• Transactions on Electrical and Electronic Materials
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• v.7 no.5
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• pp.235-239
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• 2006

Charge dynamics in polymeric materials after aged under ac electric field using the pulsed electroacoustic (PEA) technique is reported. The emphasis is placed on charge decay. The charge dynamics of the ac aged additive free low density polyethylene (LDPE) samples under dc bias differ from the sample without ac ageing, indicating changes brought in by ac ageing. It is believed that a slow decay rate of charge in the ac aged sample is related to the formation of deep traps in the material. However, chemical analysis by infrared spectroscope (FTIR) and Raman microscope reveals no significant chemical changes taken place in the bulk of the material after ac ageing. Further experiments on irradiated LDPE have revealed a similar behaviour, i.e. the charge decay is slower in irradiated samples than that of fresh sample. The findings presented clearly indicate that space charge measurement can be used as a diagnostic tool to monitor ageing in polymeric materials.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.9
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• pp.502-509
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• 2000

In this paper in order to evaluat quantitavely the formation mechanism of space charge and its effects on the conduction characteristics in LDPE we have carried out the numerical analysis on the basis of experimental results of space charge distribution cathode field and current with time which had been simultaneously measured at applied field of 50kV/mm and room temperature. As the models for numerical analysis we employ the Richarson-Schottky theory for charge injection from electrode into LDPE and the band-tail conduction at crystalline regions and the hopping conduction by traps which mainly exist at the interface regions of crystalline-amorphous region for charge transport in LDPE. Futhermore in order to investigate the influence of physical parameters on the time characteristcs of space charge distribution and measured current we have changed the values of trap density activation energies for charge injection and transport and have analyzed their effects.

• Journal of the Korea Institute of Building Construction
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• v.8 no.2
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• pp.121-129
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• 2008

Domestic exoteric construction market by opening of world construction market with recent FTA of rapidly change. On these time, need quality increase of construction to possess government official and international competitiveness of customer satisfaction by offering consumer building of good quality. Therefore, must establish direction to inspects and must advance forward formation government official's present actual conditions for building company's QI. This study is as following if summarize studying result of formation government official to improve quality in construction spot. First, formation's CEO will for QI need side improvement the formation government official enemy by important thing. Second, at checking activity and systematic action that participate of responsible persons cooperation enterprise space-time by complete charge department organization should be achieved. Third, complete charge department for quality control operation large size construction firm substantially formation Organizational well operate, but heavy hydrogen building company was construed by greatly unprepared misgovernment. AHP analysis result complete charge department is serious necessity, and the CEO under direct control organizational structure was construed by thing which can bring excellent effect in operation management side of quality business side and formation. Therefore, heavy hydrogen building company should does to occupy competitive power high position with tissue at active quality complete charge deputy.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1438-1440
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• 1998

In this work, simultaneous measur of space charge and conduction current was c out in LDPE with air gap by Pulsed-Electro-Aco Method. Also, effect of long time charging at con electric field on the formation of space charge conduction was investigated. From the experim results. we knew that the homo space charge formed near the dielectric surfaces and moving the bulk of dielectric as the electric field elevated. This was related with the deep traps b carriers and de trapping by Poole-field lowering conduction current was coincident with the Pool emission. From the long time charging experimen obtained the results that the negative space was moving into the dielectric bulk as the cha continued and the positive space charge accumulated at upper surface of LDPE.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.2
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• pp.247-253
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• 2015

The components of an aero-engine gas path cannot be monitored in a timely way due to a lack of real-time monitoring technologies. As an attempt to address this problem, we have conducted research on a condition monitoring technology based on the charging characteristics of particles in an aero-engine gas path, and emphatically analyze the formation of particles in an aero-engine gas path, the charging mechanism of carbon particles and the factors that influence the charge quantity and polarity. The verification experiments are performed on the simulated experiment platform and a turbo-shaft engine test bench. The results show the carbon particles' carry charge, and an obvious change in the total electrostatic charge level in the aero-engine gas path due to the increased carbon particles produced by burning or abnormal metal particles; the charge number is related to the size of particles, and the bigger carbon particles carry a negative charge and metal particles carry a positive charge; the change in engine power can lead to an obvious change in the level of electrostatic charge in the gas path, and the change in electrostatic charge results from the extra carbon particles formed in the rich-oil burning process. The research provides a reference for establishing the baseline of electrostatic charge while the engine runs on different power. The study also demonstrates the validity of the electrostatic monitoring technology and establishes a base for developing the application of electrostatic monitoring technology in aero-engines.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.377-378
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• 2008

Space charge formation in various glass materials under electron beam irradiation was investigated. Charging of spacecraft occurs in plasma and radiation environment. Especially, we focused on an accident caused by internal charging in a glass material that was used as the cover plate of solar panel array, and tried to measure the charge distribution in glass materials under electron beam irradiation by using a PEA (Pulsed Electro-Acoustic method) system. In the case of a quartz glass (pure $SiO_2$), no charge accumulation was observed either during or after the electron beam irradiation. On the contrary, positive charge accumulation was observed in glass samples containing metal-oxide components. It is found that the polarity of the observed charges depends on the contents of the impurities. To identify which impurity dominates the polarity of the accumulated charge, we measured charge distributions in several glass materials containing various metal-oxide components and calculated the trap energy depths from the charge decay characteristics of all glass samples. Furthermore, the dependence of the polarity of accumulated charges on the component of glass materials is discussed by using the models of energy bands.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.167-170
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• 2005

The mechanism of striation in the coplanar- and matrix-type plasma display panel (PDP) cells has been studied using the particle-in-cell Monte-Carlo Collision (PIC-MCC) model. The striation formation is related to the ionization energy of neutral atoms and the well-like deformation of space potential by space charge distribution. Negative wall charge accumulation by electrons on the MgO surface of the anode region is also one of the key factors for the formation of striation. The clearness of the striation phenomenon in PIC-MCC code in comparison with fluid code can be explained by using nonlocal electron kinetic effect.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1262-1264
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• 1994

Effects of molecular characteristics such as melt index and shapes of molecular weight distribution on the charge formation in LDPE have been investigated. Both homocharge and heterocharge were observed in LDPE depending on the value of melt index. It was found that the LDPE having intermediate melt indices shows heterocharge while the LDPE having small and high melt indecies shows homocharge. The shapes of molecular weight distributions were also found to affect the space charge in LDPE. These were explained by the role of short chains having low molecular weight in LDPE.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1428-1430
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• 1994

The accumulation of space charge in PE/PE/PE laminates was investigated using the low density polyethylenes having different melt indices from 0.25 to 45 g/10 min. Both heterocharge and homocharge accumulated in parent polyethylenes depend on the value of melt index. A general rule found in this study was that the heterocharge decreases as the melt index increases and finally the homocharge accumulates when the melt index is very high. Because of this reason, PE laminates showed different charge formation characteristics depending on melt index of polyethylene. Details of up to date results are described in the text.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.05a
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• pp.87-89
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• 1994

The effects of low molecular weight components of LDPE and sample molding condition were investigated to find the orgins for heterocharge in LDPE without any addtives. Low molecular weight chains of LDPE encourages the formation of heterocharge by being charged and migrating the counter electrode. The formation of heteroohage in LDPE was also effected by sample preparation process and the kind of a moling film. When PET film is used as a molding layer, the carbonyl, which may lead to increase the heterocharge, formed at surface of LDPE.