• Journal of the Korean earth science society
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• v.21 no.4
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• pp.437-448
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• 2000

The Middle Carboniferous Gabsan Formation is distributed in the Cheongrim area of southern Yeongwol and the Mt. Gachang area of Chungbuk Province. This study was carried out to investigate the lithological characters and geochemical composition of the limestones and to find out controlling structures of the limestones of the formation. The limestones of the Gabsan Formation are characterized by the light gray to light brown in color and fine and dense textures. The limestone grains are composed of crinoid fragments, small foraminfers, fusulinids, gastropods, ostracods, etc. Due to the recrystallization, some limestones consist of fine crystalline calcites. The chemical analysis of limestones of the formation was conducted to find out the contents of CaO, MgO, Al$_2$O$_3$, Fe$_2$O$_3$ and SiO$_2$. The content of CaO ranges from 49.78-60.63% and the content of MgO ranges from 0.74 to 4.63% The contents of Al$_2$O$_3$ and Fe$_2$O$_3$ are 0.02-0.55% and 0.02${\sim}$0.84% , respectively. The content of SiO$_2$ varies from 1.55 to 4.80%, but some samples contain more than 6.0%. The limestones of the formation can be grouped into two according to the CaO content: One is a group of which CaO content ranges from 49.78 to 56.26% and the other is a group of which CaO content varies from 59.36 to 60.38%. In the first group, the contents of Al$_2$O$_3$, Fe$_2$O$_3$ and SiO$_2$ range very irregularly according to the CaO content. In the second group, the values of MgO, Al$_2$O$_3$, Fe$_2$O$_3$ and SiO$_2$ are nearly same. Detailed structural analysis of mesoscopic structures and microstructures indicates the five phase of deformation in the study area. The first phase of deformation(D$_1$) is characterized by regional scale isoclinal folds, and bedding parallel S$_1$ axial plane foliation which is locally developed in the mudstone and sandstone. Based on the observations of microstructures, S$_1$ foliations appear to be developed by grain preferred orientation accompanying pressure-solution. During second phase of deformation, outcrop scale E-W trending folds with associated foliations and lineations are developed. Microstructural observations indicate that crenulation foliations were formed by pressure-solution, grain boundary sliding and grain rotation. NNW and SSE trending outcrop scale folds, axial plane foliations, crenulation foliations, crenulation lineations, intersection lineations are developed during the third phase of deformation. On the microscale F$_3$ fold, axial plane foliations which are formed by pressure solution are well developed. Fourth phase of deformation is characterized by map scale NNW trending folds. The pre-existing planar and linear structures are reoriented by F$_4$ folds. Fifth phase of deformation developed joints and faults. The distribution pattern of the limestones is mostly controlled by F$_1$ and F$_4$ folds.

• Journal of the Korean Magnetics Society
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• v.4 no.3
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• pp.214-218
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• 1994

$Y_{3}Fe_{5}O_{12}$ based garnet films(thin or thick) offer a great promise for the application of microwave communication components. We investigated the magnetic and crystallographic preperties of $Y_{3}Fe_{5}O_{12}$ thick films prepared by KrF eximer laser ablation of a stoichiometric garnet target. It was possible to obtain almost epitaxially oriented films on $Al_{2}O_{3}$(1102) plane. Although the crystalline quality depends on substrate temperature and $O_{2}$ partial pressure used($Po_{2}$), 4.1m thick films of $4{\pi}M_{s}=1300$ Gauss and $H_{c}=37.5$ Oe were obtained at the substrate temperature of $700^{\circ}C$ with the $Po_{2}$ of 100 mTorr after annealing the as-deposited films at $700^{\circ}C$ for 2 hours. These films are expected to be used for magnetostatic spin wave filters at narrow bandwidth frequency.

• The Journal of the Petrological Society of Korea
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• v.3 no.3
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• pp.185-195
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• 1994

An experimental study of iron-aluminium partitioning between synthetic garnet and synthetic epidote was carried out, as equilibrium was maintained in the exchange reaction expressed as follows : $Ca_3Fe_2Si_3O_12\+\2\Ca_2Al_2AlSi_3O_12$(0H) = $Ca_3Al_2Si_3O_12\+\Ca_2Al_2FeSi_3O_12$(0H) Temperature has a pronounced effect on the distribution of Fe and A1 between the minerals. However, the pressure effect is not so drastic as in the exchange reaction. With increasing temperature, $Fe^{+3}$ becomes redistributed from garnet into epidote, whereas A1 becomes redistributed from epidote into garnet. This is in line with the general principle of phase correspondence, as the temperature increases the more electropositive metal aluminium redistributes from epidote into garnet. The agreement between the experimental results of this study and the natural samples suggests that $K_D=X^{Ep}_{Fe}/X^{Gr}_{Fe}$ may be a useful geothermometer for metamorphic rocks containing garnet and epidote that are close to binary Fe-A1 compounds.

• Journal of the Korean Chemical Society
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• v.13 no.1
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• pp.49-55
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• 1969

X-ray Fluorescence Spectrographic method has been applied for the rapid determination of main components, such as $SiO_2$, $Al_2O_3$, $Fe_2O_3$, CaO, MgO and $K_2O$ in Silicate Minerals. In this method, Boric Acid was used as a binder after fusion with Lithium Tetraborate in the briquet-making process. The Lithium Flubride, Ammonium di-Hydrogen Phosphate and Ethylene Diamine d-Tartrate crystals were used with Scintillation counter and Gas Flow counter as the detectors. Several influences on this method were discussed, including the particle size of samples and reducing of the matrix effects by dilution with Boric Acid and addition of Lanthanum Oxide with the diluent. In order to test the reproducibility of this method described above, the determination of the same kind of samples were carried out repeatedly, and the results obtained were presented in the table. Calibration curves for each element were presented, and the application of the method was tested with International Rock Standard T-Ⅰ. All the results obtained by X-Ray Fluorescence Spectrographic method were compared with the results by conventional chemical method.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.1
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• pp.64-73
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• 2007

The catalytic activity of transition metals (Cu, Co, Mn, Fe and Ni) supported on ${\gamma}-Al_2O_3$ for the oxidation of toluene was investigated in the microreactor of fixed-bed type. The catalytic activity of transition metals for the oxidation of toluene turned out to be increasing in the order of Ni$Cu/{\gamma}-Al_2O_3$ catalysts for the oxidation of toluene increased with the increasing loadings of copper, reached the maximum activity at 5% loadings of copper, and decreased with higher loadings of copper in the catalysts. The activity of $Cu/{\gamma}-Al_2O_3$ catalysts for the oxidation of toluene decreased with the increasing calcination temperatures. This might result from the decreasing surface area of catalysts due to the sintering of copper oxide as well as ${\gamma}-Al_2O_3$ supports. The 5wt% $Cu/{\gamma}-Al_2O_3$ catalysts calcined at $400^{\circ}C$ for 4 hrs in the air showed the highest activity for the oxidation of toluene. Mutual inhibition was observed for the binary mixture of toluene and xylene. The activity of the easy-to-oxidize toluene was greatly decreased while the difficult-to-oxidize xylene was slightly decreased in the binary mixture of toluene and xylene. It might suggest that the inhibition of toluene and xylene in the binary mixture resulted from the competitive adsorption for the adsorbed oxygen on the catalytic surface.

• Journal of Magnetics
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• v.10 no.4
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• pp.137-141
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• 2005

We confirmed that the improvement in properties of magnetic tunnel junctions prepared by radical oxidation after thermal treatment was mostly resulted from the redistribution of oxygen at the $AIOx/Co_{90}Fe_{10}$ interface. The as-deposited Al oxide barrier was oxygen-deficient but most of it re-oxidized into $Al_2O_3$, the thermodynamically stable stoichiometric phase, through thermal treatment. As a result, the effective barrier height was increased from 1.52 eV to 2.27 eV. On the other hand, the effective barrier width was decreased from 8.2 ${\AA}$ to 7.5 ${\AA}$. X-ray absorption spectra of Fe and Co clearly showed that the oxygen in the CoFe layer diffused back into the Al barrier and thereby enriched the barrier to close to a stoichiometirc $Al_2O_3$ phase. The oxygen bonded with Co and Fe diffused back by 6.8 ${\AA}$ and 4.5 ${\AA}$ after thermal treatment, respectively. Our results confirm that controlling the chemical structures of the interface is important to improve the properties of magnetic tunnel junctions.

• Journal of Magnetics
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• v.6 no.3
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• pp.94-100
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• 2001

Fe-Co-Ni particles with an average size of 45 and 135 nm are characterized in terms of magnetic phase transformation and magnetic properties at room temperature. BCC structure of Fe-Co-Ni spherical particles can be synthesized from Fe-Co-Ni-Al-Cu precursor films by heating at 600-80$0^{\circ}C$ for the phase separation of Fe-Co rich Fe-Co-Ni particles, followed by a post heating at $600^{\circ}C$ for 5 hours. The average size of nanoparticles was directly determined by the thickness of precursor films. Exchange interactive hysteresis was observed for the nano-composite (Fe-Co-Ni)+(Fe-Ni-Al) films resulting from the short exchange interface between ferromagnetic Fe-Co-Ni particles surrounded by almost papramagnetic Ni-Al-Fe matrix. Arraying the isolated Fe-Co-Ni nano-particles in a random arrangement on $Al_2O_3$substrate the particle assembly showed a behavior of dipole interactive ferromagnetic clusters depending on their volume and inter-particle distance.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.104.2-104.2
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• 2012

미국, 중국, 일본, 인도 등과 같은 세계 여러 국가들이 달 및 화성 탐사를 수행하고 있는 현시점에서 우리나라도 2025년에 달 탐사를 계획하고 있다. 인간에게 있어서 우주공간은 고에너지 환경의 영향을 많이 받는 곳이다. 향후 달, 화성과 같은 다른 행성으로의 이주를 생각하고 있는 현 시점에서 우리는 고에너지우주방사선 환경의 영향을 고려해야 한다. 지구에서의 인간은 지구 자기장과 대기에 의해 고에너지 우주선 환경으로부터의 영향을 덜 받는다. 그러나 달과 화성의 경우는 다르다. 달의 대기는 거의 없고 자기장도 무시할 정도로 매우 작으며, 화성 또한 자기장이 거의 없으며 대기 또한 얇아서 Galactic Cosmic Ray (GCR)나 Solar Energetic Proton (SEP) 등으로부터 인간은 많은 영향을 받을 수 있다. 이러한 위험으로부터 인간이 보호받을 수 있는 곳은 달과 화성의 지표 아래나 동굴이라고 볼 수 있다. 그래서 달 및 화성의 표면과 지하 영역에 대한 고에너지 우주선 환경의 깊이에 따른 영향을 분석하여 어느 정도로 두터운 천장을 가진 동굴이어야 우주인들이 상주하는 지하공간을 지구표면에서의 방사선 환경과 같은 수준으로 유지할 수 있는지를 추정해 보려고 한다. 달 표면 토양의 화학적 구성성분은 Maria와 Highlands로 구분되어 약간의 차이가 있다. 달의 Maria 토양은 $SiO_2$ - 45.4%, $Al_2O_3$ - 14.9%, CaO - 11.8%, FeO - 14.1%, MgO - 9.2%, $TiO_2$ - 3.9%, $Na_2O$ - 0.6%이고 Highlands의 토양은 $SiO_2$ - 45.5%, $Al_2O_3$ - 24.0%, CaO - 15.9%, FeO - 5.9%, MgO - 7.5%, $TiO_2$ - 0.6%, $Na_2O$ - 0.6%의 화학적인 구성비를 가진다. 또한 화성표면은 $SiO_2$ - 43.9%, $Al_2O_3$ - 8.1%, CaO - 6.0%, FeO - 18.1%, MgO - 7.1%, $Na_2O$ - 1.4%의 토양의 화학적인 구성비를 가지고 있다. 본 연구에서는 이러한 구성비를 가지고 있는 달과 화성 표면에 대한 우주방사선의 영향을 분석하기 위해서 GEANT4를 사용하여 수행한 전산 모사의 결과를 발표할 것이다.

• Journal of the Korean institute of surface engineering
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• v.44 no.1
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• pp.13-20
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• 2011

This study investigated the high temperature oxidation behavior of Fe-22%Cr-5.8%Al alloy and the oxidation kinetics of the alloy were discussed. Bulk samples were prepared by VAM (vacuum arc melting) and hot forging. High temperature oxidation testes were isothermally conducted up to 100 hours in 79%$N_2$+21%$O_2$ environment at three different temperatures ($900^{\circ}C$, $1000^{\circ}C$, $1100^{\circ}C$). The weight gain was measured after oxidation according to oxidation time (2, 4, 6, 8, 10, 15, 20, 25, 30, 60, 80, 100 hours). The weight gain significantly increased with increasing oxidation temperature. As the temperature increased, the oxidized samples showed sequential formation of $Al_2O_3$, Cr-rich oxide, Fe-rich oxide. The activation energy of high temperature oxidation was obtained as 306.63 KJ/mol. $Al_2O_3$ were developed on the surface in the early stage of oxidation, representing protective role of oxidation. However, Fe-based and Cr-based oxides leaded to breakaway of oxide layer, thus resulted in the significant increase of additional oxidation.

• 보존과학연구
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• s.22
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• pp.93-114
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• 2001

The composition analysis of Danchung pigments at Geunjeongjeon Hall in Gyeongbokgung Palace were carried out by FXRF and MXRD. The analytical result of the inside pigments at Geunjeongjeon showed that these painted in use the mineral pigments. Gold pigment was pure gold(Au).The main composition identified in green pigments were chalcanthite($CuSO_4$.$5H_2O$) and celadonite($K(Mg, Fe, Al)_2$.$(Si, Al)_4O_10(OH)_2$ ). Red pigments werecinnnabar(HgS).The analytical result of the outside pigments at Geunjeongjeon revealed that these applied to the artificial synthetic pigment. Yellow pigment was chromeyellow($PbCrO_4$). The main composition identified in red pigments were red lead($Pb_3O_4$)and hematite($Fe_2O_3$). Green pigments were emeral green($C_2H_3A_s3Cu_2O_8$) and chromegreen($Cr_2O_3$). Blue pigment was lazurite($Na_6Ca2Al_6Si_6O_24(SO_4)_2$), titanium dioxide($TiO_2$) of white pigment.