复合材料薄壁曲面开孔孔形优化设计

复合材料薄壁曲面结构在航空航天领域中获得了广泛的应用。其上存在的冷却孔、减重孔及维修孔会导致结构容易失效。本文提出一种通用复合材料曲面上孔形优化新方法,采用参数映射方法进行曲面结构上的孔形优化,选取孔周曲线上的失效函数值作为优化设计目标。论文比较了椭圆函数描述孔形时Mises、Tsai-Hill及Tsai-Wu三种失效准则、三种不同材料体系对优化结果的影响,最后给出了样条函数描述孔形的算例。     

一类满足G2连续的三角Bézier曲线曲面

为了在相对简单的条件下满足相对较高的光滑融合,同时在不改变控制顶点的情况下也可以修改曲线曲面的形状,构造了一组低阶的带有两个形状参数的三角Bézier基函数。基于该组基函数,通过三角函数的组合方式定义了任意阶三角Bézier曲线曲面,并详细讨论曲线的基本性质,同时也讨论了曲线、曲面的光滑融合所满足的条件。根据融合条件,可构造分段光滑的组合曲线曲面。这种融合的曲线曲面可以通过修改控制顶点和参数的方法来调节曲线曲面的形状,但不会改变曲线曲面的连续性并且在一定条件下能自动保证组合曲线、曲面的G²连续且计算简单。数值实例结果显示了该方法的有效性。     

Experimental measurements and theoretical calculations of the atomic structure of materials with subangstrom resolution and picometer precision

Lattice defects are unavoidable structural units in materials and play an important role in determining material properties. Compared with the periodic structure of crystals, the atomic configurations of the lattice defects are determined by the coordinates of a large number of atoms, making it difficult to experimentally investigate them. In computational materials science, multiparameter optimization is also a difficult problem and experimental verification is usually required to determine the possibility of obtaining the structure and properties predicted by cal- culations. Using our recent studies on oxide surfaces as examples, we introduce the method of integrated aberra- tion-corrected electron microscopy and the first-principles calculations to analyze the atomic structure of lattice defects. The atomic configurations of defects were mea- sured using quantitative high-resolution electron micros- copy at subangstrom resolution and picometer precision, and then the electronic structure and dynamic behavior of materials can be studied at the atomic scale using the first- principles calculations. The two methods complement each other and can be combined to increase the understanding of the atomic structure of materials in both the time and space dimensions, which will benefit materials design at the atomic scale.     

良导体表面粗糙度对表面电流计算值准确性的影响

Danial Maystre的表面电流分段独立计算法是近期刚发展的旨在计算高度起伏接近入射波波长任意宽良导体粗糙面散射场的计算机计算方法,它揭示了平面入射波条件下粗糙面上各点电流之间的一种“短耦合程效应”,一定程度克服了过去由于表面电流相互作用距离长而无法用矩量法逐段独立地精确计算表面电流的矛盾.Maytre计算方法可适用于什     

反求工程与快速原型集成的复杂曲面产品制造技术

在研究了反求工程的输出接口与快速成型输入接口标准的基础上，提出了一种反求工程（RE）与快速原型（RP）直接集成的复杂曲面产品快速开发的方法，即利用基于断层测量及光学三角形法测量的点云数据直接构造STL（Stereo ithography)模型文件，并输入到LPS（Laser Prototyping System)快速成型系统，直接用于制作产品原型，从而避开了传统反求工程中的复杂曲面重构，因此极大地缩短了这类产品的开发周期，降低了开发成本，数字化动态人体模型快速开发的工程实例表明，该方法比传统曲面建模制造技术的效率提高了55％。     

Gd在Ba_2RCu_3O(7+δ)(R=Y,HO)高温超导体表面上引起的化学反应

本文利用X射线光电子谱(XPS)对Gd原子在Ba_2RCu_3O_(7+8)(R=Y, Ho)高温超导体表面上引起的化学反应进行了研究.实验发现,在该超导样品表面上蒸镀的Gd原子被氧化,超导体中对超导特性起重要作的Cu-O链遭到破坏,其中一部分处于Cu~(2+)态的Cu元素被还原,超导体内其它各元素也不同程度地受到了影响.当样品表面上Gd覆盖度达到22A(R=Y)和30A(R=Ho)时,界面上的化学反应不再继续     

基于区域分割技术的等距天线曲面重构

针对逆向工程中空间坐标测量时仪器测头半径或靶标厚度的误差补偿问题,提出了对散乱点云数据进行自动区域分割的方法。快速搜索出子区域中测点的最近邻域,利用测点最近邻域构造一个有约束的最小二乘切平面,得到曲面在该测点处的法线矢量。基于Prim算法的优化算法对法线矢量方向进行调整,使各测点处的法线矢量都指向曲面同一侧,进而求取了实际曲面上的点。对于经过误差补偿后的点云数据,从空间任意二次曲面的一般方程出发,基于二次曲面的误差方程和法方程提出一种通用拟合算法,并借助二次型理论得到曲面的特征参数。实验结果证明：应用该区域分割算法能够提高最近邻域的搜索速度,且曲面拟合算法具有很好的鲁棒性和有效性。     

Symmetrical Fundamental Tensors, Differential Operators, and Integral Theorems in Differential Geometry

To make the geometrical basis for soft matters with curved surfaces such as biomembranes as simple as possible, a symmetrical analytical system was developed in conventional differential geometry. The conventional second fundamental tensor is replaced by the so-called conjugate fundamental tensor. Because the differential properties of the conjugate fundamental tensor and the first fundamental tensor are symmetrical, the symmetrical analytical system including the symmetrical differential operators, symmetrical differential characteristics, and symmetrical integral theorems for tensor fields defined on curved surfaces can be constructed. From the symmetrical analytical system, the symmetrical integral theorems for mean curvature and Gauss curvature, with which the symmetrical Minkowski integral formulas are easily deduced just as special cases, can be derived. The applications of this symmetrical analytical system to biology not only display its simplicity and beauty, but also show its powers in depicting the symmetrical patterns of networks of biomembrane nanotubes. All these symmetrical patterns in soft matters should be just the reasonable and natural results of the symmetrical analytical system.     

广西主要城市倾斜面上太阳辐射总量的气候学计算

提出了倾斜面上太阳辐射总量的气候学计算公式，并据此计算了广西区主要城市各典型倾斜面上的太阳辐射月平均值。     

材料表面可逆润湿性行为研究进展

 综述了近几年制备可逆润湿性表面的常用方法及常见的控制润湿性可逆变换的手段,例如在原材料表面添加光敏性物质、热响应性物质及pH敏感性物质等,并介绍了其响应性机理;总结了目前尚不能形成规模化生产、性能不稳定等研究薄弱点;展望了未来研究方向及具有可逆润湿性生物质材料前景,认为后续研究的重点亦可放在性能稳定性等方面。