Negative stiffness mechanisms have great application potential in different fields, such as vibration isolation, energy absorption and mesh antenna unfolding. Although numerous compliant mechanisms with negative stiff...Negative stiffness mechanisms have great application potential in different fields, such as vibration isolation, energy absorption and mesh antenna unfolding. Although numerous compliant mechanisms with negative stiffness features have been implemented in literature, the designing work remains in its infancy, and proposing an original design strategy may open a new avenue for the future inventions. In this study, inspired by a toy, we developed a novel type of compliant mechanism composed of thin strips, possessing negative stiffness property under torsion. The negative stiffness feature is achieved by large deformation of the strips rather than mechanical buckling. As a consequence, the obtained negative stiffness segment covers a significantly long range. Demonstrated with examples, it was shown that the proposed mechanisms could be combined with other compliant mechanisms to realize long-range unusual torque-angle relationships, which can be used in different applications.展开更多
This study uses the difference-in differences method to test the impact of a high-speed rail(HSR)service on the issuance of municipal corporate bonds(MCB)based on panel data for prefecture-level cities in China from 2...This study uses the difference-in differences method to test the impact of a high-speed rail(HSR)service on the issuance of municipal corporate bonds(MCB)based on panel data for prefecture-level cities in China from 2003 to 2016.The study has three findings.First,HSR increased the scale of the issuance of MCB significantly.After conducting a series of robustness tests,the above conclusion remained robust.Second,HSR affected the issuance of MCB by increasing the city's financing demands and improving the city's financing capacity.Third,the effect of HSR on the issuance of MCB varied from city to city.Specifically,the promotion of the opening of HSR to the issuance of MCB was concentrated in remote and fast growing cities.High-speed rail can also effectively reduce the cost and shrink credit spreads of the MCB.This paper shows that it is necessary to further optimize the layout of HSR,release and exploit the financial resource reallocation effect of HSR,and provide financial support to the high-quality development of cities.展开更多
The onset of frictional motion couples complex spatiotemporal dynamics of discrete contacts with different orders of magnitude at time and length scales.In order to reveal how these individual scales affect the fricti...The onset of frictional motion couples complex spatiotemporal dynamics of discrete contacts with different orders of magnitude at time and length scales.In order to reveal how these individual scales affect the frictional sliding,we establish a 2D multiscale spring-block model for the frictional sliding at an elastic slider-rigid interface.In this model,the rupture of frictional interface is described by three different types of locally microscopic motion:pinned,sliding and dislocated states.By using realistic boundary conditions,our numerical results can precisely reproduce the loading curves found in previous experiments.The precursor events,corresponding to a discrete sequence of rapid crack-like fronts propagating partially in the contact zone,can also be shown in our simulation.From the analysis of the microscopic motion,we characterize the evolution of the real contact area and the corresponding interface motion at the mesoscale level,and show that the evolution corresponds to four distinct and inter-related phases:detachment,fast and slow slip motion,as well as the rest of slip.These mesoscale behaviors are completely consistent with the existing experimental results and their physical mechanisms can be explained by the detailed information of the numerical simulation.The study is established on a bottom-up multiscale model which provides a comprehensive picture about the complex spatiotemporal dynamics of frictional sliding.展开更多
基金supported by the National Natural Science Foundation of China(11872221 and 11302114)the Major State Basic Research Development Program(2012CB821203)
文摘Negative stiffness mechanisms have great application potential in different fields, such as vibration isolation, energy absorption and mesh antenna unfolding. Although numerous compliant mechanisms with negative stiffness features have been implemented in literature, the designing work remains in its infancy, and proposing an original design strategy may open a new avenue for the future inventions. In this study, inspired by a toy, we developed a novel type of compliant mechanism composed of thin strips, possessing negative stiffness property under torsion. The negative stiffness feature is achieved by large deformation of the strips rather than mechanical buckling. As a consequence, the obtained negative stiffness segment covers a significantly long range. Demonstrated with examples, it was shown that the proposed mechanisms could be combined with other compliant mechanisms to realize long-range unusual torque-angle relationships, which can be used in different applications.
基金the National Social Science Foundation of China(Nos.15AJY017 and 16BJY183).
文摘This study uses the difference-in differences method to test the impact of a high-speed rail(HSR)service on the issuance of municipal corporate bonds(MCB)based on panel data for prefecture-level cities in China from 2003 to 2016.The study has three findings.First,HSR increased the scale of the issuance of MCB significantly.After conducting a series of robustness tests,the above conclusion remained robust.Second,HSR affected the issuance of MCB by increasing the city's financing demands and improving the city's financing capacity.Third,the effect of HSR on the issuance of MCB varied from city to city.Specifically,the promotion of the opening of HSR to the issuance of MCB was concentrated in remote and fast growing cities.High-speed rail can also effectively reduce the cost and shrink credit spreads of the MCB.This paper shows that it is necessary to further optimize the layout of HSR,release and exploit the financial resource reallocation effect of HSR,and provide financial support to the high-quality development of cities.
基金supported by the National Natural Science Foundation of China(Grant 1193200).
文摘The onset of frictional motion couples complex spatiotemporal dynamics of discrete contacts with different orders of magnitude at time and length scales.In order to reveal how these individual scales affect the frictional sliding,we establish a 2D multiscale spring-block model for the frictional sliding at an elastic slider-rigid interface.In this model,the rupture of frictional interface is described by three different types of locally microscopic motion:pinned,sliding and dislocated states.By using realistic boundary conditions,our numerical results can precisely reproduce the loading curves found in previous experiments.The precursor events,corresponding to a discrete sequence of rapid crack-like fronts propagating partially in the contact zone,can also be shown in our simulation.From the analysis of the microscopic motion,we characterize the evolution of the real contact area and the corresponding interface motion at the mesoscale level,and show that the evolution corresponds to four distinct and inter-related phases:detachment,fast and slow slip motion,as well as the rest of slip.These mesoscale behaviors are completely consistent with the existing experimental results and their physical mechanisms can be explained by the detailed information of the numerical simulation.The study is established on a bottom-up multiscale model which provides a comprehensive picture about the complex spatiotemporal dynamics of frictional sliding.
