European Institute for Statistics, Probability, Stochastic Operations Research
and their Applications

November 29, 2012

Optimized Appointment Scheduling

Presentation by: Alex Kuiper and Michel Mandjes

In order to minimize the server’s idle times in a service system and, simultaneously, the customers’ waiting times, one may fix the arrival times of the customers beforehand in an appointment schedule. We propose a procedure for determining appointment schedules by sequentially minimizing the per-customer expected loss. Our approach provides schedules for any convex loss function; for the practically relevant cases of the quadratic and absolute value loss function appealing closed-form results are derived. Importantly, our approach does not impose any conditions on the service time distribution; it is even allowed that the customers’
service times have different distributions.
A next question that we address concerns the order of the customers. We develop a criterion that yields the optimal order in case the service time distributions belong to a scale family, such as the exponential family. The customers should be scheduled then in non-decreasing order of their scale parameter.
While the optimal schedule can be computed numerically under quite general circumstances, in steady- state it can be computed in closed form for exponentially distributed service times under the quadratic and absolute value loss function. Our findings are illustrated by a number of numerical examples; these also address how fast the transient schedule converges to the corresponding steady-state schedule.
In the last part of the talk, we present practical considerations regarding implementation in real-life scenarios.
These relate to the estimation of the service time distributions, explicit computation for phase-type distributions, and numerical issues.

Operations Research in healthcare

Presentation by Fred Boer and Richard Boucherie

Healthcare is absorbing more and more of the national budget, which appears to be an impossible scenario for the future. This industry will have to provide more service and more quality against lower costs. At the front end of disease processes, there is much room for prevention of illnesses, since many diseases are the result of unhealthy lifestyles. However, the impact of prevention is slow and requires many years to show its efficacy. At the back end, the hospital needs to adopt to increasing demand by the emergence of baby boomers in the coming years. Hospitals develop programs to improve their efficiency, often aimed at improving existing planning and production (local optimization). Engineers and operations researchers can assist them in discovering underlying principles and solutions for example invoking successful methods from other industries. This presentation gives an overview of recently developed methods and tools and shows that Operations Research is finding its way in the hospitals to become an accepted discipline for boards and doctors aiding them in solving the business problems they are faced with.

Optimization of garbage dumps

Presentation by: Tim Jonker and Marko Boon

The municipality of Eindhoven currently has three sites where garbage can be disposed of. As a service to the inhabitants of Eindhoven, the garbage can be dumped free of charge. Unfortunately, several problems arise at the garbage dumps. Long waiting lines appear in front of the gates, especially during weekends and holidays. These queues cause dangerous traffic situations, but they are also a major source of customer dissatisfaction. Although this customer dissatisfaction by itself is a good reason to improve the performance of the garbage dumps, another reason is that dissatisfaction easily leads to undesired customer behaviour:blocking inside the dump, and worse garbage type separation.

In this joint project of Gemeente Eindhoven and Eindhoven University of Technology, we study the current layouts of the three garbage dumps and develop a mathematical model to predict the queueing behaviour inside and outside the dumps. In this talk we will discuss the practical aspects of garbage disposal, and the mathematical model. We use a custom-made simulation tool to analyse several scenarios that could improve the situation at the various dumps, and ultimately lead to more customer satisfaction.

PRACTICAL INFORMATION

Conference Location
The workshop location is Eurandom, Den Dolech 2, 5612 AZ Eindhoven, METAFORUM Building, 4th floor, room MF 12.

Eurandom is located on the campus of Eindhoven University of Technology in the Laplace Building (marked "44" on this map). The building is located at 15 minutes walking distance from the central railway station of Eindhoven. Take the northern exit from the station and walk in the north-eastern direction until you reach a crossing at Professor Doctor Dorgelolaan. The university campus is located on the other side of that street. Detailed directions via Google Maps are available here.

For travel information to Eindhoven please check http://www.eurandom.tue.nl/contact.htm

CONTACT
For more information please contact Mrs. Patty Koorn,
Coordinator Eurandom

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