核磁共振波谱研究氟化膦配体及其金属配合物的氟谱化学位移

研究了氟化膦类系列配位体(GPF₂:G=F,Et₂N,Me₂N,C₅H₁₀N,nPrO,PhO,neoPnO,2,5-diMePh,isoPr,etc.)及其与金属镍₍₀₎铜_(I)钼₍₀₎金_(I)形成的配合物的核磁共振氟谱化学位移的定量分子建模,发现了其中的一些有用规律.     

Energy drift in molecular dynamics simulations

In molecular dynamics, Hamiltonian systems of differential equations are numerically integrated using the Störmer–Verlet method. One feature of these simulations is that there is an unphysical drift in the energy of the system over long integration periods. We study this energy drift, by considering a representative system in which it can be easily observed and studied. We show that if the system is started in a random initial configuration, the error in energy of the numerically computed solution is well modeled as a continuous-time stochastic process: geometric Brownian motion. We discuss what in our model is likely to remain the same or to change if our approach is applied to more realistic molecular dynamics simulations.     

矩阵方程ATXA=D的条件数与向后扰动分析

讨论矩阵方程ATXA=D,该方程源于振动反问题和结构模型修正.本文利用Moore-Penrose广义逆的性质,给出该方程解的条件数的上、下界估计.同时,利用Schauder不动点理论给出该方程的向后扰动界,这些结果可用于该矩阵方程的数值计算.     

Far-wing light absorption induced by resonant or near-resonant collisions

Summary We have studied the absorption of light induced by a resonant or near-resonant collision between two atoms. The calculations have been performed by taking into account also the magnetic sublevels, which makes our theoretical predictions more applicable to realistic cases. Analytical expressions for the far-wing absorption cross-section have been obtained.     

Numerical bifurcation of a delayed diffusive food‐limited model with Dirichlet boundary condition

This paper studies the Neimark–Sacker bifurcation of a diffusive food‐limited model with a finite delay and Dirichlet boundary condition by the backward Euler difference scheme, Crank‐Nicolson difference scheme, and nonstandard finite‐difference scheme. The existence of Neimark‐Sacker bifurcation at the equilibrium is obtained. Our results show that Crank‐Nicolson and nonstandard finite‐difference schemes are superior to the backward Euler difference scheme under the means of describing approximately the dynamics of the original system. Finally, numerical examples are provided to illustrate the analytical results. Copyright © 2015 John Wiley & Sons, Ltd.     

InAs/GaAs量子点激光器的增益和线宽展宽因子

利用气源分子束外延技术生长InAs/GaAs量子点激光器材料,制作了由5层量子点组成的500 μm腔长的激光器.首次使用增益拟合和波长加权的方法计算了激光器的线宽展宽因子.其中,增益拟合是对Hakki-Paoli方法计算增益的重要补充,对判断不同电流下的增益是否饱和具有重要作用.对最大模式增益求导数,当电流为50 mA时,差分增益最大值为1.33 cm-1/mA,然后迅速减小到0.34 cm-1/mA,此时电流为57mA(≈0.99Ith).第一次使用加权波长来计算中心波长的移动,发现△λ慢慢减小直至接近于0.整个计算方法避免了在直接选取数据点时造成的误差,线宽展宽因子计算值为0.12～2.75.     

计算结构力学在桥梁结构施工设计与施工控制中的应用

随着大跨径桥梁结构在工程中应用日趋广泛,其施工控制问题也越来越受到工程界的重视。本文将计算结构力学方法引入桥梁结构的施工设计与控制,给出桥梁结构竣工后受力状态、施工各阶段理想状态的确定、施工控制方法及其程序系统的设计思想。     

微分几何与向后差分相结合的多柔体系统动力学数值方法

将处理微分－代数混合方程的微分几何方法与向后差分相结合，建立了一种新的求解多柔体系统的力学方程的数值方法，通过典型算例验证了方法的正确性和有效性。     

STUDIES ON THE SYNTHESIS OF THIOLS AND THEIR S-SUBSTITUTED DERIVATIVES

Abstract

Aromatic thiols belong to a group of not yet sufficiently explored compounds. The presence of an active hydrogen atom makes it possible to conduct various chemical conversions and to obtain new S-substituted derivatives.