有线电视台CATV收费管理系统

璧山县地处重庆市郊,人口60万,城区有线电视用户为16000多户(据不完全统计),有线电视网络从1989年开始建设至今,收取收视费一直是个老大难问题。私拉乱接严重,既影响电视信号质量,又造成安全隐     

Exchange coupling and helical spin order in the triangular lattice antiferromagnet CuCrO₂ using first principles

The magnetic and electronic properties of the geometrically frustrated triangular antiferromagnet CuCrO2 are investigated by first principles through density functional theory calculations within the generalized gradient approximations (GGA)+U scheme. The spin exchange interactions up to the third nearest neighbours in the ab plane as well as the coupling between adjacent layers are calculated to examine the magnetism and spin frustration. It is found that CuCrO2 has a natural two-dimensional characteristic of the magnetic interaction. Using Monte-Carlo simulation, we obtain the Neel temperature to be 29.9 K, which accords well with the experimental value of 24 K. Based on non-collinear magnetic structure calculations, we verify that the incommensurate spiral-spin structure with (110) spiral plane is believable for the magnetic ground state, which is consistent with the experimental observations. Due to intra-layer geometric spin frustration, parallel helical-spin chains arise along the a, b, or a + b directions, each with a screw-rotation angle of about 120°. Our calculations of the density of states show that the spin frustration plays an important role in the change of d-p hybridization, while the spin-orbit coupling has a very limited influence on the electronic structure.     

广义形态滤波实现星载SAR图像斑点噪声抑制

提出了实现高分辨率星载SAR单视图像斑点噪声抑制的广义形态滤波法.它以广义形态滤波器实现斑点噪声的抑制,并加以点目标的检测和保持,获得高空间分辨率和高辐射分辨率的SAR单视图像.最后用实际数据进行实验,验证了算法的有效性.     

A Monolithically Integrated 12V/5V Switch-Capacitor DC-DC Converter

Motivated by the battery-operated applications that demand compact,lightweight andefficient DC-DC converters,many kinds of converter circuits have been published.Amongthem,resonantconverters and the soft-switching convertershave greatl...     

开关电源电磁干扰抑制方法探讨

开关电源技术是一项综合性技术,其电磁干扰问题及与其它电子设备的电磁兼容问题已成为人们关注的热点。文中对开关电源电磁干扰的产生、传播机理进行了简要介绍,并从电路结构、EMI滤波、屏蔽、印制电路板抗干扰设计等几个方面,对开关电源电磁干扰的抑制措施进行了分析讨论。     

双钙钛矿SrKFeWO6的电子结构与磁性

基于密度泛函理论框架下的第一性原理,采用考虑在位库仑作用的广义梯度近似（GGA＋U）下的投影缀加波（PAW）方法,研究了具有双钙钛矿结构的Sr₂FeWO₆和SrKFeWO₆材料的晶体结构、电子结构以及磁性性质.结构优化表明,K空穴掺杂稳定了FeO₆及WO₆八面体结构,Fe-O-W键角更加接近180°,有利于Fe-O-W-O-Fe超交换作用;对电子结构分析发现掺杂元素本身对总态密度贡献很小,空穴（p 关键词： 电子结构 磁性 6')" href="#">SrKFeWO₆ 双钙钛矿     

Energy spectrum and superfluidity of spin-2 ultracold bosons in optical lattices

This paper studies the superfluidity of ultracold spin-2 Bose atoms with weak interactions in optical lattices by calculating the excitation energy spectrum using the Bogoliubov approach. The energy spectra exhibit the characteristics of the superfluid-phase explicitly and it finds the nonvanishing critical speeds of superfluid. The obtained results display that the critical speeds of superfluid are different for five spin components and can be controlled by adjusting the lattice parameters in experiments. Finally it discusses the feasibilities of implementing and measuring superfluid.     

基于SCA的认知无线电台结构研究

认知无线电作为一种智能无线电技术,可赋予无线通信系统以电磁环境感知能力,有效解决频谱利用率和管理的问题.软件通信体系结构(简称SCA)已被软件无线电论坛采纳为嵌入式系统的标准通信软件结构.SCA提供了一种支持通信软件和硬件可移植、可配置、可扩充和可重用的软件平台.本文首先论述了认知无线电的概念、功能,接着结合开源认知无线电的概念,提出了一种基于SCA的认知无线电台的新结构,并进行了详细的阐述.     

高阶TEM_(01)模压缩态Wigner准概率分布函数的量子重构

将Nd:YVO4-KTP固体激光器输出的532nm和1064nm激光分别作为抽运光和种子光注入一个内置周期极化磷酸氧钛晶体的简并光学参量放大器,通过非线性光学参量过程产生明亮的高阶横模TEM01正交振幅压缩态光场,利用平衡零拍探测系统测得其压缩度为2.2dB,利用数字存储示波器记录经信号处理系统变换的数据,再通过自编的软件利用量子层析测量技术得到了该压缩态光场在相空间的Wigner准概率分布函数,并将其与理论结果作了对比,两者基本一致。     

浅析军用认知无线电

认知无线电作为一种智能无线电技术,可赋予军用无线通信系统以电磁环境感知能力,有效解决战场频谱利用率和管理的问题,对军事通信产生了深远的影响.本文首先论述了军用认知无线电的现状,接着提出了军用认知无线电的定义,重点分析了军用认知无线电的特点和网络要求,最后对军用认知无线电面临的机遇和挑战作了简要展望.