一种改进的小波阈值图像去噪方法

分析小波阚值去噪特点,针对软、硬阈值去噪存在伪吉布斯和边界模糊现象,提出一种改进的阈值函数和阈值估计方法,该阈值函数具有连续可导且偏差可变的特性,新的阈值估计方法具有较好的自适应性.实验结果表明,该方法可以有效地去除白噪声干扰,无论从视觉效果上还是信噪比上,都优于软、硬阈值去噪方法.     

数据筛选的低频UWB SAR图像快速可视化

目的 为了能够快速得到适于视觉解译的UWB SAR图像,提出了一种基于数据筛选的低频UWB SAR图像快速可视化算法.方法 该方法从统计学的角度出发,讨论了低频UWB SAR图像数据的统计特性和灰度分布模型;在此基础上,首次提出采用3σ准则对低频UWB SAR图像数据进行筛选;并使用修正映射函数映射.结果 对处理后所得图像进行质量评估,可以发现,所得灰度图在等效视数、中央凹特征和对比敏感度特征等方面要优于传统方法处理的处理结果,因而更符合人类视觉系统特征,更易于人眼视觉系统全面了解低频UWB SAR图像表征的场景信息.结论 与传统方法相比,该算法能自适应压缩图像动态范围,处理耗时短,所得图像细节突出,适于对低频UWB SAR图像数据实时处理.     

多物理场耦合界面数据传递的仿真研究

高超声速飞行器的系统仿真是一个气动流场、结构应力场以及结构温度场的高度耦合过程,仿真过程中,需要在耦合界面上完成数据的迭代交换,传递的内容主要包括位移、速度、压力、温度等耦合数据,主要作用就是完成各个耦合场的方程之间参数的传递,在统一的仿真时间内实现仿真的迭代.耦合界面数据传递的技术难点在于要保证耦合界面处的总功守恒以及多物理场耦合仿真的精度[1].目前大多采用以插值为主的局部数据传递方法针对二元耦合开展研究与应用[1,3],局部插值的缺点在于全局精度偏低,偏差较大,计算速度不高.采用径向基函数法(RBF),对界面数据交换方法的仿真应用进行了研究,验证结果表明,计算精度满足仿真要求,求解方程的速度较快,工程应用效果较好.     

基于映射机制的业务规则生成系统

针对业务规则语言繁杂而导致的信息系统难以升级或迁移等问题,在分析现有业务规则开发方法基础上,采用分层体系结构,提出了一种独立于规则引擎的基于映射机制的业务规则生成系统模型。该系统定义了类自然语言的业务规则描述模型,设计了基于XML的中间业务规则,并构建了中间业务规则与目标规则的映射关系,实现了不同规则引擎所识别规则之间的相互转换。     

求解互补支持向量机的非单调信赖域算法

求解支持向量机的核心问题是对一个大规模凸二次规划问题进行求解。基于支持向量机的修正模型,得到一个与之等价的互补问题,利用Fischer-Burmeister互补函数,从一个新的角度提出了求解互补支持向量机的非单调信赖域算法。新算法避免了求解Hesse矩阵或矩阵求逆运算,减少了工作量,提高了运算效率。在不需要任何假设的情况下,证明算法具有全局收敛性。数值实验结果表明,对于大规模非线性分类问题,该算法的运行速度比LSVM算法和下降法快,为求解SVM优化问题提供了一种新的可行方法。     

基于CCD技术的外观纸病检测系统

设计了CCD在线外观纸病检测系统,介绍了该系统的硬件组成情况和系统的工作原理、技术指标和软件设计,重点阐述了外观纸病检测系统中CCD技术的优势。     

Observer‐based decentralized adaptive control for large‐scale pure‐feedback systems with unknown time‐delayed nonlinear interactions

This paper presents an approximation design for a decentralized adaptive output‐feedback control of large‐scale pure‐feedback nonlinear systems with unknown time‐varying delayed interconnections. The interaction terms are bounded by unknown nonlinear bounding functions including unmeasurable state variables of subsystems. These bounding functions together with the algebraic loop problem of virtual and actual control inputs in the pure‐feedback form make the output‐feedback controller design difficult and challenging. To overcome the design difficulties, the observer‐based dynamic surface memoryless local controller for each subsystem is designed using appropriate Lyapunov‐Krasovskii functionals, the function approximation technique based on neural networks, and the additional first‐order low‐pass filter for the actual control input. It is shown that all signals in the total controlled closed‐loop system are semiglobally uniformly bounded and control errors converge to an adjustable neighborhood of the origin. Finally, simulation examples are provided to illustrate the effectiveness of the proposed decentralized control scheme. Copyright © 2013 John Wiley & Sons, Ltd.     

Connectivity maintenance and distributed tracking for double‐integrator agents with bounded potential functions

In this paper, we develop a set of decentralized control laws with bounded potential functions. The basic control law is a combination of attractive, repulsive, and alignment forces, which can keep connectivity, avoid collision, synchronize all agents, and further track a constant moving leader. Furthermore, we investigate the distributed tracking problem with a varying‐velocity leader, where the acceleration of the leader can not be measured. Two cases are considered; the acceleration of the leader is bounded, and the acceleration function satisfies Lipschitz condition. In the first case, the relative velocities of neighbors are integrated and transmitted as a new variable to account for the uncertain time‐varying acceleration. In the second case, two distributed estimators are added for the leader's position and velocity. Finally, some simulations are presented to show the effectiveness of the proposed algorithms. Copyright © 2013 John Wiley & Sons, Ltd.     

简化Lorenz系统多翅膀混沌吸引子的设计与电路实现

基于简化Lorenz系统,通过设计非线性函数,得到单方向多翅膀混沌吸引子.在此基础上,通过引入切换控制函数,得到了网格多翅膀混沌吸引子.通过相图、耗散性、平衡点、分岔图和Poincaré截面方法,分析了系统的动力学特性.结果表明,该多翅膀系统具有丰富的动力学行为.设计并实现了网格多翅膀系统的模拟电路,通过示波器观测到网格多翅膀混沌吸引子,验证了该系统的物理可实现性,电路实验结果与数值仿真结果相一致.     

Adaptive Robust Control for a Class of Uncertain MIMO Non-affine Nonlinear Systems

In this paper, the adaptive robust tracking control scheme is proposed for a class of multi-input and multioutput (MIMO) non-affine systems with uncertain structure and parameters, unknown control direction and unknown external disturbance based on backstepping technique. The MIMO nonaffine system is first transformed into a time-varying system with strict feedback structure using the mean value theorem, and then the bounded time-varying parameters are estimated by adaptive algorithms with projection. To handle the possible "controller singularity" problem caused by unknown control direction, a Nussbaum function is employed, and the dynamic surface control (DSC) method is applied to solve the problem of "explosion of complexity" in backstepping control. It is proved that the proposed control scheme can guarantee that all signals of the closed-loop system are bounded through Lyapunov stability theorem and decoupled backstepping method. Simulation results are presented to illustrate the effectiveness of the proposed control scheme.