• Journal of Korean Institute of Industrial Engineers
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• v.25 no.3
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• pp.342-350
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• 1999

Two location algorithm (TLA) considers two location areas (LAs) to track the location of a mobile station (MS). The TLA significantly outperforms the single location algorithm when the call-to-mobility ratio (CMR) is low (i.e., the user moves more frequently than to receive calls). However, because of the paging cost for the users moving back to the previously visited LA, the performance of the TLA degrades when the CMR is high. To reduce those paging cost, we propose the new algorithm called TLA with call information (TLAC). In TLAC, we use the location information of the MS within the setup message when the MS originates a call in the previously visited LA. Through the setup message, the system can know the exact location of the MS without the additional location registration operation, and the paging cost for the arriving calls in the visited LA can be reduced. An analytical model is proposed to compare the TLAC and previous TLA protocol. Our study indicates that the TLAC always guarantees better performance than the TLA. We also observe that the TLAC is much better than the TLA when the CMR is high.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.2
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• pp.113-123
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• 1997

This study was initiated to build runoff plots, install soil and water quality monitoring systems and collect background data from the plots and neighboring soils as the 1st year study of a 5 year project to assess soil quality and develop the management practices for environmentally sound agriculture in mountainous soils. Eleven $3{\times}15m$ runoff plots and monitoring systems were installed at a field of National Alpine Agricultural Experiment Station to monitor soil quality and discharge of nonpoint source pollutants. Corn and potato were cultivated under different fertilizer, tillage and residue cover treatments. The soil has a single-layered cluster structure that has a relatively good hydrologic properties and can adsorb a large amount of nutrient. Concentrations of T-N, $NH_4$-N, and $NO_3$-N of surface soil sampled in the winter were relatively high. Runoff quality in the winter and thawing season in the spring was largely dependent on surface freezing, snow accumulation, temperature, surface thawing depth and so on. Runoff during the thawing season caused serious soil erosion but runoff quality during the winter was relatively good. Serious wind erosion from unprotected fields after the fall harvest were obserbed and best management practices to reduce the erosion need to be developed.

• Journal of Advanced Navigation Technology
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• v.6 no.3
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• pp.251-257
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• 2002

Design and characteristic improvement of existing folded dipole antenna is presented to adopt W-CDMA(1.885~2.170 GHz) wideband antenna radiators. The antenna structure has +/- 45 degrees dual polarization. In order to overcome the narrow bandwidth and low gain characteristic typical of the microstrip antenna, double layered structure was employed. The antenna achieved below - 20 dB reflection coefficients each ports, - 20 dB of port isolation, above 7 dBi of gain, providing evidence that the proposed design can be used in the W-CDMA service frequency band antenna.

• Ocean Systems Engineering
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• v.3 no.3
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• pp.203-217
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• 2013

A PTO (power-take-off) mechanism by using relative heave motions between a floating buoy and its inner mass (magnet or amateur) is suggested. The inner power take-off system is characterized by a mass with linear stiffness and damping. A vertical truncated cylinder is selected as a buoy and a special station-keeping system is proposed to minimize pitch motions while not affecting heave motions. By numerical examples, it is seen that the maximum power can actually be obtained at the optimal spring and damper condition, as predicted by the developed WEC(wave energy converter) theory. Then, based on the developed theory, several design strategies are proposed to further enhance the maximum PTO, which includes the intentional mismatching among heave natural frequency of the buoy, natural frequency of the inner dynamic system, and peak frequency of input wave spectrum. By using the intentional mismatching strategy, the generated power is actually increased and the required damping value is significantly reduced, which is a big advantage in designing the proposed WEC with practical inner LEG (linear electric generator) system.

• Journal of Korean Society for Geospatial Information Science
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• v.10 no.2 s.20
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• pp.77-85
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• 2002

The intention of this study is to extract the spatial and attribute information of road facility for Geospatial Information System(GIS) using graphic solution. Terrestrial photogrammetry has a lot of possibility for the acquisition of road facility information, which has much convenience in locating camera station, selecting the direction, and taking multiple images of the object at the fixed position. This study intended to develop the technique using single frame images only for the raw image data, being able to apply in the case where comparative high accuracy is not required and rigorous photogrammetric method is not available or rapid acquisition of information is need. As the results, we can find the efficiency in plane feature mapping and determining the dimensions of the road facilities.

• Journal of the Korean Society of Safety
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• v.33 no.3
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• pp.21-26
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• 2018

Approximately 20% of the total fire is electrical fire, and electrical energy is a potential source of heat. Large-scale fault currents that occur during a line ground fault flow into electric utility poles, electric power equipment, or electric appliances of the customer, and cause simultaneous electrical fire. In this paper, we investigated the possibility of fire through the change of fault current flowing in faulty and sound feeder in case of 1 line ground fault in 22.9 kV distribution line. We propose a fire investigation analysis method for simultaneous multiple electrical fire such as evidence analysis method, and fault current occurrence confirmation method in case of fire accident by analyzing the fault current occurring in the ground fault in the distribution line using EMTP, electric power system analysis program.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.8
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• pp.752-759
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• 2008

In this paper, we propose a high accurate geo-location system based on a single base station, where its location is obtained by Time-of-Arrival(ToA) and Direction-of-Arrival(DoA) of the radio signal. For estimating accurate ToA and DoA information, a MUltiple SIgnal Classification(MUSIC) is adopted. However, the estimation of ToA and DoA using MUSIC algorithm is a time-consuming process. The position tracking bias is occurred by the time delay caused by the estimation process. In order to mitigate the bias error, we propose the estimation method of the position tracking bias and compensate the location error produced by the time delay using the position tracking bias mitigation. For accurate self-localization of mobile robot, the Unscented Kalman Filter(UKF) with position tracking bias is applied. The simulation results show the efficiency and accuracy of the proposed geo-location system and the enhanced performance when the Unscented Kalman Filter is adopted for mobile robot application.

• Korean Journal of Ichthyology
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• v.20 no.3
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• pp.228-232
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• 2008

To investigate a proper sampling method for anchovy eggs and larvae in coastal waters of the South Sea, replicated samplings were made by different towing methods with different sampling gears and compared in terms of abundance and length composition. There was no significant difference in abundance in samples from vertical and oblique tows with a ring net. The abundance by replicated vertical tows with a ring net was not significantly different, but significant difference in abundance among sampling stations were found. The ring net sampled anchovy eggs in significantly greater numbers than collected by a NORPAC net, but both gears were not effective in obtaining quantitative samples of anchovy larvae larger than 3 mm. Therefore, samples by vertical tows with a ring net during the day at various stations is more efficient at estimating the density of anchovy eggs in an area compared to replicated sampling at a single station.

• ETRI Journal
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• v.38 no.2
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• pp.314-325
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• 2016

This paper examines the resource gain that can be obtained from the creation of clusters of nodes in densely populated areas. A single node within each such cluster is designated as a "hotspot"; all other nodes then communicate with a destination node, such as a base station, through such hotspots. We propose a semi-distributed algorithm, referred to as coordinated cognitive tethering (CCT), which clusters all nodes and coordinates hotspots to tether over locally available white spaces. CCT performs the following these steps: (a) groups nodes based on a modified k-means clustering algorithm; (b) assigns white-space spectrum to each cluster based on a distributed graph-coloring approach to maximize spectrum reuse, and (c) allocates physical-layer resources to individual users based on local channel information. Unlike small cells (for example, femtocells and WiFi), this approach does not require any additions to existing infrastructure. In addition to providing parallel service to more users than conventional direct communication in cellular networks, simulation results show that CCT can increase the average battery life of devices by 30%, on average.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.563-569
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• 2001

The head-capacity curves for pumps developed by the pump manufacturer are based on tests of a single pump operating in a semi-infinite pool with no nearby walls or floors and no stray currents, Hence, flow into the pump suction is symmetrical with no vortices or swirling. Pump station designers rely on these curves to define the operating conditions for the pump selected. But various constraints such as size, cost, and limitations on storage time require walls, floors, and pump intakes to be close proximity to each other. From this background, the authors are carrying out a systematic study on the flow characteristics of intakes within a sump found in pump stations. Model pump intake basin is designed and PIV is adopted as a measuring tool to capture the instantaneous flow patterns. Special attention is paid to investigate the flow patterns near the free surface, side-wall and back-wall due to different clearances from back-wall to vertical in take pipe. Moreover, the locations and vorticities of the various types of vortices that were found in the examinations are discussed.