电化学阻抗谱法研究Cu_6Sn_5合金负极相变过程

以粗糙铜箔为基底,采用一步电沉积法获得Cu-Sn合金,X射线衍射(XRD)测试结果显示其主要为Cu6Sn5合金相.扫描电子显微镜(SEM)测试结果表明该合金表面由大量"小岛"组成,且每个"小岛"上存在大量纳米合金粒子.充放电测试结果表明,以该合金为锂离子电池负极,其初始放电(嵌锂)和充电(脱锂)容量分别为461和405 mAh·g-1.电化学阻抗谱测试结果显示,Cu6Sn5合金电极在阴极极化过程中分别出现了代表固体电解质界面膜(SEI膜)阻抗、电荷传递阻抗和相变阻抗的圆弧,并详细分析了它们的变化规律.     

基于模糊证据推理的汽车制造产业网络环境复杂性测度

环境复杂性是汽车制造产业网络复杂性的主要诱因。利用指标波动程度测度复杂性的思想,建立表征汽车制造产业网络外部环境的指标体系,构建指标变动程度的模糊信度结构模型,运用模糊证据推理算法结合熵值理论对多指标进行信息融合,并利用灰色关联分析方法评估复杂性测度结果。通过2002~2012年汽车行业数据的实证研究,结果表明:经济环境与国际环境的波动是导致汽车制造产业网络复杂性的最主要因素,技术环境和市场环境次之;近10年来我国汽车制造产业网络外部环境经历了两次较大波动,总体复杂性呈现增长趋势。本研究可为汽车产业环境复杂性测度及应对提供思路参考。     

Magnetic Properties of Transverse Ising Model under a Time Oscillating Longitudinal Field

A transverse Ising spin system, in the presence of time-dependentlongitudinal field, is studied by the effective-field theory (EFT). Theeffective-field equations of motion of the average magnetization are givenfor the simple cubic lattice (Z = 6) and the honeycomb lattice (Z = 3).The Liapunov exponent λ is calculated for discussing the stability of the magnetization and it is used to determine the phase boundary. Thedynamic phase transition diagrams in h₀/ ZJ -Γ/ZJ plane and in h₀/ZJ-T/ZJ plane have been drawn, and there is no dynamical tricritical point on the dynamic phase transition boundary. The effect of the thermal fluctuations upon the dynamic phase boundary has been discussed.     

消色散光变图像的二元光学设计与制作方法

提出了一种实现消色散光变图像的二元光学方法.以不同取向的狭缝光阑作为目标物光场,采用迭代傅里叶变换算法计算得到具有定向衍射特性的二元位相结构,并作为光变图像的微结构.面向不同图形结构的光变图像,给出了两种不同的数据方案.利用自行研制的激光直写系统以逐图形方式和矢量化直写工作方式分别光刻不同结构的光变图像,位相结构的线宽为2 μm.实验结果表明,定向衍射二元光学位相结构具有消色散特征,且适合于热压复制工艺,为制造消色散光变图像提供了一种新方法.     

LARGE DEVIATIONS FOR SYMMETRIC DIFFUSION PROCESSES

Let a(x)=(a_(ij)(x)) be a uniformly continuous, symmetric and matrix-valued function satisfying uniformly elliptic condition, p(t, x, y) be the transition density function of the diffusion process associated with the Diriehlet space (, H_0~1 (R~d)), where(u, v)=1/2 integral from n=R~d sum from i=j to d(u(x)/x_i v(x)/x_ja_(ij)(x)dx).Then by using the sharpened Arouson's estimates established by D. W. Stroock, it is shown that2t ln p(t, x, y)=-d~2(x, y).Moreover, it is proved that P_y~6 has large deviation property with rate functionI(ω)=1/2 integral from n=0 to 1<(t), α~(-1)(ω(t)),(t)>dtas s→0 and y→x, where P_y~6 denotes the diffusion measure family associated with the Dirichlet form (ε, H_0~1(R~d)).     

THEORETICAL CALCULATION OF THE MAGNETIC PROPERTIES IN DISORDERED GROUND STATE FOR SPIN-1/2 ANTIFERROMAGNET

The spin-1/2 quantum antiferromagnet in three-dimensional space can be described by Heisenberg model:two nearest-neighbor spins with strong interaction in z direction consistitute a dimer, every dimer can be considered as a lattice site in the tetragonal lattice. In z direction, the exchange interaction between two nearest-neighbor dimers is λ'J, and in xy plane it is 2 λJ. In bond-operator representation, within the mean-field decoupling approximation, we have calculated the phase diagram for order-disorder phase transition about λ and λ' at 0 K, obtained the critical value, λ_c=0.292, within which the disordered phase is stable in two-dimensional case(λ'=0), and found that the disordered phase is always stable for λ'<1 in one-dimensional case(λ=0). For the disordered phase, the physical quantities, such as energy gap, ground-state energy, two-point correlation functions and correlation lengths in xy plane and in z direction, have been calculated as functions of parameters λ and λ'.     

一些常见的错解剖析

从初等数学转入高等数学的学习,很多学生不能适应这个转变,常常忽视阅读教材,弄清弄懂高等数学的基本概念,定义,定理的条件,结论,而忙于解习题,完成作业,结果事倍功半,收获甚微.本文列举并分析学生作业中常见的错解,希望引起初学者的重视.     

用钕玻璃片观察吸收光谱

观察钠的吸收光谱线的实验,目前一般中学还感到困难。主要原因是用在酒精内,溶钠盐和在灯焰上撒钠盐的办法,不易得到稳定的钠蒸气,且装置和调节都比较麻烦。不易掌握,很难看到清晰、稳定的吸收光谱线。     

小时间区间中的条件扩散过程

本文讨论具有一致连续系数条件扩散过程的大偏差性质。设X(t)是具有Dirichlet空间(ξ、H_0~1(P_0~d))的扩散过程,其中 ξ(f,g)=1/2 integral from n=R~d to (〈▽f,▽g〉(x)dx)。 P_a~e是过程x_6(t)=x(∈t)满足条件x_6(0)=x,x_6(1)=y的律。那么当∈→0时,(P_(?)~(?),y)具有大偏差性质,且具有速率函数 J_(x,y)(ω)=1/2 integral from n=0 to 1(〈(?)(t),a(-1)(ω(t)),(?)(t)〉dt-1/2 d~2(x,y)。     

冷原子荧光法间接测定痕量砷的研究

我们研究了用冷原子荧光法间接测定痕量砷的方法,其原理是将微量砷还原为气态砷,然后与Hg~(2+)发生如下反应。 2AsH_3+3HgCl_2→As_2Hgs↓+6HCl 由于生成稳定的As_2Hg_3,使溶液中汞离子浓度降低,用冷原子荧光法测量初始的与反应后的汞原子荧光,从其差值(△F)即可间接求出砷的含量。