遗传算法在选播路由中的应用

选播是一种新型的网络服务，它使用户通过选播地址就能访问到该地址所表示的一组服务器，而传输的实时性要求传输时延尽可能的小。文章针对这种有时延约束的选播QoS路由问题，提出了一种改进的遗传算法以求解该问题。仿真实验表明，该算法是可行且有效的。     

Exact and meta-heuristic approach for a general heterogeneous dial-a-ride problem with multiple depots

Dial-a-ride problems are concerned with the design of efficient vehicle routes for transporting individual persons from specific origin to specific destination locations. In real-life this operational planning problem is often complicated by several factors. Users may have special requirements (e.g. to be transported in a wheelchair) while service providers operate a heterogeneous fleet of vehicles from multiple depots in their service area. In this paper, a general dial-a-ride problem in which these three real-life aspects may simultaneously be taken into account is introduced: the Multi-Depot Heterogeneous Dial-A-Ride Problem (MD-H-DARP). Both a three- and two-index formulation are discussed. A branch-and-cut algorithm for the standard dial-a-ride problem is adapted to exactly solve small problem instances of the MD-H-DARP. To be able to solve larger problem instances, a new deterministic annealing meta-heuristic is proposed. Extensive numerical experiments are presented on different sets of benchmark instances for the homogeneous and the heterogeneous single depot dial-a-ride problem. Instances for the MD-H-DARP are introduced as well. The branch-and-cut algorithm provides considerably better results than an existing algorithm which uses a less compact formulation. All seven previously unsolved benchmark instances for the heterogeneous dial-a-ride problem could be solved to optimality within a matter of seconds. While computation times of the exact algorithm increase drastically with problem size, the proposed meta-heuristic algorithm provides near-optimal solutions within limited computation time for all instances. Several best known solutions for unsolved instances are improved and the algorithm clearly outperforms current state-of-the-art heuristics for the homogeneous and heterogeneous dial-a-ride problem, both in terms of solution quality and computation time.     

基于改进蚁群算法的运输调度规划

在运输调度等组合优化问题的最优路线的搜索中,传统蚁群算法ACA(Ant Colony Algorithm)存在搜索时间长、收敛速度慢、易陷于局部最优解等缺点。为了克服这些缺点提出了一种改进的蚁群算法,该算法将遗传算法和蚁群算法结合起来,在蚁群算法的每一次迭代过程中,首先采用自适应策略控制它的收敛速度,然后使用变异操作来确定解值,从而提高它的搜索性能。再结合建立的运输调度性能指标,利用遗传算法、蚁群算法和改进蚁群算法3种方法分别进行运输规划,通过比较其时间花费和运输费用,验证了改进蚁群算法的有效性。实践证明,改进后的蚁群算法基本上克服了传统算法自身的不足,提高了算法性能。     

通信网簇间的自适应路由算法

船舶航行条件比较复杂,导致通信网络运行的功率消耗巨大,而且经常会发生通信中断的情况。针对船舶网络簇之间的通信特点,提出一种自适应的路由优化算法,可保证源节点和基站进行通信时能够选择最佳路由或次佳路由,有效减少由于网络没有覆盖到导致通信突然中断的情况。实际应用显示,文中所提的算法与其他算法相比,当吞吐量和误码率都相同时,经过一轮所消耗的能量更少,而且当节点密度不相同时,网络的生命周期以及网络的工作持续时间都被大大延长。     

时变交通下生鲜配送电动车辆路径优化方法

依据时变交通路网特点设计基于路段划分策略的行驶时间计算方法,综合考虑客户对生鲜产品最低新鲜度约束,车载限制和电动车电量约束,设计三约束决策因子方法.以配送总成本最小为目标,构建时变交通下电动车城市生鲜配送路径优化模型,根据模型特点设计自适应改进的蚁群算法.实验结果表明,本文方法能够根据客户生鲜新鲜度要求,客户属性和路网特性,合理安排发车时间,科学规划配送路径,有效避免交通拥堵;通过算法对比,本文模型和算法能够明显降低配送成本,提高企业经济效益.     

Optimal solution to the vehicle routing problem by adopting a meta-heuristic algorithm

The delivery service provided by large-scale retailers continues to grow as online sales occupy an increasingly large share of the market. This study aims to tease out efficient vehicle scheduling times as well as optimal delivery routes by applying meta-heuristic algorithms. Monthly data on existing routes were obtained from a branch of Korea’s leading large-scale online retailer. The first task was to examine the status of existing routes by comparing delivery routes created using Dijkstra’s algorithm with existing delivery routes and their vehicle scheduling. The second task was to identify optimal delivery routes through a comparative analysis of the genetic algorithm and Tabu search algorithm, known for its superior applicability amongst other meta-heuristic algorithms. These findings demonstrate that the optimal vehicle routing problem not only has the potential to reduce distribution costs for operators and expedite delivery for consumers, but also the added social benefit of reduced carbon emissions.     

基于链路状态因子的无线MESH网络路由判据研究

针对AODV协议的跳数路径判据的不足,以传统的ETX判据为基础,将链路质量、链路干扰和节点负载等链路状态参数相结合,提出新的路径判据计算方案,通过仿真实验证明,新的路由判据计算方案的路径选择算法有助于提高网络吞吐量,降低丢包率和平均延时,对于提高网络性能是行之有效的.     

浅谈中国沿海警戒区船舶航行

文章通过正确解读警戒区航行的有关规定,分析警戒区航行船舶碰撞的原因,提出船舶在警戒区航行的注意事项,以期为船舶安全航行提供一定的借鉴意义。     

带硬时间窗的航空路径规划模型

针对物流快递行业,以牺牲部分成本来完全满足快递时效的要求,建立了基于硬时间窗的航空路径规划模型,采用并行遗传算法进行了求解.同时建立了相应的软时间窗模型,通过构造满意度函数,与硬时间窗的结果进行了对比分析,算例结果表明硬时间窗的规划路线虽然成本较高,但是更注重时效性的客户的满意度也高,这种规划方法更适于中端物流企业的特点与要求.     

无线异构网络互连仿真研究

针对海军通信中存在的无线网络专网专用问题,提出了一种具有较强扩展性的无线异构网络互连互通解决方案,通过子网间路由协议的设计极好地解决了异构网络之间的跨子网通信问题,并通过仿真实验评价了跨子网通信能力以及网络通信性能,进一步验证方案的可行性。