• 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 Korean Society of Visualization
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• v.18 no.1
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• pp.18-25
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• 2020

The droplet impact behavior is dominated by some parameters such as surface temperature, We number, surface and fluid property. Especially, Leidenfrost effect which prevents the contact between surface and droplet is very powerful phenomenon for determining droplet impact behavior. Due to this effect, the impact regime is divided into contact boiling regime and film boiling regime whether the droplet contact with the surface. Many studies have found that surface micro-structures which processed by surface processing are effective to overcome the Leidenfrost effect. In this study, droplet impact behaviors were compared using ethanol both on flat and laser-ablated Al surface. On the flat surface, impact regime was mainly divided by surface temperature. And there is key dominant parameter for each regime. On the laser-ablated surface, we could see changed impact regime and different impact behavior such as jetting and ejection of tiny droplets despite of same impact conditions.

• Journal of Korean Physical Therapy Science
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• v.18 no.4
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• pp.81-85
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• 2011

Purpose : The purpose of this study was to investigate the changing plantar foot pressure by the backpack load of 0, 10, 15, and 20% of their body weight while level walking in flat foot and so to recommend suitable backpack weight limitations for flat foot subjects. Method : 14 young flat foot subjects($24.29{\pm}2.16yrs$) participated in this study. the subjects were assigned to carry backpack load and there was four level walking modes : (1) unloaded walking(0%), (2) 10% body weight(BW) load, (3) 15% BW load and (4) 20% BW load. Repeated ANOVA was used to compare each region data of foot according to different backpack weight. Results : As backpack load became increased, the contact area of midfoot was significantly increased, and contact area of forefoot and rearfoot were significantly decreased. maximum pressure at each region during walking tended to be greater as the load increased, but a significant difference was found only for the heel medial and lateral regions Conclusion : Based on this data, the weight of backpack could influenced structure and function of the foot in flat foot.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.10
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• pp.974-984
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• 2012

This research introduces a new method to attenuate flip-over vibration generation in the flat blade windshield wiper by adjusting the contact pressure between the windshield glass and the blade. The knocking force in the flip-over action of the blade is decreased by inducing gradual tilting-over along the rubber strip of the blade. This gradual tilting-over is induced by introducing a non-uniform contact pressure distribution between the blade and windshield glass. The contact pressure distribution is adjusted by controlling the unloaded profile of the body spring in the blade using a procedure proposed in a previous study. Two blades, one blade designed to generate a uniform pressure distribution and the other designed to generate non-uniform pressure distribution, are developed using the procedure. Contact pressure distributions of the developed blades are measured using a special device and compared with the intended distributions confirming the similarities between the two groups. Vertical and lateral vibrations of the two blades are measured under realistic operating condition simulated by a wiper test rig. The vertical vibrations of the blade with non-uniform contact pressure are substantially smaller than corresponding vibrations of the blade with uniform contact pressure over the entire rubber strip.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.156-159
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• 2003

Surface normal vector and surface velocity are very important parameters to simulate rolling processes precisely. In this study, Local displacement functions are constructed for each node on the contact surface and parameters are found by the least square fitting of displacement on the neighbor nodes. Deformation gradient tensor is calculated from the displacement function and surface normal vector and velocity also can be derived. Flat rolling simulation model is presented on the basis of the suggested contact scheme. Series of rolling process simulation are carried out and the results are compared with the experiments.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.5
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• pp.128-136
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• 1998

A mathematical model for investigating the form generation mechanism in the centerless infeed grinding process is described. For 3-D modeling of form generation, contact points are assumed to be on least squares contact lines at the grinding wheel, regulating wheel, and work-rest blade. Using force and deflection analysis, the validity of this assumption is shown. Based on the 2-D simulation model developed in the previous work and the least squares contact line assumption, a 3-D model is presented. To validate this model, simulation results were compared with the experimental works. The experiments and computer simulations were carried out using three types of cylindrical workpiece shapes with varying flat length. The experimental results agree well with the simulation. It can be seen that the effect of flat end propagated to the opposite end through workpiece reorientation.

• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.1026-1035
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• 2003

A computer simulation method for investigating the form generation mechanism in the centerless infeed (plunge) grinding process is described. For a 3-D simulation model of form generation, contact points are assumed to be on least squares contact lines at the grinding wheel, regulating wheel, and work-rest blade. Using force and deflection analyses, the validity of this assumption is shown. Based on the 2-D simulation model developed in the previous work and the least squares contact line assumption, a 3-D model is presented. To validate this model, simulation results were compared with the experimental works. The experiments and computer simulations were carried out using three types of cylindrical workpiece shapes with varying flat length. The experimental results agree well with the simulation. It can be seen that the effect of flat end propagated to the opposite end through workpiece reorientation.

• Computers and Concrete
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• v.34 no.2
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• pp.231-245
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• 2024

A 3D discrete element model integrating the rough surface contact concept with the flat-joint model is suggested to examine the mechanical characteristics of the interfacial transition zone (ITZ) in concrete. The essential components of our DEM procedure include the calculation of the actual contact area in an element contact-pair related to the bonded factor using a Gaussian probability distribution of asperity height, as well as the determination of the contact probability-relative displacement form using the least square method for further computing the force-displacement of ITZs. The present formulations are implemented in MUSEN, an open source development environment for discrete element analysis that is optimized for high performance computation. The model's meso-parameters are calibrated by using uniaxial compression and splitting tensile simulations, as well as laboratory tests of concrete from the literature. The present model's DEM predictions accord well with laboratory experimental tests of pull-out concrete specimens published in the literature.

• Journal of International Academy of Physical Therapy Research
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• v.10 no.4
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• pp.1934-1939
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• 2019

Background: Flexible flat foot is that the medial longitudinal arch collapses in weight bearing and returns normal arch when weight is removed and the weight bearing shifts toward medial part of the foot, which can cause pathological problems in the alignment of the lower extremities and the entire body. Objective: To compare the foot pressure for adults with flexible flat foot. Design: Quasi-Experimental Study Methods: 24 participants with flexible flat foot were recruited and were randomly divided into Visual feedback Short Foot Exercise (VSFE) group and Short Foot Exercise (SFE) group. To compare changes of foot pressure about pre and post intervention, the contact pressure measurement was conducted. Results: In the VSFE, significant differences were observed for the foot pressure of the 1^st toe, 1^st, 3^rd and 4-5^th metatarsal, midfoot, medial and lateral heel (p<.05). The foot pressure of the 3^rd and 4-5^th metatarsal, midfoot showed significant differences in the SFE (p<.05). The contact pressure of the 1^st toe, 3^rd metatarsal showed significant differences between the groups. Conclusions: Visual feedback short foot exercise can be useful for moving the pressure from medial to lateral part, and can prevent possible pathological problems.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.9
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• pp.2242-2251
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• 1993

The mesh-based frictional contact model has been developed which does not rely on the spatial derivatives of the tool surface. Only points on the surface are evaluated from the description. which can then be simplified because of the relaxed demands placed on it. The surface tangents, normals, and corresponding derivatives at each finite-element node are evaluated directly from the finite-element mesh, in terms of the connecting nodal positions. The advantages accrue because there is no longer a need for a smooth tool surface to assure reasonable normals and derivatives. Furthermore, it can be shown that the equilibrium equations can only be properly written with a special normal derived from the mesh itself. The validity, accuracy, computation time, and stability of mesh-based contact model were discussed with the numerical examples of rounded flat-top and rough, flat-top rounded punch forming operations. Also, the forming process of a automobile inner panel section was simulated for testing the robustness of new contact model. In the discussion, the superiority of new model was examined, comparing with tool-based contact one.