• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.3
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• pp.131-137
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• 2005

This paper describes a new approach to the algorithm and fundamental characteristics of the device for monitoring the leakage currents flowing through zinc oxide (ZnO) surge arresters. In order to obtain a technique for a new on-line monitoring device that can be used in the deterioration diagnosis of ZnO surge arresters, the new algorithm and on-line leakage current detection device for extracting the resistive and capacitive currents using the phase shift addition method were proposed. The computer-based on-line monitoring device can sense accurately the power frequency leakage currents flowing through ZnO surge arresters. The on-line leakage current monitoring device of ZnO surge arresters proposed in this work has the high sensitivity compared to the third harmonic leakage current detection devices. As a consequence, it was found that the proposed leakage current monitoring device would be useful for forecasting the defects and degradation of ZnO surge arresters.

• Bulletin of the Korean Chemical Society
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• v.21 no.12
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• pp.1239-1244
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• 2000

A study of K addition to the catalyst of CoMo/ ${\gamma}-Al_2O_3$ was studied. The catalyst with 10 at% of K to Mo atoms in 3C10M, the catalyst added 3 wt% CoO to 10 wt% $MoO_3/{\gamma}-Al_2O_3$, showed the highest activity for water gas shift reaction. The addition of K retarded the reducibility of cobalt-molybdenum catalysts. It gave, however, good dispersion and large BET surface area to the catalysts which were attributed to the disappearance of polymolybdate clustyer such as $Mo_7O_{24}^{6-}$ and the formation of small Mo$O_4^{2-}$ cluster. It was confirmed by the analyses of pore size distribution, activation energy, Raman spectroscopy, and electron diffraction. The activation energies and the frequency factors of the catalysts 3C10M and 5KC10M (the catalyst added 5 at% K for Mo to the catalyst 3C10M) were 43.1 and 47.8 kJ/mole, and 4,297 and 13,505 $sec^{-1}$, respectively. These values were also well correlated with our suggestion. These phenomena were attributed to the direct interaction between K and CoMo oxides irrelevant to the support.

• Bulletin of the Korean Chemical Society
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• v.9 no.5
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• pp.317-322
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• 1988

Premicellar precipitation, resolubilization and luminescing behaviors of $RuL_3^{2+}$ (L = bpy, phen, $Me_2bpy$) in aqueous alkylsulfate and sulfonate solutions were studied. Addition of the anionic surfactants to $RuL_3\;^{2+}$ solutions caused initial precipitation which was redissolved by further addition of the surfactants. The apparent solubility products $K_{sp}$'s of the precipitates were evaluated assuming 1:2 salt formation. The values were smaller as the ligand is more hydrophobic and the length of hydrocarbon chain of the surfactant is longer. The $K_{sp}$ values for L = bpy were constant over wide surfactant concentration range. However, those for L = $Me_2bpy$ and also for phen, but to less extent, increased with the surfactant concentration. The resolubilization of 1:2 salts was followed by red-shift of emission band and extensive emission quenching above critical concentration of the surfactants. The critical concentration was lower for more hydrophobic surfactant. For L = $Me_2bpy$, the blue-shifted emission band with enhanced emission intensity was observed in intermediate surfactant concentration region. The high ionic strength of media prevented the precipitate formation, but facilitated the red-shift of the emission bands. The results support that the precipitate is dissolved by accretion of surfactant anions to the salts to form water-soluble surfactant-rich $RuL_3$-surfactant anionic species. These species appeared to aggregate cooperatively to produce large clusters which exhibited the red-shifted emission.

• Journal of Pharmacopuncture
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• v.27 no.3
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• pp.199-210
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• 2024

Objectives: Few studies have examined the impact of healthy sleep among general workers on individuals and society. Therefore, the status and risk factors of sleep disturbances among general workers were investigated. In addition, this study assessed the degree to which cold and heat symptoms are associated with sleep disturbances. Methods: A nationwide cross-sectional study was conducted through an online questionnaire focused on sleep disturbances of the general public in 2021. The degree of cold-heat pattern Identification (CHPI) of the general public was also surveyed. Descriptive statistics and multivariate logistic regression were used to derive the study results. Results: Data from 2,822 workers out of 3,900 valid questionnaires were analyzed. Approximately half of the respondents (49.93%) had sleep disturbances. Among the types of work, self-employed, two-shift work, and working more than 53 hours were associated with sleep disturbances. Sleep disturbances were positively associated with six cold and heat symptoms: three cold symptoms (coldness of the abdomen, coldness of body, and pale face) and three heat symptoms (body feverishness, feverishness of the limbs, and drinking cold water). Conclusion: Customized policies to maintain healthy work are needed for self-employed work, two-shift work, and long working hours, which are risk factors for workers' sleep disturbances. In addition, medical personnel can effectively diagnose and treat sleep disturbances considering the worker's cold and heat symptoms.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.230.1-230.1
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• 2010

조촉매(Promotor)인 Na은 수성가스전이(Water Gas Shift, WGS) 반응 시 생성된 포름산염의 C-H결합을 쉽게 분해하는 역할을 한다. 본 연구에서는 $Pt/CeO_2$ 촉매의 성능 향상을 위해 Na의 담지량을 변화시켜 촉매적 활성을 비교하여 보았다. 제조된 담체는 침전법(Precipitation)을 사용하여 제조하였으며 $500^{\circ}C$에서 6시간 소성하였다. Pt 담지량은 1wt%로 고정하였고 Na 담지량은 1 wt%~5 wt%로 변화를 주어 동시(공)-함침법(Co-incipient wetness method)으로 담지 시켰다. 반응 실험은 공간속도(Gas Hourly Space Velocity, GHSV) $45,385h^{-1}$에서 수행하였다. WGS 반응 결과 3 wt%의 Na이 담지된 $Pt/CeO_2$ 촉매의 경우를 제외하고 나머지 Na이 담지된 촉매들은 비교적 높은 CO의 전환율을 나타내었다. 특히 2 wt%의 Na이 담지된 $Pt/CeO_2$ 촉매는 가장 높은 CO의 전환율을 나타내었다. 따라서 Na 담지량의 변화가 포름산염의 C-H결합 분해에 영향을 미친다는 것을 알 수 있다.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.2
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• pp.71-78
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• 2017

The sidereal day of a Global Positioning System (GPS) satellite was intended to equal one half of a sidereal day of the Earth. However, the sidereal day of GPS satellites has become unequal to one half of a sidereal day of the Earth. This is fundamentally caused by the non-sphericity of the Earth and the gravity of the Moon. The difference between sidereal days of GPS satellites and the Earth is known as a sidereal shift. The details surrounding sidereal shifts and their origins have yet to be fully understood. We calculated the periodicity of sidereal shifts for GPS satellites using broadcast ephemeris data. To conduct a periodic analysis of the sidereal shift, we employ the Lomb-Scargle periodogram method. It shows that the orbit periods of GPS satellites have small-amplitude perturbations with a 13.6-day period. In addition, we compare the GPS satellite orbit periods with the periodicity of geomagnetic indices and the solar wind parameters to identify the cause of the perturbations. Our results suggest that the solar wind stream might also affect the 13.6-day period of the sidereal shifts.

• Journal of Information Display
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• v.6 no.1
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• pp.28-32
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• 2005

The electronic structures of Al/RbF/tris-(8-hydroxyquinoline)aluminium ($Alq_3$) and $Al/CaF_2/Alq_3$interfaces were investigated using x-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). For both systems, the UPS showed a significant valence band shift following the deposition of the thin fluoride layers on $Alq_3$. However, the formation of gap state in valence region and the extra peak N 1s core level spectra showed different trends, suggesting that the alkali fluoride and alkali-earth fluoride interlayer have different reaction mechanisms at the interface between Al cathode and $Alq_3$. In addition, the deposition of Al has considerably less effect on the valence band shift compared to the deposition of both RbF and $CaF_2$. These results suggest that the charge transfer across the interface and the resulting gap state formation may have lesser effect on the enhancement of organic light-emitting device performance than the observed valence band shift, which is thought to lower the electron injection barrier.

• Journal of Hydrogen and New Energy
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• v.23 no.2
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• pp.111-116
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• 2012

Na promoted Pt/$CeO_2$ catalysts with various Na amounts (1, 2, and 3wt%) have been applied to water gas shift reaction (WGS) at a gas hourly space velocity (GHSV) of 45515 $h^{-1}$. 1wt%Pt-2wt%Na/$CeO_2$ catalyst exhibited the highest WGS activity at $240^{\circ}C$ among the catalysts prepared in this study. In addition, 1wt%Pt-2wt%Na/$CeO_2$ catalyst showed relatively stable activity with time on stream. The high activity/stability of 1wt%Pt-2wt%Na/$CeO_2$ catalyst was correlated to its easier reducibility and higher oxygen storage capacity (OSC). As a result, 2wt% Na promoted Pt/$CeO_2$ can be a promising candidate catalyst for the single stage WGS, which requires high intrinsic activity at very high GHSV.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.67 no.2
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• pp.82-89
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• 2018

This paper presents a novel prototype of dual mode control based phase shift ZVS PWM high frequency load resonant inverter with lossless snubber capacitors in addition to a single active auxiliary resonant snubber for electromagnetic induction heating(IH) foam metal based consumer fluid dual packs(DPA) heater. The operating principle in steady state and unique features of this voltage source soft switching high frequency inverter circuit topology are described in this paper. The lossless snubber and auxiliary active resonant snubber assisted constant frequency phase shift ZVS PWM high frequency load resonant inverter employing IGBT power modules actually is capable of achieving zero voltage soft commutation over a widely specified power regulation range from full power to low power. The steady state operating performances of this dual mode phase shift PWM series load resonant high frequency inverter are evaluated and discussed on the basis of simulation and experimental results for induction heated foam metal heater which is designed for compact and high efficient moving fluid heating appliance in the consumer pipeline systems.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.257-257
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• 2011

The amorphous indium-gallium-zinc-oxide (a-IGZO) materials for use in high performance display research fields are strongly investigated due to its good performance, such as high mobility and better transparency. However, the stability of a-IGZO materials is increasingly becoming one of critical issues due to the sub-gap electron trap sites induced by rough interfaces during deposition processing. It is well-known that the threshold voltage shift is related to interface roughness and oxygen vacancy formed by breaking weak chemical bonds. Here, we report the better properties of transparent oxide transistors by reducing the threshold voltage shift with an external rf plasma supported magnetron sputtering system. Mainly, our sputtering method causes the surface of sample to be sleek, so that it prevents the formation of various defects, such as shallow electron trap sites in the interface. External rf power was applied from 0 to 50W during RF sputtering process to enhance the stability of our oxide transistor without having a large voltage shift. To observe the effects of external rf-plasma source on the properties of our devices, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM) are carried out to observe surface roughness and morphology of sputtered thin film. In addition, typical electrical properties, such as I-V characteristics are analyzed.