• Tribology and Lubricants
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• v.31 no.1
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• pp.1-5
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• 2015

In this study, we apply an ultrasonic nanocrystal surface modification (UNSM) technique to radial journal bearings (JBs) and disks made of SUJ2 and SCM440, respectively. We investigate frictional properties of untreated and UNSM-treated specimens using a ball-on-disk tester. We construct the Stribeck curve at the boundary, under mixed and full hydrodynamic lubrication conditions for the specimens using friction data obtained from JB tests. The friction at the boundary lubrication condition and the transition period to mixed lubrication condition on the UNSM-treated specimens is reduced, which improves the service life of JBs. The major effects of this reduction in the three lubrication regimes can be explained in the terms of improved mechanical properties and the presence of micro dimples. Moreover, we estimate the friction and fatigue properties of SCM440 specimens using a ball-on-disk specimen under dry and oil-lubricated conditions. Friction test results reveal that the UNSM-treated specimens show lower friction coefficient than the untreated specimens under both dry and oil-lubricated conditions. We evaluate the fatigue properties of SCM440 specimens by calculating the Hertzian stress with respect to the failure cycles. Fatigue tests results also reveal that the UNSM-treated specimens possess a longer fatigue life than the untreated specimens. The improved properties are effective in increasing the energy efficiency of bearings.

• Proceedings of the KAIS Fall Conference
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• 2011.12b
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• pp.453-456
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• 2011

전 세계적으로 도시수변공간 개발이 이슈화 되고 있는 요즘. 우리나라에서도 급속한 경제 발전에 따라 회손 되어버린 하천들의 정비사업이 활성화 되고 있다. 이에 본 연구에서는 도시수변공간과 도시재생에 대해 조사하여 이해하고 그 사례를 들어 어떠한 방법들로 개발되었는지 살펴본 뒤, 천안천의 형장조사를 통해 상류, 중류, 하류로 나누어 각각의 구역이 어떠한 방식으로 개발되었으며 현재 이용자들에게 어떻게 활용되는지를 파악하였다.

• Proceedings of the KAIS Fall Conference
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• 2011.05a
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• pp.130-133
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• 2011

본 논문에서는 도시 공공디자인의 일부분으로서 간판개선사업의 발전에 필요한 체계적이고 지속적인 발전에 도움을 주고자, 간판사업에 대한 이론적 고찰을 토대로 최근 간판개선사업 지역인 '온양명동거리 간판이 아름다운 거리'의 옥외 간판의 시각요소가 효과적인 정보전달을 제공하고 쾌적한 도시경관을 조성하는지 알아보고, 실태조사와 도시가로 환경 구성원의 만족도 및 의식을 분석하였다.

• Proceedings of the KAIS Fall Conference
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• 2010.05b
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• pp.818-821
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• 2010

본 논문에서는 홍통거리의 신축 건물과 리모델링 건물을 통한 재생 건축의 조화의 방법에 대해 모색해 보고, 해결방안을 제시해 보도록 한다. 현재 홍통거리는 거리의 발전에 따라 오래된 건축물들을 리모델링한 건물과 신축건물들이 생겨남에 따라, 두 건물과의 조화된 모습을 찾고자 한다. 조화된 거리의 모습을 이루기 위해 거리 바닥 패턴과 일관된 시설물을 통해 거리의 형성을 해나가야겠다.

• Proceedings of the KAIS Fall Conference
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• 2010.05b
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• pp.826-829
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• 2010

도시형성의 기본요소인 건축물은 눈에 보이는 형태만이 아니라, 그 건물의 역사, 장소성 등을 알 수 있다. 선유도공원은 물을 공급하던 정수장이었으며, 현재 서울 도심의 선유도공원 안에서 어떤 용도로 Renovaion이 되어 사용되고 있는지를 생태디자인 측면에서 고찰하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.1211-1212
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• 2014

본 논문에서는 차종에 관계없이 휴대가 가능하며 사용자가 휠체어에서 차량의 좌석으로 이동시키는 로봇팔을 설계하고 경제성과 이동성, 휴대용이성이라는 사용자요구를 충족할 것이다.

• Tribology and Lubricants
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• v.30 no.6
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• pp.350-355
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• 2014

This study proposes a sustainable bearing remanufacturing process using the ultrasonic nanocrystal surface modification (UNSM) technique. The UNSM technique is a newly developed and sophisticated surface modification technique that can increase the mechanical properties and improve the friction and wear performance of materials. Taking advantage of the bearing manufacturing process is the most significant way of optimizing the life of a bearing. The proper maintenance and usage of repaired bearings can increase their life to be equal to or greater than that of new bearings. This paper discusses the restoration of certain mechanical properties of worn, damaged, and discarded bearings, and suggests a remanufacturing process for used bearings, which can impart them with a lifespan equivalent to that of new bearings. The most damaged part of the discarded bearings is the raceway, which is the site of accumulated fatigue. The existing polishing or barrel finishing processes can recover the accumulated fatigue only partially. Rolling contact fatigue tests performed on UNSM-treated new and used specimens polished after $4{\times}10^6$ cycles reveal that UNSM-treated new specimens exhibit the longest fatigue life compared to other specimens. This study verifies the proposed complete fatigue recovery process, which can increase the fatigue life of used bearings to a level greater than that of new bearings.

• The Journal of Internal Korean Medicine
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• v.23 no.1
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• pp.1-4
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• 2002

Objective : Hyperhomocysteinemia has been proven to be an independent risk factor for stroke. The genetic mutation of methylenetetrahydrofolate reductase(MTHFR) elevates serum homocysteine level, but it still remains controversial whether the MTHFR gene mutation could be a predictor of ischemic stroke. Therefore, we studied if this genetic defect could cause ischemic stroke independently. Methods : We gathered ischemic stroke subjects and age, sex-matched controls. Age, gender, past medical history, smoking habit, serum homocysteine level, and the MTHFR genotype were recorded. General characteristics of ischemic stroke subjects were compared to the controls. We classified the stroke according to the related vessels(small and large artery infarction) and single lesion and multiple infraction. Relevant risk of the MTHFR genotype was evaluated in each stroke subtype with multiple logistic regression analysis. Results : When the controls were compared to the whole ischemic stroke, there was no specific difference except some medical histories. However, further analysis based on stroke subtypes showed important results. The small artery infarction group, multiple infraction group had significant odds ratio of the MTHFR TT genotype adjusted for age, gender, medical history and smoking habit. Conclusions : The MTHFR TT genotype is an independent risk factor for certain types of ischemic stroke, small artery infarction and multiple infarction.

• Journal of Microbiology and Biotechnology
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• v.34 no.5
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• pp.1154-1163
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• 2024

Glucosylation is a well-known approach to improve the solubility, pharmacological, and biological properties of flavonoids, making flavonoid glucosides a target for large-scale biosynthesis. However, the low yield of products coupled with the requirement of expensive UDP-sugars limits the application of enzymatic systems for large-scale. C. glutamicum is a Gram-positive and generally regarded as safe (GRAS) bacteria frequently employed for the large-scale production of amino acids and biofuels. Due to the versatility of its cell factory system and its non-endotoxin producing properties, it has become an attractive system for the industrial-scale biosynthesis of alternate products. Here, we explored the cell factory of C. glutamicum for efficient glucosylation of flavonoids using apigenin as a model flavonoid, with the heterologous expression of a promiscuous glycosyltransferase, YdhE from Bacillus licheniformis and the endogenous overexpression of C. glutamicum genes galU1 encoding UDP-glucose pyrophosphorylase and pgm encoding phosphoglucomutase involved in the synthesis of UDP-glucose to create a C. glutamicum cell factory system capable of efficiently glucosylation apigenin with a high yield of glucosides production. Consequently, the production of various apigenin glucosides was controlled under different temperatures yielding almost 4.2 mM of APG1(apigenin-4'-O-β-glucoside) at 25℃, and 0.6 mM of APG2 (apigenin-7-O-β-glucoside), 1.7 mM of APG3 (apigenin-4',7-O-β-diglucoside) and 2.1 mM of APG4 (apigenin- 4',5-O-β-diglucoside) after 40 h of incubation with the supplementation of 5 mM of apigenin and 37℃. The cost-effective developed system could be used to modify a wide range of plant secondary metabolites with increased pharmacokinetic activities on a large scale without the use of expensive UDP-sugars.

• Journal of Advanced Navigation Technology
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• v.15 no.4
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• pp.664-671
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• 2011

The development of IT technology and breakthrough of the network and the wired network, wireless network boundaries disappear and wired and wireless integrated service environment is the advent in online game environment. However, the wired and wireless integrated service environment appropriate security technology is still inactive, wired and wireless integration environment due to the characteristic as well as security threats wired network and security threats in wireless networks should be considered. Therefore, This wired and wireless integrated environment has been considering studied various, Among them wired and wireless environment considering the lightweight of ID-based authentication and key management has been in progress. In recent, Moon et al. pervasive environment in authentication and ID-based key management protocol is proposed. However, Moon et al.'s scheme is use the ID-based public-key approach to decreased the amount of computation. However, pairing by using a technique similar to the existing public key scheme can represent the amount of computation. Therefore, In this paper the way of Moon etc in security vulnerability analysis.