• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.04a
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• pp.193-194
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• 2000

To investigate the characteristics of fine particles and the relationships between pollutant concentrations and long-range transport patterns in Asia area, continuous every 6-day sampling (case 1) and an intensive field sampling (case 2) had been carried out between March 1998 and July 1999 at Taean, Korea. Anionic ($Cl^{-}$, ${NO_{3}}^{-}$, ${SO_{4}}^{2-}$) and Cationic ($Na^+$, ${NH_{4}}^{ +}, $K^+$, $Mg^{2+}$, $Ca^{2+}$) concentrations of $PM_{2.5}$ particle were analyzed. The major objective of this study is to investigate the relationships between the chemical compounds of $PM_{2.5}$ and the long-range transport patterns during intensive sampling period.

• Transactions on Electrical and Electronic Materials
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• v.7 no.2
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• pp.90-95
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• 2006

An on-line diagnostic test has been studied and performed for the pumped storage generator/motor. This study aims at reducing the diagnostic cost, minimizing the technical dependency on third party manufactures. Further design of on-line diagnostic system such as shorted-turn of rotor winding, partial discharge (PD) of stator winding and air-gap between stator and rotor for pumped storage generator/motor has been verified. In addition, it needs to be validated on site performance of the developed continuous on-line monitoring system for corresponding tasks for the improvement of the availability & reliability during operation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.125-130
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• 1994

Recently,manufacturing work been transformed to small acale production from with various items to act up to user's expectation from mass production with a little items required in the past. The FMS using NC type mother machinaries has been applied actively also in domestic manufacturing line to meet thus tendancy, but there are many machining troubles occured in work process not be settled yet. Nowdays high efficiency has been required no less than high precision in grinding work for the improvement of productivity. In this study, to represent more advanced FMS can be adapted to thus situation In-process type monitoring method using AE and Current sensors is suggested to investigatethe machining condition in grinding process. As results from this experimental study, is is recoqnized well that grinding conditions and dressing point of in time can be estimated effectively using monitoring method suggested. Furthermore, surface shape of grinding wheel on voluntary point of in time can be predicted indirectly through the observation and comparison of AE signal waveform obtained as performance of continuous dressing work.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1734-1736
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• 1998

On-line partial discharge monitoring system for generator stator insulation is developed. This system consists of remote and host units. The remote unit detects partial discharge signals from SSC(Stator Slot Coupler) installed between wedge and stator windings. The host unit monitors the condition of winding insulation. This system will be used as a module of a generator on-line monitoring system utilizing global network.

• Smart Structures and Systems
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• v.5 no.2
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• pp.139-152
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• 2009

Globally, civil infrastructures are deteriorating at an alarming rate caused by overuse, overloading, aging, damage or failure due to natural or man-made hazards. With such a vast network of deteriorating infrastructure, there is a growing interest in continuous monitoring technologies. In order to provide a true distributed sensor and control system for civil structures, we are developing a Structural Nervous System that mimics key attributes of a human nervous system. This nervous system is made up of building blocks that are designed based on mechanoreceptors as a fundamentally new approach for the development of a structural health monitoring and diagnostic system that utilizes the recently developed piezo-fibers capable of sensing and actuation. In particular, our research has been focused on producing a sensory nervous system for civil structures by using piezo-fibers as sensory receptors, nerve fibers, neuronal pools, and spinocervical tract to the nodal and central processing units. This paper presents up to date results of our research, including the design and analysis of the structural nervous system.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.201-203
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• 2009

This paper presents the real time stray current monitoring techniques on the DC railway system. These techniques are two types. The first one is the rail potential measurement technique between running rail and earthing mats on the important locations such as substation, station, and so on. And the second one is measurement technique of stray current through substation earthing mats and from collection mats, and continuous monitoring of return currents through the running rails. We need to apply these techniques on DC railway system to monitor stray current periodically and maintain the system properly.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1175-1178
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• 2004

On-line partial discharge(PD) monitoring system has been developed to monitor in operating large motor stator insulations. This system makes use of remote diagnosis techniques for the evaluation of PD activity in the control center of thermal power plant. This system can be remotely accessed via a modem to build database, analyze status and interpret the pattern of PD activity. A personnel computer is generally connected to ten motors to continuous measurement of the PD activity. The test data can be easily interpreted by a maintenance staff. For assessing the condition of stator winding in motors, this system ensures a reliable measurement and accurate estimation. Capacitive couplers used for on-line PD measurement have been 80pF. The maximum PD magnitude(Qmax), PD pattern and normalized quantity number(NQN) were performed by this system.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05a
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• pp.587-593
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• 1996

Vibration analysis is one of the most powerful tools available for the detection and isolation of incipient faults in mechanical systems. The methods of vibration analysis in use today and under continuous study are broad band vibration monitoring, time domain analysis, and frequency domain analysis. In recent years, great interest has been generated concerning the use of time-frequency representation and its application for a machinery diagnostics and condition monitoring system. The objective of the research described in this paper was to develop a new diagnostic tool for the rotating machinery. This paper introduces a new time-frequency representation, Directional Wigner-Ville Distribution, which analyses the time- frequency structure of the rotating machinery vibration.

• International journal of advanced smart convergence
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• v.7 no.4
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• pp.174-184
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• 2018

The efficiency and safety of social-overhead capital (SOC) public infrastructures have become an eminent social concern. In this regard, a continuous structural health monitoring has been widely implemented to oversee the robustness of such public infrastructures for the safety of the public. This paper deals with the analysis of a distributed mobility management (DMM) support for wireless sensor network (WSN) based information transmission system. The partial DMM support separates the data and control plane infrastructures, wherein, the control plane is managed by a particular mobility management network entity, while the data plane is distributed by the mobility anchors. The system will be able to optimize the information transmission for a wireless structural health monitoring of SOC public infrastructures specifically designed for bridges, and thus, guarantees the safety of public commuters.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.867-876
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• 2019

Second harmonic generation using nonlinear ultrasonic waves have been shown to be an early indicator of possible fatigue damage in nuclear power plant components. This technique relies on measuring amplitudes, making it highly susceptible to variations in transducer coupling and instrumentation. This paper proposes an experimental procedure for in-situ surface wave nonlinear ultrasound measurements on specimen with permanently mounted transducers under high cycle fatigue loading without interrupting the experiment. It allows continuous monitoring and minimizes variation due to transducer coupling. Moreover, relations describing the effects of the measurement system nonlinearity including the effects of the material transfer function on the measured nonlinearity parameter are derived. An in-situ high cycle fatigue test was conducted using two 304 stainless steel specimens with two different excitation frequencies. A comprehensive analysis of the nonlinear sources, which result in variations in the measured nonlinearity parameters, was performed and the effects of the system nonlinearities are explained and identified. In both specimens, monotonic trend was observed in nonlinear parameter when the value of fundamental amplitude was not changing.