Airplane extraction and identification by improved PCNN with wavelet transform and modified Zernike moments

At an airport, the information of the number and positions of airplanes is very important for the applications of air navigation. Especially, the information from airplane extraction and identification is significant in both civil and military remote sensing. In this paper, according to the characteristics of airplanes and airport in satellite remote sensing images, a new airplane image segmentation algorithm is proposed based on improved pulse-coupled neural network (PCNN) with wavelet transform, and airplane identification algorithm is carried out by using modified Zernike moments. Firstly, for an original image, a PCNN model is improved and then used to do image segmentation by combining the wavelet transform. Then, in order to reduce the number of irrespective targets in the image and increase the processing speed, the airplanes in the original image are roughly detected on the characteristics of the segmented object contour geometries. Finally, the Zernike moments are modified and then applied to identify the roughly detected airplanes accurately. By comparing to the five traditional image segmentation algorithms for the same airplane images, the testing results show that the improved PCNN image segmentation algorithm can segment and detect airplane regions at an airport accurately at a high recognising rate and with high recognising stability, and it is not affected by the image shadows and rotations.     

Numerical analysis of centered-inclined coupling slots in rectangular waveguides

Numerical analysis is presented for the characteristic parameters of centered-inclined coupling slot in rectangular waveguides,taking into account the transverse distribution of the electric field across the slot aperture.Integral equations are formulated based on dyadic Green＇s function theories and solved using the method of moments.Trigonometric basis functions are adopted.It is found that the method will converge with up to ten basis functions.The characteristic parameters can be easily obtained for different slot sizes.Resonant length and resonant resistance of the coupling slots are calculated.It is shown that the calculated results have very high accuracy,compared with simulated results obtained from commercial software.Therefore,it can be effectively applied in the synthesis of antenna arrays.Effects of the transverse distribution on calculating resonant parameters of the coupling slot are also analyzed.The results show that if the transverse distribution of the electric field is neglected,the calculated error tends to become larger when the slot gets wider or thinner.     

车辆动力总成悬置系统参数识别

精确识别车辆动力总成不平衡力以及惯性参数,是对车辆发动机振动进行主动隔离的基础.根据发动机不平衡力只与发动机内部结构以及转速相关的特性,提出一种利用磁流变减振器阻尼参数的可控性,通过测试不同阻尼环境下的各悬置加速度和支座反力,进而识别发动机惯性参数以及不平衡力的新方法.该方法在应用于车辆动力总成悬置系统参数识别时,对比...     

矩法评定活塞裙部横截面线轮廓误差

本文通过组合应用矩法与最小二乘法,提出了求解被测活塞裙部横截面理想线轮廓的方法,并对评定活塞裙部横截面线轮廓误差进行了讨论。     

高精度干涉仪镜头支撑结构的光机集成分析

根据高精度干涉仪镜头的工作状况,给出了乎放时镜头的装卡方式.用Ansys Workbench有限元分析软件对镜头由重力、支撑结构所导致的面形变化进行仿真分析,在对光机结构进行有限元分析的基础上,反复优化镜头机械结构设计,从而使支撑结构引起的系统误差降到最低,以zcmike多项式为接口工具拟合镜面变形,评估了该支撑结构对...     

能动主镜的风载变形研究

风载引起的主镜变形是大口径望远镜必须考虑的问题.针对类似于Subaru望远镜的薄镜面能动光学系统,采用固定点力反馈控制方法对风载进行校正,本文引入了压强模式的概念,提取出风载产生的镜面变形的大部分信息,并据此对固定点力反馈控制方法进行了研究,得到如下结论:风载产生的镜面变形主要是平移、倾斜、像散和离焦等低阶像差;相同系...     

Zernike多项式波面拟合精度研究

光学表面检测的绝大多数情况中,被测光学表面或光学系统的出射波面总是趋于光滑且连续的,这样的波面函数一定可以表示成一个完备的基底函数的线性组合。因此常用Zernike多项式作为基底函数对测量得到的离散数据进行拟合,把实际波面或面形表示为Zernike多项式各项的线性组合。文中研究了Zernike多项式阶数对拟合精度的影响,以及采样点数对拟合精度的影响。得出Zernike多项式拟合波面并非阶数越高越好,阶数过高会使拟合结果出现病态。因此拟合波面要选择合适阶数的Zernike多项式。当多项式阶数选定时,采样点数多有利于提高拟合精度,但采样点的多少并不是提高拟合精度的先决条件。     

基于复用计算全息元件的多阶模式偏置波前传感器

提出利用复用计算全息元件实现多阶模式同步的偏置模式波前传感器。对基于复用计算全息元件的多阶模式偏置波前传感器进行了理论分析。为了实现复用计算全息元件,分别编码设计了包含4阶,10阶和20阶Zernike像差模式的复用计算全息图,讨论了复用计算全息图设计中几个关键问题。数值模拟研究了复用计算全息图对单阶和多阶像差模式的探测性能。结果表明,在一定探测范围内,传感器能够响应与全息图内预先记录像差模式相同的待测像差模式,且每一个模式的灵敏度都不同。全息图内记录模式数较少时,单阶模式探测的灵敏度较大;记录模式数越多,模式之间擦除效应越严重,单阶和多阶模式灵敏度都受到一定影响。     

Reliability-based evaluation of design and performance of steel self-centering moment frames

Recently developed steel self-centering moment-resisting frames (SC-MRFs) have been analytically and experimentally validated as having the potential to eliminate structural damage under a design basis earthquake and restore their original vertical position following a major earthquake. Using Monte Carlo simulation, we subjected three nonlinear models of prototype SC-MRFs to thousands of synthetic ground motions, and recorded peak demand responses such as story drift and beam-column relative rotation. We used this data to examine the sensitivity of SC-MRF behavior to structural properties and geometry, seeking to generate recommendations to improve the existing design procedure. A reliability-based methodology was used to assess the likelihood of reaching the limit state of post-tensioned strand yielding. This study proposes modifications to the existing design procedure and illustrates a reliability-based methodology for developing improved seismic design recommendations.