Systemically angular and planar transport investigations are performed in layered antiferromagnetic(AF)V_(5)S_(8).In this AF system,obvious anomalous Hall effect(AHE)is observed with a large Hall angle of 0.1 compared...Systemically angular and planar transport investigations are performed in layered antiferromagnetic(AF)V_(5)S_(8).In this AF system,obvious anomalous Hall effect(AHE)is observed with a large Hall angle of 0.1 compared to that in ferromagnetic(FM)system.It can persist to the temperatures above AF transition and exhibit strong angular field dependence.The phase diagram reveals various magnetic states by rotating the applied field.By analyzing the anisotropic transport behavior,magnon contributions are revealed and exhibit obvious angular dependence with a spin-flop vanishing line.The observed prominent planar Hall effect and anisotropic magnetoresisitivity exhibit two-fold systematical angular dependent oscillations.These behaviors are attributed to the scattering from spin–orbital coupling instead of nontrivial topological origin.Our results reveal anisotropic interactions of magnetism and electron in V5S8,suggesting potential opportunities for the AF spintronic sensor and devices.展开更多
A new metal-organic coordination polymer {[Nd(tci)(H2O)2]·2H2O}n(1) has been synthesized based on the flexible tricarboxylate ligand tris(2-carboxyethyl)isocyanuric acid(H3tci) and structurally characte...A new metal-organic coordination polymer {[Nd(tci)(H2O)2]·2H2O}n(1) has been synthesized based on the flexible tricarboxylate ligand tris(2-carboxyethyl)isocyanuric acid(H3tci) and structurally characterized by single-crystal X-ray diffraction analyses, elemental analysis, infrared spectra(IR), powder X-ray diffraction(PXRD) and thermogravimetric analysis(TGA). Complex 1 crystallizes in triclinic, space group P1 with a = 9.1648(11), b = 9.3326(12), c = 12.440(2) , C(12)H(20)N3O(13) Nd, Mr = 558.55, V = 886.9(2) 3, Z = 2, Dc = 2.092 g·cm-3, μ = 3.006 mm-1, F(000) = 554, 2.56〈θ〈25.00°, λ(Mo Kα) = 0.71073 , T = 293(2) K, the final R = 0.0662 and w R = 0.2071. X-ray diffraction analysis reveals that complex 1 is a two-dimensional layer, which is further assembled into a three-dimensional supramolecular architecture through hydrogen bonding interactions. The structure of complex 1 can be simplified as a rare 2-periodic uninodal {48·62} topology and a non-interpenetrating kgd topology. Furthermore, the thermal stability and photoluminescence property of 1 were investigated.展开更多
We consider a series of benzenoid isomers obtained by attaching fragments to an mradical. Some of their topological properties, such as the number of Kekule patterns and the maximum number of aromatic π-sextets are e...We consider a series of benzenoid isomers obtained by attaching fragments to an mradical. Some of their topological properties, such as the number of Kekule patterns and the maximum number of aromatic π-sextets are established.展开更多
Two-dimensional(2D)topological insulators present a special phase of matter manifesting unique electronic properties.Till now,many monolayer binary compounds of Sb element,mainly with a honeycomb lattice,have been rep...Two-dimensional(2D)topological insulators present a special phase of matter manifesting unique electronic properties.Till now,many monolayer binary compounds of Sb element,mainly with a honeycomb lattice,have been reported as 2D topological insulators.However,research of the topological insulating properties of the monolayer Sb compounds with square lattice is still lacking.Here,by means of the first-principles calculations,a monolayer SbI with square lattice is proposed to exhibit the tunable topological properties by applying strain.At different levels of the strain,the monolayer SbI shows two different structural phases:buckled square structure and buckled rectangular structure,exhibiting attracting topological properties.We find that in the buckled rectangular phase,when the strain is greater than 3.78%,the system experiences a topological phase transition from a nontrivial topological insulator to a trivial insulator,and the structure at the transition point actually is a Dirac semimetal possessing two type-ⅠDirac points.In addition,the system can achieve the maximum global energy gap of 72.5 meV in the topological insulator phase,implying its promising application at room temperature.This study extends the scope of 2D topological physics and provides a platform for exploring the low-dissipation quantum electronics devices.展开更多
In the transport studies of topological insulators, microflakes exfoliated from bulk single crystals are often used because of the convenience in sample preparation and the accessibility to high carrier mobilities. He...In the transport studies of topological insulators, microflakes exfoliated from bulk single crystals are often used because of the convenience in sample preparation and the accessibility to high carrier mobilities. Here, based on finite element analysis, we show that for the non-Hall-bar shaped topological insulator samples, the measured four-point resistances can be substantially modified by the sample geometry, bulk and surface resistivities,and magnetic field. Geometry correction factors must be introduced for accurately converting the four-point resistances to the longitudinal resistivity and Hall resistivity. The magnetic field dependence of inhomogeneous current density distribution can lead to pronounced positive magnetoresistance and nonlinear Hall effect that would not exist in the samples of ideal Hall bar geometry.展开更多
The quantum anomalous Hall(QAH) effect has attracted enormous attention since it can induce topologically protected conducting edge states in an intrinsic insulating material. For practical quantum applications, the m...The quantum anomalous Hall(QAH) effect has attracted enormous attention since it can induce topologically protected conducting edge states in an intrinsic insulating material. For practical quantum applications, the main obstacle is the non-existent room temperature QAH systems, especially with both large topological band gap and robust ferromagnetic order. Here, according to first-principles calculations, we predict the realization of the room temperature QAH effect in a two-dimensional(2D) honeycomb lattice, RuCS_(3) with a non-zero Chern number of C = 1. Especially, the nontrivial topology band gap reaches up to 336 me V for RuCS_(3). Moreover, we find that RuCS_(3) has a large magnetic anisotropy energy(2.065 me V) and high Curie temperature(696 K). We further find that the non-trivial topological properties are robust against the biaxial strain. The robust topological and magnetic properties make RuCS_(3) have great applications in room temperature spintronics and nanoelectronics.展开更多
Research on brain function after brachial plexus injury focuses on local cortical functional reorganization,and few studies have focused on brain networks after brachial plexus injury.Changes in brain networks may hel...Research on brain function after brachial plexus injury focuses on local cortical functional reorganization,and few studies have focused on brain networks after brachial plexus injury.Changes in brain networks may help understanding of brain plasticity at the global level.We hypothesized that topology of the global cerebral resting-state functional network changes after unilateral brachial plexus injury.Thus,in this cross-sectional study,we recruited eight male patients with unilateral brachial plexus injury(right handedness,mean age of 27.9±5.4years old)and eight male healthy controls(right handedness,mean age of 28.6±3.2).After acquiring and preprocessing resting-state magnetic resonance imaging data,the cerebrum was divided into 90 regions and Pearson’s correlation coefficient calculated between regions.These correlation matrices were then converted into a binary matrix with affixed sparsity values of 0.1–0.46.Under sparsity conditions,both groups satisfied this small-world property.The clustering coefficient was markedly lower,while average shortest path remarkably higher in patients compared with healthy controls.These findings confirm that cerebral functional networks in patients still show smallworld characteristics,which are highly effective in information transmission in the brain,as well as normal controls.Alternatively,varied small-worldness suggests that capacity of information transmission and integration in different brain regions in brachial plexus injury patients is damaged.展开更多
One two-dimensional coordination polymer with a formula of {[Cd(L)(imidazole)(H2O)](H2O)}n(1) was obtained by the synthetic reactions in aqueous solution using a newly synthesized H2L(H2L = methyl-3-hydroxy...One two-dimensional coordination polymer with a formula of {[Cd(L)(imidazole)(H2O)](H2O)}n(1) was obtained by the synthetic reactions in aqueous solution using a newly synthesized H2L(H2L = methyl-3-hydroxy-5-carboxy-2-thiophenecarboxylate) ligand.Compound1 crystallizes in monoclinic system,space group C2/c with a = 18.3176(11),b = 8.5366(9),c =8.4152(5)A,β = 101.789(6)°,V = 2797.1(3)A^3,Dc = 1.979 g/cm^3,C(10)H(12)N2O7SCd,Mr = 416.68 F(000) = 1648,μ = 1.745 mm^-1,F(000) = 1648,the final R = 0.0323 and wR = 0.0604 for 2604 observed reflections with I 〉 2s(I).Structure analyses reveal that the compound is constructed by dinuclear Cd(Ⅱ) clusters bridged by two hydroxyl oxygens of L^2-anions,which features a two-dimensional network with 4-connected sql topology.Furthermore,the compound exhibits high thermal stability and intense fluorescent emission,and could be explored for potentia luminescent materials.展开更多
The effect of friction behavior on the compacted density is significant, but the relationship between the topological properties of the contact network and friction behavior during powder compaction remains unclear. B...The effect of friction behavior on the compacted density is significant, but the relationship between the topological properties of the contact network and friction behavior during powder compaction remains unclear. Based on the discrete element method (DEM), a DEM model for die compaction was established, and the Hertz contact model was modified into an elastoplastic contact model that was more suitable for metal-powder compaction. The evolution of the topological properties of the contact network and its mechanism during powder compaction was explored using the elastoplastic contact model. The results demonstrate that the friction behavior between the particles is closely related to the topological properties of the contact network. Side wall friction results in smaller clustering coefficient (CC) and excess contact (EC) in the lower region near the side wall. Corresponding to this phenomenon, the upper region near the side wall has more high-stress particles when the major principal stress threshold was considered, and the CC and EC are significantly higher than those in the other regions. This study provides a theoretical basis for improving powder compaction behavior.展开更多
With the increasingly fierce market competition,manufacturing enterprises have to continuously improve their competitiveness through their collaboration and labor division with each other,i.e.forming manufacturing ent...With the increasingly fierce market competition,manufacturing enterprises have to continuously improve their competitiveness through their collaboration and labor division with each other,i.e.forming manufacturing enterprise collaborative network(MECN)through their collaboration and labor division is an effective guarantee for obtaining competitive advantages.To explore the topology and evolutionary process of MECN,in this paper we investigate an empirical MECN from the viewpoint of complex network theory,and construct an evolutionary model to reproduce the topological properties found in the empirical network.Firstly,large-size empirical data related to the automotive industry are collected to construct an MECN.Topological analysis indicates that the MECN is not a scale-free network,but a small-world network with disassortativity.Small-world property indicates that the enterprises can respond quickly to the market,but disassortativity shows the risk spreading is fast and the coordinated operation is difficult.Then,an evolutionary model based on fitness preferential attachment and entropy-TOPSIS is proposed to capture the features of MECN.Besides,the evolutionary model is compared with a degree-based model in which only node degree is taken into consideration.The simulation results show the proposed evolutionary model can reproduce a number of critical topological properties of empirical MECN,while the degree-based model does not,which validates the effectiveness of the proposed evolutionary model.展开更多
In this research, the hydrogen bonds Y···H-X (X = C, N; Y = N, O) of thymine and uracil have been theoretically studied. The results show that hydrogen bond leads to bond length elongation and stretch...In this research, the hydrogen bonds Y···H-X (X = C, N; Y = N, O) of thymine and uracil have been theoretically studied. The results show that hydrogen bond leads to bond length elongation and stretches the frequency red-shift of N-H···Y. Meanwhile, the C-H···O bonds shorten and stretch the frequency blue-shift. They all belong to traditional hydrogen bonds. The intermolecular charge transfer caused by the intermolecular hyperconjugation s*(N–H) → n(Y) and intramolecular charge redistribution by intramolecular hyperconjugation σ(C-H) →σ*(C-N) play important roles in the formation of hydrogen bonds. According to thejudgment standards proposed by Bader and Popelier, these hydrogen bonds have typical electron density topological properties. Electrostatic surface potential (ESP) is a useful physicochemical property of a molecule that provides insights into inter- and intramolecular associations, as well as the prediction of likely sites of electrophilic and nucleophilic metabolic attack.展开更多
Spintronics involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. The fascinating spin-resolved properties of graphene motivate numerous researchers to study spintron...Spintronics involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. The fascinating spin-resolved properties of graphene motivate numerous researchers to study spintronics in graphene and other two-dimensional(2D) materials. Silicene, the silicon analog of graphene, is considered to be a promising material for spintronics. Here, we present a review of theoretical advances with regard to spin-dependent properties, including the electric field- and exchange field-tunable topological properties of silicene and the corresponding spintronic device simulations.展开更多
A new coordination polymer, [Mn(3,4-pybz)2]n·3(H2O)(1), has been hydrothermally synthesized from Mn Cl2·4H2O and an unsymmetrical 3-pyridin-4-yl-benzoic acid(3,4-Hpybz), and characterized by IR, elemental an...A new coordination polymer, [Mn(3,4-pybz)2]n·3(H2O)(1), has been hydrothermally synthesized from Mn Cl2·4H2O and an unsymmetrical 3-pyridin-4-yl-benzoic acid(3,4-Hpybz), and characterized by IR, elemental analysis, thermogravimetric analysis, and singlecrystal X-ray diffraction. In complex 1, each 3,4-pybz ligand represents a three-connected node to combine with the six-connected Mn(II) ions, generating a 3D binodal(3,6)-connected ant network. In addition, magnetic investigations reveal that complex 1 exhibits an antiferromagnetic behavior. According to the crystal structure, the full-geometrical optimization of complex 1 was carried out by using hybrid DFT methods at the B3LYP/6-31G(d) level. Meantime, the DFT-BS approach was applied to study the magnetic coupling behavior for complex 1, and the result reveals that the calculated exchange coupling constants J were in good agreement with the experimental data.展开更多
Two coordination compounds with a flexible ligand N,N?-diacetic acid imidazolium(HDAM),{[Co(trans-DAM)(bipy)(H2O)2](OH)·4H2O}n 1 and {[Cd(trans-DAM)(bipy)(H2O)](NO3)?2H2O}n 2(bipy = 4,4'-bip...Two coordination compounds with a flexible ligand N,N?-diacetic acid imidazolium(HDAM),{[Co(trans-DAM)(bipy)(H2O)2](OH)·4H2O}n 1 and {[Cd(trans-DAM)(bipy)(H2O)](NO3)?2H2O}n 2(bipy = 4,4'-bipyridine),were prepared and characterized by single-crystal X-ray diffraction.Compound 1 crystallizes in monoclinic,space group P2/n with a = 7.589(6),b = 11.444(2),c = 12.894(3)(A°),β = 90.99(3)°,V = 1119.8(4)(A°)^3,Z = 4,C8.5H14N2O5.5Co0.5,Mr = 261.68,Dc = 1.552 g/cm^3,F(000) = 546,μ = 0.832 mm^-1,the final R = 0.0657 and wR = 0.1958.Compound 2 crystallizes in the monoclinic C2 space group with a = 17.479(4),b = 11.689(2),c = 11.670(2),β = 117.13(3)°,V = 2121.9(7)3,Z = 4,C17H21N5O10Cd,Mr = 567.79,Dc = 1.777 g/cm^3,F(000) = 1144,μ = 1.096 mm^-1,the final R = 0.0233 and wR = 0.0638.In 1,the Co(II) ions are linked by μ2-trans-DAM-and bipy ligands to build a 2D(4,4) rectangular grid layer,exhibiting a 4-connected sql net.As for 2,μ3-trans-DAM-and bipy bridge Cd(II) ions form a 2D double-layer,consisting of a couple of(4,4) grid layers,which can be viewed as a(3,4)-connected network.In both compounds,the 2D structures are stabilized by hydrogen bonding interactions to give 3D supramolecular frameworks.Additionally,FT-IR spectroscopy,UV-Visible spectroscopy,and the fluorescent properties are discussed.展开更多
This is a short review article in which we discuss and summarize the works of various researchers over past four decades on Zeeman topology and Zeeman-like topologies, which occur in special and general theory of rela...This is a short review article in which we discuss and summarize the works of various researchers over past four decades on Zeeman topology and Zeeman-like topologies, which occur in special and general theory of relativity. We also discuss various properties and inter-relationship of these topologies.展开更多
A new three-dimensional(3D) coordination polymer, [Cd(L)2H2O]n·5nH2O 1 with 4-[(3-pyridyl)methylamino]benzoate acid(HL), has been synthesized by slow evaporation solvent at room temperature, and structura...A new three-dimensional(3D) coordination polymer, [Cd(L)2H2O]n·5nH2O 1 with 4-[(3-pyridyl)methylamino]benzoate acid(HL), has been synthesized by slow evaporation solvent at room temperature, and structurally characterized by elemental analysis, IR spectrum, thermal analysis, fluorescence spectrum and single-crystal X-ray diffraction. Compound 1 crystallizes in the tetragonal system, space group I-4, with a = 20.7937(16), c = 13.515(2), V = 5843.5(11) 3, C26H34CdN4O10, Mr = 674.97, Dc = 1.534 g/cm3, μ(MoKα) = 0.808 mm-1, F(000) = 2768, Z = 8, the final R = 0.0276 and wR = 0.0691 for 5323 observed reflections(I 〉 2σ(I)). The result of thermal analysis shows that 1 is stable under 290 ℃. Moreover, it exhibits blue photoluminescence at room temperature.展开更多
We propose a novel class of two-dimensional(2D)Dirac materials in the MX family(M=Be,Mg,Zn and Cd,X=Cl,Br and I),which exhibit graphene-like band structures with linearly-dispersing Dirac-cone states over large energy...We propose a novel class of two-dimensional(2D)Dirac materials in the MX family(M=Be,Mg,Zn and Cd,X=Cl,Br and I),which exhibit graphene-like band structures with linearly-dispersing Dirac-cone states over large energy scales(0.8–1.8 eV)and ultra-high Fermi velocities comparable to graphene.Spin-orbit coupling opens sizable topological band gaps so that these compounds can be effectively classified as quantum spin Hall insulators.The electronic and topological properties are found to be highly tunable and amenable to modulation via anion-layer substitution and vertical electric field.Electronic structures of several members of the family are shown to host a Van-Hove singularity(VHS)close to the energy of the Dirac node.The enhanced density-of-states associated with these VHSs could provide a mechanism for inducing topological superconductivity.The presence of sizable band gaps,ultra-high carrier mobilities,and small effective masses makes the MX family promising for electronics and spintronics applications.展开更多
Link prediction is an important task that estimates the probability of there being a link between two disconnected nodes. The similarity-based algorithm is a very popular method that employs the node similarities to f...Link prediction is an important task that estimates the probability of there being a link between two disconnected nodes. The similarity-based algorithm is a very popular method that employs the node similarities to find links. Most of these types of algorithms focus only on the contribution of common neighborhoods between two nodes. In sociological theory relationships within three degrees are the strong ties that can trigger social behaviors.Thus, strong ties can provide more connection opportunities for unconnected nodes in the networks. As critical topological properties in networks, nodes degrees and node clustering coefficients are well-suited for describing the tightness of connections between nodes. In this paper, we characterize node similarity by utilizing the strong ties of the ego network(i.e., paths within three degrees) and its close connections(node degrees and node clustering coefficients). We propose a link prediction algorithm that combines topological properties with strong ties, which we called the TPSR algorithm. This algorithm includes TPSR2, TPSR3, and the TPSR4 indices. We evaluate the performance of the proposed algorithm using the metrics of precision and the Area Under the Curve(AUC). Our experimental results show the TPSR algorithm to perform remarkably better than others.展开更多
The number of common neighbor between nodes is applied to the modeling of resting-state brain function network in order to analyze the effect of anatomical distance on the modeling of resting-state brain function netw...The number of common neighbor between nodes is applied to the modeling of resting-state brain function network in order to analyze the effect of anatomical distance on the modeling of resting-state brain function network. Three models based on anatomical distance, the number of common neighbor, or anatomical distance and the number of common neighbor are designed. Basing on residuals creates the evaluation criteria for selecting the optimal brain function model network in each class model. The model is selected to simulate the human real brain function network by comparison with real data functional magnetic resonance imaging(f MRI)network. Finally, the result shows that the best model only is based on anatomical distance.展开更多
A fractal square F is essentially a planar self-similar set satisfying the set equation F=(F+D)/n with n≥2 and D?{0,1,...,n-1}~2.In this paper,we study the topological classification of fractal squares in the case of...A fractal square F is essentially a planar self-similar set satisfying the set equation F=(F+D)/n with n≥2 and D?{0,1,...,n-1}~2.In this paper,we study the topological classification of fractal squares in the case of n=4 and |D|=4.展开更多
基金Project supported by the open research fund of Songshan Lake Materials Laboratory(Grant No.2021SLABFN11)the National Natural Science Foundation of China(Grant Nos.U2130101 and 92165204)+5 种基金Natural Science Foundation of Guangdong Province(Grant No.2022A1515010035)Guangzhou Basic and Applied Basic Research Foundation(Grant No.202201011798)the Open Project of Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(Grant No.2022B1212010008)the Open Project of Key Laboratory of Optoelectronic Materials and Technologies(Grant No.OEMT-2023-ZTS-01)the National Key R&D Program of China(Grant Nos.2023YFF0718400 and 2023YFA1406500)(national)college students innovation and entrepreneurship training program,Sun Yat-sen University(Grant No.202310359).
文摘Systemically angular and planar transport investigations are performed in layered antiferromagnetic(AF)V_(5)S_(8).In this AF system,obvious anomalous Hall effect(AHE)is observed with a large Hall angle of 0.1 compared to that in ferromagnetic(FM)system.It can persist to the temperatures above AF transition and exhibit strong angular field dependence.The phase diagram reveals various magnetic states by rotating the applied field.By analyzing the anisotropic transport behavior,magnon contributions are revealed and exhibit obvious angular dependence with a spin-flop vanishing line.The observed prominent planar Hall effect and anisotropic magnetoresisitivity exhibit two-fold systematical angular dependent oscillations.These behaviors are attributed to the scattering from spin–orbital coupling instead of nontrivial topological origin.Our results reveal anisotropic interactions of magnetism and electron in V5S8,suggesting potential opportunities for the AF spintronic sensor and devices.
文摘A new metal-organic coordination polymer {[Nd(tci)(H2O)2]·2H2O}n(1) has been synthesized based on the flexible tricarboxylate ligand tris(2-carboxyethyl)isocyanuric acid(H3tci) and structurally characterized by single-crystal X-ray diffraction analyses, elemental analysis, infrared spectra(IR), powder X-ray diffraction(PXRD) and thermogravimetric analysis(TGA). Complex 1 crystallizes in triclinic, space group P1 with a = 9.1648(11), b = 9.3326(12), c = 12.440(2) , C(12)H(20)N3O(13) Nd, Mr = 558.55, V = 886.9(2) 3, Z = 2, Dc = 2.092 g·cm-3, μ = 3.006 mm-1, F(000) = 554, 2.56〈θ〈25.00°, λ(Mo Kα) = 0.71073 , T = 293(2) K, the final R = 0.0662 and w R = 0.2071. X-ray diffraction analysis reveals that complex 1 is a two-dimensional layer, which is further assembled into a three-dimensional supramolecular architecture through hydrogen bonding interactions. The structure of complex 1 can be simplified as a rare 2-periodic uninodal {48·62} topology and a non-interpenetrating kgd topology. Furthermore, the thermal stability and photoluminescence property of 1 were investigated.
文摘We consider a series of benzenoid isomers obtained by attaching fragments to an mradical. Some of their topological properties, such as the number of Kekule patterns and the maximum number of aromatic π-sextets are established.
基金Supported by the National Natural Science Foundation of China(Grant Nos.11974076 and 61804030)the Key Project of Natural Science Foundation of Fujian Province(Grant No.2021J02012)。
文摘Two-dimensional(2D)topological insulators present a special phase of matter manifesting unique electronic properties.Till now,many monolayer binary compounds of Sb element,mainly with a honeycomb lattice,have been reported as 2D topological insulators.However,research of the topological insulating properties of the monolayer Sb compounds with square lattice is still lacking.Here,by means of the first-principles calculations,a monolayer SbI with square lattice is proposed to exhibit the tunable topological properties by applying strain.At different levels of the strain,the monolayer SbI shows two different structural phases:buckled square structure and buckled rectangular structure,exhibiting attracting topological properties.We find that in the buckled rectangular phase,when the strain is greater than 3.78%,the system experiences a topological phase transition from a nontrivial topological insulator to a trivial insulator,and the structure at the transition point actually is a Dirac semimetal possessing two type-ⅠDirac points.In addition,the system can achieve the maximum global energy gap of 72.5 meV in the topological insulator phase,implying its promising application at room temperature.This study extends the scope of 2D topological physics and provides a platform for exploring the low-dissipation quantum electronics devices.
基金Supported by the National Natural Science Foundation of China (Grant No. 11961141011)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB28000000)the National Key Research and Development Program of China(Grant No. 2016YFA0300600)。
文摘In the transport studies of topological insulators, microflakes exfoliated from bulk single crystals are often used because of the convenience in sample preparation and the accessibility to high carrier mobilities. Here, based on finite element analysis, we show that for the non-Hall-bar shaped topological insulator samples, the measured four-point resistances can be substantially modified by the sample geometry, bulk and surface resistivities,and magnetic field. Geometry correction factors must be introduced for accurately converting the four-point resistances to the longitudinal resistivity and Hall resistivity. The magnetic field dependence of inhomogeneous current density distribution can lead to pronounced positive magnetoresistance and nonlinear Hall effect that would not exist in the samples of ideal Hall bar geometry.
基金the Natural Science Foundation of Shandong Province, China (Grant No. ZR2019MA041)the Taishan Scholar Project of Shandong Province, China (Grant No. ts20190939)+1 种基金the National Natural Science Foundation of China (Grant No. 62071200)the Shandong Provincial Natural Science Foundation, China (Grant No. ZR2020QA052)。
文摘The quantum anomalous Hall(QAH) effect has attracted enormous attention since it can induce topologically protected conducting edge states in an intrinsic insulating material. For practical quantum applications, the main obstacle is the non-existent room temperature QAH systems, especially with both large topological band gap and robust ferromagnetic order. Here, according to first-principles calculations, we predict the realization of the room temperature QAH effect in a two-dimensional(2D) honeycomb lattice, RuCS_(3) with a non-zero Chern number of C = 1. Especially, the nontrivial topology band gap reaches up to 336 me V for RuCS_(3). Moreover, we find that RuCS_(3) has a large magnetic anisotropy energy(2.065 me V) and high Curie temperature(696 K). We further find that the non-trivial topological properties are robust against the biaxial strain. The robust topological and magnetic properties make RuCS_(3) have great applications in room temperature spintronics and nanoelectronics.
文摘Research on brain function after brachial plexus injury focuses on local cortical functional reorganization,and few studies have focused on brain networks after brachial plexus injury.Changes in brain networks may help understanding of brain plasticity at the global level.We hypothesized that topology of the global cerebral resting-state functional network changes after unilateral brachial plexus injury.Thus,in this cross-sectional study,we recruited eight male patients with unilateral brachial plexus injury(right handedness,mean age of 27.9±5.4years old)and eight male healthy controls(right handedness,mean age of 28.6±3.2).After acquiring and preprocessing resting-state magnetic resonance imaging data,the cerebrum was divided into 90 regions and Pearson’s correlation coefficient calculated between regions.These correlation matrices were then converted into a binary matrix with affixed sparsity values of 0.1–0.46.Under sparsity conditions,both groups satisfied this small-world property.The clustering coefficient was markedly lower,while average shortest path remarkably higher in patients compared with healthy controls.These findings confirm that cerebral functional networks in patients still show smallworld characteristics,which are highly effective in information transmission in the brain,as well as normal controls.Alternatively,varied small-worldness suggests that capacity of information transmission and integration in different brain regions in brachial plexus injury patients is damaged.
基金supported by the National Natural Science Foundation of China(21401097)
文摘One two-dimensional coordination polymer with a formula of {[Cd(L)(imidazole)(H2O)](H2O)}n(1) was obtained by the synthetic reactions in aqueous solution using a newly synthesized H2L(H2L = methyl-3-hydroxy-5-carboxy-2-thiophenecarboxylate) ligand.Compound1 crystallizes in monoclinic system,space group C2/c with a = 18.3176(11),b = 8.5366(9),c =8.4152(5)A,β = 101.789(6)°,V = 2797.1(3)A^3,Dc = 1.979 g/cm^3,C(10)H(12)N2O7SCd,Mr = 416.68 F(000) = 1648,μ = 1.745 mm^-1,F(000) = 1648,the final R = 0.0323 and wR = 0.0604 for 2604 observed reflections with I 〉 2s(I).Structure analyses reveal that the compound is constructed by dinuclear Cd(Ⅱ) clusters bridged by two hydroxyl oxygens of L^2-anions,which features a two-dimensional network with 4-connected sql topology.Furthermore,the compound exhibits high thermal stability and intense fluorescent emission,and could be explored for potentia luminescent materials.
基金grateful to the Natural Science Foundation of Fujian Province(grant No.2020J01869)the Initial Scientific Research Fund in Fujian University of Technology(grant No.GY-Z19123)for providing financial support to this study.
文摘The effect of friction behavior on the compacted density is significant, but the relationship between the topological properties of the contact network and friction behavior during powder compaction remains unclear. Based on the discrete element method (DEM), a DEM model for die compaction was established, and the Hertz contact model was modified into an elastoplastic contact model that was more suitable for metal-powder compaction. The evolution of the topological properties of the contact network and its mechanism during powder compaction was explored using the elastoplastic contact model. The results demonstrate that the friction behavior between the particles is closely related to the topological properties of the contact network. Side wall friction results in smaller clustering coefficient (CC) and excess contact (EC) in the lower region near the side wall. Corresponding to this phenomenon, the upper region near the side wall has more high-stress particles when the major principal stress threshold was considered, and the CC and EC are significantly higher than those in the other regions. This study provides a theoretical basis for improving powder compaction behavior.
基金the National Natural Science Foundation of China(Grant Nos.51475347 and 51875429).
文摘With the increasingly fierce market competition,manufacturing enterprises have to continuously improve their competitiveness through their collaboration and labor division with each other,i.e.forming manufacturing enterprise collaborative network(MECN)through their collaboration and labor division is an effective guarantee for obtaining competitive advantages.To explore the topology and evolutionary process of MECN,in this paper we investigate an empirical MECN from the viewpoint of complex network theory,and construct an evolutionary model to reproduce the topological properties found in the empirical network.Firstly,large-size empirical data related to the automotive industry are collected to construct an MECN.Topological analysis indicates that the MECN is not a scale-free network,but a small-world network with disassortativity.Small-world property indicates that the enterprises can respond quickly to the market,but disassortativity shows the risk spreading is fast and the coordinated operation is difficult.Then,an evolutionary model based on fitness preferential attachment and entropy-TOPSIS is proposed to capture the features of MECN.Besides,the evolutionary model is compared with a degree-based model in which only node degree is taken into consideration.The simulation results show the proposed evolutionary model can reproduce a number of critical topological properties of empirical MECN,while the degree-based model does not,which validates the effectiveness of the proposed evolutionary model.
基金Supported by the National Natural Science Foundation of China(20873103)
文摘In this research, the hydrogen bonds Y···H-X (X = C, N; Y = N, O) of thymine and uracil have been theoretically studied. The results show that hydrogen bond leads to bond length elongation and stretches the frequency red-shift of N-H···Y. Meanwhile, the C-H···O bonds shorten and stretch the frequency blue-shift. They all belong to traditional hydrogen bonds. The intermolecular charge transfer caused by the intermolecular hyperconjugation s*(N–H) → n(Y) and intramolecular charge redistribution by intramolecular hyperconjugation σ(C-H) →σ*(C-N) play important roles in the formation of hydrogen bonds. According to thejudgment standards proposed by Bader and Popelier, these hydrogen bonds have typical electron density topological properties. Electrostatic surface potential (ESP) is a useful physicochemical property of a molecule that provides insights into inter- and intramolecular associations, as well as the prediction of likely sites of electrophilic and nucleophilic metabolic attack.
基金supported by the National Natural Science Foundation of China(Grant Nos.11274016 and 11474012)the National Basic Research Program of China(Grant Nos.2013CB932604 and 2012CB619304)
文摘Spintronics involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. The fascinating spin-resolved properties of graphene motivate numerous researchers to study spintronics in graphene and other two-dimensional(2D) materials. Silicene, the silicon analog of graphene, is considered to be a promising material for spintronics. Here, we present a review of theoretical advances with regard to spin-dependent properties, including the electric field- and exchange field-tunable topological properties of silicene and the corresponding spintronic device simulations.
基金supported by the Nature Scientific Research and Overall innovation plan major project of Shaanxi Provincial Education Office of China(No.2012KTCL03-16)the National Natural Science Foundation of China(No.21373178)+2 种基金the Nature Scientific Research Foundation of Shaanxi Provincial Education Office(No.2013Jk0668)the National College Students'innovation and entrepreneurship training program(201310719002)the special fund of Yan’an University(No.YDZ2013-10)
文摘A new coordination polymer, [Mn(3,4-pybz)2]n·3(H2O)(1), has been hydrothermally synthesized from Mn Cl2·4H2O and an unsymmetrical 3-pyridin-4-yl-benzoic acid(3,4-Hpybz), and characterized by IR, elemental analysis, thermogravimetric analysis, and singlecrystal X-ray diffraction. In complex 1, each 3,4-pybz ligand represents a three-connected node to combine with the six-connected Mn(II) ions, generating a 3D binodal(3,6)-connected ant network. In addition, magnetic investigations reveal that complex 1 exhibits an antiferromagnetic behavior. According to the crystal structure, the full-geometrical optimization of complex 1 was carried out by using hybrid DFT methods at the B3LYP/6-31G(d) level. Meantime, the DFT-BS approach was applied to study the magnetic coupling behavior for complex 1, and the result reveals that the calculated exchange coupling constants J were in good agreement with the experimental data.
基金supported by the National Natural Science Foundation of China (No. 20873021)
文摘Two coordination compounds with a flexible ligand N,N?-diacetic acid imidazolium(HDAM),{[Co(trans-DAM)(bipy)(H2O)2](OH)·4H2O}n 1 and {[Cd(trans-DAM)(bipy)(H2O)](NO3)?2H2O}n 2(bipy = 4,4'-bipyridine),were prepared and characterized by single-crystal X-ray diffraction.Compound 1 crystallizes in monoclinic,space group P2/n with a = 7.589(6),b = 11.444(2),c = 12.894(3)(A°),β = 90.99(3)°,V = 1119.8(4)(A°)^3,Z = 4,C8.5H14N2O5.5Co0.5,Mr = 261.68,Dc = 1.552 g/cm^3,F(000) = 546,μ = 0.832 mm^-1,the final R = 0.0657 and wR = 0.1958.Compound 2 crystallizes in the monoclinic C2 space group with a = 17.479(4),b = 11.689(2),c = 11.670(2),β = 117.13(3)°,V = 2121.9(7)3,Z = 4,C17H21N5O10Cd,Mr = 567.79,Dc = 1.777 g/cm^3,F(000) = 1144,μ = 1.096 mm^-1,the final R = 0.0233 and wR = 0.0638.In 1,the Co(II) ions are linked by μ2-trans-DAM-and bipy ligands to build a 2D(4,4) rectangular grid layer,exhibiting a 4-connected sql net.As for 2,μ3-trans-DAM-and bipy bridge Cd(II) ions form a 2D double-layer,consisting of a couple of(4,4) grid layers,which can be viewed as a(3,4)-connected network.In both compounds,the 2D structures are stabilized by hydrogen bonding interactions to give 3D supramolecular frameworks.Additionally,FT-IR spectroscopy,UV-Visible spectroscopy,and the fluorescent properties are discussed.
文摘This is a short review article in which we discuss and summarize the works of various researchers over past four decades on Zeeman topology and Zeeman-like topologies, which occur in special and general theory of relativity. We also discuss various properties and inter-relationship of these topologies.
基金supported by the Science and Technology Development Project of Jilin Provincial Science & Technology Department(201205080)the Science and Technology Research Projects of the Education Office of Jilin Province(No.2013.384)
文摘A new three-dimensional(3D) coordination polymer, [Cd(L)2H2O]n·5nH2O 1 with 4-[(3-pyridyl)methylamino]benzoate acid(HL), has been synthesized by slow evaporation solvent at room temperature, and structurally characterized by elemental analysis, IR spectrum, thermal analysis, fluorescence spectrum and single-crystal X-ray diffraction. Compound 1 crystallizes in the tetragonal system, space group I-4, with a = 20.7937(16), c = 13.515(2), V = 5843.5(11) 3, C26H34CdN4O10, Mr = 674.97, Dc = 1.534 g/cm3, μ(MoKα) = 0.808 mm-1, F(000) = 2768, Z = 8, the final R = 0.0276 and wR = 0.0691 for 5323 observed reflections(I 〉 2σ(I)). The result of thermal analysis shows that 1 is stable under 290 ℃. Moreover, it exhibits blue photoluminescence at room temperature.
基金This work was supported by the U.S.Department of Energy,Office of Science,Basic Energy Sciences,under Award#DE-SC0019275.It benefitted from the supercomputing resources of the National Energy Research Scientific Computing Center(NERSC),a U.S.Department of Energy Office of Science User Facility operated under Contract No.DE-AC02-05CH11231,and Temple University’s HPC resources supported in part by the National Science Foundation through major research instrumentation grant number 1625061 and by the US Army Research Laboratory under contract number W911NF-16-2-0189.S.X.D.and Y.-F.Z.acknowledge support from the National Key Research and Development Program of China(No.2016YFA0202300)Strategic Priority Research Program(No.XDB30000000)+1 种基金the National Natural Science Foundation of China(No.61888102)the International Partnership Program of the Chinese Academy of Sciences(No.112111KYSB20160061).
文摘We propose a novel class of two-dimensional(2D)Dirac materials in the MX family(M=Be,Mg,Zn and Cd,X=Cl,Br and I),which exhibit graphene-like band structures with linearly-dispersing Dirac-cone states over large energy scales(0.8–1.8 eV)and ultra-high Fermi velocities comparable to graphene.Spin-orbit coupling opens sizable topological band gaps so that these compounds can be effectively classified as quantum spin Hall insulators.The electronic and topological properties are found to be highly tunable and amenable to modulation via anion-layer substitution and vertical electric field.Electronic structures of several members of the family are shown to host a Van-Hove singularity(VHS)close to the energy of the Dirac node.The enhanced density-of-states associated with these VHSs could provide a mechanism for inducing topological superconductivity.The presence of sizable band gaps,ultra-high carrier mobilities,and small effective masses makes the MX family promising for electronics and spintronics applications.
基金partially supported by the National Natural Science Foundation of China(Nos.61673020,61402006,and 61702003)the National High-Tech Research and Development(863)Program of China(No.2015AA124102)+1 种基金Humanities and Social Science Research on Youth Fund Project,Ministry of Education(No.14YJC860020)Anhui Provincial Natural Science Foundation(No.1708085MF160)
文摘Link prediction is an important task that estimates the probability of there being a link between two disconnected nodes. The similarity-based algorithm is a very popular method that employs the node similarities to find links. Most of these types of algorithms focus only on the contribution of common neighborhoods between two nodes. In sociological theory relationships within three degrees are the strong ties that can trigger social behaviors.Thus, strong ties can provide more connection opportunities for unconnected nodes in the networks. As critical topological properties in networks, nodes degrees and node clustering coefficients are well-suited for describing the tightness of connections between nodes. In this paper, we characterize node similarity by utilizing the strong ties of the ego network(i.e., paths within three degrees) and its close connections(node degrees and node clustering coefficients). We propose a link prediction algorithm that combines topological properties with strong ties, which we called the TPSR algorithm. This algorithm includes TPSR2, TPSR3, and the TPSR4 indices. We evaluate the performance of the proposed algorithm using the metrics of precision and the Area Under the Curve(AUC). Our experimental results show the TPSR algorithm to perform remarkably better than others.
基金the National Natural Science Foundation of China(Nos.6117013661373101+3 种基金61472270 and61402318)the Natural Science Foundation of Shanxi(No.2014021022-5)the Special/Youth Foundation of Taiyuan University of Technology(No.2012L014)the Youth Team Fund of Taiyuan University of Technology(Nos.2013T047 and 2013T048)
文摘The number of common neighbor between nodes is applied to the modeling of resting-state brain function network in order to analyze the effect of anatomical distance on the modeling of resting-state brain function network. Three models based on anatomical distance, the number of common neighbor, or anatomical distance and the number of common neighbor are designed. Basing on residuals creates the evaluation criteria for selecting the optimal brain function model network in each class model. The model is selected to simulate the human real brain function network by comparison with real data functional magnetic resonance imaging(f MRI)network. Finally, the result shows that the best model only is based on anatomical distance.
基金Supported by the Soft Science Research of Xiangyang City in 2019。
文摘A fractal square F is essentially a planar self-similar set satisfying the set equation F=(F+D)/n with n≥2 and D?{0,1,...,n-1}~2.In this paper,we study the topological classification of fractal squares in the case of n=4 and |D|=4.