• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.208-211
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• 2001

This paper presents the considerations of the high frequency modulation method for the metal halide lamp electronic ballast. The acousitc resonance phenomenon is occurred, if the metal halide lamp is driven at constant high frequency. The frequency modulation method therefore, is used to avoid the acoustic resonance phenomenon, but the crest factor of lamp current is increased. In this paper, the driving characteristic of the metal halide lamp according to the waveshape and frequency variations of modulating signal is considered with a viewpoint of crest factor.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.228-232
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• 2002

In this paper, In order to solve the problem is proposed using a new type of electronic ballast that the traditional magnetic ballasts operated at 50-60Hz have been suffered from noticeable flicker, high loss, large crest factor and heavy weight which is composed of rectifier, active power corrector, series resonant half bridge inverter, micro-controller and piezoelectric transformer for driving for driving T5 fluorescent lamp were manufactured. The proposed electronic ballast operated at high frequency (about 75kHz) shows a input power factor of more than 0.995, total harmonic distortion of less than $12\%$ and lamp current crest factor of less than 1.5, respectively. Output power and efficiency showed 28w and $85\%$, respectively. Accordingly, it is considered that the ballast using piezoelectric transformer can replace the typical electronic ballast.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.6
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• pp.147-153
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• 2010

When small scale wind and solar power generation systems are connected to conventional power distribution system. It is worried that it can affect the quality of electricity such as voltage variation, power factor, frequency, harmonics and flicker. Therefore, in this research, in order to investigate the effects of wind power generation equipments(AC link method) on electrical power quality, when they are connected to distribution system. Power quality analyzer was installed respectively at the front side of power conversion system of conventional wind generation system and secondary side of consumer's power supply at distribution line. Measurements on power quality were performed and the effects of the wind generation system on distribution system were analyzed when it was and was not operated. The results show that 0.34[%] increase on voltage variation, 0.145 increase on current crest factor and 0.6[$^{\circ}$] deviation on phase difference when the power generation system was operated.

• International Journal of Stem Cells
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• v.16 no.2
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• pp.135-144
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• 2023

Background and Objectives: Melanocyte (MC), derived from neural crest stem cell (NCSC), are involved in the production of melanin. The mechanism by which NCSC differentiates to MC remains unclear. N6-methyladenosine (m6A) modification was applied to discuss the potential mechanism. Methods and Results: NCSCs were isolated from hair follicles of rats, and were obtained for differentiation. Cell viability, tyrosinase secretion and activity, and transcription factors were combined to evaluated the MC differentiation. RT-qPCR was applied to determine mRNA levels, and western blot were used for protein expression detection. Total m6A level was measured using methylated RNA immunoprecipitation (MeRIP) assay, and RNA immunoprecipitation was used to access the protein binding relationship. In current work, NCSCs were successfully differentiated into MCs. Fat mass and obesity associated gene (FTO) was aberrant downregulated in MCs, and elevated FTO suppressed the differentiation progress of NCSCs into MCs. Furthermore, microphthalmia-associated transcription factor (Mitf), a key gene involved in MC synthesis, was enriched by FTO in a m6A modification manner and degraded by FTO. Meanwhile, the suppression functions of FTO in the differentiation of NCSCs into MCs were reversed by elevated Mitf. Conclusions: In short, FTO suppressed the differentiating ability of hair follicle-derived NCSCs into MCs by m6A modifying Mitf.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1110-1112
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• 2001

This paper presents a high frequency electronic ballast with high efficiency and high power factor. The proposed ballast have driven by the half bridge inverter which is linked diode rectifier without DC link capacitor. Minimized elements of circuit configurations can make the efficiency of the ballast increase. High input power factor which is up to 0.96 can be achieved and the crest factor of lamp current waveforms is controlled with below 1.75 by using a novel control scheme which has PFM and PWM methods simultaneously. In this paper, the circuit configurations of the proposed ballast and the control schemes are described. The usefulness of the proposed ballast is confirmed with the simulation results.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.237-240
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• 2006

In this paper, a new design using a simulation method was proposed. And to estimate its validity, various electronic and optical data were measured after making a 150[W] electronic ballast for high pressure sodium lamps. Using PSpice 9.1, the best solutions of various parameters such as the resonant frequency, the lamp output voltage, and the current of the electronic ballast were obtained. The power factor of the system was 99.8[%], the crest factor 1.44, the THD 4.99[%], and the weight 0.5[kg]. These are very good characteristics compared with a conventional HPS Lamp ballast.

• Korean Journal of Agricultural Science
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• v.49 no.4
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• pp.707-717
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• 2022

As the variability of recent rainfall is increasing, it is becoming important to recognize the possibility of changes in the current reservoir state in advance and to inspect the stability based on accurate evaluation standards. However, the evaluation standards for the state change factors of reservoirs are still not suitable for agricultural reservoirs and thus much improvement is needed. Therefore, in this study, the evaluation criteria for state change factors specialized for small reservoirs were categorized and standards were prepared by considering factors that may cause state changes on the dam crest, upstream slope, and downstream slope of the embankment. The categorized results were configured based on the number of mentions of the precision safety inspection report on major defects in 102 reservoirs and the defect factors found in field investigations. The findings of the study indicated that the current state change standards require many revisions for excessive or unnecessary state change factors in the reservoir. Specifically, the deletion of measurement gauges not applicable to the reservoir, the addition of defects found in the reservoir, and the scope of use of the term were proposed. The results of this study can contribute to efficient system operation and management by improving the deficiencies in the system and introducing a new state change factor.