• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.908-911
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• 2002

Recently deep interests and attraction have been paid on the generation of ozone, which is widely used to remove bed smell and to clear water. In this paper the silent discharge and ozone generation characteristics of various typed discharge chambers were investigated experimentally. Dielectric of $Al_2O_3$ was embedded in the cylindrical type of discharge chamber to improve the ozone generation rate and to stabilize the silent discharge mode of operation. Discharge current and ozone concentration depend strongly on the applied voltage and frequency.

• Journal of the Korean Home Economics Association
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• v.35 no.3
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• pp.125-137
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• 1997

This study is based on the investigation to find a more practical way of the life etiquette education for today's family style, and also focused on the comparison of the life style between the older generation and the younger generation. The questionaire of this study were obtained by 494 high school students and their mothers living in Seoul. Collected data were processed by frequency analysis, t-test, ANOVA, and Pearson's corrlation analysis adapted by SPSS program. The conclusion shows that acceptance level is higher among the older generation, but the necessity of life etiquette education beyond the generation is needed urgently. Then life etiquette education must be kept continuously at home, school and society.

• The Journal of the Korean dental association
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• v.54 no.10
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• pp.780-788
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• 2016

Dentin bonding systems are unique dental materials which are rapidly evolute and essential materials for bonding of restorative materials to dentin. Now, 4th generation, 5th generation, 6th generation and 7th generation of dentin bonding systems are used in clinic. We investigated the frequency, motivation of choosing dentin bonding systems and satisfaction of them by survey in 2014. 5th generation of dentin bonding systems are mostly used in Korea and young dentist have tendency to choose newly developed dentin bonding systems.

• Journal of Broadcast Engineering
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• v.17 no.2
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• pp.237-251
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• 2012

Recently, the direct terrestrial broadcasting reception has been reduced rapidly and not been improved even in digital broadcast environment. The distribution plan of 700MHz frequency band(Ch.52~69) will make the problem worse because the spectrum might be allocated to mobile communication use. In this paper, we investigated the efficient frequency usage for DTV signal reception improvement and next generation broadcasting. The frequency amount required for reception improvement and for next generation broadcasting service is presented. We estimated the beneficial effect when the spectrum(108MHz Frequency Width) is used for SFN transmission technology, UHDTV and Full-HD 3DTV.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.2
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• pp.36-43
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• 2004

In this paper, the frequency spectra from respective mechanical noise signals detected using ultrasonic wave and AE(Acoustic Emission) sensor were analysed to under spark generation between brush and commutator side with arbitrarily 15$^{\circ}$ rotation for brush from the DC motor in operation. Also, the frequency spectra from respective magnetizing noise signals detected using ultrasonic wave and AE sensor were analysed to under neutral point for brush from the DC motor in normal operation. And the analyses and comparison between the mechanical noise signal and magnetizing noise signal of ultrasonic wave with brush location change from the DC motor in operation. As the experimental results, tile mechanical noise signal of ultrasonic wave under spark generation between brush and commutator side with brush location change from the DC motor in operation were increased about 2.5∼3.0 times than magnetizing noise signal of ultrasonic wave form the DC motor in normal operation. Also, the main frequency band for mechanical noise signals of AE under spark generation between brush and commutator side with brush location change from the DC motor in operation, appeared about 1.3[MHz]∼l.5[MHz] by the fast fourier transform.

• Journal of Advanced Navigation Technology
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• v.14 no.6
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• pp.859-864
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• 2010

In the next generation system, a study on realization of Multi-Core system is in progress for applying it in multi service network. Therefore some mobile systems are expected to be appeared. These systems can support WiBro, WCDMA, CDMA, etc with single terminal. These systems have to support various FA using broadband frequency and hand over to other service network. Especially, in the telecommunication system composed of cell, the transmit power can be interference at adjacent system, has effect on system channel capacity and cell size. In this paper, we improve the unstable transmit power caused by unsettled system operation, propose the RF(Radio Frequency) Calibration method which can use the transmit power stably even during hand over between heterogeneous networks causing unstable power change. Also we used proposed method and analysed used electricity of system during hand over between heterogeneous networks.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.216-222
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• 2003

Today we have excellent motor drive system using high frequency carrier PWM control voltage source inverter in the other hand, we have met serious problems caused by high frequency switching. PWM Cyclo-converter called Matrix converter is expected as the new strategy Possible to improve these problems and add some more convenient features suitable for new drive system. in this Paper, we will introduce the background, features and outline of this converter, and additionally introduce some remarkable activity on this converter

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1030-1034
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• 1993

A converter topology which is capable of four-quadrant(motoring and generation) operation is proposed for the variable speed constant frequency(hereafter referred as VSCF) power conversion scheme. The new converter topology for the VSCF power conversion scheme is made of two functional stages. One is converting stage which consists of six switches and six diodes and it interfaces a three-phase 60Hz at supply and a single-phase variable-frequency ac source. The other is the commutating stage though which each phase-winding is energized.

• 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.

• ETRI Journal
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• v.29 no.4
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• pp.437-444
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• 2007

A CMOS frequency synthesizer block for multi-band orthogonal frequency division multiplexing ultra-wideband systems is proposed. The proposed frequency synthesizer adopts a double-conversion architecture for simplicity and to mitigate spur suppression requirements for out-of-band interferers in 2.4 and 5 GHz bands. Moreover, the frequency synthesizer can consist of the fewest nonlinear components, such as divide-by-Ns and a mixer with the proposed frequency plan, leading to the generation of less spurs. To evaluate the feasibility of the proposed idea, the frequency synthesizer block is implemented in 0.18-${\mu}m$ CMOS technology. The measured sideband suppression ratio is about 32 dBc, and the phase noise is -105 dBc/Hz at an offset of 1 MHz. The fabricated chip consumes 17.6 mA from a 1.8 V supply, and the die-area including pads is $0.9{\times}1.1\;mm^2$.