Assembling hydrodynamic cloaks to conceal complex objects from drag

Transformation hydrodynamics and the corresponding metamaterials have been proposed as a means to exclude the drag force acting on an object. Here, we report a strategy to deploy the hydrodynamic cloaks in a more practical manner by assembling different-shaped cloaking parts. Our strategy is to first model a square-shaped cloak and a carpet cloak and then combine them to conceal a more complex-shaped space in the three-dimensional hydrodynamic flow. With the derivation of transformation hydrodynamics, the coordinate transformations for each hydrodynamic cloaking are demonstrated with the calculated viscosity tensors. The pressure and velocity fields of the square, triangular (carpet), and exemplary three-dimensional house-shaped cloaks are numerically simulated, thus showing a cloaking effect and reduced drag. This study suggests an efficient way of cloaking complex architectures from fluid-dynamic forces.     

Study of asymmetric charge writing on Pb(Zr,Ti)O3 thin films by Kelvin probe force microscopy

Polycrystalline Pb(Zr_0.55Ti_0.45)O₃ thin film was deposited on Pt/Ti/SiO₂/Si(1 0 0) by radio-frequency-magnetron sputtering method, and the writing of charge bits on the surface of PZT thin film was studied by Kelvin probe force microscopy. It is found that the surface potential of the negative charge bits are higher than those of the corresponding positive ones. When ferroelectric polarization switching occurs, the potential difference becomes even more remarkable. A qualitative model was proposed to explain the origin of the asymmetric charge writing. It is demonstrated that the internal field in the interface layer, which is near the ferroelectric/electrode interface in ferroelectric film, is likely to be the cause for the occurrence of this phenomenon.     

The Calibrating Theory in the Network Parameters Measurement of Microwave and MMW Devices

The paper introduces a special system calibration technology in s-parameters measurement of microwave and millimeter wave devices. The 8-term errors module is built by analyzing the signals flowing in the measurement system. Then the calibration technology using non-standard kits is designed on the base. Finally, the experiment using the calibration technology is introduced.     

外FO-群

如果群 G 的所有真商群都是 FO-群,但是群 G 本身不是 FO-群,则称 G 为外 FO-群,本文将给出外 FO-群完全的结构描述．     

幅相一致行波管高频电路CAD研究

 在行波管的设计和装配过程中，各部件的尺寸必须严格控制，高频电路参数的离散对行波管色散特性有极大的影响。使用螺旋导电面模型，模拟计算了高频结构各主要参数离散对色散特性和轴向互作用耦合阻抗的影响。分析计算了夹持杆宽度、翼片高度、螺旋线平均半径、螺距、夹持杆介电常数等离散时对色散特性和轴向互作用耦合阻抗的影响，为新型幅相一致行波管的设计和生产提供了很有价值的参考建议。     

Retailer’s optimal pricing and lot-sizing policies for deteriorating items with partial backlogging

Pricing is a major strategy for a retailer to obtain its maximum profit. Therefore, in this paper, we establish an economic order quantity model for a retailer to determine its optimal selling price, replenishment number and replenishment schedule with partial backlogging. We first prove that the optimal replenishment schedule not only exists but also is unique, for any given selling price. Next, we show that the total profit is a concave function of p when the replenishment number and schedule are given. We then provide a simple algorithm to find the optimal selling price, replenishment number and replenishment timing for the proposed model. Finally, we use a couple of numerical examples to illustrate the algorithm.     

介质加载环板慢波结构高频特性研究

 提出了一种适用于环板结构的计算等效相对介电常数的方法，利用变分法导出了介质加载环板慢波结构的色散方程和耦合阻抗表达式。计算结果表明，介质加载能够有效降低环板慢波结构的工作电压。计算结果与CST-MWS的模拟结果吻合良好，说明所提出的计算等效相对介电常数的方法和计算色散方程的方法对环板慢波结构是切实可行的。     

电子回旋共振放电的电离特性PIC/MCC模拟(Ⅰ)——物理模型与理论方法

采用粒子模拟与蒙特卡罗相结合(PIC/MCC)的方法对电子回旋共振(ECR)放电中的电离过程进行了模拟，其中带电粒子与微波的相互作用由PIC方法的电磁模型描述，粒子间的碰撞过程由MCC方法描述.考虑的碰撞类型有电子与中性粒子的弹性、激发、电离碰撞，离子与中性粒子的弹性、电荷交换碰撞，碰撞截面均依赖于能量而变化.阐述了理论分析的过程，为数值模拟ECR放电奠定了基础. 关键词： 电子回旋共振放电 粒子模拟 蒙特卡罗 电离