(n,k)-语言及左-(n,k)-语言的一些性质

利用字语言与自动机理论,研究(n,k)-语言及左-(n,k)-语言的相关性质,进一步得到了一些结论,丰富了(n,k)-语言及左-(n,k)-语言的性质。结论如下:(1)设AB是(n,k)-语言(或左-(n,k)-语言),若A(或B)是左(或右)奇异语言,则B(或A)是(n,k)-语言(或左-(n,k)-语言);(2)左-(n,k)-语言的集合在连接运算、并集、交集和补集运算下是封闭的。     

考虑负载效应的可修表决系统可靠性仿真模型

主要分析可修表决系统的可靠性指标算法。传统的基于元件寿命独立同分布假设的模型无法考虑负载效应因素,而考虑负载效应的解析算法虽然计算精度高速度快,但难以求解任意元件寿命分布和高维数问题,而且主要是针对不可修系统。基于元件加速失效模型和累积暴露模型建立了元件寿命抽样算法,并在此基础上实现了考虑负载效应的可修表决系统蒙特卡罗仿真算法和程序。以柔性输电设备换流阀可靠性计算为例,算法的高效性和结果的正确性得到验证,并且由此得到负载效应对可靠性指标的影响随系统运行时间变化的结论。     

ITER中的离散阿尔芬本征模

本文主要研究了ITER稳态运行时的离散阿尔芬本征模的稳定特性。这些磁流体力学本征模是α引起的气球模驱动势阱中的束缚态。其中,α=-q2Rdβ/dr,q是安全因子,β是等离子压强和磁场压强的比值,R和r分别是环形等离子体的大半径和小半径。这些阿尔芬本征模很容易被高能量粒子激发而演变成不稳定模式而影响环形等离子体的约束性能。     

(弱)(n,d)-环以及n-凝聚环的有限直和

设 R1,R2,…,Rm是环.证明了:(1) mi=1Ri 是右(n,d)-环(分别地,弱右 (n,d)-环,右 n-凝聚环) 当且仅当每个Ri 是右 (n,d)-环(分别地,弱 右 (n,d)-环,右 n-凝聚环);(2) rD（mi=1Ri) =sup{rD(R1),rD(R2),…,rD(Rm)};(3)wD(mi=1Ri)=sup{wD(R1),wD(R2),…,wD(Rm)}.     

Human and rodent type 1 11β-hydroxysteroid dehydrogenases are 7β-hydroxycholesterol dehydrogenases involved in oxysterol metabolism

Interconversion between cortisone and the glucocorticoid receptor ligand cortisol is carried out by 11-hydroxysteroid dehydrogenase (11-HSD)isozymes and constitutes a medically important example of pre-receptor control of steroid hormones. The enzyme 11-HSD type 1 (11-HSD1) catalyzes the conversion of cortisone to its active receptor-binding derivative cortisol, whereas 11-HSD type 2 performs the reverse reaction. Specific inhibitors against the type 1 enzyme lower intracellular levels of glucocorticoid hormone, with an important clinical application in insulin resistance and other metabolic disorders. We report here on the in vitro oxysterol-metabolizing properties of human and rodent 11-HSD1. The enzyme, either as full-length, membrane-attached, or as a transmembrane domain-deleted, soluble form, mediates exclusively conversion between 7-ketocholesterol and 7-hydroxycholesterol with similar k_cat values as observed with glucocorticoid hormones. Thus, human, rat, and mouse 11-HSD1 have dual enzyme activities like the recently described 7-hydroxysteroid dehydrogenase/11-hydroxysteroid dehydrogenase from hamster liver, but differ fundamentally from the latter in that 7-OH rather than 7-OH dehydrogenase constitutes the second activity. These results demonstrate an enzymatic origin of species differences in 7-oxysterol metabolism, establish the origin of endogenous 7-OH cholesterol in humans, and point to a possible involvement of 11-HSD1 in atherosclerosis.Received 30 December 2003; received after revision 16 February 2004; accepted 16 February 2004     

Adaptive widths of the approximation functional on the Sobolev space W r 2 with Gaussian measure

The tight orders for the Kolmogorov and adaptive (n,ε,δ)-widths of the Sobolev spaces W?r?2 equipped with a Gaussian measure in the L1-norm and L∞-norm are determined by the method of discretization, which is based on reducing the calculation of the (n,ε,δ)-widths of the Sobolev space to the calculation of (n,ε,δ)-widths of finite-dimensional set equipped with the Gaussian measure.     

最小支集样条小波变换的误差分析

分析了最小支集样条小波变换的误差，并给出了该变换的误差估计式：（Ｗψ３ＡＰｊｕ）（ｘ，ａ）－（Ｗψ３Ｐｊｕ）（ｘ，ａ）ｓ－ｒ≤∑ξ∈Ｚｎσ（ξ）φ∧３（２－ｊξ）ｅ２π２－ｊ（（ｘ－ｐ），ξ）ｉ２－ｎｊ／２－２ｎｊ／２φ３（２ｊｘ－ｐ）ｓ－ｒ     

改善直喷式油膜雾化燃烧性能的研究

文本对直喷式柴油机油膜雾化燃烧系统进行了燃烧调试．阐述了对改善燃烧性能的诸影响因素和见解．探索了改善油膜雾化燃烧性能的规律并进行了机理分析．     

Zn[i]的零因子图性质

交换环R的零因子图是一个简单图Γ(R),其顶点集为R的非零零因子集合D(R)*,两个不同的顶点x与y有一条边相连当且仅当xy=0。研究模n高斯整数环Zn[i]的零子图Γ(Zn[i])的直径、平面性和围长等问题,得到了比较完整的结果。     

一种LP问题的几何算法——点线面循环算法

提出了LP问题的一种新算法--点线面循环算法,它克服了单纯形法及其一些现有改进算法普遍存在的问题--即变量爆炸性问题,为LP问题求解在计算机上实现提供了一种更经济的途径与方法.参8.