• The Bulletin of The Korean Astronomical Society
• /
• v.42 no.2
• /
• pp.80.1-80.1
• /
• 2017

We present preliminary results of KVN single dish telescope observations of 80 dense cores in the Orion molecular cloud complex which contains the Orion A, B, and ${\lambda}$ Orionis cloud. We investigate the behavior of the different molecular tracers and look for chemical variations of cores in the three clouds in order to systematically investigate the effects of stellar feedback. The most commonly detected molecular lines (with the detection rates higher than 50%) are N2H+, HCO+, H13CO+, C2H, HCN, and H2CO. The detection rates of dense gas tracers, N2H+, HCO+, H13CO+, and C2H show the lowest values in the ${\lambda}$ Orionis cloud. We find difference between molecular D/H ratios and N2H+/H13CO+ abundance ratios towards different clouds, and between protostellar cores and starless cores. Eight starless cores in the Orion A and B clouds exhibit high deuterium fractionations, larger than 0.10, while in the ${\lambda}$ Orionis cloud, no cores reveal the high ratio. These chemical properties could support that cores in the ${\lambda}$ Orionis cloud are affected by the photo-dissociation and external heating from the nearby H II region, which is a hint of negative stellar feedback on core formation. The striking difference between the [N2H+]/[H13CO+] ratios leads us to suggest that there are significant evolutionary differences between the Orion A/B and ${\lambda}$ Orionis clouds. In order to examine whether starless cores can be candidates of pre-stellar cores, we compared the core masses estimated from the 850 um emission to their Virial masses calculated from the N2H+ line data and find that most of them are not gravitationally bound in the three clouds.

• Korean Institute of Interior Design Journal
• /
• v.22 no.5
• /
• pp.233-240
• /
• 2013

The building construction sector has been blamed as the main culprit of environmental contamination worldwide. So, there shall be some constructive alternatives in architectural engineering. As one of the alternatives, the LEED ("Leadership in Energy and Environmental Design") has been introduced since 1990s and has been well recognized in saving the resources and energy. "LEED" has also been introduced in Korea since 2002 but it has not put priority on the eco-friendliness of indoor space. In this study, the international and domestic green systems were analyzed and compared in order to restructure the checklist for indoor space. Using the restructured checklists, the questionnaire were sent to 180 people using 6 office buildings which passed the domestic "LEED" certification. LEED certification system put priority on the air quality and heating/cooling environment in its evaluation section and items. However, according to the results of the study, it was found that the people using the buildings were not satisfied enough with the air environment of buildings along with their other indoor environment items. This shows that even though the office buildings are designed according to the requirements of LEED, the buildings do not meet the occupier's needs. In addition, it showed that the evaluation items should be improved so that they are useful to enhance the satisfaction of the occupiers' needs. The paper could be useful in establishing standard for eco friendliness of indoor space of office buildings which pass the LEED certification as the basic data for increasing energy efficiency and working efficiency of occupiers of the buildings.

• The Bulletin of The Korean Astronomical Society
• /
• v.41 no.1
• /
• pp.73.1-73.1
• /
• 2016

We present preliminary results of the submillimeter continuum observations of 14 Planck Galactic Cold Clumps (PGCCs), located in the ${\lambda}$ Orionis Complex. This region is the nearest large HII region, which is an ideal site for a study of the stellar feedback to its surroundings. We observed 14 PGCCs with JCMT/SCUBA-2 and used J=1-0 transitions of CO isotopologues from the PMO mapping observation. Several sub-clumps toward three PGCCs were detected at $850{\mu}m$. In order to examine whether these clumps can be candidates for pre-stellar cores, we compared each clump mass calculated from the $850{\mu}m$ continuum map to its Virial mass and Jeans mass calculated from the $^{12}CO$ and $C^{18}O$ (1-0) spectra, respectively. All clumps have masses smaller than their Virial and Jeans masses, indicating that none of them are gravitational bound and thus in the pre-stellar core stage. Also, the CO depletion factor, which has been derived from the dust continuum and the $C^{18}O$(1-0) line and can be an indicator of core evolution, toward the clumps is in the range of 1 to 5, suggesting that they are not very evolved dense pre-stellar cores. In addition, within individual PGCCs, we found clear gradients of velocity (${\sim}1km\;s^{-1}\;pc^{-1}$) and temperature (${\sim}10K\;pc^{-1}$) in the $^{13}CO$ (1-0) first moment map and the $^{12}CO$(1-0) excitation temperature map, respectively. This can be attributed to the compression and external heating by the HII region, which may prevent clumps from forming gravitationally bound structures and eventually disperse clumps. These results could be a hint about the negative effect of stellar feedback on core formation.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.2
• /
• pp.66.3-67
• /
• 2021

Low-mass stars form by the gravitational collapse of dense molecular cores. Observations and theories of low-mass protostars both suggest that accretion bursts happen in timescales of ~100 years with high accretion rates, so called episodic accretion. One mechanism that triggers accretion bursts is infalling fragments from the outer disk. Such fragmentation happens when the disk is massive enough, preferentially activated during the embedded phase of star formation (Class 0 and I). Most observations and models focus on the gas structure of the protostars undergoing episodic accretion. However, the dust and ice composition are poorly understood, but crucial to the chemical evolution through thermal and energetic processing via accretion burst. During the burst phase, the surrounding material is heated up, and the chemical compositions of gas and ice in the disk and envelope are altered by sublimation of icy molecules from grain surfaces. Such alterations leave imprints in the ice composition even when the temperature returns to the pre-burst level. Thus, chemical compositions of gas and ice retain the history of past bursts. Infrared spectral observations of the Spitzer and AKARI revealed a signature caused by substantial heating, toward many embedded protostars at the quiescent phase. We present the AKARI IRC 2.5-5.0 ㎛ spectra for embedded protostars to trace down the characteristics of accretion burst across the evolutionary stages. The ice compositions obtained from the absorption features therein are used as a clock to measure the timescale after the burst event, comparing the analyses of the gas component that traced the burst frequency using the different refreeze-out timescales. We discuss ice abundances, whose chemical change has been carved in the icy mantle, during the different timescales after the burst ends.

• Journal of Astronomy and Space Sciences
• /
• v.26 no.3
• /
• pp.403-416
• /
• 2009

COMS (Communication, Ocean and Meteorological Satellite) is a geostationary satellite and developed by KARl for communication, ocean and meteorological observations. It will be tested under vacuum and very low temperature conditions in order to verify thermal design of COMS. The test will be performed by using KARI large thermal vacuum chamber, which was developed by KARI, and the COMS will be the first flight satellite tested in this chamber. The purposes of thermal balance test are to correlate analytical model used for design evaluation and predicting temperatures, and to verify and adjust thermal control concept. KARI has plan to use heating plates to simulate space hot condition especially for radiator panels of satellite such as north and south panels. They will be controlled from 90 K to 273 K by circulating GN2 and LN2 alternatively according to the test phases, while the main shroud of the vacuum chamber will be under constant temperature, 90 K, during all thermal balance test. This paper presents thermal modelling including test chamber, heating plates and the satellite without solar array wing and Ka-band reflectors and discusses temperature prediction during thermal balance test.

• Journal of the Korean housing association
• /
• v.18 no.3
• /
• pp.115-123
• /
• 2007

The purpose of this study was to examine how housing facilities have been progressed, how housing life has been technicalized and which factors contributed to the modernization of Korean housing in the economic development era. Review of advertising material for apartment sales in the newspaper from 1970s' to the 1990s' are mainly utilized to follow up the changes of kitchen equipment and furnitures, bathroom equipments, heating and cooking facilities and their fuel system, information and telecommunication system as well as security and intelligent system. However, high technology in apartment was a symbol of modem housing in each time. The improvement of housing facilities brought about the improvement of efficiency in household works. In other words, housing space plays as "Living Machine". And appearance of new technology systems leaded to a pluralistic activities in the home. As well as improvement on the material environments accelerated the individualization phenomena in housing space.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.8
• /
• pp.753-758
• /
• 2013

In this study, two proposals for the wall heating preconverter of an MCFC are numerically studied to resolve hot temperature generation near the wall by the low thermal conductivity of the catalyst. The numerical results show that the inserted porous cupper plates on the catalyst evidently improve heat transfer and realize more uniform reforming in the preconverter. The calculated results for the preconverter with a circumference empty space of catalyst located at center, 1/2 and 4/5 from center line are compared. The circumference empty space located at 1/2 position shows better results than other cases, but the positive effect on the uniform reforming process is less than in the case of inserted cupper porous plates on the catalyst.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.2
• /
• pp.34.2-34.2
• /
• 2015

We aim to investigate the formation of primordial globular clusters (GCs) in the isolated dwarf galaxy (${\sim}10^{10}M_{sun}$) with cosmological zoom-in simulations. For this, we modified cosmological hydrodynamic code, GADGET-3, in a way to include the radiative heating/cooling that enables gas particles cool down to T~10K, reionization (z < 8.9) of the Universe, UV shielding ($n_{shield}$ > $0.014cm^{-3}$), and star formation. Our simulation starts in a cubic box of a side length 1Mpc/h with 17 million particles from z = 49. The mass of each dark matter (DM) and gas particle is $M_{DM}=4.1{\times}10^3M_{sun}$ and $M_{gas}=7.9{\times}10^2M_{sun}$, respectively, thus the GC candidates can be resolved with more than hundreds particles. We found the following results: 1) mini halos with the more interactions before merging into the main halo form the more stars and thus have the higher star mass fraction ($M_{star}/M_{total}$), 2) the mini halos with the high $M_{star}/M_{total}$ can survive longer and thus spiral into closer to the galactic center, 3) the majority of them spiral into bulge, but some of them can survive until the last as baryon-dominated system, like the GC.

• International Journal of Aeronautical and Space Sciences
• /
• v.11 no.3
• /
• pp.193-200
• /
• 2010

Through experimental investigations utilizing hypersonic shock tunnel-coaxial thermocouples as well as blow down hypersonic wind tunnel-temperature sensitive paints, the heat flux and the temperature over a protuberance were measured and analyzed. The experimental data were subsequently compared to heat flux data that was obtained by using blow down hypersonic wind tunnel and heat flux gauges. According to the comparison, both sets of data illustrated correlation with one another. The measured heat flux was large when the height of the protuberance was large. Experimental results show that heat flux measurements taken at higher locations were greater than those taken at lower locations. For high protuberances, a severe jump in the heat flux was observed, ranging in values within 0.6-0.7 of the height of the protuberances. However, when the protuberance was sufficiently short, a rise in the heat flux was rarely observed as the protuberance was totally submerged under the separation region.

• Journal of the Korean Institute of Rural Architecture
• /
• v.13 no.4
• /
• pp.91-98
• /
• 2011

The housing environment of the weak class in rural area is inferior, the elderly ratio is high, and senior citizens whose living by themselves are increasing. This study was to analyze the actual conditions of utilization status, characterization of residency, management method of the federation of construction associate's love house and local government's case, and usage of the village hall. For better study, we reviewed the literatures and conducted field surveys. The purpose of this study is to suggest a development plan of rural community living homes. The results of this study were as follows; First, it is important for proper site of rural community living home plans to select adjacent location in the surrounding medical and welfare facilities(including community facilities). Second, the living space for one person does not need such a space; about $33m^2$ is suitable. Third, it is important to use surplus area to make kitchen garden in the site planning. Also the architectural plans must be considered to minimize the maintenance costs for the sustainability of the house and winter heating expense problem.