• 보존과학연구
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• s.34
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• pp.6-17
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• 2013

Bukjiri Seated Rock-carved Buddha of Bonghwa is a rock carved Buddhist Statues on the Two-Mica Granite with mid-size grains. The non-destructive diagnosis on the statues showed that their surfaces had been damaged by exfoliation or granular decomposition and their physical properties are also found to be weak. In addition, the evaluation of slope stability showed that there are the possibility of toppling failure, or planar and wedge failure. So, we have recovered the physical strength and structural stability of rock using the scientific conservation treatment. We also founded that the existing shelter was damaged by the poor ventilation and water leakage. So we constructed it in a way that there is no water leakage while the ventilation is good.

• Journal of the Korean Ceramic Society
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• v.31 no.2
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• pp.177-184
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• 1994

AlN-BN ceramics with BN contents in the range of 10 to 40 wt% were prepared by hot pressing using no additive, or 3 wt%, Y2O3 or CaO, which are common densification aids for AlN. And their machinability, bend strength, and microstructures were investigated. Both the main and radial cutting forces decreased with increasing BN content in all three kinds of samples. For the BN contents of 30 wt% or above, the cutting forces were lower than that of a mild steel tested at a same condition. Especially in the case of main forces, the values were less than a quarter of that of a mild steel, indicating excellent machinability. Bend strength (when the tensile surfaces of specimens were perpendicular to the hot pressing direction) also decreased with BN content mainly due to the much lower Young's modulus of BN compared to AlN. With the composition of 30 wt% BN at which the AlN-BN ceramics started to show better machinability than a mild steel, the bend strength was 150 to 160 MPa, which is greater than that of machinable glass-ceramics of a mica system. With tensile surfaces parallel to the hot pressing direction, however, the bend strength obtained for the samples processed with the sintering acids showed low values (about 40 MPa), since most BN particles had such orientation that their cleavage planes (i.e., basal planes) were perpendicular to the pressing direction.

• Journal of the Korean Ceramic Society
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• v.18 no.4
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• pp.219-228
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• 1981

To clarify influences of silicious raw materials on mineralogcal and petrological properties in clinkering process clay, shale, quartzite, sand and coal ash have been used as silicious raw materials. The tests on thermal properties, reactivity and burnability of raw mixtures which have different silicious raw materials respectively have been made by means of X-ray diffractometry, differential thermal analysis, optical microscopy and transmission electron microscopy. Limestone contains coarse crystalline grains which show 0.1-1.0mm and its decarbonation temperature is 86$0^{\circ}C$. Reaction temperatures among raw mixtures have been determined by X-ray diffractometry and their results are as follows; clay minerals under 1, 00$0^{\circ}C$, mica group, 100$0^{\circ}C$-110$0^{\circ}C$, feldspar group, 1, 10$0^{\circ}C$-1, 20$0^{\circ}C$ and quartz 1, 20$0^{\circ}C$-1, 30$0^{\circ}C$. Burnabilities of raw mixtures of different temperatures have been found that they mainly depend upon their mineral contents in silicious raw materials and their order is as follows; $clay\geq shale\gg quartzite \geq sand$.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.137-146
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• 2006

Shear wave velocity of uncemented soil can be expressed as the function of effective stresses when capillary phenomenons are negligible. However, the terms of effective stresses are divided to the direction of wave propagation and polarization because stress states are generally anisotropy. The shear wave velocities are affected by parameters and exponents that are experimentally determined. The exponents are controlled contact effects of particulate materials(sizes, shapes, and structures of particles) and the parameters are changed contact behaviors between particles, material properties of particles, and type of packing(i.e., void ratio and coordination number). In this study, consolidation tests are performed by using clay, mica and sand specimens. Shear wave velocities are measured during consolidation tests to investigate the stress-induced and inherent anisotropies through bender elements. Results show the shear wave velocities depends on the stress-induced anisotropy for round particles. Furthermore the shear wave velocity is dependent on particle alignment under the constant effective stress. This study suggests that the shear wave velocity and the shear modulus should be carefully calculated and used for the design and construction of geotechnical structures.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.10
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• pp.895-900
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• 2007

Partial discharge(PD) test can be performed either when the rotating machine is not operating(off-line) or during normal machine operation(on-line). This paper presents an on-line and off-line PD test on a large hydro-generator and induction motor using the same PD acquisition system(PDAS) and ceramic coupler(CC) sensor. PD signal characteristics of CC sensor proved similar with that of epoxy mica coupler(EMC) sensor as a results of PD test for simulated defect winding and frequency response test. A comparison of on-line and off-line PD test for PD characteristic parameters-phase resolved PD(PRPD), maximum PD value(Qmax) and PD occurrence energy(POE)-indicated that on-line PD test could reliably and effectively diagnose insulation conditions which were verified by off-line PD test.

• Economic and Environmental Geology
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• v.1 no.1
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• pp.9-34
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• 1968

Manganese ore deposits of the Samhan Changgun Properties are located at the valley of west-lope-side of Changgun-bong (1132m) occupied over the Myon border between Sochon-myon and Jaesan-myon Pongwha-gun, Kyongsang-Pukdo. Geology of the more property and it's vicinity consists of Wonnan formation and Yulri formation of pre-Cambrain and Changgun limestone formation, Mica-schist formation, quartizite formation and Jaesan formation (containing coal bearing zone the unknown age. And granites and dykes were intruded into the above formation later. 1. Management deposits is embedded the formation of Janggun limestone especially Contact zone in the contact zone to of Chunyang Granite limestone enclosed by Granite, and Maginal zone of fault line in the limestone. Therefore, Chunyang Granite is Closely related to ore deposit. Pegmatite which is near by ore deposit was intruded before mineralization and it seems to be a channelway of ore solution. The most important ore deposits of property grouped into south deposit, east deposit, east-Gachon deposit, South-Gachon deposit, Durimgok deposit and West deposit, out-crops at several place. Besides these deposits there also are several prospects on outcrop scathered. Hydrothermal alteration take place strongly in the well rock and it's sequence are Characterized as following; 1) Dolomitization 2) Carbonization 3) Mamgamotozation 4) Pyritization 5) Silicification 6) Oxidation 2. The grade of manganese dioxide is up to Mn 45% in Maximum, but generally, averaging Mn 30~35% of high grade ore and averaging Mn 30~32% of manganese carbonates are mined in his property.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.4
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• pp.178-182
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• 2006

Five model coils of 6.6 kV motor were manufactured with several defects. These stator coils have artificial defects such as void of groundwall insulation, removal of semi-conductive coating and damage of strand insulation. Epoxy-mica coupler(80 pF) was connected to five model coil terminals. The voltage applied to the coils was 3.81 kV, 4.76 kV, 6.0 kV and 6.6 kV, respectively. Partial discharge(PD) tests performed in the laboratory and shield room. Digital PD detector(PDD) and turbine generator analyzer(TGA) were used to measure PD activity. TGA summarizes each plot with two quantities such as the normalized quantity number(NQN) and the peak PD magnitude(Qm). The PD levels in pC were measured with PDD. PD patterns of model coils were indicated the internal and slot discharges. PD patterns are consistent with the result of measurement using PDD and TGA instruments. AC breakdown test was performed on five model coils in order to confirm the result of PD measurements. All the failures were located in a line-end coil at the exit from the core slot.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.95.2-95.2
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• 2012

고온형 SOFC의 개발에 있어 스택의 신뢰성을 확보하는데 가장 중요한 핵심기술은 스택 구성요소 사이를 접합하는데 필요한 고온형 밀봉재의 개발이다. SOFC 스택에서의 밀봉재는 고체전해질과 접속자 사이에서 음극에 공급되는 연료가스와 양극에 공급되는 공기가 서로 혼합되는 것을 방지하는 역할은 물론 기계적으로 취약한 단전지의 보호 및 스택전체 구조물의 구조적 일체성(Structural integrity)을 부여하는데 주목적이 있다. 현재 기체 기밀성을 유지하기 위한 밀봉재는 크게 유리 및 결정화 유리계, mica및 mica/유리복합재료, 유리/충전재 복합재료 등이 사용되고 있으나 다수의 단위전지로 구성되는 스택 구성에서 스택의 열기계적 안정성 및 장기수명을 보장하기 위해서는 본 연구에서 개발하고자 하는 복합밀봉재가 가장 적합할 것으로 예상되고 있다. 본 연구에서는 SiO-B2O3-RO계에 BaO, SrO를 일정비율로 첨가하여 제작된 유리 frit을 열처리하여 물리화학적 물성변화를 검토하였으며, $750^{\circ}C$ 이하의 연화점을 갖는 유리를 기지상으로 하고 세라믹 보강재를 첨가한 고온형 복합밀봉재를 개발하고 그 물리화학적 안정성, 열기계적 안정성 및 밀봉 특성을 평가하였다.

• Economic and Environmental Geology
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• v.33 no.3
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• pp.205-215
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• 2000

The Anyang River runs through highly industrialized area and joins the lower part of the Han River. loading out large amounts of potential pollutants. Attempts were made to understand geochemical behavior of trace elements in the stream sedimens collected from the bottom of the river and the stream water. Bottom sediments, suspended solids and stream waters were collected and analysed for the chemical and mineralogical composition. Heavy metals including Cr, Zn, Ni, and Co in the sediments were enriched appeared to reflect anthropogenic input. Pb, Cu, As were also enriched between several to 10 times , compared to background levels. Although some heavy metals were derived from anthropogeic input, geochemical associations seem to implyh much of the elements are originated from natural sources as well, mainly from granitic rocks . This is also supported by the mineralogical composition of the suspended solids, which are mainly composed of quartz, feldspar and mica. Most of the elements are associated with total carbon and clay sized fractions, with high values of correlation coefficient. Most of the elements are associated with total carbon and clay sized fractions , with high values of correlation coefficient. It was noteworthy that Hg was detected between 2 and 4 ppb in the stream water.

• Economic and Environmental Geology
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• v.19 no.1
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• pp.19-24
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• 1986

The Samkwang mine is one of gold deposits distributed mainly in the southwestern province (Chungnam) of the Korean peninsula. Golds occur in quartz veins aged of $223{\pm}4MA$ according to K-Ar age dating from muscovite in a pegmatitic quartz vein. Quantz veins intrude Precambrian biotite-granite gneiss and mica schist of unknown age. Fluid inclusions in the quartz show a range of homogenization temperatures from 159 to $274^{\circ}C$. A calculated temperature from the isotopes of the galena-sphalerite pair is $375^{\circ}C$. Two phases-fluid inclusions homogenized either by liquid or vapor phase are frequently observed in specimens over $260^{\circ}C$, which may indicate the boiling of the fluids. Pressure of formation of the quartz veins inferred by the homogenization temperatures of liquid-$CO_2$ bearing fluid is 1kb. Based on these data, it is assumed that the temperature of the formation of the Samkwang mine may lie in between $350^{\circ}-230^{\circ}C$. ${\delta}^{34}S_{{\Sigma}s}$ values of sulphide minerals show narrow range of +2.1 to +4.6, and show a trend of enrichments of $^{34}S$ in the fluid from deep to the surface. ${\delta}^{34}S_{{\Sigma}s}$ in the fluid estimated is less than 3 permil, suggesting sulphur fluid originated from the magma.