高岭石基复合材料在光催化领域应用的研究进展

环境污染和能源紧缺已成为当今社会亟须解决的重大问题。高岭石基复合材料光催化处理技术因绿色环保、经济安全、无二次污染而备受关注。鉴于高岭石在光催化领域的研究现状,本文介绍了高岭石的层状硅酸盐结构特征及其在光催化领域的应用优势,综述了高岭石基光催化材料的主要类型、基本特征、合成方法、改性过程、光催化特点及其应用进展与优势,最后,提出了高岭石基复合材料在光催化领域应用的重点研究方向。以期获得制备工艺简单、光催化性能优异、原料易获取且无环境污染的高岭石基光催化复合材料,从根本上解决环境污染问题,缓解能源紧缺危机。     

热环境下功能梯度夹层双曲壳三维自由振动分析

功能梯度夹层双曲壳结构广泛应用在航空航天、海洋工程等领域中,对于该类结构的动力学特性研究非常重要。本文以热环境下功能梯度夹层双曲壳为研究对象,在三阶剪切变形理论的基础上,考虑横向拉伸作用的影响提出了一种新的位移场,假设材料的物性参数与温度有关,且沿厚度方向表示为幂律函数。利用Hamilton原理得到简支边界条件下功能梯度夹层双曲壳三维振动系统动力学方程,利用Navier法求得两种不同夹层类型的系统固有频率。研究了几何物理参数和温度场对功能梯度夹层双曲壳自由振动固有频率的影响。     

用于空间激光通信的InGaAsP 激光二极管辐射损伤研究(英文)

对1:55 μm波长DFB 结构的InGaAsP 多量子阱激光二极管开展电子和60Co- 射线辐照试验。试验结果表明,激光二极管的斜度效率主要受带电粒子沉积的电离总剂量影响,而阈值电流和光功率主要受位移损伤剂量的影响。利用位移损伤剂量方法评价激光二极管的辐射损伤特征,并且预测其在空间辐射环境中的光功率衰退情况。模拟计算结果表明,MEO轨道辐射环境对激光二极管光功率辐射损伤远大于GEO轨道的影响,这主要是由于MEO轨道辐射环境的高能电子通量密度远大于GEO轨道的通量密度。The 1.55 μm InGaAsP multi-quantum-well laser diodes with distributed feedback structures were irradiated by electrons and 60Co- rays. The experimental results show the slope efficiency of laser diode is mostly affected by the total ionizing dose produced by charging particles, and the threshold current and the optical power mainly by displacement damage dose. The displacement damage dose methodology was employed to evaluate radiation damage of the laser diodes, and to predict the power degradations of these diodes in space. The calculated results indicate that the optical powers of the diodes will have more serious degradation for medium Earth orbit than for geosynchronous Earth orbit,due to higher fluence density of high energy electrons in GEO orbits.     

Equivalent properties of single event burnout induced by different sources

The experimental results of single event burnout induced by heavy ions and 252Cf fission fragments in power MOSFET devices have been investigated. It is concluded that the characteristics of single event burnout induced by 252Cf fission fragments is consistent to that in heavy ions. The power MOSFET in the ＂turn-off＂ state is more susceptible to single event burnout than it is in the ＂turn-on＂ state. The thresholds of the drain-source voltage for single event burnout induced by 173 MeV bromine ions and ^252Cf fission fragments are close to each other, and the burnout cross section is sensitive to variation of the drain-source voltage above the threshold of single event burnout. In addition, the current waveforms of single event burnouts induced by different sources are similar. Different power MOSFET devices may have different probabilities for the occurrence of single event burnout.     

Comparison study of the charge density distribution induced by heavy ions and pulsed lasers in silicon

Heavy ions and pulsed lasers are important means to simulate the ionization damage effects on semiconductor materials. The analytic solution of high-energy heavy ion energy loss in silicon has been obtained using the Bethe-Bloch formula and the Kobetich-Katz theory, and some ionization damage parameters of Fe ions in silicon, such as the track structure and ionized charge density distribution, have been calculated and analyzed according to the theoretical calculation results. Using the Gaussian function and Beer＇s law, the parameters of the track structure and charge density distribution induced by a pulsed laser in silicon have also been calculated and compared with those of Fe ions in silicon, which provides a theoretical basis for ionization damage effect modeling.     

考虑剪切变形影响的开口薄壁梁约束扭转的扭转角分析

以开口薄壁梁约束扭转分析理论为基础,通过初参数法推导开口薄壁梁在外扭矩作用下产生的扭转角;推导了槽钢扭转剪应力不均匀系数的精确计算公式;为得到与Timoshenko梁理论类似的简化公式,探讨圣维南扭矩可以忽略时的情形,阐述了简化方法与理论解之间的误差来源,定义了剪切变形影响参数。通过具体算例分析跨度、高宽比等参数对扭转角的影响,并与符拉索夫理论、ANSYS壳单元、简化方法的计算结果进行对比。计算结果表明:当弯扭系数、高宽比恒定时,本文方法的解与符拉索夫解的最大误差从跨径为30m的16.15%到跨径为5m的89.5%;当弯扭系数、跨径恒定时,本文方法的解与符拉索夫解的最大误差从高宽比为1的6.9%到高宽比为5的62.44%;随跨径减小或高宽比增大,剪切变形不容忽略。当弯扭系数与跨径的乘积减小到一定值时可以忽略圣维南扭矩从而得到简化公式;高宽比增大,扭转剪应力不均匀系数先减小后增大。