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161.
采用理论与实验相结合的方法研究了激光二极管阵列泵浦的Cr4+:YAG被动调Q Nd:YAG激光器的输出特性.重点分析了调Q晶体小信号透过率和反射镜的反射率对激光器的输出能量、脉冲宽度的影响.对数值模拟结果进行了实验验证,数值计算与实验结果基本一致.研究结果表明,在特定的激光晶体参数下,Cr4+:YAG被动调Q激光器的输出能量与脉冲宽度由调Q晶体的小信号透过率和输出镜的反射率决定:输出能量随着小信号透过率增加而减小,对应于一个调Q晶体透过率,有一个最佳反射率使输出能量最大;脉冲宽度随着初始透过率与反射率的增大而增大. 相似文献
162.
Javed Ahmad Muhammad Ehsan MazharMuhammad Qadeer Awan Muhammad Naeem Ashiq 《Physica B: Condensed Matter》2011,406(18):3484-3488
Potassium substituted nanosized magnesium aluminates having a nominal composition Mg1−xKxAl2O4 where x=0.0, 0.25, 0.5, 0.75, 1.0 have been synthesized by the chemical co-precipitation method. The samples have been characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), and dc electrical resistivity measurements. The XRD results reveal that the samples are spinel single phase cubic close packed crystalline materials. The calculated crystallite size ranges between 6 and 8 nm. The behaviour of the lattice constant seems to deviate from the Vegard's law. While X-ray density clearly increases, the bulk density and consequently, the percentage porosity do not exhibit a significant change on increasing the K+ content. The SEM micrographs suggest homogeneous distribution of the nanocrystallites in the samples. The dc electrical resistivity exhibits a typical semiconducting behaviour. Substitution of a Mg2+ ion by a K+ ion provides an extra hole to the system, which forms small polaron. Thermally activated hopping of these small polarons is believed to be the conduction mechanism in the Mg1−xKxAl2O4. The activation energy of hopping of small polarons has been calculated and found K+ ions content dependent. 相似文献
163.
用脉冲激光沉积法在(111)Si衬底上成功制备了高度择优取向的Fe3O4薄膜.电阻-温度关系表明Fe3O4薄膜的Verwey转变(TV)约在122 K,低温段(TV)输运特征满足Mott变程跳跃模型,高温段(T>TV)为小极化子输运.激光作用下的光电导实验发现,在整个温区表现为光致电阻率减小,而且低温段的电阻变化率比高温段要大很多.分析认为Fe3O4薄膜的光致电阻率变化主要与激光激发t2g电子的转移有关.
关键词:
3O4薄膜')" href="#">Fe3O4薄膜
小极化子
光诱导特性 相似文献
164.
The spatial structures of magnetic Co nanowire array embedded in anodic aluminium membranes were investigated by grazing incidence small angle X-ray scattering (GISAXS) and conventional small angle X-ray scattering (SAXS) techniques. Compared with SEM observation, the GISAXS and SAXS measurements can get more overall structural information in a large-area scale. In this study, the two-dimensional GISAXS pattern was well reconstructed by using the IsGISAXS program. The results demonstrate that the hexagonal lattice formed by the Co nanowires is distorted (a ≈ 105 nm, b ≈ 95 nm). These Co nanowires are isolated into many structure domains with different orientations with a size of about 2 μm. The SAXS results have also confirmed that the nanopore structures in the AAM can be retained after depositing Co nanowires although the Co nanowires can not completely but only just fill up the nanopores. These results are helpful for understanding the global structure of the Co nanowire array. 相似文献
165.
166.
Houyu Zhao 《Mathematical Methods in the Applied Sciences》2014,37(17):2689-2696
In this paper, we study the existence of analytic invariant curves of a iterative equation which from mosquito model. By constructing an invertible analytic solution g(x) of an auxiliary equation of the form invertible analytic solutions of the form g(αg ? 1(x)) for the original iterative functional equation are obtained. Besides the hyperbolic case 0 < | α | < 1, we focus on those α on the unit circle S1, that is, | α | = 1. We discuss not only those α at resonance, that is at a root of the unity, but also those α near resonance under the Brjuno condition. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
167.
168.
169.
170.
We study a system of two first-order differential equations arising in averaging nonlinear systems over fast single-frequency
oscillations. We consider the situation where the original system contains weak dissipative terms. We construct the asymptotic
form of a two-parameter solution with an unbounded increasing amplitude. This result gives a key for understanding autoresonance
in weak dissipative systems as a phenomenon of significant increase in the forced nonlinear oscillation initiated by a small
external pumping.
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Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 160, No. 1, pp. 102–111, July, 2009. 相似文献