Mechanical behaviors and damage constitutive model of ceramics under shock compression

One-stage light gas gun was utilized to study the dynamic mechanical properties of AD90 alumina subjected to the shock loading. Manganin gauges were adopted to obtain the stress-time histories. The velocity interferometer system for any reflector （VISAR） was used to obtain the free surface velocity profile and determine the Hugoniot elastic limit. The Hugoniot curves were fitted with the experimental data. From Hugoniot curves the compressive behaviors of AD90 alumina were found to change typically from elastic to ＂plastic＂. The dynamic mechanical behaviors for alumina under impact loadings were analyzed by using the path line principle of Lagrange analysis, including the nonlinear characteristics, the strain rate dependence, the dispersion and declination of shock wave in the material. A damage model applicable to ceramics subjected to dynamic compressive loading has been developed. The model was based on the damage micromechanics and wing crack nucleation and growth. The effects of parameters of both the micro-cracks nucleation and the initial crack size on the dynamic fracture strength were discussed. The results of the dynamic damage evolution model were compared with the experimental results and a good agreement was found.     

Massive格点Schwinger模型的准确基态和弦张力

本文提出Massive格点Schwinger模型的一种新的Hamiltonian,并到其准确基态.对Naive和Susskind两种费米子方案,准确计算了无穷长弦弦张力,结果均为1/2e²,与Massless格点Schwinger模型的结果相同.这表明Massive和Massless格点Schwinger模型同样地给出线性禁闭势,并且当α→0时没有解除禁闭的相变发生,与连续理论现有的结果一致.     

Thermodynamic Properties of Hard-Sphere Fluid under Confined Condition Based on Bridge Density Function

Based on the functional integral procedure, a recently proposed bridge density function [J. Chem. Phys. 112 (2000) 8079] is developed to calculate global thermodynamic properties of non-uniform fluids. The resulting surface tension of a hard wall-hard sphere interface as a function of the bulk hard sphere fluid density is in good agreement with the available simulation data. The proposed numerical procedure from the approximation of non-uniform first-order direct correlation function to a non-uniform system with excess Helmholtz free energy is of fundamental importance for phase behaviour under the confined condition due to the fact that many available simple approximations in classical density functional theory are for non-uniform first-order direct correlation function.     

“广电+”的实践路径探析

"广电+"是学界与业界共同关注的热词,尤其在当下,"广电+"深受"互联网+"深刻影响的启发,成为广电业界挽救颓势、重塑辉煌的一剂良药。但不同于"互联网+"立竿见影、摧枯拉朽的扩张进程,"广电+"的概念虽不断升温,但以其为标签实施的成功案例却乏善可陈。截止目前,将"广电+"作为拯救行业的重要手段尚未达到预期效果,实践路径亟待探索,本文将从抽象概念到具象实施探讨"广电+"的实践路径。     

模糊自适应PID控制的恒张力收卷系统研究

针对真空镀膜机收卷张力控制具有多变量、时滞性、非线性且系统难以建立精确模型的问题,为了降低张力波动,提高收卷张力精度、测试的稳定性,建立收卷恒张力模糊自适应PID系统结构模型。运用模糊推理对参数进行自整定的方法设计了一种二维自适应模糊PID控制器。应用Matlab/Simulink模块实现系统仿真,仿真结果表明模糊自适应PID算法相比常规PID控制具有较强的鲁棒性,良好的动态、静态稳定性。把该控制器运用到现场测试中,测试结果表明该控制器有效地减少了张力波动,提高了镀膜质量。     

界面张力在基板诱导共混物分散相粒子粗化生长加速现象中的作用

通过相差显微镜和计算机图像处理来研究两相聚合物体系的粗化过程 .将具有不同聚比的乙烯 聚醋酸乙烯酯 (EVAc)共聚物与聚丙烯 (PP)共混 ,制备不同相界面张力的系列共混物薄膜 .观察了在玻璃基板的作用下 ,不同界面张力体系的分散相粒子粗化行为 ,发现界面张力在约 0 4 8·1 0 - 5N cm以上的体系中分散相粒子的粗化有明显的加速现象 ,粒子体积生长与时间关系的指数大于 1 0 ;而两相界面张力较低的情况下 ,选择具有不同表面极性的基板对同一体系试验 ,我们均未发现有粗化加速现象产生 ,且采用不同基板之间的试验结果差异很小 ,亦即当高分子共混物的相界面张力大于一定值时 ,仅与基板存在有关 ,粒子的粗化行为被加速     

CTAB在硅胶表面吸附引起的润湿性变化和模拟驱油

用椭圆偏振法测定溴代十六烷基三甲胺（CTAB）水溶液在光滑的二氧化硅膜片上的吸附，其结果符合两阶段模型，即在不同浓度下发生单分子层和近似双分子层的吸附，并与其表面润湿性变化的数据吻合.用改进的Washburn方程测量改性硅胶粉末的润湿性, 研究了CTAB水溶液在硅胶粉末表面上吸附引起的润湿性变化.并由此探讨了CTAB水溶液在硅胶粉末表面的润湿性,表面活性剂的临界胶束浓度（CMC）与表面含油粉末脱油率的关系，对在非超低界面张力条件下通过改变固/液界面润湿性提高原油采收率作了实验探讨.     

[Cp*Rh(CO)2Me]BF4和二环庚二烯的反应机理研究

[Cp^*Rh(CO)₂Me]BF₄与二环庚二烯反应生成的含五元环产物可以作为烯烃/羰基共聚的潜在催化剂。本文采用密度泛函(DFT)方法对该类反应的机理进行了研究。研究表明，甲基转移是整个反应的决速步骤。计算得到，该步反应的活化焓变为71.67 kJ·mol^-1, 跟实验中得到的相应的焓变值(72 ± 2 kJ·mol^-1)吻合得很好。计算结果同时证实，该反应在热力学上非常有利。结构分析表明，二环庚二烯和金属中心配位后，二环庚二烯内的环张力得以释放以及螯合环的生成是导致热力学有利的主要原因。