• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2003.11a
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• pp.121-134
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• 2003

최근의 많은 연구로부터 인쇄광택에 대한 코팅구조의 영향이 보고되고, 거론되고 있다. 그러나, 다각적이고, 다양한 잉크량 범위에서 인쇄광택의 개별적 인자에 대한 독립적 영향은 보고된 바 없다. 본 고에서는 다양한 코팅재료와 이어진 캘린더링 공정을 조합하여 Full-factorial실험설계에 준한 모델시료를 제작하고, 특성화하였다. 더불어 공극이 없지만 넓은 범위의 거칠음 수준을 가진 필름을 포함하였다. 통계도구를 사용하여 각 인자의 독립적인 영향을 추출하므로써, 각 구조인자의 함수로서 인쇄광택의 정량적인 반응도를 얻을 수 있었다. 결과는 60도와 75도 광택으로 표현하였다. 잉크공급량의 증가는 코팅층 거칠음의 영향을 약화는 시키되 배제시킬 수는 없었다. Matte급의 코팅층에 대한 인쇄광택은 코팅거칠음이 가장 큰 영향인자로 나타났다. 이는, 잉크필름의 Leveling을 저해하는, 큰 잉크필름의 분열형태와 코팅면을 따라 흐르며 형성되는 잉크필름 때문으로 생각되었다. 공극구조의 영향은 전반적으로 높은 잉크량과 백지광택수준에서 가장 크게 나타났다. 전체적으로는 코팅거칠음이 인쇄광택에 가장 강한 인자였으며, 공극크기, 공극부피가 뒤를 이었다. 그러나, 광택지 영역에서는 공극크기가 가장 강한 영향인자로 구분되었으며, 거칠음, 공극부피가 뒤를 이었다. 이러한 결과는 인쇄품질 측면에서 코팅을 최적화하는데 활용될 수 있을 것이다.

• Journal of the Korea Concrete Institute
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• v.16 no.3 s.81
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• pp.375-382
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• 2004

The compressive strength of concrete is used as the most basic and important material Property when reinforced concrete structures are designed. It has become a problem to use this value, however, because the control specimen sizes and shapes are different from every country. In this study, the effect of specimen sizes and shapes on compressive strength of concrete specimens was experimentally investigated based on fracture mechanics. Experiments for the Mode I failure was carried out by using cylinder, cube, and prism specimens. The test results are curve fitted using least square method(LSM) to obtain the new parameters for the modified size effect law(MSEL). The analysis results show that the effect of specimen sizes and shapes on ultimate strength is apparent. In addition, correlations between compressive strengths with size, shape, and casting direction of the specimen are investigated. For cubes and prisms the effect of placing direction on the compressive strength was investigated.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.502-508
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• 1999

We prepared non-porous membrane on the $Al_2O_3$ substrate with the different pore by the size by the plasma polymerization of $CHF_3$. We studied the permeability characteristics of membrane by Ar treatment and the effect of substrate pore size on gas permeation mechanism. The selectivity was increased with Ar plasma treatment time and rf-power near the substrate to the cathode while the permeability was decreased. It was observed that the solution-diffusion model would be applied to non-porous layers while it is applied Knudsen diffusion model to the substrate. From the experimental observation, it could be concluded that the pore size of $Al_2O_3$ membrane influenced on the permeability and the selectivity.

• Journal of Energy Engineering
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• v.6 no.1
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• pp.77-86
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• 1997

In this study, numerical computations were performed to scrutinize the effect of the size of coal particles on reactive flow fields and concentration distribution of product gases for five cases with four different particle sizes (40 $\mu\textrm{m}$, 60 $\mu\textrm{m}$, 100 $\mu\textrm{m}$, 120 $\mu\textrm{m}$, 140 $\mu\textrm{m}$) in an axisymmetric cylindrical coal gasifier in which Alaska Usibelli subbituminous coals were gasified. Predictions showed that coal particle size affected the concentration distribution of product gases. When coals of 100 $\mu\textrm{m}$ were gasified, the maximum average concentrations of major products, H$_2$and CO, were predicted at the exit of the gasifier. The average mole fractions of CO and H, were shown to be 0.62, and 0.16 (dry basis, inert free), respectively. The cold gas efficiency of 83% was also predicted for the same particle size of 100 $\mu\textrm{m}$.

• The Journal of Engineering Geology
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• v.25 no.3
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• pp.369-376
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• 2015

Numerical models simulating groundwater flow are often used to estimate groundwater discharge into a tunnel. In designing numerical models, the grid size should be carefully considered to ensure that groundwater discharge is accurately predicted. However, several recent studies have employed various grid sizes without providing an adequate explanation for their choice. This paper suggests the optimal grid size based on a comparison of numerical models with analytical solutions. Discrepancies between numerical and analytical solutions result from the effect of model boundaries as well as the grid size. By nullifying boundary effects, the errors solely associated with the grid size could be analyzed. The optimal grid size yielding accurate numerical solutions was thus derived. The suggested relationship between tunnel radius and optimal grid size is analogous to the relationship between the equivalent well block radius and grid size.

• The Journal of Engineering Geology
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• v.9 no.3
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• pp.227-241
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• 1999

Groundwater flow in a fractured rock mass is related to the geometric characteristics of the fracture system. The objective of this study aims to analyze the probabilistic density function of fracture properties md their relations to the hydraulic conductivity in volcanic rocks of the northern Yosu area. Fracture characteristics were investigated by core logging and acoustic televiewer logging in four boreholes and the hydraulic conductivity was obtained from the constant pressure injection and fall-off tests. The 303 fractures were grouped into three sets by their orientation and three fracture types by the degree of opening in aperture. As a result of the study, the hydraulic conductivity in the test section intersected by open and semi-open fractures, conductive fractures, and set 1 fractures was very high, while closed fractures did rarely affect the hydraulic conductivity. It was recognized that the hydraulic conductivity in a fractured rock mass was preferentially affected by the aperture size of conductive fractures and fracture intersection frequency and size, secondly.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1587-1592
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• 2010

The effects of specimen geometry and loading conditions on the stress distribution in a sandwich specimen under combined loads are investigated by elastic finite element analysis. A commercial software NASTRAN is used in plain-strain two-dimensional finite element analysis of sandwich specimens; the analysis was performed for three different specimen shape factors and four different combined displacement conditions. The results of computational analysis suggest that the effect of the combined displacement angle, which is defined as the ratio of the shear displacement to the normal displacement, on the size of the non-homogeneous stress distribution is observed only in the case of the shear stress and von Mises stress. Also as the combined displacement angle increases, the size of the nonhomogeneous stress distribution decreases in the case of the shear stress and increases in the case of the von Mises stress. In addition, as the specimen shape factor, which is defined as the ratio of the specimen length to the height, increases, the size of the non-homogeneous stress distribution under combined displacement conditions decreases significantly.

• Journal of Soil and Groundwater Environment
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• v.8 no.3
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• pp.13-22
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• 2003

Laboratory scale study for an air injection and flowing aspect of groundwater saturated zone was conducted for three sediment grains (AMG 0.34, 1.38, 3.89 mm diameter). Air flow for AMG (Average Modal diameter Grains) 0.34 mm diameter grain size provides indication of pattern of channelized air flow in saturated zone and expansion state in above saturated zone. Maximum area of influence is approximately l5.2%/$\textrm{m}^2$for AMG of 0.34 mm diameter. For AMG of 1.38 mm and 3.89 mm modal diameter grains, air flow are pervasive air flow, forming a symmetrical cone of influence around the injection point. Maximum areas affected are 37%/$\textrm{m}^2$for AMG 1.38 mm diameter and 30%/$\textrm{m}^2$for AMG 3.89 mm diameter. AMG 1.38 mm and 3.89 mm diameter grains show onset of collapse and approach to steady state in above saturated zone, respectively. In this study, optimal sites for in situ air sparging, may be grain diameters between about AMG 1.5-2.5 mm diameter.

• Journal of Korea Water Resources Association
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• v.47 no.5
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• pp.483-490
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• 2014

The design procedures for a biological reactor and a secondary settling tank (SST) of an activated sludge system are based on the steady state design method (Ekama et al., 1986; WRC, 1984) and the 1-D flux theory design method (Ekama et al., 1997), respectively. This study combined both of the design procedures, to determine the optimum sludge concentration in the reactor and the best design with the lowest cost. The best design of the reactor volume and the SST diameter at the optimum sludge concentration were specified with varying wastewater and sludge characteristics, temperature, sludge retention time (SRT) and peak flow rate. The effects of the influent wastewater characteristics, such as substrate concentration and unbiodegradable particulate fraction, were found to be considerable, but the effect of unbiodegradable soluble fraction was to be negligible. The effects of sludge settling characteristics, were also significant. SRT, as an operating parameter, was found to be an important factor for determining the optimum sludge concentration. However, the effect of temperature was found to be small. Furthermore, for designing a large scale wastewater treatment plant, the number of reactors or SSTs could be estimated, by dividing the total reactor volume or SST area. The new combined design procedure, proposed in this research, will be able to allow engineers to provide the best design of an activated sludge system with the lowest cost.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.1003-1022
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• 2018

In the current work, a series of three-dimensional finite element analyses were carried out to understand the behaviour of a pre-existing single pile to the changes of the tunnel face pressures when a shield TBM tunnel passes underneath the pile. The numerical modelling analysed the results by considering various face pressures (25~100% of the in-situ horizontal stress prior to tunnelling at the tunnel springline). In the numerical modelling, several key issues, such as the pile settlements, the axial pile forces, the shear stresses have been thoroughly analysed for different face pressures. The head settlements of the pile with the maximum face pressure decreased by about 44% compared to corresponding settlement with the minimum face pressure. Furthermore, the maximum axial force of the pile developed with the minimum face pressure. The tunnelling-induced axial pile force at the minimum face pressure was found to be about 21% larger than that with the maximum face pressure. It has been found that the ground settlements and the pile settlements are heavily affected by the face pressures. In addition, the influence of the piles and the ground was analysed by considering characteristics of the soil deformations. Also, the apparent safety factor of the piles are substantially reduced for all the analyses conducted in the current simulation, resulting in severe effects on the adjacent piles. Therefore, the behaviour of the piles, according to change the face pressures, has been extensively examined and analysed by considering the key features in great details.