摘要：A theoretical model and mathematical description for silicon micromachined elec- trostatic or capacitive ultrasonic imaging transducers have been developed. Ac- cording to the model the basic performance parameters of such a transducer, such as natural frequencies, eigenfunctions, resonance and anti-resonance frequencies, and the mechanical impedance of the diaphragm can be predicted from the ge- ometry of the transducer and property parameters of materials used. The paper reveals that this type of transducers has two basic operation modes, correspond- ing to the resonance of a mass-spring oscillator comprised of the diaphragm and the air cushion, and the first-order bending mode of the diaphragm itself respec- tively, and presents an optimal method for extending the bandwidth by making the two modes coupled, and thereby provides a theoretical basis for the optimal de- sign.

摘要：为了满足聚合类绝缘材料老化实验及等离子体水处理高级氧化实验2项实验研究的应用要求,分别设计了双极性和单极性2种ns级高压脉冲发生器,且均主要由高压直流电源、两级脉冲储能电容器和气体开关等组成,结构紧凑,具有重复频率、脉冲宽度及电压幅值可调等优点。2种脉冲电源的主要区别在于各自的核心元件—多电极旋转火花隙开关(MER-SGS)的结构和尺寸设计,同时电源的重复工作频率也可由旋转火花隙驱动电机及电极数量调节控制。为验证火花隙开关的工作性能,采用ANSOFT/MAXWELL electrostatic 2D软件建立了仿真模型,对2种开关不同开断关合角度下的电场强度进行了仿真分析和比较。结果表明,火花隙的紧凑结构设计能够产生强烈电场畸变进而保证脉冲电源在具备良好输出特性基础上,开关可靠动作,从而达到降低绝缘要求、减少电极烧蚀、延长工作寿命等目的。通过对2种脉冲电源有载情况下实际输出波形的测量可得,脉冲上升时间(<10ns)、脉冲宽度(1～500μs)、重复工作频率(1～3kHz)、平均功率等电源参数均达到各自实验要求标准,具有良好的应用前景。

摘要：纳米材料因其特殊的抗菌机理,在抗菌领域得到了广泛应用.氧化铈纳米粒子是重要的抗菌材料之一,具有对正常细胞毒性低,且抗菌机理基于可逆价态转化的优势.目前已有许多关于氧化铈纳米粒子抗菌活性的研究报道,但系统性探究其抗菌机理的文章则极为少见.本文首先系统性地探究了氧化铈纳米粒子可能的抗菌机理,即静电相互作用在抗菌过程中发挥重要作用,此外抗菌过程还伴随活性氧物种的产生和纳米粒子对细菌的机械损伤.其次,本文分析了氧化铈纳米粒子抗菌效果的影响因素,并总结了不同研究中氧化铈纳米粒子对大肠杆菌和金黄葡萄球菌的抗菌效果.最后提出了氧化铈纳米粒子可能的应用前景.本文将有利于对氧化铈纳米粒子抗菌机理的深入理解,并为该类材料在未来的设计和应用提供借鉴.

摘要：Thermal management of microelectronics demands higher heat flux removal capabilities due to the rapid increase in component and heat flux densities generated by integrated circuits (ICs). Electrospray evaporative cooling (ESEC) is a potential package-level thermal management solution for the next generation of microelectronics. In this paper, a design methodology is presented using numerical electrostatic field modeling to indirectly design proof-of-concept, micronozzle-based ESEC chambers. The results of the numerical modeling and heat transfer experiments indicate that the potential distribution near the micronozzle tip of the ESEC chamber dominates the heat transfer performance of ESEC cooling devices. The surface charge density at the micronozzle tips has a minor impact on the heat transfer performance. The maximum enhancement ratio of 1.87 was achieved by the 8-nozzle ESEC chamber at the lowest heat flux investigated, indicating that the heat transfer capability of ESEC chambers declines as the heat source density increases. The study demonstrates that increasing the number of micronozzles and decreasing the flow rate per nozzle may not effectively improve the heat transfer performance of ESEC devices.