• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.31-33
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• 1991

A passive power converter operating on the principle of parametric excitation, called Parametric transformer, is analyzed. The energy transfer from the input to the output is achieved through the double frequency variation of magnetic path reluctance to the input frequency without mutual flux coupling between two windings. Thus, output becomes available which is essentially independant of waveform of excitation. The mathmatical model of the device is developed and its solution is obtained. The outstanding characteristics of the device is explained from the analysis.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.162-168
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• 2002

Hybrid Welding means the coupling of the energy of two different energy sources in a common process zone. This paper describes prospects in laser-arc-hybrid-welding. Different kinds of lasers ($CO_2$ laser and Nd:YAG laser) and arc processes (TIG, Plasma and GMA) are considered.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.127-133
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• 2003

In this study, a problem formulation and solution for design optimization of laminate composite cylindrical beam section is presented. The objective of this research is to determine the optimal dimension of the laminated composite cylindrical beam sections which has the equivalent flexural rigidities to those of the steel cylindrical beam sections. The analytical model is based on the laminate theory and accounts for the material coupling for arbitrary laminate stacking sequence configuration. The outer diameter and thickness of the beam are design variables. The solutions described are found using a global search algorithm, Genetic Algorithms (GA).

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.230-233
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• 2003

Simulation model of induction type fixed speed wind power generator is developed. It is shown that the peak value of inrush current during start up changes according to the firing angle control strategy of soft starter. New proposed firing angle control scheme showed $25\%$ of reduction of peak current which results in smaller drop of gird voltage at the point of common coupling during start up.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.15-16
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• 2017

The properties of concrete damaged by fire change according to the temperature. Diffusion coefficient of chloride ion also can change which affect the life expectation under salt circumstance. Diffusion coefficient was measured by NT BUILD 492 using the concrete specimen damaged by high temperature. FEM analysis was performed to predict the life expectancy which can help to diagnose the concrete diagnose and to design maintenance strategy.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.1053-1055
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• 1998

Using EMTP model which describes bipolar HVDC system, switching level simulation results are presented in this paper. Voltage synchronization at point of common coupling, gate pulse generation and current control loops are represented in TACS module. The system consists of 100 km submarine cable rated 300 MW and 12 pulse rectifier and inverter stations which are connected to equivalent three-phase sources and loads through the 154 kV AC lines, respectively. In convertor stations, harmonic filters and capacitor banks are equipped to cancel out the harmonics generated by converters and to supply the required reactive power.

• Journal of Magnetics
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• v.2 no.3
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• pp.93-95
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• 1997

We investigated the temperature dependence of magnetization of Fe/Al multilayers fabricated by dc magnetron sputtering system. As the temperature increased from 5 K in a low magnetic field (100G) the magnetization of the samples increased and made a broad peak at some critical temperature. Further increase of temperature decresed the magnetization as an ardinary ferromagnetic curve. Part of samples show rapid increase of magnetization at low temperature. A model developed in this study suggests that the biquadratic coupling yields such a rapidly increasing behavior of magnetization at low temperature.

• Journal of Magnetics
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• v.4 no.4
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• pp.128-130
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• 1999

We have measured the magnetization of Ni/Ag(Ni at %)/Ni (50$\AA$/30 $\AA$/50 $\AA$) trilayered films including Ni atoms inserted in non-magnetic Ag spacer. The magnetization as a function of applied field at 5 K and as a function of temperature at 100 Oe were investigated respectively using SQUID magnetometer. In these measurements peaks of magnetization at some critical temperatures were observed in all the samples. The antiferromagnetic coupling energy between neighboring Ni layers showed oscillatory behaviors according to the amounts of the Ni atoms inserted in Ag spacer. Loose spin model suggested by slonczews야 was used to explain such results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.9
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• pp.1010-1019
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• 1992

As the dynamics model for industrial robot is a mutural coupling of inertia, centrifugal force, gravity, etc it is very difficult to get solution to the question how it works. To control such complex non-linear features of the manipulator, it is required to develop a lot simpler algorithm on the real time.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1234-1235
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• 2007

This paper represents the generating principles of the doubly-fed induction generator (DFIG) based wind power system and developes a simulation model of DFIG by using PSCAD/EMTDC. In addition, this paper analyzes the steady state operation and the transient operation during the voltage sags in the power common coupling. The voltage sags are occurred by three phase line-to-ground faults and full-voltage startup of an induction motor in the simulation.