• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.21-25
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• 2000

An inverse finite element approach is employed for more capability to design the optimum blank shape from the desired final shape with small amount of expense and computation time For multi-stage sheet metal forming processes numerical analysis is expense difficult to carry out the to its complexities and convergence problem. It also requires lots of computation time. For the analysis of elliptic cup with large aspect ratio intermediate sliding constraint surfaces are difficult to describe. in this paper multi-stage finite element inverse analysis is applied to multi-stage elliptic cup drawing processes to calculate intermediate blank shapes and strain distributions in each stages. To describe intermediate sliding constraint surfaces an analytic scheme is introduced to deal with merged-arc type sliding surfaces.

• Tribology and Lubricants
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• v.24 no.6
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• pp.326-331
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• 2008

The contact surfaces between mold and target should be in parallel for a proper imprinting process. However, large size of contacting area makes it difficult for both mating surfaces (mold and target planes) to be in all uniform contact with the expected precision level in terms of thickness and position. This is caused by the waviness of mold and target although it is very small relative to the area scale. The gripping force for both mold and target by the vacuum chuck is other major effect to interrupt the uniform contact, which must be avoided in imprinting mechanism. In this study, the cause of non-conformal contact mechanism between mold and target is investigated with the consideration of deformation due to the vacuum gripping for the size $470{\times}370\;mm^2$ LCD panel.

• Journal of the Korean Geographical Society
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• v.38 no.2
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• pp.156-172
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• 2003

In this paper we identify that there are High Higher surfaces(HH-surface) around Jeongdongjin and Daejin area where Higher surfaces(H-surface) of marine terrace are formed on a large scale. On the basis of an altitude of the ancient shoreline of the marine terraces, geomorphic surfaces can be classified into HH I (140m a.s.l), HH II (110m a.s.l), H I (90m a.s.l), H II (70m a.s.l), M (40m a.s.l), L I (25m a.s.l) and L II (10m a.s.l). Besides, we identify that the lowest surfaces(5~6m a.s.l) are found extensively in the research area which are assumed to be formed in the Holocene. Considering that the formation mechanism of the marine terraces in the research area is similar to that of the marine terraces at both Campo area in the south east coastal region of Korea md the thalassostatic terraces of Osip River in Samchuk in a short distance from the research area, we can assume that the HH-surfaces in both areas were formed in the same period. Based on the fact that L I- surface was formed on the Last Interglacial Stage of MIS 5, we can infer that M- was formed in MIS 7, H I- in MIS 9, H II- in MIS 11, HH I- in MIS 13 and HH II- in MIS 15. The reason for that H-surfaces, similar to those at Gampo area, to remain on a large scale is that the Holsteinian Interglacial continued for a long period of time and at that time there was a large wave-cut platform in the vicinity of the shoreline.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.06a
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• pp.159-165
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• 2000

In this paper the residual stresses on lubricated sliding surfaces were measured during break-in procedure and up to scuffing by the X-ray diffraction method. The cylinder-on-disk type tribometer was used with the line-contact geometry. Scuffing tests were done using a constant load. In the break-in procedure the loads were increased from very low values in several steps. It was found that the sliding surfaces with break-in represented relatively higher values of residual compressive stresses than those without break-in. The residual stresses below the surfaces showed the small amount of stress increases. The results of scuffing tests with and without break-in showed the same trends as break-in tests did. However, in case of tests with break-in procedure the stresses below the surfaces showed very large increases in the residual compressive stresses. From the tests of break-in and scuffing, it was found that the increases in scuffing lives were related with the increases of residual stresses on the lubricated sliding surfaces with break-in.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1588-1590
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• 1997

The viewing angle characteristics of amorphous(a)-twisted nematic(TN)-liquid crystal display (LCD) on poly(vinyl)cinnamate (PVC) surfaces with photo polymerrization were investigated. It was found that the threshold voltage increases with increasing the polymerization of PVC surfaces. That the domain size of a-TN-LCD is affected by the surface crystallization with increasing the photo polymerization of the photo-alignment film. We observed that the viewing angle of a-TN-LCD increased with increasing the photo polymerization on PVC surfaces. Finally, we consider that the viewing angle of a-TN-LCD on PVC surfaces is large compared to a-TN-LCD on polyimide(PI) surface.

• Journal of electromagnetic engineering and science
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• v.18 no.2
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• pp.136-140
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• 2018

We propose an improved semi-empirical scattering model for X-band radar backscattering from rough sea surfaces. This new model has a wider validity range of wind speeds than does the existing semi-empirical sea spectrum (SESS) model. First, we retrieved the small-roughness parameters from the sea surfaces, which were numerically generated using the Pierson-Moskowitz spectrum and measurement datasets for various wind speeds. Then, we computed the backscattering coefficients of the small-roughness surfaces for various wind speeds using the integral equation method model. Finally, the large-roughness characteristics were taken into account by integrating the small-roughness backscattering coefficients multiplying them with the surface slope probability density function for all possible surface slopes. The new model includes a wind speed range below 3.46 m/s, which was not covered by the existing SESS model. The accuracy of the new model was verified with two measurement datasets for various wind speeds from 0.5 m/s to 14 m/s.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.509-509
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• 2011

Superhydrophobic surfaces on alloyed steels were fabricated with a non-conventional method of plasma etching and subsequent water immersion procedure. High aspect ratio nanopatterns of nanoflake or nano-needle were created on the steels with various Cr content in its composition. With CF4 plasma treatment in radio-frequence chemical vapor deposition (r.-f. CVD) method, steel surfaces were etched and fluorinated by CF4 plasma, which induced the nanopattern evolution through the water immersion process. It was found that fluorine ion played a role as a catalyst to form nanopatterns in water elucidated with XPS and TEM analysis. The hierarchical patterns in micro- and nano scale leads to superhydrophobic properties on the surfaces by deposition of a hydrophobic coating with a-C:H:Si:O film deposited with a gas precursor of hexamethlydisiloxane (HMDSO) with its lower surface energy of 24.2 mN/m, similar to that of curticular wax covering lotus surfaces. Since this method is based on plasma dry etching & coating, precise patterning of surface texturing would be potential on steel or metal surfaces. Patterned hydrophobic steel surfaces were demonstrated by mimicking the Robinia pseudoacacia or acacia leaf, on which water was collected from the humid air using a patterned hydrophobicity on the steels. It is expected that this facile, non-toxic and fast technique would accelerate the large-scale production of superhydrophobic engineering materials with industrial applications.

• Journal of Power System Engineering
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• v.21 no.2
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• pp.57-63
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• 2017

The large-eddy simulation(LES) was carried out to evaluate the drag and static pressure acting on the blade surface of a small-size axial fan(SSAF) under the condition of unsteady-state, incompressible fluid and three-dimensional coordination. The axial component of drag coefficient increases with the increase of operating load, but the radial components have negligible sizes regardless of operating loads. Otherwise, the static pressures acting on the blade surfaces of SSAF show different distributions around the operating point of D equivalent to the stall. Also, with the increase of operating load, the static pressures acting on the pressure and suction surfaces of blade concentrate at the tips and leading-edges as a whole.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.5
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• pp.1133-1138
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• 2012

In the paper, design of nonlinear sliding surfaces which are based on optimal control is studied, The state trajectory by the input of optimal control was obtained by Frobenius theorem and matrix decomposition method, was set the nonlinear sliding surfaces of the system. The states is maintained to sliding surfaces from initial states. As the result, robustness of the system can be guaranteed throughout an entire response of the system starting form the initial time instance, the uncertainty and external disturbance that can occur during the reaching time is removed, the problem of large control input was solved, and setting the sliding surfaces optimal path was able to reduce the tracking time. The validity of the proposed control scheme is shown in computer simulation for inverted pendulum.

• Journal of Biosystems Engineering
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• v.1 no.1
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• pp.49-54
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• 1976

No reliable basic data were available on the kinetic friction coefficients between grains and frictional surfaces being used in grain handling equipments in Korea. In order to determine appropriate kinetic friction coefficient between three grains (Tongil, Jinheung, barley) and two surfaces at four levels of moisture content of grain, the laboratory tests using the newly designed experimental apparatus and strain gage measuring system were carried out, and the relationship among factors that affect kinetic friction coefficients of grains were analyzed. The results of this study are summarized as follows ; 1. Kinetic friction coefficient of samples being tested was dependent on surfaces and moisture content of grains . The ranges of them were 0.369-0.512 for Tongil variety , 0.347-0.469 for Jinheung variety, and 0.360-0.502 for barley, respectively. 2. There was a little difference of kinetic friction coefficients between two varieties of rice at the same testing conditions. Because the interaction had been large among treatments , each value of kinetic friction coefficient determined in this study should be used only for the corresponding conditions in this study . 3. Kinetic friction coefficients in creased linearly with increase in moisture content of grains and their regression equations were shown in Table.4. 4. Kinetic friction coefficients on a PVC surfaces was shown a little lower values than on the steel surfaces at various moisture levels, but especially in Jinheung and barley, a big difference was shown.