• 전기의세계
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• v.17 no.3
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• pp.7-28
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• 1968

When a insulator plate is inserted to the discharge path of a space discharge gap in which the field strength is not uniform, the spark voltage under the atmospheric pressure between the electrodes decreases or rises according to the position of the insulating plate. Also it is reported that if a metallic barrier plate is inserted to the discharge path of the same space discharge gap, similar variations of spark voltage are found. Speaking briefly, mensioned above are the spark voltage characteristics when an insulator or metallic barrier is inserted to the space discharge gap. Also some experimental results, concerning to the surface creepage flash over characteristics at the case when an insulator barrier is inserted to the discharge path of a surface creepage discharge gap, were reported by Peek. But up to now there are no reports on surface flash over voltage characteristics at the case when a metallic barrier is inserted to the surface creepage gap. In this study the effects of a conducting metallic barrier inserted to the path of a surface creepage discharge gap on the flash over voltage characteristics are investigated theoretically and experimentally, and got some important results, clearing the effects of the position and width of a conducting barrier is inserted, the surface flash over voltage characteristics appear as an Inverse N or W Characteristics. Such theoretical or experimental results may have some relation not only with the effects of dry belt and snow on suspension insulators, but also with the effects of dirty zone or water drops on the surface creepage flash over voltage.

• Ocean Systems Engineering
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• v.11 no.1
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• pp.1-16
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• 2021

Experimental and numerical investigations were conducted to study the performance of a surface-fixed horizontal porous wave barrier in regular waves. The characteristics of the reflection and transmission coefficients, energy dissipation, and vertical wave force were examined versus different porosities of the barrier. Numerical simulations based on 3D Reynolds Averaged Navier-Stokes equations with standard low-Re k-ε turbulent closure and volume of fluid approach were accomplished and compared with the experimental results conducted in a 2D wave tank. Experimental measurements and numerical simulations were shown to be in satisfactory agreement. The qualitative wave behavior propagating over a horizontal porous barrier such as wave run-up, wave breaking, air entrapment, jet flow, and vortex generation was reproduced by CFD computation. Through the discrete harmonic decomposition of the vertical wave force on a wave barrier, the nonlinear characteristics were revealed quantitatively. It was concluded that the surface-fixed horizontal barrier is more effective in dissipating wave energy in the short wave period region and more energy conversion was observed from the first harmonic to higher harmonics with the increase of porosity. The present numerical approach will provide a predictive tool for an accurate and efficient design of the surface-fixed horizontal porous wave barrier.

• Journal of the Korean Institute of Gas
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• v.16 no.3
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• pp.65-70
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• 2012

Experimental investigations were carried out to examine the explosion characteristics by different sizes in the wall surface shape of a water gel barrier in an explosion chamber, 1,600 mm in length with a square cross-section of $100{\times}100\;mm^2$. The sizes in the wall surface shape were varied by using water gel barriers with a cross-section of $100{\times}200\;mm^2$ and its were varied in the bottom of the chamber away 300, 700 and 1,100 mm, respectively from the closed end of the chamber. The flame propagation images were photographed with a high speed camera and the pressure was recorded using a pressure transducer and a data acquisition system. It was found that as the size of the wall surface shape increased, the flame propagation process and the time taken to reach the maximum pressure were found to be faster. As a result, both the flame speed and the explosion overpressure increased as the size of the wall surface shape increased.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.9
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• pp.421-426
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• 2005

A wire-plate discharge system with a slit barrier has been proposed and investigated experimentally by focusing on the discharges on the slit barrier and ozone generation characteristics. This wire-plate discharge system with a slit barrier can generate an intensive corona discharges, and produce corona discharge twice, once from the corona wire electrode and second time from the surface and the slits of the slit dielectric barrier. As a result this propose wire-plate discharge system with the slit barrier can produce greatly increased ozone than without the slit barrier. This type of wire-plate discharge system with the slit barrier could be used for effective ozone generation as a means with retard to the removal of pollutant gas

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.28-28
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• 2010

The secondary barrier of cargo containment for membrane LNG tank is composed of composite materials such as rigid triplex (rigid secondary barrier, RSB) and flexible triplex (flexible secondary barrier, FSB). RSB and FSB are adhered to each other using an epoxy adherent and the quality of the secondary barrier depends on the bonding strength between them. The bonding strength between RSB and FSB is greatly influenced by the surface condition of RSB prior to joining. In this study, the effect of surface condition prior to joining on the joint strength and the fracture mode occurred between RSB and FSB have been examined in order to establish a proper surface treatment method for improving the bonding strength at the temperature of $-170^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.8
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• pp.505-509
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• 2016

We have investigated the characteristics of amorphous silicon (a-Si) thin-film solar cell by inserting barrier layer. The conversion efficiency of a-Si thin-film solar cells on graphite substrate shows nearly zero because of the surface roughness of the graphite substrate. To enhance the performance of solar cells, the surface morphology of the back side were modified by changing the barrier layer on graphite. The surface roughness of graphite substrate with the barrier layer grown by plasma enhanced chemical vapor deposition (PECVD) reduced from ~2 um to ~75 nm. In this study, the combination of the barrier layer on graphite substrate is important to increase solar cell efficiency. We achieved ~ 7.8% cell efficiency for an a-Si thin-film solar cell on graphite substrate with SiNx/SiOx stack barrier layer.

• Bulletin of the Korean Chemical Society
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• v.18 no.2
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• pp.149-151
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• 1997

Barrier height on the surface was monitored at 77 K by observing the inflection of V-I characteristics of ZnO(1010)-ZnO(1010) contact in the surface reaction of oxygen species with carbon monoxide. The contact showed inflections at 10-20 mV and 10-50 mV for the sample adsorbed oxygen at 298 K and 573 K, respectively. When the sample adsorbed oxygen at 573 K was exposed to carbon monoxide at 298 K and 573 K, inflections were observed at 10-40 mV and 10-30 mV, respectively. The results indicated that the adsorption of oxygen on ZnO increased the surface barrier height, and the reaction of carbon monoxide with the oxygen-preadsorbed (at 573 K) ZnO decreased the surface barrier height.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.5
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• pp.385-390
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• 1999

Surface corona discharge characteristics of a dc corona charged ferroelectric pellet barrier have been investigated experimentally. Electric charges stored on the surfaces of the ferroelectric pellets by a dc corona discharge provide partial electric fields on the surfaces of the ferroelectric pellets, which could generate surface corona discharges on the ferroelectric pellets. This system utilizes both the surface discharges on the ferroelectric pellet barrier and the corona discharge between corona tip and mesh electrode. Positive and negative dc voltages were applied to the tip to generate partial discharges, and corona currents were estimated to investigate the buildup charge on ferroelectric pellets as a function of the applied time and the charge relaxation time constants of ferroelectric pellets. As a result, in the case of the negative corona discharge with the ferroelectric pellet barrier, the mean corona current and ozone generation increase greatly, and the surface discharges on the ferroelectric pellets can be fenerated efficiently. It is also found that, charge relaxation time, dielectric constants offerroelectric pellets, polarity of applied voltage and applied time affected to the surface discharges among the ferroelectric pellets.

• Journal of Periodontal and Implant Science
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• v.25 no.2
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• pp.321-340
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• 1995

The regeneration of destructed periodontal tissues is one of the ultimate objectives of periodontal therapy. Guided tissue regeneration technique was developed for the ideal regeneration of periodontal tissues. In order to investigate the role of fibronectin, laminin and tenascin in the regenerating process of periodontal tissues, the expanded PTFE barrier membranes(Gore Associates, USA) removed from the patients who had been treated by guided tissue regeneration(GTR) and guided bone regeneration(GBR) techniques were fixed in neutral formalin for 6-24 hours, embedded with paraffin, sectioned at $4-6{\mu}m$ in thickness, and immunohistochemically processed by Avidin-Biotin peroxidase complex method for detecting fibronectin, laminin and tenascin. Monoclonal mouse anti-human fibronectin antibody(Oncogene Science, USA., 1:100), monoclonal mouse anti-human laminin antibody(Oncogene Science, USA., 1:50) and mouse anti-human tenascin antibody(Oncogene Science, USA, 1:10) were used as primary antibodies. The light microscopic findings were as follows: (1) The distribution of fibronectin, laminin and tenascin was various according to the area of barrier membranes. (2) The distribution of fibronectin in case of GBR was extensive in the tissue on the outer surface of barrier membranes, and rare in the intervening space and on the inner surface. In case of GTR it was extensive on the outer surface and in the intervening space, and rare on the inner surface. (3) The distribution of laminin was rare in the tissue on the outer, the inner surface and intervening space of barrier membranes, regardless of GBR or GTR. (4) In case 'of GBR rare distribution of tenascin was observed on the outer surface only, except the inner surface and the intervening space of barrier membranes. In case of GTR the distribution of tenascin was extensive in the tissue on the outer surface, rare in intervening space and the inner surface. The results suggest that fibronectin, laminin and tenascin may play a important role in the regenerating process of periodontal tissue, and they may affect the outcome of healing.

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.433-439
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• 1999

In this study, the diffusion barrier properties of $1000\AA$ thick molybdenum compounds (Mox=1-5 Si) were investigated using sheet resistance measurements, X-ray diffractometry (XRD), and Rutherford back scattering spectrometry (RBS). Each barrier material was deposited by the de and rf magnetron co-sputtering of Mo and Si, respectively, and annealed at $500-700^{\circ}C$ for 30 min in vacuum. Each barrier material was failed at low temperatures due to Cu diffusion through grain boundaries and defects of barrier thin films or through the reaction of Cu with Si within Mo-barrier thin films. It was found that Mo rich thin films were less effective than Si rich films to Cu penetration activating Cu reaction with the substrate at a temperature higher than $500^{\circ}C$.