Designing high-performance nanostructured electrode materials is the current core of electrochemical energy storage devices.Multi-scaled nanomaterials have triggered considerable interest because they effectively comb...Designing high-performance nanostructured electrode materials is the current core of electrochemical energy storage devices.Multi-scaled nanomaterials have triggered considerable interest because they effectively combine a library of advantages of each component on different scales for energy storage.However,serious aggregation,structural degradation,and even poor stability of nanomaterials are well-known issues during electrochemically driven volume expansion/contraction processes.The confinement strategy provides a new route to construct controllable internal void spaces to avoid the intrinsic volume effects of nanomaterials during the reaction or charge/discharge process.Herein,we discuss the confinement strategies and methods for energy storage-related electrode materials with a one-dimensional channel,two-dimensional interlayer,and three-dimensional space as reaction environments.For each confinement environment,the correlation between the confinement condition/structure and the behavioral characteristics of energy storage devices in the scope of metal-ion batteries(e.g.,Li-ion,Na-ion,K-ion,and Mg-ion batteries),Li-S batteries(LSBs),Zn-air batteries(ZIBs),and supercapacitors.Finally,we discussed the challenges and perspectives on future nanomaterial confinement strategies for electrochemical energy storage devices.展开更多
The grain reifnement limits of commercial pure Al inoculated by Al-5Ti-1B, Al-5Ti-0.25C and Al-5Ti-0.3C-0.2B master al oys were studied, and the inlfuence of melting temperature on the grain reifning performance of th...The grain reifnement limits of commercial pure Al inoculated by Al-5Ti-1B, Al-5Ti-0.25C and Al-5Ti-0.3C-0.2B master al oys were studied, and the inlfuence of melting temperature on the grain reifning performance of these three master al oys was investigated using a high scope video microscope （HSVM）, a ifeld-emission scanning electron microscope （FESEM）, an electron probe micro-analyzer （EPMA） and X-ray diffraction （XRD） method. Results show that there is a grain reifnement limit of commercial pure Al reifned by these three master al oys; with the same addition level of 1.5% under the present experimental conditions, the grain reifnement limits （smal est average grain size） of commercial pure Al reifned by Al-5Ti-1B, Al-5Ti-0.25C and Al-5Ti-0.3C-0.2B master al oys are 50 μm, 80 μm and 80 μm, respectively. In addition, with an increase in the melting temperature of the pure Al, the grain reifning performance of Al-5Ti-1B and Al-5Ti-0.25C master al oys decreases, but the grain reifning performance of Al-5Ti-0.3C-0.2B changes little.展开更多
In this review the preparation methods of polymer nanoparticles from chemical microemulsion polymerization to physical methods such as spray-drying,freeze-drying,freeze-extracting,fast evaporation and spreading evapor...In this review the preparation methods of polymer nanoparticles from chemical microemulsion polymerization to physical methods such as spray-drying,freeze-drying,freeze-extracting,fast evaporation and spreading evaporation have been summarized.The influence of nanoconfinement on glass transition temperature(T_(g))variation from significant or slight decrease,no evident T_(g) deviation,to even T_(g) increase,as well as possible explanations of T_(g) deviations were discussed.The influences of nanoconfinement or entanglement on the other properties such as structural relaxation,crystallization in polymer nanoparticle samples were also reviewed in this article.展开更多
分析信号系统与列车折返过程的关系,指出信号系统架构和进路办理时间是影响列车折返时间的关键因素。提出新一代基于通信的列车控制(Communication Based Train Control,CBTC)系统架构及高效能列车折返技术,通过研究新一代CBTC系统架构...分析信号系统与列车折返过程的关系,指出信号系统架构和进路办理时间是影响列车折返时间的关键因素。提出新一代基于通信的列车控制(Communication Based Train Control,CBTC)系统架构及高效能列车折返技术,通过研究新一代CBTC系统架构的关键特点与列车折返实现过程,对其折返能力进行分析。分析结果表明,新一代CBTC系统通过系统架构优化和高效能列车折返技术,可将列车折返间隔缩短至90 s以内。此外,该系统采用的高效能列车折返技术也可应用于已开通的CBTC线路,通过局部技术升级,可实现线路折返效率的提升,符合未来轨道交通控制系统的发展方向。展开更多
Multiphase CrMnFeCoNi high-entropy alloys(HEAs)were prepared by a powder metallurgy process com-bining mechanical alloying(MA)and vacuum hot-pressing sintering(HPS).The single-phase face-centered cubic(FCC)HEA powder ...Multiphase CrMnFeCoNi high-entropy alloys(HEAs)were prepared by a powder metallurgy process com-bining mechanical alloying(MA)and vacuum hot-pressing sintering(HPS).The single-phase face-centered cubic(FCC)HEA powder prepared by MA was sintered into a bulk HEA specimen containing FCC phase matrix along with precipitated M 23 C 6 phase and nanoscaleσphase particles.When the sintering temper-ature was 1223 K,the ultimate strength reaches 1300±11.6 MPa,and the elongation exceeds 4%±0.6%.Microstructural characterization reveals that the formation of nanoscale particles and deformation twins play critical roles in improving the strain hardening(SH)ability.Prolonging the MA time promoted the formation of the precipitated phase and enhanced the SH ability by increasing the number of precip-itated particles.The SH capacity increases significantly with increasing sintering temperature,which is attributed to a significant enhancement in the twinning capacity due to grain growth and the reduced number ofσphase particles.Through systematic studies,the planar glide of dislocations was found to be the main mode of deformation,while deformation twinning appeared as an auxiliary deformation mode when the twinning stress was reached.Although the formation of precipitates leads to grain bound-ary and precipitation strengthening effects,crack initiation is more prominent owing to increased grain boundary brittleness around the precipitated M 23 C 6 phase.The prominence of crack initiation is a contra-diction that must be reconciled with regard to precipitation strengthening.This work serves as a useful reference for the preparation of high-strength HEA parts by powder metallurgy.展开更多
A probabilistic study of a circular tunnel excavated in a soil mass using the response surface methodology(RSM)is presented.A deterministic model based on two-dimensional numerical simulations in a transversal section...A probabilistic study of a circular tunnel excavated in a soil mass using the response surface methodology(RSM)is presented.A deterministic model based on two-dimensional numerical simulations in a transversal section is used,and the serviceability limit state(SLS)is considered in the analysis.The model permits the surface settlement curve and the bending moment on the tunnel lining to be obtained.Only the soil parameters are considered as random variables.Thefirst-order reliability method(FORM)and the response surface methodology(RSM)are utilized for the assessment of the Hasofer-Lind reliability index(bHL)optimized by the use of a genetic algorithm(GA).Two assumptions(normal and non-normal distribution)were used for the random variables.The comparison analysis considering a correlation between the friction angle and the cohesion indicates that the results are conservative if a negative correlation among strength parameters is not taken into account.The assumption of a non-normal distribution for the random variables has an important effect on the reliability index for the practical range of values of surface settlements.展开更多
This present paper proposes aerodynamic forces and entropy generation characteristics on theflow past two-dimensional airfoil at low Reynolds number by multiple-relaxation-time lattice Boltzmann method to clarify theflo...This present paper proposes aerodynamic forces and entropy generation characteristics on theflow past two-dimensional airfoil at low Reynolds number by multiple-relaxation-time lattice Boltzmann method to clarify theflow loss mechanism.The block mesh refinement was adopted in which a higher accuracy was needed in parts of the domain characterized by complexflow.The interpolated bounce-back method was used to treat the irregular curve.This numerical method can effectively solve the complexflowfield simulation problems with reasonable accuracy and reli-ability by simulatingflow around plate and airfoil.Based on second law of thermo-dynamics,an expression of entropy generation rate for arbitrary control volume was derived theoretically which could accurately quantify the local irreversible loss of theflowfield at any position.After that,a comprehensive numerical study was conducted to analyze relationship of entropy generation and drag force by taking NACA0012 air-foil as the research object.For unsteady condition,entropy generation rate and the drag force are not linearly related any more.Losses due to steady effects mainly con-sider the irreversibility in the boundary layer and wake while the unsteady effects come from the interaction between the main separation vortex and the trailing shed-ding vortex.展开更多
基金funding from the National Natural Science Foundation of China(Nos.51902222,51972221).
文摘Designing high-performance nanostructured electrode materials is the current core of electrochemical energy storage devices.Multi-scaled nanomaterials have triggered considerable interest because they effectively combine a library of advantages of each component on different scales for energy storage.However,serious aggregation,structural degradation,and even poor stability of nanomaterials are well-known issues during electrochemically driven volume expansion/contraction processes.The confinement strategy provides a new route to construct controllable internal void spaces to avoid the intrinsic volume effects of nanomaterials during the reaction or charge/discharge process.Herein,we discuss the confinement strategies and methods for energy storage-related electrode materials with a one-dimensional channel,two-dimensional interlayer,and three-dimensional space as reaction environments.For each confinement environment,the correlation between the confinement condition/structure and the behavioral characteristics of energy storage devices in the scope of metal-ion batteries(e.g.,Li-ion,Na-ion,K-ion,and Mg-ion batteries),Li-S batteries(LSBs),Zn-air batteries(ZIBs),and supercapacitors.Finally,we discussed the challenges and perspectives on future nanomaterial confinement strategies for electrochemical energy storage devices.
基金financially supported by the National Natural Science Foundation of China(No.51071097)
文摘The grain reifnement limits of commercial pure Al inoculated by Al-5Ti-1B, Al-5Ti-0.25C and Al-5Ti-0.3C-0.2B master al oys were studied, and the inlfuence of melting temperature on the grain reifning performance of these three master al oys was investigated using a high scope video microscope （HSVM）, a ifeld-emission scanning electron microscope （FESEM）, an electron probe micro-analyzer （EPMA） and X-ray diffraction （XRD） method. Results show that there is a grain reifnement limit of commercial pure Al reifned by these three master al oys; with the same addition level of 1.5% under the present experimental conditions, the grain reifnement limits （smal est average grain size） of commercial pure Al reifned by Al-5Ti-1B, Al-5Ti-0.25C and Al-5Ti-0.3C-0.2B master al oys are 50 μm, 80 μm and 80 μm, respectively. In addition, with an increase in the melting temperature of the pure Al, the grain reifning performance of Al-5Ti-1B and Al-5Ti-0.25C master al oys decreases, but the grain reifning performance of Al-5Ti-0.3C-0.2B changes little.
基金supported by Ph.D.Programs Foundation of Ministry of Education of China(No.20100032110025).
文摘In this review the preparation methods of polymer nanoparticles from chemical microemulsion polymerization to physical methods such as spray-drying,freeze-drying,freeze-extracting,fast evaporation and spreading evaporation have been summarized.The influence of nanoconfinement on glass transition temperature(T_(g))variation from significant or slight decrease,no evident T_(g) deviation,to even T_(g) increase,as well as possible explanations of T_(g) deviations were discussed.The influences of nanoconfinement or entanglement on the other properties such as structural relaxation,crystallization in polymer nanoparticle samples were also reviewed in this article.
文摘分析信号系统与列车折返过程的关系,指出信号系统架构和进路办理时间是影响列车折返时间的关键因素。提出新一代基于通信的列车控制(Communication Based Train Control,CBTC)系统架构及高效能列车折返技术,通过研究新一代CBTC系统架构的关键特点与列车折返实现过程,对其折返能力进行分析。分析结果表明,新一代CBTC系统通过系统架构优化和高效能列车折返技术,可将列车折返间隔缩短至90 s以内。此外,该系统采用的高效能列车折返技术也可应用于已开通的CBTC线路,通过局部技术升级,可实现线路折返效率的提升,符合未来轨道交通控制系统的发展方向。
基金supported by the National Natu-ral Science Foundation of China(Nos.52061021,51861016,and 51871132)the Science and Technology Major Project of Yun-nan Province(Nos.202202AG050004,202002AB080001)+2 种基金the Young and Middle-Aged Academic and Technical Leaders Reserve Talent Project(No.202005AC160039)support by the Ministry of Science and Higher Educa-tion of the Russian Federation in the framework of the Increase Competitiveness Program of NUST«MISiS»(No.K2-2020-046)financial support from the China Scholarship Council(CSC,No.201906220226).
文摘Multiphase CrMnFeCoNi high-entropy alloys(HEAs)were prepared by a powder metallurgy process com-bining mechanical alloying(MA)and vacuum hot-pressing sintering(HPS).The single-phase face-centered cubic(FCC)HEA powder prepared by MA was sintered into a bulk HEA specimen containing FCC phase matrix along with precipitated M 23 C 6 phase and nanoscaleσphase particles.When the sintering temper-ature was 1223 K,the ultimate strength reaches 1300±11.6 MPa,and the elongation exceeds 4%±0.6%.Microstructural characterization reveals that the formation of nanoscale particles and deformation twins play critical roles in improving the strain hardening(SH)ability.Prolonging the MA time promoted the formation of the precipitated phase and enhanced the SH ability by increasing the number of precip-itated particles.The SH capacity increases significantly with increasing sintering temperature,which is attributed to a significant enhancement in the twinning capacity due to grain growth and the reduced number ofσphase particles.Through systematic studies,the planar glide of dislocations was found to be the main mode of deformation,while deformation twinning appeared as an auxiliary deformation mode when the twinning stress was reached.Although the formation of precipitates leads to grain bound-ary and precipitation strengthening effects,crack initiation is more prominent owing to increased grain boundary brittleness around the precipitated M 23 C 6 phase.The prominence of crack initiation is a contra-diction that must be reconciled with regard to precipitation strengthening.This work serves as a useful reference for the preparation of high-strength HEA parts by powder metallurgy.
文摘A probabilistic study of a circular tunnel excavated in a soil mass using the response surface methodology(RSM)is presented.A deterministic model based on two-dimensional numerical simulations in a transversal section is used,and the serviceability limit state(SLS)is considered in the analysis.The model permits the surface settlement curve and the bending moment on the tunnel lining to be obtained.Only the soil parameters are considered as random variables.Thefirst-order reliability method(FORM)and the response surface methodology(RSM)are utilized for the assessment of the Hasofer-Lind reliability index(bHL)optimized by the use of a genetic algorithm(GA).Two assumptions(normal and non-normal distribution)were used for the random variables.The comparison analysis considering a correlation between the friction angle and the cohesion indicates that the results are conservative if a negative correlation among strength parameters is not taken into account.The assumption of a non-normal distribution for the random variables has an important effect on the reliability index for the practical range of values of surface settlements.
基金The authors gratefully acknowledge the support by the National Key R&D Program of China(No.2018YFB0606101)Thanks to SCTS/CGCL HPCC of HUST for providing computing resources and technical support.
文摘This present paper proposes aerodynamic forces and entropy generation characteristics on theflow past two-dimensional airfoil at low Reynolds number by multiple-relaxation-time lattice Boltzmann method to clarify theflow loss mechanism.The block mesh refinement was adopted in which a higher accuracy was needed in parts of the domain characterized by complexflow.The interpolated bounce-back method was used to treat the irregular curve.This numerical method can effectively solve the complexflowfield simulation problems with reasonable accuracy and reli-ability by simulatingflow around plate and airfoil.Based on second law of thermo-dynamics,an expression of entropy generation rate for arbitrary control volume was derived theoretically which could accurately quantify the local irreversible loss of theflowfield at any position.After that,a comprehensive numerical study was conducted to analyze relationship of entropy generation and drag force by taking NACA0012 air-foil as the research object.For unsteady condition,entropy generation rate and the drag force are not linearly related any more.Losses due to steady effects mainly con-sider the irreversibility in the boundary layer and wake while the unsteady effects come from the interaction between the main separation vortex and the trailing shed-ding vortex.
