Constructing metamodel with global high-fidelity in design space is significant in engineering design. In this paper, a double-stage metamodel （DSM） which integrates advantages of both interpolation metamodel and re...Constructing metamodel with global high-fidelity in design space is significant in engineering design. In this paper, a double-stage metamodel （DSM） which integrates advantages of both interpolation metamodel and regression metamodel is constructed. It takes regression model as the first stage to fit overall distribution of the original model, and then interpolation model of regression model approximation error is used as the second stage to improve accuracy. Under the same conditions and with the same samples, DSM expresses higher fidelity and represents physical characteristics of original model better. Besides, in order to validate DSM characteristics, three examples including Ackley function, airfoil aerodynamic analysis and wing aerodynamic analysis are investigated, In the end, airfoil and wing aerodynamic design optimizations using genetic algorithm are presented to verify the engineering applicability of DSM.展开更多
Static recrystallization(SRX)behaviors and corresponding recrystallization mechanisms of 7Mo super-austenitic stainless steel were studied under different deformation conditions.The order of influence of deformation p...Static recrystallization(SRX)behaviors and corresponding recrystallization mechanisms of 7Mo super-austenitic stainless steel were studied under different deformation conditions.The order of influence of deformation parameters on static recrystallization behaviors,from high to low,is followed by temperature,first-stage strain and strain rate.Meanwhile,the effect of holding time on static recrystallization behaviors is significantly controlled by temperature.In addition,with the increase in temperature from 1000 to 1200°C,the static recrystallization mechanism evolves from discontinuous static recrystallization and continuous static recrystallization(cSRX)to metadynamic recrystallization and cSRX,and finally to cSRX.The cSRX exists at all temperatures.This is because high stacking fault energy(56 mJ m−2)promotes the movement of dislocations,making the deformation mechanism of this steel is dominated by planar slip of dislocation.Large undissolved sigma precipitates promote static recrystallization through particle-stimulated nucleation.However,small strain-induced precipitates at grain boundaries hinder the nucleation of conventional SRX and the growth of recrystallized grains,while the hindering effect decreases with the increase in temperature.展开更多
In this paper,a Double-stage Surrogate-based Shape Optimization(DSSO)strategy for Blended-Wing-Body Underwater Gliders(BWBUGs)is proposed to reduce the computational cost.In this strategy,a double-stage surrogate mode...In this paper,a Double-stage Surrogate-based Shape Optimization(DSSO)strategy for Blended-Wing-Body Underwater Gliders(BWBUGs)is proposed to reduce the computational cost.In this strategy,a double-stage surrogate model is developed to replace the high-dimensional objective in shape optimization.Specifically,several First-stage Surrogate Models(FSMs)are built for the sectional airfoils,and the second-stage surrogate model is constructed with respect to the outputs of FSMs.Besides,a Multi-start Space Reduction surrogate-based global optimization method is applied to search for the optimum.In order to validate the efficiency of the proposed method,DSSO is first compared with an ordinary One-stage Surrogate-based Optimization strategy by using the same optimization method.Then,the other three popular surrogate-based optimization methods and three heuristic algorithms are utilized to make comparisons.Results indicate that the lift-to-drag ratio of the BWBUG is improved by 9.35%with DSSO,which outperforms the comparison methods.Besides,DSSO reduces more than 50%of the time that other methods used when obtaining the same level of results.Furthermore,some considerations of the proposed strategy are further discussed and some characteristics of DSSO are identified.展开更多
A double-stage start-up structure to limit the inrush current used in current-mode charge pump with wide input range,fixed output and multimode operation is presented in this paper.As a widely utilized power source im...A double-stage start-up structure to limit the inrush current used in current-mode charge pump with wide input range,fixed output and multimode operation is presented in this paper.As a widely utilized power source implement,a Li-battery is always used as the power supply for chips.Due to the internal resistance,a potential drop will be generated at the input terminal of the chip with an input current.A false shut down with a low supply voltage will happen if the input current is too large,leading to the degradation of the Li-battery＇s service life.To solve this problem,the inrush current is limited by introducing a new start-up state.All of the circuits have been implemented with the NUVOTON 0.6 μm CMOS process.The measurement results show that the inrush current can be limited below 1 A within all input supply ranges,and the power efficiency is higher than the conventional structure.展开更多
With the accelerated development of agricultural intelligence and mechanization,the traditional premixed pesticide mixing method has been unable to meet people’s needs for safe,environmental and efficient agricultura...With the accelerated development of agricultural intelligence and mechanization,the traditional premixed pesticide mixing method has been unable to meet people’s needs for safe,environmental and efficient agricultural production.Therefore,an in-depth study on a variety of new pesticide mixing methods has been conducted at home and abroad.The single-stage on-line jet mixing method has been increasingly used because of its advantages of safety and high efficiency,which,however,proved to have some disadvantages such as difficulty in controlling the pesticide mixing ratio and poor mixing uniformity.In this experiment,a set of double-stage online jet mixing apparatus was designed to solve some shortcomings of single-stage online jet mixing apparatus,and the influence of jet nozzle parameters in the main jet mixing apparatus and the radiation flow mixing apparatus on the final pesticide mixing effect were studied for this apparatus,and the most appropriate jet nozzle parameters were selected.展开更多
文摘Constructing metamodel with global high-fidelity in design space is significant in engineering design. In this paper, a double-stage metamodel （DSM） which integrates advantages of both interpolation metamodel and regression metamodel is constructed. It takes regression model as the first stage to fit overall distribution of the original model, and then interpolation model of regression model approximation error is used as the second stage to improve accuracy. Under the same conditions and with the same samples, DSM expresses higher fidelity and represents physical characteristics of original model better. Besides, in order to validate DSM characteristics, three examples including Ackley function, airfoil aerodynamic analysis and wing aerodynamic analysis are investigated, In the end, airfoil and wing aerodynamic design optimizations using genetic algorithm are presented to verify the engineering applicability of DSM.
基金supported by National Natural Science Foundation of China(No.U1810207)the Innovation Pilot Project for Fusion of Science,Education and Industry(International Cooperation)from Qilu University of Technology(No.2020KJC-GH03).
文摘Static recrystallization(SRX)behaviors and corresponding recrystallization mechanisms of 7Mo super-austenitic stainless steel were studied under different deformation conditions.The order of influence of deformation parameters on static recrystallization behaviors,from high to low,is followed by temperature,first-stage strain and strain rate.Meanwhile,the effect of holding time on static recrystallization behaviors is significantly controlled by temperature.In addition,with the increase in temperature from 1000 to 1200°C,the static recrystallization mechanism evolves from discontinuous static recrystallization and continuous static recrystallization(cSRX)to metadynamic recrystallization and cSRX,and finally to cSRX.The cSRX exists at all temperatures.This is because high stacking fault energy(56 mJ m−2)promotes the movement of dislocations,making the deformation mechanism of this steel is dominated by planar slip of dislocation.Large undissolved sigma precipitates promote static recrystallization through particle-stimulated nucleation.However,small strain-induced precipitates at grain boundaries hinder the nucleation of conventional SRX and the growth of recrystallized grains,while the hindering effect decreases with the increase in temperature.
基金This research was financially supported by the National Natural Science Foundation of China(Grant Nos.51875466 and 51805436)the China Postdoctoral Science Foundation(Grant No.2019T120941)the China Scholarships Council(Grant No.201806290133).
文摘In this paper,a Double-stage Surrogate-based Shape Optimization(DSSO)strategy for Blended-Wing-Body Underwater Gliders(BWBUGs)is proposed to reduce the computational cost.In this strategy,a double-stage surrogate model is developed to replace the high-dimensional objective in shape optimization.Specifically,several First-stage Surrogate Models(FSMs)are built for the sectional airfoils,and the second-stage surrogate model is constructed with respect to the outputs of FSMs.Besides,a Multi-start Space Reduction surrogate-based global optimization method is applied to search for the optimum.In order to validate the efficiency of the proposed method,DSSO is first compared with an ordinary One-stage Surrogate-based Optimization strategy by using the same optimization method.Then,the other three popular surrogate-based optimization methods and three heuristic algorithms are utilized to make comparisons.Results indicate that the lift-to-drag ratio of the BWBUG is improved by 9.35%with DSSO,which outperforms the comparison methods.Besides,DSSO reduces more than 50%of the time that other methods used when obtaining the same level of results.Furthermore,some considerations of the proposed strategy are further discussed and some characteristics of DSSO are identified.
基金supported by the National Natural Science Foundation of China(No.61106026)
文摘A double-stage start-up structure to limit the inrush current used in current-mode charge pump with wide input range,fixed output and multimode operation is presented in this paper.As a widely utilized power source implement,a Li-battery is always used as the power supply for chips.Due to the internal resistance,a potential drop will be generated at the input terminal of the chip with an input current.A false shut down with a low supply voltage will happen if the input current is too large,leading to the degradation of the Li-battery＇s service life.To solve this problem,the inrush current is limited by introducing a new start-up state.All of the circuits have been implemented with the NUVOTON 0.6 μm CMOS process.The measurement results show that the inrush current can be limited below 1 A within all input supply ranges,and the power efficiency is higher than the conventional structure.
文摘With the accelerated development of agricultural intelligence and mechanization,the traditional premixed pesticide mixing method has been unable to meet people’s needs for safe,environmental and efficient agricultural production.Therefore,an in-depth study on a variety of new pesticide mixing methods has been conducted at home and abroad.The single-stage on-line jet mixing method has been increasingly used because of its advantages of safety and high efficiency,which,however,proved to have some disadvantages such as difficulty in controlling the pesticide mixing ratio and poor mixing uniformity.In this experiment,a set of double-stage online jet mixing apparatus was designed to solve some shortcomings of single-stage online jet mixing apparatus,and the influence of jet nozzle parameters in the main jet mixing apparatus and the radiation flow mixing apparatus on the final pesticide mixing effect were studied for this apparatus,and the most appropriate jet nozzle parameters were selected.
