• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.4
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• pp.21-30
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• 2012

This paper presents site survey processes and the results for installing GBAS Category-I ground system into Gimpo international airport. For siting assessment, many things should be taken into account in advance, such as installation requirement of GBAS components, future airport development plan and possible interference effects to existing facilities. Because overall performance of GBAS system can be affected by GPS signal reception environment, on-site survey should be performed carefully to measure actual GPS environmental performance and determine if any adverse multipath or RFI problems exist or not. In addtion, VDB antenna should be located to ensure line of sight for transmitting VHF signal to deliver GBAS message to aircraft. Based on the survey results, final location for GBAS system installation is selected near runway 32 in the Gimpo airport.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.3
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• pp.71-77
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• 2005

An unmanned aerial vehicle (UAV) is generally flied via a pre-planned flight path or real-time commands by an operator. To succeed in an assigned mission, analysis such as the line-of-sight analysis for communication between UAV and a ground data terminal should be performed. In this paper, various analysis algorithms which are performed by a ground control station in pre-flight and in-flight phases, are proposed for the safe flight of UAV. Note that the proposed algorithms can be applied to most UAV systems.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.11a
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• pp.100-102
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• 2023

항로추종성능은 자율운항선박(MASS)의 중요한 자율제어기능 중 하나이다. 이는 선박의 안전성을 보장하기 위해 중요하며, 자율운항선박의 설계 단계에서 사전 평가가 필수적이다. 본 연구는 자율운항선박의 항로추종성능 평가를 위한 전산유체역학(CFD) 모델과 LOS 알고리즘 연계 방안을 제안한다. 먼저, 자율운항선박의 정수 중 거리 이탈 편차를 이용한 항로 추종 성능 평가 모델 개발에 관하여 기술했다. 먼저, 항로 추종을 수행하는 선박 주변의 난류 흐름은 비압축성 뉴턴 유체의 가정하에 비정상 RANS(Reynolds Averaged Navier-Stokes) 법을 이용하여 수치적으로 계산되었다. 중첩격자계법을 CFD 모델에 적용함으로써 거리 이탈 편차를 이용하는 LOS(Line-of-Sight) 가이던스 알고리즘에 의한 타의 회전 및 이에 따른 선체의 6 자유도 움직임을 CFD 환경에서 구현하였다. 개발된 자유 항주 선박 CFD 모델을 이용하여 항로 추종 시뮬레이션 평가 결과, 설정된 항로에서 선박의 정수 중 항로 추종 제어는 파도, 조류, 및 바람과 같은 외부 교란의 부재로 LOS 알고리즘에 의한 우현/좌현 측 변침뿐만 아니라 직진 경로의 추종도 성공적으로 수행됨을 확인하였다. 선체, 프로펠러, 타의 복잡한 상호작용을 정도 높게 해석할 수 있는 자유 항주 선박 CFD 모델과 LOS 알고리즘의 결합은 자율운항선박의 항로 추종 성능 평가를 정량적으로 평가하는 데 기여할 것으로 기대된다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.12
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• pp.987-995
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• 2020

Accurate alignment between high-performance payloads and attitude control sensors is essential factor to guarantee accurate attitude orientation and high pointing stability of the satellite. Space craft developers often use theodolite measurement system for satellite alignment during ground AIT(Assembly Integration and Test) phase. When measuring theodolite, errors may occur due to line of sight error, tilting axis error, vertical index error, and vertical axis error. In addition, errors that can occur during alignment measurements with multiple theodolites are analyzed through the alignment cube measurements test. Based on the alignment cube measurements test, a technical method that can improve the alignment measurement accuracy was suggested and it's measurements results satisfied the satellite design requirements.

• Journal of the Korean Institute of Landscape Architecture
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• v.45 no.6
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• pp.160-170
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• 2017

As a monumental building in the form of an arch, an archway has the characteristics of praise and honor. More and more historic, cultural and social connotations are given during the development of history. Four archways that are located on the middle route of the Red Gate Palace in the Mount Tai Scenic Area were chosen for research. Based on a literature review and field investigation with a visual analysis method, the physical attributes, spatial scale, perceptions and functions of the archways were discussed. The results were as follows: The archways in the research area are all made of stone. According to building location, they are classified into two types: Cultural archway and temple archway. Regarding functions, they are divided into symbolic archway, memorial archway and portal archway. From the point of view of form and scale, the Confucius Boarding Archway enjoys a higher standard than the other three. This reflects the importance of Confucian culture on Mount Tai. Regarding spatial scale, the archway becomes the focus in a restrictive linear space by an object-to-object and person-to-object comparison. Visitor experience of crossing the archways is strongly enhanced as it acts as entrance and exit, and it has the function of guiding sight since the arrangement of the archways further extend the line of sight. Couplets and inscriptions on the archways increase a sense of expectation for visitors on their way to the top of Mount Tai.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.4
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• pp.97-110
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• 2007

A laser scanning technique has been attracting much attention as a new technology to acquire location information. This technique might be applicable to a wide range of areas, most notably in geomatics, due to its high accuracy of location and automation of high-density data acquisition. A alignment information extraction system on highway has been developed in this study by utilizing the advantages of the laser scanning technique. The system can accurately interpret the alignment information of highway and can be applied to actual works. To develop the alignment information extraction system on highway, an algorithm that can automatically separate a horizontal alignment into a straight line, a transition curve, and a circular curve was developed. It can increase its efficiency compared to the conventional methods. In addition, an algorithm that can automatically extract design elements of horizontal and vertical alignments of highway was developed and applied to an object highway. This yielded higher practicality with more accurate values compared to those from previous studies on the extraction of design elements of highway alignment. Furthermore, the extracted design elements were used to perform a virtual driving simulation on the object highway. Through this, data were provided for a visual judgment for judging visually whether the topography and structures were harmonized in a three-dimensional manner or not. The study also presents data that can serve as a basis to determine highway surface freezing sections and to analyze three-dimensional sight distance models. Through the establishment of a systematic database for diverse data on highway and the development of web-based operating programs, an efficient highway maintenance can be ensured and also they can provide important information to be used when estimating a highway safety in the future.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.374-388
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• 2016

In Jeju-Do, there is the 1100 Road, 516 Road, and Bijarimro, which are typical mountain sight-seeing roads in Jeju. These roads are local roads that have been the location for many traffic accidents. This study focused on these roads, categorized the type of traffic accident and analyzed the accident characteristics. The major accident factors were analyzed through trip AHP analysis, Comparative analysis of the velocity distribution and the factors affecting traffic accidents were analyzed. Tourists took many trips on these roads. The mixing rate of the rental cars was 36.70%~71.60% in 1100 road and Bijarimro. Currently, these local roads are regulated by a speed limit of 60km/h. However, it might be necessary to reduce the speed limit to 40km/h considering the geometric line form of the road and the climate in these areas. The speed limit of more than 40km/h is found 87.0% on 516 Roads, 88.57% on 1100 roads, and 93.1% on Bjarimro, In these roads, the speed ratio is higher as described above. Therefore, these roads have been found to have a higher risk of traffic accidents by overspeeding driving. The overspeed driving ratio of these roads was 87.0%~93.1%, The overspeed driving enforcement method at one spot has only the effect of reducing the speed at that enforcement place; the effect cannot be expected for the other places or sections. It is necessary to introduce a section overspeed driving enforcement system utilizing the average velocity in these areas to prevent traffic accidents.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10A
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• pp.1014-1019
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• 2006

The research deals with the measurement of electromagnetic wave propagation in subway tunnels at 2.65GHz. Measurements have been conducted in 4 different types of tunnel courses, a straight tunnel, two curved tunnels, with 245m and 500m radius of curvature, and a tunnel that has both straight and curved sections. we found that the path loss exponent for the line-of-sight(LOS) region inside all the tunnels is $1.31{\sim}2.19$. The path loss exponents for LOS regions in the tunnel is lower than $(3{\sim}4)$, which corresponds to the path loss exponent factor for outdoor cellular environments. The path loss exponents of the straight tunnel, two curved tunnels with 245m and 500m radius of curvature are 1.94, 2.92, and 4.34, respectively. This indicates that a smaller radius of curvature in tunnel results in a higher path loss exponent for nonline-of-sight(NLOS) region. The path loss exponents for the NLOS region in the combined and curved tunnel, which have the same radii of cuvature, are 5.88 and 4.34, respectively. Therefore, it can be concluded that the path loss characteristics in tunnel environments are infulenced by the radii of curvature as well as the LOS distance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.5 s.108
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• pp.430-439
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• 2006

This paper presents the a measured path-loss characteristics for mobile communications beyond 3G in microcellular residential area and street microcell at 3.4, 5.3, and 6.4 GHz band signals. The residential area is divided into two sections, one of which is composed of fifteen-story appartment buildings. The other section comprises four-story houses. The street microcell is classified line-of-sight(LOS) and nonline-of-sight(NLOS) areas. Both residential areas have standard deviations independent of the residential area classification, whereas the path loss exponents in the apartments is higher than those in area for same frequencies. A two-ray model is applied to analyse the path-loss charateristics in LOS areas. In LOS areas, an empirical breakpoint, whose distance is 6 percent shorter than a theorical breakpoint, is founded. Further, a sudden power level drop occurs at a transition point from LOS region to NLOS area. Path loss exponent is found to be significantly higher for non-LOS region than for LOS region. The power level drop due to corner loss and path-loss exponents both increase as the distance between the transmitter and the corner increases.

• Journal of Astronomy and Space Sciences
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• v.18 no.1
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• pp.33-42
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• 2001

In the spectrum of the young bipolar planetary nebula M2-9 obtained from the 1.5m telescope at the Cerro Tololo Inter-American Observatory, we detected the He II feature at 6545 $\AA$ that are proposed to be formed via Raman scattering by atomic hydrogen. However, in the same spectrum, the He II emission lines at 6527 $\AA$ and 6560 $\AA$ are absent, which implies that the He II emission region is hidden from our line of sight and that the H I scattering region is pretty much extended not to be obscured entirely. We performed photoionization computations to estimate the physical size of the He II emission line region to be $10^{16}cm$, from which the location and dimension of the obscuring circumstellar region are inferred and the temperature of the central star must exceed $10^5K$. The angular size of the circumstellar region responsible for the obscuration of the He II emission region is ~1" with the assumption of the distance 01 kpc to M2-9, which is consistent with the recent image of M2-9 obtained with the Hubble Space Telescope.