• Journal of The Korean Astronomical Society
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• v.29 no.1
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• pp.31-41
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• 1996

We present results of time-series CCD photometry for 178 stars in the young open cluster M29 (=NGC6913). Total 1036 V-band CCD frames were collected for five nights between August 12 and September 13, 1994. The photometric precision is about 7.6 mmag for 9th-10th mag stars in M29 with exposure times of 30 seconds. From the dispersion diagram and the light curves, one detached eclipsing binary (HD194378) and two suspected variables are newly discovered. $A\;\gamma\;Cas$ type variable, V1322 Cyg, which has been known as a member of M29, did not show any light variations during the period of present observations, indicating that it passed the steady phase without the eruption during our observing runs.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.11
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• pp.521-528
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• 2003

A varactor diode was utilized in order to expand variable range of the natural oscillation frequency of an active phased-array antenna. We have conformed experimentally that the variable range of the natural oscillation frequency was expanded about three times in the oscillator controlled by the varactor diode. When frequency difference was given to the oscillators in the two elements antenna system, phase difference was appeared between the oscillators. The 2-, 3-, 5-elements patch antenna array was composed for the beam scanning experiments. All the above patch antennas showed good phased array characteristics. The experimental results are as follows that the scanning angle of the 2-elements array antenna is 28.6$^{\circ}$, the 3-elements array antenna is 29.4$^{\circ}$, and the 5-elements array antenna is 26.2$^{\circ}$.

• Proceedings of the KIEE Conference
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• 2003.07e
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• pp.70-74
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• 2003

The buck-boost converter is employed as the variable output PFC power stage. From the loss analysis, this topology has a high efficiency from light load to heavy load. A modified input current sensing scheme is presented to overcome the problem of the insufficient phase margin for the PFC circuit near the maximum output voltage. The variable output PFC circuit has a good performance in the wide output voltage range, under both the Boost mode when the output voltage is high and the Buck+Boost mode when the output voltage is low.

• Structural Engineering and Mechanics
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• v.52 no.4
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• pp.739-753
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• 2014

There have been many packages that can be employed to analyze plane frames. However, because most structural analysis packages suffer from closeness of system, it is very difficult to integrate it with an optimization package. To overcome the difficulty, we proposed a possible alternative, DAMDO, which integrate Design, Analysis, Modeling, Definition, and Optimization phases into an integrative environment. The DAMDO methodology employs neural networks to integrate structural analysis package and optimization package so as not to need directly to integrate these two packages. The key problem of the DAMDO approach is how to generate a set of reasonable random designs in the first phase. According to the characteristics of optimized plane frames, we proposed the ratio variable approach to generate them. The empirical results show that the ratio variable approach can greatly improve the accuracy of the neural networks, and the plane frame optimization problems can be solved by the DAMDO methodology.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.12
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• pp.1670-1679
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• 1995

In this paper, an optimal variable structure controller with a multilayer neural inverse identifier is proposed. A multilayer neural network with error back propagation learning algorithm is used for construction the neural inverse identifier which is an observer of the external disturbances and the parameter variations of the system. The variable structure controller with the multilayer neural inverse identifier not only needs a small part of a priori knowledge of the bounds of external disturbances and parameter variations but also alleviates the chattering magnitude of the control input. Also, an optimal sliding line is designed by the optimal linear regulator technique and an integrator is introduced for solving the reaching phase problem. Computer simulation results show that the proposed approach gives the effective control results by reducing the chattering magnitude of control input.

• Journal of Advanced Marine Engineering and Technology
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• v.11 no.2
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• pp.37-50
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• 1987

In an effort to conserve electric power, variable voltage variable frequency pulse width modulated (PWM) inverters are being applied increasingly to the variable speed control of the induction motors. The use of the PWM technique in motor drive applications is considered advantageous in many ways. For industrial applications, the PWM drive obtains its DC input through simple uncontrolled rectification of the commercial AC line and is favored for its good power factor, good efficiency, its relative freedom regulation problem, and mainly for its ability to operate the motor with nearly sinusoidal current waveforms. The purpose of this paper is to design a three phase natural sampled PWM inverter using microprocessor with simple control algorithm and hybrid control circuit has been built to implement this PWM scheme. In this system, the microprocessor can be used only for calculations directly related to motor control tasks by the design of hybrid circuit which sends PWM signals to the motor.

• 전기의세계
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• v.30 no.6
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• pp.375-385
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• 1981

New algorithms are derived for nonlinear programming problems which are characterized by their large variables and equality and inequality constraints. The algorithms are based upon the introduction of the Dependent-Variable-Elimination method, Independent-Variable-Reduction method, Optimally-Ordered-Triangular-Factorization method, Equality-Inequality-Sequential-Satisfaction method, etc. For a case study problem relating to the optimal determination of load flow in a 10-bus, 13-line sample power system, several approaches are undertaken, such as SUMT, Lagrange's Multiplier method, sequential applications of linear and quadratic programming method. For applying the linear programming method, the conventional simplex algorithm is modified to the large-system-oriented one by the introduction of the Two-Phase method and Variable-Upper-Bounding method, thus resulting in remarkable savings in memory requirements and computing time. The case study shows the validity and effectivity of the algorithms presented herein.

• Proceedings of the IEEK Conference
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• summer
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• pp.218-220
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• 2004

A new wide-band VCO topology using Miller capacitance is proposed. Contrary to conventional VCO using the Miller capacitance where the variable amplifier gain is negative, the proposed VCO uses both the negative and positive variable amplifier gain to enhance the frequency tuning range significantly. The proposed VCO is simulated using HSPICE. The simulations show that 410MHz and 220MHz frequency tuning range are obtained using the negative .and positive variable amplifier gain, respectively. The tuning range of the proposed VCO is $23\%$ of the center frequency(2.8GHz). The phase noise is -104dBc/Hz at 1MHz offset by simple model. The operating current is only 3.84mA at 2.5V power supply.

• Journal of IKEEE
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• v.18 no.2
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• pp.206-213
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• 2014

In this note, a new robust nonlinear output feedback variable structure controller is first systematically and generally designed for the output control of more affine uncertain nonlinear systems with mismatched uncertainties and matched disturbance. A transformed integral output feedback sliding surface with a most simple form is applied in order to remove the reaching phase problems. The closed loop exponential stability and the existence condition of the sliding mode on the integral output feedback sliding surface is investigated with a corresponding output feedback control input in Theorem 1. For practical application the continuous implementation of the control input is made by the modified saturation function. The effectiveness of the proposed controller is verified through a design example and simulation study.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.411-416
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• 2010

In this paper, an integral variable structure static output feedback controller with an integral-augmented sliding surface is designed for the improved robust control of a uncertain system under unmatched system uncertainty and matched input matrix uncertainty and disturbance satisfying some conditions. To effectively remove the reaching phase problems, an output dependent integral augmented sliding surface is proposed. Its equivalent control and ideal sliding mode dynamics are obtained. The previous some limitations is overcome in this systematic design. A stabilizing control with the closed loop exponential stability is designed for all unmatched system matrix uncertainties and proved together with the existence condition of the sliding mode on S=0. To show the usefulness of the algorithm, a design example and computer simulations are presented.