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In this work, the influence of Al-solutes on the mechanical behavior of Cu–AlX solid solutions has been studied using indentation strain rate jump tests for single crystalline and ultrafine-grained (UFG) microstructures from high pressure torsion (HPT) processing. Al-solutes in Cu classically lead to a solid solution strengthening, coupled with a decrease in stacking fault energy, which influences also the grain size after HPT processing. For all alloys, a higher hardness is found at lower indentation depths, which can be nicely described by a modified Nix/Gao model down to 100 nm indentation depth. Among the single crystals, the largest size effects are found for the higher solute contents, indicating a stronger work hardening at small length scales for the solid solutions. The dilute UFG solid solutions showed a strong softening after a strain rate reduction test, with a pronounced transient region. Cu–Al15 is, however, quite stable, showing abrupt changes in hardness without strong transients. This indicates that solute solution strengthening does not only influence the indentation size effect and structure formation during HPT processing but also stabilizes the grain structure during subsequent deformation.
The leopard Panthera pardus, categorized globally as Near Threatened on the IUCN Red List, has the widest distribution of any wild felid species, although in Asia it has declined dramatically and five subspecies are Endangered or Critically Endangered. In China at least three subspecies have been reported to occur throughout much of the country, and in 1998 the population was estimated to be 1,000. However, recent studies have indicated that leopards have disappeared from large areas, probably as a result of habitat loss, a low prey base and poaching, indicating this species may not be as common in China as previously believed. To examine this we reviewed recent literature and interviewed specialists to determine the current status and distribution of the leopard in China. Our findings indicate that the species has declined dramatically, with confirmation of presence at only 44 sites in 11 provinces, despite extensive surveys. Current populations are small and fragmented, and occur mainly in isolated nature reserves. We estimate a total population of only 174–348 P. pardus japonensis (the north Chinese leopard), which is endemic to China, and < 30 individuals for each of the other subspecies whose distributions extend beyond China. We recommend that a separate IUCN assessment be made for P. pardus japonensis, and that this subspecies be categorized as Critically Endangered. Our findings are the first reliable estimates of the current distribution and status of the leopard in China, and provide valuable information that will help guide conservation efforts.
The main purpose of this paper is to study the mean value properties of certain Hardy sums over a short interval by using the mean-value theorems of the Dirichlet $L$-functions. Our main result is a mean-value formula for these sums.
Powder mixtures of Ti/Si/C, Ti/SiC/C, Ti/Si/TiC, Ti/SiC/TiC and Ti/TiSi2/TiC were used for the synthesis of Ti3SiC2 by using a pulse discharge sintering (PDS) process. The Ti/Si/TiC powder was found to be the best among the five powder mixtures for the Ti3SiC2 synthesis. The highest content of Ti3SiC2 can be improved to about 99wt% at the sintering temperature of 1300°C for 15 minutes. The relative density of all the synthesized samples is higher than 98–99% at the sintering temperature above 1275°C. The nearly single phase Ti3SiC2 was found to show plastic deformation at room temperature and a good machinability. Both electrical and thermal conductivity were found to be more than two times of the value of a control pure Ti sample. The high-temperature mechanical tests confirmed that the Ti3SiC2 samples synthesized by the PDS process displayed a comparable performance with those fabricated by the other techniques.
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