COREX shaft furnace（SF）is a typical screw feeder with a storage container coupled with eight screw casings and screws.The structure of screw casing plays an important role in the moving behavior of burdens,stress di...COREX shaft furnace（SF）is a typical screw feeder with a storage container coupled with eight screw casings and screws.The structure of screw casing plays an important role in the moving behavior of burdens,stress distribution,abrasive wear of screws,and energy consumption during the operation of SF.Therefore,a three-dimensional semi-cylindrical model of actual size of COREX-3000 SF was established based on discrete element method to investigate the influences of screw casing structure.The results show that the increase in the gap between the outside of screw flight and screw casing is beneficial for the smooth operation of SF,resulting in uniform descending velocity along the radius of SF in the lower part,decreasing the size of recirculation region,and alleviating stress concentration in the screw casing.Moreover,raising the gap appropriately is also beneficial to weaken screw abrasive wear,decrease energy consumption,and then prolong the service life of the screws.However,enlarging the gap also leads to more undesired high temperature reduction gas into the SF from melter gasifier,thereby deteriorating the operation of SF.Thus,an ideal distance exists between the outside of the screw flight and the screw casing,which is suggested to be equal to the average of particle diameter.展开更多
Conventional overconstrained parallel manipulators have been widely studied both in industry and academia,however the structural synthesis of hybrid mechanisms with additional constraints is seldom studied,especially ...Conventional overconstrained parallel manipulators have been widely studied both in industry and academia,however the structural synthesis of hybrid mechanisms with additional constraints is seldom studied,especially for the four degrees of freedom（DOF） hybrid mechanisms.In order to develop a manipulator with additional constraints,a class of important spatial mechanisms with coupling chains（CCs） whose motion type is two rotations and two translations（2R2T） is presented.Based on screw theory,the combination of different types of limbs which are used to construct parallel mechanisms and coupling chains is proposed.The basic types of the general parallel mechanisms and geometric conditions of the kinematic chains are given using constraint synthesis method.Moreover,the 2R2T motion pattern hybrid mechanisms which are derived by adding coupling chains between different serial kinematic chains（SKCs） of the corresponding parallel mechanisms are presented.According to the constraint analysis of the mechanisms,the movement relationship of the moving platform and the kinematic chains is derived by disassembling the coupling chains.At last,fourteen novel hybrid mechanisms with two or three serial kinematic chains are presented.The proposed novel hybrid mechanisms and construction method enrich the family of the spatial mechanisms and provide an instruction to design more complex hybrid mechanisms.展开更多
The frequent failures of small-diameter vascular grafts(SDVGs)mainly result from thrombosis and insufficient endothelialization.Despite recent biochemical modification strategies aiming to enhance long-term patency,th...The frequent failures of small-diameter vascular grafts(SDVGs)mainly result from thrombosis and insufficient endothelialization.Despite recent biochemical modification strategies aiming to enhance long-term patency,the challenges of suppressing thrombosis and promoting rapid endothelialization persist.We thus designed a biomimetic three-layer flexible vascular graft scaffold.This scaffold precisely replicates the nonlinear mechanical responses of vascular tissues and promotes vascular regeneration by minimizing the mechanical mismatch between the graft and the host.The biomimetic flexible SDVG scaffold comprises a screwed inner layer,a middle fabric layer,and a Polyethylene terephthalate(PET)helical coil.It shows excellent bending resistance and resilience,reducing thrombosis formation caused by impaired blood flow during bending.Moreover,this scaffold notably improves the adhesion,spreading,proliferation,and elongation of endothelial cells,facilitating luminal remodeling and maintaining long-term patency through its intimal topography.In vivo studies demonstrate that the endothelial layer forms within three months of implantation,ensuring long-term patency.By three months after implantation,both the endothelial and smooth muscle layers are regenerated,developing hierarchical microstructures and compositions similar to those of native vessels.The biomimetic flexible vascular graft with screwed structures exhibits excellent bending resistance and enhanced vascular remodeling,thereby promoting blood vessel regeneration and showing strong potential for clinical translation.展开更多
基金supported by the National Key Technology Research and Development Program of China (Grant No.2011BAE04B02)National Natural Science Foundation of China(Grant No.51174053)
文摘COREX shaft furnace（SF）is a typical screw feeder with a storage container coupled with eight screw casings and screws.The structure of screw casing plays an important role in the moving behavior of burdens,stress distribution,abrasive wear of screws,and energy consumption during the operation of SF.Therefore,a three-dimensional semi-cylindrical model of actual size of COREX-3000 SF was established based on discrete element method to investigate the influences of screw casing structure.The results show that the increase in the gap between the outside of screw flight and screw casing is beneficial for the smooth operation of SF,resulting in uniform descending velocity along the radius of SF in the lower part,decreasing the size of recirculation region,and alleviating stress concentration in the screw casing.Moreover,raising the gap appropriately is also beneficial to weaken screw abrasive wear,decrease energy consumption,and then prolong the service life of the screws.However,enlarging the gap also leads to more undesired high temperature reduction gas into the SF from melter gasifier,thereby deteriorating the operation of SF.Thus,an ideal distance exists between the outside of the screw flight and the screw casing,which is suggested to be equal to the average of particle diameter.
基金Supported by National Natural Science Foundation of China(Grant Nos.51175029,51475035)
文摘Conventional overconstrained parallel manipulators have been widely studied both in industry and academia,however the structural synthesis of hybrid mechanisms with additional constraints is seldom studied,especially for the four degrees of freedom（DOF） hybrid mechanisms.In order to develop a manipulator with additional constraints,a class of important spatial mechanisms with coupling chains（CCs） whose motion type is two rotations and two translations（2R2T） is presented.Based on screw theory,the combination of different types of limbs which are used to construct parallel mechanisms and coupling chains is proposed.The basic types of the general parallel mechanisms and geometric conditions of the kinematic chains are given using constraint synthesis method.Moreover,the 2R2T motion pattern hybrid mechanisms which are derived by adding coupling chains between different serial kinematic chains（SKCs） of the corresponding parallel mechanisms are presented.According to the constraint analysis of the mechanisms,the movement relationship of the moving platform and the kinematic chains is derived by disassembling the coupling chains.At last,fourteen novel hybrid mechanisms with two or three serial kinematic chains are presented.The proposed novel hybrid mechanisms and construction method enrich the family of the spatial mechanisms and provide an instruction to design more complex hybrid mechanisms.
基金supported by the National Key Research and Development Program of China(No.2023YFC2412402)the Key Research and Development Program of Hubei Province(No.2022ACA002).
文摘The frequent failures of small-diameter vascular grafts(SDVGs)mainly result from thrombosis and insufficient endothelialization.Despite recent biochemical modification strategies aiming to enhance long-term patency,the challenges of suppressing thrombosis and promoting rapid endothelialization persist.We thus designed a biomimetic three-layer flexible vascular graft scaffold.This scaffold precisely replicates the nonlinear mechanical responses of vascular tissues and promotes vascular regeneration by minimizing the mechanical mismatch between the graft and the host.The biomimetic flexible SDVG scaffold comprises a screwed inner layer,a middle fabric layer,and a Polyethylene terephthalate(PET)helical coil.It shows excellent bending resistance and resilience,reducing thrombosis formation caused by impaired blood flow during bending.Moreover,this scaffold notably improves the adhesion,spreading,proliferation,and elongation of endothelial cells,facilitating luminal remodeling and maintaining long-term patency through its intimal topography.In vivo studies demonstrate that the endothelial layer forms within three months of implantation,ensuring long-term patency.By three months after implantation,both the endothelial and smooth muscle layers are regenerated,developing hierarchical microstructures and compositions similar to those of native vessels.The biomimetic flexible vascular graft with screwed structures exhibits excellent bending resistance and enhanced vascular remodeling,thereby promoting blood vessel regeneration and showing strong potential for clinical translation.
