• 천문학회보
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• 제37권1호
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• pp.80.2-80.2
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• 2012

We firstly present the unified Far-UV continuum map of the Taurus-Auriga-Perseus (TPA) complex, one of the largest local associations of dark cloud located in (l, b)=([152,180], [-28, 0]), by merging both FIMS and GALEX. The FUV continuum map shows that dust extinction correlate well with the FUV around the complex. It says strong absorption in the dense Taurus cloud and Auriga cloud. Although the column density of Perseus and California cloud is similar to Taurus' and Auriga's, Perseus and California cloud do not show strong absorption in FUV because they are more distant than Taurus and Auriga cloud. We also present the dust scattering simulation based on Monte Carlo Radiative Transfer technique. Through the result of Monte-Carlo dust scattering simulation and comparing the result with FIMS-GALEX unified map we gain deeper understanding related to the spatial dust distribution of TPA region. As a preliminary result of the simulation we present the most probable front face, thickness, albedo, and asymmetry factor in this region, respectively. Through this work we can show a certain inclination of the spatial dust distribution. During this study we have developed the FUV dust scattering simulation code using Monte-Carlo method. We expect that it will be generally used to simulate dust scattering in the Galaxy.

• 천문학회보
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• 제39권1호
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• pp.60.2-60.2
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• 2014

The dust cloud around ${\lambda}$-Orionis is seen to be circular symmetric with the large angular extent (${\sim}8^{\circ}$). However, whether the three dimensional structure of the cloud is shell or torus ring is not yet fully resolved. We studied the structure of the dust cloud using a three-dimensional Monte-Carlo simulation code, MoCafe (Monte Carlo radiative transfer). The dust density structure of the cloud was inferred based on the star-count method. We assumed that the cloud is a spherical shell or a torus ring and calculated the radial profiles of scattered light originating from a central OB association. Comparison of the results with the S2/68 ultraviolet observations indicates that the cloud is a spherical shell. We also compared the Av map around ${\lambda}$-Orionis with the optical depth obtained based on the star-count.

• 천문학회지
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• 제31권2호
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• pp.161-171
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• 1998

We have mapped about 1.5 square degree regions of Lynds 1299, a well isolated dark cloud in the Outer Galaxy (l = $122^{\circ}$, b = $-7^{\circ}$), in the J = 1- 0 transition of $^{12}CO$ and $^{13}CO$ with the 13.7 m radio telescope at Taeduk Radio Astronomy Observatory (TRAO). We found that there are two velocity components in the molecular emission, at $V_{LSR} = -52 km S^{-1}$ (Cloud A) and -8.8 km $s^{-1}$ (Cloud B), respectively. We have derived physical parameters of two molecular clouds and discussed three different mass estimate techniques. We found that there are large discrepancies between the virial and LTE mass estimates for both clouds. The large virial mass estimate reflects the fact that both are not gravitationally bound. We adopt the mass of $5.6 {\times}10^3 \;M{\bigodot}$ for Cloud A and $1.2{\times}10^3 \;M{\bigodot}$) for Cloud B using conversion factor. Cloud A is found to be associated with a localized star forming site, and its morphology is well matching with that of far-infrared (FIR) dust emission. It shows a clear ring structure with an obvious velocity gradient. We suggest that it may be a remnant cloud from a past episode of massive star formation. Cloud B is found to be unrelated to Cloud A (d = 800 pc) and has no specific velocity structure. The average dust color temperature of the uncontaminated portion of Cloud A is estimated to be 24$\~$27.4 K. The low dust temperature may imply that there is no additional internal heating source within the cloud. The heating of the cloud is probably dominated by the interstellar radiation field except the region directly associated with the new-born B5 star. Overall, the dust properties of Cloud A are similar to those of normal dark cloud even though it does have star forming activity.

• 한국안전학회지
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• 제19권1호
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• pp.137-140
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• 2004

최근 산업현장에서는 제품의 품질과 성능을 향상시키기 위해 나노 기술로 나아가는 추세에 있으며, 이러한 연구들로 인해 많은 화학제품의 원료들이 더욱 미세한 상태로 가공 및 취급되어지고 있다. 이에 분진의 특성상 그 위험성이 따라 증가하고 있으므로, 분진폭발의 발생을 예방하기 위해 분진운의 발화온도와 폭발한계산소농도 등을 찾아내는 것은 매우 중요한 일이다. 따라서 본 연구에서는 현재 국내에서 생산되고 있는 Hydroxy Propyl Methyl Cellulose (HPMC)을 가지고 실험을 하였으며, 생산 및 취급과정에서 뜨거운 표면으로부터 발생될 수 있는 화재 및 폭발을 예방하고자, Godbert-Greenwald Furnace장치로 실험하였다. 그 결과 분진 입자의 크기가 작아짐으로서 발화온도는 낮아지는 경향을 나타내었으며, 분진입자의 크기가 45${\mu}m$에서 HPMC 분진운의 최소발화온도는 364$^{\circ}C$로 나타났으며, 폭발한계산소 농도는 11%로 나타났다.

• 천문학회보
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• 제42권2호
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• pp.48.3-49
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• 2017

Interplanetary space of the solar system contains a large number of dust particles, referred to as Interplanetary Dust Particles (IDPs) cloud complex. They are observable through meteors and zodiacal lights. The relative contribution of possible sources to the IDPs cloud complex was an controversial topic, however, recent research (Yang & Ishiguro, 2015 and references therein) suggested a dominance of cometary origin. In this study, we numerically investigated the orbital evolution of cometary dust particles, with special concerns on different evolutionary tracks and its consequences according to initial orbits, size and particle shape. The effect of dust particle density and initial size-frequency distribution (SFD) were not decisive in total cloud complex mass and mass supply rate, when these physical quantities are confined by observed zodiacal light brightness and dust particle SFD at 1 au. We noticed that, if we assume the existence of fluffy aggregates discovered in the Earth's stratosphere and the coma of 67P/Churyumov-Gerasimenko, the required mass supply rate decreases significantly. We also found out that close encounters with planets (mostly Jupiter) are the dominating factor of the orbital evolution of dust particles, as the result, the lifetime of cometary dust particles are shorter than Poynting-Robertson lifetime (around 250 thousand years). As another consequence of severe close encounters, only a small fraction of cometary dust particles can be transferred into the orbit < 1 au. This effect is significant for large size particles of ${\beta}$ < 0.01. The exceptional cases are dust particles ejected from 2P/Encke and active asteroids. Because they rarely encounter with Jupiter, most dust particles ejected from those objects are governed by Poynting-Robertson effect and well transferred into the orbits of small semimajor axis. In consideration of the above effects, we directly estimated probability of mutual collisions between dust particles and concluded that mutual collisions in the IDPs cloud complex is mostly ignorable, except for the case of large sized particles from active asteroids.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2012년도 추계학술대회
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• pp.442-444
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• 2012

이중 편광 라이다로 계측된 에어로솔과 구름의 편광소멸도를 분석하였다. 구름과 먼지, 그리고 구형 에어로솔에 대한 1064 nm와 532 nm의 파장별 후방산란비의 비(RDR)를 각각 비교하였다. 구형 에어로솔의 경우 RDR 값은 1.5~6, 먼지는 0.98~4, 그리고 구름의 경우에는 0.7~1.77의 값을 나타내었다. 먼지의 수직분포와 상대습도를 비교하였다. 평균적으로 30~60%의 상대습도가 먼지층에 분포하였다. 하지만 70%이상의 값도 빈번히 계측되었으고, 이의 경우 먼지에 대한 RDR 값은 2~4 정도로 증가하였다.

• 천문학회지
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• 제29권2호
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• pp.107-117
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• 1996

We have studied the star forming activities and dust properties of Lynds 1251, a dark cloud located at relatively high galactic latitude. Eleven IRAS point sources identified toward Lynds 1251 are discussed. Estimate of stellar masses, and far-infrared lumnosities of the young stars associated with two prominent IRAS point sources imply that these are T-Tauri stars with masses smaller than $0.3 M_\bigodot$. The low dust temperature of 27 K and low ratio of FIR emission to hydrogen column density are probably due to the lack of internal heating sources. Presumably two low mass young stars do not have enough energy to heat up the dust and gas associated. The dust heating is dominated by the interstellar heating source, and the weaker interstellar radiation field can explain the exceptionally low dust temperatures found in Lynds 1251. The estimated dust mass of Lynds 1251 is just $\~1M_\bigodot$, or about 1/1000 of gas mass, which implies that there must be a substantial amount of colder dust. The infrared flux at $100{\mu}m$ is matching well with $^{13}CO$ peak temperature, while the $^{12}CO$ integrated intensity is matching with the boundary of dust emission. Overall, the dust properties of Lynds 1251 is similar to those of normal dark clouds even though it does have star forming activities.

• 천문학회보
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• 제41권2호
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• pp.51.1-51.1
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• 2016

We revisited a recent dust emission observed at a main-belt asteroid P/2010 A2 in terms of dynamical properties of dust particles and large fragments. This is a continued research that we made a presentation at the Korean Astronomical Society 2016 Spring Meeting, but we have strengthened the dynamical analysis of the ejecta to afford the conclusive evidence for the enigmatic phenomenon. We thus constructed a model to reproduce the morphology of the dust cloud based on the dust dynamics, and succeeded in reproducing the observed morphologies in different epochs over several years. For further analysis, we reconstructed the proper motion of large fragments with respect to the dust emission source estimated from our dust model. We found that (i) the dust cloud morphologies and (ii) observed trajectories of fragments are reasonably explained only when we assumed that both were ejected from a position where no object was detected from any observations. This result suggests that the original body was shattered by an impact, leaving only debris into space. In this presentation, we will compare our results with impact laboratory studies and provide an impact interpretation of the P/2010 A2 activity.

• 천문학논총
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• 제24권1호
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• pp.43-51
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• 2009

이 연구에서는 임의의 밀도 분포를 갖는 성간 먼지 구름에 의해 산란되는 산란광을 분석할 수 있는 몬테카를로 시뮬레이션 코드를 개발하였다. 개발된 코드의 신뢰성을 확보하기 위해 구 대칭의 성간먼지 구름의 중심에 별이 있고, 별빛이 얼마만큼 산란되어 나오는 지 계산하여 Code (1973)의 결과와 비교하였으며, Code의 근사식과 매우 잘 일치하는 결과를 주는 것을 확인하였다. 이 코드는 우리 은하뿐만 아니라 외부은하의 경우에도 손 쉽게 확장이 가능하다. 개발된 코드는 과학위성 1호로 관측된 원자외선 연속복사광의 분석에 적용하여 성간먼지 구름의 특성과 우리 은하의 복사장의 분포를 연구하는 데 사용하고자 한다.

• 천문학회보
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• 제37권2호
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• pp.98.2-98.2
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• 2012

We firstly present the unified Far-UV continuum map of the Taurus-Auriga-Perseus (TPA) complex, one of the largest local associations of dark cloud located in (l, b)=([154,180], [-28, -2]), by merging both FIMS and GALEX. The FUV continuum map shows that dust extinction correlate well with the FUV around the complex. It shows strong absorption in FUV toward the dense Taurus cloud while it does not in California cloud. It turned out that it is related to the relative location of each cloud and Perseus OB2 association. We also present some results of dust scattering simulation based on Monte Carlo Radiative Transfer technique (MCRT). Through this dust scattering simulation, we have derived the scattering parameter for this region, albedo(a)=$0.42^{+0.05}{_{-0.05}}$, asymmetry factor(g)=$0.47^{+0.11}{_{-0.27}}$. The optical parameters we obtained seem reasonable compared to the theoretical model values ~0.40 and ~0.65 for the albedo and the phase function though the phase function is rather small. Using the result of simulation, we figured out the geometries of each cloud in the complex region, especially their distances and thicknesses. Our predictions from the results are in good agreement with the previous studies related to the TPA complex. For example, the Taurus cloud is within ~200pc from the Sun and the Perseus seems to be multi-layered, at least two. The California cloud is more distant than the other cloud on average at ~350 pc and Auriga cloud seems to be between the Taurus cloud and the eastern end of the California cloud. We figured out that across the TPA complex region, there might be some correlation between the LSR velocity and the distance to each cloud in the complex.