• 한국정보통신학회논문지
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• 제11권3호
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• pp.459-464
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• 2007

ITU-R 결의 122는 47/48GHz 대역에서 위성 우주국 수신기와의 주파수 공유를 위해 HAPS 지상국에 대한 전력 제한에 대한 연구를 요구하고 있으며, ITU-R 권고 SF.1481-1에서는 FSS 시스템과의 주파수 공유를 위해 HAPS 지상국의 안테나 방사 패턴의 사이드 로브 특성을 개선하도록 권고하고 있다. 이에 본 논문에서는HAPS 및 GSO FSS 서비스 커버리지간 비현실적인 이격거리를 줄이면서 결의 122에서 요구하고 있는 HAPS 지상국에 대한 전력 제한 및 권고 SF.1481-1의 지상국 안테나 사이드 로브 개선 등을 고려한 지상국의 최대 허용 off-axis e.i.r.p. 레벨을 제안함으로써 HAPS 지상국과 FSS 위성 수신기간의 주파수 공유의 가능성을 보인다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2006년도 춘계종합학술대회
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• pp.611-614
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• 2006

ITU-R 결의 122는 47/48GHz 대역에서 위성 우주국 수신기와의 주파수 공유를 위해 HAPS 지상국에 대한 전력 제한에 대한 연구를 요구하고 있으며, ITU-R 권고 SF.1481-1에서는 FSS 시스템과의 주파수 공유를 위해 HAPS 지상국의 안테나 방사 패턴의 사이드 로브 특성을 개선하도록 권고하고 있다. 이에 본 논문에서는 HAPS 및 GSO FSS 서비스 커버리지간 비현실적인 이격거리를 줄이면서 결의 122에서 요구하고 있는 HAPS 지상국에 대한 전력 제한 및 권고 SF.1481-1의 지상국 안테나 사이드 로브 개선 등을 고려한 지상국의 최대 허용 off-axis e.i.r.p. 레벨을 제안함으로서 HAPS 지상국과 FSS 위성 수신기간의 주파수 공유의 가능성을 보인다.

• 조명전기설비학회논문지
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• 제24권12호
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• pp.91-99
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• 2010

HVDC converter station consists of a number of equipment such as converter transformer, ac filter, thyristor valve and so on. They can be acoustic noise sources. In this paper, we analyzed the simulation results of the outdoor acoustic noise for HVDC converter station. It shows that maximum noise level in boundary of HVDC converter station exceeds regulation value. The main factors in generating maximum noise level are ac filter and converter transformer. Then we applied some soundproof countermeasures in HVDC converter station. Shielding wall is enough to reduce transformer noise level but not enough to reduce ac filter noise level. In case of ac filter, soundproof building is effective in satisfying noise level regulation in boundary of HVDC converter station. In addition, we also studied effects of season, soundproof woods, ground.

• Journal of Astronomy and Space Sciences
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• 제28권4호
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• pp.299-304
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• 2011

As more satellites are designed to downlink their observed image data through the X-band frequency band, it is inevitable that the occupied bandwidth of a target satellite will overlap with that of other X-band downlink satellites. For sun-synchronized low earth orbit satellites, in particular, it can be expected that two or more satellites be placed within the looking angle of a ground station antenna at the same time. Due to the overlapping in the frequency band, signals transmitted from the adjacent satellites act as interferers, leading to degraded link performance between target satellite and ground station. In this paper, link analysis was initiated by modeling the radiation pattern of ground station antenna through a validated Jet Propulsion Laboratory peak envelope model. From the relative antenna gain depending on the offset angle from center axis of maximum antenna directivity, the ratio of received interference signal level to the target signal level was calculated. As a result, it was found that the degradation increased when the offset angle was within the first point of radiation pattern. For a 7.3 m antenna, serious link degradation began at an offset angle of 0.4 degrees. From this analysis, the link performance of the coming satellite passes can be recognized, which is helpful to establish an operating procedure that will prevent the ground station from receiving corrupted image data in the event of a degraded link.

• 한국기계기술학회지
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• 제13권1호
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• pp.11-16
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• 2011

When the trains are passed the station, a serious force is applied to ground and the caused vibration is propagated to the area of the station by the ground and rocks. The caused vibration brings about the operation interruption of the equipment which is sensitive to the vibration, or will bring about the structural damage of the station. In this study, to investigate the vibrational evaluation of railway station by the train service, the vibration simulation was performed and analyzed the effect of the vibration isolating countermeasure. From the vibration measurement, all trains that passed through the station exceeded the vibration criteria. Therefore, the vibration isolating countermeasure was established and the vibration simulation was performed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 하계학술대회 논문집
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• pp.574-576
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• 2010

HVDC converter station consists of a number of noise sources such as converter transformer, ac filter, cooling system and so on. In this paper, we analyzed the simulation results of the outdoor acoustic noise characteristics for HVDC converter station. It shows that maximum noise level in boundary of HVDC converter station exceeds regulation value. The main factors in generating maximum noise level are ac filter and converter transformer. Then we applied some soundproof countermeasure in HVDC converter station. Shielding wall is enough to reduce transformer noise level but not enough to reduce ac filter noise level. In case of ac filter, soundproof building is effective in satisfying noise level regulation in boundary of HVDC converter station. In addition, we also studied effects of season, soundproof woods, ground.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
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• pp.41-48
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• 2000

We have installed the borehole seismic recording system at Hyodongri in eastern part of Kyungsan Basin, which has the advantages of reduction in noise by human activities and distorting effects of near-surface rocks. Here we describe briefly the borehole seismic station and recording system. And we analyse the characteistics of back ground the station obtained from borehole sensors. The back ground noise level in time domain is about 50~100$\mu$cm/sec. The average curve of noise spectrum is lower than NHNM(New High Noise Model)of GSN(Global Seismic Network)operated by USGS. The results could be useful prior information for study on earthquake records observed at Hydongri station.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.500-503
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• 2007

During the COMS system level test, the RF compatibility will be performed in order to verify that there is no issue in RF interface between satellite and COMS ground station, namely SOC (Satellite Operation Center) before the launch. As used for KOMPSAT1, the RF coaxial cable was chosen to be used to connect satellite and SOC with various advantages as compared with ground antennas. As the preparation step, RF cable and required multiplexer were tested in advance. This paper suggests the way for the RF compatibility tests between the satellite and the SOC over RF cable interface and presents the estimated level diagram as the signal power analysis result.

• Geomechanics and Engineering
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• 제21권2호
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• pp.143-152
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• 2020

Korean society experienced successive earthquakes exceeding 5.0 magnitude in the past three years resulting in an increasing concern about earthquake stability of urban infrastructures. This study focuses on the significant aspects of earthquake risk assessment for the cut-and-cover underground railway station based on two-dimensional dynamic numerical analysis. Presented are features from a case study performed for the railway station in Seoul, South Korea. The PLAXIS2D was employed for numerical simulation and input of the earthquake ground motion was chosen from Pohang earthquake records (M5.4). The paper shows key aspects of earthquake risk for soil-structure system varying important parameters including embedded depth, supported ground information, and applied seismicity level, and then draws several meaningful conclusions from the analysis results such as seismic risk assessment.

• 항공우주기술
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• 제7권2호
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• pp.176-186
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• 2008

COMS RF호환성 시험에서 단일 동축 선로가 사용되도록 결정됨에 따라 서로 다른 주파수의 신호를 하나의 이동경로에서 교환될 수 있도록 하는 RF지원 장비가 필요하게 되었다. 이러한 RF지원 장비는 단일 동축 선로와 연동하여 정상운영에서의 위성과 지상국간의 경로손실을 모사 할 수 있어야 한다. RF지원 장비의 설계를 위해 우선 각 단품들의 측정데이터를 반영한 level diagram을 수행하였고 이로부터 위성과 지상국간의 통신환경을 적절히 모사 할 수 있음을 확인하였다. RF지원 장비가 조립된 후에 수행된 시험을 통해서 tunable attenuator를 이용하여 위성의 MODCS와 TC&R에서 요청한 input dynamic range 가 만족됨을 확인하였다. 현재 완성된 RF지원 장비는 향후 예정된 COMS RF 호환성 시험에서 사용될 것이다.