随机旅行时间局内车辆路径问题的模型及其算法

人们在生活中会经常遇到随机旅行时间的局内车辆路径问题,如现实物流配送中的交通堵塞现象.文章在Laporte等的研究基础上,提出了一个考虑堵塞点动态产生、一个个遇到,堵塞时间为随机变量的模型,并构造了求解该模型的算法.     

考虑CO2排放量的城市专业物流中心选址研究

目前关于物流中心选址的研究多基于企业的角度,鲜有学者站在地方政府角度考虑不同行业物流特点对城市物流中心选址进行研究。本文基于钢材分销行业特征,从地方政府角度出发,构建了综合考虑CO₂排放量和物流成本的双目标整数规划模型,采用理想点法将双目标转化为单目标并用分枝定界法对该模型进行求解。本文以重庆市钢材分销行业的城市物流中心选址为例进行分析,并将CO₂排放量的测算结果以澳大利亚碳税的征收标准进行计算,发现碳税征收并不能有效降低钢材行业CO₂排放量。地方政府可通过合理选择物流中心位置、规范城市物流配送车辆选型、限速、限行和错峰限时等城市物流管理策略来实现低碳物流。     

Analysis of Two‐Level Support Systems with Time‐Dependent Overflow—A Banking Application

In this paper, we analyze the performance of call centers of financial service providers with two levels of support and a time‐dependent overflow mechanism. Waiting calls from the front‐office queue flow over to the back office if a waiting‐time limit is reached and at least one back‐office agent is available. The analysis of such a system with time‐dependent overflow is reduced to the analysis of a continuous‐time Markov chain with state‐dependent overflow probabilities. To approximate the system with time‐dependent overflow, some waiting‐based performance measures are modified. Numerical results demonstrate the reliability of this Markovian performance approximation for different parameter settings. A sensitivity analysis shows the impact of the waiting‐time limit and the dependence of the performance measures on the arrival rate.     

工业化过程中碳排放消费建设比的演变规律研究

本文从历史发展角度动态地考察了由投资和消费引发CO₂排放的变化规律,提出了碳排放中的消费型排放、建设型排放和消费建设比的概念,利用环境投入产出分析模型(EE-IOA)估计了处于不同工业化发展阶段的32个国家86组数据的消费型排放和建设型排放,得到了消费建设比在工业化过程中(包括后工业化时期)的演变规律。实证结果表明:随着工业化水平的提高,消费建设比呈上升趋势;应根据消费型排放和建设型排放的减排潜力,科学制定减排目标,更加注重引导消费者行为向绿色消费转变、依靠消费者力量促进企业节能减排。本研究对正确评价不同工业化发展阶段国家的排放水平和减排潜力,科学制定减排政策和目标具有重要意义。     

基于资源共享和温度控制的生鲜商品多中心车辆路径优化问题

针对生鲜商品多中心共同配送优化研究在资源共享和温度控制有效结合方面存在的不足,提出研究集成资源共享和温度控制的生鲜商品多中心车辆路径优化问题。首先,结合生鲜商品的易腐性和配送过程的及时性特征,构建了包含生鲜商品多中心间的运输成本、配送成本、车辆温控成本、违反时间窗惩罚成本、生鲜商品价值损失和车辆租赁成本的物流运营成本最小和配送车辆使用数最小的双目标优化模型。然后,设计了结合生鲜需求客户地理位置、需求商品温控区间和时间窗约束的K-means多维聚类算法,进而提出一种TS-NSGA-II算法,该算法设计了禁忌搜索算法(TS)和非支配排序遗传算法(NSGA-II)间有效的选择性赋予机制,进而增强了解空间的搜索和寻优能力,并通过与MOGEA和MOPSO算法的对比分析,进一步验证了模型和TS-NSGA-II算法的有效性。最后,通过实例分析探讨了不同资源共享模式和温控区间的多中心车辆路径优化方案,研究结果可为生鲜商品物流配送企业进行资源共享模式选择和温控区间设计提供方法支撑和决策支持。     

考虑差异化服务时间的多车型电动汽车路径优化与充电策略研究

在政府政策大力支持以及社会环境意识不断增长的背景下,电动汽车在物流配送行业快速普及。电动汽车参与的物流配送服务需要物流专员、电动汽车和顾客三方协作完成。因此,在传统车辆配送路径优化的基础上,车辆的多样性、充电策略、人车的匹配以及服务时间差异化等因素都会影响物流运营成本。本文提出了考虑差异化服务成本的多车型电动汽车路径优化与充电策略问题并建立了该问题的整数规划数学模型。其次,提出了混合启发式算法MCWGATS,并通过多组算例验证了算法的有效性。最后,采用多组算例分析了多车型和差异化服务时间对运营成本的影响。实验结果表明,该模型有助于物流企业提高人员、物流车辆、服务时间等资源的利用效率,降低运营成本。     

有顾客时间窗和发货量变化的车辆调度干扰管理研究

为解决由顾客需求变化引发的物流配送干扰问题,提出基于干扰管理思想构建扰动恢复策略和方案.应用虚拟多车场实现车辆调度扰动恢复问题转化.提出车辆调度扰动恢复策略和扰动度量方法,以作为车辆调度干扰管理建模的基础;分析顾客时间窗和发货量变化造成的扰动并进行辨识.建立相应的干扰管理模型,提出归一化处理办法对VRPTW、MD-VRPTW和MDVRPTW干扰管理问题进行有效兼容;结合干扰管理模型的特点,改进基于顾客的编码表示方法,可以反映出车辆调度扰动恢复策略;根据干扰管理思想,设计遗传算法对干扰管理模型进行求解.给出了一个具有代表性的算例试验结果,算例结果及其分析表明干扰管理模型和遗传算法的有效性.     

Modeling Finite‐Time Failure Probabilities in Risk Analysis Applications

In this article, we introduce a framework for analyzing the risk of systems failure based on estimating the failure probability. The latter is defined as the probability that a certain risk process, characterizing the operations of a system, reaches a possibly time‐dependent critical risk level within a finite‐time interval. Under general assumptions, we define two dually connected models for the risk process and derive explicit expressions for the failure probability and also the joint probability of the time of the occurrence of failure and the excess of the risk process over the risk level. We illustrate how these probabilistic models and results can be successfully applied in several important areas of risk analysis, among which are systems reliability, inventory management, flood control via dam management, infectious disease spread, and financial insolvency. Numerical illustrations are also presented.     

实时/时变路网环境下城市出救点选择与救援车辆路径的集成动态优化

为了提升城市突发公共事件应急资源调配效率,考虑实时/时变路网环境下出救点选择与救援车辆路径的集成优化问题(CERFSVRP),设计了一种实时/时变交通信息的结合策略,并提出了满足先进先出原则的路段行驶时间计算方法.在此基础上,综合考虑出救点选择、供应能力以及车辆路径连续性等约束条件,以应急响应时间最短为目标,基于虚拟出救点概念和滚动时域策略建立了CERFSVRP动态优化模型.针对该模型的特点,设计了一种改进遗传算法和线性规划法相结合的两阶段算法.算例分析结果表明该模型和算法可以有效解决实时/时变路网环境下城市突发公共事件CERFSVRP动态优化问题.     

电力消耗、经济增长与CO2排放量的实证分析——基于中国面板数据

本文运用计量经济学方法,如协整检验和格兰杰因果关系检验、脉冲响应函数等,深入研究了中国在1990-2013期间电力消耗、经济增长与二氧化碳排放量之间的关系。研究结果表明,电力消耗、经济增长与二氧化碳排放量之间存在协整关系,即长期均衡关系;经济增长与电力消耗之间存在双向的格兰杰因果关系,但不存在电力消耗与二氧化碳排放量,经济增长与二氧化碳排放量之间的格兰杰因果关系。与此同时,VAR模型估计结果显示,滞后一期的电力消耗对当期经济增长和二氧化碳排放量产生正向的作用,滞后一期的电力消耗促进当期的电力消耗,同时也促进当期经济增长和CO₂排放量增加;经济增长的滞后期对当期电力消耗和二氧化碳排放量产生负向的作用,而二氧化碳排放量的滞后期对当期经济增长没有显著影响。基于此,实证分析结果表明经济增长在短期内会造成二氧化碳排放量的增加,但正如环境库兹涅茨曲线描述的结论一样,从长期来看,经济增长促进了技术的进步和能源效率的提高,进而导致二氧化碳排放量的减少。该发现对于中国发展低碳经济和电力部门能源政策的制定都将有着重要现实意义。     

Daily Inhalation Rate and Time‐Activity/Location Pattern in Japanese Preschool Children

Lack of data on daily inhalation rate and activity of children has been an issue in health risk assessment of air pollutants. This study aimed to obtain the daily inhalation rate and intensity and frequency of physical activity in relation to the environment in Japanese preschool children. Children aged four–six years (n= 138) in the suburbs of Tokyo participated in this study, which involved three days' continuous monitoring of physical activity using a tri‐axial accelerometer and parent's completion of a time/location diary during daily life. The estimated three‐day mean daily inhalation rate (body temperature, pressure, saturated with water vapor) was 9.9 ± 1.6 m³/day (0.52 ± 0.09 m³/kg/day). The current daily inhalation rate value of 0.580 m³/kg/day proposed for use in health risk assessment in Japan is confirmed to be valid to calculate central value of inhaled dose of air pollutants in five‐ to six‐year‐old children. However, the 95th percentile daily inhalation rate of 0.83 m³/kg/day based on measurement for five‐year‐old children is recommended to be used to provide an upper bound estimate of exposure that ensure the protection of all five‐ to six‐year‐old children from the health risk of air pollutants. Children spent the majority of their time in sedentary and light level of physical activity (LPA) when indoors, while 85% of their time when outdoors was spent in LPA and moderate‐to‐vigorous physical activity. The results suggest the need to consider variability of minute respiratory ventilation rate according to the environment for more refined short‐term health risk assessment.     

An Analysis of Dual‐Kanban Just‐In‐Time Systems in a Non‐Repetitive Environment

Recent advances in approaches and production technologies for the production of goods and services have made just‐in‐time (JIT) a strong alternative for use in intermittent and small batch production systems, especially when time‐based competition is the norm and a low inventory is a must. However, the conventional JIT system is designed for mass production with a stable master production schedule. This paper suggests supplementing the information provided by production kanbans with information about customer waiting lines to be used by operators to schedule production in each work‐station of intermittent and small batch production systems. This paper uses simulation to analyze the effect of four scheduling policy variables—number of kanbans, length of the withdrawal cycle, information about customer waiting lines, and priority rules on two performance measures—customer wait‐time and inventory. The results show that using information about customer waiting lines reduces customer wait‐time by about 30% while also reducing inventory by about 2%. In addition, the effect of information about customer waiting lines overshadows the effect of priority rules on customer wait‐time and inventory.     

Dynamic Forecasting Conditional Probability of Bombing Attacks Based on Time‐Series and Intervention Analysis

In recent years, various types of terrorist attacks occurred, causing worldwide catastrophes. According to the Global Terrorism Database (GTD), among all attack tactics, bombing attacks happened most frequently, followed by armed assaults. In this article, a model for analyzing and forecasting the conditional probability of bombing attacks (CPBAs) based on time‐series methods is developed. In addition, intervention analysis is used to analyze the sudden increase in the time‐series process. The results show that the CPBA increased dramatically at the end of 2011. During that time, the CPBA increased by 16.0% in a two‐month period to reach the peak value, but still stays 9.0% greater than the predicted level after the temporary effect gradually decays. By contrast, no significant fluctuation can be found in the conditional probability process of armed assault. It can be inferred that some social unrest, such as America's troop withdrawal from Afghanistan and Iraq, could have led to the increase of the CPBA in Afghanistan, Iraq, and Pakistan. The integrated time‐series and intervention model is used to forecast the monthly CPBA in 2014 and through 2064. The average relative error compared with the real data in 2014 is 3.5%. The model is also applied to the total number of attacks recorded by the GTD between 2004 and 2014.     

Costs of Health Damage from Atmospheric Emissions of Toxic Metals: Part 2—Analysis for Mercury and Lead

In this part of the series we explain the detailed literature review and the calculations of impacts and damage costs of mercury and lead. Methodology and general assumptions are explained in the companion article, Part 1 of this series, and the spreadsheet with the calculations is available as a supplementary file of Part 1.³ For mercury, the damage cost is 22,937 €₂₀₁₃/kg if there is a no‐effect threshold, 52,129 €₂₀₁₃/kg if there is none; 91% is due to mortality from heart disease, the rest from loss of IQ points. For lead, the damage cost is 29,343 €₂₀₁₃/kg, about 80% due to mortality and 20% due to IQ loss; there does not seem to be a no‐effect threshold. These costs are per kg of emitted pollutant.     

Probability and Possibility‐Based Representations of Uncertainty in Fault Tree Analysis

Expert knowledge is an important source of input to risk analysis. In practice, experts might be reluctant to characterize their knowledge and the related (epistemic) uncertainty using precise probabilities. The theory of possibility allows for imprecision in probability assignments. The associated possibilistic representation of epistemic uncertainty can be combined with, and transformed into, a probabilistic representation; in this article, we show this with reference to a simple fault tree analysis. We apply an integrated (hybrid) probabilistic‐possibilistic computational framework for the joint propagation of the epistemic uncertainty on the values of the (limiting relative frequency) probabilities of the basic events of the fault tree, and we use possibility‐probability (probability‐possibility) transformations for propagating the epistemic uncertainty within purely probabilistic and possibilistic settings. The results of the different approaches (hybrid, probabilistic, and possibilistic) are compared with respect to the representation of uncertainty about the top event (limiting relative frequency) probability. Both the rationale underpinning the approaches and the computational efforts they require are critically examined. We conclude that the approaches relevant in a given setting depend on the purpose of the risk analysis, and that further research is required to make the possibilistic approaches operational in a risk analysis context.     

Why RDAs and ULs Are Incompatible Standards in the U‐Shape Micronutrient Model: A Philosophically Orientated Analysis of Micronutrients' Standardizations

Risk assessments of micronutrients are carried out in the customary deficiency‐excess model. It is regarded as straightforward and unambiguous. Nevertheless, it is a problematic amalgamation of two different and to a certain extent contrasting perspectives on risk and science that we will criticize in this contribution. Our critique is framed in a conceptual scheme of opposing perspectives highlighted by the rival characteristics of RDAs and SULs and the role of science therein. The one part of our scheme holds the typically modern approach that centers on risks that can be scientifically assessed more or less confidently. Subsequent policies are aimed at preventing major health problems that affect the majority of the population from early on in life. The RDAs are the ideal type‐case here. The other part of our scheme holds a much more postmodern approach in which health risks are explicitly recognized as “uncertain.” Dealing with those risks has little to do with major health problems from early on in life. Here, we encounter the scientific quandary of disentangling complex factors and impacts that may relate to some extra quality of life later on in life. SULs are exemplarily thereof. We will show that RDAs originally spawned from the scientific aim of securing objective knowledge “to lay down the requirements of an adequate” diet. SULs, conversely, are the upshot of generating acceptable outcomes driven by ever‐increasing safety requirements. This shift from securing objective knowledge to generating acceptable outcomes will be addressed in relation to precautionary culture.     

A Comparison Between Probabilistic and Dempster‐Shafer Theory Approaches to Model Uncertainty Analysis in the Performance Assessment of Radioactive Waste Repositories

Model uncertainty is a primary source of uncertainty in the assessment of the performance of repositories for the disposal of nuclear wastes, due to the complexity of the system and the large spatial and temporal scales involved. This work considers multiple assumptions on the system behavior and corresponding alternative plausible modeling hypotheses. To characterize the uncertainty in the correctness of the different hypotheses, the opinions of different experts are treated probabilistically or, in alternative, by the belief and plausibility functions of the Dempster‐Shafer theory. A comparison is made with reference to a flow model for the evaluation of the hydraulic head distributions present at a radioactive waste repository site. Three experts are assumed available for the evaluation of the uncertainties associated with the hydrogeological properties of the repository and the groundwater flow mechanisms.