• Journal of Korea Foundry Society
• /
• v.20 no.4
• /
• pp.254-259
• /
• 2000

Metal matrix composites(MMCs) reinforced with hard particles have many potential application in aerospace structures, auto parts, semiconductor package, heat resistant panels, wear resistant materials and so on. In this work, the effect of SiC partioel sizes(50 and 100 ${\mu}m$) and additional elements such as Si, Cu and Ti on the microstructure and the wear property of $Al-5Mg-X(Si,Cu,Ti)/SiC_p$ composites produced by pressureless infiltration method have been investigated using optical microscopy, scanning eletron microcopy(SEM) with EDS(energy dispersive spectrometry), hardness test, X-ray diffractometer(XRD) and wear test. In present study, the sound $Al-5Mg-X(Si,Cu,Ti)/SiC_p$(50 and 100 ${\mu}m$) composites were fabricated by pressureless infiltration method. The $Al-5Mg-0.3Si-O.1Cu-O.1Ti/SiC_p$ composite with $50 {\mu}m$ size of SiC particle has higher hardness and better wear property than any other composite with $100{\mu}m$ size of SiC particle produced by pressureless infiltration method. The hardness and wear property of $Al-5Mg/SiC_p$(50 and 100 ${\mu}m$) composites were enhanced by the addition of Si, Cu and Ti in Al-5%Mg matrix alloy.

• Journal of Korea Foundry Society
• /
• v.21 no.2
• /
• pp.127-134
• /
• 2001

Misch metal (rare earth element, Ce, La, Nd, Pr) which has large influence on high-temperature stability and toughness was added to the Al-5%Ni-5%Mg alloy, and squeeze casting was used for Al-5%Ni-5%Mg-(Mm) alloys. The effect of applied pressure and misch metal additions on mechanical properties in Al-5%Ni-5%Mg alloy by direct squeeze casting has been investigated. The applied pressure were 0 MPa(gravity casting), 25, 50 and 75 MPa. Squeeze-cast Al-5%Ni-5%Mg-(Mm) alloys had better mechanical properties than those of non-pressurized cast alloys because of the increased cooling rate by the application of pressure during solidification. By the addition of misch metal in Al-5%Ni-5%Mg alloy, better combination of strength and elongation was obtained. The addition of 0.3%Mm in Al-5%Ni-5%Mg alloy improved the heat resistant property due to the formation of fine eutectic phases.

• Journal of Microbiology and Biotechnology
• /
• v.29 no.3
• /
• pp.401-409
• /
• 2019

Heat-resistant microbial hosts are required for bioprocess development using high cell density cultivations at the industrial scale. We report that the thermotolerance of Escherichia coli can be enhanced by overexpressing ybeD, which was known to encode a hypothetical protein of unknown function. In the wild-type E. coli BL21(DE3), ybeD transcription level increased over five-fold when temperature was increased from $37^{\circ}C$ to either $42^{\circ}C$ or $46^{\circ}C$. To study the function of ybeD, a deletion strain and an overexpression strain were constructed. At $46^{\circ}C$, in comparison to the wild type, the ybeD-deletion reduced cell growth half-fold, and the ybeD-overexpression promoted cell growth over two-fold. The growth enhancement by ybeD-overexpression was much more pronounced at $46^{\circ}C$ than $37^{\circ}C$. The ybeD-overexpression was also effective in other E. coli strains of MG1655, W3110, DH10B, and BW25113. These findings reveal that ybeD gene plays an important role in enduring high-temperature stress, and that ybeD-overexpression can be a prospective strategy to develop thermotolerant microbial hosts.

• Journal of Korea Foundry Society
• /
• v.6 no.2
• /
• pp.93-103
• /
• 1986

It is very important to obtain wear resistant ductile iron by adding more economical alloying elements. In this study, 10 heat of Mg-treated ductile iron were made according to Sb content (0-0.1% Sb). Each melt was tasted to 30 ${\o}test$ bars in $CO_2$ mold under the same condition and inspected wear characteristics, mechanical properties and microstructures. The results obtained from this study are as follows; 1. It is confirmed that Sb should be a simple and useful additive for improving wear resistance in ductile iron. 2. Hardness of ferrite and pearlite is improved with increasing Sb amount in ductile iron. 3. For ductile iron, the recommended ladle addition of Sb amount is to 0.02-0.03%. 4. Sb has adverse influence on spheroidizing of graphite if the amount is over 0.04%.

• BMB Reports
• /
• v.37 no.2
• /
• pp.229-233
• /
• 2004

A haemagglutinating protein from the saline extracts of Kalanchoe crenata leaves, which agglutinate all human blood types, was purified to homogeneity by ion-exchange chromatography on a DEAE-Cellulose column followed by gel filtration on a Sephadex G-100 column. The purified protein showed one band, both in non-denaturing PAGE and SDS-PAGE. The $M_r$ that was determined by SDS-PAGE was 44,000 Da and that estimated from gel filtration was 47,000. Treatment of the haemagglutinating protein with 5 mM EDTA diminished the haemagglutinating activity to 50% of the original level. The addition of divalent cations, 10 mM $Mg^{2+}$, 10 mM $Mn^{2+}$, or 10 mM $Ba^{2+}$, totally restored and enhanced the activity. The protein showed maximum activity over the 3-7 pH range and was heat-resistant. It was also a glycoprotein containing about 1.5% carbohydrate.

• Journal of Welding and Joining
• /
• v.31 no.2
• /
• pp.16-20
• /
• 2013

Titanium and its alloys have been widely using in the various field of industry application due to high corrosion resistant properties and mechanical properties. Titanium is highly reactive in the high temperature state and the formation of titanium oxide and porosities in the nuggets of fusion welding will results in the degradation of the mechanical properties. For this reason the studies of friction stir welding for titanium have been investigated recently. The FSW zones of titanium were classified by the weld nugget (WN), the linear transition boundary (TB) and the heat affected zone (HAZ). The WN along with titanium parent was characterized by the presence of twins and dislocations. The average grain size and hardness of WN has been changed according to heat input. The grain refinement resulted from the FSW increased the hardness in the stir zone. Sound dissimilar joints between SUS 304 and CP-Ti were achieved using an advancing speed of 50 mm/min and rotation speeds in the range of 700-1100 rpm. Aluminum 1060 and titanium alloy Ti-6Al-4V plates were lap joined by friction stir welding, hence the ultimate tensile shear strength of joint reached 100% of Al 1060. Mg alloy and Ti were successfully butt joined by inserting a probe into the Mg alloy plate with slightly offsetting. But Ti-Al intermetallic compound layers formed at the interface of these joints.

• Journal of Microbiology and Biotechnology
• /
• v.24 no.4
• /
• pp.483-488
• /
• 2014

In order to improve the expression of heat-resistant xylanase XYNB from Aspergillus niger SCTCC 400264, XynB has been cloned into Pichia pastoris secretary vector pPIC9K. The XynB production of recombinant P. pastoris was four times that of E. coli, and the $V_{max}$ and specific activity of XynB reached $2,547.7{\mu}mol/mg$ and 4,757 U/mg, respectively. XynB still had 74% residual enzyme activity after 30 min of heat treatment at $80^{\circ}C$. From the van der Waals force analysis of XYNB (ACN89393 and AAS67299), there is one more oxygen radical in AAS67299 in their catalytic site, indicating that the local cavity is much more free, and it is more optimal for substrate binding, affinity reaction, and proton transfer, etc, and eventually increasing enzyme activity. The H-bonds analysis of XYNB indicated that there are two more H-bonds in the 33rd Ser of XYNB (AAS67299) than in the 33rd Ala(ACN89393 ), and two H-bonds between Ser70 and Asp67.

• Korean journal of food and cookery science
• /
• v.19 no.3
• /
• pp.263-270
• /
• 2003

This study was conducted to investigate the isoflavone (daidzein and genistein) contents, and the antioxidative and fibrinolytic activities of red and mung beans. Daidzein was not found in either the red or mung beans. The genistein contents of the red and mung beans were 40.7 and 27.8 mg/kg, respectively. Both samples had very high electron donating abilities and SOD-like activities. Fibrinolytic activities were not detected in the crude mung bean extract, but fibrinolytic substances were purified or activated under various pH conditions and with heat treatments. With heat treatment at 100 $^{\circ}C$ for 10 min, the specific activity was increased 4.61 fold. This study revealed that, although red and mung beans were poor in isoflavone, they could be good sources for functional products due to their strong antioxidative activities and heat- and acid-resistant proteolytic abilities.

• Journal of Korea Foundry Society
• /
• v.41 no.3
• /
• pp.252-259
• /
• 2021

The magnesium is one of the important alloying elements in the conventional aluminum alloys. The addition of magnesium to aluminum is well known to increase the mechanical strength of the aluminum without the trade-off of the decreased elongation. However, the content of magnesium in aluminum alloys has been limited to be lower than about 5wt.% because of the high oxidation tendency of magnesium element during the manufacturing processes such as casting, hot-forming and post heat-treatments, which can deteriorate the quality and properties of the final products. In this study, new 'ECO-Almag6~9' (containing 6~9wt%Mg) alloys were investigated to be made of the ECO-Mg master alloy, which has been invented to reduce the oxidation tendency of itself. It was successfully demonstrated that ECO-Almag6~9 alloys can be fabricated through the mass-production facilities of DC casting and extrusion routes without the problems of magnesium oxidation. In addition, it was confirmed that the strength and ductility were simultaneously improved due to the addition of high magnesium contents.

• Korean Journal of Food Science and Technology
• /
• v.34 no.3
• /
• pp.498-504
• /
• 2002

Isoflavone (daidzein and genistein) contents, and antioxidative and fibrinolytic activities of seven commercial Korean cooking-with-rice soybeans, including Seonbikong, Chungtae, Gangnamkong, Whangtae, Geodoo, Seolitae, and Wooltalikong were investigated. Daidzein and genistein were not found in Selitae, nor was didzein in Gangnamkong and Geodoo. Total daidzein and genistein levels in Chungtae and Whangtae were 500 and 1550 mg per kg, respectively. Wooltalikong, Whangtae, and Gangnamkong had very high electron donation abilities, over 90%, but Seonbikong and Chungtae showed significantly lower activities. SOD-like activities were also the highest in Gangnamkong and Wooltalikong. Fibrinolytic activities in Seonbikong, Whangtae, and Gangnamkong were similarly strong. Fibrinolytic substances purified from protease inhibitors or activated under various pH or heat treatment conditions, were different among the soybean varieties. This study revealed that, although several cooking-with-rice soybeans were poor in isoflavones, Wooltalikong and Gangnamkong could be good sources for functional products due to their strong antioxidative activities, and heat- and acid-resistant proteolytic abilities.