• 한국응용과학기술학회지
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• 제3권1호
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• pp.43-47
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• 1986

1.2-bis(aminoacyl)hydrazine derivatives and dipeptides were synthesized by conventional peptide synthesis procedures. Their antioxidant activity were inverstigated by over-storage test using corn oil as substrte. 1.2-bis (aminoacyl) hydrazine derivatives and dipetides containing hydrophobic side chain amino acid showed higher antioxidant activity. A free N-terminal amino group was also found to be important for the appearance of antioxidant activity. 1.2-bis (aminoacyl) hydrazine derivatives showed higher antioxidant activity than dipeptides. Antimicrobial activites of dipeptides and 1.2-bis (aminoacyl) hydrazine derivatives were also examined by the paper disc method. All of these compounds had shown no antimicrobial activity.

• 산업공학
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• 제8권2호
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• pp.171-183
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• 1995

A special purpose automated storage and retrieval system is developed in which information media such as compact disc or video tapes can be stored. Hardware system includes rack, stacker crane with robot arm, conveyor, and bar code reader. Software system includes database for address management, user interface for quick scanning of information media by displaying moving image, and algorithms for selecting the closest open location. Such system is widely applicable to CD library or broadcasting station in the forthcoming information age. In this paper we present detailed procedure and tools that are used in designing and implementing such a special AS/R system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.798-800
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• 2003

Recently, in optical storage device technical trends, the size of optical drive is slimmer to adopt notebook computer and the power of actuator is higher to achieve the high transfer rate. However, these trends of optical disc drives tend to increase the temperature of the actuator part, it causes some problems on the performance of optical parts - the resonance frequency of the actuator is down to lower band and the objective lens, coil and magnet are easily damaged. In this study, to overcome these thermal problems, the numerical simulations of heat transfer were performed. As the result of simulations, the thermal characteristic of the hybrid actuator is better than the previous design. And, it shows the good dynamic performance in experiment.

• Restorative Dentistry and Endodontics
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• 제38권1호
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• pp.36-42
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• 2013

Objectives: This study evaluated the antibacterial effect and mechanical properties of composite resins ($L_{CR}$, $M_{CR}$, $H_{CR}$) incorporating chitosan with three different molecular weights (L, Low; M, Medium; H, High). Materials and Methods: Streptococcus (S). mutans 100 mL and each chitosan powder were inoculated in sterilized 10 mL Brain-Heart Infusion (BHI) solution, and was centrifuged for 12 hr. Absorbance of the supernatent was measured at $OD_{660}$ to estimate the antibacterial activities of chitosan. After S. mutans was inoculated in the disc shaped chitosan-containing composite resins, the disc was cleansed with BHI and diluted with serial dilution method. S. mutans was spread on Mitis-salivarius bacitracin agar. After then, colony forming unit (CFU) was measured to verify the inhibitory effect on S. mutans biofilm. To ascertain the effect on the mechanical properties of composite resin, 3-point bending and Vickers hardness tests were done after 1 and 3 wk water storage, respectively. Using 2-way analysis of variance (ANOVA) and Scheffe test, statistical analysis was done with 95% significance level. Results: All chitosan powder showed inhibition effect against S. mutans. CFU number in chitosan-containing composite resins was smaller than that of control resin without chitosan. The chitosan containing composite resins did not show any significant difference in flexural strength and Vickers hardness in comparison with the control resin. However, the composite resin, $M_{CR}$ showed a slightly decreased flexural strength and the maximum load than those of control and the other composite resins $H_{CR}$ and $L_{CR}$. Conclusions: $L_{CR}$ and $H_{CR}$ would be recommended as a feasible antibacterial restorative due to its antibacterial nature and mechanical properties.

• 한국생활과학회지
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• 제20권6호
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• pp.1213-1222
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• 2011

This research evaluated antibacterial and growth inhibition effects on three kinds of lactic acid bacteria and five kinds of food poisoning bacteria using Backryencho powder, hot water, 70% ethanol, and 95% ethanol extracts. Antibacterial activity was shown against Leu. mensenteroides for 8 and 10 mg/disc of the 95% ethanol extract solution and strong proliferation inhibition effects were displayed against B. subtilis, Stap. aureus, E. coli, and S. typhimurium. High antibacterial activity according to certain clear zone formations was shown especially for the 10 mg/disc. A 3% concentration of the 95% ethanol extract showed high growth inhibition effects against lactic acid bacteria, L. brevis, L. plantarum, and Leu. mesenteroids. The measurement of viable cell counts of S. aureus, E. coli, B. subtilis, and S. typhimurium indicated suppression effects by the 3% concentration of the 95% ethanol extract, at 49.60%, 41.54%, 35.95%, 28.82%, and 26.60% respectively. The antibacterial activities of the hot water, 70% ethanol, 95% ethanol extract of Backryencho against food poisoning bacteria and Kimchi fermentation lactic acid bacteria were confirmed through various methods of antibiotic measurement. Based on these results, Backryencho extract is considered a good source for a range of applications as a natural anti-bacterial agent for the storage ability of Kimchi and as a possible food preservative.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1424-1430
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• 2013

This paper presents design procedure of the magnetic bearings used for high-speed electric machines and flywheel energy storage systems. Magnetic bearing can be categorized by inner-rotor type and outer-rotor type according to the position of the rotary disc. These two types are applicable based on application environments such as application space, required attraction force, and controllability. Magnetic bearing is generally designed based on the ratio (geometrical coefficient or geometrical efficiency) of pole width to rotor journal radius but proper ratio is only decided by the analysis. This is the difficulty of the magnetic bearing design. In this paper, proper design technology of the inner-rotor type and outer-rotor-type eight pole magnetic bearings is introduced and compared with the FEM analysis results, which verifies the proposed design procedure is suitable to be applied to the design of the magnetic bearings for the industrial applications and flywheel energy storage system.

• Restorative Dentistry and Endodontics
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• 제40권4호
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• pp.255-261
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• 2015

Objectives: The aim of this study was to evaluate the effect of three different drinks on the color parameters of four different restorative materials. Materials and Methods: Three different composites (Filtek Ultimate Universal Restorative, Filtek Ultimate Flowable, and Filtek Silorane, 3M ESPE) and a polyacid-modified composite resin material (Dyract XP, Dentsply DeTrey GmbH) were evaluated. Eighty-four disc-shaped specimens of 8 mm in diameter and 2 mm in thickness were prepared (n = 21 each). Color coordinates ($L^*a^*b^*$, ${\Delta}L^*$, ${\Delta}a^*$, ${\Delta}b^*$, and ${\Delta}E^*$) were measured using a $V{\dot{I}}TA$ Easyshade Compact ($V{\dot{I}}TA$ Zahnfabrik) after 24 hr of storage (baseline) and after 30 day of storage in three different beverages of black tea, Coca cola, or water (control) (n = 7). In each beverage, the specimens were stored three times a day, one hr each, for 30 day. The color changes (${\Delta}E$) were calculated and were analyzed by Kruskal-Wallis and Dunn multiple comparison test. Results: The color difference (${\Delta}E^*$) of the resin materials ranged between 1.31 and 15.28 after 30 day of immersion in the staining solutions. Dyract XP in Coca cola ($15.28{\pm}2.61$) and black tea ($12.22{\pm}2.73$) showed the highest mean ${\Delta}E^*$ value after 30 day, followed by Filtek Ultimate Universal Restorative ($5.99{\pm}1.25$) and Filtek Ultimate Flowable ($4.71{\pm}1.40$) in black tea (p < 0.05). Conclusions: The compomers displayed unacceptable color changes at the end of 30 day in all beverages. Among resin composites, the silorane based composite exhibited relatively good color stability than the others. Filtek Ultimate Universal Restorative and Filtek Flowable showed similar color changes in all beverages.

• 대한금속재료학회지
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• 제50권12호
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• pp.949-953
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• 2012

$MgH_2$ was employed as a starting material instead of Mg in this work. A sample with a composition of 94 wt% $MgH_2-6$ wt% Ni (called $MgH_2-6Ni$) was prepared by reactive mechanical grinding. The hydriding and dehydriding properties were then examined. An $MgH_2-Ni$ hydrogen storage alloy that does not require an activation process was developed. The alloy was prepared in a planetary ball mill by grinding for 4 h at a ball disc revolution speed of 250 rpm under a hydrogen pressure of about 12 bar. The sample absorbed 3.74 wt% H for 5 min, 4.07 wt% H for 10 min, and 4.41 wt% H for 60 min at 573 K under 12 bar $H_2$, and desorbed 0.93 wt% H for 10 min, 1.99 wt% H for 30 min, and 3.16 wt% H for 60 min at 573 K under 1.0 bar $H_2$. $MgH_2-6Ni$ after reactive mechanical grinding contained ${\beta}-MgH_2$ (a room temperature form of $MgH_2$), Ni, ${\gamma}-MgH_2$ (a high pressure form of $MgH_2$), and a very small amount of MgO. Reactive mechanical grinding of Mg with Ni is considered to facilitate nucleation, and to reduce the particle size of Mg. $Mg_2Ni$ formed during reactive mechanical grinding also increases the hydriding and dehydriding rates of the sample.

• 한국전산구조공학회논문집
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• 제34권5호
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• pp.293-300
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• 2021

본 논문은 에너지를 실시간으로 저장할 수 있는 저장장치 중 열에너지 저장 콘크리트를 대상으로 재료의 미세구조와 물성(열전도도)의 상관관계를 분석하는 연구를 수행하였다. 에너지 저장 콘크리트의 열전도 성능을 증가시키기 위해 혼화재인 그라파이트(graphite)를 사용하였다. 그라파이트가 시멘트 질량의 10%와 15%를 치환한 시편과 일반 콘크리트(OPC) 시편을 제작하여 그라파이트의 혼입에 따른 미세구조 변화 및 열전도도의 영향을 마이크로 스케일에서 분석하였다. 마이크로-CT를 활용하여 OPC와 그라파이트를 사용한 콘크리트의 공극률을 비교하였으며, 확률함수를 사용하여 미세구조 특성을 정량화하였다. 미세구조 특성 차이가 열전도도에 미치는 영향을 확인하기 위해 3차원 가상 시편을 제작하여 열해석을 수행하였으며, 이를 열평판법을 사용하여 측정한 열전도도 실험 결과와 비교하였다. 열해석 수행 시 그라파이트 재료가 지닌 열전도도 성능을 반영하기 위하여 해석 결과와 실험 결과를 기반으로 고체상의 열전도도를 역해석을 통해 계산하였으며, 그라파이트가 시편의 열전도도에 미치는 영향에 대해 분석하였다.

• 한국인쇄학회지
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• 제30권3호
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• pp.23-33
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• 2012

We studied simultaneously the electronically written data affected in the use of thermal transfer discs and the recoding strategy between recoding drives for the stable long term preservation of optical discs which are commonly used in an electronic data storage device. The most important thing in the archiving preservation might be a choice of a device, however the use of thermal transfer recording discs is not good for long term data preservation because the thermal effect on the recoding data is critical which means that the data are recorded not under best condition but under bad condition. We inspect the strategies of recoding data from 12 brands of optical discs and drives of 7 brands and it turns out the recoding strategy is needed first for the long term preservation of electronic recording data. Thus, without affecting data quality and deformation of optical discs, the choice of optimal disc and drive in recoding data will be a solution for the long term preservation of recoding data.