• International Journal of Precision Engineering and Manufacturing
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• v.7 no.4
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• pp.34-39
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• 2006

High-precision centerless grinding machines are emerging as a means of finishing the outer diameter grinding process required for ferrules, which are widely used as fiber optic connectors. In this study, a structural characteristic analysis and evaluation were carried out using a virtual prototype of a centerless grinding machine to realize systematic design technology and performance improvements required to manufacture ferrules. The prototype consisted of a concrete-filled bed, hydrostatic grinding wheel (GW) and regulating wheel (RW) spindle systems, a hydrostatic RW feed mechanism, a RW swivel mechanism, and on-machine GW and RW dressers. The loop stiffness values of the centerless grinding machine were estimated based on the relative displacements between the GW and RW caused by grinding forces. The simulated results illustrated that a concrete-filled bed considerably improved the structural stiffness and accuracy of a high-precision centerless grinding machine.

• New & Renewable Energy
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• v.2 no.4 s.8
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• pp.39-45
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• 2006

This paper introduces a preliminary work for the design of a mini-dish cluster system for power generation. Each mini-dish [typically has a 20 to 30 cm in diameter] is designed with a simple parabolic profile concentrating sun light [after the glass glazing cover to avoid dust deposition on the reflector and facilitate cleaning] onto a centrally located small plane[or concave] mirror which is placed on the bottom side of a transparent glass cover. The mirror with a mini-dish concentrator is designed to focus beam radiation onto a focal point before it enters a bundle of optical fibers connected to a remote receiver for power generation. Different options are considered in designing a mini-dish concentrator to maximize its effectiveness for the collection and use of solar energy.

• Textile Coloration and Finishing
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• v.24 no.1
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• pp.27-32
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• 2012

Generally, hair treatments by complementary actions to give a sense of activity are permanent setting, dyeing, and bleaching, etc. In this study, we investigated the wave formation ability and hair damage occuring in permanent setting and bleaching process. The wave formation ability was evaluated by the differences of length and curl diameter after permanent setting. And the hair damage was also evaluated by the protein release ability and SEM of hair. The bleached hair immediately after permanent setting treatment has better wave formation ability, but much more damaged than the bleached hair after rinsing thoroughly with warm water. It was considered that the chain of hair keratin broke down easily by the bleaching action in the existence of permanent setting agents.

• Carbon letters
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• v.16 no.2
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• pp.121-126
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• 2015

Carbon fibers are prepared by stabilizing pitch fibers accompanying electron beam (E-beam) irradiation. The carbon fibers pretreated by E-beam irradiation achieve a higher stabilization index than the carbon fibers that are only heat-stabilized. In addition, the carbon fibers subjected to E-beam irradiation in the stabilization step exhibit a comparable tensile strength to that of general purpose carbon fibers. The carbon fibers pretreated with an absorbed dose of 3000 kGy have a tensile strength of 0.54 GPa for a similar fiber diameter. Elemental, Fourier-transform infrared spectroscopy, and thermogravimetric analyses indicate that E-beam irradiation is an efficient oxidation and dehydrogenation treatment for pitch fibers by showing that the intensity of the aliphatic C-H stretching and aromatic $CH_2$ bending (out-of-plane) bands significantly decrease and carbonyl and carboxylic groups form.

• Bulletin of the Korean Chemical Society
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• v.29 no.4
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• pp.777-781
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• 2008

In this work, silver nanoparticles-containing polyacrylonitrile (PAN) solutions in N,N-dimethylformamide (DMF) were electrospun to be webs consisting of nanofibers. The inputted voltage and PAN content in the solution were fixed at 15 kV and 10 wt.% in DMF with 10 cm of tip-to-collector distance (TCD). The PAN/Ag nanofiber webs were stabilized by oxidation at 250 ${^{\circ}C}$ for 2 h in air and carbonized at 1000 ${^{\circ}C}$ for 2 h in $N_2$. The resultant diameter distribution and morphologies of the nanofibers were evaluated by scanning electron microscope analysis. The electrochemical behaviors of the nanofiber webs were also observed by cyclic voltammetry tests. It was found that the presence of silver nanoparticles in carbon nanofiber webs led to the increase of specific capacitance and the decrease of fiber diameters.

• Fibers and Polymers
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• v.3 no.4
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• pp.134-139
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• 2002

Carbon nanotubes are graphene sheets rolled up in cylinders with diameter as small as 1nm. Extensive work carried out in recent years has revealed the intriguing properties of this novel material. Exceptional property combined with low density of nanotubes makes them suitable for use as reinforcements in composites. Low volume of production and high cost is the main limitations towards their growth and application. Nanofibres bridge the gap between the conventional carbon fibre and the carbon nanotubes. With their low cost & comparatively higher volume of production along with their exceptional properties, the nanofibres are considered attractive material as nanoscale reinforcement. In this article a concise review of structure, property. production and application of carbon nanotubes and nanofibres have been discussed.

• Bulletin of the Korean Chemical Society
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• v.27 no.11
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• pp.1815-1818
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• 2006

Imogolite which has chemical composition, $(HO)_3Al_2O_3SiOH$, was synthesized with orthosilicate acid and aluminium chloride at low pH solution. It has extremely large aspect ratio with an external diameter of 2nm and the length of a few micrometers. The high aspect ratio of the imogolite could make the material as the filler for the high strength fiber and as the wire for the electronic applications. Here, Imogolite that derives considerable microporosity from a nanometer-sized tubular structure has been modified with a conducting polymer, polypyrrole. Its bonding and wiring structure were confirmed by IR and TEM. The measured conductivity after modification with polypyrrole increased with polypyrrole thickness at various voltage conditions.

• Journal of Biomedical Engineering Research
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• v.14 no.3
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• pp.243-250
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• 1993

An endoscope is a medical device which observes the inner surface of an organ inside a body. Recently, a new type of endoscope using a CCD image sensor has been developed and turned out to have many strong points over the conventional optical fiber endoscope system. A swallowable insertion tube is an insertion tube having so small a diameter that the head of the insertion tube can reach the end of stomach only by mechanical movement of the esphagus and stomach or the patient's external movement. This paper presents some of the results that the Institute of Biomedical Engineering at Seoul National University has obtained while developing an electronic endoscope having a swallowable insertion tube. After some of the features of the developed system are presented, some of the image processing techniaues are addressed.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.158-159
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• 2011

In this work, The electrochemical behavior of CF/Al composite was investigated at constant current densities in aqueous solutions. The surface and cross section of PEO-treated CF/Al were observed using SEM, EDS and OM. The CF/Al composite contains carbon fibers of about 40 Vol.% with 5~7 um diameter and 100~150 um length. The carbon fibers appeared to b removed by anodic oxidation in sulfuric acid solution, leaving a carbon-fiber free zone in the surface region. Anodic oxide films were formed in the carbon-free region by plasma electrolytic oxidation(PEO) method in alkaline solutions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.410-410
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• 2007

광섬유 내에 첨가되어 있는 $GeO_2$ 등의 물질을 얼 확산시켜서 만드는 열확산 코어 광섬유는 열확산 기술에 따른 광섬유의 MFD(Mode Field Diameter)를 국소적으로 확대하여 굴절률 분포를 변화시킨 광섬유로 혹의 비틀림 및 간격에 대한 허용범위가 넓어지게 하여 접속 손실을 감소시킬 수 있다. 본 연구에서는 열확산 코어 광섬유를 제조할 때 안정된 얼확산 문제를 해결하기 위한 방법으로 트윈 토치를 이용한 프레임 브러싱 기법의 안정화된 코어 확장형 광섬유 제조시스템을 제작하였다. 또한 제작된 열확산 코어 광섬유 제조시스템을 이용하여 단일모드 조건을 만족하는 다양한 종류의 열확산 코어 광섬유가 제작됨을 확인할 수 있었다.