基于速度向量的VANET位置预测路由协议

针对车辆自组网（VANET）中车辆快速移动引起的网络拓扑快速变化及路由路径频繁切换引起的网络性能下降问题,提出一种适用于城市环境的基于速度向量的位置预测路由协议（VPRP）。该协议根据行驶方向将车辆分组,根据速度和当前位置预测下一步位置,选择路径中所有节点总的方向差异最小且总的距离变化最小的路径作为路由路径。仿真实验结果表明,VPRP比AODV和VHRP在吞吐量、分组投递率、平均传输延迟、控制开销等方面均有改进。     

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。     

改进的Sunday模式匹配算法

在基于模式匹配的检测方法中,匹配效率是检测技术的瓶颈,间接影响入侵检测系统的实时性能。该文对4种模式匹配算法进行分析后,选择最优的Sunday算法进行改进。该算法进行匹配前先找到模式串中的特征字符（出现概率最小的字符）,进行特征字符与尾字符双重匹配,失败则移动尽可能远的距离。实验结果证明匹配效率比Sunday算法有一定的提高。     

群决策中多形式偏好信息的转换及一致性分析

描述序关系、效用值、互补判断矩阵、互逆判断矩阵4种形式的偏好信息,给出将前3种偏好信息转换到互补判断矩阵的公式。在集结前,对转换后的互补判断矩阵进行一致性分析,如果没有达到规定的一致性指标,找出该矩阵中一致性最差的元素,并提交给其决策者进行调整,直到达到一致性指标。通过一个算例说明该方法的应用过程。     

一种基于不放回抽样的图像混沌加密算法

针对现有基于混沌序列的图像加密算法的缺陷,提出一种基于不放回抽样的图像混沌加密算法。该算法采用可变模运算和间接地址映射技术,将混沌序列一对一、高度随机地转换为图像像素地址,实现图像的位置置乱和灰度扰乱加密。对混沌序列的分布无严格要求,使混沌序列的参数和初值可以作为密钥被使用。实验结果表明,与现有同类算法相比,该算法性能优越、运算速度快且易于实现。     

基于DSDV的无线Mesh网络跨层路由设计

在DSDV协议的基础上,提出一种跨层路由设计的方法,选择一条具有合理长度和最小重传概率的路由进行测试。该链路质量机制可应用到基于IEEE802.11x的无线Mesh网络中,无须对现有的MAC层进行修改,即可作为一个单独模块加入到现有协议。在多跳网络中使用该跨层方案进行路由选择,能节省系统开销,优化系统的整体性能。     

Multi‐Unit Bayesian Auction with Demand or Budget Constraints

We consider the problem of revenue maximization on multi‐unit auctions where items are distinguished by their relative values; any pair of items has the same ratio of values to all buyers. As is common in the study of revenue maximizing problems, we assume that buyers' valuations are drawn from public known distributions and they have additive valuations for multiple items. Our problem is well motivated by sponsored search auctions, which made money for Google and Yahoo! in practice. In this auction, each advertiser bids an amount b_i to compete for ad slots on a web page. The value of each ad slot corresponds to its click‐through‐rate, and each buyer has her own per‐click valuations, which is her private information. Obviously, a strategic bidder may bid an amount that is different with her true valuation to improve her utility. Our goal is to design truthful mechanisms avoiding this misreporting. We develop the optimal (with maximum revenue) truthful auction for a relaxed demand model (where each buyer i wants at most d_i items) and a sharp demand model (where buyer i wants exactly d_i items). We also find an auction that always guarantees at least half of the revenue of the optimal auction when the buyers are budget constrained. Moreover, all of the auctions we design can be computed efficiently, that is, in polynomial time.     

试析Web程序中常见字符串问题的处理

从PHP实现字符串的正确输出入手,分析了PHP中相关字符串处理函数在Web程序开发中发挥的重要作用。     

Kelvin模型黏弹性圆柱体轴向流动中的动力特性

对线、转动弹簧支承Kelvin模型黏弹性圆柱体轴向流动中的特征方程进行了推导,运用Matlab语言编程求解了其在轴向流动中的前三阶复频率,给出了在质量比β和无量纲延滞时间α一定,改变无量纲线弹簧刚度α和转动弹簧刚度b的情况下,Kelvin模型黏弹性圆柱体的前三阶模态无量纲复频率的实部及虚部与无量纲流速v之间的关系曲线图,分析了无量纲弹簧刚度对圆柱体动力特性的影响。     

Evolutionary level set method for structural topology optimization

This paper proposes an evolutionary accelerated computational level set algorithm for structure topology optimization. It integrates the merits of evolutionary structure optimization (ESO) and level set method (LSM). Traditional LSM algorithm is largely dependent on the initial guess topology. The proposed method combines the merits of ESO techniques with those of LSM algorithm, while allowing new holes to be automatically generated in low strain energy within the nodal neighboring region during optimization. The validity and robustness of the new algorithm are supported by some widely used benchmark examples in topology optimization. Numerical computations show that optimization convergence is accelerated effectively.