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941.
A sensitive, selective and rapid method for the determination of nickel based on a rapid reaction of nickel(II) with 2-(2-quinolylazo)-5-diethylaminoaniline (QADEAA) has been developed. In the presence of pH = 6.0 ammonia-ammonium chloride buffer solution and sodium dodecyl sulfonate (SDS) medium, QADEAA reacts with nickel to form a violet complex having a molar ratio of 1:2 (nickel to QADEAA). The molar absorptivity of the complex is 1.38 x 10(5) l mol(-1) cm(-1) at 595 nm. Beer's law is obeyed in the range of 0.01-0.4 microg/ml. This method had been applied to the determination of nickel with good results. 相似文献
942.
C60/PMMA复合材料的反饱和吸收与光限幅特性研究 总被引:1,自引:0,他引:1
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。 相似文献
943.
Mohapatra R. N. Vajravelu K. Yin Y. 《Journal of Optimization Theory and Applications》1998,96(3):667-682
An extension of the method of quasilinearization has been applied to first-order nonlinear initial-value problems (IVP for short). It has been shown that there exist monotone sequences which converge rapidly to the unique solution of IVP. 相似文献
944.
Hongjie Xu Kangcheng Chen Xiaoxia Guo Jianhua Fang Jie Yin 《Journal of polymer science. Part A, Polymer chemistry》2007,45(6):1150-1158
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 相似文献
945.
根据中子与天然Zr及其同位素反应的总截面,去弹截面和弹性散射角分布的实验数据,得到一组普适的光学模型势参数;应用得到的光学模型势参数,光学模型,Hauser-Feshbach理论,预平衡反应的激子模型和扭曲波玻恩近似理论,系统计算和分析了中子与90,91,92,94Zr反应的非弹散射角分布和双微分截面,理论结果与实验很好的一致. 相似文献
946.
947.
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. 相似文献
948.
949.
Longitudinal and transverse wave velocities, eight kinds of elastic parameters, and dilational and shear internal frictions of Zr55Cu30Al10Ni5 glassy alloy were simultaneously measured as a function of temperature in the range from 77 to 373 K, using an ultrasonic pulse method. The inflections at around 150 K for wave velocities, anisotropy factor and Poisson's ratio, and the 150 K peak of shear friction seem to correspond to one topological change (pseudo‐transition) associated with an interatomic readjustment or vacancy rearrangements. The behaviors from 77 to 125 K and 125 to 373 K are due to thermal relaxation of squeezed free volumes and entropy elasticity associated with vibrational motions of clusters, respectively, accompanied by an increase in atomic distance. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
950.
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. 相似文献