• 한국군사과학기술학회지
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• 제20권3호
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• pp.454-466
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• 2017

North Korea intended to increase the power of its nuclear weapons and standardize warhead to be loaded in ballistic missiles through the $4^{th}$ and $5^{th}$ nuclear tests. In this study, three kinds of nuclear weapons that North Korea might have used in the $4^{th}$ and $5^{th}$ nuclear tests to achieve their technical goals were suggested. Monte Carlo modeling and various technical assessments have shown that boosted fission weapons are most likely to be used. Also, using the empirical formula considering the burial depth of explosion, we found that the yield of the $4^{th}$ and $5^{th}$ nuclear tests is at least twice as strong as that is expected it could be and the initial design power could reach 8kt before amplification. This means that North Korea has already achieved a substantial level of nuclear fusion technology through the $4^{th}$ test and has made a breakthrough in the miniaturization of nuclear weapons through the $5^{th}$ test. After two or three additional tests, North Korea is expected to have nuclear missiles equipped with nuclear warhead by 2020, which is expected to complete ballistic missile development.

• 한국정보과학회논문지:소프트웨어및응용
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• 제37권8호
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• pp.611-619
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• 2010

본 논문에서는 사용자가 실제와 같은 촉감을 느끼면서 가상 도자기의 물레 성형을 체험할 수 있는 E-Learning 시스템을 제안한다. 원통형으로 대칭을 이루는 도자기 모양의 특징에 착안하여 부채꼴 모양을 가진 요소의 집합으로 3차원 도자기를 모델링하였다. 부채꼴 요소법에 최적화된 충돌 처리와 인접요소간 상호작용 알고리즘을 고안하였으며, GPU 기반의 빠른 햅틱 모델과 시각 모델의 동기화를 구현하였다. 성능 평가 결과 부채꼴 요소법은 기존의 변형체 렌더링 기법에 비해 훨씬 더 조밀한 도자기 모델의 현실적인 실시간 햅틱 렌더링이 가능한 것을 확인하였다. 우리가 구현한 시스템을 도자기와 관련된 교육적인 컨텐츠와 잘 결합한다면 초등학생들을 대상으로 한 E-Learning 시스템으로 성공적인 활용이 가능할 것으로 예상된다.

• Nuclear Engineering and Technology
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• 제48권4호
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• pp.859-869
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• 2016

Component-scale modeling of boiling is predominantly based on the Eulerian-Eulerian two-fluid approach. Within this framework, wall boiling is accounted for via the Rensselaer Polytechnic Institute (RPI) model and, within this model, the bubble is characterized using three main parameters: departure diameter (D), nucleation site density (N), and departure frequency (f). Typically, the magnitudes of these three parameters are obtained from empirical correlations. However, in recent years, efforts have been directed toward mechanistic modeling of the boiling process. Of the three parameters mentioned above, the departure diameter (D) is least affected by the intrinsic uncertainties of the nucleate boiling process. This feature, along with its prominence within the RPI boiling model, has made it the primary candidate for mechanistic modeling ventures. Mechanistic modeling of D is mostly carried out through solving of force balance equations on the bubble. Forces incorporated in these equations are formulated as functions of the radius of the bubble and have been developed for, and applied to, low-pressure conditions only. Conversely, for high-pressure conditions, no mechanistic information is available regarding the growth rates of bubbles and the forces acting on them. In this study, we use direct numerical simulation coupled with an interface tracking method to simulate bubble growth under high (up to 45 bar) pressure, to obtain the kind of mechanistic information required for an RPI-type approach. In this study, we compare the resulting bubble growth rate curves with predictions made with existing experimental data.

• 한국지하수토양환경학회지:지하수토양환경
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• 제22권6호
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• pp.66-73
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• 2017

Empirical erosion models like Universal Soil Loss Equation (USLE) models have been widely used to make spatially distributed soil erosion vulnerability maps. Even if the models detect vulnerable sites relatively well utilizing big data related to climate, geography, geology, land use, etc within study domains, they do not adequately describe the physical process of soil erosion on the ground surface caused by rainfall or overland flow. In other words, such models are still powerful tools to distinguish the erosion-prone areas at large scale, but physics-based models are necessary to better analyze soil erosion and deposition as well as the eroded particle transport. In this study a physics-based soil erosion modeling system was developed to produce both runoff and sediment yield time series at watershed scale and reflect them in the erosion and deposition maps. The developed modeling system consists of 3 sub-systems: rainfall pre-processor, geography pre-processor, and main modeling processor. For modeling system validation, we applied the system for various erosion cases, in particular, rainfall-runoff-sediment yield simulation and estimation of probable maximum sediment (PMS) correlated with probable maximum rainfall (PMP). The system provided acceptable performances of both applications.

• 한국초등과학교육학회지:초등과학교육
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• 제42권4호
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• pp.538-559
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• 2023

본 연구에서는 과학교육 전문가 5인으로 구성된 포커스 그룹 토의(FGD)를 활용하여 모델 및 모델링에 관한 의미를 토의하는 과정에서 주요 주제로 다루어진 '모델과 이론의 관계'를 탐색하였다. 7회 수행된 FGD는 과학교육 연구에서 활발히 진행되고 있는 '모델 및 모델링'과 관련하여 '모델 혹은 모델링이란 무엇인가'라는 질문을 출발로 하여 토의가 전개되었다. 토의 과정에서 이론과의 관계를 중심으로 모델 및 모델링에 관한 몇 가지 주요한 논제가 제기되었고, 본 연구는 그 논제를 중심으로 전개된 토의의 흐름을 추적하였다. 이 연구에서 주목한 것은 FGD에서 연구 참여자들의 이론과 모델의 관계에 대한 토의가 하나의 주장으로 수렴되지 않고, 그와 관련된 몇 가지 논제들이 새로 불거져 나오는 상황은 그 논제에 대한 기존의 개념을 탈바꿈하고 새로운 이해를 추구하는 시도로 이어졌다는 점에 있다. 연구 결과는 세 가지 논제, '모델 혹은 모델링이란 무엇인가?', '모델과 이론의 관계는 어떠한가?', '이론에 기반하지 않은 모델링은 가능한가?'를 포괄하며, 특히 모델과 이론의 관계는 1) 모델이 이론 연역적이고, 모델링이 이론을 현상에 적용하는 것으로 이해되는가, 2) 모델이 이론으로 귀납되는가, 3) 모델링이 특정 구조를 갖는 바탕이론(경험적 지식의 틀)을 기반으로 출발하거나 혹은 바탕이론이 명시적으로 드러나지 않은 채 여러 가지 다른 자원들의 연결로 이해되는가로 토의되었다. 연구의 결과를 토대로, 과학철학과 과학교육, 그리고 과학교육 연구자와 과학교사 교육에 대한 함의가 제시되었다.

• 대한기계학회논문집A
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• 제40권1호
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• pp.113-120
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• 2016

본 연구에서는 좌/우 편제동을 통해 차량의 요 모션을 제어하는 제동 기반 요모멘트 제어 시스템에서의 가상 제동 압력 센서를 개발하였다. 제동 압력을 추정하기 위해 유압시스템을 경험적 방법으로 모델링하였고 이를 기반으로 요레이트 피드백 제동 압력 관측기를 설계하였다. 차량 요레이트 동역학에 존재하는 외란의 영향을 최소화 하기 위해 외란 적응 기법, 외란 축소 기법 및 최적 이득 기법을 관측기 설계에 적용하였고 그 방법들 간의 성능 비교 및 검증을 HILS 를 통해 수행하였다. 그 결과 외란 축소 방식의 견실 관측기의 압력 추정 성능이 일반적인 Luenberger 관측기 대비 가장 우수하였으며 그 원인에 대해 분석하였다.

• 한국자동차공학회논문집
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• 제15권2호
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• pp.65-73
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• 2007

The use of an Exhaust Gas Recirculation(EGR) for a diesel engine with variable geometry turbocharger(VGT) has confronted how to obtain the amount of EGR for NOx reduction requirement at wide operating range and less side effect. Through a combined effort of modeling(wave action simulation) and experiment, an investigation into the effect of EGR area ratio and pipe length on EGR characteristics of common rail diesel engine with VGT has been performed. For accurate computation, calibration of constants involved in empirical and semi-empirical correlations has been performed at a specific operating point, before of its use for engine simulation. From the results of this study, it was found that EGR rate is sharply increased with increasing EGR area ratio until area ratio of 0.3. However, the effect of EGR area ratio on EGR rate is negligible beyond this criteria. This study also investigates the effect of EGR pipe length on a EGR amount and pulsating flow characteristics at EGR junction. The results showed that the longer EGR pipe length, the lower EGR amount was achieved due to the flow loss resulting in lower amplitude of pressure wave.

• International Journal of Contents
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• 제6권4호
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• pp.62-68
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• 2010

More and more researchers and practitioners in the field of e-commerce are paying attentions to the retention of online customers. However, only a few researches can be addressed in the context of internet shopping mall repurchase intention. This study aims at investigating and delineating the important characteristic factors which affect consumers' repurchase intentions by conducting an empirical analysis. In order to fulfill this purpose effectively, a comprehensive review of previous studies regarding information system success model was performed in order to render a stronger theoretical foundation for our study. Finally, based on the DeLone and McLean (2003) IS success model, information quality, system quality, service quality, customer satisfaction and repurchase intention were employed as five constructs in the research model and hypotheses on mutual relationships between these constructs were established accordingly. Structural equation modeling was employed to analyze the data collected from 204 internet shopping mall consumers in China. Our theoretical model exhibited a good fit with the observed data. The empirical results showed particularly strong support for the effects of information quality, service quality and user satisfaction. The findings of this research contributed to the extension of repurchase intention study in the context of Internet shopping malls. Our research also offered implications for practitioners in regards to devising internet shopping malls so as to increase consumers' repurchase intention to use these services.

• 지식경영연구
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• 제16권2호
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• pp.47-66
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• 2015

Due to multiple information sources, external information search(EIS) is the key issue on smart tourism environments. EIS is more important on experiential goods such as exhibition and convention. Despite the increasing importance of EIS, very little is known about what is the more effective information source in this area. In this paper, we attempt to examine the relations of satisfaction and between both online and offline information. This research analyzes an empirical model including EIS, affective involvement, perceived usefulness, satisfaction to student visitors on exhibition experience. Hence, six hypotheses are developed to test the relations of EIS and satisfaction using the mediating effects of affective involvement. Specifically, we developed a research model by employing the Uses and Gratification(U&G) framework and tested it to understand how student visitors' involvement and satisfaction might be changed according to EIS. Survey data was collected from 203 student visitors on "2014 Expo KCCE" was used to test the model using structural equation modeling. The implications of our empirical findings for both research and practice are discussed.

• 유통과학연구
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• 제11권3호
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• pp.39-48
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• 2013

Purpose - This study aims to analyze the main problems of spatial modernization of the economy, and to develop new approaches to way out from crisis, to accelerate of innovations process from the cities-centers to the underdeveloped regions. Research design, data, methodology - The application of scientific methods in this research will allow to systematize the available data, from both a theoretical and empirical perspective. The study employs the method of ranking regions, the rate of innovation activity and comparative evaluation of R&D indicator. In addition, the authors proposed the method of modeling of innovation diffusion in the regions. Results - This study confirms that the need help for the underdeveloped regions, but we should clearly understand the limits of opportunities and to choose the right mechanisms. Further, this study shows it's important to maintain the regions with high innovation activity, as they are growth poles, which are play the role of translator's innovations to the periphery. Conclusions - According to the results of this theoretical and empirical study proved that modernization of the economy is realized faster in the regions with the best conditions for the diffusion of innovations, the higher the concentration of the population, a more developed infrastructure and reduced of administrative barriers.