Numerical study on the dependence of ZnO thin-film transistor characteristics on grain boundary position

The dependence of transistor characteristics on grain boundary(GB) position in short-channel ZnO thin film transistors(TFTs) has been investigated using two-dimensional numerical simulations.To simulate the device accurately,both tail states and deep-level states are taken into consideration.It is shown that both the transfer and output characteristics of ZnO TFTs change dramatically with varying GB position,which is different from polycrystalline Si(poly-Si) TFTs.By analysing the mechanism of the carrier transportation in the device,it is revealed that the dependence is derived from the degrees of carrier concentration descent and mobility variation with GB position.     

Charging and rotational dependence of line position

For a charged sample the measured binding energies depend on the location of the sample within the sample chamber^{1, 2}. If it is only the angle between the sample surface and the analyser which is varied then the line position depends, in a characteristic way, on the rotation angle. This dependence can be used to prove whether or not a sample is charged. In addition, the amount of rotational dependence of line positions gives an indication of the magnitude of charging.     

An analysis of the temperature and pressure dependence of the electrical resistivity in lead

The volume dependence of the high temperature electrical resistivity has been treated in detail for lead. Volume changes caused by external pressure as well as thermal expansion have been considered. Experiments on the volume dependence of the effective electron mass have been reanalysed with an inclusion of electron-phonon interaction. Finally, we have found no experimental support for a net effect from a Debye-Waller factor and multi-phonon processes.     

An evaluation of target irradiation uniformity based on spatial-spectrum analysis

The irradiation uniformity of target spots in high-power laser driver is evaluated based on spatial-spectrum analysis. Spatial spectrum can display the detailed spatial intensity structure of the spots and show the spatial frequency modes smoothed by the beam smoothing techniques. This evaluating model is applied to two kinds of typical target spots obtained with a lens array and a random phase plate, respectively, and its validity is found to be independent of the spot profile and the degree of intensity modulation. The uniformity evaluations based on this model are in good agreement with the fractional power above intensity.     

靶源位置对强场高次谐波相位匹配的影响

为提高强激光场与惰性气体靶作用产生的孤立阿秒激光脉冲的能量,给出了一种实现高次谐波过程中最佳谐波相位匹配的定量实验方法。研究了气体靶源与高斯型驱动激光场聚焦点相对空间位置对谐波相位匹配及谐波产率的影响,得出了其最佳相位匹配位置始终位于驱动激光场聚焦点后3~5 mm,而在聚焦点之前的位置区域,严重的高次谐波相位失配导致谐波产率非常低。同时,在最佳相位匹配条件下,高次谐波场与驱动场具有相类似的空间强度分布特性,该结果印证了目前通常采用的高次谐波场为高斯光束的假设。     

Determination of angle dependence of sputtering yield for a multicomponent target by the time characteristics of the sputtering process

A method for determining the variations of sputtering yield of multicomponent target based on studies of time characteristics of the sputtered particles flux has been proposed and tested on an example of the angle dependence of sputtering yield. Time dependences of variation in the fluxes of the sputtered atoms of multicomponent oxides at different incidence angles of Ar ions were studied. Angular dependences of the sputtering yield for these compounds were obtained by direct measurements and computations. It has been shown that the angular dependence of the sputtering yield in a stationary mode can be obtained from the time dependences of the fluxes of the sputtered particles.     

美国基础物理实验教科书(讲义)的特点分析

通过选取美国5所大学自编的基础物理实验教科书,对教科书内容的栏目设置,知识点涵盖内容与范围,配套信息资源选择,教科书特色与优点等各方面进行对比分析.总结教科书在教学基本理念,教育教学目标,能力培养手段,情感态度培育方法方面的特点.希望对我国基础物理实验教学改革的进一步推进、物理实验教材的建设和发展、物理实验教学方法和理念的改进与优化提供参考与借鉴.     

光电侦察阵列对空目标定位算法研究

为扩大重点区域防御的侦察范围及对来袭目标的定位,在双单元交互测量定位算法的基础上,利用相邻阵列单元接力测量,由中心处理单元完成被动测距、坐标转换与数据融合,提出了一种基于阵列式光电侦察系统对空目标定位算法,建立mn光电侦察阵列对空目标定位算法数学模型。通过MATLAB完成了22阵列单元对单目标定位仿真验证与误差分析。结果表明,该算法实时输出了目标三维航迹数据,实现了光电侦察阵列对空目标的定位,与理论真值相比,平均定位误差绝对值小于7 m。     

Experimental analysis of the vibrational characteristics of the human skull

Analytical models of the human skull structure have generally been constructed so as to characterize the gross geometric features and material properties; however, a model should also have accurate frequency response characteristics since these are essential for collision and head injury analyses. An experimental investigation was conducted to identify the dynamic characteristics of freely vibrating human skulls. Resonant frequencies and associated mode shapes in the frequency band from 20 Hz to 5000 Hz were delineated for two dry human skulls. Osteometrically, one skull corresponds to a 50th percentile male (skull 1) and the second is representative of a 5th percentile female skull (skull 2). Digital Fourier analysis techniques were used to identify the resonant frequencies and corresponding mode shapes of each skull. Eleven resonant frequencies were identified for skull 1, with the lowest being 1385 Hz. In contrast, skull 2 exhibited only 6 resonant frequencies with the first being 1641 Hz. Nine mode shapes were identified for skull 1, but only 5 modes were recognized for skull 2. The vibrational pattern of the human skull, as indicated by its mode shapes in this limited study, seems to be a unique property of a particular skull. Skull satures did not appear to influence the modal pattern.     

Energy dependence of effective nucleon-nucleon interaction and position of the nucleon drip line

A semimicroscopic version of the self-consistent theory of finite Fermi systems is proposed. In this approach, the standard theory of finite Fermi systems is supplemented with relations that involve the external values of the invariant components of the Landau-Migdal amplitude and which follow from microscopic theory. The Landau-Migdal amplitude at the nuclear surface is expressed in terms of the off-shell T matrix for free nucleon-nucleon scattering at the energy E equal to the doubled chemical potential of the nucleus being considered. The strong energy dependence of the free T matrix at low E changes the properties of nuclei in the vicinity of the nucleon drip line. It is shown that, upon taking into account the energy dependence of the effective interaction, the neutron drip line is shifted considerably toward greater neutron-excess values. This effect is illustrated by considering the example of the tin-isotope chain.     

基于直线的运动目标相对位置姿态光学测量方法

针对运动目标的相对位置姿态测量问题,研究了一种基于目标上的两条不平行直线的光学测量方法。首先证明了使用特征光点确定目标位置姿态参数的条件;然后推导了基于直线的求取位置姿态的解析解;最后对使用该方法时的测量误差进行了仿真分析,同时给出了实际的测量误差。由于增加了带测量的测量基线,所以减少了位置姿态参数的测量精度对光学系统的依赖。实验结果表明,该方法可满足运动目标相对位置姿态的高精度测量的需求。     

等离子体的振荡及流体效应的解释

在普通物理层次内对等离子体的主要基本特性进行分析并简单介绍有关应用。     

An improved infrared dim and small target detection algorithm based on the contrast mechanism of human visual system

To achieve higher detection rate and lower false alarm rate in dim and small target detection, this paper proposed an improved algorithm based on the contrast mechanism of human visual system (HVS) for infrared small target detection in an image with complicated background. According to the contrast mechanism of HVS, Laplacian of Gaussian (LoG) filter is exploited to deal with the input image, which can not only suppress the background noise and clutter but also enhances the target intensity significantly. As a result it increases the contrast ratio between target and background. To further eliminate residual clutter, we process the filtered image with morphological method in all directions. True target is finally obtained by applying local thresholding segmentation to the pre-processed image. Experimental results demonstrate its superior and reliable detection performance by high detection rate and low false alarm rate.     

An evaluation of the time dependence of the anisotropy of the water diffusion tensor in acute human ischemia

We have performed MRI examinations to determine the water diffusion tensor in the brain of six patients who were admitted to the hospital within 12 h after the onset of cerebral ischemic symptoms. The examinations have been carried out immediately after admission, and thereafter at varying intervals up to 90 days post admission. Maps of the trace of the diffusion tensor, the fractional anisotropy and the lattice index, as well as maps of cerebral blood perfusion parameters, were generated to quantitatively assess the character of the water diffusion tensor in the infarcted area. In patients with significant perfusion deficits and substantial lesion volume changes, four of six cases, our measurements show a monotonic and significant decrease in the diffusion anisotropy within the ischemic lesion as a function of time. We propose that retrospective analysis of this quantity, in combination with brain tissue segmentation and cerebral perfusion maps, may be used in future studies to assess the severity of the ischemic event.     

Laser spot position dependence in photothermal mode cooling of a microcantilever

We explore the laser spot position (LSP) dependence of photothermal mode cooling in a microcantilever-based Fabry-Perot cavity. Experiments on photothermal cooling demonstrate that the direction of photothermal backaction on the first two cantilever modes is LSP dependent, which can be either parallel or antiparallel. A theoretical analysis of this LSP-dependent effect identifies the parallel and the antiparallel coupling regions along the lever. Simulation results are in quantitative agreement with our experimental observations. We conclude that the cooling limit imposed by photothermal mode coupling can be surmounted by operating in the parallel coupling region.     

An experimental study of the acoustic impedance characteristics of human hair

Previous analytical and empirical studies of the human auditory system have shown that the cues used for localization are modified by the inclusion of nonrigid scattering surfaces (clothing, hair etc). This paper presents an investigation into the acoustic impedance properties of human hair. The legitimacy of a locally reactive surface assumption is investigated, and an appropriate boundary condition is formulated to account for the physiological composition of a human head with hair. This utilizes an equivalent impedance parameter to allow the scattering boundary to be defined at a reference plane coincident with the inner rigid surface of the head. Experimental examination of a representative synthetic hair material at oblique incidence is used to show that a locally reactive surface assumption is legitimate. Additional experimental analysis of a simple scattering problem illustrates that the equivalent impedance must be used in favor of the traditional surface impedance to yield physically correct pressure magnitudes. The equivalent acoustic impedance properties of a representative range of human hair samples are discussed, including trends with sample thickness, fiber diameter, bulk density, and mass.     

弯管缺陷形状与位置对超声导波传播特性影响*

基于超声数值模拟,研究椭圆形冲蚀缺陷的几何尺寸和位置与接收端超声波能量之间的关系。通过控制椭圆形冲蚀缺陷几何尺寸,研究缺陷在弯管θ= 0°且ψ= 20°位置处,不同几何尺寸的缺陷对接收端压电传感器(PZT)时域信号能量的影响。此外,为研究相同几何尺寸的椭圆形冲蚀缺陷位于弯管不同位置时,对接收端时域信号能量的影响,椭圆形冲蚀缺陷位于弯管以下位置：ψ= 20°且θ取值范围为0°~ 30°,每间隔2.5°取一个值;θ= 0°且ψ取值范围为15°~ 45°,每间隔2.5°取一个值。数值模拟结果表明：缺陷位于弯管θ= 0°且ψ= 20°位置处,随着缺陷面积增加,接收端上侧PZT时域信号能量减少;随着缺陷深度和缺陷深度与面积都增加的两种情况下,上侧PZT时域信号能量均出现先减小,当缺陷深度达到弯管厚度的75%(6 mm)时,上侧PZT时域信号能量再增加;相同几何尺寸的缺陷位于弯管θ= 0°,随着ψ增加,上侧PZT时域信号能量先减小后增加;相同几何尺寸的缺陷位于弯管ψ= 20°,随着θ增加,θ与 呈现出单调递增的关系。通过上述结果可知,椭圆形冲蚀缺陷的几何尺寸和位置与接收端时域信号能量之间存在相关性,基于此可通过能量变化实现对缺陷几何尺寸大小和位置的评估。