• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.307-310
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• 2005

Ageing behavior of the Al-Mg-Si alloy was modeled for the use of optimization of Al forging product. Typical precipitates of Al-Mg-Si alloy are a wide variety of metastable phases (e.g. GP zones, $\beta',\beta'$). These rod shaped particles take a role to hinder the dislocation movement. The precipitation sequence in Al-Mg-Si alloys is quite complex and the strength of precipitate particles differs with the ageing condition. In the present study, the ageing behavior of Al-Mg-Si alloy was investigated by using an industrial grade Al 6061 alloy forged product, which was a perform for an Al impeller for turbo charger. The precipitate hardening models by Esmaeili's approach were used for the analysis of ageing behavior.

• Food Science of Animal Resources
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• v.30 no.5
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• pp.739-745
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• 2010

The objective of the current study was to compare the abilities of undigested and enzymatically digested bifidobacteria to induce nitric oxide and cytokine release in RAW 264.7 macrophage cells. Nine different Bifidobacterium strains derived from herbivorous animals were digested with pepsin and then pancreatin, and the precipitates and supernatants were acquired via centrifugation. The RAW 264.7 cells were incubated with whole cells, the precipitate, or the supernatant, and the macrophage culture supernatants were analyzed with respect to the induction of nitric oxide and cytokines. Pronounced increases in the production of nitric oxide, interleukin (IL)-$1{\beta}$, IL-6, IL-12, and tumor necrosis factor-$\alpha$ (TNF-$\alpha$) were observed when cultured with whole cells and the precipitates. It is noteworthy that the precipitates in most of the Bifidobacterium strains evidenced a trend toward superior IL-12 release compared with whole cells. The results showed that both whole cells and digested Bifidobacterium sp. are effective at stimulating RAW 264.7 cells to induce the production of nitric oxide and cytokines. The pepsin-pancreatin system used in the current study may be useful in unraveling the mechanism by which ingested lactic acid bacteria modulate the induction of macrophage mediators at the cellular level.

• Journal of Microbiology
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• v.45 no.5
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• pp.373-378
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• 2007

Based on observations that lactic acid bacteria have the ability to activate macrophages, we assessed the potential effects of eight different Lactobacillus strains treated with gastrointestinal enzymes on the production of nitric oxide and various cytokines in macrophages. RAW 264.7 murine macrophage cells were cultured with either precipitates or supernatants of Lactobacillus strains digested with pepsin followed by pancreatin. The increased production of nitric oxide and interleukin $(IL)-1{\beta}$, IL-6, IL-12 and tumour necrosis factor $(TNF)-{\alpha}$ were observed when cultured with precipitates, and this effect was largely strain-dependent. In contrast, the exposure of RAW 264.7 cells to supernatants produced weaker or nearly undetectable effects in comparison to the effects of exposure to precipitates. The induction of nitric oxide appeared to be unaffected. These results demonstrate that nitric oxide and cytokines were effectively induced when the bacterial precipitate was treated with macrophages. The results of the present study also indicate that Lactobacillus strains treated with digestive enzymes are capable of stimulating the production of nitric oxide and cytokines in macrophages, which may modulate the gastrointestinal immune function of the host when it is given as a feed additive.

• Journal of Ginseng Research
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• v.23 no.2 s.54
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• pp.93-98
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• 1999

In order to evalulate the qualities of red ginseng extract and decrease precipitate fonnation in ginseng drink, red ginseng extract was hydrolized with ${\beta}-amylase$ and transglucosidase. $5.2\%$ isomaltose was produced as isomaltooligosaccharides and glucose content was increased in the enzyme treated ginseng extract. Contents of ginsenoside $R-b_1\;and\;R-b_2$ were decreased, whereas ginsenoside-Rd was increased by the enzyme treatments. The growth of 3 strains of bifidus spp. and 4 strains of lactobacillus spp., beneficial intestinal bacteria, were enhanced by adding of the enzymatically hydrolized ginseng extract. Sweetness and sourness were increased, however, bitterness and astringency were decreased in the hydrolized ginseng extract. The fonnation of precipitates in hydrolized red ginseng extract of $pH\;3.0\~4.5$ were significantly decreased in the storage condition of $40^{\circ}C$ for 1 month compared to that of control.

• Korean Journal of Materials Research
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• v.14 no.1
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• pp.13-18
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• 2004

Titanium alloys are the one of promising candidate materials for medium high temperature parts in the aircraft, automobile, petrochemistry and electrochemistry because of their high strength with low density in medium high temperature. In this study, the effects of aging and heat treatments on the mechanical properties of Ti-15-3 alloy in medium high temperature, which was $400^{\circ}C$, were studied. Solid solution treatment was performed at $8000^{\circ}C$ of $\beta$ phase region for 1 h and the alloy was quenched in water. The alloy was aged at $5000^{\circ}C$ of $\alpha$ and $\beta$ two-phase region for 1, 2, 4, 8, ... and 100 h to increase the mechanical property. The $\beta$ single phase was observed at all parts of specimens in Ti-15-3 alloy after ST. As the aging at $500^{\circ}C$, fine precipitates of a phase was generated from matrix of $\beta$ phase and the microstructure was consisted of weaving structure such as Widmanstiitten a phase. The most suitable aging time is 24h in$ 400^{\circ}C$. At this time, strength is 1164 MPa and elongation is about 12%. In room temperature, elongation of Ti-15-3 alloy aged at $500^{\circ}C$ for 16 h is poor (=3%) in spite of high tensile strength (1458 MPa).

• Journal of Welding and Joining
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• v.19 no.5
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• pp.534-539
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• 2001

The formation mechanism of microconstituents in brazed joints of duplex stainless steel and Cr-Cu alloy which is an essential process of rocket engine manufacturing was investigated using Cu base insert metal. $SUS329J_3L$ and C18200 were used for base metal and AMS 4764 was used for insert metal. The brazing was carried out under various conditions. There were various phases in the joints, because of reaction between liquid insert metal and base metals. Since liquid insert metal reacts with duplex stainless steel, liquid Cu from insert metal infiltrated into the $\alpha/\beta$ interface of duplex stainless steel. Through the process of Cu infiltration, isolated stainless steel pieces come into the liquid insert metal. Since liquid insert metal reacts with Cr-Cu alloy. Cr precipitates from C18200 come into the liquid insert metal. With increment of bonding temperature and holding time, amounts and sizes of phases increased. but Cr-Mn compounds decreased at 1303k for 1.2ks and Mn-rich phases disappeared Fe-Cr compounds formed.

• Journal of Ocean Engineering and Technology
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• v.11 no.1
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• pp.49-54
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• 1997

On the precipitatiopn and ripening reaction of the precipitates from a lead nitrate and an oxalic acid dissolved in ethanol, a new crystalline phase was obtained, whose X-ray diffraction data have not previously been reported. The crystal system was determined to be monoclinic. The unit-cell parameters were refined to a =10.613(2)$\AA$, b =7.947(2))$\AA$, c =6.189(1)$\AA$, and $\beta$=104.48(2)$^{\circ}$.

• Journal of the Korean Ceramic Society
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• v.26 no.2
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• pp.147-156
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• 1989

The effects of starting composition, sintering temperature and porosity on the mechanical properties of hydroxyapatite ceramics were investigated. The hydroxyapatite powder were prepared by precipitation method using Ca(NO3)2.4H2O and (NH4)2.HPO4. The obtained powders were Ca-deficient hydroxyapatites and as the Ca/P mole ration in the initial solution was increased, the particle size of the precipitates was decreased, and the decomposition of hydroxyapatite to $\beta$-TCP was controlled. The porosity, as well as Ca/P mole ratio in starting composition and sintering temperature, plays major role in the mechanical properties of dense hydroxyapatite ceramics.

• Korean Journal of Materials Research
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• v.6 no.6
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• pp.585-588
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• 1996

여러 가지 Zr합금에서 생성되는 석출물의 특성을 규명하기 위하여 시편을 $600^{\circ}C$에서 1시간 동안 열처리 한후 EDX가 부착된 TEM을 이용하여 석출물에 관한 연구를 수행하였다. Zr1.4Sn0.2Fe0.1Cr 합금에서는 두 종류의 석출물이 생성되는데 하나는 석출물의 대부분을 차지하는 HCP 구조으 Zr(Cr, Fe)2 석출물로서 이는 둥근 형태를 유지하며 결정립내나 결정립계에 관계없이 널리 분산되어 분포된다. 다른 하나의 석출물은 극히 일부에서만 관찰되는 Zr2(Fe, Si)성분의 석출물로서 이는 tetragonal 구조를 갖는다. Zr0.5Nb0.6Fe0.3V 합금에서는 tetragonal (Zr, Nb)2(Fe, V) 석출물이 형성되며, Nb이 1.0 wt.% 첨가된 Zr1.0Nb0.6Fe0.3V 합금에서는 HCP 구조의 (Zr, Nb)(Fe, V)2 석출물과 BCC 구조인 $\beta$-Zr이 생성된다. Zr1.0Nb0.6Fe0.3V합금을 제외하고는 대부분의 합금에서 석출물은 약 1.0$\mu\textrm{m}$의 크기를 나타냈다. 합금 조성이 다를 경우에 석출물 크기와 35$0^{\circ}C$ 부식 특성과는 부식 특성과는 연관성이 없는 것로 나타났다.

• Journal of Welding and Joining
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• v.22 no.3
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• pp.56-61
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• 2004

Friction stir weldability of AZ31B Mg alloy was studied using microstructural observation and mechanical tests. Defect free joints was obtained under the condition of 2000rpm-100mm/min. In TMAZ, a lot of twin deformation were observed due to the mechanical effect of the FSW tool and thus relatively high hardness was obtained. In SZ, the twin deformation was disappeared by recovery and the hardness decreased because the. grain structure was coarsened by dynamic recrystallization and grain growth. The Al-Mn precipitates were observed throughout the joint regions. On the other hand, $$\beta$-Mg_{17}Al_{12}$ intermetallic compounds were not observed in either of the zone. The joint efficiency was about 80% and the impact value of the joint was almost equal to that of base metal.