The design of wide-range high-efficiency aerodynamic configurations is one of the most important key technologies in the research of near-space hypersonic vehicles.A double-sided intake configuration with different in...The design of wide-range high-efficiency aerodynamic configurations is one of the most important key technologies in the research of near-space hypersonic vehicles.A double-sided intake configuration with different inlets on the upper and lower surfaces is proposed to adapt to widerange flight.Firstly,the double-sided intake configuration’s design method and flight profile are delineated.Secondly,Computational Fluid Dynamics(CFD)numerical simulation based on multi-Graphics Processing Unit(GPU)parallel computing is adopted to evaluate the vehicle’s performance comprehensively,aiming to verify the feasibility of the proposed scheme.This evaluation encompasses a wide-range basic aerodynamic characteristics,inlet performance,and heat flux at critical locations.The results show that the inlets of the designed integration configuration can start up across Mach number 3.5 to 8.The vehicle possesses multi-point cruising capability by flipping the fuselage.Simultaneously,a 180°rotation of the fuselage can significantly decrease the heat accumulation on the lower surface of the vehicle,particularly at the inlet lip,further decreasing the temperature gradient across the vehicle structure.This study has some engineering value for the aerodynamic configuration design of wide-range vehicles.However,further study reveals that the flow phenomena at the intersection of two inlets are complex,posing potential adverse impacts on propulsion efficiency.Therefore,it is imperative to conduct additional research to delve into this matter comprehensively.展开更多
Serious startup drift of the Ring Laser Gyroscope(RLG)is observed during cold startup process,which will dramatically degrade the performances of the corresponding Inertial Navigation System(INS).In this paper,correla...Serious startup drift of the Ring Laser Gyroscope(RLG)is observed during cold startup process,which will dramatically degrade the performances of the corresponding Inertial Navigation System(INS).In this paper,correlation analysis method,which analyzes the relationship between the startup drift of the RLG and the temperature change,is used to determine the significant temperature-related terms during gyroscope startup.Based on the significant temperature-related terms and the startup time length,a startup drift compensation model for RLG based on monotonicity-constrained Radial Basis Function(RBF)neural network is proposed and validated.Compared with the raw RLG data without compensation,the standard deviation of the RLG output with the proposed constrained RBF network model is decreased by more than 46%,and the peak-to-peak value is decreased by more than 35%.Compared with the traditional multiple regression model,the standard deviation and peak-to-peak value of the RLG output are decreased by more than 10%and 6%,respectively.Compared with the common RBF network model,the standard deviation and peak-to-peak value of the RLG output are decreased by more than 8%and 3%,respectively.Navigation experiments also validate the effectiveness of the compensation model.展开更多
The service load on high temperature rotating components of aero-engines generally exhibits flight mission characteristics. The general shape of the load spectrum is that Type Ⅲ/Ⅳ cyclic loading and creep loading ar...The service load on high temperature rotating components of aero-engines generally exhibits flight mission characteristics. The general shape of the load spectrum is that Type Ⅲ/Ⅳ cyclic loading and creep loading are superimposed on Type Ⅰ cyclic loading. Meanwhile, the sequence of the Type Ⅲ/Ⅳ cyclic and creep loading varies with mission. This work performed load spectrum test with this characteristic on the Ni-based alloy FGH96. Then a life prediction method was developed based on the Chaboche fatigue damage accumulation model and a modified time fraction model. Creep followed by Fatigue (C-F) test was carried out to reveal the creep-fatigue interaction and calibrate parameters. The results show that most test results fall within the 2-fold deviation band. The sequence of creep-fatigue loading within the load spectrum exhibited a limited effect on life. Finally, simplified methods were developed to improve analysis efficiency, and cases where simplified methods could replace the proposed method were discussed.展开更多
Nanocomposite dielectrics show great promising application in developing next generation wearable all-solidstate cooling devices owing to the possessed advantages of high cooling efficiency, light-weight and small vol...Nanocomposite dielectrics show great promising application in developing next generation wearable all-solidstate cooling devices owing to the possessed advantages of high cooling efficiency, light-weight and small volume without the induced greenhouse effect or serious harm to ozone layer in the exploited refrigerants. However, low electrocaloric strength in nanocomposite dielectric is severely restricting its wide-spread application because of high applied operating voltage to improve electrocaloric effect. After addressing the chosen optimized ferroelectric ceramic and ferroelectric polymer matrix in conjunction with the analysis of crucial parameters, recent progress of electrocaloric effect(ECE) in polymer nanocomposites has been considerably reviewed. Subsequently, prior to proposing the conceptual design and devices/systems in electrocaloric nanocomposites, the existing developed devices/systems are reviewed. Finally, conclusions and prospects are conducted, including the aspects of materials chosen, structural design and key issues to be considered in improving electrocaloric effect of polymer nanocomposite dielectrics for flexible solidstate cooling devices.展开更多
The influence of oxygen vacancy-dominated carrier mobility on the performance of memristors has attractedconsiderable attention.The device’s carrier mobility can be significantly improved by forming a nano-multilayer...The influence of oxygen vacancy-dominated carrier mobility on the performance of memristors has attractedconsiderable attention.The device’s carrier mobility can be significantly improved by forming a nano-multilayeredheterostructure when the individual layer thickness is below a critical value.In this work,Pt/[ZrO_(2):Y_(2)O_(3)(YSZ)/SrTiO_(3)(STO)]n/Nb:SrTiO_(3)(NSTO)memristive devices were configurated through laser pulse deposited YSZ/STO nanomultilayeredactive layer with both Pt and NSTO acting as top and counter electrodes.Specifically,the Pt/[YSZ/STO]5/NSTO device with five consecutive layers of YSZ/STO thin film shows superior memristor performance,and itscorresponding carrier mobility presents a significantly enhanced value compared to that of other periodic numbers ofYSZ/STO composed memristive devices.This can be attributed to the increase of oxygen vacancy concentration in thedevice,as evidenced by both experimental results and theoretical analysis.This work provides a significant approach inimproving the performance of memristor dominated by oxygen vacancy transporting mechanism.展开更多
With the advantages of low cost,excellent ability of heat and mass transfer and easy accessibility to the supercritical point,supercritical CO_(2) has been applied in many engineering devices recently.Because of the s...With the advantages of low cost,excellent ability of heat and mass transfer and easy accessibility to the supercritical point,supercritical CO_(2) has been applied in many engineering devices recently.Because of the sharply-varying thermophysical properties near the supercritical point,heat transfer and flow behavior of supercritical CO_(2) in tubes become complex and have received a lot of research attention.The main purpose of this paper is to summarize the findings of the published works related to flow phenomena and heat transfer characteristics of supercritical CO_(2).Firstly,influence parameters related to boundary conditions of supercritical CO_(2) flowing in a smooth tube are introduced.Secondly,commonly-used turbulence and mathematic models dealing with internal flows of supercritical CO_(2) are summarized.Then,research works on geometric effects of design parameters,shapes and configurations are introduced.The practical applications of supercritical CO_(2) in recent years are presented.Finally,developments and future challenges of supercritical CO_(2) in tubes are analyzed and summarized.This paper provides basic knowledge of heat transfer and fluid flow mechanisms and related practical applications of supercritical CO,in tubes.展开更多
Flexible piezoresistive strain sensors have received significant attention due to their diverse applications in monitoring human activities and health,as well as in robotics,prosthetics,and human–computer interaction...Flexible piezoresistive strain sensors have received significant attention due to their diverse applications in monitoring human activities and health,as well as in robotics,prosthetics,and human–computer interaction interfaces.Among the various flexible sensor types,those with microstructure designs are considered promising for strain sensing due to their simple structure,high sensitivity,extensive operational range,rapid response time,and robust stability.This review provides a concise overview of recent advancements in flexible piezoresistive sensors based on microstructure design for enhanced strain sensing performance,including the impact of microstructure on sensing mechanisms,classification of microstructure designs,fabrication methods,and practical applications.Initially,this review delves into the analysis of piezoresistive sensor sensing mechanisms and performance parameters,exploring the relationship between microstructure design and performance enhancement.Subsequently,an in-depth discussion is presented,focusing on the primary themes of microstructure design classification,process selection,performance characteristics,and specific applications.This review employs mathematical modeling and hierarchical analysis to emphasize the directionality of different microstructures on performance enhancement and to highlight the performance advantages and applicable features of various microstructure types.In conclusion,this review examines the multifunctionality of flexible piezoresistive sensors based on microstructure design and addresses the challenges that still need to be overcome and improved,such as achieving a wide range of stretchability,high sensitivity,and robust stability.This review summarizes the research directions for enhancing sensing performance through microstructure design,aiming to assist in the advancement of flexible piezoresistive sensors.展开更多
基金co-supported by the Foundation of National Key Laboratory of Science and Technology on Aerodynamic Design and Research,China(No.614220121020114)the Key R&D Projects of Hunan Province,China(No.2023GK2022)。
文摘The design of wide-range high-efficiency aerodynamic configurations is one of the most important key technologies in the research of near-space hypersonic vehicles.A double-sided intake configuration with different inlets on the upper and lower surfaces is proposed to adapt to widerange flight.Firstly,the double-sided intake configuration’s design method and flight profile are delineated.Secondly,Computational Fluid Dynamics(CFD)numerical simulation based on multi-Graphics Processing Unit(GPU)parallel computing is adopted to evaluate the vehicle’s performance comprehensively,aiming to verify the feasibility of the proposed scheme.This evaluation encompasses a wide-range basic aerodynamic characteristics,inlet performance,and heat flux at critical locations.The results show that the inlets of the designed integration configuration can start up across Mach number 3.5 to 8.The vehicle possesses multi-point cruising capability by flipping the fuselage.Simultaneously,a 180°rotation of the fuselage can significantly decrease the heat accumulation on the lower surface of the vehicle,particularly at the inlet lip,further decreasing the temperature gradient across the vehicle structure.This study has some engineering value for the aerodynamic configuration design of wide-range vehicles.However,further study reveals that the flow phenomena at the intersection of two inlets are complex,posing potential adverse impacts on propulsion efficiency.Therefore,it is imperative to conduct additional research to delve into this matter comprehensively.
基金supported in part by the National Natural Science Foundation of China(No.61203199)。
文摘Serious startup drift of the Ring Laser Gyroscope(RLG)is observed during cold startup process,which will dramatically degrade the performances of the corresponding Inertial Navigation System(INS).In this paper,correlation analysis method,which analyzes the relationship between the startup drift of the RLG and the temperature change,is used to determine the significant temperature-related terms during gyroscope startup.Based on the significant temperature-related terms and the startup time length,a startup drift compensation model for RLG based on monotonicity-constrained Radial Basis Function(RBF)neural network is proposed and validated.Compared with the raw RLG data without compensation,the standard deviation of the RLG output with the proposed constrained RBF network model is decreased by more than 46%,and the peak-to-peak value is decreased by more than 35%.Compared with the traditional multiple regression model,the standard deviation and peak-to-peak value of the RLG output are decreased by more than 10%and 6%,respectively.Compared with the common RBF network model,the standard deviation and peak-to-peak value of the RLG output are decreased by more than 8%and 3%,respectively.Navigation experiments also validate the effectiveness of the compensation model.
基金supported by the National Science and Technology Major Project of China(No.J2019-IV-0017-0085)the National Natural Science Foundation of China(Nos.12172021,52205177)the Natural Science Foundation of Hunan Province,China(No.2021JJ40741).
文摘The service load on high temperature rotating components of aero-engines generally exhibits flight mission characteristics. The general shape of the load spectrum is that Type Ⅲ/Ⅳ cyclic loading and creep loading are superimposed on Type Ⅰ cyclic loading. Meanwhile, the sequence of the Type Ⅲ/Ⅳ cyclic and creep loading varies with mission. This work performed load spectrum test with this characteristic on the Ni-based alloy FGH96. Then a life prediction method was developed based on the Chaboche fatigue damage accumulation model and a modified time fraction model. Creep followed by Fatigue (C-F) test was carried out to reveal the creep-fatigue interaction and calibrate parameters. The results show that most test results fall within the 2-fold deviation band. The sequence of creep-fatigue loading within the load spectrum exhibited a limited effect on life. Finally, simplified methods were developed to improve analysis efficiency, and cases where simplified methods could replace the proposed method were discussed.
基金Project(202045007) supported by the Start-up Funds for Outstanding Talents in Central South University,China。
文摘Nanocomposite dielectrics show great promising application in developing next generation wearable all-solidstate cooling devices owing to the possessed advantages of high cooling efficiency, light-weight and small volume without the induced greenhouse effect or serious harm to ozone layer in the exploited refrigerants. However, low electrocaloric strength in nanocomposite dielectric is severely restricting its wide-spread application because of high applied operating voltage to improve electrocaloric effect. After addressing the chosen optimized ferroelectric ceramic and ferroelectric polymer matrix in conjunction with the analysis of crucial parameters, recent progress of electrocaloric effect(ECE) in polymer nanocomposites has been considerably reviewed. Subsequently, prior to proposing the conceptual design and devices/systems in electrocaloric nanocomposites, the existing developed devices/systems are reviewed. Finally, conclusions and prospects are conducted, including the aspects of materials chosen, structural design and key issues to be considered in improving electrocaloric effect of polymer nanocomposite dielectrics for flexible solidstate cooling devices.
基金Projects(2023JJ30690,2022JJ30722)supported by the Natural Science Foundation of Hunan Province,ChinaProject(kq2202093)supported by the Natural Science Foundation of Changsha,ChinaProject(SKL202202SIC)supported by the Opening Project of State Key Laboratory of High Performance Ceramics and Superfine Microstructure,China。
文摘The influence of oxygen vacancy-dominated carrier mobility on the performance of memristors has attractedconsiderable attention.The device’s carrier mobility can be significantly improved by forming a nano-multilayeredheterostructure when the individual layer thickness is below a critical value.In this work,Pt/[ZrO_(2):Y_(2)O_(3)(YSZ)/SrTiO_(3)(STO)]n/Nb:SrTiO_(3)(NSTO)memristive devices were configurated through laser pulse deposited YSZ/STO nanomultilayeredactive layer with both Pt and NSTO acting as top and counter electrodes.Specifically,the Pt/[YSZ/STO]5/NSTO device with five consecutive layers of YSZ/STO thin film shows superior memristor performance,and itscorresponding carrier mobility presents a significantly enhanced value compared to that of other periodic numbers ofYSZ/STO composed memristive devices.This can be attributed to the increase of oxygen vacancy concentration in thedevice,as evidenced by both experimental results and theoretical analysis.This work provides a significant approach inimproving the performance of memristor dominated by oxygen vacancy transporting mechanism.
基金supported by Key Laboratory Continuously Supporting Project(Grant No.WDZC6142703202216)the Natural Science Foundation of Hunan Province(Grant No.2023JJ40733).
文摘With the advantages of low cost,excellent ability of heat and mass transfer and easy accessibility to the supercritical point,supercritical CO_(2) has been applied in many engineering devices recently.Because of the sharply-varying thermophysical properties near the supercritical point,heat transfer and flow behavior of supercritical CO_(2) in tubes become complex and have received a lot of research attention.The main purpose of this paper is to summarize the findings of the published works related to flow phenomena and heat transfer characteristics of supercritical CO_(2).Firstly,influence parameters related to boundary conditions of supercritical CO_(2) flowing in a smooth tube are introduced.Secondly,commonly-used turbulence and mathematic models dealing with internal flows of supercritical CO_(2) are summarized.Then,research works on geometric effects of design parameters,shapes and configurations are introduced.The practical applications of supercritical CO_(2) in recent years are presented.Finally,developments and future challenges of supercritical CO_(2) in tubes are analyzed and summarized.This paper provides basic knowledge of heat transfer and fluid flow mechanisms and related practical applications of supercritical CO,in tubes.
基金supported by the National Natural Science Foundation of China(No.52204299)the Natural Science Foundation of Hunan Province(Nos.2022JJ40623 and 2022JJ30722)the Start-Up Funds for Outstanding Talents in Central South University(Nos.202045007 and 202044017).
文摘Flexible piezoresistive strain sensors have received significant attention due to their diverse applications in monitoring human activities and health,as well as in robotics,prosthetics,and human–computer interaction interfaces.Among the various flexible sensor types,those with microstructure designs are considered promising for strain sensing due to their simple structure,high sensitivity,extensive operational range,rapid response time,and robust stability.This review provides a concise overview of recent advancements in flexible piezoresistive sensors based on microstructure design for enhanced strain sensing performance,including the impact of microstructure on sensing mechanisms,classification of microstructure designs,fabrication methods,and practical applications.Initially,this review delves into the analysis of piezoresistive sensor sensing mechanisms and performance parameters,exploring the relationship between microstructure design and performance enhancement.Subsequently,an in-depth discussion is presented,focusing on the primary themes of microstructure design classification,process selection,performance characteristics,and specific applications.This review employs mathematical modeling and hierarchical analysis to emphasize the directionality of different microstructures on performance enhancement and to highlight the performance advantages and applicable features of various microstructure types.In conclusion,this review examines the multifunctionality of flexible piezoresistive sensors based on microstructure design and addresses the challenges that still need to be overcome and improved,such as achieving a wide range of stretchability,high sensitivity,and robust stability.This review summarizes the research directions for enhancing sensing performance through microstructure design,aiming to assist in the advancement of flexible piezoresistive sensors.
