High-entropy alloys(HEAs)are a new type of multi-principal metal materials that exhibit excellent me-chanical properties.However,the strength-ductility balance in the HEAs remains a challenge that needs to be addresse...High-entropy alloys(HEAs)are a new type of multi-principal metal materials that exhibit excellent me-chanical properties.However,the strength-ductility balance in the HEAs remains a challenge that needs to be addressed.The amorphous/crystalline(A/C)structure is a new design strategy to achieve high strength and excellent ductility of the HEAs.Here,the influences of amorphous layer spacing,indenter velocity,and indenter radius on the mechanical properties and microstructure evolution of the A/C dual-phase CoCrFeMnNi HEAs under nanoindentation were investigated by molecular dynamics(MD)simula-tion.The results indicate that the plastic deformation mechanism of the monocrystalline HEAs is mainly dominated by the nucleation and slip of dislocations,while the plastic deformation mechanism of the dual-phase HEAs is mainly dominated by the interaction between dislocations and amorphous phases.The results show that the average indentation force of the dual-phase HEAs increases with the increase of the amorphous layer spacing.The amorphous layer in the HEAs can hinder the expansion of disloca-tions,limiting them to the crystalline matrix between the two amorphous layers.The results also indicate that Young’s modulus of the HEAs increases with the increase of the indentation velocity and indentation radius.However,the hardness of HEAs is positively correlated with the indenter velocity,and negatively correlated with the indenter radius.It should be noted that the critical indentation depth and critical in-dentation force for the plastic deformation of the dual-phase HEAs decrease with the increase of indenter velocity,which is opposite to that of the single-phase crystalline HEAs.展开更多
To prolong the service lifetime of hot-section components used in marine environment at elevated tem-peratures,it is crucial to explore and develop high-temperature corrosion-resistant coatings.High-velocity oxygen fu...To prolong the service lifetime of hot-section components used in marine environment at elevated tem-peratures,it is crucial to explore and develop high-temperature corrosion-resistant coatings.High-velocity oxygen fuel(HVOF)sprayed NiCoCrAlY,Pt-modified NiCoCrAlY and pre-oxidized Pt-modified NiCoCrAlY coatings were prepared and investigated.This study is concerned with the performance of three coat-ings in a simulated marine environment based on the phase composition of corrosion products and mi-crostructure evolution of coating samples combined with first-principles density functional theory.The results show that the NiCoCrAlY coating was subject to accelerated corrosion and extensive aluminum depletion,leading to premature coating failure.The high-temperature corrosion resistance of Pt-modified NiCoCrAlY coating was found to be better than that of NiCoCrAlY coating.In contrast,the pre-oxidized Pt-modified NiCoCrAlY coating offered long-lasting protection and exhibited the best corrosion resistance,which is attributed to the positive synergistic effect between Pt modification and pre-oxidation.展开更多
A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatm...A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatments,wherein the electroplating procedures consisted of the composite deposition of Ni-Re followed by electroplating of Pt.In order to perform a comparison with conventional Ni Al and(Ni,Pt)Al coatings,the cyclic oxidation performance of the Ni Re Pt Al coating was evaluated at 1100 and 1150℃.We observed that the oxidation resistance of the Ni Re Pt Al coating was significantly improved by the greater presence of the residualβ-Ni Al phase in the outer layer and the lesser outward-diffusion of Mo from the substrate.In addition,the coating with the Re-rich diffusion barrier demonstrated a lower extent of interdiffusion into the substrate,where the thickness of the second reaction zone(SRZ)in the substrate alloy decreased by 25%.The mechanisms responsible for improving the oxidation resistance and decreasing the extent of SRZ formation are discussed,in which a particular attention is paid to the inhibition of the outward diffusion of Mo by the Re-based diffusion barrier.展开更多
The corrosion behavior of type 1045（AISI） carbon steel（CS） in oil-water fluids was investigated by considering the surface wetting state as the breakthrough point.The surface water wetting percentage（SWWP）and co...The corrosion behavior of type 1045（AISI） carbon steel（CS） in oil-water fluids was investigated by considering the surface wetting state as the breakthrough point.The surface water wetting percentage（SWWP）and corrosion weight loss of CS in different oil-water fluids were measured.The morphology and composition of the corrosion films were detected via scanning electron microscopy,electron-probe facescanning technology and Fourier-transform infrared spectroscopy.The results indicated that the corrosion weight loss of CS in the oil-water fluids corresponded with SWWP and that the corrosion process was influenced by the participation of oil.展开更多
As an advanced manufacturing technique,the advent of additive manufacturing(AM) has opened a new horizon of alternative ways to tackle the challenge of fundamental limits for manufacturing bulk metallic glasses(BMGs)....As an advanced manufacturing technique,the advent of additive manufacturing(AM) has opened a new horizon of alternative ways to tackle the challenge of fundamental limits for manufacturing bulk metallic glasses(BMGs).In particular,selective laser melting(SLM),direct metal deposition(DMD),electron beam melting(EBM),and laser foil printing(LFP) have been used for producing BMGs with dimensions larger than what is possible using conventional techniques such as melt-spinning,suction-casting,die-casting,etc.In this review,we analyzed the current status,issues,structural evolution,and key properties of BMGs based on these emerging AM technologies.The aim is to outline a direction for the development of BMGs using AM technology,establishing a fundamental principle to optimize processing parameters for designing alloy compositions with the high glass-forming ability(GFA),and thermal stability against crystallization.This will provide the fundamental science underpinning the future development of AM technology in the fabrication of high-density,defect-free,and completely amorphous alloy components and devices.展开更多
This paper discusses the utilization of latent variable modeling related to occupational health and safety in the mining industry.Latent variable modeling,which is a statistical model that relates observable and laten...This paper discusses the utilization of latent variable modeling related to occupational health and safety in the mining industry.Latent variable modeling,which is a statistical model that relates observable and latent variables,could be used to facilitate researchers’understandings of the underlying constructs or hypothetical factors and their magnitude of effect that constitute a complex system.This enhanced understanding,in turn,can help emphasize the important factors to improve mine safety.The most commonly used techniques include the exploratory factor analysis(EFA),the confirmatory factor analysis(CFA)and the structural equation model with latent variables(SEM).A critical comparison of the three techniques regarding mine safety is provided.Possible applications of latent variable modeling in mining engineering are explored.In this scope,relevant research papers were reviewed.They suggest that the application of such methods could prove useful in mine accident and safety research.Application of latent variables analysis in cognitive work analysis was proposed to improve the understanding of human-work relationships in mining operations.展开更多
The corrosion and tribocorrosion behaviors of AISI 304 austenitic stainless steel and Cr26Mo1 ultrapure high chromium ferrite stainless steel in 3.5 wt.%NaCl and 0.5 mol/L H2SO4 solutions were investigated.Microelectr...The corrosion and tribocorrosion behaviors of AISI 304 austenitic stainless steel and Cr26Mo1 ultrapure high chromium ferrite stainless steel in 3.5 wt.%NaCl and 0.5 mol/L H2SO4 solutions were investigated.Microelectrode electrochemical measurement technology was applied to identify electrochemistry behaviors during tribocorrosion tests in situ.The surface morphologies and compositions of the wear tracks were analyzed by scanning electron microscopy and Raman spectrum.The results showed that compositions of stainless steels,corrosive mediums and applied loads have great influence on tribocorrosion behaviors of stainless steels.Firstly,the corrosion resistance in static state of stainless steels primarily dominates its tribocorrosion behavior;meanwhile,better mechanical properties are in favor of tribocorrosion resistance.Secondly,the corrosion rate is promoted significantly in 3.5%NaCl solution by friction,while the tendency is inconspicuous in 0.5 mol/L H2SO4 solution.Last but not least,passive films on stainless steels can be wiped off by small friction force.With the increase in applied load,the effect of friction converts to forming friction oxide film from removing passivation film,so that a critical load exists below which the friction force can promote the corrosion process extremely.展开更多
The superτ-charm facility(STCF)is an electron–positron collider proposed by the Chinese particle physics community.It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of...The superτ-charm facility(STCF)is an electron–positron collider proposed by the Chinese particle physics community.It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of 0.5×10^(35) cm^(–2)·s^(–1) or higher.The STCF will produce a data sample about a factor of 100 larger than that of the presentτ-charm factory—the BEPCII,providing a unique platform for exploring the asymmetry of matter-antimatter(charge-parity violation),in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions,as well as searching for exotic hadrons and physics beyond the Standard Model.The STCF project in China is under development with an extensive R&D program.This document presents the physics opportunities at the STCF,describes conceptual designs of the STCF detector system,and discusses future plans for detector R&D and physics case studies.展开更多
In order to construct quasi-continuously networked reinforcement in titanium(Ti)matrix composites,in this study,Ti-6 Al-4 V spherical powders were uniformly coated with a graphene nanosheet(GNS)layer by high energy ba...In order to construct quasi-continuously networked reinforcement in titanium(Ti)matrix composites,in this study,Ti-6 Al-4 V spherical powders were uniformly coated with a graphene nanosheet(GNS)layer by high energy ball milling and then consolidated by spark plasma sintering.Results showed that the GNS layer on the powder surface inhibited continuous metallurgy bonding between powders during sintering,which led to the formation of quasi-networked hybrid reinforcement structure consisting of insitu Ti C and remained GNSs.The networked GNSs/Ti64 composite possessed noticeably higher tensile strength but similar ductility to the Ti64 alloy,leading to both better tensile strength and ductility than the GNSs/Ti composite with randomly dispersed GNSs and Ti C.The formation mechanism and the fracture mechanism of the networked hybrid reinforcement were discussed.The results provided a method to fabricate Ti matrix composites with high strength and good ductility.展开更多
We report the experimental results of the commissioning phase in the 10 PW laser beamline of the Shanghai Superintense Ultrafast Laser Facility(SULF).The peak power reaches 2.4 PW on target without the last amplifying...We report the experimental results of the commissioning phase in the 10 PW laser beamline of the Shanghai Superintense Ultrafast Laser Facility(SULF).The peak power reaches 2.4 PW on target without the last amplifying during the experiment.The laser energy of 72±9 J is directed to a focal spot of approximately 6μm diameter(full width at half maximum)in 30 fs pulse duration,yielding a focused peak intensity around 2.0×10^(21)W/cm^(2).The first laser-proton acceleration experiment is performed using plain copper and plastic targets.High-energy proton beams with maximum cut-off energy up to 62.5 MeV are achieved using copper foils at the optimum target thickness of 4μm via target normal sheath acceleration.For plastic targets of tens of nanometers thick,the proton cut-off energy is approximately 20 MeV,showing ring-like or flamented density distributions.These experimental results reflect the capabilities of the SULF-10 PW beamline,for example,both ultrahigh intensity and relatively good beam contrast.Further optimization for these key parameters is underway,where peak laser intensities of 10^(22)-10^(23)w/cm^(2)are anticipated to support various experiments on extreme field physics.展开更多
We report on experimental observation of non-laminar proton acceleration modulated by a strong magnetic field in laser irradiating micrometer aluminum targets.The results illustrate the coexistence of ring-like and fi...We report on experimental observation of non-laminar proton acceleration modulated by a strong magnetic field in laser irradiating micrometer aluminum targets.The results illustrate the coexistence of ring-like and filamentation structures.We implement the knife edge method into the radiochromic film detector to map the accelerated beams,measuring a source size of 30-110μm for protons of more than 5 MeV.The diagnosis reveals that the ring-like profile originates from low-energy protons far off the axis whereas the filamentation is from the near-axis high-energy protons,exhibiting non-laminar features.Particle-in-cell simulations reproduced the experimental results,showing that the short-term magnetic turbulence via Weibel instability and the long-term quasi-static annular magnetic field by the streaming electric current account for the measured beam profile.Our work provides direct mapping of laser-driven proton sources in the space-energy domain and reveals the non-laminar beam evolution at featured time scales.展开更多
A first search for the Ξ_(bc)^(+)J/ψΞ_(c)^(+) decay is performed by the LHCb experiment with a data sample of proton-proton collisions, corresponding to an integrated luminosity of 9 fb−1 recorded at centre-of-mass...A first search for the Ξ_(bc)^(+)J/ψΞ_(c)^(+) decay is performed by the LHCb experiment with a data sample of proton-proton collisions, corresponding to an integrated luminosity of 9 fb−1 recorded at centre-of-mass energies of 7, 8, and 13 TeV. Two peaking structures are seen with a local (global) significance of 4.3(2.8) and 4.1(2.4) standard deviations at masses of 6571 and 6694 MeV/c2, respectively. Upper limits are set on the Ξ+bc baryon production cross-section times the branching fraction relative to that of the B+c→J/ψD+s decay at centre-of-mass energies of 8 and 13 TeV, in the Ξ+bc and in the B+c rapidity and transverse-momentum ranges from 2.0 to 4.5 and 0 to 20GeV/c, respectively. Upper limits are presented as a function of the Ξ+bc mass and lifetime.展开更多
The first search for the doubly heavyΩ^(0)_(bc)baryon and a search for the E^(0)_(bc)baryon are performed using pp collision data collected via the LHCb experiment from 2016 to 2018 at a centre-of-mass energy of 13 T...The first search for the doubly heavyΩ^(0)_(bc)baryon and a search for the E^(0)_(bc)baryon are performed using pp collision data collected via the LHCb experiment from 2016 to 2018 at a centre-of-mass energy of 13 TeV,corresponding to an integrated luminosity of 5.2 fb^(-1).The baryons are reconstructed via their decays to Λ^(+)_(c)π^(-)and E^(+)_(c)π^(-).No significant excess is fbund for invariant masses between 6700 and 7300 MeV/c^(2),in a rapidity range from 2.0 to 4.5 and a transverse momentum range from 2 to 20 MeV/c.Upper limits are set on the ratio of the Ω^(0)_(bc)and E^(0)_(bc)production cross-section times the branching fraction to Λ^(+)_(c)π^(-)(E^(+)_(c)π^(-))relative to that of the Λ^(0)_(b)(E^(0)_(b))baryon,for different lifetime hypotheses,at 95%confidence level.The upper limits range from 0.5 x 10^(-4)to 2.5 x 10^(-4)for theΩ^(0)_(bc)→Λ^(+)_(c)π^(-)(E^(0)_(bc)→Λ^(+)_(c)π^(-))decay,and from 1.4x 10^(-3)to 6.9 x 10^(-3)for theΩ^(0)_(bc)→E^(+)_(c)π^(-)(E^(0)_(bc)→E^(+)_(c)π^(-))decay,depending on the considered mass and lifetime of theΩ^(0)_(bc)(E^(0)_(bc))baryon.展开更多
The establishment of a possible connection between neutrino emission and gravitational-wave(GW)bursts is important to our understanding of the physical processes that occur when black holes or neutron stars merge.In t...The establishment of a possible connection between neutrino emission and gravitational-wave(GW)bursts is important to our understanding of the physical processes that occur when black holes or neutron stars merge.In the Daya Bay experiment,using the data collected from December 2011 to August 2017,a search was per-formed for electron-antineutrino signals that coincided with detected GW events,including GW150914,GW151012,GW151226,GW170104,GW170608,GW 170814,and GW 170817.We used three time windows of±10,±500,and±1000 s relative to the occurrence of the GW events and a neutrino energy range of 1.8 to 100 MeV to search for correlated neutrino candidates.The detected electron-antineutrino candidates were consistent with the expected background rates for all the three time windows.Assuming monochromatic spectra,we found upper limits(90%confidence level)of the electron-antineutrino fluence of(1.13-2.44)×10^(11)cm^(-2)at 5 MeV to 8.0×10^(7)cm^(-2)at 100 MeV for the three time w indows.Under the assumption of a Fermi-Dirac spectrum,the upper limits were found to be(5.4-7.0)×10^(9)cm^(2)for the three time windows.展开更多
A search for the rare decays W^(+)→D_(s)^(+)γ and Z→D0γis performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV,corresponding to an integrated luminosity...A search for the rare decays W^(+)→D_(s)^(+)γ and Z→D0γis performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV,corresponding to an integrated luminosity of 2.0fb−1.No significant signal is observed for either decay mode and upper limits on their branching fractions are set using W^(+)→D_(s)^(+)γ and Z→μ+μ−decays as normalization channels.The upper limits are 6.5×10^(−4) and 2.1×10^(−3) at 95% confidence level for the W^(+)→D_(s)^(+)γ and Z→D^(0)γ decay modes,respectively.This is the first reported search for the Z→D^(0)γ decay,while the upper limit on the W+→D+sγbranching fraction improves upon the previous best limit.展开更多
The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era.The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by ...The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era.The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by the Daya Bay experiment,in combination with the fission rates of fissile isotopes in the reactor,is used to extract the positron energy spectra resulting from the fission of specific isotopes.This information can be used to produce a precise,data-based prediction of the antineutrino energy spectrum in other reactor antineutrino experiments with different fission fractions than Daya Bay.The positron energy spectra are unfolded to obtain the antineutrino energy spectra by removing the contribution from detector response with the Wiener-SVD unfolding method.Consistent results are obtained with other unfolding methods.A technique to construct a data-based prediction of the reactor antineutrino energy spectrum is proposed and investigated.Given the reactor fission fractions,the technique can predict the energy spectrum to a 2%precision.In addition,we illustrate how to perform a rigorous comparison between the unfolded antineutrino spectrum and a theoretical model prediction that avoids the input model bias of the unfolding method.展开更多
基金supported by the Natural Science Foundation of Shaanxi Province(No.2021JZ-53)the Program for Graduate Innovation Fund of Xi’an Shiyou University(No.YCS23212019).
文摘High-entropy alloys(HEAs)are a new type of multi-principal metal materials that exhibit excellent me-chanical properties.However,the strength-ductility balance in the HEAs remains a challenge that needs to be addressed.The amorphous/crystalline(A/C)structure is a new design strategy to achieve high strength and excellent ductility of the HEAs.Here,the influences of amorphous layer spacing,indenter velocity,and indenter radius on the mechanical properties and microstructure evolution of the A/C dual-phase CoCrFeMnNi HEAs under nanoindentation were investigated by molecular dynamics(MD)simula-tion.The results indicate that the plastic deformation mechanism of the monocrystalline HEAs is mainly dominated by the nucleation and slip of dislocations,while the plastic deformation mechanism of the dual-phase HEAs is mainly dominated by the interaction between dislocations and amorphous phases.The results show that the average indentation force of the dual-phase HEAs increases with the increase of the amorphous layer spacing.The amorphous layer in the HEAs can hinder the expansion of disloca-tions,limiting them to the crystalline matrix between the two amorphous layers.The results also indicate that Young’s modulus of the HEAs increases with the increase of the indentation velocity and indentation radius.However,the hardness of HEAs is positively correlated with the indenter velocity,and negatively correlated with the indenter radius.It should be noted that the critical indentation depth and critical in-dentation force for the plastic deformation of the dual-phase HEAs decrease with the increase of indenter velocity,which is opposite to that of the single-phase crystalline HEAs.
基金supported by the National Science and Technology Major Project(No.J2019-IV-0006-0074)the Key Research Program of the Chinese Academy of Sciences(No.ZDRW-CN-2021-2-2)+2 种基金the National Natural Science Foundation of China(No.52301116)support by the Joint Funds of the National Natural Science Foundation of China(“Ye Qisun”Science Funds,No.U2241251)the Innovation Engineering Project(No.211-XXXX-N106-01).
文摘To prolong the service lifetime of hot-section components used in marine environment at elevated tem-peratures,it is crucial to explore and develop high-temperature corrosion-resistant coatings.High-velocity oxygen fuel(HVOF)sprayed NiCoCrAlY,Pt-modified NiCoCrAlY and pre-oxidized Pt-modified NiCoCrAlY coatings were prepared and investigated.This study is concerned with the performance of three coat-ings in a simulated marine environment based on the phase composition of corrosion products and mi-crostructure evolution of coating samples combined with first-principles density functional theory.The results show that the NiCoCrAlY coating was subject to accelerated corrosion and extensive aluminum depletion,leading to premature coating failure.The high-temperature corrosion resistance of Pt-modified NiCoCrAlY coating was found to be better than that of NiCoCrAlY coating.In contrast,the pre-oxidized Pt-modified NiCoCrAlY coating offered long-lasting protection and exhibited the best corrosion resistance,which is attributed to the positive synergistic effect between Pt modification and pre-oxidation.
基金the Key-Area Research and Development Program of Guangdong Province(2019B010936001)financially supported by the National Natural Science Foundation of China(Grant Nos.51671202 and 51301184)。
文摘A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatments,wherein the electroplating procedures consisted of the composite deposition of Ni-Re followed by electroplating of Pt.In order to perform a comparison with conventional Ni Al and(Ni,Pt)Al coatings,the cyclic oxidation performance of the Ni Re Pt Al coating was evaluated at 1100 and 1150℃.We observed that the oxidation resistance of the Ni Re Pt Al coating was significantly improved by the greater presence of the residualβ-Ni Al phase in the outer layer and the lesser outward-diffusion of Mo from the substrate.In addition,the coating with the Re-rich diffusion barrier demonstrated a lower extent of interdiffusion into the substrate,where the thickness of the second reaction zone(SRZ)in the substrate alloy decreased by 25%.The mechanisms responsible for improving the oxidation resistance and decreasing the extent of SRZ formation are discussed,in which a particular attention is paid to the inhibition of the outward diffusion of Mo by the Re-based diffusion barrier.
基金supported by the National Natural Science Foundation of China (No.51041007)the Tribology Science Fund of State Key Laboratory of Tribology (No.SKLTKF10B07)
文摘The corrosion behavior of type 1045（AISI） carbon steel（CS） in oil-water fluids was investigated by considering the surface wetting state as the breakthrough point.The surface water wetting percentage（SWWP）and corrosion weight loss of CS in different oil-water fluids were measured.The morphology and composition of the corrosion films were detected via scanning electron microscopy,electron-probe facescanning technology and Fourier-transform infrared spectroscopy.The results indicated that the corrosion weight loss of CS in the oil-water fluids corresponded with SWWP and that the corrosion process was influenced by the participation of oil.
基金financially supported by the Australian Research Council Discovery Program (No. DP190103661)。
文摘As an advanced manufacturing technique,the advent of additive manufacturing(AM) has opened a new horizon of alternative ways to tackle the challenge of fundamental limits for manufacturing bulk metallic glasses(BMGs).In particular,selective laser melting(SLM),direct metal deposition(DMD),electron beam melting(EBM),and laser foil printing(LFP) have been used for producing BMGs with dimensions larger than what is possible using conventional techniques such as melt-spinning,suction-casting,die-casting,etc.In this review,we analyzed the current status,issues,structural evolution,and key properties of BMGs based on these emerging AM technologies.The aim is to outline a direction for the development of BMGs using AM technology,establishing a fundamental principle to optimize processing parameters for designing alloy compositions with the high glass-forming ability(GFA),and thermal stability against crystallization.This will provide the fundamental science underpinning the future development of AM technology in the fabrication of high-density,defect-free,and completely amorphous alloy components and devices.
基金Natural Sciences and Engineering Research Council of Canada(NSERC)(ID:236482)for supporting this research
文摘This paper discusses the utilization of latent variable modeling related to occupational health and safety in the mining industry.Latent variable modeling,which is a statistical model that relates observable and latent variables,could be used to facilitate researchers’understandings of the underlying constructs or hypothetical factors and their magnitude of effect that constitute a complex system.This enhanced understanding,in turn,can help emphasize the important factors to improve mine safety.The most commonly used techniques include the exploratory factor analysis(EFA),the confirmatory factor analysis(CFA)and the structural equation model with latent variables(SEM).A critical comparison of the three techniques regarding mine safety is provided.Possible applications of latent variable modeling in mining engineering are explored.In this scope,relevant research papers were reviewed.They suggest that the application of such methods could prove useful in mine accident and safety research.Application of latent variables analysis in cognitive work analysis was proposed to improve the understanding of human-work relationships in mining operations.
基金supported by PetroChina Key Core Technology Project(21ZG10)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDC04040400).
文摘The corrosion and tribocorrosion behaviors of AISI 304 austenitic stainless steel and Cr26Mo1 ultrapure high chromium ferrite stainless steel in 3.5 wt.%NaCl and 0.5 mol/L H2SO4 solutions were investigated.Microelectrode electrochemical measurement technology was applied to identify electrochemistry behaviors during tribocorrosion tests in situ.The surface morphologies and compositions of the wear tracks were analyzed by scanning electron microscopy and Raman spectrum.The results showed that compositions of stainless steels,corrosive mediums and applied loads have great influence on tribocorrosion behaviors of stainless steels.Firstly,the corrosion resistance in static state of stainless steels primarily dominates its tribocorrosion behavior;meanwhile,better mechanical properties are in favor of tribocorrosion resistance.Secondly,the corrosion rate is promoted significantly in 3.5%NaCl solution by friction,while the tendency is inconspicuous in 0.5 mol/L H2SO4 solution.Last but not least,passive films on stainless steels can be wiped off by small friction force.With the increase in applied load,the effect of friction converts to forming friction oxide film from removing passivation film,so that a critical load exists below which the friction force can promote the corrosion process extremely.
基金supported by the National Key R&D Program of China under Contract No.2022YFA1602200the International Partnership Program of the Chineses Academy of Sciences under Grant No.211134KYSB20200057the STCF Key Technology Research and Development Project.
文摘The superτ-charm facility(STCF)is an electron–positron collider proposed by the Chinese particle physics community.It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of 0.5×10^(35) cm^(–2)·s^(–1) or higher.The STCF will produce a data sample about a factor of 100 larger than that of the presentτ-charm factory—the BEPCII,providing a unique platform for exploring the asymmetry of matter-antimatter(charge-parity violation),in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions,as well as searching for exotic hadrons and physics beyond the Standard Model.The STCF project in China is under development with an extensive R&D program.This document presents the physics opportunities at the STCF,describes conceptual designs of the STCF detector system,and discusses future plans for detector R&D and physics case studies.
基金financially supported by the Key Research and Development Plan of Shaanxi Province(No.2020KW-034)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(CX2021058)。
文摘In order to construct quasi-continuously networked reinforcement in titanium(Ti)matrix composites,in this study,Ti-6 Al-4 V spherical powders were uniformly coated with a graphene nanosheet(GNS)layer by high energy ball milling and then consolidated by spark plasma sintering.Results showed that the GNS layer on the powder surface inhibited continuous metallurgy bonding between powders during sintering,which led to the formation of quasi-networked hybrid reinforcement structure consisting of insitu Ti C and remained GNSs.The networked GNSs/Ti64 composite possessed noticeably higher tensile strength but similar ductility to the Ti64 alloy,leading to both better tensile strength and ductility than the GNSs/Ti composite with randomly dispersed GNSs and Ti C.The formation mechanism and the fracture mechanism of the networked hybrid reinforcement were discussed.The results provided a method to fabricate Ti matrix composites with high strength and good ductility.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB16)the National Natural Science Foundation of China(Nos.11875307,11935008,11804348,11705260,11905278 and 11975302)the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2021242).
文摘We report the experimental results of the commissioning phase in the 10 PW laser beamline of the Shanghai Superintense Ultrafast Laser Facility(SULF).The peak power reaches 2.4 PW on target without the last amplifying during the experiment.The laser energy of 72±9 J is directed to a focal spot of approximately 6μm diameter(full width at half maximum)in 30 fs pulse duration,yielding a focused peak intensity around 2.0×10^(21)W/cm^(2).The first laser-proton acceleration experiment is performed using plain copper and plastic targets.High-energy proton beams with maximum cut-off energy up to 62.5 MeV are achieved using copper foils at the optimum target thickness of 4μm via target normal sheath acceleration.For plastic targets of tens of nanometers thick,the proton cut-off energy is approximately 20 MeV,showing ring-like or flamented density distributions.These experimental results reflect the capabilities of the SULF-10 PW beamline,for example,both ultrahigh intensity and relatively good beam contrast.Further optimization for these key parameters is underway,where peak laser intensities of 10^(22)-10^(23)w/cm^(2)are anticipated to support various experiments on extreme field physics.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB16)National Natural Science Foundation of China(Nos.11875307,11935008,11804348,11705260,11905278,and 11975302)Youth Innovation Promotion Association of the Chinese Academy of Sciences.
文摘We report on experimental observation of non-laminar proton acceleration modulated by a strong magnetic field in laser irradiating micrometer aluminum targets.The results illustrate the coexistence of ring-like and filamentation structures.We implement the knife edge method into the radiochromic film detector to map the accelerated beams,measuring a source size of 30-110μm for protons of more than 5 MeV.The diagnosis reveals that the ring-like profile originates from low-energy protons far off the axis whereas the filamentation is from the near-axis high-energy protons,exhibiting non-laminar features.Particle-in-cell simulations reproduced the experimental results,showing that the short-term magnetic turbulence via Weibel instability and the long-term quasi-static annular magnetic field by the streaming electric current account for the measured beam profile.Our work provides direct mapping of laser-driven proton sources in the space-energy domain and reveals the non-laminar beam evolution at featured time scales.
基金The project support from CERN and from the national agencies:CAPES,CNPq,FAPERJ and FINEP(Brazil)MOST and NSFC(China)+18 种基金CNRS/IN2P3(France)BMBF,DFG and MPG(Germany)INFN(Italy)NWO(Netherlands)MNiSW and NCN(Poland)MEN/IFA(Romania)MICINN(Spain)SNSF and SER(Switzerland)NASU(Ukraine)STFC(United Kingdom)DOE NP and NSF(USA).We acknowledge the computing resources that are provided by CERN,IN2P3(France),KIT and DESY(Germany),INFN(Italy),SURF(Netherlands),PIC(Spain),GridPP(United Kingdom),CSCS(Switzerland),IFIN-HH(Romania),CBPF(Brazil),Polish WLCG(Poland)and NERSC(USA).Individual groups or members have received support from ARC and ARDC(Australia)Minciencias(Colombia)AvH Foundation(Germany)EPLANET,Marie Sklodowska-Curie Actions and ERC(European Union)A*MIDEX,ANR,IPhU and Labex P2IO,and Région Auvergne-RhôneAlpes(France)Key Research Program of Frontier Sciences of CAS,CAS PIFI,CAS CCEPP,Fundamental Research Funds for the Central Universities,and Sci.&Tech.Program of Guangzhou(China)GVA,XuntaGal,GENCAT and Prog.Atracción Talento,CM(Spain)SRC(Sweden)the Leverhulme Trust,the Royal Society and UKRI(United Kingdom).
文摘A first search for the Ξ_(bc)^(+)J/ψΞ_(c)^(+) decay is performed by the LHCb experiment with a data sample of proton-proton collisions, corresponding to an integrated luminosity of 9 fb−1 recorded at centre-of-mass energies of 7, 8, and 13 TeV. Two peaking structures are seen with a local (global) significance of 4.3(2.8) and 4.1(2.4) standard deviations at masses of 6571 and 6694 MeV/c2, respectively. Upper limits are set on the Ξ+bc baryon production cross-section times the branching fraction relative to that of the B+c→J/ψD+s decay at centre-of-mass energies of 8 and 13 TeV, in the Ξ+bc and in the B+c rapidity and transverse-momentum ranges from 2.0 to 4.5 and 0 to 20GeV/c, respectively. Upper limits are presented as a function of the Ξ+bc mass and lifetime.
基金CAPES,CNPq,FAPERJ and FINEP(Brazil)MOST and NSFC(China)+18 种基金CNRS/IN2P3(France)BMBF,DFG,MPG(Germany)INFN(Italy)NWO(Netherlands)MNiSW,NCN(Poland)MEN/IFA(Romania)MSHE(Russia)MICINN(Spain)SNSF,SER(Switzerland)NASU(Ukraine)STFC(United Kingdom)DOE NP,NSF(USA).We acknowledge the computing resources that are provided by CERN,IN2P3(France),KIT and DESY(Germany),INFN(Italy),SURF(Netherlands),PIC(Spain),GridPP(United Kingdom),RRCKI and Yandex LLC(Russia),CSCS(Switzerland),IFIN-HH(Romania),CBPF(Brazil),PL-GRID(Poland)and NERSC(USA)AvH Foundation(Germany)EPLANET,Marie Sklodowska-Curie Actions and ERC(European Union)A*MIDEX,ANR,Labex P2IO and OCEVU,Region Auvergne-Rhdne-Alpes(France)Key Research Program of Frontier Sciences of CAS,CAS PIFI,CAS CCEPP,Fundamental Research Funds for the Central Universities,and Sci.Tech.Program of Guangzhou(China)RFBR,RSF and Yandex LLC(Russia)GVA,XuntaGal,GENCAT(Spain)the Leverhulme Trust,the Royal Society and UKRI(United Kingdom)。
文摘The first search for the doubly heavyΩ^(0)_(bc)baryon and a search for the E^(0)_(bc)baryon are performed using pp collision data collected via the LHCb experiment from 2016 to 2018 at a centre-of-mass energy of 13 TeV,corresponding to an integrated luminosity of 5.2 fb^(-1).The baryons are reconstructed via their decays to Λ^(+)_(c)π^(-)and E^(+)_(c)π^(-).No significant excess is fbund for invariant masses between 6700 and 7300 MeV/c^(2),in a rapidity range from 2.0 to 4.5 and a transverse momentum range from 2 to 20 MeV/c.Upper limits are set on the ratio of the Ω^(0)_(bc)and E^(0)_(bc)production cross-section times the branching fraction to Λ^(+)_(c)π^(-)(E^(+)_(c)π^(-))relative to that of the Λ^(0)_(b)(E^(0)_(b))baryon,for different lifetime hypotheses,at 95%confidence level.The upper limits range from 0.5 x 10^(-4)to 2.5 x 10^(-4)for theΩ^(0)_(bc)→Λ^(+)_(c)π^(-)(E^(0)_(bc)→Λ^(+)_(c)π^(-))decay,and from 1.4x 10^(-3)to 6.9 x 10^(-3)for theΩ^(0)_(bc)→E^(+)_(c)π^(-)(E^(0)_(bc)→E^(+)_(c)π^(-))decay,depending on the considered mass and lifetime of theΩ^(0)_(bc)(E^(0)_(bc))baryon.
基金Daya Bay is supported in part by the Ministry of Science and Technology o f China, the U.S. Department o f Energy, the Chinese Academy of Sciences, the CASCenter for Excellence in Particle Physics, the National Natural Science Foundation of China, the Guangdong provincial government, the Shenzhen municipal government,the China General Nuclear Power Group, Key Laboratory of Particle and Radiation Imaging (Tsinghua University), the Ministry of Education, Key Laboratory ofParticle Physics and Particle Irradiation (Shandong University), the Ministry o f Education, Shanghai Laboratory for Particle Physics and Cosmology, the ResearchGrants Council o f the Hong Kong Special Administrative Region of China, the University Development Fund of the University of Hong Kong, the MOE program forResearch of Excellence at National Taiwan University, National Chiao-Tung University, NSC fund support from Taiwan, the U.S. National Science Foundation, the AlfredP. Sloan Foundation, the Ministry o f Education, Youth, and Sports of the Czech Republic, the Charles University GAUK (284317), the Joint Institute o f NuclearResearch in Dubna, Russia, the National Commission of Scientific and Technological Research of Chile, and the Tsinghua University Initiative Scientific Research Program.
文摘The establishment of a possible connection between neutrino emission and gravitational-wave(GW)bursts is important to our understanding of the physical processes that occur when black holes or neutron stars merge.In the Daya Bay experiment,using the data collected from December 2011 to August 2017,a search was per-formed for electron-antineutrino signals that coincided with detected GW events,including GW150914,GW151012,GW151226,GW170104,GW170608,GW 170814,and GW 170817.We used three time windows of±10,±500,and±1000 s relative to the occurrence of the GW events and a neutrino energy range of 1.8 to 100 MeV to search for correlated neutrino candidates.The detected electron-antineutrino candidates were consistent with the expected background rates for all the three time windows.Assuming monochromatic spectra,we found upper limits(90%confidence level)of the electron-antineutrino fluence of(1.13-2.44)×10^(11)cm^(-2)at 5 MeV to 8.0×10^(7)cm^(-2)at 100 MeV for the three time w indows.Under the assumption of a Fermi-Dirac spectrum,the upper limits were found to be(5.4-7.0)×10^(9)cm^(2)for the three time windows.
文摘A search for the rare decays W^(+)→D_(s)^(+)γ and Z→D0γis performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV,corresponding to an integrated luminosity of 2.0fb−1.No significant signal is observed for either decay mode and upper limits on their branching fractions are set using W^(+)→D_(s)^(+)γ and Z→μ+μ−decays as normalization channels.The upper limits are 6.5×10^(−4) and 2.1×10^(−3) at 95% confidence level for the W^(+)→D_(s)^(+)γ and Z→D^(0)γ decay modes,respectively.This is the first reported search for the Z→D^(0)γ decay,while the upper limit on the W+→D+sγbranching fraction improves upon the previous best limit.
基金Supported in part by the Ministry of Science and Technology of Chinathe U.S.Department of Energy,the Chinese Academy of Sciences,the CAS Center for Excellence in Particle Physics,the National Natural Science Foundation of China+3 种基金the Guangdong provincial governmentthe Shenzhen municipal government,the China General Nuclear Power Group,the Research Grants Council of the Hong Kong Special Administrative Region of China,the Ministry of Education in TWthe U.S.National Science Foundation,the Ministry of Education,Youth,and Sports of the Czech Republic,the Charles University Research Centre UNCE,the Joint Institute of Nuclear Research in Dubna,Russiathe National Commission of Scientific and Technological Research of Chile。
文摘The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era.The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by the Daya Bay experiment,in combination with the fission rates of fissile isotopes in the reactor,is used to extract the positron energy spectra resulting from the fission of specific isotopes.This information can be used to produce a precise,data-based prediction of the antineutrino energy spectrum in other reactor antineutrino experiments with different fission fractions than Daya Bay.The positron energy spectra are unfolded to obtain the antineutrino energy spectra by removing the contribution from detector response with the Wiener-SVD unfolding method.Consistent results are obtained with other unfolding methods.A technique to construct a data-based prediction of the reactor antineutrino energy spectrum is proposed and investigated.Given the reactor fission fractions,the technique can predict the energy spectrum to a 2%precision.In addition,we illustrate how to perform a rigorous comparison between the unfolded antineutrino spectrum and a theoretical model prediction that avoids the input model bias of the unfolding method.
