• Journal of the Korean Ceramic Society
• /
• v.31 no.8
• /
• pp.927-933
• /
• 1994

Alumina composite membranes were prepared by chemical vapor deposition (CVD) using aluminum-tri-isopropoxide as a precursor. Porous alumina supports were used in deposition, which were in disk shape with mean pore diameter of 0.1 ${\mu}{\textrm}{m}$ and prepared by slip-coasting process. film deposition morphology on porous support was simulated through depositing alumina film on polycrystalline silicon pattern, and its step coverage observed by SEM showed one deviated from uniform step coverage. N2 permeability through composite membranes and the pressure dependence decreased as the deposition time increased. Initially, the N2 permeability of the top layer was tend to decrease rapidly, and then the degree of decrease in N2 permeability was tend to diminish with deposition time. The N2 permeability increased with heat treatment temperature and the crack was generated in top layer at 100$0^{\circ}C$.

• 한국가시화정보학회:학술대회논문집
• /
• 2004.11a
• /
• pp.36-39
• /
• 2004

In this study, we present the theoretical, numerical and experimental results of the sink flow from a rotating, circular tank Strikingly enough, when the upper free surface was set with no-slip boundary conditions, the Ekman boundary-layer develops not only above the bottom surface but under the free surface. The sink fluid is coming from the two Ekman layers, and the mass transfer from the bulk, inviscid region is dependent on the rotational speed. It is also remarkable to see that all the fluid gathered along the axis flows through a rapidly rotating fluid column with almost the same size as the hole.

• Journal of the Korean Society of Visualization
• /
• v.2 no.2
• /
• pp.38-44
• /
• 2004

Theoretical and numerical studies are given to the sink flows within a rotating circular tank driven by the fluid withdrawal from a bottom circular hole. It was found that, when the upper free surface was set with no-slip boundary conditions, the Ekman boundary-layer develops not only above the bottom surface but under the top surface. The sink fluid is coming from the two Ekman layers, and the mass transfer from the bulk, inviscid region is dependent on the rotational speed. It is also remarkable to see that all the fluid gathered along the axis flows in a form of rapidly rotating fluid column haying almost the same diameter as the bottom hole.

• Steel and Composite Structures
• /
• v.42 no.3
• /
• pp.389-396
• /
• 2022

This investigation in fluid mechanics surrounds around the variety of flow problems for different fluids along the stretching cylinder. Numerical procedure is carried out for the obtained resultant equations by Keller-Box technique. Numerical study of laminar, steady, viscous and incompressible two dimensional boundary layer flow of effects of suction and blowing on boundary layer slip flow of Casson fluid along permeable exponentially stretching cylinder has been carried out in the present draft. physical parameters i.e., Nusselt number and skin friction coefficient, suction parameter and the local Reynold number are investigated on velocity profile and elaborated through proper graphs and table.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2003.11a
• /
• pp.313-323
• /
• 2003

The sliding wear behaviors of Zircaloy-4 nuclear fuel rod were investigated using two support springs with convex and concave shapes in room temperature air and water. The main focus is to compare the wear behavior of various test variables such as slip amplitude, environment, contact contours with different spring shape and a number of cycles. The results indicated that wear volume and maximum wear depth increased with slip amplitude in both air and water, but their trends tended to change according to the spring shapes and test environments. In air condition, the wear volume was controlled by wear debris behavior generated on worn surface. As a result, final wear volume and maximum wear depth decreased if a ratio of protruded wear volume to worn area $(D_p)$ would be saturated to specific value. This is because wear particle layer could accommodate large strain by accumulating and transforming wear particle layer. However, in water condition, metal-to metal contact was more dominant and wear volume was greatly affected by changed mechanical behavior between contact surfaces since wear debris should be generated after repeated plastic deformation and fracture. After wear test, worn surfaces were examined using optical microscope and SEM and details of wear mechanism were discussed using a ratio of wear volume to worn area $(D_e)$ at each test condition.

• Journal of the Korean Geotechnical Society
• /
• v.21 no.5
• /
• pp.65-74
• /
• 2005

The negative skin friction on piles, which are installed in currently consolidating soft deposits, creates significant problems on the stability of pile foundations. This study investigated whether or not the pile foundation designs were appropriate in soft deposits with large amount of consolidation settlement. The final settlements of the grounds along the pile depth were estimated by the soil parameters obtained from the laboratory tests and by the field-measured settlement curves, if they were available. The displacement of the piles along the pile depth was estimated by both the load transfer method and the numerical method. Both methods gave similar locations of neutral planes and magnitudes of the maximum axial forces on the piles. The movements of the ground and the piles were compared to calculate the down drag acting on piles. For the piles whose bearing capacities were less than the design loads including the down drag, slip layer coatings and/or incrementing of the pile penetration depth into the bearing stratum were proposed to improve the pile capacities.

• Korean Journal of Materials Research
• /
• v.10 no.10
• /
• pp.677-683
• /
• 2000

Three- and five-layer 3Y-YZP/12Ce- TZP composites prepared by a slip casting method have been char­acterized in terms of mechanical properties. The fracture strength of mutilayer c$\alpha$nposites determined in a diametral compression test was 327~534 MPa. Although the indentation strength of the materials was generally reduced with i increasing Vickers indentation load up to 300 N, the damage resistance of multilayer composites was superior com­pared to monolithic layer TZP material. The four-point bend strength of the layered material remained at the values of 620~674 MPa after indentation with a load of 49 N, while that of the monolithic TZP material was 129~339 MPa. The microindentation toughness of the multilayer material was $7.7~13.1\;MPa{\cdot}m^{1/2}$.

• Journal of the Korean Geotechnical Society
• /
• v.38 no.8
• /
• pp.39-52
• /
• 2022

Multilayer perceptron neural network was trained to determine the factor of safety and slip surface of the slope. Slope geometry is a simple slope based on Korean design standards, and the case of dry and existing groundwater levels are both considered, and the properties of the soil composing the slope are considered to be sandy soil including fine particles. When curating the data required for model training, slope stability analysis was performed in 42,000 cases using the limit equilibrium method. Steady-state seepage analysis of groundwater was also performed, and the results generated were applied to slope stability analysis. Results show that the multilayer perceptron model can predict the factor of safety and failure arc with high performance when the slope's physical properties data are input. A method for quantitative validation of the model performance is presented.

• Plant Journal
• /
• v.17 no.1
• /
• pp.58-66
• /
• 2021

The government has recently come up with a policy to tighten regulations on air pollutant emissions due to public concerns over the emission of pollutants such as fine dust. The coal-fired power plant is speeding up the improvement of the performance of environmental facilities, and this paper deals with the cases of performance improvement by adding a catalyst to the 500 MW standard coal-fired power DeNox system, and examines the change in the performance factors according to the addition of catalysts and the efficiency of NOx removal. The DeNOx efficiency before and after improvement increased from 80% to 88%, and the conversion rate of SO2/SO3, ammonia slip which are performance factors satisfied the design assurance value, but exceeded the design assurance value for differential pressure. At the same time, the ammonia slip concentration and differential pressure items increased as the NOx removal efficiency increased, resulting in the need for management and improvement.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.7
• /
• pp.1159-1169
• /
• 2003

This paper investigates the effects of T-stress and plastic hardening mismatch on the interfacial crack-tip stress field via finite element analyses. Plane strain elastic-plastic crack-tip fields are modeled with both MBL formulation and a full SEC specimen under pure bending. Modified Prandtl slip line fields illustrate the effects of T-stress on crack-tip constraint in homogeneous material. Compressive T-stress substantially reduces the interfacial crack-tip constraint, but increases the J-contribution by lower hardening material, J$\_$L/. For bimaterials with two elastic-plastic materials, increasing plastic hardening mismatch increases both crack-tip stress constraint in the lower hardening material and J$\_$L/. The fracture toughness for bimaterial joints would consequently be much lower than that of lower hardening homogeneous material. The implication of unbalanced J-integral in bimaterials is also discussed.