• Journal of the Korean Society for Precision Engineering
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• v.17 no.5
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• pp.131-136
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• 2000

This paper is concerned with the surface roughness and the bending strength of ground workpiece in ZrO2 ceramic grinding. Surface roughness was measured with surface tracer and bending strength value was obtained by three-point bending test on machining center using tool dynamometer. Grinding experiments were carried out to examine the effects of grinding conditions including diamond mesh size, table speed, and depth of cut on ground surface roughness. The correlation between surface roughness and bending strength was also inspected. The experimental results indicate that the rougher surface is produced as the mesh size of diamond wheel is reduced and table speed is increased, but surface roughness is not affected by depth of cut. The values of bending strength decrease as the values of Ra, Rmax and Ku increase.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.473-477
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• 2000

The experimental study of die-sinking electrical discharge machining(EDM) was conducted for Cold Die Alloy Steel of SKD-11 with rotary electrode according to the peak current of 11A, 15A and 19A, and the duty factor of 0.24, 0.45. dielectric fluid flow through the electrode inside according to the change of electrode internal diameter during the EDM working. Material removal rate(MRR) was increased with flushing & rotation of electrode at the condition for the peak current of 15A, 19a but the MRR is decreased at the flushing only. The more surface roughness was obtained for the case of the flushing & rotation under the peak current of 19A.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.465-470
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• 2000

This paper is concerned with the surface roughness and the bending strength of ground workpiece in ZrO2 ceramic grinding. Surface roughness was measured with surface tracer and bending strength value was obtained by three-point bending test on machining center using tool dynamometer. Grinding experiments were carried out to examine the effects of grinding conditions including diamond mesh size, table speed, and depth of cut on ground surface roughness. The correlation between surface roughness and bending strength was also inspected. The experimental results indicate that the rougher surface was produced as the mesh size of diamond wheel is reduced and table speed is increased, but surface roughness is not affected by depth of cut. The values of bending strength decrease as the values of Ra, Rmax and Ku increase.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.6
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• pp.45-51
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• 1996

Silicon wafers are required to be finished under the roughness of nanometer order for the subsequent chip fabrication processes. Recently, the finish grinding techniques have been researched for the improvement of accuracy and surface roughness simultaneously. Among them, the grinding technique using fine abrasive has been known as an easily accessible method. However, the manufacture of the fine grit grinding wheel has been very difficult because of the coherence of the grits. In this paper, the development of the ultrafine grit silica($SiO_2$) grinding wheel by the combination of the binder coating and the vacuum forming techniques is reported. And, the mechanochemical removal effects of the grinding conditions are discussed. Finally, a successful result of Ra O.4nm. Rmax 4nm in the ground surface roughness of a 6 inch silicon wafer was achieved.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.4
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• pp.72-77
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• 1992

In this study, using in-process tool failure detecting system by AE method in turning machining, we measured AE signal from the tool, and the surface roughness of workpiece and then compared it with tool wear. As a result, we found that tool failure can be predicted by means of surface roughness of the workpiece and it can be predicted more precisely by the arithmetical average roughness (Ra) than by the maximum height of irregularities (Rmax) of the workpiece. Also, we found that we could judge whether it was sudden failure or the wear by means of the shape of AE signal and the range distri- bution of power spectrum frequency when tool danage was happened.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.5
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• pp.529-535
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• 2009

One of the most important things in shipbuilding is to select light and high tensile strength materials. Therefore, the use of Al alloy in shipbuilding become an increase. In cutting the aluminum plate, the quality of the cut surface is strongly influenced by the cutting conditions such as cutting speed, kerf width, plate thickness, cutting materials, and applied gas pressure. The cutting experiment of Al alloy plate(5083) were carried out using LASER cutting machine. The upper and lower of kerf width, the surface roughness(Ra, Rmax) of cut surface were measured under various cutting conditions. The morphologies of cutting surface were also monitored at various cutting conditions. The optimum cutting conditions of Al alloy among tested were indicated.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.18 no.1
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• pp.22-28
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• 2009

In order to optimize the polishing process, Run to Run control scheme has been applied to the micro mold polishing in this study. Also, to fully understand the effect of parameters on the surface roughness a design of experiment is performed. By linear approximation of main factors such as gap and rotational speed of micro quill, EWMA (Exponential Weighted Moving Average) gradual mode controller is adopted as a optimizing tool. Consequently, the process converged quickly at a target value of surface roughness Ra 10nm and Rmax 50nm, and was hardly affected by unwanted process noises like initial surface quality and wear of magnetic abrasives.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.161-163
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• 1996

The correlation coefficients among hepatic extraction fraction(HEF), DISIDA-K, and ICG Rmax methods were found using two normal rabbits and four rabbits with damaged liver. The correlation coefficient between HEF and ICG R-max which is a standard technique in evaluating liver function was found to be 0.93. Therefore HEF is a valuable diagnostic method since it is not only accurate, but possible to estimate remaining liver function after surgical of cancerous hepatic tissue.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.79.1-79.1
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• 2019

We present an algorithm for the fast computation of the general N-point spatial correlation functions of any discrete point set embedded within an Euclidean space of ${\mathbb{R}}n$. Utilizing the concepts of kd-trees and graph databases, we describe how to count all possible N-tuples in binned configurations within a given length scale, e.g. all pairs of points or all triplets of points with side lengths < rmax. Through benchmarking we show the computational advantage of our new graph-based algorithm over more traditional methods. We show that all 3-point configurations up to and beyond the Baryon Acoustic Oscillation scale (~200 Mpc in physical units) can be performed on current Sloan Digital Sky Survey (SDSS) data in reasonable time. Finally we present the first measurements of the 4-point correlation function of ~0.5 million SDSS galaxies over the redshift range 0.43< z <0.7. We present the publicly available code GRAMSCI (GRAph Made Statistics for Cosmological Information; bitbucket.org/csabiu/gramsci), under a GNU General Public License.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.10
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• pp.68-74
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• 1997

The surface finishing system using the micro abrasive film was designed and manufactured to make the mirror surface of the cylindrical workpices. An experimental study of srface finishing was carried out to investigate the performance of mirror surface finishing system. The surface roughness value of stainless steel was about 0.2 .approx. 0.25 .mu. m Rmax, 0.02 .approx. 0.04 .mu. m Ra, using abrasive grain size of 12, 9 .mu. m. The surface roughness value of chrome coated workpiece was about 0.07 .approx. 0.11 .mu. m Ra using abrasive grain size 3 .mu. m. In the same condition, the chrome coated workpiece has obtained better surface roughness charateristics than the one of stainless steel.