The turtle shell is an amazing structure optimized through the long-term evolution by nature.This paper reports the experimental study on the mechanical property at different levels and locations,and the microstructure of the shell from Trachemys scripta(Red-ear turtle) living in South China.
该文提出了一种基于协同分析和设计列式(即SAND列式,Simultaneous Analysis and Design)和序列线性规划(Sequential Linear Programming)技术的桁架结构优化新方法。与传统列式下将隐式响应函数(如位移、应力等)于设计变量(如杆件截面积等)处作线性展开的做法不同,以桁架结构为例,该文在SAND列式下,采用杆件截面积和结构节点位移同时作为设计/分析变量,仅对杆件协调条件这一显式双线性函数予以线性近似并构造LP子问题。通过求解一系列LP子问题,可以得到优化问题的近似最优解。与传统优化列式下的SLP方法相比,该文方法不仅设计变量运动极限的选取相对容易,而且线性近似的误差可以精确估计。数值算例表明,采用该文算法可以快速、稳定地得到优化问题的近似最优解。
With the fast development of computational mechanics and the capacity as well as the speed of modern computers,simulation-based structural optimization has become an indispensable tool in the design process of competitive products.This paper presents a brief description of the current status of structural optimization by reviewing some significant progress made in the last decades.Potential research topics are also discussed.The entire literatures of the field are not covered due to the limitation of the length of paper.The scope of this review is limited and closely related to the authors' own research interests.
Xu Guo·Geng-Dong Cheng State Key Laboratory of Structural Analysis for Industrial Equipment,Department of Engineering Mechanics,Dalian University of Technology, Dalian 116023,China
We report a novel oscillatory behavior of a sessile droplet on a hydrophobic surface. The droplet was placed on an electrode with a hydrophobic surface and close to, but not touching, a second needle-like electrode. The change in the contact angle was observed only when the droplet oscillated. In a traditional electro-wetting experiment, however, the contact angle decreased immediately when an alternating current electric field was applied. In addition, the non-contact mode gave rise to a true sessile condition of the droplet, whose oscillation amplitude was not linearly proportional to the driving voltage but reached a maximum value.
