组合证券投资的概率准则模型探讨

在基于概率准则的组合证券模型下，把实现一定收益率水平目标的概率优化模型的求解转化成易于求解的非线性规划问题，从而方便地得出模型的解及其意义；提出了概率准则下的β值组合证券投资决策模型，研究了它们解的存在性和求解的公式，并给出了上海股市股票的数值算例。     

时变线性系统特征根判稳的推广

本文研究了二维时变线性系统零解的稳定性，给出了一些允许系数矩阵主对角元变号，系数矩阵特征根变号的判定稳定性的充分条件。     

微光像增强器图像传递信噪比的测试研究

图像传递信噪比是微光像增强器的重要特性参数．能够全面定量地表征像增强器在探测弱辐射图像时的综合性能，对于确定像增强器的图像探测灵敏闽具有重要意义。针对其测试原理．采用高灵敏度低噪声CCD器件作为像管输出图像的探测接收器．并引入数字图像处理技术。利用设计的测试系统实现了典型目标图像传递信噪比的自动测试．多次实验结果表明．陔测试系统具有测试过程自动快速及测试数据准确稳定的优点．相同测试条件下的不确定度优于±3%。     

中国铁通企业信息化战略规划和措施

首先简单回顾了中国铁通成立之初计费管理系统的一期建设和二期扩容后支撑能力的明显不足,以及信息化建设初期各部门独立IT系统运行中的问题,然后较详细介绍了企业信息化规划的整体思路.包括业务系统和流程、组织和业务流程重组、信息技术战略和架构等.并在实践的基础上,列举了信息化系统实施过程中应避免的做法和应注意的事项.     

The structure of invertible substitutions on a three-letter alphabet

We study the structure of invertible substitutions on three-letter alphabet. We show that there exists a finite set of invertible substitutions such that any invertible substitution can be written as I_wσ₁σ₂σ_k, where I_w is the inner automorphism associated with w, and for 1jk. As a consequence, M is the matrix of an invertible substitution if and only if it is a finite product of non-negative elementary matrices.     

Vacuum System for HL-2A Tokamak

The vacuum system of today＇s tokamak devices is designed to meet the operational requirements of the experiments. The operation can be divided into five modes, （1） pumping down and leak detecting of the vacuum vessel, （2） baking, （3） plasma-facing component （PFC） conditioning, （4）evacuating and controlling of the particles at plasma edge, （5） plasma discharge experiments.     

软交换技术的发展及其应用

软交换是下一代网络NGN的核心技术，本文从软交换的概念入手，介绍了软交换的基本功能及其优点．软交换的网络系统结构、软交换的对外接口等内容，并探讨了软交换技术的应用。     

冲击噪声背景下的近场源二维参数估计方法

本文针对背景噪声为冲击噪声的情况,提出了一种新的近场源二维参数估计方法.本方法利用协变异(或协变异系数)构造矩阵,并通过求根的方法估计近场源的方向角和距离参数.该算法可以抑制冲击噪声对估计性能的影响,同时具有无需谱峰搜索的优点.仿真实验证明了该算法的有效性.     

A new distributed approximation algorithm for constructing minimum connected dominating set in wireless ad hoc networks

In recent years, constructing a virtual backbone by nodes in a connected dominating set (CDS) has been proposed to improve the performance of ad hoc wireless networks. In general, a dominating set satisfies that every vertex in the graph is either in the set or adjacent to a vertex in the set. A CDS is a dominating set that also induces a connected sub‐graph. However, finding the minimum connected dominating set (MCDS) is a well‐known NP‐hard problem in graph theory. Approximation algorithms for MCDS have been proposed in the literature. Most of these algorithms suffer from a poor approximation ratio, and from high time complexity and message complexity. In this paper, we present a new distributed approximation algorithm that constructs a MCDS for wireless ad hoc networks based on a maximal independent set (MIS). Our algorithm, which is fully localized, has a constant approximation ratio, and O(n) time and O(n) message complexity. In this algorithm, each node only requires the knowledge of its one‐hop neighbours and there is only one shortest path connecting two dominators that are at most three hops away. We not only give theoretical performance analysis for our algorithm, but also conduct extensive simulation to compare our algorithm with other algorithms in the literature. Simulation results and theoretical analysis show that our algorithm has better efficiency and performance than others. Copyright © 2005 John Wiley & Sons, Ltd.     

SPME-GC-MS快速分析炼油厂废水中痕量VOCs

采用固相微萃取-气相色谱-质谱联用(SPME-GC-MS)对炼油厂废水中痕量挥发性有机化合物(VOCs)进行了定性分析,简化了预处理过程,总分析时间为1h左右.对比处理前后的废水样品的MS定性结果,为废水处理工艺的评价以及有机物降解机理提供了依据.