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251.
A common scenario of magnetoelectric coupling in multiferroics is the electric polarization induced by spatially modulated spin structures. It is shown in this paper that the same mechanism works in magnetic dielectrics with inhomogeneous magnetization distribution: the domain walls and magnetic vortexes can be the sources of electric polarization. The electric field driven magnetic domain wall motion is observed in iron garnet films. The electric field induced nucleation of vortex state of magnetic nanodots is theoretically predicted and numerically simulated. From the practical point of view the electric field control of micromagnetic structures suggests a low-power approach for spintronics and magnonics. 相似文献
252.
Electronic spectra of the linear magnesium-containing carbon chains MgC2nH (n = 1–5): A CASPT2 study
Complete active space self-consistent-field (CASSCF) approach has been used for the geometry optimization of the X2Σ+ and A2Π electronic states for the linear magnesium-containing carbon chains MgC2nH (n = 1–5). Multireference second-order perturbation theory (CASPT2) has been used to calculate the vertical excitation energies from the ground to selected seven excited states, as well as the potential energy curves of two 2Σ+ and two 2Π electronic states. The studies indicate that the vertical excitation energies of the A2Π ← X2Σ+ transition for MgC2nH (n = 1–5) are 2.837, 2.793, 2.767, 2.714, and 2.669 eV, respectively, showing remarkable linear size dependence. Compared with the previous TD-DFT and RCCSD(T) results, our estimates for MgC2nH (n = 1–3) are in the best agreement with the available observed data of 2.83, 2.78, and 2.74 eV, respectively. In addition, the dissociation energies in MgC2nH (n = 1–5) are also been evaluated. 相似文献
253.
研究了一类具有垂直传染的脉冲免疫接种SIR模型,采用传染率βI(1+vI)S,得到了无病周期解,给出了此周期解的全局稳定性分析.并获得了系统一致持续生存的条件. 相似文献
254.
文中给出了垂直线性互补问题的一个新的光滑价值函数,不同于光滑化方法中的价值函数,它不包含任何必须趋向零的参数,因此算法中不涉及参数调整步骤,而且具有良好的强制性.基此价值函数,提出了求解垂直线性互补问题的一种阻尼Newton类算法,并证明了该算法对竖块P0+R0矩阵的垂直线性互补问题具有全局收敛性;当解满足相当于BD-正则条件时,算法具有局部二次收敛性;在不增加额外校正步骤(算法的每个迭代步只求解一个Newton方程)的情形下,算法对竖块P-矩阵垂直线性互补问题(无须假设严格互补),具有有限步收敛性.数值实验结果令人满意. 相似文献
255.
256.
This letter presents the design, simulation, fabrication, and successful demonstration of a variable optical attenuator (VOA) based on a micromachined micromirror combined with an optical fiber collimator. The micromirror has a size of 500 μm in diameter and a rotational resonance of 4.94 kHz. The micromirror was actuated by vertical comb drive which was fabricated by bulk micromachining process on a silicon on insulator (SOI) wafer. The VOA operates at a low driving voltage of 4.4 V corresponding to the rotation angle of 0.3°. The turn-on and turn-off response time of the VOA are 1.6 ms and 2.74 ms, respectively. Finally, the optical attenuation was measured and an optical attenuation as large as 40 dB was obtained. 相似文献
257.
258.
Low-resistance Cr/Al Ohmic contacts to N-polar n-type GaN for high-performance vertical light-emitting diodes 总被引:1,自引:0,他引:1
We investigated the electrical properties of Cr(30 nm)/Al(200 nm) contacts to N-polar n-type GaN for high-performance vertical light-emitting diodes and compare them with those of Ti(30 nm)/Al(200 nm) contacts. Before annealing, both the samples show ohmic behaviors with a contact resistivity of 1.9-2.3 × 10−4 Ωcm2. Upon annealing at 250 °C for 1 min in N2 ambient, the Ti/Al contacts become non-ohmic, while the Cr/Al contacts remain ohmic with a contact resistivity of 1.4 × 10−3 Ωcm2. Based on X-ray photoemission spectroscopy and secondary ion mass spectrometry results, ohmic formation and degradation mechanisms are briefly described and discussed. 相似文献
259.
在用电磁铁NMR谱仪研究细胞内外Na+浓度的实验中,发现了一些与超导谱仪实验相异的现象,对这些现象进行理论分析,且认为可以由此测得稀土金属原子的磁矩。 相似文献
260.
The effects of vertical gravity fields on the structural characteristics of electrodeposited Ni foils were investigated in a centrifuge. Analysis by atomic force microscopy (AFM) shows that the surface roughness of Ni foils reduces from 37.6 nm to 8.1 nm with the increase of gravity coefficient (G) from 1 to 354. Furthermore, the roughness of Ni foils deposited at G = 62 evolves much more slowly than that deposited at G = 1. The study of the textural perfection by X-ray diffractiometry (XRD) reveals that the degree of (2 0 0) preferred orientation parallel to the substrate plane is lowered by the vertical gravity field. Randomly oriented deposits are obtained in the vertical gravity field while deposits with uniaxial texture are obtained in the natural gravity field. Due to these variations in the structure, the Ni foils obtained in the vertical gravity field exhibit improved corrosion resistance. 相似文献