Mg-Li alloy,as a superlight metallic engineering material,shows great potential in the fields of aerospace and militarydue to its high specific strength,better formability,and excellent electromagnetic shielding perfo...Mg-Li alloy,as a superlight metallic engineering material,shows great potential in the fields of aerospace and militarydue to its high specific strength,better formability,and excellent electromagnetic shielding performance.The research process ofMg-Li alloys is reviewed and three main problems are pointed out.Aimed at the poor corrosion resistance of Mg-Li alloys,thecorrosion behavior is mainly summarized.The surface treatment technologies,including electroplating,electroless plating,plasmaspraying,molten salt replacement,conversion coating,anodizing,micro-arc oxidation,organic coating,and organic-inorganic hybridcoating,are introduced in detail.Finally,the future development of corrosion and protection of Mg?Li alloys is discussed.展开更多
Behavioral responses triggered by the perceived risk of experiencing the disease represent a key ingredient in the spread of epidemics across human population.In this paper,two forms of individual awareness(i.e.,the r...Behavioral responses triggered by the perceived risk of experiencing the disease represent a key ingredient in the spread of epidemics across human population.In this paper,two forms of individual awareness(i.e.,the risk perception of an emerging epidemic) are addressed:Contact awareness that increases with individual contact number,and local awareness that increases with the fraction of infected contacts.By extending the probability generating functionology,the author shows that it is possible to track the evolution of the degree distributions among susceptible and infected individuals when the underlying network of contacts is represented by a semi-random configuration model.It is hopefully to shed some light on the dynamic aspects of networked epidemiological models.展开更多
A chromizing coating was formed on P110 oil casing tube steel (P110 steel) via pack cementation to improve its performance and increase the lifetime during operation. The slurry erosion behaviors of the P110 steel sub...A chromizing coating was formed on P110 oil casing tube steel (P110 steel) via pack cementation to improve its performance and increase the lifetime during operation. The slurry erosion behaviors of the P110 steel substrate and the chromizing coating were assessed in a liquid-solid two-phase flow condition. The results showed that the obtained coating exhibited higher surface hardness, lower mass loss, and lower slurry erosion rate than those of P110 steel. The chromizing treatment has significantly improved the surface hardness and slurry erosion resistance of P110 steel.展开更多
We carried out direct numerical simulations of turbulent Rayleigh-Benard convection(RBC)with accounting for both the roughness and the external vibration over the Rayleigh number range 10^(7)≤Ra≤10^(11) and the vibr...We carried out direct numerical simulations of turbulent Rayleigh-Benard convection(RBC)with accounting for both the roughness and the external vibration over the Rayleigh number range 10^(7)≤Ra≤10^(11) and the vibration frequency range 0<ω<1400.The triangular rough elements are uniformly distributed over the top and bottom surfaces,and the vibration is applied in the horizontal direction.It is shown that under the combined action of roughness and horizontal vibration,with increasing the vibration frequency ω,the heat transfer is initially decreased a little and then greatly enhanced after ω exceeds the critical value.The physical reason for massive heat-transfer-enhancement is that high frequency vibration destabilizes thermal boundary layers(BL)over rough surfaces,triggers abundant emissions of thermal plumes,and strengthens the motion of large-scale circulation(LSC),which consequently thins the thickness of thermal BL and heightens the convective transport.In addition,it is shown that vibration-induced heat-transfer-enhancement can obviously affect the scaling behavior between the heat flux and the Rayleigh number,and the scaling exponent increases with increasing ω,whereas the influence of vibration on the scaling behavior between the intensity of LSC and Ra is very weak.展开更多
基金Project(2017zzts005) supported by the Fundamental Research Funds for the Central Universities of Central South University
文摘Mg-Li alloy,as a superlight metallic engineering material,shows great potential in the fields of aerospace and militarydue to its high specific strength,better formability,and excellent electromagnetic shielding performance.The research process ofMg-Li alloys is reviewed and three main problems are pointed out.Aimed at the poor corrosion resistance of Mg-Li alloys,thecorrosion behavior is mainly summarized.The surface treatment technologies,including electroplating,electroless plating,plasmaspraying,molten salt replacement,conversion coating,anodizing,micro-arc oxidation,organic coating,and organic-inorganic hybridcoating,are introduced in detail.Finally,the future development of corrosion and protection of Mg?Li alloys is discussed.
基金supported by Air Force Office of Scientific Research under Grant No.FA9550-09-1-0165
文摘Behavioral responses triggered by the perceived risk of experiencing the disease represent a key ingredient in the spread of epidemics across human population.In this paper,two forms of individual awareness(i.e.,the risk perception of an emerging epidemic) are addressed:Contact awareness that increases with individual contact number,and local awareness that increases with the fraction of infected contacts.By extending the probability generating functionology,the author shows that it is possible to track the evolution of the degree distributions among susceptible and infected individuals when the underlying network of contacts is represented by a semi-random configuration model.It is hopefully to shed some light on the dynamic aspects of networked epidemiological models.
基金supported by the National Natural Science Foundation of China (Grant No. 51171125)the China Postdoctoral Science Foundation(Grant No. 2012M520604)+1 种基金the Youth Foundation of Taiyuan University of Technology (Grant No. 2012L050)the Foundation for Talents Introduction of Taiyuan University of Technology (Grant No. tyut-rc201157a)
文摘A chromizing coating was formed on P110 oil casing tube steel (P110 steel) via pack cementation to improve its performance and increase the lifetime during operation. The slurry erosion behaviors of the P110 steel substrate and the chromizing coating were assessed in a liquid-solid two-phase flow condition. The results showed that the obtained coating exhibited higher surface hardness, lower mass loss, and lower slurry erosion rate than those of P110 steel. The chromizing treatment has significantly improved the surface hardness and slurry erosion resistance of P110 steel.
基金supported by the National Natural Science Foundation of China(Grant Nos.11988102,92052201,91852202,H825204,and 11972220)the Program of Shanghai Academic Research Leader(Grant No.19XD1421400)+1 种基金Shanghai Science and Technology Program(Grant Nos.19JC1412802 and 20ZR14I9800)China Postdoctoral Science Foundation(Grant No.2020M681259).
文摘We carried out direct numerical simulations of turbulent Rayleigh-Benard convection(RBC)with accounting for both the roughness and the external vibration over the Rayleigh number range 10^(7)≤Ra≤10^(11) and the vibration frequency range 0<ω<1400.The triangular rough elements are uniformly distributed over the top and bottom surfaces,and the vibration is applied in the horizontal direction.It is shown that under the combined action of roughness and horizontal vibration,with increasing the vibration frequency ω,the heat transfer is initially decreased a little and then greatly enhanced after ω exceeds the critical value.The physical reason for massive heat-transfer-enhancement is that high frequency vibration destabilizes thermal boundary layers(BL)over rough surfaces,triggers abundant emissions of thermal plumes,and strengthens the motion of large-scale circulation(LSC),which consequently thins the thickness of thermal BL and heightens the convective transport.In addition,it is shown that vibration-induced heat-transfer-enhancement can obviously affect the scaling behavior between the heat flux and the Rayleigh number,and the scaling exponent increases with increasing ω,whereas the influence of vibration on the scaling behavior between the intensity of LSC and Ra is very weak.
