Ultrafine tungsten carbide and fine cobalt as well as nano yttrium oxide powders were used as the raw materials. The effects of hot-press below the eutectic temperature and conventional liquid phase sintering on the s...Ultrafine tungsten carbide and fine cobalt as well as nano yttrium oxide powders were used as the raw materials. The effects of hot-press below the eutectic temperature and conventional liquid phase sintering on the structures and properties of WC-20Co-1Y2O3 cemented carbide were studied. It is shown that hot-pressed alloy has the character of isotropic properties and microstructure with homogeneous and ultrafine WC grains. However, the ultrafine and fully-densified structure is developed at the cost of the presence of large amount of cobalt-lake （unevenly distributed binder phase）, and thus lower strength. Yttrium oxide in the alloy cannot play the role of grain growth inhibitor fully when cemented carbide with high content of cobalt and ultrafine raw materials is sintered at high liquid phase sintering temperature. Peculiar platelet-enhanced bi-model structure is formed in WC-20Co-1Y2O3 cemented carbide by conventional liquid phase sintering, which points out that yttrium oxide in the alloy facilitates the formation of plate-like WC grain.展开更多
Based on mode acoustic emission theory,the paper analyses the acoustic emission analog signal of thin steel plate using matching pursuit,then obtains the characteristics interpretation of the different frequency signa...Based on mode acoustic emission theory,the paper analyses the acoustic emission analog signal of thin steel plate using matching pursuit,then obtains the characteristics interpretation of the different frequency signal energy concentration degree; Combined with four-point arc positioning method,the papers researches the damage localization of the plate-like structure. Simulation experiment shows that this method can accurately detect and locate the damage. This can provide data support for further imaging research based on time reverse theory.展开更多
Phylogenetic relations of twining chirality of Dioscorea sp.in China were analyzed based on the genes matK,rbcL and trnL;phylogenetic character of higher-level phylogeny of twining plants was analyzed at a high taxon ...Phylogenetic relations of twining chirality of Dioscorea sp.in China were analyzed based on the genes matK,rbcL and trnL;phylogenetic character of higher-level phylogeny of twining plants was analyzed at a high taxon level based on matK gene.A significant phylogenetic framework of chirality was found:(i)based on matK analysis,right-handed Dioscorea species in China congregate completely to form a monophyly;(ii)rbcL and trnL data sets also supported Chinese right-handed Dioscorea a monophyly,although with ex...展开更多
文摘Ultrafine tungsten carbide and fine cobalt as well as nano yttrium oxide powders were used as the raw materials. The effects of hot-press below the eutectic temperature and conventional liquid phase sintering on the structures and properties of WC-20Co-1Y2O3 cemented carbide were studied. It is shown that hot-pressed alloy has the character of isotropic properties and microstructure with homogeneous and ultrafine WC grains. However, the ultrafine and fully-densified structure is developed at the cost of the presence of large amount of cobalt-lake （unevenly distributed binder phase）, and thus lower strength. Yttrium oxide in the alloy cannot play the role of grain growth inhibitor fully when cemented carbide with high content of cobalt and ultrafine raw materials is sintered at high liquid phase sintering temperature. Peculiar platelet-enhanced bi-model structure is formed in WC-20Co-1Y2O3 cemented carbide by conventional liquid phase sintering, which points out that yttrium oxide in the alloy facilitates the formation of plate-like WC grain.
基金supported by the Natural Science Foundation of Naval University of Engineering(under Grant No.HGDYDJJ13152)
文摘Based on mode acoustic emission theory,the paper analyses the acoustic emission analog signal of thin steel plate using matching pursuit,then obtains the characteristics interpretation of the different frequency signal energy concentration degree; Combined with four-point arc positioning method,the papers researches the damage localization of the plate-like structure. Simulation experiment shows that this method can accurately detect and locate the damage. This can provide data support for further imaging research based on time reverse theory.
基金Supported by the CAS Special Grant for Postgraduate Research,Innovation and Practice~~
文摘Phylogenetic relations of twining chirality of Dioscorea sp.in China were analyzed based on the genes matK,rbcL and trnL;phylogenetic character of higher-level phylogeny of twining plants was analyzed at a high taxon level based on matK gene.A significant phylogenetic framework of chirality was found:(i)based on matK analysis,right-handed Dioscorea species in China congregate completely to form a monophyly;(ii)rbcL and trnL data sets also supported Chinese right-handed Dioscorea a monophyly,although with ex...
