受时滞影响的双个体自组织系统的集群性

研究了受Motsch-Tadmor影响函数控制和处理时间延迟影响的双个体Cucker-Smale自组织模型,将现有的充分性结果进行了推广,给出了双个体自组织系统产生集群行为的充分必要条件,同时也揭示了时滞的大小对系统集群性的影响.数值模拟验证了结果,并表明在固定初始条件和参数的情况下,时滞的变化会导致系统出现集群行为,集群行为消失,周期振荡等分支现象.     

从一道运动学题目的求解谈坐标系选取的重要性

通过比较一道典型运动学题目的近似求解方法与精确求解方法，探讨坐标系选取对研究曲线运动的重要性．     

Transport properties of a ladder with two random dimer chains

We investigate the transport properties of a ladder with two random dimer (RD) chains. It is found that there are two extended states in the ladder with identical RD chains and a critical state regarded as an extended state in the ladder with pairing RD chains. Such a critical state is caused by the chiral symmetry. The ladder with identical RD chains can be decoupled into two isolated RD chains and the ladder with pairing RD chains can not. The analytic expressions of the extended states are presented for the ladder with identical RD chains.     

Transport properties of a random binary side-coupled chain

We investigate the transport properties of a random binary side-coupled chain by using the transfer-matrix technique. It is found that there are resonant states in the systems with short-range correlations between the host chain atoms and the side-coupled atoms. The analytic expressions for the extended states are also presented in the systems with the side couplings between like atoms and between unlike atoms.     

Gap Caused by Strong Pairing in the Ladder Model of DNA Molecules

By directly diagonalizing the Hamiltonian of the ladder model of deoxyribonucleic acid （DNA） molecules, the density of states is obtained. It is found that DNA behaves as a conductor when the interchain hopping is smaller than twice the intrachain one, otherwise, DNA behaves as a semiconductor.     

Quantum Confinement of si Nanosphere with Radius Smaller than 1.2 nm

We calculate the density of states, the squared optical matrix element along the x direction, and the band gap of Si nanosphere with radius r smaller than 1.2 nm using the method of linear combination of atomic orbitals. It is shown that the quantum confinement effect of Si nanocrystals exists obviously, fulfilling E = 1.92 0.23/r^1.8,but the band gap exhibits fluctuation with nanocrystal size, which is caused by the dangling bonds of atoms ino uter layers. The obtained result indicates that the surface chemical bonds have larger influence on the energy band structure of Si nanosphere when its radius is smaller than 1.2nm.     

高效液相色谱法测定食品中禁用色素苏丹红Ⅰ-Ⅳ和对位红

采用高效液相色谱法测定食品中禁用色素苏丹红Ⅰ一Ⅳ和对位红.以乙腈为提取剂,超声波提取样品中苏丹红Ⅰ一Ⅳ和对位红.以ZORBAX SB-C18>柱(4.6 mm×150 mm,5μm)为分离柱,乙酸(1 999)溶液和乙腈为流动相进行梯度洗脱,流速为1 mL·min-1,检测波长为485nm的条件下进行检测.苏丹红、对位红的回收率为90%～98%,相对标准偏差小于5%,苏丹红和对位红的检出限均为0.01μg·g-1,苏丹红和对位红的质量浓度在0.2～2.0 mg·L-1范围内呈线性.     

声波在双层非线性介质中传播的二极管现象

假设声波在双层一维非线性系统中传播时线性部分满足波动方程,非线性部分类似于非线性薛定谔方程的非线性部分.对该模型正反两个方向分别入射相同的声波计算透射率发现:一定频率及强度的声波在模型中具有单向透过性,表现出声二极管的行为;随着非线性强度差异的增强,单向导通性显著提高.     

硅纳米结构中硅空位缺陷引发的双峰蓝光发射

报道了在硅纳米结构中417nm和436nm双峰结构的蓝光发射的实验和理论研究结果．制备了四种包含和没有包含β-SiC纳米晶粒的硅纳米结构，观察到了417nm和436nm的双峰蓝光发射．光致发光谱的分析和微结构的观察揭示了蓝光发射与硅纳米结构中过剩硅缺陷中心的存在有关．计算了由过剩硅原子形成的含有硅空位缺陷的纳米晶粒的电子能级，发现计算所得的态密度的特征与观察到的双峰发射吻合．这项工作提出了在许多硅纳米结构中存在417nm和436nm蓝光发射的一种可能的机制．     

Transport Properties in a One—Dimensional Chain with Randomly Side—Coupled Impurities

We investigate the transport properties of a one-dimensional(1D) chain with randomly side-coupled impurities,By using the transfer matrix technique,we present numerical results of the transmission coefficient as a function of the electron energy,It is found that an extended state will be shown in such a random 1D system if the impurities are side-coupled to the chain with not only the nearest-neighbour bonds but also the next-nearestneighbour bonds.We present an analytical expression for the energy of this extended state,which is determined by the strength of the nearest and next-nearest couplings between the impurities and the chain.The obtained results can be used to explain the transport properties of DNA chains and other quasi-1D organic structures.