A metamodel in simulation modeling, as also known as response surfaces, emulators, auxiliary mode... more A metamodel in simulation modeling, as also known as response surfaces, emulators, auxiliary models, etc. relates a simulation model's outputs to its inputs without the need for further experimentation. A metamodel is essentially a regression model and mostly known as "the model of a simulation model". A metamodel may be used for Validation and Verification, sensitivity or what-if analysis, and optimization of simulation model. In this study, we proposed a new metamodeling approach by using multiple regression integrated K-means clustering algorithm especially for simulation optimization. Our aim is to evaluate the feasibility of a new metamodeling approach in which we create multiple metamodels by clustering inputoutput variables of a simulation model according to their similarities. In this approach, first, we run the simulation model of a system, second, by using K-Means clustering algorithm, we create metamodels for each cluster, and third, we seek the minima (or maxima) for each metamodel. We also tested our approach by using a fictitious call center. We observed that this approach increases the accuracy of a metamodel and decreases the sum of squared errors. These observations give us some insights about usefulness of clustering in metamodeling for simulation optimization.
Proceedings of the Emerging M S Applications in Industry Academia Modeling and Humanities Symposium, Apr 7, 2013
A metamodel in simulation modeling, as also known as response surfaces, emulators, auxiliary mode... more A metamodel in simulation modeling, as also known as response surfaces, emulators, auxiliary models, etc. relates a simulation model's outputs to its inputs without the need for further experimentation. A metamodel is essentially a regression model and mostly known as "the model of a simulation model". A metamodel may be used for Validation and Verification, sensitivity or what-if analysis, and optimization of simulation model. In this study, we proposed a new metamodeling approach by using multiple regression integrated K-means clustering algorithm especially for simulation optimization. Our aim is to evaluate the feasibility of a new metamodeling approach in which we create multiple metamodels by clustering inputoutput variables of a simulation model according to their similarities. In this approach, first, we run the simulation model of a system, second, by using K-Means clustering algorithm, we create metamodels for each cluster, and third, we seek the minima (or maxima) for each metamodel. We also tested our approach by using a fictitious call center. We observed that this approach increases the accuracy of a metamodel and decreases the sum of squared errors. These observations give us some insights about usefulness of clustering in metamodeling for simulation optimization.
Police command and control centres are the main point of contact for the public who require help.... more Police command and control centres are the main point of contact for the public who require help. Like other areas of UK public services, police forces are set targets for their performance. Some of these targets relate to the speed at which they respond to calls for assistance from the public. In this paper we share our experience in improving the performance of command and control centres of a UK Police Force; a project which started as a classical simulation exercise and ended up with a significant reorganisation in a UK Police Force.
Like other areas of UK public services, police forces are set targets for their performance. Some... more Like other areas of UK public services, police forces are set targets for their performance. Some of these targets relate to the speed at which they respond to calls for assistance from the public. One such police force was failing to meet its targets and sought help from the authors, asking for a simulation model of their control and resource centres. What started as a simple modelling exercise turned into a fascinating piece of detective work in which different organisational options were explored, with a simulation model at the core of this work.
In this paper, a methodology for fast development of Discrete Event Simulation (DES) models is pr... more In this paper, a methodology for fast development of Discrete Event Simulation (DES) models is presented. The methodology simply works in two stages. In the first stage the modeler builds a Conceptual Model (CM) of the system to be modeled. A CM is represented as an Event Graph (EG). EGs are used to document the events and their causes in a system. In the second stage the CM is translated to an Event Based DES model. To fulfill this task we developed a DES library, SharpSim, using C# (CSharp) programming language. This paper gives an introduction to our methodology. We provide an insight into SharpSim and EGs, and illustrate a modeling example.
Proceedings of the Winter Simulation Conference, 2005., 2005
Discrete event simulation is widely used to model healthcare systems with a view to their improve... more Discrete event simulation is widely used to model healthcare systems with a view to their improvement. Most applications focus on discrete aspects of healthcare, such as accident and emergency rooms or outpatient clinics. However, despite this success with simulation at an operational level, there are no reported uses of discrete event simulation for the development and improvement of health policy. We describe the development of such a policy-oriented model, aimed at improving performance assessment in the
Proceedings of the 2006 Winter Simulation Conference, 2006
As part of a larger project examining the effect of performance targets on UK hospitals, we prese... more As part of a larger project examining the effect of performance targets on UK hospitals, we present a simulation of an Accident and Emergency (A&E) Department. Performance targets are an important part of the National Health Service (NHS) performance assessment regime in the UK. Pressures on A&Es force the medical staff to take actions meeting these targets with limited resources. We used simulation modelling to help understand the factors affecting this performance. We utilized real data from patient admission system of an A&E and presented some data analysis. Our particular focuses are the multitasking behaviour and experience level of medical staff, both of which affect A&E performance. This performance affects, in turn, the overall performance of the hospital of which it is part.
Police command and control centres are the main point of contact for the public who require help.... more Police command and control centres are the main point of contact for the public who require help. Like other areas of UK public services, police forces are set targets for their performance. Some of these targets relate to the speed at which they respond to calls for assistance from the public. In this paper we share our experience in improving the performance of command and control centres of a UK Police Force; a project which started as a classical simulation exercise and ended up with a significant reorganisation in a UK Police Force.
Many computer simulation models of emergency departments have been developed to aid clinicians an... more Many computer simulation models of emergency departments have been developed to aid clinicians and managers to maintain and improve the performance of their departments. A model is presented that can also be used to understand changes in performance that may occur as a result of the 4-hour target regime in the English NHS. The model simulates the performance resulting from normal activity, and the differences between this and actual performance are revealing. The results from two departments are presented to demonstrate this mode of model use. These reveal the extent of special action taken in some emergency departments as patients approach the target time, and also show the true underlying performance of the departments.
ACM Transactions on Modeling and Computer Simulation, 2011
The British National Health Service (NHS) has a performance management framework that aims to gua... more The British National Health Service (NHS) has a performance management framework that aims to guarantee short waiting times for patients by including mandatory targets for hospitals. DGHPSim is a suite of four components that simulates the activities of an NHS general hospital to show the effect of different policies on waiting times in these hospitals. DGHPSim has a generic structure
Discrete Event Simulation (DES) has been widely used in modelling health-care systems for many ye... more Discrete Event Simulation (DES) has been widely used in modelling health-care systems for many years and a simple citation analysis shows that the number of papers published has increased markedly since 2004. Over the last 30 years several significant reviews of DES papers have been published and we build on these to focus on the most recent era, with an interest in performance modelling within hospitals. As there are few papers that propose or illustrate general approaches, we classify papers according to the areas of application evident in the literature, discussing the apparent lack of genericity. There is considerable diversity in the objectives of reported studies and in the consequent level of detail: We discuss why specificity dominates and why more generic approaches are rare.
Unmanned Aerial Vehicles (UAVs) are used in a
variety of operations in civilian and military doma... more Unmanned Aerial Vehicles (UAVs) are used in a variety of operations in civilian and military domains including search and rescue, surveillance, monitoring, cadastral surveys, and package transportation. Although technological achievements in UAVs made them more intelligent than they were in the past, there is still human factor affecting their operations. Particularly in path planning, operators can improve effectiveness and efficiency of the mission by controlling static and dynamic criteria before the flight and during the flight. However, existence of multiple criteria has made the path planning a difficult task that operators can hardly achieve an optimal path for an UAV. In this paper, we propose a simulation model which can help UAV operators and planners achieve optimal paths. Our model considers environmental factors, performance limitations, basic aviation rules and UAV user requirements.
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Papers by Murat Gunal
variety of operations in civilian and military domains
including search and rescue, surveillance, monitoring,
cadastral surveys, and package transportation. Although
technological achievements in UAVs made them more
intelligent than they were in the past, there is still
human factor affecting their operations. Particularly in
path planning, operators can improve effectiveness and
efficiency of the mission by controlling static and
dynamic criteria before the flight and during the flight.
However, existence of multiple criteria has made the
path planning a difficult task that operators can hardly
achieve an optimal path for an UAV. In this paper, we
propose a simulation model which can help UAV
operators and planners achieve optimal paths. Our
model considers environmental factors, performance
limitations, basic aviation rules and UAV user
requirements.