• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 춘계학술발표회 논문집
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• pp.322-323
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• 2012

This study discussed the formation of phosphate conversion coatings on AZ31 Mg alloy (AZ31) from the zinc phosphating bath with various concentrations of sodium fluoride (NaF). The effects of NaF on the formation, structure, composition and electrochemical behavior of the phosphate coatings were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD) weight balances, open circuit potential (OCP) transients, potentiodynamic polarization curves and immersion test. The coatings were composed of two layers: an outer $Zn_2(PO_4)_3.4H_2O$ (hopeite) crystal layer and an inner amorphous of $MgZn_2(PO_4)_2$. NaF concentration is emphasized to be highly effective in the formation of the hopeite crystal and etching and coating rates. Potentiodynamic polarization and immersion test showed that the coatings formed in the zinc phosphating bath with addition of NaF have much higher corrosion resistance than bare AZ31.

• 생태와환경
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• 제36권3호통권104호
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• pp.322-335
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• 2003

낙동강 하류 지역에서 저질의 환경, 산소 소모량 (SOD), 무기 영양염 ($PO_4\;^{3-}$, $NH_4\;^+$, $NO_3\;^-$, $SiO_2$)의 용출량을 측정하여 용출 특성과 저질에 의한 내부 부하량을 추정하고자 하였다. 저질의 SOD는 10 ${\sim}$ $30^{\circ}C$범위에서 온도에 따라 직선적으로 증가하였으며 $Q_{10}$값은 1.1${\sim}$1.6이었고, $20^{\circ}C$기준 SOD는 76${\sim}$120 mg $O_2\;m^{-2}\;hr^{-1}$범위였다. 저질에서 영양염 용출은 호기/빈산소 조건, 온도, 저질의 유기물함량 등의 영향을 크게 받았다. $NH_4\;^+$와 $SiO_2$는 호기조건 및 빈산소 조건에서 용출이 활발하여 용존산소 농도에 관계없이 저질에서 수층으로 이동하였으나 $PO_4\;^{3-}$는 빈산소 조건에서 용출량이 높은 반면 호기 조건에서는 미미하였으며 $25^{\circ}C$이상 조건에서 크게 증가하는 양상을 띠었다. $NH_4\;^+$, $SiO_2$ 및 $PO_4\;^{3-}$의 용출량은 온도 증가에 대해 지수적으로 증가하였으며 온도에 대한 $Q_{10}$은 $PO_4\;^{3-}$가 3.7${\sim}$7.3으로 가장 높았다. 저질에서 $PO_4\;^{3-}$와 $NH_4\;^+$의 용출량은 지역적으로 차이가 컸으나, $SiO_2$ 용출량은 지역적 차이가 미미하였다. 반면 호기 및 빈산소 조건에서 $NO_3\;^-$은 수중에서 저질로 흡수되었으며 그 흡수량은 온도에 따라 직선적으로 증가하였다. 온도에 따른 흡수율 증가는 호기성보다 빈산소 조건에서 더 컸다. 낙동강 하류 지역의 저질 호기조건/빈산소 조건에서 $NH_4\;^+$, $NO_3\;^-$, $PO_4\;^{3-}$ 및 $SiO_2$의 용출량 범위는 각각 -9${\sim}$ 105 mgN $m^{-2}day^{-1}$, -156${\sim}$62 $m^{-2}day^{-1}$ -5${\sim}$5 $m^{-2}day^{-1}$, 및 12 ${\sim}$ 117 $m^{-2}day^{-1}$였다. 낙동강과 서낙동강에서 식물플랑크톤의 1차 생산성과 조체의 C:N:P의 Redfield 비율 106: 16: 1을 이용하여 추정한결과 저질에서 용출되는 $NH_4\;^+$는 식물플랑크톤의 요구량의 9 ${\sim}$23%이었고, $PO_4\;^{3-}$는 11 ${\sim}$ 22%를 차지하였다.

• 한국가금학회지
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• 제36권4호
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• pp.337-342
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• 2009

산란계의 분뇨 발생량과 이화학적 특성을 구명하기 위해 1일령 산란계 200수를 선별하여 공시하였으며, 200수 중 10수씩을 선별하여 분뇨의 채취에 이용하였다. 산란계의 일일수당 평균 분뇨 발생량은 $124.7{\pm}27.5\;g$/수/일이었으며, 계분의 수분함량은 $76.7{\pm}1.9%$, 건물 함량은 $29.1{\pm}3.9\;g$/수/일이었다. 산란계 계분(55주령)의 N, $P_2O_5$ 및 $K_2O$는 각각 $1.39{\pm}0.14$, $0.62{\pm}0.11$ 및 $0.68{\pm}0.09%$이었다. 계분뇨의 pH는 $8.19{\pm}0.71$이었으며, $BOD_5$ 농도는 $50,266{\pm}621\;mg/L$로 나타났다. $COD_{mn}$의 경우 $62,832{\pm}803\;mg/L$이었으며, SS는 $121,725{pm}16,165\;mg/L$를 나타냈다. 계분의 중금속 함량 중 Pb은 $0.008{\pm}0.0012\;ppm$으로 규제 농도인 150 ppm보다 크게 낮았고, Cd의 경우 검출되지 않았으며, As는 $0.008{\pm}0.0017\;ppm$으로 검출되었다. Hg은 $0.003{\pm}0.0013\;ppm$이었으나, 규제 농도인 2 ppm에 미치지 못하였다. 따라서, 본 시험의 결과로 국내 산란계의 평균 분뇨 발생량을 추정할 수 있었으며, 분뇨의 이화학적 성상을 조사함으로써 유기비료원로서 적절한 사용이 가능할 것으로 생각된다.

• Journal of Information Display
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• 제1권1호
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• pp.32-34
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• 2000

A new PDP cell structure called CSP(Charge Storage Pad) improves the luminous efficiency by 1.6 times and prevents cross talk between adjacent cells. The CSP, which is a conducting material, is inserted between the dielectric layer and the MgO film in the front plate. This CSP produces a longer time-averaged discharge path to get a high luminous efficiency and confines the discharge to prevent cross talk.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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• pp.196-202
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• 1998

Recently, developments in the frontier industry have brought a rapid increase in the use of brittle materials such as silicon wafer, ferrite, sintered carbide, MgO single crystal and die steel. Because of high hardness and brittleness the cracking and chipping are apt to generate in the grinding of brittle materials, but have replaced gradually the high precision grinding. In this study, the optimum system of in-process electrolytic dressing controlled by computer was developed for improving the defects, and could maintain the optimum dressing condition at all times. The control of in-process dressing was simplified using this system, was able to maintain a stable dressing current and was unrelated to the change of dressing condition according to the variation of gap and oxide layer. Therefore, the optimum in-process electrolytic dressing system was constructed and the analysis of grinding mechanism with this system was studied.

• Bulletin of the Korean Chemical Society
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• 제26권2호
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• pp.248-252
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• 2005

Synthetic layered double hydroxides (LDHs), [$Mg_4Al_2(OH)_{12}]CO_3{\cdot}nH_2O$, were prepared in the submicron size of plate-like polycrystals. Anion-exchange reactions with various linear dicarboxylic acids were performed to produce LDH/organic hybrid materials by solvothermal treatment in toluene. X-ray powder diffraction spectra for the products indicated that the interlayer spacings of LDHs remarkably changed, up to 20 $\AA$ when 1,10-decanedicarboxylic acid anions were intercalated as an organic guest. Dicarboxylates-LDHs samples could be also re-exchanged consecutively with other dicarboxylic acids or carbonate without serious destruction of layer structure under the scanning electron microscopic observation.

• Toxicological Research
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• 제17권1호
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• pp.33-39
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• 2001

To evaluate the skin toxicity oj topical toluene application, toluene (35 mg/$cm^2$) was sequentially applied to the portion rat skin for five days. The topical toluene application resulted in increased xanthine oxidase activity and CYP content, and significantly decreased superoxide dismutase and glutathione peroxidase activities at five days in rat skin. Especially catalase activity was remarkably decreased in toluene-applied rat skin. And benzylalcohol dehydrogenase activity showed also a significant decrease in toluene-applied skin. On the other hand, histopathological ultrastructural examination revealed disrupted epidermal basement membrane, rared intercellular adhensions and degenerated keratin layer due to topical toluene application. Increased deposit of cerrous perhydroxide resulted from reaction with $H_2O_2$was abserved in toluene-treated animals. These results indicate that oxygen free radical may be responsible for ultrastructural changes in skin tissue by toluene application to rat skin.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기물성,응용부문
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• pp.204-206
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• 2005

Although intensive experiments have been performed to investigate the origin of boundary image sticking, one of major factors to determine display quality in AC PDP, it has not being reported clearly why it is occurred. The relationships between boundary image sticking and its possible origins such as phosphor degradation, temporal change of MgO layer, wall charge have been discussed. In this paper, we have analyzed characteristics of the boundary image sticking more clearly by the influence of local panel temperature.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.199-202
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• 2002

In general, the background light produced during the reset period deteriorates the dark room contrast ratio in AC PDP. In this paper, we propose a modified ramp reset pulse that can reduce the background light to imperceptible level. In the new reset waveform, the discharges between the scan and sustain electrodes are minimized by applying a positive bias voltage to the sustain electrode and only the weak discharges between the scan and address electrodes occur during the reset period. We adopted a MgO coated phosphor layer to get the same level of voltage margin in the new reset pulse scheme compared to that of the conventional ramp reset pulse one. As a result, the voltage margin is maintained at the same level and the dark room contrast ratio is improved dramatically.

• 한국전기전자재료학회논문지
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• 제14권3호
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• pp.228-233
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• 2001

This paper presents the optimized design, fabrication and thermal characteristics of micro-heaters for thermal MEMS (micro elelctro mechanical system) applications usign SOI (Si-on-insulator) and trench structures. The micro-heater is based on a thermal measurement principle and contains for thermal isolation regions a 10㎛ thick Si membrane with oxide-filled trenches in the SOI membrane rim. The micro-heater was fabricated with Pt-RTD (resistance thermometer device) on the same substrate by suing MgO as medium layer. The thermal characteristics of the micro-heater wit the SOI membrane is 280$\^{C}$ at input power 0.9W; for the SOI membrane with 10 trenches, it is 580$\^{C}$ due to reduction of the external thermal loss. Therefore, the micro-heater with trenches in SOI membrane rim provides a powerful and versatile alternative technology for improving the performance of micro-thermal sensors and actuators.