• Proceedings of the Korean Radioactive Waste Society Conference
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• 2018.11a
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• pp.456-457
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• 2018

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.3
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• pp.562-570
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• 1997

In Direct Sequence Code Division Multiple Access(DS/CDMA) communication systems, it is important to contraol the power of reverse link channel evenly for overall channel capacity. To control the reverse link powers efficiently, it is necessary to estimate signal quality of each reverse link channel. In this paper, we discuss a method to estimate the signal-to-noise ratio(SNR) for each channel by measuring the powers of pilot and noises. Computer simulations are done to show the effectiveness of the scheme.

• Proceedings of the KIEE Conference
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• summer
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• pp.174-176
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• 2004

FACTS 기술은 송전계통에 전압원 인버터를 설치하여 모선 전압과 전력조류를 제어하므로 송전용량 증대 및 계통 안정도 향상을 가능케하는 신기술이다. 국내에서는 2003년 최초의 FACTS Pilot Plant인 80MVA UPFC가 154kV 강진 변전소에 설치되었다. UPFC는 STATCOM과 SSSC가 DC 커패시터를 통하여 결합된 구조로 되어 모선전압과 유효/무효전력 조류의 독립적인 제어가 가능하며 계통 운전 상황에 따라 STATCOM과 SSSC의 단독운전 또한 가능하다. 따라서 STATCOM 및 SSSC 단독운전시의 계통영향에 대한 분석이 필요하다 본 논문은 EMTDC 모델을 이용하여 현재 운전중인 강진 변전소 UPFC의 직렬 운전모드인 40MVA SSSC의 제어특성과 운전효과 분석에 대하여 기술하였다.

• Journal of Power System Engineering
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• v.14 no.6
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• pp.102-108
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• 2010

In this study, the authors investigate the basic characteristics of a two stage directional control valve with pilot spool assembled in main spool coaxially. The step response characteristics and effects of major design parameters' values on valve performances arc clarified through numerical simulations. In addition, the authors examined the possibility of applying the object valve for this study as a proportional control valve. Based on the numerical simulation results, new design values for the reformed design as a proportional control valve were suggested.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.3
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• pp.135-141
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• 2014

The inherent feature of the highly efficient spectrum usage has made Orthogonal Frequency Division Multiplexing (OFDM) preferable for Communication Standards. This study evaluated the performance of a Least Square (LS) estimator for a comb-type pilot insertion scheme over a fast fading Rayleigh channel. A High Peak-to-Average Power Ratio (PAPR) is one of the major downsides of the OFDM. The effects of an increase in the number of subcarriers on PAPR and the performance of the LS Estimator were studied. Increasing the number of subcarriers while keeping the pilots overhead constant resulted in improved performance of the LS estimator but the PAPR increased with increasing number of subcarriers. Therefore some trade-off between the number of subcarriers and the performance of the OFDM system is needed. The Mean Square Error (MSE) expression was also derived for the LS estimator in the case of a comb-type pilot arrangement. The MSE expression clearly explains the effects of the number of subcarriers on the performance of the LS estimator.

• ETRI Journal
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• v.26 no.5
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• pp.437-442
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• 2004

In this paper we address the problem of capacity optimization in a Universal Mobile Telecommunication System (UMTS) radio network. We present an optimization algorithm for finding the best settings of the antenna tilt and common pilot channel power of the base stations. This algorithm is a parametric method, based on a set of rules. We evaluated our optimization technique on a virtual network scenario with 75 cells. For this scenario we show an increase in capacity compared to the initial settings of about 60 percent.

• Journal of information and communication convergence engineering
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• v.6 no.2
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• pp.129-133
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• 2008

In this paper, modified power control algorithms are proposed for a satellite mobile communications system with ATC (ancillary terrestrial component). In order to increase system capacity and reduce the transmitting power of the user's equipment, we propose the modified power control scheme consisting of the modified closed-loop and open-loop power control. The modified CLPC (closed-loop power control) algorithm, combining the delay compensation algorithms and pilot diversity, is mainly applied to the ATC link in urban areas because it is more suitable to the short RTD (round-trip delay). In the case of rural areas where ATCs are not deployed or a signal is not received from ATCs, combining monitoring transmitting power equipment and OLPC (open-loop power control) algorithms using an efficient pilot diversity is mainly applied to the link between the user's equipment and the satellite. Two power control algorithms are applied equally to the boundary areas where two kinds of signals are received in order to ensure coverage continuity. The simulation results show that the modified power control scheme has good performance compared to conventional power control schemes in a GEO (geostationary earth orbit) satellite system with ATC.

• Journal of IKEEE
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• v.2 no.2 s.3
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• pp.200-211
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• 1998

A DS/CDMA system that makes all base stations require equal received power for all mobiles can lead to the non-uniform quality of service when mobiles are non-uniformly located over a service area. In order to resolve this problem the base-received power should be controlled according to base's load in order to make the quality of service uniform, and the pilot power also has to be adjusted to maintain the balance of cell coverage between reverse link and forward link. In this paper, we propose a generalized model including Pilot Power control, base-received power control on the reverse link, transmission power allocation on multiple forward link, and soft handoff on both links. We also apply our model to an initial system design as an example.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.8
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• pp.9-16
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• 2007

Currently, the measurement of RF parameters for a base station in operation is typically limited to easily measured forward path items. In this paper, the forward monitoring ports of base stations are used to measure the reverse RF performance. The system has been implemented and effectiveness has been proven on an operating base station. The receiver sensitivity is measured using an internal CDMA modem which is used to monitor the output power based on closed loop power control when the modem is connected to the base station via a voice call. In order to improve accuracy, in addition to the modem Tx adjust(TxAdj) parameter, the detector's actual measurement is used. For accurate receiver sensitivity, the measurement should be made when there is no traffic which is not possible on an operating base station. Therefore, pilot channel chip energy to received signal power spectral density ratio$(E_c/I_o)$ compensation method is used to offset the receiver sensitivity degradation with voice traffic increase.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.3
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• pp.549-557
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• 2012

In this paper an on-chip photo energy harvesting system with MPPT(Maximum Power Point Tracking) control is proposed. The ISC(Integrated Solar Cell) is implemented using p-diff/n-well diodes available in CMOS processes. MPPT control is implemented using the linear relationship between the open-circuit voltage of a PV(Photovoltaic) cell and its MPP(Maximum Power Point) voltage such that a small pilot PV cell can track the MPP of a main PV cell in real time. Simulation results show that the designed circuit with the MPPT control delivers the MPP voltage to load even though the load is heavy such that the load circuit can operate properly. The proposed circuit is designed in 0.18um CMOS process. The designed main PV cell and pilot PV cell occupy $8mm^2$ and $0.4mm^2$ respectively.