• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.8
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• pp.688-694
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• 2012

A study on the effect of engine nozzle configuration on the engine plume Infra-red (IR) signature characteristics is performed. Configuration design of an engine nozzle with high aspect ratio to reduce IR signature level and a cylindrical nozzle which is typically used for conventional aircraft which does not require IR signature reduction is performed. And CFD analysis for the two nozzles is performed to compare the flowfields characteristics of the two nozzles. Finally IR signature analysis for the two nozzles is accomplished to calculate the total intensity level at mid-wave infra-red and investigate the differences of IR signature characteristics between the two nozzles.

• Journal of KIISE
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• v.44 no.4
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• pp.411-416
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• 2017

The spectral radiance received by an infrared (IR) sensor is mainly influenced by the surface temperature of the target itself. Therefore, the precise temperature prediction is important for generating an IR target image. In this paper, we implement the combined three-dimensional surface temperature prediction module against target attitudes, environments and properties of a material for generating a realistic IR signal. In order to verify the calculated surface temperature, we are using the well-known IR signature analysis software, OKTAL-SE and compare the result with that. In addition, IR signal modeling is performed using the result of the surface temperature through coupling with OKTAL-SE.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.6
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• pp.375-382
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• 2020

Owing to the rapid development of infrared guided weapon systems, the threat to aircraft survivability is constantly increasing, and research on infrared stealth technologies are being conducted to ensure aircraft survival. In this study, we analyze the minimum infrared signature of an aircraft according to its flight altitude by considering the characteristics of infrared guided missiles, which detect the contrast signature between the aircraft and background. We conducted computational fluid dynamics simulations for the convective coefficient, and heat transfer simulations were performed considering convection, conduction, and radiation for flight conditions. Thus, we obtained the surface temperature distribution of the aircraft and analyzed the aircraft infrared signature based on the flow characteristics around it. Furthermore, the optimum emissivity for the minimum infrared signature was derived, and the effect of the infrared signature was analyzed when this optimum emissivity was applied to the fuselage surface for each flight condition.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.2
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• pp.109-116
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• 2019

Survivability of soldiers has been greatly threatened by the development of thermal observation device(TOD). Therefore, infrared, especially thermal, stealth technology is applied to combat suit to avoid detection from TOD. In this study, prior to the thermal camouflage performance evaluation of combat suit, thermal signature characteristic from clothed the human body was analyzed considering the realistic condition for human surface temperature compared to that from unclothed human body. To get the realistic surface temperature distribution of human, thermoregulation and multi-layer skin structure model is applied to the human model. Based on temperature distribution, surface diffuse radiance in thermal range is calculated and by assuming the background conditions, contrast radiance intensity(CRI) characteristic of human body is analyzed. By wearing clothing, the CRI between background and human body became reduced in low emissive background but in high emissive background, the contrast is much more prominent. Therefore, this issue should be considered in design process of thermal camouflage combat suit.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.4
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• pp.355-360
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• 2013

With the modern machinery towards the direction of high-speed development, the thermal issues of mechanical transmission system and its components is increasingly important. Ball bearing is one of the main parts in rotating machinery system, and is a more easily damaged part. In this paper, bearing thermal fault detection is investigated in details Using infrared thermal imaging technology to the operation state of the ball bearing, a preliminary thermal analysis, and the use of numerical simulation technology by finite element method(FEM) under thermal conditions of the bearing temperature field analysis, initially identified through these two technical analysis, bearing a temperature distribution in the normal state and failure state. It also shows the reliability of the infrared thermal imaging technology. with valuable suggestions for the future bearing fault detection.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.5
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• pp.455-461
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• 2016

Survivability of an aircraft has been greatly threatened by the development of a weapon system using infrared. Therefore, the infrared stealth technology is a very important technique to improve the survivability of an aircraft. In this study, the infrared signal of an aircraft was analyzed which corresponding to the aircraft surface temperature and environmental conditions with various surface conditions(especially emissivity changed). Based on the analyzed infrared signal, the optimized surface emissivity was suggested to reduce the average contrast radiance and contrast radiant intensity(CRI). In addition, we confirmed that the infrared contrast radiant intensity between the aircraft and the background can be minimized through an appropriately controlled surface emissivity of the aircraft at specific background.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.7
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• pp.426-439
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• 2017

This review summarizes advantage and limitation in infrared spectroscopy and computational chemistry to understand rhizospheric interaction among organic acids, oxyanions and metal oxides. Since organic acids and metal oxides determine dynamics of oxyanions in the soil environment, knowledge of fundamental mechanisms is a prerequisite for understanding the interactions at soil-water interface. Attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR) is a powerful tool to measure the interfacial reactions. However, the ATR-FTIR measurements are abstruse, because the optical characteristics for measurements are variable depending on the experimental setup. In addition, spectral overlapping is a primary obstacle to the analysis of the interfacial reaction; thus, it is essential to detect and to deconvolute bands for signal interpretation. In this review, we expained the fundamental principle for spectrum processing, and four band identification methods, such as derivative spectroscopy, two-dimension correlation spectroscopy, multivariate curve resolution, and computational chemistry with example of aqueous phosphate speciation. As a result, spectrum processing and computational chemistry improved interpretation and spectral deconvolution of overlapped spectra in relatively simple systems, but it was still unsatisfactory for the problems in more complexed system like nature. Nevertheless, we believed that our challenge would contribute practically to develop adequate analytical procedure, signal processing and protocols that could help to improve interpretation and to understand the interfacial interactions of oxyanions in natural systems.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.1
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• pp.63-69
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• 2015

In this paper, infrared reflector design targeting infrared stealth effect is presented using structural optimization based on the phase field method. The analysis model was determined to accomplish the design that an incident infrared wave was reflected to a desired direction. The design process was to maximize the objective value at the measuring domain located in a target region and the design objective was set to the Poynting vector value which represents the energy flux. Optimization results were obtained according to the variation of some parameter values related to the phase field method. The model with a maximum objective value was selected as the final optimal model. The optimal model was modified to eliminate the gray scale using the cut-off method and it confirmed improved performance. In addition, to check the desired effect in the middle wave infrared range(MWIR), the analysis was performed by changing the input wavelength. The finite element analysis and optimization process were performed by using the commercial package COMSOL combined with the Matlab programming.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.5
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• pp.62-69
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• 2014

Infrared signature of rocket plume plays an important role for detection, recognition, tracking and minimzing for low observability. Infrared signatures of rocket plume with reduced smoke propellant and smokeless propellant are measured. In order to estimate the infrared signature of rocket plume, CFD analysis for flow structure of plume is performed, and layered integration method for estimating of infrared signature is used. Numerical and experimental results were in good agreement. Both propellants had similar infrared signature. Strong peak at $4.3{\mu}m$ region in the experimental results is appeared due to experimental error arising from the calibration procedure.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.3
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• pp.75-75
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• 2001

Si₃N₄/SiO₂/Si₃N₄ 멤브레인에 의해 실리콘 기판으로부터 열차단된 비냉각 초전형 박막 (Ba,Sr)TiO₃ 적외선 검지기를 제작하고, 적외선 검지기의 특성을 논의하였다. 25℃의 공기중에서 쵸핑주파수가 1 ㎐일 때 적외선 검지기는 약 168.8 V/W의 비교적 높은 전압 감응도를 나타내었으나, 매우 작은 신호대잡음비 때문에 약 2.6×10⁴㎝·㎐/sup 1/2//W의 낮은 비검지도를 나타내었다. 또한 출력파형의 쵸핑주파수 및 온도 의존성에 대한 정성적인 해석으로부터 적외선 검지기의 열잡음전압 및 열시정수가 모두 상당히 크다는 것을 알 수 있었다.