• 한국전기전자재료학회논문지
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• 제28권9호
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• pp.598-601
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• 2015

The $Sr_{0.7}Bi_{2.3}Nb_2O_9(SBN)$ thin films are deposited on Pt electrode($Pt/Ti/SiO_2/Si$) using RF sputtering method at various deposition temperature. The deposition temperature of optimum was $300^{\circ}C$. SBN thin films were annealed at $500{\sim}700^{\circ}C$ using furnace and RTA, respectively. The surface roughness showed about 2.42 nm in annealing temperature($600^{\circ}C$) of furnace. The capacitance density of SBN thin films were increased with the increase of annealing temperature. The maximum capacitance density of $0.7{\mu}F/cm^2$ was obtained by annealing temperature($700^{\circ}C$). The frequency dependence of dielectric loss showed about 0.03 in frequency ranges of 1~1,000 kHz.

• Advances in nano research
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• 제16권6호
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• pp.601-613
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• 2024

A new analytical buckling solution of a thermo-electro-magneto-elastic (TEME) cylindrical nano-shell made of BiTiO₃-CoFe₂O₄ materials is obtained based on Hamiltonian approach. The Winkler and Pasternak elastic foundations as well as thermo-electro-magneto-mechanical loadings are applied, and two different types of edge conditions are taken into the investigation. According to nonlocal strain gradient theory (NSGT) and surface elasticity theory in conjunction with the Kirchhoff-Love theory, governing equations of the nano-shell are acquired, and the buckling bifurcation condition is obtained by adopting the Navier's method. The detailed parameter study is conducted to investigate the effects of axial and circumferential wave numbers, scale parameters, elastic foundations, edge conditions and thermo-electro-magnetic loadings on the buckling behavior of the nano-shell. The proposed model can be applied in design and analysis of TEME nano components with multi-field coupled behavior, multiple edge conditions and scale effect.

• 한국재료학회지
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• 제21권4호
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• pp.192-195
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• 2011

The electro-deposition of compound semiconductors has been attracting more attention because of its ability to rapidly deposit nanostructured materials and thin films with controlled morphology, dimensions, and crystallinity in a costeffective manner (1). In particular, low band-gap $A_2B_3$-type chalcogenides, such as $Sb_2Te_3$ and $Bi_2Te_3$, have been extensively studied because of their potential applications in thermoelectric power generator and cooler and phase change memory. Thermoelectric $Sb_xTe_y$ films were potentiostatically electrodeposited in aqueous nitric acid electrolyte solutions containing different ratios of $TeO_2$ to $Sb_2O_3$. The stoichiometric $Sb_xTe_y$ films were obtained at an applied voltage of -0.15V vs. SCE using a solution consisting of 2.4 mM $TeO_2$, 0.8 mM $Sb_2O_3$, 33 mM tartaric acid, and 1M $HNO_3$. The stoichiometric $Sb_xTe_y$ films had the rhombohedral structure with a preferred orientation along the [015] direction. The films featured hole concentration and mobility of $5.8{\times}10^{18}/cm^3$ and $54.8\;cm^2/V{\cdot}s$, respectively. More negative applied potential yielded more Sb content in the deposited $Sb_xTe_y$ films. In addition, the hole concentration and mobility decreased with more negative deposition potential and finally showed insulating property, possibly due to more defect formation. The Seebeck coefficient of as-deposited $Sb_2Te_3$ thin film deposited at -0.15V vs. SCE at room temperature was approximately 118 ${\mu}V/K$ at room temperature, which is similar to bulk counterparts.

• Earthquakes and Structures
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• 제16권2호
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• pp.209-219
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• 2019

Unbonded Post-Tensioned (UPT) precast concrete systems have been shown to provide excellent seismic resistance. In order to improve understanding of the dynamic response of UPT systems, a series of snap back tests on four UPT systems was undertaken consisting of one Single Rocking Wall (SRW) and three Precast Wall with End Columns (PreWEC) systems. The snap back tests provided both a static pushover and a nonlinear free vibration response of a system. As expected the SRW exhibited an approximate bi-linear inertia force-drift response during the free vibration decay and the PreWEC walls showed an inertia force-drift response with increased strength and energy dissipation due to the addition of steel O-connectors. All walls exhibited negligible residual drifts regardless of the number of O-connectors or the post-tensioning force. When PreWEC systems of the same strength were compared the inclusion of further energy dissipating O-connectors was found to decrease the measured peak wall acceleration. Both the local and global wall parameters measured at pseudo-static and dynamic loading rates showed similar behaviour, which demonstrates that the dynamic behaviour of UPT walls is well represented by pseudo-static tests. The SRW was found to have Equivalent Viscous Damping (EVD) between 0.9-3.8% and the three PreWEC walls were found to have maximum EVD of between 14.7-25.8%.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.292-292
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• 2017

This study was conducted to evaluate the effect of anti-obesity and antioxidant enzyme activities in vitro by different solvent fractions from the roots of Codonopsis lanceolata. The cytotoxicity of different solvent fractions of C. lanceolata on 3T3-L1 preadipocytes were evaluated using the MTT assay, the rate of cell survival progressively decreased in a dose-dependent manner. Butyl alcohol fraction at $200{\mu}g/mL$ exhibited a pronounced cytotoxic effect (75.73%) on 3T3-L1 cell comparable to that of the hexane fraction (79.82%), methylene chloride fraction (84.02%), ethyl acetate fraction (87.62%) and DW fraction (86.30%) at the same concentration. The Oil Red O solution was used to determine whether different solvent fractions of C. lanceolata induce adipocyte differentiation in 3T3-L1 preadipocytes. Confluent 3T3-L1 cells were treated with $50{\mu}g/mL$ concentration of solvent fraction extracts from C. lanceolata. Inhibitory degree of lipid accumulation against solvent fraction extracts showed a significant level compared with the control. Both lipid accumulation and adipocyte differentiation showed relatively high effect on methyl chloride fraction. The root extract of C. lanceolata had the highest SOD enzyme activity of 84.5% in ethyl acetate partition layer and while water partition layer of diploid showed the lowest SOD enzyme activity of 57.9%. The activity of CAT, APX and POD showed a significantly higher activity in ethyl acetate partition layer compared with the other fraction. These results suggested that the roots of C. lanceolata may assist in the potential biological activity on anti-obesity and antioxidant capacity.

• 한국산학기술학회논문지
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• 제20권5호
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• pp.81-86
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• 2019

금속산화물/그래핀 복합체는 고감도 가스센서 및 고용량의 이차전지와 같은 첨단 응용 분야에 활용될 수 있는 유망한 기능성 소재로 알려져 있다. 본 연구에서는 이산화주석($SnO_2$) 나노구조물을 두 영역 전기로 장치를 이용하여 화학적으로 합성된 그래핀 나노시트 위에 성장시켰다. 대면적의 그래핀 나노시트는 Cu foil 위에 열화학기상증착 장비를 이용하여 메탄가스와 수소가스로 합성하였다. 화학적으로 합성된 그래핀 나노시트는 PMMA를 이용하여 세척된 Si 기판위에 전사시켰고, $SnO_2$ 나노구조물은 그래핀 나노시트 위에 $424^{\circ}C$, 3.1 Torr 조건에서 3시간동안 성장시켰다. 합성된 그래핀의 품질과 성장된 $SnO_2$ 나노구조물의 결정학적 특성을 Raman 분광학으로 확인하였다. 그래핀 위에서 성장된 $SnO_2$ 나노구조물의 표면형상은 전계방출 주사전자현미경으로 조사하였다. 그 결과 합성된 그래핀 나노시트는 이중층 그래핀이었고, 그래핀 위에서 성장된 산화주석은 $SnO_2$ 상을 가지고 있었다. 그래핀 위에서 성장된 $SnO_2$ 나노구조물은 복잡한 표면형상을 나타내었는데, 이것은 Si 기판 위에서 성장된 $SnO_2$ 나노구조물이 nano-dots 형태인 것과 비교된다. 그래핀 위에서 성장된 $SnO_2$ 나노구조물이 복잡한 형상을 갖는 것은 그래핀 표면의 기능기의 영향인 것으로 판단된다.

• 생명과학회지
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• 제12권1호
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• pp.67-76
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• 2002

Agrobacterium(LBA4404/pBI1121)을 이용하여 형질전환된 애기장대 (Arabidopsis thaliana)를 대상으로 T2, T3, F3세대에서의 도입된 외래 유전자의 비활성화 현상을 조사하였다. Kanamaycin저항성 개체들의 GUS유전자 발현을 분석한 결과, T2세대에서 조사된 12계통 중 5계통에서 GUS 비활성 개체가 관찰되었다 (GUS유전자 비활성율 2.3%). Multi copy T-DNA 계통을 조사한 결과, GUS 비활성 정도가 더욱 심해짐이 관찰되었다 (5.8%). T3 세대에서 single copy T-DNA 계통들은 1.3%의 GUS 비활성율을 보인 반면, multi-copy T-DNA 계통에서의 비활성율은 12.6%로 급격히 증가하였다. 유사한 현상이 형질전환 식물체와 정상개체를 교배하여 생산된 F2 계통에서도 관찰되었다 (비활성율 9.9%). 본 실험으로 식물체에 도입된 외래 유전자가 후대에서의 전이과정동안 점진적으로 비활성화되고, 이 현상은 multi copy T-DNA 계통에서 훨씬 심각함이 밝혀졌다.

• 한국초전도ㆍ저온공학회논문지
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• 제2권2호
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• pp.6-10
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• 2000

1.5 kA class HTS current leads for a SMES magnet, which are connected to a conventional vapor cooled copper leads, were designed. The HTS leads are composed of Bi-2223/Ag-Au tapes and a stainless stell tube. The estimated critical current of the lead is about 1.6 kA at 77.3 K and in a self magnetic field, and the heat input to the liquid helium from the cold end of the 35 cm lead is 0.4 W/lead. It has been made clear that the heat input decreases with increase of the lead length and decrease of the warm end temperature and Ag-Au/SC ratio.

• 센서학회지
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• 제24권1호
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• pp.6-9
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• 2015

Conventional leak detectors are widely based on helium gas sensors. However, the usage of hydrogen sensors in leak detectors has increased because of the high prices of helium leak detectors and the dearth in the supply of helium gas. In this study, a hydrogen leak detector was developed using solid-state hydrogen sensors. The hydrogen sensors are based on Park-Rapp probes with heterojunctions made by oxygen-ion conducting Yttria-stabilized zirconia and proton-conducting In-doped $CaZrO_3$. The hydrogen sensors were used for determining the potential difference between air and air balanced 5 ppm of $H_2$. Even though the Park-Rapp probe shows an excellent selectivity for hydrogen, the sensitivity of the sensor was low because of the low concentration of hydrogen, and the oxygen on the surface of the sensor. In order to increase the sensitivity of the sensor, the sensors were connected in series by Pt wires to increase the potential difference. The sensors were tested at temperatures ranging from $500-600^{\circ}C$.

• 한국진공학회지
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• 제8권3A호
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• pp.231-237
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• 1999

$SrBi_{22.4}Ta_2O_9$ (SBT) thin films of 70~150 nm thickness were prepared on platinized silicon substrates by Liquid Source Misted Chemical Deposition (LSMCD) process, and their microstructure, feroelectric and leakage current characteristics were investigated. By annealing at $800^{\circ}C$ for 1 hour in oxygen ambient, SBT films were fully crystallized to the Bi layered perovskite structure without preferred orientation. The grain size of the LSMCD- derived SBT films was about 100nm, and was not varied with the film thickness. $2P_r$ and $E_c$ of the SBT films increased with decreasing the film thickness, and the 70nm-thick SBT film exhibited $2P_r$ of 17.8 $\mu$C/$\textrm{cm}^2$ and $E_c$ of 74kV/cm at applied voltage of 5V. Within the film thickness range of 70~150nm, the relative dielectric permittivity of the LSMCD-derived SBT film decreased with decreasing the film thickness. Leakage current densities lower than $10^{-7}\textrm{A/cm}^2$ at 5V were observed in the SBT films thicker than 125nm.