Fatigue growth prediction of elliptical cracks in welded joint structure: Hybrid and energy density approach

A hybrid weight function approach (HWFM) is presented for the fatigue life prediction of infinite body and welded joint structure containing elliptical cracks. A self-containing computer code has been developed for this purpose. Numerical computations were first conducted on cracked infinite body showing a physical fact, that the elliptical shape of the crack becomes circular during its evolution. The prediction of the fatigue crack growth shows that the present results are in perfect concordance with those reported in the literature. Then, numerical tests were carried out on two types of specimens of welded joint structure. The present results were compared to the experimental and predicted ones of other authors, demonstrating that the hybridization method is a powerful numerical technique, and that the SEDF approach (using the Sih’s law) is more valid for the critical cases of welded joints than the SIF approach (using the Paris law). A parametric study has been conducted on the stress ratio “R” showing that the fatigue life to failure decreases with the increase of “R”.     

几种含芯电子相关能修正的G2和G2(ACI)方法

针对冻结芯电子近似,在MP2/6-311G(d,p)级别上对G2、MP2/6-311G(d)和MP2/6-311G(d,p)级别上对G2(QCI)方法进一步考虑了芯电子相关能修正,尝试建立了G2(fu2)、G2(QCI/ful)和G2(QCI/fu2)方法。G2-l test set 的反应能量计算结果表明,这些方法进一步减小了经验修正量;G2(QCI/ful)和G2(QCI/fu2)也比G2(QCI)的总体精度有所提高;但G2(fu2)在G2基础上,总体精度没有改善。G2(fu2)、G2(QCI/ful)和G2(QCI/fu2)计算G2-l test set反应能量的平均绝对偏差分别为5.11、4.74和4.81kJ mol-1,G2和G2(QCI)分别为5.09和4.97kJ mol-1.     

空间级有机硅橡胶

介绍了用液 -液提馏和热真空处理硅橡胶 ,以减少材料在空间高真空条件下的质量损失和可凝挥发物。重点介绍了几种空间级室温硫化硅橡胶 ,及其在真空度为 1 .33× 1 0 - 4 Pa、温度1 2 5℃、处理 2 4 h后的热真空性能。     

Crack growth in glass matrix composite reinforced by long SiC fibres

Theoretical and experimental work are made for bridged cracks in chevron-notched three point bend specimens made of glass matrix composite reinforced by long SiC fibres. The fracture toughness (K_IC) values are determined using the chevron-notch technique and compared with the theoretical predictions based on micromechanical analysis exploiting weight functions. The weight functions for orthotropic material are obtained numerically by means of detailed FEM analysis using the ANSYS package and they are further used together with appropriate bridging models for the theoretical prediction of the R-curve behaviours typical of the investigated composites.     

高功率激光装置总体设计的综合评估方法

 建立了较完整的高功率激光装置总体设计的评估指标体系,并运用多目标决策理论和加权综合法,初步建立了多级综合评估数学模型,以期对复杂激光装置的总体设计做出较客观的分析评价,选出合理方案;最后利用所建立的数学模型对目前四种高功率激光装置设计结构的技术性和经济性等方面进行了初步综合评估。评估结果表明,多级综合评估模型较合理,对系统总体优化设计有重要的指导作用。     

Biomechanical evaluation of heel elevation on load transfer — experimental measurement and finite element analysis

In spite of ill-effects of high heel shoes, they are widely used for women. Hence, it is essential to understand the load transfer biomechanics in order to design better fit and comfortable shoes. In this study, both experimental measurement and finite element analysis were used to evaluate the biomechanical effects of heel height on foot load transfer. A controlled experiment was conducted using custom-designed platforms. Under different weight-bearing conditions, peak plantar pressure, contact area and center of pressure were analyzed. A three-dimensional finite element foot model was used to simulate the high-heel support and to predict the internal stress distributions and deformations for different heel heights. Results from both experiment and model indicated that heel elevations had significant effects on all variables. When heel elevation increased, the center of pressure shifted from the midfoot region to the forefoot region, the contact area was reduced by 26% from 0 to 10.2 cm heel and the internal stress of foot bones increased. Prediction results also showed that the strain and total tension force of plantar fascia was minimum at 5.1 cm heel condition. This study helps to better understand the biomechanical behavior of foot, and to provide better suggestions for design parameters of high heeled shoes.     

Intersections between the norm-trace curve and some low degree curves

In this paper we analyze the intersection between the norm-trace curve over ${\mathbb{F}}_{q^3}$ and the curves of the form $y=a{x}^3+b{x}^2+cx+d$, giving a complete characterization of the intersection between the curve and the parabolas (a=0), as well as sharp bounds for the other cases. This information is used for the determination of the weight distribution of some one-point AG codes arising from the curve.     

基于地面光谱数据的二向性反射模拟与分析

为提高地物光谱模拟精度，建立地表混合光谱模型，利用ASD FieldSpec3 Hi-Res便携式地物光谱仪和地物多角度二向性反射平台，设计试验探测不同角度下的不同叶片覆盖面积的混合光谱。以等距离/等面积模型为理论基础，将模型中二维权重系数变化规律扩展到三维空间权重系数变化中，考虑探测方向倾斜时探测区域权重系数的变化，提出新的考虑几何角度的三维权重模型对混合光谱进行模拟，并与实测混合光谱对比分析。分析结果表明，相比于等距离/等面积模型，三维权重模型对探测区域进行了细分，提高了权重系数计算精度，模拟的混合光谱误差更小，特别是在探测角度有倾斜时，模拟的效果更明显，均方根误差平均降低了0.016 1，光谱角误差平均降低了0.07。三维权重模型考虑了探测角度对权重系数的影响，提高了光谱模拟的精度，为地表模型的建立及卫星数据混合光谱分解的应用提供新的理论基础。     

Global well-posedness and asymptotic stabilization for chemotaxis system with signal-dependent sensitivity

A fully parabolic chemotaxis system

$u_t=\mathrm{\Delta }u?\mathrm{?}?(u\chi (v)\mathrm{?}v),v_t=\mathrm{\Delta }v?v+u,$

in a smooth bounded domain $\mathrm{\Omega }?{\mathbb{R}}^N$, $N\ge 2$ with homogeneous Neumann boundary conditions is considered, where the non-negative chemotactic sensitivity function χ satisfies $\chi (v)\le \mu {(a+v)}^{?k}$, for some $a\ge 0$ and $k\ge 1$. It is shown that a novel type of weight function can be applied to a weighted energy estimate for $k>1$. Consequently, the range of μ for the global existence and uniform boundedness of classical solutions established by Mizukami and Yokota [23] is enlarged. Moreover, under a convexity assumption on Ω, an asymptotic Lyapunov functional is obtained and used to establish the asymptotic stability of spatially homogeneous equilibrium solutions for $k\ge 1$ under a smallness assumption on μ. In particular, when $\chi (v)=\mu /v$ and $N<8$, it is shown that the spatially homogeneous steady state is a global attractor whenever $\mu \le 1/2$.