• Journal of Welding and Joining
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• v.32 no.6
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• pp.35-40
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• 2014

The contact tip for gas metal arc welding has important functions to transmit the welding current to the wire and to guide the wire to molten pool. If the contact tip is damaged, it is a cause of lowering the welding productivity due to removal of welding defects and replacement of contact tip. In case of the use of a contact tip for a long time the arc is unstable because the processed hole in the contact tip center is larger, and the variation of aiming position of the welding wire causes a seam tracking error. In this study, gas metal arc welding experiments using contact tip of three different materials were performed. The contact tips with Cu-P, Cu-Cr, and Cu-ODS were used at the experiments, and the welding characteristics by each contact tip were evaluated. After welding contact tip appearance, welding spatter adhesion amount of the nozzle, and weld bead appearance were evaluated. The welding current and welding voltage were measured to verify arc stability during arc welding.

• Transactions of Materials Processing
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• v.12 no.1
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• pp.34-42
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• 2003

This paper presents a rigid-plastic finite element method to handle the frictional contact problem between two deformable bodies experiencing large deformation. The variational formulation combined with incremental quasi-static model is employed for treating the contact boundary condition. The frictional behavior of the model obeys Coulomb's law of friction. The proposed contact algorithms are classified into two categories, one for searching contacting nodes and the other for calculating contact forces at the contact surface. A slave node and master contact segment are defined using the geometric condition of finite elements on the contact interface. The penalty parameter is used to limit the penetration between contacting bodies, and the finite elements are coupled with contact boundary elements.us gates and cavity thicknesses. Through this study we have observed that the jetting is related to the die swell of material. This means that the jotting is strongly affected by the elastic flow property rather than the viscous flow property in viscoelastic characteristics of molten polymer. Different resins have different elastic properties, and elastic flow behavior depends on the shear rate of flow, i.e. injection speed. Large die swell would eliminate jetting however, the retardation of die swell would stimulate jetting. In the point of mole design, reducing the thickness ratio of cavity to gate can reduce or eliminate jetting regardless of amount of elasticity of polymer melt.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.455-457
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• 1999

In this paper, the wearing characteristics of current collecting shoes, interruption phenomena and contact resistances between collecting shoes and conductor rails are established as design parameters for development of the third rail current collector. An experimental analysis for established design parameters is performed as the materials of current collector shoe, contact force, sliding velocity and contact condition(dry/wet condition) between current collectors shoe and conductor rails. As a result of this study, the magnitude of contact force is in proportion to the amount of wear in the collecting shoe, but is in inverse proportion to the interruption and contact resistance between the collecting shoe and the conductor rail. And optimal values of design parameters are pre sented through analyzing the experimental results of the amount of wear, interruption and contact resistance.

• The Journal of Advanced Prosthodontics
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• v.11 no.2
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• pp.88-94
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• 2019

PURPOSE. This study was conducted to investigate patterns of adjacent tooth displacement in the posterior implant with interproximal contact loss (ICL) by 3-D digital superimposition method. MATERIALS AND METHODS. Posterior partially edentulous patients, restored with implant fixed partial prostheses before 2011 and suffered from food impaction of ICL between 2009 and 2011, were included. Two dental casts, at the time of delivery and at the time of food impaction in a same patient, was converted into 3-D digital models through scanning and superimposition was performed to assess chronologic changes of the dentition. Directions of tooth displacement were evaluated and the amount of ICL was calculated. Correlations between the amount of ICL and elapsed time, or between the amount of ICL and age after function, were assessed at a significance level of P<.05. RESULTS. A total number of 13 patients (8 males, 5 females) with a mean age of $65.76{\pm}9.94years$ and 17 areas (4 maxillae, 13 mandibles) were included in this retrospective study. Teeth adjacent to the implant restoration showed complex displacements but characteristic tendency according to the location of the arch. The mean amount of ICL was $0.33{\pm}0.14mm$. Elapsed time from function to ICL was $61.47{\pm}31.27months$. There were no significant differences between the amount of ICL and elapsed time, or age (P>.05). CONCLUSION. Natural teeth showed various directional movements to result in occlusal change in the arch. The 3-D superimposition of chronologic digital models was a helpful method to analyze the changes of dentition and individual tooth displacement adjacent to implant restoration.

• Polymer(Korea)
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• v.38 no.2
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• pp.220-224
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• 2014

Protein adsorption kinetics was studied with the amount of proteins adsorbed to contact lens hydrogels over time scales. Hydroxyethylmethacrylate (HEMA) and silicone hydrogels were dipped in protein solutions (albumin or IgG) and adsorption amounts were measured over time scales. The amount of protein adsorbed to both hydrogel types increased rapidly in 10 min, and remained consistently in 90 min. Decreasing interfacial energetics was taken slowly up to an hour in spite of rapid diffusion of protein molecules. This is due to the fact that water deprivation from three dimensional interphase initially formed by protein diffusion took over an hour. Interpretation of adsorption kinetics on contact lens hydrogels was discussed with understanding of relationship between surface energy and protein adsorption capacity.

• Journal of Surface Science and Engineering
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• v.45 no.6
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• pp.226-231
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• 2012

Characteristics of carburized surface layers in 0.18C-3.5Ni-1.5Cr-0.2Mo steels for main shaft bearings of wind turbines have been analyzed and evaluated before and after rolling contact fatigue tests. Mixed microstructure consisting of retained austenite and tempered martensite has been formed with compressive residual stresses in the surface hardened layers of the specimens showing uniform hardness distribution with value about Hv700 after vacuum carburizing and tempering. It has been found on the raceway of the layers of the specimens after rolling contact fatigue tests that the amount of retained austenite decreased and compressive residual stresses increased, resulting from cyclic contact stresses applied during the tests. It has been also revealed that higher durability of the bearings can be obtained through controlling the amount of the retained austenite in the surface of the bearing steels to be lower in this study.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.3
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• pp.285-295
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• 2016

A contact strip shape of a high speed train pantograph system was optimized with CFD to increase the aerodynamic performance and stability of contact force, and the results were validated by a wind tunnel test. For design of the optimal contact strip shape, a Kriging model and genetic algorithm were used to ensure the global search of the optimal point and reduce the computational cost. To enhance the performance and robustness of the contact strip for high speed pantograph, the drag coefficient and the fluctuation of the lift coefficient along the angle of attack were selected as design objectives. Aerodynamic forces were measured by a load cell and HWA (Hot Wire Anemometer) was used to measure the Strouhal number of wake flow. PIV (Particle Image Velocimetry) was adopted to visualize the flow fields. The optimized contact strip shape was shown a lower drag with smaller fluctuation of vertical lift force than the general shaped contact strip. And the acoustic noise source strength of the optimized contact strip was also reduced. Finally, the reduction amount of drag and noise was assessed when the optimized contact strip was applied to three dimensional pantograph system.

• Korean Journal of Child Studies
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• v.35 no.5
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• pp.83-98
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• 2014

This study examined the influences of eye-contact upon the relationship between mothers' control behaviors and emotions of preschool children. The participants of this study were 66 children aged 6, and their mothers. The children and mothers were observed taking part in a writing task for 15 minutes, and two coders analyzed the amount of eye-contact between children and mothers, mothers' verbal and nonverbal support and coercive control, and children's emotions in the task setting. The results showed that mothers' coercive control and nonverbal support significantly accounted for children's negative and positive emotions, respectively. In addition, the interaction between eye-contact and mothers' verbal support was significant. In particular, mothers' behaviors significantly affected children's emotions only when eye-contact occurred. Mothers' behaviors in the absence of eye-contact did not affect children's emotions. The discussion section included an analysis of the social function of eye-contact on the verbal and nonverbal communication between mothers and children, and suggestions for future study were also presented.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.6
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• pp.969-974
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• 1987

High value sheet resistance (Rs, 350 \ulcorner/ -80 K \ulcorner/ ) borom implanted polysilicon resistors were fabricated under process condition compatible with bipolar integrated circuits fabrication. This paper includes the effect of contact ion implantation on Rs and the effect of electron gun(e-gun) deosition vs. non e-gun evaporated metal contacts on the Rs. From results, we observed that the contact ion implanted samples showed higher Rs value than those without contact ion implantation. Also, it was shown that there is noticeable amount of Rs degradation for e-gun samples, while sputtered samples expressed little Rs degradation after PtSi was formed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.292-300
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• 1995

According to the number of cold-rolled coils, the amount of roll wear and thermal expansion, and roll gap profile were calculated, by using the actual data from the finishing mill. Also, based on those data, the calculations of the deflection, the flattening, and the contact pressure of vwork rolls and backup rolls were made respectively. Specially, in the calculation of contact pressure, the numerical results were obtained not only during the normal rolling, but also during the abnormal rolling, by modeling mathematically the dynamic impact force which occurs when the head section of the strip is threading through rolls. With those results the growth of the fatigue region and the fatigue damage of rolls were predicted. Also the optimum roll-grinding depth was determined to maximize the roll life.