Effective short-term prediction of regional voltage load is of great significance to the implementation of energy saving and emission reduction policies in China.Accurate prediction of real-time demand voltage can red...Effective short-term prediction of regional voltage load is of great significance to the implementation of energy saving and emission reduction policies in China.Accurate prediction of real-time demand voltage can reduce power waste and carbon emissions,make outstanding contributions to delaying global climate warming,and is conducive to global environmental protection and sustainable development.On the short-term load forecasting of power system,a variant model of RNN-LSTM is tested in this paper.It effectively solves the problem of gradient explosion and disappearance caused by large amount of data input in classical RNN.On the basis of this model,optimization experiments are carried out under different super parameters to achieve better prediction results.The experimental results show that the accuracy of test set reaches 99.8%,which proves that the method proposed in this paper has certain reference value.展开更多
The fretting behaviour of the AZ91D magnesium alloy was investigated. The influence of the number of cycles, normal load (contact pressure) and the amplitude of slip on the fretting behavior of the material were focus...The fretting behaviour of the AZ91D magnesium alloy was investigated. The influence of the number of cycles, normal load (contact pressure) and the amplitude of slip on the fretting behavior of the material were focused. Fretting tests were performed under various running conditions with regard to normal load levels and slip amplitudes. The friction coefficient between the surfaces at the fretting junction was continuously recorded. The fretting damage on the magnesium specimens was studied by SEM. The results show that the wear volume increases with the increase of slip amplitude, and linearly increases with the increase of normal load in the mixed and gross slip regime, but the normal load has no obvious effect on the wear volume in the partial slip regime. The predominant fretting wear mechanism of magnesium alloy in the slip regime is the oxidation wear, delaminated wear and abrasive wear.展开更多
The inverter is one of the key components of wind turbine,and it is a complex circuit composed of a series of components such as a variety of electronic components and power devices.Therefore,it is difficult to accura...The inverter is one of the key components of wind turbine,and it is a complex circuit composed of a series of components such as a variety of electronic components and power devices.Therefore,it is difficult to accurately identify the operation states of inverter and some problems regarding its own circuit,especially in the early stages of failure.However,if the inverter temperature prediction model can be established,the early states can be identified through the judgment of the output temperature.Accordingly,considering whether the inverter heats up normally from the perspective of heat dissipation,a method for the early operation state identification of the inverter is provided in this paper.A variable selection method based on fusion analysis of correlation and physical relationship is adopted to extract variables as input variables,which have high correlation with inverter temperature.Then multi-input and multi-output temperature prediction model of inverter is established based on a nonlinear autoregressive exogenous model(NARX)network,and the prediction temperature residual is used as the real-time standard to evaluate the inverter states.For validating this,the validity and reliability of the established temperature prediction model are verified through case analysis,and the performance comparison with various models demonstrates that the proposed method has higher accuracy.The construction method of the prediction model can be used for reference to other aspects of wind turbine.All these bring huge benefits to wind energy industry.展开更多
In this study, AZ31 Mg alloy was processed by a new severe plasticity deformation methodology with multi-pass lowered temperature, and the deformation behavior and microstructure evolution were investigated by finite ...In this study, AZ31 Mg alloy was processed by a new severe plasticity deformation methodology with multi-pass lowered temperature, and the deformation behavior and microstructure evolution were investigated by finite element method and electron back-scattered diffraction technique and hardness. The results show that with the increase of deformation pass, the strain gradually springs, and its interval distribution tends to homogenize. Meanwhile, the effective strain increases dramatically with the shear force sudden upgrade in the deformation process. Moreover, the new deformation technique can refine grain size remarkably. With the passes on, {10-12} tensile twins behavior and the pyramidal < c + a > slip are triggered more frequently, leading to the completeness of dynamic recrystallization (DRX) gradually, which weaken and disperse the basal texture obviously. Besides, the standard deviation of hardness is getting smaller, and the maximum can reach 78.40 HV on average, which can be attributed to the even large strain distribution, complete DRX, and the high geometrically necessary dislocation.展开更多
Using an electron microscope to observe the microstructure of a porcupine quills cross-section and a bionic method,a new bionic structure was proposed.The performance of the structure in terms of energy absorption,max...Using an electron microscope to observe the microstructure of a porcupine quills cross-section and a bionic method,a new bionic structure was proposed.The performance of the structure in terms of energy absorption,maximum impact force withstood,and impact force efficiency was evaluated using Ansys finite element simulation software to simulate the structure's impact.To examine the impact of ribs on the structural performance of the bionic porcupine quills,a control structure was developed.According to the results of the finite element simulation,the presence of ribs in the Bionic porcupine quills structure can transfer stress uniformly to the overall structure and share stress for some of the rupture-prone regions.Ribs reduce stress concentration in specific areas and increase the impact force efficiency of the structure.The SEA and IFE values of bionic porcupine quills were 30.01 kJ/kg and 84.22%,respectively.The structure is then optimized for parameter design in order to find the optimal structure by response surface in order to improve the structure's SEA and decrease its MIF.In order to evaluate the precision of the response surface,the optimal structure predicted is validated using finite element simulation.展开更多
The condition monitoring and fault diagnosis have been identified as the key to achieving higher availabilities of wind turbines.Numerous studies show that the open-circuit fault is a significant contributor to the fa...The condition monitoring and fault diagnosis have been identified as the key to achieving higher availabilities of wind turbines.Numerous studies show that the open-circuit fault is a significant contributor to the failures of wind turbine converter.However,the multiple faults combinations and the influence of wind speed changes abruptly,grid voltage sags and noise interference have brought great challenges to fault diagnosis.Accordingly,concerning the open-circuit fault of converters in direct-driven PMSG wind turbine,a diagnostic method for multiple open-circuit faults is proposed in this paper,which is divided into two tasks:The first one is the fault detection and the second one is the fault localization.The detection method is based on the relative current residuals after exponential transformation and on an adaptive threshold,and the localization method is based on the average values of fault phase currents.The scheduled diagnosis method is available to both the generator-side converter and the grid-side converter,allowing to detect and locate single and double open-circuit faults.For validating this,robustness test and multiple open-circuit faults diagnosis are presented in a 2-MW direct-driven PMSG wind turbine system,the results validate the reliability and effectiveness of the proposed method.展开更多
A subsystem impactor test for pedestrian lower limb injury evaluation has been brought in China New Car Assessment Protocol(CNCAP).Concerning large anthropometric differences of the people from different countries,the...A subsystem impactor test for pedestrian lower limb injury evaluation has been brought in China New Car Assessment Protocol(CNCAP).Concerning large anthropometric differences of the people from different countries,the present study aims to establish and validate a finite element lower limb model representing 50th Chinese male size for pedestrian safety research,then compare its biomechanical responses with the general models currently in wide use in the world for pedestrian safety evaluation.Concerning the vehicle-pedestrian impact loading environment,the previously developed lower limb model with three-dimensional muscles was adjusted and validated through the related experiments.Then,the biomechanical responses of the validated model were compared with the Total Human Model for Safety(THUMS)and Advanced Pedestrian Legform Impactor(aPLI)models by combing with four typical vehicles.The results showed that both consistency and significant differences of biomechanical responses existed between the present model and the other two models.The injury measurements of the thigh region of the present model showed extremely large differences with the other two models,while the tibia and Medial Collateral Ligament(MCL)injury measurements show similar values.Thus,it can be concluded that directly using the aPLI or THUMS models for Chinese pedestrian safety evaluation is not robust concerning both kinematic responses and injury measurements.展开更多
基金Supported by Natural Science Foundation of Hunan Province(2020JJ4306)"Scientific Innovation Plan"of the Chinese Academy of Sciences(20194001882)。
文摘Effective short-term prediction of regional voltage load is of great significance to the implementation of energy saving and emission reduction policies in China.Accurate prediction of real-time demand voltage can reduce power waste and carbon emissions,make outstanding contributions to delaying global climate warming,and is conducive to global environmental protection and sustainable development.On the short-term load forecasting of power system,a variant model of RNN-LSTM is tested in this paper.It effectively solves the problem of gradient explosion and disappearance caused by large amount of data input in classical RNN.On the basis of this model,optimization experiments are carried out under different super parameters to achieve better prediction results.The experimental results show that the accuracy of test set reaches 99.8%,which proves that the method proposed in this paper has certain reference value.
基金Project(KFJJ0302) supported by the Hunan Provincial Key Laboratory of Health Maintenance for Mechanical Equipment, China
文摘The fretting behaviour of the AZ91D magnesium alloy was investigated. The influence of the number of cycles, normal load (contact pressure) and the amplitude of slip on the fretting behavior of the material were focused. Fretting tests were performed under various running conditions with regard to normal load levels and slip amplitudes. The friction coefficient between the surfaces at the fretting junction was continuously recorded. The fretting damage on the magnesium specimens was studied by SEM. The results show that the wear volume increases with the increase of slip amplitude, and linearly increases with the increase of normal load in the mixed and gross slip regime, but the normal load has no obvious effect on the wear volume in the partial slip regime. The predominant fretting wear mechanism of magnesium alloy in the slip regime is the oxidation wear, delaminated wear and abrasive wear.
基金This work is supported by the National Natural Science Foundation of People’s Republic of China(Grant No.51875199)Hunan Provincial Natural Science Foundation(Grant No.2019JJ50154)the Key Research and Development Program of Hunan Province,China(Grant No.2018GK2073).
文摘The inverter is one of the key components of wind turbine,and it is a complex circuit composed of a series of components such as a variety of electronic components and power devices.Therefore,it is difficult to accurately identify the operation states of inverter and some problems regarding its own circuit,especially in the early stages of failure.However,if the inverter temperature prediction model can be established,the early states can be identified through the judgment of the output temperature.Accordingly,considering whether the inverter heats up normally from the perspective of heat dissipation,a method for the early operation state identification of the inverter is provided in this paper.A variable selection method based on fusion analysis of correlation and physical relationship is adopted to extract variables as input variables,which have high correlation with inverter temperature.Then multi-input and multi-output temperature prediction model of inverter is established based on a nonlinear autoregressive exogenous model(NARX)network,and the prediction temperature residual is used as the real-time standard to evaluate the inverter states.For validating this,the validity and reliability of the established temperature prediction model are verified through case analysis,and the performance comparison with various models demonstrates that the proposed method has higher accuracy.The construction method of the prediction model can be used for reference to other aspects of wind turbine.All these bring huge benefits to wind energy industry.
基金supported by the National Natural Science Foundation of China(Grant Nos.52174362 and 51975207)the Xiangtan Special Project for Building a National Innovative City(Grant No.CG-YB20221043)the Yancheng“Talent Plan of Yellow Sea Pearl"for Leading Talent Project。
文摘In this study, AZ31 Mg alloy was processed by a new severe plasticity deformation methodology with multi-pass lowered temperature, and the deformation behavior and microstructure evolution were investigated by finite element method and electron back-scattered diffraction technique and hardness. The results show that with the increase of deformation pass, the strain gradually springs, and its interval distribution tends to homogenize. Meanwhile, the effective strain increases dramatically with the shear force sudden upgrade in the deformation process. Moreover, the new deformation technique can refine grain size remarkably. With the passes on, {10-12} tensile twins behavior and the pyramidal < c + a > slip are triggered more frequently, leading to the completeness of dynamic recrystallization (DRX) gradually, which weaken and disperse the basal texture obviously. Besides, the standard deviation of hardness is getting smaller, and the maximum can reach 78.40 HV on average, which can be attributed to the even large strain distribution, complete DRX, and the high geometrically necessary dislocation.
基金supported by the National Natural Science Foundation of China(No.11972158)the Postgraduate Scientific Research Innovation Project of Hunan Province(No.CX20221044)the Military Commission Science and Technology Committee Basic Strengthening Program Technology Fund(No.2020-JCJQ-JJ-356)and(No.2019-JCJQ-JJ-150).
文摘Using an electron microscope to observe the microstructure of a porcupine quills cross-section and a bionic method,a new bionic structure was proposed.The performance of the structure in terms of energy absorption,maximum impact force withstood,and impact force efficiency was evaluated using Ansys finite element simulation software to simulate the structure's impact.To examine the impact of ribs on the structural performance of the bionic porcupine quills,a control structure was developed.According to the results of the finite element simulation,the presence of ribs in the Bionic porcupine quills structure can transfer stress uniformly to the overall structure and share stress for some of the rupture-prone regions.Ribs reduce stress concentration in specific areas and increase the impact force efficiency of the structure.The SEA and IFE values of bionic porcupine quills were 30.01 kJ/kg and 84.22%,respectively.The structure is then optimized for parameter design in order to find the optimal structure by response surface in order to improve the structure's SEA and decrease its MIF.In order to evaluate the precision of the response surface,the optimal structure predicted is validated using finite element simulation.
基金supported by the Key Research and Development Program of Hunan Province,China under Grant 2018GK2073the Natural Science Foundation of Hunan Province,China under Grant 2019JJ50154+1 种基金the National Natural Science Foundation of China under Grant 51875199Major Technological Achievements in the Transformation of the Strategic Emerging Industry of Hunan Province of China under Grant 2018GK4024.
文摘The condition monitoring and fault diagnosis have been identified as the key to achieving higher availabilities of wind turbines.Numerous studies show that the open-circuit fault is a significant contributor to the failures of wind turbine converter.However,the multiple faults combinations and the influence of wind speed changes abruptly,grid voltage sags and noise interference have brought great challenges to fault diagnosis.Accordingly,concerning the open-circuit fault of converters in direct-driven PMSG wind turbine,a diagnostic method for multiple open-circuit faults is proposed in this paper,which is divided into two tasks:The first one is the fault detection and the second one is the fault localization.The detection method is based on the relative current residuals after exponential transformation and on an adaptive threshold,and the localization method is based on the average values of fault phase currents.The scheduled diagnosis method is available to both the generator-side converter and the grid-side converter,allowing to detect and locate single and double open-circuit faults.For validating this,robustness test and multiple open-circuit faults diagnosis are presented in a 2-MW direct-driven PMSG wind turbine system,the results validate the reliability and effectiveness of the proposed method.
基金This work is supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(Grant No.51621004)National Natural Science Foundation of China(Grant No.51875187)+1 种基金Hunan Youth Talent Program(Grant No.2020RC3016)Hunan Provincial Natural Science Foundation of China(Grant No.2019JJ40021).
文摘A subsystem impactor test for pedestrian lower limb injury evaluation has been brought in China New Car Assessment Protocol(CNCAP).Concerning large anthropometric differences of the people from different countries,the present study aims to establish and validate a finite element lower limb model representing 50th Chinese male size for pedestrian safety research,then compare its biomechanical responses with the general models currently in wide use in the world for pedestrian safety evaluation.Concerning the vehicle-pedestrian impact loading environment,the previously developed lower limb model with three-dimensional muscles was adjusted and validated through the related experiments.Then,the biomechanical responses of the validated model were compared with the Total Human Model for Safety(THUMS)and Advanced Pedestrian Legform Impactor(aPLI)models by combing with four typical vehicles.The results showed that both consistency and significant differences of biomechanical responses existed between the present model and the other two models.The injury measurements of the thigh region of the present model showed extremely large differences with the other two models,while the tibia and Medial Collateral Ligament(MCL)injury measurements show similar values.Thus,it can be concluded that directly using the aPLI or THUMS models for Chinese pedestrian safety evaluation is not robust concerning both kinematic responses and injury measurements.
