气泡从浸没孔中生成与上升的数值模拟

应用改进的Level Set方法和Navier-Stokes方程,结合ALE数值算法,三维模拟了常流量下气泡在静止黏性液体中从浸没孔中生成与上升的过程。考察了气泡在两种不同的黏性液体以及在单孔和多孔条件下的生长过程。模拟结果与实验观测定性相符。数值试验表明,改进的Level Set方法改善了气泡的容积守恒性。模拟结果显示,在不同的黏性液体中单孔气泡的生成行为很不相同,在Paratherm传热流体中生成的气泡直线上升,而在水中则是盘旋上升;多孔气泡的生成不同步,气泡的尺寸及空间分布极其不均匀。     

基于β重要度的数据隐含化

为权衡敏感或重要数据的公开及关键内容的隐含间的关系,提出一种基于变精度粗糙集模型中的β重要度和粒度原理的数据隐含方法,通过获取信息表中的重要属性,对次要属性的属性值进行扩展,从而使用户信息的粒度变粗,达到对信息表的数据隐含化效果。仿真实验结果表明,该方法是可行的。     

Experimental Analysis of Approximation Algorithms for the Vertex Cover and Set Covering Problems

Several approximation algorithms with proven performance guarantees have been proposed to find approximate solutions to classical combinatorial optimization problems. However, theoretical results may not reflect the experimental performance of the proposed algorithms. As a consequence, a question arises: how “far” from the theoretically proved performance are the experimental results? We conduct a controlled empirical study of approximation algorithms for the Vertex Cover and the Set Covering Problems. Many authors have proposed approximation algorithms for those problems. Our main goal is to better understand their strengths, weaknesses, and operation. Although we implement more than one algorithm to find feasible solutions to either problems, this work does not emphasize competition between them. The quality of the solutions related to the theoretical performance guarantees are analyzed instead. The computational experiments showed that the proven performance guarantees of all tested algorithms did not forecast well the empirical performance.     

关于办公室小型局域网的建立

介绍如何根据自身的需要建立一个高效的办公室小型局域网。     

Inapproximability Results for Set Splitting and Satisfiability Problems with No Mixed Clauses

We prove hardness results for approximating set splitting problems and also instances of satisfiability problems which have no mixed clauses, i.e., every clause has either all its literals unnegated or all of them negated. Results of Håstad imply tight hardness results for set splitting when all sets have size exactly $k \ge 4$ elements and also for non-mixed satisfiability problems with exactly $k$ literals in each clause for $k \ge 4$. We consider the case $k=3$. For the MAX E3-SET SPLITTING, problem in which all sets have size exactly 3, we prove an NP-hardness result for approximating within any factor better than ${\frac{19}{20}}$. This result holds even for satisfiable instances of MAX E3-SET SPLITTING, and is based on a PCP construction due to Håstad. For non-mixed MAX 3SAT, we give a PCP construction which is a slight variant of the one given by Håstad for MAX 3SAT, and use it to prove the NP-hardness of approximating within a factor better than ${\frac{11}{12}}$.     

A Unified Structure Theory for Polycyclic Conjugated Hydrocarbons--A Review of What Every Chemist Should Know!

The important concepts of a formula periodic table set, aufbau principle, elementary substructures, excised internal structure/circumscribing algorithm, leapfrog algorithm, and hexagonal-to-pentagonal ring contraction algorithm will be reviewed. These concepts have been instrumental in organizing polyhex/polypent systems from benzenoid hydrocarbons to fullerene carbons. Some recent experimental verification of our prior predictions in this work will be noted.     

基于粗集的决策规则生成方法

本文首先介绍了粗集理论和布尔推理相关概念 ,在此基础上给出了一种根据分辨函数的计算从决策表中生成决策规则的方法     

关于凸集的一些性质

考虑微分包含的选择问题时,对于微分包含里的集值映射F,其像集一般要求为具有非空内部的紧凸集。文章主要讨论了具有非空内部的紧凸集与其重心之间的关系,并进而给出了紧凸集的广义重心以及关于函数的重心与紧凸集的关系。     

干部人事档案"不立卷"管理的可行性

为适应形势发展要求和干部人事档案管理现代化需要，改革现行干部人事档案立卷形式，实行干部人事档案不立卷，有效缓解干部人事档案工作压力，提高工作效率，促进干部人事档案管理科学化、现代化的发展。     

Granularity of Knowledge Computed by Genetic Algorithms Based on Rough Sets Theory

1.Introduction 1.1 R ough Set T heory and G ranular of K now l- edge Rough set theory is proposed by Zdzislaw Pawlak ,and itis a new mathematical approach to granularitoyf knowledge .Itbecame a crucialissufeor computer scientis,tsparticularliyn the area o…