Electrochemical machining(ECM)has emerged as an important option for manufacturing the blisk.The inter-electrode gap(IEG)distribution is an essential parameter for the blisk precise shap-ing process in ECM,as it affec...Electrochemical machining(ECM)has emerged as an important option for manufacturing the blisk.The inter-electrode gap(IEG)distribution is an essential parameter for the blisk precise shap-ing process in ECM,as it affects the process stability,profile accuracy and surface quality.Larger IEG leads to a poor localization effect and has an adverse influence on the machining accuracy and surface quality of blisk.To achieve micro-IEG(<50 lm)blisk finishing machining,this work puts forward a novel variable-parameters blisk ECM strategy based on the synchronous coupling mode of micro-vibration amplitude and small pulse duration.The modelling and simulation of the blisk micro-IEG machining have been carried out.Exploratory experiments of variable-parameters blisk ECM were car-ried out.The results illustrated that the IEG width reduced with the progress of variable parameter pro-cess.The IEG width of the blade’s concave part and convex part could be successfully controlled to within 30 lm and 21 lm,respectively.The profile deviation for the blade’s concave surface and convex surface are 49 lm and 35 lm,while the surface roughness reaches R_(a)=0.149 lm and R_(a)=0.196 lm,respectively.The profile accuracy of the blisk leading/trailing edges was limited to within 91 lm.Com-pared with the currently-established process,the profile accuracy of the blade’s concave and convex profiles was improved by 50.5%and 53.3%,respectively.The surface quality was improved by 53.2%and 50.9%,respectively.Additionally,the machined surface was covered with small corrosion pits and weak attacks of the grain boundary due to selective dissolution.Some electrolytic products were dispersed on the machined surface,and their components were mainly composed of the carbide and oxide products of Ti and Nb elements.The results indicate that the variable-parameters strategy is effective for achieving a tiny IEG in blisk ECM,which can be used in engineering practice.展开更多
在理论分析双向FDI(Foreign Direct Investment)对经济包容性增长影响机理的基础上,利用2003~2017年中国省际面板数据,采用DEA交叉效率综合测算中国省际经济包容性增长(Inclusive Economic Growth,IEG)指数,通过构建面板向量自回归模型...在理论分析双向FDI(Foreign Direct Investment)对经济包容性增长影响机理的基础上,利用2003~2017年中国省际面板数据,采用DEA交叉效率综合测算中国省际经济包容性增长(Inclusive Economic Growth,IEG)指数,通过构建面板向量自回归模型,动态考察了双向FDI对中国经济包容性增长的影响.结果表明,样本期内中国IEG指数整体不高,且具有明显的阶段性和地区异质性;外商直接投资对中国经济包容性增长起着“绊脚石”的作用,而对外直接投资对中国经济包容性增长扮演着“助推器”的角色.展开更多
As scheduled,the 2008 Beijing Olympic torch relayed its Lhasa journey on June 21^(st).The relay in Tibet had 156 torch bearers including 75 Tibetans and covered 9.3 kilometers.
The sharp increase in the total installed capacity of natural gas generators has intensified the dynamic interaction between the electricity and natural gas systems,which could induce cascading failure propagation acr...The sharp increase in the total installed capacity of natural gas generators has intensified the dynamic interaction between the electricity and natural gas systems,which could induce cascading failure propagation across the two systems that deserves intensive research.Considering the distinct time response behaviors of the two systems,this paper discusses an integrated simulation approach to simulate the cascading failure propagation process of integrated electricity and natural gas systems(IEGSs).On one hand,considering instantaneous re-distribution of power flows after the occurrence of disturbance or failure,the steady-state AC power flow model is employed.On the other hand,gas transmission dynamics are represented by dynamic model to capture the details of its transition process.The interactions between the two systems,intensified by energy coupling components(such as gas-fired generator and electricity-driven gas compressor)as well as the switching among the operation modes of compressors during the cascading failure propagation process,are studied.An IEGS composed of the IEEE 30-bus electricity system and a 14-node 15-pipeline gas system is established to illustrate the effectiveness of the proposed simulation approach,in which two energy sub-systems are coupled by compressor and gas-fired generator.Numerical results clearly demonstrate that heterogeneous interactions between electricity and gas systems would trigger the cascading failure propagation between the two coupling systems.展开更多
基金sponsored by the National Science and Tech-nology Major Project(Grant No.2017-VII-0004-0097)National Natural Science Foundation of China for Creative Research Groups(Grant No.51921003)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX21_0191).
文摘Electrochemical machining(ECM)has emerged as an important option for manufacturing the blisk.The inter-electrode gap(IEG)distribution is an essential parameter for the blisk precise shap-ing process in ECM,as it affects the process stability,profile accuracy and surface quality.Larger IEG leads to a poor localization effect and has an adverse influence on the machining accuracy and surface quality of blisk.To achieve micro-IEG(<50 lm)blisk finishing machining,this work puts forward a novel variable-parameters blisk ECM strategy based on the synchronous coupling mode of micro-vibration amplitude and small pulse duration.The modelling and simulation of the blisk micro-IEG machining have been carried out.Exploratory experiments of variable-parameters blisk ECM were car-ried out.The results illustrated that the IEG width reduced with the progress of variable parameter pro-cess.The IEG width of the blade’s concave part and convex part could be successfully controlled to within 30 lm and 21 lm,respectively.The profile deviation for the blade’s concave surface and convex surface are 49 lm and 35 lm,while the surface roughness reaches R_(a)=0.149 lm and R_(a)=0.196 lm,respectively.The profile accuracy of the blisk leading/trailing edges was limited to within 91 lm.Com-pared with the currently-established process,the profile accuracy of the blade’s concave and convex profiles was improved by 50.5%and 53.3%,respectively.The surface quality was improved by 53.2%and 50.9%,respectively.Additionally,the machined surface was covered with small corrosion pits and weak attacks of the grain boundary due to selective dissolution.Some electrolytic products were dispersed on the machined surface,and their components were mainly composed of the carbide and oxide products of Ti and Nb elements.The results indicate that the variable-parameters strategy is effective for achieving a tiny IEG in blisk ECM,which can be used in engineering practice.
文摘在理论分析双向FDI(Foreign Direct Investment)对经济包容性增长影响机理的基础上,利用2003~2017年中国省际面板数据,采用DEA交叉效率综合测算中国省际经济包容性增长(Inclusive Economic Growth,IEG)指数,通过构建面板向量自回归模型,动态考察了双向FDI对中国经济包容性增长的影响.结果表明,样本期内中国IEG指数整体不高,且具有明显的阶段性和地区异质性;外商直接投资对中国经济包容性增长起着“绊脚石”的作用,而对外直接投资对中国经济包容性增长扮演着“助推器”的角色.
文摘As scheduled,the 2008 Beijing Olympic torch relayed its Lhasa journey on June 21^(st).The relay in Tibet had 156 torch bearers including 75 Tibetans and covered 9.3 kilometers.
基金supported by the National Natural Science Foundation of China(No.51777182)the National Natural Science Foundation(No.CMMI1635339)
文摘The sharp increase in the total installed capacity of natural gas generators has intensified the dynamic interaction between the electricity and natural gas systems,which could induce cascading failure propagation across the two systems that deserves intensive research.Considering the distinct time response behaviors of the two systems,this paper discusses an integrated simulation approach to simulate the cascading failure propagation process of integrated electricity and natural gas systems(IEGSs).On one hand,considering instantaneous re-distribution of power flows after the occurrence of disturbance or failure,the steady-state AC power flow model is employed.On the other hand,gas transmission dynamics are represented by dynamic model to capture the details of its transition process.The interactions between the two systems,intensified by energy coupling components(such as gas-fired generator and electricity-driven gas compressor)as well as the switching among the operation modes of compressors during the cascading failure propagation process,are studied.An IEGS composed of the IEEE 30-bus electricity system and a 14-node 15-pipeline gas system is established to illustrate the effectiveness of the proposed simulation approach,in which two energy sub-systems are coupled by compressor and gas-fired generator.Numerical results clearly demonstrate that heterogeneous interactions between electricity and gas systems would trigger the cascading failure propagation between the two coupling systems.
