• Journal of the Korean Applied Science and Technology
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• v.31 no.4
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• pp.748-758
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• 2014

The purpose of this study is to find the optimum conditions for manufacturing titanium dioxide using a hybrid self-assembly forming method, to confirm the shape, properties and synergy effect of UV protection for hybrid titanium dioxide. Hybrid titanium dioxide, manufactured by forming self-assembly of different sizes consisting of two kinds of titanium dioxides, has micro titanium dioxide (250nm~300nm) for support material, Nano titanium dioxide (20~30nm) for surface material, coating support material. Adjustment experiments of $AlCl_3$ concentration and both titanium dioxide ratio were conducted to find the optimized conditions for the surface coating of titanium dioxide striking a negative charge, a sample made of the optimized process was confirmed through an optical analysis, particle size analysis, and potentiometric analysis. The SPF in-vitro value of the cosmetics samples containing hybrid titanium dioxide showed 15~30% higher levels than the cosmetics samples containing both titanium dioxides mixture.

• Food Science and Preservation
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• v.16 no.3
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• pp.321-326
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• 2009

We assessed quality changes in and washing effects (time and method) on lettuce (Lactuca sativa L.) treated with micro-bubbles. Samples were treated with micro-bubbling for 1, 3, or 5 min, and the 5-min treatment yielded the best results in terms of reduced total microorganism counts, sensory aspects, and degree of washing. Total microorganism counts were 4.30 log colony-forming units (CFU)/g in unwashed lettuce(CT), 4.10 log CFU/g in hand-washed lettuce (HW), 3.98 log CFU/g in conventional, bubble-washed lettuce (BW) and 3.25 log CFU/g in micro-bubble-washed lettuce (MW). In comparison, total counts of samples examined after 10 days of storage were 7.00 log CFU/g for CT, 6.19 log CFU/g for HW, 6.02 log CFU/g for BW, and 5.89 log CFU/g for MW. The lowest counts were seen after micro-bubble treatment. BW and MW samples showed significantly higher counts than did CT and HW samples. In general, BW and MW samples did not vary significantly in count numbers. MW showed a 2.3-fold lower residual pesticide level compared with CT, and also had the lowest level of impurities. HW and BW samples were not well washed.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.113-119
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• 2022

In order to improve the mechanical reliability of next-generation electronic devices including flexible, wearable devices, a high level of mechanical reliability is required at various flexible joints. Organic adhesive materials such as epoxy for bonding existing polymer substrates inevitably have an increase in the thickness of the joint and involve problems of thermodynamic damage due to repeated deformation and high temperature hardening. Therefore, it is required to develop a low-temperature bonding process to minimize the thickness of the joint and prevent thermal damage for flexible bonding. This study developed flexible laser transmission welding (f-LTW) that allows bonding of flexible substrates with flexibility, robustness, and low thermal damage. Carbon nanotube (CNT) is thin-film coated on a flexible substrate to reduce the thickness of the joint, and a local melt bonding process on the surface of a polymer substrate by heating a CNT dispersion beam laser has been developed. The laser process conditions were constructed to minimize the thermal damage of the substrate and the mechanism of forming a CNT junction with the polymer substrate. In addition, lap shear adhesion test, peel test, and repeated bending experiment were conducted to evaluate the strength and flexibility of the flexible bonding joint.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.317-320
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• 2008

The Hot Stamping process, which is the hot pressing of steel parts using cold dies. can utilize both case of shaping and high strength due to the hardening effect of rapid quenching during the pressing. We carried out experiments of quenching rate and tempering treatments at temperatures of $200^{\circ}C$ and $300^{\circ}C$ and different soaking times. Tn this study, the mechanical properties and microstructure of micro boron alloyed steels after heat treatments are compared.

• Transactions of Materials Processing
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• v.8 no.1
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• pp.57-64
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• 1999

The press formability analysis of welding parts was studied in the current work by the tailor welded blank. As the body panel is used in the press forming of welding parts by a weld method of the tailor welded blank, the following conditions are demanded: 1) The strength of welding parts must be the higher than base metals. 2) After the welding, severe welding deformatins must be avoided. 3) The press formability of welding parts is similar to that of many base metals. 4) The productibility of a welding has to be higher. There are many welding methods satisfying these conditions, but the purpose of this study is to inbestigate the upset weldability and formability of the material (SPCC). SPCC steel sheet showed good weldability and formability under some welding conditions. The experimental results were discussed by the evaluation of the results obtained from tensile tests, hardness tests, micro-structures and Erichsen cup test was a little lower than that of parent material.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.259-262
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• 1999

In underground reinforced concrete structures, such as drainage structure, water and chloride ion penetrated into concrete through the cracks of concrete and its permeable property, cause the corrosion of reinforcing steel bar, which accelerates the expansive cracks and deterioration of concrete. It is necessary to control those deterioration of underground structure by improving its permeability and durability through the reasonable solutions in design, construction and materials. In the present study, fly ash concrete, which has good material properties in long-term period, was compared and studied with plain concrete using ordinary portland cement in terms of fundamental mechanical properties, permeability, drying shrinkage and durability. Also, the mix design and field test of low permeable concrete using fly ash were performed. From this study, fly ash concrete can control the penetration of water and chloride ion effectively by forming dense micro-structure of concrete. Therefore, fly ash concrete may increase the long-term function, performance and serviceability of underground structures.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.238-240
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• 1991

Langmuir-Blodgett(L.B) method is one of the most possible candidate for the fabrication of the micro scale memory or electrical devices. As for a fundamental study on the conduction mechanism in the organic thin membrane, N-alkyl quinolium-TCNQ complexes were synthesized and their physical properties were examined spectroscopically. LB film was produced by using Moving Wall Type LB Apparatus. The average area per molecule (N-docosylquinolium-TCNQ) was $67.97{\AA}^2$ which is ${\AA}^2$ larger than N-docosyl quinolium-TCNQ.

• Structural Engineering and Mechanics
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• v.15 no.3
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• pp.315-329
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• 2003

As shear occurs along a soil-structure interface, a localized zone with a thickness of several grain diameters will develop in soil along the interface, forming an interfacial layer. In this paper, the behaviour of a soil-structure interface is studied numerically by modelling the plane shear of a granular layer bounded by rigid plates. The mechanical behaviour of the granular material is described with a micro-polar hypoplastic continuum model. Numerical results are presented to show the development of shear localization along the interface for shearing under conditions of constant normal pressure and constant volume, respectively. Evolution of the resistance on the surface of the bounding plate is considered with respect to the influences of grain rotation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.409-412
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• 2004

Microstructures and mechanical properties of microalloyed cold forging steel and cold forged prototype automobile part are characterized. The work hardening according to the increase of plastic strain plays a major role in increasing the tensile strength of microalloyed cold forging steel during cold forming. On the other hand, inhomogeneous distribution of plastic strain causes variations in microstructure and mechanical properties. The relation between inhomogeneous distribution of plastic strain and variations in microstructure and mechanical properties is discussed. The variation of mechanical property in cold forged automobile part is analyzed using quantitative evaluation of plastic strain from finite element method.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.11 s.176
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• pp.173-181
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• 2005

We report on the design and fabrication of an electrostatic 2-axis MEMS stage possessing a platform with a size of $5{times}5mm^2$. The stage, as a key component, would be used in developing probe-based storage devices in the future. It was fabricated by forming numerous $5{\times}5{\mu}m^2$ etching holes in the central platform, as a result, reducing the total number of masks to 1, thereby simplifying the whole fabrication process. Experimental results show that the driving range of the stage was $32{\mu}m$ at the supplied voltage of 20V and the natural frequency was approximately 300Hz. The mechanical coupling between x- and y-motion was also measured and verified to be $25\%$.