• 조명전기설비학회논문지
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• 제13권4호
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• pp.27-31
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• 1999

본 연구는 산업분야의 수많은 전기설비 시스템에 널리 사용되고 있으며 또 이중여자기로도 사용될 수 있는 권선형 유도전동기의 기동특성과 설계를 다루었다. 고정자는 재래색 3상 권선형 유도 전동기의 고정자와 동일하고 회전자 권선은 새로운 방법으로 재권선한 결과 기동토크로 크고 기동전류는 작으며 운전효율은 좋아졌다. 뿐만 아니라 슬립링과 브러쉬 및 외부저항의 필요성이 없어 구조가 간단하고 시스템 비용을 절약할 수 있을 뿐 아니라 유지보수비도 절약할 수 있었다.

• 전기학회논문지
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• 제67권12호
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• pp.1602-1610
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• 2018

Induction heating can convert electrical energy to thermal energy with high conversion efficiency and quick heating. Currently, a current source rectifier/inverter-fed parallel resonant circuit is widely used as an induction heating power supply for forging applications. However, the conventional induction heating power supplies composed of phase-controlled rectifier and SCR inverter have low efficiency and low power factor at input side, and require additional starting circuitry. So this paper proposes new induction heating power supply topologies for forging applications which have high power factor, high efficiency, and large output power. It also suggests detailed design guideline.

• 전력전자학회논문지
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• 제18권6호
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• pp.523-529
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• 2013

A sensorless speed control of a permanent magnet synchronous motor(PMSM) which utilizes MRAS based scheme to estimate rotor speed and position is presented. Considering an error between real and estimated rotor position values, a state equation of PMSM in the synchronous d-q reference frame is represented. A state equation of model system which uses estimated speed and nominal parameter values is expressed. To minimize the errors between the derivatives of d-q axis currents of real and model system, MRAS based adaptation mechanisms for the estimation of rotor speed and position are derived. On the other hand, for the acceleration stage of motor just before the sensorless operation, an acceleration scheme using only d-axis current control is proposed. To show the validity of the proposed scheme, experimental works are carried out and evaluated. During acceleration stage, the acceleration scheme using only d-axis current command shows good acceleration performance and controlled current level. For the sensorless operation, at low speed (5% of rated speed), a good performance is observed.

• 천문학논총
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• 제33권3호
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• pp.45-57
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• 2018

Low-mass star-formation studies deal with the birth of individual solar-type stars as it occurs in nearby molecular clouds. While this isolated mode of star formation may not represent the most common form of stellar birth, its study often provides first evidence for the general ingredients of star formation, such as gravitational infall, disk formation, or outflow acceleration. Here I briefly review the current status and the main challenges in our understanding of low-mass star formation, with emphasis in the still mysterious pre-stellar phase. In addition to presenting by-now classical work, I also show how ALMA is starting to play a decisive role driving progress in this field.

• 전력전자학회논문지
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• 제9권1호
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• pp.17-24
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• 2004

터보 제너레이터의 시동기는 터보 샤프트 발전 시스템 시동기의 구성인 기어박스, DC 전동기, 저 전압 축전지를 대신하여 고속 발전기, 인버터 그리고 승압기로 구성된다. 터보 제너레이터는 시동 시 고속 회전이 요구되어 고속발전기는 수십 $\mu$Η의 낮은 누설 인덕턴스를 가지며, 인버터는 높은 전압의 DC link 전압이 필요하다. 본 연구에서는 시동기 구현을 위해 축전지 전압을 높은 전압으로 승압하는 대 용량 승압기를 개발하였다. 그리고 낮은 누설 인덕턴스를 갖는 전동기 권선에 높은 주파수의 전류 제어를 위해 정밀 고속 연산을 수행하는 인버터 드라이버의 설계와 안정된 점화를 위한 터보 제너레이터의 시동 알고리즘을 제안하였다. 또한 개발한 시동기로 터보 제너레이터의 시동을 수행하여 성능을 확인하였다.

• 한국수산과학회지
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• 제37권2호
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• pp.148-158
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• 2004

In the adjacent seas of Cheju Island, the oceanographic conditions show low salinity surface waters starting in May. This water flows from the southeast part of the China Coastal Water, which flows southeastward along the Great Yangtze Sand Bank until April, with the help of southeasterly winds and flows from the adjacent sea off Cheju Island. In May, the Tsushima Warm Current and the low salinity surface water fluctuate in short and long-term periods as influenced by Yellow Sea Cold Water, which flows to the bottom layer at the western entrance of Cheju Strait. Temperature and salinity fronts in the northeastern sea area of U Island are formed in the boundary area between the Tsushima Warm Current, which expands towards Cheju Island from the southeastern sea area of Cheju Island and Hows out from the eastern entrance of the strait. Seasonally, additional oceanographic conditions, such as coastal counter-currents, which flow southward, appears within limited areas in the adjacent eastern and western seas of Cheju Island.

• 대한가정학회지
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• 제18권1호
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• pp.15-23
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• 1980

Since the first dietitian was produced in Korean about 15 years ago the Korena Dietetic Association has grown up to have its 8,500 members as of March, 1979. This study was undertaken to survey the status of hospital dietitians and their bob analysis. current practices were learned and the problems identified mainly in such aspects as : 1. Do the hospitals have enough dietitians? 2.What is the administrative position of the dietetics in the hospital? 3. What is the salary level of the dietitians? 4. How professional are the dietitian's daily tasks? How appropriately are the jobs distributed among the dietary employees? and 5. Do the hospital dietetics have their own diet manuals to go by? The findings are : 1. The severly lacking number of dietitians are employed by the hospitals where one dietitian is responsible for the feeding and nutrition education of 171 in-patients on the average. 2. The administrative position of hospital dietetics appears to be low showing administrative position of hospital dietetics appears to be low showing only 45.7% of the sample hospitals recognize their dietetics as the independent department or section. 3. The starting salary of the 4-year college graduate dietitians is 151,450 won which is 89.23-87.26% of the average starting salary for the 4-year college graduates I 1979. The starting salary for the 4-year college graduates in 1979. the starting salary of the 2-year college graduate dietitians is 148,000 won which is 113.9% of the average standard salary for the 2-year college graduates in 1979. 4. The hospital dietitians spend most of their time doing clerical jobs rather than the jobs utilizing higher priority professional skills they ought to perform. the most obvious cause of the problem can be found in the lack of man power for the general clerical jobs in the dietetics which can be proven from the small number of dietary clerks hired by the sample hospitals not even one person (0.45) per hospital on the average. 5. 68.6% of the sample dietetics have some form of compiled diet manuals or guidelines. 11.4% of the samples have diet guide lines ready for the important diets only. 14.3% of the samples do not have any form of diet guideline prepared. 5.7% of the samples use reference diet manuals from other hospitals when need.

• 전기학회논문지
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• 제65권1호
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• pp.103-107
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• 2016

In general, the voltage stability of induction generator is lower than synchronous generator. Induction generator has a number of advantages over the synchronous generator on the side of price and maintenance. So Induction generator has been applied to the small hydroelectric power of low output. Induction generator usually generates a high current during grid connection. The high current that occurs during grid connection can cause a voltage drop in the system. In order to increase the supply of the induction generator, it is necessary to propose a method of reducing high current. This paper proposes some method of the soft start to reduce voltage drop caused by the large starting current. soft-start method has high voltage drop effect than direct start method, control of firing angle can be increased the voltage drop effect.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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• pp.103-104
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• 2011

This paper suggests a new starting and stopping method appropriate for the sensorless PMSM drive with air bearings. The proposed method based on the sensorless control algorithm of PMSM uses additional d-axis current control to cope with the limitation of the adopted back-emf based sensorless algorithm in the low speed region. The experimental results show that the proposed method drives appropriately the PMSM with air bearings.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.205-208
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• 2002

The single phase induction motor(SPIM) with two windings, main and auxiliary winding, is widely used due to ruggedness, low maintenance and simplicity of construction. There are several ways of starting single phase induction motor. The most common method is to use centrifugal switch that is connected in series with a capacitor. But the centrifugal switch that is the external starting system has many problems. In this paper, we use triac to overcome defects that happen by centrifugal switch, Also we used inductor that connected with main winding to get a gate trigger voltage signal. Experiments are focused on a capacitor starling single phase induction motor.