• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.1
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• pp.45-51
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• 2004

Boiler tubes in power plants are often leaked due to various material degradations including creep and thermal fatigue damage under severe operating conditions such as high temperature and high pressure over an extended period of time. To monitor and diagnose the tubes on site and in real time, the acoustic emission (AE) technology was applied. We developed an AE leak detection system, and used it to study the variation of AE signal from the on-site tubes in response to the changes in the boiler operation condition and to detect the locations of leakage based on it. Detection of leak was performed by acquiring and evaluating the signals in separate regimes of high and low frequency signal. As a result of these studies, we found that on-line monitoring and detection of leak location for boiler tubes is possible using the developed system. Thus, the system is expected to contribute to the safe operation of power plants, and prevent economic losses due to potential leak.

• Journal of the Korean Society of Safety
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• v.22 no.4
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• pp.26-31
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• 2007

According to the statistical analysis on the electrical fire of 2005 years, most of electrical fire is generated from short circuit(4,985 cases), overcurrent(755 cases) leakage current(391 cases), poor contact(378 cases), disconnection(36 cases) on the electrical wiring device. The researches for the fire hazard about normal electric wiring have already been progressing in the advanced country such as USA and Japan, but Comparative study of the disconnection has not been conducted. Therefore, in this paper, we have simulated the thermal analysis for electrical wire according to deteriorating time in a normal state and disconnection with electrical wire using the electrical-thermal finite element method(Flux 3D). This paper acquire basis data of electricity fire signal by disconnection and wish to help for electrical fire cause diagnosis business.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.4
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• pp.779-787
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• 2010

In this paper, We introduce electrical tracking generated from surface activity associated with flow of leakage current on insulator under wet and contaminated conditions and design electrical tracking pattern recognition system by using LabVIEW. We measure the leaking current of contaminated wire by using LabVIEW software and the NI-c-DAQ 9172 and NI-9239 hardware. As pattern recognition algorithm and optimization algorithm for electrical tracking system, neural networks, Radial Basis Function Neural Networks(RBFNNs) and particle swarm optimization are exploited. The designed electrical tracking recognition system consists of two parts such as the hardware part of electrical tracking generator, the NI-c-DAQ 9172 and NI-9239 hardware and the software part of LabVIEW block diagram, LabVIEW front panel and pattern recognition-related application software. The electrical tracking system decides whether electrical tracking generate or not on electrical wire.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.4
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• pp.217-225
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• 1996

This paper describes a high power resonant inverter for diagnostic X-ray generators using zero-voltage soft-switching technology. The system consists of a step-down chopper, a resonant phase-shift PWM inverter, a hihg-voltage diode, and high voltage cables a smoothing DC capacitor. The inverter makes use the leakage inductance of the hihg-voltage transformer and external capacitor as resonant components. The rectified input voltage is controlled by a step-down chopper with input voltage compensator. The output regualtion is obtained by a resonant phase-shift PWM inverter with the digital feedback controller using DSP (digital signal processor), resulting in fast rising time and wide output voltage variation. The theoretical results are correlated with results from an experimental prototype of a 7-kVp, 300mA (21kW).

• Journal of electromagnetic engineering and science
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• v.3 no.1
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• pp.7-11
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• 2003

CDMA(code division multiple access) has very large peak to average power ratio(PAR) and behave as noise-like wide band digital signals with 1.2288 Mbps transmission rate. For signals with high PAR like CDMA, it is reasonable to prescribe occupied bandwidth(OBW) as average occupied bandwidth. Bandwidth measurements of CDMA signals at remote site are affected by co-channel and adjacent channel interference from adjacent CDMA base station, distortion of signal by fading effect, spurious emission and environment noises. In this study, we have compared OBW measurements in an on-air environment with those measured in a base station using adjacent channel leakage ratio(ACLR) as a reference measurement factor. As results of analysis, the OBW at ACLR$\geq$35 ㏈ shows nearly same statistical characteristics regardless of the measurement locations and environments.

• Journal of Sensor Science and Technology
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• v.27 no.3
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• pp.143-149
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• 2018

In this paper, we introduce an edge-spike modulation method for visible light communication (VLC). This method is effective in preventing LED flicker and 120 Hz noise interference in base-band VLC. In the VLC transmitter, edge-spikes are generated by passing the digital data through a simple RC-high pass filter (HPF). The LED modulation of the edge-spikes does not change the average power of the LED light; thus it prevents LED flicker. In the VLC receiver, the 120 Hz noise from other lighting lamps is easily eliminated by RC-HPF, while the edge-spike signal is detected normally. In our experiment, the message of an air-quality sensor was successfully transmitted using edge-spike modulation. This structure is useful in constructing, e.g., wireless gas monitoring sensor systems to warn and prevent harmful gas leakage accidents in buildings using LED light.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.212-213
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• 2008

Ultrasonic fiber sensor is more cost-effective than optical fiber sensor using light. However, optical fiber lines are separately used for sensing. Thus, if it is applied for huge system, it is need many lines of the sensor systems. To overcome this point, novel ultrasonic sensor systems considering wave cancellation and modulation were newly developed. By using this schema, reference-free sensor system can be developed. By using ultrasonic waves of different excitation frequencies, multiple input-signal output sensor system was also developed by applying spectrum analyses. Using the array type sensor system, the leakage of liquid and its evaporation can be monitored successfully.

• Journal of Ocean Engineering and Technology
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• v.8 no.1
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• pp.50-61
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• 1994

A 300 meter class ROV(CROV300) is composed of three parts : a surface unit, a tether cable and an underwater vehicle. The vehicle controller is based on two processors : an Intel 8097-16-bit one chip micro-processor and a Texas Instruments TMS320E25 digital signal processor. In this paper, the surface controller, the vehicle controller and peripheral devices interfaced with the processors are described. These controllers transmit/receive measured status data and control commands through RS422 serial communication. Depth, heading, trimming, camera tilting, and leakage signals are acquired through the embedded AD converters of the 8097. On the other hand, altitude of ROV and lbstacle avoidance signals are processed by the DSP processor and periodically fetched by the 8097. The processor is interfaced with a 4-channel 12-bit D/A converter to generate control signals for DC motors an dseveral transistors to handle the relays for on/off switching of external devices.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.717-720
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• 2000

The sensorless scheme for Switched Reluctance Motor(SRM) dives must have the robustness and reliability because the noise and error are sensitive. These elements make electrically noisy environments due to the proximity of high current power circuits with small signal electronic circuits when SRM drives. Also the leakage inductances and finite coupling capacitances these can cause the noise on any low voltage current and voltage measurement. the error can occur because the current and voltage including the noise are used as the input of sensorless algorithm In this paper the high robustness and resistance of input noise are described and the fuzzy logic based rotor estimation algorithm is used to reduce the tolerance of input data.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.762-772
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• 2016

This paper studies the problem of precoding and post-coding design for multicell multiuser downlink transmissions in the absence of perfect channel state information (CSI). Using statistical information of imperfect CSI, an iterative multiuser multicell transceiver design is formulated by minimizing the mean squared error (MSE) cost function of signal and leakage interference under per-base station power constraint (PBPC). The convergence of the iterative precoding and postcoding algorithm is verified by analytical and empirical results. The proposed precoding and postcoding algorithm offers a low computational complexity and robustness against CSI imperfection.