Spanning trees set synthesis algorithm for custom VLSI global routing

In this paper, we study the problem of multi-terminal nets layout optimization. To solve the problem, we propose a polynomial-time algorithm, which first constructs minimum spanning tree and then generates spanning tree set. An algorithm for near-minimum spanning trees set with controllable length deviation from a minimum is proposed. Effective trees length deviation value and trees number are investigated.     

Unsupervised contour closure algorithm for range image edge-based segmentation.

This paper presents an efficient technique for extracting closed contours from range images' edge points. Edge points are assumed to be given as input to the algorithm (i.e., previously computed by an edge-based range image segmentation technique). The proposed approach consists of three steps. Initially, a partially connected graph is generated from those input points. Then, the minimum spanning tree of that graph is computed. Finally, a postprocessing technique generates a single path through the regions' boundaries by removing noisy links and closing open contours. The novelty of the proposed approach lies in the fact that, by representing edge points as nodes of a partially connected graph, it reduces the contour closure problem to a minimum spanning tree partitioning problem plus a cost function minimization stage to generate closed contours. Experimental results with synthetic and real range images, together with comparisons with a previous technique, are presented.     

一种利用理想拓扑的保护容量分配算法

对于通常的网状网,如何设计最小的保护容量来保证快速恢复是一个富有挑战性的问题。为了解决如何分配更少的保护容量的问题,该文提出了一些理想的拓扑结构,研究了支撑树算法。在这两者的基础上针对一条链路出现故障的问题给出了利用理想拓扑的保护容量分配算法。仿真结果说明该算法能预留比支撑树算法少得多的保护容量。     

Broadcasting in multi-radio multi-channel wireless networks using simplicial complexes

We consider the broadcasting problem in multi-radio multi-channel ad hoc networks. The objective is to minimize the total cost of the network-wide broadcast, where the cost can be of any form that is summable over all the transmissions (e.g., the transmission and reception energy, the price for accessing a specific channel). Our technical approach is based on a simplicial complex model that allows us to capture the broadcast nature of the wireless medium and the heterogeneity across radios and channels. Specifically, we show that broadcasting in multi-radio multi-channel ad hoc networks can be formulated as a minimum spanning problem in simplicial complexes. We establish the NP-completeness of the minimum spanning problem and propose two approximation algorithms with order-optimal performance guarantee. The first approximation algorithm converts the minimum spanning problem in simplical complexes to a minimum connected set cover (MCSC) problem. The second algorithm converts it to a node-weighted Steiner tree problem under the classic graph model. These two algorithms offer tradeoffs between performance and time-complexity. In a broader context, this work appears to be the first that studies the minimum spanning problem in simplicial complexes and weighted MCSC problem.     

A SAR Image Segment Method Using Gray Level Reduction Based on Graph in ICA Space

This paper proposes a new SAR image seg-mentation method based on graph and gray level reduction in Independent component analysis (ICA) space. Firstly, according to the grayscale information of SAR image, ef-fective use of gray level reduction for initial segmentation can group the pixels with same or similar values to the same homogeneous region, which can address the problem of over-segmentation. Secondly, the features of regions are extracted in ICA space, and then the similarity degree can be calculated by Euclidean distance. The initial regions are merged in fully connected graph based on minimum spanning tree in ICA space. The process of region merging is divided into two phases; the first phrase is merging the different regions with the largest similarity degree, the sec-ond will focus on updating the fully connected graph for iteration. Finally, experimental and comparative results on synthetic and real SAR images verify the efficiency of the proposed algorithm.     

Improved algorithm for image encryption based on DNA encoding and multi-chaotic maps

New image encryption based on DNA encoding combined with chaotic system is proposed. The algorithm uses chaotic system to disturb the pixel locations and pixel values and then DNA encodings according to quaternary code rules are carried out. The pseudo DNA operations are controlled by the quaternary chaotic sequences. At last the image encryption through DNA decoding is achieved. The theoretical analysis and experimental results show that the algorithm improves the encoding efficiency, enhances the security of the ciphertext, has a large key space and a high key sensitivity, it is able to resist the statistical and exhaustive attacks.     

基于稀疏方位超图匹配的图像配准算法

为提高超图匹配的正确匹配率并降低其计算复杂度,提出了一种基于稀疏方位超图匹配的图像配准算法。提取图像的结构特征点为图节点,采用最小生成树算法获取节点间的主要连接关系,并用包含邻近的节点与边的三元组结构定义超边,计算超边的方位角度信息,由此构建稀疏方位超图;利用方位信息构建亲近矩阵,并采用全局最优匹配方法实现匹配。实验表明,对于实际图像的配准,该算法既具有较低的计算复杂度,又有良好的匹配效果。     

Mobility-Based Backbone Formation in Wireless Mobile Ad-hoc Networks

In this paper, the well-known network backbone formation problem is modeled as the stochastic min-degree constrained minimum spanning tree (md-MST) problem, where the link duration is associated with the edge weight. Then, a decentralized learning automata-based algorithm is proposed to form the most stable backbone of the wireless mobile ad hoc network (MANET) by finding a near optimal solution to the stochastic md-MST problem of the network topology graph. The proposed method significantly decreases the network overhead and shortens the network delay by reducing the number of intermediate forwarding hosts. It also extends the backbone lifetime by selection of the links with the maximum expected duration. The convergence of the proposed algorithm to the most stable network backbone is proven on the basis of the Martingale theorem. Several simulation experiments are conducted to investigate the efficiency of the proposed backbone formation algorithm. Numerical results show the superiority of the proposed method over the existing methods in terms of the backbone lifetime, end-to-end delay, backbone size, packet delivery ratio, and control message overhead.     

基于混合变异差分进化算法的均匀面阵稀疏优化

差分进化算法(DE)已被广泛应用于解决稀疏面阵优化问题,针对DE 算法早熟、全局搜索能力差、容易陷于局部最优的问题,提出一种混合变异差分进化算法,通过加入概率因子来平衡算法收敛速度与全局搜索能力,以阵列孔径、阵元数量以及阵元间距为约束条件,将算法中的实数编码转化为二进制编码,以方向图平面峰值旁瓣电平之和最低为目标函数,通过优化后得到的阵元分布,得到稀疏优化阵列的三维方向图。仿真结果表明:该方法在满足约束条件的同时,能够避免算法早熟得到较优的目标函数值,概率因子为算法提供了额外的自由度。     

DNA计算在整数规划问题中的应用

基于生化反应原理的DNA计算由于在解决一类困难问题,特别是NP-完全问题上具有硅计算机无法比拟的优势,因此对DNA计算的研究具有重要意义。利用在基于表面的DNA计算中采用荧光标记的策略,提出了一种基于DNA计算的一类特殊整数规划问题最优解的求解算法,新算法利用荧光猝灭技术,通过观察DNA分子表面的荧光来排除非解。算法分析表明,新提出的基于DNA计算的求解算法具有编码简单和错误率低等特点。     

VLSI总体布线算法研究与实现

总体布线是布图设计中一个极为重要的设计环节。本文提出了基于可分离最小生成树(SMST)的优化L形直角斯坦(Steiner)树(L_RST)和优化Z_RST的算法。该算法实现上绕开计算重合度问题，以新的角度计算代价。利用基于tile的结构，实现了伪管脚(pseudo pin)的分配，适用于现代多层布线需求。最后文章研究了同时考虑串扰和时延的综合性能驱动的总体布线算法改进。     

基于滑动区域的粒子群虚拟网节能映射算法

针对传统虚拟网节能映射中存在的节点映射分散、链路映射跳数多等问题,利用虚拟网请求的最小生成树拓扑将节点和链路同时映射,该文提出了基于滑动区域的粒子群虚拟网节能映射算法(EVNE_SRPS)。当一个虚拟网请求到达时,生成其最小生成树拓扑,根节点为路径和最短的节点;在底层网络随机选取多个区域作为粒子对象,并在区域中心映射虚拟网请求的最小生成树拓扑;计算粒子的适应度,求出群体和个体最优解,并在最优解的指导下确定滑动方向、更新区域位置,经过迭代后得到虚拟网的映射方案。实验结果表明,与现有算法相比,该算法降低了网络能耗,提高了运营商的收益成本比。     

安全两方向量优势统计协议及其应用

 安全两方向量优势统计问题是百万富翁问题的推广问题,用于两方在不泄漏自己保密向量信息的前提下统计出满足大于关系的分量的数目.本文在半诚实模型下利用加同态加密体制解决了安全两方向量优势统计问题,分析了该解决方案的正确性,安全性和复杂性;利用该优势统计协议设计了一个安全两方向量分量和排序协议,并且将设计的安全两方向量分量和排序协议应用于安全生成最小树图形算法中.     

传感器网络中基于模拟退火算法的拓扑控制方案

为了研究符合网络生命期目标要求的传感器网络拓扑控制方案,针对传统方案所获拓扑的连通冗余度过高或结构健壮性较低等弊端,从理论上对拓扑需求进行了建模分析,最终转化模型为度约束最小生成树问题,并设计了一种模拟退火算法对该问题进行处理,进而提出了一种基于模拟退火算法的拓扑控制方案。通过实验对方案进行了性能分析和验证,结果表明该方案所获拓扑具有网络整体功耗低、结构健壮性高和节点间通信干扰可控的折衷特点,并能够有效地延长传感器网络生命期。     

面向服务组合的密码服务调度智能优化研究

为了提高密码服务的质量,提出了一种面向服务组合的密码服务体系结构,并针对其中的密码服务调度问题提出了一种改进的混合离散蛙跳算法。该算法利用传统混合蛙跳算法的基本框架,重新设计了编码和解码方式以及个体矢量更新方法。同时为了提高搜索的精度,利用6种邻域结构,结合变邻域搜索算法,对组内最优青蛙进行优化。最后分别进行了标准算例对比实验与模拟仿真实验,结果验证了算法高效的寻优能力以及合理地实现了服务组合的优化, 满足了用户的需求, 符合现实情况。     

The strongly connecting problem on multihop packet radio networks

The problem of strongly connecting a multihop packet radio network by using a minimal total amount of transmission power is investigated. This problem is shown to be NP-complete. An approximation algorithm with the same computational complexity as that of finding a minimum spanning tree is given. It is also shown that the approximation algorithm can find a solution no greater than twice that of the optimal solution. Experimental results show that the approximation solution may be close to the optimal solution     

基于约束非负矩阵分解的高光谱图像解混快速算法

约束非负矩阵分解是高光谱图像解混中常用的方法.该方法的求解通常采用投影梯度法,其收敛速度、求解精度和算法稳定性都有待提高.为此,本文针对较优的最小体积约束,提出一种基于约束非负矩阵分解的高光谱图像解混快速算法.首先优化原有的最小体积约束模型,然后设计了基于交替方向乘子法的非凸项约束非负矩阵分解算法,最后通过奇异值分解优化迭代步骤.模拟和实际数据实验结果验证了本文算法的有效性.     

A stable virtual backbone for wireless MANETS

Due to the highly dynamicity and absence of a fixed infrastructure in wireless mobile ad hoc networks (MANET), formation of a stable virtual backbone through which all the network hosts are connected is of great importance. In this paper, a learning automata-based distributed algorithm is proposed for constructing the most stable virtual backbone of the MANET. To do so, the backbone formation problem is first modeled by the stochastic version of the bounded diameter minimum spanning tree (BDMST) problem. Then, the network backbone is constructed by solving the stochastic BDMST problem for the network topology graph. Several simulation experiments are conducted to investigate the efficiency of the proposed backbone formation protocol. The obtained results are compared with those of the best existing methods. Numerical results show the superiority of the proposed method over the others in terms of backbone lifetime, end-to-end delay, backbone size, packet delivery ratio, and control message overhead.     

Fast vicinity-upgrade algorithm for rectilinear Steiner trees

A new algorithm for rectilinear Steiner trees (RST) is presented. The proposed algorithm is based on successively constructing a vicinity structure from a rectilinear minimum spanning tree (MST) and generating a refined RST. The algorithm achieves an 8.5-10% average cost improvement over the rectilinear MST at a time complexity of O(n log n). To address specifically the linear programming approach of global routing the algorithm is modified to generate K trees.<>     

An exact algorithm for maximum lifetime data gathering tree without aggregation in wireless sensor networks

In wireless sensor networks, maximizing the lifetime of a data gathering tree without aggregation has been proved to be NP-complete. In this paper, we prove that, unless P = NP, no polynomial-time algorithm can approximate the problem with a factor strictly greater than 2/3. The result even holds in the special case where all sensors have the same initial energy. Existing works for the problem focus on approximation algorithms, but these algorithms only find sub-optimal spanning trees and none of them can guarantee to find an optimal tree. We propose the first non-trivial exact algorithm to find an optimal spanning tree. Due to the NP-hardness nature of the problem, this proposed algorithm runs in exponential time in the worst case, but the consumed time is much less than enumerating all spanning trees. This is done by several techniques for speeding up the search. Featured techniques include how to grow the initial spanning tree and how to divide the problem into subproblems. The algorithm can handle small networks and be used as a benchmark for evaluating approximation algorithms.