Hierarchical Multi‐skill Resource Assignment in the Telecommunications Industry

We formulate a discrete time Markov decision process for a resource assignment problem for multi‐skilled resources with a hierarchical skill structure to minimize the average penalty and waiting costs for jobs with different waiting costs and uncertain service times. In contrast to most queueing models, our application leads to service times that are known before the job is actually served but only after it is accepted and assigned to a server. We formulate the corresponding Markov decision process, which is intractable for problems of realistic size due to the curse of dimensionality. Using an affine approximation of the bias function, we develop a simple linear program that yields a lower bound for the minimum average costs. We suggest how the solution of the linear program can be used in a simple heuristic and illustrate its performance in numerical examples and a case study.     

Design and Analysis of Hospital Admission Control for Operational Effectiveness

Variability in hospital occupancy negatively impacts the cost and quality of patient care delivery through increased emergency department (ED) congestion, emergency blockages and diversions, elective cancelations, backlogs in ancillary services, overstaffing, and understaffing. Controlling inpatient admissions can effectively reduce variability in hospital occupancy to mitigate these problems. Currently there are two major gateways for admission to a hospital: the ED and scheduled elective admission. Unfortunately, in highly utilized hospitals, excessive wait times make the scheduled gateway undesirable or infeasible for a subset of patients and doctors. As a result, this group often uses the ED gateway as a means to gain admission to the hospital. To better serve these patients and improve overall hospital functioning, we propose creating a third gateway: an expedited patient care queue. We first characterize an optimal admission threshold policy using controls on the scheduled and expedited gateways for a new Markov decision process model. We then present a practical policy based on insight from the analytical model that yields reduced emergency blockages, cancelations, and off‐unit census via simulation based on historical hospital data.     

随机多模式资源受限项目调度

项目调度是实现项目资源优化配置的重要手段。项目执行时往往面临大量不确定因素,并呈现出典型的多模式特性,给项目调度带来了很大挑战。鉴于此,本文研究活动工期不确定条件下的多模式资源受限项目调度问题,建立了该问题的马尔科夫决策过程模型。为了高效求解上述模型,设计了基于Rollout的近似动态规划算法。该算法可以在项目执行过程中根据最新的项目状态动态给出调度方案,从而有效优化项目期望工期。在所提算法中,利用“活动—模式”列表与并行调度机制相结合的启发式算法构建基准策略,并设计了基于离散时间马尔科夫链的动态仿真,以进一步提升算法性能。基于公开的项目调度问题库PSPLIB,通过大规模计算实验分析了本文算法的性能,探讨了多种因素对调度效果的影响。     

资源约束下多项目调度的改进遗传算法

针对资源约束下的多项目调度问题,在前人提出的有效的启发式算法研究路径基础上,本文利用遗传算法,结合进度生成机制,提出了多项目调度的改进遗传算法。与其他多项目调度启发式算法相比,该算法在平均项目延迟和最佳解比例方面都表现较好,综合利用优化后的优先规则也使得该算法更适用于不同网络复杂度和不同资源约束程度的多项目调度问题中。     

Optimal Dynamic Order Scheduling under Capacity Constraints Given Demand‐Forecast Evolution

We consider a manufacturer without any frozen periods in production schedules so that it can dynamically update the schedules as the demand forecast evolves over time until the realization of actual demand. The manufacturer has a fixed production capacity in each production period, which impacts the time to start production as well as the production schedules. We develop a dynamic optimization model to analyze the optimal production schedules under capacity constraint and demand‐forecast updating. To model the evolution of demand forecasts, we use both additive and multiplicative versions of the martingale model of forecast evolution. We first derive expressions for the optimal base stock levels for a single‐product model. We find that manufacturers located near their market bases can realize most of their potential profits (i.e., profit made when the capacity is unlimited) by building a very limited amount of capacity. For moderate demand uncertainty, we also show that it is almost impossible for manufacturers to compensate for the increase in supply–demand mismatches resulting from long delivery lead times by increasing capacity, making lead‐time reduction a better alternative than capacity expansion. We then extend the model to a multi‐product case and derive expressions for the optimal production quantities for each product given a shared capacity constraint. Using a two‐product model, we show that the manufacturer should utilize its capacity more in earlier periods when the demand for both products is more positively correlated.     

Optimal Choice for Appointment Scheduling Window under Patient No‐Show Behavior

Observing that patients with longer appointment delays tend to have higher no‐show rates, many providers place a limit on how far into the future that an appointment can be scheduled. This article studies how the choice of appointment scheduling window affects a provider's operational efficiency. We use a single server queue to model the registered appointments in a provider's work schedule, and the capacity of the queue serves as a proxy of the size of the appointment window. The provider chooses a common appointment window for all patients to maximize her long‐run average net reward, which depends on the rewards collected from patients served and the “penalty” paid for those who cannot be scheduled. Using a stylized M/M/1/K queueing model, we provide an analytical characterization for the optimal appointment queue capacity K, and study how it should be adjusted in response to changes in other model parameters. In particular, we find that simply increasing appointment window could be counterproductive when patients become more likely to show up. Patient sensitivity to incremental delays, rather than the magnitudes of no‐show probabilities, plays a more important role in determining the optimal appointment window. Via extensive numerical experiments, we confirm that our analytical results obtained under the M/M/1/K model continue to hold in more realistic settings. Our numerical study also reveals substantial efficiency gains resulted from adopting an optimal appointment scheduling window when the provider has no other operational levers available to deal with patient no‐shows. However, when the provider can adjust panel size and overbooking level, limiting the appointment window serves more as a substitute strategy, rather than a complement.     

基于风险的考虑成本和允许等待的车辆运输调度问题研究

本文同时考虑了成本约束和允许等待情形,研究了最小化风险的车辆运输调度问题,其中运输风险是随时间不同而变化的,即研究在时间依赖网络中基于风险的有约束的运输路径选择问题,以及在选定路径的顶点上决定的出发和等待时间的综合问题。建立了相应的混合整数规划模型,设计了相应的算法,并分析了算法复杂性,最后通过算例验证了该算法的有效性和可行性。     

电子商务环境下的DSS应用模式及资源描述

分析了传统DSS的弊端,引出电子商务环境下的DSS应用新模式。针对原有决策电子市场的框架结构,进行相对的完善,给出了一个新决策电子市场模型,并分析了新模式下完成一次交易事务的全过程。在此基础上,阐述了决策资源描述的重要性,并根据owl-s描述Web服务的框架,对电子市场中的DSS资源进行针对性的描述。利用新市场模型和资源描述框架,可以有效完善市场功能并形成新模式下相对通用的DSS资源描述方案。     

Scheduling and performance analysis under a stochastic model for electric vehicle charging stations

Wide-spread infrastructures for electric vehicle battery charging stations are essential in order to significantly increase the implementation of electric vehicles (EVs) in the foreseeable future. Therefore, we propose a stochastic model and charge scheduling methods for an EV battery charging system. We utilize a flexible Poisson process with a hidden Markov chain for modeling the complexity of the time-varying behavior of the EV stream into the system. Relevant random factors and constraints, which include parking times, requested amounts of electricity, the number of parking lots (charging facilities), and maximal demand level, are considered within the proposed stochastic model. Performance measures for the proposed charge scheduling are analytically derived by obtaining stationary distributions of states concerning the number of inbound EVs, waiting time distributions, and the joint distributions of parking time and electricity charged during random parking times.