Impact testing is a primary method to evaluate the impact property of resistance spot welding,which is an important quality index in automotive industry.For testing impact properties of spot welds,many customized test...Impact testing is a primary method to evaluate the impact property of resistance spot welding,which is an important quality index in automotive industry.For testing impact properties of spot welds,many customized testers have been developed.This paper summarized some of the impact testers reported in open literatures and the emphasis was placed on the equipment structures,functions,technical parameters,advantages and disadvantage,etc.Some key issues about the development of the testers such as kinematic energy input mode,fixture design,combined load testing,sensor and data acquisition were discussed.Finally,the problems and prospects in the research and development of impact testers for spot welds were pointed out.展开更多
Dirac nodal-line semimetals with the linear bands crossing along a line or loop, represent a new topological state of matter. Here, by carrying out magnetotransport measurements and performing first-principle calculat...Dirac nodal-line semimetals with the linear bands crossing along a line or loop, represent a new topological state of matter. Here, by carrying out magnetotransport measurements and performing first-principle calculations, we demonstrate that such a state has been realized in high-quality single crystals of SrAs_3.We obtain the nontrivial ∏ Berry phase by analysing the Shubnikov-de Haas quantum oscillations. We also observe a robust negative longitudinal magnetoresistance induced by the chiral anomaly.Accompanying first-principles calculations identifies that a single hole pocket enclosing the loop nodes is responsible for these observations.展开更多
The frequency dependent of the forward and reverse bias capacitance-voltage （C-V） and conductance-voltage （G/w-V） charac- teristics of Au/p-InP SBDs have been investigated in the frequency range of 20 kHz-10 MHz a...The frequency dependent of the forward and reverse bias capacitance-voltage （C-V） and conductance-voltage （G/w-V） charac- teristics of Au/p-InP SBDs have been investigated in the frequency range of 20 kHz-10 MHz and voltage range of-5 - 5 V at room temperature. The effects of surface states （Nss） and series resistance （R0 on C-V and G/w-V characteristics have been in- vestigated in detail. The frequency dependent Nss and Rs profiles were obtained for various applied bias voltages. The experi- mental results show that the main electrical parameters of Au/p-InP SBD such as barrier height （gOB）, the density of acceptor concentration （NA）, Nss and Rs were found strongly frequency and voltage dependent. The values of C and G/w decrease with increasing frequency due to a continuous distribution of Nss localized at the metal/semiconductor （M/S） interface. The effect of Rs on C and G is found considerably high especially at high frequencies. Therefore, the high frequencies of the values of C and G were corrected for the effect of Rs in the whole measured bias range to obtain the real diode capacitance Cc and conductance Gc using the Nicollian and Goetzberger technique. The distribution profile of Rs-V gives a peak depending on the frequency especially at low frequencies and disappears with increasing frequencies due to the existence of Nss at the M/S interface.展开更多
文摘Impact testing is a primary method to evaluate the impact property of resistance spot welding,which is an important quality index in automotive industry.For testing impact properties of spot welds,many customized testers have been developed.This paper summarized some of the impact testers reported in open literatures and the emphasis was placed on the equipment structures,functions,technical parameters,advantages and disadvantage,etc.Some key issues about the development of the testers such as kinematic energy input mode,fixture design,combined load testing,sensor and data acquisition were discussed.Finally,the problems and prospects in the research and development of impact testers for spot welds were pointed out.
基金supported by the National Natural Science Foundation of China(11674157,51372112 and 11574133)the National Key Research and Development Plan(2016YFA0300404)the National Basic Research Program of China(2015CB921202)
文摘Dirac nodal-line semimetals with the linear bands crossing along a line or loop, represent a new topological state of matter. Here, by carrying out magnetotransport measurements and performing first-principle calculations, we demonstrate that such a state has been realized in high-quality single crystals of SrAs_3.We obtain the nontrivial ∏ Berry phase by analysing the Shubnikov-de Haas quantum oscillations. We also observe a robust negative longitudinal magnetoresistance induced by the chiral anomaly.Accompanying first-principles calculations identifies that a single hole pocket enclosing the loop nodes is responsible for these observations.
基金supported by the Scientific and Technological Research Council of Turkey (TUBITAK)
文摘The frequency dependent of the forward and reverse bias capacitance-voltage （C-V） and conductance-voltage （G/w-V） charac- teristics of Au/p-InP SBDs have been investigated in the frequency range of 20 kHz-10 MHz and voltage range of-5 - 5 V at room temperature. The effects of surface states （Nss） and series resistance （R0 on C-V and G/w-V characteristics have been in- vestigated in detail. The frequency dependent Nss and Rs profiles were obtained for various applied bias voltages. The experi- mental results show that the main electrical parameters of Au/p-InP SBD such as barrier height （gOB）, the density of acceptor concentration （NA）, Nss and Rs were found strongly frequency and voltage dependent. The values of C and G/w decrease with increasing frequency due to a continuous distribution of Nss localized at the metal/semiconductor （M/S） interface. The effect of Rs on C and G is found considerably high especially at high frequencies. Therefore, the high frequencies of the values of C and G were corrected for the effect of Rs in the whole measured bias range to obtain the real diode capacitance Cc and conductance Gc using the Nicollian and Goetzberger technique. The distribution profile of Rs-V gives a peak depending on the frequency especially at low frequencies and disappears with increasing frequencies due to the existence of Nss at the M/S interface.
