Cascade optical chromatography for sample fractionation

Optical chromatography involves the elegant combination of opposing optical and fluid drag forces on colloidal samples within microfluidic environments to both measure analytical differences and fractionate injected samples. Particles that encounter the focused laser beam are trapped axially along the beam and are pushed upstream from the laser focal point to rest at a point where the optical and fluid forces on the particle balance. In our recent devices particles are pushed into a region of lower microfluidic flow, where they can be retained and fractionated. Because optical and fluid forces on a particle are sensitive to differences in the physical and chemical properties of a sample, separations are possible. An optical chromatography beam focused to completely fill a fluid channel is operated as an optically tunable filter for the separation of inorganic, polymeric, and biological particle samples. We demonstrate this technique coupled with an advanced microfluidic platform and show how it can be used as an effective method to fractionate particles from an injected multicomponent sample. Our advanced three-stage microfluidic design accommodates three lasers simultaneously to effectively create a sequential cascade optical chromatographic separation system.     

铝电解数字式恒流控制系统的研究与应用

随着自动控制技术、网络技术、计算机技术的快速发展,铝电解整流变电站恒流控制技术也在发生着深刻的变化,它经历了模拟式、半模拟半数字式、数字式的发展历程。本文结合国内某铝厂110KV整流所整流机组恒流系统改造方案,重点介绍数字式恒流控制系统的工作原理及网络结构,对大型铝电解整流系统设计和模拟恒流系统改造具有参考价值。