• Journal of Advanced Navigation Technology
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• v.19 no.3
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• pp.207-216
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• 2015

Since the distribution of SBAS reference stations is one of the most important factors that affect the system performance, the effects of the distribution should be analyzed carefully from the beginning of the program to develop the system conforming to given performance requirements. The reference stations of KASS, the Korean SBAS, are planned to be installed only inside South Korea, which limits the number and area of those. It differentiates KASS from others that have much larger sites. In this paper, the author analyzes the performance impact on UDRE and ${\delta}UDRE$ for GPS and GEO due to the limitations by a series of simulations, which showed that the UDRE performance depends on the diversity of the reference station distribution and the impact on the GEO UDRE is significant. The paper concludes by providing KASS design and development considerations to minimize the possible performance risks due to the limitations of KASS reference station distribution.

• IE interfaces
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• v.17 no.1
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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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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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.

• Proceedings of the KSRS Conference
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• 2007.10a
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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.

• Particle and aerosol research
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• v.16 no.2
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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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• v.13 no.4
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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.

• Journal of Navigation and Port Research
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• v.40 no.5
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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.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.5
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• pp.133-138
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• 2015

In this paper, we propose a method for improving the lifetime of the sensor network SEP through the wireless sensor network divided into two spaces by reducing the transmission distance of the cluster head in the layer in the distance. With reference to the position information of the node, the base station divides the layer based on the midpoint of the nearest node and the furthest distance away from the base station node. And the cluster head in the outer layer far from the base station is transmitted the data to the base station via the cluster head in the inner layer base station to transmit data. That is, we are proposed the layered SEP by reducing the transmission distance of the cluster head in the outer layer for the energy consumption to a minimum. The proposed algorithm is verified by comparison with the existing SEP.

• Korean Journal of Remote Sensing
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• v.29 no.5
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• pp.537-544
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• 2013

Baton Peninsula, where Sejong station is located, mainly covered with snow and vegetation. Because this area is sensitive to climate change, monitoring of surface variation is important to understand climate change on the polar region. Due to the inaccessibility, the remote sensing is useful to continuously monitor the area. The objectives of this research are 1) map classification of land-cover types in the Barton Peninsular around King Sejong station and 2) grasp distribution of vegetation species in classified area. A KOMPSAT-2 multispectral satellite image was used to classify land-cover types and vegetation species. We performed classification with hierarchical procedure using KOMPSAT-2 satellite image and ground reference data, and the result is evaluated for accuracy as well. As the results, vegetation and non-vegetation were clearly classified although species shown lower accuracies within vegetation class.

• Journal of Astronomy and Space Sciences
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• v.14 no.1
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• pp.142-149
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• 1997

This paper applied one of the well-known optimal control theory, namely, linear quadratic regulator(LQR), to the station-keeping maneuvers(SKM) for a geostationary satellite. The boundary conditions to transfer the system with a good accuracy at a terminal time were based upon the predicted orbital data which are created due to the Earth's non-uniform mass distribution's effect during 14 days and due to luni-solar effect during 28 days. Through the linearization of the nonlinear system equation with respect to reference orbit and the numerical integration of Riccati equation, the optimal trajectories and the corresponding control law have been obtained by using LQR. From the comparison of ${\Delta}V$ obtained by LQR with the ${\Delta}V$ obtained anatically by geometric method, Station Keeping Maneuvers(SKM) via LQR may provide comparable results to a real system. Furthermore it will demonstrate the possibility in fuel optimization and life extension of geostationary satellite.