• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.466-468
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• 2012

Amorphous InGaZnO (${\alpha}$-IGZO) thin-film transistors (TFTs) are are very promising due to their potential use in thin film electronics and display drivers [1]. However, the stability of AOS-TFTs under the various stresses has been issued for the practical AOSs applications [2]. Up to now, many researchers have studied to understand the sub-gap density of states (DOS) as the root cause of instability [3]. Nomura et al. reported that these deep defects are located in the surface layer of the ${\alpha}$-IGZO channel [4]. Also, Kim et al. reported that the interfacial traps can be affected by different RF-power during RF magnetron sputtering process [5]. It is well known that these trap states can influence on the performances and stabilities of ${\alpha}$-IGZO TFTs. Nevertheless, it has not been reported how these defect states are created during conventional RF magnetron sputtering. In general, during conventional RF magnetron sputtering process, negative oxygen ions (NOI) can be generated by electron attachment in oxygen atom near target surface and accelerated up to few hundreds eV by self-bias of RF magnetron sputter; the high energy bombardment of NOIs generates bulk defects in oxide thin films [6-10] and can change the defect states of ${\alpha}$-IGZO thin film. In this paper, we have confirmed that the NOIs accelerated by the self-bias were one of the dominant causes of instability in ${\alpha}$-IGZO TFTs when the channel layer was deposited by conventional RF magnetron sputtering system. Finally, we will introduce our novel technology named as Magnetic Field Shielded Sputtering (MFSS) process [9-10] to eliminate the NOI bombardment effects and present how much to be improved the instability of ${\alpha}$-IGZO TFTs by this new deposition method.

• The Journal of Advanced Prosthodontics
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• 제6권3호
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• pp.207-214
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• 2014

PURPOSE. This study characterized the synthesis of a modified PMMA (Polymethyl methacrylate) denture acrylic loading platinum nanoparticles (PtN) and assessed its bacterial inhibitory efficacy to produce novel antimicrobial denture base material. MATERIALS AND METHODS. Polymerized PMMA denture acrylic disc ($20mm{\times}2mm$) specimens containing 0 (control), 10, 50, 100 and 200 mg/L of PtN were fabricated respectively. The obtained platinum-PMMA nanocomposite (PtNC) was characterized by TEM (transmission electron microscopy), SEM/EDX (scanning electron microscope/energy dispersive X-ray spectroscopy), thermogravimetric and atomic absorption spectrophotometer analysis. In antimicrobial assay, specimens were placed on the cell culture plate, and $100{\mu}L$ of microbial suspensions of S. mutans (Streptococcus mutans) and S. sobrinus (Streptococcus sobrinus) were inoculated then incubated at $37^{\circ}C$ for 24 hours. The bacterial attachment was tested by FACS (fluorescence-activated cell sorting) analysis after staining with fluorescent probe. RESULTS. PtN were successfully loaded and uniformly immobilized into PMMA denture acrylic with a proper thermal stability and similar surface morphology as compared to control. PtNC expressed significant bacterial anti-adherent effect rather than bactericidal effect above 50 mg/L PtN loaded when compared to pristine PMMA (P=.01) with no or extremely small amounts of Pt ion eluted. CONCLUSION. This is the first report on the synthesis and its antibacterial activity of Pt-PMMA nanocomposite. PMMA denture acrylic loading PtN could be a possible intrinsic antimicrobial denture material with proper mechanical characteristics, meeting those specified for denture bases. For clinical application, future studies including biocompatibility, color stability and warranting the long-term effect were still required.

• 한국운동역학회지
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• 제20권2호
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• pp.191-196
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• 2010

The purpose of this study was to investigate the effect of gait speed and walkway slope on the body acceleration, for the future validation of using an accelerometer in the estimation of energy consumption. Ten young healthy subjects with accelerometers on the upper thigh and ankle walked on a treadmill at 9 conditions(three speeds ${\times}$ three slopes) for 5 minutes. Acceleration signals of four directions, i.e. anterior-posterior(AP), medio-lateral(ML), superior-inferior(SI) and vector sum(VS) directions, of each sensor were measured, and root means squared(RMS) values of them were used as analysis variables. As statistical analysis, repeated measure two-way ANOVA was performed for RMS accelerations at each attachment sites, with slope and velocity as independent factors. At both the upper thigh and ankle, RMS acceleration of all directions were affected by gait velocities(p<.001) showing greater accelerations for higher velocities. Contrary to expectations, no slope effect existed in RMS accelerations at hip. Moreover, RMS acceleraion at ankle decreased with slope in SI and VS directions(p<.01). These results suggests that RMS acceleration cannot reflect the change in physical activity due to the change in walkway slope.

• Journal of Periodontal and Implant Science
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• 제32권1호
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• pp.225-234
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• 2002

The purpose of this study was to evaluate the relationship between the osteoporotic condition and periodontal condition in postmenopausal women with periodontitis. Forty three female postmenopausal patients with no systemic disease were grouped into 3 groups by their periodontal conditions; 12 mild periodontitis, 11 moderate periodontitis and 20 advanced periodontitis. From each patient, age of menopause was taken, alkaline phosphatase(ALP) and osteocalcin (OC) in blood and deoxypyridinoline (DPD) in urine were measured. Bone mineral density (BMD) of lumbar spine (L2-L4) was measured by dual energy X-ray absorptiometry. Periodontal and osteoporotic parameters were compared among the groups and correlation coefficient between them was evaluated. The blood ALP and OC levels were similar among the groups with different periodontal condition, whereas the urine DPD level and BMD were significantly lower in advanced periodontitis group than the other groups(p<0.01). Probing depth was negatively related with BMD (r=-0.5, p<0.01) and positively related with patient age and the duration of menopause (r= 0.32 and 0.35 respectively, p<0.05). Clinical attachment loss was negatively related with BMD (r=-0.66, p<0.01), and positively related with urine DPD (r= 0.37, p<0.05). These results showed that postmenopausal women with advanced periodontitis had significantly decreased bone mineral density and suggests that decreased bone mineral density in postmenopausal women could be associated with periodontal tissue breakdown.

• 한국융합학회논문지
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• 제11권9호
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• pp.155-162
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• 2020

본 연구는 파리기후변화협약 이후 전 세계적으로 각광받고 있는 태양전지를 활용한 노후 건축물 그린 리모델링 디자인의 국내외 사례 분석을 바탕으로 향후 진행할 태양전지를 활용한 그린 리모델링 디자인 제안의 긍정적인 측면과 시사점을 확인하고자 하였다. 연구의 방법으로는 문헌연구를 바탕으로 이론적 고찰을 진행하였고, 이후 국내외 태양전지를 활용한 그린 리모델링 디자인의 사례를 조사·분석하였다. 그 결과 플렉서블한 특징을 통한 시공의 용이성, 박막전지의 투명도와 색상의 조절을 통한 심미적 효과, 자유로운 사이즈 제작으로 재료 낭비가 적은 경제적 효과, 외관의 직접 부착을 통한 건물과의 조화로운 측면을 확인할 수 있었다. 이러한 점을 토대로 박막 태양전지를 그린 리모델링 디자인에 활용하여 올 수 있는 기대효과와 유효성을 제시하고, 향후 진행할 태양전지를 활용한 노후 건축물 그린 리모델링 디자인 제안에 대한 방향성과 참고 자료로 활용되기를 기대한다.

• Restorative Dentistry and Endodontics
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• 제42권3호
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• pp.176-187
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• 2017

Objectives: This study aimed to evaluate the chemical and biological properties of fast-set white mineral trioxide aggregate (FS WMTA), which was WMTA combined with calcium chloride dihydrate ($CaCl_2{\cdot}2H_2O$), compared to that of WMTA. Materials and Methods: Surface morphology, elemental, and phase analysis were examined using scanning electron microscope (SEM), energy dispersive X-ray microanalysis (EDX), and X-ray diffraction (XRD), respectively. The cytotoxicity and cell attachment properties were evaluated on human periodontal ligament fibroblasts (HPLFs) using methyl-thiazoldiphenyltetrazolium (MTT) assay and under SEM after 24 and 72 hours, respectively. Results: Results showed that the addition of $CaCl_2{\cdot}2H_2O$ to WMTA affected the surface morphology and chemical composition. Although FS WMTA exhibited a non-cytotoxic profile, the cell viability values of this combination were lesser than WMTA, and the difference was significant in 7 out of 10 concentrations at the 2 time intervals (p < 0.05). HPLFs adhered over the surface of WMTA and at the interface, after 24 hours of incubation. After 72 hours, there were increased numbers of HPLFs with prominent cytoplasmic processes. Similar findings were observed with FS WMTA, but the cells were not as confluent as with WMTA. Conclusions: The addition of $CaCl_2{\cdot}2H_2O$ to WMTA affected its chemical properties. The favorable biological profile of FS WMTA towards HPLFs may have a potential impact on its clinical application for repair of perforation defects.

• 한국표면공학회지
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• 제37권5호
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• pp.253-262
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• 2004

Calcareous deposits are the consequence of pH increase of the electrolyte adjacent to metal surface affected by cathodic current in seawater. It obviously has several advantages over conventional coatings, since the calcareous deposit coating is formed from coating (Mg$^{2+}$, $Ca^{2+}$) naturally existing in seawater. In consideration of this respect, environment friendly calcareous deposit films were formed by an electro deposition technique on steel substrates submerged in 48$^{\circ}C$ natural seawater. And the influence of current density, coating time and attachment of steel mesh on composition ratio, structure and morphology of the electrodeposited films were investigated by Scanning Electron Microscopy(SEM), Energy Dispersive Spectroscopy(EDS) and X-Ray Diffractor(XRD), respectively. Accordingly, this study provides a better understanding of the composition between the growth of $Mg(OH)_2$ and $CaCO_3$ during the formation of electro deposit films on steel substrate under cathodically electrodeposition in $48^{\circ}C$ natural seawater. The Mg compositions, in general, are getting decreased regardless of current density but Ca compositions are getting increased as electrodeposition time runs. That is, $Mg(OH)_2$ compounds of brucite structure shaped as flat type is formed at the initial stage of electrodeposition, but CaCO$_3$ compounds of aragonite structure shaped as flower type is formed in large scale. Besides, $Mg(OH)_2$ compounds were much formed at 5 A/$\m^2$ environment condition compared to the 3 A/$\m^2$ and 4 A/$\m^2$ environment conditions. This is because that OH- which was comparatively largely generated at the metal surface is preferably combined with $Mg^{2+}$TEX>.

• 대한조선학회논문집
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• 제55권6호
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• pp.474-481
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• 2018

This paper is to compare by numerical analysis the flow characteristics and propulsion performance of stern with the shape change of K-duct, a pre-swirl duct developed by Korea Research Institute of Ships & Ocean Engineering (KRISO). First, the characteristics of the propeller and the resistance and self-propulsion before and after the attachment of the K-duct to the ship were verified and the validity of the calculation method was confirmed by comparing this result with the model test results. After that, resistance and self-propulsion calculations were performed by the same numerical method when the K-duct was changed into five different shapes. The efficiency of the other five cases was compared using the delivery horsepower in the model scale and the flow characteristics of the stern were analyzed as the velocity and pressure distributions in the area between the duct end and the propeller plane. For the computation, STAR-CCM +, a general-purpose flow analysis program, was used and the Reynolds Averaged Navier-Stokes (RANS) equations were applied. Rigid Body Motion (RBM) method was used for the propeller rotating motion and SST $k-{\omega}$ turbulence model was applied for the turbulence model. As a result, the tangential velocity of the propeller inflow changed according to the position angle change of the stator, and the pressure of the propeller hub and the cap changes. This regulated the propeller hub vortex. It was confirmed that the vortex of the portion where the fixed blade and the duct meet was reduced by blunt change.

• 산업식품공학
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• 제21권3호
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• pp.233-241
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• 2017

Scaffolds of cell substrates are biophysical platforms for cell attachment, proliferation, and differentiation. They ultimately play a leading-edge role in the regeneration of tissues. Recent studies have shown the potential of bioactive scaffolds (i.e., osteo-inductive) through 3D printing. In this study, rice bran-derived biocomposite was fabricated for fused deposition modeling (FDM)-based 3D printing as a potential bone-graft analogue. Rice bran by-product was blended with poly caprolactone (PCL), a synthetic commercial biodegradable polymer. An extruder with extrusion process molding was adopted to manufacture the newly blended "green material." Processing conditions affected the performance of these blends. Bio-filament composite was characterized using field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDX). Mechanical characterization of bio-filament composite was carried out to determine stress-strain and compressive strength. Biological behaviors of bio-filament composites were also investigated by assessing cell cytotoxicity and water contact angle. EDX results of bio-filament composites indicated the presence of organic compounds. These bio-filament composites were found to have higher tensile strength than conventional PCL filament. They exhibited positive response in cytotoxicity. Biological analysis revealed better compatibility of r-PCL with rice bran. Such rice bran blended bio-filament composite was found to have higher elongation and strength compared to control PCL.

• Computers and Concrete
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• 제32권5호
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• pp.487-498
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• 2023

The present study investigated the flexural behavior of reinforced concrete (RC) beams strengthened with an ultrahigh performance concrete (UHPC) panel having various thicknesses. Two fabrication methods were introduced in this study; one was the direct casting of UHPC onto the bottom surface of the RC beams (I-series), and the other was the attachment of a prefabricated UHPC panel using an adhesive (E-series). UHPC panels having thicknesses of 10, 30, 50, and 70 mm were applied to RC beams, and these specimens were subjected to four-point loading to assess the effect of the UHPC thickness on the flexural strengthening of RC beams. The test results indicated that the peak strength and initial stiffness were vastly enhanced with an increase in the thickness of the UHPC panel, showing an improved energy dissipation capacity. In particular, the peak strength of the E-series specimens was higher than that of I-series specimens, showing high compatibility between the RC beam and the UHPC panel. The experimental test results were comparatively explored with a discussion of numerical analysis. Numerical analysis results showed that the predictions are in fair agreement with experimental results.