共查询到20条相似文献,搜索用时 46 毫秒
1.
利用基于密度泛函理论的第一性原理方法,研究了掺杂铁、钴和镍原子的锯齿型磷烯纳米带(ZPNR)的磁电子学特性.研究表明,掺杂和未掺杂ZPNR的结构都是稳定的.当处于非磁态时,未掺杂和掺杂钴原子的ZPNR为半导体,而掺杂铁或者镍原子的ZPNR为金属.自旋极化计算表明,未掺杂和掺杂钴原子的ZPNR无磁性,而掺杂铁或者镍原子的ZPNR有磁性,但只能表现出铁磁性.处于铁磁态时,掺杂铁原子的ZPNR为磁性半导体,而掺杂镍原子的ZPNR为磁性半金属.掺杂铁或者镍原子的ZPNR的磁性主要由杂质原子贡献,产生磁性的原因则是在ZPNR中存在未配对电子.掺杂位置对ZPNR的磁电子学特性有一定的影响.该研究对于发展基于磷烯纳米带的纳米电子器件具有重要意义. 相似文献
2.
C. Haas 《Solid State Communications》1978,26(11):709-712
The lattice distortions of a hexagonal layer are discussed in terms of a simple model with isotropic interactions. If only nearest-neighbour interactions are considered, the only stable distorted structures are the MnP structure (with zig-zag chains) and the low-temperature NbS structure (with triangles of metal atoms). If also interactions with more distant atoms are considered, more complicated distortions, as observed in crystals with charge density waves, are possible. 相似文献
3.
勾秉聪 《原子与分子物理学报》1997,14(4):505-510
采用马鞍点变分方法和复数转动技术,计算了类锂离子2s2p2p2S三激发共振态的能量,并运用截断变分方法得到能量改进量,以及计算了相对论效应、质量极化效应,从而获得了高精度的能量计算值。还计算了该系统的Auger宽度,位移和辐射跃迁率。 相似文献
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5.
In this paper, the Noether symmetries and the conserved quantities for a Hamilton system with time delay are discussed. Firstly, the variational principles with time delay for the Hamilton system are given, and the Hamilton canonical equations with time delay are established. Secondly, according to the invariance of the function under the infinitesimal transformations of the group, the basic formulas for the variational of the Hamilton action with time delay are discussed,the definitions and the criteria of the Noether symmetric transformations and quasi-symmetric transformations with time delay are obtained, and the relationship between the Noether symmetry and the conserved quantity with time delay is studied. In addition, examples are given to illustrate the application of the results. 相似文献
6.
采用相位比对法模拟分析了HL-1M装置的磁扰动模式,模拟结果同预期的一致。在具有撕裂模不稳定性的典型放电中,探测到独立模m=2、3、4,耦合模m=2、3,并与用空间傅立叶分析方法得到的扰动模式的分析结果进行了比较。讨论了这些方法在实验分析中的可行性和有效性。 相似文献
7.
In this paper, we proposed the exactly solvable model of non-Markovian dynamics of open quantum systems. This model describes open quantum systems with memory and periodic sequence of kicks by environment. To describe these systems, the Lindblad equation for quantum observable is generalized by taking into account power-law fading memory. Dynamics of open quantum systems with power-law memory are considered. The proposed generalized Lindblad equations describe non-Markovian quantum dynamics. The quantum dynamics with power-law memory are described by using integrations and differentiation of non-integer orders, as well as fractional calculus. An example of a quantum oscillator with linear friction and power-law memory is considered. In this paper, discrete-time quantum maps with memory, which are derived from generalized Lindblad equations without any approximations, are suggested. These maps exactly correspond to the generalized Lindblad equations, which are fractional differential equations with the Caputo derivatives of non-integer orders and periodic sequence of kicks that are represented by the Dirac delta-functions. The solution of these equations for coordinates and momenta are derived. The solutions of the generalized Lindblad equations for coordinate and momentum operators are obtained for open quantum systems with memory and kicks. Using these solutions, linear and nonlinear quantum discrete-time maps are derived. 相似文献
8.
为了研究延性薄靶的穿透性能,进行了90°锥头弹丸穿透薄钢板的准静态和动态实验。通过准静态实验,得到了4种不同厚度钢板的载荷-压入位移曲线及破坏模式;结合膜力理论模型及纯弯静塑性破坏模型,对实验结果进行了分析,得出:对于薄靶,大变形膜力起主导作用,随着靶厚增加,弯距在板整体变形过程中的影响逐渐增大。通过动态穿透实验,得到了弹丸穿透4种不同厚度钢板的入射速度、残余速度及靶板破坏模式,计算得到穿透耗能。最后,将准静态实验与动态实验结果进行了对比讨论。 相似文献
9.
Signature splitting and shape coexistence at high spin in the neutron
deficient nucleus 129Nd are investigated with the
configuration-dependent cranked Nilsson-Strutinsky approach. The calculated
bands are compared with the observed signature partner bands and very good
agreement results at high spin are obtained. The observed deformed bands are confirmed as normal and highly deformed and their properties are explained theoretically. Terminating states in 129Nd and other terminations are predicted. There is shape coexistence within the same configuration from low-spin states
to high-spin states. Possible normal and highly deformed bands with
rotation around the intermediate principal axis in several interesting
configurations of 129Nd are discussed. The experimental results for 131Nd are simply discussed and the calculated bands are in good
agreement with observed bands at high spin. Triaxial shapes in 127Nd with a triaxial deformation of
γ~-12º are predicted
and should be observed experimentally. The value of negative γ of
π(h11/2)4ν(h11/2)7 configuration increases with
neutron number increasing in
127,129,131Nd. The triaxial shape evolutions with neutron number increasing in 127,129,131Nd and in 126,128,130,132Pr are explained by the strong driving force of
specified single particle orbitals towards to triaxial shape. 相似文献
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We consider a generalization of the Kuramoto model in which the oscillators are coupled to the mean field with random signs. Oscillators with positive coupling are "conformists"; they are attracted to the mean field and tend to synchronize with it. Oscillators with negative coupling are "contrarians"; they are repelled by the mean field and prefer a phase diametrically opposed to it. The model is simple and exactly solvable, yet some of its behavior is surprising. Along with the stationary states one might have expected (a desynchronized state, and a partially-synchronized state, with conformists and contrarians locked in antiphase), it also displays a traveling wave, in which the mean field oscillates at a frequency different from the population's mean natural frequency. 相似文献
12.
Two mode lasers with intensity coupling are treated by simple fluctuation theory. The intensities of the two modes as functions of pump power are calculated together with the correlation matrix. Equations of motion for the intensities are derived from which the decay times of correlations are found by a method of quasilinearization as well as by decoupling the hierarchy of correlation functions. Details of photon fluctuation linewidths are reported together with the time dependent correlations between different modes. 相似文献
13.
The experimentally observed ten rotational bands in 179Re are analyzed with the particle-number conserving method for treating the cranked shell model with pairing interaction, in which the blocking effects are taken into account exactly. The experimental moments of inertia of these bands are reproduced quite well by our calculations with no free parameter and the deformation driving effects are discussed. The bandhead energies and the variation in the occupation probability of each cranked orbital are also analyzed. 相似文献
14.
B. Nerlo-Pomorska K. Pomorski J. F. Berger J. Dechargé 《The European Physical Journal A - Hadrons and Nuclei》2000,8(1):19-29
The proton and neutron density distributions, one- and two-neutron separation energies and radii of nuclei for which neutron
halos are experimentally observed, are calculated using the self-consistent Hartree-Fock-Bogoliubov method with the effective
interaction of Gogny. Halo factors are evaluated assuming hydrogen-like antiproton wave functions. The factors agree well
with experimental data. They are close to those obtained with Skyrme forces and with the relativistic mean-field approach. 相似文献
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16.
I. P. Golyamina E. M. Greshilov M. A. Mironov D. L. Rastorguev 《Acoustical Physics》2001,47(4):392-397
Receiving electroacoustic transducers with sensing elements made of an elastic piezoelectric composite material are described. The parameters of a composite material that exhibits a bulk piezoelectric effect are presented. Results obtained by measuring the turbulent noise in a hydrodynamic channel with the use of piezoelectric composite receivers are reported. The results are compared with those of the noise measurements by a miniature piezoceramic receiver and are considered in the light of the known models of near-wall turbulence. 相似文献
17.
Periodic waves are presented in this Letter. With symbolic computation, equations for monochromatic waves are studied, and analytic periodic waves are obtained. Factors affecting properties of periodic waves are analyzed. Nonlinear metamaterials, with the continuous distribution of the dielectric permittivity obtained, are different from the ones with the discrete distribution. 相似文献
18.
In the paper the VA-characteristics of a sandwich-type thin-layer system with amorphous semiconductor are discussed, where ohmic and non-ohmic contacts are considered. The VA-characteristics are derived which, in the case of ohmic contacts, lead to a linear dependence of the current on voltage and, in the case of non-ohmic contacts (where barriers are supposed), to a nonlinear dependence, so that VA-characteristics with negative resistance are possible as well. These VA-characteristics are compared with the experimental ones, measured on thin-layer metalamorphous Si-metal and metal-amorphous CdTe-metal structures. 相似文献
19.
简单介绍了用于分析任意口径问题的通用频域方法——广义网络原理,并利用边界积分法和广义网络原理分析导电平板上任意缝隙填充各向异性介质时TM波的散射及传输特性.由于缝隙填充各向异性介质的情形尚未见公开文献报道,作为验证,将本方法退化计算各向同性介质填充时缝隙的散射和传输特性,并与文献结果进行比较.最后,给出了缝隙填充各向异性介质时的算例. 相似文献
20.
M. O. Vassell 《Optical and Quantum Electronics》1976,8(1):23-30
Properties of the solutions of the coupled equations describing the flow of average mode power in optical waveguides are investigated. All of the important properties and their theoretical foundations are first reviewed for systems with arbitrary coupling and loss coefficients. It is then shown that, for the special class of systems with nearest-neighbour coupling, the solutions are expressible in terms of orthogonal polynomials. In particular, for systems obeying a quasi-uniform loss model and having coupling coefficients with simple dependence on mode number (uniform or linear), the solutions are associated with the classical polynomials. As illustrations of this analysis, the characteristics of optical power flow in three such systems are studied in detail. These include a slab-waveguide with uniform coupling, the corresponding cylindrical waveguide with uniform coupling, and a parabolic-index fibre with linear coupling dependence. 相似文献