• 신재생에너지
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• 제5권2호
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• pp.3-8
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• 2009

Tidal current power system is one of ocean renewable energies that can minimize the environmental impact with many advantages compared to other energy sources. Not like others, the produced energy can be precisely predicted without weather conditions and also the operation rate is very high. To convert the current into power, the first device encountered to the incoming flow is the rotor that can transform into rotational energy. The performance of rotor can be determined by various design parameters including numbers of blade, sectional shape, diameter, and etc. The stream lines near the rotating rotor is very complex and the interference effects around the system is also difficult to predict. The paper introduces the experiment of rotor performance and also the fundamental study on the characteristics of three different rotors and flow near the rotor by CFD.

• 한국수소및신에너지학회논문집
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• 제24권6호
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• pp.566-572
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• 2013

In the present study, structure analysis has been performed to understand the deflection and stress distribution for a hybrid street-lamp having a vertical-axis wind turbine and a photovoltaic panel. Modal analysis is also evaluated to avoid resonance gerenerated by sychronism between a turbine and a lamppost. To analyze deflection, stress and frequency, general analysis code(ANSYS-Mechanical 13) is employed in the present work. Throughout structure analysis in the hybrid street-lamp, maximum stress is observed at the connecting position between a turbine blade and a blade supporter. Campbell diagram which is combined the natural frequency of turbine blades and blade passing frequency is presented to analyze a system resonance. It is found that the resonance of the system having a rotating turbine blade and a lamppost can avoid by the optimal selection of geometric parameters of a wind turbine.

• Journal of Magnetics
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• 제16권4호
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• pp.363-367
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• 2011

We have designed, fabricated and demonstrated a novel micro-system for programmable magnetic actuation using magnetic elliptical pathways on Si substrates. Lithographically patterned soft NiFe ellipses are arranged sequentially perpendicular to each other as stepping stones for the transport of magnetic beads. We have measured the magnetization curve of the ellipsoid ($9\;{\mu}m{\times}4\;{\mu}m{\times}0.1\;{\mu}m$) elements with respect to the long and short axes of the ellipse. We found that the magnetization in the long axis direction is larger than that in the short axis direction for an applied field of ${\leq}$ 1,000 Oe, causing a force on carriers that causes them to move from one element to another. We have successfully demonstrated a micro-system for the magnetic actuation of biomolecule carriers of superparamagnetic beads (Dynabead$^{(R)}$ 2.8 ${\mu}m$) by rotating the external magnetic field. This novel concept of magnetic actuation is useful for future integrated lab-on-a-chip systems for biomolecule manipulation, separation and analysis.

• International Journal of Fluid Machinery and Systems
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• 제3권1호
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• pp.1-10
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• 2010

The present study is a fundamental approach to develop the measuring technology for minute fluctuating pressures on the three-dimensional blade surfaces of the fan which rotates with an arbitrary rotation-axis direction. In this situation, we are required to correct the centrifugal-force effect, the gravitational-force effect and the other leading-error effects for accurate measurements of the minute pressures. The working fluid is air. A pressure transducer rotating with an arbitrary attitude is closely sealed by a twofold shroud system. The rotational motion with an arbitrary attitude is produced by fixing the pressure transducer to the cantilever which is connected to a motor-driven disc of 500mm in diameter and 5mm in thickness. As a result, we have quantitatively determined main governing effects upon the non-effective component of the pressure-transducer signal.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.321-324
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• 2007

The actuators of anti-vibration system(AVS) can be separated into several types: piezoelectric actuators, pneumatic springs, cylinders, rotating motor and linear motor. The last one has some advantages, such as low noise, low vibration, simpler configuration and possibility of direct drive. The voice coil motor(VCM) is one type of linear motor, originally used in speaker system. VCM actuators are usually used in occasions that rapid and controlled motion of devices are required. In this paper, a controller which satisfies system specification(e.g. current controller bandwidth) within whole operation range is designed. For that objective, parameters as position were initially obtained with 3D FEM analysis and motor modeling was performed. A current controller in 2-axis VCM drive system was designed and then performance of the proposed controller was verified with simulation using Simplorer and an experimental result.

• Wind and Structures
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• 제32권2호
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• pp.81-87
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• 2021

The aim of the current study is to compare the performance of large 2 MW and 3 MW wind turbines operating on existing onshore wind farms using Blade Element Momentum (BEM) theory and Angular Momentum (AM) theory and illustrate the performance characteristic curves of the turbines as a function of wind speed (U∞). To achieve this, the measurement data obtained from two different Wind Energy Power Plants (WEPPs) located in the Hatay region of Turkey was used. Two different horizontal-axis wind turbines with capacities of 2 MW and 3 MW were selected for evaluation and comparison. The hub-height wind speed (UD), turbine power output (P), atmospheric air temperature (Tatm) and turbine rotational speed (Ω) data were used in the evaluation of the turbine performance characteristics. Curves of turbine power output (P), axial flow induction factor (a), turbine rotational speed (Ω), turbine power coefficient (CP), blade tip speed ratio (λ), thrust force coefficient (CT) and thrust force (T) as a function of U∞ were obtained for the 2 MW and 3 MW wind turbines and these characteristic curves were compared. Results revealed that, for the same wind speed conditions, the higher-capacity wind turbine (3 MW) was operating at higher turbine power coefficient rates, while rotating at lower rotational speed ratios than the lower-capacity wind turbine (2 MW).

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.246-249
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• 2003

The constraints necessary guarantee using the comparison of these extrinsic parameters, which each Rotation matrix and Translation Vector must be equal to the either, except the X-axis Translation Vector. Thus, we can not yet calculate the 3D-range measurement in the end of camera calibration. To minimize this disadvantage, the Epipolar Rectification has been proposed in the literature. This paper aims to present the development of Epipolar Rectification to calibrate Stereo cameras. The required computation of the transformation mapping between points in 3D-space is based on calculating the image point that appears on new image plane by using calibrated parameters. This computation is assumed from the rotating the old ones around their optical center until focal planes becomes coplanar, thereby containing the baseline, and the Z-axis of both camera coordinate to be parallel together. The optical center positions of the new extrinsic parameters are the same as the old camera, whereas the new orientation differs from the old ones by the suitable rotations. The intrinsic parameters are the same for both cameras. So that, after completed calibration process, immediately can calculate the 3D-range measurement. And the rectification determines a transformation of each image plane such that pairs of conjugate Epipolar lines become collinear and parallel to one of the image axis. From the experimental results verify the proposed technique are agreed with the expected specifications.

• 한국항공우주학회지
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• 제31권9호
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• pp.1-8
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• 2003

연장된 앞전을 갖는 삼각날개 위에서 시위방향의 여러 위치에서 3축 hot 필름 풍속계를 사용하여 속도장 데이터를 획득하였다. 속도장 데이터는 받음각 24도와 32도에 대하여 중심 시위선을 기준으로 한 레이놀즈수 $1.76{\times}10^6$에서 날개면에 수직한 유동단면에서 측정하였다. 3축 hot 필름 프로브에 의한 세 가지 속도 성분을 측정함으로써 연장된 앞전을 갖는 삼각날개에서의 와류장을 정량적으로 분석할 수 있었다. 날개 와류와 LEX 와류는 평균 축방향 속도가 국소 최고 속도를 갖는 영역에 존재하였다. 아울러, 앞전 근처의 날개면 위에서 주와류와 반대 방향으로 회전하는 이차와류의 생성을 관찰할 수 있었다. 측정 프로브의 유동장에의 삽입은 와류 중심 위치에 크게 영향을 주지 않음을 알 수 있었다.

• 한국항공우주학회지
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• 제42권6호
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• pp.515-521
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• 2014

본 논문에서는 Ray-tracing 기법을 이용하여 그레고리안 안테나의 부반사판을 축변환 후 회전하여 급전혼으로 회귀되는 전파를 없애 이득 및 정재파비를 개선 시키고 부반사판의 크기와 전체적인 부피를 줄여 효율적인 구조를 갖는 축변위그레고리안 안테나를 설계하였다. 설계된 급전혼의 방사패턴을 이용하여 급전혼-부반사판-주반사판으로 전달되는 전파의 경로를 추적하여 주반사판 개구면에서의 전계분포를 구하고 이로부터 원거리 복사패턴을 계산하는 프로그램을 작성하여 안테나 성능을 최적화 하였다. 설계된 안테나는 CST와 제작 측정을 통해 계산결과와 비교하여 이득, 빔폭, 방사패턴, 부엽준위, 반사손실이 계산 결과와 매우 유사함을 확인함으로써 Ray-tracing기법에 대한 타당성을 검증하였다.

• 천문학회지
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• 제44권4호
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• pp.115-123
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• 2011

To perform imaging observations of optically red objects such as high redshift quasars and brown dwarfs, the Center for the Exploration of the Origin of the Universe (CEOU) recently developed an optical CCD camera, Camera for QUasars in EArly uNiverse (CQUEAN), which is sensitive at 0.7-1.1 ${\mu}m$. To enable observations with long exposures, we develop an auto-guiding system for CQUEAN. This system consists of an off-axis mirror, a baffle, a CCD camera, a motor and a differential decelerator. To increase the number of available guiding stars, we design a rotating mechanism for the off-axis guiding camera. The guiding field can be scanned along the 10 arcmin ring offset from the optical axis of the telescope. Combined with the auto-guiding software of the McDonald Observatory, we confirm that a stable image can be obtained with an exposure time as long as 1200 seconds.