• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.365-368
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• 2006

In this paper, the post cracking stress-crack width relationship of the composite is studied from a micromechanics points of view. Cook-Gordon debonding effect is studied by more refined method with considering of chemical friction of fiber interface. As a result, fiber with pre-debonding length retards stress development and shows more wide crack width for the same force level. longer pre-debonding length and lower pre-debonding bond strength results in lower full-debonding force, but same crack width.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.207-210
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• 2002

Metal matrix composites(MMCs) are increasingly attractive for high technology components such as aerospace applications and transportations due to their high strength, stiffness, and toughness. Many processes for fabricating MMCs have been developed, and relatively simple Foil-Fiber-Foil method is usually employed in solid state consolidation processes. During the consolidation processes at high temperature, densification occurs by the inelastic flow of the matrix materials, and the process is coupled with the conditions of pressure, temperature and volume fraction of fiber and matrix materials. This is particularly important in titanium matrix composites, and thus a generic model based on micro-mechanical approaches enabling the evolution of density over time to be predicted has been developed. The mode developed is then implemented into FEM so that practical process simulation has been carried out. Further the experimental investigation of the consolidation behavior of SiC/Ti-6Al-4V composites using vacuum hot pressing has been performed, and the results obtained are compared with the model predictions.

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.376-376
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• 2002

편평분할사는 복합방사법에 의한 편평 단면 형태의 분할형 초극세섬유로서, 기존 오렌지 형태인 Nylon/PET 극세사의 품종 다양화된 형태이다 분할은 Nylon과 PET의 비상용성인 특징을 이용, 물리적인 가공과 화학적인 가공에 의해 이루어지며 기존오렌지 형태의 PET/Nylon극세사에 비해 분할성이 우수하다고 보고되고 있다. 편평분할사의 용도는 Micro powder조의 Suede직물 등의 여성용 의류, 기능성 스포츠웨어, 2차 오염방지성이 우수하여 반도체 등의 정밀산업의 닦음천(Wiping Cloth)등의 크리너(Cleaner)용으로도 사용되어 질 수 있다. (중략)

• Electrical & Electronic Materials
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• v.9 no.5
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• pp.470-475
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• 1996

Fiber-textured diamond films have been deposited on scratched silicon(100) substrate by micro wave .plasma enhanced chemical vapor deposition at the condition of micro wave power : 950 W, pressure : 60 torr, H$_{2}$ gas flow rate : 50 sccm, CH$_{4}$ gas flow rate : 1.5 sccm, substrate temperature : about 900.deg. C and deposition time : 20 hours. The films were characterized by mean of scanning electron microscopy, Raman spectroscopy and X-ray analysis.

• Computers and Concrete
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• v.8 no.3
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• pp.327-341
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• 2011

Three-dimensional graphic objects created by MATLAB are exported to the AUTOCAD program through the MATLAB handle functions. The imported SAT format files are used to produce the finite element mesh for MSC.PATRAN. Based on the Monte-Carlo random sample principle, the material heterogeneity of cement composites with randomly distributed fibers is described by the WEIBULL distribution function. In this paper, a concept called "soft region" including micro-defects, micro-voids, etc. is put forward for the simulation of crack propagation in fiber-reinforced cement composites. The performance of the numerical model is demonstrated by several examples involving crack initiation and growth in the composites under three-dimensional stress conditions: tensile loading; compressive loading and crack growth along a bimaterial interface.

• Journal of the Korean Ceramic Society
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• v.36 no.6
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• pp.577-582
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• 1999

Activated carbon fibers were prepared from stabilized PAN fibers by chemical activation using hydroxide. The variations in specific surface area amount of iodine adsorption micro-structure and pore size distribution in the activated carbon fibers after the activation process were discussed. In the chemical activation using potassium hydroxide specific surface area of about 2545m2/g and amount of iodine adsorption of 2049 mg/g were obtained at the condition of KOH/fiber ratio of 1 and 800$^{\circ}C$ Nitrogen adsorption isotherms for PAN based activated carbon fibers showed the type I in the Brunauer-Deming-Deming-Teller classification indicating the micro-pores consisting the activated fibers.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.10a
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• pp.273-278
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• 1998

In this paper, basic micro-mechanical properties of unidirectional CFRP composite shell such as bonding strength, fiber volume fraction and void fraction are measured and tensile strength test is performed with a fixture. And then fracture surfaces are observed by SEM. In case of basic micro-mechanical properties, bonding strength is reduce with decreasing of radius of each ply in a shell for the effect of residual stress, fiber volume fraction is smaller than plate, and void fraction is vise versa. For these reason, tensile strength of shell is smaller than plate fabricated with same prepreg. For failure mode shell has many splitted part along its length, and it is assumed that this phenomenon is caused by the difference of bonding strength for residual stress.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.123-127
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• 2002

In order to set up the design rule of micro optical bench, optical coupling efficiencies of two sets of test benches are calculated. Simple linear connections of incoming and outgoing optical fibers with and without ball lenses are designed. Positional errors that are possible in actual fabrication processes are considered in the calculations and their tolerances are determined from 3dB conditions. For a simple fiber-to-fiber connection, the working distance is limited to $2.7\mu\textrm{m}$ and tilt error $5.8^{\circ}$. When ball lenses are located in front of each fiber, the working distance can be extended over $60\mu\textrm{m}$ , but the positional errors have the strong interaction among position parameters and thus should be considered simultaneously for tolerance design.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.9
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• pp.111-118
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• 2004

The automatic assembly system of micro optical filter is a key technology in the development of optical modules with high functionality. In order to develop an automatic assembly system of optical fiber and filter, we have firstly developed the system and program capable of characterization of 30${\mu}m$-thick film filters as well as conventional optical filters. Moreover, we have carried out the characterization of optical filter using the developed system and program, and compared experimental results with by conventional handwork. The measurement of optical filters using the present system is faster, more precise and more reliable than those based on the conventional handwork.

• Journal of Food Hygiene and Safety
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• v.7 no.4
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• pp.173-176
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• 1992

Non-absorbable substances in foods, for instance dietary fiber had been previously known as a non-nutritive part of foods. Recently , such a category has been gradually changed to as one of nutrients, As a main reason, dietary fibers includes many poly-or oligo-saccharides, which as resistant to alimentary hydrolyzing enzyme, However, parts of them are fermented by intestinal micro-organism to produce short chain fatty acids and so on. They are absorbed and utilized by human being. Now, it may be naturally accepted that dietary fiber is a kind of nutrients. Dietary fiber exerts many useful functions on body. They are classified into three large function , physicochemical function, physiological function and biological function. The last function of dietary fiber will be presented in the symphosium. Dietary fiber has several kinds of nutritional properties. One is energy source. Short chain fatty acids(SCFA) are oxidized and produced energy in body. Dietary fiber has not high energy, but not zero kilocalories. Another one is to be a constitutional component of higher animals' tissue. Last but most important one is physiological functions of dietary fiber.