• The Transactions of the Korean Institute of Electrical Engineers P
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• v.61 no.3
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• pp.116-121
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• 2012

Recently, in the field of renewable energy such as solar cells including the semiconductor and display industries, thin film deposition process is being diversified. Furthermore, to deal with trend of making high-quality and fast, the high-capacity and output plasma power supply which can control high density plasma is required. The biggest problem is arc discharge caused by using high voltage power supply. Thus, the key function of plasma power supply is to prevent arc discharge and there is a need to maintain the possible minimum arc energy. In DC sputtering power supply, on a periodic basis (-)voltage powering up is able to significantly reduce arcing, as well as arc discharge prevention, and maintaining uniform charge density. This conventional method for powering up (-)voltage requires heavy mutual inductance of the transformer to avoid distortion problem of the output voltage. This study is about energy recovery circuit for arc discharge prevention in sputtering plasma power supply. By using energy recovery circuit, it is possible to reduce the mutual inductance and size of the transformer dramatically, prevent distortion of the output voltage and has a stable output waveform. This work was proved through simulation and experimental study.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.189-199
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• 2016

Fast neutrons with a broad energy spectrum, with which it is possible to evaluate nuclear data for various research fields such as medical applications and the development of fusion reactors, can be generated by irradiating proton beams on target materials such as beryllium. To generate short-pulse proton beam, we adopted a deflector and slit system. In a simple deflector with slit system, most of the proton beam is blocked by the slit, especially when the beam pulse width is short. Therefore, the available beam current is very low, which results in low neutron flux. In this study, we proposed beam modulation using a buncher cavity to increase the available beam current. The ideal field pattern for the buncher cavity is sawtooth. To make the field pattern similar to a sawtooth waveform, a multiharmonic buncher was adopted. The design process for the multiharmonic buncher includes a beam dynamics calculation and three-dimensional electromagnetic simulation. In addition to the system design for pulsed proton generation, a test bench with a microwave ion source is under preparation to test the performance of the system. The design study results concerning the pulsed proton beam generation and the test bench preparation with some preliminary test results are presented in this paper.

• The Journal of the Convergence on Culture Technology
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• v.8 no.6
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• pp.637-646
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• 2022

In this paper the comparative study on the pronunciation of Vietnamese learners and Koreans for the Korean syllable final double consonants was performed. For many errors and the suggested teaching methods related to the pronunciation of the Korean syllable final double consonants that were investigated and analyzed through linguistic research the results of this study by using the analysis tools of speech signal processing were confirmed. Thus, we suggest the new educational method in this paper. Using SVM, which is widely used in machine learning of artificial intelligence the pronunciation of Vietnamese learners and that of Koreans were compared. Being able to obtain the decision hyperplane of the SVM means that Vietnamese learners' pronunciation of the Korean syllable final double consonants is quite different from that of Koreans. Otherwise their pronunciation are pretty similar each other. The new teaching method presented in this paper is not only composed of writing and listening but is included things such as the speech signal waveform in the time domain and its corresponding energy that can be visualized to the learners.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.12B
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• pp.1752-1757
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• 2011

In a traditional phased array radar, closely spaced antenna elements transmit a scaled version of single waveform to maximize the signal energy. On the contrary, a multiple-input multiple-output (MIMO) radar consists of widely separated antennas and transmits an arbitrary waveform from each antenna element. These waveforms and spatial diversity enable superior capabilities compared with phased array radar. At high signal-to-noise ratio (SNR), the detection performance of the MIMO radar is better than the phased array radar due to the diversity gains. However, the phased array radar outperforms the MIMO radar at low SNR, due to the energy maximization. In this paper, we investigate the compromised scheme between the MIMO radar and the phased array radar. Employing the MIMO radar equipped with phased array elements, the compromised scheme achieves both array gain and diversity gain. Also, we compare the performance degradation when the steering direction is incorrect.

• Geophysics and Geophysical Exploration
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• v.16 no.3
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• pp.139-144
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• 2013

A computer program has been developed to estimate time-domain electromagnetic (EM) responses for a onedimensional model with multiple source and receiver dipoles that are finite in length. The time-domain solution can be obtained by applying an inverse fast Fourier transform (FFT) to frequency-domain fields for efficiency. Frequency-domain responses are first obtained for 10 logarithmically equidistant frequencies per decade, and then cubic spline interpolated to get the FFT input. In the case of phases, the phase curve must be made to be continuous prior to the spline interpolation. The spline interpolated data are convolved with a source current waveform prior to FFT. In this paper, only a step-off waveform is considered. This time-domain code is verified with an analytic solution and EM responses for a marine hydrocarbon reservoir model. Through these comparisons, we can confirm that the accuracy of the developed program is fairly high.

• Korean Journal of Acupuncture
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• v.33 no.4
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• pp.213-220
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• 2016

Objectives : The aim of this paper is to develop acupuncture needle heating system by utilizing the new method which uses high frequency(HF) time-varying magnetic field. Also, it is possible to make an assessment for reliability and clinical significance of the system. Methods : We designed the system with solenoid coils for generation of HF time-varying magnetic field that oscillates at 150 kHz. Acupuncture needles are quickly magnetized and heated by 150 kHz. We assessed clinical significance of system, such as body temperature, pressure pulse waveform. Results : Temperature of acupuncture needle increased up to 60 degree. In the result for clinical significance of system, in case of manual acupuncture stimulation(MAS), body temperature change was $0.373^{\circ}C{\pm}0.224$(p<0.05), rate of pulse energy change increased about 7.6%. In case of warm acupuncture stimulation(WAS), body temperature change was $0.645^{\circ}C{\pm}0.281$(p<0.05), rate of pulse energy change remarkably increased about 35.9%. Conclusions : We confirm that the system is able to be applied clinically to various warm acupuncture needle therapy in the area of oriental medicine.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.10
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• pp.501-507
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• 2001

In this paper, new high-efficiency zero voltage switching (ZVS) AC-DC boost converter is proposed to achieve power factor correction by simplifing energy recovery circuit. A lot of high power factor correction circuits have been proposed and applied to increase input power factor and efficiency. Most of these circuits may obtain unity power factor and achieve sinusoidal current waveform with zero voltage or/and zero current switching. However, it is difficult for them to obtain low cost, small size, low weight, and low noise. The topology proposed to improve these problems can compact the devices in circuit and can achieve high efficiency ZVS AC-DC boost converter. Simulation and experimental results show that this topology is capable of obtaining high power factor and increasing the efficiency of the system.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.7
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• pp.59-68
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• 1998

This paper is to develop an algorithm for the unlimited korean speech synthesis. We present the results controlled of prosodic factors with isolated words as aynthesis basis unit int he time domain. With a new pitch-synchronous and parametric speech synthesis mehtod in the time domain here we mainly present the results of controlled prosody factors such a spitch periods, energy envelops and durations and the evaluaton of synthetic speech qualities. In the case of synthesis, it is possible ot synthesize connected words by controlling of a continuous unified prosody that makes to improve the naturalities. In the results of experiment, it also has been to be improved uncontinuities of pitch and zeroing of energy in the junction parts of speech waveforms. Specially it has been to be possible to synthesize speeches with unlimitted durations and tones. So on it makes the noisiness and the clearness better by improving the degradation effects from the phase distortion due to the discontinuities in the waveform connection parts.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.214-218
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• 2004

Switched Reluctance Motor (SRM) offers the advantages of simple and robust motor construction, high speeds and high efficiencies over a wide operating range of torque and speed, excellent controllability. However, SRM has the disadvantages of high current harmonics, and low power factor because of a capacitor filter is inserted in the power converter and inductance of SRM is high, it has pulse waveform of current. This paper deals with an energy efficient converter fed SRM system with the reduced harmonics and improved power factor and with higher efficiency. The validity of the proposed scheme is verified via experiment. We are implemented the proposed control system using 80C196KC micro-controller.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.4
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• pp.371-374
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• 2012

DC/DC switching power converters produce DC output voltages from different stable DC input sources regulated by a bi-polar transistor. The converters can be used in regenerative braking of DC motors to return energy back in the supply, resulting in energy savings for the systems containing frequent stops. The voltage mode DC/DC converter is composed of a PWM (Pulse Width Modulation) controller, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), an inductor, and capacitors, etc. PWM is applied to control and regulate the total output voltage. It is shown that the output of DC/DC converter depends on the variation of threshold voltage at MOSFET and the variation of pulse width. In the PWM operation, the missing pulses, the changes in pulse width, and a change in the period of the output waveform are studied by SPICE (Simulation Program with Integrated Circuit Emphasis) and experiments.