An Efficient Rerouting Scheme for MPLS-Based Recovery and Its Performance Evaluation

The path recovery in MPLS is the technique to reroute traffic around a failure or congestion in a LSP. Currently, there are two kinds of model for path recovery: rerouting and protection switching. The existing schemes based on rerouting model have the disadvantage of more difficulty in handling node failures or concurrent node faults. Similarly, the existing schemes based on protection switching model have some difficulty in solving problem such as resource utilization and protection of recovery path. This paper proposes an efficient rerouting scheme to establish a LSP along the least-cost recovery path of all possible alternative paths that can be found on a working path, which is calculated by the upstream LSR that has detected a failure. The proposed scheme can increase resource utilization, establish a recovery path relatively fast, support almost all failure types such as link failures, node failures, failures on both a working path and its recovery path, and concurrent faults. Through simulation, the performance of the proposed scheme is measured and compared with the existing schemes.     

基于AI问题的一种“最优”解方法及实现

基于AI的搜索方法包括深度优先搜索、最低成本法搜索等,可以从众多的解决方案中寻找一个“最优”的解决方案。文章以列车信息搜索为例,采用路径删除法生成多种解,然后再用改进的深度优先搜索与最低成本法搜索相结合的方法从中寻找一个最优解。     

厦门市绿地生态网络构建及优化策略

科学构建城市绿地生态网络,对区域生态安全、城市可持续发展及生物多样性保护具有重要意义。基于AHP法和GIS技术,定量分析厦门市自然生态本底,选取重要生态斑块和廊道,采用最小费用路径法模拟潜在廊道,综合构建城市绿地生态网络,并提出绿地生态网络优化策略。结果表明:1)AHP法可整合区域生态、经济、人文和社会等资源,全面客观评价现状生态斑块和廊道的重要程度;最小费用路径法可根据生境分布特征科学模拟连通各斑块之间的潜在廊道;2)厦门市西北部的生态基底适宜性、生态源地及廊道重要性、斑块之间有效连通性均高于东北部及中部平原区;岛内斑块面积小且分散,南北部存在断层现象,应适度增加踏脚石和连通廊道;3)结合城市生态发展需求,提出构建"一片、一环、三带、多廊道、多节点"的城市绿地生态网络。研究结果可为厦门市绿地系统规划提供科学依据。     

免疫组播路由选择算法

研究了带宽延时受限、费用最小的QoS组播路由问题，并提出了一种解决该问题的免疫算法．免疫算法的核心在于免疫算子的构造，而它又是通过接种疫苗和免疫选择两个步骤来完成的．根据QoS组播路由问题，给出了免疫疫苗选取与免疫算子构造的具体方法．将免疫算法应用于组播路由选择，是通过在基于遗传算法的组播路由选择的基础上引入免疫算子来实现的．该算法采用的进化算子简便、高效．仿真实验表明，该算法不仅有效可行，而且较好地解决了标准遗传算法中出现的退化现象，提高了收效速度和搜索能力．     

浅析RIP和OSPF协议的工作原理

本文主要分析了路由器资讯协议（RIP）和开放式最短路径优先（OSPF）协议两种网络协议的工作原理,探讨了这两者的之间的区别以及缩短收敛时间的几项改进技术。文章中还阐述了最小开销路由选择在单一服务器网络中的影响以及源路由选择机制在提高网络效率中是如何发挥作用的。     

基于InVEST模型和最小成本路径的城市绿色空间生境网络构建方法研究——以南京为例

提出以城市绿色空间为载体,选取不同生境类型、对城市化适应能力不同的物种为目标物种,结合物种观测数据和InVEST模型生境质量评估模块进行生境源地的识别及成本面信息的提取,应用最小成本路径综合模拟出城市绿色空间生境网络的方法。以南京为例,选取了9种鸟类作为目标物种,分析了其现状城市绿色空间网络结构。结果表明,迁移能力和城市化适应能力对物种分布的范围和生境类型的广泛程度影响较大。现状网络对城市化适应能力强或迁移能力强的物种较友好,对城市化适应能力差且迁移能力弱的物种有严重不良影响。对于综合的网络,中部的核心区多但被建设区割裂,北部的核心区少而分散,南部的核心区少但联系紧密,三部分的主要连通性结构为滁河、溧水河、秦淮河、秦淮新河和较连续的山林地或水库坑塘。此外,在半自然生境斑块内也生成了许多分散路径,部分联系紧密的斑块形成了组团结构。最后,根据以上结果提出了相应建议。     

On Solving Aquifer Management Problems with Simulated Annealing Algorithms

Aquifer systems play an essential role in meeting the ever increasing use of water for different purposes. Proper design and management of such systems should therefore be a very important matter of concern, not only to ensure that water will be available in adequate quantity (and quality) to satisfy demands but also to guarantee that this would be done in an optimal manner. This paper presents a model serving to define which water supply structures (especially pumping equipment and pipes) should be installed in order to minimize the sum of set-up costs and operation costs while satisfying demands, using a heuristic approach based on simulated annealing. Annealing algorithms are random local search optimization algorithms that allow, at least in theory and in probability, the determination of a global optimum of a (possibly constrained) function.     

一种分布式的PCPO单播路由算法

针对非确定多项式时间完备(NPC)的路径约束路径优化(PCPO)路由问题提出一种分布式算法:两向选择式探测QoS路由算法(TSQR)。以PCPO中的时延约束代价优化(DCLC)问题为例,TSQR基于源节点与目的节点间的最小代价和最短时延路径,由源节点向目的节点发送2种不同的探测消息(MinCProbe1/MinDProbe1, MinCProbe2/MinDProbe2),分别对应2种不同的路由选择操作;沿途节点搜集探测消息走过路径的信息,继续沿原方向转发探测消息的同时,变异此探测消息进行变向探测;目的节点从收到的探测消息所代表的可行路由集中选择一条或多条路径。TSQR具有自然无环特性,在存储和计算开销等方面都具有优越性。仿真表明,与同类参考算法相比,TSQR具有最优的路径优化性能。     

Application of an efficient search technique for solving optimal regional water quality management problems

This article presents a simple yet effective search algorithmic method for solving regional water quality management problems. Essentially, the algorithm assigns the amount of wastewater flow to be treated at each treatment plant together with the associated level of treatment. When necessary this set of assigned values is adjusted appropriately (by raising the treatment efficiency of. and/or reduction of wastewater quantity to be treated by the treatment plant concerned), so that all the physical and water quality constraints are satisfied. Optimization is achieved by the use of a Random Polyhedron Search (RPS) algorithm which identifies progressively superior solutions. The paper comprises two parts: the first, in which feasibility is confined to treatment plant/transfer capacities, and the second, in which constraints relating to the in-stream quality of the receiving water are incorporated.