Etherification of Alkali-pretreated Sugarcane Bagasse Cellulose in Tetrahydrofuran

Sugarcane bagasse (SCB) is an important by-product in the sugar industry. It is a source of cellulose fibers or cellulose for paper mills and textiles factories. In this study, SCB was ethyl etherified in tetrahydrofuran (THF) after alkali pretreatment. The alkali concentration for the pre-treatment, the ratio of ethyl bromide (EtBr) to dried SCB in the reaction, reaction time, and temperature were investigated for the etherification of SCB. The ethoxyl content and characterization of the product were determined using headspace gas chromatography (HS-GC), Fourier Transform Infrared (FT-IR) and ¹³C-NMR spectroscopy, respectively. It was found that SCB was well-etherified with EtBr in alkali-THF. Upon ethylation of SCB, the ethoxyl content of the product was high when the alkali concentration and the ratio of EtBr to dried SCB were controlled from 50% to 75% and 4:1 (V/w) to 6:1 (V/w), respectively. The reaction occurred optimally when the temperature was controlled below 110℃; above this temperature, the degree of etherification decreased. The thermal stability of ethylated SCB was higher than that of SCB but slightly lower than that of commercial ethyl cellulose. Ethylated SCB has the potential to form composites with many materials because it is soluble in a wide variety of solvents.     

半导体桥对含能材料的点火特性研究

在10μF钽电容放电激励下,对两种阻值相当质量不同的半导体桥(SCB)和细化的发火药剂斯蒂芬酸铅(LTNR)和叠氮化铅(PbN6)所组成的发火件进行了实验研究,根据发火件的电特性变化和发火现象发现半导体桥存在电热发火、电爆发火和等离子体发火三种情况,测试了SCB/LTNR和SCB/PbN6发火件的50%发火电压和发火时间。结果表明半导体桥的发火电压阈值不仅与发火药剂有关,还与半导体桥换能元有关,所以半导体桥的设计存在最佳质量,通过对比得知LTNR比PbN6感度高,PbN6比LTNR的燃速高。     

EPON系统中高效视频组播的实现方法

采用EPON系统的宽带接入网络可以为每个用户提供较高带宽,并且能较好地支持组播功能,是视频组播业务重要的用户接入手段。提供一种在EPON系统中实现高效率纽播的方法,充分发挥EPON网络点到多点结构的特点,使同一个组播组的用户共享一条流,从而提高下行带宽的利用率。     

SCB火工品的研究与发展

文章评述了半导体桥火工品问世以来的研究成果与发展趋势。主要内容有半导体桥作用机理、半导体桥的结构与封装、半导体桥火工品的特点、半导体桥火工品的应用、半导体桥火工品的研究和发展趋势。     

Residential energy use and conservation in Sweden

We describe energy use in Swedish homes from 1963 to 1980 using data assembled and analyzed for the first time. Changes in energy use by fuel and purpose before and after the 1973 oil price shock are illustrated and discussed, and savings in space heating in the year 1980, compared with the pre-embargo period, are quantified. We discuss two important elements of Swedish energy conservation policy, the building codes and the system of grants and loans to homeowners. We conclude that the grants and loans probably accelerated home retrofit measures, while the building codes will play an important role in reducing residential heat losses over the long term.     

半导体桥升温方程研究

半导体桥火工品是取代桥丝的理想火工品。本文根据半导体桥的点火特性,应用电能转化为热能、热传导和炸药的热爆炸三个方面的理论,建立了在电容放电和直流输入两种方式下半导体桥桥体的升温特性方程;并通过计算机运算绘图,验证了方程基本符合理论要求。文章最后指出升温方程需加入修正系数来进一步完善。     

补偿电容器组同步开关控制器的研制

介绍了新研制的中压补偿电容器组同步开关控制器的工作原理和基本结构,该控制器将控制和驱动永磁机构,以实现开关的选相合、分闸,从而有效地抑制投切并联电容器组时引起的过电压及涌流。     

基于围道积分及网格重剖分下的SCB裂纹扩展数值模拟研究

针对以往研究对裂纹扩展具有诸多限制,且较少利用断裂力学理论的不足,基于Abaqus平台,利用围道积分及网格重剖分技术,实现了基于断裂力学的裂纹自由扩展数值模拟,对SCB模型进行了应力强度因子及裂纹扩展过程数值仿真,结果表明：对SCB模型的仿真结果与国际岩石力学学会(ISRM)的理论结果一致；(2)I型应力强度因子随着a/R和S/R的比值的增加而增加,II型应力强度因子随裂纹倾角先增大后减小。当YI值为0时,试样受到纯II型作用,对于S/R=0.8的SCB模型,只有在a/R=0.7及α=65°时才出现II型裂纹扩展模式。纯模II的裂纹角随裂纹长度比的增大而减小,但随跨高比(S/R)的增大而增大；对裂纹扩展过程进行了数值模拟,裂纹从裂纹尖端发生,朝着上加载点处扩展。裂纹角度增大时,裂纹起始角的值增大,而其值随跨度比的增大而减小(S/R),此外,裂纹起始角的值随裂纹长度比(a/R)先增后减。裂纹起裂角几乎发生在裂纹长度比(a/R)为0.5情况。     

压敏电阻对半导体桥火工品电爆性能的影响

压敏电阻能有效抑制浪涌电压,可用于火工品电磁防护。为研究压敏电阻对半导体桥(SCB)火工品电爆性能的影响,本研究在电容放电(47μF、22 V)与恒流(100 ms)激励条件下测试了并联压敏电阻前后典型尺寸SCB火工品100μm(L)×400μm(W)×2μm(T)和低发火能量SCB火工品20μm(L)×100μm(W)×2μm(T)的爆发时间和爆发消耗能量的变化规律。电容放电实验(47μF、22 V)结果 t检验表明,并联压敏电阻前后的典型SCB火工品的爆发时间和爆发能量均无显著性变化;对于低发火能量SCB火工品,并联击穿电压较低的压敏电阻时,爆发所需能量升高14%,而爆发时间无显著性变化。而恒流(100 ms)激励实验结果表明,压敏电阻对两种SCB火工品电爆性能均无显著性影响。     

半导体桥的设计分析

半导体桥是半导体桥火工品中最为关键的元件,它的结构和性质对火工品起着十分重要的作用,设计结构合理、性能优良的半导体桥是研究半导体桥火工品首要任务.文章以理论分析和文献分析为基础并结合试验数据,提供了一套半导体桥的设计方法,并选定了合理的结构和材料,给出了一组参数,确定了最小临界能的半导体桥图形.