• 한국해양공학회지
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• 제15권4호
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• pp.28-37
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• 2001

The water quality in Yongil Bay is getting worse due to the sewage and the waste water from the surrounding industrial complex. The study aims to simulate the current system that is necessary to build ecosystem model for the optium water quality control and clarify the correlation of current system characteristics with water quality in Yongil Bay. To clarify the characteristics of coastal water movement system and verify the applicability of the 3-D model, the current system was simulated using 3-D model baroclinic model which considers tidal current and density effects. As the results of numerical experiments, it is proved the 3-D model is the most applicable on appearing the current system of the stratificated Yongil Bay difference of density. Form the results of simulation considered tidal current only, it can be clarified that the water body flows in the inner bay through the bottom layer and flows out the outer bay through the surface layer in Yongil Bay. And the fresh water from the Hyongsan river and the thermal discharge form POSCO have a little effect on the current system in Yongil Bay, but the diffusion of heat and salt has an important effect upon the formation of the density stratification of the water quality distribution is closely related with the current structure characteristics as well as the tidal residual current system in Yongil Bay.

• 태양에너지
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• 제8권2호
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• pp.12-18
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• 1988

The effect of surface recombination current density on the saturation current density in Si solar cell has been studied. Theoretical model for surface recombination current was set up from emitter transparent model of M.A. Shibib, and saturation current of Si solar cell made by ion implantation method was also measured by digital electrometer. The theoretical surface recombination current density which is the same as saturation surface recombination current density in Shibib model was $10^{-11}[A/cm^2]$ and the measured value was ranged from $8{\times}10^{-10}$ to $2{\times}10^{-9}[A/cm^2]$. Comparing with the ideal p-n junction of Shockley, transparent emitter model shows improved result by $10^2$ order of saturation current density. But there still exists $10^2$ order of difference of saturation current density between theoretical and actual values, which are assumed to be caused by 1) leakage current through solar cell edge, 2) recombination of carriers in the depletion layer, 3) the series resistance effect and 4) the tunneling of carriers between states in the band gap.

• Membrane and Water Treatment
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• 제1권1호
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• pp.13-37
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• 2010

The performance of an electrodialyzer for concentrating seawater is predicted by means of a computer simulation, which includes the following five steps; Step 1 mass transport; Step 2 current density distribution; Step 3 cell voltage; Step 4 NaCl concentration in a concentrated solution and energy consumption; Step 5 limiting current density. The program is developed on the basis of the following assumption; (1) Solution leakage and electric current leakage in an electrodialyzer are negligible. (2) Direct current electric resistance of a membrane includes the electric resistance of a boundary layer formed on the desalting surface of the membrane due to concentration polarization. (3) Frequency distribution of solution velocity ratio in desalting cells is equated by the normal distribution. (4) Current density i at x distant from the inlets of desalting cells is approximated by the quadratic equation. (5) Voltage difference between the electrodes at the entrance of desalting cells is equal to the value at the exits. (6) Limiting current density of an electrodialyzer is defined as average current density applied to an electrodialyzer when current density reaches the limit of an ion exchange membrane at the outlet of a desalting cell in which linear velocity and electrolyte concentration are the least. (7) Concentrated solutions are extracted from concentrating cells to the outside of the process. The validity of the computer simulation model is demonstrated by comparing the computed results with the performance of electrodialyzers operating in salt-manufacturing plants. The model makes it possible to discuss optimum specifications and operating conditions of a practical-scale electrodialyzer.

• 대한토목학회논문집
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• 제11권2호
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• pp.27-37
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• 1991

음부력을 갖는 유체가 소규모 저수지로 유입되어 일어나는 밀도류의 거동 및 순환이 차원해석과 수리실험을 이용하여 해석된다. 무차원침강점 및 밀도류전면속도, 밀도류전면이동거리, 머리 뒤의 밀도층내회석 등은 유입밀도후르드수, Fre의 영향을 받으며 밀도층의 두께, 흐름양상 및 저수지내 밀도의 변화는 밀도류전면이 하류단에 도달하여 반사되기 전과 후의 양상이 현저하게 다르다. 밀도층의 두께는 전자의 경우에는 Fre, 후자의 경우는 시간과 Fre의 영향을 받으며 이들은 지수식으로 표현할 수 있다.

• 한국해양공학회지
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• 제32권4호
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• pp.261-271
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• 2018

In this study, a hydraulic model test, to which Particle Image Velocimetry (PIV) system applied, was used to determine the hydrodynamic characteristics of the advection-diffusion of saltwater according to bottom conditions (impermeable/permeability, diameter, and inclination) and the difference of the initial salt. Considering quantitative and qualitative results from the experiment, the characteristics of the density current were discussed. As an experimental result, the advection-diffusion mechanism of salinity was examined by the shape of saltwater wedge and the flow structure of density currents with various bottom conditions. The vertical salt concentration obtained from the experiment was used as quantitative data to calculate the diffusion coefficient that was used in the numerical model of the advection-diffusion of saltwater.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.581-583
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• 2004

This paper analysed the induced current density characteristics inside human body by extremely low frequency magnetic fields according to varying conductivities of human model. Human model was composed of several organs and other parts of 곳 human body, whose shapes were spheroids or cylinders. Organs taken into account were the brain, heart, lungs, liver and intestines. Applying the boundary element method to the human model, effects of the organ conductivity difference to the induced current distribution were estimated.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.195.1-195.1
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• 2016

Currently, as Plasma application is expanded to the industrial and medical industrial, low temperature plasma applications became important. Especially in medical and biology, many researchers have studied about generated radical species in atmospheric pressure low temperature plasma directly adapted to human body. Therefore, so measurement their plasma parameter is very important work and is widely studied all around world. One of the plasma parameters is electron density and it is closely relative to radical production through the plasma source. some kinds of method to measuring the electron density are Thomson scattering spectroscopy and Millimeter-wave transmission measurement. But most methods have very expensive cost and complex configuration to composed of experiment system. We selected Michelson interferometer system which is very cheap and simple to setting up, so we tried to measuring electron density by laser interferometer with laser beam chopping module for measurement of temporal phase difference in plasma jet. To measuring electron density at atmospheric pressure Ar plasma jet, we obtained the temporal phase shift signal of interferometer. Phase difference of interferometer can occur because of change by refractive index of electron density in plasma jet. The electron density was able to estimate with this phase difference values by using physical formula about refractive index change of external electromagnetic wave in plasma. Our guiding laser used Helium-Neon laser of the centered wavelength of 632 nm. We installed chopper module which can make a 4kHz pulse laser signal at the laser front side. In this experiment, we obtained more exact synchronized phase difference between with and without plasma jet than reported data at last year. Especially, we found the phase difference between time range of discharge current. Electron density is changed from Townsend discharge's electron bombardment, so we observed the phase difference phenomenon and calculated the temporal electron density by using phase shift. In our result, we suggest that the electron density have approximately range between 1014~ 1015 cm-3 in atmospheric pressure Ar plasma jet.

• 한국전기전자재료학회논문지
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• 제15권9호
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• pp.822-829
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• 2002

This paper deals with the distribution characteristics of the current density and axial magnetic flux density for each slits made on the contact electrode in the vacuum interrupter with axial magnetic field type using 3-dimension finite element analysis. It has been known that the presence of an axial magnetic field parallel to the current flow in the arc plasma can increase the high current breaking capacity of vacuum interrupter by carrying out the arc plasma from constricted mode to diffusion mode. The axial magnetic field is created of itself by current flow in the segments of coil electrode behind the contact electrode. The analyzed results show that if the slits are made in the contact electrode, they can increase the current density and axial magnetic flux density in the contact electrode surface and at the gap distance, which is due to decrease the effect of eddy currents flowing in the contact electrode. The phase shift due to eddy currents, defined 3s time difference between the maximum value of current and axial magnetic field, is decreased still more by increasing the number of slits made in the contact electrode at the center point of gap distance. These results demonstrate that 3-dimension finite element analysis has a great deal of merits in the development and evaluation of new electrode at the design of vacuum interrupter.

• 한국표면공학회지
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• 제49권5호
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• pp.423-430
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• 2016

In this study, we investigated the corrosion damage characteristics of steel for offshore wind turbine tower substructure using an accelerated electrochemical test. The galvanostatic corrosion test method was employed with a conventional 3 electrode cell in natural sea water, and the steel specimen was served as a working electrode to induce corrosion in an accelerated manner. Surface and cross-sectional image of the damaged area were obtained by optical microscope and scanning electron microscope. The weight of the specimens was measured to determine the gravimetric change before and after corrosion test. The result revealed that the steel tended to suffer uniform corrosion rather than localized corrosion due to active dissolution reaction under the constant current regime. With increasing galvanostatic current density, the damage depth and surface roughness of surface was increased, showing approximately 25 times difference in damage depth between the lowest current density ($1mA/cm^2$) and the highest current density ($200mA/cm^2$). The gravimetric observation showed that the weight loss was proportionally increased with increment of current density that has 75 times different according by experimental conditions. Consequently, uniform corrosion of the steel specimen was conveniently induced by the electrochemically accelerated corrosion technique, and it was possible to control the extent of the corrosion damage by varying the current density.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 전자세라믹스 센서 및 박막재료 반도체재료 일렉트렛트 및 응용기술
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• pp.35-38
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• 2000

In this study, the rise throughput and the stability in fabrication of device can be obtained by applying of CMP process to STI structure in 0.l8um semiconductor device. Through reverse moat pattern process, reduced moat density at high moat density, STI CMP process with low selectivity could be to fit polish uniformity between low moat density and high moat density. Because this reason, in-situ motor current end point detection method is not fit to the current EPD technology with the reverse moat pattern. But we use HSS without reverse moat pattern on STI CMP and take end point current sensing signal.[1] To analyze sensing signal and test extracted signal, we can to adjust wafer difference within $110{\AA}$.