• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.3
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• pp.56-61
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• 1996

In this paper, new buck converter of a TV power system is presented. First, we devised a revised driving circuit for an emitter-coupled type buck converter, by which it is possible to reduce the material cost of transformers and voltage stress of power device. Secondly, we adopted a hybrid oscillation technique. When TV system is in off-stage, initial standby power which is necessary for remote controllable TV system is supplied by self-oscillating mode. Main power which is necessry in TV system bing on state is provided by an externally triggered oscillating mode. The switching frequency is synchronized to the oscillating frequency of horizontal deflection in TV, by which we can reduce picture noises and the size of power transformer. Thirdly, a simple error amplifier is inserted to the feed-back loop to keep the output voltage constant which means pulse width modulatio mode is added in driving part of power device. Finally, we showed by experiments that our proposed converter performs well enough to be close to the theoretically predicted values.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.11
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• pp.497-505
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• 2001

The power system stabilizer(PSS) is important for the suppression of low-frequency oscillation and the improvement of system stability. In this paper, An Adaptive Neurofuzzy-based Power System Stabilizer(ANF PSS) is proposed as the new PSS type. The proposed PSS employs a multi-layer adaptive network. The network is trained directly from the input and the output of the generating unit. The algorithm combines the advantages of the Artificial Neural Network(ANN) and Fuzzy Logic Control(FLC) schemes. Studies show that the proposed ANF PSS can provide good damping of the power system over the wide range of operating conditions and improve the dynamic performance of the system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.523-524
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• 2008

전자빔의 산란에 의한 자기 공명현상과 지파 사이크로트론과의 상호작용에 의한 해석에서 체렌코프 발진이 일어나는 것은 확인하기 위하여 대구경 후진파 발진기를 이용한 실험을 하였다. 전자계와 전자빌의 상호작용을 위한 조절을 위하여 도파관의 반경과 진폭, 파장을 조절하였으며 이에 따른 주파수의 발진을 알수 있었다.

• Journal of electromagnetic engineering and science
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• v.12 no.4
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• pp.227-233
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• 2012

This paper describes a novel and compact biosensing platform using an RF active system. The proposed sensing system is based on the oscillation frequency deviation due to the biomolecular binding mechanism on a resonator. The impedance variation of the resonator, which is caused by a specific biomolecular interaction results in a corresponding change in the oscillation frequency of the oscillator so that this change is used for the discrimination of the biomolecular binding, along with concentration variation. Also, a Surface Acoustic Wave (SAW) filter is utilized in order to enhance the biosensing performance of our system. Because the oscillator operates at the skirt frequency range of the SAW filter, a small amount of oscillation frequency deviation is transformed into a large variation in the output amplitude. Next, a power detector is used to detect the amplitude variation and convert it to DC voltage. It was also found that the frequency response of the biosensing system changes linearly with three streptavidin concentrations. Therefore, we expect that the proposed RF biosensing system can be applied to bio/medical applications capable of detecting a nano-sized biomolecular interaction.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.459-462
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• 2006

In this study, the characteristic of a vane pump of an automative power steering system is numerically analyzed. The vane pump changes the energy level of operation fluid by converting mechanical input power to hydraulic output. To simulate this mechanism, moving mesh technique is adopted. As a result, the flow rate and pressure are obtained by numerical analysis. The flow rate agrees well with the experimental data. Moreover, the variation and oscillation of the pressure around the rotating vane are confirmed. The difference of pressure appears in the vane tip as a result of the flow characteristics. Furthermore, the back flow into the rotor was observed.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.8
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• pp.353-362
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• 1986

This paper shows that 6 pulse converter instead of 12 pulse converter can be used for the control of Superconducting Magnet Energy Storage(SMES) to improve the stability and to suppress the voltage fluctuation of power system. In order to prevent the commutation failure, when 6 pulse converter used for simultaneous control of real power and reactive power is asymmetrically controlled, stable control region has been presented by analyzing the commutation phenomena at critical points which distinguish the stable control region from the unstrol control region. Harmonic components of line current and output voltage have been calculated. Finally, computer simulation of power system stabilization has been presented to show the effectiveness of the proposed method. According to the computation results, SMES controlled by the 6 pulse converter is an effective measure in reducing the oscillation and the transient instability of the power system.

• Journal of Power Electronics
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• v.17 no.3
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• pp.686-694
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• 2017

Due to the wide use of electronic products, digitally controlled DC-DC converters are attracting more and more attention in recent years. However, digital control strategies may introduce undesirable Limit Cycle Oscillation (LCO) due to quantization effects in the Analog-to-Digital Converter (ADC) and Digital Pulse Width Modulator (DPWM). This results in decreases in the quality of the output voltage and the efficiency of the system. Meanwhile, even if the resolution of the DPWM is finer than that of the ADC, LCO may still exist due to improper parameters of the digital compensator. In order to discover how LCO is generated, the state space averaging model is applied to derive equilibrium equations of a digital PID controlled DC-DC converter in this paper. Furthermore, the influences of the parameters of the digital PID compensator, and the resolutions of the ADC and DPWM on LCO are studied in detail. The amplitude together with the period of LCO as well as the corresponding PID parameters are obtained. Finally, MATLAB/Simulink simulations and FPGA verifications are carried out and no-LCO conditions are obtained.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1292-1293
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• 2011

Electric double layer capacitor (EDLC) is used to overcome power quality problem caused by output power oscillation of wind turbines. A novel EDLC application for permanent magnet synchronous generator type wind power generation system is proposed in this paper. The structure of the proposed system is cost-effective and efficient. The proposed system including an EDLC is modeled and analyzed by PSCAD/EMTDC. The simulation results show the effectiveness and major features of the proposed system.

• Korean Journal of Optics and Photonics
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• v.10 no.1
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• pp.53-57
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• 1999

We established the laser oscillator using Nd:YAG crystal grown at Ssang Yong company in Korea and investigated the characteristics of oscillation, Q-switching and wave front of output beam. We measured the single pass gain by controlling the threshold input energy with two output couplers of different output reflectances. Moreover, we compared the gain measured by different output couplers with the gain directly measured by the laser amplifier. The peak power of Q-switching, the pulse width, and the single pass gain coefficient at the threshold energy were 1.5 MW, 30ns, and 0.0958 cm-$^1$ respectively and they were compared with those of the commercial Nd:YAG crystal. Our crystal was proved to be as good as the commercial crystal.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.853-861
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• 2009

In this paper, we propose the architecture of a multi-band receiver which can receive X-band, Ku-band, K-band and Ka-band signals. For implementing this architecture, we designed a wideband and high power VCO with a buffer stage. In order that a buffer does not affect the characteristic of a oscillation in steady state condition, output impedance of a oscillation part and input impedance of a buffer are orthogonally crossed. The fabricated VCO meets the performance parameter of the multi-band receiver which has a $14.00{\sim}15.20\;GHz$ bandwidth with respect to the tuning voltage, $0.0{\sim}8.0\;V$, and output power of $12{\sim}13\;dBm$.