影像世界的未来——广角俯瞰Photokina 2008

每两年举办一次的德国Photokina影像器材大展是最新相机产品与技术的竞技场。作为欧洲最重要的影像器材博览会,谁能在Photokina上赢得关注,谁就能赢得欧洲甚至全球市场。和一年一度的美国PMA相比,数码影像厂商在Pholokina上的对决更加激烈。2008年的Photokina于9月23-28日在德国科隆拉开帷幕,究竟这场影像器材的盛宴能为我们揭示什么样的数字影像未来？明年我们又将用上什么样的数码相机？接下来就让我们一起深入Photokina大展去看看。     

A coupled creep plasticity model for residual stress relaxation of a shot-peened nickel-based superalloy

Shot peening is a commonly used surface treatment process that imparts compressive residual stresses into the surface of metal components. Compressive residual stresses retard initiation and growth of fatigue cracks. During component loading history, shot-peened residual stresses may change due to thermal exposure, creep, and cyclic loading. In these instances, taking full credit for compressive residual stresses would result in a nonconservative life prediction. This article describes a methodical approach for characterizing and modeling residual stress relaxation under elevated temperature loading, near and above the monotonic yield strength of INI 00. The model incorporates the dominant creep deformation mechanism, coupling between the creep and plasticity models, and effects of prior plastic strain to simulate surface treatment deformation.     

Insight into the micro scale dynamics of a micro fluidic wetting-based conveying system by particle based simulation

We simulate a microfluidic conveying system using the many-body dissipative particle dynamics method (MDPD). The conveying system can transport micro parts to a specified spot on a surface by letting them float inside or on top of a droplet, which is pumped by changing the wetting behaviour of the substrate, e.g., with electrowetting on dielectrics. Subsequent evaporation removes the fluid; the micro part remains on its final position, where a second substrate can pick it up. In this way, the wetting control can be separate from the final device substrate. The MDPD method represents a fluid by particles, which are interpreted as a coarse graining of the fluid’s molecules. The choice of interaction forces allows for free surfaces. To introduce a contact angle model, non-moving particles beyond the substrate interact with the fluid particles by MDPD forces such that the required contact angle emerges. The micro part is simulated by particles with spring-type interaction forces.