• Polymer(Korea)
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• v.32 no.4
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• pp.340-346
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• 2008

The aim of this study is to understand the effect of structure on the dispersion of both CNT and GNF in the phase of synthesized polyurethanes matrix. Various CNT/PU and GNF/PU composite films were prepared. Polyurethane having a different hard segment was blended with both CNT and GNF. PU having HDI as hard segment showed good dispersion with both CNT and GNF because of their linear structural character and molecular kinesis while PU having aromatic ring showed poor dispersion with those due to their structural complexity. Structural effect also induced the increase of its electro conductivity. The PU/CNT composite showed a bad dispersion (because of phase separation between PU matrix and CNT) but good electro conductivity at its surface (because CNT was collected on the surface of composite film due to low density of CNT). PU/CNT and PU/GNF composite films have quite low normalized sheet resistance value compared with silver/PU nanocomposite film because the fiber type filler could have much more contact points than that of sphere shaped silver particles have.

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.803-810
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• 1998

We have studied the catalytic combustion of soot particulate over perovskite-type oxides prepared by malic acid method. The catalysts were modified to enhance the activity by substitution of metal into A or B site of perovskite oxide. In addition, the reaction conditions, such as temperature, $O_2$ concentration, space velocity have been studied. The effect of $SO_2$ pretreatment and water introduced into reactants were also examined. In the $LaCoO_3$ catalyst, the partial substitution of alkali metals into A site enhanced the catalytic activity in the combustion of soot particulate and the activity was shown in the order : Cs>K>Na; In the $La_{0.6}Cs_{0.4}CoO_3 $; catalyst, the substitution of Fe or Mn showed no effect on the ignition temperature. The ignition temperature decreased with increasing $O_2$ concentration and contact time. The introduction of water into reactants feed decreased the ignition temperature and the pretreatment of $SO_2$ showed no effect on the catalytic activity.

• Journal of the Korean Vacuum Society
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• v.14 no.1
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• pp.17-23
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• 2005

Glow discharge mass spectrometry(GDMS) was used to determine the impurity concentrations of the deposited Cu films and the 6N Cu target. Cu films were deposited on Si (100) substrates at zero substrate bias voltage and a substrate bias voltage of -50 V using a non-mass separated ion beam deposition method. Since do GDMS has a little difficulty to apply to thin films because of the accompanying non-conducting substrate, we have used an aluminum foil to cover the edge of the Cu film in order to make an electrical contact of the Cu film deposited on the non-conducting substrate. As a result, the Cu film deposited at the substrate bias voltage of -50 V showed lower impurity contents than the Cu film deposited without the substrate bias voltage although both the Cu films were contaminated during the deposition. It was found that the concentration change of each impurity in the Cu films by applying the negative substrate bias voltage is related to the difference in their ionization potentials. The purification effect by applying the negative substrate bias voltage might result from the following reasons: 1) Penning ionization and an ionization mechanism proposed in the present study, 2) difference in the kinetic energy of accelerated Cu+ ions toward the substrate with/without the negative substrate bias voltage.

• Journal of the Korean Institute of Gas
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• v.5 no.1
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• pp.60-72
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• 2001

This paper presents the user-interactive productivity analysis model based on material balance as well as deliverability equations equipped with EOS model to perform a productivity analysis for Gorae V structure, Donghae-1 gas field. This model is designed to be able to analyse the productivity in the case of reservoir contacting with the aquifer. Also, in order to investigate the effect of condensation on productions, condensation phenomenon is considered as an apparent skin effect in the computation of bottomhole pressure from average reservoir pressure. By utilizing the developed model, we investigate the productivity analysis for B2 layer of Garae V structure with the various production cases in volumetric and non­volumetric reservoirs that contact with aquifer. From the results in the case of 5500 MMSCF/year of production and reservoir-aquifer contacting angle 270$^{\circ}C$ with aquifer size of 10 times greater than reservoir, B2 layer could maintain peak production rate even after 8.5 years of production by considering the bottomhole pressure which is estimated above the operating pressure of 1298 psia. It is also found that condensate will be formed after 1100 days of production and existed throughout the reservoir at 1270 days. Note that the computed reservoir pressure of B2 layer is maintained sufficiently high enough for production due to the water influx into the reservoir, and skin effect caused by condensation is not significant.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.771-776
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• 2020

In this study, the flexural/shear behavior characteristics of perfobond FRP-concrete composite beams using an FRP plate with perforated webs as formwork and reinforcement are analyzed through an analytical method. Compared with the existing experimental results, we have proved its usefulness and use it in future practice. When the nonlinearity is very large in this case, the nonlinear finite element analysis by an explicit method will be effective. The concrete damage plasticity (CDP) model adopted in this study is considered to be able to adequately simulate the nonlinear behavior of concrete, and the determination of several variable factors required in the model is compared with the experimental results and values used in the study. This recommendation will require review and adjustment for more diverse cases. The effect of the perfobond of the composite beam with perforated web is considered to be somewhat effective in terms of securing the initial stiffness, but in the case of the apex, it is considered that the cross-sectional loss and the effect of improving the bonding force should be properly arranged. The contact problem, such as slipping of the FRP plate and concrete, is considered to be one of the reasons that the initial stiffness is slightly larger than the test result, and the slightly difference from the experimental results is attributed to the separation problem between concrete and FRP after the peak.

• Journal of Conservation Science
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• v.36 no.2
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• pp.82-92
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• 2020

Modern artworks are constructed using a variety of materials and techniques. Sculptures, which predominantly consist of metals, usually have different shapes and consist of different material mixtures. The structural and material properties of these sculptures are often controlled by conservation treatment methods. However, the application of existing treatment methods is challenging at times, indicating that more diverse treatment materials and techniques are necessary. Therefore, in this study, a treatment method that employs volatile corrosion inhibitor(VCI) powder, rather than an anti-corrosion solution, for the conservation and management of metal artworks was used. VCI powder and VCI films containing VCI powder were used, and the results obtained confirmed that both of them showed anti-corrosion effect. Only a slight change in the chromaticity of metal samples was observed, and compared to the untreated samples, the application of the VCI powder resulted in a decrease in the rate of corrosion by half. Moreover, VCI film tests revealed that comparing to the untreated or polyethylene film-treated samples, VCI film treatment resulted in a decrease in the occurrence of corrosion compounds. The contact angle, surface energy, and surface electrical resistance were measured, and the evaluation of these surface properties established the anti-corrosion effect of VCI. Additionally, direct application of VCI and VCI films on actual sculptures further confirmed the anti-corrosion effect of VCI.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.776-780
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• 2007

A biofilm reactor packed with porous media was investigated for nitrogen removal of synthetic wastewater. The effect of different loading rates on the nitrification was sustained to be steady state with stable efficiency of 50~60% in the range of $0.0083{\sim}0.017gNH_4-N/gMLVSS{\cdot}day$ of F/MN ratio and $1{\sim}2kgNH_4-N/m^3{\cdot}day$ of media volumetric loading rate. However, nitrification efficiency was rapidly decreased to 25~30% as F/MN ratio and media volumetric loading rate were increased to the range of $0.025{\sim}0.034gNH_4-N/gMLVSS{\cdot}day$ and $3{\sim}4kgNH_4-N/m^3{\cdot}day$, respectively. Also the consumption rate of alkalinity was higher under 8 hours of HRT than unter 6 hours of HRT. Accordingly the influent loading rate variation by detention time with influent flow influenced more on the nitrification efficiency than the influent loading rate variation by the influent concentration did. The temperature effect on the nitrification showed 25% higher in summer than in winter as the results reported by other researchers who reported that the nitrification efficiency in biofilm showed 20% increase from 55% to 75% when the temperature was raised from $20^{\circ}C$ to $25^{\circ}C$. Denitrification with sulfur-media showed 90% removal efficiency under steady-state with no effect from the increase of influent concentration and empty bed contact time (EBCT) change such as EBCT was decreased from 8.4 hr to 4.3 hr and $NO_3-N$ loading rate was changed within the range of $0.1{\sim}0.4kgNO^3-N/m^3{\cdot}day$. Accordingly Denitrification with sulfur-media is feasible for post denitrification at the concentration less than $80mgNO^3-N/L$.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.34 no.4
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• pp.233-238
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• 2012

Purpose: To evaluate the effect of silvernanopartilce treated implants on the bone formation and osseointegration. Methods: Silvernanoparticle was produced using an anodic oxidation method. The size of silvernanoparticle ranged from 3.5 nm to 5.9 nm. To check the effect of the capability of osseointegration of silvernanoparticle coated Implant, 32 implants (16 piece of Implant treated with nanoparticle, and 16 piece of Implant was not treated for control) were placed at both the tibia of 8 New Zealand white rabbits. After 4 weeks, 4 rabbits were sacrificed and the removal torque was measured for comparison of the osseointagration ability. Further, 4 rabbits were sacrificed and sliced samples were made. H&E stain was done for microscopic finding. Results: The removal torque of the experimental group was $102.37{\pm}30.54$ N/cm, and the control group was $73.30{\pm}19.97$ N/cm. It was statistically significant (P<0.001). Microscopic finding also shows extinguish results in silvernanoparticle treated implants. Bone formation rate of the experimental group was 43.94% and the control group was 7.58%. It was observed to be statistically significant (P=0.017). Bone to implant contact rate of the experimental group was 58.09%, and the control group was 19.43%. It was found with statistical significance (P<0.001). Conclusion: The silvernanopartilce treated implant shows a better capability of bone regeneration and osseointegration than the non-treated one. Technology to produce smaller particles would make silver more useful and safer.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.5
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• pp.606-616
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• 2006

Purpose: This experiment examined the effect of different surface treatment on the osseointegration and stability of implants. Material and methods: In this study, 40 each of machined, SLA and RBM implants, which are the most commonly used implants, were implanted into the tibia of 20 normal rabbits using $OsseoCare^{TM}$. The rabbits were sacrificed after 1 week, 4 weeks, 8 weeks and 12 weeks for implant stability analysis, removal torque analysis, histologic and histomorphometric analysis. Result : ISQ showed significant difference between Machined and RBM at first week and at 4 weeks. There was significant difference between Machined and both SLA and RBM(p<0.05) but after 8 weeks there were no significant difference between each group. In the removal torque, RBM showd significantly higher values than SLA and Machined surface at 1st week. At 4th and 12th week, there was significant difference between Machined and SLA, RBM(p<0.05). In the bone to implant contact variable, there was no significant difference between each surface treatment method. In the Machined surface group, there was no significant difference between each time interval. but in SLA group, there were significant differences between the 1st week and 12th week and in RBM group, there were significant differences between the 1st week and 8th, 12th week and between 4th and 12th week(p<0.05). The bone area showed significantly higher values in SLA and RBM compared to Machined surface 1st and 8th week and significantly higher values in SLA than Machined surface at the 4th week(p<0.05). Conclusion: The roughened surface of implants showed positive effect in the early stages of implantation and assisted in bone formation After the bone formation stage, there was no statistical difference between Machined and roughened surface groups. In dental implantation, where initial stability is critical to the success of implants, the use of roughened surface implants should assist in reducing the healing period after implantation.

• Journal of Adhesion and Interface
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• v.21 no.3
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• pp.107-112
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• 2020

Recently, the atomically thin transition-metal dichalcogenide (TMD) semiconductors have attracted much attention owing to their remarkable properties such as tunable bandgap with high carrier mobility, flexibility, transparency, etc. However, because these TMD materials have a significant drawback that they are easily degraded in an ambient environment, various attempts have been made to improve chemical stability. In this research article, I report a method to improve the air stability of WSe₂ one of the TMD materials via surface passivation with an h-BN insulator, and its application to field-effect transistors (FETs). With a modified hot pick-up transfer technique, a vertical heterostructure of h-BN/WSe₂ was successfully made, and then the structure was used to fabricate the top-gate bottom-contact FETs. The fabricated WSe₂-based FET exhibited not only excellent air stability, but also high hole mobility of 150 ㎠/Vs at room temperature, on/off current ratios up to 3×10⁶, and 192 mV/decade of subthreshold swing.