Trace amount of water associated with the lattice defects of nominally anhydrous minerals （NAMs） can be measured using Fourier transform infrared spectroscopy （FTIR） and secondary ion mass spectrometry （SIMS）. L...Trace amount of water associated with the lattice defects of nominally anhydrous minerals （NAMs） can be measured using Fourier transform infrared spectroscopy （FTIR） and secondary ion mass spectrometry （SIMS）. Lots of data on water in NAMs from different lithologies, especially mantle peridotite xenoliths, have been published. The water distribution in olivine from peridotite xenoliths often displays a diffusion profile with high water concentration in the core and low at the rim, which indicates water loss via diffusion during the ascent of host magma. On the other hand, water is homogeneously distributed in pyroxene and its concentration is typically interpreted to represent a mantle value. The water concentration of magma in equilibrium with NAM can be estimated using specific partition coefficient, from which the water content of parental magma and the mantle source can be inferred. The accuracy of this method, however, depends on the selection of appropriate partition coefficient for the system. Using hydrogen isotope compositions and H2O/Ce ratios of mantle NAMs, water source regions can be traced and water heterogeneity can be mapped in the upper mantle. Water plays an important role in the stability of cratonic mantle. The water contents and vertical distribution patterns can be significantly different among different cratonic manties, which may result from different geologic activities. However, the mantle-plume interaction may not necessarily result in significant change of water content in cratonic mantle. The estimation of the water content in the upper mantle is still largely based on geochemical models due to the limitations of data on water in mantle NAMs.展开更多
A phase-field model with forced liquid metal flow was employed to study the effect of boundary heat flux on the dendritic structure forming of a Ni-40.8%Cu alloy with liquid flow during solidification.The effect of th...A phase-field model with forced liquid metal flow was employed to study the effect of boundary heat flux on the dendritic structure forming of a Ni-40.8%Cu alloy with liquid flow during solidification.The effect of the flow field coupling with boundary heat extractions on the morphology change and distributions of concentration and temperature fields was analyzed and discussed.The forced liquid flow could significantly affect the dendrite morphology,concentration and temperature distributions in the solidifying microstructure.And coupling with boundary heat extraction,the solute segregation and concentration diffusion were changed with different heat flux.The morphology,concentration and temperature distributions were significantly influenced by increasing the heat extraction,which could relatively make the effect of liquid flow constrained.With increasing the initial velocity of liquid flow,the lopsided rate of the primary dendrite arm was enlarged and the transition of developing manner of the secondary arms moved to the large heat extraction direction.It was the competition between heat flux and forced liquid flow that finally determined microstructure forming during solidification.展开更多
The proliferation of urban development with concentration in population and human-environment interaction has intensified around urban environments. This has resulted in the degradation of urban environments, overuse ...The proliferation of urban development with concentration in population and human-environment interaction has intensified around urban environments. This has resulted in the degradation of urban environments, overuse of natural resources and widespread pollution of ecosystems, The patterns of design initiatives continue to follow unsustainable path with impacts on stream ecosystems. Accordingly, the paper adopts geospatial information systems and sustainability principles for the identification and sequential mapping of stressors impeding natural systems in Southern Mississippi. The results not only reveal that the study area experienced some significant changes in its watershed environments, but the stream habitat ecosystem remains under stress. The recommendations for mitigating the problems range from policy considerations to the adoption of ecosystem approach.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 41590623 & 41573055)the Fundamental Research Funds for the Central Universities of China
文摘Trace amount of water associated with the lattice defects of nominally anhydrous minerals （NAMs） can be measured using Fourier transform infrared spectroscopy （FTIR） and secondary ion mass spectrometry （SIMS）. Lots of data on water in NAMs from different lithologies, especially mantle peridotite xenoliths, have been published. The water distribution in olivine from peridotite xenoliths often displays a diffusion profile with high water concentration in the core and low at the rim, which indicates water loss via diffusion during the ascent of host magma. On the other hand, water is homogeneously distributed in pyroxene and its concentration is typically interpreted to represent a mantle value. The water concentration of magma in equilibrium with NAM can be estimated using specific partition coefficient, from which the water content of parental magma and the mantle source can be inferred. The accuracy of this method, however, depends on the selection of appropriate partition coefficient for the system. Using hydrogen isotope compositions and H2O/Ce ratios of mantle NAMs, water source regions can be traced and water heterogeneity can be mapped in the upper mantle. Water plays an important role in the stability of cratonic mantle. The water contents and vertical distribution patterns can be significantly different among different cratonic manties, which may result from different geologic activities. However, the mantle-plume interaction may not necessarily result in significant change of water content in cratonic mantle. The estimation of the water content in the upper mantle is still largely based on geochemical models due to the limitations of data on water in mantle NAMs.
基金supported by the NPU Foundation of Fundamental Research,China(Grant No.JC201272)
文摘A phase-field model with forced liquid metal flow was employed to study the effect of boundary heat flux on the dendritic structure forming of a Ni-40.8%Cu alloy with liquid flow during solidification.The effect of the flow field coupling with boundary heat extractions on the morphology change and distributions of concentration and temperature fields was analyzed and discussed.The forced liquid flow could significantly affect the dendrite morphology,concentration and temperature distributions in the solidifying microstructure.And coupling with boundary heat extraction,the solute segregation and concentration diffusion were changed with different heat flux.The morphology,concentration and temperature distributions were significantly influenced by increasing the heat extraction,which could relatively make the effect of liquid flow constrained.With increasing the initial velocity of liquid flow,the lopsided rate of the primary dendrite arm was enlarged and the transition of developing manner of the secondary arms moved to the large heat extraction direction.It was the competition between heat flux and forced liquid flow that finally determined microstructure forming during solidification.
文摘The proliferation of urban development with concentration in population and human-environment interaction has intensified around urban environments. This has resulted in the degradation of urban environments, overuse of natural resources and widespread pollution of ecosystems, The patterns of design initiatives continue to follow unsustainable path with impacts on stream ecosystems. Accordingly, the paper adopts geospatial information systems and sustainability principles for the identification and sequential mapping of stressors impeding natural systems in Southern Mississippi. The results not only reveal that the study area experienced some significant changes in its watershed environments, but the stream habitat ecosystem remains under stress. The recommendations for mitigating the problems range from policy considerations to the adoption of ecosystem approach.
