Optimal Deterministic Broadcasting in Known Topology Radio Networks

We consider deterministic broadcasting in radio networks whose nodes have full topological information about the network. The aim is to design a polynomial algorithm, which, given a graph G with source s, produces a fast broadcast scheme in the radio network represented by G. The problem of finding a fastest broadcast scheme for a given graph is NP-hard, hence it is only possible to get an approximation algorithm. We give a deterministic polynomial algorithm which produces a broadcast scheme of length , for every n-node graph of diameter D, thus improving a result of Gąsieniec et al. (PODC 2005) [17] and solving a problem stated there. Unless the inclusion NP BPTIME( holds, the length of a polynomially constructible deterministic broadcast scheme is optimal.A preliminary version of this paper (with a weaker result) appeared in the Proc. 7th International Workshop on Approximation Algorithms for Combinatorial Optimization Problems (APPROX’2004), August 2004, Harvard University, Cambridge, USA, LNCS 3122, 171–182. Research of the second author supported in part by NSERC discovery grant and by the Research Chair in Distributed Computing of the Université du Québec en Outaouais. Part of this work was done during the second author’s visit at the Max-Planck-Institut für Informatik.     

基于图论的化学分子数据挖掘研究

近年来,人们提出了很多频繁图模式挖掘的算法。首先分析了贪婪搜索策略,然后对各种不同的图数据挖掘的方法进行比较。受购物篮分析的影响,基于ILP方法引起了人们的重视。如何修改各种不同的图数据挖掘方法以适用化学分子数据的挖掘是人们研究的热点问题。因为化学分子不仅是标准的图结构,而且它有典型的频繁环和链结构,还有一些频繁出现的代表原子类型的结点,所以在这个领域有一些特殊问题需要考虑。     

GIS在油气勘探数据管理中的应用研究*

油气勘探数据与地理信息密切相关,数据量大、类型复杂,传统的数据管理方法已经不适应现代管理的要求。利用地理信息系统（GIS）技术,通过建立图形库和属性库存储和管理大量与油气勘探相关的勘探数据和图形信息,并能进行有关的分析,建立油气勘探数据管理系统,可为勘探工作的管理提供先进的手段,为进一步的勘探部署和决策提供科学可靠的依据。在介绍了VC++环境下MAPGIS二次开发方法的基础上,对开发中的关键技术进行了探讨,并介绍了基于GIS技术的油气勘探数据管理系统的主要功能。     

Minimum cost source location problem with vertex-connectivity requirements in digraphs

Given a digraph (or an undirected graph) G=(V,E) with a set V of vertices v with nonnegative real costs w(v), and a set E of edges and a positive integer k, we deal with the problem of finding a minimum cost subset SV such that, for each vertex vV−S, there are k vertex-disjoint paths from S to v. In this paper, we show that the problem can be solved by a greedy algorithm in time in a digraph (or in time in an undirected graph), where n=|V| and m=|E|. Based on this, given a digraph and two integers k and ℓ, we also give a polynomial time algorithm for finding a minimum cost subset SV such that for each vertex vV−S, there are k vertex-disjoint paths from S to v as well as ℓ vertex-disjoint paths from v to S.     

On the edge-tenacity of the middle graph of a graph

We consider the problem of efficiently breaking a graph into small components by removing edges. One measure of how easily this can be done is the edge-tenacity. Given a set of edges of G, the score of S is defined as sc(S)=[| S|+τ (G?S)]/[w(G?S)]. Formally, the edge-tenacity of a graph G is defined as T′(G)=min sc(S), where the minimum is taken over all edge-sets S of G. A subset S of E(G) is said to be a T′-set of G if T′(G)=sc(S). Note that if G is disconnected, the set S may be empty. For any graph G, τ(G?S) is the number of vertices in the largest component of G?S and w(G?S) is the number of components of G?S. The middle graph M(G) of a graph G is the graph obtained from G by inserting a new vertex into every edge of G and by joining by edges those pairs of these new vertices which lie on adjacent edges of G. In this paper, we give the edge-tenacity of the middle graph of specific families of graphs and its relationships with other parameters.     

2D representation of facial surfaces for multi-pose 3D face recognition

The increasing availability of 3D facial data offers the potential to overcome the intrinsic difficulties faced by conventional face recognition using 2D images. Instead of extending 2D recognition algorithms for 3D purpose, this letter proposes a novel strategy for 3D face recognition from the perspective of representing each 3D facial surface with a 2D attribute image and taking the advantage of the advances in 2D face recognition. In our approach, each 3D facial surface is mapped homeomorphically onto a 2D lattice, where the value at each site is an attribute that represents the local 3D geometrical or textural properties on the surface, therefore invariant to pose changes. This lattice is then interpolated to generate a 2D attribute image. 3D face recognition can be achieved by applying the traditional 2D face recognition techniques to obtained attribute images. In this study, we chose the pose invariant local mean curvature calculated at each vertex on the 3D facial surface to construct the 2D attribute image and adopted the eigenface algorithm for attribute image recognition. We compared our approach to state-of-the-art 3D face recognition algorithms in the FRGC (Version 2.0), GavabDB and NPU3D database. Our results show that the proposed approach has improved the robustness to head pose variation and can produce more accurate 3D multi-pose face recognition.     

一种个性化旅游线路推荐算法

采用用户-景点-线路三部图来描述用户的行为,通过改进的随机行走算法给用户推荐合适的旅游线路,可以提供准确的旅游线路推荐并有效地解决新的线路难以推荐的问题。通过对景点的聚类,减小了数据稀疏性对推荐带来的影响并避免了过拟合问题。实验结果表明,与传统的方法相比,本文提出的算法具有较好的排序准确度,特别是对稀疏度较高的用户,优势更明显。     

OTIS网络的支配集问题算法研究

图的最小支配集问题和最小连通支配集问题在网络与并行分布式计算中有重要应用,计算上它们都属于NP难问题。OTIS网络是一类可以任意图为因子网络的复合网络,它能继承因子网络的良好特性,因而成为可扩展性、模块化、容错性的大规模并行计算机系统的体系结构形式之一。研究如何构建OTIS网络的较小支配集和连通支配集。基于OTIS网络构图规则,分别根据因子网络的支配集算法和连通支配集算法得到了求解OTIS网络的支配集算法和连通支配集算法。从理论上分析了这些算法的性能,并通过实例进行了验证。     

基于RSL筛选的WirelessHART最短路径路由算法

无线HART网络协议中提出的Graph路由是同类无线网络中健壮性最好的路由方式之一。针对目前实现该路由方式的算法非常少且性能不佳的现状,提出一种基于BFS的Graph路由算法。该算法得到的路由具有跳间冗余的特点,能够最大限度地增加路由健壮性,并且路径最短;引入RSL作为链路质量衡量标准,剔除质量较差的链路,同时对每跳的邻居数设置上限,保证了路由的健壮性,同时避免了低质量的链路带来的通信资源浪费。此外,论证了协议所没有提及的广播路由存在的必要,并给出了实现算法。