In this paper,Raman shifts of a-plane GaN layers grown on r-plane sapphire substrates by low-pressure metal-organic chemical vapor deposition(LPMOCVD) are investigated.We compare the crystal qualities and study the ...In this paper,Raman shifts of a-plane GaN layers grown on r-plane sapphire substrates by low-pressure metal-organic chemical vapor deposition(LPMOCVD) are investigated.We compare the crystal qualities and study the relationships between Raman shift and temperature for conventional a-plane GaN epilayer and insertion AlN/AlGaN superlattice layers for a-plane GaN epilayer using temperature-dependent Raman scattering in a temperature range from 83 K to 503 K.The temperature-dependences of GaN phonon modes(A1(TO),E2(high),and E1(TO)) and the linewidths of E2(high) phonon peak are studied.The results indicate that there exist two mechanisms between phonon peaks in the whole temperature range,and the relationship can be fitted to the pseudo-Voigt function.From analytic results we find a critical temperature existing in the relationship,which can characterize the anharmonic effects of a-plane GaN in different temperature ranges.In the range of higher temperature,the relationship exhibits an approximately linear behavior,which is consistent with the analyzed results theoretically.展开更多
The synchronizer is a key component of automatic mechanical transmission(AMT)equipped in electric vehicles,but the inertial lock-ring synchronizer(ILRS)commonly used there is not suitable especially for pure electric ...The synchronizer is a key component of automatic mechanical transmission(AMT)equipped in electric vehicles,but the inertial lock-ring synchronizer(ILRS)commonly used there is not suitable especially for pure electric vehicles without a clutch because of big shift impact.To make the shifting process rapid and smooth,a new synchronizer named pressure-controllable friction ring synchronizer(PCFRS)was designed.Initially,the inevitable shortcoming of ILRS was verified by simulation and test.Furthermore,the mechanical characteristics and advantages of the new synchronizer over ILRS were analyzed.Then,the formulations describing the dynamic transmission based on the working mechanism of the PCFRS were established.Finally,the shifting simulation results with PCFRS and ILRS based on the same operating conditions were compared and analyzed.The research shows that the PCFRS can meet the main shifting evaluation index of an AMT without complex control methods,as well as it takes only 0.2406 s to finish the comfortable and zero-speed-difference shifting.The shifting quality of PCFRS is better than that of the ILRS.It lays a foundation for using the new synchronizer as a part of clutchless AMTs equipped in pure electric vehicles.展开更多
基金Project supported by the Fundamental Research Funds for the Central Universities,China (Grant No. K50511250002)the National Key Science & Technology Special Project,China (Grant No. 2008ZX01002-002)+1 种基金the Major Program and State Key Program of the National Natural Science Foundation of China (Grant Nos. 60890191 and 60736033)the Science Fund for Youths Scholars (Grant Nos. 61204006)
文摘In this paper,Raman shifts of a-plane GaN layers grown on r-plane sapphire substrates by low-pressure metal-organic chemical vapor deposition(LPMOCVD) are investigated.We compare the crystal qualities and study the relationships between Raman shift and temperature for conventional a-plane GaN epilayer and insertion AlN/AlGaN superlattice layers for a-plane GaN epilayer using temperature-dependent Raman scattering in a temperature range from 83 K to 503 K.The temperature-dependences of GaN phonon modes(A1(TO),E2(high),and E1(TO)) and the linewidths of E2(high) phonon peak are studied.The results indicate that there exist two mechanisms between phonon peaks in the whole temperature range,and the relationship can be fitted to the pseudo-Voigt function.From analytic results we find a critical temperature existing in the relationship,which can characterize the anharmonic effects of a-plane GaN in different temperature ranges.In the range of higher temperature,the relationship exhibits an approximately linear behavior,which is consistent with the analyzed results theoretically.
基金Supported by National Natural Science Foundation of China(Grant No.51775478)Natural Science Foundation of Hebei Province(Grant Nos.E2020203078,E2020203174)+1 种基金Open Project of State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures(Grant No.KF2021-11)Graduate Innovation Funding Project of Hebei Province(Grant No.CXZZSS2021063)。
文摘The synchronizer is a key component of automatic mechanical transmission(AMT)equipped in electric vehicles,but the inertial lock-ring synchronizer(ILRS)commonly used there is not suitable especially for pure electric vehicles without a clutch because of big shift impact.To make the shifting process rapid and smooth,a new synchronizer named pressure-controllable friction ring synchronizer(PCFRS)was designed.Initially,the inevitable shortcoming of ILRS was verified by simulation and test.Furthermore,the mechanical characteristics and advantages of the new synchronizer over ILRS were analyzed.Then,the formulations describing the dynamic transmission based on the working mechanism of the PCFRS were established.Finally,the shifting simulation results with PCFRS and ILRS based on the same operating conditions were compared and analyzed.The research shows that the PCFRS can meet the main shifting evaluation index of an AMT without complex control methods,as well as it takes only 0.2406 s to finish the comfortable and zero-speed-difference shifting.The shifting quality of PCFRS is better than that of the ILRS.It lays a foundation for using the new synchronizer as a part of clutchless AMTs equipped in pure electric vehicles.