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991.
992.
993.
本文考虑的是转移速率族任意且费用率函数可能无界的连续时间马尔可夫决策过程的折扣模型.放弃了传统的要求相应于每个策略的 Q -过程唯一等条件,而首次考虑相应每个策略的 Q -过程不一定唯一, 转移速率族也不一定保守, 费用率函数可能无界, 且允许行动空间非空任意的情形. 本文首次用"α-折扣费用最优不等式"更新了传统的α-折扣费用最优方程,并用"最优不等式"和新的方法,不仅证明了传统的主要结果即最优平稳策略的存在性, 而且还进一步探讨了( ∈>0 )-最优平稳策略,具有单调性质的最优平稳策略, 以及(∈≥0) -最优决策过程的存在性, 得到了一些有意义的新结果. 最后, 提供了一个迁移率受控的生灭系统例子, 它满足本文的所有条件, 而传统的假设(见文献[1-14])均不成立. 相似文献
994.
Wu Minghong Chen Jie Qian Qun Bao Borong 《Journal of Radioanalytical and Nuclear Chemistry》2002,252(3):531-535
Interpenetrating polymer network (IPN) hydrogels were prepared by grafting of acrylamide (AAm), N-methylol acrylamide (NMA) and acrylic acid (AAc) onto preirradiated polypropylene (PP) membrane. To obtain PP-g-AAc/AAm/NMA IPN hydrogels, at first, AAc were grafted onto preirradiated PP and then AAm were grafted onto the PP-g-AAc membranes. Finally NMA were grafted onto PP-g-AAc/AAm membranes. In the different stages of grafting under different reaction conditions, trapped radicals in the membrane samples were probed by electron spin resonance (ESR). The temperature response behaviors of the IPN hydrogels were studied. Reversible behavior and controlled release of drug tests made reflecting the switching to on state at higher temperatures and to off state at lower temperatures were achieved. By increasing the grafted content of NMA, higher transition temperature of the hydrogel could be attained. 相似文献
995.
Dong Q Yan X Wilhoit RC Hong X Chirico RD Diky VV Frenkel M 《Journal of chemical information and computer sciences》2002,42(3):473-480
To a significant degree processes of database development are based upon human activities, which are susceptible to various errors. Propagation of errors in the processing leads to a decrease in the value of original data as well as that of any database products. Data quality is a critical issue that every database producer must handle as an inseparable part of the database management. Within the Thermodynamics Research Center (TRC), a systematic approach to implement database integrity rules was established through the use of modern database technology, statistical methods, and thermodynamic principles. The four major functions of the system--error prevention, database integrity enforcement, scientific data integrity protection, and database traceability--are detailed in this paper. 相似文献
996.
997.
The authors consider the nonlinear difference equation xn+1=xn+xn-kf(xn-k),n=0,1,(0.1) where (0,1), k 0,1, and f C1[[0,), [0,)] with f(x) < 0.They give sufficient conditions for the unique positive equilibrium of (0.1) to be a global attractor of all positive solutions. The results here are somewhat easier to apply than those of other authors. An application to a model of blood cell production is given. 相似文献
998.
999.
We present a theory of the anomalous Hall effect in ferromagnetic (III, Mn)V semiconductors. Our theory relates the anomalous Hall conductance of a homogeneous ferromagnet to the Berry phase acquired by a quasiparticle wave function upon traversing closed paths on the spin-split Fermi surface. The quantitative agreement between our theory and experimental data in both (In, Mn)As and (Ga, Mn)As systems suggests that this disorder independent contribution to the anomalous Hall conductivity dominates in diluted magnetic semiconductors. The success of this model for (III, Mn)V materials is unprecedented in the longstanding effort to understand origins of the anomalous Hall effect in itinerant ferromagnets. 相似文献
1000.
We derive the spin-wave dynamics of a magnetic material from the time-dependent spin-density-functional theory in the linear response regime. The equation of motion for the magnetization includes, besides the static spin stiffness, a "Berry curvature" correction and a damping term. A gradient expansion scheme based on the homogeneous spin-polarized electron gas is proposed for the latter two quantities, and the first few coefficients of the expansion are calculated to second order in the Coulomb interaction. 相似文献