• 전력전자학회논문지
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• 제24권6호
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• pp.389-395
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• 2019

This paper presents the sensorless position control of an auxiliary scaffolding step system for vehicles using DC motors. The designed auxiliary scaffolding step has a mechanical protector at the stop position. At this position, the scaffolding is forcibly stopped by the mechanical protector, and the motor current is dramatically increased to the stall current of the DC motor, thereby increasing the electrical damage. In this study, the estimated back EMF- and current model-based observers are proposed to estimate the motor speed and stop position. A simple V/F acceleration voltage pattern is used to operate the auxiliary scaffolding system. The estimated moving position is adopted to determine the stop position of the DC motor with the load current state. The operating current of the DC motor can be reduced by the estimated moving position and V/F acceleration pattern. At the stop position, the proposed sensorless position controller can smoothly stop the DC motor with the estimated moving position and reduced load current without any mechanical and electrical stress from the stall current from the mechanical protector. The proposed control scheme is verified by the comparison of simulations and experiments.

• 전기의세계
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• 제30권7호
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• pp.454-459
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• 1981

The aim of study in this paper is that in a system drive of the converter-inverter fed induction motor, the minimum input power can be maintained by control the voltage and frequency of the motor. In theoretical and experiment results describtion motor efficiency is improved by properly varying the ratio v/f. At lightly load condition, for example its efficiency was improved from 44% to 66% as the ratio of v/f varied from 1 to 0.57.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 전력전자학술대회
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• pp.406-407
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• 2019

본 논문에서는 유도전동기의 V/F 속도제어 시 특정 구간에 발생하는 전류 리플 저감에 대한 방법을 제안한다. V/F 속도제어 시 특정 구간에 발생하는 전류 리플을 분석하고, 주파수에 따른 극전압 보상량을 결정하여 보상하였다. 극전압 보상을 통해 유도전동기의 전류 리플을 저감시켜 인버터의 효율적인 제어가 가능하게 하였다. 이를 15kW 유도전동기 시스템에 대한 실험을 통해 제안된 방법의 효율성을 검증하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 전력전자학술대회
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• pp.404-405
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• 2019

본 논문에서는 PMSM(Permanent magnet synchronous motor)의 MTPA(Maximum Torque Per Ampere) 운전을 고려한 V/f 제어 시 안정화 기법에 대해 제안한다. PMSM은 V/f 제어 시 부하 변동에 따라 탈조할 가능성이 있다. 제안된 기법은 안정도 개선을 위해 추정된 q축 전류를 이용하여 부하 변동정보를 얻고 이를 바탕으로 고정자 주파수를 변동하여 회전자 속도가 동기속도를 유지할 수 있는 안정화 기법을 적용하였다. 제안된 안정화 기법으로 저속 영역부터 약자속 영역까지 부하변동에도 안정적인 운전이 가능하도록 하였다. 1kW SPMSM의 모의실험을 통하여 제안된 기법의 효용성을 검증하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 전력전자학술대회 논문집
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• pp.253-254
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• 2016

This paper proposes a novel starting method of a high speed induction motor with air bearings for turbo blowers. The friction of air bearings varies according to rotating speed, operating temperature and usage time. Specially, friction torque at initial starting state under low bearing temperature usually results in starting failures of the conventional V/F control method. Therefore, this paper proposes a new starting method, which consists of an initial I/F control mode and smooth transition method to V/F control mode to overcome the starting failure. The experimental results are shown to verify the analysis and the usefulness of the proposed method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 A
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• pp.50-52
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• 1995

This paper deals with the dynamic characteristics of LIM which is controlled by constant V/f ratio and the characteristics of the Inverter acted as interface between the utility power system and LIM. Though open-loop control method is less reliable than closed-loop control method, it's commonly used because it is simple and cheap. This paper shows the consideration for dynamic characteristics of LIM under open-loop control and for Inverter.

• 한국정보통신학회논문지
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• 제7권8호
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• pp.1751-1758
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• 2003

본 논문에서는 V55 마이크로프로세서로 제어되는 반브릿지 인버터를 사용하여 영구 콘덴서형 단상유도 전동기의 가변속 구동에 대해 연구하였다. Patel의 알고리즘을 이용한 SHE(Selected Harmonic Elimination) PWM 구동방식에 의한 V/F 제어로 출력전압의 고조파분을 제거할 수 있으며, 속도의 제어 범위가 넓어짐을 알 수 있었다. 제안한 방법을 시뮬레이션과 실험의 결과로 입증하였다.

• 대한한의학회지
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• 제33권1호
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• pp.160-168
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• 2012

Objectives: Cynanchi wilfordii Radix has commonly been used with or instead of Polygoni multiflori Radix in Korea. The purpose of this study was to investigate their history in the traditional Oriental medical literature and quantitative determination of conduritol F from Cynanchi wilfordii Radix according to various harvest times. Methods: We conducted studies of the traditional Oriental medical literature and analysis of the component, conduritol F, simultaneously. Efficacy and origin of Cynanchi wilfordii Radix in literature study, time of harvest in component research. Chromatographic analysis performed using Silica(2) 100A column (Phenomenex 5 um, 250 mm 4.6 mm) with a mixture of acetonitrile and water (98 : 2)(v/v). The analyses detected at UV (210 nm). Results: Conduritol F was detected in Cynanchi wilfordii Radix, but in Cynanchi auriculati Radix was not. We indicate that conduritol F is as a distinguishable indicator with other materia medica. We think the proper harvesting time is October and November. Conclusions: Measures of trunk control were significantly related with values of dynamic balance and gait. Based on these results, trunk control is an essential core component of balance and gait. Trunk control training programs after stroke should be developed and emphasized.

• Plant Breeding and Biotechnology
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• 제5권4호
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• pp.363-370
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• 2017

In this study, Quercus acutissima seedlings were subjected to drought for 30 days then analyzed to determine their response to water deficit. The growth phenotype, chlorophyll fluorescence response, fresh weight, dry weight, photosynthetic pigment levels, soluble sugar content, and malondialdehyde (MDA) were measured to evaluate the effects of drought on plant growth and physiology. The growth phenotype was observed by infrared (IR) digital thermal imaging after 30 days of drought treatment. The maximum, average, and minimum temperatures of drought-treated plant leaves were $1-2^{\circ}C$ higher than those of the control. In contrast, the fresh and dry weights of the dehydrated leaves were generally lower than those of the control. There were no significant differences between treatments in terms of chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid levels. Nevertheless, for the drought treatment, the $F_v/F_m$ and $F_v/F_o$ ratios (chlorophyll fluorescence response) were lower than those for the control. Therefore, photosynthetic activity was lower in the dehydrated plants than the control. The drought-stressed Q. acutissima S0536 had lower soluble sugar (glucose and fructose) and higher MDA levels than the controls. These findings may explain the early growth and physiological responses of Q. acutissima to dehydration and facilitate the selection of drought-resistant tree families.

• 한국식물병리학회지
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• 제11권4호
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• pp.298-303
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• 1995

The biological control effect of Trichoderma harzianum on the Fusarium wilt of strawberry and several factors affecting on its efficacy were examined through pot experiments. T. harzianum grown on wheat barn, rice straw, rice hull, sawdust or barley straw was respectively incorporated into the pathogen-infected soil, and significantly suppressed the strawberry wilt caused by Fusarium oxysporum f. sp. fragariae. The wheat bran or rice straw culture of T. harzianum suppressed the disease incidence more effectively than other substrates for culture, decreasing it to 68% of the untreated control. The conidial suspension of T. harzianum alone or the suspension mixed with crab shell also effectively reduced the disease incidence. The control effectiveness of T. harzianum was high in acid soil (pH 3.5~5.5). In sandy loam soil, the disease incidences and population densities of the pathogen were decreased by the treatment of T. harzianum, while there was no significant effect of T. harzianum on the pathogen in loam soil.