• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.3
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• pp.179-186
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• 2024

In this paper, a modification coefficient for equivalent single degree of freedom (SDOF), considering the plasticity range of the member subjected to shock wave type of blast load, was developed. The modification coefficient for the equivalent SDOF was determined through comparison with the analysis of a multi-degree of freedom (MDOF) system. The parameters influencing the equivalent SDOF system analysis were chosen as the boundary conditions of the member and the ratio of the duration of blast load to the natural period of the member. The modification coefficient was calculated based on the elastic load-mass transformation factor. The modification coefficient curve was derived using an elliptical equation to ensure it exists between the upper and lower parameter bounds. Using the modification coefficient on examples with varying cross sections and boundary conditions reduced the SDOF analysis error rate from 15% to 3%. This study shows that using the modification coefficient significantly improves the accuracy of SDOF analysis. The modification coefficient proposed in this study can be used for blast analysis.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.4
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• pp.38-43
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• 2011

Industrial reducer is in general use to Deck Crane. High-precision and high-efficient reducer is minimized the power-loss and energy-loss of a machine. So it contribute the price reduction and life extension. Reducer is usually using the Planetary gear reducer. Planetary gear reducer is composed the sun gear, planet gear, internal gear and casing. Industrial reducer's wear and breakage have a short-life. To solve this problem, it is using the profile-shifted-gear or tooth modification. This study was carried out the effect of addendum modification coefficient on tooth fillet bending strength to planetary reducer. Tooth fillet bending stress is calculate. And all parameter were expressed the function of addendum modification coefficient. And then stress concentration factor of tooth fillet curve was express the function of addendum modification coefficient using comparison between theory and finite element analysis.

• Journal of Mechanical Science and Technology
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• v.15 no.10
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• pp.1434-1441
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• 2001

A computational study has been performed to determine the effects of divergent trailing edge (DTE) modification to a supercritical airfoil in transonic flow field. For this, the computational result with the original DLBA 186 supercritical airfoil was compared to that of the modified DLBA 283. A wavier-Stokes code, Fluent 5. 1, was used with Spalart-Allmaras's one-equation turbulence model. Results in this study showed that the reduction in drag due to the DTE modification is associated with weakened shock and delayed shock appearance. The decrease in drag due to the DTE modification is greater than the increase in base drag. The effect of the recirculating flow region on lift increase was also observed. An airfoil with DTE modification achieved the same lift coefficient at a lower angle of attack while giving a lower drag coefficient. Thus, the lift-to-drag ratio increases in transonic flow conditions compared to the original airfoil. The lift coefficient increases considerably whereas the lift slope increases just a little due to DTE modification.

• Proceedings of the Korean Statistical Society Conference
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• 2003.10a
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• pp.179-182
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• 2003

This study describes a new graphical method for assessing and characterizing effect modification by a matching covariate in matched case-control studies. This method to understand effect modification is based on a semiparametric model using a varying coefficient model. The method allows for nonparametric relationships between effect modification and other covariates, or can be useful in suggesting parametric models. This method can be applied to examining effect modification by any ordered categorical or continuous covariates for which cases have been matched with controls. The method applies to effect modification when causality might be reasonably assumed. An example from veterinary medicine is used to demonstrate our approach. The simulation results show that this method, when based on linear, quadratic and nonparametric effect modification, can be more powerful than both a parametric multiplicative model fit and a fully nonparametric generalized additive model fit.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.1
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• pp.57-61
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• 2006

The research on surface modification technology has been advanced to improve the properties of engineering materials. Ion implantation is a novel surface modification technology that enhances the mechanical, chemical and electrical properties of substrate's surface using accelerated ions. In this research, nitrogen ions were implanted into AC7A aluminum substrates which would be used as molds for rubber molding. The composition of nitrogenion implanted aluminum and distribution of nitrogen ions were analyzed by Auger Electron Spectroscopy (AES). To analyze the modified surface, properties such as hardness, friction coefficient, wear resistance, contact angle, and surface roughness were measured. Hardness of ion implanted specimen was higher than that of untreated specimen. Friction coefficient was reduced, and wear resistance was improved. From the experimental results, it can be expected that implantation of nitrogen ions enhances the mechanical properties of aluminum mold.

• Journal of Industrial Technology
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• v.17
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• pp.183-189
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• 1997

The computation of the flow around a supercritical airfoil with a divergent trailing edge(DTE) modification(DLBA 243) is compared to that of original supercritical airfoil(DLBA 186). For this computation, Reynolds-Averaged Navier-Stokes equations are solved with a linearized block implicit ADI method and a mixing length turbulence model. Results show the effects of the shock and separated flow regions on drag reduction due to DTE modification. Results also show that DTE modification accelerates the boundary layer flow near the trailing edges which has an effect similar to a chordwise extension that increases circulation and is consistent with the calculated increase in the recirculation region in the wake. Airfoil with DTE modification achieves the same lift coefficient at a lower incidence and thus at a lower drag coefficient, so that lift-to-drag ratio is increased in transonic cruise conditions compared to the original airfoil. The reduction in drag due to DTE modification is associated with weakening of shock strength and delay of shock which is greater than the increase in base drag.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.254-259
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• 2004

The research on surface modification technology has been advanced to change the properties of engineering material. Ion implantation is a novel surface modification technology to enhance the mechanical, chemical and electronic properties of mechanical parts. In this research, nitrogen ions are implanted into aluminum for mold to improve endurance and life span. To analyze modification of surface properties, micro hardness, friction coefficient, wear resistance, contact angle, and surface roughness were measured. Hardness of ion implanted specimens was higher than untreated specimen and friction coefficient was also improved. In this experiment, it can be expected that nitrogen ion implantation can contribute to enhance the mechanical properties of material and ion implantation technology may also be applied to other materials.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.158-160
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• 2005

Zener coefficient on cubic shaped particle was proposed. Most previous researches about Zener coefficient were developed on the assumption that the shape of particle is spherical. But, some particle has other shape, and modification of Zener coefficient needs with shape of particle. In this research, TiN particle that has a cubic shape was considered. A Zener coefficient of a cubic shape TiN was theoretically calculated with appropriate assumptions. And, using a semi-empirical method, Zener coefficient was also measured. Finally, the proposed Zener coefficient was proved by comparing with experimentally measured data.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.3
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• pp.299-305
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• 2017

Gate-lifting devices in small- to mid-sized sluice gates mostly employ the mechanical roller rack pinion (RRP) system. This RRP system, which consists of a rack-bar and a pinion, transforms a rotation motion into a linear one. The rack-bar has a series of roller trains that mesh with the pinion. In this study, we adopt an exact involute-trochoid tooth profile of the pinion to obtain a higher contact fatigue strength using the profile modification coefficient. Further, we determine the contact forces and investigate Hertz contact stresses to predict the pitting life of the pinion according to varying the shape design parameters. The results indicate that the design fatigue life of an RRP system for sluice gate can be achieved only when the design value of the profile modification coefficient reaches or exceeds a certain level.

• KSTLE International Journal
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• v.9 no.1_2
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• pp.26-30
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• 2008

This study examined the surface modification characteristics of NBR using sealing in automobile. Surfaces of NBR were modified by RF power Ar plasma treatment. In experiment, pressure, flux, temperature were fixed and RF bias voltage. Treatment time was changed. In friction test, we used PTFE grease. After modification, surfaces of NBR showed many grooves, hydrophilic functional groups, and lipophilic functional groups. As increasing treating voltage and time, the amount of them was increased. And wetting angle and friction coefficient was decreased with increasing treating voltage and time. However, the pattern of changing friction coefficient was not fixed.