• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.106.2-106.2
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• 2010

IGCC (Integrated Gasification Combined Cycle) plants are among the most advanced and effective systems for electric energy generation. From a control perspective, IGCC plants represent a significant challenge: complex reactions, highly integrated control to simultaneously satisfy production, controllability, operability and environmental objectives. While all these requirements seem clearly to demand a multivatiable, model predictive approach, not many applications can be easily found in the literature. This paper describes the IGCC dynamic simulation that is capable of simulating plant startup, shutdown, normal, and abnormal operation and engineering studies. This high fidelity dynamic models contain the detailed process design data to produce realistic responses to process operation and upset. And the simulation is used by engineers to evaluate the transient performance and produce graphical information indicating the response of the process under study conditions.

• Journal of computational fluids engineering
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• v.7 no.3
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• pp.27-34
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• 2002

When caught in a fire inside a building or a tunnel the generated smoke is the main cause of the bad visibility, which makes it difficult for a person to find escape route. Therefore of the fire simulation it is required to visualize the simulated results of smoke realistically form a viewpoint of a person caught in a fire. In the present study, developed is a CFD post-processor which can visualize the object through smoke from the results of CFD fire simulation. Examples of some applications of the program are shown in the paper.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.11
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• pp.4224-4243
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• 2021

Cognitive radio (CR) is a feasible intelligent technology and can be used as an effective solution to spectrum scarcity and underutilization. As the key function of CR, cooperative spectrum sensing (CSS) is able to effectively prevent the harmful interference with primary users (PUs) and identify the available spectrum resources by exploiting the spatial diversity of multiple secondary users (SUs). However, the open nature of the cognitive radio networks (CRNs) framework makes CSS face many security threats, such as, the malicious user (MU) launches Byzantine attack to undermine CRNs. For this aim, we make an in-depth analysis of the motive and purpose from the MU's perspective in the interweave CR system, aiming to provide the future guideline for defense strategies. First, we formulate a dynamic Byzantine attack model by analyzing Byzantine behaviors in the process of CSS. On the basis of this, we further make an investigation on the condition of making the fusion center (FC) blind when the fusion rule is unknown for the MU. Moreover, the throughput and interference to the primary network are taken into consideration to evaluate the impact of Byzantine attack on the interweave CR system, and then analyze the optimal strategy of Byzantine attack when the fusion rule is known. Finally, theoretical proofs and simulation results verify the correctness and effectiveness of analyses about the impact of Byzantine attack strategy on the throughput and interference.

• Journal of Korean Elementary Science Education
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• v.34 no.4
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• pp.357-371
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• 2015

Even after learning electric current, elementary school students have various non-scientific conceptions and difficulties. Because flow of charge is not visible. Also elementary school students do not learn theory but phenomena, so they cannot transfer theoretical perspective to new situation. In this research, we have designed instruction based on PhET simulation visualizing flow of electric charge and applied it to 37 science-gifted students in elementary school for measuring conceptual understanding. As a result, six out of the seven Hake gains of question set are high gain and just one is middle gain because the students have understood the flow pattern of the charge through circuit elements such as light bulbs, wire, as well as battery with PhET simulation and it gives a chance to create various questions spontaneously about electric current. Also they become able to do spontaneous mental simulation without PhET simulation about flow of charges. This research, suggest that developed materials using PhET simulation could be used as not only program for gifted students in elementary school, but also the electrical circuit section in an elementary science curriculum.

• Proceedings of the Korea Society for Simulation Conference
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• 2003.11a
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• pp.43-50
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• 2003

시뮬레이션의 궁극적인 목표인 분산 시뮬레이션은 Virtual Simulation과 Constructive Simulation 이외에 Live Simulation이 동시에 참여하여 동일한 환경 내에서 상호작용 하는 것을 추구하고 있다. 따라서 서로 다른 목적과 기술로 제작된 시뮬레이션은 통합된 환경 내에서 사실적으로 상호작용 해야만 할 것이다. 통합 환경(Synthetic Environment)은 시각적 영상을 표현하기 위한 Visual Database 이상의 의미를 내포하고 있다. 상호운용성(Interoperability)은 타 Model 및 Simulation에서 부터 제공되는 기능을 사용하거나 기능을 제공할 수 있는 유용성(Availability)을 뜻하기 때문에 표준화된 통합 환경의 사용 및 교환을 요구한다. 1980년대 중반, 미 국방성은 Image Generator 제작 회사마다 독자적인 데이터베이스 포맷을 사용함으로 인해 시뮬레이터 데이터베이스의 중복성이 야기되고 있다는 것을 지적하고 통합 환경 데이터 교환 문제를 해결하기 위한 최초의 관련 연구를 수행하였다. Virtual Simulation에서 막대한 비용이 소모되는 시뮬레이터 데이터베이스의 제작 및 유지 보수에 들어가는 이중적인 비용 절감에 대한 관심은 최근 SEDRIS에 이르러 표준 교환에 대한 명세의 필요성이 보다 구체화되어 지구상에 존재하는 각종 주변 환경을 기술하기 위한 통합 환경표현 및 교환의 표준화가 진행되고 있다. 국내에서는 문화콘텐츠진흥원, 한국게임산업개발원, 한국전자통신연구원, 국방과학연구소, 서울대, 아주대, 세종대 등을 중심으로 연구가 진행 중이며, 그중 세종대학교는 SEDRIS 데이터로 사용될 원본 데이터의 충실도와 신뢰도를 향상시킬 수 있는 방법을 연구하고 있다. SEDRIS는 그 응용가능성이 무궁무진하여 향후 인공적인 가상환경을 대표하는 용어로 사용될 것이며, 공개된 표준을 통한 소스 데이터의 공유로 상호운용성을 위한 초석을 제공하여 궁극적으로는 비용 절감 효과가 있을 것으로 전망된다.

• Korean System Dynamics Review
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• v.11 no.2
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• pp.5-28
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• 2010

The purpose of this paper is to review relationship between spatial characteristics of compact city and urban sustainabiliy from system dynamics perspective using causal loop analysis. It has been argued that spatial characteristics of compact city, high population density and mixed land use, are positively related to urban sustainability. However, research results that are not consistent with pros of compact city argument have been accumulated too. It is especially true when spatial characteristics of compact city are examined with regard to each dimension of sustainablility: economic, social, and environmental sustainability. Reviewing each dimension of sustainability with regard to spatial characteristics based on causal loop analysis, this paper provides more clear understanding on relationship between compact city and sustainability. Also this paper provides a base for system dynamics simulation for future study.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.3 no.1
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• pp.75-87
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• 2004

The mobile industry is waking up to the reality that customers buy 'services', not technology. Thekey is to deliver a variety of differentiated services today and improve them as the advanced technology becomes available. In the increasingly data centric world of the future, the emphasis will be on the provision of a range of services audio, video, data and multimedia and of course speech. As we move closer to the realization of these mobile services in the conglomeration of converged networks, new challenges are being faced by the technology and application developers as well as the service providers to design, test and integrate new products and services. Functionalities like availability, scalability, performance and compatibility have become more important. This paper discusses the new test paradigms in the mobile networks, both from the applications and the protocols perspective.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.257-261
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• 2005

Over the past 30 years, numerical methods and simulation tools for fluid dynamic problems have advanced as a new discipline, namely, computational fluid dynamics (CFD). Although a wide spectrum of flow regimes are encountered in many areas of science and engineering, simulation of compressible flow has been the major driver for developing computational algorithms and tools. This Is probably due to a large demand for predicting the aerodynamic performance characteristics of flight vehicles, such as commercial, military, and space vehicles. As flow analysis is required to be more accurate and computationally efficient for both commercial and mission-oriented applications (such as those encountered in meteorology, aerospace vehicle development, general fluid engineering and biofluid analysis) CFD tools for engineering become increasingly important for predicting safety, performance and cost. This paper presents the author's perspective on the maturity of CFD, especially from an aerospace engineering point of view.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.1
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• pp.51-62
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• 2008

This paper proposes a second-order implicit constraint enforcement method which yields enhanced controllability compared to a first-order implicit constraints enforcement method. Although the proposed method requires solving a linear system twice, it yields superior accuracy from the constraints error perspective and guarantees the precise and natural movement of objects, in contrast to the first-order method. Thus, the proposed method is the most suitable for exact prediction simulations. This paper describes the numerical formulation of second-order implicit constraints enforcement. To prove its superiority, the proposed method is compared with the firstorder method using a simple two-link simulation. In this paper, there is a reasonable discussion about the comparison of constraints error and the analysis of dynamic behavior using kinetic energy and potential energy.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.4
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• pp.537-547
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• 2015

A Monte Carlo (MC) simulation was conducted to predict the reliability of a newly developed pyrotechnic pin puller. The reliability model is based on the stress-strength interference model that states that failure occurs if the stress exceeds the strength. In this study, the stress is considered to be the energy consumed by movement of a pin shaft, and the strength is considered to be the energy generated by pyrotechnic combustion for driving the pin shaft. Failure of the pin puller can thus be defined as the consumed energy being greater than the generated energy. These energies were calculated using a performance model formulated in the previous study of the present authors. The MC method was used to synthesize the probability densities of the two energies and evaluate the reliability of the pin puller. From a probabilistic perspective, the calculated reliability was compared to a deterministic safety factor. A sensitivity analysis was also conducted to determine which design parameters most affect the reliability.