• Proceedings of the KSR Conference
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• 2009.05a
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• pp.411-417
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• 2009

This paper describes the development of integrated simulator for traction power supply system with GUI (Graphic User Interface). This simulator consists of a lot of calculation modules such as TPS, time table, line constant, and power supply system analysis. Each module has input and output structure respectively. The proposed simulator is tested on both high speed railway line and metropolitan subway line. The test has confirmed the function of the developed simulator.

• Proceedings of the KIPE Conference
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• 2002.11a
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• pp.21-24
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• 2002

The vector control system of an induction motor is the high performance drive system to achieve the instantaneous torque control. The vector control system is greatly divided into the direct control, and the indirect control that the most widely is used, The indirect vector control needs the rotor time constant, which changes widely according to the temperature, frequency, and current amplitude. The incorrect time constant leads to the saturation of magnetic flux or under-excitation phenomena. As a result, that deteriorate the control performance. Therefore, in this paper, the effect of time constant variation is investigated and its on-line tuning algorithm is proposed. The time constant using the torque angles was calculated and that of the validity of algorithm proposed was proved through the computer simulation and the experiment.

• ETRI Journal
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• v.46 no.3
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• pp.413-420
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• 2024

A dual-band bio-implantable compact antenna with a meander-line structure is presented. The proposed meander-line antenna resonates at the industrial, scientific, and medical (2.4 GHz) and wireless medical telemetry (1.4 GHz) bands. The meander-line structure is selected as a radiating patch given its versatile and effective design. With a dimension of only 10 mm × 10 mm × 0.635 mm, the designed antenna is compact. Considering a skin phantom, the proposed antenna was designed, optimized, and simulated. The Rogers RT/duroid 6010 substrate material with high dielectric constant was used to fabricate the meander-line dual-band implantable antenna, which was validated experimentally. The superstrate was made of the same material. Experiments were conducted on skin-mimicking gel. The designed meander-line antenna has a high peak gain of -21 dBi at 2.4 GHz, and its maximum specific absorption rate is compliant with IEEE safety standards.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.75-85
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• 2006

In recent geotechnical engineering, geothermal approach has been on the horizon to deal with geoenvironmental issues, freezing and thawing problems, and seepage phenomenon in dams and embankments. In this study, geothermal characteristic through inner body of dams and its influence on the seepage flow were experimented by lab test and field instrumentation. Also, one of up-to-date temperature monitoring technique, called as multi-channel thermal line sensing, was evaluated its availability. As a result of lab test, it is found that the seepage flow has influence on the geothermal characteristic and a potential of finding phreatic line and seepage fluctuation could be possible by continuous temperature monitoring using thermal line sensing skills. These kine of geothermal information could be available to the modelling of water geo-structure interaction. Out of short-term field tests, clear water table and temperature distribution of a dam were easily found through temperature monitoring in holes located near a reservoir and holes within a depth of constant temperature layer. However, it is also found that the geothermal flow and finding seepage line could not be easily understandable through multi-channel temperature monitoring because of the existence of constant temperature field, thermal conductivity of soils and rocks, and unsaturated characteristics of geo-material. In this case, long-term geothermal monitoring is recommended to find sudden fluctuation of seepage line and amount of leakage.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.12 s.354
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• pp.83-88
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• 2006

In this paper, we propose a new cross bar embedded structure for improvement of attenuation characteristics along the different lossy media. A general characterization procedure based on the extraction of the characteristic impedance and propagation constant for analyzing a single MIS(Metal-Insulator-Semiconductor) transmission line used and an analysis for a new substrate shielding MIS structure consisting of grounded crossbars at the interface between Si and Sio2 layer using the Finite-Difference Time-Domain(FDTD) technique is used. In order to reduce the substrate effects on the transmission line characteristics, a shielding structure consisting of grounded cross bar lines over time-domain signal has been examined. The extracted, distributed frequency-dependent transmission line parameters as well as the line voltages and currents, and also corresponding equivalent circuit parameters have been examined as function of frequency. It is shown that the quality factor of the transmission line can be improved without significant changes in the characteristic impedance and effective dielectric constant.

• Publications of The Korean Astronomical Society
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• v.11 no.1
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• pp.91-107
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• 1996

We determine analytically the onset of thin-shell formation time of fast wind bubble with power-law energy injection $E_{in}=E_0t^s$, and power-law ambient density structure, ${\rho}_0(r)={\bar{\rho}}(r/{\bar{r}})^{-{\omega}}$. Thin-shell formation time, $t_{sf}$ can be estimated by minimizing the total time elapsed before the complete cooling of shocked gas. For uniform medium (${\omega}=0$) and constant energy injection (s = 1), the onset of shell formation is found to be at $t_{sf}=5.2{\times}10^3yr$, which agrees Quite well with the results of FCT 1D numerical calculation. We solve the line transfer problem with previous result derived by numerical calculation in order to calculate line profile of [OIII] (${\lambda}=5007{\AA}$) forbidden line. In general, radiative outer shell causes the formation of double peaked line profile. Each peak corresponds to approaching and receeding shells with large velocities. Our line profiles show good agreements with observation of expanding shell structure.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.8
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• pp.421-431
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• 2004

Line constants are composed by impedances and susceptances. A paper which was published estimated only impedances of line constants. Therefore, this paper estimates susceptances as well as impedances of equivalent five-conductors model using the reduced equivalent method. In order to verify estimated line constants, we measured line constants of real railway system. And we compared calculated results with measured data on 60Hz∼3000Hz. For the other verification, the calculation results from the proposed model and the measurement data from the test are compared focused on the amplification of harmonic current in the paper.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.729-736
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• 2013

Power grids are large complicated networks in use around. An absolute phase value for a particular unknown-phase line at a local site should be identified for the operation and management of a 3-phase distribution network. The phase shift for a specific point in the line, as compared with a phase reference point at a substation, must be within a range of ${\pm}60^{\circ}$ for correct identification. However, the phase shift at a particular point can fluctuate depending on the line constants, transformer wiring method, line length, and line amperage, etc. Conducted in this study is a theoretical formulation for the determination of phase at a specific point in the line, Simulink modeling, and analysis for a distribution network. In particular, through evaluating the effects of unbalanced current loads, the limitations of the present phase identification methods are described.

• Journal of Educational Research in Mathematics
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• v.16 no.1
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• pp.59-78
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• 2006

As a theoretical background for this research, the literatures which focus on the rationale of teaching and learning of connecting with mathematics and science in calculus were investigated. And teaching and learning material of connecting with mathematics and science in calculus was developed. And then, based on the case study using this material, the research questions were analyzed in depth. Students could understand mean-velocity, instant-velocity, and acceleration in the experimenting process of constant acceleration movement. Also Students could understand fundamental ideas that instant-velocity means slope of the tangent line at one point on the time-displacement graph and rate of distance change means rate of area change under a time-velocity graph.

• Journal of the Korean Electrochemical Society
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• v.4 no.1
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• pp.26-33
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• 2001

This article involves the application of the fractal geometry to interfacial electrochemistry. Especially, we gave our attention to impedance behaviour of the fractal electrode. First, this article briefly explained the constant phase element (CPE) in electrochemical impedance and the do Levie's transmission line model. Second, we introduced the Nyikos and Pajkossy's theoretical works to approach the CPE phenomena using the fractal geometry. Finally this article presented other various fractal models for analysing the ac response of the rough electrodes.