• Journal of the Korean Chemical Society
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• v.46 no.3
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• pp.242-251
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• 2002

We report the synthesis and characterization of the perovskite nanotubes made by sol-gel template syn-thesis.Both lead titanate (PbTiO3 : PT), lead zirconate (PbZrO3 : PZ) and lead zirconium titanate (PbZrO3 -PbTiO3 : PZT) solid solution nanotubes were prepared with a chelate sol-gel of titanium isopropoxide (Ti(OPri)4 ), zirconium tet-rabutoxide (Zr(OBu)4 ) and the respective lead acetate (Pb(OAc)2 -3H2O). WhatmanRanodisc membranes, with a 200nm pore size, served as the template. After the removal of the template in the 6M-NaOH, scanning electron microscopy shows that the shapes formed are 200 nm outer diameter tubes with 50mm lengths. Transmission electron microscopy and electron diffraction reveal that the tubes are polycrystalline. The PT nanotubes so far have shown an anomalous transition temperature, 234.4$^{\circ}C$ as measured by DSC with a small particle size, 15.4 nm determined by X-ray analysis with the aid of Scherrer's equation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5602-5609
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• 2014

This study examined the remineralization effect of CPP-ACFP according to the etching time and the frequency of application. A CPP-ACFP paste was formed from a combination of CPP-ACP paste and fluorine. The remineralization effect of CPP-ACFP was measured according to the etching time and the frequency of applications of CPP-ACFP. The microhardness of 64 teeth was measured as the sound sample and observed by scanning electron microscopy. As a result, the effect on remineralization of the enamel increased with increasing etching time and frequency of application. Therefore, a CPP-ACP paste combination to fluorine in the tooth mineral CPP-ACFP paste fluoride application can be supplied with the material-advisable enamel remineralization.

• The Journal of Korean Academy of Prosthodontics
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• v.25 no.1
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• pp.363-378
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• 1987

도재소부전장관에서 금속이 노출되지 않고 도재만이 파절시, 구강내에서 직접 행할 수 있는 심미적 수복 방법으로서 복합성 수지를 이용한 수복 방법이 널리 이용되고 있는데 본실험의 목적은 도재와 광중합성 수지간의 접합강도를 비교 측정코저 함에 있다. 본 실험에서는 주사전자 현미경을 사용하여 도재의 부식액 (5% 불화수소산용액, Excelco's porcelain etching gel) 및 부식 시간(2.5분, 5분, 10분, 20분)에 따른 부식양상을 먼저 관찰하였다. 그다음 각기 다른 시간에서 부식 처리된 도재와 대조군으로서 미부식 처리된 도재에 광중합성 수지를 부착시킬시, 첫째 Silane coupling agent(Scotch-Prime)도포후 광중합성 수지를 결합 시켰고 둘째 bonding agent(Scotch bond)도포후 광중합성 수지를 결합시켰으며 셋째 Silane coupling agent(Scotch-Prime)에 bonding agent(Scotch bond)를 도포후 광중합성 수지로 결합 시킨후, 인장강도 측정기 (Shimadzu universal testing machine)를 사용하여 결합력을 측정한 결과 다음과 같은 결론을 얻었다. 1. 부식처리된 도재가 미부식 처리된 도재 보다 결합력이 높았다. (p<0.05, P<0.001) 2. 부식 처리된 도재나 미부식 처리된 도재에 있어서 silane coupling agent 도포후 bonding agent로 처치한 경우 가장 결합력이 높았으며 그다음 silane coupling agent로 처치한 경우, bonding agent로 처치한 경우의 순이었다. 3. 도재부식 시간의 증가에 따른 결합력의 차이는 5% HF용액으로 부식 처리된 도재와 Excelco로 부식 처리된 도재에 있어서 5분 정도 까지는 결합력의 증가를 보였으나 그 후에는 결합력에 있어서 거의 증가하지 않는 양상을 보였다. 4. Excelco로 부식 처리된 도재와 5% HF 용액으로 부식처리된 도재간의 결합력 차이에 있어서 bonding agent만으로 처치한 경우에는 두결합력 사이에 서로 유의한 차이를 보이지 않았으나 (P>0.5) silane coupling agent만으로 처치한 경우와 silane coupling agent 도포후 bonding agent로 처치한 경우에는 두결합력 사이에 서로 유의한 차이를 보였다. (P<0.05, P<0.001) 5. Excelco로 부식처리된 도재가 5% HF 용액으로 부식처리된 도재보다 부식정도가 더 현저하였다.

• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.370-374
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• 2013

The effects of zinc chloride addition on pore development of porous carbon nanofibers prepared by polyacrylonitrile (PAN)/ N,N'-dimethylformamide (DMF) (10 wt%) electrospinning were investigated. The change of morphological and structural modification by zinc chloride activation was investigated by a scanning electron microscopy (SEM) analysis. $N_2$ adsorption isotherm characteristics at 77 K were confirmed by Brunauer-Emmett-Teller (BET) and Horvath-Kawazoe (H-K) equations, and the curves showed the Type I mode in the International Union of Pore and Applied Chemistry (IUPAC) classification, indicating that lots of micropores exist in the sample. In addition, specific surface areas and total pore volumes of porous carbons prepared by the zinc chloride activation were determined as 600~980 $m^2/g$ and 0.24~0.40 $cm^3/g$, respectively. As experimental results, many holes or demolished structures were found on the fiber surfaces after the zinc chloride activation as confirmed by a SEM analysis. It was also observed that various pore sizes were found to be depended on the adding content of zinc chloride in PAN/DMF solution in this system.

• Applied Microscopy
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• v.39 no.3
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• pp.205-218
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• 2009

This experiment was performed to evaluate the morphological responses of the gastric epithelial cells of the mouse, inoculated with Ehrlich carcinoma cells in the inguinal area, following administration of BCG. Healthy adult ICR mice weighing 25 gm each were divided into normal and experimental groups (tumor control group and BCG-treated group). In the experimental groups, each mouse was inoculated with $1{\times}10^7$ Ehrlich carcinoma cells subcutaneously in the inguinal area. From next day after inoculations, 0.2 mL of saline or BCG (0.5 mL/25 g B.W.: $0.03{\times}10^8{\sim}0.32{\times}10^8$ CFU) were injected subcutaneously to the animals every other day, respectively. The day following the 7th injection of saline or BCG, each mouse was injected with a single dose of 0.7 ${\mu}Ci/g$ of methyl-$^3H$-thymidine (25 Ci/mmol, Amersham Lab., England) through tail vein. Seventy minutes after the thymidine injection, animals were sacrificed, and gastric tissues were taken and fixed in 10% neutral formalin. Deparaffinized sections were coated with autoradiographic emulsion EM-1 (Amersham Lab., England) in a dark room. The number of labeled epithelial cells in the gastric mucosae (mean number of labeled epithelial cells per 3.5 mm length of mucosa) were observed and calculated. And for electron microscopic observation, gastric tissues were prefixed with 2.5% glutaraldehyde-1.5% paraformaldehyde solution, followed by post-fixation with 1% osmium tetroxide solution. On the light microscopic study, gastric mucosae had no morphological changes following the injection of BCG. On the electron microscopic study, in the BCG-treated mice, myelin figures and multivesicular bodies within the gastric epithelial cells were observed more frequently than in those of the normal control ones. On the autoradiographic study, number of the labeled cells of normal control, tumor control and BCG-treated mice were 380.2 (${\pm}31.35$), 426.1 (${\pm}28.43$) and 301.8 (${\pm}34.63$), respectively. In the BCG-treated mice, poorly-labeled cells containing only a few silver grains of 3H-thymidine were observed more frequently as compared in those of the normal control and tumor control ones. From the above results, BCG may suppress the DNA synthesis of the gastric epithelial cells, but does not results severe fine structural defect on the gastric epithelial cells. These results suggest that BCG is expected as one of the effective supplemental anticancer drugs.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2000.04a
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• pp.16-16
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• 2000

분무주조법으로 제조된 Al-25Si-(Fe,V) 합금빌렛의 미세조직을 광학현미경, 주사전자현미경, 투과전자현미경으로 분석하였으며, 빌렛내에서 관찰되는 2차상의 형성거동을 정확히 분석하기 위해 over-sprayed 분말의 미세조직을 분무주조 빌렛과 함께 관찰하였다. 먼저 분무주조 빌렛을 표면으로부터 중심부까지 관찰한 결과, 분무주조 빌렛의 미세조직은 표면부 10mm 가량을 제외하고는 매우 균일한 미세조직을 보여주었다. 이에 본 연구에서는 분무주조 빌렛의 표면부와 중심부, 그리고 over-sprayed 분말조직으로 구분하여 각각에서 관찰되는 2차상을 관찰하였으며, 이를 바탕으로 분무주조 빌렛내에 형성된 2차상의 형성기구를 규명하고자 하였다. Over-sprayed 분말의 미세조직은 기지조직내에 균일하게 분포된 침상의 $\delta$-AlFeSi 상과 각형의 Si 입자로 구성되어 있었다. 반면, 분무주조 빌렛의 경우, 그 중심부에서는 기자조직내에 균일하게 분포된 막대형의 $\beta$-AlFeSi과 부정형의 조대한 Si입자가 관찰되었으며, 표면부에서는 부정형의 Si 입자와 함께 막대형의 $\beta$-AlFeSi/$\delta$-AlFeSi 복합상이 관찰되었다. 특히, 빌렛 표면부의 $\beta$-AlFeSi 상과 $\delta$-AlFeSi 상간에는 일정한 방위관계가 존재하였으며, 이러한 결과는 분무주조 빌렛내에 분포된 $\beta$-AlFeSi상들이 분무액적내에 형성된 준안정 $\delta$-AlFeSi 상으로부터 상분해되어 형성되었음을 제시한다. 이상의 분무주조 조직과 over-sprayed 분말의 미세조직으로부터 분무주조 빌렛의 최종 주조조직은 반응고상태의 분무액적 조직에 의해 지배됨을 알 수 있다.r plate)의 단면 미세조직 사진으로써 모재부와 오버레이충을 함께 보여주고 있다. 모재와 오버레이 충간의 경계면은 모재 일부가 용융된 후 웅고하면서 형성됨으로 인해서 도금이나 용사층과는 달리 매우 견고하게 결합되어 있다. 따라서 계면부의 탈락이라는 문 제점은 거의 없어 심한 응력을 받는 기계구조물 및 부품에도 본 기술은 널리 적용되고 있다. 그리고 사진 1에서 알 수 있는 바와 같이 모재와는 전혀 상이한 재료를 자유로이 선택하여 표면 유효층 일부만 오버레이시키며I 주조 및 단조가 불가능한 재료까지도 표면부에 오버레이 시킴으로 서 부품 및 설비의 제조에 있어 재료비의 절감과 제품의 수명이 획기적으로 개선될 수 있다. 그리고 최근에는 도금 빛 용사 둥과 같은 표면처리를 할 경우임의 소재 표면에 도금 및 용 사에 용이한 재료를 오버레이용접시킨 후 표면처리를 함으로써 보다 고품질의 표면층을 얻기위한 시도가 이루어지고 있다. 따라서 국내, 외의 오버레이 용접기술의 적용현황 및 대표적인 적용사례, 오버레이 용접기술 및 용접재료의 개발현황 둥을 중심으로 살펴봄으로서 아직 국내에서는 널리 알려지지 않은 본 기 술의 활용을 넓이고자 한다. within minimum time from beginning of the shutdown.및 12.36%, $101{\sim}200$일의 경우 12.78% 및 12.44%, 201일 이상의 경우 13.17% 및 11.30%로 201일 이상의 유기의 경우에만 대조구와 삭제 구간에 유의적인(p<0.05) 차이를 나타내었다.는 담수(淡水)에서 10%o의 해수(海水)로 이주된지 14일(日) 이후에 신장(腎臟)에서 수축된 것으로 나타났다. 30%o의 해수(海水)에 적응(適應)된 틸라피아의 평균 신사구체(腎絲球體)의 면적은 담수(淡水)에 적응된 개체의 면적보다 유의성있게 나타났다. 해수(海水)에 적응(適應)된 틸라피아의 신단위(腎單位)의 사

• Korean Chemical Engineering Research
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• v.43 no.4
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• pp.495-502
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• 2005

Copper was plated on the tungsten substrate by use of a direct copper electroless plating. The optimum deposition conditions were found to be with a concentration of $CuSO_4$ 7.615 g/L, EDTA of 10.258 g/L, and glyoxylic acid of 7 g/L, respectively. The solution temperature was maintained at $60^{\circ}C$. The pH was varied from 11.0 to 12.8. After the deposition, the properties of the copper film were investigated with X-ray diffractometer (XRD), Field emission secondary electron microscope (FESEM), Atomic force microscope (AFM), X-ray photoelectron spectroscope (XPS), and Rutherford backscattering spectroscope (RBS). The best deposition condition was founded to be the solution pH of 11.8. In the case of 10 min deposition at the pH of 11.8, the grain shape was spherical, Cu phase was pure without impurity peak ($Cu_2O$ peak), and the surface root mean square roughness was about 11 nm. The thickness of the film turned out to be 140 nm after deposition for 12 min and the deposition rate was found to be about 12 nm/min. Increase in pH induced a formation of $Cu_2O$ phase with a long rectangular grain shape. The pH control seems to play an important role for the orientation of Cu in electroless deposition. The deposited copper concentration was 99 atomic percent according to RBS. The resulting Cu/W film yielded a good adhesive strength, because Cu/W alloy forms during electroless deposition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.8
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• pp.701-707
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• 2014

The ecofriendly yellow ocher is used in the manufacturing of cosmetics, construction, and food packaging. The polyethylene terephthalate (PET) used for manufacturing food containers has a microporous structure that causes aeration. Hydrophilic yellow ocher may be applied to hydrophobic PET by surface modification to overcome this issue. The aim of this study is to fabricate a yellow ocher polystyrene hybrid structure in the form of nanoparticles using an optimizing molar ratio of styrene, divinylbenzene, and potassium peroxodisulfate for use in emulsion polymerization. The polymerization was conducted in a yellow ocher suspension that was prepared by dispersing mechanically ground yellow ocher in DI water. The prepared hybrid structure was measured using scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. The measurement revealed the spherical morphology and Si component that resulted from the yellow ocher in the polystyrene particles. We expect that this hybrid structure would be used as platform material to minimize aeration in PET.

• Journal of Aquaculture
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• v.11 no.4
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• pp.465-474
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• 1998

Shell necrosis, which is found in the juvenile stage of Haliotis discus hannai in th culture process, was examine in this study. In the necrosis shell, bacteria of rod type and a blue green algal species with heterocyst were observed. However, it appears to be caused by a boring blue green alga, Mastigocoleus sp., as based on SEM data. At the time of its infection, the shell was discolored from green into bright-grey, and then began to be brittle at the 4th to 6th breathing hole. After 60 days of culture, necrosis occurred in the breathing holes with many brown tiny colony, and continued to 3 years after culture. This shell necrosis was found in the tank culture system in land rather than in the cage culture system in sea, and greatly affected to the growth of Haliotis discus hannai, resulting in very small size of 16mm in 3 year old shell.

• Clean Technology
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• v.19 no.4
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• pp.446-452
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• 2013

In this paper, the wet mixing method was introduced to prepare spinel lithium manganese oxide (LMO) with $Li_2CO_3$ and $MnCO_3$. The physical properties of the resulting lithium manganese oxide were characterized by the XRD and SEM. The adsorption properties of LMO for $Li^+$ were investigated by batch methods. The maximum adsorption capacity of lithium was calculated from Langmuir isotherm and found to be 27.25 mg/g. The LMO are found to have a remarkable lithium ion-sieve property with distribution coefficients ($K_d$) in the order of $Ca^{2+}$ < $K^+$ < $Na^+$ < $Mg^{2+}$ < $Li^+$, which is promising in the lithium extraction from seawater.