Multi-criteria assessment of offshore wind turbine support structures based on dynamic property optimization

Increasing size of wind turbine and deep water deployment have raised the issue of appropriate selection of the most suitable support structure to make offshore wind energy cost competitive.The paper presents an optimization methodology for decision making process of bottom mounted supports of offshore wind turbines （OWTs） through reasonable engineering attributes derivation.Mathematic models of support structures are reduced by the generalized single-degree-of-freedom theory with relatively fewer structural parameters.Soft-stiff design optimization based on dynamic properties of OWTs is performed for monopile and lattice supports with different wind turbines,water depth and hub height.Attributes of support structures,wind turbines and environment conditions are applied in the multi-criteria decision making method——TOPSIS for benchmarking of those options.The results illustrate the effectiveness of the proposed optimazation methodology combined with economical and environmental attributes together.     

矩阵方程AXB+CYD=E的双中心最小二乘问题

利用矩阵的Kronecker积、列拉直算子和Moore-Penrose广义逆,讨论矩阵方程AXB+CYD=E的双中心最小二乘问题,得到双中心极小范数最小二乘解和对称双中心极小范数最小二乘解的表达式,给出求双中心极小范数最小二乘解的数值解法和数值例子.     

On nonsingularity and group inverse of linear combinations of generalized and hypergeneralized projectors

In this paper, some conditions for the nonsingularity and group inverses of linear combinations of generalized and hypergeneralized projectors are established. Moreover, some formulae for the inverses and group inverses of them are derived. The work of this paper extends some previous results.     

国产玻璃纤维缝编织物性能研究

测试并比较了国产玻璃纤维纱线缝编织物和进口玻璃纤维纱线编织布的力学性能,发现国产纱线编织布的性能与进口纱线编织布的性能基本相当,能够满足纤维增强塑料复合材料的设计要求。     

某双塔斜拉桥塑性极限有限元模拟分析

结合双塔单索面预应力混凝土斜拉桥的结构特点和荷载情况,利用有限元软件ANSYS建立全桥有限元模型,给出了有限元仿真模型命令流;采用非线性静态增量有限元分析,得到了荷载-位移曲线,进而求得了该桥的极限承载力。模拟结果能为实际双塔单索面PC斜拉桥的塑性极限分析提供参考价值。     

广义二阶流体的脉冲泊肃叶流动分析

讨论了广义二阶流体的脉冲泊肃叶流动,引入黎曼-刘维尔分数阶微分建立本构方程,结合不可压缩流体时间分数阶动量方程,得到控制方程。利用傅里叶正弦变换和分数阶拉普拉斯变换,获得流体速度解析解。利用Stehfest算法对结果进行数值模拟,通过图像讨论了分数阶参数以及延迟时间对流动的影响。结果表明速度过冲现象主要取决于动量方程的时间分数阶参数。     

首尾差r-循环矩阵的判别方法及逆和广义逆的快速算法

提出了一种新的循环矩阵,称之为首尾差r-循环矩阵(简记为FLDcircr矩阵).验证了它的线性运算、矩阵乘积、逆矩阵等仍为FLDcircr矩阵.通过构造基本FLDcircr矩阵,给出FLDcircr矩阵的判别方法及逆和广义逆的快速算法.     

往复镦挤2A66铝锂合金室温拉伸性能及韧化机制

利用电子衍射背散射、透射电子显微观察、扫描电镜观察和室温拉伸试验对往复镦挤不同变形道次的2A66合金的组织和力学性能进行了检测和分析.结果表明,往复镦挤可以有效细化2A66铝锂合金组织,使组织更加均匀.随着往复镦挤变形道次增加,2A66铝锂合金中高密度位错逐渐向位错墙和亚晶界转变,粗大的第二相分布更均匀,弥散的β′相有部分回溶到2A66铝锂合金基体中.往复镦挤变形后2A66铝锂合金的塑性大幅提高,强度略有下降,其韧化主要是位错组态的变化、粗大的θ′相的均匀和细化以及弥散的β′相部分回溶的结果.     

Investigations of a nanostructured FeMnSi shape memory alloy produced via severe plastic deformation

Low-cost iron-based shape memory alloys (SMAs) show great potential for engineering applications. The developments of new processing techniques have recently enabled the production of nanocrystalline materials with improved properties. These developments have opened avenues for newer applications for SMAs. The influence of severe plastic deformation induced by the high-speed high-pressure torsion (HSHPT) process on the microstructural evolution of an Fe–Mn–Si–Cr alloy was investigated. Transmission electron microscopic analysis of the alloy revealed the existence of nanoscale grains with an abundance of stacking faults. The high density of dislocations characteristic of severe plastic deformation was not observed in this alloy. X-ray diffraction studies revealed the presence of ε-martensite with an HCP crystal structure and γ-phase with an FCC structure.     

求突变模型梁挠度的差分方程

本文根据函数在突变点的单侧泰勒展开导出了突变模型梁的挠度差分方程。结果表明,传统的挠度差分方程在一般情况下仅零阶遥近于挠度近似微分方程,而本文导出的实用差分方程二阶遇近于挠度徽分方程。对无分布力作用的果用本文的差分方程将得到挠度的精确解而与差分步长选取无关。