基于网络传输特性的链路重要性评价方法

提出了一种基于网络传输特性的链路重要性评价方法,根据链路在网络所有节点相互通信的最短路径中的使用频度来评价链路重要性,最重要链路的使用频度最高.该方法不需要像目前的链路重要性评价方法那样进行链路收缩和删除,直接反映了链路对整个网络通信的贡献大小,可以判断通信网中任意两条链路的相对重要性.算法分析和实验仿真表明,文章算法克服了目前的评价方法存在的问题,给出了更直观合理的通信网链路重要性评价准则.     

一种评价通信网节点重要性的新方法——节点孤立法

提出了一种评价通信网节点重要性的新方法--节点孤立法,并提出了节点核度积的概念,认为通信网中最重要的节点是孤立后所对应的节点核度积最大的节点.该方法考虑了网络的连接状况,并且动态地考虑了网络中所有节点相互通信的最短路径总长度的增加值.该方法是基于全网性能对节点重要性进行评价,通过比较节点的核度积,判断通信网中任意两个节点的相对重要性,而且使用了一种模2的矩阵运算方法,可以快速得到节点通信的最短路径.理论分析和仿真实验结果表明,该方法的计算复杂度和对节点重要性评价的准确性优于其它算法.     

时隙ALOHA-CDMA无线通信网络节点数目估计

针对现有的适用于时隙ALOHA系统的网络节点数目估计方法应用于时隙ALOHA-CDMA系统时估计误差很大,节点数目大于时隙数目时估计误差尤为严重的情况,提出了一种考虑了系统的时间维度和码维度的新的节点数目估计方法--码时二维估计方法.该方法考虑节点数目是已知的,然后实测一个时隙里面出现的码数目,利用码数目与节点数目的函数关系,就可以估计节点数目.理论分析和仿真结果表明,由于该方法充分利用了时隙ALOHA-CDMA系统的时间维度和码维度的二维信息,估计精度较高,在应用于节点数目大于时隙数目的ALOHA-CDMA系统时,该方法的优势尤为明显.     

基于最小生成树的动态贪婪多播路由算法研究

提出了基于最小生成树的动态贪婪算法,由于在所有节点都是多播节点时,最小生成树是最佳的,因此通过该算法产生的多播树的性能在合理的范围之内。仿真结果表明DPG算法在多播节点密度较大时显示了优越性,同时它还具有复杂度低的特点。     

基于网络性能变化梯度的通信网络节点重要程度评价方法

在传统上,在通信网络中评价节点重要程度的方法一般是基于网络中可替换路由数目。这种法发的缺陷在于当网络被分割时,评价系统就无法发挥作用。所以,针对这个情况,清华大学的研究者提出一种利用网络性能梯度的变化评价通信网络中节点重要性的方法。这种方法能够比较准确的反应节点对网络性能的影响,并且弥补前人的不足。     

三维德洛内三角剖分算法探析

三维德洛内三角剖分算法是一种新颖的适用于实时有限元分析的四面体网格生成算法,该算法在并行插入与删除网格节点的前提下,能够最大限度的保证网格生成的质量和保真度。     

改进的基于Web的频繁访问路径挖掘算法

对于连续频繁访问路径的挖掘如果采用常见的序列模式挖掘算法, 挖掘效率是比较低的, 而且只能得到频繁访问路径. 本文在研究访问路径性质的基础上给出了一种能从普通 Web 日志中挖掘出连续频繁访问路径的算法. 设计了一种新颖的数据结构压缩存储空间及存储所需挖掘信息. 同时采用分区搜索的方式, 为每个频繁节点构造一棵后缀树, 通过遍历该后缀树挖掘出连续频繁访问路径. 采用这种方法进行挖掘, 无需生成候选集, 而且一次就可以挖掘出所有以根节点为后缀的连续频繁访问路径.     

三角网格模型上的四边形曲线网生成新方法

四边形网格划分是组合曲面建模技术的首要条件。针对海量流形三角网格数据,提出了基于网格简化技术与调和映射算法的四边形网格生成新方法--映射法。该方法采用基于顶点删除的网格简化技术对三角网格模型进行简化,进而借助调和映射算法将简化网格映射到二维平面上进行四边形划分,并将所获得的平面四边形节点数据逆映射回物理域,采用短程线边界形式最终得到适于组合曲面建模的空间四边形拓扑。该方法简单、实用,运行速度较快,实际的算例也验证了方法的有效性与可行性。     

考虑多节点拥堵的城市道路网级联失效仿真

为量化城市路网在多个节点突发拥堵时出现的级联失效现象,解决网络重要节点拥堵而引起的连锁反应问题,本文构建了双层网络配流的网级联失效模型,采用计算路网拥堵度完成该情景下的级联失效仿真研究的方法,对级联失效现象进行分析。首先采用原始法构建路网的几何拓扑图,依次从拓扑图中删除拥堵节点,然后利用连通度、最大连通子图相对大小与圈数率3个鲁棒性评价指标衡量路网通行效率,计算出通行效率不低于10%条件下的最大节点失效比例,再运用双层网络配流模型测算级联失效时的路网拥堵度,最后通过Transcad 4.5和Matlab 2012a完成对包含54个节点、92条路段的成都市某地中等规模路网的仿真实验。实验结果表明：路网在最不利条件下的最大节点失效比例为19.3%;相比于单个拥堵节点,2个以上节点同时拥堵更易造成路网出现级联失效现象;当拥堵节点数目超过7个后,拥堵度逐渐趋于稳定并使路网到达其鲁棒性的极限。该研究旨在为多节点失效条件下的路网管控措施提供仿真技术参考。     

TIN模型搭建在矿山地质数据分析中的应用

通过获取TIN中对象主要通过ITinAdvanced2接口的相关方法或属性来实现。如通过NodeCount可以获得节点数目、通过TriangleCount可以获得三角形的数目、通过GetTriangle可以获得三角形等等,下面介绍一些常用的属性和方法。     

Exact algorithm for delay-constrained capacitated minimum spanning tree network

The delay-constrained capacitated minimum spanning tree (DC-CMST) problem of finding several broadcast trees from a source node is discussed. While the traditional CMST problem deals with only the traffic capacity constraint served by a port of the source node, and delay-constrained minimum spanning tree (DCMST) considers only the maximum end-end delay constraint, the DC-CMST problem deals with both the mean network delay and traffic capacity constraints. The DC-CMST problem consists of finding a set of minimum cost spanning trees to link end-nodes to a source node satisfying the traffic requirements at end-nodes and the required mean delay of the network. In the DC-CMST problem, the objective function is to minimise the total link cost. A dynamic programming-based three-phase algorithm that solves the DC-CMST problem is proposed. In the first phase, the algorithm generates feasible solutions to satisfy the traffic capacity constraint. It finds the CMSTs in the second phase, and allocates the optimal link capacities to satisfy the mean delay constraint in the third phase. Performance evaluation shows that the proposed algorithm has good efficiency for any network with less than 30 nodes and light traffic. The proposed algorithm can be applied to any network regardless of its configuration, and used for the topological design of local networks and for efficient routing algorithms capable of constructing least cost broadcast trees.     

A new approach to the d-MC problem

Many real-world systems (such as cellular telephones, transportation, etc.) are multistate-node acyclic network (MNAN) composed of multistate-nodes. Such network has a source node (position) where the signal source is located, a number of sink nodes that only receive the signal, and a number of intermediate nodes that retransmit the received signal to some other nodes. The non-sink node has different states determined by a set of nodes receiving the signal directly from it. The reliability of MNAN can be computed in terms of minimal trees (MTs). Based on the Branch-and-Bound algorithm, we developed an intuitive algorithm that is simpler than the best-known existing method. The computational complexity of the proposed algorithm is also analyzed. One example is illustrated to show how all MTs are generated by the proposed algorithm. The reliability of this example is then computed.     

EAMTR: energy aware multi-tree routing for wireless sensor networks

IEEE 802.15.4 is the prevailing standard for low-rate wireless personal area networks. It specifies the physical layer and medium access control sub-layer. Some emerging standards such as ZigBee define the network layer on top of these lower levels to support routing and multi-hop communication. Tree routing is a favourable basis for ZigBee routing because of its simplicity and limited use of resources. However, in data collection systems that are based on spanning trees rooted at a sink node, non-optimal route selection, congestion and uneven distribution of traffic in tree routing can adversely contribute to network performance and lifetime. The imbalance in workload can result in hotspot problems and early energy depletion of specific nodes that are normally the crucial routers of the network. The authors propose a novel light-weight routing protocol, energy aware multi-tree routing (EAMTR) protocol, to balance the workload of data gathering and alleviate the hotspot and single points of failure problems for high-density sink-type networks. In this scheme, multiple trees are formed in the initialisation phase and according to network traffic, each node selects the least congested route to the root node. The results of simulation and performance evaluation of EAMTR show significant improvement in network lifetime and traffic distribution.     

基于粒子群算法的水声通信网络能量优化方法

水声通信网络节点功耗是影响网络节点寿命的重要因素之一。针对水声通信网络的能量优化问题,基于网络节点发射功率与传输距离的非线性关系,结合改进的粒子群算法建立了一种能量优化方法。该方法改进了网络模型,在网络运行中根据存活节点数量和节点剩余能量的变化情况,自适应动态优化每个节点的信息传输路径。仿真结果表明,所提优化方法能有效降低网络节点总功耗,延缓首个节点的死亡,减缓网络中节点的死亡速率,也即减缓了网络有效覆盖面积随着网络运行而减小的速率。     

MINE: A Method of Multi-Interaction Heterogeneous Information Network Embedding

Interactivity is the most significant feature of network data, especially in social networks. Existing network embedding methods have achieved remarkable results in learning network structure and node attributes, but do not pay attention to the multiinteraction between nodes, which limits the extraction and mining of potential deep interactions between nodes. To tackle the problem, we propose a method called MultiInteraction heterogeneous information Network Embedding (MINE). Firstly, we introduced the multi-interactions heterogeneous information network and extracted complex heterogeneous relation sequences by the multi-interaction extraction algorithm. Secondly, we use a well-designed multi-relationship network fusion model based on the attention mechanism to fuse multiple interactional relationships. Finally, applying a multitasking model makes the learned vector contain richer semantic relationships. A large number of practical experiments prove that our proposed method outperforms existing methods on multiple data sets.     

Cutset enumeration of network systems with link and node failures

Network reliability analysis has received considerable attention and is thus widely studied to predict and prevent any network failure. However, most of such works presume perfectly reliable nodes. Although a few studies have considered both link and node failures, none of these methods has utilized the minimal paths or cuts, which are considered as fundamental approaches in the network reliability evaluation. An efficient method for deducing the minimal cutsets of a system subject to both link and node failures from the minimal cutsets of the system, which assumes perfect node reliability, is presented. The proposed method does not require re-enumeration of minimal cutsets for the additional consideration of the node failures. For a simple extension of such a method, the proposed approach can be embedded in any exact or approximate algorithm to account for link failures as well as node failures. As a result, the application of this method would be more realistic and valuable in practice for the reliability evaluation of networks with unreliable nodes.     

Fast approximate methods for the reliability analysis of computer networks

The complexity of computer communication networks has taken a dramatic upswing, following significant developments in electronic technology such as medium and large scale integrated circuits and microprocessors. Although components of a computer communication network are broadly classified into software, hardware and communications, the most important problem is that of ensuring the reliable flow of information from source to destination. An important parameter in the analysis of these networks is to find the probability of obtaining a situation in which each node in the network communicates with all other remaining communication centres (nodes). This probability, termed as overall reliability, can be determined using the concept of spanning trees. As the exact reliability evaluation becomes unmanageable even for a reasonable sized system, we present an approximate technique using clustering methods. It has been shown that when component reliability ⩾ 0.9, the suggested technique gives results quite close to those obtained by exact methods with an enormous saving in computation time and memory usage. For still quicker reliability analysis while designing the topological configuration of real-time computer systems, an empirical form of the reliability index is proposed which serves as a fairly good indicator of overall reliability and can be easily incorporated in a design procedure, such as local search, to design maximally reliable computer communication network.     

Search for all MCs in networks with unreliable nodes and arcs

A simple method is proposed to search for all minimal cutsets (MCs ) for imperfect networks reliability subject to both arc and node failures under the condition that all of the MCs in the network with perfect nodes are given in advance. The proposed method does not require re-enumeration for all of the MCs for additional node failure consideration. All of the MC candidates found in the proposed algorithm are actual MCs without any need for further verification. This algorithm is more effective than the existing algorithm in which every MC candidate is not verified as a MC. No identical MCs are found using the proposed algorithm, which does not duplicate MCs and is more efficient than the existing methods. Only simple concepts are used to implement the proposed algorithm, which makes it easier to understand and implement. With considering unreliable nodes, the proposed method is also more realistic and valuable for reliability analysis in an existing network. The correctness of the proposed algorithm will be analyzed and proven. One example is used to illustrate how all MCs are generated in a network with arc and node failures solved using the proposed algorithm.