• The Bulletin of The Korean Astronomical Society
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• v.28 no.2
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• pp.33-33
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• 2003

• The Bulletin of The Korean Astronomical Society
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• v.33 no.2
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• pp.55.1-55.1
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• 2008

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.71.1-71.1
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• 2015

We prensent the near-infrared(NIR) images of the asymmetric circumstellar disk around a T-Tauri star in the ${\rho}$ Ophiuchi star-forming region, and two faint stellar objects around central star. These results were obtainted with the Subaru Telescope with HiCIAO(the High-Contrast Instrument with Adaptive Optics) and IRCS(the InfraRed Camera and Spectrograph). The disk shows center-offset from the star and a strong morphological asymmetry along both the major and minor axis. The physical conditions in the disk is derived from the infrared visibilites results and the complete spectral energy distribution using HOCHUNK3D, Monte-Carlo radiative transfer code. Two companion candidates are separated by 11.6 arcsec(~1450 au at 125 parsec) and 4.34 arcsec(~540 au at 125 parsec). This could be the first case, which imaged both of planetary mass companions and disk around same star. We discuss physical structures of the disk, and probablity that two candidates are real companions.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.39-39
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• 2014

Studies of compact radio sources since the discovery of quasars have revealed a variety of physical properties: both in morphology and kinematics from sub-parsec to Mega-parsec scales, radiation mechanisms at frequencies from the radio to ${\gamma}$-rays, theoretical models for relativistic jets, etc. The frontier discovery of Very Long Baseline Interferometry (VLBI) observations for the compact extragalactic radio sources have triggered the extensive studies to investigate the underlying physics of the relativistic jets. In this context, the highest resolution VLBI surveys of ultra-compact radio sources provide the potentially important statistical basis for future study. As a tool of this study, a new millimeter VLBI network in Korea, the Korean VLBI Network (KVN) will paly an important role. We present results from large VLBI surveys of compact radio sources at millimeter wavelengths and discuss the prospects with the KVN on this study.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.75.1-75.1
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• 2014

We present the result of a long-slit spectroscopic study of DG Tau, which is known to emanate parsec-scale outflows. To study the kinematics and physical properties of the jet, we obtained the optical emission lines of $H{\alpha}$, [OI], [NII], and [SII] from HH 158 and HH 702 using the long-slit spectrograph at Bohyunsan Optical Astronomical Observatory. HH 158 shows the peak radial velocity in a range of ~ - 270 to - 30 km s-1. HH 702, located at 11' away from DG Tau shows the velocity of ~ - 80 km s-1. The proper motion velocities of detected knots are estimated through the comparisons with the locations of those knots in the previous studies. We also examine the variations of physical parameters depending on the velocity distribution and the distance from the source using line ratio maps derived from obtained forbidden emission lines.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.55.2-55.2
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• 2013

We present the observational study of parsec-scale jets from YSOs reaching lengths of several arc-minutes. The medium-resolution spectroscopic data were obtained between 6000 - $7000{\AA}$ with BOAO long-slit spectrograph. By performing multi-position observation, we investigated the physical variation of the jets and the ambient gas along the whole path of the jets. The flux, electron density, ionization fraction, and electron temperature are discussed with the estimated line ratios between from [OI], [NII], $H{\alpha}$ and [SII] emission lines. This study carried out with more than 8 jets of YSOs including low- to intermediate-mass stars. We also briefly discuss the kinematics of the outflows using spatial and spectroscopic data.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.63.1-63.1
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• 2014

We present a study on the parsec-scale jets from young stellar objects using long-slit spectroscopic data obtained from Bohyunsan Optical Astronomy Observatory on 2012 - 2014. Through the position-velocity diagrams, we show the radial velocity variation, peak velocity and velocity width of the outflow from several T Tauri stars and Herbig Ae/Be star. $H{\alpha}$, [OI] 6300/6363, [NII] 6548/6584 and [SII] 6716/6731 emission lines are obtained and they show various velocity features. We also compare our result with other data from literatures.

• The KIPS Transactions:PartC
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• v.11C no.6 s.95
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• pp.863-870
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• 2004

UMTS(Universal Mobile Telecommunication System) is recently recognized as a standard for 3rd generation of wireless networks and DSCH(Down-link Shared Chanel) is considered as a very effective multiplexing method in UMTS. So, it is inevitable to develope an effective packet scheduling algorithms for DSCH in UMTS. This paper describes an improved packet scheduling algorithm for DSCH of UMTS. The algorithm takes consideration in channel state for each mobile terminal to maximize link utilization, delay threshold for class 3 traffic and throughput for class 4 to get long term fairness. To verify the algorithm, we programmed a simulator using PARSEC simulation tool and got some simulation results by it. The simulation results show that the algorithm has reasonable characteristics in both of link utilization and fair-ness by trade-off.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.73.4-74
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• 2017

We report preliminary results from our radio study of X-ray selected complete AGN sample in the Local Universe (z < 0.05), using the KVN/KaVA. The main goal is to probe the parsec-scale radio properties of the X-ray selected AGNs, which has not been done systematically before. The BASS (Burst Alert Telescope AGN spectroscopic survey) sample from the Swift-BAT hard X-ray all-sky survey is the least biased AGN sample against dense gas/torus obscurations compared to optically selected AGNs, providing ideal targets to study the general properties of local AGNs in radio wavelengths. Combining our radio data with BASS X-ray/optical measurements, we will probe the relations of radio powers with the fundamental quantities of black holes such as bolometric luminosity, black hole mass, and Eddington ratio. Using these relations, we will discuss our current understandings of how accretions and jets of local AGNs are linked together, and what they imply for the nature of our AGN sample.

• The Transactions of the Korea Information Processing Society
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• v.7 no.10
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• pp.3049-3054
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• 2000

In this paper, the effects of the hardware components and runtime environments on the overall performance of a distributed shared memory system are analyzed through simulation. In simulation, the system is modeled using PARSE[1.2] closely to the real runtime environment and the 2D FFT is virtually executed on it. The results of simulation show that the minor hardware components such as bus interfaces and local bus of a processor, which are usuallyignored or neglected when analyzing performance. have significant impacts on the overall system performance. Performance variations caused from runtime environments such as loop overhead and code optimuzatio are also analyzed quantitatively.