• Journal of Internet Computing and Services
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• v.9 no.2
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• pp.43-50
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• 2008

In IEEE 802.11b wireless LAN, stations keep synchronization by receiving beacons being periodically sent by the AP (access point) when they run in low power mode. Beacon transmission is delayed if wireless channel is busy at a scheduled TBTT (target beacon transmission time), and stations must be awake until they receive the delayed beacon. In this paper, we propose a scheme that stations get their transmission delayed if they have little time for successful data transmission by the next TBTT. Beacon transmission without delay is guaranteed at every TBTT with this method so that the awake time of low power stations to receive beacon can be reduced. The proposed method is simulated and its characteristics ore described with the analysis of the results. The measured results in terms of beacon delay show some enhancement in energy consumption.

• Journal of the Korean Society for Railway
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• v.14 no.1
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• pp.19-23
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• 2011

The method to reduce interior noise of train was being studied. To improve transmission loss of train is one of the best way to reduce interior noise. But, the estimate to transmission loss requires lots of the commercial costs. In this study, the method to estimate transmission loss of high speed train is proposed using a scale reverberation chamber. The result shows that a transmission loss estimated using small scale reverberation is similar to that using huge reverberation chamber. The transmission loss estimated based on small scale reverberation chamber can be optimal with respect to the commercial coasts.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.3
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• pp.116-122
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• 2006

The underground transmission lines is continuously expanded in power systems. Therefore the fault of underground transmission lines are increased every year because of the complication of systems. However the studies dealing with fault location in the case of the underground transmission lines are rarely reported except for few papers using traveling wave method and calculating underground cable impedance. This paper describes the algorithm using fuzzy system and travelling wave method in the underground transmission line. Fuzzy inference is used for fault discrimination. To organize fuzzy algorithm, it is important to select target data reflecting various underground transmission line transient states. These data are made of voltage and average of RMS value on zero sequence current within one cycle after fault occurrence. Travelling wave based on wavelet transform is used for fault location. In this paper, a variety of underground transmission line transient states are simulated by EMTP/ATPDraw and Matlab. The input which is used to fault location algorithm are Detail 1(D1) coefficients of differential current. D1 coefficients are obtained by wavelet transform. As a result of applying the fuzzy inference and travelling wave based on wavelet transform, fault discrimination is correctly distinguished within 1/2 cycle after fault occurrence and fault location is comparatively correct.

• Journal of the Optical Society of Korea
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• v.17 no.1
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• pp.57-62
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• 2013

We have numerically implemented a receiver side all-optical signal processing method, i.e. optical backward propagation (OBP), by dispersion compensating fiber (DCF) and non-linear compensator (NLC) devised by effective negative Kerr non-linear coefficient using two highly non-linear fibers (HNLFs). The method is implemented for the post-processing of fiber transmission impairments, i.e. chromatic dispersion (CD) and non-linearities (NL). The OBP module is evaluated for dual-polarization (DP) m-ary (m=4,16,32,64,256) quadrature amplitude modulation (QAM) in 112 Gbit/s coherent transmission over 1200 km standard single mode fiber (SMF). We have also investigated an intensity limited optical backward propagation module (IL-OBP) by using a self-phase modulation-based optical limiter with an appropriate pre-chirping to compensate for the intensity fluctuations in the transmission link. Our results show that in highly non-linear sensitive 256QAM transmission, we have observed a 66% increase in the transmission distance by implementing IL-OBP as compared to conventional OBP.

• Journal of Information Processing Systems
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• v.15 no.2
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• pp.386-398
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• 2019

The transmission capacity of transmission lines is affected by environmental parameters such as ambient temperature, wind speed, wind direction and so on. The environmental parameters can be measured by the installed measuring devices. However, it is impossible to install the environmental measuring devices throughout the line, especially considering economic cost of power grid. Taking into account the limited number of measuring devices and the distribution characteristics of environment parameters and transmission lines, this paper first studies the environmental parameter estimating method of inverse distance weighted interpolation and ordinary Kriging interpolation. Dynamic thermal rating of transmission lines based on IEEE standard and CIGRE standard thermal equivalent equation is researched and the key parameters that affect the load capacity of overhead lines is identified. Finally, the distributed thermal rating of transmission line is realized by using the data obtained from China meteorological data network. The cost of the environmental measurement device is reduced, and the accuracy of dynamic rating is improved.

• Proceedings of the KIEE Conference
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• 2004.10a
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• pp.240-241
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• 2004

JP Nagoya. Inc started special work(passenger order} to transmit information to the passenger from 2001 following the eastern area' heavy rain in 2000. They introduced 'Passenger Information System' which uses self communication network(LAN, PHS) mainly and wire/wireless and internet jointly. As an information transmission method of this system, there is "train information transmission using PHS" which transmits info to LED display in special train. This system configured by adding new equipments and using existing equipments, network in maximum, this study reviewed the system, which transmits real time operation condition unified by these passenger order to passenger in high quality, more promptly.

• Journal of KSNVE
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• v.2 no.3
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• pp.181-192
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• 1992

A method of measuring the transmission loss of silencer using two microphone technique is described. Two microphone methol is used to elliminate the measurement error due to reflected wave spectra in inlet/outlet duct of silencer. Errors associated with the measurement method are studied. Henceforth the methods to effectively supress the influence are presented. Based on these considertions, the appropriate procedure of experimental set-up to measure the transmission loss a silencer is described with experimental verifications.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.283-287
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• 2003

A new method to miniaturize ${\lambda}/4$ transmission line of power divider is proposed. The method utilizes simple combination of the shorted coupled-line pair instead of the transmission line with very high impedance and shunt lumped capacitors. The length of ${\lambda}/4$ transmission line of power divider is about 16% over the conventional power divider at 1 GHz.

• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.553-555
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• 2000

Recently polymer insulators are being used for outdoor high voltage applications. Polymer insulators for transmission line have significant advantages over porcelain and glass insulators, especially for ultra-high voltage(UHV) transmission lines. In this paper, the design trend and method polymer insulator are investigated and Aging test method is analysed to know life time of insulator.

• Transactions on Electrical and Electronic Materials
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• v.16 no.3
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• pp.139-141
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• 2015

Contact resistance of interface between the channel layers and various S/D electrodes was investigated by transmission line method. Different electrodes such as Ti/Au, a-IZO, and multilayer of a-IGZO/Ag/a-IGZO were compared in terms of contact resistance, using the transmission line model. The a-IGZO TFTs with a-IGZO/Ag/a-IGZO of S/D electrodes showed good performance and low contact resistance due to the homo-junction with channel layer.