• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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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.

• Journal of ILASS-Korea
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• v.22 no.4
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• pp.185-189
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• 2017

In Korea, sales of passenger cars using diesel and LPG fuels were continuously increased in recent years. From now on 2030, the registrated vehicles will close in about twenty five million in Korea. From these reason, Investigation on the comparison of exhaust emission characteristics of passenger cars using LPG and Diesel fuel in variation of driving mode and ambient conditions were conducted in this study. Exhaust emission characteristics of test vehicles were measured and analyzed by using chassis dynamometer and emission analyzer. Also, test vehicles were selected on the diesel vehicle with 1.7L engine and LPG vehicle with 2.0L engine. In order to study on emission characteristics according to driving cycles, CVS-75, NEDC, US06, SC03, Cold-FTP and HWFET were applied and the test conditions were set up the cases of A/C on and hot start. From these results, it is revealed that the NOx emission of diesel vehicle was higher than that of LPG vehicle and the case of CO emission shows the opposite patterns. In the HC emission, the emission increasing patterns not showed but the NOx emission of diesel vehicle and CO emission of LPG vehicle were showed the variation patterns according to the various driving modes.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.6
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• pp.578-584
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• 2019

The occurrence of white plume in the cooling tower is phenomenon that the steam in the air through the cooling tower fan is condensed again by the cold ambient air to become saturated moist air. Accordingly, this can cause many problems like spoiling landscape around the cooling tower, odor of ambient air, falling accident by frozenness in the winter, and traffic accident, etc. This study was to install the heat exchanger in the inside of the cooling tower in order to prevent the white plume phenomenon in the cooling tower without affecting the performance of cooling tower. In addition, this study was to discharge the part of cooling water into the atmosphere through the recirculation of heat exchanger after creating dry air by heating the saturated moist air to the dew point temperature. At that time, this study was to conduct the experimental study in order to secure the optimal design data to prevent the white plume in the cooling tower because it checked the dry·moist temperature and relative humidity in the inside·outside of cooling tower on the moist air, and evaluated the performance of the heat exchanger.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.6
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• pp.1195-1204
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• 1992

The natural convection from upward and downward facing horizontal isothermal plate immersed in water is studied numerically. The temperature of the plate is from 0.0 .deg. C to 8.0 .deg. C and the ambient water temperature is from 1.0 .deg. C to 10.0 .deg. C. Numerical results are presented for the velocity profiles, temperature profiles, local heat transfer coefficients, and average Nusselt numbers over the entire flow fields. Flow patterns are shown in the upward and downward facing surfaces at different ambient water temperatures. For the upward facing surface, there are upflow and unsteady flow. And the regions of the ambient water temperatures which give rise to the upflow are more extensive as the temperatures of the isothermal surface become more distant from the density extremum temperature. For the downward facing surface, only the downflow region is shown. For the upward facing horizontal isothermal surface, the average Nusselt number(= N $u_{1}$$^{*}$) is 28.86(Ra)$^{0.01}$. And for the downward facing surface, the average Nusselt number(= N $u_{2}$$^{*}$) is $C_{2}$(Ra)$^{0.2}$ and the values of $C_{2}$ are enlarged in the range of 0.785 .leq. $C_{2}$ .leq. 1.250 as increasing of the temperatures of the isothermal surface.ace.ace.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.52.1-52.1
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• 2015

FIMS/SPEAR is a dual-channel far-ultraviolet imaging spectrograph on board the Korean microsatellite STSAT-1, which was launched on 2003 September 27. The primary mission goal of FIMS was to conduct a survey of diffuse far UV emissions in our Galaxy. For this purpose, FIMS completed a survey of about 84% of the sky during its operation of a year and a half. The present study aims to analyze this survey data made in the far UV wavelengths to understand the global evolution of our Galaxy. The far UV wavelength band is known to contain important cooling lines of hot gas: hence, the study will show how the hot gas in our Galaxy, produced by stellar winds and supernova explosion, evolves globally to cool down and become mixed with ambient cooler medium. One of the main findings from previous analyses of the FIMS data is that molecular hydrogen exists ubiquitously in our Galaxy. This discovery leads to another important scientific question: how is molecular hydrogen distributed in our Galaxy and how does it affect globally the evolution of our Galaxy as a cold component? Hence, the present study will cover both the hot and cold components of the ISM, which will also provide the opportunity to investigate the interactions between the two.

• Journal of Power System Engineering
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• v.17 no.2
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• pp.95-102
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• 2013

For vessels operating in the cold climate regions, the ballast water inside or hopper tanks above the waterline may be frozen, starting at the top of the tank and at the side walls. Therefore, countermeasures against freeze-up of the ballast tank such as air-bubbling system, hot steam injecting system, heating coil system and water circulating system are taken to prevent freeze-up phenomenon; however, there are no rigorous investigations of anti-freezing to examine the effectiveness and validity of systems against freeze-up of the ballast tank, in which the temperatures are about $-25^{\circ}C$ (ambient air temperature) and $0^{\circ}C$ (sea water), respectively. In this paper, to ensure reasonable specifications for cold regions if the measures from the above-mentioned systems against freeze-up are effective, the phenomenon of ballast tank freeze-up is simulated and discussed in low temperature conditions. With the results using the commercial CFD code, CFX 14, the most cost-effective solution is conducted to prevent being frozen along the outer surface.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.35 no.2
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• pp.33-38
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• 2003

In order to design the high strength corrugated fiberboard containers for agricultural products that can be used for the cold chain system, a large number of individual boxes were placed in various humidity environments at two different temperature of 5 and $20^{\circ}C$. The results indicated that temperature changes do not effect on physical strength of corrugated fiberboard containers as much as humidity changes did. The main conclusion from this study was that compression strength of corrugated fiberboard containers dropped significantly at high humidity condition, but the rates varied depending on the number of walls, temperature, and perimeter of containers. The packaging designer must consider the corrugated fiberboard boxes are also greatly affected by dimensional variations such as the length versus width ratio. Based on this study, water-resistant board would not be necessary if the ambient relative humidity does not reach to a critical point, 85 percent in the cold chain system. However, the designer must count for the unexpected fluctuation of rotative humidity resulting in severe loss of the compression strength of corrugated fiberboard container.

• Korean Journal of Materials Research
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• v.28 no.2
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• pp.113-117
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• 2018

Effects of annealing temperature on the microstructure and mechanical properties through thickness of a cold-rolled Cu-3.0Ni-0.7Si alloy were investigated in detail. The copper alloy with thickness of 3 mm was rolled to 50 % reduction at ambient temperature without lubricant and subsequently annealed for 0.5h at $200{\sim}900^{\circ}C$. The microstructure of the copper alloy after annealing was different in thickness direction depending on an amount of the shear and compressive strain introduced by rolling; the recrystallization occurred first in surface regions shear-deformed largely. The hardness distribution of the specimens annealed at $500{\sim}700^{\circ}C$ was not uniform in thickness direction due to partial recrystallization. This ununiformity of hardness corresponded well with an amount of shear strain in thickness direction. The average hardness and ultimate tensile strength showed the maximum values of 250Hv and 450MPa in specimen annealed at $400^{\circ}C$, respectively. It is considered that the complex mode of strain introduced by rolling effected directly on the microstructure and the mechanical properties of the annealed specimens.

• Journal of Power System Engineering
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• v.17 no.5
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• pp.30-37
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• 2013

For vessels operating in the cold climate regions, the ballast water inside or hopper tanks above the waterline may be frozen, starting at the top of the tank and at the side walls. Therefore, countermeasures against freeze-up of the ballast tank such as air-bubbling system, hot steam injecting system, heating coil system and water circulating system are taken to prevent freeze-up phenomenon; however, there are no rigorous investigations of anti-freezing to examine the effectiveness and validity of systems against freeze-up of the ballast tank, in which the temperatures are about -$25^{\circ}C$ (ambient air temperature) and $0^{\circ}C$ (sea water), respectively. In this paper, to ensure reasonable specifications for cold regions if the measures from the above-mentioned systems against freeze-up are effective, the phenomenon of ballast tank freeze-up is simulated and discussed in low temperature conditions. With the results using the commercial CFD code, CFX 14, the most cost-effective solution is conducted to prevent being frozen along the outer surface.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.61-65
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• 2011

Recently, LCD (liquid crystal display) industry is needed to goods of high reliability and wide range temperature condition and it is interested in products for extremely cold condition without failure of light-up. In this experiment, we made the LED backlight unit for Automotive-navigation under the extremely cold condition. And for making this backlight unit, we used to eight side emitting type white LEDs with 3W high power LED. We could know that this backlight unit releases to 18,000 nit in 24W power consumption and start up voltage time is under the 1ms in the ambient temperature at -40.