• Journal of Magnetics
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• 제10권3호
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• pp.108-112
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• 2005

GaAs nanowires were grown on GaAs (111)B substrates in a gas source molecular beam epitaxy system, using self-assembled Au particles with diameters between 25 and 200 nm as the catalytic agents. The growth rate and structure of the nanowires were investigated for substrate temperatures between 500 and $600^{\circ}C$ to study the mass transport mechanisms that drive the growth of these crystals. The possibilities for fabrication of novel magnetic nanostructures by suitable choice of growth conditions are discussed.

• 천문학회지
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• 제29권spc1호
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• pp.161-163
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• 1996

We have studied the response of molecular clouds in the Galactic disk to a rotating bar by conducting Smoothed Particle Hydrodynamics (SPH) simulations for the Galaxy in order to understand the dynamical structures of the Galactic Center (GC) molecular clouds, and their implications. In our study it was found that the structures of GC molecular clouds could be induced by the combined effects of rotating bar potential, the hydrodynamic collisions and gravitational miss collisions between the clouds.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2723-2728
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• 2008

The present study is numerically and experimentally performed to reveal the pumping characteristics of a helical-type molecular drag pump (HTDP) in the molecular transition flow region. In the experimental study, the pressures are measured simultaneously at the 5 positions along the helical channel of rotor under various conditions of outlet pressure and throughputs, and nitrogen is used as test gas. The outlet pressure is in the range of 26-533 Pa. As results, the local pressure changes are checked corresponding to the various outlet pressure and throughput of HTDP. In the numerical study, Navier-Stokes equations with slip boundary conditions are employed (Re< 1000, Kn< 0.1). The local pressure distribution and the pumping speed are calculated. The numerical results are compared with the experimental results. The numerically computed value agrees with the experimental data within an error of approximately 5%.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2005년도 제28회 학술발표회 초록집
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• pp.85-85
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• 2005

• 천문학회보
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• 제39권2호
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• pp.118.2-118.2
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• 2014

As the most sensitive radio interferometer ever operated in millimeter/submillimeter, the ALMA has opened a new window on extragalactic astronomy. Its superior resolution and sensitivity allow the community to study the gas kinematics of distant galaxies as well as the molecular gas properties of nearby galaxies in GMC scale, already in its early commissioning stage. Also the ALMA provides a great tool to probe the dust contents of extragalactic sources at all redshifts, which is important in understanding of galaxy formation and evolution history over cosmic time. In this presentation, I will review the ALMA capabilities with the emphasis on the extragalactic science. I will also revisit some highlights from the early science and discuss future perspectives.

• Bulletin of the Korean Chemical Society
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• 제10권2호
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• pp.196-200
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• 1989

Some s-triazine herbicides, namely simazine, atrazine, and propazine present as trace components in a complex mixture were analyzed by GC/MS and GC/MS/MS methods. Even though monitoring the molecular ions was the best in terms of sensitivity, adequate analysis could not be done when interfering species were present. When doubly charged ions which appeared at characteristic m/z values were monitored, chromatograms were rather free from interference. More importantly, selected reaction monitoring was found to provide a selective means of detection with general applicability.

• Animal Bioscience
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• 제34권12호
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• pp.1940-1950
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• 2021

Objective: The objective of this study was to explore the effects of maize straw treated with calcium oxide (CaO) and various moisture, on the composition and molecular structure of the fiber, and gas production by fermentation in an in vitro rumen environment. Methods: The experiment used 4×3 Factorial treatment. Maize straws were treated with 4 concentrations of CaO (0%, 3%, 5%, and 7% of dry straw weight) and 3 moisture contents (40%, 50%, and 60%). Scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray fluorescence spectroscopy were employed to measure the surface texture, secondary molecular structure of carbohydrate, and calcium (Ca) content of the maize straw, respectively. The correlation of secondary molecular structures and fiber components of maize straw were analyzed by CORR procedure of SAS 9.2. In vitro rumen fermentation was performed for 6, 12, 24, 48, and 72 h to measure gas production. Results: Overall, the moisture factor had no obvious effect on the experimental results. Neutral detergent fiber (NDF), acid detergent fiber, acid detergent lignin, hemicellulose and cellulose contents decreased (p<0.05) with increasing concentrations of CaO treatment. Surface and secondary molecular structure of maize straw were affected by various CaO and moisture treatments. NDF had positive correlation (p<0.01) with Cell-H (H, height), Cell-A (A, area), CHO-2-H. Hemicellulose had positive correlation (p<0.01) with Lignin-H, Lignin-A, Cell-H, Cell-A. Ca content of maize straw increased as the concentration of CaO was increased (p<0.01). Gas production was highest in the group treated with 7% CaO. Conclusion: CaO can adhere to the surface of the maize straw, and then improve the digestibility of the maize straw in ruminants by modifying the structure of lignocellulose and facilitating the maize straw for microbial degradation.

• 천문학회보
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• 제43권1호
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• pp.44.2-44.2
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• 2018

G33.92+0.11, classified as a core-halo UC HII region at a distance of 7.1 kpc, contains several sub-clumps (~20-200 solar masses) as identified by dust continuum emission. This source shows very complicated features associated with vigorous massive star-forming activities with a nearly face-on projection. The ambient gas is still accreting to the massive molecular clumps dynamically, while the whole cloud is under disruption by newly formed stars. Using the recent high resolution (< 0.2") ALMA observations, we investigate the detailed structure associated with the star-forming activities by comparing different chemical tracers. The sub-clumps having extremely complex morphologies still preserve cold dense gas together with the turbulent and dense warm gas resulted by newly formed stars and interaction with accreting gas. The accretion of the ambient gas may have occurred episodically to this source. Most recent star formation, which probably the third generation of star formation in this region, is taking place in the northern part (A5 clump). The relatively small mass (~ 1/3 of A1 or A2) and the lack of turbulent gas of this star-forming core may suggest that this core was formed already during the overall collapse of the whole cloud for the first star formation. We think that gravitational collapse of these sub-clumps appears as sequential star formation of this region. The later interaction with accreting gas may have not been a direct cause of the star formation activities of this source.

• 천문학회지
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• 제53권6호
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• pp.117-123
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• 2020

We investigate the plausibility of mass return, from stellar mass loss processes within the central ~100 pc region of the Milky Way (the inner nuclear bulge), as a mass supply mechanism for the Circumnuclear Disk (CND). Gas in the Galactic disk migrates inward to the Galactic centre due to the asymmetric potential caused by the Galactic bar. The inward migration of gas stops and accumulates to form the central molecular zone (CMZ), at 100-200 pc from the Galactic center. It is commonly assumed that stars have formed in the CMZ throughout the lifetime of the Galaxy and have diffused inward to form a 'r-2 stellar cusp' within the inner nuclear bulge. We propose that the stars migrating inward from the CMZ supply gas to the inner nuclear bulge via stellar mass loss, resulting in the formation of a gas disk along the Galactic plane and subsequent inward migration down to the central 10 pc region (CND). We simulate the evolution of a gas distribution that initially follows the stellar distribution of the aforementioned stellar cusp, and illustrate the potential gas supply toward the CND.

• Bulletin of the Korean Chemical Society
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• 제27권3호
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• pp.373-375
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• 2006

$CF_4$ gas is one of the most common chemicals used for dry etching in semiconductor manufacturing processes. For application to the etching process and environmental control, the low-pressure inductively coupled plasma (LP-ICP) was employed to obtain the spectrum of $CF_4$ gas. In terms of the analysis of the spectra, trace CF radical by A-X and B-X transitions was detected. The other $CF_x$ radicals, such as $CF_2$ and $CF_3$, were not seen in this experiment whereas strong C and $C_2$ emissions, dissociation products of $CF_4$ gas, were observed.