Turbulent mixing, in particular on a small scale, aff ects the growth of microalgae by changing diff usive sublayers and regulating nutrient fluxes of cells. We tested the nutrient flux hypothesis by evaluating the ce...Turbulent mixing, in particular on a small scale, aff ects the growth of microalgae by changing diff usive sublayers and regulating nutrient fluxes of cells. We tested the nutrient flux hypothesis by evaluating the cellular stoichiometry and phosphorus storage of microalgae under dif ferent turbulent mixing conditions. A phanizomenon flos-aquae were cultivated in dif ferent stirring batch reactors with turbulent dissipation rates ranging from 0.001 51 m2/s 3 to 0.050 58 m 2/s 3, the latter being the highest range observed in natural aquatic systems. Samples were taken in the exponential growth phase and compared with samples taken when the reactor was completely stagnant. Results indicate that, within a certain range, turbulent mixing stimulates the growth of A. flos-aquae. An inhibitory ef fect on growth rate was observed at the higher range. Photosynthesis activity, in terms of maximum ef fective quantum yield of PSII(the ratio of F v/F m) and cellular chlorophyll a, did not change significantly in response to turbulence. However, Chl a/C mass ratio and C/N molar ratio, showed a unimodal response under a gradient of turbulent mixing, similar to growth rate. Moreover, we found that increases in turbulent mixing might stimulate respiration rates, which might lead to the use of polyphosphate for the synthesis of cellular constituents. More research is required to test and verify the hypothesis that turbulent mixing changes the dif fusive sublayer, regulating the nutrient flux of cells.展开更多
The research works of methane concentration in water column of the Okhotsk Sea from 1984 to 2005 were reviewed.And some regularities of methane distribution in water column in the North-East Sakhalin slope of the Okho...The research works of methane concentration in water column of the Okhotsk Sea from 1984 to 2005 were reviewed.And some regularities of methane distribution in water column in the North-East Sakhalin slope of the Okhotsk Sea were concluded.展开更多
A pneumatic launcher is theoretically investigated to study its natural transverse vibration in water. Considering the mass effect of the sealing cover, the launcher is simplified as a uniform cantilever beam with a t...A pneumatic launcher is theoretically investigated to study its natural transverse vibration in water. Considering the mass effect of the sealing cover, the launcher is simplified as a uniform cantilever beam with a top point mass. By introducing the boundary and continuity conditions into the motion equation, the natural frequency equation and the mode shape function are derived. An iterative calculation method for added mass is also presented using the velocity potential function to account for the mass effect of the fluid on the launcher. The first 2 order natural frequencies and mode shapes are discussed in external flow fields and both external and internal flow fields. The results show good agreement with both natural frequencies and mode shapes between the theoretical analysis and the FEM studies. Also, the added mass is found to decrease with the increase of the mode shape orders of the launcher. And because of the larger added mass in both the external and internal flow fields than that in only the external flow field, the corresponding natural frequencies of the former are relatively smaller.展开更多
Rain infiltration into a soil slope leads to propagation of the wetting front, transport of air in pores and deformation of the soils, in which coupled processes among the solid, liquid and gas phases are typically in...Rain infiltration into a soil slope leads to propagation of the wetting front, transport of air in pores and deformation of the soils, in which coupled processes among the solid, liquid and gas phases are typically involved. Most previous studies on the unsaturated flow and its influence on slope stability were based on the singlephase water flow model (i.e., the Richards Equation) or the waterair two-phase flow model. The effects of gas transport and soil deformation on the movement of groundwater and the evolution of slope stability were less examined with a coupled solid-water-air model. In this paper, a numerical model was established based on the principles of the continuum mechanics and the averaging approach of the mixture theory and implemented in an FEM code for analysis of the coupled deformation, water flow and gas transport in porous media. The proposed model and the computer code were validated by the Liakopoulos drainage test over a sand column, and the significant effect of the lateral air boundary condition on the draining process of water was discussed. On this basis, the coupled processes of groundwater flow, gas transport and soil deformation in a homogeneous soil slope under a long heavy rainfall were simulated with the proposed three-phase model, and the numerical results revealed the remarkable delaying effects of gas transport and soil deformation on the propagation of the wetting front and the evolution of the slope stability. The results may provide a helpful reference for hazard assessment and control of rainfall-induced landslides.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.51309220,51679226)the National Key SandT Project on Water Pollution Control and Treatment(Nos.2014ZX07104-006,2015ZX07103-007)the Western Action Program funded by the Chinese Academy of Sciences(No.KZCX2-XB3-14)
文摘Turbulent mixing, in particular on a small scale, aff ects the growth of microalgae by changing diff usive sublayers and regulating nutrient fluxes of cells. We tested the nutrient flux hypothesis by evaluating the cellular stoichiometry and phosphorus storage of microalgae under dif ferent turbulent mixing conditions. A phanizomenon flos-aquae were cultivated in dif ferent stirring batch reactors with turbulent dissipation rates ranging from 0.001 51 m2/s 3 to 0.050 58 m 2/s 3, the latter being the highest range observed in natural aquatic systems. Samples were taken in the exponential growth phase and compared with samples taken when the reactor was completely stagnant. Results indicate that, within a certain range, turbulent mixing stimulates the growth of A. flos-aquae. An inhibitory ef fect on growth rate was observed at the higher range. Photosynthesis activity, in terms of maximum ef fective quantum yield of PSII(the ratio of F v/F m) and cellular chlorophyll a, did not change significantly in response to turbulence. However, Chl a/C mass ratio and C/N molar ratio, showed a unimodal response under a gradient of turbulent mixing, similar to growth rate. Moreover, we found that increases in turbulent mixing might stimulate respiration rates, which might lead to the use of polyphosphate for the synthesis of cellular constituents. More research is required to test and verify the hypothesis that turbulent mixing changes the dif fusive sublayer, regulating the nutrient flux of cells.
文摘The research works of methane concentration in water column of the Okhotsk Sea from 1984 to 2005 were reviewed.And some regularities of methane distribution in water column in the North-East Sakhalin slope of the Okhotsk Sea were concluded.
基金Foundation item： Supported by the National Natural Science Foundation of China （51379083） and the Specialized Research Fund for the Doctoral Program of Hiher Education （20120142110051）.
文摘A pneumatic launcher is theoretically investigated to study its natural transverse vibration in water. Considering the mass effect of the sealing cover, the launcher is simplified as a uniform cantilever beam with a top point mass. By introducing the boundary and continuity conditions into the motion equation, the natural frequency equation and the mode shape function are derived. An iterative calculation method for added mass is also presented using the velocity potential function to account for the mass effect of the fluid on the launcher. The first 2 order natural frequencies and mode shapes are discussed in external flow fields and both external and internal flow fields. The results show good agreement with both natural frequencies and mode shapes between the theoretical analysis and the FEM studies. Also, the added mass is found to decrease with the increase of the mode shape orders of the launcher. And because of the larger added mass in both the external and internal flow fields than that in only the external flow field, the corresponding natural frequencies of the former are relatively smaller.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50839004, 51079107) the Program for New Centu-ry Excellent Talents in University (Grant No. NCET-09-0610)
文摘Rain infiltration into a soil slope leads to propagation of the wetting front, transport of air in pores and deformation of the soils, in which coupled processes among the solid, liquid and gas phases are typically involved. Most previous studies on the unsaturated flow and its influence on slope stability were based on the singlephase water flow model (i.e., the Richards Equation) or the waterair two-phase flow model. The effects of gas transport and soil deformation on the movement of groundwater and the evolution of slope stability were less examined with a coupled solid-water-air model. In this paper, a numerical model was established based on the principles of the continuum mechanics and the averaging approach of the mixture theory and implemented in an FEM code for analysis of the coupled deformation, water flow and gas transport in porous media. The proposed model and the computer code were validated by the Liakopoulos drainage test over a sand column, and the significant effect of the lateral air boundary condition on the draining process of water was discussed. On this basis, the coupled processes of groundwater flow, gas transport and soil deformation in a homogeneous soil slope under a long heavy rainfall were simulated with the proposed three-phase model, and the numerical results revealed the remarkable delaying effects of gas transport and soil deformation on the propagation of the wetting front and the evolution of the slope stability. The results may provide a helpful reference for hazard assessment and control of rainfall-induced landslides.
