• 한국항공우주학회지
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• 제44권7호
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• pp.568-575
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• 2016

항공기로부터 방사되는 IR 신호(Infrared : IR)는 전투 생존성 관점에서 예측과 분석이 필요하다. 본 연구에서는 배기 플룸에서 발생하는 IR 신호에 대해 IR 탐지기 관점에서 신호 예측을 수행하였다. 복사 데이터베이스와 이를 활용하는 Line-By-Line 기법을 적용하여 복사 물성치를 해석하고 이를 바탕으로 1차원 Line Of Sight(LOS)에 대해 복사 강도를 해석하였다. 상용 프로그램을 이용하여 노즐의 배기 플룸 열유동장을 해석하였고, 이 플룸 열유동장에 IR 탐지기 관점에서 서로 다른 탐지 각도에 대한 LOS를 설정하여 이에 대한 IR 신호 해석을 수행하였다. 해석을 통해 플룸 내부의 국부적으로 높은 온도 영역을 지나는 LOS에서 강한 IR 신호가 확인되었다. 또한 노즐 벽면을 포함한 LOS에서 가장 강한 IR 신호가 확인되었으며, 이를 통해 고체 벽면에 의한 복사 방사가 IR 신호에 큰 영향을 미치는 것을 확인하였다.

• 한국컴퓨터정보학회논문지
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• 제23권12호
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• pp.11-19
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• 2018

In the Unmanned Aerial Vehicle Line-Of-Sight datalink system, there is a possibility that the communication line is disconnected because line of sight can not be secured by one antenna due to changes in position and posture of the air vehicle. In order to prevent this, both top and bottom of air vehicle are equipped with antennas. At this time, if the signal can be transmitted and received by switching to an antenna advantageous for securing the line of sight, communication disconnection can be minimized. The legacy antenna switching method has disadvantages such that diffraction, fading due to the surface or obstacles, interference and reflection of the air vehicle are not considered, or antenna switching standard is not clear. In this paper, we propose an airborne antenna switching method for improving the performance of UAV LOS datalink system. In the antenna switching method, the performance of each of the upper and lower parts of the mounted antenna according to the position and attitude of the air vehicle is predicted by using the deep learning in an UAV LOS datalink system in which only the antenna except the receiver is duplicated. Simulation using flying test dataset shows that it is possible to switch antennas considering the position and attitude of unmanned aerial vehicle in the datalink system.

• 한국정밀공학회지
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• 제16권7호
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• pp.119-124
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• 1999

A method to find the line of sight ray in space which corresponds to a point in an image plane is presented. The line of sight ray is defined by two points which are the intersections between the two calibration planes and the sight ray. The intersection point is found by the oblique coordinate mapping between the image plane and the calibration plane in the space. The proposed oblique coordinate mapping method has advantages over the transformation matrix method in the required memory space and computation time.

• 한국광학회:학술대회논문집
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• 한국광학회 2005년도 제16회 정기총회 및 동계학술발표회
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• pp.44-45
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• 2005

• 한국통신학회논문지
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• 제36권10B호
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• pp.1240-1245
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• 2011

본 논문에서는 실내 환경에서 LED(Light Emitting Diode)를 이용한 가시광 통신(VLC : Visible Light Communication) 채널의 특성을 모델링 및 분석하였다. LED에서 방사된 광 입자(Photon)의 일부는 직접(LOS : Line Of Sight) 또는 반사(NLOS : None Line Of Sight)의 경로를 거쳐서 PD(PhotoDiode)에 도달하며, 이것은 수신 부에서 시간 지연(delay profile)과 감쇠(attenuation)를 가진 다중 수신 신호 특성을 나타낸다. 가로, 세로, 높이의 크기가 20*8*2.3m로 가정된 실내 환경에서 2개의 LED와 3개의 PD를 사용하여, 각 PD에서 직접파, 반사파에 의한 채널 특성을 컴퓨터 모의실험하고 분석하였다. 채널 모델별 특성은 BPSK 기반의 통신 모의실험을 통하여 그 유용성을 입증하였다.

• Journal of Electrical Engineering and Technology
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• 제2권1호
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• pp.123-128
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• 2007

SPWPM traditional software development is surveyed and essential problems are investigated on the basis of system wireless link considerations. This paper presents the current state software planning tools for wireless LAN link optimization. The software directory is based on combination of MatLab and MapInfo software and measurement which gives the best grouping parameters to build up the software development. Among the requirements assumed, the WLAN site selections must be Line-of-sight (LOS) or near line of sight (NLOS) field strength prediction for either point to point or point to multi points. The results obtainable the out put of the program include two-dimensional (2D) and three dimensional (3D) plots for creating the link; design parameters through GUI representing the height and location for each antenna is depending on K-factor of the area and transmit antenna location.

• 천문학회보
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• 제44권1호
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• pp.56.2-56.2
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• 2019

Measurement of the location of the baryon acoustic oscillation (BAO) feature in the clustering of galaxies has proven to be a robust and precise method to measure the expansion of the Universe. The best constraints so far have been provided from spectroscopic surveys because the errors on the redshift obtained from spectroscopy are minimal. This in turn means that the errors along the line-of-sight are reduced and so one can expect constraints on both angular diameter distance $D_A$ and expansion rate $H^{-1}$. But, future surveys will probe a larger part of the sky and go to deeper redshifts, which correspond to more number of galaxies. Analysing each galaxy using spectroscopy, which is a time consuming task, will not be practically possible. So, photometry will be the most convenient way to measure redshifts for future surveys such as LSST, Euclid, etc. The advantage of photometry is measuring the redshift of vast number of galaxies in a single exposure, but the disadvantage are the errors associated with the measured redshifts. Using a wedge approach, wherein the clustering is split into different wedges along the line-of-sight ${\pi}$ and across the line-of-sight ${\sigma}$, we show that the BAO information can be recovered even for photometric catalogues with errors along the line-of-sight. This means that we can get cosmological distance constraints even if we don't have spectroscopic information.

• Journal of Positioning, Navigation, and Timing
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• 제11권4호
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• pp.361-368
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• 2022

An indoor navigation system that utilizes long-term evolution (LTE) signals has the benefit of no additional infrastructure installation expenses and low base station database management costs. Among the LTE signal measurements, received signal strength (RSS) is particularly appealing because it can be easily obtained with mobile devices. Propagation channel models can be used to estimate the position of mobile devices with RSS. However, conventional channel models have a shortcoming in that they do not discriminate between line-of-sight (LOS) and non-line-of-sight (NLOS) conditions of the received signal. Accordingly, a previous study has suggested separated LOS and NLOS channel models. However, a method for determining LOS and NLOS conditions was not devised. In this study, a machine learning-based LOS/NLOS classification method using RSS measurements is developed. We suggest several machine-learning features and evaluate various machine-learning algorithms. As an indoor experimental result, up to 87.5% classification accuracy was achieved with an ensemble algorithm. Furthermore, the range estimation accuracy with an average error of 13.54 m was demonstrated, which is a 25.3% improvement over the conventional channel model.

• Journal of Advanced Marine Engineering and Technology
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• 제36권1호
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• pp.179-184
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• 2012

기존의 무선 RF 통신은 근거리에서 전력손실이 상대적으로 크고, 전파간섭 및 방해, 재밍 등에 민감하다. 이러한 단점을 보완하는 대안으로 자외선을 이용한 통신 방식에 대한 연구가 최근 관심을 받고 있다. 본 논문에서 자외선을 이용한 비가시거리 통신의 data rate 특성에 대해 시뮬레이션한 결과를 제시하였다. On-off keying 방식을 사용하는 비가시거리 자외선 통신에서 data rate는 송신 빔의 방향, 수신빔의 빔 폭, 송신 전력에 의해 큰 영향을 받는다는 것을 확인하였다.

• 한국정보통신학회논문지
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• 제8권2호
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• pp.232-238
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• 2004

본 논문에서는 각각 2.4㎓ 대역과 5.8㎓ 대역에서 팬빔 안테나, 원형편파 안테나 그리고 지향성 안테나를 사용하여 지하철 터널에서의 전파 특성을 실험하였다. 협대역 채널 측정의 격과, NLOS (Non-Line-Of-Sight) 경로에서 수신전력 레벨이 LOS(Line-Of-Sight)에 비하여 급격히 감소함을 보였다. 광대역채널 측정은 PN sliding correlation 방법을 사용하여 수행하였다. 2.4㎓ 대역과 5.8㎓ 대역을 포함하는 IEEE 802.11 무선랜 대역에서 다양한 지향성 빔에 대한 평균초과지연(mean access delay)과 RMS 지연확산(RMS delay spread) 등의 채널 파라미터를 비교하였다.