探地雷达回波信号预处理方法的研究与应用

探地雷达以宽频带记录回波信号,在记录各种有效信号的同时,不可避免地记录下各种干扰噪声,能否有效去除干扰噪声将直接影响到探地雷达对地下目标体的识别能力。探地雷达回波信号属于非平稳信号,FFT只适用于平稳信号的滤波、而小波变换对非平稳信号却能取得良好的滤波效果。为此,文中提出了采用小波阈值萎缩进行数据预处理的方法,以去除雷达回波噪声,并给出了基于DSP的电路和软件实现方法。     

基于MUSIC谱估计的探地雷达回波处理方法

为了克服现有信号处理算法对探地雷达噪声及杂波滤除的不足,提出了一种基于MUSIC谱估计时域与频域联合滤波方法。利用常用的去直流波和均值滤波抑制方法进行雷达信号预处理,在此基础上,引入谱分析中信号子空间与噪声子空间的概念,将MUSIC算法与最小二乘法相结合来进行探地雷达杂波及噪声处理。仿真及实验结果表明,提出的回波处理方法可以有效地抑制雷达信号中的噪声和杂波,能提高测量数据的精度,具有较高的实用性和可用性。     

偏移技术在探地雷达数据处理中的应用

探地雷达是近年来快速发展的高精度无损探测技术,被广泛应用于各个工程领域.但往往由于地下介质分布复杂使得回波剖面包含有大量的绕射波及各种干扰波,严重影响被测物的识别甚至掩盖了被测物体.本文主要介绍了探地雷达回波信号处理中的几何偏移和绕射叠加偏移,可用来有效地消除噪声及绕射干扰,使回波剖面清晰、直观的呈现出被测物体.     

分层均衡器在探地雷达成像中的设计研究

探地雷达回波因为地下介质的损耗造成其随着深度的增加而衰减增大,导致对深埋目标探测更加困难,分辨率因此而降低。文章针对该问题提出了一种分层均衡器设计的方法。该方法采用多测线平均得到回波的平均值,并根据回波次数进行分段,计算各段的极大值与极小值的差值。将其中一次回波的最大差值与其它回波差值的比值作为各段的均衡放大因子矢量,再将测线组的各段与对应放大因子相乘,从而得到回波分层均衡放大后的结果。通过实测数据对该方法进行了实验和分析,实验结果表明该方法是解决深层目标检测和提高信噪比的一种有效方法。     

探地雷达数据实时成像技术研究

为解决探地雷达在工作过程中回波数据的实时成像问题,设计了基于VC＋＋平台的回波数据实时成像系统;采用基底去除技术及其色域划分的方法对回波数据进行处理及其实时成像,满足了探地雷达工作中实时成像的要求;实验表明,利用这种方法形成的图像能够真实反映地下目标体的变化。且有利于对采集到的数据进行进一步处理和分析。     

基于小波包的去噪方法在地雷识别中的应用

作为一种新的探雷方法,探地雷达在探雷领域得到了广泛的应用。由于雷达回波信号包含有很多杂散信号,目标信号很容易被强噪声信号所淹没,为了提高雷达回波信号的信噪比,有利于地雷的识别和检测,提出了一种基于信息熵的最优基选择与小波包阈值去噪相结合的方法对回波信号进行杂波抑制,采用该方法对DeTeC的数据进行分析的实验结果表明,该方法在有效地去除了直达波的同时,抑制了背景噪声,分离出目标信号。     

超宽带探地雷达目标回波信号特征提取与材质识别

基于探地雷达信号传输机理,建立了超宽带探地雷达宽带回波模型,揭示了多谱分量对目标回波信号特征提取与材质识别的影响。超宽带探地雷达由于回波信号信息丰富的特点,特征向量的选取成为目标识别的关键。利用子波变换在宽相关处理中的应用,对回波信号进行滤波和典型数据提取。提取纵向和横向典型数据用于目标形状识别;提取回波道数据进行Welch功率谱分析,用于目标材质识别。     

基于经验模态分解的探地雷达信号去噪处理

探地雷达作为一种先进的地球物理探测方法,具有探测效率高、操作简单、采样迅速、无损伤探测、探测分辨率高等优点。探地雷达的信号的去噪问题已成为一个公认的技术难题。本文用经验模态分解的方法对探地雷达信号进行信号去噪处理,并取得了良好的效果。     

多站数据采集在探地雷达中的应用

由于地下介质组成相当复杂,且具有非均匀、损耗和色散等特性,以及各种杂散回波的存在,探地雷达(GroundPene-tratingRadar,GPR)信号处理与一般的空间雷达有较大差别,其成像效果不尽如人意。本文将衍射层析成像(DiffractionTo-mography,DT)中的多站数据采集应用在探地雷达中来实现高质量成像,并经过数值验证,说明了多站数据采集较传统单站数据采集有很大的优越性。     

探地雷达测定土壤含水率研究综述

准确快速测定土壤含水率,在理论研究与实际应用中都具有重要意义.在综合分析烘干法、中子法、时域反射法和遥感4种土壤含水率测定方法的优缺点基础上,指出探地雷达是一种适合于中尺度的土壤含水率测定的技术.对探地雷达以及探地雷达测定土壤含水率的技术原理与方法进行全面介绍,并以介电常数与土壤含水率的关系模型为主,对国内外这方面的研究工作以及存在的问题进行了总结.最后指出,探地雷达测定土壤含水率是一项非常有前景的技术,但目前国内在这方面的研究工作与国外相比远远不够,今后应加强这方面的研究工作.     

K(Knowledge)-net: building up and its dynamics

The essence of intelligence is to use certain abilities to obtain knowledge, to use that knowledge, and to operate with that knowledge. New knowledge learned by a human is often related to old existing knowledge, and sometimes we could have more conceptual knowledge based on old knowledge. So, the knowledge in the brain exists in a related structural form, and this structure is dynamic, and therefore is evolvable. Based on the understanding of the real process of learning by a human being, we discuss how to make a model to describe the dynamic structure of knowledge. This model is also a principle of artificial brain design. Most of the knowledge a child learns is from natural language and perception information, and we define this as semantic knowledge. The model to describe the process and structure of knowledge growing in a network form is called a K-net. It is a dynamic network with two main dynamics: one is new knowledge added, and the other is aggregating knowledge existing in the network with some probability. Under these very natural conditions, we found that the network is originally a simple random net, and then some characteristics of a complex network gradually appear when more new knowledge is added and aggregated. A more interesting phenomenon is the appearance of a random hierarchical structure. Does this mean emergence?     

Coherent processing of character skeletal forms

It is well known that in the general context the similarity relation is very fuzzy and hard to define. Unfortunately, the intuitive notion of similarity is not a transitive relation: knowing that A is similar to B and that B is similar to C does not necessarily imply similarity between A and C. This is a main obstacle when trying to express formally what a coherent font design is. In this paper we suggest a method to decompose complex letter forms into simpler elements and we suggest a formal transitive definition of a similarity relation between these elements. In the context of digital typography, this definition enables developing an algorithm to recover classes of similar elements within different characters of a given font. This knowledge is further exploited to ensure coherent type processing. For example, a modification (e.g. by a type designer) of a character element is propagated automatically to all the other characters that include a similar element. For the moment, the discussion is limited to the class of stroke fonts.     

基于嵌入式技术的开关寿命测试仪的设计

为了对开关的寿命进行快速准确地测试,设计了开关寿命测试仪。设计过程如下:首先设计了测试仪的硬件,该硬件使用LPC2138CPU芯片采集开关触头对应的开关量,并与TG12864液晶模块接口输出提示信息;其次设计了判断开关好坏算法和识别坏触头算法;最后根据算法给出了测试仪软件的流程图。应用表明,用这种设计方法实现的测试仪工作可靠、容易使用,适合在开关生产行业推广应用。     

基于通用比较模型的t-可诊断系统的特征化及并行诊断算法

文中介绍了一种系统级故障诊断模型－－通用比较模型,该模型处理器作为自身的比较器,综合经典的ＰＭＣ模型和Ｍａｅｎｇ／Ｍａｌｅｋ模型的优点,基于该报多处理器系统的ｔ＿可诊断性问题,给出了ｔ＿可诊断系统的特征化,证明了一个系统成为ｔ－可诊断系统的新的充分必要条件,其次,证明在通用比较模型中,确定故障顺集的问题等价于求解一个超图的最小横切集（Ｍｉｎｉｍｕｍ ｔｒａｖｅｒｓａｌ）,该超图是根据多处理器的通信     

基于Struts和JDO的信息管理系统

Struts是广泛应用的Web框架，但它没有提供如何访问数据的方法。JDO是数据访问框架，利用O-R映射来访问数据库，而一般要用JDBC和SQL来访问数据库，较之JDO更加方便和快捷。一个成熟的应用需要两者结合起来才能形成一个完整的方案。这里提出用Struts作为前台和逻辑控制，用JDO作为后台数据访问层来开发B/S架构的信息管理系统的一种方案。     

Can the terminal condition of time-invariant linear control systems be made immune against small parameter variations?

Discussed in this short paper is a controllability question pertaining to a class of sensitivity problems. More specifically, the possibility is considered of transferring a time-invariant linear system from each initial state to any terminal state in a finite time and in such a way that the terminal condition is insensitive to small parameter variations. Partial controllability, suitably defined, leads to a necessary and sufficient condition for the existence of the solution to such a problem. Terminal output insensitivity is also discussed and a similar result is proved when the output transformation is not affected by some parameter variations.     

二进神经网络中汉明球的逻辑意义及一般判别方法

剖析二进神经元的逻辑意义对二进神经网络的规则提取是十分重要的，在布尔空间中，汉明球是一种线性可分的空间结构，如何从汉明球中提取出具有清晰逻辑意义的规则是二进神经网络研究的一个问题，通过对MofN规则表达形式的扩展，分析了汉明球的逻辑意义，提出了表达汉明球逻辑意义的LEM规则和GEM规则方法，并且讨论了汉明球和汉明补球的等价性，另一个重要的结果是证明了二进神经元和汉明球等价的充要条件，从而建立了判别汉明球的一般方法。     

混合关系中的函数依赖及其相关规则

在实际应用中有这样一类关系数据库,其中数据项在某个属性上的取值本身又是一个关系。讨论这种混合关系中的函数依赖及其相应的相关规则具有一定的理论意义和实际应用价值。给出这种混合关系的形式定义、混合关系中4种类型的函数依赖关系以及相应的4种类型的相关规则;并给出混合关系到一般关系的转换,通过这个转换说明了混合关系与普通关系的联系及其差别。给出一个实际应用中的例子,来说明混合关系中的函数依赖和相关规则的形式多样性。     

Reduced-order modelling of linear discrete-time systems via continued-fraction expansion of a z transfer function about z = 1 and z = a alternately

A new time-domain procedure is suggested for obtaining reduced-order models of linear time-invariant discrete-time systems. The procedure is based on presenting a new form of continued-fraction expansion (CFE) about z = 1 and z = a alternately, and deriving a realization form for the CFE. An algorithm is presented for obtaining the new CFE of the z transfer function of a linear discrete-time system from its state-space model directly, without having to determine the corresponding rational z transfer function. Also presented is a systematic approach to deriving two similarity transformation matrices: one is used to transform a state-space model from a general form to the CFE canonical form, and the other is used to transform a state-space model from the phase-variable canonical form to the CFE canonical form. Finally, an approximate aggregation matrix is constructed to relate the state vector of the original system to that of a reduced model obtained by the present method. The proposed procedure is illustrated with examples.     

An Order-Based Theory of Updates for Closed Database Views

The fundamental problem in the design of update strategies for views of database schemata is that of selecting how the view update is to be reflected back to the base schema. This work presents a solution to this problem, based upon the dual philosophies of closed update strategies and order-based database mappings. A closed update strategy is one in which the entire set of updates exhibit natural closure properties, including transitivity and reversibility. The order-based paradigm is a natural one; most database formalisms endow the database states with a natural order structure, under which update by insertion is an increasing operation, and update by deletion is decreasing. Upon augmenting the original constant-complement strategy of Bancilhon and Spyratos – which is an early version of a closed update strategy – with compatible order-based notions, the reflection to the base schema of any update to the view schema which is an insertion, a deletion, or a modification which is realizable as a sequence of insertions and deletions is shown to be unique and independent of the choice of complement. In addition to this uniqueness characterization, the paper also develops a theory which identifies conditions under which a natural, maximal, update strategy exists for a view. This theory is then applied to a ubiquitous example – single-relational schemata constrained by equality-generating dependencies. Within this framework it is shown that for a view defined as a projection of the main relation, the only possibility is that the complement defining the update process is also a projection, and that the reconstruction is based upon functional dependencies.