• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.843-845
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• 2011

Due to the short lifetime of the battery-based sensor network, study on the environmental energy-harvesting sensor network is being performed widely. In this paper, we analyze the system-level requirements on the sensor node which is needed for the efficient solar-powered wireless sensor network for the target application. In addition, we explain how the HW/SW components of our real solar-powered sensor node can satisfy the requirements mentioned above.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.467-470
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• 2001

Power electronic converters generate the harmonic voltage and current, and these harmonics have the harmful effects on the various components. For example, passive components such as capacitor and inductor, transformer, motor and other components are mainly affected in the power electronic system. Thus, the design and manufacturing of the power converters, which have the harmonic-free or mitigation strategies, are required. In particular, the lifetime and durability of these components are main requirement for enhancing the overall stability of the system. So, in this paper, the harmonics-related problems to the neighbouring components and mitigation research trends are presented.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.3
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• pp.43-49
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• 2013

Recently harmonics flowing into power system is increasing as the usage of semiconductor equipments and switching mode power equipments are increasing. Harmonics cause problems such as heat increasing and reduction in capacity of transformers, especially the harmonics flowing into a distribution transformer can lead to the lifetime reduction of transformer. In this paper, we are about to develop a device that can monitor harmonics in real-time as it is affixed to a distribution transformer. Unlike the existing expensive harmonic analysis device, a new harmonic analysis algorithm is proposed in order to implement low-cost equipment. The real-time harmonic analysis algorithm proposed in this paper allows implementation on low performance microcontrollers, thus it can monitor the harmonic in real-time as it is individually affixed to the transformer. Therefore, it would improve the reliability of the transformer and stable power system operation would be possible as it can prevent the transformer accidents in advance.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.55-56
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• 2012

In general, a power decoupling method using electrolytic capacitor is used to solve a problem that appears 120[Hz] ripple of grid at the PV module output. But electrolytic capacitor has a effect on the short lifetime and low reliability of PV system. Therefore, studies which replace the large electrolytic capacitor with small film capacitor have been researched in resent years. This paper proposes flyback inverter which can be replaced with film capacitor by connecting the circuit implementing zero voltage switching in PV side. The proposed system is validated by PSIM simulation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.207-210
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• 2004

In oil-filled equipment such as transformers, partial discharge or local overheating will make insulating material(oil, kraft paper, proclain and wood) be stressed and generate many sort of gases($CO,\;CO_2,\;H_2,\;C_2H_4$) which are dissolved in transformer oil. The ratio of this gas can make diagnostic tecchniques of the lifetime of transfomer so, it is important to monitoring $H_2$ gas continuously. This paper developes a system of detecting about $H_2$ gas by using $H_2$ gas sensor, and we describe operation and performance of this system

• Bulletin of the Korean Chemical Society
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• v.20 no.7
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• pp.796-800
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• 1999

Three anthrylazacrown ethers in which the anthracene fluorophore π system is separated from the electron donor atoms by one methylene group were synthesized, and their photophysical study was accomplished. These fluorescent compounds showed a maximum fluorescence intensity at pH=5 in aqueous solutions and a decrease in fluorescence intensity upon binding of paramagnetic metal cations (Mn 2+ (d 5 ), Co 2+ (d 7 ), Cu 2+ (d 9 )). The decrease in fluorescence intensity may be attributed to the paramagnetic effect of metal cations to deactivate the excited state by the nonradiative quenching process. The benzylic nitrogen was found to play an important role in changing fluorescence intensity. From the observed linear Stern-Volmer plot and the fluorescence lifetime independence of the presence of metal ions, it was inferred that the chelation enhanced fluorescence quenching (CHEQ) mechanism in the system is a ground state static quenching process. Enhanced fluorescence was also observed when an excess Na + ion was added to the quenched aqueous solution, and it was attributed to cation displacement of a complexed fluorescence quencher.

• Journal of Aerospace System Engineering
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• v.3 no.4
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• pp.27-34
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• 2009

This paper deals with the lifetime prediction of Aircraft Flaperon Joint made of AISI 4130 steel. Reviews are performed on the published damage models at first. And three different damage models are used for predicting the fatigue life of the structure subjected to variable amplitude fatigue loading. These models require no increase in complexity of use, nor do they require additional material property or mission loading information to achieve the improved accuracy. Finally a comparison among the fatigue results is performed. It is observed that the Miner's rule could predict longer life than other cumulative damage models which take into account loads below the endurance limit.

• Nuclear Engineering and Technology
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• v.34 no.2
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• pp.176-185
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• 2002

A 4-bundle shift refuelling method of CANDU6 F/H (Fuel Handling) System is analyzed to assess the operational flexibility and capacity of F/H system. The current 8-bundle shift refuelling scheme requires to refuel eight fuel bundles from a single fuel channel, and to refuel 14 fuel channels in a week on average assuming that the reactor is in a steady state. The analysis showed that the 4-bundle shift refuelling method increases F/M (Fuelling Machine) duty cycle and operator load. However, the fuellin’g method change from the 8- to 4-bundle shift refuelling ill not require additional team of operators. A marginal increase in the maintenance cost may be resulted in by the change of fuelling method and the increase of fatigue usage factors requires some components to be replaced during the FM lifetime.

• Journal of Electrochemical Science and Technology
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• v.12 no.1
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• pp.159-165
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• 2021

YSZ based anode supported solid oxide fuel cells (SOFCs) were prepared, and two cells with different electrolyte thicknesses were connected in series for the simulation of a cell-imbalanced fuel cell stack. Pure YSZ cells in a series connection exhibited a rapid degradation when a thick electrolyte cell was operated under a negative voltage. On the other hand, ceria added-YSZ cells in a series connection were stable under similar operating conditions, and the power density and impedance were about the same as those before tests. The improved stability was due to the reduction of internal partial pressure in the electrolyte by locally increasing the electronic conduction. Thus, we propose a new protection method, i.e., the local addition of ceria in the YSZ electrolyte, to extend the lifetime of a cell-imbalanced SOFC stack.

• Journal of the Semiconductor & Display Technology
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• v.19 no.4
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• pp.88-93
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• 2020

Based on the capture-emission energy (CEE) maps of CMOS devices, a physics-informed machine learning model for the bias temperature instability (BTI)-induced threshold voltage shifts and low frequency noise is presented. In order to incorporate physics theories into the machine learning model, the integration of artificial neural network (IANN) is employed for the computation of the threshold voltage shifts and low frequency noise. The model combines the computational efficiency of IANN with the optimal estimation of Gaussian mixture model (GMM) with soft clustering. It enables full lifetime prediction of BTI under various stress and recovery conditions and provides accurate prediction of the dynamic behavior of the original measured data.