• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 하계종합학술대회 논문집
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• pp.587-590
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• 1989

Bilateral Variable-Ratio chopper system performs Step-down chopper and Step-up chopper operations automatically every operating period of the chopper. The Ratio between Step-down chopper and Step-up chopper operations is determined by a Tine- ratio and the circuit elements. In this paper, we suggest that this chopper system can operate variable speed control of the electric motorcar when it is applied to the electric motorcar.

• Journal of Power Electronics
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• 제18권1호
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• pp.137-146
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• 2018

This paper describes a single pulse-width modulation control strategy using the Single Pulse-Width Modulation (SPWM) method with a soft-switching technique for a wide range of output voltages from a bidirectional Dual-Active Bridge (DAB) converter. This method selects two typical inductor current waveforms for soft-switching, and proposes a rule that makes it possible to achieve soft-switching without any compensation algorithm from the waveforms. In addition, both the step-up and step-down conditions are analyzed. This paper verifies that the leakage inductance is independent from the rule, which makes it easier to apply in DAB converters. An integrated algorithm, which includes step-up and step-down techniques, is proposed. The results of experiments conducted on a 50-kW prototype are presented. The system efficiency is experimentally verified to be from 85.6% to 97.5% over the entire range.

• Asian-Australasian Journal of Animal Sciences
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• 제6권1호
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• pp.127-132
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• 1993

Ten-week-old White Leghorn immature males and females were exposed to four lighting regimens: a constant light (12L : 12D); repeated up and slow down (13 min. up and 1 min. down per day for 13 consecutive days, and repeated on two-week cycle) lighting; repeated slow up and down (1 min. up per day for 13 consecutive days and 13 min. down, and repeated on two-week cycle) lighting; and step-up (14 min. up every second week) lighting. At 15 weeks of age, significantly larger testis and comb weights and significantly higher concentrations of plasma LH and testosterone were observed in the cockerels under the repeated slow up and down lighting regimen than those under the other lighting regimens. At 20 weeks of age, significantly larger oviduct weights and significantly higher concentrations of plasma estradiol were observed in the pullets under the repeated up and slow down, and the step-up lighting regimens than those under the other lighting regimens.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.340-343
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• 2003

This paper presents characteristics of piezo transformer for AC-DC converter. This transformer uses transverse vibration mode and the origin of the structure was the ring dot type transformer. Because, the ring dot type transformers produce only step-up phenomenon, we made a multi-layered ring dot structure for a step-down output. The characteristics of the transformer were simulated by using the ANSYS. And frequency and voltage were measured by changing the load resistance and current. Frequencies that have the maximum output voltage and current were gradually increased, when the resistance were increased. Output voltage and current show a stable linearity according to the input voltage. The maximum output power was expected greater than 20 [W]. So, we expect that this type of multi-layered step-down ring dot transformer can be adopted for a small AC adapters.

• 전기전자학회논문지
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• 제16권4호
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• pp.335-342
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• 2012

본 논문에서는 고효율과 고역률을 위한 새로운 DCM-ZVS 스텝 업-다운 AC-DC 컨버터에 대해 연구된다. 제안한 DCM-ZVS 컨버터에 사용된 스위칭 소자들은 새로운 유사공진 회로에 의해 소프트 스위칭 기법으로 동작되고, 펄스폭변조(PWM) 방식에 의한 전류불연속모드(DCM)로 구동된다. 제안한 컨버터의 유사공진 회로는 스텝 업-다운 인덕터와 무손실 스너버 커패시터로 구성되고, 또한 DCM에 의해 제어회로 기법과 제어회로 구성이 간단한 장점이 주어진다. 입력 교류 전류파형은 일정 스위칭 주파수에 의한 교류 입력전압의 크기에 비례한 유사 정현파형으로 된다. 그 결과, 제안한 DCM-ZVS 컨버터는 낮은 스위칭 손실과 고효율을 얻을 수 있으며, 컨버터의 입력역률은 거의 단위역률로 된다. 해석적 결과의 타당성은 다양한 컴퓨터 시뮬레이션과 실험 결과를 통해 입증된다.

• Journal of Multimedia Information System
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• 제6권1호
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• pp.15-22
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• 2019

There are many ways to perform face recognition. The first step of face recognition is the face detection step. If the face is not found in the first step, the face recognition fails. Face detection research has many difficulties because it can be varied according to face size change, left and right rotation and up and down rotation, side face and front face, facial expression, and light condition. In this study, facial features are extracted and the extracted features are geometrically reconstructed in order to improve face recognition rate in extracted face region. Also, it is aimed to adjust face angle using reconstructed facial feature vector, and to improve recognition rate for each face angle. In the recognition attempt using the result after the geometric reconstruction, both the up and down and the left and right facial angles have improved recognition performance.

• 지질공학
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• 제29권3호
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• pp.201-209
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• 2019

국내 사면 및 터널에서 주로 적용되고 있는 다단 압력을 이용한 그라우팅 방법들은 천공 후 지중에서 지표 방향으로 스텝주입을 하는 상향식 다단압력 그라우팅 방법이며 다수의 연구결과와 축척된 시공실적을 토대로 현재 여러 현장에서 적용되고 있다. 국내에서 하향식 다단압력 그라우팅 방법의 연구결과는 미미한 실정이다. 본 논문에서는 토조시험과 현장시험을 통해 기존 상향식 다단압력 그라우팅 방법과 지표부에서부터 주입을 실시하는 하향식 다단압력 그라우팅 방법의 주입효과를 비교 분석하였다. 토조 시험 결과 하향식 다단압력 그라우팅 방법의 경우 상향식 다단압력 그라우팅 방법에 비해 구근체의 부피는 약 24% 증가하는 것으로 나타났다. 현장시험 결과 하향식 다단 압력 그라우팅 방법이 상향식 다단 압력 그라우팅 방법에 비해 주입 범위가 넓고 면적당 주입 밀집도가 높은 것으로 확인되었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.652-655
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• 2003

In this paper, step-down piezoelectric transformer is studied. The piezoelectric transformer, made of lead zirconate titanate solid solution ceramic, is operated by a fundamental contour-extensional vibration mode. The transformer of 14mm length, 14mm width and 4.5mm thickness was made up two shape(Type I and II). The resonant frequency (fr) is 144kHz and 128kHz at the load resistant of $7.5{\Omega}$ that is a similar to calculating matching impedance. The gain (G) obtained 0.19 and 0.08 at each resonant frequency, when applied input voltage is 25V. The temperature difference with the variation of load resistant was increased with increasing load resistant and was the lowest at $7.5{\Omega}$ near the matching of output impedance.

• 대한통합의학회지
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• 제2권3호
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• pp.49-55
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• 2014

Purpose : The purpose of this study was to investigate the effect of cross bag weight and carrying bag position type on vastus medialis oblique and vastus lateralis muscle activity ratio during step up. Method : Twenty healthy subjects participated in this study. subjects randomized performed step up with bag weight less than 15%, more than 15% of totalbody weight and without bag and carrying bag position ipsilateral and contralateral. muscle activity was measured with surface electromyography. One-way analysis of variance with repeated measures was used with a significance level of 0.05 Result : The results of this study were as follows: 1. The muscle activity ratio decreased significantly ipsilateral bag position more than 15% of body weight(p<.05). Also, the muscle activity ratio increased significantly contra lateral bag position more than 15% of body weight(p<.05). Conclusion : In conclusion, it was found that applied carrying bag position with weight on VMO,VL muscle activity ratio during step up down. Therefore carrying bag position can be used to selective activate vastus medialis oblique muscle in subjects with patellofemoral pain syndrome.

• Journal of Power Electronics
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• 제18권5호
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• pp.1536-1544
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• 2018

The existing 24-pulse autotransformer rectifier unit (ATRU) needs interphase reactors for parallel work of the rectifier bridges, and its output voltage cannot be regulated. Aiming at these problems, a step-up and step-down asymmetrical 24-pulse ATRU is proposed in this paper. The connections and turns ratios among transformer windings are well designed. In addition, a 15-degree phase difference is formed between two of the 24 voltage vectors produced by the transformer, which makes the four rectifier bridge groups produce a 24-pulse DC voltage without interphase reactors. Meanwhile, by adding extended winding to each phase of the transformer, wide-range regulation of the ATRU output voltage can be realized, and the reasonable voltage regulation range is between 0.2 and 1.6. The superposition of the voltage vectors and the principle of the voltage regulation are analyzed in detail. Furthermore, the turns ratio of the windings, winding current, output voltage, and kilovolt-ampere rating are all derived. Finally, the simulations and experiments are carried out, and the correctness of the principle and theoretical analysis of the new 24-pulse ATRU are verified.