一类矩阵秩的恒等式

利用分块矩阵的初等变换,证明了李书超等于2004年提出的一类矩阵秩的猜想.并把此结论推广到了更一般情形.     

结构力学法求解碳纳米管的临界应变

采用宏观的力学模型,研究了具有不同长径比的锯齿型和扶手椅型碳纳米管的屈曲变形.其结果表明在长径比不变的情况下,随着碳纳米管半径的增加,临界应变值降低;长径比对临界应变有重要的影响;对于小的长径比,连续体壳理论是有效的,但是随着长径比的增加,碳纳米管半径小于0.8 mm的情况下,出现了分歧.因此宏观力学框架模型能有效地模拟碳纳米管的屈曲,预测临界应变.     

风力/太阳能发电的发展现状和展望

风能和太阳能是资源丰富的可再生能源,发展风能和太阳能发电是改善能源结构、减少环境污染和保护生态环境的重要举措.阐述了国内外风力发电和太阳能发电的发展现状及趋势,针对风能和太阳能间歇性的特点,提出利用风能和太阳能互补发电,并介绍国内外相关研究现状.     

矩阵方程X+A*F(X)A=Q解的存在性与扰动分析

主要研究了非线性矩阵方程X A*F(X)A=Q唯一存在半正定解的充分条件.通过对解的扰动分析,得到了解算子的误差估计.     

基于小波变换的PCB图像拼接

在印刷电路板(PCB)的机器视觉检测中需要通过图像拼接来得到整个PCB的图像,传统的图像配准拼接技术由于光照干扰效果不好.用图像的小波分解高频系数去掉反映光照渐变的低能量系数后,可以较好地避免光照不均匀的干扰,分别利用有效垂直高频系数的垂直投影和水平高频系数的水平投影可以快速水平配准和垂直配准,低频部分作拼接的灰度渐变平滑处理.     

解广义线性互补问题的一个基于梯度的神经网络模型

给出求解广义线性互补问题的一个基于梯度的神经网络模型,分析了模型的平衡点与原问题解的关系,运用Lyapunov稳定性理论和LaSalle不变集原理,证明了该网络全局收敛于问题的解集,数值模拟表明网络不仅可行而且有效。     

变论域自适应模糊PID控制器设计

针对一类大时滞、时变系统，提出一种基于变论域模糊控制理论及模糊PID控制原理的变论域自适应模糊PID控制方法。该方法结合了常规模糊PID控制器和变论域模糊控制器各自的优点，通过论域调整改善模糊PID控制器参数调整精度和范围，具有良好的自适应能力和鲁棒性能。仿真结果验证了该方法的优越性。     

基于L1与空间点分类的3维场景重建

针对多视图的3维重建问题,提出一种基于L1与空间点分类的3维场景重建技术.首先采用效率较高的L1方法剔除残留局外点,以避免重建过程中受到局外点的干扰;再将空间点分为两类,第1类为两视图可见空间点,第2类为多于两视图可见空间点;针对第1类空间点采用高精度的最优三角形法进行重建,而第2类空间点采用L∞范数方法进行重建,并不断调整二分搜索的上下界,以减少迭代次数.实验结果表明了本文方法的优越性.     

The Finite Analysis of Deformation and Stress Triaxiality of a Mixed I + II Mode Elastic-Plastic Crack Tip

The deformation and distribution of stress triaxiality σ_{_m}/σ of mixed I + II mode elastic-plastic cracks under plane strain and plane stress conditions were analysed by the large strain finite element method and were compared with the HRR field. The results show that, (1) the model of crack-tip deformation under mixed I + II mode loading is sharpening-blunting, the sharpening and blunting deformation is acted on by compressive stress (σ_{_m}/σ > 0) and tensile stress (σ_{_m}/σ > 0), respectively; (2) in the plane strain case, the (σ_{_m}/σ)_{_max} of the real crack tip decreases with an increase of mode II component, but increases with an increasing strain hardening n for every mixed ratio. For the loading of K_{_I}/K_{_II} > 0.5, the (σ_{_m}/σ)_{_max} value of the real crack tip is less than that of the (σ_{_m}/σ)_{_max} given by the HRR field, but the opposite holds true cases where K_{_I}/K_{_II} > 0.5; (3) in the plane stress case, the (σ_{_m}/σ)_{_max} decreases a few values with an increasing mode II component, the values of (σ_{_m}/σ)_{_max} of every mixed ratio are far less than these of the corresponding loading condition in the plane strain case. In the plane stress case, the (σ_{_m}/σ)_{_max} values of every mixed ratio for any strain hardening exponent n are almost constant. This revised version was published online in August 2006 with corrections to the Cover Date.     

Processing dependent morphology, interfacial interaction and shear behavior of short carbon fiber reinforced PEEK

Shear properties of compression-molded discontinuous AS4 carbon fiber reinforced poly(ether ether ketone) composites are evaluated with Iosipescu tests. It is found that both shear modulus and shear strength strongly depend on the molding conditions. A comparison between shear behavior of the composites and composites morphology reveals that fusion of the composite pellets and fiber/matrix interfacial interaction on molecular scale are the two dominant factors which determine the processing dependent shear properties of the materials studied.