We have established an elastoplastic analysis model to explore the effect of loading path in an incompressible thin-walled tube under the combined action of axial force and torque based on Mises yield condition and is...We have established an elastoplastic analysis model to explore the effect of loading path in an incompressible thin-walled tube under the combined action of axial force and torque based on Mises yield condition and isotropic linear hardening assumption.Further,four stress areas(σx,τx)are divided according to the characteristics of the final stress,and the plastic stress-strain relationship of twelve stress paths in different stress areas is derived.The"primary effect"of the stress path on plastic strain is demonstrated,namely,the plastic strain caused by the pre-loaded stress in path A(tensile stress is initially applied,followed by shear stress)is always greater than that caused by the post-loaded stress in path C(shear stress is initially applied,followed by tensile stress)irrespective of the value of final stress.The"recency effect"of the strain path on the stress is also established,which indicates that the stress caused by the post-loaded strain in path A is always greater than that caused by the pre-loaded strain in path C irrespective of the value of final strain.From the perspective of deformation,the"primary effect"of the stress path on the plastic strain and the"recency effect"of the strain path on the stress are unified.These effects are succinct and universal,and they provide useful insights on the plastic stress-strain relationship under different loading paths.Furthermore,they can serve as a useful reference for optimizing the processing technologies and construction procedures.展开更多
In this letter, a class of reaction-diffusion equations, which arise in chemical reaction or ecology and other fields of physics, are investigated. A more general analytical solution of the equation is obtained by usi...In this letter, a class of reaction-diffusion equations, which arise in chemical reaction or ecology and other fields of physics, are investigated. A more general analytical solution of the equation is obtained by using the first integral method.展开更多
Luanda bay has been acting as a sink for the untreated municipal and industrial effluents from a part of the city. Sediment samples were analyzed for their total organic carbon contents and pseudo-total concentrations...Luanda bay has been acting as a sink for the untreated municipal and industrial effluents from a part of the city. Sediment samples were analyzed for their total organic carbon contents and pseudo-total concentrations ofFe, Mn, Hg, Cd, Pb, Cu, Zn, Ni and Cr The highest concentrations of organic carbon and Hg, Cd, Pb, Cu and Zn were found near the sewerage discharge outlets, exceeding in these points the lowest Sediment Quality Guidelines for the occurrence of adverse biological effects. A further study, based on the latest version of the BCR sequential extraction procedure, was undertaken in order to assess the physical/chemical binding and bioavailability ofFe, Mn, Cd, Pb, Cu and Zn in these sediments. The toxic metals Cd, Zn, Pb and Cu pose a potential environmental risk, because they were extracted from the sediment labile fractions in concentrations that exceeded the corresponding ERL （Effects Range Low） values, entering the range within which adverse biological effects occur. The non-residual fractions of metals ranged from 91 to 100% for Cd, 89 to 94% for Zn, 67 to 100% for Pb, 71 to 82% for Cu, 30 to 77% for Mn and 39 to 48% for Fe. Measures to be taken for the disposal of the polluted dredged sediments are shown in this work.展开更多
基金Project(51979280)supported by the National Natural Science Foundation of ChinaProjects(2016M602972,2018M643852)supported by the Postdoctoral Science Foundation of China。
文摘We have established an elastoplastic analysis model to explore the effect of loading path in an incompressible thin-walled tube under the combined action of axial force and torque based on Mises yield condition and isotropic linear hardening assumption.Further,four stress areas(σx,τx)are divided according to the characteristics of the final stress,and the plastic stress-strain relationship of twelve stress paths in different stress areas is derived.The"primary effect"of the stress path on plastic strain is demonstrated,namely,the plastic strain caused by the pre-loaded stress in path A(tensile stress is initially applied,followed by shear stress)is always greater than that caused by the post-loaded stress in path C(shear stress is initially applied,followed by tensile stress)irrespective of the value of final stress.The"recency effect"of the strain path on the stress is also established,which indicates that the stress caused by the post-loaded strain in path A is always greater than that caused by the pre-loaded strain in path C irrespective of the value of final strain.From the perspective of deformation,the"primary effect"of the stress path on the plastic strain and the"recency effect"of the strain path on the stress are unified.These effects are succinct and universal,and they provide useful insights on the plastic stress-strain relationship under different loading paths.Furthermore,they can serve as a useful reference for optimizing the processing technologies and construction procedures.
文摘In this letter, a class of reaction-diffusion equations, which arise in chemical reaction or ecology and other fields of physics, are investigated. A more general analytical solution of the equation is obtained by using the first integral method.
文摘Luanda bay has been acting as a sink for the untreated municipal and industrial effluents from a part of the city. Sediment samples were analyzed for their total organic carbon contents and pseudo-total concentrations ofFe, Mn, Hg, Cd, Pb, Cu, Zn, Ni and Cr The highest concentrations of organic carbon and Hg, Cd, Pb, Cu and Zn were found near the sewerage discharge outlets, exceeding in these points the lowest Sediment Quality Guidelines for the occurrence of adverse biological effects. A further study, based on the latest version of the BCR sequential extraction procedure, was undertaken in order to assess the physical/chemical binding and bioavailability ofFe, Mn, Cd, Pb, Cu and Zn in these sediments. The toxic metals Cd, Zn, Pb and Cu pose a potential environmental risk, because they were extracted from the sediment labile fractions in concentrations that exceeded the corresponding ERL （Effects Range Low） values, entering the range within which adverse biological effects occur. The non-residual fractions of metals ranged from 91 to 100% for Cd, 89 to 94% for Zn, 67 to 100% for Pb, 71 to 82% for Cu, 30 to 77% for Mn and 39 to 48% for Fe. Measures to be taken for the disposal of the polluted dredged sediments are shown in this work.
