Random Network Coding Based Schemes for Perfect Wireless Packet Retransmission Problems in Multiple Channel Networks

Solving WPRTPs (wireless packet retransmission problems) using NC (network coding) is increasingly attracting research efforts. However, no work on NC based schemes for WPRTPs in MCNs (multiple channel networks) has been found. In this paper, RNC (random network coding) based schemes for P-WPRTPs (perfect WPRTPs) in MCNs, denoted as MC-P-WPRTPs (multiple channel perfect WPRTPs), are studied by transforming MC-P-WPRTPs into ILP (integer linear programming) problems. The ILP problems corresponding to MC-P-WPRTPs with four typical configurations are derived. Then the corresponding packet retransmission schedule schemes for MC-P-WPRTPs are proposed based on the solutions to the ILP problems and random network coding. To solve the ILP problems efficiently, an algorithm named as progressively fixing algorithm is proposed which recursively reduce the size of the ILP problem by fixing some of the variables according to some criteria. The criteria are related to the solution to the LP problem obtained by relaxing the integral constraints on the variables in the original ILP problem. Simulation results show that the NC based schemes for MC-P-WPRTPs are effective in saving packet retransmissions. In some situations, NC based schemes can save about 50 % packet retransmissions.     

电视节目安全监测与应急处理系统的设计方案

1概述 为保证广播电视网络和节目播出的安全,对广播电视前端节目播出内容和传输质量进行实时安全监测和应急处理,是广电行业管理的重要任务.为了加强广播电视网络管理和技术防范工作,通过建立广播电视前端节目播出监测与应急处理系统,可以高效、实时地对卫星节目及本地节目进行监测和应急处理,提高对广电网络的监管及处理突发事件的能力和管理水平,确保广电网络播出和传输的安全.     

小区OLT建设必要性研究

全业务运营背景下,电信运营商正逐步加快宽带接入网的建设与优化,密集小区大量家庭客户的宽带接入催生了小区OLT的建设需求,文章通过对密集小区情况下集中式OLT和小区OLT建设的利弊进行比较并给出建设实例对比,指出了小区OLT建设模式的必要性。     

透明导电薄膜对太阳能平板集热器性能的影响

在介绍透明导电薄膜光学性质的基础上,分别讨论了不同情况下,太阳能平板集热器盖板采用镀有透明导电薄膜的玻璃对集热器的光热转换效率和保温性能的影响。结果表明,当集热器吸热板表面没有覆盖选择性吸收涂层,在盖板玻璃下表面镀有透明导电薄膜可以在一定温度范围内提高集热器的转换效率和保温性能,而当吸热板已覆盖有选择性吸收涂层时,盖板玻璃再镀透明导电薄膜,集热器辐射热损则减少很少,甚至不足以补偿由于玻璃透过率降低而增加的光反射损失,在这种情况下,盖板不宜再采用镀有透明导电薄膜的玻璃。     

用CS5460和μPD75P3116实现功率和电能计量

本文介绍了用CS5460和μPD75P3116单片机实现功率和电能计量的方法,给出了系统的工作原理、硬件设计、软件设计等.     

铁电随机存储器的研究进展

铁电薄膜与半导体集成技术相结合而发展起来的铁电存储器．以其高密度、高速度、非易失性及抗辐射性而大大优于目前任何一种半导体存储器。该文介绍了铁电存储器的存储原理、特点、基本存储单元、研究进展、应用及存在的问题，并指出1T结构的铁电随机存储器(FRAM)将会成为下一代随机存储器。     

Effect of Heat Treatments on the Structural and Magnetic Properties of La-Co Substituted Strontium Ferrite Films

A sputter-deposited strontium ferrite film with perpendicular anisotropy has been developed. The film, composed of La_0.33Sr_0.67Co_0.25Fe_11.75O₁₉, has been fabricated directly on quartz glass substrates by radio frequency magnetron sputtering with various heat treatments. The structural and magnetic property dependence of those films on heat treatments has also been studied. The optimized condition is the heat treatment of in situ heating at 400°C and post-annealing at 850°C–900°C. When post-annealing temperature exceeds 900°C, parasitic phases of γ-Fe₂O₃ and LaFeO₃ appear and gradually increase; meanwhile, the magneto plumbite phase gradually decreases. High c-axis perpendicularly oriented films with the coercivity (4148 Oe), remanence squareness ratio (0.89) and perpendicular magnetic anisotropy energy density (1.65 × 10⁶ erg/cm³) are achieved, which is attributed to the single magneto plumbite phase with compact platelet grains and almost complete (0 0 l) texture of the c-axis normal to the film plane.     

基于逆向导航算法的捷联式惯性导航系统改进优化对准方法

快速性和精度是捷联式惯性导航系统动基座初始对准的重要指标。优化对准方法（OAM）在短时间内难以获取足够多的观测信息,导致对准性能降低。针对此问题,提出一种基于逆向导航算法的改进动基座初始粗对准（IMCA）方法。通过逆向导航算法对存储的陀螺仪和加速度计数据进行虚拟延长并加以反复利用,扩展积分区间长度,以构建新的观测矢量、实现对准精度的提升。推导了载体坐标系下的OAM,分析了观测矢量包含的信息量对姿态确定精度的影响。基于车载实测数据,分别利用OAM和IMCA方法进行动基座初始对准试验,结果表明：相比于OAM,IMCA方法可在相同条件下实现更高精度的初始对准;IMCA方法应用在载体坐标系下动基座初始对准中是可行、有效的。     

摩擦对电动直线负载模拟器的影响及其抑制研究

为抑制摩擦非线性因素对电动直线负载模拟器（ELLS）的影响,采用仿真与实验结合的方法分析摩擦对ELLS的影响。利用遗传算法对系统中的摩擦模型进行辨识,并得出了系统摩擦力与速度的关系;提出了一种摩擦前馈加变增益PID的混合控制方法,摩擦前馈用于消除摩擦对系统的影响,变增益PID用于进一步抑制系统在低速时的相位滞后;进行了对比仿真与实验。仿真分析与实验结果表明：与传统PID控制相比,采用摩擦前馈加变增益PID控制的ELLS加载波形畸变被抑制、加载误差与相位滞后均明显减少;所提出控制方法能够较好地抑制摩擦对ELLS的影响,提高加载精度。     

基于改进型入侵野草算法的三轴磁传感器非正交误差校正

由于加工工艺和安装工艺的限制,三轴磁传感器必然存在非正交误差。为校正该误差以获取准确的三轴磁数据,建立了三轴磁传感器的非正交误差模型,并通过最小二乘法求解该模型。利用4种智能优化算法对上述最小二乘问题进行求解,并对入侵野草算法进行了改进。仿真与实验结果表明：基于改进型入侵野草算法的最小二乘误差校正方法对因三轴非正交导致的运动噪声抑制率分别为85.42%和86.50%,可以较好地对三轴磁传感器非正交误差进行校正。