• 환경위생공학
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• 제21권1호
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• pp.44-51
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• 2006

This study was conducted to investigate air quality in the underground parking lot of department store. Sampling sites were selected to the three sites in one department store. Measuring instrument started from November 3rd, 2005 to November 9, 2005. Target air quality parameters include a number of criteria pollutants such as NOx, $O_3$. The purpose of this study was to find out the present condition of indoor air quality in underground parking space of department store. Through the field measurement, the current situation and the behavior of contaminants were investigated and then was compared with the advice standards. The result of this study was as follows; The Average density of NOx gas and $O_3$ gas was maintained below the indoor air advice standards. The Average density of NOx gas and $O_3$ gas was highly measured during the weekend than during the week day. Average density of NOx gas and $O_3$ gas was highly measured at daytime than that of afternoon. Average density of NOx gas was highly measured in the center area than the other area. Average density of $O_3$ gas was highly measured at the entrance than the other area. NOx gas concentration was maintained below 0.3ppm, an average for 1 hours, as defined in the parking space law. $O_3$ gas concentration was maintained below 0.08ppm, an average for 1 hours, as defined in the parking space law.

• 천문학회보
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• 제36권1호
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• pp.62.2-62.2
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• 2011

It is well known that the cluster environment can change the atomic gas properties of galaxies through tidal interactions and/or by the hot cluster medium. Meanwhile, the molecular gas is expected to be less vulnerable to its surroundings due to its higher density, and no obvious influence of the environment on the molecular gas properties had been found among cluster spirals until recently. However, in a recent study by Fumagalli et al. (2009) of a sub-sample of Virgo spirals, it has been suggested that HI deficient galaxies can be also CO deficient. In order to further investigate if the HI deficiency indeed can result in the deficiency in molecular gas content, we compare the global CO and HI gas properties of Virgo spirals with those of galaxies in the Ursa Major cluster and the Pisces cluster, much lower density environments than Virgo. We discuss possible consequences of molecular gas deficiency in star formation activity of spiral galaxies in high density environment.

• 천문학회보
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• 제39권1호
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• pp.47.1-47.1
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• 2014

We examine the effect of environment on star formation activity of a sample of galaxy group catalogue given in Tempel et al.(2012) constructed from the Sloan Digital Sky Survey Data Release 8. In order to compare galaxies in different environment, we classify galaxies into two groups: galaxies in low density environment and galaxies in high density environment. After matching colors and apparent magnitudes of the galaxies, we are left with 5912 galaxies in each of the environment category. The fraction of star-forming galaxies in low-density environment is ~34%, higher than ~15% in high-density environment. Star-forming galaxies in low density environment have a higher average SFR value than those in high density environment. The bulge-to-disk ratio for galaxies in two different environment shows bimodal distribution. Regardless of the environment, we find galaxies with high star formation rate despite their red (g-r) color, for which the origin enhancing their star formation rate is investigated.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권3호
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• pp.156-160
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• 2006

In whole world consciousness of environment maintenance have increased very quickly for the end of the 20th century. To use and disuse toxic substances have been controled at the field of industry. Also the field of lighting source belong to environmental control. And in the future the control will be strong. In radiational mechanism of fluorescence lamp mercury is the worst environmental problem and root. In the mercury free lighting source system the Xe gas lamp is one type. And the Ne:Xe and Ne:Ar mixed gas lamp improve firing voltage of Xe gas lamp. Purpose of this study is to understand ideal mixing-ratio of Ne:Xe and Ne:Ar gas by electron temperature and electron density for mercury free lamp. Before ICP was designed, basic parameters of plasma, which are electron temperature and electron density, were measured and calculated by single-Langmuir probe. Property of electron temperature and electron density were confirmed by changing ratio of Ne:Xe and Ne:Ar.

• 한국분무공학회지
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• 제27권3호
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• pp.134-143
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• 2022

When a recess is applied to a swirl coaxial injector that uses liquid and gas propellants, a self-pulsation phenomenon in which the spray oscillates at regular intervals may occur. The phenomenon is caused by the interaction between the liquid and gas propellants inside the injector recess region. The propellants' kinetic energies are expected to affect significantly the spray oscillation. Therefore, cold-flow tests using helium as a gas-simulating propellant were conducted and compared with the results of the previous study using air. Dynamic pressure was measured in the injector manifold and frequency characteristics were investigated through the fast Fourier transform analysis. In the experimental environment, the helium density was about seven times lower than the air density. Accordingly, the intensity of pressure fluctuations was confirmed to be greater when air was used. At the same kinetic energy condition, the perturbation frequency was almost identical in the low flow rate conditions. However, as the flow rate increased, the self-pulsation frequency was higher when helium was used.

• Progress in Superconductivity
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• 제14권2호
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• pp.116-121
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• 2012

Effect of mixed gas and additional Mg powder in an annealing process of the $MgB_2$ is investigated. Four different type of samples were prepared, each in different annealing environment of Ar, $Ar+4%H_2$, Ar with Mg powder and $Ar+4%H_2$ with Mg powder. Different annealing environment did not affect the electron-phonon interaction which is reflected from the same superconducting transition of 36.6 K for all samples. The reducing effect of hydrogen is clearly depicted from the presence of excess Mg in sample synthesized in $Ar+4%H_2$ gas implying the reduced rate of reaction between Mg and B. This has manifested itself in terms of slightly increased high-field critical current density of the sample. In contrast, the sample synthesized in $Ar+4%H_2$ with Mg powder, has shown overall enhancement in the superconducting properties as presented by higher diamagnetic saturation and critical current density.

• 한국분말재료학회지
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• 제22권1호
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• pp.32-38
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• 2015

The effect of heat treatment environment on the microstructure and properties of tantalum coating layer manufactured by kinetic spraying was examined. Heat treatments are conducted for one hour at $800^{\circ}C$, $900^{\circ}C$, and $1000^{\circ}C$ in two different environments of vacuum and Ar gas. Evaluation of microstructure and physical properties are conducted. High density ${\alpha}$-tantalum single phase coating layer with a porosity of 0.04% and hardness of 550 Hv can be obtained. As heat treatment temperature increases, porosity identically decreases regardless of heat treatment environment (vacuum and Ar gas). Hardness of heat treated coating layer especially in Ar gas environment deceases from 550 Hv to 490 Hv with increasing heat treatment temperature. That in vacuum environment deceases from 550 Hv to 530 Hv. The boundary between particles became vague as heat treatment temperature increases. Oxygen distribution of tantalum coating layer is minute after heat treatment in vacuum environment than Ar gas environment.

• 천문학회보
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• 제40권1호
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• pp.77.2-77.2
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• 2015

Galaxies are known to evolve passively in the cluster environment. Indeed, much evidence for HI stripping has been found in cluster galaxies to date, which is likely to be connected to their low star formation rate. What is still puzzling however, is that the molecular gas, which is believed to be more directly related to star formation, shows no significant difference in its fraction between the cluster population and the field galaxies. Therefore, HI stripping alone does not seem to be enough to fully understand how galaxies become passive in galaxy clusters. Intriguingly, our recent high resolution CO study of a subsample of Virgo spirals which are undergoing strong ICM pressure has revealed a highly disturbed molecular gas morphology and kinematics. The morphological and kinematical peculiarities in their CO data have many properties in common with those of HI gas in the sample, indicating that strong ICM pressure in fact can have impacts on dense gas deep inside of a galaxy. This implies that it is the molecular gas conditions rather than the molecular gas stripping which is more responsible for quenching of star formation in cluster galaxies. In this study, using multi transitions of 12CO and 13CO, we investigate the density and temperature distributions of CO gas of a Virgo spiral galaxy, NGC 4402 to probe the physical and chemical properties of molecular gas and their relations to star formation activities.

• 천문학논총
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• 제30권2호
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• pp.491-494
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• 2015

We present 12CO (2-1) data for four spiral galaxies (NGC 4330, NGC 4402, NGC 4522, NGC 4569) in the Virgo cluster that are undergoing different ram pressure stages. The goal is to probe the detailed molecular gas properties under strong intra-cluster medium (ICM) pressure using high-resolution millimeter data taken with the Submillimeter Array (SMA). Combining this with Institut de RadioAstronomie $Millim{\acute{e}}trique$ (IRAM) data, we also study spatially resolved temperature and density distributions of the molecular gas. Comparing with multi-wavelength data (optical, $H\small{I}$, UV, $H{\alpha}$), we discuss how molecular gas properties and star formation activity change when a galaxy experiences $H\small{I}$ stripping. This study suggests that ICM pressure can modify the physical and chemical properties of the molecular gas significantly even if stripping does not take place. We discuss how this affects the star formation rate and galaxy evolution in the cluster environment.

• 한국대기환경학회지
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• 제17권1호
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• pp.75-84
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• 2001

Hot gas filtration method via using ceramic filters is an evolving technology applicable to numerous industrial and air pollution control processes. Alumino silicate, organic and inorganic binders were the major raw materials in manufacturing ceramic filters. In this work, disc type ceramic filters(50$\phi$$\times$10t) were manufactured by vacuum forming processes using ceramic raw materials. The porosity and bulk density of disc type ceramic filers ranged from 86 to 89% and from 0.27 to 0.36 g/㎤, respectively. In this work disc type ceramic medium were tested utilizing coupon experimental apparatus. Disc type filters showed high collection efficiencies over 99.96% with Darchs law coefficients of 4.1$\times$10(sup)10~9.63$\times$10(sup)10/$m^2$ depending on mean pore sizes. In addition, filtration and detachment of ceramic filters turned out to be performed effectively using 10 cm/sec face velocity, 5 minutes filtration cycle, 100msec pulse jet valve opening time and 3 bar pulsing pressure.