• Proceedings of the KOSOMBE Conference
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• v.1989 no.05
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• pp.7-8
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• 1989

The graft copolymer of chitosan with amino acid, L-lysine was synthesized by heterogeneous copolymerization and was evaluated as an artificial skin. The mechanical properties under dry and wet state, water content, water vapor transmittance rate and biodegradability were measured. The tensile strength and elongation under wet state ranged $0.3-0.5\;kg/mm^2$, 10-13%, respectively. Water vapor transmittance rate ranged $450-500\;g/m^2{\cdot}day$ like that of the normal skin. The weight loss of prepared membrane by protease IV was measured for the degree of biodegradation. The degree of biodegradation was around 15% and after 4 days it was slow. Biocompatibility was evaluated by studying the attachment of human fibroblast on the prepared membrane surface.

• Nuclear Engineering and Technology
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• v.21 no.3
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• pp.186-192
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• 1989

As a part of the design of the top end piece(TEP) for the 14$\times$14 reload fuel, various models of top end piece structure were analysed, using the ANSYS code, under fuel assembly shipping and handling load conditions. The 3-dimensional isoparametric elements were used in each model. By rearrangement of slots and holes on the adapter plate, without violating the design requirements, and also by changing the enclosure attachment method used on the adapter plate from pin joints to through-weld, the load carving capacity of the adapter plate was greatly strengthened. These concepts were adopted for the design of the 14$\times$14 reload fuel.

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.3950-3956
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• 2012

In order to improve the bioactivity and mechanical properties of hydroxyapatite (HAp), chitosan (Chi) was in situ combined into HAp to fabricate a composite scaffold by a sublimation-assisted compression method. A highly porous film with sufficient mechanical strength was prepared and the bioactivity was investigated by examining the apatite formed on the scaffolds incubated in simulated body fluid. In addition, the cytotoxicity of the HAp/Chi composite was studied by evaluating the viability of murine fibroblasts (L-929 cells) exposed to diluted extracts of the composite films. The apatite layer was assessed using scanning electronic microscopy, inductively coupled plasma-optical emission spectrometry and weight measurement. Composite analysis showed that a layer of micro-sized, needle-like crystals was formed on the surface of the composite film. Additionally, the WST-8 assay after L-929 cells were exposed to diluted extracts of the composite indicated that the HAp/Chi scaffold has good in vitro cytocompatibility. The results indicated that HAp/Chi composites with porous structure are promising scaffolding materials for bone-patch engineering because their porous morphology can provide an environment conductive to attachment and growth of osteoblasts and osteogenic cells.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.56 no.1
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• pp.1-5
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• 2007

Study on the electron transport coefficient in mixtures of CF4 and Ar, have been analyzed over a range of the reduced electric field strength between 0.1 and 350[Td] by the two-term approximation of the Boltzmann equation (BEq.) method and the Monte Carlo simulation (MCS). The calculations of electron swarm parameters require the knowledge of several collision cross-sections of electron beam. Thus, published momentum transfer, ionization, vibration, attachment, electronic excitation, and dissociation cross-sections of electrons for $CF_4$ and Ar, were used. The differences of the transport coefficients of electrons in $CF_4$ mixtures of Ar, have been explained by the deduced energy distribution functions for electrons and the complete collision cross-sections for electrons. The results of the Boltzmann equation and the Monte Carlo simulation have been compared with the data presented by several workers. The deduced transport coefficients for electrons agree reasonably well with the experimental and simulation data obtained by Nakamura and Hayashi. The energy distribution function of electrons in $CF_4-Ar$ mixtures shows the Maxwellian distribution for energy. That is, $f({\varepsilon})$ has the symmetrical shape whose axis of symmetry is a most probably energy. The proposed theoretical simulation techniques in this work will be useful to predict the fundamental process of charged particles and the breakdown properties of gas mixtures. A two-term approximation of the Boltzmann equation analysis and Monte Carlo simulation have been used to study electron transport coefficients.

• Clinics in Shoulder and Elbow
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• v.19 no.1
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• pp.51-58
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• 2016

The arthroscopic rotator cuff repair is now considered a mainstream technique with highly satisfactory clinical results. However, concerns remain regarding healing failures for large and massive tears and high revision rate. In recent decades, various repair strategies and construct configurations have been developed for rotator cuff repair with the understanding that many factors contribute to the structural integrity of the repaired construct. The focus of biomechanical test in arthroscopic repair has been on increasing fixation strength and restoration of the footprint contact characteristics to provide early rehabilitation and improve healing. These include repaired rotator cuff tendon-footprint motion, increased tendon-footprint contact area and pressure, and tissue quality of tendon and bone. Recent studies have shown that a transosseous tunnel technique provides improved contact area and pressure between rotator cuff tendon and insertion footprint, and the technique of using double rows of suture anchors to recreate the native footprint attachment has been recently described. The transosseous equivalent suture bridge technique has the highest contact pressure and fixation force. In this review, the biomechanical tests about repair techniques of rotator cuff tear will be reviewed and discussed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.11
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• pp.41-46
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• 2015

This study was conducted to discover a substitute of $SF_6$ gas. $SF_6$ gas is widely used across the industries. Thanks to superior electrical properties, in particular, it has been commonly used in electrical industry. However, there have been a lot of studies on its serious effect on global warming. As a substitute of this synthetic gas, a mixture of dry air and $N_2/O_2$ was chosen in this study. In case of $N_2/O_2$, dielectric strength differs depending on the mixing ratio. This study examined dielectric breakdown and flashover after adjusting oxygen percentage in the dry air. This test was conducted in a quasi-uniform electric field depending on pressure, oxygen concentration and gas mixtures. The test results found that dielectric voltage and flashover voltage were the highest at a certain oxygen concentration. It is the results of this photoionization and electron attachment of oxygen.

• Korean Journal of Materials Research
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• v.31 no.5
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• pp.278-285
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• 2021

This study produces electroconductive polycaprolactone (PCL)-based film with different amounts of graphene (G) through electrospinning, and the characteristics of the produced G/PCL composites are investigated. The G/PCL results are analyzed by comparing them with those obtained using pure PCL electrospun film as a control. The morphology of electrospun material is analyzed through scanning electron microscopy and transmission electron microscopy. Mechanical and electrical properties are also evaluated. Composites containing 1 % graphene have the highest elongation rate, and 5 % samples have the highest strength and elasticity. Graphene contents > 25 % show electro-conductivity, which level improves with increase of graphene content. Biological characteristics of G/PCL composites are assessed through behavioral analysis of neural cell attachment and proliferation. Cell experiments reveal that compositions < 50 % show slightly reduced cell viability. Moreover, graphene combinations facilitated cell proliferation compared to pure PCL. These results confirm that a 25 % G/PCL composition is best for application to systems that introduce external stimuli such as electric fields and electrodes to lead to synergistic efficiency of tissue regeneration.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.14-15
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• 2021

Recently, the size of tiles used for bathroom walls in apartment houses is gradually increasing in size. The problem is that when these large-sized tiles are attached by the sticking method, due to the nature of the method, there is a concern about the stability of the attachment to the part (pupil) where the tile and the adhesive are not attached. The problem is serious as it leads to lawsuits in the outbreak court. In addition, it is urgent to verify the adhesion stability of the sticking method because secondary damage occurs due to a safety accident caused by the falling of the tile. Ministry of Land, Infrastructure and Transport [Investigation of defects in apartment houses, calculation of repair cost and defect determination criteria] ① The tile adhesion strength is 0.39N/mm² or more and ② It is specified to fill 80% or more of the base area of the tile backside, but this is currently trendy. It is considered that large-sized tiles need to be verified from multiple angles, and as part of that, we intend to verify the adhesion stability according to the area to be attached to large-sized tiles.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.4
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• pp.284-291
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• 2013

Purpose: This study compared fracture strength and fracture modes between metal wire reinforcement and glass fiber reinforcement in repaired maxillary complete denture. Materials and methods: In this study, fracture was reproduced on center of maxillary complete dentures and the denture was repaired with auto-polymerizing resin. The experimental groups (n = 10) were subjected to the following condition: without reinforcing material (control group), reinforcing with metal wire (W group), reinforcing with glass fiber pre-impregnated with light-curing resin (SES MESH, INNO Dental Co., Yeoncheon, Korea, G group). The fracture strength and fracture modes of a maxillary complete denture were tested using Instron test machine (Instron Co., Canton, MA, USA) at a 5.0 mm/min crosshead speed. The flexure load was applied to center of denture with a 20 mm diameter ball attachment. When fracture occurred, the fracture mode was classified based on fracture lines. The Kruskal-wallis test and the Mann-whitney U test were performed to identify statistical differences at ${\alpha}=.05$. Results: W group showed the highest value of fracture strength, there was no significant difference (P>.05) between control group and G group. Control group and W group showed anteroposterior fracture mainly, group W showed adhesive fracture of denture base and reinforcing material. Conclusion: In limitation of this study, the glass fiber did not improve the fracture strength of repaired maxillary complete denture, and adhesive failure was occurred along the lines of glass fiber.

• Journal of the korean academy of Pediatric Dentistry
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• v.40 no.3
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• pp.159-167
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• 2013

The aim of this study was to evaluate changes in demineralization resistance and bonding strength of light cured glass ionomer after the addition of nano hydroxyapatite in various ratios. Fuji II LC GIC (GC Co., Japan) was used as the control group and also as a base material for experimental group. HA was mixed into the RMGIC at various ratio to create a HA-LC GIC mixture, preparing six experimental groups, i.e. 5%, 10%, 15%, 20%, 25%, 30% HA-LC GIC. According to the results, the bonding strength increased due to the addition of HA, showing the maximum value at the 15% nano HA group (p < 0.05). Under CLSM observation after 4 days of demineralization, the HA groups were more resistant to demineralization compared to the control group. No significant difference was observed between HA groups. In analysis through SEM, the HA groups showed attachment of granular materials and decreased demineralized tooth surfaces under influence of HA particles.