• Journal of the Korean Chemical Society
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• v.54 no.3
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• pp.291-294
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• 2010

In this study, we demonstrated high-efficiency blue organic light-emitting diodes (OLEDs) employing BCzVBi as a blue fluorescent dye doped into blue host material, DPVBi with various concentration. The optimized blue OLED device having high-efficiency was constructed with structure of NPB (500 ${\AA}$) / DPVBi:BCzVBi-6% (150 ${\AA}$)/$Alq_3$(300 ${\AA}$) / Liq (20 ${\AA}$) / Al (1000 ${\AA}$). The maximum luminescence of blue OLED was 13200 cd/$m^2$ at 13.8 V and current density and maximum efficiency were 26.4 mA/$cm^2$ at 1000 cd/$m^2$ and 4.24 cd/A at 3.9 V, respectively. Luminous efficiency shows two times higher than comparing with non-doped BCzVBi blue OLED whereas $CIE_{x,y}$ coordinate was similar with bare DPVBi blue OLED such as (0.16, 0.19). Electroluminescence of BCzVBi-6% doped blue OLED has two major peaks at 445 nm and 470 nm whereas pure DPVBi's blue peak appears at 456 nm and it is happened through endothermic Forster energy transfer by molecule's vibration between LUMO of DPVBi as host material and LUMO of BCzVBi as dopant in device.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.376-382
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• 2008

There are many accidents such as fire and explosion in laboratories that have caused a great loss to lives and property in spite of the effort to the enhancement of laboratory safety level for years. Development of laboratory safety management system is a necessary to improve safety level because the accidents of similar types have periodically occurred in laboratories. The laboratory safety management system may reduce many accidents and a serious loss in laboratory. In this study, we summarized major items for a risk management and safety improvement based on the analysis results of various accidents in the laboratories. And then the laboratory safety management system was developed containing a laboratory safety management manual, a laboratory management system, a education management system, a MSDS (material safety data sheet) management system and a laboratory safety audit system. It may have a potential application for the laboratory safety management in the chemical laboratories.

• Journal of the Korean Ceramic Society
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• v.40 no.8
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• pp.804-810
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• 2003

The fine powder produced by heating and grinding of the waste concrete in the waste construction was investigated whether utilize as substitution raw material of SiO$_2$, CaO, and Al$_2$O$_3$ source for OPC clinker manufacture is possible or not. In order to synthesize OPC clinker, limestone, shale, converter slag and fly ash were used as main raw materials, and modulus was fixed LSF 91.0, SM 2.60, IM 1.60. The synthesized clinkers were characterized. The Main products of synthesized clinker were C$_3$S, ${\beta}$-C$_2$S, C$_3$A, C$_4$AF as OPC clinker at 1,43$^{\circ}C$. As a result of TG-DTA and burnability index(B.U) analysis of each raw mixtures, the formation temperature of clinker phases was similar and B.I was showed easy burning as 48.6∼51.4.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.7
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• pp.511-515
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• 2012

A road energy harvester was designed and fabricated to convert mechanical energy from the vehicle load to electrical energy. The road energy harvester is composed of 24 piezoelectric cantilevers and a vehicle load transfer mechanism. Applying a vehicle load transfer mechanism rather than directly installing energy harvesters under roads decreases the area of road construction and allows more energy harvesters to be installed on the side of the road. The power generation amount with respect to the vehicular velocity change was assessed by installing the vehicle load transfer mechanism and the energy harvester in the form of speed bumps and underground. The energy harvester installed in a speed bump form generated power of 7.61 mW at the vehicular velocity of 20 km/h. Also, power generation of the energy harvester installed in the underground form was 63.9 mW at the vehicular velocity of 28 km/h. Although the number of piezoelectric cantilevers was reduced by 1/3 to 24 in comparison to the previous research results with 72 piezoelectric cantilevers, similar power generation characteristic value was obtained within the vehicular velocity of 20 km/h by altering the vehicle load transfer mechanism and cantilever vibration method.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.99-106
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• 2013

Concrete materials subjected to impact by high velocity projectiles exhibit responses that differ from those when they are under static loading. Projectiles generate localized effects characterized by penetration of front, spalling of rear and perforation as well as more widespread crack propagation. The magnitude of damage depends on a variety of factors such as material properties of the projectile, impact velocity, the mass and geometry as well as the material properties of concrete specimen size and thickness, reinforcement materials type and method of the concrete target. In this study, penetration depth of front, spalling thickness of rear and effect of spalling suppression of concrete by fiber reinforcement was evaluated according to compressive strength of concrete. As a result, it was similar to results of the modified NDRC formula and US ACE formula that the more compressive strength is increased, the penetration depth of front is suppressed. On the other hand, the increase in compressive strength of concrete does not affect spalling of rear suppression. Spalling of rear is controlled by the increase of flexural, tensile strength and deformation capacity.

• Journal of the korean academy of Pediatric Dentistry
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• v.38 no.3
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• pp.229-236
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• 2011

ProRoot MTA(Dentsply Tulsa, U.S.A) which has similar component with Portland cement has setting expansion character and long setting time. Excessive expansion can cause fracture at the apical portion of the root and decreasing of volume stability. And the long setting time makes additional visits for crown restoration and slow setting process of this material can change physical properties itself. In this study, among requirements of root canal filling material(KS P ISO 6876) which is revised at 2008, we investigated the setting time and setting expansion. Objects are recently developed OrthoMTA(BioMTA, Korea), conventional ProRoot white MTA(Dentsply Tulsa, U.S.A) and White portland cement(Union, Korea). The results in setting expansion, OrthoMTA was $0.08{\pm}0.02%$, ProRoot white MTA and White portland cement were each $0.28{\pm}0.06$, $0.80{\pm}0.25%$(p<0.05). The results in setting time, OrthoMTA, ProRoot white MTA, White portland cement were each $307.78{\pm}3.83$ min, $150.44{\pm}2.35$ min, $235.33{\pm}9.07$ min(p<0.05).

• Journal of Life Science
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• v.28 no.1
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• pp.110-115
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• 2018

This study was conducted to investigate the potential of medicinal plants as oral health materials derived from natural products. Among the extracts from 200 medicinal plants grown in Nepal, Laos, Mongolia, Bangladesh, Vietnam, and China, stem extracts from Diospyros malabarica (1 mg/disc) showed the highest antibacterial activity against Porphyromonas gingivalis ATCC33277 and Streptococcus mutans ATCC25175. The D. malabarica stem extracts showed antibacterial activity similar to chlorhexidine, sodium lauryl sulfate, and triclosan, which were used as a positive control, as well as higher antibacterial activity against S. mutans ATCC25175 than P. gingivalis ATCC33277. The D. malabarica stem extracts showed bactericidal action (MBC, 0.4 mg/ml) against P. gingivalis ATCC33277 and bacteriostatic action against S. mutans ATCC25175. The biofilm production rate of S. mutans ATCC25175 and the expression of the comX gene associated to biofilm formation in the cultures treated with 0.2-1.0 mg/ml of D. malabarica stem extracts were suppressed in a concentration-dependent manner. Based on the above results, it can be concluded that D. malabarica stem extracts can be used as oral health material derived from natural materials, as demonstrated by the bacteriostatic action and inhibition of biofilm formation against S. mutans ATCC25175.

• Journal of Life Science
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• v.30 no.8
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• pp.695-700
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• 2020

The purpose of this study is to evaluate the anti-oxidant and anti-microbial activity of syringin isolated from Cortex Fraxini to investigate their potential for use as safe natural compounds. Purified syringin was dissolved in distilled water for each concentration and used in each experiment. Syringin showed higher 2,2-Diphenyl-1-picrylhydrazyl radical scavenging than butylated hydroxytoluene (BHT) at a concentration of 50 ㎍/ml. In 2,2'-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging, activity was similar to that of BHT at all concentrations. In antioxidant protection factor measurement, activity of syringin slightly increased as the concentration increased, as did the inhibitory effect of thiobarbutric acid reactive substances. In evaluating anti-microbial activity, the clear zones of Listeria monocytogenes KCTC 13064, Staphylococcus aureus KCTC 1916, Escherichia coli KCTC 2571, and Helicobacter pylori HPKCTC B0150 at a concentration of 200 ㎍/ml were found to be 17.8 mm, 20.45 mm, 17.05 mm, and 16.8 mm, respectively, but no clear zone was observed in the case of Candida albicans ATCC 10231. The activity against water-soluble antioxidants was therefore superior to that against lipid-soluble antioxidants. Anti-microbial activity was examined by inhibiting growth against gram-positive and -negative strains, and anti-fungal activity was not observed. Based on the results of this study, syringin has possible applications as a natural anti-oxidant and anti-microbial material.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.694-700
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• 2018

Korea has disposed of medium and low level radioactive waste generated by operating nuclear power plants permanently through the radioactive waste repository located in Gyeongju. However, the maritime transport of radioactive waste is exposed to the risk of marine accidents, and it will be necessary to introduce a system to secure safety from the viewpoint of the function and role of the Korea Coast Guard. Especially, Korea is affected by large-scale marine accidents, such as the Hebei Spirit or Sewol accidents. From this point of view, we analyzed the current status of Korea radioactive waste shipping and examined the response systems of major foreign countries. As a result of examining major cases of accidents, we have operated an Emergency Towing Vessel (ETV) fleet centering on European countries in order to respond urgently to marine casualties that may have social, regional and international effects, such as accidents of similar nuclear material carriers and dangerous cargo ships. It proves a partial effect. Based on this, we propose the introduction of the Korean ETV System. In other words, it is necessary to respond to large-scale marine accidents that could lead to enormous environmental, property, and personal damage, such as marine accidents involving nuclear material ships, large oil tankers, and large passenger ships. For this, it seems necessary to introduce Korea ETV, which can carry out emergency towing, oil pollution control function, large - scale rescue equipment and manpower. This will lead to the enhancement of the Korea Coast Guard response to marine accidents, and will not miss the golden time of the initial response to the national disaster, which will help protect precious people, property and the environment.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.46 no.3
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• pp.231-241
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• 2020

In this study in order to develop new approaches we investigated using high voltage pulsed electric fields (PEF) technology to reduce the risks, protect the phyto-constituents and improve skin biological activities. After preparing a Chaga mushroom (Inonotus obliquus) extracts pretreated with PEF, components measurement and skin efficacy evaluation were performed. As a result of the content measurement, the content of polysaccharide and polyphenol were higher in the order of extracts treated with 50 Hz and 25 Hz at 0.5 kV/cm, and the content of protein was the highest in extracts treated with 25 Hz at 0.5k V/cm. Similar to the results of the polyphenol measurements, extracts treated with 25 Hz and 50 Hz at 0.5 kV/cm showed leading DPPH scavenging ability. The cell protection effect against sodium dodecyl sulfate (SDS) and UVB was finest in extracts treated with 25 Hz at 0.5 kV/cm, which had the highest protein content. And the hyaluronic acid synthesis was leading in extracts treated with 50 Hz and 100 Hz at 0.5 kV/cm. Therefore, the active ingredient of the high-voltage PEF pre-treatment Chaga mushroom extract can be developed as a functional material with cell protection and moisturizing effect, and such green technology is expected to be used in various fields of cosmetics and material development.