工程力学矢量的规范表示与弹性力学的不变性

通过引入规范变换，消除了工程力学矢量数学表示上的物理缺陷，使规范化力学矢量与力学张量具有物理上的等价表示，从而奠定了不变性弹性力学的基础，为它在不同坐标下的具体应用提供了理论保障。     

自重体积力作用下坡体张应力及坡面位移的变化规律

为了提高对边坡体力学行为的认识,借助于FLAC有限差分软件的数值模拟,并结和相似理论的推导验证,研究了在仅有自重体积力作用的条件下,线弹性边坡体的一些力学特征及其与相关变量或物理力学参数的相关关系。没有外载荷影响时边坡地表最大主应力和最小主应力分别平行和垂直于地表,当深度增加时,主应力的取向逐渐变成竖直和水平两个方向,坡面处既有张应力区也有拉应力区,坡脚处亦存在较大的张应力,这是自重体积力作用下边坡体应力分布的一般性特征,在本文和前人的研究中都能体现。本文还重点揭露了：坡角线性增加时坡顶最大张应力的变化速率表现为：快——慢——快; 沿坡顶面竖直向下张应力随深度增加线性减小; 小变形条件下边坡应力场与弹性模量无关; 最后验证了满足相似理论的坡体,坡面对应点的位移比是其几何尺寸比的平方倍。本文不仅是对既有研究成果的进一步补充,而且为以后研究复杂条件下边坡体的力学特征奠定了基础,对于理论和实践都有一定的启发意义。     

水沙流中离散颗粒流动应力关系

在已有的基于膨胀体模型、动理论模型和连续介质理论得到的关系式基础上,分析了水沙流中颗粒流动的应力关系应由摩擦应力、滑动应力和碰撞应力3部分组成,并将颗粒弹性恢复系数引入,对颗粒碰撞项进行了修正。根据颗粒碰撞时间间隔T_c和颗粒弛豫时间T_e的对比,提出了颗粒流动进入碰撞惯性区的临界值,即当T_c/T_e<0.02时,水沙流中颗粒流动碰撞作用占优,可忽略摩擦应力和滑动应力,并将提出的临界值与实验资料进行了比较。利用修正后的水沙流中颗粒流动应力关系,对缓槽水沙流动进行了模拟计算,获得了与实测资料一致的结果。     

塞曼效应仿真实验平台

塞曼效应实验是学生了解原子具有磁矩和空间取向量子化现象的重要实验,至今塞曼效应仍是研究能级结构的重要方法之一.为了能够让学生更加清楚地了解塞曼效应实验的基本原理和操作规程,针对教学中的重点和难点,运用flash软件制作出塞曼效应仿真实验.该程序可全程高度仿真实验过程,具有界面友好、易于操作、无需安装等优点.为实验教学提供了一种新的辅助方式.     

?4模型真空态间的转换算符

本工作在正则量子化的基础上，对$\phi^4$模型的哈密顿量采取正规序来正规化真空零点能，然后微扰计算了至次领头阶的真空态修正。同时首次得到可以在$\phi^4$模型的两个真空态之间转换的算符，我们相信这个算符也是适当极限条件下产生$\phi^4$扭结(kink)的算符的形式。最后简要说明了真空能的应用。     

Free-space propagation of autofocusing Airy vortex beams with controllable intensity gradients

Vortex splitting is one of the main causes of instability in orbital angular momentum(OAM) modes transmission. Recent advances in OAM modes free-space propagation have demonstrated that abruptly autofocusing Airy vortex beams(AAVBs) can potentially mitigate the vortex splitting effect. However, different modes of vortex embedding will affect the intensity gradients of the background beams, leading to changes in the propagation characteristics of vortex beams. This study presents the unification of two common methods of coupling autofocusing Airy beams with vortices by introducing a parameter(m), which also controls the intensity gradients and focusing properties of the AAVBs. We demonstrate that vortex splitting can be effectively reduced by selecting an appropriate value of the parameter(m) according to different turbulence conditions. In this manner,the performance of OAM-based free-space optical systems can be improved.     

Image charge effect on the light emission of rutile TiO_2(110) induced by a scanning tunneling microscope

The plasmon-enhanced light emission of rutile TiO_2(110) surface has been investigated by a low-temperature scanning tunneling microscope(STM). We found that the photon emission arises from the inelastic electron tunneling between the STM tip and the conduction band or defect states of TiO_2(110). In contrast to the Au(111) surface, the maximum photon energy as a function of the bias voltage clearly deviates from the linear scaling behavior, suggesting the non-negligible effect of the STM tip on the band structure of TiO_2. By performing differential conductance( dI/dV) measurements, it was revealed that such a deviation is not related to the tip-induced band bending, but is attributed to the image charge effect of the metal tip, which significantly shifts the band edges of the TiO_2(110) towards the Femi level(E_F) during the tunneling process. This work not only sheds new lights onto the understanding of plasmon-enhanced light emission of semiconductor surfaces, but also opens up a new avenue for engineering the plasmon-mediated interfacial charge transfer in molecular and semiconducting materials.     

Improved performance of Au nanocrystal nonvolatile memory by N_2-plasma treatment on HfO_2 blocking layer

The N_2-plasma treatment on a HfO_2 blocking layer of Au nanocrystal nonvolatile memory without any post annealing is investigated. The electrical characteristics of the MOS capacitor with structure of Al–Ta N/HfO_2/Si O2/p-Si are also characterized. After N_2-plasma treatment, the nitrogen atoms are incorporated into HfO_2 film and may passivate the oxygen vacancy states. The surface roughness of HfO_2 film can also be reduced. Those improvements of HfO_2 film lead to a smaller hysteresis and lower leakage current density of the MOS capacitor. The N_2-plasma is introduced into Au nanocrystal(NC) nonvolatile memory to treat the HfO_2 blocking layer. For the N_2-plasma treated device, it shows a better retention characteristic and is twice as large in the memory window than that for the no N_2-plasma treated device. It can be concluded that the N_2-plasma treatment method can be applied to future nonvolatile memory applications.