• 한국지반공학회지:지반
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• 제14권1호
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• pp.109-126
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• 1998

본 논문에서는 플라이애쉬를 폐기물 매립장 차수재의 건설재료로 활용하기 위한 방안으로 실행한 일련의 실내실험연구결과를 보고한다. 폐기물 매립장 차수재의 투수계수 기준을 만족하기 위한 플라이애쉬와 벤토나이트의 적정 혼합비를 구하였다. 혼합차수재의 투수 메카니즘과 CaO가 차수층의 투수계수에 미치는 영향을 다양한 조건에 대한 투수시험과 X선 회절분석, 전자주사현미경분석, 헬릅 간극측정 법, 확대영상분석기법 등의 미세구조적 접근을 통하여 연구하였다. 벤토나이트의 첨가에 따라 플라이애쉬 혼합차수재의 투수계수는 감소하였다. 이는 주로 벤토나이트의 팽창에 의해 간극이 충진되었기 때문이며, 플라이애쉬-벤토나이트 간 포졸란 반응 및 그 에 따른 투수계수 저감효과는 시험에 사용된 국내 플라이애쉬의 CaO성분이 적고 $SiO_2$ 반응성이 낮아 크지 않은 것으로 나타났다. 혼합차수재에서 구성물질간 화학반응의 효과를 높이려 인위적으로 석회를 첨가하고 시행한 실험결과에 의하면 혼합차수재에서 구성성분간 화학반응성 및 그에 따른 투수계수에 미치는 영향은 구성성분의 외형적 총량보다는 구성성분의 형태와 활성도에 따라 크게 좌우되는 것으로 나타났다.

• Geomechanics and Engineering
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• 제21권5호
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• pp.423-432
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• 2020

Hydraulic conductivity is one of the engineering properties of soil. This study focusses on the influence of cement content on the hydraulic conductivity of cemented sand, which is investigated based on the results from numerical analysis and laboratory testing. For numerical analysis the cemented samples were scanned using X-ray Computed Tomography (CT) while laboratory testing was carried out using a triaxial setup. Numerical analysis enables us to simulate flow through the sample and provides insight to the microstructure. It quantifies the pore volume, proportion of interconnected voids and pore size distribution in both cemented and uncemented samples, which could be computed only through empirical equations in case of laboratory testing. With reduction in global voids, the interconnecting voids within the samples also reduce with cement content. Gamma cumulative distribution function is used to predict the percentage of voids lesser than a given pore volume. Finally, the results obtained from both numerical analysis and laboratory testing are compared.

• Fibers and Polymers
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• 제5권3호
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• pp.198-203
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• 2004

Composite films were prepared by casting the solution of polyacrylonitrile (PAN) and single wall nanotube (SWNT) in DMF subsequent to sonication. The SWNTs in the films are well dispersed as ropes with 20-30 nm thickness. Moreover, AFM surface image of the composite film displays an interwoven fibrous structure of nanotubes which may give rise to conductive passways and lead to high conductivity. The polarized Raman spectroscopy is an ideal characterization technique for identification and the orientation study of SWNT. The well-defined G-peak intensity at 1580 $cm^{-1}$shows a dependency on the draw ratio under cross-Nicol. The degree of nanotube orientation in the drawn film was measurable from the sine curve obtained by rotating the drawn film on the plane of cross-Nicol of polarized Raman microscope. The threshold loading of SWNT for electrical conductivity in PAN is found to be lower than 1 wt% in the composite film. The electrical conductivity of the SWNT/PAN composite film decreased with increasing of draw ratio due to the collapse of the interwoven fibrous network of the nanotubes with uniaxial orientation.

• 한국분말재료학회지
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• 제17권4호
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• pp.276-280
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• 2010

In the present work, ethylene glycol-based (EG) copper oxide nanofluids were synthesized by pulsed wire evaporation method. In order to explode the pure copper wire, high voltage of 23 kV was applied to the both ends of wire and argon/oxygen gas mixture was used as reactant gas. EG-based copper oxide nanofluids with different volume fraction were prepared by controlling explosion number of copper wire. From the transmission electron microscope (TEM) image, it was found that the copper oxide nanoparticles exhibited an average diameter about 100 nm with the oxide layer of 2~3 nm. The synthesized copper oxide consists of CuO/$Cu_2O$ phases and the Brunauer Emmett Teller (BET) surface area was estimated to be $6.86\;m^2\;g^{-1}$. From the analyses of thermal properties, it is suggested that viscosity and thermal conductivity of EG-based copper oxide nanofluids do not show temperature-dependent behavior over the range of 20 to $90^{\circ}C$. On the other hand, the viscosity and thermal conductivity of EG-based copper oxide nanofluids increase with volume fraction due to the active Brownian motion of the nanoparticles, i.e., nanoconvection.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제18권2호
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• pp.167-180
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• 2014

In this paper we consider a novel reconstruction method in electrical impedance tomography (EIT) and its application for monitoring and detecting a hydrargyrum (mercury) polluted soil near to the surface of underground. We use electrodes placed on the surface of land to collect the data which provides the relations of voltage and current map and to produce a projected image of interior conductivity distribution onto the surface of land. Here the projected image reconstruction method is used to monitor the pollution in soil underneath the ground without any destruction and any digging into a land.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권8호
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• pp.371-375
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• 2001

We attempted to fabricate polyurethane derivatives (PU-CN, PU-DCM) LB films by using LB method. Also, we investigated the monolayer behavior at the air-water interface by surface pressure-area (${\pi}$-A) isotherms. The surface morphologies and the physicochemical properties of LB films were investigated by atomic force microscopy(AFM) and UV-vis spectroscopy, respectively. And, the electrical properties of polyurethane derivatives LB films were investigated by using the conductivity and the dielectric constant. In the surface morphologies, physicochemical and electrical properties of polyurethane derivatives LB films, the properties is different as to the polyurethane derivatives, it is considered that this phenomena could be described by the difference of lumophore pendant which was adhered at PU main chain.

• 설비공학논문집
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• 제15권4호
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• pp.268-273
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• 2003

In the present study, the characteristics of upward bubble flow were experimentally investigated in a liquid bath. An electro-conductivity probe was used to measure local volume fraction and bubble frequency. Since the gas is concentrated at the near nozzle, the flow parameters are high near the nozzle. In general their axial and radial values tended to decrease with increasing distance. For visualization of flow characteristics, a Particle Image Velocimetry (P.I..V) and a thermo-vision camera were used in the present study. The experimental results show that heat transfer from bubble surface to water is largely completed within z=10mm from the nozzle, and then the temperature of bubble surface reaches that of water rapidly. Due to the centrifugal force, the flow was more developed near the wall than at bubble-water plume. Vortex flow in the bottom region was relatively weaker than that in the upper region.

• 한국생산제조학회지
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• 제21권6호
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• pp.1003-1007
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• 2012

A nondestructive technique would be very useful. Advanced NDE T-ray (terahertz ray) techniques of technology and instrumentation has provided a probing field on the electromagnetic spectrum. However, the T-ray is limited in order to penetrate a conducting material to some degree. Here, the T-ray would not go through easily the CFRP composite laminates since carbon fibers are electrically conducting while the epoxy matrix is not. So, investigation of terahertz time domain spectroscopy (THz TDS) was made and reflection and transmission configurations were studied for a 48-ply thermoplastic PPS(poly-phenylene sulfide)-based CFRP solid laminate. It is found that the electrical conductivity of CFRP composites depends on the direction of unidirectional fibers.

• Current Photovoltaic Research
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• 제5권4호
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• pp.109-112
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• 2017

Various wt. ratios of indium were doped to the poly(3,4-ethylenedioxythiophene)-poly(styreneswulfonate) (PEDOT:PSS) to enhance the conductivity and transmittance. The transmittance of the films increased with increasing the amount of indium. The field emission scanning electron microscope (FESEM) image of 2.54 wt. % of indium doped PEDOT:PSS film shows large number of aggregated indium particles. However, more than 2.54 wt. % of indium doped PEDOT:PSS films showed reduced aggregated indium particles. Moreover, 4.47 wt. % of indium doped PEDOT:PSS film showed no aggregated particles. The resistivity of pure PEDOT:PSS film showed $880k{\Omega}{\cdot}cm$. The resistivity of 1.03 wt. % indium doped film reduced approximately 26 times compared with pure PEDOT:PSS film. The resistivity of indium doped film further reduced with increasing the amount of indium, which showed approximately $0.55k{\Omega}{\cdot}cm$ for the PEDOT:PSS film doped 4.47 wt. % of indium.

• Korean Chemical Engineering Research
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• 제43권3호
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• pp.393-400
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• 2005

산증식제가 가지고 있는 산증식 능력을 측정하기 위한 새로운 평가 방법이 연구되어지고 있다. 그 방법은 UV 조사에 따른 산의 발생으로 인한 전도도 변화를 측정하는 것에 그 원리를 두고 있다. 본 연구자는 실험을 통해 다음과 같은 사실을 알 수 있었다. Inks film의 UV 경화반응 동안의 epoxy monomer의 광중합과 UV 경화율에 의해 전기 전도도가 감소하게 된다는 것이다. 본 논문에서는 새로운 산증식제를 합성하고, 합성된 산증식제의 열적 안정성을 DSC로 측정하였다. 여기서는 mono-type의 산증식제가 di-type의 산증식제보다 열적으로 더 안정하였다. 이러한 결과를 바탕으로 경화과정에 있어 UV 경화형 ink의 경화속도를 동적으로 평가할 수 있었다.