• Ocean and Polar Research
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• v.44 no.4
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• pp.269-285
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• 2022

The interaction between ocean and ice shelf is a critical physical process in relation to water mass transformations and ice shelf melting/freezing at the ocean-ice interface. However, it remains challenging to thoroughly understand the process due to a lack of observational data with respect to ice shelf cavities. This is the first study to simulate the variability and circulation of water mass both overlying the continental shelf and underneath an ice shelf and an ice tongue in the Terra Nova Bay (TNB), East Antarctica. To explore the properties of water mass and circulation patterns in the TNB and the corresponding effects on sub ice shelf basal melting, we explicitly incorporate the dynamic-thermodynamic processes acting on the ice shelf in the Regional Ocean Modeling System. The simulated water mass formation and circulation in the TNB region agree well with previous studies. The model results show that the TNB circulation is dominated by the geostrophic currents driven by lateral density gradients induced by the releasing of brine or freshwater at the polynya of the TNB. Meanwhile, the circulation dynamics in the cavity under the Nansen Ice shelf (NIS) are different from those in the TNB. The gravity-driven bottom current induced by High Salinity Shelf Water (HSSW) formed at the TNB polynya flows towards the grounding line, and the buoyance-driven flow associated with glacial meltwater generated by the HSSW emerges from the cavity along the ice base. Both current systems compose the thermohaline overturning circulation in the NIS cavity. This study estimates the NIS basal melting rate to be 0.98 m/a, which is comparable to the previously observed melt rate. However, the melting rate shows a significant variation in space and time.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.816-823
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• 2007

Electric car tract plays the role of supply high electric power to the electric car from the substation by using Pantograph of the electric car. It is always exposed to the external atmosphere, which results in quite substantial fluctuations in current and voltage during operation of electric car. This generates possibility of occurrence of accident at all times. Since range of wiring metallic globe installed on the catenary cannot achieve complete electrical contact, accidents are occurring due to circulating current caused by arc caused by incomplete contact due to occurrence of hairline fracture of Pantograph due to pressure or vibration of wiring. Furthermore, rapid increase in the operational current due to increase in the operational frequency of the electric car is causing erosion and short circuit of the metallic globe at the contact points. This study on arc is generated as current transmitted out of the substation courses through power line or wiring metallic globe other than the main circuit as the current is being collected at the electric car through feeder and feeder divergence device. Accordingly, since heat generated by the arc becomes the cause for generation of circulating current due to melting of metal or softening of metal due to increase in temperature accompanying increase in contact resistance, this research shall describe causes and measures against occurrence of circulation current.

• Progress in Superconductivity
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• v.8 no.1
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• pp.98-103
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• 2006

[$Bi_2Sr_2Ca_1Cu_2O_x$](BSCCO 2212) tubes were fabricated by centrifugal melting process(CMP). BSCCO 2212 powder was melted in a Pt crucible and solidified in a rotating steel mold. The BSCCO 2212 tube samples separated from steel mold were heat-treated at $800^{\circ}C\;and\;810^{\circ}C$ in oxygen flow. The critical current($I_c$) of the samples was measured by transport measurement at 77K, and the microstructure was investigated by scanning electron microscope. The $J_c$ at 77K of the tubes heated treated at $800^{\circ}C\;and\;810^{\circ}C$ were 197 and 240 $A/cm^2$, respectively. It was observed that the plate like grains in BSCCO 2212 tube was more developed in the sample heat treated at $810^{\circ}C\;and\;800^{\circ}C$ heated tube. It is found that the critical current($I_c$) of the BSCCO 2212 sample was dependent on the heating schedule regarding the growth of the BSCCO 2212 grains.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.1
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• pp.34-40
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• 1998

Conductive metal matrix composite(MMC) material of 30% silicon carbide particulated based on aluminum matrix was machined by die sinking electrical discharge machining(EDM) process according to different current and duty factor for reverse polarity of electrode. Material removal rate(MRR) was examined by process under various operation conditions. The surface morphology was evaluated by surface roughness parameter and scanning electron microscopy(SEM) research. The MRR was suddenly increased over 11 ampere of current, and it was slightly changed over 0.3 of duty factor. The maximum surface roughness of EDMed surface was affected by the duty factor. The SEM photograghs of EDMed surface showed wide recast distribution region of melting materials as increased of current and duty factor.

• Journal of the Korean institute of surface engineering
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• v.37 no.2
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• pp.128-136
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• 2004

Effects of alloying elements on the surface characteristics of Fe-38Al intermetallic compounds were investigated using potentiostat. The specimens were casted by the vacuum arc melting. The subsequent homogenization and the stabilization led to the homogeneous DO$_3$ structure of the specimen. After the corrosion tests, the surface of the tested specimen was observed by the optical microscopy and scanning electron microscopy(SEM). For Fe-38 at.% Al intermetallic compound, the addition of Cr and Mo proved to be beneficial in decreasing the grain boundary attack by decreasing the active current density. Addition of Band Nb resulted in a higher active current density and also a higher passive current density. These results indicated the role of Cr and Mo in improving the pitting corrosion resistance of Fe-38 at.%Al intermetallic compound. Band Nb addition to Fe-38 at.%Al accelerated the granular corrosion. Fe-38 at.%Al containing Cr and Mo showed remarkably improved pitting corrosion resistance in comparison with Band Nb addition to Fe-38 at. %Al.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.9
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• pp.80-89
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• 1997

Die sinking electrical discharge machining(EDM) was conducted for ceramic composite of 33 weight percent TiC based on AI$_{2}$O$_{3}$ ceramic matrix according to the change of current and duty factor(DF). Material removal rate(MRR) was increased as the current and the duty factor increased, but better surface mor-pholoty was obtained in the region of lower current and duty factor. From the scanning electron microscopy(SEM) photographs and the energy dispersive X-ray spectroscopy(EDX) of the EDMed surface, EDM trace formed by one discharge spark was analyzed. Although the bending strength after EDM was highly decreased, reliability obtained by weibull analysis was increased twice. The bending strength was recovered or more by barrel polishing after EDM. From the FEM analysis of temperature for one spark, the possible melting region of AI$_{2}$O$_{3}$and TiC was obtained.

• Journal of Electrical Engineering and Technology
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• v.2 no.3
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• pp.366-372
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• 2007

Joining thin aluminum alloy is difficult using most welding techniques. Many of the problems are associated with bum-through by the high heat input. Common welding techniques are TIG (Tungsten Inert Gas), MIG (Metal Inert Gas), and PULSE-MIG welding. The method provides more control of the heat balance in the welding arc by taking advantage of the different arc characteristics obtained with each of the two polarities. In this paper, we proposed a new welding method by control DSP 320C32, and the characteristic and experiment result-voltage, current, welding bead, and penetrations by this method are presented.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.132-135
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• 2001

To improve the fault coordination of underground distribution line we study the several contents such as the magnitude of fault current in distribution line tripping time of CB by acting of over current relay with instantaneous trip and time delay trip. We also examine the melting time of current limiting fuse inside power fuse Through the research as above. we suggest the modification scheme of fault coordination to reduce the interruption times of power failure.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1463-1465
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• 2003

In this paper, we studied on the growing characteristics of dendrite structure of melted wire deteriorated by over current. Electric wire was melted by Jolue's heat. By using HSIS(High Speed Imaging System), we found out a lot of melted parts of wire were dispersed and radiated. Electric wire had narrow melted areas in case of short fusing time. A lot of very small dots generated around the grain of copper cross-section and they were changed into dendrite structure. Dendrite structure appeared at the values lower than 2.5[A/sec]. In case of very short fusing time, fusing current was calculated by empirical formula. The Preece equation was not enough to analyze a variety of characteristics of melted wire because it did not consider melting time, atmosphere, etc.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.3
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• pp.254-258
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• 2000

Current leads of high $T_{c}$ superconductor were fabricated with Bi excess B $i_{2.2}$/S $r_{1.8}$/C $a_{1}$/C $u_{2}$/ $O_{x}$ composition by rapid cooling method. The dimensions of final samples were fixed 3 mm and 8 mm diameter with 50 mm length each To control uniform density the samples were preformed by CIP(Cold Isostatic Press) process and followed by partial or full melting process after raising up to 90$0^{\circ}C$ for 30min. Plate shaped microstructure was clearly observed adjacent to the Ag tube wall and the size of plate was about 100$\mu$m. However the severe destruction of growth orientation was shown in the inner growth part. critical temperature ( $T_{c}$) was about 53~71K after directional growth while Tc was decreased about 77~80 K before directional growth. After directional growth critical current( $I_{c}$) and critical current density( $J_{c}$) in the specimen of 8 mm diameter at 50 K were about 110 A and 280 A/c $m^2$ respectively.pectively.ely.