• Journal of Powder Materials
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• v.9 no.4
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• pp.218-226
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• 2002

The purpose of the present study is to investigate the influence of thermal debinding and sintering conditions on the sintering behavior and mechanical properties of PIMed 316L stainless steel. The water atomized powders were mixed with multi-component wax-base binder system, injection molded into flat tensile specimens. Binder was removed by solvent immersion method followed by thermal debinding, which was carried out in air and hydrogen atmospheres. Sintering was done in hydrogen for 1 hour at temperatures ranging from 1000℃ to 1350℃ The weight loss, residual carbon and oxygen contents were monitored at each stage of debinding and sintering processes. Tensile properties of the sintered specimen varied depending on the densification and the characteristics of the grain boundaries, which includes the pore morphology and residual oxides at the boundaries. The sinter density, tensile strength (UTS), and elongation to fracture of the optimized specimen were 95%, 540 MPa, and 53%, respectively.

• Journal of the Korean Chemical Society
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• v.9 no.2
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• pp.81-87
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• 1965

Furfurylacetate was prepared and was chlorinated under various reaction conditions. At the low reaction temperature the chlorination product was composed of the stable trans-tetrachloride (yield, 25∼30%), decomposition product (low chlorine content), and unstable cis-tetrachloride. There were no appreciable quantity of the trichloride. At the high reaction temperature the chlorination products were exclusively decomposed. The reaction conditions, separation scheme, and the configurataion of the product were discussed.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.42-47
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• 2004

Metallic glasses are amorphous meta-stable solids and are now being processed in bulk form suitable for structural applications including impact. Bulk metallic glasses have many unique mechanical properties such as high yield strength and fracture toughness, good corrosion and wear resistance that distinguish them from crystalline metals and alloys. However, only a few studies could be found mentioning the dynamic response and damage of metallic glasses under impact or shock loading. In this study, we employed a small explosive detonator for the dynamic indentation on a Zr-based bulk amorphous metal in order to evaluate the damage behavior of bulk amorphous metal under impact loading. These results were compared with those of spherical indentation under quasi-static and impact loading. The interface bonded specimens were adopted to observe the appearances of subsurface damage induced during indentation under different loading conditions.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.2
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• pp.96-103
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• 2011

Rotor grip is used as a component of rotor system in unmanned helicopter. Instead of usual machining, hot forging process has been considered to improve its proof stress against repeated loading conditions and crash in the farm-field. Die design and forming analysis have been performed according to the conditions such as billet volume, flash, cavity filling, and the distribution of damage during the forming by using FE analysis. In the results of analysis, the possibility of structural failure in the model has not been found because its maximum effective stress is much lower than yield strength of the titanium alloy. In the forging die design, flash has been allowed because of low production in the industrial field. Preform design was studied by using FE-analysis, and its optimal dimension was obtained in the hot forging of rotor grip with titanium alloy.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.105.2-105.2
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• 2012

The upper ionosphere of Mars has been explored by many spacecraft like Mariners, Mars, Viking, and recently by MGS and MEX. MARSIS (Mars Advanced Radar for Subsurface and Ionospheric Sounding) aboard Mars Express Orbiter is operating from August 2005. MARSIS provides topside ionospheric traces, of which yield electron density profiles for altitudes above the primary ionospheric peak. A large amounts of data is useful for investigation of the Martian ionospheric environments under the changing conditions like solar activity, seasons, and solar zenith angle. We studied the characteristics of the Martian ionosphere through analysis of MARSIS data in the various conditions. We expect that our results contribute for understanding of the Martian ionospheric environment.

• Journal of Ginseng Research
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• v.18 no.3
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• pp.182-186
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• 1994

This study was conducted to define the effects of color of polyethylene (P.E.) net shading on the meteorological conditions under the shading growth status, photosynthesis and saponin contents of ginseng plant. Red and blue polyethylene net shading (4 fold) showed a good light intensity of ginseng growth, but red one not only increased air temperature but also resulted in early defoliation. Photosynthetic rate of ginseng leaves was increased in order of red, blue and black shade, Root yield and saponin contents were significantly increased red and blue net as compared with those of common straw shading. Blue color appeared to be most recommendable.

• 전기의세계
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• v.27 no.5
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• pp.69-75
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• 1978

3 phase induction motor applied in the method of connecting it directly across the line needs large current when it starts. At that time, leakage magnetic pathes of interior of the motor are severely saturated and leakage reactances are decreased because of saturation. Consequently, increased current and raised powerfactor yield increase of starting torque. The author, noticing those phenomena, derived experimentally the raion of decreasing leakage reactance from the fact that when voltage applied to motor is increased under locked condition the magnitude of current and phase angle are varied, and determined tha equations of starting current and starting torque, considering the decrease of leakage reactance by the large starting current. The author calculated the characteristics of Current-Time and Speed-Time with the determined equation at specific load conditions, and compared the values obtained from above calculations with those from circle diagram's method and the practically recorded values at same load conditions. Therefore, the authos got a confidience that the results of the derived theory coincide with the practically measured values more well than circle diagram's results and circle diagram's equation should be modified in order to analize the starting status of a induction motor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.432-435
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• 1997

In AC PDP, electrodes are covered with dielectric layer and the discharge is formed on the surface of the dielectric layer. MgO protection layer on the dielectric layer in PDP prevents a dielectric layer from sputtering and lowers the firing voltage due to a large secondary electron emission yield( ${\gamma}$ ). Until now, the MgO protection layer is mainly prepared by E-beam evaporation. However, there are some problems that is easy pollution and change of its characteristics with time and delamination. Therefore, in this study, MgO protection layer is prepared on dielectric layer by reactive R.F. magnetron sputtering with MgO target. Discharge characteristics and secondary electron emission coefficients of PDP are studied as a parameter of preparation conditions. Discharge voltage characteristics of the prepared MgO layer can be stable and improved by the annealing process in vacuum chamber.

• Journal of Microbiology and Biotechnology
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• v.24 no.3
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• pp.359-362
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• 2014

15-Hydroxyeicosatetraenoic acid (HETE), as a mammalian biologically active metabolite, has anticarcinogenic effect. The conditions of producing 15-HETE from arachidonic acid by using soybean lipoxygenase were optimal at pH 8.5 and $20^{\circ}C$ with 9 g/l arachidonic acid, 54.4 U/ml soybean lipoxygenase, and 4% methanol. Under these optimized conditions, the enzyme produced 9.5 g/l 15-HETE after 25 min, with a molar conversion yield of 99% and a productivity of $22.8gl^{-1}h^{-1}$. To the best of our knowledge, this is the first biotechnological production of 15-HETE.

• Journal of Korea Foundry Society
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• v.2 no.2
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• pp.18-30
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• 1982

For the purpose of improving the casting yields of ductile iron castings, the casting conditions for riserlese design were investigated with 150mm cube. As the important casting conditions, chemical composition, pouring temperature, mold rigidity and cooling rate were confirmed. 1. We could obtain the sound castings with the hypereutectic ductile iron. 2. In order to reduce liquid contraction, the pouring temperature should be low as much as possible 3. We could obtain the sound castings through using the rigid mold without mold cavity deformation 4. The modulus of the castings should be 2.5cm one or larger.