• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.3
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• pp.273-277
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• 2016

In this paper, we deals with the digitization of high frequency sine wave power supply using power source of high frequency surgical equipment and RF device. High frequency surgical equipment has been using commonly on medical surgery because of its merits such as programmable depth of incision, availability of incision and coagulation in the same device, increasing the usability on surgical side. However, the core part of the device is consists of vacuum tubes which are expensive, not ease to use and must be imported, therefore it is inevitable of high prices, forces to develop the fully digitized alternative technology. The fully digitized high frequency sine wave power supply for surgical device is proposed and verified by experimental results.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1416-1417
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• 2007

The high frequency pulsed power system is widely available for use in high frequency generator applications. We designed and fabricated our own high frequency pulsed power system to obtain very sort pulse width and high peak value and investigated microbe removal characteristics using it. This paper introduces a simple high voltage high frequency pulsed power system for removing various bacteria caused by dirty water. This system include power supply circuit, switching MOSFET, and flyback converter. We can also control the switching using a PIC one chip microprocessor. As a result, we can obtain good removing characteristics of various bacteria by adjusting the charging voltage, the pulse repetition rate and the electrical field inducing time.

• Journal of Magnetics
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• v.19 no.3
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• pp.295-299
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• 2014

Recently, module-integrated converter (MIC) research has shown interest in small-scale photovoltaic (PV) generation. The converter is capable of efficient power generation. In this system, the high frequency transformer should be made compact, and demonstrate high efficiency characteristics. This paper presents a core structure optimization procedure to improve the efficiency of a high frequency transformer of compact size. The converter circuit is considered in the finite element analysis (FEA) model, in order to obtain an accurate FEA result. The results are verified by the testing of prototypes.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.7 no.1
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• pp.20-26
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• 1996

The purposes of this study were to analyze the sound of bird's frequency region and pattern and to discuss hearing impaired children's auditory discrimination. The results were ie follows; 1) The sounds of bird's frequency region were divided into Low(below 1, 000Hz), Mid(between 1, 000 and 4, 000Hz) and High(between 2, 000 and 4, 000Hz). 2) The sounds of bird, which were same, long, high pattern, were in Mid ＆ High. Short and high pattern were above High.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.402-407
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• 2005

The PLL synthesizer is used in communication system until now because it have several merits, such as broad bandwidth, high accuracy and stability of frequency But it is difficult to use in the third generation mobile communication systems that need frequency hopping at a high speed because of its long frequency hopping time. In this paper, we designed the frequency synthesizer that generate frequencies randomly at a high speed using the DDS technology.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.449-452
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• 2014

We present a multi-tap microwave photonic filter with high selectivity through applying time-to-frequency mapping and optical frequency comb shaping techniques. When arranged in the time-to-frequency mapping stage, by a Fourier transform, the deviation of the optical taps to the target profile is significantly reduced while maintaining the apodization profile, resulting in high sidelobe suppression in the filters. By applying a simple time-to-frequency mapping stage to the conventional optical frequency combs, we demonstrate a substantially enhanced (>10dB) sidelobe suppression, resulting in filter lineshapes exhibiting a significantly high (>40dB) main lobe to sidelobe suppression ratio. These results highlight the potential of the technique for implementation in various passband filters with high sidelobe suppression.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1364-1367
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• 2005

In this paper, a novel prototype topology of soft switching PWM controlled high frequency AC power conversion circuit without DC voltage smoothing chemical capacitor filter link from the voltage grid of utility frequency AC power supply source with 60Hz-100V or 60Hz-200V is proposed and introduced for innovative consumer induction heating(IH) boiler applications as hot water producer, steamer and super heated vapor steamer.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.3
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• pp.138-144
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• 2017

In this paper, we propose a high frequency boosting circuits compensating for age-related hearing loss. The frequency response of this hearing loss is quite similar to that of a low-pass filter of which the critical frequency get lower with age. Therefore the voltage gain of this compensation circuits increase proportionally to the frequency of signals when the frequency is higher than the critical frequency and the voltage is constant irrespective of the frequency of signals when the frequency is lower than the critical frequency. The proposed circuits consist of a differential circuit and a unity gain amplifier. Because the critical frequency of the proposed circuits is controlled simply in the shape of a volume control lever, the aged people can adjust the high frequency boosting level easily according to one's hearing loss level. The critical frequency is continuously controllable in the whole audible frequency band and the gain of this high frequency boosting circuits is above 80dB at 10kHz.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.4
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• pp.19-27
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• 2007

This paper presents a novel soft-switching PWM utility frequency AC to high frequency AC power conversion circuit incorporating boost H-bridge inverter topology, which is more suitable and acceptable for cost effective consumer induction heating applications. The operating principle and the operation modes are presented using the switch mode equivalent circuits and the operating voltage and current waveforms. The performances of this high-frequency inverter using the latest IGBTs are illustrated, which includes high frequency power regulation and actual efficiency characteristics based on zero voltage soft-switching(ZVS) operation ranges, and the power dissipation as compared with those of the conventional type high frequency inverter. In addition, a dual mode control scheme of this high frequency inverter based on asymmetrical pulse width modulation(PWM) and pulse density modulation(PDM) control scheme is discussed in this paper in order to extend the soft switching operation ranges and to improve the power conversion efficiency at the low power settings. The power converter practical effectiveness is substantially proved based on experimental results from practical design example.

• The Korean Journal of Applied Statistics
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• v.30 no.5
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• pp.747-757
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• 2017

We investigate multivariate volatilities based on high frequency time series. The PCA (principal component analysis) method is employed to achieve a dimension reduction in multivariate volatility. Multivariate realized volatilities (RV) with various frequencies are calculated from high frequency data and "optimum" frequency is suggested using PCA. Specifically, RVs with various frequencies are compared with existing daily volatilities such as Cholesky, EWMA and BEKK after dimension reduction via PCA. An analysis of high frequency stock prices of KOSPI, Samsung Electronics and Hyundai motor company is illustrated.