• The KIPS Transactions:PartB
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• v.14B no.4
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• pp.241-248
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• 2007

An L-curve corner detection method is proposed for the determination of the regularization parameter in optical flow estimation. The method locates the positive peak whose curvature difference from the just right-hand negative valley is the maximum in the curvature plot of the L-curve. while the existing curvature-method simply finds the maximum in the plot. Experimental results show that RMSE of the estimated optical flow is greater only by 0.02 pixels-per-frame than the least in the average sense. The proposed method is also compared with an existing curvature-method and the adaptive pruning method, resulting in the optical flow estimation closest to the least RMSE.

• Tribology and Lubricants
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• v.31 no.4
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• pp.163-169
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• 2015

This paper describes a design method for the corner radius of a contacting body using the theoretical approach of contact mechanics. A complete contact, as in the case of a sharp-cornered punch, produces singular contact traction: whereas, in an incomplete contact, the singular contact traction disappears because of the rounded corners, and the contact edges are within the rounded regions. The design method aims to determine the conditions of the contact force as well as the material properties in an incomplete contact. The incomplete contact changes into the complete contact again when the contact edges exceed the rounded regions owing to either an increased contact force or the compliance of the materials. The contact length of a rounded punch is used as a parameter to derive the required conditions. As a result, a design formula is obtained, which provides a minimum allowable radius when the materials, normal contact force, and the length of a flat region of the punch are predetermined. This work consists of two parts: Part I includes a theoretical background, design method, and formula, and Part II describes the actual process with the investigation of design parameters.

• Tribology and Lubricants
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• v.31 no.4
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• pp.170-176
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• 2015

As a continuation of Part I, which developed a design formula of the minimum corner radius (R_min) for restraining tribological failures, Part II investigates design parameters such as material properties and contact force. As design examples, Al 7075-T651, SST 304 and HT-9 are chosen for the materials and 1, 10 and 100 kN are used for the forces. The results show that the difference in R_min decreases as either the elastic modulus increases or the contact force decreases. Given the same material and force, the permissible R_min decreases as the flat region increases and vice versa. Because the R_min values obtained from the examples are very small, the dimensions of the corner radius normally designed in engineering structures are regarded acceptable. The von Mises stress evaluated for a typical example, which is far below the yield strength, confirms this interpretation. Nevertheless, the present work can provide a design criterion as well as a guideline for quality control in the manufacturing of, in particular, contact corners, which has not been attempted before to the best of the author’s knowledge. In addition, this paper considers the problem of a step that may be formed in the contact contour by using a similar approach. The result shows that no size of the step is permissible.

• Computational Structural Engineering
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• v.10 no.2
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• pp.131-138
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• 1997

This paper concerns the stress singularity at the interface corner of the viscoelastic adhesive layer bonded between rigid adherends, subjected to a uniform transverse tensile strain. The characteristic equation is derived in the Laplace transformed space, following Williams, and the transformed characteristic equation is inverted analytically into real time space for the viscoelastic model considered here. The order of the singularity is obtained numerically. The time-domain boundary element method is employed to investigate the nature of stresses along the interface. Numerical results show that the order of the singularity increases with time while the free-edge stress intensity factors are relaxed with time.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.185-191
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• 2008

The aerodynamic losses so attributed to the endwall - usually termed secondary flow losses or secondary losses - can be as high as 30$\sim$50% of the total aerodynamic losses in a blade or stator row. Inlet guide vanes, with lower total turning and higher convergence ratios, will have smaller secondary losses, amounting to as much as 20% of total loss for an inlet stator row. These are important part for improving a turbine efficiency. The present study deals with a leading edge chamfer groove on a wing-body to investigate the vortex generation and characteristics of a horseshoe vortex with the installed height, and depth of the groove. The current study is investigated with $FLUENT^{TM}$.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.2
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• pp.26-34
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• 2009

Secondary flow losses can be as high as 30~50% of the total aerodynamic losses for a turbo-machinery blade or stator row. These are important part for improving a turbine efficiency. Therefore, many studies have been performed to decrease the secondary flow losses. The present study deals with the chamfered leading-edge at a generic wing-body junction to decrease the horseshoe vortex, one of factors to generate the secondary flow losses, and investigates the vortex generation and the characteristics of the horseshoe vortex with the chamfered height, and depth of the chamfer by using $FLUENT^{TM}$. It was found that the total pressure loss for the best case can be decreased about 1.55% compare to the baseline case.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.3
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• pp.121-128
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• 2021

Piloti-type buildings in Korea are usually composed of lower frames and upper shear wall structures. Piloti-type buildings have been seriously damaged during earthquakes because of the construction of soft and weak stories. Piloti-type buildings with edge cores are two-way unsymmetric planes. This paper analyzed and obtained the dynamic response for structures modeled using a multistory two-way asymmetric system. The numerical results, obtained using the Newmark-β method, show the time-history responses and trends of maximum displacements and shear forces. The purpose of this study is to evaluate the effect of reinforcement on dynamic response when a shear wall or brace is reinforced in the corner opposite the piloti.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.1
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• pp.97-106
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• 2011

Purpose: This review article was written to theoretically compare the depressing force (pressure, adhesion) to the cornea between when the spherical lenses were being tightly and flat fitted. Methods: Mathematical equations and their numerical solution programs (model) were formulated to calculate the depressing (adhesion) force to the cornea by both the tightly and flat fitted contact lenses. Based on this proposed model the effects of parameters characterizing a contact lens such as BCs, diameters, edge shape and corneal shape (ratio of long and short corneal axis, p) on the depressing force to the cornea were predicted/analyzed in both tightly and flat fitting regimes. Results: Corneal adhesion increased as the corneal p-value increased. Adhesion increase caused by the increased p-value was much larger in flat fitted case than in tight fitted one. Corneal adhesion reduced abruptly as the BC increased in flat fitting regimes while the adhesion rise was insignificant in tight fitting ones. Reduction in corneal adhesion due to lens-size increase was predicted to be insignificant in both tight and flat fitting regimes. Both the lens edge shape (edge angle) and thickness were relevant only in tight fitting regime. Corneal adhesion increased as the increased with tight-fitted lenses. As the thickness of tight fitted lenses increased, corneal adhesion inversely decreased. Conclusions: The two most significantly affecting the depressing force to cornea were found to be the degree of corneal bending toward the periphery and the BCs of lenses.

• Journal of the Mineralogical Society of Korea
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• v.17 no.3
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• pp.235-243
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• 2004

Illite has been known to adsorb Cs preferentially to other alkali cations, especially at lower Cs concentration due to the frayed edge site. This frayed edge site was only verified by isotherm experiments, but not by other analytical methods. To investigate the Cs sorption properties on the surface of illite, artificially weathered illite with increasing frayed edge sites was reacted with Cs at different solution concentrations. The illite was weathered f3r 1 hour, 2 days, 14 days in 0.001 M HCl solution. With increasing reaction time, increasing amount of K in solution was observed, indicating formation of frayed edges by weathering, which was also verified by XRD, SEM, and TEM analysis. Original and weathered illites were converted to the homoionic Na form and reacted with $10^{-3}$ / ～ $10^{-7}$ M CsCl solutions for 24 hour. The aspect of Cs sorption was clearly distinguished around $10^{-5}$ M Cs concentration. The relative Cs amount sorbed on illite at low concentration (<10$^{-5}$ M) was higher than high concentration and increased with decreasing Cs concentration. In general, the amount of sorbed Cs increases with increasing weathering time and this trend is more noticeable at lower concentration while not much differentiated with weathering time at high concentration. These results indicate that the selective Cs sorption site exists in illite at low concentration, known as frayed edge site, and the number of those sites increases with weathering time.

• Journal of the Korean Geosynthetics Society
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• v.12 no.2
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• pp.55-66
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• 2013

The experiment of model soil structures has been executed for the soil retaining wall in various conditions of excavation, in this study, to analyze the behavior of the corner of opening. The ground for experiment has been constituted with the sandy soil of relatively loose density, the construction condition has been divided into the opening length of corner, embedded depth, existence of strut, etc., and the excavation has been carried out for 4 stages in total. The behavior characteristics at the corner of opening area has been verified by concentrate analysis of the displacement of wall and the subsidence of ground surface, for each construction and excavation condition, using the measuring instrument mounted inside the model soil structure. In the result of experiment, it has been analyzed that the opening area of corner is unstable structurally compared to the linear area, as it shows that the wall displacement and subsidence of ground surface have been increased when the opening length of corner gets longer. The longer the embedded depth, ground surface settlement of coner was decreased 40%. To apply deeper embedded depth than designed estimate was an advantage in the safety. As a result of the analysis of coner behavior with added struts, maximum surface settlement and maximum horizontal displacement was evaluated 40% and 30%, respectively. Hence increased embedded depth with the added struts in coner edge was effective in the safety.