• Economic and Environmental Geology
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• v.5 no.4
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• pp.211-217
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• 1972

The Second Yeon Hwa Mine which belongs to a so called Lead-Zines Belt Area in the central east Korea is located at about 10 km northeast of the Seogpo railway station on Yeongdong Line. The exploitation of the mine started in June, 1969 and furnished the machinary ore dressing plant in November, 1971. The current monthly production of rude ore is 15,000 meteric tons. The results of the study on the lead-zinc-copper deposits of the Second Yeonhwa mine are summerized as follows: (1) main ore deposits of the mine are localized in the Pungchon Limestion formation of Cambrian age, (2) related ingneous rock with ore deposits is granite porphyry, which distributed in NS and $N50^{\circ}W$ trend, (3) ore solution ascended along the $N50^{\circ}W$ trend which represents folding axis and fault plane and mineralized selectively in the limestone formation. (4) high grade ore deposits are localized in concave and convex boundaries of granite porphyry, and hanging walls of shale bed ($P_2S$ shale bed) in Pungchon Limestone formation and (5) skarn minerals are consisted of garnet, hedenbergite, diopside, and sulfide minerals are composed of zincblenede, galena, phyrhotite, pyrite and some amount of chalcopyrite and arsenopyrite.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.284-287
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• 2006

In this paper variety test results were discussed regarding to the ground potential increase. The tests conducted with a joint box simulating leakage point having an insulator fault. Inside the joint box three-phase cables and one neutral line were connected and the insulator at jointed part was peeled from the one of three-phase cables. The potentials around manhole cover were measured with the variation of manhole material, ground resistance and water resistance when the manhole was flooded. The potentials induced by an electric leakage were drastically decreased with increasing the distance from the leakage location and with less ground resistance.

• Nuclear Engineering and Technology
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• v.37 no.4
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• pp.317-326
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• 2005

The burning-out of excess plutonium from the reprocessing of spent nuclear fuel and from the dismantlement of nuclear weapons is recently emphasized due to the difficulties in securing the final repository for the spent fuel and the necessity to consume the ex-weapons plutonium. An irradiation test in the Halden reactor was launched by the OECD Halden Reactor Project (HRP) to investigate the in-pile behavior of plutonium-embedded fuel as a form of mixed oxide (MOX) and of inert matrix fuel (IMF). The first cycle of irradiation was successfully accomplished with good integrity of test fuel rods and without any undesirable fault of instrumentations. The test results revealed that the MOX fuel is more stable under irradiation environments than IMF. In addition, MOX fuel shows lower thermal resistance due to its better thermal conductivity than IMF. The on-line measured in-pile performance data of attrition milled MOX fuel are used in the analysis of the in-pile performance of the fuel with the fuel performance code, COSMOS. The COSMOS code has been developed for the analysis of MOX fuel as well as $UO_2$ fuel up to high burnup and showed good capability to analyze the in-reactor behavior of MOX fuel even with different instrumentation.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.6
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• pp.1435-1441
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• 2014

The fire took place in the synthetic heat transfer fluid boiler used in production process of medium density fiberboard. This study investigated pressure distribution of the first, second and third passes and the temperature in the fire burner. The boiler's internal fluid is unsteady due to the out of order inverter. As the operation continues, the flame's flow and speed are unsteady. The synthetic heat transfer fluid leak spouted about 120kg/min in the form of vapor in the early period of the fire. The flame extended to the second and third passes. The highest temperature of the second and third pass is $1059^{\circ}C$ and $1007^{\circ}C$, respectively. The synthetic heat transfer fluid spouted through the cracked part of the fire box in the first pass and accumulated on the turn table. Therefore, it is expected that the temperature of the interior of the fire box is above $1200^{\circ}C$. The temperature of the burner rises to a maximum level several times in a short period. On account of that, several explosions occur in the fire burner. Pressure distribution at steady state in combustion furnace is 2~5mAq and pressure distribution at inverter under fault condition in combustion furnace is 10~-53mAq. The decrement of coil thickness measurement for synthetic heat transfer fluid boiler is 0~5mm.

• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.55-59
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• 2018

Currently, the development of industry makes needs larger electric supply. Providers must consider the efficiency about losses and reliability of the system. In this case, DC power system can save electrical energy; long-distance transmission line losses. Relevance to switch technology with a voltage-source converter (VSC) in AC-DC conversion system have been researched. But, protection device of DC-link against fault current is still needed to study much. VSC DC power system is vulnerable to DC-cable short-circuit and ground faults, because DC-link has a huge size of capacitor filter which releases extremely large current during DC faults. Furthermore, DC has a fatal flaw that current zero crossing is nonexistence. To interrupt the DC, several methods which make a zero crossing is used; parallel connecting self-excited series LC circuit with main switch, LC circuit with power electronic device called hybrid DC circuit breaker. Meanwhile, self-excited oscillator needs a huge size capacitor that produces big oscillation current which makes zero crossing. This capacitor has a quite effective on the price of DCCB. In this paper, hybrid self-excited type superconducting DCCB which are using AC circuit breaker system is studied by simulation tool PSCAD/EMTDC.

• Journal of Power Electronics
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• v.19 no.1
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• pp.288-295
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• 2019

Rectifiers are widely used in industrial applications. Although detailed models of rectifiers are usually used to evaluate their performance, they are complex and time-consuming. Therefore, the Average Value Model (AVM) has been introduced to meet the demand for a simple and accurate model. This type of rectifier modeling can be used to simplify the simulations of large systems. The AVM of diode rectifiers has been an area of interest for many electrical engineers. However, healthy diode rectifiers are only considered for average value modeling. By contrast, faults occur frequently on diodes, which eventually cause the diodes to open-circuit. Therefore, it is essential to model bridge rectifiers under this faulty condition. Indeed, conventional AVMs are not appropriate or accurate for faulty rectifiers. In addition, they are significantly different in modeling. In this paper, a novel application of the parametric average value of a three-phase line-commutated rectifier is proposed in which one diode of the rectifier is considered open-circuited. In order to evaluate the proposed AVM, it is compared with experimental and simulation results for the application of a brushless synchronous generator field. The results clearly demonstrate the accuracy of the proposed model.

• Journal of the Semiconductor & Display Technology
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• v.18 no.1
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• pp.5-9
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• 2019

Optical emission spectroscopy is used to identify chemical species and monitor the changes of process results during the plasma process. However, plasma process monitoring or fault detection by using emission signal variation monitoring is vulnerable to background signal fluctuations. IR heaters are used in semiconductor manufacturing chambers where high temperature uniformity and fast response are required. During the process, the IR lamp output fluctuates to maintain a stable process temperature. This IR signal fluctuation reacts as a background signal fluctuation to the spectrometer. In this research, we evaluate the effect of infrared background signal fluctuation on plasma process monitoring and improve the plasma process monitoring accuracy by using simple infrared background signal subtraction method. The effect of infrared background signal fluctuation on plasma process monitoring was evaluated on $SiO_2$ PECVD process. Comparing the $SiO_2$ film thickness and the measured emission line intensity from the by-product molecules, the effect of infrared background signal on plasma process monitoring and the necessity of background signal subtraction method were confirmed.

• Fire Science and Engineering
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• v.17 no.1
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• pp.8-20
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• 2003

Natural gas has been supplied through underground pipelines and valve stations as a new city gas in Seoul. In contrast to its handiness the natural gas has very substantial hazards due to fires and explosions occurring from careless treatments or malfunctions of the transporting system. The main objectives of this study are to identify major hazards and to perform risk assessments after assessing reliabilities of the composing units in dealing with typical pipeline networks. there-fore two method, fault tree analysis ;1nd event tree analysis, are used here. Random valve stations are selected and considered its situation in location. The value of small leakage, large rupture, and no supply of liquefied natural gas is estimated as that of top event. By this calculation the values of small leakage are 3.29 in I)C valve station, 1.41 in DS valve station, those of large rup-lure are $1.90Times10_{-2}$ in DC valve station, $2.32$\times$10^{-2}$ in DS valve station, and those of no supply of LNG to civil gas company are $2.33$\times$10 ^{-2}$ , $2.89$\times$10^{-2}$ in each valve station. And through minimal cut set we can find the parts that is important and should be more important in overall system. In DC valve station one line must be added between basic event 26,27 because the potential hazard of these parts is the highest value. If it is added the failure rate of no supply of LNG is reduced to one fourth. In DS valve station the failure rate of basic event 4 is 92eye of no supply of LNG. Therefore if the portion of this part is reduced (one line added) the total failure rate can be decreased to one tenth. This analytical study on the risk assessment is very useful to prepare emergency actions or procedures in case of gas accidents around underground pipeline networks and to establish a resolute gas safety management system for loss prevention in Seoul metropolitan area.

• The Korean Journal of Petroleum Geology
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• v.5 no.1_2 s.6
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• pp.1-8
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• 1997

Seismic stratigraphic analysis of the high resolution profiles obtained from the southeastern shelf of Korea divided the deposits into 4 sequences; 1) sequence D, 2) sequence C, 3) sequence B and 4) sequence A (Holocene sediments). Sequence D was deposited in shallow-water environment at west of the Yangsan Fault as the basin subsided. On the other hand, the eastern part was formed at the slope front. Landward part of the slope-front fill sediments were eroded and redeposited nearby slope due to the syndepositional tilting of the basin. This tilting probably resulted from the continuous closing of the Ulleung Basin. Sequence C is made of stacked successions of the lowstand fluvial sediments, transgressive sediments and marine highstand sediments derived from the paleo-river in the western part of the Yangsan Fault. Sequence C in the eastern part of the Yanshan Fault was formed at the shelf break. Progradation of the lowstand sediments resulted in broadening of the shelf. Sequence C in the eastern part was also tilted but the tilting was weaker than in Sequence D. During the formation of sequence B the tilting stopped and the point source instead of the line source started in both sides of the Yangsan Fault. Sequence B was composed of the highstand systems tract partially preserved around the Yokji island, lowstand systems tract mainly preserved in the Korea Trough and transgressive systems tract. After the stop of the tilting, the force of compression due to the closing of the Ulleung Basin may be released by the strike-slip faults instead of tilting.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.9
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• pp.42-51
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• 2017

This paper deals with the power supply facility providing wireless power transmission for a type of electric vehicles called the on-line electric vehicle(OLEV) and proposes optimal protection coordination methods which analyze the faultsin the 60Hz and 20kHz bands using PSCAD/EMTDC, which is the typical commercial software for the distribution system. The simulation results show that the proposed methods can reduce the fault current by introducing an NGR (Neutral Ground Resistor) in the 60Hz band and prevent the malfunctioning of the protection device by installing a CT in the neutral wire in the 20kHz band when a ground fault occurs.