• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.113-128
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• 2021

In this paper, we present a simple ground receiving station as an educational method for a satellite system. Our system is produced similarly to the existing fixed ground station in terms of function by using satellite communication technology and related software commonly used in the amateur radio field. In addition, we conducted operation test to receive signals from operating satellites and confirmed the possibility of using them as a way to educate satellite systems, such as understanding ground station systems through satellite reception experience and satellite state information acquisition, and further designing satellite systems.

• Journal of Digital Convergence
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• v.17 no.2
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• pp.187-194
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• 2019

A security company has been proposed for various healthcare systems. However, there are improvements in order to achieve better efficiency and stability in the various protocols presented. The purpose of this paper is to provide cryptanalysis and solution on Vijayakumar et al.'s secure communication scheme for healthcare system using wearable devices. Especially, it is weak against denial of service attack and it does not provide integrity of the transmitted messages. Thereby, this paper proposes a new secure communication scheme to cope from the problems in Vijayakumar et al.'s scheme. It provides authentication and integrity, which could be the security solution against Vijayakumar et al.'s scheme. Furthermore, it also provides a good computational overhead compared to Vijayakumar et al.'s scheme.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.12
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• pp.1039-1047
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• 2017

This paper presents a test development of a Fly-By-Wireless flight control system for a fixed-wing unmanned aerial vehicle (UAV). Fly-By-Wireless system (FBWLS) refers to a system that uses a wireless network instead of a wired network to connect sensors and actuators with a flight control computer (FCC), reducing considerable amount of wires. FBWLS enables to design a much lighter aircraft along with decreased maintenance time and cost. In this research we developed a Zigbee-based FWBLS UAV in which sensors (GPS and AHRS) are wirelessly connected via a FCC to aileron and elevator servo motors. In order to see the effect of time delay due to wireless signal on the flight stability of the UAV, several flight tests were conducted. From the tests, it was confirmed that the effect is minor by comparing the flight response of the FBWLS with the corresponding Fly-By-Wire system.

• Aerospace Engineering and Technology
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• v.12 no.1
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• pp.46-53
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• 2013

In this study, the analysis of electromagnetic environment of goheung aviation center was performed. If the test object has restrictions to be tested in indoor test facility, open area test site can be used to perform EMC test. Open area test site shall have no obstacles that can generate or reflect the electric field so as to prevent the measurement result from being influenced by unnecessary field. Goheung aviation center is surrounded by fields, and has no buildings that can reflect electric field, so the center can be a good candidate for open area test site. Ambient noise at Goheung aviation center was measured, and the result show that the center has good electromagnetic environment to perform EMC test for large volume object.

• Journal of Advanced Navigation Technology
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• v.17 no.5
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• pp.516-523
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• 2013

In this paper, The path loss model of Air Traffic Control(ATC) telecommunication radio channel has been studied at the Incheon International Airport(IIA) with the terminal with two antlers. We measured two frequencies among VHF/UHF channel bands. The transmitting site radiated the Continuous Wave(CW). The propagation measurement was taken using the moving vehicle equipped with receiver and antenna. The transmitting power, frequency and antenna height are the same as the current operating condition. The path loss exponent and intercept parameters were extracted by the basic path loss model and hata model. The path loss exponents at passager terminal areas were 3.32 and 3.10 respectively in 128.2 MHz and 269.1 MHz. The deviation of prediction error is 9.69 and 9.65. The new path loss equation at the terminal area was also developed using the derived path loss parameters. The new path loss was compared with other models. This result will be helpful for the ATC site selection and service quality evaluation.

• Aerospace Engineering and Technology
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• v.2 no.1
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• pp.98-107
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• 2003

In this study, a survey of time synchronization methods between the remote places. Generally, there are many kinds of time synchronization methods for distant places and they can be grouped three categories according to the type of time transfer methods. The three methods are ground based network, GPS/NAVSTAR and geostationary satellite. Especially, the relay base stations for wireless digital communication are operated based on the timing signal service of the GPS/NAVSTAR satellite network. And as the back-up of the timing signal service of the GPS/NAVSTAR, the geostationary satellite based time synchronization method have researched. In this short paper, the brief explanations about each category were presented.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.11
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• pp.1042-1051
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• 2011

In this paper, a total operating environment equipped with onboard wireless communication systems and ground-based mission control systems is proposed for simultaneous operation of multiple UAVs. A variety of operating structures are studied and classified systematically based on types and usages of the components. For each operating system, the strength, weakness and reliability aspects are investigated. Based on these results, a proper operating system configuration is determined and components are developed for mission formation flight. Proposed system can make a formation flight of various UAVs, execute complex missions decentralizing mission to several UAVs and cooperate several missions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.5
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• pp.104-108
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• 2004

The most of the CDMA mobile communication depends on the GPS for the time synchronization. Then, we must prepare alternative system against the unusable GPS like a unexpectable accident or strategic purpose by the USA government. In this study, we have constructed ground test segment for the time synchronization system using the geostationary satellite. In addition. we have designed, manufactured and tested the transmitting and receiving board to receive 1 PPS signal from atomic clock for transmitting stored data in buffer to satellite modem and to produce 1 PPS signal from satellite modem for measuring time delay.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.5
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• pp.429-436
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• 2017

Since the telemetry performance using the time-delayed data dissipates the wireless channel resources, we propose the spectral efficient retransmission scheme in this paper. In the proposed scheme, the telemetry data is retransmitted based on triggered memory to improve the spectral efficiency. The proposed scheme minimizes the error caused by multipath fading, antenna pattern as well as the error caused by the flight events. In the flight simulation data, we show the proposed scheme improves the telemetry performance based on spectral efficient retransmission.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.228-228
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• 2020

과거 무분별하게 획일화되어 개발되었던 하천 개발 사업으로 인해 수질오염과 생태계 훼손으로 하천의 건천화 현상이 발생함에 따라 최근 하천복원 사업이 적극적으로 계획·추진되고 있다. 수생태계의 건강성과 종적 연속성을 회복하기 위한 하천복원사업에 앞서 하천환경의 현상태에 대한 평가는 매우 중요한 부분이다. 유럽과 미국에서는 드론을 활용하여 하천관리 및 재해 피해조사가 활발하게 이루어지고 있었다. 국내의 센서기술과 무선통신 기술의 발전으로 인해 실시간 수집 가능한 정보의 범위가 늘어남에 따라 국내 하천환경 분야에서는 드론을 활용하여 획득된 원격탐사(RS) 자료와 지리정보 데이터베이스를 접목한 하천 공간조사 연구가 증가하고 있는 추세이다. 본 연구에서는 2019년 국토부에서 제시한 하천환경 평가체계에 따라 국내 도시하천중 하천복원사업을 시행하였던 청미천 지역에 대해 현장 조사와 UAV 영상, 항공영상을 활용하여 하천환경평가 결과를 비교하고자 한다. 하천환경평가체계 지침서는 캐나다(2013) 온타리오 하천평가기법을 참조하였으며, 급경사/중경사/완경사로 구분되며 사전조사와 현장조사 야장으로 구성되나 본 연구에서는 물리 평가지표만을 대상으로 하였다. UAV를 이용하여 촬영한 영상을 PIX4D 프로그램을 활용하여 정합한 후 획득된 색체정보를 활용하여 하천환경평가를 실시하였으며, 항공영상은 국토지리정보원의 국토정보플랫폼 국토정보맵에서 다운받은 자료를 활용하였다.