结构数字化样机在舰载雷达上的探索

随着数字化、网络化和三维技术的发展,雷达的结构设计从传统的CAD／CAE向全三维数字化协同设计和仿真的方向发展。本文对舰栽雷达结构数字化样机的建设进行了探索。通过协同研发平台实现了雷达研制过程中过程、工具、数据、知识的一体化管理,提高了雷达结构设计效率和质量。     

构建更加开放的移动互联网

随着HSPA+等网络的部署,移动互联网业务将进一步丰富,移动通信与互联网将会融合出更大的产业。文章探讨移动互联网的现状、发展趋势,并对运营商部署移动互联网业务提出了相关建议。     

Influence of La substitution on the electrical properties of metal-ferroelectric (BiFeO3)-insulator (CeO2)-semiconductor nonvolatile memory structures

Metal-multiferroic (La-substituted BiFeO₃)-insulator (CeO₂)-semiconductor (MFIS) capacitors has been fabricated. The crystalline phase and amount of La³⁺ substitution at Bi-site were investigated by XRD and XPS in the postannealing temperature range from 500 to 700 °C, respectively. The microstructure and interfacial layer between CeO₂ and Si substrate were characterized by HRTEM. The memory windows as functions of insulator film thickness and DC power for La were measured. The maximum memory window is about 1.9 V under ±6 V applied voltage. The ferroelectric polarization increases with increasing substitution amount. The morphologies of La-substituted BiFeO₃ films were also studied by AFM.     

NdAlO3-CaTiO3微波介质陶瓷材料的研究

为实现NdAlO3-CaTiO3体系陶瓷材料的优异微波介电性能,采用传统固相反应法制备了(1-x)NdAlO3-xCaTiO3粉末,研究了不同x值对NdAlO3-CaTiO3陶瓷结构和性能的影响.结果表明,当x取0.60,0.65,0.70,0.75,0.80时,所制陶瓷的结构均比较致密,无气孔,晶界清晰,主晶相为(1...     

Derivation of power gain for three types of three dimensional photovoltaics cells

In order to quantify the higher power output seen from solar cells with a three‐dimensional (3D) topology due to the increased interactions between photons and the cell surface, we have derived a formula for the average number of interactions, Γ, between a photon and the cell surface for 3D cells with vertical sidewalls and flat tops. We have derived Γ for three different cell morphologies, an infinite trench in the x‐ or y‐direction, an enclosed box, and an infinite two‐dimensional (2D) array of towers. Monte Carlo simulations were carried out in order to compare computational results for Γ with those derived. For varying distance between features, d, and photon azimuthal angle, the data fits the derived expressions quite well for a large range of values. For varying tower height, the data fits theory well for both the trench and box morphologies, however, theory overestimates the value of Γ for the 2D array of towers. This is due to simplifications made when deriving Γ. However, the error associated with Γ is small enough that it propagates to a measured power output error of less than 1% for cells with an absorbance efficiency of at least 25%. Even with simplifications, the derived expression for Γ should be usable for predicting the increased power output for 3D cells with vertical sidewalls and flat tops. Copyright © 2011 John Wiley & Sons, Ltd.     

5G双小区协作流动热点补偿研究

在通信用户数密集用户业务总量较多的UMi场景下,无线网络节点较多小区覆盖半径较小,用户在小区间移动导致小区间用户分布不均匀,原有用户数及业务量标准部署的5G异构网络相对稀疏,无法满足用户流动产生热点热时容量需求时,双小区协作流动热点补偿采用异构网络多点协作传输技术对小区进行补热,将处于相同移动状态的多个用户虚拟成一个以中心用户为中心的用户簇,建立3D MIMO流动热点模型,提出在两小区以用户最小传输速率为约束条件,最小化小区基站总功率的优化算法,得出高容量、高速率用户体验的"潮汐效应"解决方案。     

基于粒子群算法的矩形件优化排样

针对矩形件排样问题,提出了一种应用粒子群算法优化求解的方法.该方法首先将矩形件的排样问题转化为适于优化的排列问题,然后用粒子群优化算法对整个解空间进行高效搜索,在进化计算过程中应用了自适应调整规则,最终可获得全局最优的排样结果.排样实例表明,该优化排样算法行之有效,具有广泛的适应性.     

TD-SCDMA综合视讯业务

针对3G时代的业务模式，业界提出了“综合视讯”的概念。综合视讯的核心则在于其独有的语音和视频交互平台，其使用方式则更加具有普遍性。介绍了TD—SCDMA支持的综合视讯业务种类。以及TD—SCDMA系统支持综合视讯业务的组成部分。详述了大唐移动在TD—SCDMA特色业务发展方面采取的推动措施。     

基于FPGA的高精度TDI-CCD信号发生器的设计

由于航天相机所使用的TDI-CCD(Time Delay and Integration Charge Coupled Devices)芯片价格昂贵而且极易损坏,提出了一种利用FPGA(Field Pmgrammable Gate Array)和多通道D/A转换器构成的宽频、高精度TDI-CCD信号发生器的原理方案和实现方法。通过对FPGA器件APA075和D/A转换器件DAC2900的配置,得到频率为11MHz的相关双采样形式的模拟TDI-CCD信号,同时通过改进PCB设计和滤波电路,提高了输出信号的精度,降低了噪声。本设计具有可编程、宽频、高精度和低硬件复杂度等特点,目前已成功应用到新一代高分辨率航天相机数据采集系统的研制中。     

3G室内分布系统设计与优化关键问题

首先对3G室内分布系统特点进行介绍,然后对其设计过程中的关键问题进行分析,并给出在后续网络优化过程中的常见问题和相应解决方案。