A Globally Convergent and Efficient Method for Unconstrained Discrete-Time Optimal Control

Shift schemes are commonly used in non-convex situations when solving unconstrained discrete-time optimal control problems by the differential dynamic programming (DDP) method. However, the existing shift schemes are inefficient when the shift becomes too large. In this paper, a new method of combining the DDP method with a shift scheme and the steepest descent method is proposed to cope with non-convex situations. Under certain assumptions, the proposed method is globally convergent and has q-quadratic local conve rgence. Extensive numerical experiments on many test problems in the literature are reported. These numerical results illustrate the robustness and efficiency of the proposed method.     

引力闪烁、背景辐射的各向异性及宇宙物质分布的非均匀性

宇宙物质分布的非均匀性中的随机成分,会引起宇宙距离上的辐射源的强度闪烁。这种引力闪烁效应是背景辐射的小角度各向异性的一个起因,亦即复合时期之后的密度非均匀性,也会对背景辐射的各向异性有所贡献,因此,根据背景辐射的观测结果,可以给出宇宙物质分布的非均匀性的一个上限。结果表明,如果宇宙是封闭的,则宇宙中的物质总合(包括发光物质及不发光物质)的分布可能始终没有发展出较大的非均匀性,即目前宇宙中的总质量分布可能依然是相当均匀的。     

岩石孔隙表面流体弛豫强度和分子层特征厚度的观测

孔隙介质中流体的核磁共振(NMR)驰豫受到固液界面效应的强烈影响.孔隙表面弛豫强度的定量观测对孔隙介质弛豫机制的研究和应用都具有十分重要的意义.利用弛豫和扩散测量,提出一种确定表面弛豫强度和分子层厚度的方法,同时得到表面流体分子的纵向与横向弛豫强度和表面相分子层厚度,并对孔隙介质双指数弛豫理论进行了讨论.     

联苯二胺分子器件电输运特性的取代效应

在第一性原理基础上,理论研究了苯环上含有不同取代物的四个联苯分子的电输运特性.计算结果表明,当苯环上的氢被取代时,联苯分子的两个苯环之间的扭转角增大.分子结的电导随苯环间扭转角的增加而减少,且电导值与扭转角余弦平方成线性关系.在低偏压下,分子结的电输运机制是电子通过π轨道的隧穿过程.计算结果与实验结果符合的较好.     

基于X射线的空间语音通信系统

提出了栅控X射线源作为发射器和基于微通道板的X射线单光子探测器作为接收器的X射线通信方案. 搭建了基于X射线的空间语音通信系统, 详细介绍了信号调制发射器、基于微通道板的X射线单光子探测器及信号接收解调器的设计及工作原理. 报道了基于X射线的空间语音通信系统的初步实验结果, 实现了优于20 kbit/s的基于语音信号调制的X射线通信. 实验分析了在不同X射线强度、信号整形时间和阈值设置下通信性能影响, 得出了X射线发射功率限制X射线通信速率的结论, 提出了下一步提高X射线通信性能的改进方案. 关键词： X射线通信 X射线源 探测器     

重组灵芝免疫调节蛋白的纯化及其性质

采用超滤浓缩、强阴离子交换、疏水作用和凝胶色谱等方法, 对毕赤酵母表达的rGlip进行分离和纯化, 对离子交换色谱中rGlip与固相结合的最佳pH值进行了考察, 并对纯化产物的活性进行了鉴定. rGlip在215 nm处有强的紫外吸收, 经激光解析电离时间飞行质谱鉴定其相对分子量为12722, 经反相液相色谱鉴定纯度≥97%. 设计rGlip的疏水作用色谱, 有效地去除色素. 凝血实验结果表明, rGlip可以凝集绵羊血红细胞, 但对人血A, B, AB和O型等红细胞无凝集作用, 有类似凝集素的生物学活性.     

微波硫灯发射光谱的理论模拟

通过实验观测了微波硫灯的发光光谱. 利用从头计算的多组态准简并微扰理论方法, 采用cc-pVQZ基组计算了S2分子B3Σu--X3Σg-态和B″3Πu-X3Σg-态的跃迁矩及其振动态之间跃迁的弗兰克-康登因子, 导出了S2分子振动分辨发射谱. 同时, 利用含时密度泛函方法计算了Sn(n=2~8)分子的吸收谱. 将计算得到的S2分子振动分辨发射谱与实验所测得的光谱分布进行了比较分析, 解释了微波硫灯的宽谱区发光光谱的特性.     

Heat and moisture transfer in application scale parallel-plates enthalpy exchangers with novel membrane materials

Parallel-plates enthalpy exchangers are one of the most commonly encountered energy recovery devices that are used to simultaneously transfer both sensible heat and moisture between fresh air and exhaust ventilation air. For such equipments, the water vapor sorption properties of the plate materials have tremendous impacts on system performance. In this investigation, three different materials, namely, common paper, CA (cellulose acetate) membrane and a modified CA membrane) are selected as the plate materials for three enthalpy exchangers. Sorption curves and contact angles of these three materials are measured to reflect their hydrophilicity. The steady-state sensible and latent effectiveness of the three exchangers are tested in a special test rig, and the test results are compared with the model predictions. A heat and moisture transfer model for the enthalpy exchangers is proposed. The effects of the varying operating conditions like air flow rates, temperature, and humidity on the sensible and latent effectiveness are evaluated. Both the numerical and experimental results indicate that the moisture resistance through plates is co-determined by thickness, sorption slope, and sorption potential. Moisture diffusivity in various materials is in the same order. So when the plate thickness is fixed, the higher the sorption slopes are, the higher the latent performance is. Of the three exchangers, the exchanger with the modified CA membrane material has the highest performance due to small thickness, steep sorption slope, and large sorption potentials. The paper exchanger has a latent effectiveness of 0.4, while the membranes have latent effectiveness of greater than 0.7.     

聚乙烯醇辅助合成CdS纳米线及其表征

以聚乙烯醇为辅助剂, 使用溶剂热法成功制备CdS纳米线, 并用XRD、TEM、HRTEM、UV-Vis和PL(荧光)发射谱等方法对样品进行表征. 结果表明, 该法制备的CdS纳米线为六方纤锌矿结构, 直径为70 nm, 长约10 μm, 沿[001]晶向择优生长, 具有量子禁域效应. 同时, 根据对比实验结果提出了CdS纳米线的聚合物辅助生长机理.     

新型调压装置在液体饱和蒸气压测定实验中的应用

引入可控进气量和具有独立操作的增、减压缓冲瓶的调压装置,使气压调节缓慢可控,能连续调节缓冲瓶内气体压力以适应不同温度点的液体饱和蒸气压;可通过控制U形液柱缓慢移动来读取气液平衡状态下饱和气压值,较好地克服了以往实验中存在的调压操作困难、易发生空气倒灌及未知蒸气饱和的问题,取得了良好的实验效果,提高了实验数据的准确性。