The Mg-Gd-Y-Zn-Zr alloys are representational and potential age-hardening systems as reported in the past ten years,but their mechanical properties are still dependent on the grain size and its distribution.The effect...The Mg-Gd-Y-Zn-Zr alloys are representational and potential age-hardening systems as reported in the past ten years,but their mechanical properties are still dependent on the grain size and its distribution.The effect of bimodal structure on mechanical properties of Mg-8Gd-3Y-0.5Zr alloy with bimodal grain size distributions was investigated.The results suggested that the volume fraction of fine grain(FG)and coarse grain(CG)could be controlled by combined processes of hot forging,extrusion and annealing.And for the present alloys with bimodal grain size distribution,the improvement of strength is still attributed to the grain refinement.The morphology of bimodal grain size distribution has a marked impact on the ductility of the alloy,i.e.with the increase of coarse grain volume fraction,the elongation to failure increases at the beginning and then decreases.The mechanism of the toughening effect of bimodal grain size distribution on the Mg-Gd-Y-Zn-Zr alloys with bimodal grain size structure has been discussed.展开更多
Symmetry plays fundamental role in physics and the nature of symmetry changes in non-Hermitian physics.Here the symmetry-protected scattering in non-Hermitian linear systems is investigated by employing the discrete s...Symmetry plays fundamental role in physics and the nature of symmetry changes in non-Hermitian physics.Here the symmetry-protected scattering in non-Hermitian linear systems is investigated by employing the discrete symmetries that classify the random matrices.The even-parity symmetries impose strict constraints on the scattering coefficients:the time-reversal(C and K) symmetries protect the symmetric transmission or reflection;the pseudo-Hermiticity(Q symmetry) or the inversion(P) symmetry protects the symmetric transmission and reflection.For the inversion-combined time-reversal symmetries,the symmetric features on the transmission and reflection interchange.The odd-parity symmetries including the particle-hole symmetry,chiral symmetry,and sublattice symmetry cannot ensure the scattering to be symmetric.These guiding principles are valid for both Hermitian and non-Hermitian linear systems.Our findings provide fundamental insights into symmetry and scattering ranging from condensed matter physics to quantum physics and optics.展开更多
Hermitian systems possess unitary scattering.However,the Hermiticity is unnecessary for a unitary scattering although the scattering under the influence of non-Hermiticity is mostly non-unitary.Here we prove that the ...Hermitian systems possess unitary scattering.However,the Hermiticity is unnecessary for a unitary scattering although the scattering under the influence of non-Hermiticity is mostly non-unitary.Here we prove that the unitary scattering is protected by certain type of pseudo-Hermiticity and unaffected by the degree of non-Hermiticity.The energy conservation is violated in the scattering process and recovers after scattering.The subsystem of the pseudo-Hermitian scattering center including only the connection sites is Hermitian.These findings provide fundamental insights on the unitary scattering,pseudo-Hermiticity,and energy conservation,and are promising for light propagation,mesoscopic electron transport,and quantum interference in non-Hermitian systems.展开更多
Knot theory provides a powerful tool for understanding topological matters in biology,chemistry,and physics.Here knot theory is introduced to describe topological phases in a quantum spin system.Exactly solvable model...Knot theory provides a powerful tool for understanding topological matters in biology,chemistry,and physics.Here knot theory is introduced to describe topological phases in a quantum spin system.Exactly solvable models with long-range interactions are investigated,and Majorana modes of the quantum spin system are mapped into different knots and links.The topological properties of ground states of the spin system are visualized and characterized using crossing and linking numbers,which capture the geometric topologies of knots and links.The interactivity of energy bands is highlighted.In gapped phases,eigenstate curves are tangled and braided around each other,forming links.In gapless phases,the tangled eigenstate curves may form knots.Our findings provide an alternative understanding of phases in the quantum spin system,and provide insights into one-dimension topological phases of matter.展开更多
We demonstrated stable midinfrared(MIR) optical frequency comb at the 3.0 μm region with difference frequency generation pumped by a high power, Er-doped, ultrashort pulse fiber laser system. A soliton mode-locked161...We demonstrated stable midinfrared(MIR) optical frequency comb at the 3.0 μm region with difference frequency generation pumped by a high power, Er-doped, ultrashort pulse fiber laser system. A soliton mode-locked161 MHz high repetition rate fiber laser using a single wall carbon nanotube was fabricated. The output pulse was amplified in an Er-doped single mode fiber amplifier, and a 1.1–2.2 μm wideband supercontinuum(SC) with an average power of 205 m W was generated in highly nonlinear fiber. The spectrogram of the generated SC was examined both experimentally and numerically. The generated SC was focused into a nonlinear crystal, and stable generation of MIR comb around the 3 μm wavelength region was realized.展开更多
基金supports of the National Key Research and Development Plan(Grant Nos.2016YFB0701201 and 2016YFB0301103)the National Natural Science Foundation of China(Grant Nos.51771109 and 51631006).
文摘The Mg-Gd-Y-Zn-Zr alloys are representational and potential age-hardening systems as reported in the past ten years,but their mechanical properties are still dependent on the grain size and its distribution.The effect of bimodal structure on mechanical properties of Mg-8Gd-3Y-0.5Zr alloy with bimodal grain size distributions was investigated.The results suggested that the volume fraction of fine grain(FG)and coarse grain(CG)could be controlled by combined processes of hot forging,extrusion and annealing.And for the present alloys with bimodal grain size distribution,the improvement of strength is still attributed to the grain refinement.The morphology of bimodal grain size distribution has a marked impact on the ductility of the alloy,i.e.with the increase of coarse grain volume fraction,the elongation to failure increases at the beginning and then decreases.The mechanism of the toughening effect of bimodal grain size distribution on the Mg-Gd-Y-Zn-Zr alloys with bimodal grain size structure has been discussed.
基金Supported by the National Natural Science Foundation of China(Grant Nos.11975128 and 11874225).
文摘Symmetry plays fundamental role in physics and the nature of symmetry changes in non-Hermitian physics.Here the symmetry-protected scattering in non-Hermitian linear systems is investigated by employing the discrete symmetries that classify the random matrices.The even-parity symmetries impose strict constraints on the scattering coefficients:the time-reversal(C and K) symmetries protect the symmetric transmission or reflection;the pseudo-Hermiticity(Q symmetry) or the inversion(P) symmetry protects the symmetric transmission and reflection.For the inversion-combined time-reversal symmetries,the symmetric features on the transmission and reflection interchange.The odd-parity symmetries including the particle-hole symmetry,chiral symmetry,and sublattice symmetry cannot ensure the scattering to be symmetric.These guiding principles are valid for both Hermitian and non-Hermitian linear systems.Our findings provide fundamental insights into symmetry and scattering ranging from condensed matter physics to quantum physics and optics.
基金supported by the National Natural Science Foundation of China(Grant No.11975128)。
文摘Hermitian systems possess unitary scattering.However,the Hermiticity is unnecessary for a unitary scattering although the scattering under the influence of non-Hermiticity is mostly non-unitary.Here we prove that the unitary scattering is protected by certain type of pseudo-Hermiticity and unaffected by the degree of non-Hermiticity.The energy conservation is violated in the scattering process and recovers after scattering.The subsystem of the pseudo-Hermitian scattering center including only the connection sites is Hermitian.These findings provide fundamental insights on the unitary scattering,pseudo-Hermiticity,and energy conservation,and are promising for light propagation,mesoscopic electron transport,and quantum interference in non-Hermitian systems.
基金Supported by the National Natural Science Foundation of China(Grants Nos.11874225,11975128,and 11605094)。
文摘Knot theory provides a powerful tool for understanding topological matters in biology,chemistry,and physics.Here knot theory is introduced to describe topological phases in a quantum spin system.Exactly solvable models with long-range interactions are investigated,and Majorana modes of the quantum spin system are mapped into different knots and links.The topological properties of ground states of the spin system are visualized and characterized using crossing and linking numbers,which capture the geometric topologies of knots and links.The interactivity of energy bands is highlighted.In gapped phases,eigenstate curves are tangled and braided around each other,forming links.In gapless phases,the tangled eigenstate curves may form knots.Our findings provide an alternative understanding of phases in the quantum spin system,and provide insights into one-dimension topological phases of matter.
基金Japan Science and Technology Agency(JST)Japan Agency for Medical Research and Development(AMED)
文摘We demonstrated stable midinfrared(MIR) optical frequency comb at the 3.0 μm region with difference frequency generation pumped by a high power, Er-doped, ultrashort pulse fiber laser system. A soliton mode-locked161 MHz high repetition rate fiber laser using a single wall carbon nanotube was fabricated. The output pulse was amplified in an Er-doped single mode fiber amplifier, and a 1.1–2.2 μm wideband supercontinuum(SC) with an average power of 205 m W was generated in highly nonlinear fiber. The spectrogram of the generated SC was examined both experimentally and numerically. The generated SC was focused into a nonlinear crystal, and stable generation of MIR comb around the 3 μm wavelength region was realized.
