OR in healthcare: A European perspective

The European Working Group “Operational Research Applied to Health Services” (ORAHS) is one of the domain specific EURO Working Groups organized by EURO - the European Association of Operational Research Societies. In this paper we report on the development of ORAHS as a platform for OR in health, and analyse the papers presented at meetings over the 35 years of its existence. We propose a two-way framework for analysis, where one dimension is the nine stages of the product life cycle: identifying consumer requirements, designing a new service to meet these requirements, forecasting demand for such a service, securing resources for it, allocating these resources, developing Programs & Plans to use these resources for delivering the service, establishing criteria for service delivery, managing the performance of the service, and finally, evaluating its performance. The other dimension is a three-level classification into broad application areas referring to processes at different levels in healthcare: Patients & Providers, Units & Hospitals, and Regional & National. We use this framework to carry out a quantitative analysis of all the papers presented during the meetings of ORAHS since its inception in 1975. We then describe developments over this period in applying OR approaches and techniques to healthcare, and present an overview of the main application areas and challenges.     

云计算技术在输电线路状态监测系统中的应用

在分析输电线路状态监测系统特点的基础上,提出了在系统中引入云计算存储与并行处理技术的设计方案,将关系型数据库与开源的Hadoop云计算平台结合使用,解决了关系型数据库在系统使用中存储和访问效率等方面的问题.介绍了所开发的原型系统提供的服务及其主要功能,并针对系统中的典型应用进行了性能测试.测试结果表明所提方案可以满足输电线路状态监测系统对数据存储与读取、分析的性能要求.     

A stochastic and dynamic model for the single-vehicle pick-up and delivery problem

In this paper a stochastic and dynamic model for the Pick-up and Delivery Problem is developed and analyzed. Demands for service arrive according to a Poisson process in time. The pick-up locations of the demands are independent and uniformly distributed over a service region. A single vehicle must transport the demands from the pick-up to the delivery location. Once a demand has been picked up it can only be dropped off at its desired delivery location. The delivery locations are independent and uniformly distributed over the region, and they are independent of the pick-up locations. The objective is to minimize the expected time in the system for the demands. Unit-capacity vehicle and multiple-capacity vehicle variations are considered. For each variation, bounds on the performance of the routing policies are derived for light and heavy traffic. The policies are analyzed using both analytical methods and simulation.     

Resource,service quality and performance triad: a framework for measuring efficiency of banking services

In this paper, we present the development of a theoretical framework for measuring the efficiency of banking services taking into account physical and human resources, service quality and performance. Expenditures on quality improvement efforts and the impact of service quality on financial outcomes have long intrigued researchers. Banks have traditionally focused on how to transform their physical resources to generate financial performance, and they inadvertently ignored the mediating intangible factor of service quality. A theoretical framework on the optimization triad of resource, service quality and performance is proposed here, thereby linking the marketing variables to the financial metrics. A measure for the return on quality is developed as the ratio of the potential improvements in financial performance by enhancement of service quality to the observed performance figures. Empirical results obtained from a study of 27 Indian public sector banks and their customers allow us to measure the impact of service quality on financial performance, optimal level of service quality that can be generated using existing resources and the opportunity cost for sub-optimal service delivery. Banks delivering better service are shown to have better transformation of resource to performance using superior service delivery as the medium. Our results confirm the linkage between resource, service quality and performance for services.     

面向云服务的网络参数建模与定量分析

网络作为云服务向终端用户交付的载体,其性能对云服务质量起着至关重要的作用.基于网络微积分理论提出一种面向云服务的网络参数模型,得到云服务交付过程中端到端时延和数据积压上界的定量数学解析式.用于分析云服务类型、网络服务速率、流量分配方式以及路径数对端到端时延和数据积压上界的影响.数值实验结果表明所提出的网络参数建模分析方法在云服务交付时能够为用户提供性能保障,验证了模型和解析式的有效性.     

Statistical process control for monitoring scheduling performance—addressing the problem of correlated data

In both manufacturing and service operations effective scheduling plays an important role in achieving delivery performance and in utilizing resources economically. Classical scheduling theory takes a narrow, static view of performance. In reality the assessment of scheduling performance is a particularly difficult task. Typically scheduling is an activity that takes place repeatedly over time in the context of an overall planning and control architecture. Scheduling may be viewed as an activity within a process. Statistical Process Control (SPC) provides an attractive option for monitoring performance. In this paper we investigate the potential of applying SPC control charts in this context. The feasibility of monitoring flow time in a single processor model using control charts is studied using simulation. The application of control charts to monitor time-related measures in operational systems raises fundamental statistical problems. The need for approaches that are robust with respect to data correlation and lack of normality is shown to be an essential requirement. Residual-based approaches and the Exponentially Weighted Moving Average (EWMA) chart are shown to be reasonably effective in avoiding false alarms and in detecting process shifts. The applicability of the single processor model to more complex operational systems is discussed. The implications of the work for the design of performance monitoring and continuous improvement systems for time-related measures in manufacturing and service operations are considered. A number of areas are highlighted for further theoretical and practical studies.     

Evaluating systems thinking in housing

This paper describes and evaluates work carried out in the social housing context in the United Kingdom using a systems thinking approach called ‘lean systems’ (LS). The work, sponsored by the Office of the Deputy Prime Minister, was designed to test whether LS could improve the efficiency of delivery of housing management and maintenance services. A pilot programme was developed in which three housing organizations used the approach in different service areas. The results indicate that LS can yield efficiency gains and improvements in service performance, customer satisfaction and staff morale—although securing and sustaining these results requires considerable organizational commitment. The LS approach is outlined, work in the pilots described and the results presented. A theoretical analysis seeks to locate LS in the spectrum of systems methodologies and to delimit its particular area of competence.     

Performance Monitoring and Competence Assessment in Health Services

Health and health service monitoring is among the most promising research area today and the world work towards efficient and cost effective health care. This paper deals with monitoring health service performance using more than one performance outcome variable (multi-attribute processes), which is common in most health services. Although monitoring whether a health service changes or improves over time is important this is well covered in the current literature. Therefore this paper focuses on comparing similar health services in terms of their performance. The proposed procedure is based on an appropriate control chart. The paper deals with firstly the case when no risk adjustment is required because the health services being compared treat the same patient case-mix which does not vary over time. Secondly it deals with comparing health services where risk adjustment is required because the patient case-mix they service do differ because they service either very different geographical locations or service very different demographics of the same population. The technology developed in this paper could be used for example to assess and compare health practitioners’ competence over time, i.e. to decide if two doctors are equivalent in terms of their outcome performances. The waiting time random variable associated with the run length distribution of the control charts (as well as to competence testing) is studied using a Markov Chain embedding technique. Numerical results are provided that exhibit the value of the proposed procedures.     

Performance analysis of virtual circuit connections for bursty data sources in ATM networks

ATM is a packet-like transmission mode that has been proposed for BISDN. It is characterized by an asynchronous slotted transmission mechanism that provides a high bandwidth, low delay connection-oriented transport service to the end user. In this paper, we provide an analytical approach for determining the performance of a virtual circuit connection for data transmission in a high-speed ATM network with finite buffers at the network nodes. The analysis assumes that the network operates using thebest effort delivery strategy and that the end-to-end virtual circuit is responsible for guaranteeing the integrity of the connection. Since the normal Markovian assumptions do not apply, a concise exact solution is impossible to obtain. This provides motivation for developing approximate techniques such as those found in Whitt's QNA paper that allow us to use general distributions for the traffic streams and service times. However, even these techniques assume infinite buffer capacities and hence cannot model buffer overflow. We have therefore developed a hybrid model that allows us to incorporate finite buffers at the nodes. This enables us to study the effect on the performance of both link errors and buffer overflow in conjunction with an end-to-end packet loss recovery scheme.This work was supported in part by a grant from AT&T and in part by NSF under Grant No. 8914447.Work done while at the University of Pennsylvania, Philadelphia, PA 19104, USA     

A hybrid fuzzy-optimization approach to customer grouping-based logistics distribution operations

This paper presents an integrated fuzzy-optimization customer grouping based logistics distribution methodology for quickly responding to a variety of customer demands. The proposed methodology involves three main mechanisms: (1) pre-route customer classification using fuzzy clustering techniques, (2) determination of customer group-based delivery service priority and (3) en-route goods delivery using multi-objective optimization programming methods. In the process of pre-route customer classification, the proposed method groups customers’ orders primarily based on the multiple attributes of customer demands, rather than by static geographic attributes, which are mainly considered in classical vehicle routing algorithms. Numerical studies including a real-world application are conducted to illustrate the applicability of the proposed method and its potential advantages over existing operational strategies. Using the proposed method, it is shown that the overall performance of a logistics distribution system can be improved by more than 20%, according to the numerical results from the case studied.     

二级物流服务供应链的契约协调机制研究

研究一个物流服务集成商和一个物流服务提供商所组成的二级物流服务供应链的系统协调问题。分别建立了集中控制模型、批发价格契约下的Stackelberg主从协调模型、收益共享契约下的协调模型,得到不同协调方法下的最优解所满足的条件。通过模型间的对比,证明了收益共享契约可使得该物流服务供应链达到整体最优的状态,相对于批发价格契约,实现了Pareto改进。最后,用数值试验的方式进一步验证了收益共享契约在协调物流服务供应链运作的有效性。     

Towards a general condition based maintenance model for a stochastic dynamic system

This paper considers a stochastic dynamic system subject to random deterioration, with regular condition monitoring and preventive maintenance. A model is presented to advise at a monitoring check what maintenance action to take based upon the condition monitoring and preventive maintenance information obtained to date. A general assumption adopted in the paper is that the performance of the system concerned can not be described directly by the monitored information, but is correlated with it stochastically. The model is relevant to a large class of condition monitoring techniques currently employed in industry including vibration and oil analysis. The model is constructed under fairly general conditions and includes two novel developments. Firstly, the concept of the conditional residual time is used to measure the condition of the monitored system at the time of a monitoring check, and secondly, contrary to previous practice, the monitored observation is now assumed to be a function of the system condition. Relationships between the observed history of condition monitoring, preventive maintenance actions, and the condition of the system are established. Methods for estimating model parameters are discussed. Since the model presented is generally beyond the scope for an analytical solution, a numerical approximation method is also proposed. Finally, a case example is presented to illustrate the modelling concepts in the case of non-maintained plant.     

Supply chain scheduling with receiving deadlines and non-linear penalty

We study the operations scheduling problem with delivery deadlines in a three-stage supply chain process consisting of (1) heterogeneous suppliers, (2) capacitated processing centres (PCs), and (3) a network of business customers. The suppliers make and ship semi-finished products to the PCs where products are finalized and packaged before they are shipped to customers. Each business customer has an order quantity to fulfil and a specified delivery date, and the customer network has a required service level so that if the total quantity delivered to the network falls below a given targeted fill rate, a non-linear penalty will apply. Since the PCs are capacitated and both shipping and production operations are non-instantaneous, not all the customer orders may be fulfilled on time. The optimization problem is therefore to select a subset of customers whose orders can be fulfilled on time and a subset of suppliers to ensure the supplies to minimize the total cost, which includes processing cost, shipping cost, cost of unfilled orders (if any), and a non-linear penalty if the target service level is not met. The general version of this problem is difficult because of its combinatorial nature. In this paper, we solve a special case of this problem when the number of PCs equals one, and develop a dynamic programming-based algorithm that identifies the optimal subset of customer orders to be fulfilled under each given utilization level of the PC capacity. We then construct a cost function of a recursive form, and prove that the resulting search algorithm always converges to the optimal solution within pseudo-polynomial time. Two numerical examples are presented to test the computational performance of the proposed algorithm.     

A dynamic vehicle routing problem with multiple delivery routes

This paper considers a vehicle routing problem where each vehicle performs delivery operations over multiple routes during its workday and where new customer requests occur dynamically. The proposed methodology for addressing the problem is based on an adaptive large neighborhood search heuristic, previously developed for the static version of the problem. In the dynamic case, multiple possible scenarios for the occurrence of future requests are considered to decide about the opportunity to include a new request into the current solution. It is worth noting that the real-time decision is about the acceptance of the new request, not about its service which can only take place in some future routes (a delivery route being closed as soon as a vehicle departs from the depot). In the computational results, a comparison is provided with a myopic approach which does not consider scenarios of future requests.     

联合监测过程位置参数和尺度参数的非参数Shewhart控制图

用于检测生产服务过程的传统控制图多数都假定过程的分布是已知的。这些控制困经常是在正态分布的假设下构建的,然而在服务质量实时监控中数据往往是非正态的。在这种情况下,基于正态分布假设的控制图的结果是不可靠的。为了解决这个问题,通常考虑非参数方法,因为在过程分布未知情况下,非参数控制图比参数图更加稳健有效。本文提出一个新的基于Van der Waerden和Klotz检验的Lepage型非参数Shewhart控制图(称为LPN图)用于同时检测未知连续过程分布的位置参数和尺度参数。文中给出了LPN图在不同参数下的控制限。依据运行长度分布的均值,方差和分位数,分析了LPN图在过程受控和失控时的性能,并与其他一些现有的非参数控制图进行比较。基于蒙特卡洛的模拟结果表明,LPN图对非正态分布具有很好的稳健性,并且在不同的过程分布下对检测位置参数和尺度参数,尤其对检测尺度参数的漂移都具有很好的性能。最后通过监控出租车服务质量说明LPN图在实际中的应用。     

Loss pattern of DBMAP/DMSP/1/K queue and its application in wireless local communications

This paper applies a matrix-analytical approach to analyze the packet loss pattern of finite buffer single server queue with discrete-time batch Markovian arrival process (DBMAP). The service process is correlated and its structure is presented through discrete-time Markovian service process (DMSP). The bursty nature of packet loss pattern will be examined by means of statistics with respect to alternating loss periods and loss distances. The loss period is the period that loss once it starts; loss distance refers to the spacing between the loss periods. All of the two related performance measurement are derived, including probability distributions of a loss period and a loss distance, average length of a loss period and a loss distance. Queueing systems of this type arise in the domain of wireless local communications. Based on the numerical analysis of such a queueing system, some performance measures for the wireless local communication are presented.     

Managing Reforms on a Large Scale: What Role for OR/MS?

In this paper evidence is presented regarding the degree to which social reforms have been systematically managed by the Public Sector in Greece between 1975-1992. The findings reported here concur with the findings of others that, by and large, in developing countries, important social reforms tend not to be systematically handled. A twofold explanation is advanced for what seems to be an inverse relationship between the importance of social reforms and the use of OR/MS techniques for their management. First, the subsidiary role of OR/MS techniques in both developing and developed countries is partly due to the conflict-ridden and complex nature of important social reforms, which are not as amenable to systematic analysis as small-scale reforms. It is also partly due to the competitive nature of liberal democracies which compels governments to use social policies not only in a problem-solving mode but also in a tactical mode. Secondly, the low degrees of bureaucratization and rationalization that characterize developing countries, in particular, account for seeing social reforms not so much as manifestations of rational calculation designed to solve problems but as political tools in the service of their masters. It is concluded that OR/MS may be useful in developing countries not so much for its techniques as for its ideology; not for what it is but for what it stands for.     

Managerial and economic impacts of reducing delivery variance in the supply chain

This paper addresses the managerial and economic impacts of improving delivery performance in a serial supply chain when delivery performance is evaluated with respect to a delivery window. Building on contemporary management theories that advocate variance reduction as the critical step in improving the overall performance of a system, we model the variance of delivery time to the final customer as a function of the investment to reduce delivery variance and the costs associated with untimely delivery (expected earliness and lateness). A logarithmic investment function is used and the model solution involves the minimization of a convex–concave total cost function. A numerical example is provided to illustrate the model and the solution procedure. The model presented provides guidelines for determining the optimal level of financial investment for reducing delivery variance. The managerial implications as well as the economic aspects of delivery variance reduction in supply chain management are discussed.     

基于时间敏感需求及随机完工期的承诺交货期决策

在新的经济形势和高新技术指引下,产品更新换代的速度加快,基于时间的竞争成为供应链竞争的焦点.在制造商为核心的供应链中,产品需求除了与价格有关外,与承诺交货期也有一定关联,且部分客户愿意为快速交货而支付更高价格.当需求与时间及价格具有敏感性且实际完工期服从一定的随机分布时,建立利润最大化及服务水平约束的承诺交货期决策模型,并对模型进行讨论及优化分析.通过算例验证了模型的有效性,通过参数敏感性分析得出的结论是:当客户服务水平达到一定阈值时,最优承诺交货期将发生改变;价格及交货期敏感系数不影响承诺交货期,但影响产品需求及最终利润;最优承诺交货期与单位提早完工成本是反向变动的关系而与单位延迟完工成本是正向变动的关系;随着完工期均值及标准差的不断增大,最优承诺交货期呈上升趋势,利润、市场需求及价格不断下降.     

A new AATP model with considering supply chain lead-times and resources and scheduling of the orders in flowshop production systems: A graph-theoretic view

The present study attempts to synchronize the scheduling problem with determining the advanced available-to-promise (AATP) in a flowshop system to enhance supplier profitability and service level. In the proposed model the AATP, scheduling and graph theory concept have been combined to find the optimum resource allocation and enable accurate estimations of machines scheduling, production costs and delivery dates. To find the near optimum solutions for the large size problems a genetic algorithm is developed, first the orders are ranked based on their scores which are estimated then the optimum cost is calculated by balancing profitability and constraints such as the availability of the machines or the available material in each workstation. Some computer simulated experiments are provided to evaluate the performance of the proposed algorithm.