The capacity to predict X-ray transition and K-edge energies in dense finite-temperatur plasmas with high precision is of primary importance for atomic physics of matter under extreme conditions.The dual characteristi...The capacity to predict X-ray transition and K-edge energies in dense finite-temperatur plasmas with high precision is of primary importance for atomic physics of matter under extreme conditions.The dual characteristics of bound and continuum states in dense matter are modeled by a valence-band-like structure in a generalized ion-sphere approach with states that are either bound,free,or mixed.The self-consistent combination of this model with the Dirac wave equations of multielectron bound states allows one to fully respect the Pauli principle and to take into account the exact nonlocal exchange terms.The generalized method allows very high precision without implication of calibration shifts and scaling parameters and therefore has predictive power.This leads to new insights in the analysis of various data.The simple ionization model representing the K-edge is generalized to excitation–ionization phenomena resulting in an advanced interpretation of ionization depression data in near-solid-density plasmas.The model predicts scaling relations along the isoelectronic sequences and the existence of bound M-states that are in excellent agreement with experimental data,whereas other methods have failed.The application to unexplained data from compound materials also gives good agreement without the need to invoke any additional assumptions in the generalized model,whereas other methods have lacked consistency.展开更多
X-ray tomography was used to characterize the porosity in high pressure die casting of AM60B alloy. In situ tensile deformation was performed to observe the change of porosities and their influences on crack initiatio...X-ray tomography was used to characterize the porosity in high pressure die casting of AM60B alloy. In situ tensile deformation was performed to observe the change of porosities and their influences on crack initiation, propagation and subsequent fracture of specimen. Results showed that four types of porosi- ties, including gas-shrinkage pore, gas pore, net-shrinkage and island-shrinkage, could be identified according to the formation mechanism and morphology characterization. During tensile deformation, it was shown that the gas-shrinkage pore and net-shrinkage, rather than gas pore or island-shrinkage, were the main sources for crack initiation. In addition, the crack propagated by interconnecting the po- rosities at the cross section with minimum efficient force bearing area. At these locations where externally solidified crystals （ESCs） were present, the crack would propagate along the ESC boundaries in an inter- granular mode, while at these locations without ESCs, the crack would propagate roughly along the direction perpendicular to the tensile stress in a combination of trans-granular and inter-granular modes.展开更多
The Mg-12Gd-3Y-0.6Zr(GW123,wt.%)alloy was prepared by cast,and thermo-mechanically treated by single and secondary hot extrusion techniques.The microstructure,texture and mechanical properties of the extruded alloy we...The Mg-12Gd-3Y-0.6Zr(GW123,wt.%)alloy was prepared by cast,and thermo-mechanically treated by single and secondary hot extrusion techniques.The microstructure,texture and mechanical properties of the extruded alloy were investigated.The results show that in different treated conditions the microstructure is mainly composed ofα-Mg solid solution and second phases of Mg_(3)Y_(3)Gd_(2) and Mg_(5)(GdY)precipitates.The best mechanical properties are achieved in the secondary extruded alloy after ageing,with the ultimate tensile strength(UTS),tensile yield strength(TYS)and elongation(ɛ)being 446 MPa,350 MPa and 10.2%at room temperature.A weak texture aligned with〈101¯0〉||ED(extrusion direction)component and spread from〈101¯0〉to〈112¯0〉poles was obtained in secondary extrusion,which is caused by the occurrence of dynamic recrystallization(DRX)in shear bands for texture randomization.The fracture modes in extruded GW123 alloy are mixed pattern of transgranular and intergranular fracture,as well as cleavage fracture.The strengthening mechanisms were quantitatively analysed from the different aspects using the measured microstructural parameters.The grain boundaries and solid solution strengthening were the main contributors to the high tensile strength of the GW123 alloy.展开更多
Based on the general [Mo] equivalent criterion and d-electron orbital theory, a new ultrahigh-strength βtitanium alloy with eight major elements(Ti-4.5Al-6.5Mo-2Cr-2.6Nb-2Zr-2Sn-1V, TB17) for industrial applications ...Based on the general [Mo] equivalent criterion and d-electron orbital theory, a new ultrahigh-strength βtitanium alloy with eight major elements(Ti-4.5Al-6.5Mo-2Cr-2.6Nb-2Zr-2Sn-1V, TB17) for industrial applications was developed. An ingot of five tons was successfully melted by thrice vacuum consumable arc melting. The microstructure and elements partitioning of different conditions were investigated systematically. The results suggest that the hierarchical structures of micro-scale first α phase(αf), nano-scale secondary α phase(αs), and ultrafine FCC substructures can be tailored by solution plus aging(STA) heat treatment. The lateral and epitaxial growth of αfphase promotes the HCP-α to FCC substructure transformation with the help of elements partitioning during the aging process. Moreover, the element V, generally regarded as β stabilizer, is found to mainly concentrate in the Al-rich αfphase in this study probably due to its relatively lower content and the strong bonding energy of Al-V. The hierarchical structure has a strong interaction with dislocations, which contributes to achieve a superhigh strength of 1376 MPa.In addition, the plastic strain is partitioned in the multi-scale precipitates(such as the α and FCC substructures) and β matrix, resulting in a considerable plasticity. TEM observation demonstrates that high density entangled dislocations at interfaces and mechanical twins exist in the STA sample after tensile test. It can be deduced that both dislocation slipping and twinning mechanisms are present in this alloy.Therefore, TB17 alloy can serve as an excellent candidate for structural materials on aircrafts that require high strength and lightweight.展开更多
The partitioning effect of Al（α-phase stabilizer） and V elements（β-phase stabilizer） on strength of the primary α phases in the α/β Ti-6 Al-4 V alloy with the bimodal microstructure was investigated.It was fo...The partitioning effect of Al（α-phase stabilizer） and V elements（β-phase stabilizer） on strength of the primary α phases in the α/β Ti-6 Al-4 V alloy with the bimodal microstructure was investigated.It was found that partitioning of Al and V elements took place in the Ti-6 Al-4 V alloy during the recrystallization process,leading to the variation of the content of Al and V elements in the primary α phases with changing the volume fraction of the primary α phase.Nanoindentation tests reveal a general trend that the strength of the primary α phases increases with decreasing the volume fraction of the primary α phases,and such trend is independent on the loading direction relative to the c-axis of the α phase.The enhanced strength is attributed to the increase of the content of Al element in the primary α phase,but it is not dominated evidently by the change of the V content.The solid solution strengthening contributed from both the elastic strain introduced by the solute atoms and the variation of the density of states was estimated theoretically.展开更多
In 2018,the STAR collaboration collected data from^(96)_(44)Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr at√^(S)NN=200 Ge V to search for the presence of the chiral magnetic effect in collisions of nuclei.The isobar ...In 2018,the STAR collaboration collected data from^(96)_(44)Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr at√^(S)NN=200 Ge V to search for the presence of the chiral magnetic effect in collisions of nuclei.The isobar collision species alternated frequently between 9644 Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr.In order to conduct blind analyses of studies related to the chiral magnetic effect in these isobar data,STAR developed a three-step blind analysis procedure.Analysts are initially provided a"reference sample"of data,comprised of a mix of events from the two species,the order of which respects time-dependent changes in run conditions.After tuning analysis codes and performing time-dependent quality assurance on the reference sample,analysts are provided a species-blind sample suitable for calculating efficiencies and corrections for individual≈30-min data-taking runs.For this sample,species-specific information is disguised,but individual output files contain data from a single isobar species.Only run-by-run corrections and code alteration subsequent to these corrections are allowed at this stage.Following these modifications,the"frozen"code is passed over the fully un-blind data,completing the blind analysis.As a check of the feasibility of the blind analysis procedure,analysts completed a"mock data challenge,"analyzing data from Au+Au collisions at√^(S)NN=27 Ge V,collected in 2018.The Au+Au data were prepared in the same manner intended for the isobar blind data.The details of the blind analysis procedure and results from the mock data challenge are presented.展开更多
In this work, three widely used commercial Zn alloys （ZA4-1, ZA4-3, ZA6-1 ） were purchased and pre- pared by hot extrusion at 200℃. The microstructure, mechanical properties, corrosion behaviors, biocompatibility a...In this work, three widely used commercial Zn alloys （ZA4-1, ZA4-3, ZA6-1 ） were purchased and pre- pared by hot extrusion at 200℃. The microstructure, mechanical properties, corrosion behaviors, biocompatibility and hemocompatibility of Zn alloys were studied with pure Zn as control, Commercial Zn alloys demonstrated increased strength and superb elongation compared with pure Zn. Accelerated corrosion rates and uniform corrosion morphologies were observed in terms of commercial Zn alloys due to galvanic effects between Zn matrix and α-Al phases. 100% extracts of ZA4-1 and ZA6-1 alloys showed mild cytotoxicity while 50% extracts of all samples displayed good biocompatibility. Retardant cell cycle and inhibited stress fibers expression were observed induced by high concentration of Zn^2＋ releasing during corrosion. The hemolysis ratios of Zn alloys were lower than 1% while the adhered platelets showed slightly activated morphologies. In general, commercial Zn alloys possess promising mechanical properties, appropriate corrosion rates, significantly improved biocompatibility and good hemocompatibility in comparison to pure Zn. It is feasible to develop biodegradable metals based on commercial Zn alloys.展开更多
The thermal stability and mechanical properties of a gradient-nanograined structure(GNS)CoCrNi medium entropy alloy(MEA)processed by ultrasonic surface rolling were studied by using isothermal/isochronal annealing tes...The thermal stability and mechanical properties of a gradient-nanograined structure(GNS)CoCrNi medium entropy alloy(MEA)processed by ultrasonic surface rolling were studied by using isothermal/isochronal annealing tests combined with quasi-in-situ electron backscatter diffraction(EBSD)characterization and Vickers micro-hardness(HV)measurements.A layer by layer high-throughput investigation method was used to quantitatively study the grain growth kinetics and grain boundary evolution with different initial grain sizes,which could effectively save specimen and time costs.The grain nucleation and growth,as well as shrink and disappearance process throughΣ3 coincidence site lattice boundary migration with slightly lattice rotation during annealing were directly revealed.The layer by layer grain growth kinetics and calculated activation energy indicate that the thermal stability of nanograined top surface layer is relatively higher than that of nano-twined subsurface layer for the gradient CoCrNi MEA processed by ultrasonic surface rolling.Further analysis show that the grain boundary relaxation and dynamic recrystallization of the topmost nano-grains led to the decrease of grain boundary energy,thus improving their thermal stability.The present work provided theoretical basis for the application of CoCrNi MEA at high temperatures.Moreover,the high-throughput method on the investigation of grain stability by using gradient structure can be easily extended to other materials and it is of great significance for understanding the microstructural evolution of gradient materials.展开更多
Composite structure materials were potential sensing elements for magnetic sensors due to Giant magnetoimpedance(GMI) effect. Two kinds of composite wires with different magnetic/non-magnetic structures were fabricate...Composite structure materials were potential sensing elements for magnetic sensors due to Giant magnetoimpedance(GMI) effect. Two kinds of composite wires with different magnetic/non-magnetic structures were fabricated by using electroless deposition methods and the magnetoimpedance properties were investigated. The maximum GMI ratio of 114% was acquired at 60 MHz in the composite wires with a ferromagnetic core, whereas, 116% of maximum GMI ratio was found in the composite wires with a conductive core at low frequency of 600 k Hz. These results exhibit that the GMI ratio reaches the maximum when magnetoresistance ratio ?R/R and magnetoinductance ratio ?X/X make the comparative contributions to the total magnetoimpedance(MI). The obvious GMI effect obtained in the composite wires with conductive core frequency may provide a candidate for applications in magnetic sensors, especially at low frequencies.展开更多
In this work, a Fe-based nanocrystalline microwire of 20 mm in length and 25 μm in diameter was placed in the center of a 316 stainless steel pipe. The pipe was 500 μm in diameter and a little shorter than the micro...In this work, a Fe-based nanocrystalline microwire of 20 mm in length and 25 μm in diameter was placed in the center of a 316 stainless steel pipe. The pipe was 500 μm in diameter and a little shorter than the microwire. A series of voltages were applied on the pipe to study the influence of the electrical field on the Giant-Magneto-Impedance(GMI) effect of the microwire. Experimental results showed that the electronic field between the wire and the pipe reduced the hysteresis of the GMI effect. The results were explained based on equivalent circuit and eddy current consumptions analysis.展开更多
In the present work the fatigue crack growth in AISI304 specimens is investigated experimentally. In 3D finite element analysis the virtual crack closure technique is applied to calculate distributions and variations ...In the present work the fatigue crack growth in AISI304 specimens is investigated experimentally. In 3D finite element analysis the virtual crack closure technique is applied to calculate distributions and variations of the stress intensity factor along the surface crack front. It is confirmed that the stress intensity factor along the surface crack front varies non-uniformly with crack growth. Crack growth rate is proportional to the stress intensity factor distribution in the 3D cracked specimen. The fatigue crack growth in surface cracked specimens can be described by the Forman model identified in conventional compact tension specimens. For crack growth in the free specimen surface the arc length seems more suitable to quantify crack progress. Geometry and loading configuration of the surface cracked specimen seem to not affect the fatigue crack growth substantially.展开更多
CuBe composite wires of 100 μm in diameter coated with a layer of NiCoP were prepared by a chemical plating method under DC current(CPUDC). The influences of DC current on coating morphology,deposition rate, composit...CuBe composite wires of 100 μm in diameter coated with a layer of NiCoP were prepared by a chemical plating method under DC current(CPUDC). The influences of DC current on coating morphology,deposition rate, composition, giant magneto-impedance(GMI) effect and magnetic properties were investigated.It was shown that the circumferential domain structure of coating layer was induced by the DC current going through the wires. A maximum GMI ratio of 870% was obtained in the composite wire prepared under 150 m A and tested at 180 k Hz. It is 30 times higher than that of the composite wire plated in the same condition by conventional chemical plating method, indicating that CPUDC is an easy and effective approach to obtain composite wires and its applications will be further extended on magnetic sensors.展开更多
A bimodal-structured Mg^(-1)5Gd binary alloy with 45%volume fraction of elongated grains and 55%of dynamically recrystallized(DRXed)grains is fabricated by the extrusion process.The precipitating behavior correlating ...A bimodal-structured Mg^(-1)5Gd binary alloy with 45%volume fraction of elongated grains and 55%of dynamically recrystallized(DRXed)grains is fabricated by the extrusion process.The precipitating behavior correlating with the evolution of mechanical properties is systematically characterized during the subsequent aging treatment at 200°C.The extruded alloy presents an outstanding strength with tensile yield strength of 466 MPa and ultimate tensile strength of 500 MPa at peak aging condition,while the elongation drops from 9.2%in extrusion state to 3.1%.It is found there obviously exist a rapidly decreasing range of ductility at the early stage of aging.Just during this time,the nano precipitates form preferentially at lamellar dislocation boundaries(LDBs)within the elongated grains,but there is no dense and uniform precipitation in the matrix.The results suggest that the low elongation in the aged Mg^(-1)5Gd alloy is mainly attributed to the nano precipitates prior formed at the LDBs with a high density in the elongated grains.The related mechanism has been clarified.展开更多
Based on(10087±44)×10^(6) J/ψevents collected with the BESⅢdetector,we search for the lepton number violating decay J/ψ→K^(+)K^(+)e^(-)e^(-)+c.c.for the first time.The upper limit on the branching fracti...Based on(10087±44)×10^(6) J/ψevents collected with the BESⅢdetector,we search for the lepton number violating decay J/ψ→K^(+)K^(+)e^(-)e^(-)+c.c.for the first time.The upper limit on the branching fraction of this decay is set to 2.1×10^(-9)at the 90%confidence level with a frequentist method.This is the first search for J/ψdecays with a lepton number change by two,offering valuable insights into the underlying physical processes.展开更多
The cosmic-ray(CR)electrons and positrons in space are of considerable significance for studying the origin and propagation of CRs.The satellite-borne detector Dark Matter Particle Explorer(DAMPE)has been used to meas...The cosmic-ray(CR)electrons and positrons in space are of considerable significance for studying the origin and propagation of CRs.The satellite-borne detector Dark Matter Particle Explorer(DAMPE)has been used to measure the separate electron and positron spectra,as well as the positron fraction.In this study,the Earth's magnetic field is used to distinguish CR electrons and positrons,as the DAMPE detector does not carry an onboard magnet.The energy for the measurements ranges from 10 to 20 GeV,which is currently limited at high energy by the zenith-pointing orientation of DAMPE.The results are consistent with previous measurements based on the magnetic spectrometer by AMS-02 and PAMELA,whereas the results of Fermi-LAT appear to be systematically shifted to larger values.展开更多
By analyzing ψ(3686) data sample containing (107.7±0.6)×10^(6) events taken with the BESIII detector at the BEPCII storage ring in 2009,the χ_(c 0) resonance parameters are precisely measured using χ_(c 0...By analyzing ψ(3686) data sample containing (107.7±0.6)×10^(6) events taken with the BESIII detector at the BEPCII storage ring in 2009,the χ_(c 0) resonance parameters are precisely measured using χ_(c 0,c 2)→π^(+)π^(−)/K^(+)K^(−) events.The mass of χ_(c 0) is determined to be M (χ_(c 0))=(3415.63±0.07±0.07±0.07)MeV/c^(2),and its full width is F (χ_(c 0))=(12.52±0.12±0.13)MeV,where the first uncertainty is statistical,the second systematic,and the third for mass comes from χ_(c 2) mass uncertainty.These measurements improve the precision of χ_(c 0) mass by a factor of four and width by one order of magnitude over the previous individual measurements,and significantly boost our knowledge about the charmonium spectrum.Together with additional (345.4±2.6)×10^(6)(3686) data events taken in 2012,the decay branching fractions of χ_(c 0,c 2)→π^(+)π^(−)/K^(+)K^(−) are measured as well,with precision improved by a factor of three compared to previous measurements.These χ_(c 0) decay branching fractions provide important inputs for the study of glueballs.展开更多
Using 20.3 fb^(-1)of e^(+)e^(-)annihilation data collected at a center-of-mass energy of 3.773 GeV with the BESⅢdetector,we report on an improved search for the radiative leptonic decay D^(+)→γe^(+)ve.An upper limi...Using 20.3 fb^(-1)of e^(+)e^(-)annihilation data collected at a center-of-mass energy of 3.773 GeV with the BESⅢdetector,we report on an improved search for the radiative leptonic decay D^(+)→γe^(+)ve.An upper limit on its partial branching fraction for photon energies E_(γ)>10 MeV was determined to be 1.2×10^(-5)at a 90%confidence level;this excludes most current theoretical predictions.A sophisticated deep learning approach,which includes thorough validation and is based on the Transformer architecture,was implemented to efficiently distinguish the signal from massive backgrounds.展开更多
Based on a sample of 2.7x 10^(9)ψ(3686)events collected by the BESIII detector operating at the BEP-CII collider,the decay 4(3686)→YX_(cJ),X_(cJ)→ηηη’is analyzed.The decay modes X_(c1)and X_(c2)→ηηη’are ob...Based on a sample of 2.7x 10^(9)ψ(3686)events collected by the BESIII detector operating at the BEP-CII collider,the decay 4(3686)→YX_(cJ),X_(cJ)→ηηη’is analyzed.The decay modes X_(c1)and X_(c2)→ηηη’are observed for the first time,and their corresponding branching fractions are determined to be B(X_(c1)→ηηη’)=(1.40±0.13(stat.)±0.09(sys.))×10^(-4)and B(X_(c2)→ηηη’)=(4.18±0.84(stat.)±0.48(sys.))×10^(-5).An upper limit on the branching fraction of x_(co)→ηηη’is set as 2.59×10^(-5)at a 90%confidence level(CL).A partial wave analys-is(PWA)of the decay X_(c1)→ηηη’is performed to search for the 1^(-+)exotic stateη1(1855).The PWA result indic-ates that the structure in theηη’mass spectrum is attributed to f_(0)(1500),while in the m mass spectrum,it is attrib-uted to the 0^(++)phase space.The upper limit of B(x_(cl)→η1(1855)η)·B(η1(1855)→ηη')<9.79×10^(-5)is set based on the PWA at 90%CL.展开更多
Lepton number violation decayω→π^(+)π^(+)e^(-)e^(-)+c.c.is searched for via J/ψ→ωηusing a data sample of(1.0087±0.0044)×10^(10)J/ψevents collected via the BESIII detector at the BEPCII collider.No s...Lepton number violation decayω→π^(+)π^(+)e^(-)e^(-)+c.c.is searched for via J/ψ→ωηusing a data sample of(1.0087±0.0044)×10^(10)J/ψevents collected via the BESIII detector at the BEPCII collider.No significant signal is observed,and the upper limit on the branching fraction ofω→π^(+)π^(+)e^(-)e^(-)+c.c.at the 90%confidence level is determined for the first time to be 2.8×10^(-6).展开更多
We search for the leptonic decay D^(+)→e^(+)ν_(e)using an e+e-collision data sample with an integrated luminosity of 20.3 fb-1collected with the BESIII detector at a center-of-mass energy of 3.773 GeV.Significant si...We search for the leptonic decay D^(+)→e^(+)ν_(e)using an e+e-collision data sample with an integrated luminosity of 20.3 fb-1collected with the BESIII detector at a center-of-mass energy of 3.773 GeV.Significant signal is not observed,and an upper limit on the branching fraction of D^(+)→e^(+)ν_(e)is set as 9.7×10^(-7),at a confidence level of 90%.Our upper limit is an order of magnitude smaller than the previous limit for this decay mode.展开更多
基金supported by the NSFC under Grant Nos.11374315 and 12074395the Invited Scientist Program of CNRS at Ecole Polytechnique,Palaiseau,France。
文摘The capacity to predict X-ray transition and K-edge energies in dense finite-temperatur plasmas with high precision is of primary importance for atomic physics of matter under extreme conditions.The dual characteristics of bound and continuum states in dense matter are modeled by a valence-band-like structure in a generalized ion-sphere approach with states that are either bound,free,or mixed.The self-consistent combination of this model with the Dirac wave equations of multielectron bound states allows one to fully respect the Pauli principle and to take into account the exact nonlocal exchange terms.The generalized method allows very high precision without implication of calibration shifts and scaling parameters and therefore has predictive power.This leads to new insights in the analysis of various data.The simple ionization model representing the K-edge is generalized to excitation–ionization phenomena resulting in an advanced interpretation of ionization depression data in near-solid-density plasmas.The model predicts scaling relations along the isoelectronic sequences and the existence of bound M-states that are in excellent agreement with experimental data,whereas other methods have failed.The application to unexplained data from compound materials also gives good agreement without the need to invoke any additional assumptions in the generalized model,whereas other methods have lacked consistency.
基金the National Natural Science Foundation of China (No.51275269)the Tsinghua University Initiative Scientific Research Program (No.20121087918)the National Science and Technology Major Project of the Ministry of Science and Technology of the People’s Republic of China (No.2012ZX04012011) for financial support
文摘X-ray tomography was used to characterize the porosity in high pressure die casting of AM60B alloy. In situ tensile deformation was performed to observe the change of porosities and their influences on crack initiation, propagation and subsequent fracture of specimen. Results showed that four types of porosi- ties, including gas-shrinkage pore, gas pore, net-shrinkage and island-shrinkage, could be identified according to the formation mechanism and morphology characterization. During tensile deformation, it was shown that the gas-shrinkage pore and net-shrinkage, rather than gas pore or island-shrinkage, were the main sources for crack initiation. In addition, the crack propagated by interconnecting the po- rosities at the cross section with minimum efficient force bearing area. At these locations where externally solidified crystals （ESCs） were present, the crack would propagate along the ESC boundaries in an inter- granular mode, while at these locations without ESCs, the crack would propagate roughly along the direction perpendicular to the tensile stress in a combination of trans-granular and inter-granular modes.
基金support from the Special Project on the Integration of Industry,Education and Research of Guangdong Province(No.2010A090200078).
文摘The Mg-12Gd-3Y-0.6Zr(GW123,wt.%)alloy was prepared by cast,and thermo-mechanically treated by single and secondary hot extrusion techniques.The microstructure,texture and mechanical properties of the extruded alloy were investigated.The results show that in different treated conditions the microstructure is mainly composed ofα-Mg solid solution and second phases of Mg_(3)Y_(3)Gd_(2) and Mg_(5)(GdY)precipitates.The best mechanical properties are achieved in the secondary extruded alloy after ageing,with the ultimate tensile strength(UTS),tensile yield strength(TYS)and elongation(ɛ)being 446 MPa,350 MPa and 10.2%at room temperature.A weak texture aligned with〈101¯0〉||ED(extrusion direction)component and spread from〈101¯0〉to〈112¯0〉poles was obtained in secondary extrusion,which is caused by the occurrence of dynamic recrystallization(DRX)in shear bands for texture randomization.The fracture modes in extruded GW123 alloy are mixed pattern of transgranular and intergranular fracture,as well as cleavage fracture.The strengthening mechanisms were quantitatively analysed from the different aspects using the measured microstructural parameters.The grain boundaries and solid solution strengthening were the main contributors to the high tensile strength of the GW123 alloy.
基金financial support from “13th five-year plan” equipment pre-research project of China (41422010501)。
文摘Based on the general [Mo] equivalent criterion and d-electron orbital theory, a new ultrahigh-strength βtitanium alloy with eight major elements(Ti-4.5Al-6.5Mo-2Cr-2.6Nb-2Zr-2Sn-1V, TB17) for industrial applications was developed. An ingot of five tons was successfully melted by thrice vacuum consumable arc melting. The microstructure and elements partitioning of different conditions were investigated systematically. The results suggest that the hierarchical structures of micro-scale first α phase(αf), nano-scale secondary α phase(αs), and ultrafine FCC substructures can be tailored by solution plus aging(STA) heat treatment. The lateral and epitaxial growth of αfphase promotes the HCP-α to FCC substructure transformation with the help of elements partitioning during the aging process. Moreover, the element V, generally regarded as β stabilizer, is found to mainly concentrate in the Al-rich αfphase in this study probably due to its relatively lower content and the strong bonding energy of Al-V. The hierarchical structure has a strong interaction with dislocations, which contributes to achieve a superhigh strength of 1376 MPa.In addition, the plastic strain is partitioned in the multi-scale precipitates(such as the α and FCC substructures) and β matrix, resulting in a considerable plasticity. TEM observation demonstrates that high density entangled dislocations at interfaces and mechanical twins exist in the STA sample after tensile test. It can be deduced that both dislocation slipping and twinning mechanisms are present in this alloy.Therefore, TB17 alloy can serve as an excellent candidate for structural materials on aircrafts that require high strength and lightweight.
基金supported by the National Natural Science Foundation of China (Grant Nos.51371180 and 51571199)
文摘The partitioning effect of Al（α-phase stabilizer） and V elements（β-phase stabilizer） on strength of the primary α phases in the α/β Ti-6 Al-4 V alloy with the bimodal microstructure was investigated.It was found that partitioning of Al and V elements took place in the Ti-6 Al-4 V alloy during the recrystallization process,leading to the variation of the content of Al and V elements in the primary α phases with changing the volume fraction of the primary α phase.Nanoindentation tests reveal a general trend that the strength of the primary α phases increases with decreasing the volume fraction of the primary α phases,and such trend is independent on the loading direction relative to the c-axis of the α phase.The enhanced strength is attributed to the increase of the content of Al element in the primary α phase,but it is not dominated evidently by the change of the V content.The solid solution strengthening contributed from both the elastic strain introduced by the solute atoms and the variation of the density of states was estimated theoretically.
文摘In 2018,the STAR collaboration collected data from^(96)_(44)Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr at√^(S)NN=200 Ge V to search for the presence of the chiral magnetic effect in collisions of nuclei.The isobar collision species alternated frequently between 9644 Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr.In order to conduct blind analyses of studies related to the chiral magnetic effect in these isobar data,STAR developed a three-step blind analysis procedure.Analysts are initially provided a"reference sample"of data,comprised of a mix of events from the two species,the order of which respects time-dependent changes in run conditions.After tuning analysis codes and performing time-dependent quality assurance on the reference sample,analysts are provided a species-blind sample suitable for calculating efficiencies and corrections for individual≈30-min data-taking runs.For this sample,species-specific information is disguised,but individual output files contain data from a single isobar species.Only run-by-run corrections and code alteration subsequent to these corrections are allowed at this stage.Following these modifications,the"frozen"code is passed over the fully un-blind data,completing the blind analysis.As a check of the feasibility of the blind analysis procedure,analysts completed a"mock data challenge,"analyzing data from Au+Au collisions at√^(S)NN=27 Ge V,collected in 2018.The Au+Au data were prepared in the same manner intended for the isobar blind data.The details of the blind analysis procedure and results from the mock data challenge are presented.
基金supported by the National Basic Research Program of China (973 Program) (Grant Nos. 2012CB619102 and 012CB619100)National Science Fund for Distinguished Young Scholars (Grant No. 51225101)+3 种基金National Natural Science Foundation of China (Grant Nos. 51431002 and 31170909)the NSFC/RGC Joint Research Scheme (Grant No. 51361165101)State Key Laboratory for Mechanical Behavior of Materials (Grant No. 20141615)Beijing Municipal Science and Technology Project (No. Z141100002814008)
文摘In this work, three widely used commercial Zn alloys （ZA4-1, ZA4-3, ZA6-1 ） were purchased and pre- pared by hot extrusion at 200℃. The microstructure, mechanical properties, corrosion behaviors, biocompatibility and hemocompatibility of Zn alloys were studied with pure Zn as control, Commercial Zn alloys demonstrated increased strength and superb elongation compared with pure Zn. Accelerated corrosion rates and uniform corrosion morphologies were observed in terms of commercial Zn alloys due to galvanic effects between Zn matrix and α-Al phases. 100% extracts of ZA4-1 and ZA6-1 alloys showed mild cytotoxicity while 50% extracts of all samples displayed good biocompatibility. Retardant cell cycle and inhibited stress fibers expression were observed induced by high concentration of Zn^2＋ releasing during corrosion. The hemolysis ratios of Zn alloys were lower than 1% while the adhered platelets showed slightly activated morphologies. In general, commercial Zn alloys possess promising mechanical properties, appropriate corrosion rates, significantly improved biocompatibility and good hemocompatibility in comparison to pure Zn. It is feasible to develop biodegradable metals based on commercial Zn alloys.
基金financial supports from the National Natural Science Foundation of China(Nos.51725503,52105144 and 52005185)Shanghai Super Postdoctoral Incentive Plan(No.2020134)Postdoctoral Fellowship for Research in Japan(FY2020 P20350)by the Japan Society for the Promotion of Science(JSPS)。
文摘The thermal stability and mechanical properties of a gradient-nanograined structure(GNS)CoCrNi medium entropy alloy(MEA)processed by ultrasonic surface rolling were studied by using isothermal/isochronal annealing tests combined with quasi-in-situ electron backscatter diffraction(EBSD)characterization and Vickers micro-hardness(HV)measurements.A layer by layer high-throughput investigation method was used to quantitatively study the grain growth kinetics and grain boundary evolution with different initial grain sizes,which could effectively save specimen and time costs.The grain nucleation and growth,as well as shrink and disappearance process throughΣ3 coincidence site lattice boundary migration with slightly lattice rotation during annealing were directly revealed.The layer by layer grain growth kinetics and calculated activation energy indicate that the thermal stability of nanograined top surface layer is relatively higher than that of nano-twined subsurface layer for the gradient CoCrNi MEA processed by ultrasonic surface rolling.Further analysis show that the grain boundary relaxation and dynamic recrystallization of the topmost nano-grains led to the decrease of grain boundary energy,thus improving their thermal stability.The present work provided theoretical basis for the application of CoCrNi MEA at high temperatures.Moreover,the high-throughput method on the investigation of grain stability by using gradient structure can be easily extended to other materials and it is of great significance for understanding the microstructural evolution of gradient materials.
基金Shanghai Automotive Science and Technology Development Foundation (SAISTDF/12-06)East China Normal University Program (78210142, 78210183)Shanghai Ocean University Program (A-2600-10-0054, B-5406-12-0012)
文摘Composite structure materials were potential sensing elements for magnetic sensors due to Giant magnetoimpedance(GMI) effect. Two kinds of composite wires with different magnetic/non-magnetic structures were fabricated by using electroless deposition methods and the magnetoimpedance properties were investigated. The maximum GMI ratio of 114% was acquired at 60 MHz in the composite wires with a ferromagnetic core, whereas, 116% of maximum GMI ratio was found in the composite wires with a conductive core at low frequency of 600 k Hz. These results exhibit that the GMI ratio reaches the maximum when magnetoresistance ratio ?R/R and magnetoinductance ratio ?X/X make the comparative contributions to the total magnetoimpedance(MI). The obvious GMI effect obtained in the composite wires with conductive core frequency may provide a candidate for applications in magnetic sensors, especially at low frequencies.
文摘In this work, a Fe-based nanocrystalline microwire of 20 mm in length and 25 μm in diameter was placed in the center of a 316 stainless steel pipe. The pipe was 500 μm in diameter and a little shorter than the microwire. A series of voltages were applied on the pipe to study the influence of the electrical field on the Giant-Magneto-Impedance(GMI) effect of the microwire. Experimental results showed that the electronic field between the wire and the pipe reduced the hysteresis of the GMI effect. The results were explained based on equivalent circuit and eddy current consumptions analysis.
基金supported by the German Science Foundation(DFG, YU119/5-2)
文摘In the present work the fatigue crack growth in AISI304 specimens is investigated experimentally. In 3D finite element analysis the virtual crack closure technique is applied to calculate distributions and variations of the stress intensity factor along the surface crack front. It is confirmed that the stress intensity factor along the surface crack front varies non-uniformly with crack growth. Crack growth rate is proportional to the stress intensity factor distribution in the 3D cracked specimen. The fatigue crack growth in surface cracked specimens can be described by the Forman model identified in conventional compact tension specimens. For crack growth in the free specimen surface the arc length seems more suitable to quantify crack progress. Geometry and loading configuration of the surface cracked specimen seem to not affect the fatigue crack growth substantially.
基金supported by Shanghai Automotive Science and Technology Development Foundation (SAISTDF/12-06)East China Normal University Program (78210142, 78210183)+1 种基金Large Instruments Open Foundation of East China Normal University (201369)National Natural Science Foundation of China(51302085)
文摘CuBe composite wires of 100 μm in diameter coated with a layer of NiCoP were prepared by a chemical plating method under DC current(CPUDC). The influences of DC current on coating morphology,deposition rate, composition, giant magneto-impedance(GMI) effect and magnetic properties were investigated.It was shown that the circumferential domain structure of coating layer was induced by the DC current going through the wires. A maximum GMI ratio of 870% was obtained in the composite wire prepared under 150 m A and tested at 180 k Hz. It is 30 times higher than that of the composite wire plated in the same condition by conventional chemical plating method, indicating that CPUDC is an easy and effective approach to obtain composite wires and its applications will be further extended on magnetic sensors.
基金supported by National Natural Science Foundation of China(Grant Nos.52171121,51971151,52201131,52201132,52171055 and 52071220)Liao Ning Xingliao Program(XLYC1907083)+1 种基金Natural Science Foundation of Liaoning Province of China(2022-NLTS-18-01)the Open Foundation of Key Laboratory of Superlight Materials&Surface Technology of Ministry of Education(HEU10202205).
文摘A bimodal-structured Mg^(-1)5Gd binary alloy with 45%volume fraction of elongated grains and 55%of dynamically recrystallized(DRXed)grains is fabricated by the extrusion process.The precipitating behavior correlating with the evolution of mechanical properties is systematically characterized during the subsequent aging treatment at 200°C.The extruded alloy presents an outstanding strength with tensile yield strength of 466 MPa and ultimate tensile strength of 500 MPa at peak aging condition,while the elongation drops from 9.2%in extrusion state to 3.1%.It is found there obviously exist a rapidly decreasing range of ductility at the early stage of aging.Just during this time,the nano precipitates form preferentially at lamellar dislocation boundaries(LDBs)within the elongated grains,but there is no dense and uniform precipitation in the matrix.The results suggest that the low elongation in the aged Mg^(-1)5Gd alloy is mainly attributed to the nano precipitates prior formed at the LDBs with a high density in the elongated grains.The related mechanism has been clarified.
基金supported in part by National Key R&D Program of China under Contracts Nos.2023YFA1606000,2023YFA1606704National Natural Science Foundation of China(NSFC)under Contracts Nos.12035009,11635010,11935015,11935016,11935018,12025502,12035013,12061131003,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017,12361141819+15 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramCAS under Contract No.YSBR-101100 Talents Program of CASThe Institute of Nuclear and Particle Physics(INPAC)Shanghai Key Laboratory for Particle Physics and CosmologyGerman Research Foundation DFG under Contract No.FOR5327Istituto Nazionale di Fisica Nucleare,ItalyKnut and Alice Wallenberg Foundation under Contracts Nos.2021.0174,2021.0299Ministry of Development of Turkey under Contract No.DPT2006K-120470National Research Foundation of Korea under Contract No.NRF-2022R1A2C1092335National Science and Technology fund of MongoliaNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional DevelopmentResearch and Innovation of Thailand under Contract No.B50G670107Polish National Science Centre under Contract No.2024/53/B/ST2/00975Swedish Research Council under Contract No.2019.04595U.S.Department of Energy under Contract No.DE-FG02-05ER41374。
文摘Based on(10087±44)×10^(6) J/ψevents collected with the BESⅢdetector,we search for the lepton number violating decay J/ψ→K^(+)K^(+)e^(-)e^(-)+c.c.for the first time.The upper limit on the branching fraction of this decay is set to 2.1×10^(-9)at the 90%confidence level with a frequentist method.This is the first search for J/ψdecays with a lepton number change by two,offering valuable insights into the underlying physical processes.
基金supported by the National Key Research and Development Program of China(No.2022YFF0503303)the National Natural Science Foundation of China(Nos.12220101003,12275266,12003076,12022503,12103094 and U2031149)+8 种基金Outstanding Youth Science Foundation of NSFC(No.12022503)the Project for Young Scientists in Basic Research of the Chinese Academy of Sciences(No.YSBR-061)the Strategic Priority Program on Space Science of Chinese Academy of Sciences(No.E02212A02S)the Youth Innovation Promotion Association of CAS(No.2021450)the Young Elite Scientists Sponsorship Program by CAST(No.YESS20220197)the New Cornerstone Science Foundation through the XPLORER PRIZEthe Program for Innovative Talents and Entrepreneur in Jiangsu.In Europesupported by the Swiss National Science Foundation(SNSF),Switzerland,the National Institute for Nuclear Physics(INFN),Italythe European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation programme(No.851103).
文摘The cosmic-ray(CR)electrons and positrons in space are of considerable significance for studying the origin and propagation of CRs.The satellite-borne detector Dark Matter Particle Explorer(DAMPE)has been used to measure the separate electron and positron spectra,as well as the positron fraction.In this study,the Earth's magnetic field is used to distinguish CR electrons and positrons,as the DAMPE detector does not carry an onboard magnet.The energy for the measurements ranges from 10 to 20 GeV,which is currently limited at high energy by the zenith-pointing orientation of DAMPE.The results are consistent with previous measurements based on the magnetic spectrometer by AMS-02 and PAMELA,whereas the results of Fermi-LAT appear to be systematically shifted to larger values.
基金Supported in part by National Key R&D Program of China(2020YFA0406300,2020YFA0406400,2023YFA1606000)National Natural Science Foundation of China(NSFC)(11635010,11735014,11935015,11935016,11935018,12025502,12035009,12035013,12061131003,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017,12361141819)+17 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility Programthe CAS Center for Excellence in Particle Physics(CCEPP)Joint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1832207)100 Talents Program of CAS(ZR2022JQ02,ZR2024QA151)supported by Shandong Provincial Natural Science Foundationsupported by the China Postdoctoral Science Foundation(2023M742100)The Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and CosmologyGerman Research Foundation DFG(FOR5327,GRK 2149)Istituto Nazionale di Fisica Nucleare,ItalyKnut and Alice Wallenberg Foundation(2021.0174,2021.0299)Ministry of Development of Turkey(DPT2006K-120470)National Research Foundation of Korea(NRF-2022R1A2C1092335)National Science and Technology fund of MongoliaNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation of Thailand(B16F640076,B50G670107)Polish National Science Centre(2019/35/O/ST2/02907)Swedish Research Council(2019.04595)The Swedish Foundation for International Cooperation in Research and Higher Education(CH2018-7756)U.S.Department of Energy(DE-FG02-05ER41374)。
文摘By analyzing ψ(3686) data sample containing (107.7±0.6)×10^(6) events taken with the BESIII detector at the BEPCII storage ring in 2009,the χ_(c 0) resonance parameters are precisely measured using χ_(c 0,c 2)→π^(+)π^(−)/K^(+)K^(−) events.The mass of χ_(c 0) is determined to be M (χ_(c 0))=(3415.63±0.07±0.07±0.07)MeV/c^(2),and its full width is F (χ_(c 0))=(12.52±0.12±0.13)MeV,where the first uncertainty is statistical,the second systematic,and the third for mass comes from χ_(c 2) mass uncertainty.These measurements improve the precision of χ_(c 0) mass by a factor of four and width by one order of magnitude over the previous individual measurements,and significantly boost our knowledge about the charmonium spectrum.Together with additional (345.4±2.6)×10^(6)(3686) data events taken in 2012,the decay branching fractions of χ_(c 0,c 2)→π^(+)π^(−)/K^(+)K^(−) are measured as well,with precision improved by a factor of three compared to previous measurements.These χ_(c 0) decay branching fractions provide important inputs for the study of glueballs.
基金supported in part by National Key R&D Program of China(2020YFA0406400,2023YFA1606000,2020YFA0406300)National Natural Science Foundation of China(NSFC)(11635010,11735014,11935015,11935016,11935018,12025502,12035009,12035013,12061131003,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017,12361141819)+18 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility Programthe CAS Center for Excellence in Particle Physics(CCEPP)Joint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1832207)CAS(YSBR-101)100 Talents Program of CASCAS Project for Young Scientists in Basic Research(YSBR-117)The Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and CosmologyAgencia Nacional de Investigación y Desarrollo de Chile(ANID),Chile(ANID PIA/APOYO AFB230003)German Research Foundation DFG(FOR5327)Istituto Nazionale di Fisica Nucleare,ItalyKnut and Alice Wallenberg Foundation(2021.0174,2021.0299)Ministry of Development of Turkey(DPT2006K-120470)National Research Foundation of Korea(NRF-2022R1A2C1092335)National Science and Technology fund of MongoliaNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation of Thailand(B50G670107)Polish National Science Centre(2019/35/O/ST2/02907)Swedish Research Council(2019.04595)The Swedish Foundation for International Cooperation in Research and Higher Education(CH2018-7756)U.S.Department of Energy(DE-FG02-05ER41374)。
文摘Using 20.3 fb^(-1)of e^(+)e^(-)annihilation data collected at a center-of-mass energy of 3.773 GeV with the BESⅢdetector,we report on an improved search for the radiative leptonic decay D^(+)→γe^(+)ve.An upper limit on its partial branching fraction for photon energies E_(γ)>10 MeV was determined to be 1.2×10^(-5)at a 90%confidence level;this excludes most current theoretical predictions.A sophisticated deep learning approach,which includes thorough validation and is based on the Transformer architecture,was implemented to efficiently distinguish the signal from massive backgrounds.
基金National Key R&D Program of China(2023YFA1606000,2023YFA1606704)National Natural Science Foundation of China(NSFC)(11635010,11935015,11935016,11935018,12025502,12035009,12035013,12061131003,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017,12361141819)+14 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramCAS(YSBR-101)100 Talents Program of CASThe Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and CosmologyAgencia Nacional de Investigación y Desarrollo de Chile(ANID),Chile(ANID PIA/APOYO AFB230003)German Research Foundation DFG(FOR5327)Istituto Nazionale di Fisica Nucleare,ItalyKnut and Alice Wallenberg Foundation(2021.0174,2021.0299)Ministry of Development of Turkey(DPT2006K-120470)National Research Foundation of Korea(NRF-2022R1A2C1092335)National Science and Technology fund of MongoliaNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources Institutional Development,Research and Innovation of Thailand(B50G670107)Polish National Science Centre(2024/53/B/ST2/00975)Swedish Research Council(2019.04595)U.S.Department of Energy(DE-FG02-05ER41374)。
文摘Based on a sample of 2.7x 10^(9)ψ(3686)events collected by the BESIII detector operating at the BEP-CII collider,the decay 4(3686)→YX_(cJ),X_(cJ)→ηηη’is analyzed.The decay modes X_(c1)and X_(c2)→ηηη’are observed for the first time,and their corresponding branching fractions are determined to be B(X_(c1)→ηηη’)=(1.40±0.13(stat.)±0.09(sys.))×10^(-4)and B(X_(c2)→ηηη’)=(4.18±0.84(stat.)±0.48(sys.))×10^(-5).An upper limit on the branching fraction of x_(co)→ηηη’is set as 2.59×10^(-5)at a 90%confidence level(CL).A partial wave analys-is(PWA)of the decay X_(c1)→ηηη’is performed to search for the 1^(-+)exotic stateη1(1855).The PWA result indic-ates that the structure in theηη’mass spectrum is attributed to f_(0)(1500),while in the m mass spectrum,it is attrib-uted to the 0^(++)phase space.The upper limit of B(x_(cl)→η1(1855)η)·B(η1(1855)→ηη')<9.79×10^(-5)is set based on the PWA at 90%CL.
基金Supported in part by National Key R&D Program of China(2023YFA1606000,2023YFA1606704)National Natural Science Foundation of China(NSFC)(12035009,11875170,11635010,11935015,11935016,11935018,12025502,12035013,12061131003,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017,12361141819)+16 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility Program,CAS(YSBR-101)100 Talents Program of CASThe Institute of Nuclear and Particle Physics(INPAC)Shanghai Key Laboratory for Particle Physics and CosmologyAgencia Nacional de Investigación y Desarrollo de Chile(ANID)Chile(ANID PIA/APOYO AFB230003)ERC(758462)German Research Foundation DFG(FOR5327)Istituto Nazionale di Fisica Nucleare,ItalyKnut and Alice Wallenberg Foundation(2021.0174,2021.0299)Ministry of Development of Turkey(DPT2006K-120470)National Research Foundation of Korea(NRF-2022R1A2C1092335)National Science and Technology fund of MongoliaPolish National Science Centre(2024/53/B/ST2/00975)STFC(United Kingdom)Swedish Research Council(2019.04595)U.S.Department of Energy(DE-FG02-05ER41374)。
文摘Lepton number violation decayω→π^(+)π^(+)e^(-)e^(-)+c.c.is searched for via J/ψ→ωηusing a data sample of(1.0087±0.0044)×10^(10)J/ψevents collected via the BESIII detector at the BEPCII collider.No significant signal is observed,and the upper limit on the branching fraction ofω→π^(+)π^(+)e^(-)e^(-)+c.c.at the 90%confidence level is determined for the first time to be 2.8×10^(-6).
基金Supported in part by the National Key R&D Program of China(2023YFA1606000,2020YFA0406400,2020YFA0406300)the National Natural Science Foundation of China(NSFC)(11635010,11735014,11935015,11935016,11875054,11935018,12025502,12035009,12035013,12061131003,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017,12361141819)+12 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility Programthe CAS Center for Excellence in Particle Physics(CCEPP)the Joint Large-Scale Scientific Facility Funds of the NSFC and CAS(U2032104,U1832207)the 100 Talents Program of CAS,the Excellent Youth Foundation of Henan Scientific Commitee(242300421044)the Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and Cosmology,the German Research Foundation DFG(FOR5327)the Istituto Nazionale di Fisica Nucleare,Italy,the Knut and Alice Wallenberg Foundation(2021.0174,2021.0299)the Ministry of Development of Turkey(DPT2006K-120470),the National Research Foundation of Korea(NRF-2022R1A2C1092335)the National Science and Technology Fund of Mongoliathe National Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research,and Innovation of Thailand(B16F640076,B50G670107)the Polish National Science Center(2019/35/O/ST2/02907)the Swedish Research Council(2019.04595)the Swedish Foundation for International Cooperation in Research and Higher Education(CH2018-7756)the US Department of Energy(DE-FG02-05ER41374)。
文摘We search for the leptonic decay D^(+)→e^(+)ν_(e)using an e+e-collision data sample with an integrated luminosity of 20.3 fb-1collected with the BESIII detector at a center-of-mass energy of 3.773 GeV.Significant signal is not observed,and an upper limit on the branching fraction of D^(+)→e^(+)ν_(e)is set as 9.7×10^(-7),at a confidence level of 90%.Our upper limit is an order of magnitude smaller than the previous limit for this decay mode.
