基于证据熵对不确定性度量的决策表约简

知识约简是粗糙集理论的核心内容之一,产生的粗糙决策规则往往具有一定的不确定性.在变精度粗糙集的基础上,本文构造了符合证据理论框架的一组焦元,利用基本概率分配函数计算了证据的总体信息熵,度量了决策表的不确定性;以该度量作为启发信息,给出了决策表的启发式知识约简算法.计算实例表明了本文方法的有效性.     

A new importance sampling Monte Carlo method for a flow network reliability problem

The exact evaluation of the probability that the maximum st‐flow is greater than or equal to a fixed demand in a stochastic flow network is an NP‐hard problem. This limitation leads one to consider Monte Carlo alternatives. In this paper, we propose a new importance sampling Monte Carlo method. It is based on a recursive use of the state space decomposition methodology of Doulliez and Jamoulle during the simulation process. We show theoretically that the resulting estimator belongs to the variance‐reduction family and we give an upper bound on its variance. As shown by experimental tests, the new sampling principle offers, in many cases, substantial speedups with respect to a previous importance sampling based on the same decomposition procedure and its best performances are obtained when highly reliable networks are analyzed. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 204–228, 2002; DOI 10.1002/nav.10004     

基于稀疏表示和非参数判别分析的降维算法

针对人脸识别问题提出一种新的监督降维算法。算法首先基于稀疏表示理论,利用同类样本间的稀疏重构来构建图。此方案不仅可以克服传统图构造方法中参数选择的困难,而且能够更好地刻画类内信息。然后,算法采用非参数类间离差来刻画类间信息,非参数类间离差在处理复杂分布数据时相比于参数类间离差更具判别力。最后,算法通过保持类内稀疏重构关系的同时最大化非参数类间离差来求得最优的投影矩阵。在ORL和Extended Yale B公共人脸数据库的实验表明,该算法能够获得较好的识别结果。     

基于四维空间相似度的军械紧急调运方案优选方法

分析了军械紧急调运方案优选决策的混合多属性特点。基于TOPSIS方法的基本原理,首先通过方案属性值的四维属性值转化,将不同类型的属性值统一成相同的形式,然后通过定义四维空间相似度,将各类型属性值的相似度计算规范到统一的度量空间,解决了含有实数、区间数、语言值和不确定语言值等多种不同决策属性值的的军械紧急调运方案优选这一混合型多属性决策问题。计算示例表明了该方法的可操性和有效性。     

普通建筑用钢与耐火钢火灾高温力学性能对比研究

钢材的高温力学性能是建筑结构耐火设计的重要参数。介绍了耐火钢的特点,通过试验对普通建筑用钢与两种耐火钢从常温到700℃高温的力学性能进行了对比研究,结果表明:温度在400~700℃之间,耐火钢的强度折减系数比普通建筑用钢高出很多;以钢材常温屈服强度的50%为破坏标准,普通建筑用钢与两种耐火钢的临界温度分别为550℃、650℃、660℃。     

Impact of tax reduction policies on consumer purchase of new automobiles: An analytical investigation with real data‐based experiments

We investigate and compare the impact of the tax reduction policies implemented in the United States and China to stimulate consumer purchase of new automobiles and improve manufacturers' profits. The U.S. policy provides each qualifying consumer with a federal income tax deduction on state and local sales and excise taxes paid on the purchase price (up to a cutoff level), whereas the Chinese policy reduces the vehicle sales tax rate for consumers. We observe that these policy designs are consistent with the tax management system and the economic environment in the respective country. We analytically determine the effects of the two tax reduction policies on the automobile sales and the manufacturer's and the retailer's profits. Numerical examples are then used to provide insights on the importance of certain factors that influence the effects of the two policies. Finally, a numerical experiment with sensitivity analysis based on real data is conducted to compare the merits and characteristics of the two policies under comparable conditions. We find that the U.S. policy is better than the Chinese policy in stimulating the sales of high‐end automobiles, whereas the Chinese policy is better than the U.S. policy in improving the sales of low‐end automobiles. The U.S. policy is slightly more effective in increasing the profitability of the automobile supply chain; but, in general, the Chinese policy is more cost effective. The methodology developed herein can be used to evaluate other tax reduction policies such as those related to the purchase of energy‐saving vehicles and to serve as a decision model to guide the choice of alternative tax reduction policies. © 2014 Wiley Periodicals, Inc. Naval Research Logistics, 61: 577–598, 2014     

新疆少数民族大学生就业能力结构维度研究

以新疆地区的6所高校少数民族大学生为研究对象进行问卷调查,采用分层整群抽样、数理统计的方法。得出新疆少数民族大学生就业能力的结构维度。包括专业知识能力、实践能力、自我学习发展能力、人际交往能力、情绪调适能力、职业发展能力。新疆少数民族大学生就业能力六个维度的确定,有助于我们有针对性地开展就业指导工作,促进更高质量的就业。     

Cu/C复合型润滑添加剂减摩抗磨性能研究

将纳米Cu和纳米金刚石复配成Cu/C复合添加剂,对其在500SN基础油中的减摩抗磨性能进行了研究.结果表明,加入了Cu/C复合添加剂的试油能明显改善500SN基础油的摩擦学性能:当纳米Cu添加量为4%,纳米C添加量为2%时,加入了Cu/C复合添加剂的试油减摩性能最好,同500SN空白试油相比,摩擦因数可降低94.8%;...     

用有限元强度折减法进行加筋土挡土墙稳定性分析

加筋土挡土墙边坡是一种新型的边坡加固形式,传统的理论分析主要是考虑力的平衡关系,因此还有不少的缺陷,而有限元分析不仅满足力与位移的平衡关系,而且考虑了筋带与土体的协调变形作用,模拟的结果能使人们方便地掌握挡墙的整体与局部变化。结合某加筋土挡土墙的实例,利用有限元对其进行了数值模拟,用强度折减法计算了边坡的安全系数,并与极限平衡进行比较,对类似的工程有一定的指导作用。     

本原BCH码的维数与周期分布

本文给出了求分圆陪集首集中元素个数新的计算公式，确定了长度为ｋ的分圆陪集的个数。给出了ｑ元域上狭义本原ＢＣＨ码的维数的计算公式，确定了狭义本原ＢＣＨ码的周期分布。