• Journal of the Korean Society for Precision Engineering
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• v.29 no.3
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• pp.339-345
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• 2012

Electrospun meshed poly-caprolactone PCL was patterned by femtosecond laser with linear grooves. As parametric variables, focus spot size, pulse energy, and scanning speed were varied to determine the affects on groove size and the characteristics of the electrospun fiber at the edges of these grooves. The femtosecond laser was seen to be an effective means for flexibly structuring the surface of ES PCL scaffolds and the width of the ablated grooves was well controlled by laser energy and focus spot size. The ablation threshold was measured to be $14.9J/cm^2$ which is a little higher than other polymers. These affects were attributed to optical multiple reflections inside nano-fibers. By the laser-induced plasma at higher pulse energies, some melting of fibers was observed.

• Journal of Korea Ship Safrty Technology Authority
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• s.36
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• pp.28-42
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• 2014

본 연구는 예인선 해양사고로 인한 사망사건 중 예인삭 절단사건이 큰 비중을 차지하고 있어 인명사고 예방이 시급한 가운데 예인 로프의 아이스플라이스에 대한 기준이 현재 국내에 마련되어 있지 않아 본선의 임의대로 제작?사용하는 실정이다. 이에 우리 공단에서 수검 중인 예인선을 대상으로 예인선에서 주로 사용하는 예인삭의 종류와 구조, 재질 등에 대한 국내 사용실태를 조사하고, 조사를 바탕으로 선정된 로프의 인장강도 시험을 통하여 스플라이스 횟수에 따른 유의성 평가를 시행하며, 국내 외 유사 기준 및 표준을 조사 분석하여 최종적으로 국내에서 적용할 수 있는 예인삭 아이스플라이스 기준을 제시하였다.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.409-416
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• 2002

In order to apply seismic isolators to the low-cost buildings, seismic isolators have to be low-cost and light. In this paper fiber reinforced strip form isolator in which the steel plates of conventional rubber bearing was replaced by fiber was proposed. The proposed fiber reinforced strip form isolator was designed, fabricated, cut and subjected to vertical test and harizontal test. Therefore fiber reinforced strip form isolator was to be shown valid in the view point of fabrication and application to desired size. The harizontal test and vertical test have shown that fiber reinforced strip form isolator could replace the rubber isolator. By these results, low-cost and light seismic isolator can be applied to the low-cost building. These fiber reinforced strip form isolator can be applied to the low-cost building.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.6
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• pp.1-6
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• 2002

In order to apply seismic isolators to low-cost buildings, seismic isolators have to be low-cost and light. In this paper fiber reinforced strip form isolator in which the steel plates of conventional rubber bearing were replaced by fiber was proposed. The proposed fiber reinforced strip form isolator was designed, fabricated, cut and subjected to vertical test and horizontal test. Therefore, fiber reinforced strip form isolator was to be shown valid in the view point of fabrication and application to desired size. The horizontal test and vertical test have shown that fiber reinforce strip form isolator could be replaced the rubber isolator. By these results, low-cost and light seismic isolator can be applied to the low-cost building.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.6 s.58
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• pp.166-175
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• 2009

An experimental study was carried out to estimate the flexural performance of steel fiberreinforced self-compacting concrete. Seven slabs with three different steel fiber-reinforced concretes were prepared to make beam specimens. After proper curing period, each slab was cut to five beams with a diamond saw. The beam specimen was tested with displacement control method to obtain load-deflection curve. As the results, the self-compacting concrete beam showed higher flexural strength, ductility and toughness index compared to the normal concrete beam. This means that steel fiber-reinforced self-compacting concrete can be used more widely in the field of architecture and civil engineering because of its self-compactability and good mechanical properties.

• Restorative Dentistry and Endodontics
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• v.34 no.4
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• pp.364-370
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• 2009

The aim of this study was to evaluate the effect of fiber direction on the polymerization shrinkage of fiber-reinforced composite. The disc-shaped flowable composite specimens (d = 10 mm, h = 2 mm, Aeliteflo A2, Bisco, Inc., IL, USA) with or without glass fiber bundle (X-80821P Glass Fiber, Bisco, Inc., IL, USA) inside were prepared, and the longitudinal and transversal polymerization shrinkage of the specimens on radial plane were measured with strain gages (Linear S-series 350${\Omega}$, CAS, Seoul, Korea). In order to measure the free polymerization shrinkage of the flowable composite itself, the disc-shaped specimens (d = 7 mm, h = 1 mm) without fiber were prepared, and the axial shrinkage was measured with an LVDT (linear variable differential transformer) displacement sensor. The cross-section of the polymerized specimens was observed with a scanning electron microscope to examine the arrangement of the fiber bundle in composite. The mean polymerization shrinkage value of each specimen group was analyzed with ANOVA and Scheffe post-hoc test (${\alpha}$=0.05). The radial polymerization shrinkage of fiber-reinforced composite was decreased in the longitudinal direction of fiber, but increased in the transversal direction of fiber (p<0.05). We can conclude that the polymerization shrinkage of fiber-reinforced composite splint or restoratives is dependent on the direction of fiber.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.2
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• pp.74-81
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• 2014

Purpose: While studies have examined microleakage in endodontically treated teeth restored with posts, microleakage among post and adhesive systems remains a concern. This study compared the sealing properties of 3 adhesively luted post systems. Materials and methods: Thirty-six endodontically treated permanent maxillary central incisors were divided into 3 groups: Zirconia-glass fiber, Quartz-glass fiber, Polyethylene fiber posts. Post space was prepared and each post was adhesively luted with 3 systems. The specimens were separately immersed in freshly prepared 2% methylene blue solution for 1 week. The cleaned specimens were then embedded in autopolymerizing acrylic resin. The root portion of tooth were horizontally sectioned into three pieces (apical, middle, and coronal portions). An occlusal view of each section was digitally photographed with a stereomicroscope. The methylene blue-infiltrated surface for each specimen was measured. Dye penetration was estimated as the ratio of the methylene blue-infiltrated surface to the total dentin surface. Results: No significant differences were found among post types. The variables of middle section and 3-stage adhesive produced significant differences in microleakage between the following post pairs: zirconia-glass fiber versus quartz-glass fiber, zirconia-glass fiber versus polyethylene fiber, and quartz-glass fiber versus polyethylene fiber (P<.05). There were significant differences between the apical and coronal sections of each post type, and between apical versus middle sections of quarze-glass fiber and polyethylene fiber posts (P<.05). Conclusion: No significant differences were found among post types. The 3-stage adhesive produced significant differences in microleakage between the following post pairs.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.25 no.2
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• pp.77-127
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• 1999

활성 산소종은 노화, 특히 피부노화의 원인 물질로 작용하고 있다. 피부는 자외선에 노출되어 있어 활성 산소종을 만드는 광화학적 반응들이 계속해서 일어나고 있다. 이들 활성 산소종들은 피부 세포 및 조직 손상을 주도한다. 이들은 항산화 효소와 비효소적 항산화제들로 구성된 항산화 방어망을 파괴함으로써 산화제/항산화제 균형을 산화 상태 쪽으로 기울게 한다. 결과적으로 계속된 산화적 스트레스는 지질 과산화, 단백질 산화, 간질 성분을 파괴시키는 단백질분해효소의 활성화, 탄력 섬유인 콜라겐과 엘라스틴의 사슬절단 및 비정상적인 교차결합, 히아루론산 사슬의 절단, 멜라닌 생성반웅 촉진, DNA 산화와 같은 생체 구성 성분들의 손상을 야기시킨다. 결국에는 탄력감수 주름살 및 기미.주근깨 둥으로 특징 지워지는 피부노화가 가속화된다. 따라서 피부노화 방지를 위해서는, 과잉의 활성 산소종 생성을 억제하고 또한 생성된 활성산소를 효율적으로 제거할 수 있는 시스템이 화장품의 처방에 반드시 포함될 필요가 있다. 즉, 산화제/항산화제 밸런스가 유지되는 피부의 항산화 방어 시스템 구축이 필요하다. 피부노화 방지에 있어서 천연물의 역할로 (1) 자외선 흡수제로서의 역할, (2) 항산화제로서의 역할, (3) 주름 개선제로서의 역할, (4) 미백제로서의 역할, (5) 항균\ulcorner항염작용 및면역 조절제로서의 역할에 대하여 살펴 보았다. 21세기는 본격적으로 기능성 화장품 시대가 개막될 것으로 예측하고 있다. 이에 맞춰 천연물들은 피부노화를 방지하는데 주도적인 역할을 할 것으로 기대된다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.10
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• pp.72-79
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• 2021

A circular saw is an effective tool for cutting glass and carbon-fiber hybrid composites. This study investigated tool wear and cut quality when reusing saw blades. The carbide saws wear four times faster than the new ones, and polycrystalline diamond (PCD) is very resistant to tool wear, except at the end of its lifespan. The cut cross-section quality is affected by the blade type, tool wear, and spindle speed. Alternate top bevel (ATB)-type blades are suitable for cutting fiber-reinforced plastics, but triple-chip grind (TCG)-type blades are unsuitable because they cause fiber-pullout defects. Tool wear and low spindle speeds increase the occurrence of arc scratches, due to the rear saw blade. A microscopic examination showed that the burr, which is a mixture of fiber chips and epoxy matrix, was bonded on top, and glass-fiber delamination occurred on the bottom glass-fiber-reinforced polymer (GFRP) surface.

• The Korean Journal of Physiology
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• v.4 no.2
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• pp.83-89
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• 1970

전기적 자극법은 심맥관계기능의 신경성조절을 이해하기위해 널리 이용되는 방법이며, 일반적으로 중추신경에는 고빈도, 말초신경에서는 저빈도 자극에 의해 최대반응이 유발된다고 알려지고 있으며, 이는 흥분파의 민도가 말초로 내려오며 감소되기 때물이라 해석되고 있다. 또한편 신경계의 어떤 단위위에서건 자극민도가 어느 한계를 넘으면 유발된 반응은 유지되지를 못하고 감쇠소실되는 것으로 이는 주로 시납스간 흥분파전달능 부전에 기인될 것이라고 믿어지고있다. 그러나 고위주추계와 말초를 연결하고 있는 척수에 있어서는 아직 최적전기적 자극조건도 분명히 알려져 있지 않을 뿐 아니라 이 부위에서도 고빈도자극시에 반응이 어느 정도 감쇠하는지에 대한 보고가 없기에 이를 추구코자 저자는 고양이의 상부경수를 면수와 연결부에서 완전 절단하기 전후 여러가지 자극조건으로 자극하여 몇 가지 결론을 얻었기에 보고하는 바이다. 1) 연수와 연결부에서 완전절단을 하기 전에는 경수$(C_1{\sim}C_2)$의 백질, 회백질의 여러부위에서 심맥관반응이 유발되었으나 절단후에는 백질중의 만두부위(좌 $2{\sim}3\;mm$, 배면으로 부터 $0.3{\sim}1.0\;mm$및 $2.5{\sim}3.5\;mm$)에만 반응이 유발되었으며, 이 두 부위는 심맥관계기능을 지배조절하는 원심성 섬유의 통로라고 사료되었다. 2) 최대반응은 자극조건(빈도 자극파지속시간 강도) 100/sec-1 mesc-3V 및 20/sec-3 msec-3V에서. 최장지속반응은 20/sec-3msec에서 유발되었으므로, 후자가 척수부에 있어 심맥관계반응을 유발키 위한 최적자극조건으로 생각된다. 3) 자극면도 20/sec 이하에서 반응유지가 잘된다는 결과는 생리적 조건하에서 척수를 통과하는 흥분파의 빈도가 20/sec를 넘지 않을 것이란 것을 시사한다. 4) 반응지속정도는 최초의 최대반응의 반으로 감쇠되기까지 소요되는시간 즉 50% 반응감쇠시간으로 표시하였으며, 척수에서는 대뇌피질 및 간뇌에서보다 심맥관계반응의 50%반응감쇠시간이 현저히 긴 것을 알 수 있었다.