• Journal of the Korean institute of surface engineering
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• v.55 no.1
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• pp.9-17
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• 2022

This work is concerned with the formation behavior of PEO (Plasma Electrolytic Oxidation) films on Al6082 alloy under the application of direct current (DC) and alternating current (AC) in an alkaline solution. Arc initiation voltage became much lower by the application of AC than DC, and arc initiation time became shorter under DC than AC. The number of pores present in the PEO films was much larger than that on the surface, irrespective of DC and AC. It was also found that the number of pores in the PEO films formed under AC was more than that under DC and the size of pores is smaller under AC than DC. During the formation of PEO films, a lot of heat was generated and solution temperature increased more rapidly under DC than under AC which is attributed to high PEO film formation voltage under DC than AC.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.69-69
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• 2012

• Journal of the korean society of oceanography
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• v.32 no.1
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• pp.1-7
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• 1997

Surface current fields in the eastern East China Sea (ECS) were constructed by analyzing trajectories of 58 satellite-tracked surface drifters released during 1991-1996. Composite trajectories and 20-minute-by-20-minute box-averaged current vectors show that the basic current pattern composes of: the Kuroshio main stream, which turns eastward toward the Tokara Strait; a northward branch current of the Kuroshio on the ECS outer shelf deeper than 100 m; and an anticyclonic circulation in the northern Okinawa Trough west of Kyushu. The northward branch current sharply changes its direction to the northeast when it crosses a line connecting Cheju Island, Korea and Goto Islands, Japan. The basic pattern of current field changes slightly from winter to summer, and the main axis of the Tsushima Current in the Korea Strait is found to shift seasonally. The drifter experiment does not support the claim that the Yellow Sea Warm Current is separated from the northward branch current on the outer shelf southeast of Cheju Island. We suggest that the use of the term 'Tsushima Current' be limited to the northeast channel flow in the Korea Strait. The new term 'Kuroshio Branch Current' is suggested for the northward branch current on the outer shelf south of Cheju-do, which is separated from the Kuroshio.

• Journal of the Semiconductor & Display Technology
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• v.5 no.1 s.14
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• pp.21-25
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• 2006

To improve the performance of organic thin film transistor, we investigated the properties of gate insulator's surface according to the leakage current by I-V measurement. The surface was treated by the dilute n-octadecyltrichlorosilane solution. The alkyl group of n-octadecyltrichlorosilane induced the electron tunneling and the electron tunneling current caused the breakdown at high electric field, consequently shifting the breakdown voltage. The 0.5% sample with an electron-rich group was found to have a large leakage current and a low barrier height because of the effect of an energy barrier lowered by, thermionic current, which is called the Schottky contact. The surface properties of the insulator were analyzed by I-V measurement using the effect of Poole-Frankel emission.

• Journal of the Korean institute of surface engineering
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• v.27 no.5
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• pp.285-291
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• 1994

The effects of pulse current parameters on the composition and the microstructure of Pd-Ni alloy electrodeposits were studied. The cathode current efficiency of p.c. electrolysis conditions decreased with increasing both mean and peak current density and was lower than those under D.C. electrolysis condition. Palladium content of Pd-Ni alloy increased with increasing both peak current density and on-time, while it decreased with increasing mean current density and duty cycle. The preferred orientation of Pd-Ni alloys changed with increasing mean current density in the sequence of (111)+(110).(100) or (110)longrightarrow(111)longrightarrow(100) or random distribution of crystal structure. The surface morphology of Pd-Ni alloy changed mainly according to the mean current density and was related to the preferred orientation.

• Journal of Sensor Science and Technology
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• v.25 no.4
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• pp.252-256
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• 2016

Epitaxially grown GaN layers have a high surface state density, which typically results in a surface leakage current and a photoresponse in undesirable wavelengths in GaN optoelectronic devices. Surface passivation is, therefore, an important process necessary to prevent performance degradation of GaN UV photodetectors. In this study, we propose oxygen-enhanced thermal treatment as a simple surface passivation process without capping layers. The GaN UV photodetector fabricated using a thermal annealing process exhibits improved electrical and photoresponsive characteristics such as a reduced dark current and an enhanced photoresponsive current and UV-to-visible rejection ratio. The results of this study show that the proposed surface passivation method would be useful to enhance the reliability of GaN-based optoelectronic devices.

• Journal of the Korean institute of surface engineering
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• v.39 no.5
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• pp.223-228
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• 2006

The current efficiency of copper anode containing impurities in copper sulfate solution for electrorefining was studied at various current type such as direct current, variable current and periodic reverse current. The passivity behavior was investigated by galvanostatic technique. The results obtained were that current efficiency of variable current was higher than those of direct current and periodic reverse current. The increased current efficiency could be explained by the formation of slime structure with lower average resistance due to variable current. The frequency of various factors in variable current condition has a greatest effect on current efficiency. It appeared that frequency increased current efficiency when increased from 1 to 4, but further increases did not have an effect.

• Ocean and Polar Research
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• v.31 no.4
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• pp.389-399
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• 2009

Subsurface pressure gauge has many advantages in measuring a wide range of wave spectra in coastal waters from wind waves to long waves. However, a shortcoming of the gauge is related to the difficulties in recovering surface wave spectra from subsurface pressure records. In this study, the effect of current on the pressure transfer function of the pressure gauge, and hence on the surface wave energy spectrum, was investigated by analyzing the subsurface pressure data based on the linear wave theory. For this purpose, laboratory experiments were carried out in a wave-current flume. Subsurface pressure records, as well as the surface elevation data, were obtained simultaneously under different wave and current conditions. Pressure transfer functions were obtained and compared with those estimated from the linear wave theory, both with and without inclusion of the current-effect. It was established that wave spectra obtained from subsurface pressure gauge were in closer agreement with those from surface wave gauge when current-effect on the pressure transfer function was taken into consideration for analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05b
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• pp.76-81
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• 2004

This paper presents the results of spectral analysis of leakage current waveforms on contaminated insulators under various fog and environment conditions(salt fog, clean fog, rain) The larger the leakage current during 200ms, the higer the power spectrum at 60Hz. For almost equal maximum current during 200ms, however, the spectrum at 60hz and the odd order harmonics increase emphatically when discharges occur continuously for several half-waves. If contaminated insulators suffers from high salt-density fog, the leakage current occurs with high crest value intermittently, results in the low spectrum. Analysis of leakage current data showed that this electrical activity was characterized by transient arcing behavior contaminants are deposited on the insulator surface during salt fog tests. This provides a path for the leakage current to flow along the surface of the insulator. It is important to have an indication of the pollution accumulation in order to evulate the test performance of a particular insulator. If the drop in surface resistivity is severe enough, then the leakage current may escalate into s service interrupting flashover that degrade power quality.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1025-1034
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• 2015

This paper presented an improved analytical method for calculating the open-circuit magnetic field in the surface-mounted permanent magnet machines accounting for slots and eccentric magnet pole. Magnetic field produced by radial and parallel permanent magnet is equivalent to that produced by surface current according to equivalent surface-current method of permanent magnet. The model is divided into two types of subdomains. The field solution of each subdomain is obtained by applying the interface and boundary conditions. The magnet field produced by equivalent surface current is superposed according to superposition principle of vector potential. The investigation shows harmonic contents of radial flux density can be reduced a lot by changing eccentric distance of eccentric magnet poles compared with conventional surface-mounted permanent-magnet machines with concentric magnet poles. The FE(finite element) results confirm the validity of the analytical results with the proposed model.