• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권5호
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• pp.2186-2203
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• 2020

Security administrators of companies and organizations need to come up with proper countermeasures against cyber-attacks considering infrastructures and security policies in their possession. In order to develop and verify such countermeasures, the administrators should be able to reenact both cyber-attacks and defenses. Simulations can be useful for the reenactment by overcoming its limitations including high risk and cost. If the administrators are able to design various scenarios of cyber-attacks and to develop simulation models from their viewpoints, they can simulate desired situations and observe the results more easily. It is challenging to simulate cyber-security issues, because there is lack of theoretical basis for modeling a wide range of the security field as well as pre-defined basic components used to model cyber-attacks. In this paper, we propose a modeling method for cyber-security simulations by developing a basic component and a composite model, called Abstracted Cyber-Security Unit Model (ACSUM) and Abstracted Cyber-security SIMulation model (ACSIM), respectively. The proposed models are based on DEVS(Discrete Event systems Specification) formalism, a modeling theory for discrete event simulations. We develop attack scenarios by sequencing attack behaviors using ACSUMs and then model ACSIMs by combining and abstracting the ACSUMs from a security perspective. The concepts of ACSUM and ACSIM enable the security administrators to simulate numerous cyber-security issues from their viewpoints. As a case study, we model a worm scenario using ACSUM and simulate three types of simulation models based on ACSIM from a different security perspective.

• Nuclear Engineering and Technology
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• 제51권8호
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• pp.1916-1938
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• 2019

The objective of this paper is to discuss the modeling principles of phenomena governing core degradation/melting and in-vessel melt relocation during severe accidents in light water reactors. The proposed modeling approach has been applied in the development of a new accident simulation package, COMPASS (COre Meltdown Progression Accident Simulation Software). COMPASS can be used either as a stand-alone tool to simulate in-vessel meltdown progression up to and including RPV failure, or as a component of an integrated simulation package being developed in Korea for the APR1400 reactor. Interestingly, since the emphasis in the development of COMPASS modeling framework has been on capturing generic mechanistic aspects of accident progression in light water reactors, several parts of the overall model should be useful for future accident studies of other reactor designs, both PWRs and BWRs. The issues discussed in the paper include the overall structure of the model, the rationale behind the formulation of the governing equations and the associated simplifying assumptions, as well as the methodology used to verify both the physical and numerical consistencies of the overall solver. Furthermore, the results of COMPASS validation against two experimental data sets (CORA and PHEBUS) are shown, as well as of the predicted accident progression at TMI-2 reactor.

• 한국시뮬레이션학회논문지
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• 제19권2호
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• pp.51-62
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• 2010

모델링 및 시뮬레이션 기술은 실 전장 환경과 유사한 실험환경을 컴퓨터상에 구성하여 무기 체계에 대한 효과도를 효율적으로 실제와 유사하게 분석 할 수 있도록 한다. 그러나 기 개발된 무기체계 모델들은 각 시뮬레이션 목적에 맞도록 편중 개발되어 재사용성이 낮으며, 개발된 무기체계 모델을 수행하기 위한 모의엔진의 구조도 서로 상이하여 확장성 측면에서 한계를 갖고 있다. 본 논문에서는 무기체계 분석을 위해 국방 M&S 모의 엔진에서 제공해야 할 요구사항을 식별하고, 식별된 요구사항을 반영하는 모의 엔진의 소프트웨어 아키텍처를 정의한다. 정의된 아키텍처는 모델러에게 사용상 편이성을 제공하고, 컴포넌트 기반의 재사용, 다양한 사용자 범주, 최대화된 연동능력, 모델링 및 시뮬레이션 전체 단계에 걸친 재사용을 지원하도록 설계 되었다.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2001년도 The Seoul International Simulation Conference
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• pp.405-424
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• 2001

Many simulation models have been built to facilitate simulation technique in designing, evaluating, and optimizing supply chains. Simulation is preferred to deal with stochastic natures existing in the supply chain. Moreover simulation has a capability to find local optimum value within each component through entire supply chain. Most of supply chain simulation models have been developed on the basis of discrete-event simulation. Since supply chain systems are neither completely discrete nor continuous, the need of constructing a model with aspects of both discrete-event and continuous simulation is provoked, resulting in a combined discrete-continuous simulation. In this paper, an architecture of combined modeling for supply chain simulation is proposed, which includes the equation of continuous portion in supply chain and how these equations are used in the supply chain simulation models. A simple example of supply chain model dealing with the strategic level of supply chain presented in this paper shows the possibility and the prospect of this approach.

• 한국시뮬레이션학회논문지
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• 제10권2호
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• pp.75-89
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• 2001

Many simulation models have been built to facilitate simulation technique in designing, evaluating, and optimizing supply chains. Simulation is preferred to deal with stochastic natures existing in the supply chain. Moreover simulation has a capability to find local optimum value within each component through entire supply chain. Most of supply chain simulation models have been developed on the basis of discrete-event simulation. Since supply chain systems are neither completely discrete nor continuous, the need of constructing a model with aspects of both discrete-event and continuous simulation is provoked, resulting in a combined discrete-continuous simulation. In this paper, an architecture of combined modeling for supply chain simulation is proposed, which includes the equation of continuous portion in supply chain and how these equations are used in the supply chain simulation models. A simple example of supply chain model dealing with the strategic level of supply chain presented in this paper shows the possibility and the prospect of this approach.

• 전기학회논문지
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• 제56권12호
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• pp.2098-2102
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• 2007

The conventional CCPU(Cable Covering Protective Unit) modeling methods which are used by Type 99 and Type 92 in EMTP simulation are firstly discussed in this paper, and then some problems of them are also investigated. Modeling method using Type 99 causes unstable characteristic at initial transient of CCPU operation. Time delay has also effect on the output of CCPU modeling. So, in this paper, a new modeling method for CCPU is designed by DBM(Data Base Module) of EMTP. The characteristic of Type 92 is used for the new modeling method. The reliability of this one is proved by comparing simulation with measured data. Specially, at initial transient, the waveform of the new method shows more stable result than that of conventional method using Type 99. Also, the peak value is similar to measured data.

• 한국시스템다이내믹스연구
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• 제7권1호
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• pp.27-49
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• 2006

A system dynamics model is developed to investigate the applicability of the agent based modeling concept in the system dynamics model. The assumed problem is to forecast the size and structure of the organization with the developing market environment. The agent based modeling concept is applied to the organization part, and the other parts of the model such as market, facilities, etc. are developed with the traditional system dynamics technique. The simulation results show the agent based modeling part can be combined with the traditional system dynamics modeling with more precisions. However, the complexity increases and the simulation times are longer than those of the traditional method.

• 대한전기학회논문지:전력기술부문A
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• 제54권3호
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• pp.107-116
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• 2005

The paper addresses modeling and analysis of a grid-connected photovoltaic generation system (PV system). PSCAD/EMTDC, an industry standard simulation tool for studying the transient behavior of electric power system and apparatus, is used to conduct all aspects of model implementation and to carry out extensive simulation study. This paper is aimed at sharing with the PSCAD/EMTDC user community our user-defined model for PV system applications, which is not yet available as a standard model within PSCAD/EMTDC. An equivalent circuit model of a solar cell has been used for modeling solar array. A series of parameters required for array modeling have been estimated from general specification data of a solar module. A PWM voltage source inverter (VSI) and its current control scheme have been implemented. A maximum power point tracking (MPPT) technique is employed for drawing the maximum available energy from the PV array. Comprehensive simulation results are presented to examine PV array behaviors and PV system control performance in response to irradiation changes. In addition, dynamic responses of PV array and system to network fault conditions are simulated and analysed.

• 한국실천공학교육학회논문지
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• 제3권1호
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• pp.15-24
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• 2011

녹색에너지의 모델링과 시뮬레이션은 연구하고자 하는 시스템의 형태에 따라 크게 의존한다. 모델링과 시뮬레이션의 주요내용은 반도체 물리(태양전지), 전기모터/발전기(풍력터빈), 전형적인 제어전략에 의한 전력전자(계통연계)등 매우 다양하다. 이들 기술들을 정확하게 모델링하는 것은 다양한 시뮬레이션 기술과 많은 모델들을 필요로 한다. 시뮬레이션을 더욱 정확하게 혹은 상세하게 하기 위해서 모델링은 특정레벨 즉, 시스템, 회로, 요소 레벨 등으로 수행하여야 한다. 다양한 레벨의 조합은 모델 방정식과 이용 가능한 매개변수들에 대한 전체적인 모델의 유용성을 크게 개선할 수 있다.

• 대한조선학회논문집
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• 제52권4호
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• pp.330-337
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• 2015

When a tower crane is carried by a transporter in shipyard, the height and length of the tower crane should be adjusted to meet the safety guidelines. Since the guidelines came from the field experience, the safety limitation needs to be analyzed by a computer simulation. In this paper, modeling methods are addressed to implement the appropriate transportation simulation of a tower crane. For the relation between the tower crane and the transporter, normal contact force, friction force, and kinematic constraints are compared. Assignment of relevant linear acceleration and angular velocity is considered for the transporter to start or move on an inclined ground surface. By using the examined modeling methods, the dynamic motion of tower crane transportation is analyzed by a dynamic simulation program, and comparison between the simulation result and analytic solution is made to verify the feasibility of the modeling methods.