http://repub.eur.nl/res/aut/48/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/32996/ 2012-05-17T00:00:00Z In this paper we describe how rolling stock and passenger connections in a cyclic railway timetable can be modeled in a flexible way within the model for the Periodic Event Scheduling Problem (PESP). The PESP model was introduced by Serani and Ukovich (1989). Usually, PESP-models assume that the constraints for rolling stock or passenger connections specify in detail which trains should connect with each other. However, the flexibility described in this paper allows the model to choose which trains should connect with each other in a rolling stock or passenger connection. We express the required number of train compositions in terms of the integer cycle variables of the constraint graph. We also describe an abstract framework, demonstrating that, under certain conditions, the extra flexibility can be modeled purely in terms of PESP constraints. The concept of flexible rolling stock and passenger connections is illustrated by an example based on three intercity lines of Netherlands Railways. http://repub.eur.nl/res/pub/37877/ 2012-03-01T00:00:00Z Different firms in multimodal hinterland networks, such as terminal operators, freight forwarders, information service providers, infrastructure managers, shippers and receivers, aim to contribute to a better performance of the overall supply chain. Terminal operators, for instance, are more and more involved in linking sea terminals with inland terminals, or linking terminals with end points in the chain, such as warehouses. Thus, they assume new responsibilities in addition to being a stocking point. This article addresses a crucial innovation that is currently developing in the hinterland of the main ports of Rotterdam and Amsterdam: Supply chain and transportation network integration by extending the sea terminal gate into the hinterland. The article explores the relationship between the extended gate concept and the better known concept of dry ports. We argue that extended gates, when implemented correctly, can generate substantial benefits in terms of modal shift, logistics performance and regional development. Substantial bottlenecks still exist that hamper the development of extended gates in multimodal transport networks. The article will identify these bottlenecks, and suggest avenues for solutions. The full implementation and adoption of an extended gate network in a port's hinterland will result in a fundamental change in the role of seaports in global supply chains. http://repub.eur.nl/res/pub/32042/ 2012-01-05T00:00:00Z Demand for spare parts is often difficult to forecast using historical data only. In this paper, we give an overview of installed based management and provide several ways in which installed base information can be used to support forecasting. We discuss cases where installed base information is used in forecasting at four companies and list the issues involved. Moreover, we review some models to illustrate the potential value of the installed base information and conclude that forecasts of spare parts demand and return can be made considerably more timely and accurate using installed base information. http://repub.eur.nl/res/pub/22767/ 2011-03-01T00:00:00Z Many of the challenges in spare parts logistics emerge due to the combination of large service networks, and sporadic/slow-moving demand. Customer heterogeneity and stringent service deadlines entail further challenges. Meanwhile, high revenue rates in service operations motivate companies to invest and optimize the service logistics function. An important aspect of the spare parts logistics function is its ability to support customer-specific requirements with respect to service deadlines. To support customer specific operations, many companies are actively maintaining and utilizing installed base data during forecasting, planning and execution stages. In this paper, we highlight the potential economic value of installed base data for spare parts logistics. We also discuss various data quality issues that are associated with the use of installed base data and show that planning performance depends on the quality dimensions. http://repub.eur.nl/res/pub/21942/ 2010-12-22T00:00:00Z Demand for spare parts is often difficult to forecast using historical data only. In this paper, we give an overview of installed based information and provide several ways in which installed base forecasting can be used. We discuss cases of installed based forecasting at four companies and list the issues involved. Moreover, we provide some models to assess the value of installed base information and conclude that forecasts of spare parts demand and return can be made considerably more timely and accurate by using installed base information. http://repub.eur.nl/res/pub/20994/ 2010-10-12T00:00:00Z Planning the transport of maritime containers from the sea port to final destinations while using multiple transport modes is challenged by uncertainties regarding the time the container is released for further transport or the transit time from the port to its final destination. This paper assesses the value of information in container transport in terms of multiple performance dimensions, i.e. logistics costs, reliability, security, and emissions. The analysis is done using a single period model where a decision maker allocates arriving containers to two transport modes (slow, low price, no flexible departure times, versus fast, high price, flexible departure times). We construct a frontier of Pareto optimal decisions under each of the information scenarios and show that these frontiers move in a favorable direction when the level of information progresses. Each of the Pareto frontiers help strike the balance between the aforementioned performance dimensions. The mathematical results are illustrated using two numerical examples involving barge transport and train transport. http://repub.eur.nl/res/pub/20883/ 2010-10-04T00:00:00Z This paper describes five sets of 33 Mixed Integer Problem instances each, for a total of 165 instances, derived from a real-world full-truckload pick-up and delivery problem with time windows at the Port of Rotterdam. These instances represent 33 individual days of data encompassing 65 jobs and 40 trucks. We report, in this paper, on the structure of the real-world problem, the mechanism by which the real data was transformed into the test instances, the Mixed Integer Programming formulation used to solve these instances, the results obtained, and sources in the literature describing alternative uses for these instances. http://repub.eur.nl/res/pub/22250/ 2010-06-01T00:00:00Z Our research addresses a firm that sells a product to consumers who are sensitive to both price and return policy. The operational decisions of interest are the selling price, return policy, and quantity of new product to purchase. We model a single selling season that is split into two periods where the boundary between periods is delineated by the opportunity to recover product returns and resell them. That is, returns in the first period can be recovered and sold in the second period. Returns also arise in the second period, but these may only be salvaged. We first analyze both deterministic and stochastic models, finding that the deterministic results largely carry over to the stochastic case. In addition, our results indicate that the model is quite insensitive to errors in the estimates of the parameter values, except for purchase cost and parameters related to demand. Finally, we perform an analysis on the value of various investments to improve financial performance. Results indicate that investments to reduce the recovery cost of returns or reduce returns uncertainty are minimal, while investments to increase recovery speed, reduce market uncertainty, and reduce the return rate can be quite valuable. http://repub.eur.nl/res/pub/19367/ 2010-05-02T00:00:00Z In this case the Dutch Flower Auctions (DFA) are discussed. The DFA are part of the supply network in which flowers are produced, stocked, and then sold through either mediation or auctioning. This case focuses on the buyers’ and auctioneers’ positions when flowers are traded through auctions. This case deals with the application of personalized agents as part of a Decision Support System which empowers the decision maker. The decision makers discussed in this case are the auctioneers who control the auction process, and the buyers who bid at the clock auction. Agents are defined as software programs that sense their environment and react autonomously on their environment in order to maximize a certain outcome. The agents, as envisioned in this case, are able to determine users’ preferences and based on these preferences agents can proactively make recommendations. Agents as applied to the auction process could empower the auctioneers in their decisions. Another type of agent could empower the buyer, since buyers have the high-pressure task of buying at the clock auction. http://repub.eur.nl/res/pub/14529/ 2009-01-13T00:00:00Z Many of the challenges in spare parts logistics emerge due to the combination of large service networks, and sporadic/slow-moving demand. Customer heterogeneity and stringent service deadlines entail further challenges. Meanwhile, high revenues rates in service operations motivate companies to invest and optimize the service logistics function. An important aspect of the spare parts logistics function is its ability to support customer-specific requirements with respect to service deadlines. To support customer specific operations, many companies are actively maintaining and utilizing installed base data during forecasting, planning and execution stages. In this paper, we highlight the potential economic value of installed base data for spare parts logistics. We also discuss various data quality issues that are associated with the use of installed base data and show that planning performance depends on the quality dimensions. http://repub.eur.nl/res/pub/13661/ 2008-12-16T00:00:00Z In this paper we study how industry should strategically respond to imposed producer responsibility by regulation such as the WEEE-directive. Product eco-design covers both Design for Disassembly and Recovery (DfX) and Product Data Management (PDM). On the process side, X-ray technologies and Post-shredder Separation Techniques (PST) can also improve the overall efficiency of recovery strategies. We revisit the Roteb case on monitors published in some of our previous work and add characteristics to make it up-to-date. We develop four scenarios with each three different information levels on the disassembly Bill Of Material (dBOM) and on return quality, namely perfect information, partial information, and a scenario with no information. For the three information scenarios, we deploy different decision support models, namely an integer program in case of perfect information, a number of decision rules in case of partial information, and a default strategy in case of no information. Within each scenario, we carry out a sensitivity analysis on those operational parameters affected by the strategic choices mentioned. We conclude with recommendations to OEMs on strategic response related to recovery and elaborate on future research using our modeling approach in the EEE and other types of industry. http://repub.eur.nl/res/pub/13837/ 2008-11-13T00:00:00Z In this paper we derive the worst-case ratio of an online algorithm for the Traveling Salesman Problem (TSP) with two disclosure dates. This problem, a variant of the online TSP with release dates, is characterized by the disclosure of a job’s location at one point in time followed by the disclosure of that job’s release date at a later point in time. We present an online algorithm for this problem restricted to the positive real number line. We then derive the worst-case ratio of our algorithm and show that it is best-possible in two contexts – the first, one in which the amount of time between the disclosure events and release time are fixed and equal for all jobs; and a second in which the time between disclosure events varies for each job. We conclude that the value of advanced information can be attributed to the location information alone – yielding an optimal solution in favorable instances. http://repub.eur.nl/res/pub/12902/ 2008-07-31T00:00:00Z Based on a literature survey, we aim to answer our main question: “How should we plan and execute logistics in supply chains that aim to meet today’s requirements, and how can we support such planning and execution using IT?” Today’s requirements in supply chains include inter-organizational collaboration and more responsive and tailored supply to meet specific demand. Enterprise systems fall short in meeting these requirements The focus of planning and execution systems should move towards an inter-enterprise and event-driven mode. Inter-organizational systems may support planning going from supporting information exchange and henceforth enable synchronized planning within the organizations towards the capability to do network planning based on available information throughout the network. We provide a framework for planning systems, constituting a rich landscape of possible configurations, where the centralized and fully decentralized approaches are two extremes. We define and discuss agent based systems and in particular multi agent systems (MAS). We emphasize the issue of the role of MAS coordination architectures, and then explain that transportation is, next to production, an important domain in which MAS can and actually are applied. However, implementation is not widespread and some implementation issues are explored. In this manner, we conclude that planning problems in transportation have characteristics that comply with the specific capabilities of agent systems. In particular, these systems are capable to deal with inter-organizational and event-driven planning settings, hence meeting today’s requirements in supply chain planning and execution. http://repub.eur.nl/res/pub/6991/ 2005-10-14T00:00:00Z Sensitivity analysis is used to quantify the impact of changes in the initial data of linear programs on the optimal value. In particular, parametric sensitivity analysis involves a perturbation analysis in which the effects of small changes of some or all of the initial data on an optimal solution are investigated, and the optimal solution is studied on a so-called critical range of the initial data, in which certain properties such as the optimal basis in linear programming are not changed. Linear one-parameter perturbations of the objective function or of the so-called ”right-hand side” of linear programs and their effect on the optimal value is very well known and can be found in most college textbooks on Management Science or Operations Research. In contrast, no explicit formulas have been established that describe the behavior of the optimal value under linear one-parameter perturbations of the constraint coefficient matrix. In this paper, such explicit formulas are derived in terms of local expressions of the optimal value function and intervals on which these expressions are valid. We illustrate this result using two simple examples. http://repub.eur.nl/res/pub/14833/ 2005-01-01T00:00:00Z Océ enables organizations to manage their document flow and exchange information effectively and efficiently. Océ produces and delivers copiers, printers, plotters, and hybrid systems that integrate various functions like copying, scanning, and printing. Further, Océ delivers consumables and supplies, as well as services and support. Océ tries to have a proactive attitude towards environmental legislation and regulations, and is constantly looking for new information about product safety and environmental issues. At the beginning of the 1980s, Océ started to remanufacture machines. Machines that came back to the organization were cleaned and sold to its Operating Companies (OpCos) that operate local markets worldwide. At the beginning of the 1990s, Océ started recovery activities for parts of machines within an assembly department. Parts of machines were taken out and installed in other machines, after the parts were thoroughly cleaned. In December 1995, a separate unit was formed within Océ in Venlo, the Netherlands, called Asset Recovery (AR). http://repub.eur.nl/res/pub/2300/ 2004-01-01T00:00:00Z http://repub.eur.nl/res/pub/332/ 2003-04-30T00:00:00Z In this paper we describe how computer systems can provide planners with active planning support, when these planners are carrying out their daily planning activities. This means that computer systems actively participate in the planning process by automatically generating plans or partial plans. Active planning support by computer systems requires the application of mathematical models and solution techniques. In this paper we describe the modeling process in general terms, as well as several modeling and solution techniques. We also present some background information on computational complexity theory, since most practical planning problems are hard to solve. We also describe how several objective functions can be handled, since it is rare that solutions can be evaluated by just one single objective. Furthermore, we give an introduction into the use of mathematical modeling systems, which are useful tools in a modeling context, especially during the development phases of a mathematical model. We finish the paper with a real life example related to the planning process of the rolling stock circulation of a railway operator. http://repub.eur.nl/res/pub/14/ 2000-05-02T00:00:00Z The scheduling of train services is subject to a number of constraints describing railway infrastructure, required train services and reasonable time-intervals for waiting and transits. Timetable planners at Dutch Railways are nowadays supported by a software tool, called CADANS, which produces a feasible timetable on an hourly basis. In this paper, connection requirements between train series are written in the format of the CADANS model. It turns out that this leads to nontrivial combinatorial scheduling issues. http://repub.eur.nl/res/pub/14310/ 1999-07-15T00:00:00Z A connection is made between the Two Machine Flow Shop Problem (2MFSP) from job scheduling theory and the issue of quasicomplete factorization of rational matrix functions. A quasicomplete factorization is a factorization into elementary (i.e., degree one) factors such that the number of factors is minimal. For a companion based matrix function W, the number of factors in a quasicomplete factorization of W is related in a simple way to the minimum makespan of an instance J of 2MFSP which can be associated to W. As a consequence of this result, variants of the 2MFSP and other types of factorization can be related too.