费用-时间优化的网格有向无环图调度算法

网格环境下,基于时间限制和费用最小的有向无环图(DAG)调度算法运用经济规律把网格用户中的任务映射到网格资源中运行,弥补了Buyya R提出的算法中未考虑任务运行的优先关系.该算法有两个关键技术:DAG中有效路径的提取能够定位任务何时在资源上运行;DAG中在作业运行时间尽可能允许的情况下,把任务映射到价格便宜的资源上运行.通过仿真实例,论证了该算法的优越性.     

基于有向无环图的区间覆盖率求解算法

给定一个有向无环图,回答可达性查询是图的基本操作之一.虽然很多方法使用树区间来加速可达查询的处理速度,但并不明确使用多少个区间比较合适.本文提出一种快速计算区间覆盖率的算法,该方法通过使用有效的剪枝策略来支持高效的覆盖率计算.基于所得到的区间覆盖率,可针对不同数据图确定合适的区间个数,以便在加速查询处理的同时,降低索引...     

基于多约束的电力通信网最大不相交路由选择机制

在智能电网中,提高业务服务质量并进一步降低网络风险是目前主要的研究方向。如何选择一条高可靠、稳定而且低风险的路由是智能电网中最关键的一环。现有的很多算法考虑的因素过于单一而导致优化程度不够。所以,文章结合业务通道压力与电力通信网的特殊性因素,提出了一种基于多条件约束下的最大不相交主备用路由选择机制,并且通过某省电网通信拓扑进行了仿真,阐述了该算法的优越性。     

基于有向无环图的P2P流媒体播放系统

文中针对P2P流媒体播放中的网络拓扑构建问题,通过抽象和刻画播放节点之间的媒体同步关系,提出了基于有向无环图结构的网络拓扑构建技术。实验表明,该技术具有数据传输率高,播放延迟小等优点。基于该技术实现的P2P流媒体播放系统已经部署在Cernet2网络中。     

超立方体网络的不相交路径通信策略研究综述

超立方体是一类具有良好的拓扑性质的互连网络模型。不相：交路径的实现是超立方体网络中容错通信的有效保证。介绍了超立方体网络的不相交路径路由策略中的主要研究内容和研究现状,对近年来该方面取得的研究成果进行分析和总结,并指出了其中存在的问题和该策略研究的方向。     

一种基于有向无环图的依赖管理机制及实现

一个复杂系统内部通常包含众多状态信息,这些状态信息相互依赖,增加了软件各模块之间的耦合度,且把依赖信息硬编码也将导致软件代码后续维护困难。为了解决这些问题,提出了一种基于有向无环图的依赖管理机制,把单个状态信息抽象为顶点,把依赖关系抽象为有向边,把依赖管理问题归结为经典的有向图问题,从而简化软件设计,降低软件模块耦合度。最后,通过动态剪枝、拓扑排序等手段,优化了求解算法。     

一种基于不变量的从工作流网到PERT图的转换方法

 工作流管理系统为现代企业提供了一种协同工作环境,可以管理企业的业务过程,并提高企业的商业竞争能力.为了有效管理业务过程的进度,需要提供一种基于工作流过程模型的进度估算方法.基于Petri网的工作流网模型难以直接估算工作流过程模型的进度与工期,而在传统的项目进度计划中,PERT图是一种成熟的技术,为此,本文在工作流网的基础上增加了时间的概念,基于LMST-不变量的分解技术,提出了一种将LMST-不变量分解得到的子网转换为PERT图的算法,由此达到估算工作流过程模型的进度与工期的目的.     

QoS约束下的链路分离路径问题研究

研究了QoS约束下的链路分离路径问题,建立了2种QoS约束下的链路分离优化路径问题的模型。首先证明无向图的不具备端到端QoS约束的链路分离路径问题可以转化为其链路分裂图的对应问题,而具备端到端QoS约束的相应问题则无法进行类似转换。同时证明2种QoS约束下的链路分离优化路径问题都属于NP完全问题,最后对其近似算法进行研究并对算法进行比较测试。     

Routing and wavelength assignment in optical WDM networks with maximum quantity of edge disjoint paths

In the present paper, routing and wavelength assignment (RWA) in optical WDM networks is discussed. Previous techniques based on the combination of integer linear programming based lpsolver and graph coloring are complex and require extensive use of heuristics such as rounding heuristic which makes them slow and sometimes practically not reasonable. Another method employs the greedy approach in graph theory for obtaining available edge disjoint paths. Even though it is fast, it produces a solution for any connection request which is far from the optimal utilization of wavelengths. We propose a novel algorithm, which is based on the maximum flow to have the maximum quantity of edge disjoint paths. Here, we compare the offered method with previous edge disjoint paths algorithms applied to the RWA. Comprehensive computer simulation shows that the proposed method outperforms previous ones significantly in terms of running time. Furthermore, the new method shows compatible or better performance comparing to others in number of wavelengths used.The earlier version was published in ICCS 2004, Poland (Krakow). This research was supported by the Ministry of Information and Communication, Korea under the Information Technology Research Center support program supervised by the Institute of Information Technology Assessment, IITA-2005-(C1090-0501-0019).     

Link‐disjoint paths for reliable QoS routing

The problem of finding link/node‐disjoint paths between a pair of nodes in a network has received much attention in the past. This problem is fairly well understood when the links in a network are only specified by a single link weight. However, in the context of quality of service routing, links are specified by multiple link weights and restricted by multiple constraints. Unfortunately, the problem of finding link/node disjoint paths in multiple dimensions faces different conceptual problems. This paper presents a first step to understanding these conceptual problems in link‐disjoint quality of service routing and proposes a heuristic link‐disjoint QoS algorithm that circumvents these problems. Copyright © 2003 John Wiley & Sons, Ltd.     

Authentication scheme for industrial Internet of things based on DAG blockchain

Internet of things ( IoT) can provide the function of product traceability for industrial systems. Emerging blockchain technology can solve the problem that the current industrial Internet of things ( IIoT) system lacks unified product data sharing services. Blockchain technology based on the directed acyclic graph (DAG) structure is more suitable for high concurrency environments. But due to its distributed architecture foundation, direct storage of product data will cause authentication problems in data management. In response, IIoT based on DAG blockchain is proposed in this paper, which can provide efficient data management for product data stored on DAG blockchain, and an authentication scheme suitable for this structure is given. The security of the scheme is based on a discrete-logarithm-based assumption put forth by Lysyanskaya, Rivest, Sahai and Wolf(LRSW) who also show that it holds for generic groups. The sequential aggregation signature scheme is more secure and efficient, and the new scheme is safe in theory and it is more efficient in engineering.     

Restoration performance study of k-shortest disjoint paths in WDM optical networks

Many researchers have proposed restoration techniques incorporating the concept of k-shortest disjoint paths in survivable WDM (Wavelength Division Multiplexing) optical networks, but without considering network performance and network costs simultaneously. In this paper we need to carefully look into how well the concept of shortest disjoint paths is incorporated for given objective functions. Seven objective functions and four algorithms are presented to evaluate the concept of k-shortest disjoint paths for the design of a robust WDM optical network. A case study based on simulation experiments is conducted to illustrate the application and efficiency of k-shortest disjoint paths in terms of following objective goals: minimal wavelengths, minimal wavelength link distance, minimal wavelength mileage costs, even distribution of traffic flows, average restoration time of backup lightpaths, and physical topology constraints. Sungwoo Takis an assistant professor in the Department of Computer Science and Engineering at Pusan National University. He is also a research member at Research Institute of Computer Information and Communication at Pusan National University. He received a Ph.D. degree in Computer Science from the University of Missouri Kansas City. He has served as a TPC member for the IEEE ICCCN (International Conference on Computer Communications and Networks) since 2004. His research interests include Computer Networks, Wireless Networks, Software Architecture, WDM Optical Networks, Real-time Systems, and SoC (System on Chips) based Communication Chip Design. E. K. Park is a Professor of Computer Science at the University of Missouri at Kansas City. He received a Ph.D. degree in Computer Science from the Northwestern University. His research interests include software engineering, software architectures, software agents, distributed systems, object-oriented methodology, software tolerance and reliability, computer networks and management, optical networks, database/data mining, and information/knowledge management.     

光网络中分离路由算法的研究

光网络比传统的包含节点、链路的图论网络更为复杂,使用分离路径能够有效地改善光网络的可靠性.文章提出了一种基于改进蚁群算法的分离路由算法,通过与最短路径优先算法进行仿真比较可知,该算法在多条分离路径的搜索上具有较明显的优势.     

一种应急条件对地观测卫星成像调度方法

 通过分析CBERS系列对地观测卫星(EOS,Earth Observation Satellites)应急条件下的成像调度问题,本文提出了一种应急成像调度解决方法.首先建立问题的多目标无圈有向图模型;然后引入延迟非支配路径的概念,提出基于标记更新的成像路径搜索算法,通过限制延迟受支配路径来提高搜索效率.理论分析和实验结果表明该方法能在规定时间内有效的解决应急条件成像调度问题.     

基于改进RRT算法的无人机航迹规划

针对快速扩展随机树（RRT）算法用于无人机自主在线航迹规划时,只能快速获得可行的航迹,无法获得接近于最短航迹的较优航迹的缺点,提出了一种改进的RRT算法.该算法将无人机动力学约束融入到节点扩展过程中,通过改进离随机采样点最近的根节点的选取策略和引入航迹距离约束,搜索树将沿着航迹距离较短的方向朝着目标点进行扩展,使得规划出来的航迹接近最优,并采用基于B样条曲线的航迹平滑方法生成平滑可跟踪的航迹.仿真结果表明该算法能够快速地搜索安全并且满足无人机动力学约束的较优航迹.