• Coupled systems mechanics
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• v.6 no.2
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• pp.207-227
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• 2017

In this paper Timoshenko beam theory is employed to investigate the vibration characteristics of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) Beams with a stiff core in thermal environment. The material characteristic of carbon nanotubes (CNT) are supposed to change in the thickness direction in a functionally graded form. They can also be calculated through a micromechanical model where the CNT efficiency parameter is determined by matching the elastic modulus of CNTRCs calculated from the rule of mixture with those gained from the molecular dynamics simulations. The differential transform method (DTM) which is established upon the Taylor series expansion is one of the effective mathematical techniques employed to the differential governing equations of sandwich beams. Effects of carbon nanotube volume fraction, slenderness ratio, core-to-face sheet thickness ratio, different thermal environment and various boundary conditions on the free vibration characteristics of FG-CNTRC sandwich beams are studied. It is observed that vibration response of FG-CNTRC sandwich beams is prominently influenced by these parameters.

• Electrical & Electronic Materials
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• v.11 no.10
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• pp.1-5
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• 1998

Complex dynamic relaxation processes of mechanical as well as dielectric character in polymeric anelastic solids are closely related through the movement of molecular chain segment in morphological structure, and the morphology can easily be modified by the treatments such as mechanical drawing or irradiation, those of which result, in turn, the complicated change on the appearance of the observed complex relaxation peak. In order to extract any meaningful understanding from the modified appearance of the peak, the relaxation peak must be resolved into the sum of the dynamic single relaxation peaks, each of which can be characterized respectively by three factors such as activation energy, magnitude of peak height and peak point temperature on the temperature dependent characteristics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.194-197
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• 1997

The LB technique is one of the most powerful fabricating methods of organic ultra-thin film, which deposits a monolayer films in molecular level on the surface of the substrate. We have investigated the electrical characteristics of Myristic acid, Stearic acid and Arachidic acid LB films for horizontal direction to develop for the gas sensor. The optimum conditions for a film deposition were obtained by measurement of $\pi$-A isotherm. The status of the deposited film was confirmed by measurement of UV absorbance. We could distingished the difference of I-V characteristics for the fatty acid for the horizontal direction. The conductivity of fatty acid LB films for horizontal direction was 10$^{-7}$ ~ 10$^{-9}$ [S/cm] that mean like semiconductor.

• Journal of Species Research
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• v.5 no.3
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• pp.313-317
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• 2016

Two marine isopods, Elaphognathia sugashimaensis (Nunomura, 1981) and Metacirolana shijikiensis Nunomura, 2008, have been reported for the first time in South Korea. Specimens of E. sugashimaensis and M. shijikiensis were collected using light traps from Yeongdeok-gun and Gageo-do Island in South Korea, respectively. The genera Elaphognathia Monod, 1926 and Metacirolana Kussakin, 1979 are new to South Korea. In this paper, we provide descriptions of diagnostic characteristics and illustrations of their morphologies. Additionally, the partial sequences of mitochondrial cytochrome c oxidase subunit 1 (CO1) of two species are provided as molecular characteristics.

• Macromolecular Research
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• v.9 no.2
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• pp.92-99
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• 2001

Silica-filled rubber compounds have slower cure characteristics than carbon black-filled ones due to the adsorption of curatives on the silica surface. Fatty acid was used as a cure activator along with zinc oxide in a sulfur cure system. Poly(ethylene glycol), PEG, was used in silica-filled rubber compounds to prevent adsorption of the curatives on the silica surface. In this study, influence of the size of fatty acid and PEG on properties of silica-filled NR compounds was investigated. It was found that the size of fatty acid and PEG affected the curt: characteristics and physical properties. The cure rate becomes faster as the PEG size increases. By increasing the size of fatty acid or PEG, the delta torque of the compound decreases while the Mooney viscosity increases. The modulus of the vulcanizate decreases with increasing the molecular weight of fatty acid or PEG. The experimental results were explained by the filler dispersion and by the prevention of the curative-adsorption on the silica surface.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.1
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• pp.24-29
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• 2004

Alkaline cellulolytic enzymes from cultured medium of Coprinus cinereus 2249 were purified with gel and ion-exchange chromatography and characteristics of those enzyme proteins were investigated. A fiber length distribution and a crystallinity of cellulose and sugar composition of enzyme treated Mixed Office Wastepaper(MOW) and Unbleached Kraft Pulp(UKP) were analysed. The conclusion could summarized as follows; \circled1 Alkaline and acidic, endo- and exo-glucanases were purified from cultured medium of Coprinus cinereus 2249. \circled2 The approximate molecular weight of alkaline endo-glucanase was 42 kDa, and also that of alkaline exo-glucanase was 50 kDa. A fiber length distribution and a crystallization of cellulose and sugar composition of enzyme treated MOW and UKP were not so much changed with original paper and pulp.

• Proceedings of the Membrane Society of Korea Conference
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• 1997.10a
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• pp.5-8
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• 1997

Introduction : Membranes made from inorganic materials are generally superior to organo-polymeric materials in thermal and mechanical stability, and chemical resistance. Among inorganic materials zeolite is a promising candidate for a high performance membrane because of the unique characteristics of zeolite crystals such as molecular sieving, ion exchange, selective adsorption and catalysis. Although there are many recent reportsl on the preparation of zeolitc membranes and the gas permeation through the membranes, only a limited number of publications deal with pervaporation studies. Recently, we have reported a high pervaporation performance of NaA zeolite membrane for the separation of water/organic liquid mixtures. and of NaY zeolite menlbrane for the separation of methanol/MTBE. Here, preparation of zeolite (LTA, ZSM-5 and FAU) membranes and their permeation properties are discussed.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.10
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• pp.71-78
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• 1994

We have developed GaAs power metal semiconductor field effect transistors (MESFETs) for 4.7V operation under 900 MHz using a low-high deped structures grown by molecular beam epitaxy (MBE). The fabricted MESFETs with a gate widty of 7.5 mm and a gate length of 1.0.mu.m show a saturated drain current (Idss) of 1.7A and an uniform transconductance (Gm) of around 600mS, for gate bias ranged from -2.4 V to 0.5 V. The gate-drain breakdown voltage is measured to be higher than 25 V. The measured rf characteristics of the MESFETs at a frequency of 900 MHz are the output power of 31.4 dBm and the power added efficiency of 63% at a drain bias of 4.7 V.

• The Korean Journal of Malacology
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• v.31 no.3
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• pp.249-252
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• 2015

An aeolid nudibranch species Flabellina athadona (Bergh, 1875) is newly recorded from Korean waters. This species is distinguished from other congeneric species by the following characteristics: translucent white body, deep orange colored digestive glands, plenty of white specks, and a reversed Y-shaped marking on the head between rhinophores and oral tentacles. In this report, we also provide an identification key for the genus Flabellina in Korea, photographs, and diagnostic characteristics of F. athadona. Molecular identification using mtDNA cox1 partial sequences is also provided to help differentiate F. athadona from some of its closely related congeneric species.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.649-652
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• 2003

Organic thin-film transistors were fabricated using pentacene as an active electronic material. Device characteristics are improved with increasing the deposition rate of pentacene. It is observed that the deposition rate influences on the interface properties between pentacene and polystyrene, and the molecular ordering of pentacene film. In this paper, we report the effects of the deposition rate of pentacene film on the device performance.