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基于带输运模型理论建立了 LiNbO3 晶体屏蔽光伏孤子的时空演化动力学方程, 用有限差分方法求解发现, LiNbO3 晶体中明、暗屏蔽光伏孤子存在大的自偏转, 并且光孤子形状变得具有不对称性, 偏转方向的曲线斜率绝对值变大, 偏转反方向的曲线斜率绝对值变小. 分析研究表明影响其自偏转度和形变的因素包括受主浓度 NA, 暗辐射强度 Id 和外加电场 E0 . 其他条件不变的情况下NA 越大, 明孤子的自偏转度与形变越小, 暗孤子的自偏转度与形变反而越大; 对于 Id , 它对明暗孤子的影响是相同的, Id 越小, 晶体里诱导出的空间电荷场越容易达到饱和, 当信号光中心光强与暗辐射强度之比为 10-1时无饱和现象产生; 随着 E0 数值的增大, 明孤子的自偏转度和形变减小, 而暗孤子的自偏转度和形变反而增大. 相似文献
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Antiproton (ˉp) and antilambda (ˉΛ) production has been measured for minimum bias in p+A collisions and central A1+ A2 collisions at the CERN-SPS by the collaborations NA35/49 and NA44. The measurements are extrapolated from rapidity distributions
to absolute minimum bias cross sections. It is shown that the ˉp cross sections divided by A1· A2 follow an exponential trend as a function of a characteristic length obtained from a Glauber type absorption model, while
the ˉΛ cross sections divided by A1· A2 are constant. The exponential trend also holds for ˉp production at the lower energies of the Brookhaven AGS. A discussion of the physics interpretation of the established trends
in terms of an effective absorption cross section is presented.
Received: 15 July 1999 / Revised version: 10 November 1999 相似文献
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Stability of the positively charged manganese centre in GaAs heterostructures examined theoretically by the effective mass approximation calculation near the Γ critical point 下载免费PDF全文
This paper describes an n-i-p-i-n model heterostructure with a manganese (Mn)-doped p-type base region to check the stability of a positively charged manganese AMn+ centre with two holes weakly bound by a negatively charged 3d5(Mn) core of a local spin S=5/2 in the framework of the effective mass approximation near the Γ critical point (k~0). By including the carrier screening effect, the ground state energy and the binding energy of the second hole in the positively charged centre AMn+ are calculated within a hole concentration range from 1 × 1016 cm-3 to 1 × 1017 cm-3, which is achievable by biasing the structure under photo-excitation. For comparison, the ground-state energy of a single hole in the neutral AMn0 centre is calculated in the same concentration range. It turns out that the binding energy of the second hole in the AMn+ centre varies from 9.27 meV to 4.57 meV. We propose that the presence of the AMn+ centre can be examined by measuring the photoluminescence from recombination of electrons in the conduction band with the bound holes in the AMn+ centre since a high frequency dielectric constant of varepsilon ∞ =10.66 can be safely adopted in this case. The novel feature of the ability to tune the impurity level of the AMn+ centre makes it attractive for optically and electrically manipulating local magnetic spins in semiconductors. 相似文献
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通过分析系统的杂质位与其余部分间的纠缠N1-A以及单个正常位与其余部分间的纠缠NL-A研究了匀强磁场作用下含杂质Heisenberg XX链的纠缠特性.研究表明三量子位时纠缠存在的临界温度依赖于杂质参数J1和匀强磁场B.研究发现,当量子位L为奇数时,纠缠N1-A随量子位的增加而增大,而L为偶数时则相反,并且量子位L为偶数时的纠缠大于量子位L为奇数时的纠缠;对NL-A, 量子位L为奇数时,纠缠随杂质参数J1的变化与L=3类似,而L为偶数时纠缠随杂质参数|J1|的增加而增加. 相似文献
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本工作对完整大豆叶片直接地进行了电子自旋共振谱的测量.通过求解薛定格方程,给出IP-700+的数值解析表达式,该式与ESR实验曲线符合的很好.从而证实电子自旋极化理论对大豆叶片中光诱导信号I动力学和线型分析的适用性,以及得到A1是叶绿素A二聚物的判断. 相似文献
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应用群论及原子分子反应静力学方法推导了SiO2分子的电子态及其离解极限,采用B3P86方法,在6-311G**水平上,优化出SiO2基态分子稳定构型为单重态的C2V构型,其平衡核间距Re=RSi—O=0.1587 nm,∠OSiO=111.2°,能量为-440.4392 a.u..同时计算出基态的简正振动频率:对称伸缩振动频率ν(B2)=945.4cm-1,弯曲振动频率ν(A1)=273.5 cm-1和反对称伸缩振动频率ν(A1)=1362.9cm-1.在此基础上,使用多体项展式理论方法,导出了基态SiO2分子的全空间解析势能函数,该势能函数准确再现了SiO2(C2V)平衡结构. 相似文献
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The resonance Raman scattering phenomenon via the predissociated state is described in the four crossing terms A-(1, 2)-B model when terms 1 and 2 strongly interact. The Green's function closed representation for the coupled intermediate electronic terms 1 and 2 is obtained. The transition amplitude I A-(1, 2)-B is found in the WKB approximation. The resonance Raman scattering via the predissociated 3ΠOu + state of the interhalogen molecules is treated in detail. 相似文献
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在周期力调制噪声驱动下单模激光系统的光强方程中加入调幅波, 用线性化近似方法计算了系统的光强关联函数和输出信噪比, 并对信噪比进行数值计算和分析, 发现低频调制频率Ω、高频载波频率ω和周期力频率Ωλ对系统的输出信噪比有很大的影响. 具体表现为信噪比R 随低频调制频率Ω 的变化过程中出现了多重随机共振和极强的单峰共振, 当Ω << ω 时, 系统出现的是多峰共振, 且随着Ωλ 增加, 共振峰间的距离增大, 峰值位置不变; 当Ω → ω 时, 输出信噪比R迅速增大, 而Ωλ 的影响被削弱甚至可以忽略, 多峰共振消失; 当Ω = ω 时, 系统出现了极强的单峰共振. 此外, 信噪比随周期力频率的变化呈现振幅减小的多重随机共振, 而随载流频率的变化出现单峰随机共振. 相似文献
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The harmonic stochastic resonance-enhanced signal detecting in Newman-Watts small-world neural network is studied using the Hodgkin-Huxley dynamical equation with noise.If the connection probability p,coupling strength g syn and noise intensity D matches well,higher order resonance will be found and an optimal signal-to-noise ratio will be obtained.Then,the reasons are given to explain the mechanism of this appearance. 相似文献
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In this paper, a theoretical analysis is carried out to estimate the sensitivity and the signal-to-noise ratio (SNR) of a fiber optic surface plasmon resonance (SPR) sensor when fibers with different dopants and different doping concentrations are used. The dopants considered are germanium oxide (GeO2), boron oxide (B2O3), and phosphorus pentoxide (P2O5) in a pure silica fiber. The variation of the dispersion relation with different dopants and doping concentrations are taken into account for the analysis. It is shown that the doping of B2O3 increases the sensitivity of the sensor while the effect of dopant on SNR is negligible. The analysis is extended to fiber optic SPR sensor with bimetallic layers. 相似文献
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Y. Tao G. Bergmann 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(1):42
The Friedel oscillations in the vicinity of a Friedel-Anderson (FA) impurity are investigated numerically. For an FA impurity
in the local moment limit the normalized amplitude A(ξ) is S-shaped, approximately zero at short distances, approaching two at large distances and crossing the value one at the
characteristic length ξ
1/2. Surprisingly, the Friedel oscillations of a simple non-interacting Friedel impurity with a narrow resonance at the Fermi
level show a very similar behavior of their amplitude A(ξ). A comparison correlates the resonance width and the Kondo energy of the FA impurity with the characteristic length ξ
1/2 of the Friedel oscillations. 相似文献
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A highly sensitive method for infrared radiation detection based on thermal resonance in an active bolometer is set forth. An active bolometer is a self-oscillating system consisting of an IR-sensitive cell in a feedback circuit of an adjustable proportional controller. The analysis of an active bolometer autonomous (dark) dynamics reveals that with a generalized gain factor A variation the system evolves from relaxation type towards oscillating and self-oscillating type. When A=Ac, where Ac is a critical value of the generalized gain factor A, the steady state loses stability through self-excited thermal oscillations. The resonance in a system weakly perturbed by IR radiation modulated at self-oscillation frequency q0[1+exp(iωct)] is considered. It is shown that in a small precritical vicinity =(A−Ac)/Ac of the gain factor the amplitude of forced thermal oscillations is proportional to q0/Ac. The D* calculation reveals that the detection power of a passive (A=0) bolometer increases with feedback introduction by a factor of 1/||. The detection powers of feasible versions of an active bolometer are compared. 相似文献
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Vorotynov A. M. Petrakovski? G. A. Sablina K. A. Bovina A. F. Vasil’ev A. D. 《Physics of the Solid State》2010,52(11):2415-2418
The Jahn-Teller effect in the ZnGa2O4 spinel single crystal has been investigated using electron paramagnetic resonance of Cu2+ ions in the temperature range 110–560 K. It has been shown that copper ions occupy octahedral sites 16d in the ZnGa2O4 crystal with cubic symmetry O
h
7 (Fd-3m). At T < 560 K, the octahedra undergo tetragonal distortions (predominantly tension) and rotation around the fourfold axes by the
angle θ ≈ 2.6°. The parameters of the spin Hamiltonian, which characterize the prolate (g
‖ = 2.355, g
⊥ = 2.077, A
‖ = 116 Oe, A
tp = 12 Oe) and oblate (g
‖ = 2.018, g
⊥ = 2.246, A
‖ = 75 Oe, A
⊥ = 44 Oe) octahedra, have been determined. At temperatures above 560 K, the static Jahn-Teller effect transforms into the
dynamic effect and the spectrum of the magnetic resonance becomes isotropic with g = 2.116 (the experimental frequency corresponds to the X band). 相似文献
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Topological probability and connection strength induced activity in complex neural networks 下载免费PDF全文
Recent experimental evidence suggests that some brain activities can be assigned to small-world networks. In this work, we investigate how the topological probability p and connection strength C affect the activities of discrete neural networks with small-world (SW) connections. Network elements are described by two-dimensional map neurons (2DMNs) with the values of parameters at which no activity occurs. It is found that when the value of p is smaller or larger, there are no active neurons in the network, no matter what the value of connection strength is; for a given appropriate connection strength, there is an intermediate range of topological probability where the activity of 2DMN network is induced and enhanced. On the other hand, for a given intermediate topological probability level, there exists an optimal value of connection strength such that the frequency of activity reaches its maximum. The possible mechanism behind the action of topological probability and connection strength is addressed based on the bifurcation method. Furthermore, the effects of noise and transmission delay on the activity of neural network are also studied. 相似文献
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The electron paramagnetic resonance (EPR) parameters (g factors g //, g ⊥ and hyperfine structure constants A //, A ⊥) for 15MgO-15Na2O-69B2O3 (MNB):Cu2+ ternary glasses were calculated based on the high-order perturbation formulae of 3d9 ion in a tetragonal symmetry. From the calculations, the defect structures of MNB:Cu2+ ternary glasses were obtained and a negative sign for A // and A⊥ for the Cu2+ center is suggested in the discussion. 相似文献