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On Mathematical Aspects of the Theory of Topological Insulators

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Acta Mathematica Sinica,English Series 2024年第1期40卷 81-106页

作者： Innocenti MARESIN armen SERgEEV Egor TEPLYAKOV Department of Complex Analysis Steklov Mathematical Institute119991Gubkina 8MoscowRussia Moscow Institute of Physics and Technology 141701Institute per.9DolgoprudnyMoscow RegionRussia

This review is devoted to one of the most interesting and actively developing fields in condensed matter physics—theory of topological *** from its importance for theoretical physics,this theory enjoys numerous connections with modern mathematics,in particular,with topology and homotopy theory,Clifford algebras,K-theory and non-commutative *** the physical point of view topological invariance is equivalent to adiabatic *** insulators are characterized by the broad energy gap,stable under small deformations,which motivates application of topological methods.A key role in the study of topological ob jects in the solid state physics is played by their symmetry *** are three main types of symmetries—time reversion symmetry,preservation of the number of particles(charge symmetry)and PH-symmetry(particle-hole symmetry).Based on the study of symmetry groups and representation theory of Clifford algebras Kitaev proposed a classification of topological ob jects in solid state *** this review we pay special attention to the topological insulators invariant under time reversion.

关键词： Topological insulators Bloch theory fermionic Fock spaces Kramers degeneration Maiorana states

gIANT ANHYSTERETIC RESPONSE OF FERROELECTRIC SOLID SOLUTIONS WITH MORPHOTROPIC BOUNDARIES: THE ROLE OF POLAR ANISOTROPY

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Acta Mechanica Solida Sinica 2012年第4期25卷 429-440页

作者： Yong Ni armen g. khachaturyan CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern Mechanics University of Science and Technology of China Hefei 230026 China Department of Materials Science&Engineering Rutgers University 607 Taylor Road Piscataway NJ 08854 USA

Computer modeling and simulation for the Pb（Zr1-x Tix ）O3 （PZT） system reveal the role of polar anisotropy on the giant anhysteretic response and structural properties of morphotropic phase boundary （MPB） ferroelectrics. It is shown that a drastic reduction of the compositiondependent polar anisotropy near the MPB flattens energy surfaces and thus facilitates reversible polarization rotation. It is further shown that the polar anisotropy favors formation of polar domains, promotes phase decomposition and results in a two-phase multidomain state, which response to applied electric field is anhysteretic when the polar domain reorientation is only caused by polarization rotation other than polar domain wall movement. This is the case for the decomposing ferroelectrics under a poling electric field with the formation of a two-phase multidomain microstructure, wherein most domain walls are pinned at the two-phase boundaries. Indication of the microstructure dependence of the anhysteretic strain response opens new avenues to improve the piezoelectric properties of these materials through the microstructure engineering.

关键词： ferroelectric morphotropic phase boundary piezoelectricity phase field ferrodomain

Quasiparticle approach to diffusional atomic scale self-assembly of complex structures: from disorder to complex crystals and double-helix polymers

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npj Computational Materials 2016年第1期2卷 256-264页

作者： Mykola Lavrskyi Helena Zapolsky armen g.khachaturyan gPM UMR 6634University of RouenSaint-Etienne du RouvrayFrance Department of Materials Science&Engineering Rutgers UniversityPiscatawayNJUSA Department of Materials Science&Engineering University of CaliforniaBerkeleyBerkeleyCAUSA

A self-organisation is an universal phenomenon in nature and,in particular,is highly important in materials *** goal was to develop a new theory that provides a computationally effective approach to this *** this paper a quasiparticle theory of a diffusional self-organisation of atoms in continuum space during the diffusional time scale has been *** became possible due to two novelties,a concept of quasiparticles,fratons,used for a description of dynamic degrees of freedom and model Hamiltonian taking into account a directionality,length and strength of interatomic *** illustrate a predictive power and achievable level of complexity of self-assembled structures,the challenging cases of self-assembling of the diamond,zinc-blende,helix and double-helix structures,from a random atomic distribution,have been successfully *** approach opens a way to model a self-assembling of complex atomic and molecular structures in the atomic scale during diffusional time.

关键词： diffusion helix particle

gate-controlled supercurrent effect in dry-etched Dayem bridges of non-centrosymmetric niobium rhenium

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Nano Research 2024年第7期17卷 6575-6581页

作者： Jennifer Koch Carla Cirillo Sebastiano Battisti Leon Ruf Zahra Makhdoumi Kakhaki Alessandro Paghi armen gulian Serafim Teknowijoyo giorgio De Simoni Francesco giazotto Carmine Attanasio Elke Scheer Angelo Di Bernardo Department of Physics University of KonstanzUniversitätsstraße 1078464 KonstanzGermany CNR-Spin c/o Universitàdegli Studi di Salernovia Giovanni Paolo II 13284084 Fisciano(SA)Italy NEST Istituto Nanoscienze-CNR and Scuola Normale SuperiorePiazza San Silvestro 1256127 PisaItaly Dipartimento di Fisica“E.R.Caianiello” Universitàdegli Studi di SalernoVia Giovanni Paolo II 13284084 Fisciano(SA)Italy Advanced Physics Laboratory Institute for Quantum StudiesChapman UniversityBurtonsvilleMD 20866USA

The application of a gate voltage to control the superconducting current flowing through a nanoscale superconducting constriction,named as gate-controlled supercurrent(gCS),has raised great interest for fundamental and technological *** gain a deeper understanding of this effect and develop superconducting technologies based on it,the material and physical parameters crucial for the gCS effect must be ***-down fabrication protocols should also be optimized to increase device scalability,although studies suggest that top-down fabricated devices are more resilient to show a ***,we investigate gated superconducting nanobridges made with a top-down fabrication process from thin films of the noncentrosymmetric superconductor niobium rhenium with varying ratios of the constituents(NbRe).Unlike other devices previously reported and made with a top-down approach,our NbRe devices systematically exhibit a gCS effect when they were fabricated from NbRe thin films with small grain size and etched in specific *** observations pave the way for the realization of top-down-made gCS devices with high *** results also imply that physical parameters like structural disorder and surface physical properties of the nanobridges,which can be in turn modified by the fabrication process,are crucial for a gCS observation,providing therefore also important insights into the physics underlying the gCS effect.

关键词： superconductivity non-centrosymmetric superconductors superconducting devices gated devices gate-controlled supercurrent top-down fabrication

Challenges and opportunities in the production of magnesium parts by directed energy deposition processes

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Journal of Magnesium and Alloys 2024年第5期12卷 1663-1686页

作者： gürel Cam Ali günen Iskenderun Technical University Faculty of Engineering and Natural SciencesDepartment of Mechanical Engineering31200 Iskenderun-HatayTurkey Iskenderun Technical University Faculty of Engineering and Natural SciencesDepartment of Metallurgy and Materials Engineering31200 Iskenderun-HatayTurkey

Mg-alloys have gained considerable attention in recent years for their outstanding properties such as lightweight,high specific strength,and corrosion resistance,making them attractive for applications in medical,aerospace,automotive,and other transport ***,their widespread application is hindered by their low formability at room temperature due to limited slip *** Mg-alloys have low mechanical properties due to the presence of casting defects such as porosity and anisotropy in addition to the high *** casting methods benefit from established process optimization techniques for these problems,additive manufacturing methods are increasingly replacing casting methods in Mg alloys as they provide more precise control over the microstructure and allow specific grain orientations,potentially enabling easier optimization of anisotropy properties in certain *** metal additive manufacturing(MAM)technology also results in some manufacturing defects such as inhomogeneous microstructural evolution and porosity and additively manufactured Mg alloy parts exhibit lower properties than the wrought parts,they in general exhibit superior properties than the cast ***,MAM is a promising technique to produce Mg alloy *** energy deposition processes,particularly wire arc directed energy deposition(WA-DED),have emerged as an advantageous additive manufacturing(AM)technique for metallic materials including magnesium alloys,offering advantages such as high deposition rates,improved material efficiency,and reduced production costs compared to subtractive ***,the inherent challenges associated with magnesium,such as its high reactivity and susceptibility to oxidation,pose unique hurdles in the application of this *** review paper delves into the progress made in the application of DED technology to Mg-alloys,its challenges,and ***,the predominant imperfections,notably inhomo

关键词： Additive manufacturing DED processes Arc-DED Wire arc additive manufacturing(WAAM) 3-D printing High deposition rate

Recent research in mechanical properties of geopolymer-based ultrahigh-performance concrete:A review

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Defence Technology（防务技术） 2024年第2期32卷 67-88页

作者： g.Murali Division of Research&Innovation Uttaranchal UniversityDehradun 248007India

Due to the growing need for sustainable and ultra-high-strength construction materials,scientists have created an innovative ultra-high-performance concrete called geopolymer based ultra-highperformance concrete(gUHPC).Besides,in the last few decades,there have been a lot of explosions and ballistic attacks around the world,which have killed many civilians and fighters in border *** this context,this article reviews the fresh state and mechanical properties of ***,the ingredients of gUHPC and fresh properties such as setting time and flowability are briefly ***,the review of compressive strength,flexure strength,tensile strength and modulus of elasticity of fibrous ***,the blast and projectile impact resistance performance was ***,the microstructural characteristics were reviewed using the scanning electron microscope and X-ray Powder *** review outcome reveals that the mechanical properties were increased when 30%silica fume was added to a higher dose of steel fibre to improve the microstructure of *** is hypothesized that the brittleness of gUHPC was mitigated by adding 1.5%steel fibre reinforcement,which played a role in the decrease of contact explosion cratering and *** the need for cement in gUHPC was a key factor in the review,indicating a promising potential for lowering carbon ***,gUHPC research is still in its early stages,so more study is required before its full potential can be utilized.

关键词： Mechanical properties Blast Projectile impact Fibre geopolymer Silica fume Alkaline activators

Nitrogen mineralization in the oldest climax communities in the eastern Mediterranean region

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Journal of Forestry Research 2024年第1期35卷 213-228页

作者： Fatma Selcen Sakar gürcan güleryüz Department of Biology Section Ecology GörükleGraduate School of Natural and Applied ScienceUniversity of Bursa Uludağ16059 NilüferBursaTurkey Department of Biology Section Ecology GörükleFaculty of Science and ArtsUniversity of Bursa Uludağ16059 NilüferBursaTurkey

In this study,we investigated how tree species affect N mineralization in connection to some soil properties and seconder metabolite levels of litter,in the soil of the old-est native forest *** the oldest pure communi-ties of Pinus nigra(PN),Fagus orientalis(FO),and Abies bornmuelleriana(AB)in the mountain range of Mount Uludağ,Bursa,Turkey,annual net yield and N mineraliza-tion in the 0-5-and 5-20-cm soil layers were determined in a field incubation study over 1 *** locations were chosen from 1300 to 1600 m a.s.l.,and moisture content(%),pH,water-holding capacity(%),organic C,total N,and C/N ratio,and annual net mineral N yield of the soil and hydro-lyzed tannic acid and total phenolic compounds in litter were compared for these forest *** had the highest annual net Nmin yield(43.9±4.8 kg ha^(-1) a^(-1)),*** the lowest(30.5±4.2 kg ha^(-1) a^(-1)).Our findings show that in the oldest forest ecosystems,the seasonal soil moisture content and tree species play an essential role in N cycling and that hydrolyzed tannic acids and total phenolic compounds effectively control N *** acid and total phenolics in the litter were found to inhibit nitrification,but total phenolics were found to stimulate ammonification.

关键词： Oldest forest communities Nitrogen mineralization Nitrification Tannic acid Total phenolic Litter

Adiabatic paths and pseudoholomorphic curves

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Science China Mathematics 2005年第z1期48卷 168-179页

作者： armen g.Sergeev Steklov Mathematical Institute gubkina 8 Moscow119991GSP-1Russia

We consider the (2+1)-dimensional Abelian Higgs model, governed by the ginzburg-Landau action functional and describe the adiabatic limit construction for this model. Then we switch to the 4-dimensional case and Show that the Taubes correspondence may be considered as a (2+2)-dimensional analogue of the adiabatic limit construction.

关键词： adiabatic path, ginzburg-Landau equation, Seiberg-Witten equation.

Shell-model representations of the microscopic version of the Bohr-Mottelson collective model

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Communications in Theoretical Physics 2024年第8期76卷 79-90页

作者： H g ganev Joint Institute for Nuclear Research DubnaRussia Institute of Mechanics Bulgarian Academy of SciencesSofiaBulgaria

The structure of the irreducible collective spaces of the group Sp(12,R),which many-particle nuclear states are classified according to the chain Sp(12,R)⊃U(6)⊃SO(6)⊃SU_(pn)(3)⊗SO(2)⊃SO(3)of the proton-neutron symplectic model(PNSM),is considered in *** chain of the PNSM was recently shown to correspond to a microscopic shell-model version of the Bohr-Mottelson collective *** construction of the relevant shell-model representations of the Sp(12,R)group along this chain is considered for three nuclei with varying collective properties and from different mass *** is shown that the SU_(pn)(3)basis states of the Sp(12,R)representations belonging to the SO(6)irreps with seniorityυ≥υ0,withυ0 denoting the maximal seniority SO(6)irrep contained in the Sp(12,R)bandhead,are always Pauli allowed,but organized in a different way into different SO(6)*** is in contrast to the case of filling the levels of the standard three-dimensional harmonic oscillator and using the plethysm *** the SU_(pn)(3)multiplets withinυ<υ0 are not all Pauli forbidden,it is safe to discard *** results obtained in the present work are important for the practical application of the microscopic version of the Bohr-Mottelson collective model.

关键词： microscopic shell-model version of the Bohr-Mottelson model proton-neutron symplectic model Sp(12,R)dynamical algebra shell-model representations