• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.9
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• pp.813-819
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• 2011

This paper predicted nonlinear dynamic responses of a cantilevered carbon nanotube(CNT) resonator incorporating the electrostatic forces and van der Waals interactions between the CNT cantilever and ground plane. The structural model of CNT includes geometric and inertial nonlinearities to investigate various phenomena of nonlinear responses of the CNT due to the electrostatic excitation. In order to solve this problem, we used Galerkin's approximation and the numerical integration techniques. As a result, the CNT nano-resonator shows the softening effect through saddle-node bifurcation near primary resonance frequency with increasing the applied AC and DC voltages. Also we can predict nonlinear secondary resonances such as superharmonic and subharmonic resonances. The superharmonic resonance of the nano-resonator is influenced by applied AC voltage. The period-doubling bifurcation leads to the subharmonic resonance which occurs when the nano-resonator is actuated by electrostatic forces as parametric excitation.

• Journal of Physiology & Pathology in Korean Medicine
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• v.19 no.1
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• pp.179-183
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• 2005

Recent interest in the possible protective effects of dietary antioxidant compounds against human degenerative disease has prompted investigation of foods such as blueberries, which have a high antioxidant capacity. This study was performed to determine the antioxidative activity of methanol extract and solvent fractions from blueberry. Blueberry was extracted with methanol and then fractionated with n-hexane, EtOAc, BuOH and water to get active fractions. And their antioxidant capacities in each fraction were determined by using the DPPH and FRAP assay, and tyrosinase inhibitor. Ethyl acetate fraction of blueberry exhibited antioxidant capacity.

• Journal of the Mineralogical Society of Korea
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• v.12 no.1
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• pp.32-42
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• 1999

Microbial mats, the yellow and reddish brown deposits formed from the mine drainage, occur on the bottom of drain and mine tailing pond of the Ilkwang mine in Pusan, Korea. The constituents of microbial mats and their biomineralization were studied by using XRD, IR, and SEM-EDX. The upper part of the microbial mat is yellow-colored and composed of tube-shaped and small spheroid bacterial materials, which are mainly made up of amorphous and poor-crystalline iron-oxide minerals. The shape and composition of bacterial materials suggest that they are probably belong to iron-oxide mineral aggregates. The iron-oxide minerals of the yellow microbial mats are mainly goethite, but those of the reddish brown microbial mats contain abundant hematite along with goethite. This implies that with the evolution of biomats, goethite may be transformed to hematite.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.88-89
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• 2014

In dynamic force microscopy, the cantilever oscillates at a resonant frequency, and the tip deflection is measured at this frequency. The cantilever deflection is, however, highly nonlinear, and the surface properties can be embedded in the deflection at the frequencies other than the original resonant frequency of the cantilever. Multifrequency atomic force microscopy includes the excitation and detection of the deflection in two or more frequencies which are higher harmonics or eigenmodes. This can overcome the limitations of conventional atomic force microscope. We reviewed the multifrequency atomic force microscopy and its applications in many fields.

• Textile Coloration and Finishing
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• v.5 no.2
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• pp.117-124
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• 1993

The Silk fabric was dyed with various acid dyes, and than treated with copper sulfate or copper sulfate/thiourea. Munsell color system, dye exhaustion and light fastness were investigated for the treated fabrics. The results obtaind are as follows: 1) The color variation of the silk-dyed fabric by aftertreatment with copper sulfate was shown redish, but original color with copper sulfate/thiourea. 2) Copper sulfate/thiourea was much more effective than copper sulfate only to increase the light fastness. 3) The crease recovery was increased by aftertreatment with copper sulfate/thiourea. 4) Dye exhaustion and tensile strength of the silk-dyed fabric by aftertreatment with copper sulfate was decreased about 8-15% more than those of untreated.

• Textile Coloration and Finishing
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• v.16 no.6
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• pp.23-29
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• 2004

The purpose of this study is to improve the dyeability and the color fastness to light of cotton fabric dyed with extraction of cinnamon cassia. Cotton fabric was pretreated with chito-colla to enhance the dyeability, and K/S values were compared chito-colla pretreated fabric and untreated fabric. In addition, to improve of color fastness to light of dyed fabric, it was used FFC compound as mordant. Also, it was measured SOD-liked activity of FFC compound and lifht fastness of dyed fabrics. The results are as follow; K/S value of cotton fabric pretreated with chito-colla(5%) was much more increased than untreated fabric. SOD-liked activity of FFC compound was observed over 70%. Light fastness of cotton fabric treated with FFC compound was 3～4 grades.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.101-101
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• 2012

천연가죽에 색상을 부여하기 위한 염색공정에서 종전의 합성염료가 아닌 자연에서 추출한 천연염료를 이용하여 블루색상을 가지는 피혁 제조 공정을 확립하였다. 피혁에 적용 가능한 블루색상을 가지는 천연염료 중에 쪽 염료가 유일한 상황이다. 가죽 무게 대비 5%의 쪽염료를 가죽 제조 드럼에 투입하여 100분간 충분히 회전시킨 후에 가죽의 유연성을 부여하는 가지제를 12% 추가로 투입하여 블루 색상을 가지는 가죽을 제조하였다. 그 결과 마찰견뢰도, 일광견뢰도, K/S가 우수한 피혁 염색공정을 확립하였다.

• Journal of Korean Institute of Industrial Engineers
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• v.33 no.4
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• pp.487-493
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• 2007

In this paper, we deal with an optimal software-release problem of determining the time to stop testing and release the software system to the user. The optimal release time problem is considered from maintenance like the periodic distribution of service packs and the unpredictable distribution of patches after the release. Moreover, the environment of software error-detection during operation differs from the environment during testing. This paper proposes the software reliability growth model which incorporates periodic service packs, unpredictable patches and operational environment. Based on the proposed model, we derive optimal release time to minimize total cost composed of fixing an error, testing and maintenance. Using numerical examples, optimal release time is determined and illustrated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.05a
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• pp.104-108
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• 1993

Thin films of MgO-doped and CaO-doped iron oxide were prepared y spray pyrolysis. The films were characterized b X-ray diffraction, scanning electron microscopy and voltammetric techniques. The photoelectrochemical behavior of thin film electrodes depended greatly on the doping level, sintering temperature, substrate temperature and added photosensitizing compounds in solution, showed p-type photoelectrochemical behavior, while the CaO-doped iron oxide thin films prepared at low temperature showed n-type photoelectrochemical behavior. This characteristic change was interpreted in terms of the surface structure change of the thin films and doping effect of metal oxide.

• Textile Coloration and Finishing
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• v.10 no.4
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• pp.53-61
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• 1998

The absorptions of ultraviolet rays of benzophenone derivatives were investigated in terms of the position of substituent, especially hydroxyl group. When the derivatives were added to the aqueous solution of Rhodamin B, which has very low light-fastness, all of them delayed the photofading of Rhodamin B solution. But on the fabrics, only the derivatives with the hydroxyl group at 2-position showed the good ability of ultraviolet rays absorption. The benzophenone derivatives absorb ultraviolet rays to form a hydrogen bond between hydroxyl group and carbonyl group, and return to their original structure by releasing heat energy. In solution, the derivatives can form a intermolecular hydrogen bond, and absorb the ultraviolet rays. But on the fabric, the intermolecular hydrogen bond is impossible, only hydroxyl group of 2-position forms a intramolecular hydrogen bond, and that makes the derivatives on the fabric absorb ultraviolet rays.