• Special Issue of the Society of Naval Architects of Korea
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• 2006.09a
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• pp.23-33
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• 2006

Generally wave buoy and visual observation are used to measure sea waves. But the wave buoy cannot be applicable for the ship moving in deep sea. So the visual observation has been used for it. But it has several defects and limitation related to environmental condition and observer. To overcome this problem, various wave measurement systems have been suggested. Recently, the wave measurement systems using nautical X-band radar have been developed and extended its application area. In this report, we introduce the wave measurement system, WaveFinder, developed by authors. The system was calibrated and verified with the measurement results of wave buoy. The system was adopted to measure wave condition during sea trials. The system will be a device to support safe navigation in ship's voyage.

• Korean Journal of Remote Sensing
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• v.40 no.2
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• pp.141-150
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• 2024

Ground subsidence in urban areas is mainly caused by anthropogenic factors such as excessive groundwater extraction and underground infrastructure development in the subsurface composed of soft materials. Global Navigation Satellite System data with high temporal resolution have been widely used to measure surface displacements accurately. However, these point-based terrestrial measurements with the low spatial resolution are somewhat limited in observing two-dimensional continuous surface displacements over large areas. The synthetic aperture radar interferometry (InSAR) technique can construct relatively high spatial resolution surface displacement information with accuracy ranging from millimeters to centimeters. Although constellation operations of SAR satellites have improved the revisit cycle, the temporal resolution of space-based observations is still low compared to in-situ observations. In this study, we evaluate the extraction of a time-series of surface displacement in Incheon Metropolitan City, South Korea, using the small baseline subset technique implemented using the commercial software, Gamma. For this purpose, 24 COSMO-SkyMed X-band SAR observations were collected from July 12, 2011, to August 27, 2012. The time-series surface displacement results were improved by reducing random phase noise, correcting residual phase due to satellite orbit errors, and mitigating nonlinear atmospheric phase artifacts. The perpendicular baseline of the collected COSMO-SkyMed SAR images was set to approximately 2-300 m. The surface displacement related to the ground subsidence was detected approximately 1 cm annually around a few Incheon Subway Line 2 route stations. The sufficient coherence indicates that the satellite orbit has been precisely managed for the interferometric processing.

• Journal of electromagnetic engineering and science
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• v.8 no.3
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• pp.110-113
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• 2008

In this paper, we designed and fabricated an electromagnetic(EM) wave absorber for automotive radar in cars using $TiO_2$ as a dielectric material and chlorinated polyethylene(CPE) as a binder. First of all, we confirmed that the optimum composition ratio of $TiO_2$ was about 70 wt.%. The complex relative permittivity of a sample containing $TiO_2$: CPE=70:30 wt.% was calculated from S-parameter. The EM wave absorption abilities were simulated for the EM wave absorbers of different thickness using the calculated relative permittivity, and the EM wave absorber was manufactured based on the simulated design. A comparison of simulated and measured results is in good agreement. Measurement shows that a 1.85 mm thick absorber has absorption ability higher than 20 dB in the frequency range of $76{\sim}77$ GHz for automotive radars.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.4
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• pp.39-49
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• 2006

LYNX ESM has not only ESM function but Datalink function. The LYNX boarded equipment Interface and Channel coding is needed for LYNX Datalink to support the mother ship with tactical data included threat radar analysis data of LYNX ESM, navigation data, Radar and Sonar of LYNX. The interface of loaded equipments are various protocol like as ARINC419/429, RS232, Synchro, Sync Serial. The Channel coding of Convolution-Scrambler-Interleaver-Bit Stuffing is applied for recovering the transmission data mixed with propagation errors in sea environment.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.2
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• pp.13-17
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• 2012

The solar storm generated by solar activity can be impact on earth in various area. If solar storm impact on Navaids system, it will be a serious problem for aviation and human safety. The impact analysis of solar strom on Navaids system are performed in three area, ILS, GPS navigation and radio communication for aviation. Analysis result show that Instrument Landing System(LLZ, GP, MB) and Navaids system(VOR, DME, Radar) are not impacted by the solar storm, but GPS system is impacted by solar storm. Also analysis result show that VHF/UHF radio system are not impacted by solar storm, but HF radio system is impacted by solar storm.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.435-440
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• 2006

The Reduced Vertical Separation Minimum (RVSM), which is the reduced minimum from 2,000 ft to 1,000 ft at flight levels (FL) between 290 and FL410 inclusive, was implemented in 30 September 2005 within the Japanese domestic airspace. Prior to the implementation, safety assessment for the airspace in assumed RVSM environments was carried out. Some model parameter values of collision risk model were estimated using flight plan (progress) data and radar data. An estimate of vertical collision risk including operational risk was calculated using these together with given parameter values. The results obtained from this analysis are as follows. (1) Contribution of the vertical collision risk for the crossing routes is about 9 percents of the total technical risk. (2) The estimate of the collision risk is $4.1{\times}10^{-9}$ [fatal accidents / flight hour] and the value is smaller than a maximum allowable level of collision risk, i.e. $5{\times}10^{-9}$ [fatal accidents / flight hour], called the Target Level of Safety.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.2
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• pp.177-184
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• 2023

In order to reserve frequency bands for stable operation of the Korean Positioning System (KPS), it must be demonstrated that the impact of interference caused by KPS on other services operating in the same bands is tolerable. The International Telecommunication Union (ITU) provides the radio regulations and a compatibility assessment methodology for the coexistence of different services in limited frequency resources. The purpose of this paper is to investigate the radio regulations regarding the compatibility issues between the KPS and other services sharing the same frequency bands. The results of the investigation show that the RNSS system can be operated in the L5-band under the condition that the Power Flux Density (PFD) and Aggregated Equivalent PFD (AEPFD) thresholds specified in the radio regulations are met. In addition, the ITU recommends that the interference-to-noise ratio (INR) protection criteria be met to prevent degradation of the performance of radar systems operating in the L2/L6-band. In the case of the S-band, coordination of allocations for RDSS space stations with respect to terrestrial services is not required if the PFD does not exceed regulated thresholds regulated by ITU.

• Journal of Astronomy and Space Sciences
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• v.37 no.2
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• pp.105-115
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• 2020

The Korean Institute of Technology Satellite (KITSAT-1) is the first satellite developed by the Satellite Technology Research Center and the University of Surrey. KITSAT-1 is orbiting the Earth's orbit as space debris with a 1,320 km altitude after the planned mission. Due to its relatively small size and altitude, tracking the KITSAT-1 was a difficult task. In this research, we analyzed the tracking results of KITSAT-1 for one year using the Midland Space Radar (MSR) in Texas and the Poker Flat Incoherent Scatter Radar (PFISR) in Alaska operated by LeoLabs, Inc. The tracking results were analyzed on a weekly basis for MSR and PFISR. The observation was conducted by using both stations at an average frequency of 10 times per week. The overall corrected range measurements for MSR and PFISR by LeoLabs were under 50 m and 25 m, respectively. The ionospheric delay, the dominant error source, was confirmed with the International Reference of Ionosphere-16 model and Global Navigation Satellite System data. The weekly basis orbit determination results were compared with two-line element data. The comparison results were used to confirm the orbital consistency of the estimated orbits.

• Journal of Navigation and Port Research
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• v.35 no.9
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• pp.729-733
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• 2011

The maritime risk assessment is important not only to evaluate the safety level of the ports and waterways but also to reduce potential maritime accidents at sea in terms of the proactive measures of the maritime accidents. In this paper, the collision risk assessment in Mokpo waterways has been carried out based on the IALA recommended model, IWRAP. To evaluate the accident probabilities in Mokpo waterways, all data of vessels were collected from AIS and Radar observations data and the computer simulations were carried out. To assess the risk on the traffic, the scenario-base approach has been applied to the Mokpo waterway by using the maritime accident statics over the past 5 years.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.276-278
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• 2016

해상교통관제는 RADAR, AIS, CCTV 등 수많은 장비로부터 얻을 수 있는 정보들을 관찰, 판단, 해석하는 상황인식 과정을 거쳐 이를 바탕으로 선박 안전운항에 필요한 '정보제공, 조언 권고, 지시'를 무선통신기기(VHF무선전화)를 통해 전달하는 일련의 과정이다. 선박과의 최종적인 정보교환체계인 무선통신기술은 과학기술의 발전에 힘입어 꾸준히 발전되고 개선돼 오고 있지만, 여전히 많은 한계점들을 내재하고 있다. 이 글을 통해 VHF를 통한 해상교통관제의 한계점들에 대해 알아봄으로써 관제사들의 VHF에 대한 특성 및 한계점에 대한 이해를 돕고 이를 극복하기 위한 방안들을 제시하고자 한다.