• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.79.1-79.1
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• 2017

The B-fields In STar-forming Region Observations (BISTRO) is the 3-year large program of the James Clerk Maxwell Telescope (JCMT) using SCUBA-2 and POL-2, started in 2016. We aim to study the roles of magnetic fields in star formation by observing 16 fields of nearby star forming regions, e.g., Orion and Ophiuchus molecular clouds. The angular resolution and wavelength provided by JCMT (14 arcsecond at 850 micrometer) is ideal to investigate the intermediate scales of magnetic fields (1000-10000 au) associated in cold dense cores and filaments. This year, moreover, we were awarded JCMT time for additional 16 fields (BISTRO-2), which allows us to cover broader physical properties of star forming regions. We report the current status of BISTRO and introduce BISTRO-2.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.77.2-77.2
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• 2017

We investigate star formation activities of ~400 barred and unbarred faced-on late-type galaxies from the SDSS-IV MaNGA (Mapping Nearby Galaxies at APO) IFU survey. We find the star formation activities in gas-poor, barred galaxies are considerably suppressed than gas-rich, barred galaxies, while there is no difference among unbarred galaxies regardless of their HI gas content. The gas-poor and barred galaxies show the steeper difference of gradient in metallicity and age with respect to the stellar mass than gas-rich or unbarred galaxies, in that their centre is more metal-rich and younger. The results suggest that, combined with the gas contents available, the bar structure plays a significant role in quenching star formation in a galaxy by transporting/mixing gas via gas inflow.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.40.1-40.1
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• 2017

Massive early-type galaxies (ETG) have been spectroscopically confirmed up to z>3 which, together with their ages and abundances at z>1.5, implies that their progenitors must have converted gas into stars on short timescales. The termination of star formation in these galaxies can occur through several channels, but they remain largely conjectural, in part due to the current lack of direct measurements of the amount of residual gas in high redshift ETGs. Here I will present constraints on the star formation rate and dust/gas content of z=1.4-2.5 ETGs. These galaxies, close to their epoch of quenching, contained more than 2 orders of magnitude more dust than their local counterparts, which suggests the presence of substantial amounts of gas and a low star formation efficiency.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.7
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• pp.102-109
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• 1994

Low cost high efficiency single crystal silicon solar cells for terrestrial applications have been fabricated by using inexpensive materials such as solar grade silicon wafer and pastes, and mass production processes such as screen printing and spray. Under 100 mW/cm$^2$ (AM 1.5) and $25^{\circ}C$ conditions conversion efficiency of 16.48% was obtained by anon fire-thru process and 15.55% by fire-thru process.

• Journal of The Korean Astronomical Society
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• v.21 no.2
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• pp.155-171
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• 1988

We have examined how sensitively the extinction value determined by the method of star-count depends on such factors as the plate limit, the size of counting reseau, the non-linearity in the number distribution of stars with magnitude, and the angular resolution demanded by the given problem. We let the Poisson distribution portray the statistical nature of the countings, and chose the region containing the globule Barnard 361 as an example field. Uncertainties due to various combinations of the factors are presented in graphic forms: (1) Dynamic range in the extinction measurements is evaluated as a function of reseau size for varying plate limits. (2) Statistical errors involved in the star-count are analized in terms of the signal-to-noise ratio, the plate limit and the reseau size. (3) Systematic error due to the non-linearity in the number distribution are thoroughly analized. (4) Finally, a methodology is presented for correcting the systematic error in the observed radial density gradient. These graphs are meant to be used in selecting proper size of the reseau and in estimating errors inherent to the star-count analysis.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.55.4-56
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• 2017

Complex organic molecules (COMs) are commonly detected in star forming regions and considered important species since they are seeds of prebiotic molecules. Although COMs form in ice mantles on dust grains, they are preferentially detected in the gas phase. The origin of the gaseous COMs highly depends on the circumstance of each star forming region. Therefore, the distribution of COMs emission reflects the physical and chemical conditions of the region. We present the newly detected COMs, especially methanol emission lines toward two massive star forming regions, G19.61-0.23 and G75.78+0.34 in the Atacama Large Millimeter/submillimeter Array Band 3 observations during the Cycle 2 phase. Multiple transitions of methanol are detected in both regions but show different emission morphology. The origin of the desorption (e.g. shocks or high energy photons) is discussed.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.32.3-32.3
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• 2018

We report a possible discovery of a relic of a dissolved star cluster in the Sextans dwarf spheroidal galaxy. Using the hk index (${\equiv}$(Ca-b)-(b-y)) as a photometric metallicity indicator, we have successfully discriminated the metal-poor and metal-rich stars in the galaxy and found an unexpected number density peak of metal-poor stars near the galaxy center. The analysis of color-magnitude diagrams reveals that they appear to be originated from an old, metal-poor globular cluster which might be slightly farther than the bulk of field stars in the galaxy. This supports the presence of the star cluster remnants in the galaxy which have been suggested by previous studies. If confirmed, dissolution of a star cluster provides a piece of evidence of a cored dark-matter halo profile for the Sextans dwarf galaxy.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.9
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• pp.31-40
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• 1997

This paper presents a hybrid WDM/TDM channel acess protocol for high speed WDM networks based on passive double star topology. In the proposed scheme, all nodes in a network are splitted into groups forming passive double star topology and each node has a tunable transmitter and a fixed receiver. WDM channels are allocated to the groups, which are used as home channels to transmit or receive packets. TDM frames of the WDM channel are composed of the same number of slots as that of groups, and all nodes in a group transmit packets simultaneously at each slot. The proposed scheme reduces the system complexity and the number of the required WDM channels. It was proved that the proposed protocol is less sensitive to the propagation delay and maintaining its superior transmission performance by employing the efficient transmission schedule based on passive double star topology.

• Journal of Communications and Networks
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• v.17 no.4
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• pp.428-439
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• 2015

In this study, we present an approach for reducing the information inaccuracy of existing star aggregation based on bypass links when there are multi-constraint QoS parameters in asymmetric networks. In our approach, bypass links with low similarity are selected. Links that are not chosen as bypass links are included in each group depending on the star's link characteristics. Moreover, each link group is aggregated differently according to the similarity of the links that make up the group. The selection of a bypass link by using link similarity reduces the existing time complexity of O($N^3$) to O(N) by virtue of the simplification of the selection process. In addition, the adaptive integration according to the characteristics of the links in each group is designed to reduce the information inaccuracy caused by static aggregation. Simulation results show that the proposed method maintains low information distortion; specifically, it is 3.8 times lower than that of the existing method, even when the number of nodes in a network increases.

• Molecules and Cells
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• v.26 no.3
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• pp.308-313
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• 2008

In animals, microRNAs (miRNAs) and small interfering RNAs (siRNAs) repress expression of protein coding genes by assembling distinct RNA-induced silencing complexes (RISCs). It has previously been shown that passenger-strand cleavage is the predominant mechanism when siRNA duplexes are loaded into Argonaute2 (Ago2)-containing RISC, while an unwinding bypass mechanism is favored for miRNA duplexes with mismatches. Here I present experimental data indicating that some mammalian miRNAs are assembled into Ago2-containing RISC by cleaving their corresponding miRNA star strands. This phenomenon may depend on the secondary structure near the scissile phosphate of the miRNA duplex. In addition, I show that ATP is not required for star-strand cleavage in this process. Taken together, the data here provide insight into the miRNA-loading mechanisms in mammals.