• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.415-421
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• 1999

This paper indicate that phase resolved partial discharge patterns are investigated on PET films containing artificial void of varing dimensions. In this study, we measured phase-resolved PD patterns and statistical parameter from PET specimens with IGT(insulation/airgap/insulation) structure by IEC 270 standard. Measurement system is the conventional PD detector using digital signal processing technique. The relationship of diameter and location of artificial void was discussed through the difference of $\pi$-q-n distribution and statistical analysis.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.64-71
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• 2016

Void fraction is an important parameter in the oil industry. This quantity is necessary for volume rate measurement in multiphase flows. In this study, the void fraction percentage was estimated precisely, independent of the flow regime in gas-liquid two-phase flows by using ${\gamma}-ray$ attenuation and a multilayer perceptron neural network. In all previous studies that implemented a multibeam ${\gamma}-ray$ attenuation technique to determine void fraction independent of the flow regime in two-phase flows, three or more detectors were used while in this study just two NaI detectors were used. Using fewer detectors is of advantage in industrial nuclear gauges because of reduced expense and improved simplicity. In this work, an artificial neural network is also implemented to predict the void fraction percentage independent of the flow regime. To do this, a multilayer perceptron neural network is used for developing the artificial neural network model in MATLAB. The required data for training and testing the network in three different regimes (annular, stratified, and bubbly) were obtained using an experimental setup. Using the technique developed in this work, void fraction percentages were predicted with mean relative error of <1.4%.

• Electrical & Electronic Materials
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• v.8 no.4
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• pp.495-503
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• 1995

As lengthen gap leng of artificial needle shape void 0.24.rarw.1.5[mm]), the amplitude of AE(Acoustic Emission) pulses was enlarged and number of pulses be generated was few. The longer gap length of void, the shorter breakdown time. As a result of this, I found that existen of void in insulation mate was fatal deterioration of insulation. According to phase angle of applied voltage, time being void was scattered largely in region of phase angle of pulses of origination in phase angle of applied voltage. The result will be used to analysis of void diagnosis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.301-304
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• 1997

Effects of volatile impurities on deterioration characteristics of XLPE were investigated. Block type plate with needle-plane electrode and artificial void filled with $N_2$gas or humidity was subjected under high electric field. The dyed region by oxidation reaction around the artificial void filled with humidity was detected before tee initiation. Electrical tree was started from the tip of void filled with $N_2$gas earlier than humidity.

• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4776-4797
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• 2022

In the one-dimensional thermal-hydraulic (TH) codes, a subcooled boiling model to predict the void fraction profiles in a vertical channel consists of wall heat flux partitioning, the vapor condensation rate, the bubbly-to-slug flow transition criterion, and drift-flux models. Model performance has been investigated in detail, and necessary refinements have been incorporated into the Safety and Performance Analysis Code (SPACE) developed by the Korean nuclear industry for the safety analysis of pressurized water reactors (PWRs). The necessary refinements to models related to pumping factor, net vapor generation (NVG), vapor condensation, and drift-flux velocity were investigated in this study. In particular, a new NVG empirical correlation was also developed using artificial neural network (ANN) techniques. Simulations of a series of subcooled flow boiling experiments at pressures ranging from 1 to 149.9 bar were performed with the refined SPACE code, and reasonable agreement with the experimental data for the void fraction in the vertical channel was obtained. From the root-mean-square (RMS) error analysis for the predicted void fraction in the subcooled boiling region, the results with the refined SPACE code produce the best predictions for the entire pressure range compared to those using the original SPACE and RELAP5 codes.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1391-1398
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• 2009

The vibrating table method is widely used to estimate the minimum void ratio $e_{min}$. The existing method recommended in ASTM and KS F, however, can not consider the particle crushing during the vibrating table test. In this study, the particle cursing phenomenon was investigated by comparing vibrating table test with pluviation method using artificial sand (K-7). Vibrating table test for the artificial sand was confirmed which can crush of particle during the test. This study demonstrates that vibrating table test is an ineffective method to produce the more reliable $e_{min}$ of artificial sand.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.485-488
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• 2005

The results of an experiment on the sea water purification of the porous concrete using granular artificial zoelite and its influence on the physical and mechanical properties are reported in this paper. Two different sizes of coarse aggregate of 5$\∼$13, 13$\∼$20mm, and three of void ratio(15, 20 and 30 percent) for a given size of aggregate were used. In the water permeability, an aggregate of the size of 13$\∼$20mm is much higher than that of the 13$\∼$20mm, but the water permeability is smaller in the less design void ratio. and In the compressive strength, an aggregate of the size of 5$\∼$13mm is much higher strength than that of the 13$\∼$20mm, but the compressive strength is higher in the less design void ratio.

• Korean Journal of Hydrosciences
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• v.3
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• pp.11-29
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• 1992

Recently, rapid industrialization, urbanization and higher living standards accelerate to increase groundwater consumption resulting in continuously dropping groundwater elevations. To maintain enough groundwater volume without dropping groundwater elevations, the proper groundwater rechatge is necessary. The groundwater rechatge can be classified into two categories which are natural rechatge and artiticial rechatge. Even though the natural rechatge through by dired infiltration from the rainfall is desirable, the artificial groundwater rechatge is necessaty when the increment of groundwater consumption exceeds natural recharge rate. Well method and scattering method are utilized as artificial rechatging method, a severe disadvantage, which is the reduction of the void of soil surface, is indicated in the well method. Recently, the underground piping method, which is a scattering method, is receiving increasing attention as a proper recharging method. The method is indirectly to supply water to the underground using an underground piping system. Therefore, the void of soil surface is not severely reduced and better infiltration rate can be achieved. In this paper, the artificial groundwater rechatge using underground piping method is investigated through experiments and numerical analysis. The influence of the groundwater by underground piping method is evaluated through comparing recharging heights. Good agreements between experiments and numerical analysis are obtained and the artificial groundwater recharge by underground piping method is well tested and verified.

• Journal of the Korean Ceramic Society
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• v.45 no.11
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• pp.750-754
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• 2008

The artificial aggregates with dense surface layer (shell) was fabricated and the dependence of water emission rate upon the shell structures was studied. The EAF dust containing many flux components and waste white clay with ignition loss of above 48% were used as for liquid phase and gas forming agents during a sintering process respectively. In addition, the shell structure was modified with various processes and the modification effect on water emission rate was analyzed. The pores under $10{\mu}m$ were found in the sintered artificial light aggregates and disappeared by incorporating to a bigger pore during re-sintering. The water emission rate in an initial step depended on a void content of aggregates filled in a bottle rather than a shell structure. But, after 7 days where the water emission of the aggregate with a shell is above 40%, the shell of aggregates suppressed the water emission. The core of aggregates was exposed and most shell was lost when crushed to smaller size so, the ability for suppressing water emission of the crushed aggregates decreased. The activation energy for the water emission was $3.46{\pm}0.25{\times}10^{-1}$J/mol for the most specimens showing that the activation energy is irrelevant to the pore size distribution and shell structure.

• Journal of Ocean Engineering and Technology
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• v.21 no.4
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• pp.21-27
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• 2007

The multiplication equipment of marine products with artificial upwelling structures could be useful in the fishing grounds near coastal areas. Artificial upwelling structures could move the inorganic nutrients from the bottom to the surface. Artificial upwelling structures have been used to improve the productivity of fishing grounds. Until now, research on artificial upwelling structures has been related to the distribution of the upwelling region, upwelling structures, and the marine environment. However, little work on the optimum design of the rubber-mound artificial upwelling structures has been done to increase the efficiency of drawing up the inorganic nutrients. This study investigated the optimum cross-section of rubber-mound artificial upwelling structures by means of hydraulic experiments. The hydraulic experiments include the falling test of rubber. Based on the results of the falling test, the relationship between the length of the rubber mound and water velocity, and the relationship between the shape of the rubber and the stratification parameter were established. In addition, the effect of the void ratio of various artificial structures on the stratification parameter was studied. From the experiment, it was found that upwelling could be enhanced when the ratio of structure height to water depth was 0.3 and stratification parameter was 3.0. The upwelling was not improved when the void ratio exceeded 0.43. The optimum size of rubber mounds was determined when the incident velocity was influenced by the mean horizontal length rather than size of block.