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통계적 방법을 이용한 적외선 신호 대비값 계산 방법 연구
한국일(K.I. Han),최준혁(J.H. Choi),하남구(N.K. Ha),장현성(H.S. Jang),이승하(S.H. Lee),김동건(D.G. Kim),김태국(T.K. Kim) 한국전산유체공학회 2017 한국전산유체공학회지 Vol.22 No.1
Infrared signals are frequently used to detect objects exposed to wide variety of environmental conditions. Detection by infrared signature is accomplished by distinguishing objects by using the IR radiant contrast between objects and the background. There are several methods of estimating the IR radiant contrast. The inverse distance weighting method, which is one of the IR radiant contrast estimation method using the effect of distance from objects, is known to be an effective way to analyze radiant contrast for complex backgrounds. However this method has a disadvantage of requiring a long calculation time. In this study we propose a statistical method of estimating the IR radiant contrast by using randomly selected pixels of arbitrary number among background pixels to reduce calculation time. Some measured IR images in MWIR and LWIR regions are used to test the applicability of the method proposed and we found that the proposed method is very effective in determining the IR radiant contrast showing very rapid estimation with minar accuracy loss.
야외 환경에 노출된 입체 구조물에 대한 열적외선 신호 예측 소프트웨어 개발 및 실험적 검증 연구
김동건(D.G. Kim),권구용(K.Y. Kwon),장현성(H.S. Jang),연윤모(Y.M. Yeon),하남구(N.K. Ha) 한국전산유체공학회 2021 한국전산유체공학회지 Vol.26 No.3
This paper contains experimental validation of surface temperature and IR(infrared) signal prediction performance for a 3D object placed in an outdoor environment as part of a software development process to predict thermal infrared signals based on computational thermal analysis with considering 3D thermal conduction and unsteady state. For experimental validation, CUBI targets, which are introduced as major verification cases abroad, were produced and installed on the experimental site. Also, thermocouple wires, infrared cameras, a solar tracker and a weather station were installed on the experimental site. Performance validation was carried out step by step, and as the first step, the suitability of the algorithm applied to the developed software was determined through comparison and analysis of prediction results for surface temperature. As a second step, the self-emitted radiance calculation result and the solar and sky reflected radiance calculation algorithm were validated through the analysis of the prediction result for infrared signals. In addition, by assigning the same input conditions to the other commercial software with similar concepts and comparing the calculated results together, the limitations of modeling inevitably appear in the comparison between modeling and measurement were considered. As a result of the validation, it is judged that the thermal infrared signal prediction performance of the software developed through this study is applicable to stereoscopic objects placed in an outdoor environment. In the future, it is necessary to prepare to become software with higher reliability through performance validation of 3D objects that have more complex forms or contain heat sources.
소형 제트엔진 배기플룸의 열유동장 및 화학성분의 IR 신호 영향성 전산해석
채준혁(J.H. Chae),이지현(J.H. Lee),이지원(J.W. Lee),하남구(N.K. Ha),김동건(D.G. Kim),장현성(H.S. Jang),명노신(R.S. Myong) 한국전산유체공학회 2019 한국전산유체공학회지 Vol.24 No.3
Because of high levels of infrared signature generated by engine exhaust plume, aircraft can be detected by infrared guided missiles equipped with a modern detector. In order to investigate the characteristics of plume IR and reduce the level of its signature, the exhaust plume around an engine nozzle was calculated with a Navier-Stokes-Fourier computational code. The narrow-band model was employed to calculate the spectral characteristics of the IR signature. Computational models were compared with the experimental results of a micro jet engine. By considering an aircraft flying at an altitude of 20,000 ft, the effects of thermal flow field and chemical components on the IR signature was investigated. As expected, the plume IR signature showed the greatest effect at 4~4.5 μm CO₂ and 5~8 μm H₂O, and the temperature affected the IR signature over the whole band. In addition, the molar fraction change in CO₂ and H₂O resulted in higher variation in plume IR signature.
비균일 대기상태를 고려한 함정의 적외선 신호 특성 분석
최준혁(J.H. Choi),김도휘(D.H. Kim),한국일(K.I. Han),하남구(N.K. Ha),장현성(H.S. Jang),이승하(S.H. Lee),김동건(D.G. Kim),김태국(T.K. Kim) 한국전산유체공학회 2017 한국전산유체공학회지 Vol.22 No.1
The IR signal entering into a sensor is composed of the following components: the self-emitted component directly from the object surface, the reflected components of the solar and sky irradiance at the object surface, and the scattered component by the atmosphere without reference to any object surfaces. The self-emitted and reflected components from the object can be lowered by the atmospheric layer between the object and the IR sensor. The principle factors influencing the atmospheric transmittance are the air temperature, the relative humidity and the observation distance. Previous studies on IR signal transmission through the atmosphere are focused on uniform atmospheric conditions and the non-uniform nature of the atmosphere was not properly treated in modeling. In this study, we use the local atmospheric transmittance to simulate the non-uniform atmosphere in analyzing the IR signal from the object surface. The results show that the nonuniform analysis of the atmosphere becomes more important as the wavelength of IR signal increases.