壳聚糖硫酸盐的催化酯化反应研究进展

本文综述了壳聚糖硫酸盐的制备和作为催化剂在酯化反应中的应用研究。     

大学生自主学习效果的调查研究--基于新疆高校1081份调查问卷的分析

基于新疆高校1081份调查问卷,从受访学生自习效果以及早起学习效果两个方面研究新疆高校受访学生的自主学习效果,同时以性别、户籍、生源地及专业为分组变量,以大学生自主学习效果作为因变量进行方差分析。总体来说,多数受访学生对其自主学习效果是比较满意的。通过方差分析发现,性别、生源地对受访学生的自习效果和早起学习效果均有显著影响;户籍、专业对受访学生的早起学习效果有显著影响,但是无法充分证明户籍、专业对受访学生的自习效果有显著影响。     

阿拉伯国家高等教育的新进展

文章主要介绍了阿拉伯国家高等教育的最新进展，并就其未来发展应给予关注的问题做了初步探讨。     

超声波提取独活中总香豆素的工艺研究

研究超声波提取独活中总香豆素的工艺影响因素。采用紫外可见分光光度法作为分析手段,以总香豆素的提取得率为评价标准。通过单因素分析,得到最佳提取条件为:溶剂倍量10倍,乙醇体积分数60%,超声波功率240W,提取时间20min,提取温度30℃,粒度40～100目。     

Active control for flexible mechanical systems with mixed deadzone-saturation input nonlinearities and output constraint

There exist mixed deadzone-saturation input nonlinearities and output constraint in the practical implementation environment for flexible mechanical systems, and they have crucial influences on the performance of flexible systems. In this paper, two class of flexible structures are investigated and analyzed by designing the active boundary vibration control with auxiliary systems. Based on the infinite dimensional dynamic model of flexible mechanical systems, the barrier logarithmic terms are brought into the Lyapunov function and boundary vibration control laws for maintaining the output signals within the constrained region. Besides, the auxiliary terms are designed in the control laws to compensate for mixed nonlinear inputs which integrate the deadzone and saturation characteristics. With the simulation results, the theoretical analysis for the flexible mechanical systems is verified to be correct and the designed control laws are effective.     

活塞挤压铸造用高性能铝合金材料的制备研究

针对现有铝合金材料不能满足动力机械用的薄壁高强韧铝合金零件的要求,通过改进材料配方和制备方法,得到符合铝合金挤压铸造工艺要求的高强韧新材料。实验结果表明,利用该材料生产的铸件平均抗拉强度达到300MPa,高温抗拉强度268MPa,伸长率超过1.73％,硬度超过HB95,微观组织晶粒致密,基本无缩松缩孔等缺陷,达到了高性能要求。     

DMF萃取精馏法精制乙酸乙酯的过程模拟研究

本文利用化工流程模拟软件AspenPlus采用萃取精馏,以DMF为萃取剂,对乙酸乙酯生产中的产品精制进行了模拟计算,详细分析了理论板数、进料位置、溶剂比和回流比对产品浓度的影响。结果表明,最优工艺方案为：理论板数40,粗酯进料位置29,萃取剂进料位置6,溶剂比1.6,回流比2.0,塔顶产品乙酸乙酯含量达到99.9%,质量达到GB/T3728-2007优等品标准,为分离过程的优化操作和设计提供依据。     

高校生理学创新实验教学设计方法和评测

为适应《国家中长期教育改革和发展规划纲要(2010-2020年)》要求,对北京师范大学生理学实验创新课程教学目标做了一定的修订,主要以生理学创新实验为例详细介绍了基于引导激发式教学的创新实验设计方法和评测。     

柠檬酸三辛酯（TOC）的催化合成研究

研究了几种固体酸催化合成柠檬酸三辛酯的催化活性。结果表明：四氯化锡的催化酯化活性最好,并讨论了以四氯化锡为催化剂时,醇酸物质的量比、催化剂用量、反应时间与酯化程度的关系,确定了合成柠檬酸三辛酯的最佳条件：醇酸物质的量比为5：1,催化剂用量为0.2g,反应时间为50min。在最佳条件下,酯化率可达95.58%。     

Synthesis of Modified Epoxy Resin Undercoat for Resistor by Nano-SiO2

A kind of undercoat for resistor with high temperature and humidity resistance was obtained by modifying epoxy resin with proper nano-SiO2 added at 80 ℃. The structure, thermal stability, humidity resistance, and morphological characteristics of the modified epoxy resin undercoat were studied by electrical tests, infrared spectra (IR) analysis, and scanning electron microscopy (SEM). The results show that more compact and steady inter-crosslinked network structures are formed in the modified epoxy resin undercoat added with nano-SiO2, which greatly improves the performance of modified epoxy resin undercoat. The undercoat with nano-SiO2 of about 2.71%, kept for six months at room temperature without flocculating and aggregating, is of good stability, and the surface of painted resistor is uniform, tight and without air holes on it. The varying ratio of resistance with such undercoat painted is less than one in a thousand after high temperature and humidity resistance tests.