• 전력전자학회논문지
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• 제11권3호
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• pp.209-215
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• 2006

본 논문에서는 전압원 인버터의 출력전압 파형을 개선하여 PWM방식을 사용할 수 없는 중 대용량급 모터드라이버 및 UPS, STATCOM, SVC등에 적용하기 위한 새로운 3상 전압원 24-스텝 인버터를 제안한다 보조회로로서 사용한 컨버터로 리플전압을 발생시키고 이를 기존의 12-스텝 인버터에 주입하는데 한대의 링크를 사용하면 12-스텝 동작이 24-스텝으로 전환되며 보조 변압기의 1차 권선을 2N(N=1,2,3...)으로 늘리면 12M-스텝(M=2,3,4..)으로 전환된다. 본 방식의 타당성을 실험 및 시뮬레이션을 통하여 입증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.258-260
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• 1995

This paper deals with the voltage unbalance of DC link voltage in series connected two 6-step inverters with double chopper preregulator. Each output of the 6-step inverter is connected to each transformer. The secondary windings of one of the transformers is zig-zag connected and the other star connected. The secondary terminals of the two transformers are series connected which makes 12-step output voltage waveform. In this case, the characteristics of the two transformers are rather different each other. The difference results in the voltage unbalance of the two 6-step inverter input capacitor voltages which make the DC link voltage. The degree of the voltage unbalance is analysied with the variations of load power, load power factor and % impedance of the transformer.

• 한국대기환경학회지
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• 제16권5호
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• pp.445-451
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• 2000

To estimate dry deposition flux of 12 elements in aerosols, aerosol particles were sampled by a low-pressure impactor(LPI) and a dust jar. The concentrations of 12 elements in aerosol particle and dry deposition were analyzed by a PIXE analysis using as a 2.0 MeV-proton beam. The mean dry deposition velocities of 12 elements were estimated by ranges of 0.74∼2.62 cm/sec. The results showed that the highest value was 3.26 cm/sec for Ca and the lowest value 0.74 cm/sec for Fe. The dry deposition flux for elements was calculated as a function of particle size by 1-step method and 12-step method. In this work, dry deposition velocities were computed with the two existing models; the coarse-particle fraction(4∼30 mm diameter) using the dry deposition velocity model of the Noll and Fang(1998) and the fine-particle fraction (0.05∼4mm diameter) using the Shemel and Hodgson(1980) model. The ratios of the mean calculated/measured fluxes were 3.59 for 1-step method and 0.60 for 12-step method respectively.

• 소성∙가공
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• 제12권5호
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• pp.449-456
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• 2003

Multi-step induction heating process was applied to the powder compact melting technique as a new heating process to achieve pinpoint accuracy, faster cycle time, repeatability, non-contact and energy-efficient heat in a minimal amount of time. The objective of this study is the establishment of the input data diagram of multi step induction heating process for automation of the fabrication process of 6061 Al foams with desired density. At first, proper induction coil was designed to obtain a uniform temperature distribution over the entire cross sectional area of specimen. By using this coil, foaming experiments were performed to investigate the multi-step induction heating conditions such as capacity, temperature and time conditions of each heating and holding step. On the basis of the obtained multi-step induction heating conditions, relationship between final heating temperature and fraction of porosity was investigated.

• 대한기계학회논문집
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• 제12권5호
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• pp.984-991
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• 1988

본 연구에서는 유압관로에서 액주분리를 수반하는 유체 과도현상의 압력파형 에 때때로 관측되는 2단적 압력상승현상의 발생기구를 실험 및 이론적인 추론, 특성곡 선법을 사용한 수치해석을 통하여 명확히 구명함을 목적으로 한다.

• 산업기술연구
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• 제35권
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• pp.9-13
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• 2015

In this paper, a new excitation scheme is developed to increase the output torque of the sensorless BLDC(Brushless DC) motor(BLDCM), which drives fins to control the flight attitude of a guided artillery munition. The proposed scheme is based on a 12-step excitation strategy combining two-phase and three-phase excitations. The proposed 12-step excitation scheme can produce more torque than a typical 6-step scheme for the start-up and synchronous operation in the sensorless BLDCM drive. The simulation and experimental results on the sensorless BLDCM drive system to control the fin were verified the validity of the proposed scheme.

• 한국환경생태학회지
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• 제12권4호
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• pp.398-405
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• 1999

한려해상국립공원 남해도지구에 위치한 금산의 등산로를 대상으로 하여 등산로에 설치된 계단의 물리적 특성을 조사한 결과, 등산로 총 연장 2,126m 중에 계단이 설치된 구간은 15개 구간이며, 총 길이는 1,000.4m로 나타났다. 대다수의 등산로 계단구역의 물매는 20~40%로 나타났으나, 11번 구간, 12번 구간과 같이 경사도 45.7%, 58.4%의 계단이 268.5m, 188.6m인 구간과 13번 구간과 같이 물매가 67.8%의 급경사 등산로 구간도 설치되어 있었다. 계단형 등산로에서 등산시 탐방객이 느끼는 운동강도를 조사한 결과, 전체 구간에 있어서 등산시의 심박수는 약 104~184회/분으로 나타났으며, 계단형 등산로 구간 중 11번 구간과 12번 구간, 그리고 13번 구간의 등산시 심박수 증가율, 운동강도지수, %HRmax는 각각 166.5%, 89.1%, 92.9%와 167.4%, 89.6%, 93.2%, 그리고 157.8%, 84.5%, 89.9%로 조사되었다.

• 전기전자학회논문지
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• 제23권1호
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• pp.9-13
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• 2019

본 논문에서는 원가 절감을 위한 개선된 $165^{\circ}$ 12 스텝 제어를 고려한 브러시리스 DC 전동기의 최적화 설계에 대하여 논한다. 개선된 12 스텝 제어는 기존 제어의 도통각 $150^{\circ}$을 확장시켜 전동기의 출력을 향상 시킬 수 있다. 향상된 전동기 출력을 고려한 반응 표면법을 이용한 최적화 설계를 통해서 회전자, 고정자 및 영구자석의 부피를 감소시켜 원가절감이 가능한 설계를 제시한다. 제안된 설계는 기존 전동기의 요구 사양 및 효율 향상을 만족하고 기존 전동기 중량의 약 3.5%를 저감하였다. 유한요소법을 이용한 전자계 해석을 통해 최적화 설계의 타당성을 입증하였다.

• Communications for Statistical Applications and Methods
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• 제12권2호
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• pp.473-481
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• 2005

The testing problem for sphericity structure of the covariance matrix in a multivariate normal distribution is introduced when there is a sample with 2-step monotone missing data pattern. The maximum likelihood method is described to estimate the parameters on the basis of the sample. Using these estimates, the likelihood ratio criterion for testing sphericity is derived.

• 대한기계학회논문집A
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• 제25권12호
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• pp.1974-1980
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• 2001

The control algorithm of a new type self-bearing step motor is presented. The motor actuator is used for both motor and bearing functionality without any redundant coil windings or redundant electromagnets. The self$.$bearing step motor layout and its control method are described. A linearized farce-current-displacement relationship is derived. As the result of the unbalance response approach, the constant torque production is possible fur the supply current regulation algorithm. And even if the bearing functionality is added in the motor functionality, no additional current for bearing functionality is possible, and this leads to minimize the net power loss. Also, the unbalance response shows the independent bearing force and motor torque.