• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.23-29
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• 2018

Contrail is type of clouds which are formed by a condensation of water vapour from the aircraft exhaust when the aircraft is flying the cold atmosphere. Since contrails have considerable effect on greenhouse-effect and military stealth efficiency, researches about contrail avoidance technology has been conducted for decades. However, none of the previous researches concerning contrail avoidance was carried out in Korea. Thus, review of the previous study regarding contrail reduction is absolutely needed. In this paper, researches conducted by several countries are categorically introduced, and practicabilities of their methods are analyzed. This paper also suggests some practical and systematized way to conduct future researches about contrail avoidance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.1
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• pp.47-57
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• 2022

UAVs have been deployed various missions such as deception, reconnaissance and attack since they have been applied in battlefield and achieved missions successfully instead of man. In the past, it is impossible for UAVs to conduct autonomous missions or cooperative mission between manned aircraft due to the limitation of the technology. However, theses missions are possible owing to the advance in communication and AI Technology. In this research, we identified the possible cooperative missions between manned and unmanned team based on air-to-air mission. We studied cooperative manned and unmanned tactics about fighter sweep mission which is the core and basic operation among various air-to-air missions. We also developed cooperative tactics of manned and unmanned team by classifying nonstealth and stealth confrontational tactics. Hereafter, we verified the validity of the suggested tactics using computer simulations.

• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.3
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• pp.311-318
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• 2024

In this paper, a design for a radio frequency(RF) and infrared(IR) absorber with metasurfaces is discussed in microwave frequency bands. The RF absorber includes double layers of metasurfaces to operate in S- and X-bands. Effects of sheet resistance of the metasurfaces and thicknesses of dielectric supporting layers on reflection responses are investigated. An IR stealth layer incorporates an array of conductive grids with slits to reflect IR signals but to transmit RF signals and visible rays. Periodicity of the grids and slits is studied for transmission responses in the X-band and a surface area ratio. Reflection responses of the RF/IR multispectral absorber are found to be lower than -10 dB and -16 dB in the S- and X-bands, respectively, from full-wave simulation. Finally, the RF/IR multispectral absorber is fabricated and its reflection responses are measured to verify designed performance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.4
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• pp.297-305
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• 2018

The role of UCAV is to carry out various missions in hostile situations such as penetration and attack on the enemy territory. To this end, application of RF stealth technology is indispensable so as not to be caught by enemy radar. The X-47B UCAV with blended wing body configuration is a representative aircraft in which modern RCS reduction schemes are heavily applied. In this study, a model UCAV was first designed based on the X-47B platform and then an extensive RCS analysis was conducted to the model UCAV in the high-frequency regime using the Ray Launching Geometrical Optics (RL-GO) method. In particular, the effects of configuration of UCAV considering IR reduction on RCS were investigated. Finally, the effects of RAM optimized for the air intake of the model UCAV were analyzed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.3
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• pp.317-325
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• 2016

This paper describes the technique for Radar Particle filter for TBD(Track Before Detect) processing. TBD technique is applied when target is difficult to detect due to low signal-to-noise ratio caused by strong clutter environments, small RCS targets and stealth targets. Particle filter is suitable for a recursive TBD algorithm and has improved estimation accuracy than Kalman filter. In this paper, we will present a new method of calculating particle weight, when observation values(including strong clutter) are received at the same time. Estimation error performance of the particle filter algorithm is analyzed by using the virtual radar observation scenario.

• Journal of Advanced Navigation Technology
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• v.15 no.3
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• pp.378-385
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• 2011

This paper introduces technical aspects of the privacy exposure problem of the video and the audio information on the personal computer and proposes a countermeasure to them. According to the increased number of peripherals for computers, especially including the cameras and the mikes, it is required to be careful on the privacy exposure. Currently, some incorporated or standalone cameras have a pilot lamp to indicate their usage. However, many other cameras and all mikes have not equipped with the pilot lamp or other dedicated indicator. Even though this problem doesn't obstruct their assigned functionalities, it should make the devices susceptible to be exposed with the information they are gathering without any notice to the owners. As a countermeasure to the problem, this paper proposes a reasonable solution that alarms the access trials to the devices and implements programs for the practical sniffing and its counterpart.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.6
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• pp.11-20
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• 2019

A Radome protects the radar from the external environment, and as a part of the stealth technology, a frequency-selective surface (FSS) was applied to the radome. Our study investigates the changes in the electrical transmission characteristics of the missile's FSS radome due to aerodynamic heating in various flight scenarios. Accordingly, we designed a FSS radome with a Jerusalem-cross(JSC) geometry and referred the missile flight scenario in the precedent research. Subsequently, electrical transmission characteristics affected by aerodynamic heating were numerically analyzed over time according to the position of radome. As a result, we found that the average transmission value maximally varies -14.3 dB compared to the initial bandwidth owing to changes in electrical transmission characteristics in flight scenarios.

• The Journal of the Acoustical Society of Korea
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• v.33 no.6
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• pp.366-374
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• 2014

With the advent of submarine detection technology using low-frequency active sonar there is a call for a new submarine stealth device that can replace the existing passive anechoic tiles. Proposed in this study is a low-frequency echo reduction technique based on active impedance matching, which employs a tile projector designed to cover a wide area such as the surface of a ship. To judge the feasibility of the active impedance matching technique finite-element simulations of low-frequency echo reduction are performed. Based on the analysis, a tile projector is designed, fabricated, and tested in an acoustic tank for its low-frequency echo reduction performance.

• Journal of Convergence for Information Technology
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• v.11 no.12
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• pp.97-105
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• 2021

Countries such as the United States, Russia, and Europe are developing and operating UAVs for various purposes, including stealth UAVs. North Korea is also operating unmanned aerial vehicles, and it is presumed that it is continuously flying south of the demarcation line to obtain information on the national security zone, but it is difficult to detect and neutralize it effectively. Therefore, this paper analyzed the military UAV development trends and military radar specifications in Western countries such as the United States and communist countries such as Russia, China, and North Korea through literature research. In addition, based on the investigation of the AESA radar-based UAV response system in the country, not only general responses but also countermeasures such as direct strike and electromagnetic pulses to North Korean UAVs that cannot be jammed were suggested.

• Convergence Security Journal
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• v.19 no.1
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• pp.49-60
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• 2019

Medical record is part of the personal information that values the dignity and value of an individual, and can lead to serious social prejudice and disadvantage to an individual when it is breached illegally. In addition, the medical record has been highly threatened because its value is relatively high, and external threats are continuing. In this paper, we propose a medical record sharing framework that guarantees patient's privacy based on blockchain using ciphertext policy-based attribute based proxy re-encryption scheme. The proposed framework first uses the blockchain technology to ensure the integrity and transparency of medical records, and uses the stealth address to build the unlinkability between physician and patient. Besides, the ciphertext policy attribute-based proxy re-encryption scheme is used to enable fine-grained access control, and it is possible to share information in emergency situations without patient's agreement.