非经典法制备锂离子蓄电池电极材料

随着其它技术的发展,锂离子蓄电池电极材料的制备技术亦得相应的发展。综述了近几年来一些非经典的制备方法,如机械化学法、溶液氧化还原法、离子交换法、水热法、模板法、炭棒电弧放电法、脉冲激光沉积法、等离子提升化学气相沉积法和射频磁旋喷射法等。这些方法有的简单、方便易行;有的能降低反应温度,容易得到单一相结构;有的方法设计独特,能制备纳米材料,电化学性能非常优良。这些非经典技术除了降低成本、提高电化学性能外,还将推动锂离子蓄电池向两极化发展:大型化和微型化,从而推动相应应用技术的发展,如电动汽车和先进的微型军事技术。

大型塔式桁架组合结构分析的非经典能量法

本文针对工程上常见的各种塔式桁架系统组合结构的静力和动力分析,提出一种半连续半离散式基于非经典能变形理论的量法。文中,把整体桁架组合结构模拟成变截面的非经典梁,结构中任意结点的三向位移用其截面的四个广义位移(弯、剪、挤、拉)表示,由此导出每根杆件的两端位移,从而可仔细考虑每根杆件的应变、内力及相应的变形能、动能和外力功等。并由能量变分原理导出一组线性代数方程,方程阶次仅与所假定的四个广义位移试函数中待定系数的个数有关,与杆件数目,结点数目,层数等均无关,把大型塔架有限元分析的成百上千个自由度降为十几阶的数值计算问题,因此仅需求解阶次极低的代数方程组。同时,还可方便地考虑各种附加设施的影响。文中给出了实际电视塔结构和海洋平台导管架模型的静动力计算结果,并与其它方法计算结果和试验结果作了比较,表明本法是一种工程上较为通用有效的适于微机分析的简捷计算方法。本文方法也可称为非经典综合离散法。

基于对称约化的偏微分方程相似解研究

由于非线性系统的复杂性,对于其求解问题的研究目前还没有通用的方法,为了丰富非线性系统的求解方法,在此通过偏微分方程的决定方程确定点对称无穷小生成元,结合对称约化中的非经典Lie群法得到热方程新的相似解,并基于符号计算系统Maple给出相应的符号计算方法和实现步骤。结果表明,该算法能够有效求解PDEs的相似解,并且不需要显示地求解对应于不变曲面条件的特征方程,同时也适用于其他的发展方程。

Symmetries and Exact Solutions of the Breaking Soliton Equation

With the aid of the classical Lie group method and nonclassical Lie group method,we derive the classicalLie point symmetry and the nonclassical Lie point symmetry of (2+1)-dimensional breaking soliton (BS)equation.Usingthe symmetries,we find six classical similarity reductions and two nonclassical similarity reductions of the BS equation.Varieties of exact solutions of the BS equation are obtained by solving the reduced equations.

Similarity Reduction Analysis for a Coupled KdV System

Using the direct method for a coupled KdV system, six types of the similarity reductions are obtained. The group explanation of the results is also given. It is pointed out that, in order to find all the results by nonclassical Lie approach, two additional condition equations should be satisfied at the same time together with two original equations.

Theories and Applications of Mixed Quantum-Classical Non-adiabatic Dynamics

Electronically non-adiabatic processes are essential parts of photochemical process, collisions of excited species, electron transfer processes, and quantum information processing. Various non-adiabatic dynamics methods and their numerical implementation have been developed in the last decades. This review summarizes the most significant development of mixed quantum-classical methods and their applications which mainly include the Liouville equa- tion, Ehrenfest mean-field, trajectory surface hopping, and multiple spawning methods. The recently developed quantum trajectory mean-field method that accounts for the decoherence corrections in a parameter-free fashion is discussed in more detail.

Symmetry Reductions of Two-Dimensional Variable Coefficient Burgers Equation

By use of a direct method, we discuss symmetries and reductions of the two-dimensional Burgers equation with variable coefficient (VCBurgers). Five types of symmetry-reducing VCBurgers to (1+1)-dimensional partial differential equation and three types of symmetry reducing VCBurgers to ordinary differential equation are obtained.

A Hierarchical-Equation-of-Motion Based Semiclassical Approach to Quantum Dissipation

We present a semiclassical （SC） approach for quantum dissipative dynamics, constructed on basis of the hierarchical-equation-of-motion （HEOM） formalism. The dynamical components considered in the developed SC-HEOM are wavepackets＇ phase-space moments of not only the primary reduced system density operator but also the auxiliary density operators （ADOs） of HEOM. It is a highly numerically efficient method, meanwhile taking into account the high-order effcts of system-bath couplings. The SC-HEOM methodology is exemplified in this work on the hierarchical quantum master equation [J. Chem. Phys. 131, 214111 （2009）] and numerically demonstrated on linear spectra of anharmonic oscillators.

风荷载作用下混凝土房屋及顶上钢塔结构动力时程分析

混凝土房屋及顶上钢塔结构正被广泛应用,采用非比例阻尼与折算阻尼两种模型,对此类阻尼具有明显分界的结构在风荷载作用下进行动力分析,计算采用直接积分法和非经典振型法。计算结果表明:折算阻尼法不能反映此类结构钢塔阻尼突然变小,位移、内力突然增大的现象;而非比例阻尼模型可以准确反映此现象。直接积分法计算结果精确,但计算工作繁重,费用较高;非经典振型分解法计算成本较低,但是参与叠加的振型阶数应比满足位移精度要求的振型阶数至少多一倍以上时才能达到满意的内力结果。