Ammonium dinitramide(ADN),which has the advantages of high energy density,no halogen and low characteristic signal,is not only considered as a new high-energy oxidizer that is expected to replace the traditional oxidi...Ammonium dinitramide(ADN),which has the advantages of high energy density,no halogen and low characteristic signal,is not only considered as a new high-energy oxidizer that is expected to replace the traditional oxidizer ammonium perchlorate(AP)in solid propellants,but also a good performance explosive in itself.However,due to the strong hygroscopicity of ADN,its application in solid propellants and explosives is greatly limited.Solving the hygroscopicity of ADN is the key to realize the wide application of ADN.In this paper,we systematically review the research progress of anti-hygroscopic strategies of ADN coating.The surface coating methods are focusing on solvent volatilization,solvent-non-solvent,melt crystallization and atomic layer deposition technology.The characteristics of the different methods are compared and analyzed,and the basis for the classification and selection of the coating materials are introduced in detail.In addition,the feasibility of material for surface coating of ADN is evaluated by several compatibility analysis methods.It is highly expected that the liquid phase method(solvent volatilization method,solvent-non-solvent method)would be the promising method for future ADN coating because of its effective,safety and facile operation.Furthermore,polymer materials,are the preferred coating materials due to their high viscosity,easy adhesion,good anti-hygroscopic effect,and heat resistance,which make ADN weak hygroscopicity,less sensitive,easier to preserve and good compatibility.展开更多
A hybrid bidirectional DC/DC converter(BDC)is proposed as the fundamental DC/DC module in solid-state transformers,which combines a bidirectional LLC converter and a dual-active-bridge(DAB)converter.Integrated with a ...A hybrid bidirectional DC/DC converter(BDC)is proposed as the fundamental DC/DC module in solid-state transformers,which combines a bidirectional LLC converter and a dual-active-bridge(DAB)converter.Integrated with a mutual control scheme,both parts of this hybrid BDC can be unified into an interdependent community.In this hybrid BDC,the LLC converter supports the output voltage and improves stability by working at the resonant frequency mode and the DAB converter enhances the BDC power capability by controlling the LLC output current constant.The BDC can achieve the full-load-range soft switching of all active switches by designing the auxiliary inductor of LLC and the minimum output current of DAB.By comparing to the single DAB,the proposed BDC has the higher phase and gain margin which means the BDC improved the relative stability based on Nyquist criterion.To solve the bidirectional power control problem,a dead-band voltage control logic is adopted which can determine the BDC’s power direction based on the output voltage change.A 200 V experimental system has verified the aforementioned features and functions of the BDC.展开更多
Material surfaces can induce cell responses such as contact guidance, yet little attention has been paid to further cell orientation. Herein, we report an interesting phenomenon of cell orientation beyond the classic ...Material surfaces can induce cell responses such as contact guidance, yet little attention has been paid to further cell orientation. Herein, we report an interesting phenomenon of cell orientation beyond the classic contact guidance on a stripe-like micropattern with cell-adhesive arginineglycine-aspartate （RGD） peptides on a nonfouling background decorated by poly（ethylene glycol） （PEG）. Such a micropattern with cell adhesion contrast led to significant contact guidance after cell seeding. What is more, the localized and elongated cells were found to be further orientated out of the adhesive stripes, and even an anticlockwise rotation was observed for rat mesenchymal stem cells （rMSCs）. The left-right asymmetry of rMSCs stood only in statistics, for we observed all cases including clockwise orientation, anticlockwise orientation or just keeping the orientation of previous contact guidance. We further found that human foreskin fibroblasts （HFFs） preferred a clockwise rotation, while human mesenchymal stem cells （hMSCs） and human umbilical vascular endothelial cells （HUVECs） exhibited no significant preference to either direction, which indicated that the left-right symmetry or asymmetry was cell-type dependent. The present report has partially confirmed the cell chirality and revealed its complexity, calling for further careful and comprehensive investigation of the challenging topic of cell chirality on material surfaces.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.21805139,12102194 and 22005144)the Joint Funds of the National Natural Science Foundation of China(Grant No.U2141202)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.30921011203)the Young Elite Scientists Sponsorship Program by CAST(YESS Program,2021QNRC001)。
文摘Ammonium dinitramide(ADN),which has the advantages of high energy density,no halogen and low characteristic signal,is not only considered as a new high-energy oxidizer that is expected to replace the traditional oxidizer ammonium perchlorate(AP)in solid propellants,but also a good performance explosive in itself.However,due to the strong hygroscopicity of ADN,its application in solid propellants and explosives is greatly limited.Solving the hygroscopicity of ADN is the key to realize the wide application of ADN.In this paper,we systematically review the research progress of anti-hygroscopic strategies of ADN coating.The surface coating methods are focusing on solvent volatilization,solvent-non-solvent,melt crystallization and atomic layer deposition technology.The characteristics of the different methods are compared and analyzed,and the basis for the classification and selection of the coating materials are introduced in detail.In addition,the feasibility of material for surface coating of ADN is evaluated by several compatibility analysis methods.It is highly expected that the liquid phase method(solvent volatilization method,solvent-non-solvent method)would be the promising method for future ADN coating because of its effective,safety and facile operation.Furthermore,polymer materials,are the preferred coating materials due to their high viscosity,easy adhesion,good anti-hygroscopic effect,and heat resistance,which make ADN weak hygroscopicity,less sensitive,easier to preserve and good compatibility.
文摘A hybrid bidirectional DC/DC converter(BDC)is proposed as the fundamental DC/DC module in solid-state transformers,which combines a bidirectional LLC converter and a dual-active-bridge(DAB)converter.Integrated with a mutual control scheme,both parts of this hybrid BDC can be unified into an interdependent community.In this hybrid BDC,the LLC converter supports the output voltage and improves stability by working at the resonant frequency mode and the DAB converter enhances the BDC power capability by controlling the LLC output current constant.The BDC can achieve the full-load-range soft switching of all active switches by designing the auxiliary inductor of LLC and the minimum output current of DAB.By comparing to the single DAB,the proposed BDC has the higher phase and gain margin which means the BDC improved the relative stability based on Nyquist criterion.To solve the bidirectional power control problem,a dead-band voltage control logic is adopted which can determine the BDC’s power direction based on the output voltage change.A 200 V experimental system has verified the aforementioned features and functions of the BDC.
基金supported by the National Key R&D Program of China through Contract 2021YFA0718700the final support from the National Natural Science Foundation of China(11974052 and 12004036)+1 种基金Beijing Natural Science Foundation(Z190008)the Natural Science Basic Research Program of Shaanxi(2021JQ-332)。
文摘Material surfaces can induce cell responses such as contact guidance, yet little attention has been paid to further cell orientation. Herein, we report an interesting phenomenon of cell orientation beyond the classic contact guidance on a stripe-like micropattern with cell-adhesive arginineglycine-aspartate （RGD） peptides on a nonfouling background decorated by poly（ethylene glycol） （PEG）. Such a micropattern with cell adhesion contrast led to significant contact guidance after cell seeding. What is more, the localized and elongated cells were found to be further orientated out of the adhesive stripes, and even an anticlockwise rotation was observed for rat mesenchymal stem cells （rMSCs）. The left-right asymmetry of rMSCs stood only in statistics, for we observed all cases including clockwise orientation, anticlockwise orientation or just keeping the orientation of previous contact guidance. We further found that human foreskin fibroblasts （HFFs） preferred a clockwise rotation, while human mesenchymal stem cells （hMSCs） and human umbilical vascular endothelial cells （HUVECs） exhibited no significant preference to either direction, which indicated that the left-right symmetry or asymmetry was cell-type dependent. The present report has partially confirmed the cell chirality and revealed its complexity, calling for further careful and comprehensive investigation of the challenging topic of cell chirality on material surfaces.
