• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.2
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• pp.123-132
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• 2015

In this study, an arrangement design process for multiple wind turbines, placed on the 10MW class floating wave-offshore wind hybrid power generation system, was presented, and the aerodynamic performance was evaluated by using a computational fluid dynamics. An arrangement design, which produces a maximum power in the site wind field, was found by using a commercial program, WindPRO, based on a blade element momentum theory, then the effect of wake interference on the system between multiple wind turbines was studied and evaluated by using ANSYS CFX.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.1
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• pp.38-42
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• 2006

Spark plasma sintering processes have been rapidly introduced recently to improve the quality and productivity of ceramic products and to solve the problem of environmental pollutions. Sintering temperatures and pressing pressures in the spark plasma sintering process are known to be the important factors highly affecting the quality of the ceramics. In this research, in order to see the effects of sintering temperatures and pressing pressures on the grain growth during the spark plasma sintering process of $Al_2O_3$ the grain growth processes associated with sintering temperatures and pressing pressures are simulated by the Monte Carlo method (MCM) and the finite element method (FEM). In this Part 1, the formulations for the simulation, which is the theoretical background of Part 2, are introduced.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.4
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• pp.14-26
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• 1989

This paper describes the method of statistical analysis and its programs for predicting the ship's powering performance. The equation for the wavemaking resistance coefficient is derived as the sectional area coefficients by using the wavemaking resistance theory and its regression coefficients are determined from the regression analysis of the model test results. The equations for the form factor, wake franction and thrust deduction fraction are derived by purely regression analysis of the principal dimensions, sectional area coefficients and model test results. The statistical analyses are performed using the various descriptive statistic and stepwise regression analysis techniques. The powering performance prognosis program is developed to cover the prediction of resistance coefficients, propulsive coefficients, propeller open-water efficiency and various scale effect corrections.

• Journal of the military operations research society of Korea
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• v.36 no.3
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• pp.43-56
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• 2010

Recently, the acquisition environment of the Korean defense weapon system is emphasizing more the importance of cost analysis in terms of efficient execution for defense acquisition budget. While cost analysis, however, is emphasized in law and process, its infrastructures are still insufficient We have been using computerized cost models to obtain an estimate at early phase of project. But those models have been developed by foreign companies, and so they have many limitations when using in Korean defense environment. For this reason, it began to sympathize that we need the development of the Korean version cost estimation model suitable for our defense industry environment, and now many studies are proceeding. In this study, we suggest Cost Estimating Relationships(CERs) developing methodologies which is key logics of Korean version cost estimation model. Especially, we proposed a new CER's development process depending upon data characteristics such as, multicolinearity, outlier, small samples and heteroscedasticity. Also, we presented a case study for artillery weapon system using these methods we developed. We find that these CERs could be verified through theoretical methods.

• The Journal of the Acoustical Society of Korea
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• v.37 no.4
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• pp.163-173
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• 2018

This paper performed the prediction of the acoustic loads applied to the surface of the flight vehicle during flight. Acoustic loads during flight arise from the pressure fluctuations on the surface of body. The conventional method of predicting the acoustic loads in flight uses semi-empirical method derived from theoretical and experimental results. However, there is a limit in obtaining the flow characteristics and the boundary layer parameters of the flight vehicle which are used as the input values of the empirical equation through experiments. Therefore, in this paper, we use the hybrid method which combines the results of CFD (Computational Fluid Dynamics) with semi-empirical methods to predict the acoustic loads acting on flight vehicle during flight. For the flight vehicle with cone-cylinder-flare shape, acoustic loads were estimated for the subsonic, transonic, supersonic, and Max-q (Maximum dynamic pressure) condition flight. For the hybrid method, two kind of boundary layer edge estimation methods based on CFD results are compared and the acoustic loads prediction results were compared according to empirical equations presented by various researchers.

• Journal of the KSME
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• v.29 no.4
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• pp.360-375
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• 1989

이 논평에서는 수치해석에 관련된 국내의 난류모델의 연구현황을 살펴보았다. 국내에서 연구가 많이 되었던 혼합거리모델, R, .epsilon. 2차방정식모델, 대수응력모델의 연구현황을 주로 살펴 보았다. 국내에서는 아직 연구인력이 적기 때문에 꼭 필요한 부분이지만 연구가 되지 않은 부 분이 많았으며 현재 연구가 되고 있는 부분도 그 연구량이 적은 형편이다. 앞으로 전산유체역 학에 의해 열유체기계내의 복잡한 난류유동을 해석하여 기계설계와 운전을 개선하는데 활용하기 위해서는 더욱 많은 연구가 요구된다. 그 중에서 특히 더 관심을 갖고 연구될 분야를 열거 해 보면 (1) 벽면부근의 저 레이놀즈 R, .epsilon. 방정식모델과 대수응력모델에 관한 연구 (2) 복잡한 3차원유동을 정확히 해석할 난류모델 개발에 관한 연구 (3) 복잡한 난류유동에서 열전 달모델에 관한 연구 (4) 레이놀즈응력모델에 관한 연구 (5) Large Eddy Simulation에 관한 연구를 들 수 있다. 이들 연구에서는 난류모델의 물리적 의미에 관한 이론적 연구와 이 모델들 을 여러 경우의 실제유동에 적용하여 검증하는 연구가 병행되어야 할 것이다.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.1
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• pp.84-98
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• 1990

Fifteen(l5) series hull forms for full slow-speed ships were prepared by expanding the basic parent hull form developed through the extensive theoretical and experimental studies, and model tests were carried out for each of the series hull forms. A set of systematic data was prepared from the test results and utilized to derive regression equations for the prediction of resistance and powering characteristics by statistical analysis. Computer program has been prepared based on the results of analysis and a sample run is presented.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.143-144
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• 2016

빅 데이터 분석은 기존 데이터베이스 관리 도구로부터 데이터를 수집, 저장, 관리, 분석할 수 있는 역량을 말한다. 또한, 대량의 정형 또는 비정형 데이터 집합으로부터 가치를 추출하고 결과를 분석하는 기술을 의미한다. 대부분의 빅 데이터 분석 기술 방법들은 기존 통계학과 전산학에서 사용되던 데이터 마이닝, 기계 학습, 자연 언어 처리, 패턴 인식 등이 해당된다. 글로벌 리서치 기관들은 빅 데이터를 2011년 이래로 최근 가장 주목받는 신기술로 지목해오고 있다. 따라서 대부분의 산업에서 기업들은 빅 데이터의 적용을 통해 가치 창출을 위한 노력을 기하고 있다. 본 연구에서는 다음 커뮤니케이션의 빅 데이터 분석도구인 소셜 매트릭스를 활용하여 키워드 분석을 통해 창조경제 키워드 의미를 분석하고자 한다. 또한, 분석결과를 바탕으로 이론적 실무적 시사점을 제시하고자 한다.

• Journal for History of Mathematics
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• v.21 no.3
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• pp.127-142
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• 2008

In this paper, we introduce four different approaches of proving Cayley formula, which counts the number of trees(acyclic connected simple graphs). The first proof was done by Cayley using recursive formulas. On the other hands the core idea of the other three proofs is the bijective method-find an one to one correspondence between the set of trees and a suitable family of combinatorial objects. Each of the three bijection gives its own generalization of Cayley formula. In particular, the last proof, done by Seo and Shin, has an application to computer science(theoretical computation), which is a typical example that pure mathematics supply powerful tools to other research fields.

• Journal of the Korean Society for Marine Environment & Energy
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• v.20 no.2
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• pp.63-75
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• 2017

In offshore environment, an accurate estimation of a wave-structure interaction has been an important issue for safe and cost effective design of fixed and floating offshore structures exposed to a harsh environment. In this study, a wave-structure interaction around a circular column was investigated with regular waves. To simulate 3D two-phase flow, open source computational fluid dynamics libraries, called OpenFOAM, were used. Wave generation and absorption in the wave tank were activated by the relaxation method, which implemented in a source term. To validate the numerical methods, generated Stokes 2nd-order wave profiles were compared with the analytic solution with deep water condition. From the validation test, grid longitudinal and vertical sizes for wave length and amplitude were selected. The simulated wave run-up and wave loads on the circular column were studied and compared with existing experimental data.