甘油三乙酸酯超临界酯交换反应及其动力学研究

研究了在超临界条件下甘油三乙酸酯与甲醇或乙醇的酯交换反应,分别考察了超临界状态下醇油摩尔比和温度对反应的影响。实验结果表明,甲醇或乙醇与甘油三乙酸酯的摩尔比为14、反应温度为350℃、反应时间为20m in时,乙酸甲酯或乙酸乙酯的收率分别达100%和60%。对超临界状态下动力学的研究结果表明,甘油三乙酸酯与甲醇或乙醇的酯交换反应为拟一级反应,在相同的反应条件下,采用甲醇时酯交换反应速率比用乙醇时快,相应的甘油三乙酸酯的转化率也高;甘油三乙酸酯在超临界甲醇或乙醇中酯交换反应的表观活化能分别为58.7 kJ/mol和75.1 kJ/mol,甘油三乙酸酯与甲醇酯交换反应的活化能低于与乙醇酯交换反应的活化能,表明碳链短的醇更易进行酯交换反应。     

Stability studies on methyl and ethyl fatty acid esters of sunflowerseed oil

Fatty acid esters, high in linoleic acid, were prepared and stored for long-term engine tests. Storage tests with these esters were undertaken to obtain more information on optimal storage requirements and general stability characteristics. Samples were kept at three temperature levels (20 C, 30 C and fluctuating around 50 C) for a 90-day period and were removed at regular intervals for chemical and physical analysis. The influence of air, temperature, light, TBHQ and contact with mild steel was evaluated by comparing the free fatty acid, peroxide, anisidine, ultraviolet absorption, viscosity and induction periods. A statistical model was used to evaluate the data and to reduce the large number of data points to comparable curves. Storage of esters in contact with air, especially at a temperature above 30 C, resulted in significant increases in peroxide, ultraviolet absorption, free fatty acid, viscosity and anisidine values. Exclusion of air retarded oxidation at all temperature levels. A direct relationship between viscosity increases and oxidation parameters was evident. Exposure to light caused a small increase in the oxidation parameters of esters stored at the highest temperature level. Addition of TBHQ prevented oxidation of samples stored under moderate conditions. Under unfavorable storage conditions the anti-oxidant was no longer effective. Mild steel had very little effect on the oxidation parameters. Only the anisidine values of samples stored at the highest temperature level were slightly increased. Methyl esters performed slightly better than ethyl esters during the storage test. The following practical guidelines for storage of fatty acid ester fuels are: (i) airtight containers should be used; (ii) the storage temperature should be <30 C; (iii) mild steel (rust free) containers may be used, and (iv) TBHQ has a beneficial effect on oxidation stability.     

连轧机用人字轮齿轴断裂失效分析

用宏观断口分析、化学检验、力学性能测定、低倍检查、金相组织及夹杂物评定鉴别、受力分析及强度寿命定量估算的方法，对人字轮被动齿轴端断裂失效原因进行分析，并提出改进措施。     

C语言编程在智能化重力加速度测试仪中的应用

在基于单片机的智能化重力加速度测试仪中采用Ｃ语言编程简化了程序设计任务，对于汇编语言难于处理的浮点数运算及汉字打印输出可通过Ｃ语言编译器的内部库函数调用实现，介绍了一种专为８０５１系列单片机设计的Ｃ语言编译器Ｆｒａｎｋｉｌｉｎ Ｃ５１，它具有代码优化功能，能产生极高效率的机器码，并且提供了丰富的内部函数库。描述了Ｃ５１函数库所支持的ＩＥＥＥ标准浮点数的内存格式以及采用ｓｐｒｉｎｔｆ（）函数处理包括     

Implementation of secure digital communication by hyperchaoticsynchronisation

By active-passive-decomposition synchronisation, the application of the one-way coupled ring map lattice hyperchaotic system in secure digital speech communication is demonstrated. Synchronisation guarantees strong security and recovery without error     

NH_4Cl水溶液在成膜过程中的致孔作用

本文以ＮＨ４Ｃｌ饱和水溶液做添加剂，对ＰＶＤＦ／ＮＭＰ体系在成膜过程中的致孔作用做了研究。铸膜液中随ＮＨ４Ｃｌ水溶液加入量的改变，膜孔径也发生变化，并出现最大值。通过Ｘ－射线衍射扫描发现制膜液中存在无机盐时膜中无定形态结构增加，表明无机盐的加入有助于膜孔形成     

军事卫星通信系统的发展趋势

卫星通信在C~3I系统中将发挥越来越重要的作用,而目前卫星通信又处在一个大发展的时期,可以预计在未来的十年到二十年间卫星通信将面临许多重大变革。论文从四个方面论述了军事卫星通信系统的发展趋势。     

在柔性变焦系统中的压力变焦镜

从理论上和实验上对水冷镜的镜面曲率半径随压力变化的规律作了研究。对压力变形后镜面相对于球面作了波像差分析，分析表明压力变焦镜用于中红外激光系统是合适的     

定向爆破拆除煤矿主井井塔

文章论述了井塔拆除爆破中，把框架承重立柱的裸露钢筋骨架失稳看作为压杆失稳以及井塔在倾斜撞地时下部不解体破坏的估算。