• Applied Science and Convergence Technology
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• 제27권3호
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• pp.47-51
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• 2018

We fabricated an anode-type ion beam source and studied its driving characteristics of the initial extraction of ions using two driving mechanisms: a diffusion phenomenon and a charge repulsion phenomenon. For specimen exposed to the ion beam in two methods, the surface impurity element was investigated by using X-ray photoelectron spectroscopy. Upon Ar gas injection for plasma generation the ion beam source was operated for 48 hours. We found a Fe 2p peak 5.4 at. % in the initial ions by the diffusion mechanism while no indication of Fe in the ions released in the charge repulsion mechanism. As for a long operation of 200 min, the temperature of ion beam sources was measured to increase at the rate of ${\sim}0.1^{\circ}C/min$ and kept at the initial value of $27^{\circ}C$ for driving by diffusion and charge repulsion mechanism, respectively. In this study, we confirmed that the ion beam source driven by the charge repulsion mechanism was very efficient for a long operation as proved by little electrode damage and thermal stability.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.532-537
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• 2000

The purpose of this study is to determine the performance of a commercial air cleaner in removing tobacco smoke indoors. Following injection of tobacco smoke in a room, decay rates for particle concentrations were obtained far mass concentration at each point. The size distribution of the tobacco smoke particles was approximately $1.266{\mu}m$ in mass median diameter with a geometric standard deviation of 1.313. The air cleaner consisted of an electrostatic filtration unit and a fan operated at a flow rate of 5.98 CMM. The collection efficiency for $>1\;{\mu}m$ was more than 99%. Without air cleaner operation, tobacco smoke concentration ratio in room decreased to 30% of initial values within 30 minutes and with air cleaner operation, decreased to 90% of initial values in the test chamber, volume $51.27\;m^3$. Without air cleaner operation, tobacco smoke concentration ratio in room decreased to 10% of initial values within 30 minutes and with air cleaner operation, decreased to 30-70% of initial values in the test chamber, volume $149.2\;m^3$.

• 전기학회논문지
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• 제59권2호
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• pp.311-317
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• 2010

This paper deals with operation characteristics of a written-pole motor (WPM), having that of a permanent magnet (PM) synchronous motor and induction motor at once. The WPM also has a magnet layer on the surface of the rotor and the exciter pole that is a device to make the magnet layer magnetized during the operation. This study, introducing a fundamental structure and operation characteristics of a single-phase WPM, proposes a initial design method. With those ground, a 130W, single-phase WPM that is designed for a home appliance is presented and verified with a performance through the experiment.

• International Journal of Internet, Broadcasting and Communication
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• 제7권2호
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• pp.117-122
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• 2015

Our research team proposed a flux-offset type fault current limiter as a new limiter. The flux-offset type fault current limiter uses a fault current limit technology based on the flux offset principle of the primary and secondary windings of a transformer. Stable fault current limit characteristics were achieved through a preliminary study. However, it was discovered that the initial fault current was not limited. Therefore, in this paper, a high-speed interrupter and a superconducting element were separately applied to the secondary winding of the flux-offset type fault current limiter and the operating characteristics were comparatively analyzed. In the experiment, when the superconducting element was applied to the secondary winding of the transformer, the initial fault current was limited while the limitation in the operation time was further shortened.

• 한국초전도ㆍ저온공학회논문지
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• 제16권3호
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• pp.10-14
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• 2014

Due to continuous increase of electric power consumption, couple of resolutions for improving accuracy in power system like line separation are being studied. The increase of the power demand can cause problems such as supply difficulties of the electricity and broadband outages, failure, etc. When a fault occurs in the power system, a fault current also increases. Fault current creates problems like reduction of lifespan and failure on the power system. In order to resolve these problems, the reduction of initial fault current using the characteristics of superconducting element was applied to fault current limiter. We applied the system to high speed fault current limiter. We found that the superconducting element effectively reduced initial fault current and the fault current was limited by changing operation of high speed interrupter.

• 전력전자학회논문지
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• 제9권2호
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• pp.142-149
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• 2004

선형 영구자석형 동기 전동기는 기구학적인 변환 장치를 사용하는 기존의 방식과 비교하여 소음, 진동의 저감 및 가속도, 속도에 있어서 우수한 동특성을 가지고 있기 때문에 자동화 분야, 공작기계 및 반도체 장비를 중심으로 널리 사용되고 있다. 그러나 수직축(Z-axis)에 선형 영구자석형 동기 전동기가 적용될 경우에 제어를 위한 초기각 설정 및 상승, 하강 운전 특성을 향상시키기 위한 방법이 필요하다. 본 논문에서는 수직축 구조를 갖는 선형 영구자석형 동기 전동기의 초기각 설정 알고리즘 및 상승, 하강 운전 특성을 향상시키기 위해 실제 속도와 운전 방향을 변수로 하는 가변 이득 조절 알고리즘을 제안한다. 제안된 알고리즘들을 증명하기 위해서 4점의 절대위치 프로파일(profile)을 통해서 기존의 이득 시스템과 가변 이득 조절 시스템을 비교하여 제안된 알고리즘의 효용성을 검증하였다.

• 한국산학기술학회논문지
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• 제15권8호
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• pp.4809-4814
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• 2014

본 논문은 미세물분무 작동에 따른 화재 거동 및 제압 특성을 예측하는 데 있어서 FDS(Fire Dynamic Simulator)의 예측 성능을 평가하는 것을 목적으로 한다. 미세물분무의 초기액적분포 입력을 위해 Rosin-Rammler /log-normal 분포를 사용하였으며 모델 상수의 영향을 살펴보았다. 또한 미세물분무의 분사압력에 따른 화재 제압특성을 이전의 실험 결과와 비교함으로써 해석 모델을 검증하고 열유동 특성 및 가스 농도 변화를 분석하였다. 결과로부터 동일한 평균입경을 갖는 미세물분무도 액적분포의 특성에 따라 하부 위치에서의 액적 크기 및 속도에 큰 영향을 받고 있음을 확인할 수 있었다. 분무특성에 대한 실험결과와의 비교를 통해 적절한 초기입경분포를 결정하였으며 이를 이용하여 화재 시뮬레이션을 진행하였다. FDS 화재 시뮬레이션 결과는 온도의 변화 및 화재 제압 특성에 대하여 실험 결과와 좋은 일치를 보여주었다. 또한 미세물분무의 작동압력에 따른 열유동장 변화, 가스상 농도 변화의 예측에 있어 유용한 데이터를 제공할 수 있음을 확인하였다.

• Wind and Structures
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• 제32권2호
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• pp.169-177
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• 2021

This study investigates the effects of blade configuration and solidity of Darrieus wind turbine on the starting torque characteristics. Generally, the configuration of Darrieus wind turbine is divided into Troposkien, parabola, Catenary, Sandia, modified-parabola and straight types. A numerical analysis has been carried out using Multiple Stream Tube (MST) method to investigate the effect of blade configuration and solidity of Darrieus wind turbine on the starting torque under the initial low range of rotational speed. The simulation results show that the starting torque of Darrieus wind turbine varies considerably depending on the blade configuration. The initial starting torque was larger with Troposkien, Parabola, Catenary, and Sandia configurations than with modified parabola or straight types. The increase in solidity with increasing number of blades raised the starting torque and improved the dynamic stability during the initial operational speed of Darrieus wind turbine. Additionally, these torque results represent basic data for fluid-structure interaction (FSI) simulation of the steady-dynamic operation of the turbine.

• 생명과학회지
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• 제21권1호
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• pp.127-133
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• 2011

${\beta}$-galactosidase를 공유결합으로 키토산 담체에 고정화하여 고정화 효소의 특성을 조사하였다. 또한 충진층 반응기에서 연속 조업을 실시하여 공정 최적화를 실시하였다. 키토산 담체에 대한 효소 고정화 효율은 최대 75%을 나타내었다. 고정화 효소에 대한 최적의 pH는 7.0이었고 최적의 온도는 $50^{\circ}C$였다. pH와 온도의 실험 범위에서 고정화 효소가 자유 효소에 비해 넓은 분포를 보여 pH와 온도에 덜 민감하게 작용하였다. 충진층 반응기에서 고정화 효소의 운전에 대한 수학적 모델을 세우고 수치적으로 해를 구하였다. 투입되는 유당의 농도와 유량에 대해서 충진층 반응기의 출구에서 유당의 전환율을 측정하였다. 실험 결과를 경쟁적 저해 효소 반응식과 물질전달 저항을 고려한 수학적 모델의 결과와 비교하였다. 모델의 결과는 실험 결과를 5% 이내의 오차로 잘 예측하였다. 그리고 충진층 반응기의 길이에 따른 유당 전환율과 연속운전 시간에 따른 효소의 비활성화를 고려한 전환율을 모델로부터 예측하였다.

• Journal of Trauma and Injury
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• 제34권2호
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• pp.105-111
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• 2021

Purpose: Open extremity fractures require prompt antibiotic medication and initial debridement surgery to reduce the infection rate and restore functional stabilization. We aimed to report the effects and positive outcomes of a trauma team approach on the management of open extremity fractures in polytrauma patients. Methods: This retrospective review included all polytrauma patients with open extremity fractures admitted between March 2009 and December 2019. Patients were divided into two groups according to whether they were treated before or after the implementation of the trauma team approach (March 2014). We analyzed the outcomes in each group with respect to the time interval until the doctor's arrival, total length of stay in the emergency department, the time interval until initial antibiotic treatment and operation, whether the initial operation was performed within 24 hours, and the rate of deep infections. Results: A total of 123 patients met the inclusion criteria. There were no statistically significant differences in demographic characteristics. The time interval until the doctor's arrival (64.12±49.2 minutes vs. 19.82±15.23 minutes; p=0.035) and initial antibiotic treatment (115.47±72.12 minutes vs. 48.78±30.12 minutes; p=0.023) significantly improved after implementing the trauma team approach. The union rate was not significantly different. However, the time interval until initial debridement, opportunity for initial debridement within 24 hours, and the rate of deep infections demonstrated better results. Conclusions: The reduced time interval until initial antibiotic treatment and debridement could be attributed to the positive effect of the trauma team approach on the management of open extremity fractures in polytrauma patients.