钻机柴油机的动向和190系列柴油机的发展

本文概括介绍了国内外钻机柴油机发展的水平及动向,比较了国内钻机柴油机与国外钻机柴油机在发展上的差距。重点介绍了作为国产钻机主要动力的190系列柴油机的发展状况及最新技术在该机型上的应用。     

电视机监督检验电磁兼容结果分析和对策

本文讨论了电磁兼容对电视机的技术要求和相应对策。     

提高水平集方法初始化计算速度的研究

本文对水平集方法的初始化步骤进行了改进。在水平集方法中，初始化是一个很重要的步骤。它包括计算图像平面中每个点的初始水平集距离，同时找到与当前点距离最近的曲线上的点。这是一个费时的过程，影响到整个水个集方法的计算速度。本文基于快速推进法提出了一种快速初始化方法。这种方法只需要Ｏ（Ｎ）的时间就能够遍历所有的图像点，完成初始化。最后，对三种不同的初始化方法：直接法、快速推进法和本文的方法在计算速度上作了对比。实验表明，最终得到理想的分割结果的情况下，本文的方法在时间上优于其他两种方法。     

国内电子商务门户网站的现状研究

从电子商务在我国迅速发展的角度出发，系统地介绍了我国电子商务网站的典范：阿里巴巴、淘宝。从电子商务的模式出发分析了其经营理念，成功因素及其不足，对中国的电子商务目前状况作了分析，并提出展望。     

船用低速五缸柴油机推进轴系扭振性能的改进与计算

国内的低速柴油机制造厂 ,船舶设计部门、造船厂和船东好象已经有一种共识 :艉机舱推进轴系使用低速五缸柴油机作主机时 ,都要用扭振减振器。但是 ,只要在设计时合理选用柴油机转速 ,并采用高强度低合金钢来制造中间轴 ,这类轴系大部分是不需要扭振减振器的。     

添加剂组成对通用内燃机油性能的影响

通过相关模拟试验，分析研究了添加剂组成对通用内燃机油的抗磨性能，抗氧化性能以及清净分散性能的影响。     

三峡地下电站变顶高尾水洞水动力特性

在国内首次应用模型水轮发电机组对三峡地下电站变顶高尾水洞方案进行水力过渡过程试验研究。对水轮机导叶实行分段关闭 ,并求出了二段关闭的最佳拐点 ,试验证实了二段关闭对减小尾水管进口的负压和机组转速上升有明显的作用。通过有关水力参数的测试 ,认为变顶高尾水洞可以满足各项技术要求 ,是一个减少山体开挖、节省投资的新型设计方案。在地下电站中具有广泛的应用前景     

The solution of the inverse problem of gravitational potential using a set of measurements of different field elements

A numerical solution of the inverse problem of the gravitational field at a single point is obtained using six field elements for a point, a spherical cap, a differential spherical sector and a vertical segment. In the system of six equations obtained, the unknowns are the mass of the body, the depth of its center, and the second, third, and fourth degree moments. The accuracy of the solution of this system is ten times higher than when using three field elements. __________ Translated from Izmeritel’naya Tekhnika, No. 5, pp. 3–8, May, 2007.     

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.     

Probabilistic output admissible set for systems with time-varying uncertainties

This paper considers time-varying uncertain constrained systems, and develops a method for computing a probabilistic output admissible (POA) set. This set consists of the initial states probabilistically assured to satisfy the constraint. The time-invariant counterpart has already been investigated in Hatanaka and Takaba [Computations of probabilistic output admissible set for uncertain constrained systems, Automatica 44 (2) (2008), to appear]. We first define the POA set for time-varying uncertainties with finite dimensional probability space. Then, we show that an algorithm similar to Hatanaka and Takaba [Computations of probabilistic output admissible set for uncertain constrained systems, Automatica 44 (2) (2008), to appear] provides the POA set also in the time-varying case, as long as an upper bound of a what we call future output admissibility (FOA) index is available. We moreover present two methods for computing the upper bound of the FOA index: probabilistic and deterministic methods. A numerical simulation demonstrates the effectiveness of our algorithm.