• 천문학회지
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• 제43권4호
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• pp.105-113
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• 2010

We study the dynamical evolution of the M87 globular cluster (GC) system using the most advanced and realistic Fokker-Planck (FP) model.By comparing our FP models with both mass function (MF) and radial distribution (RD) of the observed GC system, we find the best-fit initial (at M87's age of 2-3 Gyr) MF and RD for three GC groups: all GCs, blue GCs, and red GCs. We estimate the initial total mass in GCs to be $1.8^{+0.3}_{-0.2}{\times}10^{10}M_{\bigodot}$, which is about 100 times larger than that of the Milky Way GC system. We also find that the fraction of the total mass currently in GCs is 34\%. When blue and red GCs are fitted separately, blue GCs initially have a larger total mass and a shallower radial distribution than red GCs. If one assumes that most of the significant major merger events of M87 have ended by the age of 2-3 Gyr, our finding that blue (metal-poor) GCs initially had a shallower radial distribution supports the major merger scenario for the origin of metallicity bimodality.

• 태양에너지
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• 제15권1호
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• pp.3-11
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• 1995

본 연구는 수평원통내에 물을 체적비($V_l/V_{tot}$) 0.50, 0.91로 각각 장입한 후 물의 조기 과열온도와 벽면 냉각온도를 각각 변화시키면서 내향 응고시켰을 경우, 시간에 따른 상변화물질의 평균온도, 상경계면의 형상, 응고율, 응고에너지 등을 실험적으로 구하여 이를 비교 검토한 것이다. 응고진행시 상경계면은 물의 초기 과열온도가 높을수록 응고초기에 상단부분이 하단부분보다 빠르게 진행되었으나 응고가 진행됨에 따라 상하단의 상격계면 전진속도는 거의 동일하게 나타났다. 동일한 온도조건에서 전과정에 걸친 응고율($M_s/M_{tot}$)은 체적비 0.5인 경우가 0.91인 경우 보다 크게 나타나 수평원통내 물의 내향응고시 물의 체적비($V_l/V_{tot}$) 변화에 의한 영향도 고려하여야 함을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제31권5호
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• pp.1143-1148
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• 2010

We investigated the separation of nitrogen heterocyclic compound (NHC) contained in a model coal tar fraction comprising four kinds of NHC [indole (In), quinoline (Q), iso-quinoline (iQ), quinaldine (Qu)], three kinds of bicyclic aromatic compound (BAC) [1-methylnaphthalene (1MN), 2-methylnaphthalene (2MN), dimethylnaphthalene (DMN) mixture with ten structural isomers (DMNs; regarded as one component)], biphenyl (Bp) and phenyl ether (Pe) by liquid membrane permeation (LMP). A batch-stirred tank was used as the permeation unit. An aqueous solution of saponin and n-hexane were used as the liquid membrane and the outer oil phase, respectively. Yield and selectivity of individual NHC was much larger than that of BAC, Bp and Pe. Increasing the initial mass fraction of the saponin to the membrane solution ($C_{sap,0}$) and the initial volume fraction of O/W emulsion to total liquid in a stirred tank (${\phi}_{OW,0}$) resulted in deteriorating the yield of individual NHC, but increasing the stirring speed (N) resulted in improving the yield of each NHC. With increasing $C_{sap,0}$, the selectivity of each NHC based on DMNs increased. Increasing ${\phi}_{OW,0}$ and N resulted in decreasing the selectivity of individual NHC based on DMNs. At an experimental condition fixed, the sequence of the yield and selectivity in reference to DMNs for each NHC was Q > Qu = iQ > In. Furthermore, we compared LPM method with methanol extraction method in view of the separation efficiency (yield, selectivity) of NHC.

• 공업화학
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• 제30권2호
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• pp.155-159
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• 2019

폐플라스틱 열분해유(WPPO) 유분의 품질향상의 일환으로 WPPO 유분 중에 함유된 파라핀 성분의 회수를 디메틸포름 아마이드(DMF) 평형추출에 의해 검토했다. 원료로서는 WPPO를 단증류하여 회수한 유출온도 $120{\sim}350^{\circ}C$의 유분을, 용매로서는 DMF 수용액을 각각 사용했다. 초기 용매 중의 물의 질량분율($y_{w,0}$)이 증가할수록 추잔유 중의 파라핀 성분($C_{12}$, $C_{14}$, $C_{16}$, $C_{18}$)의 농도는 감소했으나, 초기 용매/원료의 질량비$(S/F)_0$의 증가는 역으로 추잔유 중의 파라핀 성분의 농도를 증가시켰다. $(S/F)_0=10$에서 회수된 추잔유 중의 $C_{12}$, $C_{14}$, $C_{16}$, $C_{18}$ 파라핀 성분의 농도는 원료의 농도에 비해 약 1.37, 2.00, 2.46, 3.13배 각각 높았다. 또한 $y_{w,0}$의 증가와 $(S/F)_0$의 감소는 파라핀 성분의 회수율(추잔유 중의 잔류율)을 급격히 증가시켰다. 본 연구를 통해 회수한 추잔유는 신재생에너지로 사용이 가능할 것이라 기대된다.

• Corrosion Science and Technology
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• 제7권2호
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• pp.112-118
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• 2008

We observed initial rusting process of steel containing Al under wet/dry cyclic condition with NaCl solution film using in situ X-ray diffraction spectroscopy at SPring-8 synchrotron radiation facility. It was found that mass fraction of iron oxides such as ${\alpha}-FeOOH$, ${\beta}-FeOOH$ and ${\gamma}-FeOOH$ varied with Al content. Some kinds of Al oxides were also found at the initial stage of corrosion. Those corrosion products might affect the corrosion process and corrosion rate of the steel.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.48-57
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• 2003

A cylindrical constant volume combustion chamber was used to investigate the flow characteristics at spark plug and the combustion characteristics of homogeneous charge methane-air mixture under various initial pressure, excess air ratio and ignition times in quiescent mixture. The flow characteristics such as mean velocity and turbulence intensity was analyzed by hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer and flame propagation acquired by ICCD camera were used to investigate the effect of initial pressure, excess air ratio and ignition times on pressure, combustion duration, flame speed and burning velocity. Mean velocity and turbulence intensity had the maximum value at 200 or 300ms and then decreased to near 0 value gradually after 3 seconds. Combustion duration, flame speed and burning velocity were observed to be promoted with excess air ratio of 1.1, lower initial pressure and ignition time of 300ms.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2004년도 한국우주과학회보 제13권1호
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• pp.24-24
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• 2004

Using stellar population synthesis techniques, we explore the photometric signatures of white dwarf progenitor dominated galactic halos, in order to constrain the fraction of halo mass that may be locked-up in white dwarf stellar remnants. We first construct a 10＾9 M_sun stellar halo using the canonical Salpeter initial stellar mass distribution, and then allow for an additional component of low-and intermediate-mass stars, which ultimately give rise to white dwarf remnants. (omitted)

• 대한기계학회논문집
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• 제13권6호
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• pp.1310-1320
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• 1989

본 논문에서는 비교적 많은 계산이 수행되어온 수평원관 주위의 상변화 열전달 문제를 예로 들어, 상변화 물질이 유한한 열전도율을 갖는 일정 두께의 원관 주위에 존재할 때의 상변화 문제에 대하여 초기 액상의 영역을 임의로 가정하는 불합리점을 제거하고 문제를 풀 수 있는 수치해석 방법을 제시하고자 한다.

• 제어로봇시스템학회논문지
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• 제10권12호
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• pp.1155-1163
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• 2004

Extracellular signal-regulated kinase (ERK) signaling pathway is one of the mitogen-activated protein kinase (MAPK) signal transduction pathways. This pathway is known as pivotal in many signaling networks that govern proliferation, differentiation and cell survival. The ERK signaling pathway comprises positive and negative feedback loops, depending on whether the terminal kinase stimulates or inhibits the activation of the initial level. In this paper, we attempt to model the ERK pathway by considering both of the positive and negative feedback mechanisms based on Michaelis-Menten kinetics. In addition, we propose a fraction ratio model based on the mass action law. We first develop a mathematical model of the ERK pathway with fraction ratios. Secondly, we analyze the dynamical properties of the fraction ratio model based on simulation studies. Furthermore, we propose a concept of an inhibitor, catalyst, and substrate (ICS) controller which regulates the inhibitor, catalyst, and substrate concentrations of the ERK signal transduction pathway. The ICS controller can be designed through dynamical analysis of the ERK signaling transduction pathway within limited concentration ranges.

• Nuclear Engineering and Technology
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• 제47권7호
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• pp.907-914
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• 2015

The energetic steam explosion caused by contact between the high temperature molten core and water is one of the phenomena that may threaten the integrity of the containment vessel during severe accidents of light water reactors (LWRs). We examined the dependence of steam explosion loads in a typical reactor cavity geometry on selected model parameters and initial/boundary conditions by using a steam explosion simulation code, JASMINE, developed at Japan Atomic Energy Agency (JAEA). Among the parameters, we put an emphasis on the water pool depth that has significance in terms of accident mitigation strategies including cavity flooding. The results showed a strong correlation between the load and the premixed mass, defined as the mass of the molten material in low void zones (void fraction < 0.75). The jet diameter and velocity that comprise the flow rate were the primary factors to determine the premixed mass and the load. The water pool depth also showed a significant impact. The energy conversion ratio based on the enthalpy in the premixed mass was in a narrow range ~4%. Based on this observation, we proposed a simplified method for evaluation of the steam explosion load. The results showed fair agreement with JASMINE.