• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1983.10a
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• pp.44-47
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• 1983

Through intensity modulation induced by micro bending of an optical fiber, a sensor detects the pressure and frequency of acoustic wave has been implemented. Axial slots on the cylinder suface with a period of 5.5 mm induce efficient microbending of the fiber, and a rubber sleeve covering the fiber enhances the fiber. Compared with a conventional hydrophone, it has a low minimum detectable pressure and can detect acoustic wave in 100Hz - 2KHz range.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.4
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• pp.194-201
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• 2004

Optical fibers are indispensable fer optical communication systems that transmit large volumes of data at high speed. But the aligning technology under the sub-micron accuracy is required for the precise axis adjustment and connection. For the purpose of precise alignment of the optical arrays, in this research, we have developed the 12-axis(with 8 automated axis and 4 manual axis) automatic optical fiber alignment system including the image processing-based searching system, the automatic loading system using the robot and the suction toot and the automatic UV bonding system. In order to obtain the sub-micron alignment accuracy, two 4-axis PC-based motion controllers and the two 50nm resolution 6-aixs micro-stage actuated by micro stepping motors are adopted. The fiber aligning procedure consists of two steps. Firstly, the optical wave guide and an input optical array are aligned by the 6-axis input micro-stage with the IR camera. The image processing technique is introduced to reduce primary manual aligning time and result in achieving the 50% decrease of aligning time. Secondly, the IR camera is replaced by the output micro-stage and a wave guide and two optical arrays are aligned simultaneously before the laser power intensity delivered to the optical powermeter reached the threshold value. When the aligning procedure is finished, the wave guide and arrays are W bonded. The automatic loading/unloading system is also introduced and the entire wave guide handing time is reduced significantly compared to the former commercial aligning system.

• Advances in nano research
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• v.12 no.2
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• pp.151-165
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• 2022

Micro-scale serpentine structure fibers are widely used as flexible sensor in the manufacturing of micro-nano flexible electronic devices because of their outstanding non-linear mechanical properties and organizational flexibility. The use of melt electrowriting (MEW) technology, combined with the axial bending effect of the Taylor cone jet in the process, can achieve the micro-scale serpentine structure fibers. Due to the interference of the process parameters, it is still challenging to achieve the precise deposition of micro-scale and high-consistency serpentine structure fibers. In this paper, the micro-scale serpentine structure fiber is produced by MEW combined with axial bending effect. Based on the controlled deposition of MEW, applied voltage, collector speed, nozzle height and nozzle diameter are adjusted to achieve the precise deposition of micro-scale serpentine structure fibers with different morphologies in a single motion dimension. Finally, the influence mechanism of the above four parameters on the precise deposition of micro-scale serpentine fibers is explored.

• Composites Research
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• v.17 no.1
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• pp.47-54
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• 2004

Vacuum hot pressing has been used for the development of titanium metal matrix composites using foil-fiber-foil technique. Subsequent micro-mechanical characteristics of the composites are then investigated by means of several experimental methods. The levels of consolidation, together with mechanism based failure processes of the materials have been analyzed by employing a thermo-acoustic emission technique. As shown by the results, fiber strength degradation occurs during the consolidation, and particularly residual stresses results from the thermal expansion mismatch between fiber and matrix materials during cooling process are incorporated in the changes of mechanical properties of the finished products. In industrial applications, both qualitative and quantitative evaluations of the material-mechanical characteristics are particularly important, and therefore must be included in process development. The present paper represents a methodology by which this can be achieved.

• Textile Coloration and Finishing
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• v.21 no.6
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• pp.12-21
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• 2009

The dyeing property of direct-spinning type and seaisland type 0.2D micro polyester nonwoven fabrics was characterized by three disperse dyes (Dorosperse Red KFFB, Blue KGBR, Yellow KRL) at $120^{\circ}C$ and $130^{\circ}C$. Before and after reduction cleaning, dyeing fastness was evaluated and the thermomigaration after heat setting at $180^{\circ}C$ for 60 min were also evaluated. Direct-spinning type fabric showed better dyeing property, wash fastness, and light fastness, but worse rub fastness than seaisland type fabric. The dyeing property and fastness of direct-spinning type fabric increased at higher dyeing temperature, whereas seaisland type fabric exhibited lower dyeing fastness and the increase of thermomigration at higher dyeing temperature. Non-fixed dye in fiber surface was removed by reduction cleaning process, then dyeing fastness was improved and thermomigration decreased. The higher dye uptake of direct-spinning type non-woven fabric caused the increase of dye molecule migration from fiber internal to fiber surface, so this fabric showed larger thermomigration than seaisland type non-woven fabric.

• Journal of Fashion Business
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• v.13 no.1
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• pp.82-90
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• 2009

This research was made to manufacture the fabric for interior uses by spinning a low melting mono 4 denier PET staple fiber with a soluble 1.4 denier fine PET fiber. The blended yarn has a thickness ranging from 10's to 14's, and the soluble PET fine fiber was dissolved to make a pore in the polymer. Thereby a snap property was decreased and a resilience property was improved to be suitable for a functional synthetic leather. In order to attain the optimum condition, a mechanical property according to fineness, and mixing ratio of low melting polymer, warp density, weft density and blending ratio, and a heat contraction ratio according to blending ratio were experimented. The warp density, 220 T/inch of fine denier PET and the weft density, 64 T/inch of thick denier PET were generated to 4/4 both twill weave fabric having constant tensile property and thickness.

• Journal of the Korean Society for Advanced Composite Structures
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• v.4 no.4
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• pp.15-21
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• 2013

This study carried out finite element deflection analysis of cylindrical shell structures made of composite materials, which is based on the micro-mechanical approach for different fiber-volume fractions. The finite element (FE) models for composite structures using multi-scale approaches described in this paper is attractive not only because it shows excellent accuracy in analysis but also it shows the effect of the material combination. New results reported in this paper are focused on the significant effects of the fiber-volume fraction for various parameters, such as fiber angles, layup sequences, and length-thickness ratios. It may be concluded from this study that the combination effect of fiber and matrix, largely governing the dynamic characteristics of composite shell structures, should not be neglected and thus the optimal combination could be used to design such civil structures for better dynamic performance.

• Transactions of Materials Processing
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• v.18 no.1
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• pp.45-51
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• 2009

Shape memory alloy has been used to improve the tensile strength of composite by the occurrence of compressive residual stress in matrix using its shape memory effect. In order to fabricate shape memory alloy composite, TiNi alloy fiber and Al2024 sheets were used as reinforcing material and matrix, respectively. In this study, TiNi/Al2024 shape memory alloy composite was made by using hot press method. In order to investigate bonding condition between TiNi reinforcement and Al matrix, the micro-structure of interface was observed by using optical microscope and diffusion layer of interface was measured by using Electron Probe Micro Analyser. And the mechanical properties of composite with three parameters(volume fraction of fiber, cold rolling amount and test temperature) were obtained by tensile test. The most optimum bonding condition for fabrication the TiNi/Al2024 composite material was obtained as holding for 30min. under the pressure of 60MPa at 793K. The strength of composite material increased considerably with the volume fraction of fiber up to 7.0%. And the tensile strength of this composite increased with the reduction ratio and it also depends on the volume fraction of fiber.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.403-418
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• 1999

Fiber growth of Al2O3/R-Al-O(R=Y, Gd, Dy, Ho, Er) eutectic by the micro-pulling down methods is described. The thermal stability and strength at elevated temperature of each material is evaluated in relation to the microstructure. PACS: 81.05 Mh, 81.10 Fq, 81.30-t.

• Journal of the Korea Concrete Institute
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• v.17 no.2 s.86
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• pp.263-271
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• 2005

HPFRCC(High Performance Fiber Reinforced Cementitious Composite) is a class of FRCCs(Fiber Reinforced Cementitious Composites) that exhibit multiple cracking. Multiple cracking leads to improvement in properties such as ductility, toughness, fracture energy, strain hardening, strain capacity, and deformation capacity under tension, compression, and bending. These improved properties of HPFRCCs have triggered unique and versatile structural applications, including damage reduction, damage tolerance, energy absorption, crack distribution, deformation compatibility, and delamination resistance. These mechanical properties of HPFRCCs become different from the kinds and shapes of used fiber, and it is known that the effective size of fiber in macro crack is different from that in micro crack. This paper reports an experimental findings on the mechanical properties of HPFRCCs reinforced with the micro fiber(PP50, PVA100 and PVA200) and macro fiber(PVA660, SF500). Uniaxial compressive tests and three point bending tests are carried out in order to compare with the mechanical properties of HPFRCCs reinforced with micro fibers or hybrid fibers such as compressive strength, ultimate bending stress, toughness, deformation capacity and crack pattern under bending, etc.,