Near optimality of stochastic control in systems with unknown parameter processes

Stochastic control for systems with an unknown parameter is considered in this paper. The underlying problem is to minimize a functional subject to a system described by a singularly perturbed differential equation with an unknown parameter process driven by fast fluctuating random disturbances. This problem arises in the context of stochastic adaptive control, adaptive signal processing, and failure-prone manufacturing systems. Due to the nature of the wide-bandwidth noise processes, identifying the parameter process for eacht is very hard since the driving noise changes very rapidly. An alternative approach is used, and an auxiliary control problem is introduced to overcome the difficulties. By means of weak convergence methods and comparison control techniques, nearly optimal controls are obtained.This research was supported in part by the National Science Foundation under Grant DMS-9022139 and DMS-9224372.     

方解石棱镜分束角高度对称性的设计

研究ｏ、ｅ双输出棱镜分束角的对称性。指出经特殊设计的双渥拉斯顿棱镜产生的ｏ、ｅ光的分束角具有高度的对称性。     

C60/PMMA复合材料的反饱和吸收与光限幅特性研究

本文报导C₆₀/PMMA复合材料的制备方法,并采用调QNd:YAG倍频脉冲激光照射C₆₀/PMMA夏合材料,研究了其反饱和吸收与光限幅将性。在线性透射率为46%条件下,光限幅阈值能量密度为65mJ/cm²,材料破坏能量密度阈值为600mJ/cm².与C₆₀甲苯溶液相比具有一定的优点。     

Using stochastic optimization to determine threshold values for the control of unreliable manufacturing systems

A manufacturing system with two tandem machines producing one part type is considered in this work. The machines are unreliable, each having two states, up and down. Both surplus controls and Kanban systems are considered. Algorithms for approximating the optimal threshold values are developed. First, perturbation analysis techniques are employed to obtain consistent gradient estimates based on a single simulation run. Then, iterative algorithms of the stochastic optimization type are constructed. It is shown that the algorithms converge to the optimal threshold values in an appropriate sense. Numerical examples are provided to demonstrate the performance of the algorithms.The research of these authors was supported in part by grants from URIF, MRCO, National Science Foundation, and Wayne State University. The authors would like to thank Dr. X. R. Cao, Digital Equipment Corporation, for the valuable initial discussion and Dr. X. Y. Zhou, University of Toronto, for his helpful comments.     

金属离子和热激处理对菊芋(Helianthus tuberosus L.)类金属硫蛋白基因htMT2表达的影响

使用不同金属离子及热激对菊芋进行了处理，并对菊芋不同组织器官中类金属硫蛋白基因(htMT2)mRNA水平的变化进行了研究．结果表明，htMT2在根中不表达，而且其表达不受金属离子的影响．Cu^2 降低叶中htMT2的表达，Cu^2 浓度与茎、叶中的htMT2 mRNA水平呈负相关性．在低浓度范围内，Zn^2 浓度与茎、叶中的htMT2 mRNA水平呈正相关性，而在高浓度范围内，Zn^2 浓度与htMT2 mRNA水平呈负相关性．Ca^2 对叶中htMT2表达的影响与Zn^2 的作用相似，但Ca^2 诱导茎中htMT2 mRNA水平升高．热激处理对不同组织中htMT2的表达无显著影响．研究的结果表明，htMT2表达受金属离子影响的特征与植物MT基因一致，进一步证实了我们前期工作中分离到的htMT2是一个新的植物MT基因．     

基于系统非线性的红外焦平面非均匀性校正

采用系统非线性描述和分析方法,从基于红外参考辐射源的校正算法原理入手,提出了一种新的红外焦平面非均匀性校正方法.该算法将每个探测器单元视为一个非线性系统,因此,该算法原理既对基于红外参考辐射源的非均匀性校正算法成立,对基于场景的校正算法在一定条件下也有效,能够适应非均匀性随时间和环境改变而发生缓慢变化的情形,是一种自适应算法.     

邻菲咯啉荧光熄灭法测定铜

研究了在pH 6 2 5～ 7 5 5KH2 PO4 Na2 HPO4 缓冲介质中 ,铜与邻菲咯啉形成配合物而使荧光熄灭的实验条件 ,建立了荧光熄灭法测定微量铜的新方法。该方法的λex =2 6 6nm ,λem =36 8nm ,铜含量在 8～ 30 0ng·mL- 1 范围内 ,有良好的线性关系 ,相关系数r=0 9996 ,检出下限为 10 4ng·mL- 1 。用本法经巯基棉分离测定了环境水样中的微量铜。     

咪唑类氮氧自由基的ESR波谱的酸度相关性-pH自旋探针应用研究之一

根据咪唑类氮氧自由基的结构特性合成了一系列的pH自旅探针,其ESR波谱参数均在一定范围内与介质的酸性呈明显的相关性.可望为较精确地测量化学胶束、细胞等微观体系的pH值开辟一个新的途径.本文研究了灵敏变化的pH范围与取代基的关系,得到了5种自旅探针的ESR参数-pH曲线、pKa值以及Hanmmett相关图,分析了如何通过改变取代基合成出不同pH变化范围并适用于不同生物和化学体系的pH自旅探针,最终达到付诸应用的目的.     

Synthesis and properties of hyperbranched polybenzimidazoles via A2 + B3 approach

Hyperbranched polybenzimidazoles (HBPBIs) were successfully synthesized by condensation polymerization of 1,3,5‐benzenetricarboxylic acid (BTA) and 3,3′‐diaminobenzidine (DAB) in polyphosphoric acid (PPA) at 190 °C. Different monomer addition manners and molar ratios resulted in different polymers, that is, simultaneous addition of BTA and DAB with the molar ratio of 1:1 (manner 1) gave carboxyl‐terminated HBPBI (HBPBI‐1), whereas the addition of BTA portion‐wise to DAB solution in PPA with the molar ratio of DAB:BTA = 2:1 (manner 2) yielded amine‐terminated HBPBI (HBPBI‐2). The free carboxyl and amino groups of HBPBI‐1 and HBPBI‐2 could further react with o‐diaminobenzene and benzoic acid, respectively, to form the chemically modified polymers. Except HBPBI‐2, all the HBPBIs showed good solubility in some organic solvents (e.g., dimethyl sulfoxide and N,N‐dimethylacetamide). Thermogravimetric analysis measurement revealed that HBPBIs except HBPBI‐1 had high thermal stability (>450 °C). HBPBI membranes with good mechanical properties were obtained by crosslinking treatment of partially chemically modified HBPBIs with terephthaldehyde (TPA) during the film cast process. The HBPBI membranes had high phosphoric acid uptake and the phosphoric acid‐doped HBPBI‐6 (40% o‐diamino groups were reacted with benzoic acid) membrane showed higher tensile strength than the acid‐doped commercial PBI despite the higher doping level of the former. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1150–1158, 2007