• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1424-1426
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• 1997

저전압 구동이 가능한 교류구동형 박막전기발광소자를 구현하기 위해 높은 유전상수를 가지며 특히 광학적 굴절률이 발광박막과 유사하여 광학적 특성 개선에도 효과적인 것으로 알려져 있는 $Ta_2O_5$를 제조하였다. $Ta_2O_5$박막은 rf-magnetron sputtering방법으로 형성하였으며 기판온도, working pressure, 박막의 두께에 따른 전기적인 특성을 조사하였다. 10mTorr에서 제조된 $Ta_2O_5$박막은 $22{\sim}26$의 비유전율을 보였고, 유전손실은 $0.007{\sim}0.03(1kHz{\sim}10kHz)$의 값을 보였다. $100^{\circ}C$에서 제조된 박막의 전하저장용량은 $7.9{\mu}C/cm^2$이었다. 제조된 박막의 항복전압은 인가 전압의 극성에 의존하며, 전류특성은 기판온도와 200nm와 300nm의 두께에서는 $V^{1.95}{\sim}V^{2.35}$에 비례하는 space charge limited current특성을 보였고, 400nm에서는 Poole Frenkel특성을 보였다. 이상의 결과로 TFEL소자에 응용에 적합한 $Ta_2O_3$ 박막은 $200^{\circ}C$에서 증착되고 200nm와 300nm인 것으로 나타났으며, 제조된 MIS구조(ITO-$Ta_2O_5$-ZnS-Al)의 ACTFEL소자에서의 전도전하는 각각 $13uC/cm^2$, $8.3uC/cm^2$로 조사되었다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.2
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• pp.107-112
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• 1982

In order to analyze and investigate in the fatigue behavior of the notched specimens under the two level stressing, the U-notched specimens of structural carbon steel which is generally used is prepared. The obtained results are summarized as follows; (1) The fatigue limit of the U-notched specimens is lower than that of the unnotched. The fatifue notch factor (.betha.) of the U-notched specimens is 1.44 for mild steel and 1.52 for harden steel. The notch sensitivity (q) is 0.68 for mild steel and o.8 for harden steel. That is, these facts show that harden steel is more sensitive to the notch than mild steel. (2) The fatigue life time of the U-notched specimens under the overstressing is shorter than under the constant stressing, and the degree of fatigue life time decrease is different to each stress level; the degree for the high stress level is more than for the low stress level. (3) The fatigue life time of the U-notched specimes under the understressing is longer than under the constant stressing, and the degree of fatigue life time increase for the low stress level is more than for the high stress level.

• Journal of The Korean Astronomical Society
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• v.36 no.1
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• pp.1-12
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• 2003

Nonthermal particles can be produced due to incomplete thermalization at collisionless shocks and further accelerated to very high energies via diffusive shock acceleration. In a previous study we explored the cosmic ray (CR) acceleration at cosmic shocks through numerical simulations of CR modified, quasi-parallel shocks in 1D plane-parallel geometry with the physical parameters relevant for the shocks emerging in the large scale structure formation of the universe (Kang & Jones 2002). Specifically we considered pancake shocks driven by accretion flows with $U_o = 1500 km\;s^{-l}$ and the preshock gas temperature of $T_o = 10^4 - 10^8K$. In order to consider the CR acceleration at shocks with a broader range of physical properties, in this contribution we present additional simulations with accretion flows with $U_o = 75 - 1500 km\;s^{-l}$ and $T_o = 10^4K$. We also compare the new simulation results with those reported in the previous study. For a given Mach number, shocks with higher speeds accelerate CRs faster with a greater number of particles, since the acceleration time scale is $t_{acc}\;{\propto}\;U_o^{-2}$. However, two shocks with a same Mach number but with different shock speeds evolve qualitatively similarly when the results are presented in terms of diffusion length and time scales. Therefore, the time asymptotic value for the fraction of shock kinetic energy transferred to CRs is mainly controlled by shock Mach number rather than shock speed. Although the CR acceleration efficiency depends weakly on a well-constrained injection parameter, $\epsilon$, and on shock speed for low shock Mach numbers, the dependence disappears for high shock Mach numbers. We present the 'CR energy ratio', ${\phi}(M_s)$, for a wide range of shock parameters and for $\epsilon$ = 0.2 - 0.3 at terminal time of our simulations. We suggest that these values can be considered as time-asymptotic values for the CR acceleration efficiency, since the time-dependent evolution of CR modified shocks has become approximately self-similar before the terminal time.

• Economic and Environmental Geology
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• v.25 no.1
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• pp.27-39
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• 1992

Several pyrophyllite deposits occur around the Milyang area where Cretaceous andesitic rocks and spatially related granitic rocks are widely distributed. Pyrophyllite ores consist mainly of pyrophyllite, and quartz with small amount of sericite, pyrite, dumortierite, and diaspore. The andesitic rocks and spatially related granitic rocks in this area suggest that they could be formed from the same series of a calc-alkaline magma series. The contents of $SiO_2$, $Al_2O_3$, LOI(loss on ignition) are enriched, and $K_2O$, $Na_2O$, CaO, MgO, $Fe_2O_3$ are depleted in altered andesitic rocks and ores. Enrichment of As, Cr, Sr, V, Sb and depletion of Ba, Cs, Ni, Rb, U, Y, Co, Sc, Zn are characteristic during mineralization. The pyrophyllite ores can be discriminated from the altered-and unaltered wall-rocks by an increasing of $(La/Lu)_{cn}$ from 4.18~22.13 to 8.98~55.05. In R-mode cluster analysis, Yb-Lu-Y, La-Ce-Hf-Th-U-Zr, $TiO_2-V-Al_2O_3$, Sm-Eu, $CaO-Na_2O-MnO$, Cu-Zn-Ag, $K_2O-Rb$ are closely correlated. In the discriminant analysis of multi-element data, $P_2O_5$, As, Cr and $Fe_2O_3$, Sr are helpful to identify the ores from the unaltered-and altered wall-rocks. In the factor analysis, the factors of alteration of andesitic rocks and ore mineralization were extracted. In the change of ions per unit volume, $SiO_2$, $Al^{3+}$ and LOI are enriched and $Na^+$, $K^+$, $Ca^{2+}$, $Mg^{2+}$, $Mn^{2+}$ and $Fe^{3+}$ are depleted during the alteration processes. The Milyang and the Sungjin pyrophyllite deposits could be mineralized by hydrothermal alteration in a geochemical condition of low activity ratio of alkaline ions to hydrogen ion with reference to spatially related granitic rocks.

• Economic and Environmental Geology
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• v.42 no.6
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• pp.549-559
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• 2009

The objectives of this study are to investigate the biomineralization of goethite and lepidocrocite formed on the twisted-stalk and the sheathed-filament structure that is suggest microbe origin, and heavy metal in the yellow Fe-hydroxide. On the ratio of Cl and the Cl/Br ratios that are a pollution and non-pollution of groundwaters, it is indicated that the groundwater in this areas were relatively contaminated by human activity. The composition of the yellow Fe-hydroxide consisted mainly of $Fe_2O_3$ and $SiO_2$. The content of $Fe_2O_3$ ranges from 58.57 wt.% to 75.7 3wt.%, and $SiO_2$ content ranges from 5.8 wt.% to 16.17 wt.%. Heavy metal elements such as Zn(max. 6,160 mg/kg), Pb(max. 377 mg/kg), U(max. 503 mg/kg), Cr(max. 203 mg/kg), Cu(max. 77 mg/kg), V(max. 162 mg/kg), Ni(max. 105 mg/kg) were observed to be rich in those yellow Fe-hydroxide. The lath and platy crystals and needle-shaped crystals were clearly observed on the twisted-stalks and sheathed-filaments structure. The goethite, gypsum, and lepidocrocite were identified in the yellow Fe-hydroxide by x-ray powder diffraction.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.123-124
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• 2011

Tris(8-quinolinolato)aluminum(III) (Alq3)와 Cathode 사이에 Ba o f 1nm를 삽입함으로써 OLED device의 성능이 향상되었다. 이 소자에 삽입된 Ba는 electron-injection barrier height를 낮추어서 전자주입에 영향을 주었다. 그러나 Ba 의 두께가 1nm이상일 경우에는 특성이 안 좋은 소자 성능을 보여줌을 알 수 있었다.

• Journal of Korean Society for Atmospheric Environment
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• v.32 no.6
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• pp.559-574
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• 2016

Based on air quality monitoring data ('10~'14) of Suwon City provided by the Korean Department of Environment, a fundamental statistic for 5 criteria pollutants such as $SO_2$, CO, $NO_2$, $O_3$, and $PM_{10}$ was initially investigated. The purpose of this paper was to review the ambient air quality standards(AAQS) of Korea, the U.S.A. and the EU and further to assess the degree of standard strength by the achievability of the AAQS comparing each national standard. Since the level and the way of standards for each air pollutant are various among countries, it is difficult to determine the degree of relative attainment using the same set of data above. Further when all the areas having bad air quality for a specific pollutant are classified as non-attainment case, it is more difficult to assess the degree of standard strength. Thus we introduced a new concept called the average concentration distance (ACD) to quantitatively estimate the strength. As results, the Korean 1-hr $NO_2$ AAQS is slightly stronger than the US standard and weaker than the EU standard. The Korean $O_3$ standard is strongest; however, the Korean $PM_{10}$ standard is weakest. Furthermore the equivalent levels of 8-hr $O_3$ standards in the U.S.A. and the EU were respectively estimated as 97.5 and 95.7 percentiles of the Korean standard with maintaining the existing standard of 60 ppb.

• Korean Journal of Ecology and Environment
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• v.36 no.2 s.103
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• pp.139-149
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• 2003

This study was conducted to determine limiting nutrients and the physiological characteristics of phytoplankton in response of nutrients in Lake Paldang from March 2002 to October 2002. A field research was conducted along with laboratory batch culture experiment to find the limiting nutrients and the growth kinetics. According the results of Chl. a TP relationship, TN/TP ratio, and nutrient addition bioassay, phosphorus appeared to be a major limiting nutrient in Lake Paldang and thus the lake productivity was greatly influenced by it. P limitation for the phytoplankton of Lake Paldang varied with season, and the possibility of limitation by nitrogen and silica also occurred. The degree of P limitation was greatest during spring when the concentration of dissolved phosphorus is relatively much lower than summer and autumn. The maximum growth rate (${\mu}_{max}$) and half saturation concentration ($K_u$) of Lake Paldang phytoplankton ranged from 0.8${\sim}$1.1$day^1$ and from 0.1${\sim}$O.8${\mu}M$, respectively. $K_u$ was highest during May ($0.8{\mu}M$) and the lowest during September ($0.1{\mu}M$). Such result may be induced by the phytoplankton cell quota that showed the lowest concentration ($0.13{\mu}gP/{\mu}gChl.$ a) during May. The growth kinetics showed that phytoplankton growth in Lake Paldang was faster during summer and autumn than spring, suggesting that the Potential of algal bloom is high after the summer monsoon season.

• Animal Systematics, Evolution and Diversity
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• v.12 no.1
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• pp.1-15
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• 1996

Twenty six species of 8 genera of the Korean Cochylini belonging to Tortricidae, excluding a genus Phalonidia, are recognized during the course of this study. Among them 7 species, Aethes citreoflavus Kuznetsov, Cochylidia heydeniana (Herrich- Sch$\ddot{a}$ffer), C. moguntiana (R$\ddot{o}$sier), Eupoecilia angustana (H$\ddot{u}$bner), E. kobeana Razowski, Pseudargyrotoza calvicaput (Walsingham), and Stenodes cuspidatus Ge, are reported for the first time from Korea. A key to the genera is given. Male and female genitalic structures of 7 unrecorded species are briefly redescribed and illustrated.

• Journal of the Optical Society of Korea
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• v.20 no.5
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• pp.567-574
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• 2016

We propose a highly birefringent and dispersion compensating photonic crystal fiber based on a double line defect core. Using a finite element method (FEM) with a perfectly matched layer (PML), it is demonstrated that it is possible to obtain broadband large negative dispersion of about -400 to -427 ps/(nm.km) covering all optical communication bands (from O to U band) and to achieve the dispersion coefficient of -425 ps/(nm.km) at 1.55μm. In addition, the highest birefringence of the proposed PCF at 1.55 μm is 1.92 × 10^-2 and the value of birefringence from the wavelength of 1.26 to 1.8 μm (covering O to U bands) is about 1.8 × 10^-2 to 1.92 × 10^-2. It is confirmed that from the simulation results, the confinement loss of the proposed PCF is always less than 10^-3 dB/km at 1.55 μm with seven fiber rings of air holes in the cladding.