锥部外部导磁结构对重介旋流器分选效果的影响

为了调控重介旋流器二段分选密度以改善分选效果,在其锥部附加导磁结构,并施加电磁场,研究了导磁结构在磁场作用下的旋流器的分选效果,通过考察不同磁场强度,进行介质分配试验和粗煤泥(-3mm)分选试验。试验结果表明,当在旋流器锥部的线圈上部附加内导磁结构时,同单独使用线圈相比,在特定的磁场强度下,精煤灰分降低,尾煤灰分升高,提高了分选效率。利用有限元软件ANSYS对磁系进行模拟分析,模拟结果表明,附加导磁结构可人为改变磁场走向,增大对磁场能量的富集,提高磁场力,从而提高分选效果。

重介旋流器柱锥面处导磁结构位置对煤泥分选的影响

为了探索复合力场的煤泥分选问题,优化重介旋流器外加磁场对煤泥分选的调控,本文选择了重介旋流器外加导磁结构,利用导磁结果位置的变化,探究了导磁结构存在下的介质分配规律以及煤泥分选试验效果。结果表明:当电流强度为5.0A时,旋流器柱锥面的上导磁结构可以明显提高旋流器的分选密度;且能有效降低精煤、尾煤灰分;当电流增加到20~30A时,精煤、尾煤灰分又升高了。

磁耦合谐振式无线电能传输电动汽车充电系统研究

为研究电动汽车无线充电系统,解决电动汽车有线充电时的不安全、不便利问题,采用磁耦合谐振式无线电能传输技术,从改进传输线圈结构出发,在传输线圈外侧增加导磁体,将磁通尽可能束缚在两传输线圈之间,减小向外界的泄漏,缩短磁通在空气中的磁路长度,从而有效增强无线电能传输系统的耦合程度,大大增加传输功率,提高低频条件下的传输距离和效率。设计了具有频率自动跟踪控制的12 k W/70 k Hz高效磁耦合谐振式电动汽车无线充电系统,并进行实验研究,得到一系列传输线圈距离和负载阻抗、传输功率及传输效率之间关系的实验数据。特别地,实验结果表明在传输距离0.3 m、输入功率12.6 k W时,谐振频率为72.6 k Hz,传输效率达到94.33%。

电磁效应对重介旋流器粗煤泥分选的影响

本文通过研究螺线圈的励磁电流和磁场位置等,探究了电磁场对重介旋流器分选煤泥的影响。通过精煤产率、精煤灰分和尾煤灰分三个指标来判断电磁场对重介旋流器煤泥分选的效果。实验结果表明:外加螺线圈的电磁效应可以调节旋流器的分选密度,且B型螺线圈在提高旋流器分选密度的方面,有着比A型螺线圈更广泛的电流调节范围;螺线圈位于旋流器筒体段,弱电流作用时其对煤泥分选精度的提高较有益,螺线圈越靠近筒体上端,强电流产生的磁感应使旋流器的分选工况得到影响;微电流作用下,螺线圈的位置不同,产生的磁感应强度均能提高旋流器对煤泥分选。

Energy Stabilities, Magnetic Properties, and Electronic Structures of Diluted Magnetic Semiconductor Zn1-xMnxS（001） Thin Films

We investigate the electronic and magnetic properties of the diluted magnetic semiconductors Zn1-xMnxS（001） thin films with different Mn doping concentrations using the total energy density functional theory. The energy stability and density of states of a single Mn atom and two Mn atoms at various doped configurations and different magnetic coupling state were calculated. Different doping configurations have different degrees of p-d hybridization, and because Mn atoms are located in different crystal-field environment, the 3d projected densities of states peak splitting of different Mn doping configurations are quite different. In the two Mn atoms doped, the calculated ground states of three kinds of stable configurations are anti-ferromagnetic state. We analyzed the 3d density of states diagram of three kinds of energy stability configurations with the two Mn atoms in different magnetic coupling state. When the two Mn atoms are ferromagnetic coupling, due to d-d electron interactions, density of states of anti-bonding state have significant broadening peaks. As the concentration of Mn atoms increases, there is a tendency for Mn atoms to form nearest neighbors and cluster around S. For such these configurations, the antiferromagnetic coupling between Mn atoms is energetically more favorable.

Updating method of a high-speed maglev guideway model based on wavelet transform

The structure of a high-speed maglev guideway is taken as the research object.With the aim of identifying the inconsistency of modal parameters between the simulation model and the actual model,and based on the 600 km/h high-speed maglev vehicle and the high-speed maglev test line,the arrangement of sensors and the vibration acceleration data collection of the 12.384 m concrete guideway were conducted.The modal parameters were identified from the guideway response signal using wavelet transform,after which the wavelet ridge was extracted by using the maximum slope method.Next,the vibration modes and frequency parameters of the interaction vibration characteristics of the high-speed maglev guideway and 600 km/h maglev vehicle were analyzed.The updating objective function for the finite element model of the guideway was established,and the initial guideway finite element model was modified and updated by repeatedly iterating the parameters.In doing so,the model structure of the high-speed maglev guideway was obtained,which is consistent with the actual structure.The accuracy of the updated guideway model in the calculation of the dynamic response was verified by combining this with the vehicle-guideway coupling dynamic model of the high-speed maglev system with 18 degrees of freedom.The research results reveal that the model update method based on the wavelet transform and the maximum slope method has the characteristics of high accuracy and fast recognition speed.This can effectively obtain an accurate guideway model that ensures the correctness of the vehicle-guideway coupling dynamic analysis and calculation while meeting the parameters of the measured structure model.This method is also suitable for updating other structural models of high-speed maglev systems.

Influence of Rare Earth.Ho3＋ Doping on the Structural, Microstructure and Magnetic Properties of ZnO Bulk and Thin Film Systems

We have investigated the doping behavior of rare earth element holmium （Ho3＋） in ZnO semiconductor. The structural, microstructure, and magnetic properties of Zn1-xHoxO （x=0.0, 0.04, and 0.05） thin films deposited on Si（100） substrate by thermal evaporation technique were studied. The ceramic targets were prepared by conventional solid state ceramic technique. The pallets used as target were final sintered at 900℃ in the presence of N2 atmosphere. The experimental results of X-ray diffraction （XRD） spectra, surface morphology, and magnetic properties show that the Ho3＋ doped ZnO thin films has a strong influence on the materials properties. The higher angle shift in peak position and most preferred （101） orientation were observed in XRD pattern. These spectra confirmed the substitution of Ho3＋ in ZnO lattice. The surface morphology and stoichiometry for both bulk and thin films were analyzed by scanning electron microscopy and energy dispersive spectroscopy. It was observed that grain size decreases with the increase of Ho3＋. Room temperature ferromagnetism was observed for Zn0.95Ho0.050 films. The ferromagnetism might be attributed to the substitution of Ho ions for Zn2＋ in ZnO lattices.

Formation mechanism and modulation of electromagnetically induced transparency-like transmission in side-coupled structures

Based on Fabry model and finite-different time-domain(FDTD) method, the plasmonic structure composed of a metal-insulator-metal(MIM) bus waveguide and a side-coupled resonator was investigated. It is found that the transmission features can be regulated by the cavity width and coupling distance. Electromagnetically induced transparency(EIT)-like transmission can be excited by adding an identical resonator on the pre-existing structure. Combining the foregoing theoretical analysis with coupled mode theory(CMT), the formation process of the EIT-like transmission was detailedly analyzed. EIT-like transmission can also be excited in plasmonic structure with two detuned resonators. By altering the structure parameters, the transparency window can be purposefully modulated. With the merits of compact structure and simplicity in fabrication, the proposed structures may have a broad prospect of applications in highly integrated optical circuits.

Analysis of the Microstructure and Permeability of the Laminates with Different Fiber Volume Fraction

Microstructures of laminates produced by epoxy/carbon fibers with different fiber volume fraction were studied by analyzing the composite cross-sections.The main result of the compaction of reinforcement is the flatting of bundle shape,the reducing of gap and the embedment of bundles among each layer.The void content outside the bundle decreased sharply during the compaction until it is less than that inside the bundle when the fiber volume fraction is over 60%.The resin flow velocity in the fiber tow is 102-104 times greater than the flow velocity out the fiber tow no matter the capillary pressure is taken into account or not.

The critical role of spin rotation in the giant magnetostriction of La(Fe,Al)_(13)

As an efficient converter between electromagnetic and mechanical energies, magnetostriction is an intriguing property for not only fundamental studies but also technological applications. However, the understanding of its microscopic origin remains challenging, which is critical for the development of magnetostriction materials. Here, the critical role of spin rotation in the giant magnetostriction of La(Fe,Al)_(13) is first revealed by the in-situ magnetic and temperature field of neutron powder diffraction. The giant magnetostriction originates from magnetic-field-driven spin moment rotation of canting structure, in which the sharp increase of ferromagnetic component causes the elongation of icosahedron inside of lattice. Furthermore, it is the first time to reveal the accurate canting antiferromagnetic structure in La(Fe,Al)_(13). The present study provides a new strategy, i.e., the spin rotation, for exploring new magnetostriction functional materials.

Enhancement of the Curie temperature of ferromagnetic semiconductor(Ga,Mn)As

In this review article,we review the progress made in the past several years mainly regarding the efforts devoted to increasing the Curie temperature(T C) of(Ga,Mn)As,which is most widely considered as the prototype ferromagnetic semiconductor.Heavy Mn doping,nanostructure engineering and post-growth annealing which increase T C are described in detail.

Diluted ferromagnetic semiconductor(LaCa)(ZnMn)SbO isostructural to “1111” type iron pnictide superconductors

We report discovery of ferromagnetism in(LaCa)(ZnMn)SbO isostructural to the well-studied iron-based superconductor LaFeAs(O1 xFx).Spin is induced by partial substitution of Mn2+for Zn2+,while charge is induced by substitution of Ca2+for La3+within the parent compound LaZnSbO.Ferromagnetism with Curie temperature(TC)is observed up to 40 K at the spin doping 0.15 by introducing Mn2+into the Zn2+sites for(La0.95Ca0.05)(Zn1 xMnx)SbO.The Hall coefficient measurement indicates p-type carrier for(La0.95Ca0.05)(Zn0.9Mn0.1)SbO with concentration of n^1020cm 3showing anomalous Hall effect below TC.

Three new MOFs with unusual Cu_6~Ⅱcluster, linear Cu~Ⅱ chain and triangular Cu_3~Ⅱcore motifs tuned by sulfonate group: Synthesis, structures and magnetic properties

Three new MOFs with the same components but different structures and magnetic behavior, {[Cu6（atr）6（H20）2（,u3- OH）2（SOa）5]＇5.25H20}n （1）, {[Cu2（atr）2（,t/-OH）2（SOa）].3H20}n （2）, and {[CuT（atr）6（H20）6（fl3-OH）2（SOn）6].2H20}n （3） （atr= 4-amino-l,2,4-triazole）, were respectively synthesized by diffusion reactions in the presence of different structure-directing agents. Complex 1 is a slightly spin-frustrated antiferromagnetic layer with sulfonate aggregated Cun6 clusters periodically ex- tended by ditopic sulfonate linkers. 2 is a grid-based coplanar sheet with hydroxyl group bridged -CuOCu- linear-chain inter- linked by pairs of p3-atr ligands, exhibiting strong antiferromagnetic interactions to lead to an S = 0 spin ground state at low temperature. In contrast, air-instable 3 has a ladder-like broad-ribbon structure constructed from triangular CuII3 cores and cen- trosymmetric CuII1 octahedra. Obviously, the variable Cun-ligand connectivity and the involving magnetic properties are sig- nificantly dominated by the cooperative and variable binding modes of the mixed sulfonate-atr ligands and bi-/tridentate bridging hydroxyl heterobridges.

Atomic scale electronic structure of the ferromagnetic semiconductor Cr2Ge2Te6

Cr_2Ge_2Te_6is an intrinsic ferromagnetic semiconductor with van der Waals type layered structure,thus represents a promising material for novel electronic and spintronic devices.Here we combine scanning tunneling microscopy and first-principles calculations to investigate the electronic structure of Cr_2Ge_2Te_6.Tunneling spectroscopy reveals a surprising large energy level shift and change of energy gap size across the ferromagnetic to paramagnetic phase transition,as well as a peculiar double-peak electronic state on the Cr-site defect.These features can be quantitatively explained by density functional theory calculations,which uncover a close relationship between the electronic structure and magnetic order.These findings shed important new lights on the microscopic electronic structure and origin of magnetic order in Cr_2Ge_2Te_6.

Spin filtering magnetic modulation and spin-polarization switching in hybrid ferromagnet/semiconductor structures

Electron spin-polarization modulation with a ferromagnetic strip of in-plane magnetization is analyzed in a hybrid ferromagnet/semiconductor filter device.The dependencies of electron spin-polarization on the strip’s magnetization strength,width and position have been systematically investigated.A novel magnetic control spin-polarization switch is proposed by inserting a ferromagnetic metal(FM)strip eccentric in relation to off the center of the spin filter,which produces the first energy level spin-polarization reversal.It is believed to be of significant importance for the realization of semiconductor spintronics multiple-value logic devices.

Identifying the genes of unconventional high temperature superconductors

We elucidate a recently emergent framework in unifying the two families of high temperature （high To） superconductors, cuprates and iron-based superconductors. The unification suggests that the latter is simply the counterpart of the former to realize robust extended s-wave pairing symmetries in a square lattice. The unification identifies that the key ingredients （gene） of high Tc superconductors is a quasi two dimensional electronic environment in which the d-orbitals of cations that partic- ipate in strong in-plane couplings to the p-orbitals of anions are isolated near Fermi energy. With this gene, the superexchange magnetic interactions mediated by anions could maximize their contributions to superconductivity. Creating the gene requires special arrangements between local electronic structures and crystal lattice structures. The speciality explains why high Tc superconductors are so rare. An explicit prediction is made to realize high Tc superconductivity in Co/Ni-based materials with a quasi two dimensional hexagonal lattice structure formed by trigonal bipyramidal complexes.

Structural phase transition, antiferromagnetism and two superconducting domes in LaFeAsO_(1-x)F_x(0

We report^(75) As nuclear magnetic resonance(NMR)/nuclear quadrupole resonance(NQR) and transmission electron microscopy(TEM) studies on LaFeAsO_(1-x)F_x. There are two superconducting domes in this material. The first one appears at 0.03 ≤ x ≤0.2 with T_c^(max) = 27 K, and the second one at 0.25 ≤x≤0.75 with T_c^(max) = 30 K. By NMR and TEM, we demonstrate that a C4-to-C2 structural phase transition(SPT) takes place above both domes, with the transition temperature T_s varying strongly with x. In the first dome, the SPT is followed by an antiferromagnetic(AF) transition, but neither AF order nor low-energy spin fluctuations are found in the second dome. By ^(75) As nuclear spin-lattice relaxation rate(1/T_1) measurements, we find that AF order and superconductivity coexist microscopically in LaFeAsO_(0.97) F_(0.03). In the coexisting region, 1/T_1 decreases at T_c but becomes proportional to T below 0.6 T_c, indicating gapless excitations. Therefore, in contrast to the early reports, the obtained phase diagram for x ≤ 0.2 is quite similar to the doped BaFe_2As_2 system. The electrical resistivity p in the second dome can be fitted by ρ = ρ0 + AT^n with n = 1 and a maximal coefficient A at around xopt = 0.5-0.55 at which T_s extrapolates to zero and Tc is the maximal, which suggests the importance of quantum critical fluctuations associated with the SPT. We have constructed a complete phase diagram of LaFeAsO_(1-x)F_x, which provides insight into the relationship between SPT, antiferromagnetism and superconductivity.

High-Order Energy Decay for Structural Damped Systems in the Electromagnetical Field

This paper is concerned with the decay estimate of high-order energy for a class of special time-dependent structural damped systems represented by Fourier multipliers. This model is widely used in the fields of semiconductivity, superconductivity, electromagnetic waves, electrolyte and electrode materials, etc.

Structure,magnetic properties and magnetocaloric effects of Fe_(50)Mn_(15-x)Co_xNi_(35) alloys

FesoMn15-xCoxNi35 （x=0, 1, 3, 5, 7） alloys were prepared by arc melting under purified argon atmosphere. The ingots were homogenized at 930℃ for 90 h followed by water quenching. The crystal structure, magnetic properties and magnetocaloric effects of the alloys were studied by X-ray diffraction （XRD） and MPMS-7-type SQUID. The results show that all samples still maintained a single γ-（Fe, Ni）-type phase structure. With the increase of the content of Co, the Curie temperatures of these alloys increased and exhibited a second-order magnetic transition from ferromagnetic （FM） to paramagnetic （PM） state near Curie temperature. The maximum magnetic entropy change and the relative cooling power of Fe50Mn10CosNi35 alloy was 2.55 J/kg.K and 181 J/kg, respectively, for an external field change of 5 T. Compared with rare earth metal Gd, FesoMnls-xCoxNi35 series of alloys have obvious advantage in resource price; their Curie temperatures can be tuned to near room temperature, maintain a relatively large magnetic entropy change at the same time and they are a type of potential magnetic refrigeration materials near room temperature.