To overcome the challenges of limited experimental data and improve the accuracy of empirical formulas,we propose a low-cycle fatigue(LCF)life prediction model for nickel-based superalloys using a data augmentation me...To overcome the challenges of limited experimental data and improve the accuracy of empirical formulas,we propose a low-cycle fatigue(LCF)life prediction model for nickel-based superalloys using a data augmentation method.This method utilizes a variational autoencoder(VAE)to generate low-cycle fatigue data and form an augmented dataset.The Pearson correlation coefficient(PCC)is employed to verify the similarity of feature distributions between the original and augmented datasets.Six machine learning models,namely random forest(RF),artificial neural network(ANN),support vector machine(SVM),gradient-boosted decision tree(GBDT),eXtreme Gradient Boosting(XGBoost),and Categorical Boosting(CatBoost),are utilized to predict the LCF life of nickel-based superalloys.Results indicate that the proposed data augmentation method based on VAE can effectively expand the dataset,and the mean absolute error(MAE),root mean square error(RMSE),and R-squared(R^(2))values achieved using the CatBoost model,with respective values of 0.0242,0.0391,and 0.9538,are superior to those of the other models.The proposed method reduces the cost and time associated with LCF experiments and accurately establishes the relationship between fatigue characteristics and LCF life of nickel-based superalloys.展开更多
This paper introduces a nonlinear finite element analysis on damage propagation behavior of composite sandwich panels under in-plane uniaxial quasi-static compression after a low velocity impact. The major damage mode...This paper introduces a nonlinear finite element analysis on damage propagation behavior of composite sandwich panels under in-plane uniaxial quasi-static compression after a low velocity impact. The major damage modes due to the impact, including the residual indentation on the impacted facesheet, the initially crushed core under the impacted area, and the delamination are incorporated into the model. A consequential core crushing mechanism is incorporated into the analysis by using an element deactivation technique. Damage propagation behavior, which corresponds to those observed in sandwich compression after impact （SCAI） tests, has been successfully captured in the numerical simulation. The critical far field stress corresponding to the onset of damage propagation at specified critical locations near the damage zone are captured successfully. They show a good correlation with experimental data. These values can be used to effectively predict the residual compressive strength of low-velocity impact damaged composite sandwich panels.展开更多
In order to increase the fault diagnosis efficiency and make the fault data mining be realized, the decision table containing numerical attributes must be discretized for further calculations. The discernibility matri...In order to increase the fault diagnosis efficiency and make the fault data mining be realized, the decision table containing numerical attributes must be discretized for further calculations. The discernibility matrix-based reduction method depends on whether the numerical attributes can be properly discretized or not.So a discretization algorithm based on particle swarm optimization(PSO) is proposed. Moreover, hybrid weights are adopted in the process of particles evolution. Comparative calculations for certain equipment are completed to demonstrate the effectiveness of the proposed algorithm. The results indicate that the proposed algorithm has better performance than other popular algorithms such as class-attribute interdependence maximization(CAIM)discretization method and entropy-based discretization method.展开更多
To obtain the influence of fluid pressure and temperature on warm hydroforming of 5A06-O aluminum alloy sheet, the unified mechanics equilibrium equations, which take through- thickness normal stress and friction into...To obtain the influence of fluid pressure and temperature on warm hydroforming of 5A06-O aluminum alloy sheet, the unified mechanics equilibrium equations, which take through- thickness normal stress and friction into account, were established in spherical coordinate system. The distribution of through-thickness normal stress in the thickness direction was determined. The relation between through-thickness normal stress and fluid pressure was also analyzed in different regions of cylindrical cup. Based on the method of subtracting one increasing function from another, the constitutive equation of 5A06-O applied to warm hydroforming was established and in a good agreement with uniaxial tensile data. Based on whether the thickness variation was taken into account, two mechanic models were established to do the comparative study. The results for the studied case show that the calculated stress values are pretty close according to the two models and consistent with results of finite element analysis; the thickness distribution in flange computed by the second model conforms to the experimental data. Finally, the influences of fluid pressure on the flange thickness and radial stress were analyzed.展开更多
Stitched composite materials are emerging as a promising material due to their high interlaminar strength,combined performance and light weight.The mechanical properties of stitch yarns are very essential for stitched...Stitched composite materials are emerging as a promising material due to their high interlaminar strength,combined performance and light weight.The mechanical properties of stitch yarns are very essential for stitched composite structures.In this study,the tensile behaviors of the twisted fiber yarn in stitched composites were investigated experimentally,analytically and numerically.Two kinds of cross-sectional area of twisted yarn are proposed and discussed.The paper presents an intersecting circle model to describe the cross-section of twisted fiber yarns,and a physics-based theoretical model to predict the effective tensile moduli.The numerical models take into account the cross-sectional characteristic and the twist architecture.The investigation shows that:the sum of each fiber area should be used for experimental analysis;and the crosssectional area surrounded by the yarn profile should be used for theoretical predictions and finite element(FE)simulations.The relative errors of the prediction method and the FE simulation are less than 2%and 1%,respectively.The friction between the fibers is derived,and the effect of friction on mechanical properties is discussed.The investigation method will serve as a fundamental component of twisted fiber bundle/yarn analysis.展开更多
The flow and heat transfer of molten GaAs under the interaction of buoyancy, Marangoni and crystal rotation in the Czochralski configuration are numerically studied by using a time-dependent and three-dimensional turb...The flow and heat transfer of molten GaAs under the interaction of buoyancy, Marangoni and crystal rotation in the Czochralski configuration are numerically studied by using a time-dependent and three-dimensional turbulent flow model for the first time. The transition from axisymmetric flow to non-axisymmetric flow and then returning to axisymmetric flow again with increasing centrifugal and coriolis forces by increasing the crystal rotation rate was numerically observed. The origin of the transition to non-axisymmetric flow has been proved to be baroclinic instability. Several important characteristics of baroclinic instability in the CZ GaAs melt have been predicted. These characteristics are found to be in agreement with experimental observations.展开更多
To enhance the robustness of a proxy multi-signature scheme and improve its efficiency, a novel proxy signature paradigm is proposed referred to as In this paradigm, multiple proxy signer candidates identity-based pro...To enhance the robustness of a proxy multi-signature scheme and improve its efficiency, a novel proxy signature paradigm is proposed referred to as In this paradigm, multiple proxy signer candidates identity-based proxy multi-signature （IBPMS）. are employed to play a role of the single proxy signer in the existing model. A provably secure IBPMS scheme is presented which requires only one round broadcast operation. Performance analysis demonstrates that the new scheme outperforms the existing multi-signature schemes in robustness and communication. These properties are rendered to our IBPMS scheme as a more practical solution to secure e-transaction delegation applications of proxy signatures.展开更多
It is critical to study efficient,stable oxygen reduction reaction(ORR)electrocatalysts due to insufficient stability and expensive price of Pt/C catalysts for Zn-air batteries.Fe–N–C electrocatalysts was synthesize...It is critical to study efficient,stable oxygen reduction reaction(ORR)electrocatalysts due to insufficient stability and expensive price of Pt/C catalysts for Zn-air batteries.Fe–N–C electrocatalysts was synthesized by a facile solvent-green method and the efficiency of Fe–N–C optimized was studied as potential ORR electrocatalysts under alkaline condition.Results indicated that it had excellent ORR activity with E_(1/2)of 0.93 V,which was competitive to that of Pt/C-JM under the same conditions.Moreover,the assembled Zn-air battery exhibited discharge potential and charge potential of 1.2 V,2.32 V at 5 mA cm^(−2)with high stability,respectively.Overall,all results illustrated that Fe–N–C is an excellent ORR electrocatalyst in the field of metal air battery.Additionally,this work opens a good way to synthesize highly efficient electrocatalysts from metal organic framework and to investigate ORR mechanism of efficient chemical energy to electricity conversion.展开更多
Ultraviolet （UV） fire detector is used to detect fire according to the ultraviolet radiation of the flame. High detecting sensitivity of the sensor requires high ultraviolet transmission property of the detecting wi...Ultraviolet （UV） fire detector is used to detect fire according to the ultraviolet radiation of the flame. High detecting sensitivity of the sensor requires high ultraviolet transmission property of the detecting window. In this paper, high performance JGS-1 （type name of glass） ultraviolet quartz glass is used as the sensor detecting window material and the ultraviolet transmission characteristics of the glass is studied. A new method with the smart fire detecting module to test the ultraviolet transmission parameter of quartz glass is demonstrated. The comparison results of UV spectrometer and this new method manifest that JGS-1 quartz glass has good ultraviolet transmission character and the new test method with fire detecting module is direct and feasible.展开更多
A novel porous mullite ceramic with overlapping and interlocking mullite whiskers was prepared using in-situ whisker growth technology.Without the use of any pore-foaming agents,the formation of a porous structure was...A novel porous mullite ceramic with overlapping and interlocking mullite whiskers was prepared using in-situ whisker growth technology.Without the use of any pore-foaming agents,the formation of a porous structure was facilitated by the atomic rearrangement of Al_(2)O_(3) and SiO_(2) catalyzed with MoO_(3).The effects of the molar ratio of Al_(2)O_(3) to SiO_(2),MoO_(3) content,sintering time,and sintering temperature on the structure and properties of(xAl_(2)O_(3)·ySiO_(2))m(MoO_(3))n-T-t(T=sintering temperature,and t=sintering duration)ceramics were comprehensively studied.The molar ratio of Al_(2)O_(3) to SiO_(2) had a more significant effect on the morphology of the whiskers,while the other three conditions generally promote whisker growth.Under conditions of x:y=3:1.8,m:n=9:1,T=1300℃,and t=3 h,(3Al_(2)O_(3)·1.8SiO_(2))9(MoO_(3))1-1300℃-3 h ceramics exhibited a satisfactory compressive strength of 4.81 MPa at a density of 0.76 g/cm3.Microstructural analysis revealed that a multi-level reinforcement structure was obtained by the interlaced distribution of tiny and large whiskers,significantly increasing the crack deflection area and enhancing the crack deflection resistance when resisting external forces.After 100 thermal shock cycles between room temperature and 1300℃,the compressive strength retention rate was 77.13%.In addition,the multi-scale whisker-overlapping structure also has a high specific surface area(1.83 m^(2)/g),high porosity(74.18%),and small pore size(7.44μm).The thermal conductivity was as low as 0.260 W/(m·K),and the ceramic maintained a rear-side temperature below 200℃ when subjected to a 1300℃ butane flame.In addition,the regulatory mechanism between parameters,structure,and properties was analyzed in detail,providing data support for research on porous materials.展开更多
基金Financial support from the Fundamental Research Funds for the Central Universities(ZJ2022-003,JG2022-27,J2020-060,and J2021-060)Sichuan Province Engineering Technology Research Center of General Aircraft Maintenance(GAMRC2021YB08)the Young Scientists Fund of the National Natural Science Foundation of China(No.52105417)is acknowledged.
文摘To overcome the challenges of limited experimental data and improve the accuracy of empirical formulas,we propose a low-cycle fatigue(LCF)life prediction model for nickel-based superalloys using a data augmentation method.This method utilizes a variational autoencoder(VAE)to generate low-cycle fatigue data and form an augmented dataset.The Pearson correlation coefficient(PCC)is employed to verify the similarity of feature distributions between the original and augmented datasets.Six machine learning models,namely random forest(RF),artificial neural network(ANN),support vector machine(SVM),gradient-boosted decision tree(GBDT),eXtreme Gradient Boosting(XGBoost),and Categorical Boosting(CatBoost),are utilized to predict the LCF life of nickel-based superalloys.Results indicate that the proposed data augmentation method based on VAE can effectively expand the dataset,and the mean absolute error(MAE),root mean square error(RMSE),and R-squared(R^(2))values achieved using the CatBoost model,with respective values of 0.0242,0.0391,and 0.9538,are superior to those of the other models.The proposed method reduces the cost and time associated with LCF experiments and accurately establishes the relationship between fatigue characteristics and LCF life of nickel-based superalloys.
基金Project supported by the Scientific and Technological Innovation Foundation and the Developing Program for Outstanding Persons in NPU.
文摘This paper introduces a nonlinear finite element analysis on damage propagation behavior of composite sandwich panels under in-plane uniaxial quasi-static compression after a low velocity impact. The major damage modes due to the impact, including the residual indentation on the impacted facesheet, the initially crushed core under the impacted area, and the delamination are incorporated into the model. A consequential core crushing mechanism is incorporated into the analysis by using an element deactivation technique. Damage propagation behavior, which corresponds to those observed in sandwich compression after impact （SCAI） tests, has been successfully captured in the numerical simulation. The critical far field stress corresponding to the onset of damage propagation at specified critical locations near the damage zone are captured successfully. They show a good correlation with experimental data. These values can be used to effectively predict the residual compressive strength of low-velocity impact damaged composite sandwich panels.
基金the National Natural Science Foundation of China(No.51775090)the General Program of Civil Aviation Flight University of China(No.J2015-39)
文摘In order to increase the fault diagnosis efficiency and make the fault data mining be realized, the decision table containing numerical attributes must be discretized for further calculations. The discernibility matrix-based reduction method depends on whether the numerical attributes can be properly discretized or not.So a discretization algorithm based on particle swarm optimization(PSO) is proposed. Moreover, hybrid weights are adopted in the process of particles evolution. Comparative calculations for certain equipment are completed to demonstrate the effectiveness of the proposed algorithm. The results indicate that the proposed algorithm has better performance than other popular algorithms such as class-attribute interdependence maximization(CAIM)discretization method and entropy-based discretization method.
基金co-supported by the International Cooperation of RFBR-NSFC (No. 51111120088)the financial support from the National Natural Science Foundation of China (No. 50975014)
文摘To obtain the influence of fluid pressure and temperature on warm hydroforming of 5A06-O aluminum alloy sheet, the unified mechanics equilibrium equations, which take through- thickness normal stress and friction into account, were established in spherical coordinate system. The distribution of through-thickness normal stress in the thickness direction was determined. The relation between through-thickness normal stress and fluid pressure was also analyzed in different regions of cylindrical cup. Based on the method of subtracting one increasing function from another, the constitutive equation of 5A06-O applied to warm hydroforming was established and in a good agreement with uniaxial tensile data. Based on whether the thickness variation was taken into account, two mechanic models were established to do the comparative study. The results for the studied case show that the calculated stress values are pretty close according to the two models and consistent with results of finite element analysis; the thickness distribution in flange computed by the second model conforms to the experimental data. Finally, the influences of fluid pressure on the flange thickness and radial stress were analyzed.
基金co-supported by the National Natural Science Foundation of China(Nos.51772009,51911530201,51802264 and 51275023)。
文摘Stitched composite materials are emerging as a promising material due to their high interlaminar strength,combined performance and light weight.The mechanical properties of stitch yarns are very essential for stitched composite structures.In this study,the tensile behaviors of the twisted fiber yarn in stitched composites were investigated experimentally,analytically and numerically.Two kinds of cross-sectional area of twisted yarn are proposed and discussed.The paper presents an intersecting circle model to describe the cross-section of twisted fiber yarns,and a physics-based theoretical model to predict the effective tensile moduli.The numerical models take into account the cross-sectional characteristic and the twist architecture.The investigation shows that:the sum of each fiber area should be used for experimental analysis;and the crosssectional area surrounded by the yarn profile should be used for theoretical predictions and finite element(FE)simulations.The relative errors of the prediction method and the FE simulation are less than 2%and 1%,respectively.The friction between the fibers is derived,and the effect of friction on mechanical properties is discussed.The investigation method will serve as a fundamental component of twisted fiber bundle/yarn analysis.
基金supported by the National Natural Science Foundation of China(NSFC)under grant No.50376078the Second-Term National 985 Project within Research Center of Biological Function Information and Instruments of Chongqing University.
文摘The flow and heat transfer of molten GaAs under the interaction of buoyancy, Marangoni and crystal rotation in the Czochralski configuration are numerically studied by using a time-dependent and three-dimensional turbulent flow model for the first time. The transition from axisymmetric flow to non-axisymmetric flow and then returning to axisymmetric flow again with increasing centrifugal and coriolis forces by increasing the crystal rotation rate was numerically observed. The origin of the transition to non-axisymmetric flow has been proved to be baroclinic instability. Several important characteristics of baroclinic instability in the CZ GaAs melt have been predicted. These characteristics are found to be in agreement with experimental observations.
基金Supported by the National Basic Research Program of China(No.2012CB315905)the National Natural Science Foundation of China(No.61272501)the Fund of Tianjin Key Laboratory of Civil Aircraft Airworthiness and Maintenance in CAUC and a General grant from Civil Aviation Flight University of China(No.J2013-31,Q2014-48)
文摘To enhance the robustness of a proxy multi-signature scheme and improve its efficiency, a novel proxy signature paradigm is proposed referred to as In this paradigm, multiple proxy signer candidates identity-based proxy multi-signature （IBPMS）. are employed to play a role of the single proxy signer in the existing model. A provably secure IBPMS scheme is presented which requires only one round broadcast operation. Performance analysis demonstrates that the new scheme outperforms the existing multi-signature schemes in robustness and communication. These properties are rendered to our IBPMS scheme as a more practical solution to secure e-transaction delegation applications of proxy signatures.
基金Authors received the funding from 2021 Special Innovative Talents Project by Education Department of Guangdong Province。
文摘It is critical to study efficient,stable oxygen reduction reaction(ORR)electrocatalysts due to insufficient stability and expensive price of Pt/C catalysts for Zn-air batteries.Fe–N–C electrocatalysts was synthesized by a facile solvent-green method and the efficiency of Fe–N–C optimized was studied as potential ORR electrocatalysts under alkaline condition.Results indicated that it had excellent ORR activity with E_(1/2)of 0.93 V,which was competitive to that of Pt/C-JM under the same conditions.Moreover,the assembled Zn-air battery exhibited discharge potential and charge potential of 1.2 V,2.32 V at 5 mA cm^(−2)with high stability,respectively.Overall,all results illustrated that Fe–N–C is an excellent ORR electrocatalyst in the field of metal air battery.Additionally,this work opens a good way to synthesize highly efficient electrocatalysts from metal organic framework and to investigate ORR mechanism of efficient chemical energy to electricity conversion.
基金Supported by the National Nature Science Foundation of China (No. 60572007) and the Ministry of Education Program of China (No.20040614004)
文摘Ultraviolet （UV） fire detector is used to detect fire according to the ultraviolet radiation of the flame. High detecting sensitivity of the sensor requires high ultraviolet transmission property of the detecting window. In this paper, high performance JGS-1 （type name of glass） ultraviolet quartz glass is used as the sensor detecting window material and the ultraviolet transmission characteristics of the glass is studied. A new method with the smart fire detecting module to test the ultraviolet transmission parameter of quartz glass is demonstrated. The comparison results of UV spectrometer and this new method manifest that JGS-1 quartz glass has good ultraviolet transmission character and the new test method with fire detecting module is direct and feasible.
基金supported by the Fundamental Research Funds for the Central Universities of Civil Aviation University of China(No.3122024050)the Undergraduate Innovation Project of Civil Aviation University of China(Nos.202410059049 and IECAUC2025043).
文摘A novel porous mullite ceramic with overlapping and interlocking mullite whiskers was prepared using in-situ whisker growth technology.Without the use of any pore-foaming agents,the formation of a porous structure was facilitated by the atomic rearrangement of Al_(2)O_(3) and SiO_(2) catalyzed with MoO_(3).The effects of the molar ratio of Al_(2)O_(3) to SiO_(2),MoO_(3) content,sintering time,and sintering temperature on the structure and properties of(xAl_(2)O_(3)·ySiO_(2))m(MoO_(3))n-T-t(T=sintering temperature,and t=sintering duration)ceramics were comprehensively studied.The molar ratio of Al_(2)O_(3) to SiO_(2) had a more significant effect on the morphology of the whiskers,while the other three conditions generally promote whisker growth.Under conditions of x:y=3:1.8,m:n=9:1,T=1300℃,and t=3 h,(3Al_(2)O_(3)·1.8SiO_(2))9(MoO_(3))1-1300℃-3 h ceramics exhibited a satisfactory compressive strength of 4.81 MPa at a density of 0.76 g/cm3.Microstructural analysis revealed that a multi-level reinforcement structure was obtained by the interlaced distribution of tiny and large whiskers,significantly increasing the crack deflection area and enhancing the crack deflection resistance when resisting external forces.After 100 thermal shock cycles between room temperature and 1300℃,the compressive strength retention rate was 77.13%.In addition,the multi-scale whisker-overlapping structure also has a high specific surface area(1.83 m^(2)/g),high porosity(74.18%),and small pore size(7.44μm).The thermal conductivity was as low as 0.260 W/(m·K),and the ceramic maintained a rear-side temperature below 200℃ when subjected to a 1300℃ butane flame.In addition,the regulatory mechanism between parameters,structure,and properties was analyzed in detail,providing data support for research on porous materials.
