A stochastic programming winner determination model for truckload procurement under shipment uncertainty

We propose a two-stage stochastic integer programming model for the winner determination problem (WDP) in combinatorial auctions to hedge the shipper’s risk under shipment uncertainty. The shipper allows bids on combinations of lanes and solves the WDP to determine which carriers are to be awarded lanes. In addition, many other important comprehensive business side constraints are included in the model. We demonstrate the value of the stochastic solution over one obtained by a deterministic model based on using average shipment volumes. Computational results are given that indicate that moderately sized realistic instances can be solved by commercial branch and bound solvers in reasonable time.     

Stochastic programming approach to re-designing a warehouse network under uncertainty

The warehouse network re-design problem includes integrating or eliminating existing warehouses and establishing new sites. In this paper, we incorporate variability in product demand and operational costs with a two-stage stochastic modeling approach. We use the Sample Average Approximation (SAA) approach together with Benders decomposition to provide a solution method. Our results indicate not only that the stochastic solution is an improvement over the deterministic solution but also that the solutions’ differences grow with increasing uncertainty. The stochastic solutions show more robustness than the deterministic solutions. The computational results show that a change in the type of probability distribution of the stochastic parameters does not significantly affect the value of the stochastic solutions.     

不确定型层次分析法在桥梁综合评估中的应用研究

采用确定型层次分析法评估桥梁状态,存在指标的不确定性和模糊性。而利用不确定型层次分析法进行桥梁结构的多级模糊综合评估,建立桥梁的安全性评估模型及指标体系,运用不确定型权重判断矩阵和区间相离度概念,建立桥梁状态综合评估的单目标模型,求解区间权重的最优值,利用等级隶属度函数得出桥梁的评估等级。并通过实例证明不确定型层次分析法在桥梁状态综合评估中的可行性。     

基于随机机会约束的空车调整模型的研究

通过对比空车调整问题的确定性模型与实际问题之间的差异，提出一类随机机会约束模型来模拟实际空车调整问题。通过引入概率模拟实际问题中的不确定因素，将确定性模型转化为不确定性模型，以使模型能更准确的反映实际，并将经济学指标作为评价标准。通过遗传算法求解算例，表明模型和方法的有效性。     

铁路车站值班员应急处置能力评价体系构建

车站值班员应急处置能力评价,可以为新入职人员选拔和在岗职业培训提供理论依据和参考。结合车站值班员的作业内容和要求,以安全意识、响应能力、联系能力和操作能力为准则层,选取行车簿册、凭证填记准确率、命令下达、办理准确率和揭挂标识准确率等共计11项指标建立评价体系,并给出每项指标的量化测度方法。通过AHP法确定准则层之间的权重和指标之间的权重,构建基于模糊综合评价法的数学模型。随机选取某个车站值班员进行实例计算,由8位专家对车站值班员应急处置各项指标给出评语等级,验证所提出方法的可行性和有效性,并根据权重的高低,提出优化途径,即提升风险研判精确度与信息通报准确率2项指标的优秀率,能够显著提升车站值班员综合评价的结果。     

A review of deterministic, stochastic and hybrid vehicular exhaust emission models

Vehicles spend more time near junctions and intersections in different driving modes, i.e., queuing, decelerating or accelerating and thus generating more pollutants than at road links [Claggett, M., Shrock, J., Noll, K.E., 1981. Carbon monoxide near an urban intersection. Atmos. Environ. 15, 1633-1642]. As a result, the receptors in these urban corridors are prone to frequent exposures of high pollutant concentrations (episodic conditions). In order to predict such ‘episodes’, an air quality model, capable of estimating the entire range (middle and extremes) of pollutant concentration distribution is needed. Hybrid models (combining deterministic and statistical distribution models) have demonstrated the ability to predict the entire range of pollutant concentrations in such co mplex dispersion situations with reasonable accuracy [Jakeman, A., Simpson, R.W., Taylor, J.A., 1988. Modelling distributions of air pollutant concentrations-III: Hybrid modelling deterministic-statistical distributions. Atmos. Environ. 22 (1) 163-174]. The present paper reviews the relevant deterministic and stochastic based vehicular exhaust emission models that may be hybridized and thus generate a hybrid model with improved prediction accuracy. The paper also describes the implications of hybrid models in formulating the Episodic-Urban Air Quality Management Plan (e-UAQMP).     

Evaluating spatial accessibility to healthcare services under travel time uncertainty: A reliability-based floating catchment area approach

Most existing healthcare accessibility studies ignore the travel time uncertainty that are commonly encountered in road networks. This study aims to examine the impacts of travel time uncertainty on healthcare accessibility. A reliability-based two-step floating catchment area (2SFCA) method is proposed to evaluate healthcare accessibility under travel time uncertainty. The proposed measure generalizes the conventional 2SFCA measure by explicitly considering individuals' reliability constraints when scheduling visits to healthcare facilities in the face of travel time uncertainty. The proposed measure is further used to investigate travel time uncertainty impacts in a comprehensive case study. A big dataset of taxi trajectories is collected in the case study to extract dynamic information on travel time distributions. The results of the case study highlight the significant but heterogeneous impacts of travel time uncertainty on healthcare accessibility for various parts of the city at different times of the day. They also have several methodological implications for the evaluation of healthcare accessibility under travel time uncertainty.     

Robust optimization for fleet planning under uncertainty

We create a formulation and a solution procedure for fleet sizing under uncertainty in future demands and operating conditions. The formulation focuses on robust optimization, using a partial moment measure of risk. This risk measure is incorporated into the expected recourse function of a two-stage stochastic programming formulation, and stochastic decomposition is used as a solution procedure. A numerical example illustrates the importance of including uncertainty in the fleet sizing problem formulation, and the nature of the fundamental tradeoff between acquiring more vehicles and accepting the risk of potentially high costs if insufficient resources are available.     

Dynamic network design for reverse logistics operations under uncertainty

The design of reverse logistics network has attracted growing attention with the stringent pressures from environmental and social requirements. In general, decisions about reverse logistics network configurations are made on a long-term basis and factors influencing such reverse logistics network design may also vary over time. This paper proposes dynamic location and allocation models to cope with such issues. A two-stage stochastic programming model is further developed by which a deterministic model for multiperiod reverse logistics network design can be extended to account for the uncertainties. A solution approach integrating a recently proposed sampling method with a heuristic algorithm is also proposed in this research. A numerical experiment is presented to demonstrate the significance of the developed stochastic model as well as the efficiency of the proposed solution method.     

Dispatching trucks for drayage operations

We propose a novel model for dispatching trucks given the constraints and sources of uncertainty that arise in drayage operations. The proposed model is designed to minimize the expected cost and is generally applicable to cases including different distributions of random parameters. Numerical examples illustrate this robustness of the model, as well as the potential for reducing the drayage cost by increasing the available storage capacity and permitted number of terminal truck entries. Mathematical results derived within this paper (e.g. expected dwell time) can be used more generally in analyzing transfers in transportation networks under stochastic conditions.     

基于安全影响因素的铁路集装箱物流中心选址的评价方法

对铁路集装箱物流中心的选址问题,给出了基于安全影响因素的铁路集装箱物流中心选址的模糊综合评价方法,并辅以算例分析,证明利用该方法,对考虑安全因素的铁路集装箱物流中心选址进行综合评价是可行的。     

基于旅客心理需求的铁路客运服务综合评价模型研究

在分析铁路旅客心理因素的基础上,建立了基于旅客心理需求的铁路客运服务综合评价指标体系。通过突出旅客心理的情感性反应指标、乘坐兴趣与意向指标,以及主观综合评价指标在铁路客运服务综合评价中的重要作用,结合算例分析,运用随机与模糊数学中的评价分析方法,对铁路客运服务指标进行综合评价分析。     

A deterministic mathematical model to support temporal and spatial decisions of the soybean supply chain

A novel deterministic mathematical model is presented as part of research into a stochastic optimization model for the soybean supply chain in Brazil. The model was conceived as a tool to aid in the decision-making of any trader involved in this highly complex market. The model is intended to be applied to decisions related to tactical planning over a time span of one year. The major spatial and temporal components of the soybean complex, including transportation mode decisions, are incorporated into the model. The mathematical model is described in detail. Several stochastic parameters are used with fixed values in the deterministic model to construct various scenarios. These parameters are the purchase and sale prices of the grain on the market, the crop failure rate and the volumes of demand. The model was tested using data from a large trade in Brazil with consistent results.     

高速铁路应急调度协同处置流程结构化分析方法研究

高速铁路应急调度处置流程的结构化分析,对于提升应急调度处置效率和质量,推动应急调度智能化进程具有重要意义。针对结构化分析需求,提出一种基于铁路规章的应急调度处置流程分解与重构方法,以图形化方式重构应急调度处置流程,并基于随机Petri网理论建立高速铁路应急调度协同处置流程模型,给出多工种协同的SPN模型建立与等价化简、性能分析的方法,通过计算识别处置流程风险控制点和关键环节,选取场景“运行途中司机发现晃车”建模并分析,分析结果符合现场实际情况,表明该结构化分析方法能够从信息传递和处置流程角度提示风险控制点和关键环节,为多工种协同的应急调度指挥工作提供决策参考。     

铁路客运站与市内交通换乘效率评价

铁路客运站与市内交通的换乘衔接是交通一体化研究的重要内容。通过建立定量化的评价指标体系,制定评价准则和评价指标,用综合评价方法给出计算实例,得到的综合评价结果可以准确反映铁路与市内交通换乘的规律及特征,为进一步协调、密切两者的换乘关系提供决策依据。     

A three-stage stochastic facility routing model for disaster response planning

This paper presents a three-stage mixed-integer stochastic programming model for disaster response planning, considering the opening of local distribution facilities, initial allocation of supplies, and last mile distribution of aid. The vehicles available for transportation, the state of the infrastructure and the demand of the potential beneficiaries are considered as stochastic elements. Extensive computational testing performed on realistic instances shows that the solutions produced by the stochastic programming model are significantly better than those produced by a deterministic expected value approach.     

A scenario planning approach for the flood emergency logistics preparation problem under uncertainty

This paper aims to develop a decision-making tool that can be used by government agencies in planning for flood emergency logistics. In this article, the flood emergency logistics problem with uncertainty is formulated as two stochastic programming models that allow for the determination of a rescue resource distribution system for urban flood disasters. The decision variables include the structure of rescue organizations, locations of rescue resource storehouses, allocations of rescue resources under capacity restrictions, and distributions of rescue resources. By applying the data processing and network analysis functions of the geographic information system, flooding potential maps can estimate the possible locations of rescue demand points and the required amount of rescue equipment. The proposed models are solved using a sample average approximation scheme. Finally, a real example of planning for flood emergency logistics is presented to highlight the significance of the proposed model as well as the efficacy of the proposed solution strategy.     

A method for reducing information asymmetry in destination–airline relationships

We propose a measure of business risk in air travel demand at the route level that can reduce information asymmetry during route development negotiations between tourism destinations and airlines. Aviation-exposed risk (AER) conveys information about the level of uncertainty with regard to air travel demand from an airline’s perspective. Using AER, tourism destinations and air service development teams can evaluate their risks from the perspective of the airline and its network. From there, an assessment can be made as to the value of air services in certain circumstances, including whether a direct underwrite or risk share between airlines and destinations is viable and necessary. By applying a portfolio analysis to an airline’s network, we find evidence that AER does indeed mimic the actual capacity distribution of the network. This provides support for AER as a useful risk measure to be used in practice.     

Functional efficiency in airport terminals: A review on Overall and Stratified Service Quality

This paper presents a review of the existing approaches for functional efficiency assessment in airport passenger terminal buildings (PTB). The literature has been classified into two broad study levels and a set of 58 Key Performance Indicators are identified. These are further classified based on their application in processing, holding and circulation activities and sub-classified as objective and subjective indicators. Analytical methods adapted for service quality (SQ) assessments are comprehended. This paper identifies emerging Stratified SQ indicators and stochastic approaches for performance evaluation considering the spatial, operational and technological transformations of PTBs. Critical gaps from literature and scope for further research are discussed.     

基于供应链的制造商合作伙伴风险评估研究

在对制造商合作伙伴的关系结构、风险来源进行分析的基础上,论述了风险评估的步骤,根据指标体系的确定原则,建立了风险评估指标体系。根据制造商合作伙伴风险的综合评估建立了模糊综合评判的数学模型,通过算法举例,对制造商与销售商的风险进行了综合评价。