• Journal of Adhesion and Interface
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• v.22 no.4
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• pp.136-143
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• 2021

Polyurea has been investigated as a polymer matrix for composite materials because of its high mechanical strength. Although polyurea has a similar chemical structure to polyurethane, it has much higher strength and durability. In this study, the fabrication of polyurea composites reinforced with carbon nanotube (CNT) and graphene oxide (GO) is demonstrated to enhance the tensile strength of the glass fibers composite. Using FTIR and Raman spectroscopies, the chemical structures of polyurea, CNT, and GO are investigated. As a result, spectroscopy analysis reveals that the chemical structure of CNT, GO, and polyurea is maintained during the fabrication of the composite structure. Scanning electron microscopy reveals the uniform distribution of CNT and GO across the polyurea matrix. The reinforcement of 1 wt% CNT in polyurea enhances the tensile strength of CNT/polyurea composites. In contrast, the reinforcement of GO in polyurea induces the degradation of the tensile strength of GO/polyurea composites.

• Venture DIGEST
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• s.116
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• pp.12-13
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• 2008

• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.47-52
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• 2015

To improve both the GOD immobilization capability and sensitivity of MWCNTs-based biosensor electrode, the electrode was prepared by adding different quantities of GO. The addition of GO increased hydrophilicity and the surface free energy of electrodes for glucose sensing as well as the dispersion of MWCNTs. In addition, the GOD immobilization capability was enhanced and the sensitivity was improved up to $121{\mu}A\;mM^{-1}$ even though having a high $K_m$ value (0.105) when adding 0.05 g GO to 0.05 g MWCNTs. These experimental results were attributed to the fact that the improvement in dispersion stability for MWCNTs, hydrophilicity, and surface free energy of electrode surface due to the addition of GO affected GOD immobilization capability.

• Journal of Korea Game Society
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• v.14 no.3
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• pp.47-54
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• 2014

The game of Go is one of the oldest games and originated at least more than 2,500 years ago. In game programming the most successful approach is to use game tree searches using evaluation functions. However it is really difficult to construct feasible evaluation function in computer Go. Monte-Carlo Tree Search(MCTS) has created strong computer Go programs such as MoGo and CrazyStone which defeated human Go professionals played on the $9{\times}9$ board. MCTS is based on the winning rate estimated by Monte-Carlo simulation. Prior to implementing MCTS into computer Go, we tried to measure each winning rate of three positions, center, corner and side, in Tic-Tac-Toe playing as the best first move. The experimental result revealed that the center is the best, a corner the next and a side the last as the best first move.

• Journal of Sensor Science and Technology
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• v.24 no.1
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• pp.41-46
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• 2015

In this work, pure hierarchical ZnO structure was prepared using a simple hydrothermal method, and Ag nanoparticles doped hierarchical ZnO structure was synthesized uniformly through photochemical route. The reduced graphene oxide (rGO) has been synthesized by typical Hummer's method and reduced by hydrazine. Prepared Ag/ZnO nanostructures are uniformly dispersed on the surface of rGO sheets using ultrasonication process. The synthesized samples were characterized by SEM, TEM, EDS, XRD and PL spectra. The average size of prepared ZnO microspheres was around $2{\sim}3{\mu}m$ and showed highly uniform. The average size of doped-Ag nanoparticles was 50 nm and decorated into ZnO/rGO network. The $C_2H_2$ gas sensing properties of as-prepared products were investigated using resistivity-type gas sensor. Ag/ZnO-rGO based sensors exhibited good performances for $C_2H_2$ gas in comparison with the Ag/ZnO. The $C_2H_2$ sensor based on Ag/ZnO-rGO had linear response property from 3~1000 ppm of $C_2H_2$ concentration at working temperature of $200^{\circ}C$. The response values with 100 ppm $C_2H_2$ at $200^{\circ}C$ were 22% and 78% for Ag/ZnO and Ag/ZnO-rGO, respectively. In additions, the sensor still shows high sensitivity and quick response/recovery to $C_2H_2$ under high relative humidity conditions. Moreover, the device shows excellent selectivity towards to $C_2H_2$ gas at optimal working temperature of $200^{\circ}C$.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.8
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• pp.774-780
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• 2010

This paper deals with the choice of guidance gain for the time-to-go polynomial (POLY) guidance law when the acceleration limit is existed. POLY is derived based on the assumption that guidance commands are formed by a time-to-go polynomial function. The main characteristic of POLY is that any positive values can be used for its guidance gain. For this reason, it is ambiguous to choose a proper guidance gain. To relieve this difficulty, we firstly derive the closed-form solution of acceleration command and figure out the relationship between the maximum acceleration and guidance gain. From this analysis, we provide a guideline for choosing a guidance gain which satisfies the desired acceleration limit. Finally, the proposed method is demonstrated by simulation study.

• Journal of Oral Medicine and Pain
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• v.43 no.1
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• pp.1-7
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• 2018

Purpose: The purpose of the study was to investigate the influences of hyaluronic acid on the candidacidal activities of lysozyme, the peroxidase system, and the glucose oxidase-mediated peroxidase (GO-PO) system at different concentrations of antimicrobial enzymes. Methods: Hyaluronic acid was used at a final concentration of 0.5 mg/mL. Hen egg-white lysozyme (HEWL) was used at concentrations ranging from 10 to $100{\mu}g/mL$. The peroxidase system included bovine lactoperoxidase (bLPO), potassium thiocyanate (KSCN, 1 mM), and hydrogen peroxide ($100{\mu}M$). The GO-PO system included bLPO, KSCN (1 mM), glucose oxidase (10 units/mL), and glucose ($30{\mu}g/mL$). The final concentration of bLPO in the peroxidase and GO-PO systems ranged from 12.5 to $100{\mu}g/mL$. Candida albicans strains ATCC 10231, 11006, and 18804 were utilized. Candidacidal activities of antimicrobials and the influence of hyaluronic acid on their candidacidal activities were determined based on colony forming units. Results: Candidacidal activities of the peroxidase and GO-PO systems increased with increasing concentrations of bLPO. This tendency was the same in the presence or absence of hyaluronic acid. Candidacidal activity of HEWL was not significantly concentration-dependent. Candidacidal activities of the GO-PO system were higher than those of the corresponding peroxidase system. Candidacidal activity was inhibited in the presence of hyaluronic acid in the following order: HEWL, the peroxidase system, and the GO-PO system. Conclusions: Hyaluronic acid inhibited the candidacidal activities of HEWL, the peroxidase system, and the GO-PO system. The GO-PO system exhibited better candidacidal activity than HEWL and the peroxidase system both in the presence and absence of hyaluronic acid.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.431-431
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• 2011

Graphene, two dimensional sheet of sp2-hybridized carbon, has attracted an enormous amount of interest due to excellent electrical, chemical and mechanical properties for the application of transparent conducting films, clean energy devices, field-effect transistors, optoelectronic devices and chemical sensors. Especially, graphene is promising candidate to detect the gas molecules and biomolecules due to the large specific surface area and signal-to-noise ratios. Despite of importance to the disease diagnosis, there are a few reports to demonstrate the graphene- and rGO-FET for biological sensors and the sensing mechanism are not fully understood. Here we describe scalable and facile fabrication of rGO-FET with the capability of label-free, ultrasensitive electrical detection of a cancer biomarker, prostate specific antigen/${\alpha}1$-antichymotrypsin (PSA-ACT) complex, in which the ultrathin rGO sensing channel was simply formed by a uniform self-assembly of two-dimensional rGO nanosheets on aminated pattern generated by inkjet printing. Sensing characteristics of rGO-FET immunosensor showed the highly precise, reliable, and linear shift in the Dirac point with the analyte concentration of PSA-ACT complex and extremely low detection limit as low as 1 fg/ml. We further analyzed the charge doping mechanism, which is the change in the charge carrier in the rGO channel varying by the concentration of biomolecules. Amenability of solution-based scalable fabrication and extremely high performance may enable rGO-FET device as a versatile multiplexed diagnostic biosensor for disease biomarkers.

• Journal of KIISE:Computing Practices and Letters
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• v.12 no.4
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• pp.219-228
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• 2006

Many biomedical research groups have been trying to share their outputs to increase the efficiency of research. As part of their efforts, a common ontology named Gene Ontology(GO), which comprises controlled vocabulary for the functions of genes, was built. However, data from many research groups are distributed and most systems don't support integrated semantic queries on them. Furthermore, the semantics of the associations between concepts from external classification systems and GO are still not clarified, which makes integrated semantic query infeasible. In this paper we present an ontology matching and integration system, called AutoGOA, which first resolves the semantics of the associations between concepts semi-automatically, and then constructs integrated ontology containing concepts from GO and external classification systems. Also we describe a web-based application, named GOGuide II, which allows the user to browse, query and visualize integrated data.

• Polymer(Korea)
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• v.35 no.3
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• pp.265-271
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• 2011

Graphene oxide (GO) was prepared by the Hummers and Offeman method from graphite. Reduced graphene oxide (EGO) and functionalized graphenes were synthesized from GO by using hydrazine hydrate and amine-functionalized alkyl groups, respectively. The structures of the GO, EGO, and functionalized graphenes were identified by FTIR and $^{13}C$ NMR. In addition, we examined the thermal stability, morphology and dispersibility of the materials in various organic solvents. AFM disclosed that GO and RGO consisted of one- or two-layer graphene regions throughout the film. However, the functionalized graphene films showed average thicknesses of 2.26~3.30 nm, The thermal stability of the functionalized graphenes was poorer than that of the EGO. The functionalized graphenes were well dispersed in toluene or chloroform, as evidenced by the lack of the characteristic graphite reflection in the solutions.