• Atmosphere
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• v.19 no.4
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• pp.331-344
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• 2009

A sensitivity study has been performed using ARPS (Advanced Regional Prediction System) version 5.2.10 in a downslope windstorm case of 12-13 February 2006. The purpose of this study was to find out the role of the inversion layer of temperature mainly in relation to the strength of the downslope winds over the Yeongdong region located downstream of the Taebaek mountains. Under the conditions of N (Brunt-$V{\ddot{a}}is{\ddot{a}}la$ frequency)=0.008 and N=0.016, the effects of the presence of the inversion layer, its variation of height of the layer, and the depth of the layer were identified. The sensitivity experiments suggested that the inversion layer effected the downstream wind speed of the mountains under both conditions of N=0.008 and N=0.016, and notably when the inversion layer was located near the mountain crest the downstream wind speed of the mountains was strong (~ $27ms^{-1}$) only under the condition of N=0.016. In addition, when the atmosphere was rather stable (N=0.016) and the depth of the layer was relatively thin (765 m) the downstream wind speed of the mountains was the strongest (~ $30ms^{-1}$) among the sensitivity experiments.

• Journal of Powder Materials
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• v.17 no.4
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• pp.295-301
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• 2010

Multi shell graphite coated Ag nano particles with core/shell structure were successfully synthesized by pulsed wire evaporation (PWE) method. Ar and $CH_4$ (10 vol.%) gases were mixed in chamber, which played a role of carrier gas and reaction gas, respectively. Graphite layers on the surface of silver nano particles were coated indiscretely. However, the graphite layers are detached, when the particles are heated up to $250^{\circ}C$ in the air atmosphere. In contrast, the graphite coated layer was stable under Ar and $N_2$ atmosphere, though the core/shell structured particles were heated up to $800^{\circ}C$. The presence of graphite coated layer prevent agglomeration of nanoparticles during heat treatment. The dispersion stability of the carbon coated Ag nanoparticles was higher than those of pure Ag nanoparticles.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.73-76
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• 2003

SF$_{6}$ (Sulfur Hexafluoride) is a gaseous compound whose use is being greatly increased recently. The compound has a negligible background concentration from natural sources and is stable in most of groundwater environments. Therefore, SF$_{6}$ has potential for a dating tool for young groundwater. It has many advantages over chlorofluorocarbons (CFCs) for groundwater investigation that sampling procedure is much simpler than CFCs and its growth is continued up to at least near future in the atmosphere. However, solubility of SF$^{6}$ is so low that excess air causes large uncertainties in recharge date of groundwater. To compensate the limitation, $N_2$/Ar method can be employed to estimate excess air content. A groundwater study is currently carrying out in Jeju Island using SF$_{6}$ as an environmental tracer, Well waters and spring waters were sampled for SF$_{6}$ and $N_2$/Ar. To establish SF$_{6}$ input history in the study area, air sampling is being conducted in the area near the center of the island on a monthly and weekly basis. Based on the present data, the level of SF$_{6}$ concentration in the atmosphere of the Island is corresponding to the trend of the Northern Hemisphere.

• Transactions on Electrical and Electronic Materials
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• v.5 no.2
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• pp.50-54
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• 2004

The AgInS$_2$epilayers with chalcopyrite structure grown by using a hot-wall epitaxy (HWE) method have been confirmed to be a high quality crystal. From the optical absorption measurement, the temperature dependence of the energy band gap on the AgInS$_2$/GaAs was derived as the Varshni's relation of E$\_$g/(T) = 2.1365 eV - (9.89${\times}$10$\^$－3/ eV/K) T$^2$/(2930＋T eV). After the as-grown AgInS$_2$/GaAs was annealed in Ag－, S－. and In-atmosphere, the origin of point defects of the AgInS$_2$/GaAs has been investigated by using the photoluminescence (PL) at 10 K. The native defects of $V_{Ag}$, $V_s$, $Ag_{int}$, and $S_{int}$ obtained from PL measurement were classified to donors or accepters type. And, we concluded that the heat-treatment in the S- atmosphere converted the AgInS$_2$/GaAs to optical p-type. Also, we confirmed that the In in the AgInS$_2$/GaAs did not form the native defects because the In in AgInS$_2$did exist as the form of stable bonds.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.6
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• pp.189-197
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• 2012

In this paper, we propose an optimal path search algorithm that applies the received signal strength between a mobile device and a satellite. Because the common path search algorithm is only based on the shortest path search, it is difficult to provide stable multimedia services for the satellite mobile devices. The proposed algorithm provides the stable communication environment for the satellite mobile devices based on received signal strength. In Satellite communications, changes in the radio quality are severe depending on the receiving environment. Therefore, an accurate analysis of the receiving environment characteristics is very important for providing stable multimedia services of satellite communications. The causes of radio attenuation are atmosphere attenuation, vegetation attenuation and buildings attenuation. These factors were applied to analyze the received signal strength. The proposed algorithm can search the optimal path in urban for stable satellite multimedia services.

• Journal of Soil and Groundwater Environment
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• v.20 no.3
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• pp.34-40
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• 2015

Studies using stable water vapor isotopes have been recently conducted over the past two decades because of difficulties in analysis and sample collection in the past. Stable water vapor isotope data provide information of the moisture transport from ocean to continent, which are also used to validate an isotope enabled general circulation model for paleoclimate reconstructions. The isotopic compositions of groundwater and water vapor also provide a clue to how moisture moves from soil to atmosphere by evapotranspiration. International Atomic Energy Agency designates the stations over the world to observe the water vapor isotopes. To analyze the water vapor isotopes, a cryogenic sampling method has been used over the past two decades. Recently, two types of laser-based spectroscopy have been developed and remotely sensed data from satellites have the global coverage. In this review, measurements of isotopic compositions of water vapor will be introduced and some studies using the water vapor isotopes will also be introduced. Finally, we will suggest the future study in Korea.

• Bulletin of the Korean Chemical Society
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• v.17 no.7
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• pp.637-642
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• 1996

Preparation and properties of potential CVD (Chemical Vapor Deposition) precursors for the TiO2, a major component of the perovskite materials such as PT, PLT, PZT, and PLZT were investigated. Reactions between β-diketones and TiMe3, formed in situ failed to produce stable Ti(β-diketonate)3 complexes but a stable purple solid, characterized as (OTi(BPP)2)2 (BPP=1,3-biphenyl-1,3-propanedione) was obtained when BPP was used. Several new Ti(Oi-Pr)2(β-diketonate)2 complexes with aromatic or ring substituents were synthesized by the substitution reaction of Ti(OiPr)4by β-diketones and characterized with 1H NMR, IR, ICP, and TGA. Solid complexes such as Ti(Oi-Pr)2(BAC)2 (BAC=1.-phenyl-2,4-pentanedione), Ti(Oi-Pr)2(BPP)2, Ti(Oi-Pr)2(1-HAN)2 (1-HAN=2-hydroxy-1-acetonaphthone), Ti(Oi-Pr)2(2-HAN)2 (2-HAN=1-hydroxy-2-acetonaphthone), Ti(Oi-Pr)2(ACCP)2 (ACCP=2-acetylcyclopentanone), and Ti(Oi-Pr)2(HBP)2 (HBP=2-hydroxybenzophenone) were found to be stable toward moisture and air. Ti(Oi-Pr)2(ACCP)2 and Ti(Oi-Pr)2(HBP)2 were proved to have lower melting points and higher decomposition temperatures. However, these complexes are thermally stable and pyrolysis under an inert atmosphere resulted in incomplete decomposition. Ti(Oi-Pr)2(DPM)2 (DPM=dipivaloylmethane) and Ti(Oi-Pr)2(HFAA)2 (HFAA=hexafluoroacetylacetone) were sublimed substantially during the thermal decomposition. Pyrolysis mechanism of these complexes are dependent on type of β-diketone but removal of Oi-Pr ligands occurs before the decomposition of β-diketonate ligands.

• Korean Journal of Materials Research
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• v.8 no.12
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• pp.1090-1098
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• 1998

$RuO_2$ thin films were deposited on Si and Ru/Si substrates by rf magnetron reactive sputtering and annealed in oxygen atmosphere(1atm) to investigate their thermal stability and diffusion barrier property. $RuO_2$ thin films were thermally stable up to 700\ulcorner for 10min. in oxygen atmosphere and showed excellent barrier property against the interdiffusion of silicon and oxygen. After annealing at $750^{\circ}C$ , however, volatilization to higher oxide occurred at the surface and inside of $RuO_2$ thin film and diffusion barrier property was also deteriorated. When annealed at $800^{\circ}C$, $RuO_2$thin film showed a different microstructure from that of $RuO_2$ thin film annealed at 75$0^{\circ}C$. It is likely that surface defect structure of $RuO_2$, $RuO_3$, and excess oxygen had an influence on the mode of volatilization with increasing annealing temperature.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.3
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• pp.56-63
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• 2023

In this paper, we studied the effect of electron beam irradiation on sol-gel indium-gallium-zinc oxide (IGZO) thin films under air and nitrogen atmosphere and carried out the electrical characterization of the s ol-gel IGZO thin film transistors (TFTs). To investigate the optical properties, crystalline structure and chemical state of the sol-gel IGZO thin films after electron beam irradiation, UV-Visible spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were carried out. The sol-gel IGZO thin films exhibited over 80% transmittance in the visible range. The XRD analysis confirmed the amorphous nature of the sol-gel IGZO films regardless of electron beam irradiation. When electron beam irradiation was conducted in a nitrogen (N₂) atmosphere, we observed an increased proportion of peaks related to M-O bonding contributed to the improved quality of the thin films. Sol-gel IGZO TFTs subjected to electron beam exposure in a nitrogen atmosphere exhibited enhanced electrical characteristics in terms of on/off ratio and electron mobility. In addition, the electrical parameters of the transistor (on/off ratio, threshold voltage, electron mobility, subthreshold swing) remained relatively stable over time, indicating that the electron beam exposure process in a nitrogen atmosphere could enhance the reliability of IGZO-based thin-film transistors in the fabrication of sol-gel processed TFTs.

• Journal of Mechanical Science and Technology
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• v.17 no.3
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• pp.440-448
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• 2003

In the present paper, numerical simulations of buoyant plume dispersion in a neutral and stable atmospheric boundary layer have been carride out. A Lagrangian Stochastic Model (LSM) with a Non-Linear Eddy Viscosity Model (NLEVM) for turbulence is used to generate a Reynolds stress field as an input condition of dispersion simulation. A modified plume-rise equation is included in dispersion simulation in order to consider momentum effect in an initial stage of plume rise resulting in an improved prediction by comparing with the experimental data. The LSM is validated by comparing with the prediction of an Eulerian Dispersion Model (EDM) and by the measured results of vertical profiles of mean concentration in the downstream of an elevated source in an atmospheric boundary layer. The LSM predicts accurate results especially in the vicinity of the source where the EDM underestimates the peak concentration by 40% due to inherent limitations of gradient diffusion theory. As a verification study, the LSM simulation of buoyant plume dispersions under a neutral and stable atmospheric condition is compared with a wind-tunnel experiment, which shows good qualitative agreements.