• Nuclear Engineering and Technology
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• 제51권2호
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• pp.444-452
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• 2019

To assess the availability of a nuclear power plant's dynamic systems, it is necessary to consider the impact of dynamic interactions, such as components, software, and operating processes. However, there is currently no simple, easy-to-use tool for assessing the availability of these dynamic systems. The existing method, such as Markov chains, derives an accurate solution but has difficulty in modeling the system. When using conventional fault trees, the reliability of a system with dynamic characteristics cannot be evaluated accurately because the fault trees consider reliability of a specific operating configuration of the system. The dynamic reliability graph with general gates (DRGGG) allows an intuitive modeling similar to the actual system configuration, which can reduce the human errors that can occur during modeling of the target system. However, because the current DRGGG is able to evaluate the dynamic system in terms of only reliability without repair, a new evaluation method that can calculate the availability of the dynamic system with repair is proposed through this study. The proposed method extends the DRGGG by adding the repair condition to the dynamic gates. As a result of comparing the proposed method with Markov chains regarding a simple verification model, it is confirmed that the quantified value converges to the solution.

• 한국전자통신학회논문지
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• 제14권5호
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• pp.825-836
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• 2019

군 병력의 효율적 운용을 위한 정보공유의 수단으로서 높은 망 유연성을 제공할 수 있는 드론형 기지국이 최적의 플랫폼이 될 것으로 예상된다. 또한 넓은 대역폭을 활용 가능한 밀리미터파 주파수대역은 대용량 데이터를 송수신하는데 적합하지만 shadowing에 취약한 특성을 가지게 되는데, 자유롭게 고도를 조절할 수 있는 드론형 기지국의 특성을 활용하면 LoS를 안정적으로 확보하여 취약점을 상쇄할 것으로 기대된다. 본 논문에서는 다양한 요소가 반영된 드론형 기지국의 성능분석을 위한 모델링을 수행함으로써, 차후 군 통신망으로써 활용가능성이 기대되는 드론형 기지국의 성능평가에 대한 틀을 제공하고자 한다.

• ETRI Journal
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• 제44권6호
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• pp.991-1003
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• 2022

Industrial control systems (ICSs) used to be operated in closed networks, that is, separated physically from the Internet and corporate networks, and independent protocols were used for each manufacturer. Thus, their operation was relatively safe from cyberattacks. However, with advances in recent technologies, such as big data and internet of things, companies have been trying to use data generated from the ICS environment to improve production yield and minimize process downtime. Thus, ICSs are being connected to the internet or corporate networks. These changes have increased the frequency of attacks on ICSs. Despite this increased cybersecurity risk, research on ICS security remains insufficient. In this paper, we analyze threats in detail using STRIDE threat analysis modeling and DREAD evaluation for distributed control systems, a type of ICSs, based on our work experience as cybersecurity specialists at a refinery. Furthermore, we verify the validity of threats identified using STRIDE through case studies of major ICS cybersecurity incidents: Stuxnet, BlackEnergy 3, and Triton. Finally, we present countermeasures and strategies to improve risk assessment of identified threats.

• Structural Engineering and Mechanics
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• 제88권1호
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• pp.67-81
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• 2023

The reinforced concrete (RC) structures might need strengthening or upgradation due to adverse environmental conditions, design defects, modification requirements, and to prolong the expected lifespan. The RC beams have been efficiently strengthened using the near surface mounted (NSM) approach over the externally bonded reinforcing (EBR) system. In this study, the performance of RC beam elements strengthened with NSM-steel rebars was investigated using an experimental program and nonlinear finite element modeling (FEM). Nine medium-sized, rectangular cross-section RC beams total in number made up for the experimental evaluation. The beams strengthened with varying percentages of NSM reinforcement, and the number of grooves was assessed in four-point bending experiments up to failure. Based on the experimental evaluation, the load-displacement response, crack features, and failure modes of the strengthened beams were recorded and considered. According to the experimental findings, NSM steel greatly improved the flexural strength (up to about 84%) and stiffness of RC beams. The flexural response of the tested beams was simulated using a 3D non-linear finite element (FE) model. The findings of the experiments and the numerical analysis showed good agreement. The effect of the NSM groove and reinforcement on the structural response was then assessed parametrically.

• 제어로봇시스템학회논문지
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• 제10권5호
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• pp.450-457
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• 2004

In this research, the automatic synthesis of knowledge models is proposed. which are the basis of the methods using qualitative models adapted widely in fault diagnosis and hazard evaluation of chemical processes. To provide an easy and fast way to construct accurate causal model of the target process, the Role-Behavior modeling method is developed to represent the knowledge of modularized process units. In this modeling method, Fault-Behavior model and Structure-Role model present the relationship of the internal behaviors and faults in the process units and the relationship between process units respectively. Through the multiple modeling techniques, the knowledge is separated into what is independent of process and dependent on process to provide the extensibility and portability in model building, and possibility in the automatic synthesis. By taking advantage of the Role-Behavior Model, an algorithm is proposed to synthesize the plant-wide causal model, Fault-Causality Graph (FCG) from specific Fault-Behavior models of the each unit process, which are derived from generic Fault-Behavior models and Structure-Role model. To validate the proposed modeling method and algorithm, a system for building FCG model is developed on G2, an expert system development tool. Case study such as CSTR with recycle using the developed system showed that the proposed method and algorithm were remarkably effective in synthesizing the causal knowledge models for diagnosis of chemical processes.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2002년도 춘계학술대회논문집
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• pp.253-258
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• 2002

This paper proposes a methodology for development of protocol models. The methodology attempts to employ two modeling environments in models development, NS2 and DEVSim++, which will interoperate during simulation. NS2 is a widely used network simulator in protocol research, which employs an informal modeling approach. Within the approach time and state information of protocol models are not explicitly described, thus being hard to validate model. On the other hand the DEVS formalism is a mathematical framework for modeling a discrete event system in a hierarchical, modular manner. In DEVS, model's time and state information is described explicitly, By using DEVS formalism, models can easily be validated and errors in the modeling stage can be reduced. However, the DEVS simulator, DEVSim++, supports a small amount of models library which are required to build simulation models of general communication network. Although NS2 employs an informal modeling approach and models validation is difficult, it supports abundant models library validated by experimental users. Thus, combination of DEVS models and NS2 models may be an effective solution for network modeling. Such combination requires interoperation between DEVSim++ simulator and NS2 simulator. This paper develops an environment for such interoperation. Correctness and effectiveness of the implemented interoperation environment have been validated by simulation of UDP and TCP models.

• 상하수도학회지
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• 제23권5호
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• pp.565-572
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• 2009

Hydraulic modeling is widely used to simulate wastewater flow. The simulated models are used to prevent flood and many other problems associated with wastewater flow in planning or rehabilitating sewer systems. In this study, MAKESW (An engineer, South Korea), MOUSE (DHI, Denmark), and SWMM (XPSoftware, USA) are used to for hydraulic modeling of wastewater in C-city, South Korea and E-city, Iraq. These modeling tools produced different results. SWMM comparably overpredicted runoff and peak flow. In using SWMM, use of accurate data with a high confidential level, detail examination over the target basin surface, and the careful selection of a runoff model, which describes Korea's unique hydraulic characteristics are recommended. Modification of existing models through the optimization of variables cannot be achieved at this moment. Setting up an integrated modeling environment is considered to be essential to utilize modeling and further apply the results for various projects. Standardization of GIS database, the criteria for and the scope of model application, and database management systems need to be prepared to expand modeling application.

• 한국시뮬레이션학회논문지
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• 제25권3호
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• pp.97-105
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• 2016

본 논문에서는 철근 모사 방법에 따른 관통자의 콘크리트 관통성능 변화를 수치적으로 분석하였다. 관통해석은 상용 전산해석 프로그램인 AUTODYN-3D을 사용하여 수행하였고, Hanchak의 시험 데이터를 사용하여 해석 방법의 신뢰성을 입증하였으며, 철근의 강도와 지름 및 관통자의 충돌위치, 속도를 변수로 사용하여 충돌 해석을 수행하였다. 철근 모사가 관통성능에 미치는 영향을 정량적으로 분석하기 위해, 관통자의 잔류 속도를 계산하여 침투/관통성능을 평가하였다.

• 품질경영학회지
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• 제32권4호
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• pp.113-124
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• 2004

Customer satisfaction is becoming an increasingly salient topic in many firms and in academic research. One main rationale behind this interest is that customer satisfaction is believed to be associated with fruitful customer re-visit from the firm's point of view. Some country already had index models which can measure the degree of customer satisfaction. But, such models are ordinary models which used generally the scope of nation-wide /industry. Therefore, we needs some modifications to measure customer satisfaction for specific product & service and to provide the valuable feedback to specific firms. In this Perspectives, this study will evaluate the customer satisfaction index about automobile company and analyze it's result for valuable feedback. This study will present a model for an integrated customer satisfaction evaluation system which used structural equation modeling. Through this study, we anticipate that it will offer the measuring method about customer satisfaction and some guideline for product design process.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.756_757
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• 2009

This paper deal with the efficiency evaluations in a Synchronous reluctance motor(SynRM) Vs. PMASynRM using a coupled transient finite element methed(FEM) and preisach modeling, which is presented to analyze the characteristics under the effect of saturation and hysteresis loss. The focus of this paper is the efficiency evaluation relative to hysteresis loss, copper loss, etc. on the basis of load condition in a SynRM and PMASynRM. Computer simulation and experimental result for the efficiency using dynamometer shoe the propriety of the proposed method.