• Proceedings of the Korean Society for Quality Management Conference
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• 1998.11a
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• pp.680-695
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• 1998

The objective of this study is to optimize the responses of the creep feed ceramic grinding process simultaneously by an off-1ine multicriteria optimization methodology. The responses considered as objectives are material removal rate, flexural strength, normal grinding force, workpiece surface roughness and grinder power. Alumina material was ground by the creep feed grinding mode using superabrasive grinding wheels. The process variables optimized for the above objectives include grinding wheel specification, such as bond type, mesh size, and grit concentration, and grinding process parameters, such as depth of cut and feed rate. A weighting method transforms the multi-objective problem into a single-objective programming format and then, by parametric variation of weights, the set of non-dominated optimum solutions are obtained. Finally, the multi-objective optimization methodology was tested by a sensitivity analysis to check the stability of the model.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1566-1570
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• 2005

The aspherical lenses are used as optical lens of HMD optical system. The optimum cutting condition of PMMA lens sample with ultra precision SPDT, the diamond tool nose radius, the cutting speed, the feed rate, the depth of cut, and cutting fluid type are found. The demanded surface roughness 10 nm Ra, aspherical form error $1.0\;\mu{m}$ P-V for aspherical lens of optical data storage device are satisfied.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1552-1560
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• 1994

Glasses in K2O-Na2O-MgO-Al2O3-SiO2-F system were crystallized to prepare machinable glass-ceramics. The optimum nucleating and crystal growing temperatures were approximately $700^{\circ}C$ and 1060~112$0^{\circ}C$, respectively for the samples investigated. Crystalline phases of sellaite, norbergite, and fluorphlogopite appeared progressively as heat-treatment temperature was increased. Surface roughness of the crystallized specimens after the machining was similar to that of metal aluminum (2.18 ${\mu}{\textrm}{m}$). Thermal expansion coefficient, Vickers hardness and dielectric constants of the fluorphlogopite glass-ceramics prepared were 7.37~10.21 ($\times$10-6/$^{\circ}C$), 302~456kgf/$\textrm{mm}^2$ and 5.97~16 respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.439-442
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• 2002

The interface between two different materials in the insulation systems is the weak-link in the underground power transmission systems, In this paper, Optimum conditions of the interface between Epoxy and EPDM is studied. The variation factor condition of interface is roughness of surface, spreading of oils, interfacial pressure and temperature. The breakdown times under the constant voltage below the breakdown voltage were also gained. The breakdown voltage at the after laying time equivalent to is calculated by the V-t characteristic and the inverse power law. When this is done, the characteristic life exponent n is used and the long time breakdown voltage can be evaluated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.535-538
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• 2002

Cube-textured Ni substrates for YBCO coated conductors were fabricated by cold-rolling and annealing of Ni powder compacts. To establish the optimum sintering temperature, tensile test was performed for the Ni rod sintered at various temperatures. The Ni rods prepared at above 100$0^{\circ}C$ showed good mechanical properties due to the complete densification of the Ni rods. The Ni rods were rolled to final thickness of 100 ${\mu}{\textrm}{m}$ and then annealed at 100$0^{\circ}C$ for various annealing time for texture development. The texture analysis made by 2 $\theta$ scan and pole-figure showed that the cube texture was developed in a short time of a few munitues. The FWHM of in-plane and out of plane texture of the prepared Ni tapes was 8-10$^{\circ}$. The AEM surface roughness of the Ni tapes was as smooth as 3 nm.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.6
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• pp.901-907
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• 2008

The measurements of velocity vectors are made in the wake(X/d=8) of a circular cylinder with arc grooves. The experiments are conducted by changing the groove number. groove depth, Reynolds number(Re) and the angle of the first formed groove. We know that the optimum groove angle is 70 degree and the wake velocity profiles are improved at a few conditions. According to vortex shedding frequency distributions. the key solutions to vary the flow field behind the circular cylinder are 70 degree groove angle and more deeper grooves than 0.2mm depth.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.927-931
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• 1997

In process of the finish face milling of the hardended STD11 steel(H /sab r/ c50,55) by CBN tool, the optimum tool shape is suggested,which can minimize the tool fracture and by chipping by impact. The obtained results are as follows. (1) The optimal chamfer angel was about 25 .deg. , and the suitable chamfer width was 0.2mm. (2) The nose radius of tool was most excellent at 1.2mm in the viewpoint of tool wear and surface roughness. (3) Wear speed was effected by sintering method of CBN tool B.U.E

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.4
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• pp.37-42
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• 2004

End-milling have been widely used in aircraft, automobile part and moulding industry. However, various working factors such as spindle speed, feed rate and depth of cut in end-milling have an effect on spindle vibration. There it is demanded the quantitative analysis of spindle vibration in order to get the optimum surface roughness. This study was carried out to analyze an influence of working factors on spindle vibration by design of Experiment. The results are shown that mathematical model of regression equation for an influence of working factors on vibration acceleration of spindle in end-milling by regression analysis is presented.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.113-114
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• 2005

We present the effect of substrate temperature on the structural and optical properties of ZnO films grown on sapphire substrate by pulsed laser deposition. Growing at higher substrate temperature results in an increase in the surface roughness. The optimum c-axis orientation of the ZnO films occurs at the substrate temperature of 700$^{\circ}C$ The decay time shows a rapid increase in the substrate temperature from 400$^{\circ}C$ to 500$^{\circ}C$ and falls down gradually as the substrate temperature is approached to 700$^{\circ}C$.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.276-279
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• 2004

The factors affecting Ni-Co alloy electroforming were investigated to determine the optimum bath composition and electroplating parameters, like pH, temperature, and current density, suitable for high speed fabrication of a micro mold with longer lifetime. To obtain alloy deposits having uniform thickness and composition, electroplating parameters were finely tuned with home-made electroforming apparatus. Ni-Co alloy deposits had linearly increased Co with $Co^{2+}$ ion concentration in electroplating bath, and showing $412H_v$ of Victors hardness at $23wt\%$ of Co content. For Ni-Co alloy, sulfonate and diol related organic additives were very effective to alleviate its residual stress and surface roughness. The maximum deposition rate was $106{\mu}m/hr$ at 10ASD and the tensile strength of alloy deposit was 2 times larger than that of Ni only case.