• Journal of the Korean Solar Energy Society
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• v.32 no.5
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• pp.31-40
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• 2012

This paper introduces a methodology for NREL 5MW wind turbine, which is the variable speed and variable pitch(VSVP) control system. This control strategy maximizes the power extraction capability from the wind in the low wind speed region and regulates the wind turbine power as the rated one for the high wind speed region. Also, pitch control efficiency is raised by using pitch scheduling.Torque schedule is made of torque table depending on the rotor speed. Torque control is used for vertical region in a torque-rotor speed chart. In addition to these, mechanical loads reduction using a drive train damper and exclusion zone on a torque schedule is tried. The NREL 5MW wind turbine control strategy is comprised by the generator torque and blade pitch control. Finally, proposed control system is verified through GH Bladed simulation.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.1
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• pp.1-7
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• 2003

A recent technology trends in synthetic aperture radar(SAR) requires the ultra high resolution performance in detecting and precisely identifying the targets. In this paper, as a technique for enhancing the radar range resolution, the wideband chirp connection algorithm is presented by stitching the several chirp modules with unit bandwidth based on the linear frequency modulated chirp signal waveform. The principles of the digital chirp signal generation and its architecture for implementation is briefly described, and the wideband chirp signal generator, modulator, and demodulator are designed. The performance analysis for the presented algorithm is given with the simulation results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5A
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• pp.494-499
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• 2008

In this study, a Software Defined Radio(SDR) technology-based digital filtering technique applicable to a multiple channel processing system such as a wireless mobile communication system using Code Division Multiple Access(CDMA) technology is proposed. The technique includes a micro-processor to redesign Finite Impulse Response(FIR) filter coefficients according to specific system information and to download the filter coefficients to one digital Band Pass Filter(BPF) to reconfigure another system. The feasibility of the algorithm is verified by implementing a multiple channel signal generator that is reconfigurable to other system profiles, including those for a CDMA system and a WCDMA system on identical hardware platform.

• The Transactions of the Korea Information Processing Society
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• v.4 no.8
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• pp.1975-1986
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• 1997

Recent evolution of communication networks has led toward increasingly a complex, large-scale protocol. Protocol conformance tests therefore, which consider only control flow, have many problems on testing data flow, transition condition, delay and so on. We propose, design, and implement the tool to solve these problems. The tool, which solves nondeterminism, generates test suites from an integrated flow graph and excludes infeasible path with reachable tree. The presented tool reduces the length of UIO sequence and is efficient partially to test the path that error rate is high. Our automatic test suite generator provides basis of protocol testing environment and high production.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.9
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• pp.642-649
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• 2006

In order to recognize a situation from a environment which provides an intelligent service, we propose state-transition based situation modeling which is suitable for a low computing power and restricted resources like embedded systems, and we designed its application to a situation-action converter(SAC)which is consist of two parts; situation detector recognized wanted situations and action generator generated various control actions. Then, we implemented a situation manager for smart scheduler service by using a SAC which is installed to a ARM processor based embedded Linux evaluation board.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10b
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• pp.142-144
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• 2004

다양한 지리 관측 기술 및 GPS 그리고 무선통신 기술의 발달로 인해, 해수의 흐름 변화 관측이나 PDA를 장착한 물류 차량 관리와 같이 시간에 따라 이동하는 여러 객체들의 변화를 추적하고 관리하는 것이 용이해지고 있다. 그리고. 이로 인해 지능형 교통 시스템. 물류 차량 관리 시스템 등이 활발히 개발되고 있다. 그러나 개발된 시스템에서 차량 운송 계획 평가 및 테스트를 할 경우 차량의 실제 데이터가 부족하기 때문에 적절한 평가 및 다양한 테스트를 하기 힘들고, 실생활에 알맞은 시스템을 만들기 어려움 점이 있다. 이렇게 부족한 차량 데이터를 보충하기 위해, 대부분의 연구에서는 몇몇의 이동 객체 위치 데이터 생성기를 활용하고 있다. 그러나 기존의 이동 객체 데이터 생성기는 단순히 정규 분포, 가우스 분포. 랜덤 데이터. 도로 정보 등을 고려하여 데이터를 생성하기 때문에. 사용자가 물류 수송 계획 등에 활용하기 위해 의도한 시나리오에 따른 데이터를 생성하지 못하고 있다. 따라서, 이 논문에서는 차량 위치 데이터 생성기에 사용자가 지정한 시나리오를 생성, 저장하는 이동 객체 패턴 제공기를 추가하여. 사용자 지정 시나리오를 지원하는 차량 위치 데이터 생성기를 설계한다 이 논문에서 설계된 차랑 위치 데이터 생성기는 사용자가 원하는 계획대로 차량의 위치 정보를 생성함으로써, 물류 수송 및 도로 건설계획 등을 검토할 때 도움이 될 수 있을 것이다.

• Journal of Digital Convergence
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• v.11 no.2
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• pp.287-297
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• 2013

In this paper, we propose an efficient variable-length radix-8/4/2 FFT architecture for OFDM systems. The FFT processor is based on radix-8 FFT algorithm and also supports radix-4 or radix-2 FFT computation. We are using efficient "In-place" memory access method to maintain conflict-free data access and minimize memory size. Also we replace a very large lookup table with a twiddle factor generator which consumes less area then a ROM-based lookup table. The proposed FFT processor performs variable-length FFT including 64, 256, 512, 1024, 2048, 4096 and 8192 points which cover all the required FFT lengths used in 802.11a, 802.16a, DAB, DVB-T, VDSL and ADSL.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1122-1123
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• 2015

본 논문에서는 회전전기자형 고온초전도 발전기의 이중 계자를 제안하고 설계를 하였다. 기존의 동기발전기는 회전자가 계자이지만, 본 논문에서는 전기자를 회전자로 설계하였다. 고정자인 계자는 전기자의 내측과 외측에 위치하게 설계하여 이중계자라고 하였다. 초전도 선재는 제조사에 의해 규격이 정해져있다. 계자에 대전류를 사용하기 위해서는 적층등의 방법들이 있다. 적층하여 구리 권선으로 계자를 권선시 저항과 인덕턴스의 불균등을 제거하기 위하여 구리 권선을 일정한 간격으로 위치를 변환시키는 전위의 방법이 사용된다. 하지만 초전도 선재의 경우는 꺽기, 비틀기등의 방법이 불가능하므로 이 방법을 사용할 수 없다. 그래서 선재를 펀칭하여 선재를 전위시키는 CTCC(Continuously Transposed Coated Conductors) 등의 방법을 사용한다. 본 연구에서는 CTCC 형태의 초전도 권선을 사용하여 기본 모델과 이중계자 권선을 설계하고 특성을 비교하였다. 초전도 선재를 적층하여 사용함으로 계자부의 면적은 증가하지만 인덕턴스, 길이등의 불균등을 제거할 수 있으며 적층 선재수가 증가할수록 계자부 면적은 감소하는 장점이 발생한다.

• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.251-256
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• 2004

A stable reference voltage generator is necessary to the infrared image signal readout circuit(ROIC) to improve noise characteristics in comparison with signals originated from infrared devices, that is, to gain good images. In this study, bandgap reference circuit operating at cryogenic temperature of 77K for Infrared image ROIC(readout integrated circuit) was propose. Most of bandgap reference circuits which are presented so far operate at room temperature, and they are not suitable for infrared image ROIC operating at liquid nitrogen temperature, 77K. To design bandgap reference circuit operating at cryogenic temperature, the parameter characteristics of used devices as temperature change are seen, and then bandgap reference circuit is proposed with considering such characteristics. It demonstrates practical use possibility through taking measurements and estimations.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.6
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• pp.527-534
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• 2018

The segment of the piston type wave board has been expressed as a submerged vertical line segment in the two dimensional wave flume. Either end of vertical line segment representing wave board could be located in fluid domain from free surface to the bottom of the flume. Naturally the segment could be extended from the bottom to the free surface of the flume. It is assumed that the piston motion of the wave board could be defined by the sinusoidal oscillation in horizontal direction. Simplified analytic solution of the submerged segment of wave board has been derived through the first order perturbation method in water of finite depth. The analytic solution has been utilized in expressing the wave generated by the piston type wave board installed on the upper or lower half of the flume. The wave form derived by the analytic solution have been compared with the wave profile obtained through the CFD calculation for the either of the above cases. It is appeared that the wave length and the wave height are coincided each other between analytic solution and CFD calculation. However the wave form obtained by CFD calculations are more closer to real wave form than those from analytic calculation. It is appeared that the linear solutions could be not only superposed by segment but also integrated by finite elements without limitation. Finally it is proven that the wave generated by the oscillation of flap type wave board could be derived by integrating the wave generated by the sinusoidal motion of the finite segment of the piston type wave board.