应力约束下预应力平面实体钢结构拓扑优化设计

对预应力平面实体钢结构拓扑优化设计问题进行研究,建立了以索力值、单元尺寸和结构拓扑为设计变量,以应力为约束条件,以结构重量最小为目标函数的数学优化模型.在求解方法上,首先以满应力设计准则法建立索力值与结构重量之间的优化模型,通过该模型的求解确定索力值,并通过满应力设计选取单元尺寸,然后对单元体厚度按闻值进行分类,从而删除低厚度单元实现结构的拓扑优化.算例结果与预应力钢结构理论相吻合,表明本文所提出的方法是有效的,可为预应力钢结构体系创新提供理论方法.     

局部狭窄血管中流动分离和临界雷诺数的判定

采用Karman-Pohlhausen方法,对过去轴对称局部狭窄血管内流动分离的理论计算进行修正,导出了确定流动分离位置轴向坐标的方程。对该方程数值求解的结果表明:(1)随着雷诺数或狭窄度的增加,在狭窄的舒张区(x>0)会出现分离和再附着现象,并且分离和再附着之间的区域会逐渐扩展;(2)分离和再附着点的坐标随雷诺数变化的理论曲线与以前的实验结果基本一致。     

PRESSURE AND PRESSURE GRADIENT IN AN AXISYMMETRIC RIGID VESSEL WITH STENOSIS

Based on an improvement of the Karman-Pohlhausen's method, using nonlinear polynomial fitting and numerical integral, the axial distributions of pressure and its gradient in an axisymmetric rigid vessel with stenosis were obtained, and the distributions related to Reynolds number and the geometry of stenotic vessel were discussed. It shows that with the increasing of stenotic degree or Reynolds number, the fluctuation of pressure and its gradient in stenotic area is intense rapidly, and negative pressure occurs subsequently in the diverging part of stenotic area. Especially when the axial range of stenosis extends, the flow of blood in the diverging part will be more obviously changed. In higher Reynolds number or heavy stenosis, theoretical calculation is mainly in accordance with nast experiments.     

Multi-scale studies of glass transition and uniaxial tensile properties of a commercially available epoxy adhesive using experimental measurements and molecular dynamics simulation

In this study, the glass transition and uniaxial tensile properties of a commercially available epoxy adhesive were investigated using experimental measurements and molecular dynamics(MD) simulation. Differential scanning calorimetry(DSC) was used to study the change of glass transition temperature(T g) with cross-link density(CLD). Uniaxial tensile test was performed to measure the Young's modulus(E), Poisson's ratio(ν) and yielding strength(σY). In MD simulation, the complicated epoxy system was simplified as the mixture of two kinds of simple molecules, with the key information well preserved and the less important details omitted. The molecular model of the cross-linked epoxy network was constructed and its mechanical properties were calculated using MD simulation. Overall, the MD simulation results agreed with experimental ones, which proved the validity of the molecular model and justified the simplification method of the industrylevel epoxy system.     

对少学时力学课程改革的探讨

根据给排水、供热通风专业少学时力学课程的特点,认为有必要将流体力学合并于理论力学教学之中,并对其可行性、合理性及课程内容作了探讨．     

朗伯-比耳定律的近似线性关系应用于原子吸收光谱法的超微量分析

对原子吸收光谱法在超微量测试中,给出了朗伯-比耳定律的近似公式,建立了测定值和透光度的变化值之间的近似线性关系。试验表明,可使原子吸收光谱法的灵敏度提高2~3个数量级。     

刚性轴对称狭窄血管内压强及其梯度的研究

基于对Karman-Pohlhausen方法的改进,运用非线性多项式拟合和数值积分,导出了刚性轴对称狭窄管内压强及其梯度的轴向分布,讨论了该分布与雷诺数和狭窄管几何形状之间的关系．结果表明随狭窄度和雷诺数的增加,压强及其梯度在狭窄区域的振荡会迅速加剧,并逐渐导致舒张区出现负压强．尤其在狭窄的轴向区域变宽时,舒张区的血流状态会受到较大影响．在高雷诺数和重度狭窄时,理论计算与过去的实验结果基本一致．     

退化(K_1,K_2)拟正则映射的充分条件

研究了退化弱(k1,k2)拟正则映射的正则性.利用H lder不等式、Sobolev空间的空间分析方法,以及内插定理等工具,给出了退化弱(k1,k2)拟正则映射事实上为退化(k1,k2)拟正则映射的一个充分条件,其结果对非退化情形也成立.     

Banach空间中两类压缩映射的迭代逼近

讨论了Banach空间中拟压缩映射和广义压缩映射的具误差的Ishikawa迭代序列的收敛性,得出了在一定条件下,这两类压缩映射分别强收敛于它们的不动点.这些结论推广和发展了已有的相关结果,使这些结果的适用范围更广.