基于跟踪回路误差限制的INS辅助载波跟踪回路模式研究

INS对接收机载波跟踪回路的辅助,能够减弱或抵消载体动态影响,降低回路带宽,减少回路跟踪误差,也是实施超紧耦合技术的主要特点。具体分析了FLL和PLL的各组成误差,推导了稳态载波相位误差、载波多普勒频移误差与INS速度误差之间的关系,基于跟踪回路误差的限制和稳定回路的门限,具体给出了在相位辅助和频率辅助两种不同模式下对INS速度误差的限制条件,分析表明考虑到INS辅助精度的影响,采用INS对载波跟踪的频率辅助更具可行性,最后仿真验证了频率辅助的有效性。     

西双版纳地区土地利用/覆盖变化对气温的影响

 应用标准化均方根误差和相关性,分析3种再分析资料在西双版纳地区的适用性.通过相减法(Observation minus Reanalysis,简称OMR)探讨西双版纳土地利用/覆盖变化对气温的影响,结果表明:NCEP-1、NECP-2和ERA-40数据及其距平值和实际观测气温的相关性均达到极显著水平(P＜0.01),均方根误差总体小于1,ERA-40的可信度最高.研究区4个气象站(勐海、景洪、勐仑和勐腊)月平均气温和再分析气温均呈上升趋势.剧烈的土地利用变化显著影响了平均气温变化,对景洪站、勐腊站、勐仑站和勐海站平均气温变化贡献值分别为0.08、0.07、0.01、0.05 ℃/10 a.景洪气象站气温变化受土地利用变化影响最明显.不同年代观测气温和再分析资料差值得到,20世纪80年代土地利用变化对气温影响最大,贡献值为 0.09 ℃.有林地、灌木林地、水田面积的减少,橡胶园和建设用地面积的增加影响了气温变化.     

主动同步法实现Mathieu方程的混沌同步

首先通过全局分岔图和吸引子图对所研究的Mathieu方程的动力学行为进行了分析.在此基础上,对该方程的混沌同步进行了研究.利用主动同步方法实现了2个不同初值的Mathieu方程间的自同步,同时利用该方法实现了Mathieu方程与非线性陀螺系统间的异结构同步.数值仿真验证了该方法对实现Mathieu方程混沌同步的有效性.     

不同屋面雨水径流中PAHs污染特性对比分析

对南京市典型沥青屋面、瓦屋面径流中PAHs含量进行了9场降雨事件的现场取样监测,对比分析了2种不同屋面径流中PAHs的EMC值及其各组分的浓度,并对其初期效应及影响因素进行了分析和探讨.结果表明,沥青屋面径流PAHs污染较严重,其平均浓度为4 261.7 ng/L,而瓦屋面径流PAHs平均浓度仅为351.2 ng/L.沥青屋面、瓦屋面径流中PAHs均以4环组分为主,沥青屋面径流中3环组分占较大含量,而瓦屋面径流中5环和6环PAHs浓度仅次于4环PAHs.大多数降雨事件中总PAHs及各组分均存在较显著的初期效应;前期晴天数对PAHs在屋面的累积影响最大,瓦屋面径流PAHs含量受降雨强度影响较大,而沥青屋面径流PAHs含量受降雨量影响较大.     

有限开区间上的柯西中值定理

通过给出一个反例,指出了文献[2]中有限开区间上柯西中值定理的错误,给出了有限开区间上的柯西中值定理,推广了柯西中值定理,使得利用导数研究开区间上函数的整体性态更为方便。     

宽带数字接收机的I/Q通道失配校正

由于各种因素的影响,I/Q通道之间通常会发生失配现象,影响接收机的性能.分析了幅相误差校正参数的提取方法,提出了基于FIR滤波器的宽带数字接收机的数字域校正方法,研究了校正频点数、校正频点位置对系统性能的影响.仿真结果表明,这种方法能有效提高宽带接收机I/Q通道的正交一致性.     

Benjamin-Bona-Mahony方程的平均隐式差分格式

本文对Benjamin-Bona-Mahony(BBM)方程的初边值问题进行了数值研究,提出了一个平均隐式差分格式,讨论了差分解的存在唯一性.然后利用离散泛函分析方法分析了该格式的二阶收敛性与稳定性,然后利用数值实验进行了验证.     

二维液晶环型光子晶体的可调完全带隙

利用平面波展开法研究了二维三角晶格液晶环型光子晶体的完全带隙的动态可调节性.数值模拟结果表明:环中所填充的5CB液晶指向矢的旋转角从0°到90°改变,二维环型光子晶体一直出现完全带隙,并且完全带隙随着液晶指向矢的旋转角的变化可以实现动态可调.分析完全带隙可调范围与二维液晶环型光子晶体的结构参数(液晶环内/外径、基底材料的折射率、液晶正常/反常折射率、内介质柱折射率)的变化关系.     

Real-time filter based on the quasi-accurate detection of gross errors

Because of the sensitivity of the Kalman framework to gross errors, proper techniques for detection of gross errors are necessary. By integrating the selection of quasi-accurate observations and the Kalman framework, a new filter called the quasi-accurate filter (QUAF) is developed. The expansibility and implementation scheme of the new algorithm are then discussed in detail, and the reliability matrix for the Kalman filter is proposed to analyze the reliability of the filters with different detection technologies. Finally, the experimental results from a real world case study are used to validate the conclusions. The QUAF carries out the preliminary selection of the quasi-accurate observations (QAOs) using the innovation of the Kalman filter, and use the check QAOs to determine reasonable observations. This causes the QUAF to handle more easily and possess wider expansibility. QUAF can be reformulated to the special cases of several common detection methods, such as the innovation method, robust estimation and quasi-accurate detection (QUAD). Since only reasonable observations are used, the QUAF has better detection accuracy and stronger avoidance of gross errors than the innovation method and robust estimation. Meanwhile, compared with QUAD methods, QUAF introduces the state-predicted model, requiring fewer quasi-accurate observations and making it more suitable for systems with complicated observation structures or sparse observations.     

Spatial discretization error in an artificial benchmark model of oblique laser incidence by finite volume approximation for radiative heat transfer

The spatial discretization error in a finite volume method approximation for radiative heat transfer is investigated. An artificial benchmark model for oblique laser incidence on a two-dimensional rectangle containing a semi-transparent medium is proposed, in addition to using reference data from the Monte Carlo method. Within the framework of the current model, it is shown that numerical scattering in the finite volume method is affected by the spatial grid values and the different spatial discretization schemes to a large degree. Numerical scattering also varies with the degree of absorption coefficient deviation. Numerical scattering is distributed in a symmetrical profile along the laser incidence direction, and all of the schemes show symmetrical cross-scattering.