• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.10
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• pp.494-499
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• 2001

The effects of accelerated Ultraviolet (UV) radiation on High temperature vulcanized (HTV), Room temperature vulcanized (RTV) silicone rubber and two types of ethylene propylene diene terpolymer (EPDM) used for composite insulator were investigated by hydrophobicity class (HC), surface voltage decay after corona charging, SEM-ES, FTIR and XPS. The contact angle in two kinds of silicone rubber was scarcely change, but EPDM occurred to the loss of hydrophobicity followed by surface cracking and chalking. The surface voltage decay on UV-treated silicone rubber and EPDM showed a different decay trend with UV treatment. EDS and XPS analysis indicated that the oxygen content increased with UV treatment time in all samples. For silicone rubber, the oxidized groups of inorganic silica-like structure increased with UV treatment time. The oxidized carbon of C=O, O=C-O in EPDM increased. These oxidized surface for each material had different electrostatic characteristics, so deposited charges were expected to have different impacts on their surface hydrophobicity. The degradation mechanism based on our results was discussed.

• Journal of the Korean Society of Safety
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• v.23 no.5
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• pp.49-53
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• 2008

Glow discharge has lots of attractive properties, such as lower discharge sustaining voltage, no generation of ozone, and so on. And more, ionizer was developed recently using an atmospheric pressure glow discharge. On the other hand, ionizer needs a compressed or blown air to transport ion for charged objects. This air is very useful in explosive hazardous area to prevent the explosion of flammable gas and/or vapor by ignition sources, e.g. electrical spark. In this paper, we investigated the ionizing characteristic of atmospheric pressure glow discharge by controlled air flow rate from 5 liters to 60 liters a minute, and compared with decay time between the corona discharge and glow discharge as a function of some direction and distance from discharge ion source. We confirmed that an air flow rate needs 25 liters a minute to sustain the most suitable atmospheric pressure glow discharge and to increase an ionizing efficiency.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1817-1819
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• 2004

From the plasma application point of view, electron temperature and density are one of the most important parameters for plasma process. But it is only available to control plasma by adjusting external factors like gas pressure and input power. In this paper, pulse-modulated plasma is generated by modulating 13.56GHz RF power with 1, 5, 10kHz pulse. And Langmuir probe technique is used to study the distribution of electron temperature and density. When modulated pulse is off, electron temperature decreases gradually in form of exponential decay. The value t of exponential decay slope is 33.619, 13.834, 10.803 in 1kHz. 5kHz. 10kHz. This implies that this method can be used to control electron temperature and density.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.8
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• pp.1083-1090
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• 1998

A kind of three-way check valve, so called hydraulic calve was proposed for the substitute of the density lock of passive reactor such as SPWR (System-Integrated Pressurized Water Reactor). The function of the valve are the separation of the borated water from main coolant loop for normal operation and the insurge of the water into the loop for shutdown and the removal of the decay power when the main coolant flow rate is not enough. To verify the operability and the characteristics of the valve, experimental works were executed with 1/3 scale model calve. Also a diffuser model was proposed for the theoretical analysis of the valve.

• Journal of the Korea Furniture Society
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• v.19 no.1
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• pp.83-90
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• 2008

Gypsum-wood composites were made by introducing inorganic substances into wood using calcium chloride, first treating solution, and sodium sulfate, secondary treating solution, by double diffusion process under atmospheric pressure at room temperature. The process conducted as follows: water saturated specimens were soaked in calcium chloride solutions at several concentration. Then the specimens were soaked further in saturated sodium sulfate solution, and they were leached in flowing tap water for 24h. To attain sufficient weight percent gain (WPG) values, the suitable concentration of calcium chloride and soaking time in saturated sodium sulfate solution were 20% and 48h, respectively. Inorganic substances were produced mainly in the lumina of tracheides. It was made sure that these substances were dihydrate gypsum($CaSO_4$ $2H_2O$) by X -ray microanalysis (SEM-EDX). The composites had good fire resistance due to low heat transfer rate of gypsum formed in wood. However, the composites had little decay resistances, because they showed high weight losses by test fungi attacks.

• Korean Journal Plant Pathology
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• v.14 no.5
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• pp.526-530
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• 1998

The effect of field sanitation using ecological characters of the pathogen was investigated for controlling Phomopsis seed decay in soybean. Field sanitation which was eliminated the inoculum by removing host debris, abscised petioles and cotyledones out of field, reduced remarkably infection percentage of pods and seeds by Phomopsis spp. as compared to the inoculated field. Neverthless, seed infection was 28.7% in the sanitized field. The fields sanitized by benlate application around the soybean plants also decreased seed infection with Phomopsis spp. Total seed infection including that with miscellaneous pathogens occurred as much as 75∼79% to the no application and their control values were 34∼42% over the routine application schedule. Even though it was not satisfactory, field sanitation seemed to be effective in controlling Phomopsis seed decay when infection pressure was low level. Diaporthe phseolorum va. sojae, D. phaseolorum var. caulivora and Phomopsis longicolla were mostly identified from soybean seeds and Colletotrichum truncatum, Cercospora kikuchiana were also isolated in sequence. Field sanitation did not significantly increase in soybean yield over the no application, while routine application schedule did in field.

• Journal of Biomedical Engineering Research
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• v.6 no.2
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• pp.63-68
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• 1985

Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70$\pm$1.32mmHg/min)compared to CF dialyzers(4.32$\pm$0.55mmHg/min)(p<0.05). However, there was no observable difference in the UFR between the two dialyzers. Neither APD nor UFR showed any significant increase with an increasing number of reuses for up to more than 20reuses. A substantial number of failures observed in APD(larger than 20mmHe/min)on the reused dialyzers(2 out of 40 CP and S out 26 C-DAK) were attributed to the Possible damage on the fibers. The CF 15-11 HFDs which failed APD test did not show changes in the UFR compared to normal dialyzers indicating that APD is a more sensitive test than UFR test to evaluate the integrity of the fibers.

• Korean Chemical Engineering Research
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• v.52 no.1
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• pp.75-80
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• 2014

The convective flow structures in the vapor phase on earth are shown to be single unicellular, indicating the solutally dominant convection is important. These findings reflect that the total molar fluxes show asymmetrical patterns in a viewpoint of interfacial distributions. With decreasing the gravitational level form $1g_0$ down to $1.0{\times}10^{-4}g_0$, the total molar fluxes decay first order exponentially. It is also found that the total molar fluxes decay first order exponentially with increasing the partial pressure of component B, PB (Torr) form 5 Torr up to 400 Torr. Under microgravity environments less than $1g_0$, a diffusive-convection mode is dominant and, results in much uniformity in front of the crystal regions in comparisons with a normal gravity acceleration of $1g_0$.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.5
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• pp.271-280
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• 2021

The code developed using a pressure-based method for unified conservation laws of incompressible/compressible fluids is expanded to handle moving or deforming body boundaries using the hybrid Cartesian/immersed boundary method. An instantaneous pressure field is calculated from a pressure Poisson equation for the whole fluid domain, including the compressible gas region. The polytropic gas is assumed for the compressible fluid so that the energy equation is decoupled. Immersed boundary nodes are identified based on edges crossing body boundaries. The velocity vector is reconstructed at the immersed boundary node using an interpolation along the assigned local normal line. The developed code is validated by comparing the time histories of pressure and wave elevation for sloshing in a rectangular and a membrane-type tank. The validated code is applied to simulate air cushion effects in a rectangular tank under sway motion. Time variations of pressure fields are analyzed in detail as the air pocket pulsates. It is shown that the contraction and expansion of the air pocket dominate the pressure loads on the wall of the tank. The present results are in good agreement with other experimental and computational results for the amplitude and the decay of the pressure oscillations measured at the pressure gauges.

• Explosives and Blasting
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• v.35 no.1
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• pp.1-17
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• 2017

The understanding of the pressure associated with air blast, which travels through air, and its effect on surface and underground structures is highly important. It is necessary to determine the pressure change with time and distance for a computer simulation of the explosion impact on a structure. From the previous studies, many empirical equations for estimating the parameters related to the pressure change. In this study, the empirical equations for predicting peak overpressure, duration of positive phase, impulse, minimum negative pressure, duration of negative pressure, arrival time, and decay constant were reviewed and analyzed. Also, the pressure changes predicted from the Kingery equation, which is the most commonly used, and from the other empirical equations were compared.