• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.5
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• pp.335-342
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• 2020

Tailless aircraft designed for stealth efficiency uses spoilers instead of rudders for the directional control. When the spoiler is rapidly deployed, highly nonlinear and unsteady aerodynamic characteristics can be generated, resulting in adverse effects on aircraft flight performance. This paper investigates the aerodynamic characteristics of an airfoil with moving spoiler using dynamic mesh CFD technique. The effects of spoiler operation speed, mounting location, and deployment scheduling are analyzed to reduce the adverse effects of the spoiler's dynamic operation. The results shows that the adverse effects of dynamic spoiler can be reduced by appropriate selection of the spoiler mounting location and deployment scheduling.

• The Journal of the Korea Contents Association
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• v.6 no.9
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• pp.85-97
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• 2006

Schemes to case analysis and cope with on-line game crimes net supervision system, a real name confirmation process, and a self-examination system to check by themselves if they are addicted to on-line games with a view to prevent the addiction. In addition, this study found that general precuations should comprise measures to change the awareness of the users of the internet and to establish their ethical senses because most on-line garners are not aware that their actions are a crime and believe their crimes are not disclosed to the outsiders.

• 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.

• Journal of The Korean Association For Science Education
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• v.32 no.2
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• pp.346-371
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• 2012

The purpose of this study is to investigate the possibilities of science ethics education with history of science (HOS) and to develop its teaching and learning model for secondary school students. A total of 72 cases about science ethics were extracted from 20 or more HOS books, journal articles, and newspaper articles. These cases were categorized into 8 areas, such as forgery, fabrication, violation of bioethics in testing, plagiarism and stealth, unfair allocation of credit, over slander, conjunction with ideologies, and social responsibility problems. The results of this study are as follows. First, research forgery, occurring in the process of the research, was the most frequent in HOS. Second, we developed eight teaching lesson plans for each area. Third, we proposed a teaching and learning model based on the developed lesson plans as well as related teaching and learning models in the fields of science ethics education, ethics education, and history education. Our model has five steps, 'investigating-suggesting casesclarifying problems-finding alternatives-summarizing'.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.8
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• pp.843-850
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• 2012

To satisfy the operational requirements of surveillance radar and the operational concept of a ship combat system, an active-array-type antenna was designed using solid-state transmitters and receivers. The arrangement of the constituent electronic components of the antenna system, considerably large in size, and therefore, the antenna needs to be housed in a box. The rotational antenna system installed on a ship mast is installed in a sealed housing to protect the interior equipment from environmental conditions. The outer shape of the housing is that the antenna should be capable of rotating normally despite strong winds. Furthermore, in recent times, designs with low radar cross section (RCS) have attracted attention from the viewpoint of improving the stealth of the ship. In this light, four types of models are proposed for the outer shape design of the antenna system, and they are investigated from the viewpoint of low RCS design as well as wind load.

• 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 the Korean Society of Propulsion Engineers
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• v.17 no.5
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• pp.10-17
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• 2013

This paper describes a study on after-burning suppressant in a solid propellant to reduce the plume formed outside of rocket nozzles, which could expose the launch site and the flight track. The minimum smoke propellant to enhance the stealth ability was formulated in terms of the kinds and the effects of after-burning suppressant on the ballistic performance and the amount of primary smoke. A after-burning suppressant, $K_2SO_4$ of about 1.1% weight content was found to show profound reduction of the rocket plume, giving negligibly slight increase in pressure exponent of burning rate. Also minimum smoke propellant with less than 1.1% of $K_2SO_4$ corresponds to A-class satisfaction in primary smoke by AGARD standard.

• 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.

• The Journal of the Acoustical Society of Korea
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• v.30 no.2
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• pp.63-72
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• 2011

Since the detection probability is critically dependent on the target strength (TS) in active sonar and on the radiated noise level (RNL) in passive sonar, the acoustic materials for echo reduction (ER) and transmission loss (TL) are widely used for the stealth of underwater targets. In this paper, a measurement system based on the small water tank, for the frequency range of greater than 30 kHz, is developed and verified using reference targets. In order to design the water tank and the geometry of test samples, a program is developed to calculate the arrival time of interfering signals due to the reflection from water tank walls and also due to the diffraction from the edge of the test samples. Considering all the interfering signals, an optimal experimental configuration for water tank and test samples is designed and used throughout the experiment. Next, the signal processing algorithms to estimate ER and TL are developed based on the measured propagation loss reflecting the geometric spreading characteristics of the transducer. Finally, a set of reference targets such as aluminium plate and perfectly reflecting plate are used in a small water tank to verify the developed measurement system.