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The Effect of Li Additions on Wear Properties of Al-Mg₂Si Cast In-situ Composites
M. R. Ghorbani,M. Emamy,J.Ghiasinejad,A. Malekan 한국소성가공학회 2010 기타자료 Vol.2010 No.6
Wear rate of a modified Al-Mg₂Si composite was studied by the use of a conventional pin-on-disc technique. In-situ Al-Mg₂Si composites (15, 20, 25 wt.%) were cast in a simple cylindrical mold. 0.3 wt.% Li was added into the molten composite to modify its microstructure. It has been found that Li addition decreases the mean size of primary Mg₂Si particles. The wear behavior of different composites at different rates revealed that Li addition increases the wear properties of Al-15%Mg₂Si to some extent but it did not have any significant influence on wear properties of two other composites.
Bagheri, M.,Ghorbani, G.R.,Rahmani, H.R.,Khorvash, M.,Nili, N.,Sudekum, K.-H. Asian Australasian Association of Animal Productio 2009 Animal Bioscience Vol.22 No.6
This study evaluated the effects of live yeast and yeast cell-wall mannan-oligosaccharide supplementation onperformance and nutrient digestibility during early lactation in cows fed a diet based on a mixture of corn silage and alfalfa hay as forage sources. Eight multiparous Holstein dairy cows (average days in milk, 27${\pm}$6) were used in a replicated 4${\times}$4 Latin square design. Diets contained 45% forage and 55% concentrate on a dry matter (DM) basis and treatments were: i) basal diet without additive (Control), ii) basal diet with 32 g/d of mannan-oligosaccharides (MOS), iii) basal diet with $1.2{\times}10^{10}$ colony forming units per day (cfu/d) of live yeast (Saccharomyces cerevisiae CNCM 1-1077; SC), and iv) basal diet with a mixture of MOS (32 g/d) and SC ($1.2{\times}10^{10}$ cfu/d; MOS+SC). Treatments had no effect (p>0.05) on DM intake and yields of milk, 3.5% fat-(FCM) and energy-corrected milk (ECM), and on milk fat percentage, body condition score and blood metabolites. Compared with the Control, only supplementation of SC resulted in numerically higher yields of FCM (41.9 vs. 40.1 kg/d) and ECM (41.8 vs. 40.3 kg/d), and milk fat percentage (3.64 vs. 3.43%). While the MOS diet had no effects on performance compared to the Control, the combination treatment MOS+SC increased milk protein percentage (p<0.05). Also, the MOS supplementation, both alone or in combination with SC, numerically increased milk fat percentage. The SC supplementation increased apparent digestibility of DM and crude protein while the MOS supplementation did not affect digestibility. Concentrations of total volatile fatty acids (VFA) and ruminal pH were similar across treatments. Overall results indicated that supplementation of MOS produced variable and inconsistent effects on rumen metabolism and performance, whereas SC supplementation improved nutrient digestibility and numerically increased FCM and ECM yields, which could not be enhanced by the combined supplementation of MOS+SC. According to our experimental condition, there was no effect of MOS alone or in combination with SC on dairy cow performance.
A. Malekana, M. Emamy,M. Emamy,J. Ghiasinejad,M.R.Ghorbani 한국소성가공학회 2010 기타자료 Vol.2010 No.6
An isothermal reheating approach was used to study the effect of isothermal holding time on the microstructure of Al-Mg₂Si in-situ cast composite. Process temperature was selected at 590℃ which is in the semi solid state with respect to the phase diagram of Al-Mg₂Si system. The morphology of primary Mg₂Si particles was identified as irregular shape. The microstructures of the composite at two different states of reheated and as-cast, were compared to reveal the degree of particle modification. The results showed that higher holding time have more significance influence on the nodularity and also decreasing the size of primary Mg₂Si particles. An optimum time was also obtained for isothermal reheating processwhich can be affected by different parameters discussed in this work.
Ghorbani, S R,Wang, X L,Hossain, M S A,Dou, S X,Lee, Sung-Ik IOP Publishing Ltd 2010 Superconductor science & technology Vol.23 No.2
<P>The flux pinning mechanisms of nano-Si-doped MgB<SUB>2</SUB> are reported in this work. The field dependence of the critical current density, <I>J</I><SUB>c</SUB>(<I>B</I>), was analyzed within the collective pinning model. We found that the mechanisms for both δ<I>l</I> pinning, i.e., pinning associated with charge-carrier mean free path fluctuations, and δ<I>T</I><SUB>c</SUB> pinning, which is associated with spatial fluctuations of the transition temperature, coexist in the nano-Si-doped MgB<SUB>2</SUB> samples, while <I>H</I><SUB>c2</SUB> increases greatly with increasing nano-Si doping level. However, their contributions are strongly temperature dependent. The δ<I>l</I> pinning is dominant at low temperatures, decreases with increasing temperature, and is suppressed completely at temperatures close to the critical temperature, <I>T</I><SUB>c</SUB>. However, the δ<I>T</I><SUB>c</SUB> pinning mechanism shows opposite trends. </P>
Wear Behavior of Al-Mg2Si Cast In-situ Composite
J. Ghiasinejad,M. Emamy,M. R. Ghorbani,A. Malekan 한국소성가공학회 2010 기타자료 Vol.2010 No.6
Al-Mg₂Si in situ composites are great candidates for automobile brake discs due to their low density, reasonably high young"s modulus and low thermal expansion coefficient. Thus, understanding wear properties of this composite is of a great importance. In this study wear behavior of an in-situ Al-Mg₂Si composite, prepared from a simple casting route, has been investigated using a pin-on-disc configuration concerning the effect of Mg₂Si volume fractions, 15, 20 and 25% respectively. It was found that the weight loss increases with increase in reinforce volume fraction which can be due to a coarse morphology of primary Mg₂Si particles. It was found that the variations of weight loss with sliding distance comprise different regimes of which the mechanisms are discussed.