一种改进的基于混合高斯模型的运动目标检测方法

混合高斯模型方法被广泛应用于运动目标检测,但是现有的混合高斯模型方法在应对噪声和光照突变时效果不佳,其运动目标检测的效果会受到严重影响。为了解决上述问题,提出了一种结合边缘混合高斯模型方法以及改进的基于邻域差方法的综合方法。该方法充分利用了边缘图像对于噪声和光照突变不敏感,以及邻域差方法可以去除部分噪声的特点,对图像序列进行综合处理。实验结果证明,该方法可以提升运动目标的检测率,降低误警率,可以更有效地应对噪声和光照突变的干扰,从而具有更准确的目标检测效果。     

基于视频图像测量的母线折弯技术研究

现有折弯机在母线的角度测量中一般采用光栅尺或编码器,针对这种接触式检测方法存在的局限性,提出了基于视频技术的角度检测方法,这种非接触式测量方法不仅使角度的检测更加方便,而且增加了折弯机机头机械设计的灵活性.分析了母线在进行边缘检测时角度存在跳动的原因,提出了一种通过抑制伪边缘的方法来控制检测角度的不稳定性.以铜、铝母线...     

GeO2-Bi2O3-MOx(MOx=WO3, BaO)玻璃近红外超宽带发光的研究

用高温熔融法制备了(99.5-χ) GeO₂-χBaO-0.5Bi₂O₃(χ=3, 6, 9mol%)与(99.5-φ)GeO₂-φWO₃-0.5Bi₂O₃(φ=3，6，9mol%)玻璃，测定了样品的发射光谱(800nmLD激发)、吸收光谱、荧光衰减和差热曲线.实验结果表明，在GeO₂-WO₃-Bi₂O₃系统玻璃中，随着WO₃含量的增加，在1260nm处的发光强度增强，荧光半高宽(FWHM)增宽，荧光寿命增长，而且玻璃的吸收边带发生明显的红移；在GeO₂-BaO-Bi₂O₃系统玻璃中，随着BaO含量的增加，玻璃在1290nm处发光强度增强，FWHM增宽，荧光寿命增长，吸收边带也有明显的红移.从吸收边带发生红移的情况，结合发射光谱和荧光衰减曲线特性，我们推断玻璃样品在近红外的宽带发光可能由Bi⁵⁺离子所引起.从荧光特性估算了玻璃的σ_p×τ和σ_p×Δλ值，这些玻璃均具有较小的σ_p×τ和较大的σ_p×Δλ特性，说明GeO₂-Bi₂O₃-MO_x(MO_x=WO₃, BaO) 系统玻璃是研制成近红外(O到S波段)超宽带光纤放大器的良好材料.     

A generalized model of TiO_x-based memristive devices and its application for image processing

Memristive technology has been widely explored, due to its distinctive properties, such as nonvolatility, high density,versatility, and CMOS compatibility. For memristive devices, a general compact model is highly favorable for the realization of its circuits and applications. In this paper, we propose a novel memristive model of TiO_x-based devices, which considers the negative differential resistance(NDR) behavior. This model is physics-oriented and passes Linn's criteria. It not only exhibits sufficient accuracy(IV characteristics within 1.5% RMS), lower latency(below half the VTEAM model),and preferable generality compared to previous models, but also yields more precise predictions of long-term potentiation/depression(LTP/LTD). Finally, novel methods based on memristive models are proposed for gray sketching and edge detection applications. These methods avoid complex nonlinear functions required by their original counterparts. When the proposed model is utilized in these methods, they achieve increased contrast ratio and accuracy(for gray sketching and edge detection, respectively) compared to the Simmons model. Our results suggest a memristor-based network is a promising candidate to tackle the existing inefficiencies in traditional image processing methods.     

Effect of disorders on topological phases in one-dimensional optical superlattices

In a recent paper, Lang et al. proposed that edge states and topological phases can be observed in one-dimensional optical superlattices. They showed that the topological phases can be revealed by observing the density profile of a trapped fermion system, which displays plateaus with their positions. However, disorders are not considered in their model. To study the effect of disorders on the topological phases, we introduce random potentials to the model for optical superlattcies.Our calculations show that edge states are robust against the disorders. We find the edge states are very sensitive to the number of the sites in the optical superlattice and we propose a simple rule to describe the relationship between the edge states and the number of sites. The density plateaus are also robust against weak disorders provided that the average density is calculated over a long interval. The widths of the plateaus are proportional to the widths of the bulk energy gaps when there are disorders. The disorders can diminish the bulk energy gaps. So the widths of the plateaus decrease with the increase of disorders and the density plateaus disappear when disorders are too strong. The results in our paper can be used to guide the experimental detection of topological phases in one-dimensional systems.     

Al-Mg合金中锯齿形屈服现象的热分析

研究了在室温、定加载应变率拉伸的情况下Al-Mg合金中的锯齿形屈服现象.伴随着锯齿形屈服现象的发生,试件表面温度场会发生变化.而红外相机能以较高的时间、空间分辨率记录下随时间变化的试件表面温度场图像.通过分析这些热图像,探讨了A,B两种类型带的传播规律,得到了局域变形带的带宽、倾角、传播速度等特征参数.在此基础上,引入热传导方程,求得了带内的应变率.实验和计算都发现B类型带产生时试件表面带外区域存在弹性收缩现象,由此提出以是否存在带外收缩变形作为划分A,B类型带的新标准.     

Elastic behaviour of an edge dislocation near a sharp crack emanating from a semi-elliptical blunt crack

The interaction between an edge dislocation and a crack emanating from a semi-elliptic hole is dealt with. Utilizing the complex variable method, closed form solutions are derived for complex potentials and stress fields. The stress intensity factor at the tip of the crack and the image force acting on the edge dislocation are also calculated. The influence of the morphology of the blunt crack and the position of the edge dislocation on the shielding effect to the crack and the image force is examined in detail. The results indicate that the shielding or anti-shielding effect to the stress intensity factor increases acutely when the dislocation approaches the tip of the crack. The effect of the morphology of the blunt crack on the stress intensity factor of the crack and the image force is very significant.     

苝四甲酸二酐在Au(111)表面的取向生长及电子结构研究

利用X射线光电子能谱(XPS),同步辐射紫外光电子能谱(SRUPS),近边X射线吸收精细结构(NEXAFS)以及原子力显微镜(AFM)等技术研究了苝四甲酸二酐(PTCDA)与Au(111)的界面电子结构、PTCDA分子取向及有机薄膜的表面形貌.SRUPS价带谱显示,伴随PTCDA分子的微量沉积(0·5ML),位于费米能级附近Au的表面电子态迅速消失,但却观察不到明显的界面杂化态,这说明PTCDA分子和Au(111)界面间存在弱电子传输过程,但并没有发生明显的化学反应.角分辨NEXAFS以及SRUPS结果证明PTCDA分子是平铺在衬底表面.根据Au4f7/2和C1s峰积分强度随薄膜厚度的变化以及AFM图像可知,PTCDA分子在Au(111)表面是一种典型的Stranski-Krastanov生长模式,即先层状生长,再岛状生长,并且在层状生长到岛状生长的转变过程中,存在有机分子的去润湿过程.     

彩色半色调墨点边缘羽化的Clapper-Yule扩展模型

研究了墨点边缘发生羽化现象(非二值理想墨点)对印品光谱反射率的影响,为色彩预测模型的理论研究提供一个新的思路。采用二维高斯函数模拟墨点表面的形态,利用多重积分计算出墨点羽化后的体积,根据体积的恒常性即羽化前后墨点体积相等,推导出含边缘坡度因子σ的网点面积率以及含墨层相对厚度因子的油墨透射率,由此建立了一个Clapper-Yule扩展模型。模型的数值模拟结果表明墨点边缘油墨铺展所导致的网点物理扩大,增加了油墨对光的吸收,从而降低了最终的光谱反射率。采用Clapper-Yule分程模型对颜色进行预测时需考虑墨点边缘羽化所带来的物理网点扩大,该模型适用于彩色半色调印品的颜色预测与控制。     

Climb via vacancy diffusion of edge dislocations in 2D dislocation microstructures

The prevention of strength degradation of components is one of the great challenges in solid mechanics. In particular, at high temperatures material may deform even at low stresses, a deformation mode known as deformation creep. One of the microstructural mechanisms that governs deformation creep is dislocation motion due to the absorption or emission of vacancies, which results in motion perpendicular to the glide plane, called dislocation climb. However, the importance of the dislocation network for the deformation creep remains far from being understood. In this study, a climb model that accounts for the dislocation network is developed, by solving the diffusion equation for vacancies in a region with a general dislocation distribution. The definition of the sink strength is extended, to account for the contributions of neighbouring dislocations to the climb rate. The model is then applied to dislocation dipoles and dislocation pile-ups, which are dense dislocation structures and it is found that the sink strength of dislocations in a pile-up is reduced since the vacancy field is distributed between the dislocations. Finally, the importance of the results for modelling deformation creep is discussed.