• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 1993년도 한국우주과학회보 제2권2호
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• pp.18-18
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• 1993

According to the CCD photometric studies, the color distributions of globular clusters with collapsed cores, which are characterized by a power law cusp in thier surface brighness pronto, become bluer toward their centers, but this is not the case in the flat core clusters which are fit by the King model. To test the statistical implication of the color distribution within globular clusters, we built the sample dusters which follows the surface brightness pofile of the King model and power law cusp profile with the Sandage's standao luminosity function for M3 and the Salpter's initial mass functions. On the results from simulations based on the uniform random number generation the color gadients within globualr dusters mar be not likely to come from the statistical random distributions of stars but from the dynamical process on the cluster evolution.

• 천문학회지
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• 제28권2호
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• pp.245-253
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• 1995

We have analyzed the time series of Ca II H,K and ${\lambda}8498$ line profiles taken for a sunspot (SPO 5007) with the Echelle spectrograph attached to Vacuum Tower Telescope at Sacramento Peak Solar Observatory. Each set of spectra was taken simultaneously for 20 minutes at a time interval of 30 seconds. A total of 40 photographic films for each line was scanned by a PDS at Korea Astronomy Observatory. The central peak intensity of Ca II H ($I_{max}$), the intensity measured at ${\Delta}{\lambda}=-0.1{\AA}$ from the line center of ${\lambda}8498(I_{{\lambda}8489})$, the radial velocity ($V_r$) and the Doppler width (${\Delta}{\lambda}_D$) estimated from Ca II H have been measured to study the dynamical behaviors of the sunspot chromosphere. Fourier analysis has been carried out for these measured quantities. Our main results are as follows: (1) We have confirmed the 3-minute oscillation being dominant throughout the umbra. The period of oscillations jumps from 180 sec in the umbra to 500 to 1000 sec in the penumbra. (2) The nonlinear character of the umbral oscillation is noted from the observed sawtooth shaped radial velocity fluctuations with amplitudes reaching up to $5{\sim}6\;km/sec$. (3) The spatial distribution of the maximum powers shows that the power of oscillations is stronger in the umbra than in the penumbra. (4) The spatial distributions of the time averaged < $I_{max}$ > and < $V_r$ > across the spot are found to be nearly axially symmetric, implying that the physical quantities derived from the line profiles of Ca II H and ${\lambda}8498$ are inherently associated with the geometry of the magnetic field distribution of the spot. (5) The central peaks of the CaII H emission core lead the upward motions of the umbral atmosphere by $90^{\circ}$, while no phase delay is found in intensities between $I_{max}$ and $I_{{\lambda}8498}$, suggesting that the umbral oscillation is of standing waves.

• 복식
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• 제62권5호
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• pp.1-15
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• 2012

In a fast changing postmodern society, contemporary fashion is becoming more complicated and ambiguous along with other genres of art than ever before. This phenomenon reigning as a sociocultural paradigm can be defined as 'indeterminacy' and it means 'undecidability'. The purpose of this study is to clarify and analyze the indeterminate characteristics of contemporary fashion reviewing the theoretical background and the architectural formativeness as a comparative research. The core idea of deconstructivism dismantles a causal relationship between function and form in fashion and the conventional notion about clothes. Complexity theory, which is the study of chaotic dynamical systems, suggests the creative idea and concept of infinite possibilities on a formative method. Meanwhile, catastrophe theory of discontinuous change can be used as interpretative strategies for the process of deconstruction and reconstruction. As a result of this study, the indeterminacy of fashion can be analyzed into five semantic categories: irregularity, immateriality, randomness, complexity and changeability. The intrinsic value of the indeterminacy in contemporary fashion is the interaction with a sociocultural ideology and a technological environment as well as an expansion of formative expression. To conclude, it can be said that the indeterminacy in fashion is a new interpretation of the relationship among body and space, clothes and society.

• 설비공학논문집
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• 제11권4호
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• pp.549-559
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• 1999

An experimental study was peformed to measure the viscosity of microencapsulated PCM slurries as the functions of its concentration and temperature, and also influence to its fluid dynamics. For the viscosity measurement, a rotary type viscometer, which was equipped with temperature control system, was adopted. The slurry was mixed with water and Sodium Lauryl Sulphate as a surfactant by which its suspended particles were dispersed well without the segregation of particles during the experiment. The viscosity was increased as the concentration of MicroPCM particle added. The surfactant increased 5% of the viscosity over the working fluid without particles. Experiments were proceeded by changing parameters such as PCM particles'concentration as well as the temperature of working fluid. As a result, a model to the functions of temperature for the working fluid and its particle concentration is proposed. The proposed model, for which its standard deviation shows 0.8068, is agreed well with the reference's data. The pressure drop was measured by U-tube manometer, and then the friction factor was obtained. It was noted that the pressure drop was not influenced by the state of PCM phase, that is solid or liquid in its core materials at their same concentration. On the other hand, it was described that the pressure drop of the slurry was much increased over the working fluid without particles. A friction factor was placed on a straight line in all working fluids of the laminar flow regardless of existing particles as we expected.

• 한국대기환경학회지
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• 제23권6호
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• pp.640-652
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• 2007

The MM5, RAMS and WRF, meteorological models have provided the dynamical parameters as inputs to air quality model. A major content of this study is that significant characteristics of three models for high-ozone occurrence analyze for surface wind and air temperature fields and compare with observation data in Seoul metropolitan area. An analysis of air temperature field revealed that location of core in high temperature of MM5 and WRF differed from that of RAMS. MM5 and WRF indicated high temperature in Seoul but RAMS represented it on the outskirts of Seoul. MM5 and WRF were underestimated maximum temperature during daytime but RAMS simulated similar value with observation data. Surface wind field with three models, it was shown many differences at horizontal distribution of wind direction. RAMS indicated weak wind speed in land and strong sea breeze at coastal areas than MM5 and WRF. However wind speed simulated by three model were overestimated during both daytime and nighttime.

• 천문학회보
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• 제43권2호
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• pp.33.2-33.2
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• 2018

Fossil galaxy cluster has a dominant central elliptical galaxy (${\Delta}M12$ >2 in 0.5Rvir) embedded in highly relaxed X-ray halo, which indicates dynamically stable and passively evolved system. These features are expected as a final stage of the cluster evolution in the hierarchical structure formation paradigm. It is known that Abell 2261(A2261 hereafter) is classified as a fossil cluster, but has unusual features such as a high central X-ray entropy (i.e., non-cool core system), which is not expected in normal fossil clusters. We perform a kinematic study with a spectroscopic data of 589 galaxies in the A2261 field. We define cluster member galaxies using the caustic method and discover a new second bright galaxy at ~1.5 Rvir (nearly the splash-back region). It implies the current fossil state of the cluster can break in the near future. In addition, with three independent substructure finding methods, we find that A2261 has many substructures within 3 Mpc from the center of the cluster. These findings support that A2261 is not in a dynamically stable state. We argue that A2261 is in a transitional phase of dynamical evolution of the galaxy cluster and maybe previously defined fossil cluster does not mean the final stage of the evolution of galaxy clusters.

• Applied Microscopy
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• 제39권4호
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• pp.341-348
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• 2009

본 연구에서는 평균 입자크기가 100 nm인 $BaTiO_3$ 나노 결정체의 결정 구조를 전자회절을 이용하여 분석하였다. 전자회절을 이용하여 구조분석을 수행하기 위해 PED 장치의 실험인자를 보정한 후, PED와 일반적인 SAED를 이용하여 전자회절도형을 획득하여 비교 분석을 수행하였다. $BaTiO_3$ 나노 결정체에 대해 PED를 이용한 구조분석을 수행한 결과, $BaTiO_3$ 나노입자는 상온에서 입방정계와 정방정계의 구조가 혼합되어 존재함을 알 수 있었다. 또한 이론적 계산을 통해 두 상이 혼재된 $BaTiO_3$ 나노입자는 입방정계의 구조가 약 8.5nm의 표면을 형성하고 있는 coreshell 구조를 이루고 있음을 예측할 수 있었다. 이러한 $BaTiO_3$ 나노입자에 대한 입방정계와 정방정계 구조의 각각의 격자상수는 a=3.999${\AA}$과 a=3.999${\AA}$, c=4.022${\AA}$이었다. 이와 같이 일반적인 SAED에 비해 뛰어난 공간분해능과 다중산란 효과를 억제할 수 있는 PED 기법은 복합 나노 구조체의 결정구조분석에 보다 유용한 분석 기술로 활용할 수 있을 것으로 기대된다.

• 대기
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• 제25권3호
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• pp.529-541
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• 2015

Korea Institute of Atmospheric Prediction System (KIAPS) has been developing a global numerial prediction model and data assimilation system. We has implemented LETKF (Local Ensemble Transform Kalman Filter, Hunt et al., 2007) data assimilation system to NCAR CAM-SE (National Center for Atmospheric Research Community Atmosphere Model with Spectral Element dynamical core, Dennis et al., 2012) that has cubed-sphere grid, known as the same grid system of KIAPS Integrated Model (KIM) now developing. In this study, we have assimilated Global Positioning System Radio Occultation (GPS-RO) bending angle measurements in addition to conventional data within ensemble-based data assimilation system. Before assimilating bending angle data, we performed a vertical unit conversion. The information of vertical localization for GPS-RO data is given by the unit of meter, but the vertical localization method in the LETKF system is based on pressure unit. Therefore, with a clever conversion of the vertical information, we have conducted experiments to search for the best vertical localization scale on GPS-RO data under the Observing System Simulation Experiments (OSSEs). As a result, we found the optimal setting of vertical localization for the GPS-RO bending angle data assimilation. We plan to apply the selected localization strategy to the LETKF system implemented to KIM which is expected to give better analysis of GPS-RO data assimilation due to much higher model top.

• 한국지구과학회지
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• 제34권7호
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• pp.645-661
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• 2013

본 연구에서는 2010년 12월 27일부터 28일까지 서울을 포함한 수도권 지역에 많은 강설을 일으킨 사례의 종관적, 열역학적 및 역학적 특징을 조사하였다. 이 사례는 극저기압으로 분류할 수 있는 특성을 지녔다. 분석에 사용된 자료는 지상 및 상층 일기도, 강설량, 해수면온도, 위성사진, 연직프로파일 및 미국 국립환경예측센터의 전구 $1^{\circ}{\times}1^{\circ}$ 재분석자료 등이다. 극저기압은 대기 하층에서 양의 경압성이 강하게 나타나며 925 hPa에 온난이류가, 700 hPa에 한랭이류가 있어 조건부 불안정층이 뚜렷하게 보이는 곳에서 형성되는 것으로 사료된다. 극저기압의 발달기구는 대류권계면 접힘에 의한 성층권 공기의 유입과 그에 따른 위치 소용돌이도의 증가로 하층에 수렴과 저기압성 순환의 유발에 기인한다. 이는 눈구름의 발달로 이어져 서울 지역에는 10 cm, 남부지방에는 최고 20 cm까지 적설을 보였다. 강설의 발달기간동안 상층 500 hPa에는 $-45^{\circ}C$의 한랭핵이 존재하였고 단파골과 지상 기압골간의 위상차도 $3-5^{\circ}$를 이루어 극저기압이 온난역의 저기압성 소용돌이도 이류 지역에서 발달할 수 있었다. 발달의 최성기에는 역학적 대류권계면이 700 hpa까지 하강하였고 위치소용돌이도의 증가로 상승기류도 강화되었다. 전반적으로 강설의 발생과 대류권계면의 파상운동과는 깊은 관련을 보였다. 극저기압이 한반도를 통과하는 동안 대류권계면이 하강하는 지점의 동쪽에 소용돌이도와 상승기류가 강화되었고 동시에 많은 습기가 이류되는 곳에서 강설량도 최대로 나타났다.

• 천문학회지
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• 제33권2호
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• pp.111-121
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• 2000

Many models of globular cluster formation assume the presence of cold dense clouds in early universe. Here we re-examine the Fall & Rees (1985) model for formation of proto-globular cluster clouds (PGCCs) via thermal instabilities in a protogalactic halo. We first argue, based on the previous study of two-dimensional numerical simulations of thermally unstable clouds in a stratified halo of galaxy clusters by Real et al. (1991), that under the protogalactic environments only nonlinear (${\delta}{\ge}1$) density inhomogeneities can condense into PGCCs without being disrupted by the buoyancy-driven dynamical instabilities. We then carry out numerical simulations of the collapse of overdense douds in one-dimensional spherical geometry, including self-gravity and radiative cooling down to T = $10^4$ K. Since imprinting of Jeans mass at $10^4$ K is essential to this model, here we focus on the cases where external UV background radiation prevents the formation of $H_2$ molecules and so prevent the cloud from cooling below $10^4$ K. The quantitative results from these simulations can be summarized as follows: 1) Perturbations smaller than $M_{min}\~(10^{5.6}\;M{\bigodot})(nh/0.05cm^{-3})^{-2}$ cool isobarically, where nh is the unperturbed halo density, while perturbations larger than $M_{min}\~(10^8\;M{\bigodot})(nh/0.05cm^{-3})^{-2}$ cool isochorically and thermal instabilities do not operate. On the other hand, intermediate size perturbations ($M_{min} < M_{pgcc} < M_{max}$) are compressed supersonically, accompanied by strong accretion shocks. 2) For supersonically collapsing clouds, the density compression factor after they cool to $T_c = 10^4$ K range $10^{2.5} - 10^6$, while the isobaric compression factor is only $10^{2.5}$. 3) Isobarically collapsed clouds ($M < M_{min}$) are too small to be gravitationally bound. For supersonically collapsing clouds, however, the Jeans mass can be reduced to as small as $10^{5.5}\;M_{\bigodot}(nh/0.05cm^{-3})^{-1/2}$ at the maximum compression owing to the increased density compression. 4) The density profile of simulated PGCCs can be approximated by a constant core with a halo of $p{\infty} r^{-2}$ rather than a singular isothermal sphere.