复杂可修复系统故障数据分析处理中的两个问题

马良河等．复杂可修复系统故障数据分析处理中的两个问题．数理统计与管理，１９９８，１７（３），３７～４０．本文给出了利用部件的故障数据对复杂可修复系统的可靠性状态进行分析和估计时应首先解决的两个问题：应选取合适的故障数据及应分析系统部件的固有属性对故障数据的影响。进而给出了这两个问题的解决方法及对系统性能的分析方法。最后针对飞机发动机的一组故障数据给出了计算实例。所用工具主要是假设检验和方差分析的理论     

XML-Data模式的一致性问题

运用键、外键和XML-Data模式篱笆等概念研究了XM-Data模式的一致性问题，XML-Data模式的一致性问题就是判断是否存在一个既满足XML-Data模式又满足完整性约束的XML-Data模式篱笆．提出了XML-Data模式及XML-Data模式篱笆的概念．给出了如何从现有的XML-Data模式构造XML-Data模式篱笆的算法并且证明了XML-Data模式的一致性问题是不可判定的。     

Construction of highly enantiopure β,β-diaryl substituted glycine containing two contiguous stereocenters via asymmetric 1,6-conjugate addition

Asymmetric construction of β,β-diaryl substituted glycine bearing two contiguous chiral centers remains a significant challenge. Herein, the application of the para-quinone methides (p-QMs) and Ni(II)- complex of glycine via 1,6-conjugate addition to achieve asymmetric synthesis of β,β-diaryl substituted glycine has been explored successfully. This protocol features operational simplicity, high diastereoselectivity, and recyclable chiral ligand, which provides a versatile approach to the synthesis of highly enantiopure β,β-diaryl substituted glycine.     

The quantum ground state of a Heisenberg ferromagnet with an “easy-plane” type anisotropy

For the Heisenberg ferromagnet with the easy-plane type anisotropy the ground state energy and the magnetization are found with the help of perturbation theory supposing that the anisotropy energy is less than the exchange one. The study is carried out exactly without using any spin operators representation. Therefore, it is valid for a spin of any magnitude.     

Diastereoselective α-Alkylation of β-Amino Esters: Preparation of Novel α-Substituted β-Amino Esters from α-Amino Acids

b-Amino acids and their derivatives have attracted considerable attention in recent years due to their occurrence in biologically active natural products, such as dolastatins 11, cyclohexylnorstatine 22 and taxol 33. bAmino acids also find application in the synthesis of blactams4, piperidines5, indolizidines6. Moreover, the peptides consisting of bamino acids, the so called bpeptides, have been extensively studied recently7. Consequently, considerable efforts have been directed to the synt…     

热漫散射在聚合物中的应用

从热漫散射可以获得与聚合物材料中无序结构和热运动有关的电子密度涨落、纵声子群速和等温压缩率等参数.本文介绍和评述了热漫散射的理论及其应用.     

On Serre's Problem for RIT Algebras

Abstract

We construct a counterexample to Serre's problem for over a RIT algebra, which is a noncommutative quadratic algebra, given by quadratic relations, more general than the relations of the Weyl algebra and of a universal enveloping of finite dimensional Lie algebra.     

Electrical Properties of Silver Photodoped Amorphous Red Phosphorus

Abstract

Effects of photodoping and thermal doping of silver into sputtered amorphous red phosphorus films (a-P_red) on the electrical properties are studied. The d. c. efectrical conductivity of the photodoped a-p_red at room temperature is about 1×10^?5 Scm^?1 which is a very high value comparing with that of the undoped a-p_red (1×10^?14 Scm^?1). The activation energy for the conduction of the photodoped a-P_red is lower than that of the a-p^red. In contrast, the activation energy of the thermally doped a-p_red is essentially the same as that of the undoped a-p_red. SEM-EDX analyses show that colloidal silver was deposited in the thermally doped a-p_red but not in the photodoped a-p_red. It seems that the photo-doping involves the ionization process of silver by illumination, i.e., Ag^o → Ag⁺ + e^?.     

Reactivity and Synthetic Utility of 1,3,2λ5-Dioxaphospholanes

Abstract

The kinetics of Lewis acid-mediated decomposition and definitions of the synthetic applicability of 1,3,2λ⁵-dioxaphospholanes for (i) the syntheses of highly-hindered epoxides, and (ii) the stereospecific functionalizations of stereocenters in 1,2-diol arrays are described.