• Title/Summary/Keyword: discrete event model

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An Operation Simulation of MAGLEV using DEVS Formalism Considering Traffic Wave (승객 유동을 고려한 DEVS 기반 자기부상열차 운행 시뮬레이션)

  • Cha, Moo-Hyun;Lee, Jai-Kyung;Beak, Jin-Gi
    • Journal of the Korea Society for Simulation
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    • v.20 no.3
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    • pp.89-100
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    • 2011
  • The MAGLEV (Magnetically Levitated Vehicle) system, which is under commercialization as a new transportation system in Korea, is operated by means of unmanned automatic control system. Therefore the plan of train operation should be carefully established and validated in advance. In general, when making the train operation plan, the statistically predicted traffic data is used. However, traffic wave can occur when real train service is operated, and the demand-driven simulation technology is required to review train operation plans and service qualities considering traffic wave. This paper presents a method and model to simulate the MAGLEV's operation considering continuous demand changes. For this purpose, we employed the discrete event model which is suitable for modeling the behavior of railway passenger transportation, and modeled the system hierarchically using DEVS (Discrete Event System Specification) formalism. In addition, through the implementation and experiment using DEVSim++ simulation environment, we tested the feasibility of the proposed model and it is also verified that our demand-driven simulation technology could be used for the prior review of the train operation plans and strategies.

Method for Detecting Modification of Transmitted Message in C/C++ Based Discrete Event System Specification Simulation

  • Lee, Hae Young
    • Journal of the Korea Society of Computer and Information
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    • v.26 no.1
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    • pp.171-178
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    • 2021
  • In this paper, the author proposes a method for detecting modification of transmitted messages in C/C++ based Discrete Event System Specification (DEVS) simulation. When a message generated by a model instance is delivered to other model instances, it may be modified by some of the recipients. Such modifications may corrupt simulation results, which may lead to wrong decision making. In the proposed method, every model instance stores a copy of every transmitted message. Before the deletion of the transmitted message, the instance compares them. Once a modification has been detected, the method interrupt the current simulation run. The procedure is automatically performed by a simulator instance. Thus, the method does not require programmers to follow secure coding or to add specific codes in their models. The performance of the method is compared with a DEVS simulator.

A study on the co-operative modeling between discrete-event system and continuous-time system for UAV system (UAV를 위한 이산사건 및 연속시간 시스템간의 연동 모델링에 대한 연구)

  • Kang, Kwang-Chun;Choi, Sung-Do;You, Yong-Jun
    • Journal of the Korea Society for Simulation
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    • v.15 no.1
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    • pp.43-50
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    • 2006
  • The major objective of this paper is to propose a hybrid simulation environment for autonomous UAV system by integrating the continuous-time model with discrete-event model. Proposed system is able to support high autonomous behavior by combining the planner, recognizer, and controller model to deal with the HL20 AIRPLANE model. Thus, the high level decision may be efficiently issued even upon the unexpected circumstance. The proposed system model has been successfully verified by several simulation test performed on the DEVS simulation S/W environment.

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A Genetic Algorithm and Discrete-Event Simulation Approach to the Dynamic Scheduling (유전 알고리즘과 시뮬레이션을 통한 동적 스케줄링)

  • Yoon, Sanghan;Lee, Jonghwan;Jung, Gwan-Young;Lee, Hyunsoo;Wie, Doyeong;Jeong, Jiyong;Seo, Yeongbok
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.36 no.4
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    • pp.116-122
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    • 2013
  • This study develops a dynamic scheduling model for parallel machine scheduling problem based on genetic algorithm (GA). GA combined with discrete event simulation to minimize the makespan and verifies the effectiveness of the developed model. This research consists of two stages. In the first stage, work sequence will be generated using GA, and the second stage developed work schedule applied to a real work area to verify that it could be executed in real work environment and remove the overlapping work, which causes bottleneck and long lead time. If not, go back to the first stage and develop another schedule until satisfied. Small size problem was experimented and suggested a reasonable schedule within limited resources. As a result of this research, work efficiency is increased, cycle time is decreased, and due date is satisfied within existed resources.

Structured DEVS Formalism: A Structural Modelling Method of Discrete Event Systems (Structured DEVS Formalism: 이산사건 시스템의 구조적 모델링 기법)

  • Song, Hae-Sang
    • Journal of the Korea Society for Simulation
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    • v.21 no.2
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    • pp.19-30
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    • 2012
  • In recent decades, it has been known that the Discrete Event System Specification, or DEVS, formalism provides sound semantics to design a modular and hierarchical model of a discrete event system. In spite of this benefit, practitioners have difficulties in applying the semantics to real-world systems modeling because DEVS needs to specify a large size of sets of events and/or states in an unstructured form. To resolve the difficulties, this paper proposes an extension of the DEVS formalism, called the Structured DEVS formalism, with an associated graphical representation, called the DEVS diagram, by means of structural representation of such sets based on closure property of set theory. The proposed formalism is proved to be equivalent to the original DEVS formalism in their model specification, yet the new formalism specifies sets in a structured form with a concept of phases, variables and ports. A simplified example of the structured DEVS with the DEVS diagram shows the effectiveness of the proposed formalism which can be easily implemented in an objected-oriented simulation environment.

Web-based Distributed Experimental Frame for Discrete Event Simulation System (이산사건 시뮬레이션 시스템을 위한 웹 기반 분산 실험 틀)

  • Jung, Inho;Choi, Jaewoong;Choi, Changbeom
    • Journal of the Korea Society for Simulation
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    • v.26 no.2
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    • pp.9-17
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    • 2017
  • The problem of social phenomenon is getting more complicated than past decades, and the simulation engineers need more computation power to solve the problem. Therefore, the needs of the computational resources of the modeling and simulation environment are increasing. In the perspective of the simulation, it is necessary to allocate computational resources flexibly so that the simulation can be performed per the available budget range. As an alternative to the simulation environment to accommodate these requirements, cloud service has emerged as an environment in which computing resources can be used flexibly. This paper proposes a web-based simulation framework which consists of a front-end that reconstructs the simulation model using the web, and a back-end that executes the discrete event simulation. This paper also carried out a case study which shows web-based simulation framework has better overall runtime than standalone simulation framework.

Script-based Test System for Rapid Verification of Atomic Models in Discrete Event System Specification Simulation

  • Nam, Su-Man
    • Journal of the Korea Society of Computer and Information
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    • v.27 no.5
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    • pp.101-107
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    • 2022
  • Modeling and simulation is a technique used for operational verification, performance analysis, operational optimization, and prediction of target systems. Discrete Event System Specification (DEVS) of this representative technology defines models with a strict formalism and stratifies the structures between the models. When the atomic DEVS models operate with an intention different the target system, the simulation may lead to erroneous decision-making. However, most DEVS systems have the exclusion of the model test or provision of the manual test, so developers spend a lot of time verifying the atomic models. In this paper, we propose a script-based automated test system for accurate and fast validation of atomic models in Python-based DEVS. The proposed system uses both the existing method of manual testing and the new method of the script-based testing. As Experimental results in our system, the script-based test method was executed within 24 millisecond when the script was executed 10 times consecutively. Thus, the proposed system guarantees a fast verification time of the atomic models in our script-based test and improves the reusability of the test script.

Application of Fuzzy Transition Timed Petri Net for Discrete Event Dynamic Systems (퍼지 트랜지션 시간 페트리 네트의 이산 사건 시스템에 응용)

  • 모영승;김진권;김정철;탁상아;황형수
    • 제어로봇시스템학회:학술대회논문집
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    • 2000.10a
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    • pp.364-364
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    • 2000
  • Timed Petri Net(TPN) is one of methods to model and to analyze Discrete Event Dynamic Systems(DEDSs) with real time values. It has two time values, earliest firing time ($\alpha$$_{i}$) and latest firing time ($\beta$$_{I}$) for the each transition. A transition of TPN is fired at arbitrary time of time interval ($\alpha$$_{I}$, $\beta$$_{i}$). Uncertainty of firing time gives difficulty to analyze and estimate a modeled system. In this paper, we proposed the Fuzzy Transition Timed Petri Net(FTTPN) with fuzzy theory to determine the optimal transition time (${\gamma}$$_{i}$). The transition firing time (${\gamma}$$_{i}$) of FTTPN is determined from fuzzy controller which is modeled with information of state transition. Each of the traffic signal controllers are modeled using the proposed method and timed petri net. And its Performance is evaluated by simulation of traffic signal controller. controller.

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The Staffing Problem at the Call Center by Optimization and Simulation (최적화와 시뮬레이션을 이용한 콜센터의 인력 배치 연구)

  • Kim, Seong-Moon;Nah, Jeong-Eun;Kim, Su-Mi
    • IE interfaces
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    • v.24 no.1
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    • pp.40-50
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    • 2011
  • We develop a nonlinear integer programming model which minimizes the total cost with the optimal number of operators to hire and their optimal allocation to the tasks under the diverse constraints such as the weekly, daily, and hourly maximum allowable abandonment rates for the time-varying inbound call volume. We present a case study based on actual data at a call center, in order to prove the validity of applying the optimization method proposed. By the one-sample two-tailed t-test, we confirm that the expected abandonment rates resulting from the optimization method are identical with the ones from the discrete-event simulation within specified confidence intervals.

Hierarchical Verification Methodology of Discrete Event Systems (이산사건 시스템의 계층적 검증방법론)

  • Song, Hae-Sang;Lee, Wan-Bok
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.11 no.5
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    • pp.1029-1036
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    • 2007
  • State explosion is a well-known problem that impedes analysis md testing of discrete event systems, thus making the verification of large systems intrinsically difficult job. This paper suggests a hierarchical verification methodology of untimed DEVS model which can alleviate the state explosion problem. The method is a repetitive procedure of designing and verifying between the upper level and the lower level models abstracting away the unnecessary information with respect to a given verification task. A small example was employed to show our suggested method in detail.