In allusion to the problem of friction,leakage,vibration and noise existing in continuous rotary motor electro-hydraulic servo system,highly nonlinearity and uncertainties affecting the system performance,based on the...In allusion to the problem of friction,leakage,vibration and noise existing in continuous rotary motor electro-hydraulic servo system,highly nonlinearity and uncertainties affecting the system performance,based on the transfer function of electro-hydraulic servo system,a kind of Pol-Ind friction model is proposed.The parameters of Pol-Ind friction model are identified and the accurate mathematical model of friction torque is obtained by experiment.The self-correcting wavelet neural network(WNN)controller is proposed,and Adam optimization algorithm is used to perform gradient optimization on scale factor and displacement factor in wavelet basis function,so as to improve the speed and precision of parameter optimization.Through comparative simulation analysis,it is clearly that the self-correcting WNN controller can effectively improve the frequency response and tracking accuracy of continuous rotary motor electro-hydraulic servo system.展开更多
On January 17,China announced a GDP growth rate of 5.2 percent for 2023,successfully reaching the major projected targets.In 2024,the Chinese economy will continue to seek progress while maintaining stability and prov...On January 17,China announced a GDP growth rate of 5.2 percent for 2023,successfully reaching the major projected targets.In 2024,the Chinese economy will continue to seek progress while maintaining stability and provide great dynamism for the stability and recovery of the world economy.New quality productive forces will become a new driver for economic growth in China.展开更多
大规模开发和利用风能有利于实现电力系统清洁低碳转型,是实现国家“碳达峰、碳中和”战略目标的重要技术手段,但风电出力的强不确定性对电力系统区域间可用输电能力(available transfer capability,ATC)评估带来了全新的挑战,传统用于...大规模开发和利用风能有利于实现电力系统清洁低碳转型,是实现国家“碳达峰、碳中和”战略目标的重要技术手段,但风电出力的强不确定性对电力系统区域间可用输电能力(available transfer capability,ATC)评估带来了全新的挑战,传统用于求解计及风电出力不确定性的概率ATC评估模型在计算效率和计算精度方面均存在一定的不足。为此,该文提出一种基于多项式混沌展开(polynomialchaos expansion,PCE)的电力系统概率ATC评估方法,该方法首先构建基于机会约束的电力系统概率ATC评估模型;然后,根据风电出力预测误差的概率分布特征,选择对应的正交多项式为基函数以近似风电出力预测误差及电力网络中与之相关联的其他随机变量;进一步,借助Galerkin投影和基于一阶矩、二阶矩的机会约束转化方法,将所构建的机会约束模型的概率约束转化为确定性约束,实现基于机会约束的概率ATC评估模型向易于求解的确定性优化模型的转化;进而,将概率ATC评估模型的求解问题转化为ATC的最优多项式逼近系数的求解问题,根据求得的最优多项式逼近系数和选取的基函数计算电力系统ATC的概率分布特征;最后,通过修改后的PJM-5节点测试系统、IEEE-118节点测试系统及吉林西部电网实际算例验证了所提基于多项式混沌展开的电力系统概率ATC评估方法的准确性和有效性。展开更多
In order to study the influence of inlet and outlet pressure difference and triangular buffer groove on the internal leakage of continuous rotary electro-hydraulic servo motor,the flow field model of motor with and wi...In order to study the influence of inlet and outlet pressure difference and triangular buffer groove on the internal leakage of continuous rotary electro-hydraulic servo motor,the flow field model of motor with and without triangular groove is established respectively.The mesh model is divided.The pressure distribution of the internal flow field under different pressure difference is analyzed by Fluent.Then,the gap leakage under different pressure difference is calculated,and the leakage curve is obtained.Finally,continuous rotary electro-hydraulic servo motor experimental system is built to conduct the internal leakage test,and the leakage under different pressure difference is measured and compared with the simulation results.The results show that the occurrence of leakage in the motor can be reduced by setting the triangular buffer groove on the flow plate,the simulation and experimental results are consistent.It can be concluded that the larger the pressure difference between the inlet and the outlet of the motor,the larger the gap leakage.The research lays foundation for the application of continuous rotary electro-hydraulic servo motor.展开更多
An unusually warm East Asia in spring 2018,when exceptionally high surface air temperatures were recorded in large areas of Asia,such as northern China,southern China,and Japan,was investigated based on the ERA-Interi...An unusually warm East Asia in spring 2018,when exceptionally high surface air temperatures were recorded in large areas of Asia,such as northern China,southern China,and Japan,was investigated based on the ERA-Interim reanalysis.The East Asian warming anomalies were primarily attributed to a tripole mode of North Atlantic SST anomalies,which could have triggered anomalous Rossby wave trains over the North Atlantic and Eurasia through modulating the North Atlantic baroclinic instability.Atlantic-forced Rossby waves tend to propagate eastward and induce anomalously high pressure and anticyclonic activity over East Asia,leading to a northward displacement of the Pacific subtropical high.As a result,descending motion,reduced precipitation,and increased surface solar radiation due to less cloud cover appear over East Asia,accompanied by remarkably warm advection from the ocean to southern China,northern China,and Japan.The transportation of anomalously warm advection and the feedbacks between soil moisture and surface temperature were both favorable for the recordbreaking warmth in East Asia during spring 2018.The seasonal‘memory’of the North Atlantic tripole SST mode from the previous winter to the following spring may provide useful implications for the seasonal prediction of East Asian weather and climate.展开更多
CNPC started its oil and gas cooperation in Central Asia with the acquisition of the Aktobe MunaiGas Project in June 1997.Through more than 20 years of hard work,CNPC has developed from one project(the Aktobe Project ...CNPC started its oil and gas cooperation in Central Asia with the acquisition of the Aktobe MunaiGas Project in June 1997.Through more than 20 years of hard work,CNPC has developed from one project(the Aktobe Project mentioned above)to 24 oil and gas inves tment projects in seven countries,formed a complete upstream,midstream and downstream business chain integrating oil and gas exploration and development,pipeline construction and operation,engineering and technical services and oil refining and sales,and established a corporate management structure and control system in accordance with the local laws and regulations.展开更多
为实现对使用中超声流量计准确度的实时监测,基于高压环道式气体流量标准装置,采用随机森林算法,建立了信号参数(含声速偏差)与示值误差间关系的超声流量计预测模型,同时结合LabVIEW软件开发平台研制出一套超声流量计实时使用中检验系...为实现对使用中超声流量计准确度的实时监测,基于高压环道式气体流量标准装置,采用随机森林算法,建立了信号参数(含声速偏差)与示值误差间关系的超声流量计预测模型,同时结合LabVIEW软件开发平台研制出一套超声流量计实时使用中检验系统。基于该系统,可实现超声流量计信号质量参数、流态指标参数、声速指标参数3类信号参数的实时采集,并利用预测模型开展流量计示值误差的同步预测。在160~800 m 3/h范围内的实验测试表明,流量计示值误差与系统预测误差间的偏差为±0.42%。展开更多
基金Supported by the National Natural Science Foundation of China(No.51975164)the China Scholarship Council(No.201908230358)the Fundamental Research Fundation for Universities of Heilongjiang Province。
文摘In allusion to the problem of friction,leakage,vibration and noise existing in continuous rotary motor electro-hydraulic servo system,highly nonlinearity and uncertainties affecting the system performance,based on the transfer function of electro-hydraulic servo system,a kind of Pol-Ind friction model is proposed.The parameters of Pol-Ind friction model are identified and the accurate mathematical model of friction torque is obtained by experiment.The self-correcting wavelet neural network(WNN)controller is proposed,and Adam optimization algorithm is used to perform gradient optimization on scale factor and displacement factor in wavelet basis function,so as to improve the speed and precision of parameter optimization.Through comparative simulation analysis,it is clearly that the self-correcting WNN controller can effectively improve the frequency response and tracking accuracy of continuous rotary motor electro-hydraulic servo system.
文摘On January 17,China announced a GDP growth rate of 5.2 percent for 2023,successfully reaching the major projected targets.In 2024,the Chinese economy will continue to seek progress while maintaining stability and provide great dynamism for the stability and recovery of the world economy.New quality productive forces will become a new driver for economic growth in China.
文摘大规模开发和利用风能有利于实现电力系统清洁低碳转型,是实现国家“碳达峰、碳中和”战略目标的重要技术手段,但风电出力的强不确定性对电力系统区域间可用输电能力(available transfer capability,ATC)评估带来了全新的挑战,传统用于求解计及风电出力不确定性的概率ATC评估模型在计算效率和计算精度方面均存在一定的不足。为此,该文提出一种基于多项式混沌展开(polynomialchaos expansion,PCE)的电力系统概率ATC评估方法,该方法首先构建基于机会约束的电力系统概率ATC评估模型;然后,根据风电出力预测误差的概率分布特征,选择对应的正交多项式为基函数以近似风电出力预测误差及电力网络中与之相关联的其他随机变量;进一步,借助Galerkin投影和基于一阶矩、二阶矩的机会约束转化方法,将所构建的机会约束模型的概率约束转化为确定性约束,实现基于机会约束的概率ATC评估模型向易于求解的确定性优化模型的转化;进而,将概率ATC评估模型的求解问题转化为ATC的最优多项式逼近系数的求解问题,根据求得的最优多项式逼近系数和选取的基函数计算电力系统ATC的概率分布特征;最后,通过修改后的PJM-5节点测试系统、IEEE-118节点测试系统及吉林西部电网实际算例验证了所提基于多项式混沌展开的电力系统概率ATC评估方法的准确性和有效性。
基金the National Natural Science Foundation of China(No.51975164)the China Scholarship Council(No.201908230358)the Fundamental Research Fundation for Universities of Heilongjiang Province(No.2019-KYYWF-0205)。
文摘In order to study the influence of inlet and outlet pressure difference and triangular buffer groove on the internal leakage of continuous rotary electro-hydraulic servo motor,the flow field model of motor with and without triangular groove is established respectively.The mesh model is divided.The pressure distribution of the internal flow field under different pressure difference is analyzed by Fluent.Then,the gap leakage under different pressure difference is calculated,and the leakage curve is obtained.Finally,continuous rotary electro-hydraulic servo motor experimental system is built to conduct the internal leakage test,and the leakage under different pressure difference is measured and compared with the simulation results.The results show that the occurrence of leakage in the motor can be reduced by setting the triangular buffer groove on the flow plate,the simulation and experimental results are consistent.It can be concluded that the larger the pressure difference between the inlet and the outlet of the motor,the larger the gap leakage.The research lays foundation for the application of continuous rotary electro-hydraulic servo motor.
基金supported by the National Key Research and Development Program of China [grant number2016YFA0602703]the National Natural Science Foundation of China [grant numbers 41661144019,41690123,41690120,and91637208]+1 种基金the CMA Guangzhou Joint Research Center for Atmospheric Sciencesthe Jiangsu Collaborative Innovation Center for Climate Change
文摘An unusually warm East Asia in spring 2018,when exceptionally high surface air temperatures were recorded in large areas of Asia,such as northern China,southern China,and Japan,was investigated based on the ERA-Interim reanalysis.The East Asian warming anomalies were primarily attributed to a tripole mode of North Atlantic SST anomalies,which could have triggered anomalous Rossby wave trains over the North Atlantic and Eurasia through modulating the North Atlantic baroclinic instability.Atlantic-forced Rossby waves tend to propagate eastward and induce anomalously high pressure and anticyclonic activity over East Asia,leading to a northward displacement of the Pacific subtropical high.As a result,descending motion,reduced precipitation,and increased surface solar radiation due to less cloud cover appear over East Asia,accompanied by remarkably warm advection from the ocean to southern China,northern China,and Japan.The transportation of anomalously warm advection and the feedbacks between soil moisture and surface temperature were both favorable for the recordbreaking warmth in East Asia during spring 2018.The seasonal‘memory’of the North Atlantic tripole SST mode from the previous winter to the following spring may provide useful implications for the seasonal prediction of East Asian weather and climate.
文摘CNPC started its oil and gas cooperation in Central Asia with the acquisition of the Aktobe MunaiGas Project in June 1997.Through more than 20 years of hard work,CNPC has developed from one project(the Aktobe Project mentioned above)to 24 oil and gas inves tment projects in seven countries,formed a complete upstream,midstream and downstream business chain integrating oil and gas exploration and development,pipeline construction and operation,engineering and technical services and oil refining and sales,and established a corporate management structure and control system in accordance with the local laws and regulations.
文摘为实现对使用中超声流量计准确度的实时监测,基于高压环道式气体流量标准装置,采用随机森林算法,建立了信号参数(含声速偏差)与示值误差间关系的超声流量计预测模型,同时结合LabVIEW软件开发平台研制出一套超声流量计实时使用中检验系统。基于该系统,可实现超声流量计信号质量参数、流态指标参数、声速指标参数3类信号参数的实时采集,并利用预测模型开展流量计示值误差的同步预测。在160~800 m 3/h范围内的实验测试表明,流量计示值误差与系统预测误差间的偏差为±0.42%。
