A molecular network model to describe the nonlinear viscoelastic behavior of polymers

A transient molecular network model is built to describe the nonlinear viscoelasticity of polymers by considering the effect of entanglement loss and regeneration on the relaxation of molecular strands. It is an extension of previous network theories. The experimental data on three thermoplastic polymers (ABS, PVC and PA6) obtained under various loading conditions are used to test the model. Agreement between the theoretical and experimental curves shows that the suggested model can describe successfully the relaxation behavior of the thermoplastic polymers under different loading rates by using relatively few relaxation modes. Thus the micromechanism responsible for strain-rate dependence of relaxation process and the origin of nonlinear viscoelasticity may be disclosed. The project supported by the National Natural Science Foundation of China and Doctorial Fund     

析氢反应动力学的交流阻抗法研究

利用交流阻抗法测定析氢电化学动力学参数，得到与极化曲线法一致的结果，为确定复杂析氢过程速率的决定步骤提供了判据。     

用光学多通道分析仪系统作高分辨光谱测量的技术

通常的光多通道分析仪(OMA)存在着同时谱宽与分辨率的矛盾.本文所述方法,在不减小谱宽的前提下,可将该分析仪光谱分辨率提高1～2量级,使之可适用于高分辨率谱研究.     

A diffusion approximation result for two parameter processes

Summary We consider a one-dimensional linear wave equation with a small mean zero dissipative field and with the boundary condition imposed by the so-called Goursat problem. In order to observe the effect of the randomness on the solution we perform a space-time rescaling and we rewrite the problem in a diffusion approximation form for two parameter processes. We prove that the solution converges in distribution toward the solution of a two-parameter stochastic differential equation which we identify. The diffusion approximation results for oneparameter processes are well known and well understood. In fact, the solution of the one-parameter analog of the problem we consider here is immediate. Unfortunately, the situation is much more complicated for two-parameter processes and we believe that our result is the first one of its kind.Partially supported by ONR N00014-91-J-1010     

R_2Fe_17_C化合物的结构与内禀磁性的研究

本文系统研究了R_2Fe_17_C(R=Y,Sm,Gd,Tb、Dy.Er) 化合物的结构与内享磁性, 井与相应的R_2Fe_17_C 化合物进行了比较.R_2Fe_17_C 的居里温度比相应氏R_2Fe_17 的居里温度增加大约200K. 本文讨论了C 原子对该化合物结构与磁性的影响, 同时, 还对Sm_2(Fe_1-xCo_x)_17C系列化合物进行了研充. 关键词：     

Four-wave mixing based 10-Gb/s tunable wavelength conversion in dispersion-flattened microstructure fibers

All-optical wavelength conversion of 10-Gb/s signal based on four-wave mixing is experimentally demonstrated in a 30-m-long dispersion-flattened microstructure fiber with small positive dispersion. For an average pump power of 26 dBm, the conversion efficiency was around -19.5 dB with the fluctuation less than ±1.4 dB, covering a conversion bandwidth of 20 nm. The eye diagram of the converted signal shows good eye opening.     

关于可达矩阵的求法探讨

在《离散数学》、《图论》课程中 ,用矩阵表示图时 ,涉及到一类重要的矩阵——可达矩阵 ,它是判别图中任意两点是否有通路的重要手段 ,也是求强分图的重要方法 ,但是可达矩阵的求法比较复杂 .本文针对这一问题 ,对可达矩阵的求法进行了改进 ,提出了一种简单可行的算法 .     

纳米WO3的制备及其光解水析氧性能研究

用溶胶凝胶法,灼烧法合成了纳米级WO3,采用X-射线衍射、紫外可见漫反射光谱对WO3进行表征.在Fe3 为电子受体、溶液酸度pH为2.0情况下,研究了纳米级WO3在365nm紫外辐射下光解水析氧的光催化活性,并讨论了不同方法制备的催化剂活性差异的原因.结果表明,结晶程度越高、尺寸越小、比表面积越大的纳米级WO3具有更高的光分解水析氧活性,电子受体的浓度、溶液的酸度对析氧活性有明显的影响.     

上海光源储存环磁聚焦结构设计

上海光源是一台正在建设中的低发射度第三代同步辐射光源. 经过优化后, 储存环有两种直线节长度, 周长432m,在能量3.5GeV下束流发射度为3.9nm.rad, 直线节处的β函数和色散函数有足够的调节范围. 跟踪研究表明, 即使带上磁铁高阶场误差, 储存环仍有足够大的动力学孔径和能量接受度.