From the synopical CTD sections in the WOCE PR11 repeated cruises, the South Pacific Subtropical Mode Water (SPSTMW) has been identified in the region of the Tasman Front Extension (TFE) around 29?S to the east of Aus...From the synopical CTD sections in the WOCE PR11 repeated cruises, the South Pacific Subtropical Mode Water (SPSTMW) has been identified in the region of the Tasman Front Extension (TFE) around 29?S to the east of Australia. In the depth range of 150-250 m, the SPSTMW appears as a thermostad with vertical temperature gradient lower than 1.6℃(100 m)-1 and a tem- perature range of 16.5-19.5℃ and as a pycnostad with PV lower than 2×10-10 m-1 s-1 and a potential density range of 25.4-26.0 kg m-3. Like the subtropical mode waters in the North Atlantic and North Pacific, the formation of the SPSTMW is associated with the convective mixing during the austral wintertime as manifested from the time series of the Argo floats. And cold water entrains into the mixed layer with the deepening mixed layer from September to the middle of October. During the wintertime formation process, mesoscale eddies prevailing in the TFE region play an important role in the SPSTMW formation, and have a great effect on the SPSTMW distribution in the next year. The deeper (shallower) mixed layer in wintertime, consistent with the depressed (uplifted) permanent thermocline, is formed by the anticyclonic (cyclonic) eddies, and the substantial mode water thicker than 50 m is mainly found in the region of the anticyclonic eddies where the permanent thermocline is deeper than 450 m.展开更多
PrrOll nanoparticles were obtained by subsequent thermal decomposition of the as-prepared precipitate formed under ambient temperature and pressure using NaOH as precipitant. The calcination process was affected, for ...PrrOll nanoparticles were obtained by subsequent thermal decomposition of the as-prepared precipitate formed under ambient temperature and pressure using NaOH as precipitant. The calcination process was affected, for 1 h in static air atmosphere, at 400-700 ℃ temperature range. The different samples were characterized using X-ray diffraction （XRD）, transmission electron microscopy （TEM）, field emission scanning electron microscopy （FE-SEM）, thermogravimetric analysis （TGA）, in situ electrical conductivity, and N2 adsorption/desorption. The obtained results demonstrated that nano-crystalline Pr6O11, with crystallites size of 6-12 nm, started to form at 500 ℃. Such value increased to 20-33 nm for the sample calcined at 700℃. The as-synthesized PrrOll nanoparticles presented high electrical conductivity due to electron hopping between Pr（III）-Pr（IV） pairs.展开更多
To improve the strength, hardness and heat resistance of Mg-6Al-lZn （AZ61） alloy, the effects of Pr addition on the as-cast microstructure and mechanical properties of AZ61 alloy were investigated at room and elevat...To improve the strength, hardness and heat resistance of Mg-6Al-lZn （AZ61） alloy, the effects of Pr addition on the as-cast microstructure and mechanical properties of AZ61 alloy were investigated at room and elevated temperatures by means of Brinell hardness measurement, optical microscope （OM）, scanning electron microscope （SEM）, energy dispersive spectroscopy （EDS）, X-ray diffractometer （XRD） and DNS100 electronic universal testing machine. The results show that the microstructures of Pr-containing AZ61 alloys were refined, with primary,β-MglTAI12 phase distributed homogeneously. When the addition of Pr is up to 1.2wt.%, theβ phase becomes finer, and new needle-like or short-rod shaped AI11Pr3 phase and blocky AIPr phase appear. As a result, optimal tensile properties are obtained. However, greater than 1.2wt.% Pr addition leads to poorer mechanical properties due to the aggregation of the needle-like phase and large size of grains. The present research findings provide a new way for strengthening of magnesium alloys at room and elevated temperatures, and a method of producing thermally-stable AZ61 magnesium alloy.展开更多
基金This study was supported by the Chinese Natural Science Foundation of China(NSFC)(Nos.40276009 and 90411010)
文摘From the synopical CTD sections in the WOCE PR11 repeated cruises, the South Pacific Subtropical Mode Water (SPSTMW) has been identified in the region of the Tasman Front Extension (TFE) around 29?S to the east of Australia. In the depth range of 150-250 m, the SPSTMW appears as a thermostad with vertical temperature gradient lower than 1.6℃(100 m)-1 and a tem- perature range of 16.5-19.5℃ and as a pycnostad with PV lower than 2×10-10 m-1 s-1 and a potential density range of 25.4-26.0 kg m-3. Like the subtropical mode waters in the North Atlantic and North Pacific, the formation of the SPSTMW is associated with the convective mixing during the austral wintertime as manifested from the time series of the Argo floats. And cold water entrains into the mixed layer with the deepening mixed layer from September to the middle of October. During the wintertime formation process, mesoscale eddies prevailing in the TFE region play an important role in the SPSTMW formation, and have a great effect on the SPSTMW distribution in the next year. The deeper (shallower) mixed layer in wintertime, consistent with the depressed (uplifted) permanent thermocline, is formed by the anticyclonic (cyclonic) eddies, and the substantial mode water thicker than 50 m is mainly found in the region of the anticyclonic eddies where the permanent thermocline is deeper than 450 m.
文摘PrrOll nanoparticles were obtained by subsequent thermal decomposition of the as-prepared precipitate formed under ambient temperature and pressure using NaOH as precipitant. The calcination process was affected, for 1 h in static air atmosphere, at 400-700 ℃ temperature range. The different samples were characterized using X-ray diffraction （XRD）, transmission electron microscopy （TEM）, field emission scanning electron microscopy （FE-SEM）, thermogravimetric analysis （TGA）, in situ electrical conductivity, and N2 adsorption/desorption. The obtained results demonstrated that nano-crystalline Pr6O11, with crystallites size of 6-12 nm, started to form at 500 ℃. Such value increased to 20-33 nm for the sample calcined at 700℃. The as-synthesized PrrOll nanoparticles presented high electrical conductivity due to electron hopping between Pr（III）-Pr（IV） pairs.
基金supported by the National Natural Science Foundation of China(No.50571073)the Natural Science Foundation of Shanxi Province(No.2009011028-3,20051052)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20111402110004)
文摘To improve the strength, hardness and heat resistance of Mg-6Al-lZn （AZ61） alloy, the effects of Pr addition on the as-cast microstructure and mechanical properties of AZ61 alloy were investigated at room and elevated temperatures by means of Brinell hardness measurement, optical microscope （OM）, scanning electron microscope （SEM）, energy dispersive spectroscopy （EDS）, X-ray diffractometer （XRD） and DNS100 electronic universal testing machine. The results show that the microstructures of Pr-containing AZ61 alloys were refined, with primary,β-MglTAI12 phase distributed homogeneously. When the addition of Pr is up to 1.2wt.%, theβ phase becomes finer, and new needle-like or short-rod shaped AI11Pr3 phase and blocky AIPr phase appear. As a result, optimal tensile properties are obtained. However, greater than 1.2wt.% Pr addition leads to poorer mechanical properties due to the aggregation of the needle-like phase and large size of grains. The present research findings provide a new way for strengthening of magnesium alloys at room and elevated temperatures, and a method of producing thermally-stable AZ61 magnesium alloy.
