• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.29.1-29.1
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• 2011

쌍성 중에서 관측자의 시선방향과 두 별의 공전면이 거의 일치할 경우에 두 별이 서로 식(eclipse)을 일으키며 밝기가 주기적으로 변하는 항성계를 식쌍성이라고 한다. 같은 원리로 행성이 별의 표면을 가로질러 횡단하면서 별빛을 가려 어두워지는 경우가 있는데, 이러한 방법에 의해 발견된 행성을 transit 행성이라고 한다. Transit 행성은 질량비가 매우 작은 쌍성계 (태양-목성의 경우 약 0.001)로 생각할 수 있기 때문에, 식쌍성의 분석방법을 이 행성계를 이해하기 위한 도구로 사용할 수 있다. 식쌍성 연구는 이전에 주류를 이루었던 질량, 반경, 광도 등과 같은 천문학적 기본변수의 결정연구에서 보다 정밀한 다파장 관측에 의한 특이현상의 검출과 분석 연구로 점차 변화해 가고 있다. 이 연구에서는 근접쌍성계의 여러 특이현상 중에서 광도와 궤도 공전주기 변화를 보이는 쌍성들의 최근 연구결과를 제시하고자 한다. 이와 더불어, 식쌍성의 분석방법을 활용한 쌍성계 주위를 공전하는 외계행성계 (circumbinary planetary system)의 탐색 및 transit 행성계의 물리량 도출에 대하여 논의하고자 한다.

• Fire Science and Engineering
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• v.25 no.2
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• pp.126-131
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• 2011

This study is intended to understand mass loss rate and air entrainment rate of the whirl fire by height of fire source. Liquid fuels were methanol and n-Heptane which are used in many studies of whirl fire. Size of vessel was 100 mm ${\times}$ 100 mm ${\times}$ 50 mm and the vessel was made by stainless steel. When height of fire source changed from 0 cm to 30 cm, air entrainment rate showed the fastest in case of 0 cm. And in the same height of fire source, average and maximum air entrainment rate showed the fastest in 30 cm of anemometer. From the results of whirl fire for methanol and n-Heptane, mass loss rate and air entrainment rate of n-Heptane was found to faster 1.33 to 1.58 times and 4.38 to 5.44 times compared with methanol, respectively. Consequently, mass loss rate and air entrainment rate in whirl fire was able to identified decrease as height of fire source increases and the higher the heating value, increases the that's value.

• Journal of ILASS-Korea
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• v.1 no.1
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• pp.63-75
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• 1996

The purpose of this study is to investigate the break-up characteristics by taking advantage of a two-phase coaxial nozzle. Air and water are utilized as working fluids and the mass ratio air/water has been controlled to characterize the atomization, diffusion and development of mixing process. By way of a photographic technique, conventional developing structures and diffusion angles have been analyzed systematically with variations of mass ratios. The turbulent flow components of the atomized particles were measured by a two channel LDV system and the data were treated by an on-lined measurement equipment. According to the photographic results the spreading angles decreased because the axial inertia moment was relatively higher than the lateral one with respect to the increase of mass ratio. It is found the jet flow diffuses linearly in a certain limit region while the atomizing characteristics, in terms of the distributions of particle diameters did not show particular differences. It may be expected that these fundamental results can be used as reference data in studying the atomization, breakup and diffusions.

• The Korean Journal of Zoology
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• v.6 no.2
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• pp.6-10
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• 1963

가물치( Ophicephalus argus CANTOR) 2 년생(168$\pm$4g)107마리를 대조군과 실험적으로 나누고 실험군에는 일시에 2.9mg/kg 체동의 potassium cyanide을 배근에 직접 주사하였다. 약물 처리후 시간의 경과에 따라 나타나는 Albumin/Blbulin(A/G)비, 총혈청단백질량, hematocrit 비 및 간장 및 신장의 중량변화를 측정하였다. 약물 처리 직후는 A/G 비 , 총혈청단백질량 및 hematocrit 비는 각각 현저하게 감소되었으나 많은 시간이 경과함에 따라 점차 증가되어 228시간이후는 거의 대조군과 그것과 가까운 결과를 얻었다. 그러나 간장과 신장의 중량은 약물 처리 직후는 오히려 약간 증가되는 상태였으나 , 48시간이후 급히 감소되었다가 점차 역시 대조군과 가까운 결과를 나타냈다. 이상의 결과로서 KCN가 어류의 호흡 억제작용뿐만 아니라 단백질대사에도 영향을 미치는 것으로 생각된다.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.5
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• pp.757-762
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• 2013

The purpose of this study is to compare and evaluate the change of Body Mass Index(BMI) and body composition after having performed vibration exercise equipment at different ground conditions. The subjects were divided into 4 groups; Standing Group(SG)(n=10) and Horseback riding Group(BG)(n=10), Four point kneeling Group(FG)(n=10), Complex position Group(CG)(n=11). The period of intervention was for four weeks. Such as BMI and Waist Hip Ratio(WHR), Body Fat Ratio(BFR) were measured before and after exercise. The results from the above three measurements, only the CG showed significant differences. We were able to confirm that obesity change through complex position combines vibration exercise.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.285-290
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• 1992

기계 구조물의 과도한 진동은 기계의 성능 및 수명에 나쁜 영향을 미치며 기계및 부품의 파괴까지 유발하게 되는 원인이되므로 이를 제진하기위한 각종 방법이 오래전부터 연구되고 있다. 본 연구에서는 현재까지 진행된 충격식 댐퍼의 이론을 기초로 한 사이클당 두번의 충돌이일어난다는 가정하에, 파라메타 의 변화에따른 최적 감쇠특성을 얻기위한 최적간극과 최적 질량비를 쉽게구할 수 있는 식을 유도하였다. 그리고, 실험에 의하여 공진상태에 있어서 불의 충격력에 의한 감쇠특성을 조사하였고, 이론으로구한 식과 비교 검토함으로서, 실제 현장등에서 간편하게 근사식을 이용하여 최적조건을 구하고, 이 자료를 기초로하여 설계, 제작시 보다 간편하게 사용할 수 있도록 하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.5
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• pp.22-31
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• 2018

In this study, numerical simulations were performed to determine the dynamic characteristics of a pintle nozzle, with changes to the chamber boundary conditions. To apply movement, to the pintle, the nozzle and pintle were created separately by an auto-grid generation program using an overset grid method. The chamber boundary conditions were selected between a constant mass-flow rate condition and a propellant burn-back condition. The pressure and thrust characteristics of the constant mass-flow rate condition were determined by changing the ratio of the mass-flow rate in the inlet. The propellant burn-back condition was considered by formulation of the combustion rate. The burn-back conditions represented nonlinear phenomena, unlike the constant mass flow rate, and a small flow rate resulted in a large change in the chamber pressure.

• Journal of The Korean Astronomical Society
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• v.10 no.1
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• pp.23-30
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• 1977

We have collected times of minimum light available in the literature for WZ Andromedae and analyzed the nature of the period variations. The O-C diagram of WZ And clearly shows that two abrupt changes near JD 2418000 and JD 2435000 are deduced by dp/p=$+4.24{\timesa}10^{-6}$ and dp/p=$-2.46{\times}10^{-6}$, respectively. For these period changes, we have introduced the equations which represent mass exchange in the close binery systems given by Biermann and Hall (1973), and the computation yieleled a mass flow of $7.42{\times}10^{-5}M$. from the hotter component to the cooler one. Due to the amount of mass flow, the period decrease may also be calculated. The theoritical new period after JD 2435000 became 0.69565858 days, which is in good agreement with the value 0.69566034 days found in the O-C diagram. In this computation, the mass ratio of WZ And suggested that the hotter star is the filling its Rochclooe, and thus WZ And is in Paczynski's stage II.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.683-688
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• 2007

Water flow into unsaturated soils is most often modeled by Richards equation consisting of the mass conservation law and Darcy's law. Three standard forms of Richards equation are presented as the head (${\Psi}$)-based form, the moisture content (${\theta}$) based form, and the mixed form. Numerical solutions of these partial differential equations with highly nonlinear terms can cause poor results along with significant mass balance errors. The numerical solution based on the mixed form of Richards equation is known that the mass is perfectly conserved without any additional computational efforts. The aim of this study is to develop fully implicit numerical scheme of Richards equation for one-dimensional vertical unsaturated flow in homogeneous soils using the finite difference approximation, and then to perform sensitivity analysis of infiltration to the variations in the unsaturated soil properties and to different soil types.

• Journal of the Korean earth science society
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• v.41 no.1
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• pp.1-18
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• 2020

This study presented the effects of the assumed mass-size relationship for snow on the simulated surface precipitation by using cloud microphysics parameterizations in Weather Research and Forecasting (WRF) model. The selected cloud microphysics parameterizations are WRF Double-Moment 6-class (WDM6) and WRF Single-Moment 6-class (WSM6) in the WRF model. We replaced the mass-size relationship for snow in WDM6 and WSM6 with Thompson's mass-size relationship retrieved from measurement data. The sensitivity of the modified WDM6 and WSM6 was tested for the idealized 2-dimensional squall line and winter precipitation system over the Korean peninsula, respectively. The modified WDM6 and WSM6 resulted in the increase of graupel/rain mixing ratios and the decrease of snow mixing ratio in the low atmosphere. The changes of hydrometeor mixing ratio and surface precipitation could be due to the collision-coalescence process between raindrops and snow and the graupel melting process.