• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.6
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• pp.24-33
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• 2000

Switching behaviour of the ferroelectric thin film and device characteristics of the MFSFET(Metal-Ferroelectric-Semiconductor FET) are simulated with taking into account the accumulation of oxygen vacancies near interface between the ferroelectric thin film and the bottom electrode caused by the progress of fatigue. In our switching model, relative switched charge is 0.74 nC before fatigue, but after the progress of fatigue it reduces to 0.15 nC with the generation of oxygen vacancies. It indicates that the generation of oxygen vacancies strongly suppresses polarization reversal. $C-V_G\;and\;I_D-V_G$ curves in our MFSFET device model exhibit the memory window of 2 V and show the accumulation, the depletion and the inversion regions in capacitance characteristic clearly. The difference of saturation drain current of the device before fatigue in shown by the dual threshold voltages in $I_D-V_G$ curve as 6nA/$cm^2$ and decreases as much as 50% after fatigue. Decrease of the difference of saturation drain currents by fatigue implies that the accumulation of oxygen vacancies with the fatigue should be avoided in the device application. Our simulation model is expected to play an important role in estimation of the behavior of MFSFET device with various ferroelectric thin films.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.3
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• pp.232-239
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• 2013

This paper proposes an improved stator flux estimator through ensuring conventional PLPF to act as a pure integrator for sensorless control of induction motors. Conventional PLPF uses the estimated synchronous speed as a cut-off frequency and has the gain and phase compensators. The gain and phase compensators are determined on the assumption that the estimated synchronous angular speed is coincident with the real speed. Therefore, if the synchronous angular speed is not same as the real speed, the gain and phase compensation will not be appropriate. To overcome the problem of conventional PLPF, this paper analyzes the relationship between the synchronous speed error and the phase lag error of the stator flux. Based on the analysis, this paper proposes the synchronous speed error compensation scheme. To achieve a start-up without speed sensor, the current model is used as the stator flux estimator at the standstill. When the motor starts up, the current model should be switched into the voltage model. So a stable transition between the voltage model and the current model is required. This paper proposes the simple transition method which determines the initial values of the voltage model and the current model at the transition moment. The validity of the proposed schemes is proved through the simulation results and the experimental results.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.12
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• pp.1-11
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• 1991

Multi rate circuit switching ISDN which assumes a star topology consisting of LANs(local area networks) interconnected through a backbone MAN (metropolitan area network) is considered. The stations are classified into two categories data and voice stations they are characterized by different arrival rate and session-length (holding time) statistics. We first model the data and voice terminals as finite-source stations and derive analytically exact expressions for the end-to-end blocking probabilities. For more exact evaluation, these probabilities are calculated in terms of three components:circuit blocking probability, destination busy probability and concurrent busy probability. For large size systems, we develop an develop an iterative algorithm that provides a computationally efficient and fast method for the calculation of the end-to-end blocking probabilities.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.06a
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• pp.612-618
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• 1998

The success of a fuzzy logic control system solving any given problem critically depends on the architecture of th network. Various attempts have been made in optimizing its structure its structure using genetic algorithm automated designs. In a regular genetic algorithm , a difficulty exists which lies in the encoding of the problem by highly fit gene combinations of a fixed-length. This paper presents a new approach to structurally optimized designs of a fuzzy model. We use a messy genetic algorithm, whose main characteristics is the variable length of chromosomes. A messy genetic algorithms used to obtain structurally optimized fuzzy models. Structural optimization is regarded important before neural network based learning is switched into. We have applied the method to the exampled of a cart-pole balancing.

• ETRI Journal
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• v.30 no.2
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• pp.282-289
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• 2008

We propose a new mini-slot transmission scheme for a passive optical network (PON) in which each customer can be switched either to access mode or to internetworking mode dynamically. In this paper, we present the system implementation (called LAN-PON) as well as the performance of the proposed transmission scheme to illustrate its feasibility and benefits. A mini-slot scheme can rapidly reduce the queuing delay, which increases due to the flooding of the deflected packets in a deflection scheme. We evaluate the impact of mode switching time on the bandwidth gain (throughput) and delay of local area network (LAN) traffic in the LAN-PON with a mini-slot scheme. We also analyze a theoretical delay model of the proposed scheme. The simulation results demonstrate that switching time has an impact on LAN performance, and the average packet delay of the proposed scheme is significantly improved compared to that of the deflection scheme.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1389-1399
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• 2013

A discrete controller is designed for low power dc-dc switched mode power supplies. The approach is based on time domain and the control loop continuously and concurrently tunes the compensator parameters to meet the converter specifications. A digital state feedback control combined with the load estimator provides a complete compensation, which further improves the dynamic performance of the closed loop system. Simulation of digitally controlled Buck converter is performed with MATLAB/Simulink. Experimental results are given to demonstrate the effectiveness of the controller using LabVIEW with a data acquisition card (model DAQ Pad - 6009).

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.71-73
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• 2007

This paper deals with dynamic characteristics of LSRM. Position choose mover of LSRM and inductance. When approved current in each phase by decided position, we made sure current and voltage according to turn-on, turn-off. In dynamic simulation of LSRM, through an experiment, we decided turn-on position of inductance profile. Also, we presented dynamic characteristic analysis model which is consisted at motor and sensor signal part, etc., and substitute circuit constant that get using magnetic equivalent circuit method, we confirmed current and voltage waveform.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.95-97
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• 2007

This paper proposes a mathematical modelling about Leviation Force and Propulsion Force in a system, where Primary and Secondary LSRM air-gap is irregular. This can be a suitable model for Magnetically levitation Train, where Primary and Secondary air-gap mechanically has to control simultaneously Levitation Force and Propulsion Force.

• Journal of the Korean Operations Research and Management Science Society
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• v.18 no.1
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• pp.45-54
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• 1993

Monitoring processor in a circuit switched network is considered. Monitoring processor monitors communication links offers a grade of service in each link to controller. Such an information is useful for an effective maintenance of system. Two links with asymmetric system parameters and multi-symmetric links are respectively considered. Each links is to be an independent M /M/ 1/ 1/ type. Markov modeling technique is used to represent a model of monitoring processor with FCFS steering protocol. Performance measures considered are ratio of monitored jobs in each link, availability of minitoring processor and throughput of virtual processor in each link. The value of the performance meausres are compared with existing and simulation results.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.940-943
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• 2004

This Paper analysis variable characteristics of inductance profiles and basic magnetic fields for Switched Reluctance Motors(SRM). The varying Inductance and flux linkage on operating control condition are very important for developing control algorithm and SRM accurate drive system. Therefore, we have analytical model for varying inductance and flux linkage with simulation and experimental method, and to find an analytical expression for the SRM coenergy. There are shown some good results that comparison of simulated and analytical inductance, flux linkage and current waves.