• Bulletin of the Korean Chemical Society
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• 제19권11호
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• pp.1185-1188
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• 1998

Layered nanocomposite, SiO2/TiO2 sol pillared clay, has been prepared by the ion exchange reaction of Na' ion in montmorillonite with positively charged mixed SiO2/TiO2 sol. The nanosized sol particles were synthesized by mixing SiO2 sol solution with TiO2 one, which is obtained by acidic hydrolysis of TEOS and TiCl4, respectively. From powder XRD, the basal spacing (d001) of the sample calcined at 400 ℃ was found to be ca. 60 Å, due to the multistacking of nanosized SiO2 and TiO2 sol particles, which was confirmed by the pore size analysis from 129Xe NMR and micropore analysis calculated from nitrogen adsorption. The BET specific surface area shows the value of 684 m2g-1 (Langmuir 1115 m2g-1), which is the highest among various pillared clays ever reported previously, and the total porosity is found to be 0.51 mlg-1, and the pores are mainly composed of micropore with a size of ca. 11.8 Å. This result agrees with the adsorption capacity obtained from water adsorption. According to diffuse reflectance ultraviolet-visible spectroscopy, it is found that the TiO2 particles stabilized in the interlayer space of montmorillonite are quantum-sized of ca. 20 Å.

• Geomechanics and Engineering
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• 제6권2호
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• pp.139-151
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• 2014

Mudstone is a very common rock that, when in contact with water, can exhibit considerable volume change and breakdown. This behavior of mudstone is frequently encountered in geotechnical engineering and has a considerable influence on infrastructure stability. This is particularly important in the present work, which focuses on mitigating the harmful properties of mudstone. The samples studied are of Permian Age mudstone from Shandong Province, China. Modification tests using organic silicone additive material were carried out. The mechanisms of physical properties modification of mudstone were comparatively studied using corresponding test methods, and the modification mechanism of organic silicone additive material acting on mudstone was analyzed. The following conclusions were drawn. The surface texture and characters of mudstone changed dramatically, surface character turns from hydrophilic to hydrophobic after organic silicone additive material modification. The changes in the surface character indicate a reduction in the water sensitivity of mudstone. After modification, the shape of porosity and fracture of mudstone changed unremarkable, and the total and free expansion ratios decreased obviously, whereas the strength increased markedly.

• Steel and Composite Structures
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• 제32권6호
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• pp.753-767
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• 2019

Vibration control in mechanical equipments is an important problem where unwanted vibrations are vanish or at least diminished. In this paper, free vibration active control of the porous sandwich piezoelectric polymeric nanocomposite microbeam with microsensor and microactuater layers are investigated. The aim of this research is to reduce amplitude of vibration in micro beam based on linear quadratic regulator (LQR). Modified couple stress theory (MCST) according to sinusoidal shear deformation theory is presented. The porous sandwich microbeam is rested on elastic foundation. The core and face sheet are made of porous and three-phase carbon nanotubes/resin/fiber nanocomposite materials. The equations of motion are extracted by Hamilton's principle and then Navier's type solution are employed for solving them. The governing equations of motion are written in space state form and linear quadratic regulator (LQR) is used for active control approach. The various parameters are conducted to investigate on the frequency response function (FRF) of the sandwich microbeam for vibration active control. The results indicate that the higher length scale to the thickness, the face sheet thickness to total thickness and the considering microsensor and microactutor significantly affect LQR and uncontrolled FRF. Also, the porosity coefficient increasing, Skempton coefficient and Winkler spring constant shift the frequency response to higher frequencies. The obtained results can be useful for micro-electro-mechanical (MEMS) and nano-electro-mechanical (NEMS) systems.

• Computers and Concrete
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• 제32권5호
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• pp.439-454
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• 2023

In this article, the surface stress effects on the buckling analysis of the annular sandwich plate is developed. The proposed plate is composed of two face layers made of carbon nanotubes (CNT) reinforced composite with assuming of fully bonded to functionally graded porous core. The generalized rule of the mixture is employed to predict the mechanical properties of the microcomposite sandwich plate. The derived potentials energy based on higher order shear deformation theory (HSDT) and modified couple stress theory (MCST) is solved by employing the Ritz method. An exact analytical solution is presented to calculate the critical buckling loads of the annular sandwich plate. The predicted results are validated by carrying out the comparison studies for the buckling analysis of annular plates with those obtained by other analytical and finite element methods. The effects of various parameters such as material length scale parameter, core thickness to total thickness ratio (hc/h), surface elastic constants based on surface stress effect, various boundary condition and porosity distributions, size of the internal pores (e0), Skempton coefficient and elastic foundation on the critical buckling load have been studied. The results can be served as benchmark data for future works and also in the design of materials science, injunction high-pressure micropipe connections, nanotechnology, and smart systems.

• 원예과학기술지
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• 제34권6호
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• pp.886-897
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• 2016

공정육묘장들이 계절별 기상환경에 적합하도록 혼합상토의 조성을 변화시키고 있다. 본 연구는 계절별(하절기, 동절기, 봄 가을) 육묘에 적합한 상토를 선발하기 위해 수행되었다. 실험을 위해 다양한 국가에서 수입된 8종류의 피트모스와 입경이 다른 4종류의 펄라이트를 수집한 후 비율을 피트모스 7: 펄라이트3(v/v)으로 고정시킨 32종류의 상토를 만들었다. 이 후 공극률, 기상률 및 액상률의 삼상분포, 그리고 pH, EC 및 무기물 함량 등 화학성을 분석한 후 6종류 상토를 선발하였다. 선발 된 상토를 대상을 추가로 쉽게 이용할 수 있는 수분량(EAW)과 완충수분(BW), cation exchange capacity(CEC) 그리고 각종 화학성을 분석하여 기비 혼합을 위한 판단기준으로 삼았다. 피트모스와 펄라이트를 혼합한 상토는 공극률 64.7-96.0%, 용기용 수량 42.9-90.1%, 그리고 기상률이 1.3-27.8%의 범위로 측정되었고, 혼합되는 피트모스와 펄라이트 종류에 따라 물리성의 차이가 컸다. 피트모스의 pH와 EC가 각각 2.96-3.81 및 $0.08-0.47dS{\cdot}m^{-1}$로 분석되었지만 펄라이트를 혼합한 후 pH가 상승하고 EC가 낮아졌다. 하절기용으로 선발한 Blonde Golden peatmoss(BG) + 펄라이트(입경 1mm 이하) 1호(PE1)와 Latagro 10mm 이하(L1) + 펄라이트(1-2mm) 2호(PE2) 상토는 공극률, 용기용수량 및 기상률이 각각 89.8-90.9, 80.8-81.3 및 9.0-9.7%였다. 동절기용으로 선발한 Sfagnumi Turvas(ST) + PE2와 Laragro 20-40mm(L3) + PE2 상토는 이들 세 종류 항목이 각각 79.9-86.7, 60.4-74.9 및 11.8-19.6% 그리고 봄 가을용인 BG + 펄라이트 2-5mm(PE3)와 Orange peatmoss(O) + PE3이 각각 85.2-87.3, 77.9 및 7.4-9.4%이었다. EAW는 봄 가을과 하절기용이 각각 24.2-24.9%, 22.0-28.6%의 범위였지만 동절기용은 각각 18.0-21.8%로 측정되었으며, BW는 계절별로 선발한 상토에 따른 차이가 뚜렷하지 않았다. 선발된 6종류 혼합상토의 pH는 3.11-3.97, EC는 $0.06-0.26dS{\cdot}m^{-1}$, 그리고 양이온치환용량은 $97-119meq{\cdot}100g^{-1}$ 범위에 포함되었다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2002년도 총회 및 춘계학술발표회
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• pp.66-69
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• 2002

In this work, cost effective venting is considered by comparing flow rates of 5$m\ell$/min, 10$m\ell$/min, and 20$m\ell$/min. Studies were performed on a soil artificially contaminated with diesel oil (the initial TPH(Total Petroleum Hydrocarbon) concentration of 7098mg/kg), and nutrient condition was C:N:P rate of 100:10:1. The soil has a sandy texture with pH of 6.8, 2.16 ~2.38% organic matter, a total porosity of 47~52% and field capacity 16.2~ 17.2%. The column experiments was made of glass column of 60cm length and 10cm I.D. at controlled temperature of 2$0^{\circ}C$($\pm$2.5$^{\circ}C$). The efficiency of continuous flow rate of 5, 10 and 20$m\ell$/min resulted in separately 61.3%, 58.1%, and 55% reduction of initial TPH concentration(7098mg/kg). Hydrocarbon utilizing microbial count and dehydrogenase activity in air flow of 5$m\ell$/min were higher than those of the others. The first order degradation rate of n-alkanes ranging from C10 to C28 was higher than that of pristane and phytane as isoprenoids. The $C_{17}$/pristane and $C_{18}$phytane ratios for monitoring the degree of biodegradation were useful only during the early stages of oil degradation. Degradation contributed from about 89% to 93% of TPH removal. Volatilization loss of diesel oil in contaminated soil was about 7% to 11%, which was significantly small compared to degradation.n.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.790-799
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• 2010

The Upper Devonian Grossmont Formation in Alberta, Canada reserves an estimated 50 billion cubic meters of bitumen and possess about 1/6 of the total bitumen resources in northern Alberta. However, unlike the overlying Athabasca oil sands, non conventional bitumen resources has not been developed as yet. The carbonate rocks of Grosmont Formation have been subject to various stages of diagenesis, including dolomatization and karstification with a strong effect on the distribution of porosity and permeability, which resulted in highly heterogeneous reservoirs. An extensive fracture logging and mapping was performed on total of six boreholes located in the study area to explore the characteristics of fracture geometry system and the subsurface structures of carbonates reservoir that holds bitumen. Fractal dimension was used as a measure of the statistical homogeneity of the fractured rock masses. The applicability of random Cantor dust, Dc, as a fractal parameter was examined systematically. The statistical homogeneity of fractured carbonates rock masses was investigated in the study area. The structural domains of the rock masses were delineated depthwise according to estimated Dc. The major fracture orientation was dominated by horizontal beddings having dip of $0-20^{\circ}$. Also, fractures having high dip angles existed with relatively low frequency. Three dimensional fracture network modeling for each structural domain has been performed based on fracture orientation and intensity, and some representative conceptual models for carbonates reservoir in the study area has been proposed. The developed subsurface conceptual models will be used to capture the geomechanical characteristics of the carbonates reservoir.

• 대한기계학회논문집B
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• 제36권9호
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• pp.953-960
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• 2012

AMTEC기술은 열을 직접 전기로 변환시키는 기술로서 소디움을 작동유체로 사용하고 있으며, 작동유체의 순환은 모세관윅을 사용한다. 순환계통에는 증발부윅, 순환윅 및 응축부윅으로 구성되고, 각각의 윅은 소디움의 액체 또는 증기가 순환하면서 압력손실이 발생하므로 소디움의 순환을 위해서는 증발부윅의 모세관압력이 윅내의 총압력손실보다 커야만 한다. 본 연구에서는 100 watt급의 AMTEC시제품설계을 위해 소디움의 순환계통으로 구성되는 증발부윅, 순환윅 및 응축부윅에서의 압력손실과 증발부에서 응축부로의 열손실을 순환윅의 직경과 길이에 대해 분석하여 증발부윅의 소결입자 직경과 순환윅의 설계에 활용하코저 하였으며, 분석결과에서 순환계통의 총압력손실보다 큰 모세관압력을 위해서는 증발부윅의 소결입자크기는 10 ${\mu}m$이 적합한 결과를 얻었다.

• 공업화학
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• 제5권3호
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• pp.385-394
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• 1994

세공분포가 서로 다른 두 종류(KHT, X-5)의 ${\gamma}$-알루미나 pellet에 아황산가스를 흡착 제거시킬 경우 반응이 진행되면서 각각의 세공벽에 반응생성층이 형성되어 반응속도 상수($K_v$), 세공률(${\varepsilon}_p$), 유효내부 확산계수($D_e$)의 변화와 세공반경이 줄어들어 세공막힘 현상이 일어나게 된다. 이들 영향을 고려하여 세공분포를 이용한 Random pore model로 최적반응온도 $450^{\circ}C$에서 산화구리의 각 담지농도(4, 6, 8, l0 wt%)와 아황산가스의 농도(1000, 2000ppm)에 대한 전환율을 수학적 모델로부터 계산하였다. 산화구리의 담지농도가 증가할수록 세공내의 유효반응 표면적과 세공률의 감소, 내부확산저항의 증가, 미세세공의 세공막힘 현상으로 전환율은 감소하였다. 총괄 전환율은 ${\gamma}$-알루미나 pallet의 표면 국부 전환율에 크게 의존하였으며 산화구리의 담지농도가 낮고 아황산가스의 농도가 클수록 증가하였다. 반응기에 유입되는 아황산가스의 유속은 반응초기 CuO의 전환율에 영향을 주었고 세공분포가 발달하여 세공율이 큰 ${\gamma}$-알루미나 pellet일수록 전환율은 높게 나타났다.

• 한국결정성장학회지
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• 제29권6호
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• pp.359-364
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• 2019

서스펜션 플라즈마 스프레이 법은 미세한 분말을 용사 공정에 적용함으로써 전통적인 플라즈마 스프레이 법의 단점을 극복하고자 개발된 코팅법이다. 본 연구에서는 고밀도의 Y₂O₃ 코팅막을 제조하기 위해 서스펜션 플라즈마 스프레이법을 이용하여 플라즈마 건의 전류량과 총 가스 유량을 공정변수로 하여 코팅막을 제조하였으며, 그에 따른 코팅막 특성에 대한 연구를 하였다. 코팅막의 미세구조 및 물리적 특성 평가 결과 플라즈마 건 전류량 200 A, 총 가스 유량 220 L/min의 조건에서 층상 결함 없이 0.2 vol%의 매우 낮은 기공률을 갖는 고밀도의 Y₂O₃ 코팅막을 제조할 수 있었다.