• 한국항행학회논문지
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• 제19권3호
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• pp.207-216
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• 2015

SBAS 기준국의 배치는 시스템 성능에 영향을 미치는 가장 중요한 요소 중 하나이므로 기준국 배치가 주어진 성능 요구사항을 만족시킬 수 있는지 시스템 개발 초기에 신중하게 분석하여야 한다. 특히 한국형 SBAS로 개발이 진행 중인 KASS의 기준국은 대한민국 내에 설치될 예정이므로 기준국의 개수와 영역이 제한될 수밖에 없으며 이는 넓게 기준국을 배치할 수 있는 타 SBAS 시스템과 구별이 되는 부분이다. 본 논문에서는 이러한 한계로 인한 GPS 및 GEO에 대한 UDRE와 ${\delta}UDRE$ 성능 영향을 시뮬레이션을 통하여 분석하였으며 그 결과 UDRE 성능은 기준국이 얼마나 넓게 분포하는지에 크게 영향을 받으며 특히 GEO UDRE에 미치는 영향이 매우 심각한 것을 확인하였다. 이 결과를 바탕으로 기준국 배치 영향으로 인한 시스템 성능 위험을 최소화하기 위한 KASS설계 및 개발 고려 사항을 제시한다.

• 산업공학
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• 제17권1호
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• pp.121-127
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• 2004

In this paper, we present the base station(BS) processing capacity to provide the multimedia services in IMT-2000 wireless communication network. The IMT-2000 services are classified into two types, circuit and packet services, and user‘s environments such as indoor, pedestrian and vehicle are considered. Using the parameters of service economics and wireless technology, the user's reference traffic and BS‘s traffic are computed. The traffic is measured by throughput(kbps). Based on the measured traffic, the accommodating users in BS are also evaluated. In addition to, the BS design capacity is presented for varying the number of users and traffic distribution in different user's environments.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.1158-1161
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• 2004

This paper presents structural characteristics of station class lightning arresters and electrical characteristics of manufactured ZnO varistor blocks which are usable in those arresters. Three types of station class lightning arresters were investigated and those are a ceramic arrester, a FRP tube type polymer arrester, and a FRP rod type polymer arrester. Each arrester has merits and demerits with structural characteristics. In general, polymer arresters were made of silicon rubber for housing materials, FRP tube or rod for mechanical strength, ZnO blocks for electrical characteristics, and metal parts for electrical contact and the silicon rubber, the housing materials, was directly injected to the arrester module which was assembly composed of electrodes, ZnO blocks and FRP tube or rod, and to prevent the nonlinear electric fields distribution on upper parts of arresters, the grade ring was adopted to the upper electrodes. The reference voltage, nonlinear coefficient, residual voltage, and voltage ratio of manufactured ZnO varistors are 4.90kV, 50, 9.54kV, 1.94, respectively. Compared to designed electrical characteristics, the reference voltage was low for 600v and the voltage ratio was slightly high. However, the characteristics of discharge withstand was so excellent that the mechanical destruction does not occur at the impulse current of $8/20{\mu}s$ 10kA for 100 times.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.410-413
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• 2007

Water vapor in the atmosphere is an influential factor of the hydrosphere cycle, which exchanges heat through phase change and is essential to precipitation. Because of its significance in altering weather, the estimation of water vapor amount and distribution is crucial to determine the precision of the weather forecasting and the understanding of regional/local climate. It is shown that it is reliable to measure precipitable water (PW) using long baseline (500-2000km) GPS observations. However, it becomes infeasible to derive absolute PW from GPS observations in Taiwan due to geometric limitation of relatively short-baseline network. In this study, a method of deriving Near-Real-Time PW from short baseline GPS observations is proposed. This method uses a reference station to derive a regression model for wet delay, and to interpolate the difference of wet delay among stations. Then, the precipitable water is obtained by using a conversion factor derived from radiosondes. The method has been tested by using the reference station located on Mt. Ho-Hwan with eleven stations around Taiwan. The result indicates that short baseline GPS observations can be used to precisely estimate the precipitable water in near-real-time.

• 한국입자에어로졸학회지
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• 제16권2호
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• pp.31-47
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• 2020

Although interest in air quality has increased due to the frequent occurrence of high-concentration fine particulate matter recently, the official fine particulate matter measuring network has failed to provide spatial detailed air quality information. This is because current measurement equipment has a high cost of installation and maintenance, which limits the composition of the measuring network at high resolution. To compensate for the limitations of the current official measuring network, this study constructed a spatial high density measuring network using the fine particulate matter simple measuring device developed by Observer, W-Station. W-Station installed 48 units on Jeju Island and measured PM_2.5 for six months. The data collected in W-Station were corrected by applying the first regression equation for each section, and these measurements were compared and analyzed based on the official measurements installed in Jeju Island. As a result, the time series of PM_2.5 concentrations measured in W-Station showed concentration characteristics similar to those of the environmental pollution measuring network. In particular, the results of comparing the measurements of W-Station within a 2 km radius of the reference station and the reference station showed that the coefficient of determination (R²) was 0.79, 0.81, 0.67, respectively. In addition, for W-Station within a 1 km radius, the coefficient of determination was 0.85, 0.82, 0.68, respectively, showing slightly higher correlation. In addition, the local concentration deviation of some regions could be confirmed through 48 high density measuring networks. These results show that if a network of measurements is constructed with adequate spatial distribution using a number of simple meters with a certain degree of proven performance, the measurements are effective in monitoring local air quality and can be fully utilized to supplement or replace formal measurements.

• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1655-1662
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• 2018

This paper studies the magnetic fields between the power lines which are finite length and other ones which are infinitely long around the first tower in the proximity of the power transformers. They will be used as a source of disturbance applied to the power line. The method applied in this study was gradual; develop the theoretical formulation of the magnetic fields of these lines which are finite length and other ones which are infinitely long, examine the effects of different couplings between the different neighboring lines and the distribution transformers on behavior of magnetic fields. The method also focused on the experimental results analyzing the magnetic fields which will be used as a source applied to the auditory implants EMC. The theoretical and experimental results were compared and discussed for three power lines (90kV, 150kV and 225kV) near the power station, and it proved the effect of these substations on the simulated and measured results of the magnetic field. The maximum intensities of magnetic fields measured at the height of 1m from the ground for the circuit of three lines close to each substation were significantly lower than the ICNIRP reference levels for occupational and non occupational exposures.

• 한국항해항만학회지
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• 제40권5호
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• pp.265-270
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• 2016

Extreme tropospheric anomalies such as typhoons or regional torrential rain can degrade positioning accuracy of the GPS signal. It becomes one of the main error terms affecting high-precision positioning solutions in network RTK. This paper proposed a detection algorithm to be used during atmospheric anomalies in order to detect the tropospheric irregularities that can degrade the quality of correction data due to network errors caused by inhomogeneous atmospheric conditions between multi-reference stations. It uses an atmospheric grid that consists of four meteorological stations and estimates the troposphere zenith total delay difference at a low performance point in an atmospheric grid. AWS (automatic weather station) meteorological data can be applied to the proposed tropospheric anomaly detection algorithm when there are different atmospheric conditions between the stations. The concept of probability density distribution of the delta troposphere slant delay was proposed for the threshold determination.

• 한국인터넷방송통신학회논문지
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• 제15권5호
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• pp.133-138
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• 2015

본 논문에서는 무선 센서 네트워크 공간을 둘로 나누어 멀리 있는 층의 클러스터 헤드의 전송 거리를 줄여 SEP 센서 네트워크의 수명을 개선하는 방법을 제안하고자 한다. 기지국은 노드의 위치 정보를 참고하여, 기지국으로부터 가장 가까운 노드 거리와 가장 먼 노드 거리의 중간 지점을 기준으로 층을 나눈 후, 기지국으로부터 먼 바깥쪽 층의 클러스터 헤드는 안쪽 층의 클러스터 헤드를 경유하여 기지국으로 데이터를 전송한다. 즉, 바깥쪽 층의 클러스터 헤드의 전송 거리를 줄임으로써 에너지 소비를 최소화하는 Layered SEP를 제안하였다. 제안된 알고리즘을 기존의 SEP와 비교하여 검증하였다.

• 대한원격탐사학회지
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• 제29권5호
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• pp.537-544
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• 2013

남극 세종 과학 기지가 위치하고 있는 바톤반도는 눈과 식생이 주를 이루고 있고, 기후변화와 같은 환경변화에 민감하게 반응한다. 극지역의 지표 모니터링은 기후변화 이해를 위해 중요하다. 그러나 극 지역은 접근성 및 공간규모로 인해 지속적으로 모니터링 하기에 어려움이 있다. 위성영상은 지속적으로 동일지역을 모니터링 할 수 있다는 장점과 함께 다중분광영역을 이용하여 지표의 상태를 파악하는데 효율적이다. 따라서 본 연구에서는 바톤반도의 지표의 상태를 지속적으로 모니터링하기 위한 기초자료로 KOMPSAT-2 다중 분광 위성영상을 이용하여 토지피복분류를 수행하였고, 나아가 분류된 토지피복 중 식생 종의 분포를 파악하였다. 다중분광영상인 KOMPSAT-2 위성영상과 현장관측자료를 이용하여 계층적 분류를 수행하였고 정확도를 평가하였다. 전반적으로 식생지역과 비식생 지역이 명확하게 분류되었으나 식생 종 분류에는 낮은 정확도를 보였다.

• Journal of Astronomy and Space Sciences
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• 제14권1호
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• pp.142-149
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• 1997

잘 알려진 최적제어 이론의 선형제차조절법을 정지궤도 위성의 위치보존 궤도조정 문제에 적용하였다. 정지궤도 위성의 운동에 가장 큰 영향을 미치는 섭동향을 선택하여 동서방향과 남북방향 궤도조정의 경우 각각 14일간 지구비대칭 중력장의 영향, 28일간 태양과 달의 영향을 예측한 결과로 궤도조정할 경계조건을 적절하게 설정하였다. 비선형방정식을 선형화하여 리카티 방정식(Riccati Equation)을 두 번 적분함으로써 최적궤도와 이에 상응하는 추진 가속도를 알아내었다. 선형제차조절법으로 구한 속도변화량과 기하학적으로 계산한 ${\Delta}V$(속도변화량)을 비교해 봄으로써 제어이론을 통한 궤도조정 방법이 실제상황에 거의 근사한 해를 제공할 수 있는가와 제어이론을 위치보존 궤도조정 문제에 적용한 방법이 경제적인 측면에서의 연료최적화와 이에 따른 정지궤도 위성의 수명연장에 기여할 수 있는가에 대한 해석을 시도하였다.