Developing An Object-oriented Approach For Operations Simulation In Speedes

Using simulation techniques, performance of any proposed system can be tested for different scenarios with a generated model. However, it is difficult to rapidly create simulation models that will accurately represent the complexity of the system. In recent years, Object-Oriented Discrete-Event Simulation has emerged as the potential technology to implement rapid simulation schemes. A number of software based on programming languages like C++ and Java are available for carrying out Object Oriented Discrete-Event Simulation. These software packages establish a general framework for simulation in computer programs, but need to be further customized for desired end-use applications. In this thesis, a generic simulation library is created for the distributed Synchronous Parallel Environment for Emulation and Discrete-Event Simulation (SPEEDES). This library offers classes to model the functionality of servers, processes, resources, transporters, and decisions. The library is expected to produce efficient simulation models in less time and with a lesser amount of coding. The class hierarchy is modeled using the Unified Modeling Language (UML). To test the library, the existing SPEEDES Space Shuttle Model is enhanced and recreated. This enhanced model is successfully validated against the original Arena model

Introducing Explicit Causality in Object-oriented Hybrid System Modeling

International audienceAlong with the rapid development of embedded devices and network technology, the area of CyberPhysical Systems (CPS), has arisen. In terms of modeling and simulation, CPS—like many technical systems—have ahybrid nature, i.e., discrete-event behavior and continuous-time dynamics have to be integrated with each other.Basically, this integration is supported by modern object-oriented modeling paradigms such as Modelica®. Theequation-based concept resolves the causality between interconnected components, which qualifies this modelingscheme for complex multi-domain systems. However, in hybrid systems, explicit causality is required to correctlymanage iterative events. This paper highlights these issues, including algorithmic loops and instantaneous multipleupdates, which essentially arise from incompatibilities between the object-oriented concept and specific discrete-eventphenomena. We discuss several possible solutions and introduce the concept of re-allocating the objects’ behavioralintelligence

Knowledge-based simulation using object-oriented programming

Simulations have become a powerful mechanism for understanding and modeling complex phenomena. Their results have had substantial impact on a broad range of decisions in the military, government, and industry. Because of this, new techniques are continually being explored and developed to make them even more useful, understandable, extendable, and efficient. One such area of research is the application of the knowledge-based methods of artificial intelligence (AI) to the computer simulation field. The goal of knowledge-based simulation is to facilitate building simulations of greatly increased power and comprehensibility by making use of deeper knowledge about the behavior of the simulated world. One technique for representing and manipulating knowledge that has been enhanced by the AI community is object-oriented programming. Using this technique, the entities of a discrete-event simulation can be viewed as objects in an object-oriented formulation. Knowledge can be factual (i.e., attributes of an entity) or behavioral (i.e., how the entity is to behave in certain circumstances). Rome Laboratory's Advanced Simulation Environment (RASE) was developed as a research vehicle to provide an enhanced simulation development environment for building more intelligent, interactive, flexible, and realistic simulations. This capability will support current and future battle management research and provide a test of the object-oriented paradigm for use in large scale military applications

CONFIG: Integrated engineering of systems and their operation

This article discusses CONFIG 3, a prototype software tool that supports integrated conceptual design evaluation from early in the product life cycle, by supporting isolated or integrated modeling, simulation, and analysis of the function, structure, behavior, failures and operations of system designs. Integration and reuse of models is supported in an object-oriented environment providing capabilities for graph analysis and discrete event simulation. CONFIG supports integration among diverse modeling approaches (component view, configuration or flow path view, and procedure view) and diverse simulation and analysis approaches. CONFIG is designed to support integrated engineering in diverse design domains, including mechanical and electro-mechanical systems, distributed computer systems, and chemical processing and transport systems

Studying the Performance of a Firewall in Network Courses

This paper presents a simple simulation model of a firewall to derive several performance metrics and briefly argues on the importance and value of modeling and simulation in courses that study various aspects of perimeter defense in network security. The simulation model mentioned previously is part of an effort by faculty of our department to develop a multi-disciplinary repository of computational models that includes object-oriented discrete-event simulation models. One of the goals of this repository is to build resources that help educate students of computer science, software engineering, and information technology, in modeling and information security. This and other network simulation models are implemented in Java with the PsimJ simulation package. Other models have been implemented in C++ using the Psim3 package. The source code for the models, the downloadable simulation package, and more detailed description can be found on the Psim Web page

Modeling Cardiovascular Patient Pathways in an Accident and Emergency Department from a System Dynamic Perspective Using a Patient Oriented Modeling Approach

This thesis provides a detailed overview of a system dynamics model that focuses on the accident and emergency department and the clinical pathways of cardiovascular patients at Haukeland University hospital. A patient-oriented approach was chosen and sub-models representing patient attributes and accident and emergency resources were developed based on this approach. The simulation model illustrates accident and emergency processes and patient attributes in a disaggregated system. In addition to System Dynamics, other modeling concepts facilitated the modeling process. This included object-based and discrete event modeling concepts where object-based modeling concepts were used to create interactive objects, and stock and flow structures were constructed to be discrete in time and space. As such, the model is considered a hybrid model. The model serves as a network of resources aiding the patient in the most appropriate direction in order to place him or her in the right location at the right time. The patient-oriented modeling approach has proven useful, as it has enabled a systematic observation on the emergence of various cardiovascular pathways based on patient attributes incorporated in the model. The use of objects to represent attributes and AED processes make this model a unique take on System Dynamics. The attributes arising from the model were built on predetermined values in the form of graphical functions, enabling scenario testing to capture the resources the patient claimed in the AED. To this end, a successful simulation model has been created that permits a detailed observation of clinical pathways for cardiovascular patients.Masteroppgave i systemdynamikkGEO-SD350MASV-SYSD

Introducing Explicit Causality in Object-oriented Hybrid System Modeling

International audienceAlong with the rapid development of embedded devices and network technology, the area of CyberPhysical Systems (CPS), has arisen. In terms of modeling and simulation, CPS—like many technical systems—have ahybrid nature, i.e., discrete-event behavior and continuous-time dynamics have to be integrated with each other.Basically, this integration is supported by modern object-oriented modeling paradigms such as Modelica®. Theequation-based concept resolves the causality between interconnected components, which qualifies this modelingscheme for complex multi-domain systems. However, in hybrid systems, explicit causality is required to correctlymanage iterative events. This paper highlights these issues, including algorithmic loops and instantaneous multipleupdates, which essentially arise from incompatibilities between the object-oriented concept and specific discrete-eventphenomena. We discuss several possible solutions and introduce the concept of re-allocating the objects’ behavioralintelligence

Simulation Modeling of Cross-Dock and Distribution Center Based Supply Chains

Companies are implementing new strategies to meet the customer requirements in terms of quality, timing, and cost. One of these strategies is cross-docking, which can be defined as the process of consolidating the products coming from different suppliers, but having the same destination, with minimal handling and almost no storage between loading and unloading of the goods. The purpose of this research is to investigate the benefits of having a cross-docking facility in a supply chain. In this research, we focus on developing discrete event simulation models using the opensource Java Simulation Library (JSL). Also, we work on augmenting an object-oriented library for simulating supply chains to include the modeling of cross-dock facilities. The modeling of a crossdock facility includes the receiving, staging/sorting, and load building activities. Because the operational performance of the inner workings of the cross-dock is not needed, detailed modeling of the resources within the cross-dock such as the number of workers, and pieces of equipment are not included in the modeling. However, the flow, time delays, and inventory aspects are modeled because the key emphasis is on how the cross-dock affects the performance of the supply chain. Simulation experiments are conducted to test the performance of the object-oriented library and to compare the performance of two multi-echelon inventory networks with and without crossdocking to identify the significant factors which affect the performance of the two types of supply chains

Using Specification and Description Language to define and implement discrete simulation models

The formal languages become important tools since they allow the complete understanding of the model and help in its implementation. However only a few simulation tools allow an automatic execution of a simulation model based in a formalization of the system. Specification and Description Language is a modern object oriented graphical formal language that allows the definition of distributed systems. It has focused on the modeling of reactive, state/event driven systems, and has been standardized by the International Telecommunications Union (ITU) in the Z.100. Since it is a graphical formalism simplifies the understanding of the model. In this paper we show how we can use Specification and Description Language to represent a discrete simulation model. We propose a solution, implemented in SDLPS, regarding how to manage the time in Specification and Description Language. Also, we show how SDLPS infrastructure allows a distribute simulation of the models.Postprint (published version

SIMLIB : a class library for object-oriented simulation

Ankara : The Department of Computer Engineering and Information Science and Institute of Engineering and Science of Bilkent University, 1993.Thesis (Master's) -- Bilkent University, 1993.Includes bibliographical references leaves 83-85.Simulation is one of the most widely used techniques in decision making. Mathematical modeling of a real world system is a major task of the simulation analyst. The selection of a computer language for implementing the model is also important. Recent research in this area has focused on the compatibility between simulation implementations and the object-oriented paradigm. It is the purpose of this thesis to explore the use of an object-oriented approach for the implementation of discrete event simulation applications. We present a class library which provides the skeletal elements of a simulation. The advantages and the disadvantages of the approach are discussed with the help of three prototype implementations: the single-queue/single-server system, the production-line system, and the elevator system.Işıklı, OğuzM.S