一种改进的广义曲线坐标变换的电磁材料设计方法

提出一种改进的基于麦克斯韦Maxwell方程的广义曲线坐标变换的电磁超材料设计方法,首先介绍了该方法的转换方程,然后通过高增益喇叭天线、圆环聚焦和角度旋转的人工电磁超材料这三个例子验证该方法的可行性。将转换公式运用于二维的有限元仿真软件COMSOL Multiphysics中,得到了三种例子的仿真结果,并进行了讨论。仿真结果表明通过广义曲线坐标变换可以得到具有良好场分布特性的人工电磁超材料,具有更广泛的适用性。     

Design and FE analysis of integrated sensing using gas compressibility for microdroplet generation

As trends in biology, chemistry, medicine and manufacturing have pushed macroscopic processes onto the microscale, robust technologies have become necessary to encapsulate liquids into microdroplets for further manipulation and use. In order to most effectively utilize these microdroplets, real-time sensing is needed during the generation process to monitor the size of the droplet generated, or if generation failed to occur. Current droplet generating technologies operate either in open-loop, with no direct feedback available to the control system to monitor the process, or in closed loop with external sensing, using photography or droplet weight measurement to measure droplet size. By utilizing internal system-based sensing to close the loop, corrections in the dispensing process could be made in real-time in response to malfunctions as they occur. Furthermore, the generator’s operator could be more quickly alerted when a systemic error, such as a clog, continues to occur. One candidate solution to provide system-based sensing is to monitor the pressure of a reservoir of compressible gas kept adjacent to the reservoir of droplet liquid, both within a constant volume fluid chamber. The gas reservoir pressure during the actuation sequence can be related both analytically and empirically to the volume of the droplet ejected from the device, including instances where generation fails and a droplet is not ejected. This paper describes the designs of potential systems to realize this design concept, and the development of a finite element simulation for one of the concepts capable of generating droplets while simultaneously monitoring the pressure of the gas reservoir. A linear relationship between this calculated pressure and the volume of the dispensed droplet is found, validating the sensible property as workable for implementation in a physical system.     

Corrosion informatics: an integrated approach to modelling corrosion

Materials informatics is based on the integration of tools for generating, classifying, analysing and disseminating knowledge in the domain of materials science and engineering, a subset of which includes corrosion science. The purpose of integration is to decrease costs and time associated with research and development. In the context of corrosion, it is proposed that informatics can produce superior decision making tools, decrease risks of failure and improve asset management. An integrated approach is necessary for corrosion because of the multiphysics nature of its contributing mechanisms that include processes at the megascale, materials deformation, electrochemical reactions and fluid dynamics. A hierarchy is introduced that combines models from these subdisciplines with models at more fundamental scientific levels (thermodynamics, microstructural, quantum mechanical and density functional theory/atomistics) and methods for treating uncertainty (Bayesian inference, Monte Carlo and reliability methods). To demonstrate the multiphysics approaches currently available for corrosion prediction, applications are drawn from the recent literature and categorised by topic: general corrosion, localised corrosion and passivity, environmentally assisted cracking, and coatings and inhibitors. Opportunities for integration in each of these subthemes are suggested. Some remarks concerning the integration of probabilistic with deterministic models are made because of the importance of attaching uncertainties to the predictions made by corrosion models, and applying a time-invariant scientific approach to the interpretation of a time-dependent historical record. Finally, a strategy for implementing the integrated approach to corrosion modelling is presented, under the name ‘corrosion informatics’.     

Mg合金AE44/低碳钢在3.5%NaCl溶液中的电偶腐蚀研究

基于大型仿真软件COMSOL Multiphysics,研究了25℃阴阳极面积变化时低碳钢/Mg合金AE44电偶对在3.5%NaCl溶液中的腐蚀行为,并在此基础上加入Al合金隔离器,研究Al合金面积的大小对低碳钢/Mg合金/引起电极极性逆转,且随着阴阳极面积比的增加Mg合金的腐蚀速率变快;当阴阳极面积比小于1∶1 200时阳极的腐蚀速率将会达到最小极限值;面积比为1∶1∶1的低碳钢/Al合金/Mg合金复杂电偶对的最大电解质电流密度仅为面积比为1∶1的低碳钢/Mg合金电偶对最大电解质电流密度的40%左右;低碳钢/Al合金/Mg合金组成的复杂电偶对中,Mg合金AE44表面最大电流密度随Al合金的长度的增加而减小,且符合对数关系。     

封闭腔体通风散热系统仿真分析

为了解决封闭腔体内器件散热的问题,设计了通风散热系统,基于COMSOL的多场耦合仿真,对其进行有限元分析,研究对比了不同的通风口位置、腔体结构的散热效果,得到温度和气流的仿真结果,分析了不同位置的通风口对于系统散热的利弊,以及腔体和器件内气体的流向。结果表明:腔体通风口的布局对于散热有明显的影响,优化的布局可以提高散热效率;通过在腔体内增加挡板的方式,将腔体分割成两部分,配合器件的内部结构,形成了良好的风道,能够提高散热效率。     

毫秒脉冲磁场作用下细胞内带电粒子的受力分析

为从微观角度研究脉冲磁场生物效应的基础机理,通过构建细胞模型从理论上分析了细胞中带电粒子的力学环境,借助Comsol Multiphysics仿真软件分析了这些带电粒子的受力,并根据带电粒子的运动速度和运动轨迹研究了脉冲磁场参数对不同属性带电粒子受力的影响规律。结果表明:在带电粒子的各个受力因素中,感应电场力起主导作用,黏滞力限制了粒子的运动速度,Lorentz力的作用较小,且粒子整体受力小于感应电场力。脉冲磁场强度的变化率直接决定了感应电场力大小,是对粒子受力影响最大的波形参数,且变化率由脉冲波形幅值、上升沿时间和下降沿时间共同决定。电场力的方向会随着脉冲磁场的上升沿和下降沿发生交替改变,使带电粒子来回摆动;若上升沿和下降沿时间不相等,则粒子摆动距离不相等,此时带电粒子偏离原点的距离增大,呈进动式运动。     

Modeling the Molten Salt Electrorefining Process for Spent Metal Fuel Using COMSOL

Molten salt electrorefining process is one of the key steps of the pyrochemical reprocessing flow sheet for the spent metallic fuel from fast reactors. The electrorefining process is simulated using COMSOL Multiphysics. This involves solving multiple equations corresponding to electrochemical reactions at the electrode surfaces, mass transfer of metal ions in the electrolyte, potential distribution in the electrolyte, and overall material balance of metal ions in a coupled manner. The model is validated using the data of laboratory scale electrorefining experiments from literature. The results show a good agreement with the present experimental data, the variation being less than 10% for the U and Pu concentration changes in liquid Cd anode and molten salt, and U deposit on solid cathode.     

基于PCB线圈吸附式铁磁传感器的研究

运用PCB线圈作为感应元件的铁磁传感器越来越成熟,但PCB线圈由于其结构限制,使得铁磁颗粒不能通过其检测区域,另也没有相关研究证实PCB线圈对于铁磁颗粒测量的精确性。为此提出一种基于磁塞与电感检测原理的新型铁磁传感器。使用有限元仿真软件COMSOL Multiphysics建立传感器的仿真模型,对PCB线圈的磁场分布进行仿真分析。结果表明：PCB线圈表面磁场强度具有良好的均匀性,适当减小PCB线圈的内径,有利于提高PCB线圈的磁场均匀性。基于仿真分析结果,设计5种不同尺寸规格的PCB线圈,并设计实验验证该传感器的检测精度。实验结果表明：该传感器具有良好的灵敏度,能有效检测出粒径100μm以下的铁磁颗粒。     

一种新型电调FBAR结构的仿真分析

针对目前薄膜体声波谐振器(FBAR)调谐范围小的问题,提出了一种新型电调FBAR结构,在传统FBAR的压电薄膜和底电极之间引入一层n型掺杂AlN半导体(n-AlN)薄膜。利用COMSOL Multiphysics对新型FBAR进行建模仿真计算,得到其谐振频率为1.92 GHz,阻抗特性曲线中存在寄生谐振峰,通过调整顶电极厚度进行优化,结果表明,当顶电极厚为0.1μm时,寄生谐振峰消失,此时器件谐振频率为1.976 GHz,且顶电极厚度调整后器件整体性能有较大提升。对优化后的新型FBAR进行电调仿真分析,得到其调谐量为600 kHz/V,比传统FBAR的150 kHz/V有很大的提高,另外,仿真结果显示,谐振频率与外加调谐电压呈指数正相关。