，在文献[4]中讨论了k-单圈划分，本文进一步研究基于k-单圈划分的优化问题，即在一个赋权图中求一个最小权可k-单圈划分的支撑子图，以及对一个不存在k-单圈划分支撑子图的图，如何添最少的边使得它有k-单圈划分的支撑子图。     

A numerically stable restrained electrostatic potential charge fitting method

Inspired by the idea of charge decomposition in calculation of the dipole preserving and polarization consistent charges (Zhang et al., J. Comput. Chem. 2011, 32, 2127), we have proposed a numerically stable restrained electrostatic potential (ESP)‐based charge fitting method for protein. The atomic charge is composed of two parts. The dominant part is fixed to a predefined value (e.g., AMBER charge), and the residual part is to be determined by restrained fitting to residual ESP on grid points around the molecule. Nonuniform weighting factors as a function of the dominant charge are assigned to the atoms. Because the residual part is several folds to several orders smaller than the dominant part, the impact of ill‐conditioning is alleviated. This charge fitting method can be used in quantum mechanical/molecular mechanical (QM/MM) simulations and similar studies, where QM calculated electronic properties are frequently mapped to partial atomic charges. © 2012 Wiley Periodicals, Inc.     

弹性约束边界圆环板面内自由振动的二维弹性解

基于二维线弹性理论,应用哈密顿原理导出弹性约束边界圆环板面内自由振动的控制微分方程。采用微分求积法(DQM)数值研究了弹性约束边界圆环板面内自由振动的频率特性。通过设置弹性刚度系数为0或∞,问题退化为四种典型边界圆环板的面内自由振动,与已有文献的计算数值结果进行比较,证实本文的分析求解方法行之有效。最后全面考虑了圆环板边界条件、几何系数及刚度系数对自振频率的影响。     

电场和应力作用下氮钝化扶手型氧化锌纳米带的电子结构和磁特性

采用密度泛函理论(DFT)方法,在LDA+U水平下详细研究了电场和应力作用下氮钝化扶手型氧化锌纳米带(NA8-ZnONRs)的电子结构和磁特性。对体系的电子结构和磁性进行详细的计算,结果表明：本征扶手型氧化锌纳米带(A8-ZnONRs)是无磁性P型半导体。氮钝化后NA8-ZnONRs具有铁磁金属性,其磁性主要来源于N2p轨道(2.56μ_B)和O2p轨道(0.69μ_B)电子的自旋极化,总磁矩为3.21μ_B。NA8-ZnONRs体系对X方向电场有较强的响应,通过调节X方向电场的幅度,可以有效调节体系的磁矩。在X方向电场作用下体系仍具有铁磁金属性,磁性也主要来源于N2p和O2p轨道电子的自旋极化。施加X方向应力作用后,体系仍表现为铁磁金属性。与NA8-ZnONRs纳米带磁矩相比,体系的总磁矩均发生了较大幅度的增长,表明体系对应力作用具有较明显的相应。但随着应力幅度的调节,总磁矩的变化较平坦。表明施加应力可以有效调节体系的磁矩,但在较小应力范围内,体系对应力变化的相应不明显。     

薄壁箱梁广义坐标法刚度矩阵的推导及应用

在符拉索夫广义坐标法初参数方程的基础上,推导出可用于均布扭转荷载作用下薄壁箱梁翘曲分析的刚度矩阵,该刚度矩阵具有较高的单元精度,可用于由较多薄壁箱梁组成的复杂结构的整体有限元分析。通过对广义坐标法刚度矩阵和乌曼斯基理论、修正乌曼斯基理论求得薄壁箱梁的位移和应力进行分析比较,为各方法在实际工程中的应用提供一定的参考。