The hybrid extended Born approximation and CG-FFT method forelectromagnetic induction problems

The authors propose the hybridization of the extended Born approximation (EBA) with the conjugate-gradient fast Fourier transform (CG-FFT) method to improve the efficiency of numerical solution of electromagnetic induction problems. This combination improves the solution efficiency in two ways. First, using the FFT in the extended Born approximation decreases the computational cost of the conventional EBA method from O(N²) to O(N log₂ N) arithmetic operations, where N is the number of unknowns in the problem. This approach, referred to as the FFT-EBA method, applies to problems with a fairly large contrast. Secondly, using the EBA as a partial preconditioner for the CG-FFT method increases the convergence speed of the conventional CG-FFT method. This second approach, referred to as the EBA-CGFFT method, is in principle applicable to all problems with a homogeneous background, but is particularly efficient for problems with a higher contrast. Numerical experiments suggest that the combination of these two methods is more accurate and more efficient for electromagnetic induction problems     

A Distributed Node Localization Scheme for Wireless Sensor Networks

A distributed node localization scheme for wireless sensor networks (WSNs) is presented in this paper, and it includes three generic phases: (1) determine node-beacon distances, (2) compute node positions, and (3) refine the positions. Different from previous researches, we propose an algorithm combination Min–max + LI for the position derivation and SD method for the refinement in our scheme. Simulation shows that our proposed scheme can perform more robust than some representative distributed node localization schemes presented in previous researches in terms of the trade-off among accuracy, coverage, computation cost, and communication overhead.     

电磁干扰抑制技术及整改(五)

随着光电技术的迅速发展、传感器的不断更新,以及现代军事装备电子化程度的大幅度提高,电子设备之间的电磁干扰问题越来越突出。电磁兼容设计是一个不可或缺的环节,它能避免设备的误动作、图像噪声等,     

基于云原生服务网格的AI模型部署方案

人工智能模型训练完成后并不适合直接运行在互联网生产环境,需要对其进行一定的封装和部署.探讨基于容器和云原生服务网格对AI模型进行自动封装和部署,以微服务形式对外提供Restful API,能够提高模型的兼容性和部署灵活性.封装过程采用适用多框架的通用AI模型代码打包方法,解决AI模型运行环境配置问题;通过部署在云原生平...     

浅谈电子行业委托监造与自主监造利与弊

电力设备监造工作是促进设备监造活动规范有序进行的有效手段,是电力工程项目全面质量管理的一项重要环节,本文对电力设备监造的方式进行比较分析,探讨最合适的电力设备监造的管理方法。     

An FDTD algorithm with perfectly matched layers for generaldispersive media

A three-dimensional (3-D) finite difference time domain (FDTD) algorithm with perfectly matched layer (PML) absorbing boundary condition (ABC) is presented for general inhomogeneous, dispersive, conductive media. The modified time-domain Maxwell's equations for dispersive media are expressed in terms of coordinate-stretching variables. We extend the recursive convolution (RC) and piecewise linear recursive convolution (PLRC) approaches to arbitrary dispersive media in a more general form. The algorithm is tested for homogeneous and inhomogeneous media with three typical kinds of dispersive media, i.e., Lorentz medium, unmagnetized plasma, and Debye medium. Excellent agreement between the FDTD results and analytical solutions is obtained for all testing cases with both RC and PLRC approaches. We demonstrate the applications of the algorithm with several examples in subsurface radar detection of mine-like objects, cylinders, and spheres buried in a dispersive half-space and the mapping of a curved interface. Because of their generality, the algorithm and computer program can be used to model biological materials, artificial dielectrics, optical materials, and other dispersive media     

Iron Oxyhydroxide: Structure and Applications in Electrocatalytic Oxygen Evolution Reaction

Oxygen evolution reaction (OER) is the anodic half-reaction for crucial energy devices, such as water electrolysis, metal–air battery, and electrochemical CO₂ reduction. Fe-based materials are recognized as one of the most promising electrocatalysts for OER because of its extremely low price and high activity. In particular, iron oxyhydroxide (FeOOH) is not only highly active toward OER, but also widely accepted as the true active species of Fe-based OER electrocatalysts for plenty of Fe-based materials are converted into FeOOH during OER test. Herein, the recent advances of FeOOH-based nano-structure and its application in OER are reviewed. The relationship between FeOOH structure and its catalytic performance, followed by the introduction of current strategies for enhancing the OER activity (i.e., crystalline phase engineering, element doping, and construction of hybrid materials) is mainly focused. Finally, a summary and perspective about the remaining challenges and future opportunities in this area and further the design of Fe-based OER electrocatalysts are provided.     

X波段GaN五位数字移相器MMIC的设计

采用0.5μm GaN HEMT工艺设计了X波段五位数字移相器的单片微波集成电路(MMIC),描述了移相器的设计过程,并进行了版图电磁仿真。该移相器采用高低通滤波器型网络和加载线型结构。利用电路匹配技术设计移相器电路的开关结构,将GaN器件的插入损耗从14 dB降至1 dB。版图仿真结果表明,在9.2 GHz~10.2 GHz频带范围内,均方根移相误差小于3.5°,插入损耗典型值为17.4 dB,回波损耗小于-12 dB,版图尺寸为5.0 mm×4.7 mm。     

微机控制自动调谐的NYAB自倍频激光器的研究

研制出国内第一台微机控制自动调谐的LD泵浦NYAB自倍频激光器。利用计算机控制激光器输出镜作二维扫描,精度达10~(-2)度的量级。激光器产生0.531μm的线偏振绿色激光,基横模运转,阈值泵浦功率为14mW,输出功率达3.6mW,斜效率达3％,偏振度大于99.8％。     

直接栅MOSFET静电场传感器温度漂移模型和模拟

推导出了直接栅MOSFET静电场传感器的温度漂移系数,并研究了温度漂移的主要原因。此研究工作对消除直接栅MOSFET静电场传感器的温度漂移有一定的帮助。首先,建立了直接栅MOSFET静电场传感器沟道中电荷随温度变化的模型。其次,根据直接栅MOSFET沟道载流子浓度和载流子迁移率都为温度的函数,将直接栅MOSFET静电场传感器的温度漂移定义为由沟道载流子迁移率随温度变化引起的温度漂移系数αμ和由沟道载流子浓度随温度变化引起的温度漂移系数αQ,并对它们与温度的关系作了推导和研究。最后,对沟道载流子迁移率随温度变化引起的温度漂移系数αμ和由沟道载流子浓度随温度变化引起的温度漂移系数αQ进行了模拟和比较。模拟结果表明,温度漂移系数αμ远小于温度漂移系数αQ。因此沟道载流子浓度随温度变化是直接栅MOSFET静电场传感器的温度漂移的主要原因。