关于最大度确定的树的谱半径

讨论了点数和最大度均固定的一类树的谱半径, 分别给出了这类树的谱半径的上界和下界, 并分别 刻画了达到上下界的极图.     

应用时间序列分析的液压溢流阀故障诊断法

基于液压溢流阀体工况,提出一种振动频率特性的故障诊断方法.利用溢流阀体振动信号的相关性、自回归模型的参数和功率谱特性,获得故障的突变信息,从而确认溢流阀的工作状态,为液压系统故障的诊断提供判断依据.测试系统采用LabVIEW虚拟仪器构建,并通过计算机自动完成测试和分析.实验结果表明,正常状态和故障状态下的电压信号没有明显的趋势,是一种平稳时间序列;有故障时,相关函数衰减比正常状态慢,但都不够明显;正常状态和故障状态下的特征根分布明显不同,故障状态下的系统可能处于某种稳定状态;正常状态的自回归(AR)功率谱比任何一种溢流阀常见故障的功率谱都低.     

Zq上长为pkn的循环码的谱表示

使用离散傅立叶变换(DFT),得到Zq(q=ps)上长度为N=pkn(其中(n,p)=1,p为素数)的循环码的谱表示和结构,并利用循环码的谱表示计算出了码的汉明重量,这对Zq上长为pkn循环码的构造和译码有重要作用。     

方差分量的谱分解估计

就线性混合模型中含有两个方差分量的情形,对方差分量的方差分析估计和谱分解估计进行比较,得到它们相等的充要条件,由此推出谱分解估计的优良性.     

功率谱估计在超声波桩检中的应用研究

公路桥梁桩基施工中,利用超声波检测施工质量是有效的手段,但如果耦合面不好,测得的反射波将不能直观读出。采用现代功率谱估计技术,对测量信号处理后的效果比较理想。     

频率域电磁法数值模拟进展

频率域电磁法在矿产普查、地球深部结构探查、地质调查、环境和工程勘查等领域都有着广泛的应用.频率域电磁法的数值模拟对提高电磁法的数据解释技术、电磁勘探设计水平,以及研究复杂地质条件下的电磁响应特征具有重要意义.近年来计算技术的进步、数据采集系统的提高和高性能计算机的迅速发展,大大促进了频率域电磁法数值模拟技术的发展,尤其...     

图的Laplacian谱半径的一个新上界

设G为n阶简单连通图.若Q(G)为图G的对角矩阵与邻接矩阵的和,称Q(G)为G的拟-Laplacian矩阵.讨论了Q(G)的性质并利用G的顶点数、边数、最大度和最小度给出了图G的Laplacian矩阵谱半径的一个新上界.     

Super-resolution processing of passive millimeter-wave images based on conjugate-gradient algorithm

This paper designs a 3 mm radiometer and validate with experiments based on the principle of passive millimeter wave (PMMW) imaging. The poor spatial resolution, which is limited by antenna size, should be improved by post data processing. A conjugate-gradient (CG) algorithm is adopted to circumvent this drawback. Simulation and real data collected in laboratory environment are given, and the results show that the CG algorithm improves the spatial resolution and convergent rate. Further, it can reduce the ringing effects which are caused by regularizing the image restoration. Thus, the CG algorithm is easily implemented for PMMW imaging.     

Novel method of improving the alignment accuracy of SINS on revolving mounting base

In the process of initial alignment for a strapdown inertial navigation system (SINS) on a stationary base, the east gyro drift rate is an important factor affecting the alignment accuracy of the azimuth misalignment angle. When the Kalman filtering algorithm is adopted in initial alignment, it yields a constant error in the estimation of the azimuth misalignment angle because the east gyro drift rate cannot be estimated. To improve the alignment accuracy, a novel alignment method on revolving mounting base is proposed. The Kalman filtering algorithm of extending the measured values is studied. The theory of spectral condition number is utilized to analyze the degrees of observability of states. Simulation results show that the estimation accuracy of the azimuth misalignment angle is greatly improved through a revolving mounting base, and the proposed method is efficient in initial alignment for a medium accurate SINS.     

基于实测风谱的润扬悬索桥桥址区三维脉动风场模拟

针对大跨度悬索桥的结构形式和振动模态特点,结合自然风的相关特性,给出了一种简化的三维脉动风场模拟方法,将实际面状的三维脉动风场简化为多个线状的一维脉动风场.基于谐波合成法,并运用FFT技术,进行了润扬悬索桥桥址区三维脉动风场的模拟.为了真实反映桥址区强风特性,模拟目标功率谱采用由该桥结构健康监测系统实测台风数据运用非线性最小二乘法拟合而得的拟合谱.结果表明,该风场模拟方法计算效率较高,主梁与主塔结构脉动风场的模拟值均与目标值吻合较好,验证了该风谱模拟方法的有效性和可靠性.