Ni_(47)Ti_(44)Nb_(9)shape memory alloy(SMA)is a promising material in the aerospace field due to its wide transformation hysteresis.The application of shape memory effect depends on multistep thermomechan-ical loading...Ni_(47)Ti_(44)Nb_(9)shape memory alloy(SMA)is a promising material in the aerospace field due to its wide transformation hysteresis.The application of shape memory effect depends on multistep thermomechan-ical loading,viz.,low-temperature deformation and subsequent heating to recovery.Low-temperature deformation prestrain plays a pivotal role in shape memory properties tailoring of SMA components.However,microstructure evolution and deformation mechanisms of Ni_(47)Ti_(44)Nb_(9)SMA subjected to vari-ous prestrain levels are still unclear.To this end,microstructure evolution and shape memory behaviors of Ni_(47)Ti_(44)Nb_(9)alloy subjected to multistep thermomechanical loading with prestrain levels of 8%-16%at-28℃(M_(s)+30℃)were investigated.The results demonstrate that the stress-strain curve of the specimen exhibits four distinct stages at a maximal prestrain of 16%.Whereas stageⅡand stageⅢend at prestrains of∼8%and∼12%,respectively.In stageⅡ,the stress-induced martensitic transformation is accompanied by the dislocation slip of the NiTi matrix andβ-Nb inclusions.In stageⅢ,in addition to the higher density of dislocations and further growth of stress-induced martensite variants(SIMVs),(001)compound twins are introduced as a result of the(001)deformation twinning in stress-induced martensite.More{20-1}martensite twins are gradually introduced in stageⅣ.Correspondingly,after subsequent unloading and heating,a higher density of{114}austenite twins form in the specimen with a larger prestrain of 16%.With increasing prestrain from 8%to 16%,the recoverable strainε_(re)^(T)upon heating increases first and then decreases.Theε_(re)^(T)obtains a maximum of 7.03%at 10%prestrain and de-creases to 6.17%at 16%prestrain.The increase ofε_(re)^(T)can be attributed to the formation of new SIMVs,the further growth of existing SIMVs,and the recoverable(001)compound twins.While the decrease ofε_(re)^(T)is mainly associated with the irrecoverable strain by{20−1}martensite twins.The effect ofβ-Nb inclusions on the evolution of SIMVs is also found herein that deformedβ-Nb inclusions can significantly hinder the growth and recoverability of adjacent stress-induced martensite.展开更多
Cold rolling process can regulate the microstructure and mechanical properties of amorphous alloys,but it is still a challenging task to reveal their microscopic mechanism.Here,we designed an in-situ SEM observation d...Cold rolling process can regulate the microstructure and mechanical properties of amorphous alloys,but it is still a challenging task to reveal their microscopic mechanism.Here,we designed an in-situ SEM observation device for the cold rolling process of amorphous alloy,and visually observed the formation and evolution of shear bands during single-pass and multi-pass rolling process of the Zr_(55)Cu_(30)Al_(10)Ni_(5)amorphous alloy sheets.It is found that the evolution process of shear bands in the rolling process of amorphous alloy shows heritability,which is mainly reflected in two aspects:one is that the shear band formation pattern in the single-pass rolling process is more inclined to inherit the previous shear band formation pattern;the other is that the shear deformation is more likely to occur in the pre-existing shear bands in the multi-pass rolling process.This rule can be used to guide the controlled genera-tion of shear bands in amorphous alloys.Moreover,we emphasized the importance of pre-existing shear band orientations and systematically investigated the mechanical behavior of the amorphous alloys with pre-existing shear bands by in-situ SEM observation.It is found that the mechanical properties of the as-rolled amorphous alloys are determined by the competition between the work-softening of the pre-existing shear band itself and the work-hardening caused by the blocking effect of the pre-existing shear bands on the shear deformation.Based on this,we enhance the tensile fracture strength and the tensile ductility of the amorphous alloy by adjusting the orientation of the pre-existing shear bands parallel to the tensile stress axis so that the pre-existing shear bands prevent the linear propagation and destruction of the new shear bands.展开更多
Defect formation is a critical challenge for powder-based metal additive manufacturing(AM).Current understanding on the three important issues including formation mechanism,influence and control method of metal AM def...Defect formation is a critical challenge for powder-based metal additive manufacturing(AM).Current understanding on the three important issues including formation mechanism,influence and control method of metal AM defects should be updated.In this review paper,multi-scale defects in AMed metals and alloys are identified and for the first time classified into three categories,including geometry related,surface integrity related and microstructural defects.In particular,the microstructural defects are further divided into internal cracks and pores,textured columnar grains,compositional defects and dislocation cells.The root causes of the multi-scale defects are discussed.The key factors that affect the defect formation are identified and analyzed.The detection methods and modeling of the multi-scale defects are briefly introduced.The effects of the multi-scale defects on the mechanical properties especially for tensile properties and fatigue performance of AMed metallic components are reviewed.Various control and mitigation methods for the corresponding defects,include process parameter control,post processing,alloy design and hybrid AM techniques,are summarized and discussed.From research aspect,current research gaps and future prospects from three important aspects of the multi-scale AM defects are identified and delineated.展开更多
Solid-state diffusion bonding is an advanced joining technique, which has been widely used to join similar or dissimilar materials. Generally, it is easy to observe the diffusion behavior during dissimilar bonding, bu...Solid-state diffusion bonding is an advanced joining technique, which has been widely used to join similar or dissimilar materials. Generally, it is easy to observe the diffusion behavior during dissimilar bonding, but for similar bonding the diffusion behavior has yet been observed via experiments. In this study, the diffusion behavior at void tip was firstly observed during similar bonding of stainless steel. Scanning electron microscopy with energy dispersive spectroscopy was used to examine the interface charac- teristic and diffusion behavior. The results showed that a diffusion region was discovered at void tip. Element concentrations of diffusion region were more than those of void region, but less than those of bonded region. This behavior indicated that the diffusion was ongoing at void tip, but the perfect bond has yet formed. The diffusion region was attributed to the interface diffusion from adjacent region to void tip due to the stress gradient along bonding interface. The mass accumulation at void tip transformed the sharp void tip into smooth one at the beginning of void shrinkage, and then resulted in shorter voids.展开更多
Bulk laminate structure of Ti-alloy/Ti-based metallic glass composite （MGC） was prepared by melting a preform of alternate stack-up foils in the high vacuum atmosphere. The composite demonstrates a good combination ...Bulk laminate structure of Ti-alloy/Ti-based metallic glass composite （MGC） was prepared by melting a preform of alternate stack-up foils in the high vacuum atmosphere. The composite demonstrates a good combination of yield strength （-1618MPa）, plasticity （-4.3%） and specific fracture strength （384 × 10^3 N m kg^-1 ） in compression. The maintained yield strength results from the unique microstruc- ture composed of the Ti layer, the solution layer with gradient structure and the MGC layer. Such a multilayer structure effectively inhibits the propagation of shear band, leading to the enhanced plastic- ity. Those extraordinary properities suggest that combining ductile lamella with brittle metallic glass （MG） by such a lay-up method can be an effective way to improve mechanical properties of MG.展开更多
In this paper,the quasi-static large deformation,wrinkling and fracture behaviors of bimodular structures and membranes are studied with an implicit bond-based peridynamic computational framework.Firstly,the constant ...In this paper,the quasi-static large deformation,wrinkling and fracture behaviors of bimodular structures and membranes are studied with an implicit bond-based peridynamic computational framework.Firstly,the constant and tangential stiffness matrices of the implicit peridynamic formulations for the nonlinear problems are derived,respectively.The former is con structed from the linearization of the bond strain on the basis of the geometric approximation while the latter is established according to the linearization of the pairwise force by using first-order Taylor’s expansion.Then,a bimodular material model in peridynamics is developed,in which the tensile or compressive behavior of the material at each point is conveniently described by the tensile or compressive states of the bonds in its neighborhood.Moreover,the bimodular material model is extended to deal with the wrinkling and fracture problems of membranes by setting the compressive micro-modulus to be zero.In addition,the incremental-iterative algorithm is adopted to obtain the convergent solutions of the nonlinear problems.Finally,several representative numerical examples are presented and the results demonstrate the accuracy and efficiency of the proposed method for the large deformation,wrinkling and fracture analyses of bimodular structures and membranes.展开更多
The Lobster Eye Imager for Astronomy(LEIA),a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe mission,was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on20...The Lobster Eye Imager for Astronomy(LEIA),a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe mission,was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on2022 July 27.In this paper,we introduce the design and on-ground test results of the LEIA instrument.Using stateof-the-art Micro-Pore Optics(MPO),a wide field of view of 346 square degrees(18.6°×18.6°)of the X-ray imager is realized.An optical assembly composed of 36 MPO chips is used to focus incident X-ray photons,and four large-format complementary metal-oxide semiconductor(CMOS)sensors,each of size 6 cm×6 cm,are used as the focal plane detectors.The instrument has an angular resolution of 4’-8’(in terms of FWHM)for the central focal spot of the point-spread function,and an effective area of 2-3 cm^(2) at 1 keV in essentially all the directions within the field of view.The detection passband is 0.5-4 keV in soft X-rays and the sensitivity is2-3×10^(-11) erg s^(-1) cm^(-2)(about 1 milliCrab)with a 1000 s observation.The total weight of LEIA is 56 kg and the power is 85 W.The satellite,with a design lifetime of 2 yr,operates in a Sun-synchronous orbit of 500 km with an orbital period of 95 minutes.LEIA is paving the way for future missions by verifying in flight the technologies of both novel focusing imaging optics and CMOS sensors for X-ray observation,and by optimizing the working setups of the instrumental parameters.In addition,LEIA is able to carry out scientific observations to find new transients and to monitor known sources in the soft X-ray band,albeit with limited useful observing time available.展开更多
In order to obtain a glassy matrix during quenching, Be is often selected as a constituent of the compositions of Ti/Zr-based bulk metallic glass composites（BMGCs）. The in situ formed β phase in Be-bearing BMGCs wa...In order to obtain a glassy matrix during quenching, Be is often selected as a constituent of the compositions of Ti/Zr-based bulk metallic glass composites（BMGCs）. The in situ formed β phase in Be-bearing BMGCs was reported to be Be-free. However, a thorough investigation of the distribution of Be in BMGCs is still missing to date. In this work, the distribution of Be in a Ti_（47.5）Zr_（33）Cu_（5.8）Co_3Be_（12.5）（at.%） BMGC was studied by the secondary ion mass spectrometry（SIMS） and the electron energy loss spectroscopy（EELS）.It is found that Be almost totally dissolves in the glassy matrix, but a very weak intensity of Be in β phase is still detectable by SIMS, and the content of Be in β-Ti is estimated to be about 0.3 at.%. Based on the recently established two-phase quasi-equilibrium of BMGCs, the distinct solubility of Be in the glassy matrix and in β-Ti has been explained.展开更多
In this work, the previously developed coarse-grained （CG） particle models for biomembranes and red blood cells （RBCs） are reviewed, and the advantages of the CG particle methods over the continuum and atomistic s...In this work, the previously developed coarse-grained （CG） particle models for biomembranes and red blood cells （RBCs） are reviewed, and the advantages of the CG particle methods over the continuum and atomistic simulations for modeling biological phenomena are discussed. CG particle models can largely increase the length scale and time scale of atomistic simulations by eliminating the fast degrees of freedom while preserving the mesoscopic structures and properties of the simulated system. Moreover, CG particle models can be used to capture the microstructural alternations in diseased RBCs and simulate the topological changes of biomembranes and RBCs, which are the major challenges to the typical continuum representations of membranes and RBCs. The power and versatility of CG particle methods are demonstrated：through simulating the dynamical processes mvolving significant topological .changes e.g. lipid self-assembly vesicle fusion and membrane budding.展开更多
Dopants play a critical role in tailoring the microstructure during sintering of compacts. These dopants may form solid solution within the bulk, and/or segregate to the grain boundaries（GBs） and the solidvapor inte...Dopants play a critical role in tailoring the microstructure during sintering of compacts. These dopants may form solid solution within the bulk, and/or segregate to the grain boundaries（GBs） and the solidvapor interfaces（free surfaces）, each causing a distinct energetic scenario governing mass transports during densification and grain growth. In this work, the forces controlling the dopant distribution, in particular the possibility of concurrent segregation at both surfaces and GBs, are discussed based on the respective enthalpy of segregation. An equation is derived based on the minimum Gibbs energy of the system to determine enthalpy of segregation from experimental interface energy data, and the results applied to depict the role of La as a dopant on the interface energetics of yttria stabilized zirconia during its final stage of sintering. It is shown that La substantially decreases both GB and surface energies（differently）as sintering progresses, dynamically affecting its driving forces, and consequent grain growth and densification in this stage.展开更多
Nd1-xSrxMnO3 （x ： 0.3, 0.5） ceramics containing a secondary phase are synthesized by high-energy ball milling and post heat-treatment method. The 4-wire and 2-wire measuring modes are used to investigate the transp...Nd1-xSrxMnO3 （x ： 0.3, 0.5） ceramics containing a secondary phase are synthesized by high-energy ball milling and post heat-treatment method. The 4-wire and 2-wire measuring modes are used to investigate the transport character of the grain/phase boundary （inner interface） and electrode-bulk interface （outer interface）, respectively, and the results indicate that there is a similar nonlinear I-V behaviour for both of the inner and outer interfaces, however, the electric pulse induced resistance change （EPIR） effect can only be observed at the outer interface.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
With the increasing application of steroid drugs as therapeutics,the demand for steroid drugs is increasing.In recent years,biological synthesis has become the standard approach to produce steroid intermediates,while ...With the increasing application of steroid drugs as therapeutics,the demand for steroid drugs is increasing.In recent years,biological synthesis has become the standard approach to produce steroid intermediates,while this method still faces some problems such as unclear metabolic pathway and low yield.Mycobacterium sp.LY-1 can convert phytosterols into 9α-hydroxyandrost-4-ene-3,17-dione(9α-OH-AD)which is a key intermediate for the synthesis of steroid drugs with long effective time and significant pharmacological activity.In this work,the whole-genome sequence of the Mycobacterium sp.LY-1 was analyzed,and the side-chain degradation pathway of phytosterols in Mycobacterium sp.LY-1 was proposed.Meanwhile,the related key enzymes of phytosterol metabolism were identified through qRT-PCR.Through overexpressing the key enzymes including KshA2,KshB,and HsdB,the yield of 9α-OH-AD increased by 12.7%compared to that of the control.Furthermore,by optimizing the medium and culture conditions,the yield of 9α-OH-AD reached 50.4%.The maxi-mum yield was 30.7%higher than that of the original strain.The results are of significance for the industrial production of 9α-OH-AD using metabolic engineering methods.展开更多
Using e^(+)e^(−)annihilation data corresponding to an integrated luminosity of 2.93 fb^(−1)taken at the center-of-mass energy√s=3.773 GeV with the BESIII detector,a joint amplitude analysis is performed on the decays...Using e^(+)e^(−)annihilation data corresponding to an integrated luminosity of 2.93 fb^(−1)taken at the center-of-mass energy√s=3.773 GeV with the BESIII detector,a joint amplitude analysis is performed on the decays D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η).The fit fractions of individual components are obtained,and large interferences among the dominant components of the decays D^(0)→a_(1)(1260)π,D^(0)→π(1300)π,D^(0)→ρ(770)ρ(770),and D^(0)→2(ππ)_(S)are observed in both channels.With the obtained amplitude model,the CP-even fractions of D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η)are determined to be(75.2±1.1_(stat).±1.5_(syst.))%and(68.9±1.5_(stat).±2.4_(syst.))%,respectively.The branching fractions of D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η)are measured to be(0.688±0.010_(stat.)±0.010_(syst.))%and(0.951±0.025_(stat.)±0.021_(syst.))%,respectively.The amplitude analysis provides an important model for the binning strategy in measuring the strong phase parameters of D^(0)→4πwhen used to determine the CKM angleγ(ϕ_(3))via the B^(−)→DK^(−)decay.展开更多
During the 2016-17 and 2018-19 running periods,the BESIII experiment collected 7.5 fb of e^(+)e^(-)collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV.These data samples are primarily used for the ...During the 2016-17 and 2018-19 running periods,the BESIII experiment collected 7.5 fb of e^(+)e^(-)collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV.These data samples are primarily used for the study of excited charmonium and charmoniumlike states.By analyzing the di-muon process e^(+)e^(-)→(γISR=FSR)μ^(+)μ^(-),we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV.Through a run-by-run study,we find that the center-of-mass energies were stable throughout most of the data-collection period.展开更多
Boldenone is a protein-assimilating androgen steroid that can promote protein synthesis,support nitrogen storage,and enhance renal erythropoietin release.The industrial production of boldenone mainly relies on chemica...Boldenone is a protein-assimilating androgen steroid that can promote protein synthesis,support nitrogen storage,and enhance renal erythropoietin release.The industrial production of boldenone mainly relies on chemical synthesis,which has various problems,such as a complex conversion process,excessive byproducts,and serious environmental pollution.There-fore,it is of great significance to explore a new biosynthetic route.Recently,the enzymatic synthesis of steroid compounds has been performed more frequently than in the past.In this work,boldenone was produced from androstenedione(AD)in two steps by a dual-enzyme cascade of 17β-hydroxysteroid dehydrogenase(17β-HSD)and 3-sterone-Δ^(1)-dehydrogenase(KstD).The conversion efficiency of three isoenzymes of 17β-HSD from Mycobacterium sp.LY-1 for substrate AD was first analyzed.After that,the 17β-HSD2 with high selectivity and specificity for AD was screened and co-expressed with KstD3 in Escherichia coli BL21 to construct a dual-enzyme catalytic system.The results showed that the synthesis of boldenone from AD could be achieved by constructing the dual-enzyme expression system of 17β-HSD and KstD,as we determined that the concentration of boldenone reached 24.3 mg/L.To further improve the synthesis efficiency of boldenone,the expression conditions of the dual-enzyme system were optimized,and the concentration of boldenone reached 31.9 mg/L.The explora-tion of this route will provide a foundation for the efficient enzymatic synthesis of boldenone.展开更多
The integrated luminosities of data samples collected in the BESⅢ experiment in 2016-2017 at centerof-mass energies between 4.19 and 4.28 GeV are measured with a precision better than 1% by analyzing large-angle Bhab...The integrated luminosities of data samples collected in the BESⅢ experiment in 2016-2017 at centerof-mass energies between 4.19 and 4.28 GeV are measured with a precision better than 1% by analyzing large-angle Bhabha scattering events.The integrated luminosities of old datasets collected in 2010-2014 are updated by considering corrections related to detector performance,offsetting the effect of newly discovered readout errors in the electromagnetic calorimeter,which can haphazardly occur.展开更多
From December 2019 to June 2021,the BESⅢ experiment collected approximately 5.85 fb^(−1) of data at center-of-mass energies between 4.61 and 4.95 GeV.This is the highest collision energy BEPCⅡ has reached to date.Th...From December 2019 to June 2021,the BESⅢ experiment collected approximately 5.85 fb^(−1) of data at center-of-mass energies between 4.61 and 4.95 GeV.This is the highest collision energy BEPCⅡ has reached to date.The accumulated e^(+)e^(−) annihilation data samples are useful for studying charmonium(-like)states and charmed-hadron decays.By adopting a novel method of analyzing the production of A_(c)^(+)A_(c)^(-) pairs in e^(+)e^(−) annihilation,the center-of-mass energies are measured with a precision of 0.6 MeV.Integrated luminosities are measured with a precision of better than 1% by analyzing the events of large-angle Bhabha scattering.These measurements provide important inputs to analyses based on these data samples.展开更多
基金support from the National Natural Science Foundation of China(No.51775441)the National Science Fund for Excellent Young Scholars(No.51522509).
文摘Ni_(47)Ti_(44)Nb_(9)shape memory alloy(SMA)is a promising material in the aerospace field due to its wide transformation hysteresis.The application of shape memory effect depends on multistep thermomechan-ical loading,viz.,low-temperature deformation and subsequent heating to recovery.Low-temperature deformation prestrain plays a pivotal role in shape memory properties tailoring of SMA components.However,microstructure evolution and deformation mechanisms of Ni_(47)Ti_(44)Nb_(9)SMA subjected to vari-ous prestrain levels are still unclear.To this end,microstructure evolution and shape memory behaviors of Ni_(47)Ti_(44)Nb_(9)alloy subjected to multistep thermomechanical loading with prestrain levels of 8%-16%at-28℃(M_(s)+30℃)were investigated.The results demonstrate that the stress-strain curve of the specimen exhibits four distinct stages at a maximal prestrain of 16%.Whereas stageⅡand stageⅢend at prestrains of∼8%and∼12%,respectively.In stageⅡ,the stress-induced martensitic transformation is accompanied by the dislocation slip of the NiTi matrix andβ-Nb inclusions.In stageⅢ,in addition to the higher density of dislocations and further growth of stress-induced martensite variants(SIMVs),(001)compound twins are introduced as a result of the(001)deformation twinning in stress-induced martensite.More{20-1}martensite twins are gradually introduced in stageⅣ.Correspondingly,after subsequent unloading and heating,a higher density of{114}austenite twins form in the specimen with a larger prestrain of 16%.With increasing prestrain from 8%to 16%,the recoverable strainε_(re)^(T)upon heating increases first and then decreases.Theε_(re)^(T)obtains a maximum of 7.03%at 10%prestrain and de-creases to 6.17%at 16%prestrain.The increase ofε_(re)^(T)can be attributed to the formation of new SIMVs,the further growth of existing SIMVs,and the recoverable(001)compound twins.While the decrease ofε_(re)^(T)is mainly associated with the irrecoverable strain by{20−1}martensite twins.The effect ofβ-Nb inclusions on the evolution of SIMVs is also found herein that deformedβ-Nb inclusions can significantly hinder the growth and recoverability of adjacent stress-induced martensite.
基金supported by the National Natural Science Foundation of China(No.52074257)the Project supported by the Space Application System of China Manned Space Program(No.YYMT1201-EXP08).
文摘Cold rolling process can regulate the microstructure and mechanical properties of amorphous alloys,but it is still a challenging task to reveal their microscopic mechanism.Here,we designed an in-situ SEM observation device for the cold rolling process of amorphous alloy,and visually observed the formation and evolution of shear bands during single-pass and multi-pass rolling process of the Zr_(55)Cu_(30)Al_(10)Ni_(5)amorphous alloy sheets.It is found that the evolution process of shear bands in the rolling process of amorphous alloy shows heritability,which is mainly reflected in two aspects:one is that the shear band formation pattern in the single-pass rolling process is more inclined to inherit the previous shear band formation pattern;the other is that the shear deformation is more likely to occur in the pre-existing shear bands in the multi-pass rolling process.This rule can be used to guide the controlled genera-tion of shear bands in amorphous alloys.Moreover,we emphasized the importance of pre-existing shear band orientations and systematically investigated the mechanical behavior of the amorphous alloys with pre-existing shear bands by in-situ SEM observation.It is found that the mechanical properties of the as-rolled amorphous alloys are determined by the competition between the work-softening of the pre-existing shear band itself and the work-hardening caused by the blocking effect of the pre-existing shear bands on the shear deformation.Based on this,we enhance the tensile fracture strength and the tensile ductility of the amorphous alloy by adjusting the orientation of the pre-existing shear bands parallel to the tensile stress axis so that the pre-existing shear bands prevent the linear propagation and destruction of the new shear bands.
基金the funding support to this research via the projects of ZVMR,BBAT and ZE1W from The Hong Kong Polytechnic Universityproject#RNE-p2–21 of the Shun Hing Institute of Advanced EngineeringThe Chinese University of Hong Kong and the GRF projects(Nos.15223520 and 15228621)。
文摘Defect formation is a critical challenge for powder-based metal additive manufacturing(AM).Current understanding on the three important issues including formation mechanism,influence and control method of metal AM defects should be updated.In this review paper,multi-scale defects in AMed metals and alloys are identified and for the first time classified into three categories,including geometry related,surface integrity related and microstructural defects.In particular,the microstructural defects are further divided into internal cracks and pores,textured columnar grains,compositional defects and dislocation cells.The root causes of the multi-scale defects are discussed.The key factors that affect the defect formation are identified and analyzed.The detection methods and modeling of the multi-scale defects are briefly introduced.The effects of the multi-scale defects on the mechanical properties especially for tensile properties and fatigue performance of AMed metallic components are reviewed.Various control and mitigation methods for the corresponding defects,include process parameter control,post processing,alloy design and hybrid AM techniques,are summarized and discussed.From research aspect,current research gaps and future prospects from three important aspects of the multi-scale AM defects are identified and delineated.
基金financially supported by the National Natural Science Foundation of China (Nos.51505386 and 51275416)the Fundamental Research funds for the Central Universities (No.3102017GX06003)
文摘Solid-state diffusion bonding is an advanced joining technique, which has been widely used to join similar or dissimilar materials. Generally, it is easy to observe the diffusion behavior during dissimilar bonding, but for similar bonding the diffusion behavior has yet been observed via experiments. In this study, the diffusion behavior at void tip was firstly observed during similar bonding of stainless steel. Scanning electron microscopy with energy dispersive spectroscopy was used to examine the interface charac- teristic and diffusion behavior. The results showed that a diffusion region was discovered at void tip. Element concentrations of diffusion region were more than those of void region, but less than those of bonded region. This behavior indicated that the diffusion was ongoing at void tip, but the perfect bond has yet formed. The diffusion region was attributed to the interface diffusion from adjacent region to void tip due to the stress gradient along bonding interface. The mass accumulation at void tip transformed the sharp void tip into smooth one at the beginning of void shrinkage, and then resulted in shorter voids.
基金supported by the National Natural Science Foundation of China (Nos. 51434008 (U1435204) and 51531005)the China’s Manned Space Station Project (No. TGJZ800-2-RW024)+2 种基金Science and Technology Planning Project of Guangdong Province, China (Nos. 2015B090926001 and 2015B010122001)the Youth Innovation Promotion Association CASShuangchuang Project of Jiangsu Province, China
文摘Bulk laminate structure of Ti-alloy/Ti-based metallic glass composite （MGC） was prepared by melting a preform of alternate stack-up foils in the high vacuum atmosphere. The composite demonstrates a good combination of yield strength （-1618MPa）, plasticity （-4.3%） and specific fracture strength （384 × 10^3 N m kg^-1 ） in compression. The maintained yield strength results from the unique microstruc- ture composed of the Ti layer, the solution layer with gradient structure and the MGC layer. Such a multilayer structure effectively inhibits the propagation of shear band, leading to the enhanced plastic- ity. Those extraordinary properities suggest that combining ductile lamella with brittle metallic glass （MG） by such a lay-up method can be an effective way to improve mechanical properties of MG.
基金The work was supported by the National Natural Science Foundation of China(Grants 11672062,11772082,and 11672063)the 111 Project(Grant B08014)the Fundamental Research Funds for the Central Universities.
文摘In this paper,the quasi-static large deformation,wrinkling and fracture behaviors of bimodular structures and membranes are studied with an implicit bond-based peridynamic computational framework.Firstly,the constant and tangential stiffness matrices of the implicit peridynamic formulations for the nonlinear problems are derived,respectively.The former is con structed from the linearization of the bond strain on the basis of the geometric approximation while the latter is established according to the linearization of the pairwise force by using first-order Taylor’s expansion.Then,a bimodular material model in peridynamics is developed,in which the tensile or compressive behavior of the material at each point is conveniently described by the tensile or compressive states of the bonds in its neighborhood.Moreover,the bimodular material model is extended to deal with the wrinkling and fracture problems of membranes by setting the compressive micro-modulus to be zero.In addition,the incremental-iterative algorithm is adopted to obtain the convergent solutions of the nonlinear problems.Finally,several representative numerical examples are presented and the results demonstrate the accuracy and efficiency of the proposed method for the large deformation,wrinkling and fracture analyses of bimodular structures and membranes.
基金supported by the Einstein Probe project,a mission in the Strategic Priority Program on Space Science of CAS(grant Nos.XDA15310000,XDA15052100)in part been supported by the European Union’s Horizon 2020 Program under the AHEAD2020 project(grant No.871158).
文摘The Lobster Eye Imager for Astronomy(LEIA),a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe mission,was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on2022 July 27.In this paper,we introduce the design and on-ground test results of the LEIA instrument.Using stateof-the-art Micro-Pore Optics(MPO),a wide field of view of 346 square degrees(18.6°×18.6°)of the X-ray imager is realized.An optical assembly composed of 36 MPO chips is used to focus incident X-ray photons,and four large-format complementary metal-oxide semiconductor(CMOS)sensors,each of size 6 cm×6 cm,are used as the focal plane detectors.The instrument has an angular resolution of 4’-8’(in terms of FWHM)for the central focal spot of the point-spread function,and an effective area of 2-3 cm^(2) at 1 keV in essentially all the directions within the field of view.The detection passband is 0.5-4 keV in soft X-rays and the sensitivity is2-3×10^(-11) erg s^(-1) cm^(-2)(about 1 milliCrab)with a 1000 s observation.The total weight of LEIA is 56 kg and the power is 85 W.The satellite,with a design lifetime of 2 yr,operates in a Sun-synchronous orbit of 500 km with an orbital period of 95 minutes.LEIA is paving the way for future missions by verifying in flight the technologies of both novel focusing imaging optics and CMOS sensors for X-ray observation,and by optimizing the working setups of the instrumental parameters.In addition,LEIA is able to carry out scientific observations to find new transients and to monitor known sources in the soft X-ray band,albeit with limited useful observing time available.
基金support from the National Natural Science Foundation of China (Nos. 51434008, U1435204, and 51531005)the China’s Manned Space Station Project (Mission No.: TGJZ800-2-RW024)the Shuangchuang Project of Jiangsu Province, China
文摘In order to obtain a glassy matrix during quenching, Be is often selected as a constituent of the compositions of Ti/Zr-based bulk metallic glass composites（BMGCs）. The in situ formed β phase in Be-bearing BMGCs was reported to be Be-free. However, a thorough investigation of the distribution of Be in BMGCs is still missing to date. In this work, the distribution of Be in a Ti_（47.5）Zr_（33）Cu_（5.8）Co_3Be_（12.5）（at.%） BMGC was studied by the secondary ion mass spectrometry（SIMS） and the electron energy loss spectroscopy（EELS）.It is found that Be almost totally dissolves in the glassy matrix, but a very weak intensity of Be in β phase is still detectable by SIMS, and the content of Be in β-Ti is estimated to be about 0.3 at.%. Based on the recently established two-phase quasi-equilibrium of BMGCs, the distinct solubility of Be in the glassy matrix and in β-Ti has been explained.
基金Project supported by the National Institutes of Health of U.S.A.(No.U01HL114476)the National Science Foundation of U.S.A.(Nos.CMMI-1235025 and PHY-1205910)
文摘In this work, the previously developed coarse-grained （CG） particle models for biomembranes and red blood cells （RBCs） are reviewed, and the advantages of the CG particle methods over the continuum and atomistic simulations for modeling biological phenomena are discussed. CG particle models can largely increase the length scale and time scale of atomistic simulations by eliminating the fast degrees of freedom while preserving the mesoscopic structures and properties of the simulated system. Moreover, CG particle models can be used to capture the microstructural alternations in diseased RBCs and simulate the topological changes of biomembranes and RBCs, which are the major challenges to the typical continuum representations of membranes and RBCs. The power and versatility of CG particle methods are demonstrated：through simulating the dynamical processes mvolving significant topological .changes e.g. lipid self-assembly vesicle fusion and membrane budding.
基金support of the National Basic Research Program of China (No. 2011CB610403)the National Natural Science Foundation of China (Nos. 51134011 and 51431008)+3 种基金Research Fund of the State Key Laboratory of Solidification Processing (117-TZ-2015)the China National Funds for Distinguished Young Scientists (No. 51125002)supports of the Doctorate Foundation of Northwestern Polytechnical University (No. CX201204)support of the National Science Foundation (No. DMR 1055504)
文摘Dopants play a critical role in tailoring the microstructure during sintering of compacts. These dopants may form solid solution within the bulk, and/or segregate to the grain boundaries（GBs） and the solidvapor interfaces（free surfaces）, each causing a distinct energetic scenario governing mass transports during densification and grain growth. In this work, the forces controlling the dopant distribution, in particular the possibility of concurrent segregation at both surfaces and GBs, are discussed based on the respective enthalpy of segregation. An equation is derived based on the minimum Gibbs energy of the system to determine enthalpy of segregation from experimental interface energy data, and the results applied to depict the role of La as a dopant on the interface energetics of yttria stabilized zirconia during its final stage of sintering. It is shown that La substantially decreases both GB and surface energies（differently）as sintering progresses, dynamically affecting its driving forces, and consequent grain growth and densification in this stage.
基金the Project of Hubei Polytechnic University (No.12xjz01R)The Natural Science Foundation of Hubei Province(No.2012FFB01001)the Program of Ministry of Education of China(for New Century Excellent Talents in University, No.NCET-08-0674)for their financial supports
文摘Nd1-xSrxMnO3 （x ： 0.3, 0.5） ceramics containing a secondary phase are synthesized by high-energy ball milling and post heat-treatment method. The 4-wire and 2-wire measuring modes are used to investigate the transport character of the grain/phase boundary （inner interface） and electrode-bulk interface （outer interface）, respectively, and the results indicate that there is a similar nonlinear I-V behaviour for both of the inner and outer interfaces, however, the electric pulse induced resistance change （EPIR） effect can only be observed at the outer interface.
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supported by the National Key R&D Program of China(No.2019YFA0905300)Tianjin Synthetic Biotechnology Innovation Capacity Improvement Project(No.TSBICIPKJGG-001-14)+1 种基金the National Natural Science Foundation of China(No.22078126)Qing Lan Project in Jiangsu Province and Fundamental Research Funds for the Central Universities(JUSRP221025).
文摘With the increasing application of steroid drugs as therapeutics,the demand for steroid drugs is increasing.In recent years,biological synthesis has become the standard approach to produce steroid intermediates,while this method still faces some problems such as unclear metabolic pathway and low yield.Mycobacterium sp.LY-1 can convert phytosterols into 9α-hydroxyandrost-4-ene-3,17-dione(9α-OH-AD)which is a key intermediate for the synthesis of steroid drugs with long effective time and significant pharmacological activity.In this work,the whole-genome sequence of the Mycobacterium sp.LY-1 was analyzed,and the side-chain degradation pathway of phytosterols in Mycobacterium sp.LY-1 was proposed.Meanwhile,the related key enzymes of phytosterol metabolism were identified through qRT-PCR.Through overexpressing the key enzymes including KshA2,KshB,and HsdB,the yield of 9α-OH-AD increased by 12.7%compared to that of the control.Furthermore,by optimizing the medium and culture conditions,the yield of 9α-OH-AD reached 50.4%.The maxi-mum yield was 30.7%higher than that of the original strain.The results are of significance for the industrial production of 9α-OH-AD using metabolic engineering methods.
基金Supported in part by the National Key R&D Program of China(2020YFA0406300,2020YFA0406400)the National Natural Science Foundation of China(NSFC)(11625523,11635010,11735014,11835012,11935015,11935016,11935018,11961141012,12025502,12035009,12035013,12061131003,12105276,12122509,12192260,12192261,12192262,12192263,12192264,12192265,12221005,12225509,12235017)+15 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(U1732263,U1832103,U1832207,U2032111)CAS Key Research Program of Frontier Sciences(QYZDJ-SSW-SLH003,QYZDJ-SSW-SLH040)100 Talents Program of CASThe Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and CosmologyEuropean Union's Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement(894790)German Research Foundation DFG(455635585),Collaborative Research Center CRC 1044,FOR5327,GRK 2149Istituto Nazionale di Fisica Nucleare,ItalyMinistry 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)Polish National Science Centre(2019/35/O/ST2/02907)The Swedish Research CouncilU.S.Department of Energy(DE-FG02-05ER41374)。
文摘Using e^(+)e^(−)annihilation data corresponding to an integrated luminosity of 2.93 fb^(−1)taken at the center-of-mass energy√s=3.773 GeV with the BESIII detector,a joint amplitude analysis is performed on the decays D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η).The fit fractions of individual components are obtained,and large interferences among the dominant components of the decays D^(0)→a_(1)(1260)π,D^(0)→π(1300)π,D^(0)→ρ(770)ρ(770),and D^(0)→2(ππ)_(S)are observed in both channels.With the obtained amplitude model,the CP-even fractions of D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η)are determined to be(75.2±1.1_(stat).±1.5_(syst.))%and(68.9±1.5_(stat).±2.4_(syst.))%,respectively.The branching fractions of D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η)are measured to be(0.688±0.010_(stat.)±0.010_(syst.))%and(0.951±0.025_(stat.)±0.021_(syst.))%,respectively.The amplitude analysis provides an important model for the binning strategy in measuring the strong phase parameters of D^(0)→4πwhen used to determine the CKM angleγ(ϕ_(3))via the B^(−)→DK^(−)decay.
基金Supported in part by National Key Research and Development Program of China(2020YFA0406300,2020YFA0406400)National Natural Science Foundation of China(NSFC)(11625523,11635010,11735014,11822506,11835012,11935015,11935016,11935018,11961141012)+12 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramJoint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1732263,U1832207)CAS Key Research Program of Frontier Sciences(QYZDJ-SSW-SLH003,QYZDJ-SSW-SLH040)100 Talents Program of CAS,INPAC and Shanghai Key Laboratory for Particle Physics and Cosmology,ERC(758462)European Union Horizon 2020 research and innovation programme(Marie Sklodowska-Curie grant agreement No 894790)German Research Foundation DFG(443159800)Collaborative Research Center CRC 1044,FOR 2359,FOR 2359,GRK 214Istituto Nazionale di Fisica Nucleare,Italy,Ministry of Development of Turkey(DPT2006K-120470)National Science and Technology fund,Olle Engkvist Foundation(200-0605)STFC(United Kingdom)The Knut and Alice Wallenberg Foundation(Sweden)(2016.0157)The Royal Society,UK(DH140054,DH160214)The Swedish Research Council,U.S.Department of Energy(DE-FG02-05ER41374,DE-SC-0012069)。
文摘During the 2016-17 and 2018-19 running periods,the BESIII experiment collected 7.5 fb of e^(+)e^(-)collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV.These data samples are primarily used for the study of excited charmonium and charmoniumlike states.By analyzing the di-muon process e^(+)e^(-)→(γISR=FSR)μ^(+)μ^(-),we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV.Through a run-by-run study,we find that the center-of-mass energies were stable throughout most of the data-collection period.
基金supported by National Key Research and Development Program of China(No.2019YFA0905300)the National Natural Science Foundation of China(No.22078126)+1 种基金Qing Lan Project in Jiangsu ProvinceFundamental Research Funds for Central Universities of China(No.JUSRP221025).
文摘Boldenone is a protein-assimilating androgen steroid that can promote protein synthesis,support nitrogen storage,and enhance renal erythropoietin release.The industrial production of boldenone mainly relies on chemical synthesis,which has various problems,such as a complex conversion process,excessive byproducts,and serious environmental pollution.There-fore,it is of great significance to explore a new biosynthetic route.Recently,the enzymatic synthesis of steroid compounds has been performed more frequently than in the past.In this work,boldenone was produced from androstenedione(AD)in two steps by a dual-enzyme cascade of 17β-hydroxysteroid dehydrogenase(17β-HSD)and 3-sterone-Δ^(1)-dehydrogenase(KstD).The conversion efficiency of three isoenzymes of 17β-HSD from Mycobacterium sp.LY-1 for substrate AD was first analyzed.After that,the 17β-HSD2 with high selectivity and specificity for AD was screened and co-expressed with KstD3 in Escherichia coli BL21 to construct a dual-enzyme catalytic system.The results showed that the synthesis of boldenone from AD could be achieved by constructing the dual-enzyme expression system of 17β-HSD and KstD,as we determined that the concentration of boldenone reached 24.3 mg/L.To further improve the synthesis efficiency of boldenone,the expression conditions of the dual-enzyme system were optimized,and the concentration of boldenone reached 31.9 mg/L.The explora-tion of this route will provide a foundation for the efficient enzymatic synthesis of boldenone.
基金Supported in part by National Key R&D Program of China(2020YFA0406300,2020YFA0406400)National Natural Science Foundation of China(NSFC)(11625523,11635010,11735014,11822506,11835012,11935015,11935016,11935018,11961141012,12022510,12025502,12035009,12035013,12061131003)+16 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramJoint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1732263,U1832207)CAS Key Research Program of Frontier Sciences(QYZDJ-SSW-SLH040)100 Talents Program of CASINPAC and Shanghai Key Laboratory for Particle Physics and CosmologyERC(758462)European Union Horizon 2020 research and innovation programme(Marie Sklodowska-Curie grant agreement No 894790)German Research Foundation DFG(443159800),Collaborative Research Center CRC 1044,GRK 2149Istituto Nazionale di Fisica Nucleare,ItalyMinistry of Development of Turkey(DPT2006K-120470)National Science and Technology fundOlle Engkvist Foundation(200-0605)STFC(United Kingdom)The Knut and Alice Wallenberg Foundation(Sweden)(2016.0157)The Royal Society,UK(DH140054,DH160214)The Swedish Research CouncilU.S.Department of Energy(DE-FG02-05ER41374,DE-SC-0012069)。
文摘The integrated luminosities of data samples collected in the BESⅢ experiment in 2016-2017 at centerof-mass energies between 4.19 and 4.28 GeV are measured with a precision better than 1% by analyzing large-angle Bhabha scattering events.The integrated luminosities of old datasets collected in 2010-2014 are updated by considering corrections related to detector performance,offsetting the effect of newly discovered readout errors in the electromagnetic calorimeter,which can haphazardly occur.
基金Supported in part by National Key R&D Program of China(2020YFA0406400,2020YFA0406300)National Natural Science Foundation of China(NSFC)(11635010,11735014,11805086,11835012,11935015,11935016,11935018,11961141012,12022510,12025502,12035009,12035013,12192260,12192261,12192262,12192263,12192264,12192265)+17 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramJoint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1832207)CAS Key Research Program of Frontier Sciences(QYZDJ-SSW-SLH040)100 Talents Program of CASFundamental Research Funds for the Central Universities,Lanzhou University,University of Chinese Academy of SciencesThe Institute of Nuclear and Particle Physics(INPAC)and Shanghai Key Laboratory for Particle Physics and CosmologyERC(758462)European Union's Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement(894790)German Research Foundation DFG(443159800),Collaborative Research Center CRC 1044,GRK 2149Istituto Nazionale di Fisica Nucleare,ItalyMinistry of Development of Turkey(DPT2006K-120470)National Science and Technology fundNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation(B16F640076)STFC(United Kingdom)Suranaree University of Technology(SUT),Thailand Science Research and Innovation(TSRI),and National Science Research and Innovation Fund(NSRF)(160355)The Royal Society,UK(DH140054,DH160214)The Swedish Research CouncilU.S.Department of Energy(DE-FG02-05ER41374)。
文摘From December 2019 to June 2021,the BESⅢ experiment collected approximately 5.85 fb^(−1) of data at center-of-mass energies between 4.61 and 4.95 GeV.This is the highest collision energy BEPCⅡ has reached to date.The accumulated e^(+)e^(−) annihilation data samples are useful for studying charmonium(-like)states and charmed-hadron decays.By adopting a novel method of analyzing the production of A_(c)^(+)A_(c)^(-) pairs in e^(+)e^(−) annihilation,the center-of-mass energies are measured with a precision of 0.6 MeV.Integrated luminosities are measured with a precision of better than 1% by analyzing the events of large-angle Bhabha scattering.These measurements provide important inputs to analyses based on these data samples.
