• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.7
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• pp.599-604
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• 2012

In this study, the safety of the driving gear reducer of ESW(essential service water) traveling sea water screen was evaluated through seismic analysis. Mode analysis of gear reducer was performed for reliability of analysis. Seismic analysis was performed in operating basis earthquake(OBE) and safe shutdown earthquake(SSE), which were applied as design condition using floor response spectrum( FRS). The maximum strain of gear reducer under OBE and SSE were 20.4 ${\mu}$ and 33.6 ${\mu}$, respectively. The maximum stresses were 2.42 MPa under OBE condition and 4.36 MPa under SSE condition, which were smaller than the allowable strength of material.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.9-9
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• 2008

Recently, the thickness of solar cell gets thinner to reduce the quantity of silicon. And the reduced thickness make it easy to be broken while PV module fabrication process. This phenomenon might make PV module's maximum power and durability down. So, when using thin solar cell for PV module fabrication, it is needed to optimize the material and fabrication condition which is quite different from normal thick solar cell process. Normally, gel-content of EVA sheet should be higher than 80% so PV module has long term durability. But high gel-content characteristic might cause micro-crack on solar cell. In this experiment, we fabricated several specimen by varying curing temperature and time condition. And from the gel-content measurement, we figure the best fabrication condition. Also we examine the crack generation phenomenon during experiment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.336-338
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• 2006

Diagnostic tests are used to evaluate the insulation condition of stator windings in traction motor. These tests included ac current, tan delta and maximum partial discharge. The insulation condition of stator windings was assessed by three test items. The stator windings of traction motor were m good condition. After completing the diagnostic tests, the stator windings of traction motors were subjected to gradually increasing ac voltage, until the insulation punctured. No.5 stator windings failed near rated voltage of 18.9 kV. The breakdown voltage of No.1 stator windings was 13.0. The failure was located m a line-end coil at the exit from the core slot.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.7
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• pp.631-635
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• 2007

Diagnostic, surge and ac breakdown tests are widely used to evaluate the insulation condition of stator winding in traction motor. Diagnostic test included ac current, tan delta and maximum partial discharge. The result of diagnostic test indicates that five kinds of stator windings are good condition. Surge test was peformed to confirm the healthy of turn insulation in stator windings. This test is very easy to detect the turn insulation failure between normal and defect stator windings. After completing the diagnostic test, ac breakdown test has conducted gradually increasing ac voltage, until the stator winding punctured. No. 5 stator windings failed near rated voltage of 18.9 kV The breakdown voltage of No. 1 stator windings was 13.0 kV The ac breakdown voltage of normal winding is about 1.45 times higher than that of defect windings. The failure was located in a line-end coil at the exit from the core slot.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04a
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• pp.27-30
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• 2004

Different types of hybrid negative materials on pitch based carbon and natural graphite for lithium ion batteries were studied. Two types of active materials were prepared, that is, pitch based graphite carbon, and pitch based carbon impregnating natural graphite. The specific capacity, capacity recovery in high temperature condition, and other electrochemical properties were achieved for these materials. We found that addition of natural graphite type to the pitch based carbon can significant1y improve the specific capacity and interfacial resistance. However, use of natural graphite will cause a serious capacity loss in the high temperature condition owing to its increasing interface resistance. The specific capacity ranged from 321 to 348 mAh/g and the maximum specific capacity was obtained in the case of pitch based carbon impregnating natural graphite.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.1
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• pp.33-39
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• 2023

In this study, the effect of mixing condition of raw material powders possessing various particle size and particle size distribution on thermite reaction efficiency was investigated. When fine raw powders are used, rather the reaction yield tends to decrease due to agglomeration. In contrast, coarse raw powders make deteriorate the contact area between raw material powders containing Al reducing agent. To ensure the optimal thermite reaction efficiency, it is required to optimize a mixture condition of raw material powders prior to thermite reaction. From the current experiment, the maximum thermite reaction efficiency is 77%, which came from Nb₂O₅ + NiO +Al mixtures with size distribution from 9.25 to 22.63 ㎛.

• Bulletin of the Society of Naval Architects of Korea
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• v.17 no.1
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• pp.1-10
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• 1980

The nonlinear analysis of ship plating with flat bar stiffners has been carried out by the finite element method based on the load incremental approach. The large deflection analysis has been done by using the Lagrangian description. The elastoplastic analysis has been performed by adopting the flow theory of plasticity and the von Mises yield condition. The layered elements are used to show the process of yielding through the plate thickness in the elasto-plastic analysis. The following results are obtained; 1) According to the large deflection analysis, it is shown that the small deflection theory to the plate is applicable in the range of the lateral deflection-the thickness ratio $w/h{\leqq}0.3$ and ship plating in the range of $w/h{\leqq}0.5$. 2) By means of the elasto-plastic analysis, it is found that the maximum load-carrying capacity of the plate increases as much as 1.8 times of the initial yield load in the case of the simply supported condition and 2.2 times in the clamped condition. It is also shown that the maximum load-carrying capacity of ship plating increase as much as 4.3 times in the simply supported condition and 4.2 times in the clamped condition. This method would be applied and extended to solve combined nonlinear problems which involve both material nonlinearity and geometric nonlinearity.

• Electrical & Electronic Materials
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• v.8 no.3
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• pp.357-361
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• 1995

An experiment on characteristics of nMOSFET's in the long stress condition with the maximum of the substrate current has been carried out in order to study on the degradation due to the hot-carrier effect. Based on the measured result of the threshold voltage, the damage is mostly due to the hole injection into the oxide. After long stress, it was shown that the drain current increased at low gate voltages and hence decreased at high gate voltages.

• Journal of Welding and Joining
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• v.24 no.1
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• pp.56-63
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• 2006

The characteristics of $CO_2$ or Nd:YAG laser welded 600MPa ade TRIP steel was investigated. He or Ar gas was used as a shield gas in case of $CO_2$ laser welding, but the shield gas was not used in case of Nd:YAG laser welding. Bead on plate welding was performed with various welding conditions. Defects in the joints of both welding type occurred at 1.8m/min but were not observed over the welding speed of 2.1m/min in case of Nd:YAG laser welding. However, porosity occurred in $CO_2$ laser welding and the tendency of decreasing with the increase of welding speed. The hardness was the highest at heat affected zone near fusion zone as well as at the fusion zone and decreased on approaching the base metal. In a perpendicular tensile test to the weld line, all specimens that have been welded at optimum conditions were fractured at the base metal, and the tensile properties showed the rather higher than those of raw material. In a parallel tensile test, the strength of the joints was higher than that of the base metal. Elongation was found to be lower than that of the raw material. Forming height by Erichsen test and elongation were deeply related with the ratio of base metal/weld metal and the maximum hardness of the weld metal. Also porosity induced to decrease the strength and the elongation. The maximum formability was recorded at approximately 80% as compared with that of the raw material with the optimum condition.

• Journal of the Korean Geosynthetics Society
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• v.10 no.4
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• pp.113-121
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• 2011

River sand has generally used for the backfill material of underground power cables. The thermal resistivity of it has $150^{\circ}C$-cm/Watt in wet condition and more than double in dry condition. The final goal of this study is to find the backfill material which has a small change in thermal resistivity with various water contents, for example thermal resistivity is $50^{\circ}C$-cm/Watt and $100^{\circ}C$-cm/Watt in wet and dry conditions respectively. In this study it is presented that the comparison of thermal resistivity using stone powder, crush rock, weathered granite soil and Jumunjin sand as well as river sand in the needle method regarding water content, dry unit weight and particle size distribution. As a result, the thermal resistivity of a material is minimized when they have maximum dry unit weight at optimum moisture content and maximum density by appropriately mixing materials for particle size distribution. Therefore thermal resistivity characteristics should be considered two factors: one is the difference between natural dry condition and dry state after optimum moisture content, and the other is the difference between unit weight of raw material and maximum dry density.