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압축기 정익, 터빈 노즐 가변 메카니즘 및 제어기법 연구
김상조(Sangjo Kim),김동현(Donghyun Kim),배경욱(Kyoungwook Bae),김대일(Dae-il Kim),손창민(Changmin Son),김귀순(Kuisoon Kim),이대우(Daewoo Lee),고정상(Jeungsang Go),최동환(Dong-Whan Choi),김명호(Myungho Kim),민성기(Seongki Min) 한국추진공학회 2015 한국추진공학회지 Vol.19 No.5
In case of a gas turbine engine for supersonic operation, the engine have a wide range of operating inlet mass flow rate and required high performance such as thrust and fuel consumption. Therefore, variable system and its optimal control logic are essentially needed. In this work, a method for performance prediction of a gas turbine engine with variable system compressor and its control scheme were developed. Conceptual design of compact acuation system for the operation of the variable system was also conducted. The performance of a low-bypass ratio mixed flow turbofan engine was analyzed, and it was observed that the surge margin of the engine is improved at off-design condition by applying the control scheme.
Aqueous Hydrogel System of One-Dimensional Carbon Materials
Daewoo Kim(김대우) 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
The preparation of carbon materials based hydrogels and their viscoelastic properties are essential for their broad application and scale-up. However, existing studies are mainly focused on graphene derivatives and two-dimensional materials, and the behavior of one-dimensional (1D) materials such as graphene nanoribbon (GNR) and carbon nanotubes (CNTs) remains elusive. Poor dispersion of the 1D materials in the solvent is one of the key bottlenecks for utilizing the materials in many applications. Herein, the dispersion of the 1D materials in an aqueous system is suggested and its unique assembly behavior is systematically investigated. Particularly, we demonstrate the concentration-driven gelation of oxidized GNR (graphene oxide nanoribbon, GONR) and the GONR hydrogels exhibit viscoelastic shear-thinning behavior and can be shear-coated to form large-area GONR films on substrates. The hydrogel system also can be used
Two-stage trajectory planning for stable image acquisition of a fixed wing uav
Jonghun Kim,Daewoo Lee,Kyeumrae Cho,Jeongho Kim,Dongin Han IEEE 2014 IEEE transactions on aerospace and electronic syst Vol.50 No.3
<P>We propose a two-stage trajectory planning (TSTP) method using monocular vision for keeping continuous surveillance or reconnaissance of a target, and for relaying communication between a ground vehicle and an unmanned aerial vehicle (UAV). The cost function for optimal trajectory includes the variation of the altitude and speed of the UAV to prevent sudden maneuvering. The position of the target in the image is also included in a cost function for continuous observation. A virtual image can be calculated from the relationship between the coordinates of the UAV and those of the camera. The proposed cost function can be affected to a greater degree than in generic optimization problems because it has the position of the target in the image. Therefore, TSTP is introduced to mitigate the problem induced by the image included in the cost function. TSTP consists of two stages of optimization. The stability of the UAV, and the relative distance between the target and the UAV on the horizontal plane, are optimized in the first stage. The results are used as initial guesses for the second stage to improve optimality. The second stage optimizes the stability of the UAV and the position of the target in the image. Proportional-integral-derivative (PID) controllers are employed to follow the optimized trajectory in both the lateral and longitudinal directions. Our simulation results show stable optimized trajectories, with a stable image and target tracking performance.</P>
입출력 변수 조작에 의한 임베디드 소프트웨어 테스트 방법
김대우 ( Daewoo Kim ),정기현 ( Kihyun Jung ),최경희 ( Kyunghee Choi ) 한국정보처리학회 2005 한국정보처리학회 학술대회논문집 Vol.12 No.1
임베디드 소프트웨어가 날이 갈수록 그 규모가 커지고 복잡해짐에 따라 임베디드 소프트웨어의 품질에 대한 검증 및 테스트는 중요한 문제로 부각하고 있다. 임베디드 소프트웨어의 신뢰성을 확보와 비용절감을 위한 테스트 자동화 시스템의 개발이 필요하다. 이 문서는 테스트 자동화 시스템을 구축하는 과정에서 테스트 대상인 임베디드 시스템의 입출력 변수들의 조작을 통하여 시스템 의존적인 부분을 효과적으로 일반화 시키는 방법을 제시한다. 이 방법을 통하여 테스트 명령을 간소화 할 수 있었으며 테스트 자동화 시스템의 모델을 보다 일반적이고 쉽게 표현할 수 있었다.