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991.
The mechanism of sintering in chromium oxide in the presence of varying amounts of magnesium oxide in a firing condition that
simulates a controlled reducing atmosphere has been investigated. The investigation is based on isothermal shrinkage measurements
at different temperatures. The data suggest grain boundary diffusion to be the main process with evidence of vapour transport. 相似文献
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The distribution of ABO blood groups was studied in 459 Chinese and 65 Malay newborns with deficiency of G6PD, and in 1181 Chinese and 535 Malay newborns with normal levels of the enzyme. Similarly, the distribution of Rhesus blood groups was studied in 248 G6PD deficient Chinese newborns and in 255 normal subjects. No association between the ABO blood groups and G6PD deficiency was observed in either Chinese or Malays. For the Rhesus system there was found to be a statistically significant decrease in the frequency of genotypes containing the complex R1, in G6PD deficient subjects compared with that in normal subjects. 相似文献
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K.K. Sahu N.A. Mauro L. Longstreth-Spoor D. Saha Z. Nussinov M.K. Miller K.F. Kelton 《Acta Materialia》2010,58(12):4199-4206
The mechanisms responsible for the nanoscale devitrification of Al-based metallic glasses are unclear. A particularly well-studied case is Al88Y7Fe5, where non-isothermal differential scanning calorimetry (DSC) measurements show an exothermic peak that is consistent with glass devitrification to α-Al, but with no glass transition. Additionally, isothermal DSC studies show a monotonic decrease in enthalpy release with annealing, a feature generally taken to indicate grain coarsening. The results of coordinated DSC, bright field transmission electron microscopy, in situ electrical resistivity and atom probe tomography (APT) studies of Al88Y7Fe5 support a nucleation/growth-based crystallization process. The APT data indicate the presence of sub-nanometer pure Al zones and coarser scale (separation distance ~74–126 nm) Al-rich regions in the glass. The pure Al zones dispersed in the Al-rich regions appear to catalyze α-Al nucleation, explaining the high nucleation rates. The solute-rich regions between the Al-rich regions inhibit long-range diffusion, explaining the low growth rates. 相似文献
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In this article, an attempt has been made to revisit the design of well‐established log periodic dipole array (LPDA) in light of recent optimization technique, the bacteria foraging algorithm (BFA). Although there are many works published in the literatures based on various optimization techniques, this article deals with the optimization of the LPDA for the entire ultra high frequency (UHF) television (TV) spectrum (470–870 MHz) covering 400 MHz bandwidth and accommodating 49 channels. The challenges of this design lie in selecting suitable values of τ and σ for 134 frequency points for which different sets of all the output parameters such as gain, input impedance (Zin), front‐to‐back ratio (FTBR), first side lobe level (FSLL), voltage standing wave ratio (VSWR), and so forth are obtained and then averaged over to get Gainav, ZinAav, FTBRav, FSLLav, and VSWRav close to the desired values. These average values are used to design suitable fitness function. Another important aspect of this article is to provide exhaustive design details for LPDA using network theory that would couple to the BFA for getting the optimized number of elements to satisfy the desired values of Zinav, Gainav, FTBRav, FSLLav, and VSWRav, set as 50 Ω, 9 dBi, 40 dB, 40 dB, and 1.1, respectively. Moreover, this LPDA design considers the standard wire gauge dipole elements, which is just a very practical approach in the design procedure. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013. 相似文献