• Bulletin of the Korean Chemical Society
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• 제34권3호
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• pp.753-758
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• 2013

Molecular dynamics (MD) simulations have been used to study the diffusion behavior of small gas molecules ($CO_2$) in polyethylene terephthalate (PET)/polylactide (PLA) blends. The Flory-Huggins interaction parameters (${\chi}$) determined from the cohesive energy densities are smaller than the critical value of Flory-Huggins interaction parameters (${\chi}_{critical}$), and that indicates the good compatibility of PET/PLA blends. The diffusion coefficients of $CO_2$ are determined via MD simulations at 298 K. That the order of diffusion coefficients is correlated with the availably fractional free volume (FFV) of $CO_2$ in the PET/PLA blends means that the FFV plays a vital role in the diffusion behavior of $CO_2$ molecules in PET/PLA blends. The slopes of the log (MSD) as a function of log (t) are close to unity over the entire composition range of PET/PLA blends, which confirmes the feasibility of MD approach reaches the normal diffusion regime of $CO_2$ in PET/PLA blends.

• Korean Chemical Engineering Research
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• 제58권2호
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• pp.307-312
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• 2020

최근 대기압이하 진공 압력 상태에서 운전되는 유동층 반응기는 진공건조 공정이나 플라즈마 화학증착과 같이 감압 유동화가 요구되기에 관심이 증대되어 왔다. 그러나 대기압 이하에서 운전되는 유동층의 수력학적 특성 연구는 많이 연구되지 않았다. 본 연구에서는 대기압 이하에서 운전하는 유동층의 압력강하를 층내 압력을 1.33 에서 101.3kPa 까지 변화시키며 측정하였다. 유동층의 운전 압력이 진공인 상태에서는 최소유동화속도가 압력이 감소함에 따라 증가하며, 이는 기체 밀도와 평균 자유경로 변화와 같은 slip 흐름에 의한 변화이다. 또한 기존의 상압 상태에서 운전되는 유동층의 최소유동화속도 상관식과 비교함으로써 압력 감소에 따른 slip 흐름의 영향 뚜렷하게 나타남을 가리키는 임계 Knudsen 수를 결정하였다. 이로부터 slip 흐름이 주도하기 시작하는 임계 압력을 실험적으로 결정하였다.

• 한국전기전자재료학회논문지
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• 제18권6호
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• pp.521-526
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• 2005

Within wafer non-uniformity(WIWNU) improves as the stiffness of pad decrease. We designed the pad groove to study of pad stiffness on WIWNU in Chemical mechanical polishing(CMP) and measured the pad stiffness according to groove width. The groove influences effective pad stiffness although original mechanical properties of pad are unchanged by grooving. Also, it affects the flow of slurry that has an effect on the lubrication regime and polishing results. An Increase of the apparent contact area of pad by groove width results in decrease of effective pad stiffness. WIWNU and profile of removal tate improved as effective pad stiffness decreased. Because grooving the pad reduce its effective stiffness and it makes slurry distribution to be uniform. Futhermore, it ensures that pad conforms to wafer-scale flatness variability. By grooving the top pad, it is possible to reduce its stiffness and hence reduce WIWNU and edge effect.

• 한국전기전자재료학회논문지
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• 제17권10호
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• pp.1041-1048
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• 2004

Chemical mechanical polishing (CMP) process was studied in terms of tribology in this paper. CMP performed by the down force and the relative motion of pad and wafer with slurry is typically tribological system composed of friction, wear and lubrication. The piezoelectric quartz sensor for friction force measurement was installed and the friction force was detected during CMP process. Various friction signals were attained and analyzed with the kind of pad, abrasive and abrasive concentration. As a result of experiment, the lubrication regime is classified with ηv/p(η, v and p; the viscosity, relative velocity and pressure). The characteristics of friction and material removal mechanism is also different as a function of the kind of abrasive and the abrasive concentration in slurry. Especially, the material removal per unit distance is directly proportional to the friction force and the non~uniformity has relation to the coefficient of friction.

• 한국환경과학회지
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• 제12권11호
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• pp.1159-1165
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• 2003

The Carbon Bond Mechanism IV has been developed for use in urban- and regional-scale oxidant models. The photochemical mechanism, CBM4, contains extensive improvements to earlier carbon bond mechanisms in the chemical representations of aromatics, biogenic hydrocarbons, peroxyacetyl nitartes, and formaldehyde. Ozone is produced mainly by nitrogen oxides and hydrocarbon. By altering the initial concentrations of the mechanism, an analysis of the sensitivity of ozone concentrations to VOC/NO$\_$x/ ratios and VOC composition is conducted in this one-dimensional mechanism. Note that it is considered a chemical mechanism in order to understand the photochemical reactions within this mechanism. It analyzed the results of these simulations by applying a NO$\_$x/-sensitive and a VOC-sensitive regime. These sensitivity regimes are changed to match the relative contribution of VOC and NO$\_$x/ concentrations to ozone production in simulations of two sets.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 센서 박막재료 반도체 세라믹
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• pp.41-44
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• 2003

As the device feature size is reduced to the deep sub-micron regime, the chemical mechanical polishing (CMP) technology is widely recognized as the most promising method to achieve the global planarization of the multilevel interconnection for ULSI applications. However, cost of ownership (COO) and cost of consumables (COC) were relatively increased because of expensive slurry. In this paper, the effects of different slurry composition on the oxide CMP characteristics were investigated to obtain the higher removal rate and lower non-uniformity. We prepared the various kinds of slurry. In order to save the costs of slurry, the original slurry was diluted by de-ionized water (DIW). And then, alunima abrasives were added in the diluted slurry in order to promote the mechanical force of diluted slurry.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.231-234
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• 2004

Chemical mechanical polishing(CMP) process was studied in terms of tribology in this paper. CMP performed by the down force and the relative motion of pad and wafer with the slurry is typically tribological system composed of friction, wear and lubrication. The piezoelectric quartz sensor for friction force measurement was installed and the friction force was detected during CMP process. Various coefficient of friction was attained and analyzed with the kind of pad, abrasive and the abrasive concentration. The lubrication regime is also classified with ${\eta}v/p(\eta,\;v\;and\;p;$ the viscosity, relative velocity and pressure). Especially, the co-relation not only between the friction force and the removal per unit distance but also between the coefficient of friction and within-wafer-nonuniformity was estimated.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.392-392
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• 2010

In this study, high-speed chemical dry thinning process of Si wafer and evolution of surface roughness were investigated. Direct injection of NO gas into the reactor during the supply of F radicals from $NF_3$ remote plasmas was very effective in increasing the Si thinning rate due to the NO-induced enhancement of surface reaction but thinned Si surface became roughened significantly. Addition of Ar gas, together with NO gas, decreased root mean square (RMS) surface roughness of thinned Si wafer significantly. The process regime for the thinning rate enhancement with reduced surface roughness was extended at higher Ar gas flow rate. Si wafer thinning rate as high as $22.8\;{\mu}m/min$ and root-mean-squared (RMS) surface roughness as small as 0.75 nm could be obtained. It is expected that high-speed chemical dry thinning process has possibility of application to ultra-thin Si wafer thinning with no mechanical damage.

• Journal of Ecology and Environment
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• 제38권4호
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• pp.505-515
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• 2015

The objectives of this study were to determine the effects of stream nutrient regime, N:P ratios and suspended solids on fish tolerance/trophic compositions and stream ecosystem health, based on multi-metric model, during 2008-2013. Also, stream ecosystem health was evaluated in relation to chlorophyll-a (CHL) as a measure of algal productivity or indicators of trophic state to water chemical parameters. Total number of sampled fish species were 50 and showed a decreasing trend from 2008 to 2013. The minnow of Zacco platypus, based on the catch per unit effort (CPUE), was the most dominant species (25.9%) among the all species. Spatial heterogeneity was evident in the fish tolerance guilds that showed the dominance of sensitive species (89%) in the headwaters (S1) and the dominance of tolerant species (57%) in the urban. These conditions were directly influenced by concentrations of nutrients and organic matter (COD). The N:P ratios, as a barometer of water pollution, had a negative linear function (R² = 0.40, P < 0.01) with CHL, and the ratios had an important role in changes of COD concentration (R² = 0.40, P < 0.01). Under the circumstances, the N:P ratio directly influenced the relative proportions of fish trophic/tolerance compositions. According to the regression analysis of omnivore (O_m) and insectivore sp. (I_n) on total nitrogen and total phosphorus, nitrogen had no significant influences (P > 0.05) to the two compositions, but phosphorus influenced directly the two guilds [slope (a) = -32.3, R² = 0.25, P < 0.01 in the I_n; a = 40.7, R² = 0.19, P < 0.01 in the O_m]. Such water chemistry and fish trophic guilds determined the stream ecosystem health, based on the multi-metric fish model.

• 전기화학회지
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• 제14권4호
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• pp.219-224
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• 2011

옥살산 수용액에서의 전기화학적 양극산화에 의한 자기정렬된 알루미나 나노템플레이트의 제조에 있어서 전해액 첨가제를 이용하여 기존 양극산화 법으로는 보고된 바 없는 160~200 V 범위의 자기 정렬 구간을 관찰하였다. 고전계 양극산화와 펄스분리법 및 화학적 기공확장을 거쳐 생성된 자기 정렬구조를 FE-SEM 으로 관찰한 결과 이 전압구간에서의 기공간격과 전압과의 관계는 2.2 nm/V 으로 기존 고전계 양극산화의 결과와 유사하게 나타남을 알 수 있었다. 또한 양극산화막의 성장속도는 약 60 ${\mu}m$/hr로 유사한 기공구조를 얻을 수 있는 인산 수용액에서의 연질 양극산화에 비해 약 30배로 높은 것을 알 수 있었다. 이러한 고찰을 통하여 기공간격 300 nm 이상의 나노템플레이트를 고속으로 제조할 수 있는 조건을 확립하였다.