• Structural Engineering and Mechanics
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• 제71권3호
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• pp.257-269
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• 2019

This paper develops a nonlocal strain gradient plate model for damping vibration analysis of smart magneto-electro-viscoelastic nanoplates resting on visco-Pasternak medium. For more accurate analysis of nanoplate, the proposed theory contains two scale parameters related to the nonlocal and strain gradient effects. Viscoelastic effect which is neglected in all previous papers on magneto-electro-viscoelastic nanoplates is considered based on Kelvin-Voigt model. Governing equations of a nonlocal strain gradient smart nanoplate on viscoelastic substrate are derived via Hamilton's principle. Galerkin's method is implemented to solve the governing equations. Effects of different factors such as viscoelasticity, nonlocal parameter, length scale parameter, applied voltage and magnetic potential on damping vibration characteristics of a nanoplate are studied.

• 센서학회지
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• 제4권4호
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• pp.41-46
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• 1995

세포의 흐름을 감지할 수 있는 감지 시스템을 반도체 공정과 EDM(Electro-chemical Discharge drilling Method)을 사용하여 설계 및 제작하였다. 이 감지 장치에서는 세포의 통로관 상하에 광을 투과시켜 감지하는 투과광 방법과 세포 통로관에 평형 전극을 만들어 세포의 흐름에 따른 임피던스의 변화를 측정하는 방법을 사용하였다. 담배잎의 세포를 이용하여 실험한 결과, 광을 이용한 방식에서는 세포의 유무에 따라 출력전압이 0.2V에서 0.7V의 변화를 보였고, 임피던스 방식에서는 0.2V에서 2V의 변화를 감지할 수 있었으나 노이즈의 영향을 받았다.

• Korean Chemical Engineering Research
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• 제57권3호
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• pp.338-343
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• 2019

고분자전해질 연료전지에서 전해질막의 물이동과 함수율은 고분자막의 성능에 많은 영향을 미친다. 본 연구에서는 간단한 방법에 의해 물이동에 관한 고분자막의 물성(전기삼투계수, 물 확산계수)을 측정하고 이들을 이용해 막을 통한 물의 이동량과 이온전도도를 모델식에 의해 모사한 후 실험값과 비교하였다. 물이동의 구동력은 전기삼투와 확산만이 라고 본 1차원 정상상태 지배방정식을 매트랩으로 수치해석하였다. $144{\mu}m$ 두께의 고분자막의 전기삼투계수를 수소펌핑셀에서 구한 결과 1.11을 얻었다. 물확산계수를 상대습도의 함수로 나타냈고 물확산에 대한 활성화에너지는 $2,889kJ/mol{\cdot}K$였다. 이들 계수를 적용해 모사한 물이동량과 이온전도도 결과는 실험값과 잘 일치함을 보였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.412-412
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• 2008

ENIG(Electroless Nickel Immersion Gold)is a surface treatment method that is used most widely at fine pitch's SMT and BGA packaging process. ENIG has good diffusion barrier of Ni against solder and good wettability due to Au finish. But when the discoloration occurred on the Au finish of ENIG, some key characteristics related to the quality and reliability of PCB such as bondability, solderability and electrical flowing of packaging process could be deteriorated. In this paper, we have performed the water dip test ($88^{\circ}C$ purified water) which accelerates the galvanic corrosion of Ni diffused from the Ni-P layer. That is, the excessive oxidation of the Ni layer could result in non-wetting of the solder because the flux may not be able to remove excessive oxides. Though Au discoloration have been reported to be caused by Ni oxides in many literature, it is still open to verify and discuss The microstructures and chemical compositions have been investigated using FE-SEM, TEM, FIB, EDS and XPS. As a result, authors have found that the Au discoloration in ENIG type is severely caused by the oxidation of the Ni and the mechanism of Au discoloration can be confirmed through the experiment result of water dip test.

• Bulletin of the Korean Chemical Society
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• 제35권12호
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• pp.3576-3582
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• 2014

Zeolite-templated carbons (ZTCs), which have high specific surface area, were prepared by a conventional templating method using microporous zeolite-Y for catalyst supports in direct methanol fuel cells. The ZTCs were synthesized at different temperatures to investigate the characteristics of the surface produced and their electrochemical properties. Thereafter, Pt-Ru was deposited at different carbonization temperatures by a chemical reduction method. The crystalline and structural features were investigated using X-ray diffraction and scanning electron microscopy. The textural properties of the ZTCs were investigated by analyzing $N_2$/77 K adsorption isotherms using the Brunauer-Emmett-Teller equation, while the micro- and meso-pore size distributions were analyzed using the Barrett-Joyner-Halenda and Harvarth-Kawazoe methods, respectively. The surface morphology was characterized using transmission electron microscopy and inductively coupled plasma-mass spectrometry. The electrochemical properties of the Pt-Ru/ZTCs catalysts were also analyzed by cyclic voltammetry measurements. From the results, the ZTCs carbonized at $900^{\circ}C$ show the highest specific surface areas. In addition, ZTC900-PR led to uniform dispersion of Pt-Ru on the ZTCs, which enhanced the electro-catalytic activity of the Pt-Ru catalysts. The particle size of ZTC900-PR catalyst is about 3.4 nm, also peak current density from the CV plot is $12.5mA/cm^2$. Therefore, electro-catalytic activity of the ZTC900-PR catalyst is higher than those of ZTC1000-PR catalyst.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.398-400
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• 1998

In this paper, the etching studies for n-GaN were carried out using the wet chemical, the photo-enhanced-chemical, and the electro-chemical etching methods. The experimental results show that n-GaN is etched in diluted NaOH solution at room temperture and the etched thickness of NaOH and electron concentrations. Te etching rate of n-GaN samples with n.simeq.1*10$^{19}$ cm$^{-3}$ were used to compare the photo-enhanced-chemical etching with the electrochemical etching methods. The removed thickness was 680.angs./25min by the electrochemical etching methods. The removed thickness was 680 .angs./25min by the electrochemical etching method ad 784.angs./25min by the photoenhanced-chemical etching method. The patterns are 100.mu.m*100.mu.m rectangulars covered with SiO$_{2}$film. It is shown that the profile of etched side-wall of the pattern is vertical without dependance of the n-GaN orientations.

• Bulletin of the Korean Chemical Society
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• 제32권10호
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• pp.3660-3665
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• 2011

CO-tolerant PtMo/C alloy electrocatalyst was prepared by a colloidal method, and its electrocatalytic activity toward CO oxidation was investigated. Electrochemical study revealed that the alloy catalyst significantly enhanced catalytic activity toward the electro-oxidation of CO compared to Pt/C counterpart. Cyclic voltammetry suggested that Mo plays an important role in promoting CO electro-oxidation by facilitating the formation of active oxygen species. The effect of Mo on the electronic structure of Pt was investigated using X-ray absorption spectroscopy to elucidate the synergetic effect of alloying. Our in-depth spectroscopic analysis revealed that CO is less strongly adsorbed on PtMo/C catalyst than on Pt/C catalyst due to the modulation of the electronic structure of Pt d-band. Our investigation shows that the enhanced CO electrooxidation in PtMo alloy electrocatalyst is originated from two factors; one comes from the facile formation of active oxygen species, and the other from the weak interaction between Pt and CO.

• 대한화학회지
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• 제57권3호
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• pp.316-321
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• 2013

Electrocoagulation (EC) technique is applied for the treatment of wastewater containing heavy metals ions such as nickle (Ni), lead (Pb) and cadmium (Cd) by using sacrificial anodes corrode to release active coagulant flocs usually aluminium or iron cations into the solution. During electrolytic reactions hydrogen gas evolve at the cathode. All the experiments were carried out in Batch mode. The tank was filled with synthetic wastewater containing heavy metals and efficiency of electro-coagulation in combination with aluminum and iron electrodes were investigated for removal of such metals. Several parameters, such as contact time, pH, electro-coagulant concentration, and current density were optimized to achieve maximum removal efficiency (%). The concentrations of heavy metals were determined by using Atomic Absorption Spectroscopy (AAS). It is found that the electro-coagulation process has potential to be utilized for the cost-effective removal of heavy metals from wastewater specially using iron electrodes in terms of high removal efficiencies and operating cost.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.449-452
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• 2004

To obtain the ultra-sharp tungsten tip, an analog to digital converter circuit aided by a personal computer has been setup. At the moment the lower part of the needle drops off during the etching process, a maximum current change across the reference resistor is detected by the PC interface card and the applied voltage is then cut off within a few milliseconds. Out experiment has been able to fabricate an ultra-sharp tungsten tip ~200 $\AA$ radius with a higher reproduction rate and reliability than the conventional method.

• 한국전기전자재료학회논문지
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• 제23권11호
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• pp.891-895
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• 2010

Polymer dispersed liquid crystal (PDLC) films were prepared by the phase separation method using the liquid crystal (E7) and prepolymers. This work investigated the electro-optical characteristics of various PDLC films. In order to have good contrast ratio, the polymer refractive index must be adjusted to the ordinary refractive index of the liquid crystal. The driving voltage of PDLC films were mainly affected by elastic deformation. E7-Ebecryl810-IOA-TMPTA-HMPPO system had good threshold voltage and driving voltage and E7-Ebecryl810-EHA-PEGDA-HMPPO system had good contrast ratio.