• 한국군사과학기술학회지
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• 제15권4호
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• pp.417-423
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• 2012

Radar Cross Section(RCS) is a measure of how detectable an object is with a radar. A larger RCS indicates that an object is more easily detected. Informally, the RCS of an object is the cross-sectional area of a perfectly reflecting sphere that would produce the same amount of reflection strength as the object in question would. In order to estimate RCS of aircraft weapons the external surface is modeled as a collection of simple shape elements. And the overall RCS is estimated as a vector sum of configuring elements' cross-sections which are well known given by analytic formulae. A RCS estimation code is developed for a typical shape of Air-To-Surface bombs and missiles. Size of weapons and location of fins are implemented in the code in addition to the presence of canards. The ability to predict radar return from flying vehicles becomes a critical technology issue in the development of stealth configurations. This simplified method of RCS estimation is known to be fast and accurate enough in an optical region of high frequency incident radio wave.

• 대한전기학회논문지
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• 제41권5호
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• pp.468-473
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• 1992

A boundary element analysis using parallel algorithm on transputers is described for three-dimensional magnetostatic field computations. The parallel algorithm are applied to assembling the system matrix and solving the matrix equation. Through the numerical results, it is shown that the computation time is ideally inverse proportional to the number of transputers, and the computational efficiency increases as the size of the system matrix becomes large. The easiness and simplicity in configuring the system hardware and making programs and computation times are compared in three kinds of topologies.

• Journal of Advanced Marine Engineering and Technology
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• 제39권8호
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• pp.856-862
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• 2015

Tidal current energy is an important alternative energy resource among the various ocean energy resources available. The tidal currents in the South-Western sea of Korea can be utilized for the development of tidal current power generation. Tidal power generation can be beneficial for many fishing nurseries and nearby islands in the southwest region of Korea. Moreover, tidal power generation is necessary for promoting energy self-sufficient islands. As tidal currents are always available, power generation is predictable; thus, tidal power is a reliable renewable energy resource. The selection of an appropriate hydrofoil is important for designing a tidal current turbine. This study concentrates on the selection and numerical analysis of four different hydrofoils (MNU26, NACA63421, DU91_W2_250, and DU93_W_210LM). Blade element momentum theory is used for configuring the design of a 50 W class turbine rotor blade. The optimized blade geometry is used for computational fluid dynamics (CFD) analysis with hexahedral numerical grids. Among the four blades, NACA63421 blade showed the maximum power coefficient of 0.45 at a tip speed ratio of 6. CFD analysis is used to investigate the power coefficient, pressure coefficient, and streamline distribution of a 50 W class horizontal axis tidal current turbine for different hydrofoils.

• 한국노년학
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• 제38권1호
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• pp.65-82
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• 2018

본 연구는 노인의 신체건강을 주제로 수행된 다양한 기공프로그램에 대해 메타분석을 사용하여 효과크기를 통계적으로 요약해보고자 하였다. 2016년까지 국내에서 보고된 학술지 논문 23편과 학위 논문 11편 총 34편을 선정하여 프로그램과 프로그램의 유형, 측정변수 및 활동요소에 대한 효과크기를 확인한 결과, 첫째, 전체평균 효과크기는 .748(p<.001)로써 중간크기의 효과가 나타났다. 가장 효과크기가 큰 프로그램은 타이치로 .836 (p<.001)이었으며, 측정변수는 체력이 .806(p<.001)으로 가장 높게 나타났다. 집단의 성별에서는 남성만으로 구성된 집단이 2.388 (p<.001)로 높았고, 집단의 질병유무에 따른 효과크기는 정상집단이 .804(p<.001)로 높게 나타났다, 둘째, 활동요소 중 집단크기는 31~60명이 .873(p<.001), 총회기수는 31~40회가 .829(p<.001)로 높게 나타났다. 주회기수는 5회가 .918(p<.001)로 가장 높았고, 활동시간에 따른 효과크기는 50분이 1.391(p<.001)로 높은 효과크기를 보였다. 상기와 같이 기공프로그램은 노인의 신체건강에 중간크기의 효과가 나타났으며, 향후 기공프로그램 구성 시 집단크기 31~60명, 총회기수 31~40회, 주회기수 5회, 활동시간은 50분으로 제안하고자 한다.