Speeding Up Network Simulations Using Discrete Time

We develop a way of simulating disease spread in networks faster at the cost of some accuracy. Instead of a discrete event simulation (DES) we use a discrete time simulation. This aggregates events into time periods. We prove a bound on the accuracy attained. We also discuss the choice of step size and do an analytical comparison of the computational costs. Our error bound concept comes from the theory of numerical methods for SDEs and the basic proof structure comes from the theory of numerical methods for ODEs

Using discrete event simulation (DES) to manage theatre operations in healthcare: An audit-based case study

This paper discusses the application of Discrete Event Simulation (DES) in modelling the complex relationship between patient types, case-mix and operating theatre allocation in a large National Health Service (NHS) Trust in London. The simulation model that was constructed described the main features of nine theatres, focusing on operational processes and patient throughput times. The model was used to test three scenarios of case-mix and to demonstrate the potential of using simulation modelling as a cost effective method for understanding the issues of healthcare operations management and the role of simulation techniques in problem solving. The results indicated that removing all day cases will reduce patient throughput by 23.3% and the utilization of the orthopaedic theatre in particular by 6.5%. This represents a case example of how DES can be used by healthcare managers to inform decision making

Manufacturing System Lean Improvement Design Using Discrete Event Simulation

Lean manufacturing (LM) has been used widely in the past for the continuous improvement of existing production systems. A Lean Assessment Tool (LAT) is used for assessing the overall performance of lean practices within a system, while a Discrete Event Simulation (DES) can be used for the optimization of such systems operations. Lean improvements are typically suggested after a LAT has been deployed, but validation of such improvements is rarely carried out. In the present article a methodology is presented that uses DES to model lean practices within a manufacturing system. Lean improvement scenarios are then be simulated and investigated prior to implementation, thereby enabling a systematic design of lean improvements

A 3D immersive discrete event simulator for enabling prototyping of factory layouts

There is an increasing need to eliminate wasted time and money during factory layout design and subsequent construction. It is presently difficult for engineers to foresee if a certain layout is optimal for work and material flows. By exploiting modelling, simulation and visualisation techniques, this paper presents a tool concept called immersive WITNESS that combines the modelling strengths of Discrete Event Simulation (DES) with the 3D visualisation strengths of recent 3D low cost gaming technology to enable decision makers make informed design choices for future factories layouts. The tool enables engineers to receive immediate feedback on their design choices. Our results show that this tool has the potential to reduce rework as well as the associated costs of making physical prototypes

Application of Discrete Event Simulation (DES) for Queuing System Improvement at Hypermarket

This paper focuses on the development of a computer simulation model for improving the queuing system at a hypermarket using Discrete Event Simulation (DES) and to propose the most efficient hypermarket queuing system for overall improvement. Data were collected from the Hypermarket A using the time study. The method of this study is using modeling and simulation. Arena Simulation Software is used to develop the model to replicate the actual system. Three scenarios had been tested, and the alternatives will be ranked based on the level of the efficiency of the system performance. The most efficient queuing system is identified based on the scenario analysis. In this study, the waiting time for each customer can be improved by up to 26%, which equivalent to 5.24 minutes. Overall, this study contributes to a better understanding of the queuing system performance.   Keywords: hypermarket, queuing system, waiting time, simulation, Discrete EventSimulation (DES)

Airlift operations modeling using Discrete Event Simulation (DES)

The recently completed integrated project by the Systems Engineering and Analysis Cohort 15 at NPS has devised a regional Maritime Theater Security Force to conduct Phase Zero operations based on a tasking from OPNAV N8F. The force's airlift capability was identified as a critical component in the accomplishment of the missions and the required force structure was determined using a mix of mathematical and linear optimization modeling. The goal for this thesis is to develop a stochastic model using Discrete Event Simulation (DES) that can be employed to analyze the devised force structure's airlift operation performance at the operational/tactical level to augment the analysis work performed under that project. The intent is to provide a more complete solution for any stakeholders who want to take the project further to the next level. The resulting model demonstrates the ability to measure the airlift operation performance and provide insights into the operation workflow efficiency. The experiments conducted support the earlier findings on the devised Phase Zero force's ability to meet the most stringent mission requirements but suggested a different maximum airlift capability.http://archive.org/details/airliftoperation109454442Singapore Defence Science and Technology Agency author (civilian).Approved for public release; distribution is unlimited

Low Earth Orbit Rendezvous Strategy for Lunar Missions

On January 14, 2004 President George W. Bush announced a new Vision for Space Exploration calling for NASA to return humans to the moon. In 2005 NASA decided to use a Low Earth Orbit (LEO) rendezvous strategy for the lunar missions. A Discrete Event Simulation (DES) based model of this strategy was constructed. Results of the model were then used for subsequent analysis to explore the ramifications of the LEO rendezvous strategy

Modeling emergency departments using discrete event simulation techniques

This paper discusses the application of Discrete Event Simulation (DES) for modeling the operations of an Emer-gency Department (ED). The model was developed to help the ED managers understand the behavior of the system with regards to the hidden causes of excessive waiting times. It served as a tool for assessing the impact of major departmental resources on Key Performance Indicators (KPIs), and was also used as a cost effective method for testing various what-if scenarios for possible system im-provement. The study greatly enhanced managers’ under-standing of the system and how patient flow is influenced by process changes and resource availability. The results of this work also helped managers to either reverse or modify some proposed changes to the system that were previously being considered. The results also show a possible reduc-tion of more than 20% in patients waiting times

Simulation and the Fourth Industrial Revolution

Advancements in systems simulation over the past decade have propelled simulationinto a new position as a decision-making tool in Industry 4.0 applications. This paperaddresses the specific benefits of simulation which can be utilized to enable greaterflexibility in decision making in the Industry 4.0 environment. It is stressed thatboth discrete event simulation (DES) and agent-based simulation (ABS) can be usedto represent complex interactions in a fully integrated set of virtual and physicalsystems