Fabrication of submicrometer- to micrometer-scale ferroelectric copolymer particles by solution mixture method

In this paper we reported the fabrication of submicrometer- to micrometer-scale ferroelectric copolymer particles by a simple solution mixture method. Particle diameter could be controlled by the second solvent and/or the volume ratio of the second solvent to copolymer butanone solution. These particles were also ferroelectric and could be re-dispersed into water to form a suspension, as facilitated by the potential applications of these particles.     

翅片管的传热分析及其表面几何参数的优化

对翅片管的强化传热过程进行了分析。建立了以单位传热量下翅片管的体积最小为目标函数的最优化薮学模型，并对翅片管的最佳表面几何参数(翅片高度、翅片节距、翅片厚度)进行了分析，这些研究对翅片管的应用具有一定指导作用。     

一种特种机器人控制系统的设计与实现

针对组成某特种机器人控制系统时,采用单一控制芯片难以在满足系统体积小、精度高、响应快等基本要求的前提下,又同时满足数据处理速度快和运动控制能力高等的特殊要求;设计了一种基于TMS320DM6437和TMS320F28015的双核分布式控制系统,给出了该系统的硬件结构、选型和接口设计,采用两级缓存解决了CPU与内存的带宽问题,设计了复位电路以提高系统的可靠性;控制软件采用了在CCSV3.3环境下开发的模块化设计方案,根据其工作流程,进行了云台运动控制和信号高效可靠传输等项目的性能测试;调试结果表明,该系统信息处理速度快、数据读取可靠性高、运动控制精度高、动态响应时间短,能够最大程度地满足该特种机器人在使用性能上的各项要求.     

Size-dependent elastic properties of thin films: surface anisotropy and surface bonding

Surface eigenstress and eigendisplacement models were used to investigate the surface stress,surface relaxation and surface elasticity of thin films with different surface orientations.Molecular dynamics simulations and first-principles calculations were conducted on face-centered cubic Au films with the focus on relaxation induced nonlinear initial deformation.The simulation results verify the theoretical predictions of the size dependency of surface energy density and surface stress,and the nonlinear scaling law of the size-dependent Young’s modulus of thin films.The mechanism of the size-dependent behaviors was further explored at the atomic bonding level with the charge density field.The Au atomic bonding at surfaces is enhanced compared to its interior counterpart and therefore the nominal Young’s modulus of the Au thin films is larger when the film thickness is smaller.     

Effects of the number of inducer blades on the anti-cavitation characteristics and external performance of a centrifugal pump

Installing an inducer upstream of the main impeller is an effective approach for improving the anti-cavitation performance of a highspeed centrifugal pump. For a high-speed centrifugal pump with an inducer, the number of inducer blades can affect its internal flow and external performance. We studied the manner in which the number of inducer blades can affect the anti-cavitation characteristics and external performance of a centrifugal pump. We first use the Rayleigh-Plesset equation and the mixture model to simulate the vaporliquid flow in a centrifugal pump with an inducer, and then predict its external performance. Finally, we tested the external performance of a centrifugal pump with 2-, 3-and 4-bladed inducers, respectively. The results show that the simulations of external performance in a centrifugal pump are in accordance with our experiments. Based on this, we obtained vapor volume fraction distributions for the inducer, the impeller, and in the corresponding whole flow parts. We discovered that the vapor volume fraction of a centrifugal pump with a 3-bladed inducer is less than that of a centrifugal pump with 2-or 4-bladed inducers, which means that a centrifugal pump with a 3-bladed inducer has a better external and anti-cavitation performance.

     

巧记C语言运算符优先级

C语言中的运算符优先级关系复杂难记,结合编程和教学实践,给出了C语言运算符优先级的巧记规则,辅以实例加以说明。     

Anti-cavitation performance of a splitter-bladed inducer under different flow rates and different inlet pressures

The anti-cavitation performance of a high-speed centrifugal pump with a splitter-bladed inducer is investigated under different flow rates and different inlet pressures. Simulations and external characteristics experiments are carried out. Static pressure and the vapor volume fraction distributions on the inducer and the impeller of the pump under various operation conditions are obtained. The results show that the cavitation developments on the impeller and on the inducer with the flow rates are reverse, while the development of the inlet pressure on the inducer and the impeller is the same. Cavitation on the impeller increases with the increase of flow rates, and it extends to the near passages with rotating, while cavitation on the inducer is more complex than that on the impeller. Cavitation at the inlet of the inducer decreases with the increase of flow rates, while cavitation at the outlet of the inducer is opposite. The results also show that cavitation development on the impeller and on the inducer with the inlet pressure is the same. Cavitation both decreases with the increase of the inlet pressure at the same flow rate. Furthermore, asymmetric cavitation on the impeller and on the inducer is both observed. And the asymmetric degree of cavitation on the impeller is higher than that on the inducer.