The DEVS Formalism

2013 ◽  
pp. 62-102
Author(s):  
Rhys Goldstein ◽  
Gabriel A. Wainer ◽  
Azam Khan
Keyword(s):  
Formal Specification ◽  
Discrete Event ◽  
Simulation Models ◽  
Object Oriented Programming ◽  
Event Simulation ◽  
The Core ◽  
Modular Model ◽  
Core Concepts ◽  
Devs Formalism ◽  
The Relationship

The DEVS formalism is a set of conventions introduced in 1976 for the specification of discrete event simulation models. This chapter explains the core concepts of DEVS by applying the formalism to a single ongoing example. First, the example is introduced as a set of informal requirements from which a formal specification is to be developed. Readers are then presented with alternative sets of modeling conventions which, lacking the DEVS formalism’s approach to representing state, prove inadequate for the example. The chapter exploits the DEVS formalism’s support for modular model design, as the system in the example is specified first in parts and later as a combination of those parts. The concept of legitimacy is demonstrated on various model specifications, and the relationship between DEVS and both object-oriented programming and parallel computing is discussed.

scholarly journals Solving Traffic Problems in the State of Kerala, India: Forecasting, Regression and Simulation Models

2016 ◽  
Vol 41 (4) ◽  
pp. 325-343 ◽  
Author(s):  
Ramesh Bollapragada ◽  
Sudesh Poduval ◽  
Chetty Bingi S ◽  
Bhoomi Brahmbhatt
Keyword(s):  
Waiting Times ◽  
Discrete Event ◽  
Simulation Models ◽  
Simulation Software ◽  
The State ◽  
Executive Summary ◽  
Indian States ◽  
Event Simulation ◽  
Time Period ◽  
The Relationship

Executive Summary Indian states have been facing traffic related issues including traffic congestions and accidents for decades. The situation has worsened with time due to the increasing population. This article investigates the causes behind the accidents and provides recommendations and measures that would bring forth an improvement in the traffic conditions. The research uses forecasting models to confirm the existence of traffic problem in the State of Kerala. The various reasons for the accidents were enumerated and classified. Using regression models, the relationship between the number of accidents, deaths, and injured were obtained. In addition, the relationship between the number of accidents and the number of vehicles on road were examined along with the type of vehicle, design of the roads, the design of traffic, and the design of road network. In addition, a simulation model is presented to study the effect of the change in design of roads on the traffic situation. As an example, a 15-minute time period can be used to count the number of vehicles of each type (buses, cars, and trucks) travelling in both directions on a major highway. This data can then be categorized into slow and fast moving traffic. The Mean time between arrivals, percentages of slow and fast vehicles, percentages of vehicles travelling in both directions can be calculated and used in ARENA simulation software to perform discrete event simulation. Various scenarios are simulated; and waiting times and potential number of accidents are found for each of the scenarios. Based on forecasting, regression and simulation models, this article provides several recommendations and managerial insights, which are believed to alleviate the traffic problems in the State of Kerala. The solution approaches from this research could be used for addressing similar traffic situations in other states of India, which could result in saving millions of lives over the next decade.

Hierarchical, modular discrete-event modelling in an object-oriented environment

SIMULATION ◽  
1987 ◽  
Vol 49 (5) ◽  
pp. 219-230 ◽  
Author(s):  
Bernard P. Zeigler
Keyword(s):  
Distributed Simulation ◽  
Discrete Event ◽  
Object Oriented ◽  
Simulation Models ◽  
Object Oriented Programming ◽  
Model Base ◽  
Knowl Edge ◽  
Design Alternatives ◽  
Event Models ◽  
Devs Formalism

Hierarchical, modular specification of discrete-event models of fers a basis for reusable model bases and hence for enhanced simulation of truly varied design alternatives. We describe an envi ronment which realizes the DEVS formalism developed in Zeigler (1984) for hierarchical, modular models. It is implemented in PC-Scheme, a powerful Lisp dialect for microcomputers contain ing an object-oriented programming subsystem. Since both the implementation and the underlying language are accessible to the user, the result is a capable medium for combining simula tion modelling and artificial intelligence techniques. The envi ronment is developed in an object-oriented manner which lends itself to model base organization using the entity structure knowl edge representation. It also serves as a medium for developing hierarchical distributed simulation models and architectures.

scholarly journals Simulation modeling and analysis of primary health center operations

SIMULATION ◽  
2021 ◽  
pp. 003754972110309
Author(s):  
Mohd Shoaib ◽  
Varun Ramamohan
Keyword(s):  
Resource Utilization ◽  
Waiting Times ◽  
Discrete Event ◽  
Simulation Models ◽  
Modeling And Analysis ◽  
Healthcare Facilities ◽  
Event Simulation ◽  
Analytical Approximations ◽  
Primary Health ◽  
Generic Modeling

We present discrete-event simulation models of the operations of primary health centers (PHCs) in the Indian context. Our PHC simulation models incorporate four types of patients seeking medical care: outpatients, inpatients, childbirth cases, and patients seeking antenatal care. A generic modeling approach was adopted to develop simulation models of PHC operations. This involved developing an archetype PHC simulation, which was then adapted to represent two other PHC configurations, differing in numbers of resources and types of services provided, encountered during PHC visits. A model representing a benchmark configuration conforming to government-mandated operational guidelines, with demand estimated from disease burden data and service times closer to international estimates (higher than observed), was also developed. Simulation outcomes for the three observed configurations indicate negligible patient waiting times and low resource utilization values at observed patient demand estimates. However, simulation outcomes for the benchmark configuration indicated significantly higher resource utilization. Simulation experiments to evaluate the effect of potential changes in operational patterns on reducing the utilization of stressed resources for the benchmark case were performed. Our analysis also motivated the development of simple analytical approximations of the average utilization of a server in a queueing system with characteristics similar to the PHC doctor/patient system. Our study represents the first step in an ongoing effort to establish the computational infrastructure required to analyze public health operations in India and can provide researchers in other settings with hierarchical health systems, a template for the development of simulation models of their primary healthcare facilities.

scholarly journals Assessing asset monitoring levels for maintenance operations

2015 ◽  
Vol 26 (5) ◽  
pp. 632-659 ◽  
Author(s):  
Abdullah A Alabdulkarim ◽  
Peter Ball ◽  
Ashutosh Tiwari
Keyword(s):  
Asset Management ◽  
Business Models ◽  
Discrete Event ◽  
Dynamic Modelling ◽  
Simulation Models ◽  
Content Type ◽  
Event Simulation ◽  
Product Service ◽  
Asset Monitoring ◽  
The Impact

Purpose – Asset management has recently gained significance due to emerging business models such as Product Service Systems where the sale of asset use, rather than the sale of the asset itself, is applied. This leaves the responsibility of the maintenance tasks to fall on the shoulders of the manufacturer/supplier to provide high asset availability. The use of asset monitoring assists in providing high availability but the level of monitoring and maintenance needs to be assessed for cost effectiveness. There is a lack of available tools and understanding of their value in assessing monitoring levels. The paper aims to discuss these issues. Design/methodology/approach – This research aims to develop a dynamic modelling approach using Discrete Event Simulation (DES) to assess such maintenance systems in order to provide a better understanding of the behaviour of complex maintenance operations. Interviews were conducted and literature was analysed to gather modelling requirements. Generic models were created, followed by simulation models, to examine how maintenance operation systems behave regarding different levels of asset monitoring. Findings – This research indicates that DES discerns varying levels of complexity of maintenance operations but that more sophisticated asset monitoring levels will not necessarily result in a higher asset performance. The paper shows that it is possible to assess the impact of monitoring levels as well as make other changes to system operation that may be more or less effective. Practical implications – The proposed tool supports the maintenance operations decision makers to select the appropriate asset monitoring level that suits their operational needs. Originality/value – A novel DES approach was developed to assess asset monitoring levels for maintenance operations. In applying this quantitative approach, it was demonstrated that higher asset monitoring levels do not necessarily result in higher asset availability. The work provides a means of evaluating the constraints in the system that an asset is part of rather than focusing on the asset in isolation.

Using the Core Concepts Framework to Understand Three Generations of Inclusive Practices

Inclusion ◽  
2014 ◽  
Vol 2 (3) ◽  
pp. 237-247 ◽  
Author(s):  
Karrie A. Shogren ◽  
Michael L. Wehmeyer
Keyword(s):  
Research Policy ◽  
Future Research ◽  
Third Generation ◽  
Inclusive Practices ◽  
Policy And Practice ◽  
Inclusive Practice ◽  
The Core ◽  
Three Generations ◽  
Core Concepts ◽  
The Relationship

Abstract This article analyzes the relationship between the core concepts of disability policy and the three generations of inclusive practices. Specifically, we review the three generations of inclusive practice, highlighting the core concepts that have been most strongly emphasized during each generation of inclusive practices. Because we are early in the third generation of inclusive practices, we conclude by examining how the core concepts can guide and direct third generation inclusive practices and how future research, policy, and practice can actualize the aspirational values of all of the core concepts to enable desired outcomes.

scholarly journals Evaluation of a proposed optimization method for discrete-event simulation models

2012 ◽  
Vol 32 (3) ◽  
pp. 543-560 ◽  
Author(s):  
Alexandre Ferreira de Pinho ◽  
José Arnaldo Barra Montevechi ◽  
Fernando Augusto Silva Marins ◽  
Rafael Florêncio da Silva Costa ◽  
Rafael de Carvalho Miranda ◽  
...  
Keyword(s):  
Discrete Event Simulation ◽  
Discrete Event ◽  
Simulation Models ◽  
Optimization Method ◽  
Event Simulation

Improving outpatient phlebotomy service efficiency and patient experience using discrete-event simulation

2016 ◽  
Vol 29 (7) ◽  
pp. 733-743 ◽  
Author(s):  
Kenneth Yip ◽  
Suk-King Pang ◽  
Kui-Tim Chan ◽  
Chi-Kuen Chan ◽  
Tsz-Leung Lee
Keyword(s):  
Discrete Event Simulation ◽  
Scenario Analysis ◽  
Performance Metrics ◽  
Discrete Event ◽  
Evidence Based ◽  
Content Type ◽  
Event Simulation ◽  
Service Efficiency ◽  
Related Service ◽  
The Relationship

Purpose – The purpose of this paper is to present a simulation modeling application to reconfigure the outpatient phlebotomy service of an acute regional and teaching hospital in Hong Kong, with an aim to improve service efficiency, shorten patient queuing time and enhance workforce utilization. Design/methodology/approach – The system was modeled as an inhomogeneous Poisson process and a discrete-event simulation model was developed to simulate the current setting, and to evaluate how various performance metrics would change if switched from a decentralized to a centralized model. Variations were then made to the model to test different workforce arrangements for the centralized service, so that managers could decide on the service’s final configuration via an evidence-based and data-driven approach. Findings – This paper provides empirical insights about the relationship between staffing arrangement and system performance via a detailed scenario analysis. One particular staffing scenario was chosen by manages as it was considered to strike the best balance between performance and workforce scheduled. The resulting centralized phlebotomy service was successfully commissioned. Practical implications – This paper demonstrates how analytics could be used for operational planning at the hospital level. The authors show that a transparent and evidence-based scenario analysis, made available through analytics and simulation, greatly facilitates management and clinical stakeholders to arrive at the ideal service configuration. Originality/value – The authors provide a robust method in evaluating the relationship between workforce investment, queuing reduction and workforce utilization, which is crucial for managers when deciding the delivery model for any outpatient-related service.

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