• The KSFM Journal of Fluid Machinery
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• v.14 no.2
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• pp.5-10
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• 2011

The purpose of this study is to develop a software for the performance evaluation and blade design of a pitch-controlled HAWT using BEMT(Blade Element Momentum Theory) with Prandtl's tip loss. The HERACLES V2.0 software consist of three major part ; basic blade design, aerodynamic coefficient mapping and performance calculation including stall or pitch control option. A 1MW wind turbine blade was designed at the rated wind speed(12m/s) composing five different airfoils such as FFA-W-301, DU91-W250, DU93-W-210, NACA 63418 and NACA 63415 from hub to tip. The mechanical power predicted by BEMT at the rated wind speed is about 1.27MW. Also, CFD analysis was performed to confirm the validity of the BEMT results. The comparison results show good agreement about the error of 6.5% in rated mechanical power.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.2
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• pp.142-149
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• 2004

This paper presents a neural network controller of a grid-connected wind energy conversion system for extracting maximum power from wind and a power controller to transfer the maximum power extracted into a utility grid. It discusses the modeling and simulation of the wind energy conversion system with the controllers, which consists of an induction generator, a transformer, a link of a rectifier, and an inverter. The paper describes tile drive train model, induction generator model and grid-interface model for dynamics analysis. Maximum power extraction is achieved by controlling the pitch angle of the rotor blades by a neural network controller. Pitch control method is mechanically complicated, but the control performance is better than that of the stall regulation. The simulation results performed on MATLAB show the variation of the generator torque, the generator rotor speed, the pitch angle, and real/reactive power injected into the grid, etc. Based on the simulation results, the effectiveness of the proposed controllers is verified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1065-1071
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• 2012

Wind energy is becoming one of the most preferable alternatives to conventional sources of electric power that rely on fossil fuels. For stable electric power generation, constant rotating speed control of a wind turbine is performed through pitch control and stall control of the turbine blades. Recently, variable pitch control has been implemented in modern wind turbines to harvest more energy at variable wind speeds that are even lower than the rated one. Although wind turbine pitch controllers are currently optimized using a step response via the Ziegler-Nichols auto-tuning process, this approach does not satisfy the requirements of variable pitch control. In this study, the variable pitch controller was optimized by a genetic algorithm using a neural network model that was constructed by the Latin Hypercube sampling method to improve the Ziegler-Nichols auto-tuning process. The optimized solution shows that the root mean square error, rise time, and settle time are respectively improved by more than 7.64%, 15.8%, and 15.3% compared with the corresponding initial solutions obtained by the Ziegler-Nichols auto-tuning process.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1701-1704
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• 2010

기존 안드로이드 응용프로그램에 대한 자원 접근 제어는 응용프로그램을 작성한 개발자가 XML 파일에 미리 선언한 권한을 검사하는 방식으로 이루어진다. 이 권한은 인스톨되는 시점에 사용자의 동의를 얻어 해당 응용프로그램에 수여되며 응용프로그램이 특정 권한을 의도적으로 사용자로부터 은닉하는 것을 방지할 수 있다. 하지만 사용자는 해당 응용프로그램에 허용하고자 하는 일부 권한만을 수여할 선택권이 없다. 선언된 모든 권한을 허락하거나 그렇지 않으면 아예 응용프로그램을 설치할 수 없게 된다. 또한, 응용프로그램에 부여한 권한을 변경할 수는 없고 박탈하는 방법은 응용프로그램을 삭제하는 방법밖에 없었다. 따라서 본 논문에서 제안하는 기법은 응용프로그램의 자원 접근을 사용자가 fine-grained 하게 제어할 수 있도록 하는 기법이다. 이를 위해 응용프로그램을 사용하는 시점에도 각 접근 권한을 '항상 허용', '항상 사용자가 확인' 그리고 '항상 거부'로 세부적으로 설정 및 변경이 가능하도록 하였다. 또한, MS Windows Vista 에서 적용하고 있는 '사용자계정컨트롤'(User Account Control)과 같이 응용프로그램이 요구하는 권한 중 '항상 사용자가 확인'으로 설정 된 권한은 요청 시점에 사용자에게 팝업을 띄워 접근 제어에 대한 가시성을 확보하여 사용자가 확인할 수 있도록 하였고 사용자가 이를 수락한 경우에만 해당 권한을 수여 받을 수 있도록 하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.6
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• pp.556-565
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• 1991

Using the WDZ decomposition algorithm, a parallel algorithm is presented for solving the linear system Ax=b which has an nxn nonsingular tridiagonal matrix. For implementing this algorithm a CAM systolic arrary is proposed, and each processing element of this array has its own CAM to store the nonzero elements of the tridiagonal matrix. In order to evaluate this array the algorithm presented is compared to theis compared to the LU decomposition algorithm. It is found that the execution time of the algorithm presented is reduced to about 1/4 than that of the LU decomposition algorithm. If each computation process step can be dome in one time unit, the system of eqations is solved in a systolic fashion without central control is obtained in 2n+1 time steps.