• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.10
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• pp.1873-1880
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• 2016

Most of the energy used to operate a cellular network is consumed by a base station (BS), and reducing the transmission power of a BS is required for energy-efficient cellular networks. In this paper, a distributed transmit power control (TPC) algorithm is proposed based on the flocking model to improve the energy efficiency of a cellular network. Just as each bird in a flock attempts to match its velocity with the average velocity of adjacent birds, in the proposed algorithm each mobile station (MS) in a cell matches its rate with the average rate of the co-channel MSs in adjacent cells by controlling the transmit power of its serving BS. Simulation results show that the proposed TPC algorithm follows the same convergence properties as the flocking model and also effectively reduces the power consumption at the BSs while maintaining a low outage probability as the inter-cell interference increases. Consequently, it significantly improves the energy efficiency of a cellular network.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.5
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• pp.685-690
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• 2021

In this paper, we propose a deep learning-based transmit power control scheme to maximize the sum-rates while satisfying the minimum data-rate in downlink non-orthogonal multiple access (NOMA) systems. In downlink NOMA, we consider the co-channel interference that occurs from a base station other than the cell where the user is located, and the user feeds back the signal-to-interference plus noise power ratio (SINR) information instead of channel state information to reduce system feedback overhead. Therefore, the base station controls transmit power using only SINR information. The use of implicit SINR information has the advantage of decreasing the information dimension, but has disadvantage of reducing the data-rate. In this paper, we resolve this problem with deep learning-based training methods and show that the performance of training can be improved if the dimension of deep learning inputs is effectively reduced. Through simulation, we verify that the proposed deep learning-based power control scheme improves the sum-rate while satisfying the minimum data-rate.

• The KSFM Journal of Fluid Machinery
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• v.8 no.4 s.31
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• pp.20-26
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• 2005

When the pumps are started or stopped for the operation or tripped due to the power failure, the hydraulic transients occur as a result of the sudden change in velocity. The field tests on the waterhammer were carried out for Pangyo booster pumping station in which had six booster pumps and two in-line pumps with the motor of output 1,700 kW, respectively. The booster pumping station was equipped with the pump control valve as the main surge suppression device, and the surge relief valve as auxiliary one. But the pump control valve had not early controlled in the planned closing mode, the slamming occurred to the valve of which abruptly closed during the large reverse flow. Because the positive pressure wave caused by the pump failure was superposed on the slam surge, the upsurge increased so extremely that the pump control valve was damaged. After the air chambers were additionally installed in the booster pumping station, it was preyed that the water supply system acquire the safety and reliability on the pressure surge.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.208-216
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• 2004

The waterhammer occured when the pumps are started or stopped for the operation or tripped due to the power failure, the hydraulic transients occur as a result of the sudden change in velocity. The field tests of the waterhammer were carried out for PanGyo booster pumping station. The PanGyo pumuing station was installed booster pump of 6 sets and in-line pump of 2 sets. The main surge suppression device was equipped with the pump control valve and the surge relief valve as auxiliary. However, the pump control valve had not early controlled in the planned closing mode, and the slamming occurred to the valve of which abruptly closed during the large reverse flow. Because the pressure wave caused by the pump failure was superposed on the slam surge, the upsurge increased so extremely that the shaft of the valve was damaged. After the addition surge suppression device was equipped with air chamber. Further more in-line pump is needed surge suppression device that the pumping station acquired the safety and reliability for the pressure surge.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.1
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• pp.91-96
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• 2015

Heterogeneous cellular networks support various wireless environments for mobile service. Recently, data services as well as voice services are exponentially increased in cellular networks and the technical transition of LTE-A and IEEE 802.16m so that more base stations are requested to provide suitable service. Base stations consume most of energy in cellular networks, and the energy saving is needed for the base station. In this paper, we propose a saving power scheme by the dynamic energy management. In this paper we consider the simulation evaluations of handover for the low powered base station.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1654-1660
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• 2011

The korea Electric Railway feeder voltage is DC 1500V and AC 250000V. The auxiliary power supply of the vehicle auxiliary power units for domestic electrical feed has been developed with domestic technology hyeonchae mounted station, and domestic uses, such as voltage, have been exported to other countries. However, do not use at domestic that can be used for DC 3000V voltage auxiliary power unit does not develop, vehicle exports global. This has already been replaced by imported products from other nations is a real situation. Thus, our auxiliary power unit for the DC 3000V was developed, it will be exported to Ukraine. In this paper, We introduced circuit and structure of developed auxiliary power supply unit, and verified the performance with output characteristic of the auxiliary power unit.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.292-293
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• 2011

We proposed a new power system, Superconducting Power System. The SPS consists of superconducting power cables, fault current limiters, and transformers. The basic concept is to replace 154kV conventional cables with 22.9kV superconducting cables and to convert a 154kV substation into a 22.9kV switching station in downtown area. For the application of the SPS to real power system, it is very important to construct the protection system of the SPS. This study presents a protection system for the new Superconducting Power System (SPS).

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.107-109
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• 2008

Cheju-Haenam HVDC transmission system start it's commercial operation since 1998. JEJU island is supplied with it's about 45% of total electric power from main land with HVDC link. In JEJU island, the demand of electric power is growing every year. With a current power supply, electric power reserve rate will be below the recommended one. For a stable power supply to JEJU island, KEPCO start a construction of #2 HVDC transmission system. This report is for introduction and understanding of #2 HVDC system which will be installed between JEJU island and main land. This report includes a specification of converter station and DC cable. KEPCO expect that this system will solve the power supply problem and maximum wind power plant capacity problem as well.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.58_59
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• 2009

Generator excitation system, supplying the voltage to power system, is controlled by various manners as aspects of power system. Previously excitation systems mainly used AVR(Automatic Voltage Regulator) and FCR(Field Current Regulator) to control voltage, but nowadays the excitation systems have the tendency to adopt AQR(Automatic Reactive power Regulator) and APFR(Automatic Power Factor Regulator) to do it so as to get into step with diverse requirements of power system and high digital technology. This paper presents which operation methods is effective for the equipment, according to increase the unmanned power station thanks to automation technic.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1157-1158
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• 2015

This work is to study the effect of load current on 6.6 kV power cables in operation. In order to figure out the relationship between load current and temperature of the power cables, we have developed measuring equipment for insulation resistance, temperature, and current tested on 9 cables at power station, Western Power Co. Ltd. The cables used in our test were in operation for the last 18 years. Our research over a year showed that the remaining lifetime of 8 cables was more than 20 years. The remaining lifetime of one cable was about 16 to 18 years.