单变量Dahlin控制器设计的新方法

分析了振铃现象产生的本质原因,在改进原有方法的基础上提出一种新的单变量 Dahlin控制器设计方法.克服了原有方法的局限,设计的控制器不会产生振铃现象.     

单变量Dahlin控制器设计的新方法1)

分析了振铃现象产生的本质原因,在改进原有方法的基础上提出一种新的单变量Dahlin控制器设计方法.克服了原有方法的局限,设计的控制器不会产生振铃现象.     

盲复原图像振铃效应评价

线性空不变盲复原算法通常会在较为明显的边缘处产生振铃效应。振铃现象主要受噪声,复原算法种类,以及复原算法参数的选择的影响。提出了一种盲复原图像振铃效应评价方法。方法根据振铃效应的不同类型,使用Gabor滤波器,共生向量等方法分别对其进行评价,最后提出整体的振铃效应评价方法。实验结果表明,该方法可以有效地评价不同复原算法和不同复原参数下的复原图像中的振铃效应,评价结果符合主观评价结果。     

车辆运动模糊图像分块恢复的新方法

利用维纳滤波进行真实运动模糊图像恢复的过程中,振铃效应和局部恢复不理想的现象严重影响恢复结果,通过理论分析、实验对比以及研究真实运动模糊过程的特点,找出了问题发生的主要原因。提出采用人工边界补偿和分块恢复的方法来抑制振铃和局部不理想的现象,并给出了模糊参数与空间位置和速度的关系以及具体的分块策略。实验结果表明,所提出的边界补偿和分块恢复方法能很好地减少振铃效应,并保持整体图像恢复效果的一致性。     

一种基于边界处理的图像复原方法

图像复原试图利用退化现象的某种先验知识来重建或复原被退化的图像。其中维纳滤波是一种常见的图像复原的方法,该方法的思想是使复原的图像与原图像的均方误差最小原则来复原图像,但是该法具有一定的限制性,且在复原过程中易产生振铃效应。本文在分析维纳滤波复原图像的基础上,提出了一种对复原后的图像边界进行处理的方法。实验结果表明,该方法有效地降低图像恢复过程中产生的振铃现象,且复原的图像质量较好。     

处理异常值的相机抖动模糊图像复原

摘 要：目的：在曝光过程中由于相机抖动而导致的图像模糊,是一种常见的图像降质现象,并且模糊图像中存在的异常值会导致复原结果的振铃效应,为了解决这些问题,本文提出一种处理异常值的相机抖动模糊图像复原算法。方法：该算法以自然图像统计为先验模型,结合变分贝叶斯方法和KL散度构造易于优化的代价函数,进而求出模糊核。针对异常值造成的振铃效应,在解卷积的过程中采用期望-最大值算法估计并处理异常值以抑制振铃效应。结果：采用本文方法对大量模糊图片进行复原,实验结果表明该方法能有效地去除相机抖动产生的模糊,在保持图像边缘和细节的同时,可有效抑制振铃效应。结论：本文提出了一种通过处理异常值达到抑制振铃效应目的,进而提高复原效果的图像盲复原新方法。实验结果表明该方法切实有效,并且该方法引出了一种抑制振铃效应的新思路。     

基于相对清晰度的多焦距图像融合算法

针对现有图像域融合算法难以合理度量区域清晰度,导致融合结果出现"振铃"现象的问题,提出一种基于图像区域相对清晰度的多焦距图像融合算法.该算法定义了图像区域的相对清晰度判定指标,并根据多焦距图像像素邻域的相对清晰度来逐个选取聚焦清晰的像素点从而构成融合图像.实验表明,所提算法能取得优于其它算法的融合效果;特别是,它能较好保留源图像包含的细节信息,从而显著减弱融合结果中的"振铃"现象.     

一种盲复原图像振铃效应的后处理与质量评价方法

由于图像盲复原过程中先验信息的不足，往往造成复原图像质量不尽如人意，振铃效应就是影响复原图像质量的重要因素之一。振铃效应的存在使得对复原图像的后续处理难于进行，并使得一些图像质量的评价方法失效。针对图像盲复原的特点，提出了一种振铃效应的后处理方法，并基于将振铃与清晰度分别评价的思想，提出了一种复原图像的无参考评价方案。实验证明该去振铃方法简单有效，该复原图像的评价方案也很好地反映了人类的视觉特性。     

预测PI控制系统的根轨迹分析

研究预测PI控制器的根轨迹.根据根轨迹的性质,当存在模型失配时,较小的期望闭环时间常数将导致控制器的输出产生振铃现象.可以通过增大期望闭环时间常数来消除振铃现象.此外,通过根轨迹法,推导出存在增益失配时,预测PI控制系统的稳定性判据.根据稳定性判据,当期望闭环时间常数增大时,增益稳定区间随之而增大;当模型时滞增大时,增益稳定区间随之而减小.数值仿真结果验证了上述结论.     

2维加窗全相位图像滤波模板的设计

为克服常用滤波模板的缺陷,消除传统图像滤波中存在的振铃现象和方块效应,提出了任意正交变换下的2维加窗全相位滤波算法.在严格证明任意正交变换下的2维全相位模板的计算通式基础上,进一步推导出傅里叶变换下的加窗全相位模板的简化公式.通过对亚奈图像的恢复实验证明：相比于反傅氏变换法生成的模板,用全相位DFT（discrete Fourier transform）模板恢复出的图像PSNR（峰值信噪比）值要高出7dB以上,且消除了振铃现象.通过实验还证明,用全相位DCT（discrete cosine transform）模板滤波可完全消除传统分块滤波中的方块效应.     

二维圆环结构中弹性波传播的谱单元分析

为研究弹性波在结构中的波场特征,推导建立一种任意四边形二维谱单元,将其应用于二维圆环结构中的波传播行为模拟.以矩形平板结构中弹性导波传播分析为例,通过与传统有限元分析结果对比,验证所建立谱单元的有效性.有裂纹和无裂纹二维圆环结构谱单元模拟结果表明:弹性波在圆环结构中传播会发生频散;圆环结构表面的裂纹对瑞利波的传播影响最大;根据其反射波包位置可以确定损伤位置.     

Real-time fault tolerant operation of the 802.5 token ring

Scheduling a hard real time application on a token ring requires that the delays to capture the token be known. Previous studies considered only a small subset of the token ring mechanisms in schedulability analyses. In this paper, we study the influence of three types of faults on the time to capture the token. These are token losses, failures of the active monitor and cable faults. We also show the influence of the stack mechanism on the delay to capture the token. The paper ends with an evaluation of these delays in various ring configurations in which the transmission speed, token hold time and ring latency are variables. We conclude that the token ring may be very difficult to schedule for hard real time applications because we do not know if other mechanisms or combinations of phenomena can introduce additional delays that make the operation of the ring unpredictable in the present state of knowledge.     

图像复原技术的研究

针对原有Lucy-Richardson算法极易引起噪声放大、边缘环现象明显等缺点,提出了改进的Lucy-Richardson图像盲复原算法。仿真结果表明,该算法在噪声抑制、稳定性、细节保存以及视觉效果方面都优于原有Lucy-Richardson算法,并且有广泛的应用领域。     

数字闭环光纤电流互感器死区形成机理分析

死区是闭环反馈控制系统中常见非线性现象之一,其产生原因是由于增量型非比例反馈通道干扰的存在.在干涉型数字闭环光纤电流互感器系统中,死区将引致系统零偏、零漂等非线性现象.通过系统模型的建立与分析发现,除正常相位补偿机制需要的比例反馈通道外,相位调制信号与光电探测器输出间的交叉电信号耦合、相位调制信号控制误差与相位调制器性能漂移,将在闭环光纤电流互感器中形成了另外一条非比例的干扰反馈通道;干扰通道与干扰信号的相关参数,不仅决定着死区的产生条件,也为抑制死区现象提供有效的解决途径;实验表明,死区现象的非比例反馈通道解释,不仅具有理论上的合理性,而且得到实验结果的支持.     

混合环上带惩罚费用的负载平衡问题

在过去的20多年里,环负载平衡问题得到了广泛的研究。带惩罚费用的环负载平衡问题是环负载平衡问题的推广形式,在无向环和有向环上有一些研究结果。提出了带惩罚费用的混合环负载平衡问题,对于给定的混合环C和点对集,每1个点对r_j都有1个流量d_j和1个惩罚费用p_j,当点对r_j被接收时,其流量可以沿环上的顺时针路和逆时针路进行运输,点对r_j也可以被拒绝,此时将产生惩罚费用p_j,目标是使得环C上连接边的最大负载和惩罚费用之和达到最小。在流量可分的情况下,利用线性规划取整技巧,给出了1个2-近似算法,进一步地,利用随机取整技巧,得到1个更好的近似算法,近似比为1.58。类似地,在流量不可分的情况下,给出了1个3-近似算法和1个(1.58+ε)-近似算法,其中ε>0是一个固定的常数。     

Simulation algorithm for piston ring dynamics

Piston ring dynamics play important roles on the lubricant characteristic of reciprocating engines which lead to the consequences of engine wear and vast amount of lubricating oil consumption. Due to the complexity of motion, a study of motions and effects of the piston ring is mostly conducted in a simulation program. This paper shows a theoretical work and a new simulation algorithm of the 3D piston ring motions. The simulation concept is to determine the positions of the piston ring, which are the solutions of the Newton and Euler equations. Well known models like mixed lubrication model, asperity contact model, and blow-by/blow-back flow model were used in this study. The new simulation algorithm consists of four processes: construction of calculation nodes, use of finite different method, determination of the non-linear equation system, use of parallel computational technique.Two sets of the experimental studies were conducted for simulation verification. First, the gas flows through the static rectangular piston ring pack. Second, the blow-by/blow-back gas flow through the piston ring pack of a single cylinder diesel engine. The good agreement between the experimental and simulation results indicates that the developed simulation program can illustrate the piston ring motions and blow-by/blow-back flow. Since there is no algebraic equation in the ring profile, the presented simulation technique is suitable for the complicated surface of the piston and piston rings.     

利用三次剩余构造的基于身份环签名方案

传统的基于身份环签名方案大多采用双线性配对实现,但配对方法的运算复杂度较高,会大幅降低签名方案的效率。为此,提出一种非配对的环签名方案。给出用于有效计算三次剩余3′次根的算法,在该算法的基础上生成签名密钥,并结合三次剩余理论构造基于身份的环签名方案。分析结果表明,在大整数分解困难问题的假设前提下,该方案在随机预言模型下被证明是选择消息和身份安全的。同时,该方案也满足签名者无条件匿名性。     

基于小世界现象的网页消重和排序

纯P2P网络具有小世界现象的特征。该文通过对P2P网页搜索引擎机制与原理的论述,结合小世界现象,推导出基于小世界现象的网页消重和排序。模拟实验的结果显示,利用小世界现象进行外消重和外排序能够很好地均衡查询源节点的处理负担、等待时间以及网络带宽的无谓消耗间的关系。     

Original Finger Image Extraction by Morphological Technique and Finger Image Comparisons for Persons' Identification

This research uses the object extracting technique to extract the index, middle and ring fingers from the hand images. The algorithm developed in this research can find the precise locations of the different fingers' fingertips and the finger-to-finger-valleys. After finding the positions of the fingertips and finger-valleys, the index, middle and ring fingers can be extracted from the hand images by using morphological technique. The extracted index, middle and ring fingers contain many useful geometry features. One can use these features to do the person's identification. The orientations of the index, middle and ring fingers are found in this research. Image rotating, image shifting, and image interpolating techniques are used to align different persons' index, middle and ring fingers. Image subtraction is used to exam the difference of two index, middle and ring finger images. In this research so far only use the index, middle and the ring fingers as the features to identify different persons. ^★This work was supported by National Science Council under grant NSC 93-2213-E-212-011.     

Phenomena Detection in Mobile Wireless Sensor Networks

Environmental phenomena, such as fires, poisonous gases, and oil spills, can be detected by wireless sensor networks (WSNs) that cover the geographical area of the phenomena. These sensors collaboratively monitor the area to detect the sensors’ readings that deviate from normal reading patterns after which a phenomena is declared. This research proposes a distributed algorithm to detect dynamic phenomena using mobile WSNs under the assumption that there is no centralized server to collect and aggregate the sensors data. Therefore, the sensors self-organize into disjoint groups by first electing a few sensors to be group heads (GHs) and then the rest of the sensors group themselves with the nearest GH. Each group of sensors detect phenomena locally. Then, the GHs communicate the detected local phenomena information among themselves to aggregate the information and detect the global phenomena. Moreover, the paper proposes two GH election algorithms, namely the Last Group Head election algorithm and the Distributed Group Head election algorithm. The experimental results show that the proposed election algorithms reduce the energy costs of the mobile WSN by 54–66 % as compared with the straightforward election algorithm. In addition, this paper proposes an optimization technique to further reduce the energy costs of reporting the global phenomena to about 33 % by reducing the size of the reported phenomena information. The proposed algorithms are validated through a comprehensive set of experiments conducted using the NS2 network simulator.