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61.
本文研究了混合时滞的随机微分方程的稳定性,利用Lyapunov函数方法和半鞅收敛定理得到了p阶矩指数稳定和几乎必然指数稳定的判定定理.M矩阵技巧的使用使所得结果更便于应用.最后举例说明了结果的实用性. 相似文献
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用中频脉冲反应磁控溅射法,在溅射功率为78 W,93 W和124 W以及衬底温度分别为室温,500 ℃及677 ℃下制备了氧化铒涂层.采用原子力显微镜、纳米压痕、X射线衍射和掠入射X射线衍射法研究了涂层的形貌、力学性能及物相结构.测量了涂层的电学性能.结果显示,脉冲磁控溅射沉积氧化铒涂层具有较高的沉积速率.实验制备得到了单斜相结构的氧化铒涂层.提高溅射功率时,沉积速率从28 nm/min增大至68 nm/min,涂层的结晶质量显著下降.提高衬底温度至500 ℃和677 ℃时,单斜相衍射峰强度下降.分析认为
关键词:
氧化铒
脉冲磁控溅射
单斜晶相 相似文献
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We present a theoretical study on collective excitation modes associated with plasmon and surface-plasmon oscilla- tions in cylindrical metallic nanowires. Based on a two-subband model, the dynamical dielectric function matrix is derived under the random-phase approximation. An optic-like branch and an acoustic-like branch, which are free of Landau damp- ing, are observed for both plasmon and surface-plasmon modes. Interestingly, for surface-plasmon modes, we find that two branches of the dispersion relation curves converge at a wavevector qz = qrnax beyond which no surface-plasmon mode exists. Moreover, we examine the dependence of these excitation modes on sample parameters such as the radius of the nanowires. It is found that in metallic nanowires realized by state-of-the-art nanotechnology the intra- and inter-subband plasmon and surface-plasmon frequencies are in the terahertz bandwidth. The frequency of the optic-like modes decreases with increasing radius of the nanowires, whereas that of the acoustic-like modes is not sensitive to the variation of the radius. This study is pertinent to the application of metallic nanowires as frequency-tunable terahertz plasmonic devices. 相似文献
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Increasing the phonon scattering center by adding nanoparticles to thermoelectric materials is an effective method of regulating the thermal conductivity. In this study, a series of Ca$_{3}$Co$_{4}$O$_{9}/x$ wt.% CNTs ($x=0$, 3, 5, 7, 10) polycrystalline ceramic thermoelectric materials by adding carbon nanotubes (CNTs) were prepared with sol-gel method and cold-pressing sintering technology. The results of x-ray diffraction and field emission scanning electron microscopy show that the materials have a single-phase structure with high orientation and sheet like microstructure. The effect of adding carbon nanotubes to the thermoelectric properties of Ca$_{3}$Co$_{4}$O$_{9}$ was systematically measured. The test results of thermoelectric properties show that the addition of carbon nanotubes reduces the electrical conductivity and Seebeck coefficient of the material. Nevertheless, the thermal conductivity of the samples with carbon nanotubes addition is lower than that of the samples without carbon nanotubes. At 625 K, the thermal conductivity of Ca$_{3}$Co$_{4}$O$_{9}$/10 wt.% CNTs sample is reduced to 0.408 W$\cdot$m$^{-1}\cdot$K$^{-1}$, which is about 73% lower than that of the original sample. When the three parameters are coupled, the figure of merit of Ca$_{3}$Co$_{4}$O$_{9}$/3 wt.% CNTs sample reaches 0.052, which is 29% higher than that of the original sample. This shows that an appropriate amount of carbon nanotubes addition can reduce the thermal conductivity of Ca$_{3}$Co$_{4}$O$_{9}$ ceramic samples and improve their thermoelectric properties. 相似文献
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硼的径迹显微照相技术是检测材料中微量硼的含量与分布的有效的手段.本文开发建立了Windows环境下对硼径迹显微照片进行图像转换处理和定量测量的软件,利用该软件能够快速处理测量大批量硼径迹显微照片,测量结果的准确性和重复性良好. 相似文献
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探讨加拿大一枝黄花(Solidago canadensis L.)花序乙酸乙酯提取物中酸性成分体外及体内抗肿瘤活性.采用MTT法跟踪提取物细胞毒活性;用S180和EAC昆明小鼠模型进行提取物的体内抗肿瘤活性评价.结果表明,加拿大一枝黄花花序的酸性成分具有显著抑制多株人肿瘤细胞株生长的作用,并呈明显的量效关系.乙酸乙酯提取物中的酸性成分对小鼠移植性肿瘤S180和EAC的生长也有显著的抑制作用,并和剂量正相关,高剂量组对小鼠移植性肿瘤S180和EAC的抑制率分别为52.06%,32.90%.显示了加拿大一枝黄花具有较强的体内和体外抗肿瘤作用. 相似文献