基于瞬时无功理论的无功电流检测方法研究

基于瞬时无功功率理论,对用于无功功率补偿设备的无功电流检测方法进行了研究.通过分析目前常用的各种电力系统无功电流检测方法的优劣,按照不同补偿要求,采用了iP-iP法和Hilbert法两种具体的检测方法.运用Maflab对两种方法的仿真模型进行了稳态和动态性能分析,最终在工控机硬件平台下进行了验证.结果表明,这两种算法均能很好地检测出三相系统中的无功电流,从而达到无功补偿的目的.     

Comparison of the Acquisition Performance of the Matched Filter and Integrate-and-Dump Receivers in a Multipath Delay and Fading Environment

The Matched Filter and the Integrate-and-Dump circuit techniques are both attractive acquisition methods for CDMA systems. Acquisition using the matched filter technique has attracted considerable interest in recent years since it shows a better performance in the presence of Gaussian noise. On the other hand acquisition using an integrate-and-dump circuit is attractive because it is less complex to implement. However, the acquisition performance can be affected significantly by the channel characteristics. In this paper, a numerical method and a computer simulation have been developed in order to compare the two acquisition systems in different propagation environments. Results show that the acquisition using a matched filter is much faster than that using the integrate-and-dump circuit for the reception of spread-spectrum signals in the presence of Gaussian noise. However, in a multipath delay and fading environment, the results show that the mean acquisition time using the matched filter is not always faster than that using the integrate-and-dump circuit. The results show that it depends on the fading, the delay, the number of users and the signal-to-noise ratio.     

最优群孔激光打孔自动编程软件的开发

阐述在数控激光打孔机上进行群孔激光打孔时,最佳打孔路线数学模型的建立以及解决该模型的算法。在此基础上开发了适应于数控激光打孔系统的自动编程软件。     

2D Boron Sheets: Structure,Growth, and Electronic and Thermal Transport Properties

The structures of boron clusters, such as flat clusters and fullerenes, resemble those of carbon. Various two‐dimensional (2D) borophenes have been proposed since the production of graphene. The recent successful fabrication of borophene sheets has prompted extensive researches, and some unique properties are revealed. In this review, the recent theoretical and experimental progress on the structure, growth, and electronic and thermal transport properties of borophene sheets is summarized. The history of prediction of boron sheet structures is introduced. Existing with a mixture of triangle lattice and hexagonal lattice, the structures of boron sheets have peculiar characteristics of polymorphism and show significant dependence on the substrate. Due to the unique structure and complex B? B bonds, borophene sheets have many interesting electronic and thermal transport properties, such as strong nonlinear effect, strong thermal transport anisotropy, high thermal conductance in the ballistic transport and low thermal conductivity in the diffusive transport. The growth mechanism and synthesis of borophene sheets on different metal substrates are also presented. The successful prediction and synthesis will shed light on the exploration of new novel materials. Besides, the outstanding and peculiar properties of borophene make them tempting platform for exploring novel physical phenomena and extensive applications.     

Macroscopic and Microscopic Structures of Cesium Lead Iodide Perovskite from Atomistic Simulations

A first‐principles‐based effective Hamiltonian is developed and employed to investigate finite‐temperature structural properties of a prototype of perovskite halides, that is CsPbI₃. Such simulations, when using first‐principles‐extracted coefficients, successfully reproduce the existence of an orthorhombic Pnma state and its iodine octahedral tilting angles around room temperature. However, they also yield a direct transformation from Pnma to cubic $Pm\overline{3}m$ upon heating, unlike measurements that reported the occurrence of an intermediate long‐range‐tilted tetragonal P4/mbm phase in‐between the orthorhombic and cubic phases. Such disagreement, which may cast some doubts about the extent to which first‐principle methods can be trusted to mimic hybrid perovskites, can be resolved by “only” changing one short‐range tilting parameter in the whole set of effective Hamiltonian coefficients. In such a case, some reasonable values of this specific parameter result in the predictions that i) the intermediate P4/mbm state originates from fluctuations over many different tilted states; and ii) the cubic $Pm\overline{3}m$ phase is highly locally distorted and develops strong transverse antiphase correlation between first‐nearest neighbor iodine octahedral tiltings, before undergoing a phase transition to P4/mbm under cooling.     

结合强化学习自适应候选框挑选的SAR目标检测方法

大场景合成孔径雷达(SAR)图像相对于通用光学图像,复杂背景杂波对目标特征提取影响更大,由于传统基于候选框的深度目标检测算法会在整张特征图上产生大量冗余候选框,因而在SAR图像复杂背景杂波影响下会产生大量的虚警,降低目标检测精度。针对该问题,该文基于Faster R-CNN检测模型,提出结合强化学习自适应候选框挑选的SAR目标检测方法。该方法能够通过强化学习自适应搜索特征图中可能含有目标的区域,并挑选搜索区域内的候选框继续进行分类、回归。通过准确搜索到含有目标的区域,可以减少复杂背景杂波的影响并减少传统强化学习应用于检测问题的计算量。所提方法利用强化学习序列决策的特点,能够根据图像信息通过强化学习迭代搜索自适应确定图像中可能含有目标的搜索区域的位置。同时,该方法通过在强化学习中使用距离约束,可以根据之前的搜索结果自适应调整下一次搜索区域的尺寸。基于实测数据的实验结果表明,所提方法能够提升传统深度学习目标检测方法的检测性能。     

基于频率分集阵列的多功能一体化波形设计与信号处理方法

频率分集阵(FDA)是在相控阵基础上的一次体制革新,其通过在发射天线阵元间进行频率步进,得到的发射方向图是角度、距离、时间的多维函数,显著提升了波束控制能力与信号处理维度,经过收发联合处理后,可应用于多维参数联合估计、主瓣欺骗式干扰抑制、模糊杂波抑制、高分宽幅成像等方面。该文从系统层面出发,研究基于FDA的多功能一体化波形设计与信号处理方法,重点对其在检测与估计一体化、解模糊与抗干扰一体化、合成孔径雷达(SAR)成像与动目标检测一体化的信号处理新方法进行综述、评述及研究,并对FDA多功能一体化系统的应用前景进行展望。     

"十一五"规划国家级重点通信项目

《信息产业科技发展“十一五”规划》提出设立部分重大项目,力争实现重点突破,形成一批具有自主知识产权的核心技术和创新产品,打造较为完整的产业链,形成世界一流的产业群。这其中,与通信相关的重点项目主要有:宽带无线移动通信、下一代网络、家庭网络、智能终端、数字电视等。本部分将对我国在以上领域的现状、项目的具体内容和目标、实现这些目标的具体计划以及相关厂商在各领域的努力和成绩进行介绍。     

电子设备对于电磁脉冲的屏效研究

应用CST分析带有孔缝的屏蔽体的电磁耦合规律.对不同形状以及不同位置的孔缝对屏蔽体屏蔽效能的影响进行分析,并对电磁干扰对内置电路的影响进行了分析,利用外部电磁干扰对内置电路导线上的感、应电压来分析电磁耦合对电路的影响程度.