Experimental study of similarity subgrid-scale models of turbulence in the far-field of a jet

Several versions of similarity subgrid-scale turbulence models are testeda-priori using high Reynolds number experimental data. Measurements are performed by two-dimensional Particle Image Velocimetry (PIV) in the far field of a turbulent round jet. It is first verified that the usual Smagorinsky model is poorly correlated with the real stress _ij . On the other hand, a similarity subgrid-scale model based on the resolved stress tensorL _ij , which is obtained by filtering products of resolved velocities at a scale equal to twice the grid scale, displays a much higher level of correlation. Several variants of this model are examined: the mixed model, and the global and local dynamic procedure. Model coefficients are measured, based on the condition that the subgrid models dissipate energy at the correct rate. The experimental data are employed to show that the dynamic procedure [4] yields appropriate model coefficients based only on the resolved portion of the velocity field. Some features of the dynamic procedure in its local formulation are also explored.     

研制开发大学物理实验CAI课件提高物理实验教学质量

本文结合实际介绍了CAI课件的开发与应用,并阐述了CAI课件在提高物理实验教学质量中所起到的作用。     

高分子科学实验教学改革初探

设想将高分子化学、高分子物理和高分子成型加工三门实验课程有机地串联起来,组建成一门包括从高分子材料设计(用计算机软件进行分子设计、性能模拟)、聚合物合成、性能测试(物性表征)到加工成型(制作成高分子材料制品),能环环相扣、互动式的、柔性化的高分子科学实验课程;提出了初步的实践方案.     

Alkyl phosphines promoted reductive coupling of acyl cyanides: formation of O-acyl cyanohydrins

The reductive coupling of acyl cyanides promoted by alkyl phosphines has been discovered. Under mild reaction conditions, the substituted cyanohydrins were obtained in moderate to high yields by using trimethylphosphine or tributylphosphine as a promoter. The possible mechanism involved in the reaction was discussed on the basis of deuterium labeling and control experiments, indicating that one hydride transfer took place from alkyl phosphine to O-acyl cyanohydrin.     

基于IrYdium Chemistry Lab的可视化教学设计——以“盐类的水解”为例

利用虚拟化学实验软件IrYdium Chemistry Lab为基本工具，探讨其在“盐类的水解”一节进行可视化教学设计的具体方法和教学应用价值。说明基于虚拟化学实验的可视化教学设计，能兼顾表达思维可视化过程和结果，有利于强化学生的学科理解能力。     

Hooke numbers of polymers

Hooke numbers He ≡ σ_b/(E) are calculated from published ultimate tensile strengths σ_b, tensile moduli E, and ultimate elongations ?_b. Data for common thermoplastics and natural fibers each follow a function He = [1 + (?_b/?_crit)^ab]^?1/b with a Hookean region I (He = 1) at ?_b ? ?_crit, a non-Hookean region III at ?_b ? _crit, and a transition region II for ?_b ≈ ?_crit. Only non-Hookean regions III were found for semisimultaneous interpenetrating networks from polyisobutylene-polymethyl methacrylate, thermoplastic elastomers from segmented polyamide-polyethers, molecular composites from poly(p-phenylene benzobisthiazole) and poly[2,5(6)-benzimidazole], and three groups of various synthetic fibers. The Hooke numbers of lyotropic and thermotropic liquid-crystalline polymers vary with the heat treatment and depend on orientation angles for orientation angles greater than ca. 10°. Hooke numbers much greater than 1 are observed for highly stressed polymers. ©1995 John Wiley & Sons, Inc.     

应用扫描电镜拉伸台测定激光熔覆层结合强度

采用扫描电镜的拉伸台测定了合金表面激光熔覆层与基体的结合强度，分析了基材预热温度对界面结合强度的影响，观察了界面裂纹的形成及扩展过程。结果表明，这种方法较为准确地测量了熔支与基体之间的结合强度。     

新加坡Chemistry Matters教材中实验内容的分析及启示

以新加坡初中化学Chemistry Matters教材为研究对象，对教材中涉及的实验案例、实验类型及数量进行了统计。结合新加坡新版科学教学大纲及PISA测试，从教材实验的内容选取、设计意图、呈现方式等方面进行分析，并对教材实验部分蕴含的核心素养进行一定程度地挖掘。研究得出：Chemistry Matters教材中实验的设置具有"内容选取彰显与时俱进，设计意图注重学以致用，呈现方式突出图表结合，活动过程强化问题引导"等特点。     

反散射理论导出He-Ne相互作用势

以Ｈｅ原子束与Ｎｅ原子束交叉碰撞实验数据为基础。以反散射方法为手段，理论上导出Ｈｅ－Ｎｅ原子相互作用势，所得的势呈显出ｖａｎ ｄｅｒ Ｗａａｌｓ势的特征，即短程为强排斥，中程为碗形吸收，远程为零，这样的势能正确的，符合实验的弹发型用射微分截面。     

综合化学实验:变色传感金属有机框架材料的制备

为了有效提升学生在化学实验过程中的学习积极性及效果,特推荐一个综合型化学实验--变色传感金属有机框架材料的制备。该实验设计思路是将前沿科学研究内容与本科生实验教学相结合,使学生在学习本科基础知识的同时又能了解科学研究的前沿领域。该实验涉及了有机物合成、无机领域金属有机框架材料的制备,还包括了红外、热重、X射线粉末衍射、紫外可见等仪器的使用及分析。鉴于本实验内容涵盖面较广,建议作为高年级本科生综合化学实验设置。