Setting up a pair of moving frames on the two pitch circles, the instantaneous contact point being considered the attendant point of the frames, the equation of the trace of the contact points in the frame being p = p...Setting up a pair of moving frames on the two pitch circles, the instantaneous contact point being considered the attendant point of the frames, the equation of the trace of the contact points in the frame being p = p(t~), we can deduce that the basic rule for the gear profiles is dp / ds = - csos 0 where s is the are length of the pitch circles. Giving a known function of p = p (0), we can obtain the equations of the two conjugate gear profiles and the curvatures and inductive curvature of the profiles. The second order contact phenomenon that a given gear profile can contact with the mating gear at two points simultaneously is discussed by the method of moving frames.展开更多
In this paper,an innovative type of thin-walled structures,the convex-concave honeycomb columns(CCHCs)with transverse negative Poisson’s ratio(NPR),is proposed for energy absorbers by replacing the cell walls of squa...In this paper,an innovative type of thin-walled structures,the convex-concave honeycomb columns(CCHCs)with transverse negative Poisson’s ratio(NPR),is proposed for energy absorbers by replacing the cell walls of square honeycomb lattice columns with sine-shaped or zigzag-shaped walls of equal mass.Numerical simulations show that,under axial impact,contrary to the conventional square honeycomb columns of equal mass,the transverse cross section of NPR CCHC shrinks inward,making the cell walls of CCHC contact and interact sufficiently with each other and thus dissipate the impact energy much more effectively.By suitably adjusting the transverse NPR,the CCHC can have the combined advantages of effective total energy absorption,high specific energy absorption and low maximum peak crushing force.The research of this paper provides a new strategy for the design of high-performance energy absorbers widely used in the engineering fields of vehicle engineering,aerospace engineering etc.展开更多
Photovoltaic(PV)inverter,as a promising voltage/var control(VVC)resource,can supply flexible reactive power to reduce microgrid power loss and regulate bus voltage.Meanwhile,active power plays a significant role in mi...Photovoltaic(PV)inverter,as a promising voltage/var control(VVC)resource,can supply flexible reactive power to reduce microgrid power loss and regulate bus voltage.Meanwhile,active power plays a significant role in microgrid voltage profile.Price-based demand response(PBDR)can shift load demand via determining time-varying prices,which can be regarded as an effective means for active power shifting.However,due to the different characteristics,PBDR and inverter-based VVC lack systematic coordination.Thus,this paper proposes a PBDR-supported three-stage hierarchically coordinated voltage control method,including day-ahead PBDR price scheduling,hour-ahead reactive power dispatch of PV inverters,and realtime local droop control of PV inverters.Considering their mutual influence,a stochastic optimization method is utilized to centrally or hierarchically coordinate adjacent two stages.To solve the bilinear constraints of droop control function,the problem is reformulated into a second-order cone programming relaxation model.Then,the concave constraints are convexified,forming a penalty convex-concave model for feasible solution recovery.Lastly,a convex-concave procedure-based solution algorithm is proposed to iteratively solve the penalty model.The proposed method is tested on 33-bus and IEEE 123-bus distribution networks and compared with other methods.The results verify the high efficiency of the proposed method to achieve power loss reduction and voltage regulation.展开更多
文摘Setting up a pair of moving frames on the two pitch circles, the instantaneous contact point being considered the attendant point of the frames, the equation of the trace of the contact points in the frame being p = p(t~), we can deduce that the basic rule for the gear profiles is dp / ds = - csos 0 where s is the are length of the pitch circles. Giving a known function of p = p (0), we can obtain the equations of the two conjugate gear profiles and the curvatures and inductive curvature of the profiles. The second order contact phenomenon that a given gear profile can contact with the mating gear at two points simultaneously is discussed by the method of moving frames.
基金supported by the National Natural Science Foundation of China(Grant Nos.12021002,12072222,12132010 and 11991032)the State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures(Grant No.SKLTESKF1901).
文摘In this paper,an innovative type of thin-walled structures,the convex-concave honeycomb columns(CCHCs)with transverse negative Poisson’s ratio(NPR),is proposed for energy absorbers by replacing the cell walls of square honeycomb lattice columns with sine-shaped or zigzag-shaped walls of equal mass.Numerical simulations show that,under axial impact,contrary to the conventional square honeycomb columns of equal mass,the transverse cross section of NPR CCHC shrinks inward,making the cell walls of CCHC contact and interact sufficiently with each other and thus dissipate the impact energy much more effectively.By suitably adjusting the transverse NPR,the CCHC can have the combined advantages of effective total energy absorption,high specific energy absorption and low maximum peak crushing force.The research of this paper provides a new strategy for the design of high-performance energy absorbers widely used in the engineering fields of vehicle engineering,aerospace engineering etc.
基金supported in part by the National Natural Science Foundation of China(No.52307091)in part by the Natural Science Foundation of Jiangsu Province(No.BK20230952)+1 种基金in part by the China Postdoctoral Science Foundation(No.2023M740976)in part by the Start Up Grant of City University of Hong Kong(No.9380163)。
文摘Photovoltaic(PV)inverter,as a promising voltage/var control(VVC)resource,can supply flexible reactive power to reduce microgrid power loss and regulate bus voltage.Meanwhile,active power plays a significant role in microgrid voltage profile.Price-based demand response(PBDR)can shift load demand via determining time-varying prices,which can be regarded as an effective means for active power shifting.However,due to the different characteristics,PBDR and inverter-based VVC lack systematic coordination.Thus,this paper proposes a PBDR-supported three-stage hierarchically coordinated voltage control method,including day-ahead PBDR price scheduling,hour-ahead reactive power dispatch of PV inverters,and realtime local droop control of PV inverters.Considering their mutual influence,a stochastic optimization method is utilized to centrally or hierarchically coordinate adjacent two stages.To solve the bilinear constraints of droop control function,the problem is reformulated into a second-order cone programming relaxation model.Then,the concave constraints are convexified,forming a penalty convex-concave model for feasible solution recovery.Lastly,a convex-concave procedure-based solution algorithm is proposed to iteratively solve the penalty model.The proposed method is tested on 33-bus and IEEE 123-bus distribution networks and compared with other methods.The results verify the high efficiency of the proposed method to achieve power loss reduction and voltage regulation.
