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Topological phases of a non-Hermitian coupled SSH ladder

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Chinese Physics B 2019年第10期28卷 269-273页

作者： J S liu Y z Han C S liu Hebei Key Laboratory of Microstructural Material Physics School of Science Yanshan University

we study topological phases of a non-Hermitian coupled Su-Schrieffer-Heeger(SSH) ladder. The model originates from the brick-wall lattices in the two-row limit. The Hamiltonian can be brought into block off-diagonal form and the winding number can be defined with the determine of the block off-diagonal matrix. we find the determine of the offdiagonal matrix has nothing to do with the interleg hopping of the ladder. So the topological phases of the model are the same as those of the chains. Further numerical simulations verify the analysis.

关键词： topological phase non-Hermitian Su-Schrieffer-Heeger(SSH) ladder winding number

A new way to construct topological invariants of non-Hermitian systems with the non-Hermitian skin effect

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Chinese Physics B 2020年第1期29卷 119-123页

作者： J S liu Y z Han C S liu Hebei Key Laboratory of Microstructural Material Physics School of ScienceYanshan UniversityQinhuangdao 066004China

The non-Hermitian skin effect breaks the conventional bulk–boundary correspondence and leads to non-Bloch topological *** by the fact that the topological protected zero modes are immune to perturbations,we construct a partner of a non-Hermitian system by getting rid of the non-Hermitian skin *** adjusting the imbalance hopping,we find that the existence of zero-energy boundary states still dictate the bulk topological invariants based on the band-theory *** non-Hermitian Su–Schrieffer–Heeger(SSH)models are used to illuminate the ***,we obtain the winding numbers in analytical form without the introduction of the generalized Brillouin *** work gives an alternative method to calculate the topological invariants of non-Hermitian systems.

关键词： non-Hermitian skin effect Su–Schrieffer–Heeger(SSH)model bulk–boundary correspondence topological invariant

Reversal of radial glow distribution in helicon plasma induced by reversed magnetic field

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Plasma Science and Technology 2017年第2期19卷 15-19页

作者： Y wANG G zHAO C NIU z.w.liu J T OUYANG Q CHEN School of Physics Beijing institute of technology Beijing 100081 People＇s Republic of China Laboratory of Plasma Physics ＆ Materials Beijing Institute of Graphic Communication Beijing 102600 People＇s Republic of China

In this work, the reversal of radial glow distribution induced by reversed magnetic field is reported. Based on the Boswell antenna which is symmetric and insensitive to the magnetic field direction, it seems such a phenomenon in theory appears impossible. However, according to the diagnostic of the helicon waves by magnetic probe, it is found that the direction of magnetic field significantly affects the propagation characteristic of helicon waves, i.e., the interchange of the helicon waves at the upper and the lower half of tube was caused by reversing the direction of magnetic field. It is suggested that the variation of helicon wave against the direction of magnetic field causes the reversed radial glow distribution. The appearance of the traveling wave does not only improve the discharge strength, but also determines the transition of the discharge mode.

关键词： helicon plasma reversal of radial glow distribution the direction of magnetic field

Magnetization reversal of antiferromagnetically coupled perpendicular anisotropy films driven by current

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Journal of Materials Science & Technology 2018年第5期34卷 832-835页

作者： X.T.zhao Y.Q.zhao w.liu z.M.Dai T.T.wang X.G.zhao z.D.zhang Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

By inserting an ultrathin Pt layer at Co/Ru interface,we established antiferromagnetic coupling with outof-plane magnetization in Co/Ru/Co film stacks fabricated by *** achieve configuration suitable for free layer,the magnetic properties of the stacks have been investigated by changing the thickness of Co,Ru and Pt layers using an orthogonal wedges *** is found that magnetic properties for upper Co layer thinner than 0.5 nm are sensitive to little change in Ru *** continuity of upper Co layer by slightly increasing the thickness can effectively increase the squareness of minor *** switching magnetization of synthetic antiferromagnetic（SAF） structure is achieved by DC current under an in-plane static magnetic field of ± 500 *** structure is very promising for free layer in spintronic application.

关键词： Magnetic materials Multilayer structure wedge Exchange coupling Antiferromagnetic

A practical model for efficient anti-fatigue design and selection of metallic materials:Ⅰ.Model building and fatigue strength prediction

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Journal of Materials Science & Technology 2021年第11期70卷 233-249页

作者： R.liu P.zhang z.J.zhang B.wang z.F.zhang Laboratory of Fatigue and Fracture for Materials Shi-changxu Innovation Center for Advanced MaterialsInstitute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China

The high cost and low efficiency of fatigue tests are bottleneck problem for the anti-fatigue design of metallic *** this problem,a theoretical fatigue model is proposed in this study,the possible applications have also been *** results would be introduced in two serial papers,in which the first paper focuses on the model building and the applications on fatigue strength prediction;the second paper put emphasis on the influencing factors of the model parameters and the applications on fatigue strength *** this first paper,a theoretical model is proposed considering both the strength and plastic restrictions of fatigue *** the model builds up a brief relationship among yield strength(Y),tensile strength(T)and fatigue strength(F),it is named as the Y-T-F *** the verification with fatigue strength data covering various kinds of metallic materials and loading conditions,this Y-T-F model exhibits both generality and *** the Y-T-F model,the efficient fatigue strength prediction could be conducted by brief linear fitting and calculation,just through yield strength,tensile strength and several known fatigue strength ***,through its deduced Y-F model,the analytical formula of fatigue strength continuously changing with materials strengthening can be obtained,as well as the maximum value of fatigue strength and corresponding critical yield *** summary,the Y-T-F model would be useful for reducing the fatigue tests,thus providing new possibilities on the efficient anti-fatigue design and selection of metallic materials.

关键词： Yield strength Tensile strength Plasticity Fatigue strength Anti-fatigue design

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Microscopic stresses in carbon nanotube reinforced aluminum matrix composites determined by in-situ neutron diffraction

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Journal of Materials Science & Technology 2020年第19期54卷 58-68页

作者： X.X.zhang J.F.zhang z.Y.liu w.M.Gan M.Hofmann H.Andrä B.L.Xiao z.Y.Ma Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China German Engineering Materials Science Centre at MLz Helmholtz-Zentrum GeesthachtD-85747 GarchingGermany Heinz Maier-Leibnitz zentrum(MLz) Technische Universität MünchenD-85747 GarchingGermany Fraunhofer Institute for Industrial Mathematics Fraunhofer-Platz 1Kaiserslautern 67663Germany

One of the most desired strengthening mechanisms in the carbon nanotube reinforced aluminum matrix composites(CNT/Al)composites is the load transfer strengthening mechanism(LTSM).However,a fundamental issue concerning the LTSM is that quantitative measurements of load partitioning in these composites during loading are very *** this study,in-situ neutron diffraction study on the tensile deformation of the 3 vol.%CNT/2009 Al composite and the unreinforced 2009 Al alloy was ***{311}and{220}diffraction elastic constants(DECs)of the 2009 Al alloy were *** those DECs the average stress in the 2009 Al matrix of the composite was *** the average stress in the CNTs was separated by using the stress equilibrium *** homogenization models were also applied to explain the stress evolution in each *** results agree with experimental *** the present case,the average stress in the CNTs reaches 1630 MPa at the yield strength of the composite based on linear regression of the measured data,which leads to an increment of yield strength by about 37 *** the result of this work,an approach to quantify load partitioning in the CNTs is developed for the CNT/Al composites,which can be applied to optimize the mechanical properties of the composites.

关键词： Carbon nanotubes Aluminum matrix composites In-situ neutron diffraction Load partitioning

Non-monotonic temperature evolution of nonlocal structure–dynamics correlation in Cuzr glass-forming liquids

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Chinese Physics B 2021年第7期30卷 370-375页

作者： w J Jiang M z Li Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials&Micro-nano Devices Renmin University of ChinaBeijing 100872China

The structure–dynamics correlations in a nonlocal manner were investigated in Cuzr metallic glass-forming liquids via classical molecular dynamics simulations.A spatial coarse-graining approach was employed to incorporate the nonlocal structural information of given structural order parameters in the structure–dynamics *** is found that the correlation between structure order parameters and dynamics increases with increasing coarse-graining length and has a characteristic length ***,the characteristic correlation length exhibits a non-monotonic temperature evolution as temperature approaches glass transition temperature,which is not sensitive to the considered structure order *** results unveil a striking change in the structure–dynamics correlation,which involves no fitting theoretical *** findings provide new insight into the structure–dynamics correlation in glass transition.

关键词： metallic glass-forming liquid structure–dynamics correlation molecular dynamics simulation

Diagnosing the Dynamic and Thermodynamic Effects for the Exceptional 2020 Summer Rainy Season in the Yangtze River Valley

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Journal of Meteorological Research 2022年第1期36卷 26-36页

作者： Na wEN Shujie liu Laurent z.X.LI College of Atmospheric Sciences Nanjing University of Information Science&TechnologyNanjing 210044China Key Laboratory of Meteorological Disaster of Ministry of Education Nanjing University of Information Science&TechnologyNanjing 210044China Qingdao Engineering Technology Research Center for Meteorological Disaster Prevention Qingdao Meteorological BureauQingdao 266003China Laboratoire de Météorologie Dynamique Centre National de la Recherche ScientifiqueSorbonne UniversitéEcole Normale SupérieureEcole PolytechniqueParis 75252France

An exceptional rainy season occurred in the Yangtze River valley of eastern China in June-July *** relative importance of the dynamic and thermodynamic effects on this unusual event is evaluated through the budget equations of moisture and moist static energy(MSE).The moisture budget analysis suggests that the thermodynamic effect contributes to the precipitation anomaly by 8.5%through the advection of abnormal water vapor by mean vertical motion,while the dynamic effect,related to water vapor advection by anomalous vertical motion,has the dominant *** MSE budget analysis further reveals that the anomalous vertical motion is both constrained by the dynamic effect related to changes in atmospheric circulation and the thermodynamic effect related to changes of the atmospheric thermal state,with a ratio of thermodynamic versus total effects estimated at 45.3%.The dynamic effect is linked to the advection of warm and humid air by the abnormal southwesterly wind,which is related with an anomalous anticyclone over the Philippine *** thermodynamic effect is partly induced by the positive advection of anomalous MSE(mainly latent energy)by the mean vertical *** analysis of the dynamic and thermodynamic effects is useful to understand the underlying physical mechanisms leading to the unusual rainy season in the Yangtze River valley in summer *** is also helpful to put forward a few speculations on the potential role of global warming whose primary effect is,after all,to change the thermal state of the atmosphere.

关键词： exceptional rainfall Yangtze River valley global warming dynamic and thermodynamic effects

Synthesis of Single-Crystal TiO_2 Nanowire Using Titanium Monoxide Powder by Thermal Evaporation

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Journal of Materials Science & Technology 2012年第5期28卷 385-390页

作者： z.G.Shang z.Q.liu P.J.Shang J.K.Shang Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

TiO 2 nanowires were synthesized successfully in a large quantity by thermal evaporation using titanium monoxide powder as precursor. X-ray diffraction results showed that all the products were pure rutile phase of TiO 2 . According to microstructural observations, the nanowires have two typical morphologies, a long straight type and a short tortuous type. The straight nanowires were obtained at a wide temperature range of 900–1050 ℃, while the tortuous ones were formed below 900 ℃. Transmission electron microscopy characterization revealed that both the straight and the tortuous nanowires are single-crystal rutile TiO 2 . The preferential growth direction of the nanowires was determined as [110] orientation according to electron diffraction and high-resolution image analyses. The morphological change of TiO 2 nanowires was discussed by considering the different atomic diffusion rates of Ti atoms caused by the phase transformation in Ti substrate at around 900 ℃.

关键词： Rutile-TiO 2 Alloy nanowires Transmission electron microscopy (TEM) characterization Crystal structure identification Growth mechanism Thermal evaporation