UA5000构筑可信赖的接入网络

自2005年全球电信业提出“向综合信息服务提供商转型”的观念后，国内各电信企业已经纷纷行动起来．经过长达一年时间的策划和筹备，目前已进入具体实施阶段。但是，转型不是推倒重来，而是要兼顾效益和成本，这是各运营商成功实施转型所必须遵从的一个基本原则。     

射频电缆组件组装工艺浅谈

近年来国内外射频电缆组件的发展很快,射频电缆组件的性能不断提高,对射频电缆组件组装工艺也提出了更高的要求.射频电缆组件组装过程多是手工操作,产品的一致性及性能很难控制,要求有良好的工艺保证,为此介绍了射频电缆组件组装工艺,包括电缆的裁剪及剥皮、内导体的连接、外导体的连接和电气性能的测试;探讨了在组装过程中应注意的问题,以及针对内导体焊接易出现虚焊问题进行研究.     

熔融LiCl及其急冷非晶键取向序的分子动力学模拟研究

本文进一步讨论了我们新近提出的等近邻数键球谐函数方法,并通过分子动力学模拟研究了熔融LiCl及其急冷过程。对计算机模拟各时间步产生的瞬态构型进行平均,计算了不同温度下键序Q_l谱.将模拟Q_l谱与线性组合模型Q_l谱比较,观察到模拟Q_l谱与含90％局部正四面体结构的组合模型十分相似,表明熔融Licl及其急冷非晶中局部键取向序明显倾向于正四面体序。急冷过程中不同温度下局部键取向序可用同一线性组合模型描述,但模型方差随模拟温度明显变化。方差随温度而降低,且在发生玻璃态转变时有一显著下降。不同温度下的键角分布也作了计算,观察到键角分布在109°(正四面体局部结构键角)附近且分布峰随温度升高而展宽,与键序Q_l得到的结论一致。     

铁铝催化体系催化丙烯酸丁酯聚合

研究了Fe(acac)3-Al(i-Bu)3-8-羟基喹啉(acac=乙酰丙酮)催化体系催化丙烯酸丁酯(BA)聚合，考察了聚合规律，用凝胶渗透色谱研究了聚合物分子量和分子量分布．动力学研究表明聚合反应对单体浓度呈一级关系，表观活化能为13．9kJ／mol．     

Photochemistry of trifluromethyl substituted 1‐methylpyrazoles

Trifluromethyl substitution on the pyrazole ring was found to enhance photoreactivity via the P₄ pathway which involves interchange of the N2‐C3 ring atoms. Thus, 1‐methyl‐3‐(trifluromethyl)pyrazole (1) and 1‐methyl‐5‐(trifluromethyl)pyrazole (3) transposed with a P₄/P₆ or P₄/P₆+P₇ ratio of 2.1:1. 1‐methyl‐4‐(trifluromethyl)pyrazole (2) transposed regiospecifically by the P₄ transposition pathway. Compounds 2 and 3 were also observed to undergo photocleavage to yield enaminonitrile and enaminoisocyanide products.     

Time-resolved chemiluminescence technique for the microdetermination of proteins based on their complexation with copper(II).

Based on the complexation between proteins and Cu(II) coupled with the time-resolved chemiluminescence (CL) technique, a highly sensitive and quantitative assay for measuring proteins in solution is described. The complexes of proteins with Cu(II) have a strongly catalytic effect on the luminol-H2O2 CL reaction. Because the CL emission produced by the complexes is much more long-lived than that by Cu(II), the CL signals originating from proteins can be easily identified and measured with a time-resolved technique. On this basis, bovine albumin fraction V (BAF V) can be quantitatively determined in the range of 0.01 - 5.0 microg/ml with a detection limit of 5.8 ng/ml. The results show that the proposed assay exhibits a small variation in the response values for the same amount of different proteins, as compared to the Lowry as well as Bradford assays. The CL assay has also been studied for the detection of immobilized proteins.     

PURIFICATION OF L-METHIONINE AND N-ACETYL-D-METHIONINE FROM THE MIXTURE OF ENZYMATICALLY DEACYLATED N-ACETYL-DL-METHIONINE

1. INTRODUCTION Methionine, namely 2-amido-4-thiomethyl butyric acid with a structure of CH3SCH2CH2CHCOOH, is one of the essential amino acids and has two natural enantionmers, D and L-methionine. The mixture of L- and D-isomers can be used as analeptics or nutritive additives to maintain the equilibrium of amino acids of feed [1,2]. L-methionine can release active methyl and accelerate the synthesis of choline, which further speeds up the conversion of the lipid accumulated in liv…     

Luttinger liquid with asymmetric dispersion

We present an extension of the Tomonaga-Luttinger model in which left and right-moving particles have different Fermi velocities. We derive expressions for one-particle Green's functions, momentum-distributions, density of states, charge compressibility and conductivity as functions of both the velocity difference ε and the strength of the interaction β. This allows us to identify a novel restricted region in the parameter space in which the system keeps the main features of a Luttinger liquid but with an unusual behavior of the density of states and the static charge compressibility κ. In particular κ diverges on the boundary of the restricted region, indicating the occurrence of a phase transition. Received 20 May 2002 / Received in final form 23 August 2002 Published online 19 November 2002     

谱任意的符号模式矩阵

一个n阶符号模式矩阵A称为是谱任意的,如果对任意的实系数n次首1多项式r(x),在A的定性矩阵类Q(A)中至少存在一个实矩阵B,使得B的特征多项式是r(x),文中证明了当n为奇数时n阶谱任意符号模式矩阵是存在的。     

Some results on fractionaln-factor-critical graphs

A simple graphG is said to be fractionaln-factor-critical if after deleting anyn vertices the remaining subgraph still has a fractional perfect matching. For fractionaln-factor-criticality, in this paper, one necessary and sufficient condition, and three sufficient conditions related to maximum matching, complete closure are given.