• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.04b
• /
• pp.451-456
• /
• 1995

This study investigates the feasibility of the real time detection of tool breadage in face milling operation. The proposed methodology using an ART2 neural network overcomes a cumbersome task in terms of the learning or determining a threshold value. The features taken in the researchare the AR parameters modelled from a RLS, and those are proven to be good features for tool breakage from experiments. From the results of the off line application, we can conclude that an ART2 neural network can be well applied to the clustering of tool states in real time regardless of the unsupervised learning.

• Progress in Superconductivity
• /
• v.3 no.1
• /
• pp.60-64
• /
• 2001

We have studied properties of step-edge Junction prepared with crystal orientation of sapphire substrate. The Step on sapphire substrates fabricated by conventional photolithography method and Ar ion milling method. $CeO_2$ buffer layer and in-situ YBCO thin film were deposited on the stepped sapphire substrates by a pulsed laser deposition method with the predetermined optimized condition. The step angle was centre fled low angle of about $25^{\circ}$. The YBCO film thickness was varied to obtain various thickness ratios of the film to the step height in a range from 0.7 to 1.2. I-V curves of junction were showed RSJ-behavior, double junction structure, and hysteresis due to the crystal orientation of substrate.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2003.02a
• /
• pp.51-54
• /
• 2003

We investigated the quench characteristics of thin film type SFCLs with shunt layers of various thickness. The SFCLs ware based on 2 inch diameter YBa$_2$Cu$_3$O$_{7}$ thin films coated in-situ with a gold shunt layer. The shunt layer thickness was varied by Ar ion milling. The limiters were tested with simulated fault currents at various source voltages. The thinner the shunt layer was, the slower was the rise of SFCL temperatures. This means SFCLs of thinner shunt layers had higher voltage ratings. The voltage rating was approximately inversely proportional to the square root of the shunt layer thickness. This result could be understood through the concept of heat balance.e.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2003.02a
• /
• pp.242-245
• /
• 2003

We investigated the quench characteristics of thin film type SFCLs with shunt layers of various thickness. The SFCLs ware based on 2 inch diameter YBa$_2$Cu$_3$3O$_{7}$ thin films coated in-situ with a gold shunt layer. The shunt layer thickness was varied by Ar ion milling. The limiters were tested with simulated fault currents at various source voltages. The thinner the shunt layer was, the slower was the rise of SFCL temperatures. This means SFCLs of thinner shunt layers had higher voltage ratings. The voltage rating was approximately inversely proportional to the square root of the shunt layer thickness. This result could be understood through the concept of heat balance.e.

• Journal of the Korean Ceramic Society
• /
• v.34 no.8
• /
• pp.834-842
• /
• 1997

Controlled Ca impurity implanted inner crack-like pore in the high purity alumina single crystal, sapphire, had been created by micro-fabrication technique, which includes ion implantation, photo-lithography, Ar ion milling, and hot press technique. The morphological change and the healing of cracklike pore in Ca doped high purity single crystal alumina, sapphire, during high temperature heat treatment in vacuum were observed using optical microscopy. The dot-like surface roughening was developed and hexagon like crystal appeared on inner surface of crack-like pore after heat treatment. Bar type crystals, probably CaO.6Al2O3, were observed on the inner surface after 1 hour heat treatment at 1, 50$0^{\circ}C$, but this bar type crystal disappeared after 1 hour heat treatment at 1, $600^{\circ}C$. This disappearance means that there should be a little increase of Ca solubility limit to alumina at this temperatures.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.642-643
• /
• 2006

Direct reduction and carburization process was thought one of the best methods to make nano-sized WC powder. The oxide powders were mixed with graphite powder by ball milling in the compositions of WC-5,-10wt%Co. The mixture was heated at the temperatures of $600{\sim}800^{\circ}C$ for 5 hours in Ar. The reaction time of the reduction and carburization was decreased as heating temperatures and cobalt content increased. The mean size of WC/Co composite powders was about 260 nm after the reactions. And the mean size of WC grains in WC/Co composite powders was about 38 nm after the reaction at $800^{\circ}C$ for 5 hours.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.646-647
• /
• 2006

Nano-sized WC particles in WC/Co composite powders were synthesized by mechanochemical method. The raw powders$(WO_3,\;Co_3O_4,\;VC,\;Cr_3C_2$ and graphite) were mixed by planetary milling for 30 hours. The compositions were WC-10 and -20 wt% Co added VC and $Cr_3C_2$. The direct reduction and carburization of the mixed powders were carried at $900\;^{\circ}C$ for 1 to 3 hours under flowing Ar gas. The mean size of WC particles in WC/Co composite powders was about 16 nm. The resultant powders were compacted and sintered at $1300{\sim}1360\;^{\circ}C$ for 0.5 hour. After sintering the mean size of WC particles was about 50 nm.

• Journal of the Korean Society for Precision Engineering
• /
• v.12 no.4
• /
• pp.28-38
• /
• 1995

The flank wear at the minor cutting edge significantly affects the geometric accuracy and surface roughness in finish machining. A fuzzy estimator based on a fuzzy inference algorithm with a max-min composition rule is introduced to evaluate the minor flank wear length. The features sensitive to minor flank wear are extracted from the dispersion analysis of a time series AR model of the feed directional acceleration signal. These features, dispersions, are used for constructing linguistic rules, and then the fuzzy inferences are carried out with test data sets collected under various cutting conditions. The proposed system turns out to be effective for estimating minor flank wear length.

• Journal of the Korean Magnetics Society
• /
• v.25 no.4
• /
• pp.117-122
• /
• 2015

The holes with a diameter of $35{\mu}m$ inside the GMR-SV (giant magnetoresistance-spin valve) film were patterned by using the photolithography process and ECR (electron cyclotron resonance) Ar-ion milling. From the magnetoresistance curves of the GMR-SV film with holes measuring by 4-electrode method, the MR (magnetoresistance ratio) and MS (magnetic sensitivity) are almost same as the values of initial states. On other side hand, the $H_{ex}$ (exchange bias coupling field) and $H_c$ (coercivity) dominantly increased from 120 Oe and 10 Oe to 190 Oe and 41 Oe as increment of the number of holes inside GMR-SV film respectively. These results were shown to be attributed to major effect of EMD (easy magnetic domian) having a region positioned between two holes perpendicular to the sensing current. On the basis of this study, the fabrication of GMR-SV applying to the hole formation improved the magnetoresistance properties having the thermal stability and durability of bio-device.

• Journal of Powder Materials
• /
• v.6 no.4
• /
• pp.314-319
• /
• 1999

The solid state reaction by mechanical alloying(MA) generally proceeds by lowering the free energy as the result of a chemical reaction at the interface between the two adjacent layers. However, Lee et $al.^{1-5)}$ reported that a mixture of Cu and Ta, the combination of which is characterized by a positive heat of mixing of +2kJ/mol, could be amorphized by mechanical alloying. This implies that there exists an up-hill process to raise the free energy of a mixture of pure Cu and la to that of an amorphous phase. It is our aim to investigate to what extent the MA is capable of producing a non-equilibrium phase with increasing the heat of mixing. The system chosen was the ternary $Cu_{30}Ta_{ 70-x}Mo_ x$ (x=35, 10). The mechanical alloying was carried out using a Fritsch P-5 planetary mill under Ar gas atmosphere. The MA powders were characterized by the X-ray diffraction with Cu-K $\alpha$ radiation, thermal analysis, electron diffraction and TEM micrographs. In the case of x=35, where pure Cu powders were mixed with equal amount of pure Ta and Mo powders, we revealed the formation of bcc solid solution after 150 h milling but its gradual decomposition by releasing fcc-Cu when milling time exceeded 200 h. However, an amorphous phase was clearly formed when the Mo content was lowered to x=10. It is believed that the amorphization of ternary $Cu_{30}Ta_{60}Mo_{10}$ powders is essentially identical to the solid state amorphization process in binary $Cu_{30}Ta_{70}$ powders.