• Journal of Ocean Engineering and Technology
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• v.11 no.4
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• pp.141-151
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• 1997

This paper deals with a numerical study of flow-guider applied to controlling current in a bay. Two dimensional numerical model for tidal currents based on the depth averaged equation is developed and standard k-.epsilon. model is adopted to determine the turbulence diffusion. Equations are described in a generalized coordinate system to be implemented by non-staggered grid system and discretized by using finite volume method. Unsteady flow is simulated by fully implicit scheme. Hybrid scheme and central differencing are used to compute the convective terms and source terms, respectively. The tidal current in a rectangular bay is simulated and it gives satisfactory results. The realistic and distinct models of a large structure placed in bay are also exemplified with or without flow-guiders. The simulation results show that the flow-guider gives the residual tidal current in the bay by the different flux with respect to the direction of tidal current.

• Journal of Biomedical Engineering Research
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• v.15 no.4
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• pp.413-418
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• 1994

In electrical impedance tomography (EIT), we use boundary current and voltage measurements to provide the information about the cross-sectional distribution of electrical impedance or resistivity One of the major problems in EIT has been the inaccessibility of internal voltage or current data in finding the internal impedance values. We propose a new image reconstruction method using internal current density data measured by NMR. We obtained a two-dimensional current density distribution within a phantom by processing the real and imaginary MR images from a 4.7T NMR machine. We implemented a resistivity image reconstruction algorithm using the finite element method and sensitivity matrix. We presented computer simulation results of the image reconstruction algorithm and furture direction of the research.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.487-490
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• 1999

The Maxwell displacement current was generated from 4-octyl-4'-(5-carboxyl-pentamethyleneoxy)- azobenzene (denoted as 8A5H) monolayer Langmuir-Blodgett films prepared on Cr/Au-coated glass substrates due to trans-cis photoisomerization of 8A5H by application of alternate irradiation with UV light and Visible light. The displacement current was generated due to the trans-to-CIS photoisomerization by irradiation with ultraviolet light($\lambda_1$=360nm). Whereas the displacement current was generated in the opposite direction due to the cis-to-trans photoisomerization by photoirradiation with visible light($\lambda_2$=450nm). Finally, We concluded that Displacement current change according to power capacity photoirradiation, the more higher generate the more higher power capacity magnitude.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.37.1-37
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• 2001

Electric plating is used in various industry field. Specially, pulse plating is able to deposit material at high current density compared to conventional DC plating. For example, pulse plating can get more fine grain, can improve adhesion and metal distribution and current efficiency, can reduce internal stress and crack. Therefore, we developed bidirection pulse power supply(BPPS) which has high speed pulse current and high current density and improve deposition quality and increase plating speed in this paper. BPPS(Bidirection pulse power supply) needs high speed rising time, falling time and output current accuracy. BPPS consists of rectifier part, chopper part, invertor part, and control part. Rectifier part changes outprt current direction.

• The Journal of the Korea Contents Association
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• v.7 no.12
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• pp.83-94
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• 2007

The portfolio can be used as a methodology supporting the learning of constructivism. Recently, the use of portfolios has been increased gradually in the education field, but a study on the current state analysis and design direction of portfolios leaves much to be desired. In this paper, we analyze statistical data on the portfolio application of teachers in domestic elementary, middle, and high school. We also propose a design direction of e-portfolio needed in the society of knowledge information based on this analysis. The results of research show that the following problems will be improved: understanding portfolio, analyzing the current state according to the types of portfolio application, designing a distinguished system according to the level of school, expanding education of teachers with high career, and developing a guide helper. The design of total system that combines the learning and evaluation is needed to improve a problem that spends lots of time to make portfolio, and operates temporally and formally achievement evaluation. In addition, the design of e-portfolio supporting efficiently interaction and self-directed teaming is required.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.6
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• pp.574-585
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• 2007

To analyze the incident wave characteristics around Haeundae beach the long-term deep water wave data computed by wave hindcast method were used and a continuous wave observation was carried out for 1 year at the 20 m of water depth in front of Haeundae beach. Wave observation data showd that the prevalent wave direction was SSW-S in spring and summer seasons while E-SE in autumn and winter. A numerical modeling shows that the waves from E-SE are refracted strongly due to the shoal developed at the south-east side of Haeundae beach. The simulation also shows inflowing nearshore current along the east coast of the beach develops strongly in autumn and winter. Radioactive isotope tracer experiment for 155 days indicated that the tracers moves to the on-shore direction in the 1st and 2nd tracking then dispersed to the E-W direction along the shore.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.6
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• pp.610-617
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• 2011

This paper proposes a novel and direct dead-time compensation method of the 3-phase inverter using space vector pulse width modulation(SVPWM) topology. The proposed dead-time compensation method directly compensates the dead-time to the turn-on time of the effective voltage vector according to the current direction of the medium voltage reference. Each phase voltages are determined by the switching times of the effective voltage vectors, and the practical switching times have loss according to the current direction by the dead-time effect in the 3-phase inverter. The proposed method adds the dead-time to the switching time of the effective voltage vector according to the current direction, so it does not require complex d-q transform and controller to compensate the voltage error. The proposed dead-time compensation scheme is verified by the computer simulation and experiments of 3-phase R-L load.

• 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.

• Korean Journal of Applied Biomechanics
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• v.28 no.3
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• pp.193-197
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• 2018

Objective: The relationship between the rest intervals during physical tasks and performance enhancement has been studied. However, whether or not different rest intervals would result in altered multiplanar ankle kinematics during performance of the Star Excursion Balance Test (SEBT) is unknown. Method: Fifteen healthy subjects (7 males and 8 females) without a history of ankle injuries were participated in this study. 3 rest intervals of 10, 20, and 40 seconds were used during the current study. Three visits were required in order to complete the 3 rest intervals. Variables of interest included dorsiflexion (DF) excursion, tibial internal rotation (TIR), and eversion (EV) excursions. The means of ankle angular excursions were compared across the 3 directions in the 3 rest interval groups. Results: There were no significant main effects for any variables between restintervals. However, DF excursion in the anteromedial (AM) direction was greaterthan in both the medial (M) and posteromedial (PM) directions and was greater in the M direction compared to the PM direction. TIR excursion in the AM direction was less than in both the M and PM directions. Conclusion: Different rest intervals ranging from 10 to 40 seconds did not influence ankle angular excursions during the SEBT in a healthy population. However, our results suggest that multiplanar motion is necessary during the SEBT and differs depending on the direction of movement.

• Journal of the Korean Solar Energy Society
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• v.32 no.6
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• pp.76-84
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• 2012

This study conducted experiments to measure air currents in an experimental building according to external conditions, types of induction ducts, and types of internal sockets by applying an external induction duct comprised of inducing openings and lines and induction units to the kitchen and bathroom vents at the rooftop of a super high-rise apartment building in order to help to improve the venting performance. The study also proposed the optimization of the external induction-style kitchen and bathroom vents capable of wind power generation. (1) As for air current distribution according to vent velocity changes, it increased the venting performance of the kitchen and bathroom by 1.0m/s at vent velocity of 2.0m/s or higher and allowed for wind power generation. (2)As for air current distribution according to external velocity changes, it increased the venting performance of the kitchen and bathroom by 1.2m/s at external velocity of 2.0m/s or higher and allowed for wind power generation. (3)As for air current distribution according to wind direction changes($0{\sim}180^{\circ}$), it was favorable for higher vent velocity when the angle between the external induction duct direction and prevailing wind direction was within ${\pm}30^{\circ}$. (4)As for air current distribution according to induction duct type, the[M1] type combining the inducing openings and lines with the induction units recorded the highest improvement effects in the kitchen and bathroom venting performance by increasing vent velocity by 46%. (5)As for air current distribution according to the changing types of internal sockets where the main ducts of the kitchen and bathroom are connected to the external induction ducts, the venturi tube type[Sv] increased vent velocity by 66% based on the smoothest external inflow.