• Journal of Magnetics
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• v.2 no.1
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• pp.22-24
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• 1997

FeN thin films were deposited by RF-reactive diode sputtering to investigate magnetic characteristics variation due to substrate tilt during the film deposition, and their magnetic properties were measured by VSM, SEM and AFM. When the substrate tilt pivot edges were parallel to the applied field, the magnetic anisotropy was increased When the substrate tilt pivot edges were perpendicular to the applied field, the easy magnetization axis became the hard magnetization axis, and the hard axis became the easy axis as the tilt angles were increased. The reason is believed to be due to the fact that the tilt induced shape magnetic anisotropy became larger than the field induced magnetic anisotropy by DC magnetic field as the crystal grains are enlongated along the substrate tilt pivot edges due to "oblique incidence anisotropy" commonly found in eveporated thin films.

• KSTLE International Journal
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• v.2 no.2
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• pp.85-92
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• 2001

The variation of contact traction induced by different contact shapes is studied experimentally and theoretically. Considerations fer the contact shape are rounded, truncated and truncated with rounding punches. A fretting wear experiment is conducted with the contact configuration of the strip on the tube specimens. The strip specimen is pressed to form the end profile of a rounded and truncated with rounding punches shape. Wear on the tube is investigated, which is regarded as the slip region of the contact surface. Taken into consideration is the general solution of the normal traction in the case of the indentation by a punch with its end profile of the combination of parabolas. Then, partial slip solution is obtained numerically, which is compared with the wear on the tube. The radius of the rounding and the obliquity of the edge truncation affect the tractions considerably. It is found that the proper choice of the end profile can restrain the contact-induced failure such aswear.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.60-64
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• 2008

According to previous research, welding-induced stress in steel structures can significantly affect the fatigue behaviour; it produces initial damage of weldiug part of structure locally and residual stresses reduce the fatigue strength after welding precess. In this study, through continuum damage mechanics, we can estimate the weldiug damage using the stress and strain history during welding process and the effect of welding residual stress for assessment of fatigue life. The variation of welding-induced stresses and strains need be traced precisely in advance for a reliable weldiug damage assessment. In this study, a damage and fatigue analysis techniques for steel structures with welding-induced residual stress are presented. First, We calculate the history of temperature according with welding process. And residual stress with a welding thermal history was evaluated by non-linear thermal stress analysis. Secondly, welding damage and fatigue life are estimated with kinetic damage law.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.4
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• pp.32-38
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• 2004

Laser-induced thermochemical wet etching of titanium in phosphoric acid has been investigated to examine the feasibility of this method fur fabrication of microstructures. Cutting, drilling, and milling of titanium foil were carried out while examining the influence of process parameters on etch width, etch depth, and edge straightness. Laser power, scanning speed of workpiece, and etchant concentration were chosen as major process parameters influencing on temperature distribution and reaction rate. Etch width increased almost linearly with laser power showing little dependence on scanning speed while etch depth showed wide variation with both laser power and scanning speed. A well-defined etch profile with good surface quality was obtained at high concentration condition. Fabrication of a hole, micro cantilever beam, and rectangular slot with dimension of tess than 100${\mu}{\textrm}{m}$ has been demonstrated.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.7-12
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• 2003

Mixture formation in the cylinder of a lean bum engine has been observed by Laser Induced Fluorescence technique. XeCl laser (308nm) was used to produce a laser sheet. 3-pentanone has been added to iso-octane fuel to produce fluorescence, the intensity of which is proportional to the concentration of the fuel. The laser sheet was introduced through the piston window and the fuel distribution in the vertical plane was observed through a side window. Comparison has been made for the cases of selected fuel injection timing as 0, 360, 405, and 450 CA. For the case of 0 and 360 CA injection, uniform fuel distribution in the combustion chamber has been obtained at the ignition time which is favorable for the high load mode. And the late injection cases, 405 and 450 CA, revealed the stratified formation of rich mixture around the spark plug. That extends the lean misfire limit and reduces cyclic variation in the low load mode.

• Bulletin of the Society of Naval Architects of Korea
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• v.22 no.2
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• pp.12-26
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• 1985

This paper describes the experimental method to predict the propeller induced fluctuating pressure on the hull surface. Cavitations of the three model propellers with varying degree of skews, $0^{\circ},\;36^{\circ}\;and\;72^{\circ}$, were observed and the fluctuating pressure induced by the cavitating propellers in the flat plate above these propellers were measured simultaneously at 9 points in the wake field generated by the wire-mesh screens. Another model propeller designed for the dummy model ship was tested in a similar way behind the dummy model ship. The effects of skew variation on the cavitation patterns and fluctuating pressures were illustrated, and the influence of tip-clearances on the fluctuating pressures was also demonstrated. As a result, it is shown that the level of fluctuating pressure and cavity extent could be controlled to some extent by introducing the skews and tip clearances.

• Korean Journal of Microbiology
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• v.18 no.2
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• pp.51-58
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• 1980

Mutational experiments were performed to improved to improve the protease productivity of Aspergillus flavus KU 153, which is selected among the wild strains. A UV-induced mutant strain having high protease productivity was obtained by the use of the clear zone method as a simple criterion for a primary screening test. Neutral and alkaline protease activities of hte mutant strain were higher than 1.8 times, comopared with those of the parental strain, respectively, while in the case of acid protease, it was 2.7 times. The mutant strain selected was more powerful in the production of cellulase and amylase, as well s protease in wheat bran, compared with those of the parental strain. protease production of the parental strain has reached maximum level at 3 days culture, while alkaline nad neutral protease production of the mutantstrain has reached at 2 days culture. On the other hand, the mutant strain formed the spore slowly, compared with the parental strain. Column chromatography of the neutral protease on DEAE-Sephadex A-50 showed that the mutant strain was not induced the formation of another neutral protease isozyme, but induced the variation in the function of regulatory gene.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.3
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• pp.449-454
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• 2006

We present a pressure sensor based on the mechanically induced long-period fiber gratings (LPFG) for detecting the multi-location strain variation. The theoretical analysis is performed using a graphic method for a weakly guiding step-index fiber. The calculated results are in good agreement with the experimental results. In this study, from the fact that the optical parameters of a single-mode fiber slightly differ from manufacturing company to manufacturing company, the multipoint pressure-detection sensor systems composed two identical LPFGs are realized. When the pressure is applied two LPFG sensors at once, the resonance peaks are separated as much as about 40 nm. These types of sensor systems are well suited as a multipoint monitoring of strain or temperature in the ship or the smart structure.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.849-855
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• 2000

This study evaluated the effect of restraint of pressure induced bending(PIB) on crack mouth opening displacement(CMOD) for circumferential through-wall crack in pipe by using both elastic and elastic-plastic finite element analyses. The analyses results showed the restraint of PIB was decreased crack opening for a given crack length and tensile stress, and the effect was considerable for large crack and short restraint length. Also, the restraint effect on CMOD was independent on the variation in pipe diameter and decreased with increasing pipe thickness, and it depended on not total restraint length but short restraint length for non-symmetrically restrained. Additionally, the effect of restraint of PIB was more significant in the elastic-plastic analysis results compared with in the elastic analysis results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.65-69
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• 2004

A computer code was developed to simulate the filling stage of the injection/compression molding process by a finite element method. The constitutive equation used here was the compressible Leonov model. The PVT relationship was assumed to follow the Tait equation. The flow-induced birefringence was related to the calculated flow stresses through the linear stress-optical law. Simulations of a disk part under different processing conditions including the variation of compression stroke and compression speed were carried out to understand their effects on flow-induced birefringence. The simulated results were also compared with those by conventional injection molding and with experimental data from literature.