• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.581-583
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• 1993

One of the principal problems encountered in the use of fiber reinforced composites is to establish an active fiber surface to achieve maximum adhesion between resin and fiber surface. In order to improve the interface bonding, the surface of glass fiber should be treated with silane coupling agent in ordinary composite manufacturing processes. However, the price of the coupling agent is very high and in the treating process voids are formed, which decreasees electrical and mechanical strength. We want to develope new process that will overcome the disadvantage of the coupling agent and achieve maximum adhesion at the interface between resin and fiber by active plasma treatment on the glass fiber surface. In this study, we investigate the improvement of contact angle on the glass plate surface as the first step in developing new GFRP.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.3
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• pp.341-349
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• 2010

It is well known that manganese is hard to oxidize under neutral pH condition in the atmosphere while iron can be easily oxidized to insoluble iron oxide. The purpose of this study is to identify removal mechanism of manganese in the D water treatment plant where is treating bank filtered water in aeration and rapid sand filtration. Average concentration of iron and manganese in bank filtered water were 5.9 mg/L and 3.6 mg/L in 2008, respectively. However, their concentration in rapid sand filtrate were only 0.11 mg/L and 0.03 mg/L, respectively. Most of the sand was coated with black colored manganese oxide except surface layer. According to EDX analysis of sand which was collected in different depth of sand filter, the content of i ron in the upper part sand was relatively higher than that in the lower part. while manganese content increased with a depth. The presence of iron and manganese oxidizing bacteria have been identified in sand of rapid sand filtration. It is supposed that these bacteria contributed some to remove iron and manganese in rapid sand filter. In conclusion, manganese has been simultaneously removed by physicochemical reaction and biological reaction. However, it is considered that the former reaction is dominant than the latter. That is, Mn(II) ion is rapidly adsorbed on ${\gamma}$-FeOOH which is intermediate iron oxidant and then adsorbed Mn(II) ion is oxidized to insoluble manganese oxide. In addition, manganese oxidation is accelerated by autocatalytic reaction of manganese oxide. The iron and manganese oxides deposited on the surface of the sand and then are aged with coating sand surface.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.581-585
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• 2010

The surface of Alnico, one of the industrial dust waste, was treated with 1,3,5-trivinyl-1,3,5-trimethylcyclotrisilazane (VMS) as a surface treating agent and used as the filler for vibration isolator rubber. Maleated EPDM prepared from bulk polymerization of EPDM with maleic anhydride was copolymerized with ${\alpha},{\omega}$-bis(3-aminopropyl)polydimethylsiloxane to obtain maleated EPDM-polydimethylsiloxane copolymer (MEPDM-PDMS). EPDM/Alnico/MEPDM-PDMS vibration isolator rubber was prepared from compounding with Alnico treated with surface treating agent, 25 and 50 phrs to EPDM, respectvely based on 1 to 10 wt% of MEPDM-PDMS to EPDM. From the measurement of the thermal properties to the rubber, the glass transition temperatures (Tg) for the rubber containing maleated EPDM-PDMS copolymer was slightly lower temperature, $33^{\circ}C$ than EPDM rubber, and also DMA results showed higher tan ${\delta}$ peak to the rubber prepared from compounding with EPDM-PDMS copolymer. From the results, rubber prepared using EPDM-PDMS copolymer had better vibration isolator property.

• Journal of Ocean Engineering and Technology
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• v.9 no.2
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• pp.71-74
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• 1995

A numerical model capable of simulating a 2-D airfoil flying over in the vicinity of the waves is discussed. Instead of treating the problem as a heaving oscillation one above the rigid flat wall, sources are distributed on the prescribed wave profile. The wave deformation due to the airfoil is assumed to be negligible and treated as a rigid undulated wall. The source and vortex are distributed on the surface of the foil. It is found that the variation of $C_L$ with wave steepness in severe and that the lift variation due to waves decreases as the wing height above the water surface increases.

• Journal of the Korean Society for Heat Treatment
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• v.9 no.1
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• pp.45-52
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• 1996

Different crystallographic planes, at a gas-metal interface, have different surface energy. To grow the (100) grains of 6.5wt%Si-Fe alloy preferentially, it was heat-treated in the atmosphere of sulfur by using the surface energy. When the specimen is heat-treated for 1 hour at $1175^{\circ}C$ by using the atmosphere of sulfur produced by heating at $75^{\circ}C$, (100) grains were grown to 3.5mm. Owing to the growth of (100) grains, the coercive force was decreased to 2.1 A/mm, and the magnetic induction at 800(A/mm) was increased to 1.61T.

• Electrical & Electronic Materials
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• v.8 no.2
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• pp.136-143
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• 1995

With the contact angle of phase dropping epoxy resin on the inorganic filler(glass plate) surface treated with air plasma, we have studied about the interfacial wettability between epoxy resin and glass plate as a simple model of glass fiber reinforced composite materials. The contact angle on the inorganic filler surface varied with surface treatment conditions. The contact angle significantly depends on plasma treating time and environment temperature in the oven. From the view point of plasma treatment condition in this work, when discharge conditions were pressure 200mtorr, voltage 800V, magnetic flux density 8OGauss, optimum treatment time were proved as 3,4 and 5 minutes for the environment of >$80^{\circ}C$, >$100^{\circ}C$ and >$120^{\circ}C$, respectively.

• Journal of the Korean institute of surface engineering
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• v.29 no.2
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• pp.132-139
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• 1996

Experiments on the automatic control of NaOH concentration and on the spraying condition of NaOH solution in the alkaline degreasing process of a continuous hot-dip galvanizing line have been carried out in order to improve degreasing performance of a galvanizing sheet steel using laboratory degreasing and galvanizing simulators. The concentration of NaOH for the good degreasing has been determined to be 6.0% and more and this concentration has been able to be automatically well controlled within $\pm$0.1% by employing a solution electrical conductivity meter under a flow injection analysis condition rather than by employing a sodium ion selective electrode in the degreasing simulator. Frequent blocking of the spraying nozzles of the solution has been reduced considerably by the set-up and periodical operation of an automatic valve system in the nozzle system. By applying this automatic valve system and by automatic controlling the NaOH concentration and other ordinary variables in the degreasing process, the degreasing performance has been increased from the conventional 76% to the new 85%.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.602-605
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• 2008

The anode sheath structure in the hollow anode of an anode-layer type Hall thruster was numerically computed using a fully kinetic 2D3V Particle-in-Cell and Direct Simulation Monte Carlo(PIC-DSMC) code. By treating both ions and electrons as particles, anode surface region, which is electrically non-neutral, was analyzed. In order to analyze in detail, the calculation code was parallelized using Message Passing Interface (MPI). The code successfully simulated the discharge current oscillation. In the low magnetic induction case, ion sheath appears in the anode surface because ionization is enough to maintain the plasma occurs in the anode hollow. As the magnetic induction increases, main ionization region move to outside of the anode. At the same time, anode sheath voltage decreases. In the high magnetic induction case, electron sheath appears on the anode surface periodically because the ionization occurs mainly in the discharge channel. This anode sheath condition shift can be explained using the simple sheath model.

• Structural Engineering and Mechanics
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• v.78 no.4
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• pp.497-518
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• 2021

In this study, a new method for treating the wall boundary in smoothed particle hydrodynamics (SPH) is proposed to simulate free surface flows effectively. Unlike conventional methods of wall boundary treatment through boundary particles, in the proposed method, the wall boundary condition is directly imposed by adding boundary truncation terms to the mass and momentum conservation equations. Thus, boundary particles are not used in boundary modeling. Doing so, the wall boundary condition is accurately imposed, boundary modeling is simplified, and computation is made efficient without losing stability in SPH. Performance of the proposed method is demonstrated through several numerical examples: dam break, dam break with a wedge, sloshing, inclined bed, cross-lever rotation, pulsating tank and sloshing with a flexible baffle. These results are compared with available experimental results, analytical solutions, and results obtained using the boundary particle method.

• Journal of Periodontal and Implant Science
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• v.38 no.3
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• pp.453-466
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• 2008

Purpose: The purpose of this research is to study about initial adhesion, proliferation and activation of osteoblast to titanium surface treated with machined, hydroxyapatite coating, resorbable blast material blasting and anodizing method. Material and Methods: After treating the titanium surface of each block with machined, impurities were removed and sterilized. The number of cells attached from cultured osteoblast of respective experimental groups were measured at 1, 4, 7, and 14day and alkaline phosphatase, calcium, and inorganic phosphate concentration of cultured solution was measured. Result: Anodizing group showed the highest rate of cell attachment and proliferation activity. RBM treated group showed the highest increasing on their alkaline phosphatase activity, on the calcium apposition, on inorganic phosphate apposition of 1 and 4 days in cultured osteoblast to compare with other groups. Conclusion: On the basis of these findings, we conclude that surface modification of titanium was profoundly effected on the attachment, proliferation and activation of osteoblast in initial stage osseointegration.