Achieving long spin coherence times is crucial for quantum precision measurements,and closed-loop control techniques are often employed to accomplish this goal.Here,we demonstrate the impact of closed-loop feedback co...Achieving long spin coherence times is crucial for quantum precision measurements,and closed-loop control techniques are often employed to accomplish this goal.Here,we demonstrate the impact of closed-loop feedback control on nuclear spin precession in a metastability exchange optical pumping(MEOP)-based polarized^(3)He system.We analyze the effects of feedback theoretically and validate our predictions experimentally.With optimized feedback parameters,the spin coherence time T_(2)is extended by an order of magnitude.When the feedback strength surpasses a critical threshold,robust maser oscillations are spontaneously excited,demonstrating remarkable resistance to environmental noise and maintaining stable oscillation.This proof-of-principle experiment highlights the viability of MEOP-based^(3)He spin oscillators,especially in low-frequency domains.The operational simplicity and easy integration associated with MEOP-based systems make them particularly promising for fast,high-precision magnetic field measurements.展开更多
In this paper, the equilibrium properties of spin-1 Blume–Emery–Griffiths model are studied by using constant-coupling approximation. The dipolar and quadrupolar order parameters, the stable, metastable and unstable...In this paper, the equilibrium properties of spin-1 Blume–Emery–Griffiths model are studied by using constant-coupling approximation. The dipolar and quadrupolar order parameters, the stable, metastable and unstable states and free energy of the model are investigated. The states are defined in terms of local minima of the free energy of system. The numerical calculations are presented for several values of exchange interactions on the simple cubic lattice with q = 6.展开更多
This study investigates the development of novel high-entropy alloys(HEAs)with enhanced mechanical properties through an innovative fabrication method of direct energy deposition(DED).The focus is on the creation of m...This study investigates the development of novel high-entropy alloys(HEAs)with enhanced mechanical properties through an innovative fabrication method of direct energy deposition(DED).The focus is on the creation of metastable core-shell precipitation-strengthened HEAs that exhibit a unique multi-stage terrace-like slip wave toughening mechanism,a novel approach to improving both strength and ductility simultaneously.Mechanical testing reveals that the developed HEAs exhibit superior mechanical proper-ties,including high yield strength,ultimate tensile strength,and exceptional ductility.The improvement in these properties is attributed to the multi-stage terrace-like slip wave toughening mechanism activated by the unique microstructural features.This toughening mechanism involves the sequential activation of slip systems,facilitated by the stress concentration around the core-shell precipitates and the subsequent propagation of slip waves across the material.The terrace-like pattern of these slip waves enhances the material's ability to deform plastically,providing a significant toughening effect while maintaining high strength levels.Furthermore,the study delves into the fundamental interactions between the microstruc-tural elements and the deformation mechanisms.It elucidates how the core-shell precipitates and the matrix cooperate to distribute stress uniformly,delay the onset of necking,and prevent premature failure.This synergistic interaction between the microstructural features and the slip wave toughening mecha-nism is central to the remarkable balance of strength and ductility achieved in the HEAs.The introduction of a multi-stage terrace-like slip wave toughening mechanism offers a new pathway to designing HEAs with an exceptional amalgamation of strength and ductility.展开更多
The effect of hot deformation onα-phase precipitation during the subsequent heat treatment,as well as the mechanical properties of TB18 Ti-alloy,was investigated.Results show that the round bar obtained by the dual-p...The effect of hot deformation onα-phase precipitation during the subsequent heat treatment,as well as the mechanical properties of TB18 Ti-alloy,was investigated.Results show that the round bar obtained by the dual-phase field forging of the cast ingot exhibits uniform composition distribution on its cross-section.However,various degrees of deformation are detected at different positions on the cross-section,which is attributed to the characteristics of the forging process.Under the forging condition,the microstructure is mainly composed ofβ-phase matrix and coarsened discontinuous primaryα-phases.After solution and following artificial aging treatment,the primaryα-phases disappear,while needle-like secondaryα-phases precipitate in the matrix.Additionally,dispersed white zones are observed in the samples after aging,which are analyzed to be the precipitation-free zones of secondaryα-phase.Despite a uniform compositional distribution among various regions,these dispersed white zones exhibit higher content and larger size in the positions that have undergone lower forging deformation.It indicates that the insufficient forging deformation inhibits the precipitation of the secondaryα-phase,ultimately resulting in the lower strengthening effect by heat treatment.Thus,consistent with the characteristics of the forging process,a periodic variation of sample in strength is detected along the circumferential direction of the forged round bar.展开更多
High-pressure β-Sn germanium may transform into diverse metastable allotropes with distinctive nanostructures and unique physical properties via multiple pathways under decompression.However,the mechanism and transit...High-pressure β-Sn germanium may transform into diverse metastable allotropes with distinctive nanostructures and unique physical properties via multiple pathways under decompression.However,the mechanism and transition kinetics remain poorly understood.Here,we investigate the formation of metastable phases and nanostructures in germanium via controllable transition pathways of β-Sn Ge under rapid decompression at different rates.High-resolution transmission electron microscopy reveals three distinct metastable phases with the distinctive nanostructures:an almost perfect st12 Ge crystal,nanosized bc8/r8 structures with amorphous boundaries,and amorphous Ge with nanosized clusters (0.8–2.5 nm).Fast in situ x-ray diffraction and x-ray absorption measurements indicate that these nanostructured products form in certain pressure regions via distinct kinetic pathways and are strongly correlated with nucleation rates and electronic transitions mediated by compression rate,temperature,and stress.This work provides deep insight into the controllable synthesis of metastable materials with unique crystal symmetries and nanostructures for potential applications.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.U2230207)。
文摘Achieving long spin coherence times is crucial for quantum precision measurements,and closed-loop control techniques are often employed to accomplish this goal.Here,we demonstrate the impact of closed-loop feedback control on nuclear spin precession in a metastability exchange optical pumping(MEOP)-based polarized^(3)He system.We analyze the effects of feedback theoretically and validate our predictions experimentally.With optimized feedback parameters,the spin coherence time T_(2)is extended by an order of magnitude.When the feedback strength surpasses a critical threshold,robust maser oscillations are spontaneously excited,demonstrating remarkable resistance to environmental noise and maintaining stable oscillation.This proof-of-principle experiment highlights the viability of MEOP-based^(3)He spin oscillators,especially in low-frequency domains.The operational simplicity and easy integration associated with MEOP-based systems make them particularly promising for fast,high-precision magnetic field measurements.
文摘In this paper, the equilibrium properties of spin-1 Blume–Emery–Griffiths model are studied by using constant-coupling approximation. The dipolar and quadrupolar order parameters, the stable, metastable and unstable states and free energy of the model are investigated. The states are defined in terms of local minima of the free energy of system. The numerical calculations are presented for several values of exchange interactions on the simple cubic lattice with q = 6.
文摘This study investigates the development of novel high-entropy alloys(HEAs)with enhanced mechanical properties through an innovative fabrication method of direct energy deposition(DED).The focus is on the creation of metastable core-shell precipitation-strengthened HEAs that exhibit a unique multi-stage terrace-like slip wave toughening mechanism,a novel approach to improving both strength and ductility simultaneously.Mechanical testing reveals that the developed HEAs exhibit superior mechanical proper-ties,including high yield strength,ultimate tensile strength,and exceptional ductility.The improvement in these properties is attributed to the multi-stage terrace-like slip wave toughening mechanism activated by the unique microstructural features.This toughening mechanism involves the sequential activation of slip systems,facilitated by the stress concentration around the core-shell precipitates and the subsequent propagation of slip waves across the material.The terrace-like pattern of these slip waves enhances the material's ability to deform plastically,providing a significant toughening effect while maintaining high strength levels.Furthermore,the study delves into the fundamental interactions between the microstruc-tural elements and the deformation mechanisms.It elucidates how the core-shell precipitates and the matrix cooperate to distribute stress uniformly,delay the onset of necking,and prevent premature failure.This synergistic interaction between the microstructural features and the slip wave toughening mecha-nism is central to the remarkable balance of strength and ductility achieved in the HEAs.The introduction of a multi-stage terrace-like slip wave toughening mechanism offers a new pathway to designing HEAs with an exceptional amalgamation of strength and ductility.
基金Qin Chuangyuan Cites High-Level Innovation,Entrepreneurship Talent Project(QCYRCXM-2023-003)Innovation Capability Support Program of Shaanxi(2022KJXX-84)。
文摘The effect of hot deformation onα-phase precipitation during the subsequent heat treatment,as well as the mechanical properties of TB18 Ti-alloy,was investigated.Results show that the round bar obtained by the dual-phase field forging of the cast ingot exhibits uniform composition distribution on its cross-section.However,various degrees of deformation are detected at different positions on the cross-section,which is attributed to the characteristics of the forging process.Under the forging condition,the microstructure is mainly composed ofβ-phase matrix and coarsened discontinuous primaryα-phases.After solution and following artificial aging treatment,the primaryα-phases disappear,while needle-like secondaryα-phases precipitate in the matrix.Additionally,dispersed white zones are observed in the samples after aging,which are analyzed to be the precipitation-free zones of secondaryα-phase.Despite a uniform compositional distribution among various regions,these dispersed white zones exhibit higher content and larger size in the positions that have undergone lower forging deformation.It indicates that the insufficient forging deformation inhibits the precipitation of the secondaryα-phase,ultimately resulting in the lower strengthening effect by heat treatment.Thus,consistent with the characteristics of the forging process,a periodic variation of sample in strength is detected along the circumferential direction of the forged round bar.
基金supported by the National Nature Science Foundation of China(NSFC)(Grant No.11974033)Xuqiang Liu acknowledges support from the National Postdoctoral Foundation Project of China under Grant No.GZC20230215+2 种基金the National Nature Science Foundation of China under Grants No.12404001The XRD measurements at room and high temperatures were performed at the 4W2 HPStation of the Beijing Synchrotron Radiation Facility(BSRF)and beamline 15U1 of the Shanghai Synchrotron Radiation Facility(SSRF)In situ high-pressure,low-temperature XRD measurements were conducted at sector 16 ID-B,HPCAT of the Advanced Photon Source,and were supported by DOE-NNSA under Award No.DE-NA0001974.
文摘High-pressure β-Sn germanium may transform into diverse metastable allotropes with distinctive nanostructures and unique physical properties via multiple pathways under decompression.However,the mechanism and transition kinetics remain poorly understood.Here,we investigate the formation of metastable phases and nanostructures in germanium via controllable transition pathways of β-Sn Ge under rapid decompression at different rates.High-resolution transmission electron microscopy reveals three distinct metastable phases with the distinctive nanostructures:an almost perfect st12 Ge crystal,nanosized bc8/r8 structures with amorphous boundaries,and amorphous Ge with nanosized clusters (0.8–2.5 nm).Fast in situ x-ray diffraction and x-ray absorption measurements indicate that these nanostructured products form in certain pressure regions via distinct kinetic pathways and are strongly correlated with nucleation rates and electronic transitions mediated by compression rate,temperature,and stress.This work provides deep insight into the controllable synthesis of metastable materials with unique crystal symmetries and nanostructures for potential applications.
