• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.117-121
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• 2017

We show Akari data, Herschel data and data from the SCUBA2 camera on JCMT, of molecular clouds. We focus on pre-stellar cores within the clouds. We present Akari data of the L1147-1157 ring in Cepheus and show how the data indicate that the cores are being externally heated. We present SCUBA2 and Herschel data of the Ophiuchus region and show how the environment is also affecting core evolution in this region. We discuss the effects of the magnetic field in the Lupus I region, and how this lends support to a model for the formation and evolution of cores in filamentary molecular clouds.

• Proceedings of the KSRS Conference
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• 2001.03a
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• pp.92-97
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• 2001

The intra-annual and interannual variations of total, high, middle, low clouds, and cloud forcing net solar radiation flux, cloud forcing net long-wave radiation flux, and SSTs over the tropical oceans are investigated with the use of ISCP D2, NCEP/NCAR Reanalysis for January 1983-December 1993. The intra-annual variation of total cloudiness is dominated by high and middle clouds in the western Pacific and central tropical oceans, the interannual variation of total cloudiness is also dominated by high and middle clouds in the central Pacific and Atlantic. The dominant intra-annual and interannual EOFs of total cloudiness have spatially coherent link with those SSTs. For the interannual EOFs, total cloudiness and SSTs are related to E1 nino-Southern Oscillation(ENSO). The second most important intra-annual EOFs of total cloudiness are related to Inter Tropical Convergence Zone(ITCZ). The third most important intra-annual EOFs show coherent relation in the western Pacific. The correlation analysis between cloud radiative effects and SSTs show spatially coherent relation over the tropical oceans even though cloud forcing cooling effect is much higher than heating effect.

• Proceedings of the KSRS Conference
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• v.2
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• pp.680-683
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• 2006

A one-dimensional planar model is considered of the atmosphere with multi-layer clouds illuminated by a mono-directional parallel flux of solar radiation. A new approach is proposed to radiation transfer modeling and daylight background formation for the atmosphere with such clouds that is represented as a heterogeneous multi-layer system each layer of which is described by different optical characteristics. The influence functions of each layer are determined by solutions of the radiation transfer boundary problem with an external monodirectional wide flux while the contribution of multiple scattering and absorption in the layer is taking into account.

• Journal of the Korean Data and Information Science Society
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• v.22 no.5
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• pp.989-998
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• 2011

Cloud computing provides computation, software, data access, and storage services that do not require end-user knowledge of the physical location and configuration of the system that delivers the services. Cloud computing providers have setup several data centers at different geographical locations over the Internet in order to optimally serve needs of their customers around the world. One of the fundamental challenges in geographically distributed clouds is to provide efficient algorithms for supporting inter-cloud data management and dissemination. In this paper, we propose a group quorum system (GQS)-based dissemination for improving the interoperability of inter-cloud in time-critical event dissemination service, such as computing policy updating, message sharing, event notification and so forth. The proposed GQS-based method organizes these distributed clouds into a group quorum ring overlay to support a constant event dissemination latency. Our numerical results show that the GQS-based method improves the efficiency as compared with Chord-based and Plume methods.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.75.2-75.2
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• 2010

We have studied the statistical properties of turbulence in molecular clouds identified in the Boston University - Five College Radio Astronomy Observatory (BU-FCRAO) Galactic Ring Survey (GRS). Toward this end, the probability density function (PDF) and velocity distribution were measured for about 50 molecular clouds. We found there exists a good correlation between the PDF width and the velocity dispersion for these molecular clouds. In order to investigate how general properties of astrophysical turbulence depends on the plasma parameters such as magnetic field strength and sonic Mach number, we performed three-dimensional MHD simulations. We then examined if the observed characteristics of interstellar turbulence are consistent with theoretical results from MHD simulations.

• Journal of Astronomy and Space Sciences
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• v.35 no.1
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• pp.19-30
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• 2018

The analysis of the high-resolution spectra of 31 Magellanic Clouds Cepheid variables enabled the identification of thorium lines. The abundances of thorium were found with spectrum synthesis method. The calculated thorium abundances exhibit correlations with the abundances of other chemical elements and atmospheric parameters of the program stars. These correlations are similar for both Clouds. The correlations of iron abundances of thorium, europium, neodymium, and yttrium relative to the pulsational periods are different in the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC), namely the correlations are negative for LMC and positive or close to zero for SMC. One of the possible explanations can be the higher activity of nucleosynthesis in SMC with respect to LMC in the recent several hundred million years.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.25 no.3
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• pp.28-33
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• 2002

Several studies indicated that an independent visual background (IVB) reduced simulator sickness (SS) and balance disturbance associated with exposure to virtual environments (VEs) and motion simulators. A recent study showed that an IVB comprised of an earth-fixed grid was less effective in a complex driving simulator than in a simple VE. Subjects' post-experiment reports indicated that the VE motion "induced" motion of the earth-fixed grid m. This led to the suggestion that an IVB comprised of clouds would be less subject to induced motion and therefore would alleviate nausea more effectively than a grid IVB. Clouds are "natural" and are usually perceived as relatively stable, whereas a grid has no inherent stability. 12 subjects were exposed to complex motion through a simulated environment in a driving simulator under 3 IVB conditions: grid, less clouds, many clouds. They reported less nausea when the many-cloud IVB was used relative to the grid IVB condition. grid IVB condition.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.149-153
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• 2015

We present an ongoing study of the complete sample of supernova remnants (SNRs) and candidates in the Magellanic Clouds. 108 objects in both Clouds are considered to be either SNR or reliable candidates. This represents the most complete sample of all known SNRs in any galaxy. It therefore allows us to study SNR population properties such as the age-diameter (Age-D) relation. Here, we show that this Age-D relation is strongly dependant on the local environment in which SNRs are residing.

• Journal of The Korean Astronomical Society
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• v.54 no.6
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• pp.183-190
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• 2021

We have revisited Monte Carlo radiative transfer calculations for clumpy molecular clouds. Instead of introducing a three-dimensional geometry to implement clumpy structure, we have made use of its stochastic properties in a one-dimensional geometry. Taking into account the reduction of spontaneous emission and optical depth due to clumpiness, we have derived the excitation conditions of clumpy clouds and compared them with those of three-dimensional calculations. We found that the proposed approach reproduces the excitation conditions in a way compatible to those from three-dimensional models, and reveals the dependencies of the excitation conditions on the size of clumps. When bulk motions are involved, the applicability of the approach is rather vague, but the one-dimensional approach can be an excellent proxy for more rigorous three-dimensional calculations.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.69.2-69.2
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• 2019

Recent high resolution IR observations reveal that molecular clouds are filamentary and such a structure is ubiquitous over various star-forming environments, and it is clear that filaments play a crucial role in the formation of cores and stars. However, the formation process of dense cores in the filaments are still unknown. To investigate this issue in detail, we have carried out TRAO FUNS (TRAO survey of nearby Filamentary molecular clouds, the Universal Nursery of Stars) toward various star forming filamentary molecular clouds. In this presentation, we will report the first look results of filaments and dense cores in MCLD 123.5+24.9 and IC 5146, which are known as a quiescent, non-star-forming region and an active, high-mass star forming region, respectively. By comparing the kinematic properties of filaments and dense cores in different star forming environments, we verified the formation scenario of filaments and dense core, i.e., gravoturbulent fragmentation via supersonic motions.