Erik Demeulemeester

KU Leuven | ku leuven ·  Faculty of Economics and Business

In this paper, the research and development project scheduling problem (RDPSP) under uncertain failure of activities is formulated where an activity’s failure results in the project’s overall failure. A scenario-based bi-objective model to maximize the expected net present value (eNPV) and to minimize the NPV’s risk by conditional value-at-risk (CV...

In healthcare, the planning and the management of resources are challenging as there are always many complex and stochastic factors in both demand and supply. Simulation optimization (SO) that combines simulation analysis and optimization techniques is well suited for solving complicated, stochastic, and mathematically intractable decision problems...

In this paper, we investigate a variant of the unrelated parallel machine scheduling problem with multiple time windows that is widely employed in the scheduling of earth observation satellites. Two mixed-integer linear programming formulations are proposed based on the concept of non-immediate precedence and the deep analysis of the relationship o...

In hospitals, the efficient planning of the operating rooms (ORs) is difficult due to the uncertainty inherent to surgical services. This is especially true for the inpatient surgical department where complex and long surgeries are often performed along with surgeries on emergency patients. This paper aims to improve the scheduling of the inpatient...

As a subproblem of the multi-mode resource-constrained project scheduling problem, the discrete time/resource trade-off problem (DTRTP) has occurred widely in practice. This paper tries to generate a robust schedule for the DTRTP with a given due date under uncertainty of the work content. Nine free slack-based measures are adopted as surrogate mea...

The automotive industry is facing a rapid technological evolution and the request of a very high level of customization of the products. This requires production systems able to manage a high variety of products with low volumes. To this aim, this paper focuses on multi-product assembly lines consisting of a set of stations with a robot operating t...

In this paper, the performance of activity-based and resource-based policies with newly designed priority rules for the stochastic resource-constrained project scheduling problem is considered. The aim of the paper is to maximize the expected net present value (eNPV) and to minimize the risk of the project's net present value by semivariance risk m...

In hospitals, surgeries are treated either on an outpatient or on an inpatient basis. Outpatients are normally routine patients that enter and leave the hospital on the same day, while inpatients who need more complex surgeries have to stay overnight. More recently, a shift from inpatient surgery to outpatient surgery is occurring due to scientific...

In the explosively increased number of applications of earth observation satellites (EOSs), scheduling is a significative issue to satisfy more requests and obtain a high observation efficiency. This article investigates the scheduling of multiple EOSs under the impact of clouds. First, we formulate the presences of clouds as stochastic events, and...

Resource allocation is one of the core issues in project scheduling to ensure the effective use of scare renewable resources, and has been regularly encountered in production systems in the manufacturing and service industries. The transfers of renewable resources between activities generally incur certain scheduling costs and affect the robustness...

In the recent decades, the recognition that uncertainty lies at the heart of modern project management has induced considerable research efforts on robust project scheduling for dealing with uncertainty in a scheduling environment. The literature generally provides two main strategies for the development of a robust predictive project schedule, nam...

In this paper, we address the project schedule control problem under an uncertain environment. We propose a new method to set the tolerance limits based on the Earned Value Management/Earned Schedule (EVM/ES) schedule performance metrics. These tolerance limits can help a project manager to identify whether the schedule deviations from the baseline...

Uncertainty has become an inevitable aspect of project scheduling. We study the resource-constrained project scheduling problem (RCPSP) with stochastic durations. One of the most studied approaches to deal with stochastic durations is that of proactive and reactive scheduling. Previous researches often studied proactive and reactive scheduling rath...

The proactive and reactive resource-constrained project scheduling problem (PR-RCPSP), that has been introduced recently (Davari and Demeulemeester, 2017), deals with activity duration uncertainty in a very unique way. The optimal solution to an instance of the PR-RCPSP is a proactive and reactive policy (PR-policy) that is a combination of a basel...

This study investigates the robust resource-constrained max-NPV project problem with stochastic activity duration. First, the project net present value (NPV) and the expected penalty cost are proposed to measure quality robustness and solution robustness from the perspective of discounted cash flows, respectively. Then, a composite robust schedulin...

The resource-constrained project scheduling problem (RCPSP) has been widely studied during the last few decades. In real-world projects, however, not all information is known in advance and uncertainty is an inevitable part of these projects. The chance-constrained resource-constrained project scheduling problem (CC-RCPSP) has been recently introdu...

Most earth observation satellites are equipped with optical sensors, which cannot see through clouds. Hence, many observations will be useless due to the presence of clouds. In this paper, we study the scheduling problem of multiple EOSs under uncertainties of clouds. In order to improve the possibility of completing tasks, we take the scheduling o...

s In this study we examine the performance of 17 priority rule heuristics and the justification technique on the stochastic resource-constrained project scheduling problem (SRCPSP). Among the 17 priority rules, 12 are selected from the literature that is addressing the deterministic resource-constrained project scheduling problem (RCPSP), and the o...

This paper presents a three-stage mixed integer programming approach for optimizing the skill mix and training schedule for aircraft maintenance workers. When all workers are trained for all skills, cheaper workforce schedules are possible. However, the training that is required to acquire all those skills can become very expensive. In the first an...

In many hospitals there are patients who receive surgery later than what is medically indicated. In one of Europe's largest hospitals, the University Hospital Leuven, this is the case for approximately every third patient. Serving patients late cannot always be avoided as a highly utilized OR department will sometimes suffer capacity shortage, occa...

This paper presents a model enhancement approach for the integrated problem of developing shift schedules and waste collection routes. Given a variable amount of waste to be collected the objective is to find fixed, minimal cost shift schedules and collection routes under a service level constraint. While regular shifts during traffic peak hours ar...

The critical chain scheduling and buffer management (CC/BM) methodology has proven to be a favorable approach to schedule resource-constrained projects and to offer a valuable control tool for monitoring projects under uncertainty. The previous studies on CC/BM seem to have neglected the cost performance, which might render its wider applications t...

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In hospitals, the operating room (OR) is a particularly expensive facility and thus efficient scheduling is imperative. This can be greatly supported by using advanced methods that are discussed in the academic literature. In order to help researchers and practitioners to select new relevant articles, we classify the recent OR planning and scheduli...

We study a single-machine scheduling problem that is a generalization of a number of problems for which computational procedures have already been published. Each job has a processing time, a release date, a due date, a deadline and a weight representing the penalty per unit-time delay beyond the due date. The goal is to schedule all jobs such that...

Because of the extensive time frames and the transfer of risk toward the contractor, there is a large value at stake in public-private partnerships (PPP). The complexity and the high bidding cost are open sesames for inexperienced contractors to refrain from the opportunity. On the one hand, this study builds a game-theoretic bidding model that rep...

Most earth observation satellites (EOSs) are equipped with optical sensors, which cannot see through clouds. Hence, observations are significantly affected and blocked by clouds. In this work, with the inspiration of the notion of a forbidden sequence, we propose a novel assignment formulation for EOS scheduling. Considering the uncertainties of cl...

Public–private partnerships have seen the daylight in response to the adagio that project responsibilities and risks should be efficiently allocated between the public and the private sector. Nevertheless, the considerable bidding costs inhibit the competition in the market. A trustworthy project agenda, also called a project pipeline, could substa...

The inherent risky nature of public–private partnerships requires contractors to develop expensive project proposals, which is seen as a burden to enter the playing field. It is believed that a pipeline of projects could succeed in triggering contractors' enthusiasm and increasing competition. This paper theoretically assesses whether the pipeline...

This paper presents a review and classification of the literature regarding workforce planning problems incorporating skills. In many cases, technical research regarding workforce planning focuses very hard on the mathematical model and neglects the real life implications of the simplifications that were needed for the model to perform well. On the...

The goal of project risk management is to mitigate the impact of risks on project objectives such as budget and time. A popular approach to determine where to focus mitigation efforts, is the use of so-called "ranking indices". Ranking indices produce a ranking of activities (or even better, risks) based on their impact on project objectives. In tu...

In many hospitals there are patients who re-ceive surgery later than what is medically indicated. In one of Europe’s largest hospitals, the University Hos-pital Leuven, this is the case for approximately every third patient. Serving patients late cannot always be avoided as a highly utilized OR department will some-times suffer capacity shortage, oc...

Most earth observation satellites (EOSs) are equipped with optical sensors, which cannot see through clouds. Hence, many observations will be useless due to the presence of clouds. In this work, in order to improve the possibility of completing the tasks under uncertainties of clouds, we take the scheduling of each task to multiple resources into a...

Fault-tolerance plays an important role in improving the reliability of multiple earth-observing satellites, especially in emergent scenarios such as obtaining photographs on battlefields or earthquake areas. Fault tolerance can be implemented through scheduling approaches. Unfortunately, little attention has been paid to fault-tolerant scheduling...

Project risk management aims to provide insight into the risk profile of a project as to facilitate decision makers to mitigate the impact of risks on project objectives such as budget and time. A popular approach to determine where to focus mitigation efforts, is the use of so-called ranking indices (e.g. the criticality index, the significance in...

The Critical Chain Scheduling and Buffer Management (CC/BM) methodology, proposed by Goldratt (Critical chain, 1997), introduced the concepts of feeding buffers, project buffers and resource buffers as well as the roadrunner mentality. This last concept, in which activities are started as soon as possible, was introduced in order to speed up projec...

This paper presents a fast heuristic approach to optimize staffing and scheduling of the workforce at an aircraft maintenance company. Two linked Tabu Search algorithms are proposed to minimize the labour costs and to maximize employee satisfaction. To enhance the performance of the algorithm, strategic oscillation and pattern creation are used. We...

Due to the extensive timeframes and the transfer of risk towards the preferred special purpose vehicle, there is more value at stake in public-private partnership projects in relation to traditional public procurement projects. The contractual complexity and the high bidding cost are open sesames for inexperienced contractors to refrain from the op...

The inherent risky nature of public-private partnerships requires contractors to make detailed and expensive project proposals. These high bidding costs are often seen as a burden for contractors to enter the playing field. Governments are seeking for ways to increase competition. It is a common belief that a project pipeline could succeed in trigg...

This paper presents a heuristic approach to optimize staffing and scheduling at an aircraft maintenance company. The goal is to build robust aircraft maintenance personnel rosters that can achieve a certain service level while minimizing the total labor costs. Robust personnel rosters are rosters that can handle delays associated with stochastic fl...

The planning of the operating rooms (ORs) is a difficult process due to the different stakeholders involved. The real complexity, however, results from various sources of variability entering the processes. These uncertain processes cannot be ignored since they greatly influence the trade-offs between the hospital costs and the patient waiting time...

Personnel scheduling problems need to cope with personnel preferences, coverage constraints, legal restrictions, and many other constraints. We present a three-stage methodology that can be used to select personnel rosters. In the first stage we generate multiple personnel rosters with a mathematical programming model. In the second stage, the perf...

This paper presents a review of the literature on personnel scheduling problems. Firstly, we discuss the classification methods in former review papers. Secondly, we evaluate the literature in the many fields that are related to either the problem setting or the technical features. Each perspective is presented as a table in which the classificatio...

This paper presents a method for constructing the workforce schedules of an aircraft maintenance company. The method integrates both the stang and the scheduling decision. We formulate the optimization problem using a mixed integer linear programming approach and solve it heuristically using a branch-and-bound enumeration framework. Each node of th...

Public-private partnerships are cutting edge long-term contractual arrangements between a private contractor and the government. The contractual complexity and the high pre-tender research cost are open sesames for inexperienced contractors to refrain from the opportunity. This study encompasses the bidding framework in a game-theoretical fashion w...

This paper presents our application of a visualization tool and optimization model based on mixed-integer linear programming to solve a workforce staffing and scheduling problem at Sabena Technics, a major aircraft maintenance company in Belgium.We used the software to generate many alternative, cost-efficient schedules and to analyze multiple scen...

In previous research (Tian and Demeulemeester 2010), we have shown that in realistic situations railway scheduling improves both the stability and the expected project length over roadrunner scheduling. In this paper, we introduce the concept of resource flow networks in this analysis and determine what the impact of combining roadrunner or railway...

Hospital case mix and capacity planning involves the decision making both on patient volumes that can be taken care of at a hospital and on resource requirements and capacity management. In this research, to advance both the hospital resource efficiency and the health care service level, a multilevel integrative approach to the planning problem is...

The goal of project risk management is to provide insight into the risk profile of a project as to facilitate decision makers to mitigate the impact of risks on project objectives such as budget and time. A popular approach to determine where to focus mitigation efforts, is the use of so-called ranking indices. Ranking indices allow the ranking of...

The resource-constrained project scheduling problem involves the determination of a schedule of the project activities, satisfying the precedence and resource constraints while minimizing the project duration. In practice, activity durations may be subject to variability. We propose a stochastic methodology for the determination of a project execut...

In this article we discuss a freely downloadable educational software tool for illustrating project scheduling and project management concepts. The tool features exact and heuristic scheduling procedures and visualizes project networks, project schedules, resource profiles, activity slacks, and project duration distributions. © 2009 Wiley Periodica...

In this paper, we test the applicability of a decision support system (DSS) that is developed to optimize the sequence of surgeries in the day-care center of the UZ Leuven Campus Gasthuisberg (Belgium). We introduce a multi-objective function in which children and prioritized patients are scheduled as early as possible on the day of surgery, recove...

This paper describes a methodology for the case mix problem in the health care sector. Aiming at maximizing the overall financial contribution of the given resource capacity within a hospital, the case mix problem is formulated as an integer linear programming model to produce the optimal patient mix pattern together with its associated resource al...

The multi-mode resource-constrained project scheduling problem (MRCPSP) involves the determination of a baseline schedule of the project activities, which can be executed in multiple modes, satisfying the precedence relations and resource constraints while minimizing the project duration. During the execution of the project, the baseline schedule m...

The increasing interest in the domain of operating room planning and scheduling leads to a proliferation of problem types. The statement and the scope of the particular problems, however, are often unclear. In this paper, we report on a scheme to classify operating room planning and scheduling problems using multiple fields. Each field describes a...

This paper presents an overview of the operating theatre planning and scheduling practice of hospitals in Flanders (Belgium). An electronic survey was sent to 95 hospitals in which surgeries are performed, which eventually resulted in a response set of 52 hospitals (55%). The questionnaire did not only focus on issues related to the elective (inpat...

The resource-constrained project scheduling problem (RCPSP) has been the subject of a great deal of research during the previous decades. This is not surprising given the high practical relevance of this scheduling problem. Nevertheless, extensions are needed to be able to cope with situations arising in practice such as multiple activity execution...

This paper provides a review of recent operational research on operating room planning and scheduling. We evaluate the literature on multiple fields that are related to either the problem setting (e.g., performance measures or patient classes) or the technical features (e.g., solution technique or uncertainty incorporation). Since papers are pooled...

The resource-constrained project scheduling problem involves the determination of a schedule of the project activities, satisfying the precedence relations and resource constraints while minimizing the project duration. In practice, activity durations may be subject to variability, such that a stochastic approach to the problem is more appropriate....

Introduction Solution robust scheduling under activity duration uncertainty Solution robust scheduling under resource availability uncertainty Conclusions and suggestions for further research Acknowledgements

Hospital capacity planning at the tactical level produces the optimal patient case mix that can be taken care of at a hospital with the associated time-phased allocation of resources. However, different generated scenarios may result in dissimilar effects on the delivery of health care when variability comes into play. Therefore, it is important to...

The increasing interest in the domain of operating room planning and scheduling leads to a proliferation of problem types. The statement and the scope of the particular problems, however, are often unclear. In this paper, we report on a scheme to classify operating room planning and scheduling problems using multiple fields. Each field describes a...

In previous research (Tian & Demeulemeester, 2010), we have shown that in realistic situations railway scheduling improves both the stability and the expected project length over roadrunner scheduling. In this paper, we introduce the concept of resource flow networks in this analysis and determine what the impact is of the resulting combinations on...

The Critical Chain Scheduling and Buffer Management (CC/BM) methodology, proposed by Goldratt (1997), introduced the concepts of feeding buffers, project buffers and resource buffers as well as the roadrunner mentality. This last concept, in which activities are started as soon as possible, was introduced in order to speed up projects by taking adv...

In this paper we investigate how to sequence surgical cases in a day-care facility. We specify a multi-criteria objective function in which we minimize the peak use of recovery beds, the occurrence of recovery overtime and the violation of various patient and surgeon preferences. The limited availability of resources and the occurrence of medical p...