• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2002.11a
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• pp.165-169
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• 2002

BaTiO$_3$ 분말을 Ba(OH)$_2$ㆍ8$H_2O$와 아나타제형의 TiO$_2$ㆍ$\chi$$H_2O$를 이용하여 광화제 첨가 없이 열수처리에 의한 탈수(dehydration) 및 재결정화(recrystallization) 과정을 통한 수열합성법에 의해 제조하였다. Autoclave 반응기를 이용한 실험의 경우, BaTiO$_3$ 분말을 생성하기 위한 최적 반응온도 및 시간은 각각 21$0^{\circ}C$, 4시간으로 확인되었으며, 이 때 생성된 BaTiO$_3$ 분말의 크기는 0.1~0.2$mu extrm{m}$로 입도분포가 양호하였다. 그리고, 바륨과 티타늄의 농도비가 증가됨에 따라 결정화도(tetragonality)가 증가하는 경향을 나타내고 있다. 이는 반응하지 않고 남아 있는 바륨의 영향으로 생각되며, 이는 반응물의 pH와도 관련이 있다. 또한, 반응온도 및 시간도 결정화도에 커다란 영향을 미치는 변수로 주로 반응온도 및 시간이 증가함에 따라 결정화도도 함께 증가하는 추세를 나타내고 있다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.2
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• pp.292-300
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• 1997

PSZT powders having the particle size of 0.5~5 $\mu\textrm{m}$ with cubic shapes, were prepared by a hydrothermal reaction in the temperature range of 150~$^{\190circ}C$ for a 2 h reaction. Experimental results showed that as the reaction temperature increased, the nucleation and crystal growth were accelerated and the the particle size became larger. However, the particle size became smaller with its narrow distribution as the concentration of a mineralizer (KOH) increased. It was possible to reduce the reaction temperature by increasing mineralizer concentrations. With increase in Zr/Ti ratio, the major crystal phase of synthetic PSZT powders was seen to change from tetragonal phase to rhombohedral phase.

• Korean Journal of Food Science and Technology
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• v.1 no.1
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• pp.45-50
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• 1969

On the basis of UV spectral changes and TBA reaction, malonaldehyde (MA) in aqueous solution receives considerable photochemical modification by UV light of short wavelengths around $260m{\mu}$. When aflatoxin is added in the solution, UV light of long wavelengths around $360m{\mu}$ induces such changes quite rapidly and although the rate of change is rather slow, it is also true even with ordinary laboratory illumination(fluorescent). The modification is irreversible in nature and the role of aflatoxin in this reaction is identified as a photosensitizer. The mechanism involved in this modification is apparently due to the parallel dimerization of MA molecules, but not by head to tail combination of the molecules.

• Journal of the Korean Ceramic Society
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• v.15 no.1
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• pp.9-15
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• 1978

The possiblity of mullitization from the domestic alunite by adding of $Fe_2O_3-MnO_2$, $Fe_2O_3-MnO_2-TiO_2$, $Fe_2O_3-MnO_2-CaF_2$, and $Fe_2O_3-MnO_2-CaF_2-TiO_2$ mixtures as mineralizers was studied at the temperature range between $1, 250^{\circ}C$~$1, 430^{\circ}C$. The modifying method of domestic alunite was performed by calcination, wet ballmilling, and washing with water. The following results were obtained; 1) When added of 3.0% $Fe_2O_3$ plus 1.0-1.5% $MnO_2$ to modified alunite, the appropriate temperature range of mullite-forming was $1, 350^{\circ}C$-$1, 400^{\circ}C$. 2) When added of $TiO_2$ as mineralizer, the mullite-forming temperature was higher than not added. 3) When added of $CaF_2$ as mineralizer, the synthesized mullite was resolve at the temperature above $1, 350^{\circ}C$.

• Journal of the Korean earth science society
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• v.35 no.6
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• pp.422-428
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• 2014

Korea Institute of Geoscience and Mineral Resources (KIGAM) and Mineral Resources Authority of Mongolia (MRAM) performed a joint survey on Ugii Nuur Fe-Mn mineralized area. Following the survey, we carried out magnetic survey and 3D magnetic susceptibility inversion. Based on the inversion results, basic feasibility study and 3D imaging of Fe-Mn mineralized area were performed using 3D geological modeling technique. Using the distribution of total magnetic field data, we were confirmed for the possibility of horizontal extension of ore bodies from surface outcrops. The 3D magnetic susceptibility model, which is highly related with Fe content, analyzed by inversion shows that the ore bodies of Deposit 1 and Deposit 2 are extended to the underground and ore bodies that are not exposed on the surface are largely distributed in the underground. If we perform the integration analysis using this magnetic susceptibility model and the ore grade data analyzed by drilling survey, it is possible to carry out the effective potential evaluation of Ugii Nuur Fe-Mn ore deposit.

• Journal of the Korean Chemical Society
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• v.20 no.3
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• pp.212-220
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• 1976

The photocyclization of 1,1'-dicycloalkenyls (1,1'-dicyclohexenyl, 1,1'-dicyclopentenyl, 1,1'-dicycloheptenyl and 1,1'-dicyclooctenyl) is studied. Irradiation at liquid nitrogen temperature does not show trans double bond band in IR spectra. Even though naphthalene and pyrene fluorescence are quenched very efficiently by 1, 1'-dicycloalkenyls, no or trace amount of cyclobutenes are accompanied. When acetophenone or benzophenone is used, cyclobutene is obtained only from 1,1'-dicyclohexenyls, 1,1'-dicycloheptenyl giving some adducts. Naphthalene and pyrene sensitizes adduct formation but not cyclization. From above observations, it is concluded that photocyclization occurs from the planar s-cis triplet state rather than twisted triplet, singlet excited state or vibrationally excited ground state in sensitized photocyclization of 1,1'-dicycloalkenyls.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.04a
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• pp.123-124
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• 2000

오존($O_3$)은 이산화질소, 일산화탄소, 휘발성유기화합물 둥을 포함하는 다양한 물질과 광화학반응에 의하여 생성되는 2차적인 오염물질로 사람과 식물에 영향을 미치고 있는 중요한 오염물질로 알려지고 있으며, 국내에서는 이와 관련하여 오존예보제, 경보제 둥을 운영하여 오존에 의한 피해 영향을 줄이고자 노력하고 있다. 현재 오존을 측정할 수 있는 방법은 환경오염공정시험방법과 정부에서 운영하고 있는 대기오염 자동측정망의 오존 측정방법인 자외선광도법(Ultra Violate Photometric Method)으로 구분되어 지고 있으나, 자동측정장비는 매우 고가의 장비이며, 관리를 위하여 전문적인 지식이 요구되고 있고, 측정소의 개수가 매우 부족한 실정이기 때문에 대기중 오존농도의 지역적인 자료와, 실내공기 측정, 그리고 공간적인 분포 해석을 위해서는 다른 측정방법이 요구된다고 하겠다. (중략)

• Economic and Environmental Geology
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• v.40 no.5
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• pp.517-535
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• 2007

Two distinctive Mesozoic hydrothermal systems occurred in South Korea: the Jurassic/Early Cretaceous(ca. $200{\sim}130$ Ma) deep-level ones during the Daebo orogeny and the Late Cretaceous/Tertiary(ca. $110{\sim}45$ Ma) shallow hydrothermal ones during the Bulgugsa event. The Mesozoic hydrothermal system and the metallic mineralization in the Korean Peninsula document a close spatial and temporal relationship with syn- to post-tectonic magmatism. The calculated ${\delta}^{18}O_{H2O}$ values of the ore-forming fluids from the Mesozoic metallic mineral deposits show limited range for the Jurassic ones but variable range for the Late Cretaceous ones. The orogenic mineral deposits were formed at relatively high temperatures and deep-crustal levels. The mineralizing fluids that were responsible for the formation of theses deposits are characterized by the reasonably homogeneous and similar ranges of ${\delta}^{18}O_{H2O}$ values. This implies that the ore-forming fluids were principally derived from spatially associated Jurassic granitoids and related pegmatite. On the contrary, the Late Cretaceous ferroalloy, base-metal and precious-metal deposits in the Taebaeksan, Okcheon and Gyeongsang basins occurred as vein, replacement, breccia-pipe, porphyry-style and skarn deposits. Diverse mineralization styles represent a spatial and temporal distinction between the proximal environment of subvolcanic activity and the distal to transitional condition derived from volcanic environments. The Cu(-Au) or Fe-Mo-W deposits are proximal to a magmatic source, whereas the polymetallic or the precious-metal deposits are more distal to transitional. On the basis of the overall ${\delta}^{18}O_{H2O}$ values of various ore deposits in these areas, it can be briefed that the ore fluids show very extensive oxygen isotope exchange with country rocks, though the ${\delta}D_{H2O}$ values are relatively homogeneous and similarly restricted.

• Journal of the Korean Chemical Society
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• v.46 no.5
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• pp.437-471
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• 2002

The photosensitivity enhancement of photoresist achieved by the addition of acid amplifiers stems from the autocatalytic decomposition of the acid amplifiers triggered by acidic species generated from a photoacid gen-erator. In this research we synthesized and evaluated 4-hydroxy-4'-p-styrenesulfonyloxy isopropylidene dicyclohex-ane(1), 4,4'-di-p-styrenesulfonyloxy isopropylidene dicyclohexane(2) and 4-p-styrenesulfonyloxy-4'-tosyloxy isopropylidene dicyclohexane(3) as novel acid amplifiers. These acid amplifiers(1-3) showed reasonable thermal stability for resist pro-cessing temperature. As estimated by the sensitivity curve, 1-3 were 2X-12X sensitive than poly(tert-butyl meth-acrylate) film in the presence of a photoacid generator and, therefore, provides practical applicability for photoimaging.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.2
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• pp.278-286
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• 2008

Many studies regarding Casein phosphopeptides-amorphous calcium phosphate(CPP-ACP) have demonstrated the remineralization ability on the demineralized enamel surface. A question is still remained that how deep can the calcium (Ca) and phosphorus (P) ions supplied by the CPP-ACP paste penetrate into the enamel subsurface. The aims of this study were to measure the penetrating depth of Ca and P ions in the demineralized human enamel in vitro, and were to determine the amount and depth of Ca and P ions according to the duration. The amount and depth of Ca and P ions were measured by microscopic observation with Field Emission Scanning Electron Microscopy (FE-SEM; LEO SUPRA 55, Carl Zeiss, Germany) and Energy Dispersive X-ray Spectrometer (EDS; GENESIS 2000, EDAX, USA: Linescan of Calcium and Phosphorus). Freshly extracted four human 1st premolars were obtained from the Dept. of Pediatric Dent., Kyung Hee Univ. Buccal surfaces of the 1st premolars were covered with nail varnish to form a window on the middle third of buccal surface. All of the teeth with enamel windows were immersed in a solution of 0.1 M lactic acid, Carbopol C907 (carboxypolymethylene BF Goodrich, Cleveland, OH, USA) at pH 4.8, and then incubated for 7 days. Each tooth crown was sawn in half through the midline of buccal window along the long axis of premolar. The four blocks of premolars were immersed in a 10-times diluted solution of CPP-ACP paste (Tooth Mousse, GC Corp., Tokyo, Japan) for 1, 2, 3 and 5 weeks while the rests were immersed in a placebo solution (distilled water) for the same duration. Each specimen was embedded in epoxy resin, and was sectioned perpendicular to the window, using a water-cooled diamond blade saw. The spectrum density indices of Ca and P were measured in the sound, de- and remineralized enamels by FE-SEM and EDS. The Student's t test was performed to compare the Spectrum Density Indices (SDI) of sound, re-and demineralized enamels, and to compare the differences among the durations. Followings are the conclusion : 1. The penetration depth of the remineralizing ions (Ca & P) of CPP-ACP paste is related to the depth of demineralized enamel (approximately $1050{\sim}1350{\mu}m$). It is revealed that the penetration depth of both ions reaches full thickness of decalcification and even slightly into the sound enamel. 2. The Ca & P levels of remineralized enamels in 1, 2 weeks were significantly higher than those of the sound enamels (p<0.05). 3. No statistically significant difference of Ca & P levels was found in relation with the increasing duration of remineralization (p>0.05).