Copper cladding aluminum(CCA)rods with the section dimensions of12mm in diameter and2mm in sheath thickness were fabricated by vertical core-filling continuous casting(VCFC)technology.The kinds and morphology of inter...Copper cladding aluminum(CCA)rods with the section dimensions of12mm in diameter and2mm in sheath thickness were fabricated by vertical core-filling continuous casting(VCFC)technology.The kinds and morphology of interfacial intermetallic compounds(IMCs)were investigated by SEM,XRD and TEM.The results showed that the interfacial structure of Cu/Al was mainly composed of layeredγ1(Cu9Al4),cellularθ(CuAl2),andα(Al)+θ(CuAl2)phases.Moreover,residual acicularε2(Cu3Al2+x)phase was observed at the Cu/Al interface.By comparing the driving force of formation forε2(Cu3Al2+x)andγ1(Cu9Al4)phases,the conclusion was drawn that theε2(Cu3Al2+x)formed firstly at the Cu/Al interface.In addition,the interfacial formation mechanism of copper cladding aluminum composites was revealed completely.展开更多
Carbon encapsulated iron nanoparticles （CEINPs） with very thin shells and good core-shell structures were prepared by DC arc discharge at argon intake temperature （AIT） of 800 ℃. The results of high resolution tr...Carbon encapsulated iron nanoparticles （CEINPs） with very thin shells and good core-shell structures were prepared by DC arc discharge at argon intake temperature （AIT） of 800 ℃. The results of high resolution transmission electron microscope （HRTEM）, energy dispersive X-ray （EDX） spectroscope, X-ray diffraction （XRD）, and X-ray photoelectron spectroscope （XPS） characterizations on the product B show that the thickness of the carbon shells of CEINPs in the product B is in the range of ca. 0.5-5.3 nm, i. e., which can be as thin as only two layers of graphite. The average diameter of the CEINPs is about 24. 7 nm. The total content of Fe element in the product B is 77.0 wt%. The saturation magnetization （Ms） and coercivity （Hc） of the product B are 107.4 emu/g and 143 Oe. resnectivelv. The formation of the CEINPs in the oroduct B is discussed briefly.展开更多
Data envelopment analysis was applied to determine relative efficiencies of state-owned and joint-stock banks in Chongqing,P. R. China,during the years 1996 to 2000. We found that state-owned banks have low levels of ...Data envelopment analysis was applied to determine relative efficiencies of state-owned and joint-stock banks in Chongqing,P. R. China,during the years 1996 to 2000. We found that state-owned banks have low levels of efficiency when compared with joint-stock banks,but some joint-stock bank branches have low efficiency scores. Efficiency difference testing by using the Mann-Whitney rank order statistic indicates that the efficiency gap between state-owned and joint-stock banks is insignificant,which is characteristic of regional banks. We also presented some factors that may affect bank efficiency,and offer suggestions to improve bank management and efficiency.展开更多
Encapsulation of DASP （4-[4-（dimethylamino）styryl]-l-octylpyridinium bromide） with amylose, and conformational transitions of amylose upon complexation with the dyes were investigated using UV-vis, fluorescence an...Encapsulation of DASP （4-[4-（dimethylamino）styryl]-l-octylpyridinium bromide） with amylose, and conformational transitions of amylose upon complexation with the dyes were investigated using UV-vis, fluorescence and two-photon absorption properties in various Dimethyl Sulfoxide （ DMSO）/H20 mixtures. Encapsulation of the dye was achieved by dilution of DMSO stock solutions of the chromophores （1 x 10^-3 M） and amylose （1 x 10^-1 M） with DMSO, followed by a dropwise addition of H20 with continuous stirring at room temperature. At less than 40% aqueous DMSO solutions, the chromophores had a stable encapsulation with amylose and showed over 100 times the fluorescence intensity of non-encapsulated chromophores. Both of the dye solution with and without amylose also exhibit 2PA （two-photon absorption）, as determined by nonlinear absorption measurements using 10 ns laser pulses at 800 nm. The respective values of two-photon cross-sections are 13.3 x 10.20 for encapsulated dye solution and 2.53 x 10.20 cma/GW for non encapsulated dye solution. The data clearly indicate that the contribution of the encapsulated dye dominates the two-photon absorption cross-section of the non encapsulated dye at 800 nm.展开更多
The nonlinear evolution of a finite-amplitude disturbance in a 3-D supersonic boundary layer over a cone was investigated recently by Liu et al. using direct numerical simulation （DNS）. It was found that certain sma...The nonlinear evolution of a finite-amplitude disturbance in a 3-D supersonic boundary layer over a cone was investigated recently by Liu et al. using direct numerical simulation （DNS）. It was found that certain small-scale 3-D disturbances amplified rapidly. These disturbances exhibit the characteristics of second modes, and the most amplified components have a well- defined spanwise wavelength, indicating a clear selectivity of the amplification. In the case of a cone, the three-dimensionality of the base flow and the disturbances themselves may be responsible for the rapid amplification. In order to ascertain which of these two effects are essential, in this study we carried out DNS of the nonlinear evolution of a spanwise localized disturbance （wavepacket） in a flat-plate boundary layer. A similar amplification of small-scale disturbances was observed, suggesting that the direct reason for the rapid amplification is the three-dimensionality of the disturbances rather than the three-dimensional nature of the base flow, even though the latter does alter the spanwise distribution of the disturbance. The rapid growth of 3-D waves may be attributed to the secondary instability mechanism. Further simulations were performed for a wavepacket of first modes in a supersonic boundary layer and of Tollmien-Schlichting （T-S） waves in an incompressible boundary layer. The re- suits show that the amplifying components are in the band centered at zero spanwise wavenumber rather than at a finite spanwise wavenumber. It is therefore concluded that the rapid growth of 3-D disturbances in a band centered at a preferred large spanwise wavenumber is the main characteristic of nonlinear evolution of second mode disturbances in supersonic boundary layers.展开更多
基金Project(51274038)supported by the National Natural Science Foundation of China
文摘Copper cladding aluminum(CCA)rods with the section dimensions of12mm in diameter and2mm in sheath thickness were fabricated by vertical core-filling continuous casting(VCFC)technology.The kinds and morphology of interfacial intermetallic compounds(IMCs)were investigated by SEM,XRD and TEM.The results showed that the interfacial structure of Cu/Al was mainly composed of layeredγ1(Cu9Al4),cellularθ(CuAl2),andα(Al)+θ(CuAl2)phases.Moreover,residual acicularε2(Cu3Al2+x)phase was observed at the Cu/Al interface.By comparing the driving force of formation forε2(Cu3Al2+x)andγ1(Cu9Al4)phases,the conclusion was drawn that theε2(Cu3Al2+x)formed firstly at the Cu/Al interface.In addition,the interfacial formation mechanism of copper cladding aluminum composites was revealed completely.
文摘Carbon encapsulated iron nanoparticles （CEINPs） with very thin shells and good core-shell structures were prepared by DC arc discharge at argon intake temperature （AIT） of 800 ℃. The results of high resolution transmission electron microscope （HRTEM）, energy dispersive X-ray （EDX） spectroscope, X-ray diffraction （XRD）, and X-ray photoelectron spectroscope （XPS） characterizations on the product B show that the thickness of the carbon shells of CEINPs in the product B is in the range of ca. 0.5-5.3 nm, i. e., which can be as thin as only two layers of graphite. The average diameter of the CEINPs is about 24. 7 nm. The total content of Fe element in the product B is 77.0 wt%. The saturation magnetization （Ms） and coercivity （Hc） of the product B are 107.4 emu/g and 143 Oe. resnectivelv. The formation of the CEINPs in the oroduct B is discussed briefly.
基金the National Science Fund for Distinguished Young Scholars from Natural Science Foundation of China (No.70525005).
文摘Data envelopment analysis was applied to determine relative efficiencies of state-owned and joint-stock banks in Chongqing,P. R. China,during the years 1996 to 2000. We found that state-owned banks have low levels of efficiency when compared with joint-stock banks,but some joint-stock bank branches have low efficiency scores. Efficiency difference testing by using the Mann-Whitney rank order statistic indicates that the efficiency gap between state-owned and joint-stock banks is insignificant,which is characteristic of regional banks. We also presented some factors that may affect bank efficiency,and offer suggestions to improve bank management and efficiency.
文摘Encapsulation of DASP （4-[4-（dimethylamino）styryl]-l-octylpyridinium bromide） with amylose, and conformational transitions of amylose upon complexation with the dyes were investigated using UV-vis, fluorescence and two-photon absorption properties in various Dimethyl Sulfoxide （ DMSO）/H20 mixtures. Encapsulation of the dye was achieved by dilution of DMSO stock solutions of the chromophores （1 x 10^-3 M） and amylose （1 x 10^-1 M） with DMSO, followed by a dropwise addition of H20 with continuous stirring at room temperature. At less than 40% aqueous DMSO solutions, the chromophores had a stable encapsulation with amylose and showed over 100 times the fluorescence intensity of non-encapsulated chromophores. Both of the dye solution with and without amylose also exhibit 2PA （two-photon absorption）, as determined by nonlinear absorption measurements using 10 ns laser pulses at 800 nm. The respective values of two-photon cross-sections are 13.3 x 10.20 for encapsulated dye solution and 2.53 x 10.20 cma/GW for non encapsulated dye solution. The data clearly indicate that the contribution of the encapsulated dye dominates the two-photon absorption cross-section of the non encapsulated dye at 800 nm.
基金supported by the National Basic Research Program of China (Grant No. 2009CB724103)
文摘The nonlinear evolution of a finite-amplitude disturbance in a 3-D supersonic boundary layer over a cone was investigated recently by Liu et al. using direct numerical simulation （DNS）. It was found that certain small-scale 3-D disturbances amplified rapidly. These disturbances exhibit the characteristics of second modes, and the most amplified components have a well- defined spanwise wavelength, indicating a clear selectivity of the amplification. In the case of a cone, the three-dimensionality of the base flow and the disturbances themselves may be responsible for the rapid amplification. In order to ascertain which of these two effects are essential, in this study we carried out DNS of the nonlinear evolution of a spanwise localized disturbance （wavepacket） in a flat-plate boundary layer. A similar amplification of small-scale disturbances was observed, suggesting that the direct reason for the rapid amplification is the three-dimensionality of the disturbances rather than the three-dimensional nature of the base flow, even though the latter does alter the spanwise distribution of the disturbance. The rapid growth of 3-D waves may be attributed to the secondary instability mechanism. Further simulations were performed for a wavepacket of first modes in a supersonic boundary layer and of Tollmien-Schlichting （T-S） waves in an incompressible boundary layer. The re- suits show that the amplifying components are in the band centered at zero spanwise wavenumber rather than at a finite spanwise wavenumber. It is therefore concluded that the rapid growth of 3-D disturbances in a band centered at a preferred large spanwise wavenumber is the main characteristic of nonlinear evolution of second mode disturbances in supersonic boundary layers.
