A generic framework for hybrid simulation in healthcare

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University, 11/01/2010.Healthcare problems are complex; they exhibit both detail and dynamic complexity. It has been argued that Discrete Event Simulation (DES), with its ability to capture detail, is ideal for problems exhibiting this type of complexity. On the other hand, System Dynamics (SD) with its focus on feedback and nonlinear relationships lends itself naturally to comprehend dynamic complexity. Although these modelling paradigms provide valuable insights, neither of them are proficient in capturing both detail and dynamic complexity to the same extent. It has been argued in literature that a hybrid approach, wherein SD and DES are integrated symbiotically, will provide more realistic picture of complex systems with fewer assumptions and less complexity. In spite of wide recognition of healthcare as a complex multi- dimensional system, there has not been any reported study which utilises hybrid simulation. This could be attributed to the fact that due to fundamental differences, the mixing of methodologies is quite challenging. In order to overcome these challenges a generic theoretical framework for hybrid simulation is required. However, there is presently no such generic framework which provides guidance about integration of SD and DES to form hybrid models. This research has attempted to provide such a framework for hybrid simulation which can be utilised in healthcare domain. On the basis of knowledge induced from literature, three requirements for the generic framework have been established. It is argued that the framework for hybrid simulation should be able to provide answers to Why (why hybrid simulation is required), What (what information is exchanged between SD and DES models) and How (how SD and DES models are going to interact with each other over the time to exchange information) within the context of implementation of hybrid simulation to different problem scenarios. In order to meet these requirements, a three-phase generic framework for hybrid simulation has been proposed. Each phase of the framework is mapped to an established requirement and provides guidelines for addressing that requirement. The proposed framework is then evaluated theoretically based on its ability to meet these requirements by using multiple cases, and accordingly modified. It is further evaluated empirically with a single case study comprising of Accident and Emergency department of a London district general hospital. The purpose of this empirical evaluation is to identify the limitations of the framework with regard to the implementation of hybrid models. It is realised during implementation that the modified framework has certain limitations pertaining to the exchange of information between SD and DES models. These limitations are reflected upon and addressed in the final framework. The main contribution of this thesis is the generic framework for hybrid simulation which has been applied within healthcare context. Through an extensive review of existing literature in hybrid simulation, the thesis has also contributed to knowledge in multi-method approaches. A further contribution is that this research has attempted to quantify the impact of intangible benefits of information systems into tangible business process improvements. It is expected that this work will encourage those engaged in simulation (e.g., researchers, practitioners, decision makers) to realise the potential of cross-fertilisation of the two simulation paradigms

Toward a Theory of Multi-Method Modeling and Simulation Approach

The representation via simulation models can easily lead to simulation models too simple for their intended purpose, or with too much detail, making them hard to understand. This problem is related to limitations of the modeling and simulation methods. A multi-method Modeling and Simulation (M&S) approach has the potential for improved representation by taking advantage of methods\u27 strengths and mitigating their weaknesses. Despite a high appeal for using multiple M&S methods, several related problems should be addressed first. The current level of theoretical, methodological, and pragmatic knowledge related to a multi-method M&S approach is limited. It is problematic that there is no clearly identified purpose and definition of the multi-method M&S approach. Theoretical and methodological advances are vital to enhancing the application of a multi-method M&S approach to address a broader range of scientific inquiries, improve quality of research, and enable finding common ground between scientific domains. This dissertation explored theoretical principles and research guidelines of a multi-method M&S approach. The analyzed literature offered perspectives related to the purpose, terms, and research guidelines of a multi-method M&S approach. A pragmatic philosophical stance was used to provide the basis for the choice of terms and definitions relevant to a multi-method M&S approach were proposed. The degrees of falsifiability are adapted to the M&S domain, which allowed for developing complementarity principles as the theoretical basis of a multi-method M&S approach. Next, a blueprint of a multi-method M&S approach called method formats was derived, because transitions toward formats must seek justifications in order to increase research objectivity and transparency. A sample set of methods was explored in the context of a proposed sample set of criteria. None of the methods were evaluated with the maximum score for every criterion, which implied that if all those characteristics were required within a research context, then, none of the methods could provide the highest possible score without combining methods. Finally, a case study that included a multi-method simulation model was developed, providing a data layer for evaluation of complementarity principles. The case study contributed to the credibility of complementarity principles as a reason to use a multi-method M&S approach and value of pseudo-triangulation as a mean of verification of a selected approach

Hybrid Simulation for Construction Operations

Developing realistic and unbiased simulation models for construction operations require addressing the operational and strategic decision making levels. The dynamics and feedback processes observed in construction systems are responsible for the real behavior of such systems and drive the needs for hybrid and integrated simulation tools. The dominant simulation methods such as discrete event simulation (DES) and system dynamics (SD) are limited individually of capturing all the significant construction operation aspects that are responsible for generating the behaviour of realistic models. Therefore, this thesis presents a hybrid simulation method for simulating construction operations by utilizing the joint powerful features of the DES and SD methods. The proposed method provides a framework to integrate DES and SD on single computational platform. Developing a hybrid simulation model commences by decomposing the construction project into units, form which simulation models (e.g. DES or SD) are developed. A unidirectional variables interaction from DES to SD models is used. The interfacing process among simulation models is achieved by defining three variables: sender, interface, and receiver. The mechanism that controls data mapping processes between variables is outlined in a new developed synchronization method. The variables interaction protocol is described using formalism. Finally, a Hybrid Simulation Application (HiSim) is coded in VB.NET to demonstrate a sequential implementation of the developed method. A real-world earthmoving project is modeled and simulated to test the developed hybrid simulation method. The hybrid simulation structure uses unidirectional and sequential interactions between the components of DES and SD models. The simulation is run under three scenarios, is able to predict the real project completion duration with 92% accuracy, and captures the influences of the context level variables. The findings are expected to enhance hybrid simulation applications in construction and to allow for better understanding of the impact of various internal and external factors on the project schedule and its productivity performance

Proceedings /5th International Symposium on Industrial Engineering – SIE2012, June 14-15, 2012., Belgrade

editors Dragan D. Milanović, Vesna Spasojević-Brkić, Mirjana Misit

Proceedings /5th International Symposium on Industrial Engineering – SIE2012, June 14-15, 2012., Belgrade

editors Dragan D. Milanović, Vesna Spasojević-Brkić, Mirjana Misit