有时间窗的车辆路径问题改进蚁群算法研究

针对目前蚁群算法在求解有时间窗的车辆路径问题上较少对蚁群算法本身进行优化的问题,提出了一种改进蚁群算法,通过改进状态转移概率和信息素更新规则,以及使用改进的精英蚂蚁策略,改善蚁群算法搜索能力。通过对Solomon标准数据集的实验,结果表明改进的蚁群算法在求解有时间窗车辆路径问题上是有效的。     

基于自适应的改进蚁群算法在餐饮连锁物流配送中的应用

在基本蚁群算法的基础上进行改进,运用了一种信息素自适应调整策略,在旅行商问题(TSP)的搜索过程中自适应的调整信息素挥发系数,适当抑制算法的正反馈作用,拓展了搜索空间,扩大可行解的范围,提高蚁群算法的求解性能和运行效率。通过使用matlab对实际问题进行实验,证实了该自适应蚁群算法在求解物流配送问题时,搜索能力及收敛速度比传统的蚁群算法有较大提高。     

混合柔性充电策略支持下的电动汽车配送路径优化

针对电动汽车在市区配送中应用越来越广泛的现象,提出了混合充电策略支持下带时间窗的电动汽车路径规划问题。在充电站,电动汽车可以选择快速充电方式充满电池或充一部分必须的电量,也可以选择直接更换满电状态的电池,这种柔性的充电策略为电动汽车提供了更灵活的运作方式,降低配送的时间和成本。通过引入充电策略相关的决策变量,在车辆路径问题的基础上,建立了混合充电策略的电动汽车路径优化的非线性混合整数规划模型。设计了一种改进的蚁群算法,通过集成局部搜索算法,提高了问题求解的效率。最后通过三个具有不同客户点分布特征的实例验证了算法的有效性,并分析了混合充电策略的影响。     

基于改进蚁群算法的数控机床主轴优化设计

通过机床主轴结构的分析,建立数学模型优化主轴。改进的蚁群算法,将寻优过程分为粗搜索和精搜索两个步骤,将粗搜索获得的可行解进行变异交叉操作,最后通过精搜索完成整个寻优过程。分别采用改进蚁群算法、基本蚁群算法和常规优化设计对主轴进行优化,对比分析优化结果可知,采用改进蚁群算法优化后体积减少了5.6%,刚度提高了8.2%,并且改进蚁群算法比基本蚁群算法优化耗时减少了36%,比常规优化设计减少了57%,这为机床主轴系统的优化提供了一种切实可行的优化算法。     

Financial Distress Prediction in an International Context: A Review and Empirical Analysis of Altman's Z‐Score Model

This paper assesses the classification performance of the Z‐Score model in predicting bankruptcy and other types of firm distress, with the goal of examining the model's usefulness for all parties, especially banks that operate internationally and need to assess the failure risk of firms. We analyze the performance of the Z‐Score model for firms from 31 European and three non‐European countries using different modifications of the original model. This study is the first to offer such a comprehensive international analysis. Except for the United States and China, the firms in the sample are primarily private, and include non‐financial companies across all industrial sectors. We use the original Z′′‐Score model developed by Altman, Corporate Financial Distress: A Complete Guide to Predicting, Avoiding, and Dealing with Bankruptcy (1983) for private and public manufacturing and non‐manufacturing firms. While there is some evidence that Z‐Score models of bankruptcy prediction have been outperformed by competing market‐based or hazard models, in other studies, Z‐Score models perform very well. Without a comprehensive international comparison, however, the results of competing models are difficult to generalize. This study offers evidence that the general Z‐Score model works reasonably well for most countries (the prediction accuracy is approximately 0.75) and classification accuracy can be improved further (above 0.90) by using country‐specific estimation that incorporates additional variables.     

混合蚁群算法求解物流配送车辆路径优化问题研究

文中在分析VRP与旅行商问题（TSP）区别的基础上,构造了求解VRP的混合蚁群算法。将蚁群系统（ACS）算法同节约量和局部搜索策略2-opt法相结合来改进基本蚁群算法。仿真实验结果表明混合蚁群算法性能优良,能够有效地求解VRP问题。     

改进的蚁群算法在TSP中的应用

介绍了蚁群算法的特点,提出了基于蚁群算法的TSP问题的求解方法,并分别建立基本蚁群算法及MAX-MIN蚁群算法模型,并引入“三步走”法确定模型参数的最优组合,还结合了交叉局部优化相关的求凸壳顶点的算法进行预处理,进行仿真分析比较。实验结果表明基于MMAS模型相对于基本蚁群算法模型,有比较好最短路径选择能力及良好的可扩展性能,能够较好地适应物流配送系统的要求。     

基于聚类算法和蚁群算法的物流配送路径优化研究

物流配送的研究已经成为提高物流效率、降低物流成本的关键。文中在研究物流问题现状以及相关配送路径算法的基础上,提出了一种新的物流配送路径优化方案,对于一个城市内的多个配送点,首先通过K均值算法进行聚类分析得到局部配送中心及其配送范围内的客户点,然后利用蚁群算法设计该配送区域内的最优配送路径。通过仿真实验得知,文中方案设计出的最优配送路径长度较单纯采用蚁群算法有了较大改善。     

结合局部优化的蚁群优化算法的研究与实现

蚁群算法是一种成功的启发式算法,但在解决TSP问题时存在着收敛速度慢和易陷入局部最优解的问题。本文针对这两个问题,提出了定期交流和模范带头学习模型,前者是在蚂蚁每走过一定城市后,进行学习交流,选出所走路径相对较短的蚂蚁进行信息素影响,从而加快总体的收敛速度;后者是当所有蚂蚁都旅行一圈后,选出最优秀的蚂蚁,在其走过的路径上释放大量信息素,对下一周期蚂蚁的旅行进行引导,避免陷入局部最优解。实验结果表明新算法在求解质量上比传统蚁群算法有了明显提高。本文也通过实验分析了蚂蚁数量等参数对算法性能的影响。     

基于蚁群算法考虑路线安排的单配送中心选址

对一类要求考虑路线安排的单配送中心选址问题建立基于蚁群算法的选址模型,模型目标以配送中心建设费用与运输费用之和最小;同时构造模型的蚁群算法求解结构;最后初步应用证明了该模型解决此类问题的有效性,为单配送选址提供又一种方法。     

基于免疫—蚁群算法的应急物流配送网络优化研究

论文针对应急物流的配送车辆路径优化问题,建立以应急物流初期有限资源的分配达到整体的最优化（时间短、效率高、安全高、成本低）的多目标模型,结合模型的特点,利用免疫算法和蚁群算法相融合的启发式算法进行求解,最后进行算例分析,解决应急物流配送车辆路径选择的实际问题。     

基于蚁群算法的应急物流配送车辆调度研究

以车辆配送问题为背景,运用了蚁群算法来求解应急物流配送车辆调度模型。在带有时间窗的基础上考虑应急系统各节点的运输距离和费用构造模型。根据模型的特点,设计了蚁群算法求解方法,并针对蚂蚁路径选择做了改进性分析。实例研究结果表明．蚁群算法在应急物流配送车辆调度问题中具有合理性、可行性和有效性。     

The duality of bankruptcy process in Finland

Standard bankruptcy prediction methods lead to models weighted by the types of failure firms included in the estimation sample. These kinds of weighted models may lead to severe classification errors when they are applied to such types of failing (and non-failing) firms which are in the minority in the estimation sample (frequency effect). The purpose of this study is to present a bankruptcy prediction method based on identifying two different failure types, i.e. the solidity and liquidity bankruptcy firms, to avoid the frequency effect. Both of the types are depicted by a theoretical gambler's ruin model of its own to yield an approximation of failure probability separately for both types. These models are applied to the data of randomly selected Finnish bankrupt and non-bankrupt firms. A logistic regression model based on a set of financial variables is used as a benchmark model. Empirical results show that the resulting heavily solidity-weighted logistic model may lead to severe errors in classifying non-bankrupt firms. The present approach will avoid these kinds of error by separately evaluating the probability of the solidity and liquidity bankruptcy; the firm is not classified bankrupt as long as neither of the probabilities exceeds the critical value. This leads the present prediction method slightly to outperform the logistic model in the overall classification accuracy.     

基于OpenMP的并行蚁群物流调度算法研究

物流中心调度问题是物流管理的核心问题,基于OpenMP并行编程规范,提出了基于蚁群的物流调度并行优化算法,挖掘多核高性能计算能力,提高物流过程中物件的动态分配效率,提高物流调度系统的可扩展性。     

多点配送中心选址及求解蚁群算法

将多点配送中心选址问题(multi-distribution center location problem,MDLP)映射为扩展K-TSP过程并设计了改进的蚁群算法。为提高算法的求解性能,在蚂蚁的选择规则里加入了代价引导函数,使用2-opt策略优化可行解并优化了信息素的更新方式。仿真算例及算法对比表明,模型和算法可以有效地表达和求解MDLP。     

蚁群算法在卷烟配送路径优化中的应用研究

针对目前烟草商业企业的物流配送中存在的问题,提出用仿生学的蚁群优化算法对卷烟配送路径的选择进行优化,以基本的蚁群优化算法模型和原理为理论基础,建立了相应的数学模型,并结合某烟草公司的案例对本算法的应用进行了计算机仿真,实验结果表明该算法在求解卷烟配送的路径优化问题上是行之有效的。     

The role of corporate governance in forecasting bankruptcy: Pre- and post-SOX enactment

This paper contributes to the literature by documenting the improved performance of bankruptcy prediction models after including corporate governance variables. The empirical results demonstrate better predictive power for financial bankruptcy than previous bankruptcy prediction models, particularly in the post-SOX period. Our theoretical argument emphasizes the urgent need for such improvements to the bankruptcy prediction model following the introduction of the SOX Act, with the empirical results providing intuitive economic meaning for all relevant market participants. Policymakers may consider enacting laws to include designs for corporate governance monitoring mechanisms, entrepreneurs may use this model to improve their own governance structures and compensation mechanisms to avoid financial bankruptcy, and investors may refer to it to ensure that ‘losers’ are excluded from their investment portfolios.     

带时间窗的应急救助物资配送车辆路径优化模型研究

在自然灾害突发后,必须将救助物资在规定的时间内运送到受灾点。针对带有时间窗的应急救助物资配送车辆路径优化问题进行研究,建立车辆路径优化模型并运用了蚁群算法进行求解,取得了较好的效果。     

三种常见现代优化算法的比较

现代最优化算法比较常见的有遗传算法、蚁群算法、粒子群算法、鱼群算法和模拟退火算法。这些算法主要是解决优化问题中的难解问题。文章主要是对遗传算法、粒子群算法和模拟退火算法三个算法的优化性能进行比较。首先介绍了三个算法的基本思想,以此可以了解三种算法有着自身的特点和优势,而后用这三种算法对典型函数进行计算,并对优化结果比较分析,提出了今后研究的方向。     

Business fluctuations and bankruptcy avalanches in an evolving network economy

We analyze the properties of a three-sector network economy characterized by credit relationships connecting downstream and upstream firms (inside credit) and credit relationships connecting firms and banks (outside credit). The network topology changes over time due to an endogenous process of partner selection (the preferred-partner choice rule). The output of simulations shows that a business cycle at the macroeconomic level can develop as a consequence of the complex interaction of the heterogeneous financial conditions of the agents involved. In this paper we focus on the emergence of bankruptcy crises: the bankruptcy of one agent can bring about the bankruptcy of one or more other agents in a snowball effect of more or less large size, depending on the network structure and the incidence of non-performing loans on balance sheets of agents involved.