The influence of Al3Zr particles on the hot compression behavior and processing map(PM)of Al-Cu-Li based alloys under isothermal plane-strain compression in the temperature range of 400-500℃and at the strain rates of...The influence of Al3Zr particles on the hot compression behavior and processing map(PM)of Al-Cu-Li based alloys under isothermal plane-strain compression in the temperature range of 400-500℃and at the strain rates of 0.01-10 s^-1 was investigated.The corresponding microstructure was analyzed using optical microscopy(OM),electron back-scattered diffraction(EBSD)and transmission electron microscope(TEM).The results showed that dynamic recovery(DRV)played a greater role than dynamic recrystallization(DRX)in dynamic softening.At low temperatures,the Al3Zr particles were the significant barriers to inhibit DRV and DRX grain growth.When the temperature reached 500℃,the Al3Zr particles readily spread along grain boundaries just like a necklace due to the dissolution of Al3Zr particles and rapid diffusion of Zr through grain boundary,resulting in generating the macroscopic cracks and forming an instability domain at 490-500℃,0.01 s^-1 in the PM.展开更多
The present work inainly focuses on tlie effect of minor cofiteut of Gd cicmcnt on the micrGstmcturc and mechanical properties of Mg Zn alloy.The Mg-4Zn-xGd(x=0,0.5,1,2)alloys were fabricated and subjected to extrusio...The present work inainly focuses on tlie effect of minor cofiteut of Gd cicmcnt on the micrGstmcturc and mechanical properties of Mg Zn alloy.The Mg-4Zn-xGd(x=0,0.5,1,2)alloys were fabricated and subjected to extrusion at 280℃ with the ratio of 25:1.Results revealed that the addition of Gd could inhibit the dynamic recrystallization(DRX)of Mg-4Zn alloy,and both the size and volume fraction of DRXed grains demonstrated a decreasing tendency as the Gd content increased from 0.5 to 2 wt.%.It is the weakening effect on DRX behavior that lead to the smaller amount of fine precipitate and the stronger texture intensity.As compared with the Mg-4Zn alloy,the yield strength and ultimate tensile strength of Mg-4Zn-xGd alloys were improved obviously by the addition of minor content of Gd,however,at the expense of elongation.Excellent tensile properties with the yield strength of〜369.8 MPa and ultimate tensile strength of〜400.3 MPa were obtained when the Gd content was 2 wt.%.展开更多
Background The Cylindrical Gas ElectronMultiplier Inner Tracker(CGEM-IT)is one of the candidates for the replacement of the current BESIII inner drift chamber,which has developed serious aging effects due to beam-rela...Background The Cylindrical Gas ElectronMultiplier Inner Tracker(CGEM-IT)is one of the candidates for the replacement of the current BESIII inner drift chamber,which has developed serious aging effects due to beam-related backgrounds.Purpose To build a full digitization model,it is necessary to understand the electron drift behavior and signal induction.Methods A simulation study based on Garfield++and ANSYS software has been performed.Results Parameters describing the Lorentz angle,diffusion effect,drift time,multiplication,and induction are obtained from the Garfield++simulation.Based on these results,a preliminary digitization model is implemented in the BESIII offline software system.展开更多
Purpose The end cap time of flight at Beijing Spectrometer is upgraded with multi-gap resistive plate chamber technology in order to improve the charged particle identification capability.The time-over-threshold is us...Purpose The end cap time of flight at Beijing Spectrometer is upgraded with multi-gap resistive plate chamber technology in order to improve the charged particle identification capability.The time-over-threshold is used for the time slewing correction instead of the signal amplitude.Methods The correlation of the multi-peak time-over-threshold and the hit position along the strip of the charged particle is investigated.Implementation of the off-line data calibration method is discussed in detail.Results and conclusion The overall time resolution for pions with momentum around 0.8 GeV/c is about 65 ps.展开更多
Background The multilayer drift chamber(MDC)is one of the key detectors at the BESIII,which is mainly responsible for the precise measurement of charged particles.High reconstruction efficiency of charged particles wi...Background The multilayer drift chamber(MDC)is one of the key detectors at the BESIII,which is mainly responsible for the precise measurement of charged particles.High reconstruction efficiency of charged particles with a wide range of momentums is a basic requirement for the MDC reconstruction software.Purpose The purpose is to improve the tracking efficiency at the low transverse momentum region.Methods The Hough transform is a mathematical method that can map hits in a detector to parameter space to find tracks globally.In this paper,we have used it as the basis for developing a new tracking algorithm to find tracks in MDC.In addition,the drift distances of hits are considered when implementing Hough transform.Results This tracking algorithm is implemented in the BESIII offline software system,and its performance is checked using both Monte Carlo and data.The results show that this tracking method improves reconstruction efficiency at the low transverse momentum region.Conclusions The tracking algorithm based on Hough transform is proved to be beneficial for the MDC low transverse momentum tracking,and has been used in BESIII offline data reconstruction .展开更多
基金Project(11727802)supported by the National Natural Science Foundation of ChinaProjects(2018CDJSK04XK09,106112017CDJQJ328840)supported by the Fundamental Research Funds for the Central Universities,China。
文摘The influence of Al3Zr particles on the hot compression behavior and processing map(PM)of Al-Cu-Li based alloys under isothermal plane-strain compression in the temperature range of 400-500℃and at the strain rates of 0.01-10 s^-1 was investigated.The corresponding microstructure was analyzed using optical microscopy(OM),electron back-scattered diffraction(EBSD)and transmission electron microscope(TEM).The results showed that dynamic recovery(DRV)played a greater role than dynamic recrystallization(DRX)in dynamic softening.At low temperatures,the Al3Zr particles were the significant barriers to inhibit DRV and DRX grain growth.When the temperature reached 500℃,the Al3Zr particles readily spread along grain boundaries just like a necklace due to the dissolution of Al3Zr particles and rapid diffusion of Zr through grain boundary,resulting in generating the macroscopic cracks and forming an instability domain at 490-500℃,0.01 s^-1 in the PM.
基金This work was supported by"National Natural Science Foundation of China"(Grant nos.51771128,51771129 and 51201112)Projects of International Cooperation in Shanxi(Grant no.201703D421039)+1 种基金Shanxi province science and technology major projects(20181101008)The authors also thank to the Support from Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi,and the Special Fund Project for Guiding Local Science and Technology Development by the Central Government(YDZX20191400002734).
文摘The present work inainly focuses on tlie effect of minor cofiteut of Gd cicmcnt on the micrGstmcturc and mechanical properties of Mg Zn alloy.The Mg-4Zn-xGd(x=0,0.5,1,2)alloys were fabricated and subjected to extrusion at 280℃ with the ratio of 25:1.Results revealed that the addition of Gd could inhibit the dynamic recrystallization(DRX)of Mg-4Zn alloy,and both the size and volume fraction of DRXed grains demonstrated a decreasing tendency as the Gd content increased from 0.5 to 2 wt.%.It is the weakening effect on DRX behavior that lead to the smaller amount of fine precipitate and the stronger texture intensity.As compared with the Mg-4Zn alloy,the yield strength and ultimate tensile strength of Mg-4Zn-xGd alloys were improved obviously by the addition of minor content of Gd,however,at the expense of elongation.Excellent tensile properties with the yield strength of〜369.8 MPa and ultimate tensile strength of〜400.3 MPa were obtained when the Gd content was 2 wt.%.
基金Funding was provided by National Natural Sci-ence Foundation of China(NSFC)under Contracts Nos.11575222,11475208,11775245,11335009,U1832204,and 11521505National Key Basic Research Program of China under Contract No.2015CB856706+2 种基金Chinese Academy of Sciences(CAS)President’s International Fellowship Initiative underContract No.2018PM0004European Com-mission under Contract No.H2020-MSCA-RISE-2014National 1000Talents Program of China,and U.S.Department of Energy under Con-tract No.DE-FG02-05ER41374.
文摘Background The Cylindrical Gas ElectronMultiplier Inner Tracker(CGEM-IT)is one of the candidates for the replacement of the current BESIII inner drift chamber,which has developed serious aging effects due to beam-related backgrounds.Purpose To build a full digitization model,it is necessary to understand the electron drift behavior and signal induction.Methods A simulation study based on Garfield++and ANSYS software has been performed.Results Parameters describing the Lorentz angle,diffusion effect,drift time,multiplication,and induction are obtained from the Garfield++simulation.Based on these results,a preliminary digitization model is implemented in the BESIII offline software system.
基金Supported in part by National Natural Science Foundation of China(U1232201,11575225,11605220)National Key Basic Research Program of China(2015CB856700)Chinese Academy of Sciences(1G201331231172010).
文摘Purpose The end cap time of flight at Beijing Spectrometer is upgraded with multi-gap resistive plate chamber technology in order to improve the charged particle identification capability.The time-over-threshold is used for the time slewing correction instead of the signal amplitude.Methods The correlation of the multi-peak time-over-threshold and the hit position along the strip of the charged particle is investigated.Implementation of the off-line data calibration method is discussed in detail.Results and conclusion The overall time resolution for pions with momentum around 0.8 GeV/c is about 65 ps.
基金Funding was provided by National Key Basic Research Program of China under Contract No.2015CB856706National Natural Science Foundation of China(NSFC)under Contracts Nos.11475208,11775245,11335009,U1632106,11575222Chinese Academy of Sciences(CAS)President’s International Fellowship Initiative under Contract No.2018PM0004.
文摘Background The multilayer drift chamber(MDC)is one of the key detectors at the BESIII,which is mainly responsible for the precise measurement of charged particles.High reconstruction efficiency of charged particles with a wide range of momentums is a basic requirement for the MDC reconstruction software.Purpose The purpose is to improve the tracking efficiency at the low transverse momentum region.Methods The Hough transform is a mathematical method that can map hits in a detector to parameter space to find tracks globally.In this paper,we have used it as the basis for developing a new tracking algorithm to find tracks in MDC.In addition,the drift distances of hits are considered when implementing Hough transform.Results This tracking algorithm is implemented in the BESIII offline software system,and its performance is checked using both Monte Carlo and data.The results show that this tracking method improves reconstruction efficiency at the low transverse momentum region.Conclusions The tracking algorithm based on Hough transform is proved to be beneficial for the MDC low transverse momentum tracking,and has been used in BESIII offline data reconstruction .
