一种基于比幅比相测角解模糊方法

比幅比相测角是宽带被动雷达测向系统中的一种重要方法，由于比幅比相测角系统存在相位多值模糊，因此采用长短基线和幅度信息，提出了划分幅度差门限设置滑动粗相位的方法．并通过实验证实了其有效性，实现了比幅比相测角的解多值模糊，在实际工程应用上具有一定的实用价值和参考价值．     

雷达角误差信号的数字化算法

阐述了一种数字化的雷达单脉冲系统,在比幅体制的单脉冲天线下,提出了相应的角误差计算方法,并给出了一种工程中实际使用的方法,总结了该方法的使用效果。     

一种数字信道化接收机参数编码方法

研究一种基于多波束比幅测角的数字信道化接收机参数编码方法.描述了数字信道化接收机的参数编码流程,详细论述编码过程中通道间幅度测量同步和脉冲到达角(DOA)测量方法.采用该方法的数字信道化接收机的脉冲描述字(PDW)编码与典型接收机的一致.实践证明,该方法可以满足复杂电磁环境下雷达信号处理实时性的要求.     

基于差波束逆合成孔径雷达成像的角运动参数估计方法

针对单脉冲三维成像时的目标角运动估计问题，提出一种基于差波束逆合成孔径雷达成像的新的角运动参数估计方法．该方法利用了各阶运动参数对差波束回波谱宽度的不同贡献以及熵与谱宽度的关系，通过最大熵和最小熵分剐对0阶和1阶以上角运动参数进行搜索，得到全局最优估计．有别于传统比幅测角方法，所提方法通过全局搜索得到目标的角运动参数，可以较好地抑制角闪烁的发生．对飞机目标角运动参数估计过程的仿真结果表明，与传统高分辨测角方法相对比，所提方法的平均误差降低了72％．     

被动雷达导引头非相干两点源角度测量

在非相干两点源存在的情况下,对被动雷达导引头的干涉仪测角进行了研究.在一定条件下,由比相均值得到的测角结果将会指向大功率源,提出了一种基于双采样点的角度测量方法,该方法利用干涉仪两通道在两个采样点的信号就能得到两点源的角度.通过仿真对该方法的有效性进行验证.结果表明,该方法可以对非相干两点源进行分辨,并且在一定相位条件下能够得到比传统比相方法更高的测角精度.     

基于TMS320C6711的幅度相位量化

比相法在雷达测向系统中具有高精度的特点．相位量化是比相测向系统中的重要组成部分，实现方法主要有极性相位量化法和幅度相位量化法．极性相位量化方法现在较为普遍，着重介绍了另一种量化方法的实现：基于TMS320C6711的幅度相位量化方法，并介绍了TTMS320C6711在设计应用中需要注意的事项．     

浅谈机载雷达角误差处理

比较机载雷达的比幅单脉冲体制下的两种角误差提取算法,即数字接收机的角误差提取算法、零中频接收机的角误差提取算法,得出前者在角跟踪的精度上更优于后者。通过分析影响角误差的因素,探讨了角误差的滤波方法,为提高雷达角度跟踪的质量误差提供了坚实的基础。     

基于改进自适应扰动观测的最大转矩电流比控制

针对内置式永磁同步电机(IPMSM)的最大转矩电流比控制(MTPA)受电机参数变化影响的问题,提出一种改进的自适应扰动观测的MTPA控制策略.该方法以定子电流矢量角作为扰动量,比较控制系统前后两个时刻的电流幅值大小,确定搜索方向.将自适应PI控制融入扰动观测法中,跟踪系统随机选择相应的扰动步长,解决动稳态性能,提高精度和系统运行效率,克服传统MTPA控制方法对电机参数依赖性、提高系统整体效率优化和电流矢量角搜索精度.考虑外界因素对电感和磁链等参数变化的影响,得到内置式永磁电机(IPMSM)dq轴下最优电流矢量角.仿真和试验结果表明,所提方法具有一定的有效性.     

低信噪比地震记录中信号初至的估计

给出一种基于赤池信息量准则(AIC)算法和信号幅值比的混合方法来估计低信噪比地震记录中信号的初至．用信号的AIC曲线和幅值比曲线构造一种叠如曲线，对叠加曲线进行类似于坐标旋转的校正，利用校正后的叠加曲线可以准确估计低信噪比记录中信号的初至．用该方法对乌鲁木齐台记录到的35次天然地震中P波、S波和Lg波进行初至估计，P波初至估计误差的均方误差为0．71，后续震相(S波、Lg波)初至估计误差的均方误差为1．64，其结果均优于传统AIC算法的估计结果．     

基于信噪杂比最大能量分配认知雷达波形设计

针对认知雷达信号处理中基于信噪杂比（SINR：Signal to Interference plus Noise Ratio）最优波形设计中因对拉格朗日乘子进行搜索而导致计算量大的问题, 提出一种基于信噪杂比最大能量分配方法。该方法通过离散化的能量进行合理分配, 获取回波的最大SINR, 从而得到认知雷达的最优发射波形。仿真实验表明, 基于信噪杂比最大能量分配方法与拉格朗日乘子算法获取的认知雷达最优波形相近, 但该方法因不需对乘子进行搜索而减少了计算量, 提高了计算速度。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

英文诗歌中的喻类修辞

为了有助于提高英文爱好者的个人情操、文化素养和学习兴趣,以及专业人员对英语学习和研究进行多途径的探索,本文通过一些精选诗歌的引证和分析,着重论述了喻类修辞法在英文诗歌中的运用其及效果。     

Man Is Unable to Change the Miserable Life——Analysis of the Arrangement of Four Characters in The Glass Menagerie

Tennessee Williams is considered as one of the most important American playwrights since World War II.The Glass Menagerie is his first successful drama,which describes a tragic situation of family and means to say that Man is unable to change the miserable life,no matter whatever means he try,This essay focuses on the analysis of the arrangement of the four main characters:Laura.Amanda,Jim and Tom to reveal the theme.Laura is fragile.Amanda is brave.Jim is vital.Tom is sensible.And all of them develop and try the different means to struggle against life,but fail tragically.With the evidence,the paper comes to conclusion naturally that Man is unable to change the miserable life,and he dooms to fail.     

Characterization of root-nodulating bacteria on Retama raetam in arid Tunisian soils

The aim of this study is to investigate the diversity of Retama raetam root-nodule bacteria isolated from arid regions of Tunisia. Twelve isolates, chosen as representative for different 16S rRNA gene patterns, were characterized by 16S rRNA gene sequencing and phenotypic analysis. Isolates were assigned to Sinorhizobium, Rhizobium and Agrobacterium. Symbiotic properties of Sinorhizobium and Rhizobium isolates showed a large diversity in their capacity to infect their host plant and fix atmospheric nitrogen. Strain RK 22 identified as Rhizobium was the most effective isolate.     

An Affordable Accurate Evaluation of the Binding Conformations Predicted by Molecular Docking Studies in Bio-System

正Recently,docking has been widely used to predict the binding-modes of protein-inhibitors,when the crystal complexes structure was absent.Most docking algorithms are able to generate a large number of probable conformations,it,however,is difficult to effectively evaluate these docking poses and identify the most reasonable bindingmode.In the present study,on the basis of the crystallographic data of human 3-hydroxy-3-methylglutaryl coenzyme     

WIMAX与WI-FI技术分析及联合组网

介绍了WiMAX与Wi-Fi两种无线宽带接入技术,并对两者之间的关系及相互之间的影响做了对比及分析,并对WiMAX的关键技术进行了详细说明,最后对两者的联合组网方式做了简单的探讨。