• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.4
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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.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.5
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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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• v.39 no.8
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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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• v.38 no.1
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• pp.65-82
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• 2018

The purpose of this study is to statistically summarize the effect sizes using meta-analysis of various Kigong programs implemented on the subject of physical health of the elderly. Including 23 academic journal studies and 11 thesis studies reported domestically until 2016, a total of 34 studies were selected and analyzed to verify the effect sizes of programs, program types, measuring variables, and activity elements. The findings are as follows. First, it was found that the programs were midium effective with overall average effect size showing .748(p<.001). A program of Tai-Chi indicated the largest effect size of .836(p<.001). In terms of measuring variables, physical strength showed the largest effect size of .806(p<.001). In terms of gender by group, it was found that groups consisting only of men indicated the largest effect size of 2.388(p<.001). As for effect size by group of disease state, normal group with showed the highest effect size of .804(p<.001). Second, in activity elements, 31~60 by the group size has the largest effect size of .873(p<.001), total number of sessions for 31~40 sessions indicated the largest effect value of .829(p<.001). As for number of sessions per week, 5 sessions showed largest effect value of .918(p<.001), in terms of activity time, 50 minutes showed large effect value of 1.391(p<.001). As summarized above, Kigong programs are midium effective for physical health of the elderly, as an activity elements to consider when configuring the program, for group size 31~60, 31~40 sessions in total, 5 sessions per week and 50 minutes per sessions were recommended.