Iron isotopic composition of the upper continental crust(UCC) is critical for understanding Fe mobilization and migration through the Earth. Because rocks exposed at Earth's surface have heterogeneous δ^(56)Fe, f...Iron isotopic composition of the upper continental crust(UCC) is critical for understanding Fe mobilization and migration through the Earth. Because rocks exposed at Earth's surface have heterogeneous δ^(56)Fe, finegrained clastic sediments can be used to estimate the average composition of UCC. In this study, we report δ^(56)Fe of loess-paleosol sequences from Yimaguan, Chinese Loess Plateau(CLP), to constrain the average Fe isotopic composition of UCC. The loess-paleosol sequences in this area formed in glacial-interglacial cycles and are characterized by varying degrees of weathering. Our data show that the loess-paleosol layers have extremely homogeneous Fe isotopic compositions with δ^(56)Fe ranging from 0.06‰ to 0.12‰, regardless of variations in the major element composition and weathering intensity. Our study indicates that since Fe isotopes are not significantly fractionated during loess deposition, the loess can be regarded as representative of UCC. It follows that the average δ^(56)Fe of UCC is 0.09‰± 0.03‰(2SD), consistent with previous estimates based on igneous rock data.展开更多
In this study,a new method is presented to correlate the shear viscosity of nanofluids by local composition theory.The Eyring theory and nonrandom two-liquid(NRTL)equation are used for this purpose.The effects of temp...In this study,a new method is presented to correlate the shear viscosity of nanofluids by local composition theory.The Eyring theory and nonrandom two-liquid(NRTL)equation are used for this purpose.The effects of temperature and particle volume concentration on the viscosity are investigated.The adjustable parameters of NRTL equation are obtained by fitting with experimental data.The calculated shear viscosities for nanofluids of CuO/water with 29 nm particle size,Al2O3/water with two different particle diameters,36 nm and 47 nm,and CuO/(ethylene glycol,water)are compared with experimental data and the average absolute deviation(AAD)is 1.2%,while the results from some conventional models yield an AAD of 190%.The results of this study are in excellent agreement with experimental data.展开更多
Climatic factor＇s effect was studied on the radial growth of teak （Tectona grandis L.F.） by using the stem analysis of 36 trees distributed in 6 plantations in Parakou and Tchaourou districts in northern Benin. The...Climatic factor＇s effect was studied on the radial growth of teak （Tectona grandis L.F.） by using the stem analysis of 36 trees distributed in 6 plantations in Parakou and Tchaourou districts in northern Benin. The results showed that the plantations of Parakou were in general more productive than those of Tchaourou. The annual average growth was estimated in the first five years at 0.86 cm/year for Parakou and 0.76 cm/year at Tchaourou. The analysis of the radial growth showed that a significant percentage of the variance was allotted to the growth model. It follows that a big part of the ring width was predetermined before the intervention of the other factors, in particular the climatic conditions. The percentage of the variance related to the climatic conditions was thus more reduced for the plantations of Tchaourou than those of Parakou. The radial growth was influenced by the conditions of humidity （evapotranspiration, humidity and rain） of February to May on the one hand and those from August to October on the other hand.展开更多
基金financially supported by the National Science Foundation of China(41173031,41325011 and 41503001)the Fundamental Research Funds for the Central Universities(WK3410000004)
文摘Iron isotopic composition of the upper continental crust(UCC) is critical for understanding Fe mobilization and migration through the Earth. Because rocks exposed at Earth's surface have heterogeneous δ^(56)Fe, finegrained clastic sediments can be used to estimate the average composition of UCC. In this study, we report δ^(56)Fe of loess-paleosol sequences from Yimaguan, Chinese Loess Plateau(CLP), to constrain the average Fe isotopic composition of UCC. The loess-paleosol sequences in this area formed in glacial-interglacial cycles and are characterized by varying degrees of weathering. Our data show that the loess-paleosol layers have extremely homogeneous Fe isotopic compositions with δ^(56)Fe ranging from 0.06‰ to 0.12‰, regardless of variations in the major element composition and weathering intensity. Our study indicates that since Fe isotopes are not significantly fractionated during loess deposition, the loess can be regarded as representative of UCC. It follows that the average δ^(56)Fe of UCC is 0.09‰± 0.03‰(2SD), consistent with previous estimates based on igneous rock data.
文摘In this study,a new method is presented to correlate the shear viscosity of nanofluids by local composition theory.The Eyring theory and nonrandom two-liquid(NRTL)equation are used for this purpose.The effects of temperature and particle volume concentration on the viscosity are investigated.The adjustable parameters of NRTL equation are obtained by fitting with experimental data.The calculated shear viscosities for nanofluids of CuO/water with 29 nm particle size,Al2O3/water with two different particle diameters,36 nm and 47 nm,and CuO/(ethylene glycol,water)are compared with experimental data and the average absolute deviation(AAD)is 1.2%,while the results from some conventional models yield an AAD of 190%.The results of this study are in excellent agreement with experimental data.
文摘Climatic factor＇s effect was studied on the radial growth of teak （Tectona grandis L.F.） by using the stem analysis of 36 trees distributed in 6 plantations in Parakou and Tchaourou districts in northern Benin. The results showed that the plantations of Parakou were in general more productive than those of Tchaourou. The annual average growth was estimated in the first five years at 0.86 cm/year for Parakou and 0.76 cm/year at Tchaourou. The analysis of the radial growth showed that a significant percentage of the variance was allotted to the growth model. It follows that a big part of the ring width was predetermined before the intervention of the other factors, in particular the climatic conditions. The percentage of the variance related to the climatic conditions was thus more reduced for the plantations of Tchaourou than those of Parakou. The radial growth was influenced by the conditions of humidity （evapotranspiration, humidity and rain） of February to May on the one hand and those from August to October on the other hand.
