一类多站循环服务系统的状态与状态转移

探讨具有如下特征的多站循环服务系统：（１）队列容量有限;（２）每次服务对象受限;（３）实施非门限方式。论述的主要内容有：系统与队列运行特点;队列在服务期间的状态转移;队列在周期中的状态与状态转移;系统与队列的有关参量近似求解。     

一类多站循环服务系统的动态与状态转移

探讨具有如下特征的多站循环服务系统：（1）队列容量有限;（2）每次服务对象受限;（3）实施非门限方式。论述的主要内容有：系统与队列运行特点,队列在服务期间的状态转移;队列在周期中的状态与状态转移;系统与队列的有关参量近似于求解。     

多服务商竞争环境下的服务价格与服务能力决策:以物流服务为例

以物流服务为研究对象,通过对不同服务商物流服务能力差异性的分析,建立了多服务商竞争环境下的排队模型,以利润最大化为目标,对服务商的服务价格和服务能力决策进行了研究,研究结果对进一步探讨多服务商横向联盟、区域物流市场规模等问题提供了一定的基础.     

一类多服务排队系统正解的存在性与渐进稳定性

运用算子半群理论讨论了一类多服务排队系统正解的存在唯一性,并证明了所得的半群为Markov半群.另外,进一步得到了系统的稳态解是渐进稳定的.     

多星测控调度效能评价指标体系研究

分析了建立多星测控调度问题评价指标体系的工程需求.从测控网管理方的角度,定义了反映测控系统服务能力、利用效率和资源配置合理性的指标;针对航天器拥有方的需求,建立了反映接受测控服务情况和反映航天任务满足程度的指标.通过两大部分指标构建了多星测控调度问题的指标体系.通过算例说明了利用该指标体系进行多星测控系统效能分析的可行性.     

多队列循环服务系统──全服务与门限服务方式的分析与建模

本文讨论全服务方式与门限服务方式的多队列循环服务系统，在平稳状态和单服务员的前提下，对服务时间为离散型的上述两类服务方式进行分析与建模，并作比较．     

溢出效应下多个竞争零售商的定价与服务决策

考虑分销渠道中多个零售商进行价格竞争的同时决定提供产品服务,但服务存在着溢出效应,研究它们在什么条件下才会提供服务,设定何种水平的服务和零售价格以及二者的相互影响等问题.运用博弈论构建了无服务、部分零售商提供服务和全部零售商提供服务等情形下的决策模型,采用逆向法求解得到均衡结果,找出了各零售商提供服务的条件.结果表明,零售商是否愿意提供服务、选择何种水平的服务和零售价格不仅取决于溢出效应的强弱,还受服务竞争激烈程度的影响,并且博弈均衡随零售商数量的变化而存在着差异.研究结论为竞争环境下多个企业面临服务溢出时的服务策略选择和产品定价提供了参考.     

多队列循环服务系统——全服务与门限服务方式的分析与建模

本讨论全服务方式与门限服务方式的多队列循环服务系统，在平稳状态和单服务员的前提下，对服务时间为离散型的上述两类服务方式进行分析与建模，并作比较。     

基于多智能体的旅游云服务组合模型

针对目前研究服务组合自动化程度低及合作成功率低等情况,提出了基于多智能体的旅游云服务模型.首先提出了基于多智能体的旅游云服务组合框架,其次以旅游服务为例,设计了旅游服务本体;再次提出云服务组合求解的方法.云服务组合求解方法包括服务形成、合作产生、角色指定、团队初步形成、服务分解、服务团队最终形成、服务分配、执行服务8个阶段.最后举例进行说明旅游服务组合合作求解过程,仿真验证团队形成的有效性.     

无穷服务台多级服务系统

本文讨论了成批输入的多级服务系统M~([X])/G_1,G_2,…,G_N/∞,此系统有无穷多个服务台,每个服务台都分为N级,顾客进入服务台后顺次接受各级服务,直到完成所有N级服务后才离开系统,在此顾客离开系统之前,该服务台不再接纳其它顾客.文中给出了任意时刻t正进行各级服务的服务台台数的联合分布的母函数,以及其平稳分布的母函数,还研究了该系统的输出过程和忙期.     

Optimal management of cross-trained workers in services with negligible switching costs

In this paper we consider a retail service facility with cross-trained workers who can switch between the front room and the back room depending on the size of the queue in the front room. Two problems are presented. In the first problem, given a fixed number of cross-trained workers the objective is to find optimal switching points so that the expected customer waiting time is minimized subject to a back room service level constraint. In the second problem the number of workers is also a decision variable and the objective is to minimize it subject to both front room and back room service level constraints. The paper includes an analysis of the model and based on it several heuristics are suggested. Computational analysis with the recommended heuristics is presented and comparison to optimal solutions derived by complete enumeration shows excellent results.     

The combined manpower planning and preventive maintenance strategies by aggregate planning for the service division of vending machines

This paper presents a mathematical model of aggregate planning for the service division of vending machines, which determines its workforce size and the preventive maintenance level that may affect the failure rate. The unique aspect of this problem is that it exhibits two types of failures requiring different repair and preventive maintenance. The practice is to divide the service division into two groups, within which there are hierarchies according to these types of failures, and in each group, there are full-time workers with annual contracts and temporary workers hired only during the peak season. A case study based on actual operational data demonstrates how effective the introduced model and the policy are in reducing the total cost and improving the quality of service, and thus enhancing the overall system performance of the service division. We perform sensitivity analysis on key parameters, which helps us change maintenance strategies under diverse operating situations.     

On the Introduction of an Agile, Temporary Workforce into a Tandem Queueing System

We consider a two-station tandem queueing system where customers arrive according to a Poisson process and must receive service at both stations before leaving the system. Neither queue is equipped with dedicated servers. Instead, we consider three scenarios for the fluctuations of workforce level. In the first, a decision-maker can increase and decrease the capacity as is deemed appropriate; the unrestricted case. In the other two cases, workers arrive randomly and can be rejected or allocated to either station. In one case the number of workers can then be reduced (the controlled capacity reduction case). In the other they leave randomly (the uncontrolled capacity reduction case). All servers are capable of working collaboratively on a single job and can work at either station as long as they remain in the system. We show in each scenario that all workers should be allocated to one queue or the other (never split between queues) and that they should serve exhaustively at one of the queues depending on the direction of an inequality. This extends previous studies on flexible systems to the case where the capacity varies over time. We then show in the unrestricted case that the optimal number of workers to have in the system is non-decreasing in the number of customers in either queue. AMS subject classification: 90B22, 90B36     

Evaluating two new heuristics for constructing customer clusters in a VRPTW with multiple service workers

Central European Journal of Operations Research - The vehicle routing problem with time windows and multiple service workers is a novel approach allowing to efficiently deliver goods to customers...     

Queueing network modelling of flexible manufacturing system using mean value analysis

In the present investigation, we develop queueing model for the performance prediction of flexible manufacturing systems (FMSs) with a multiple discrete material-handling devices (MHD). An iterative method has been suggested using mean value analysis (MVA) for the state-dependent routing. Two queueing network models are considered to determine the material-handling device interference. In the first one, we model the interference from the MHD by inflating the station service times but neglect queueing at the MHD. In another network, the queueing for the MHD is taken into consideration. The performance of FMS configuration is obtained by iterating between two networks. The suggested algorithms demonstrate better results than the algorithm used by earlier workers for single MHD. Some performance indices viz. throughput, mean service time, mean waiting time, etc. are obtained. Numerical results are provided to highlight the effect of the system parameters on performance indices, which are further evaluated by using neuro-fuzzy controller system to validate the tactability of soft computing approach.     

Capacitated emergency facility siting with multiple levels of backup

In many service systems, the primary objective is to provide continuous service and/or service within a prespecified time interval. In the public sector, emergency service systems fit into this category. In the private sector, systems providing repair service to critical production facilities and computers constitute another example. In these systems, the concept of multiple service facilities providing backup to each other becomes an important element in the design process. In this paper, we study the capacitated facility siting problem with multiple levels of backup coverage. The problem is formulated as a mathematical program; an efficient solution procedure is developed and computational experiments are reported.     

Self-Organized Task Allocation for Service Tasks in Computing Systems with Reconfigurable Components

A self-organized scheme for the allocation service tasks in adaptive or organic computing systems is proposed. Such computing systems are highly self-organized and the components ideally adapt to the needs of users or the environment. Typically, the components of such systems need some service from time to time in order perform their work efficiently. Since the type of service tasks will often change in this systems it is attractive to use reconfigurable hardware to perform the service tasks. The studied system consists of normal worker components and the helper components which have reconfigurable hardware and can perform different service tasks. The speed with which a service task is executed by a helper depends on its actual configuration. Different strategies for the helpers to decide about service task acceptance and reconfiguration are proposed. These task acceptance strategies are inspired by stimulus-threshold models that are used to explain task allocation in social insects. Analytical results for a system with two reconfigurable helpers are presented together with simulation results for larger systems. This work was supported by the German Research Foundation (DFG) through the project Organisation and Control of Self-Organising Systems in Technical Compounds within SPP 1183.     

A two-stage stochastic program for scheduling and allocating cross-trained workers

A two-stage stochastic program is developed for scheduling and allocating cross-trained workers in a multi-department service environment with random demands. The first stage corresponds to scheduling days-off over a time horizon such as a week or month. The second stage is the recourse action that deals with allocating available workers at the beginning of a day to accommodate realized demands. After the general two-stage model is formulated, a special case is introduced for computational testing. The testing helps quantify the value of cross-training as a function of problem characteristics. Results show that cross-training can be more valuable than perfect information, especially when demand uncertainty is high.     

Staffing decisions for heterogeneous workers with turnover

In this paper we consider a firm that employs heterogeneous workers to meet demand for its product or service. Workers differ in their skills, speed, and/or quality, and they randomly leave, or turn over. Each period the firm must decide how many workers of each type to hire or fire in order to meet randomly changing demand forecasts at minimal expense. When the number of workers of each type can by continuously varied, the operational cost is jointly convex in the number of workers of each type, hiring and firing costs are linear, and a random fraction of workers of each type leave in each period, the optimal policy has a simple hire- up-to/fire-down-to structure. However, under the more realistic assumption that the number of workers of each type is discrete, the optimal policy is much more difficult to characterize, and depends on the particular notion of discrete convexity used for the cost function. We explore several different notions of discrete convexity and their impact on structural results for the optimal policy.     

Optimizing steady state Markov chains by state reduction

Many service systems have a parameter which can be changed continuously within a certain range. In queueing, for instance, one may be able to change the service rate by means of faster servers, or the arrival rate through advertising. The question to be addressed is how to choose the value of the parameter in order to maximize rewards. In this paper, service systems are formulated as Markov chains in equilibrium. The optimum is then found by Newton's method. This requires one to determine the first and second derivative of the rewards, and an effective method for doing this is proposed. The method is based on state reduction, which is a technique for finding equilibrium probabilities for finite and even for infinite state Markov chains. The optimization technique is then used to obtain a number of curves involving two simple service systems.