• Journal of the Society of Naval Architects of Korea
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• v.48 no.4
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• pp.336-341
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• 2011

Ship infrared signature is the cause of detection and tracking by infrared sensor and anti-ship missile seeker. Recent warships have been applied the infrared stealth technology to reduce own ship infrared signature and tested to validate own ship infrared signature level. This study describes the two issues. Firstly, we describe the infrared measurement concept and infrared signature level establishment method that have been performed. Secondly, we compare and analyze the error components between the infrared measurement and simulation result.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.7
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• pp.652-659
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• 2011

A computational system to predict flowfield and infrared signature in aircraft exhaust system is developed. As the first step, a virtual mission profile is considered and an engine is selected through a performance analysis. Then a nozzle that meets the requirement of each mission is designed. The internal flow in the exhaustion nozzle at the maximum thrust is analyzed using a state-of-the-art CFD code. In addition, a system to combine information of the skin temperature distribution of the nozzle and after-body surface with an infrared prediction code is developed. Finally, qualitative results for the infrared signature reduction design are obtained by investigating the infrared signature level under various conditions.

• Journal of Ocean Engineering and Technology
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• v.23 no.3
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• pp.53-58
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• 2009

A scale model test for ship Infra-Red signature measurements at sea is impossible, because it is sensitive to the environment. Since we can't control the meteorological environment of the real sea, it can't be carried out with the desired maritime environments. Therefore, in the sea, we made measurements of the weather, operating conditions of the ship, and ship IR signatures under given conditions, and then analyzed them. Conversely, we compared the results of the test with a prediction for a given scenario condition. This paper describes the test items, procedures, and measuring instruments of the experiments at sea and the results from basic researches for methods of estimation and analysis of the measured data.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.8
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• pp.640-647
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• 2014

Infrared signature of aircraft exhaust plume is the critical factor for aircraft survivability. To improve the military aircraft survivability, the accurate prediction of infrared signature for the propulsion system is needed. The numerical analysis of thermal fluid field for nozzle inflow, free stream flow, and plume region is conducted by using the in-house code. Weighted Sum of Gray Gases Model based on Narrow Band with regrouping is adopted to calculate the spectral infrared signature emitted from aircraft exhaust plume. The accuracy and reliability of the developed code are validated in the one-dimensional band model. It is found that the infrared radiant intensity is relatively more strong in the plume through the analysis, the results show the different characteristic of the spectral infrared signature along the temperature, the partial pressure, and the species distribution. The continuous spectral radiant intensity is shown near the nozzle exit due to the emission from the nozzle wall.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.4
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• pp.456-462
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• 2014

Infrared(IR) guided heat-seeking missiles uses IR emissions from aircraft to detect and track a target. Due to passive characteristic of the IR guidance, early detection of the missile is difficult and it is significant threat to aircraft survivability. Therefore, IR signature prediction of the aircraft is an important aspect of the stealth technology. In this study, we simulated IR signature of the aircraft in real atmospheric conditions. Aircraft surface temperature distribution was calculated by using RadthermIR code. Based on temperature distribution, IR radiance and BRDF(Bidirectional Reflectance Distribution Function) image were simulated for different weather(seasonal) and background(sky/soil) conditions. The IR contrast tendencies are not aligned with surface temperature or magnitude of target IR radiance. Therefore, it is essential to simulate IR signature with various conditions and background to acquire reliable database.

• 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 Korea Institute of Military Science and Technology
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• v.11 no.5
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• pp.84-91
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• 2008

The spectral radiance received by a remote sensor at a given temperature and wavelength region is consisted of the self-emitted component directly from the object surface, the reflected component of the solar irradiation at the object surface, and the scattered component by the atmosphere without ever reaching the object surface. The IR image of a ship is mainly affected by location, meteorological condition(atmosphere temperature, wind direction and velocity, humidity etc.), atmospheric transmittance, solar position and ship surface temperature etc. Computer simulations for prediction of the IR signatures of ships are very useful to examine the effects of various meteorological conditions. In this paper, we have acquired the IR signature for different meteorological conditions by using two different computer programs. The numerical results show that the IR image contrast as compared to the background sea considering the atmosphere temperature and wind velocity.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.4
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• pp.242-246
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• 2000

The Near Infrared Reflectance Spectroscopy(NIR) was used to evaluate nutritional diagnosis for rapid leaf analysis method, 177 'Fuji' apple and 130 'Campbell Early' grape leaves were measured by Near Infrared reflectance spectra in the NIR region(1,100~2.500nm). Total nitrogen content was measured by kjelldhal distillation, after salycilic acid-sulfuric acid digestion. An empirical equation to predict total nitrogen content from its spectral signature was developed by adapting the Near Infrared Reflectance Spectroscopy analysis(NIRa) technique and the results were apple-0.965(R). 0.086(SEC), grape-0.926(R), 0.152(SEC). Standard Error of Prediction(SEP) of NIRa for predicting the total nitrogen of apple and grape leaves was 0.360 and 0.210, respectively. It was concluded that Near infrared reflectance spectroscopy analysis is promising method for rapid analysis of apple and grape leaves.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.4
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• pp.545-552
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• 2013

This paper is a part of developing a computer code that can be used to generate IR images of a naval ship by considering the emitted and reflected infrared signals. The spectral radiance received by an IR sensor is consisted of the self-emitted component from the ship surface, the reflected component of the solar/sky irradiance at the ship surface, the emitted radiance from the ship surface and the exhaust plume gas, and the scattered radiance by the atmosphere. The plume gas radiance occupies a large part of the emitted radiance from a naval ship in operation. Therefore plume gas radiance must be taken into account when calculating the radiance from a naval ship for reliable IR images. In this paper, IR images of a naval ship with the exhaust gas effect in various environmental conditions are generated by using an exhaust gas prediction model called the JPL model. The contrast radiance (CR) values of the IR images are calculated to analyze the effect of the exhaust gas radiance quantitatively. The results obtained by quantitative analysis show that the IR signatures with the exhaust plume gas are 2.26 times larger than those neglecting the plume gas effect. The effect of the exhaust plume gas is shown to be more eminent in winter than in summer in the daytime.