• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.6
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• pp.731-738
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• 2010

Cavitation is described by formation and collapse of the bubbles in a liquid when the ambient pressure decreases. Formed bubbles grow and collapse by change of pressure, and when they collapse, shockwave by high pressure is generated. In general, bubble behavior can be described by Rayleigh-Plesset equation under adiabatic or isothermal condition and hence, phase shift by the pressure change in a bubble cannot be considered in the equation. In our study, a numerical model is developed from the mathematical model considering the phase shift from the previous study. In the developed numerical model, size of single spherical bubble is calculated by the change of mass calculated from the change of the ambient pressure in a liquid. The developed numerical model is verified by a case of liquid flow in a narrow channel.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.04a
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• pp.204-211
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• 1998

Floors in a structure are often subject to periodic forces which induce excessive oscillations. For control of such oscillations, TMDs(Tuned Mass Dampers) have been widely used and prooved effective. But it is very difficult to estimate the natural frequency of a TMD when it is installed to a structure. Therefore to achieve the TMD properties that are required for satisfactory performances of the structure, it is necessary to tune the TMDs to the optimal state. This paper is intended to suggest the efficient tuning method for simple and economically designed TMDs and to investigate the validity of the method by installing TMDs to a real structure.

• Journal of the Korean Chemical Society
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• v.38 no.3
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• pp.246-253
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• 1994

The simultaneous analysis of 11 semi-volatile organic acid compound which are listed as priority pollutants by EPA, were performed by GC/MS-SIM(selected ion monitoring). Two extraction procedures, sonication extraction and Soxhlet extraction, were studied as an extraction and concentration method for priority pollutants in soil. Accurecy and precision of the methods were measured by the calculation of mean recovery, mean relative standard deviation, and method detection limit. Finally, limitations and prospects were discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.8
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• pp.589-596
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• 2008

An orifice type of aerodynamic lens is generally used to focus nanoparticles. However, it is impossible to focus particles smaller than 10nm in air due to flow instability of fluid in a lens. In this study, we propose a new converging-diverging type of the aerodynamic lens capable of focusing particles of 5-50nm in air. Designing factors of the lens configurations is also extracted and explained in detail through a numerical simulation. It was demonstrated that the aerosols are delivered from the entrance to the downstream of the lens system with 90% transmission efficiency. The final beam diameters are shown to be more or less 1mm in the range of particle size.

• Solar Energy
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• v.12 no.2
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• pp.51-61
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• 1992

A numerical study on the Trombe wall system, a kind of passive solar systems, has been peformed. The system is modelled as the 2-dimensional steady laminar flow with the natural convection. The PHOENICS code was employed to analyse the performance variation due to the change in the geometrical factor. The mass flow rate and the maximum temperature are changed by the variations in the width of the vents, the width between the window and the wall, and the location of the vents. And there exists the optimal condition to maximize the utilization factor. Further precise analysis has been performed to show the optimal geometry with regard to the above three factors.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.10a
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• pp.49-54
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• 1993

The nonlinear dynamic characteristics of a two-degree-of-freedom beam-mass structure is investigated. The flexible L-shaped structure with a two-to-one internal resonance is subject to a primary resonance and the resulting planar dynamic responses are examined. A quadratic damping, which has been avoided to use because of the difficulties in the analysis, is considered to take into account the effect of viscous damping due to the surrounding fluid. The method of multiple scales is used to determine first-order approximations to the solutions. Force-response and frequency-response curves are generated.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.427-434
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• 2003

In this study, the control performances of Tuned Mass Damper (TMD) and Tuned Liquid Column Damper (TLCD) are evaluated and compared for seismically excited structures. Results show that TLCD is more effective than TMD for interstory drift control while TLCD is as effective as TMD for acceleration control. In special, it is shown that interstory drifts are maximally controlled in lower floors and accelerations are reduced most in upper floors. This indicates that TLCD is an effective controller for earthquake-induced structures in terms of structural safety as well as serviceability.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1440-1446
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• 2012

This paper presents an experimental study of heat transfer and pressure drop characteristics of supercritical carbon dioxide with PAG inside a horizontal microfin tube. Heat transfer coefficient and pressure drop gradients were measured at 10 MPa in pressure and 520 kg/$m^2s$ in mass flux with variation of PAG mass concentration from 0.06% to 2.26%. The tendencies of both heat transfer and frictional pressure drop characteristics show the same as those of pure $CO_2$ up to 0.3% in PAG mass concentration. In case of 2.26% in PAG mass concentration, measured heat transfer coefficients showed 50% lower than those of pure $CO_2$ near the pseudocritical temperature and measured frictional pressure drop gradients show 1.6 times higher in comparison with those of pure $CO_2$ at $60^{\circ}C$ in $CO_2$ bulk temperature.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.2
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• pp.1-8
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• 1999

The present paper describes an approximation for estimation of earthquake-induced hydrodynamic loads in rigid storage tank which accelerated in horizontal direction. The storage tank is vertically cylindrical, and the sectional shape may be circular, rectangular or irregular. The solution for harmonic excitation is studied based on velocity potential theory, and then the time domain solution for earthquake is obtained by using design response spectrum. As a result, earthquake load is influenced primarily by the inertia force of high frequency effective mass of the storage tank, responding to the characteristics of design response spectrum, tank sectional shape, and the ratio of tank base length to depth. Earthquake-induced hydrodynamic loads in rigid storage tank can be effectively obtained by using the high frequency approximation method in case of quite large, or small ratio of the tank base length to water depth.

• Proceedings of the KHEEA Conference
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• 2002.08a
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• pp.5-19
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• 2002

재한국, 1995년제일차출대국가제정적가정과교육과정. 지후, 한국적가정과교육과정경마료7차적수정여개혁과정. 재차과정중, 가정과정불단지추극출신, 기과목명칭재변화, 필수자선 등 선과성질야재변화, 과치함축, 여기술과정합. 이차, 가정과변위남녀생공수적과목, 저취순응료사회발전적수요. 종한국적교육과정래간, 1년급도10년급시국민공용기본교육계단, 11년급도12년급시자선교육계단. 거차, 가정과교육과정적접배위여하 : 소학(5~6학년)위실과, 중학화고중(7~10학년)위"기술.가정", 고중(11~12학년)위"가전과학". 장종2003년개시실시적가정과과시안배위여하 : 소학각2과시, 7~12학년시각2.3.3.3과시, 11~12학년위6개등차. 최근, 청소년문제, 교육환경, 상시인성, 가정파양, 소비과잉, 학대아동, 등사회문제도근가정생활유착밀절적연계, 인차, 재반지교육중, 가정교육응수중시. 단시, 실제상병불시여차. 작위교육주체적교사화부모도몰유인식도저개실정. 인차, 가정학자여교사유심요주근지거연구가정교육. 우기시, 유필요근중국, 일본, 등저사아주국가호상교류화합작적과정중거탐색가정교육적안정발전. 하면파미래가정학육발전적방향건의여하 : 1) "가정" 과시이가정과위연구대상적가정학적독립적연구요영역. 가정경적연구감상시 "가정", 타이가정생활질량적제고위기연구목적. 인차, 재가정교육중, 과목적명칭명명위 "기술. 가정", "가정일반". "가사" 시부합리적. 이응위 "가정" 2) 가정교육웅사중시성각색적변환, 직업적인직변고적각도출발, 사소학도고중분개위필수화선수과, 유남녀생공수. 3) 가정과과시재축점축단. 도시유우교육과정적축단이인기적피면불료적현상. 단시고 여가정과시실천, 실험성과목응보장기최저적과시, 최기마필수유지현재적과시. 4) 향래, 한국적가정교육과정기이가정과위기본철학배경화리념, 우급시파국가교육과정적배경화이념, 가정학적발전동태반영재교육과정중, 즉강조즘요교. 단시, 경력료반복적변혁지후, 최근, 각중시즘양거배양학생적십 요 양적능력여가치. 인차, 가정교육파교육목라방재즘루거제고가정생활적질량, 즘루거호조화가정생활화직업생활, 즘양거개발합리지해결화실천가정생활적가치관. 5) 최근, 가정교육파교육방향화목라방재거배양학생작위독립적개인, 작위가족적성원, 작위사회성원래주인생도로적능력. 인차, 가정교육이인적생활위중심. 우거섭급학생재성장과정중소우도적문제,재거포괄재가정화사회생활중소우도적문제. 즉거배양해결가정생활중소우도적소유적 문종적종합능력. 6) 가정과재교학방법화교학평개상, 응채용실험, 실습, 관찰 등방식, 응반체험성, 실천성경험. 위차, 응필편기험적실험, 실습설비. 7) 확정교육과정편제적치후, 응제고일반교육학자적참여율, 가정교육학자응적극참여 제정교청정책적유관교육적각종위원회. 재제정정책적과정중각진소능, 적극제출건고성적의황. 8) 한, 중, 일 삼국권원층립가정교육과정도작사, 위삼국교육과정적량호발전주공헌.