International Series in Operations Research & Management Science, 2003
It is a great honour to contribute to a book dedicated to celebrate the life-time achievements of... more It is a great honour to contribute to a book dedicated to celebrate the life-time achievements of John Buzacott in the field of modelling stochastic processes in various application areas. John's work has been both fundamental and synthetic, by which other researchers found a well-guided path through the field and were able to develop their own models and applications. In
Recent software developments in system modelling via transfer function analysis now enables a muc... more Recent software developments in system modelling via transfer function analysis now enables a much broader understanding of the dynamics of aggregate planning to be gained. In particular it opens up the possibility of exploiting filter theory as a focal point during algorithm design. This is particularly attractive in view of the fact that we have established, via transfer function models,
The objective of this paper is to introduce the concept of safety time in a make-to-order product... more The objective of this paper is to introduce the concept of safety time in a make-to-order production environment. The production facility is represented as a queueing model, explicitly including a non-zero setup time. A methodology is presented to quantify the safety time and to compute the associated service level based on the queueing delay. The main result is a convex
Many service systems require customers to make an appointment prior to receiving service. After m... more Many service systems require customers to make an appointment prior to receiving service. After making an appointment, customers joi n a queue and wait for the appointment date to take place. We refer to such systems as appointment -driven queueing systems. Appointment- driven queueing systems may be found in many services and manufacturing industries. Their analysis and optimization are topics that are curre ntly unaddressed in the literature. In this article we provide a definition of an appointment-driven sy stem and illustrate the dynamics at work. In addition, we provide a number of insights in the op timization of such systems .
Summary An updated version of the obstacle resolving microscale model MITRAS has been developed. ... more Summary An updated version of the obstacle resolving microscale model MITRAS has been developed. Several modules of the model (turbulence parameterization, chemistry, soot transport, solvers) have been updated, tested stand-alone and are now tested in the framework of MITRAS. For comparison with model results wind tunnel measurements are available. An evaluation scheme for microscale obstacle resolving models has been finalised.
Healthcare systems differ intrinsically from manufacturing systems. As such, they require a disti... more Healthcare systems differ intrinsically from manufacturing systems. As such, they require a distinct modeling approach. In this article, we show how to construct a queueing model of a general class of healthcare systems. We develop new expressions to assess the impact of service outages and use the resulting model to approximate patient flow times and to evaluate a number of practical applications. We illustrate the devastating impact of service interruptions on patient flow times and show the potential gains obtained by pooling hospital resources. In addition, we present an optimization model to determine the optimal number of patients to be treated during a service session.
The health care sector is a fast-growing segment of GNP in almost every economy. No wonder that w... more The health care sector is a fast-growing segment of GNP in almost every economy. No wonder that we witnessed a tremendous increase in research to improve both medical practice and management practice. Patient flow management is an example of such a management practice and represents the ability of the health care system to serve patients quickly, reliably, and efficiently as they move through stages of care. This is basically a supply chain issue in the service sector in which we try to match demand and supply. Unfortunately patients still experience delays and waiting lists. This is an immediate consequence of a mismatch between demand and supply. A queueing model offers an excellent tool to analyze and improve the performance of health care systems. The purpose of this article is to discuss differences with the modeling of manufacturing systems (or more broadly supply chain issues in the health care industry compared to supply chain issues in services) and to focus on modeling iss...
We examine project scheduling with net-present-value objective and exponential activity durations... more We examine project scheduling with net-present-value objective and exponential activity durations, using a continuous-time Markov decision chain. Based on a judicious partitioning of the state space, we achieve a significant performance improvement compared to the existing algorithms.
International Series in Operations Research & Management Science, 2003
It is a great honour to contribute to a book dedicated to celebrate the life-time achievements of... more It is a great honour to contribute to a book dedicated to celebrate the life-time achievements of John Buzacott in the field of modelling stochastic processes in various application areas. John's work has been both fundamental and synthetic, by which other researchers found a well-guided path through the field and were able to develop their own models and applications. In
Recent software developments in system modelling via transfer function analysis now enables a muc... more Recent software developments in system modelling via transfer function analysis now enables a much broader understanding of the dynamics of aggregate planning to be gained. In particular it opens up the possibility of exploiting filter theory as a focal point during algorithm design. This is particularly attractive in view of the fact that we have established, via transfer function models,
The objective of this paper is to introduce the concept of safety time in a make-to-order product... more The objective of this paper is to introduce the concept of safety time in a make-to-order production environment. The production facility is represented as a queueing model, explicitly including a non-zero setup time. A methodology is presented to quantify the safety time and to compute the associated service level based on the queueing delay. The main result is a convex
Many service systems require customers to make an appointment prior to receiving service. After m... more Many service systems require customers to make an appointment prior to receiving service. After making an appointment, customers joi n a queue and wait for the appointment date to take place. We refer to such systems as appointment -driven queueing systems. Appointment- driven queueing systems may be found in many services and manufacturing industries. Their analysis and optimization are topics that are curre ntly unaddressed in the literature. In this article we provide a definition of an appointment-driven sy stem and illustrate the dynamics at work. In addition, we provide a number of insights in the op timization of such systems .
Summary An updated version of the obstacle resolving microscale model MITRAS has been developed. ... more Summary An updated version of the obstacle resolving microscale model MITRAS has been developed. Several modules of the model (turbulence parameterization, chemistry, soot transport, solvers) have been updated, tested stand-alone and are now tested in the framework of MITRAS. For comparison with model results wind tunnel measurements are available. An evaluation scheme for microscale obstacle resolving models has been finalised.
Healthcare systems differ intrinsically from manufacturing systems. As such, they require a disti... more Healthcare systems differ intrinsically from manufacturing systems. As such, they require a distinct modeling approach. In this article, we show how to construct a queueing model of a general class of healthcare systems. We develop new expressions to assess the impact of service outages and use the resulting model to approximate patient flow times and to evaluate a number of practical applications. We illustrate the devastating impact of service interruptions on patient flow times and show the potential gains obtained by pooling hospital resources. In addition, we present an optimization model to determine the optimal number of patients to be treated during a service session.
The health care sector is a fast-growing segment of GNP in almost every economy. No wonder that w... more The health care sector is a fast-growing segment of GNP in almost every economy. No wonder that we witnessed a tremendous increase in research to improve both medical practice and management practice. Patient flow management is an example of such a management practice and represents the ability of the health care system to serve patients quickly, reliably, and efficiently as they move through stages of care. This is basically a supply chain issue in the service sector in which we try to match demand and supply. Unfortunately patients still experience delays and waiting lists. This is an immediate consequence of a mismatch between demand and supply. A queueing model offers an excellent tool to analyze and improve the performance of health care systems. The purpose of this article is to discuss differences with the modeling of manufacturing systems (or more broadly supply chain issues in the health care industry compared to supply chain issues in services) and to focus on modeling iss...
We examine project scheduling with net-present-value objective and exponential activity durations... more We examine project scheduling with net-present-value objective and exponential activity durations, using a continuous-time Markov decision chain. Based on a judicious partitioning of the state space, we achieve a significant performance improvement compared to the existing algorithms.
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