Facilitated post-model coding in discrete event simulation (DES): a case study in healthcare

Research on facilitated discrete event simulation (DES) is gathering pace but there is still a need to put forward real examples to explain the process to newcomers. This paper is part of a line of research on the methodology of facilitated DES. In this paper we explain in more detail the facilitation process and the tools used to support the experimentation and implementation stages in a DES study involving workshops with a group of stakeholders, after an initial simulation model has been coded on the computer. A real case study is used to describe the process followed and the interactions at the workshops. Extracts from the transcripts are also included, with the view to providing evidence of the stakeholders’ involvement and their mood during the workshops. We conclude with a discussion on the process and tools used to support the facilitation process. Future research directions are also put forward

Exploring the model development process in discrete-event simulation: insights from six expert modellers

This paper explores the model development process in discrete-event simulation (DES) by reporting on an empirical study that follows six expert modellers while building simulation models. DES is a widely used modelling approach, however little is known about the modelling processes and methodology adopted by modellers in practice. Verbal Protocol Analysis is used to collect data, where the participants are asked to speak aloud while modelling. The results show that the expert modellers spend a significant amount of time on model coding, verification & validation and data inputs. The modellers iterate often between modelling activities. Patterns of modelling behaviour are identified, suggesting that the modellers adopt distinct modelling styles. This study is useful in that it provides an empirical view of existing DES modelling practice, which in turn can inform existing research and simulation practice as well as teaching of DES modelling to novices

A Facilitation Workshop for the Implementation Stage: A Case Study in health care

Research on facilitation in discrete event simulation (DES) is gathering pace but there is still a need to put forward real examples to explain the process to newcomers. Most of the research has focussed on facilitation in the initial stages of the simulation modelling process. In this paper we focus on one of the postmodel coding stages. More specifically we focus on the implementation stage, the final stage in the modelling process. The primary contributions of this paper are the description of the process followed and the introduction of tools that can be used during this stage to support workshop activities. A real case study is provided describing the sequence of the interactions undertaken in the workshop. Extracts from the transcripts are also included, with the view to bringing evidence of the stakeholders’ involvement and their mood during the workshop. The paper concludes with a discussion on the process followed and the importance of using tools in this stage

Development and use of simulation models in Operational Research: a comparison of discrete-event simulation and system dynamics

The thesis presents a comparison study of the two most established simulation approaches in Operational Research, Discrete-Event Simulation (DES) and System Dynamics (SD). The aim of the research implemented is to provide an empirical view of the differences and similarities between DES and SD, in terms of model building and model use. More specifically, the main objectives of this work are: 1. To determine how different the modelling process followed by DES and SD modellers is. 2. To establish the differences and similarities in the modelling approach taken by DES and SD modellers in each stage of simulation modelling. 3. To assess how different DES and SD models of an equivalent problem are from the users’ point of view. In line with the 3 research objectives, two separate studies are implemented: a model building study based on the first and second research objectives and a model use study, dealing with the third research objective. In the former study, Verbal Protocol Analysis is used, where expert DES and SD modellers are asked to ‘think aloud’ while developing simulation models. In the model use study a questionnaire survey with managers (executive MBA students) is implemented, where participants are requested to provide opinions about two equivalent DES and SD models. The model building study suggests that DES and SD modelling are different regarding the model building process and the stages followed. Considering the approach taken to modelling, some similarities are found in DES and SD modellers’ approach to problem structuring, data inputs, validation & verification. Meanwhile, the modellers’ approach to conceptual modelling, model coding, data inputs and model results is considered different. The model use study does not identify many significant differences in the users’ opinions regarding the specific DES and SD models used, implying that from the user’s point of view the type of simulation approach used makes little difference if any. The work described in this thesis is the first of its kind. It provides an understanding of the DES and SD simulation approaches in terms of the differences and similarities involved. The key contribution of this study is that it provides empirical evidence on the differences and similarities between DES and SD from the model building and model use point of view. Albeit the study does not provide a comprehensive comparison of the two simulation approaches, the findings of the study, provide new insights about the comparison of the two simulation approaches and contribute to the limited existing comparison literature

A facilitation workshop for the implementation stage: A case study in health care

Research on facilitation in discrete event simulation (DES) is gathering pace but there is still a need to put forward real examples to explain the process to newcomers. Most of the research has focussed on facilitation in the initial stages of the simulation modelling process. In this paper we focus on one of the postmodel coding stages. More specifically we focus on the implementation stage, the final stage in the modelling process. The primary contributions of this paper are the description of the process followed and the introduction of tools that can be used during this stage to support workshop activities. A real case study is provided describing the sequence of the interactions undertaken in the workshop. Extracts from the transcripts are also included, with the view to bringing evidence of the stakeholders’ involvement and their mood during the workshop. The paper concludes with a discussion on the process followed and the importance of using tools in this stage

Is simulation in health different and is it more difficult?

It is often stated that health simulation is quite different and even that it is more difficult. But, is simulation in health really different to simulation in other sectors? In this paper we explore this question through a survey of simulation modellers and academics. We elicit their opinions across a range of factors concerning the difficulties of health modelling against modelling in other domains. The results seem to corroborate the view that health simulation is different and that it is more difficult. However, further investigation into the backgrounds of those responding and the development of objective measures for the factors surveyed may show quite a different picture

Is simulation in health different?

It is often stated that health simulation is quite different and even that it is more difficult than in other sectors. But, is simulation in health really different to simulation in other sectors elsewhere? In this paper we explore this question through a survey of simulation modellers and academics. We elicit their opinions across a range of factors concerning the difficulties of health modelling against modelling in other domains. The analysis considers the responses of the whole group of respondents and the sub-group of respondents who have experience both in and outside of health modelling. The results show that, overall, there is a perception that health modelling is different and that it is more difficult across a range of factors. The implications for simulation research and practice in health are discussed

Model Validation and Testing in Simulation: a Literature Review

Model validation is a key activity undertaken during the model development process in simulation. There is a large body of literature on model validation, albeit there exists little convergence in terms of the definitions, types of validity, and tests used. Yet it is not clear what standards should be taken into consideration to avoid developing what could be considered to be invalid or wrong models. In this paper we examine existing literature on model validation with the view to identifying the existing validation approaches and types of tests used to assess model validity. In this review we focus our attention on three domains that usually overlap in methods and techniques: general Operational Research (OR), Modelling & Simulation (M&S) and Computer Science (CS). We analyze each field to identify the aspects of validity considered including the tests used, the validation approach taken, i.e. the suggested level of validity achieved (if this applies) and the reported outcome. The analysis shows that there are common validation practices used in all three fields as well as new ideas that could be adopted in discrete event simulation. Some main points of concurrence include the lack of universal validation, the continuous need for validation, and, the indispensable need for modelers and users to work closely together during the model validation process. This review provides an initial categorization of literature on model validation which can in turn be used as a basis for future work in investigating how and to what extent models are considered sufficiently valid

Study of CW gaseous lasers for space communications Semiannual status report, 1 Jul. - 30 Nov. 1966

Helium-xenon continuous wave gas lasers for space communications - testing of ultrahigh vacuum system and cascade pumping technique

The application of discrete event simulation and system dynamics in the logistics and supply chain context

Discrete event simulation (DES) and system dynamics (SD) are two modelling approaches widely used as decision support tools in logistics and supply chain management (LSCM). A widely held belief exists that SD is mostly used to model problems at a strategic level, whereas DES is used at an operational/tactical level. This paper explores the application of DES and SD as decision support systems (DSS) for LSCM by looking at the nature and level of issues modelled. Peer reviewed journal papers that use these modelling approaches to study supply chains, published between 1996 and 2006 are reviewed. A total of 127 journal articles are analysed to identify the frequency with which the two simulation approaches are used as modelling tools for DSS in LSCM. Our findings suggest that DES has been used more frequently to model supply chains, with the exception of the bullwhip effect, which is mostly modelled using SD. Based on the most commonly used modelling approach, issues in LSCM are categorised into four groups: the DES domain, the SD domain, the common domain and the less common domain. The study furthermore suggests that in terms of the level of decision making involved, strategic or operational/tactical, there is no difference in the use of either DES or SD. The results of this study inform the existing literature about the use of DES and SD as DSS tools in LSCM