船舶机械振动源激励力的间接估计工程方法

船舶机械设备输出到船体上的激励力对船舶结构振动预报有着重要意义,文章讨论了两种间接估算激励力的方法,目的是希望在工程现场应用这些工程方法取代激励力的直接测量.对刚性安装的机器推荐采用最小二乘方法,该方法是基于支撑结构的加速度导纳特性进行估算.对弹性安装的机器而言,推荐采用基于隔振器阻抗特性的激励力间接估算方法.力的估算是逆问题,文中采用奇异值分解技术来处理会遇到的病态问题,从而尽量降低估算误差.文中还对估算的准确度、估算质量评价等进行了讨论.条件数的倒数在最小二乘法响应点的选取时可作为优选的先验判据,归一化残差可作为估算质量的后验判据.实验证明了间接估算方法是确定船舶机械激励力的恰当选择,实验结果的最小二乘法相对误差为3分贝.测试中的信噪比被认为在力估算过程中有重要影响,低信噪比很可能是实际测试时的首要误差来源.该文也可用于指导船舶振动源特性描述的研究.     

环境激励下钢筋混凝土拱桥模态参数识别

为正确选择模态参数识别方法,对某钢筋混凝土拱桥进行了环境振动试验,采用频域、时域和时频分析方法——峰值拾取法(PP)、随机子空间识别(SSI)以及基于经验模态分解(EMD)和随机减量技术(RDT)的方法——识别其模态参数;比较了3种模态参数识别方法的特点和识别结果,并与有限元法计算结果进行了比较.研究结果表明:峰值拾取法的识别速度快,识别的频率较可靠,但识别过程需要较多人工干预;随机子空间识别的理论体系完备,适合程序实现,识别过程能较好地抵消测试过程中噪声等的影响;由于模态混叠的影响,EMD-RDT识别结果具有一定随机性.     

Formation of nanometer coherent structures during spinodal decomposition and ordering coexistence phase transformation in Fe-24Al alloys

The nanometer coherent structure evolution of spinodal decomposition and ordering coexistence phase transformation in Fe-24Al alloys is investigated by the microscopic phase field kinetic model. The results show that the concentration and long-range order parameters all continuously change towards to their equilibrium values during phase transformation. With the increase of elastic interaction energy, the anisotropy along [01] or [10] elastic soft direction is more obvious and the time reaching equilibrium state is also shortened. According to the results, the formation of nanometer coherent structures during phase transformation is composed of the initial decreasing stage of order degree stage, the incubation stage, the continuous increasing stage of concentration order parameter and long-range order parameter, and the later stable stage. The spinodal decomposition and ordering is interaction; the initial ordering stage is a necessary condition of the coexistence phase transformation. The nanometer coherent structures are not found to grow during the whole phase transformation. The simulation results are in accordance with the results in experiment obtained by the aging treatment in Fe-24Al alloys.     

基于小波变换的频谱检测算法分析

文章分析了认知无线电频谱检测中匹配滤波检测、能量检测、周期平稳过程特征检测的性能,指出了噪声对各自检测性能的影响,给出了一种基于小波变换的信号频谱检测算法,着重对含噪2FSK、2PSK信号进行分离仿真。仿真结果表明,该算法可以有效地进行信号的成分分离,降低了噪声的频谱检测的影响。     

隧道中地铁车辆内部噪声分析

采用Artemis测试分析系统对隧道内运行的大连厂地铁车辆进行噪声测试,在地铁车辆内选择了六个测试点,通过对测试数据的分析、讨论.并对测试数据进行了分析,结果表明：地铁车辆运行时,车辆内噪声的最主要的噪声源是轮轨噪声.噪声级随着地铁车辆的速度的增加而增加.主频带一般都在315～5 000 Hz之间.低频率的声压级很小.研究地铁车辆内的噪声特性只需研究中高频声压级.     

基于QR分解的低复杂度RLS算法研究

为避免RLS算法在迭代过程中的数值发散现象,研究了复数域下基于QR分解的RLS估计算法,推导了基于Givens旋转的免开方、免除法的逆QR-RLS算法,通过变换可直接得到滤波系数更新所需增益向量,避免了QR-RLS算法的回代运算,同时消除了逆QR-RLS算法在每次迭代时的N次开方、2N次除法运算,有效降低了运算量。     

小波分析在GPS动态监测数据粗差探测中的应用

文章分析了GPS监测数据序列中粗差的不确定性,提出了采用小波分析检测成片粗差,并通过实例进行应用分析,在此基础上进而对原变形数据序列中包含大量粗差的情况进行探测。实例分析表明,合理选择小波函数进行分析可以准确探测出粗差所在位置．解决了传统方法每次只能探测单个粗差的不足。     

Synchronized Production and Transportation Planning Using Subcontracted Vehicles in a Production-Distribution Network

Abstract

Effective management of interfaces between procurement, supply, production and distribution for higher efficiency in the supply chain is an important issue in global manufacturing, where the synchronization of production and transportation planning represents important savings in operational costs. This paper focuses on the synchronization of production planning and transportation planning in a production distribution network, where transportation is subcontracted to a professional transportation enterprise (PTE) for vehicle-hiring. Dynamic and flexible numbers of vehicles are used to cater for fast changing market demands. Thus, the number of vehicles to be hired is viewed from the planning point of view as an operational decision considered simultaneously with production and transportation planning. A mathematical model – SPTP/MTDS – for synchronized production and transportation planning under multiple times and direct shipping strategy (MTDS) is discussed, and a Lagrange relaxation decomposition-based two layer decision procedure (LRD-TLDP) is developed. By introducing artificial decision variables and Lagrange multipliers, SPTP/MTDS is decomposed into a production decision sub-problem (SPTP-PD), and a distribution decision sub-problem (SPTP-DD). A priority-based assignment heuristic and a partial chain-based genetic algorithm are developed to solve SPTP-PD and SPTP-DD, respectively. An illustration of the application of the model in an electronic appliance manufacturing enterprise in China is presented.     

基于EMD和Gabor变换的发动机曲轴轴承故障特征提取

针对发动机振动信号的非平稳特点,提出了一种基于经验模态分解(EMD)和Gabor变换相结合的曲轴轴承故障特征提取新方法。通过EMD方法将发动机非稳态加速振动信号分解成多个本征模态函数(IMF),对与原信号相关性强的前4阶IMF分量进行Gabor变换,从各阶分量Gabor时频分布图的频带能量累加曲线中提取能够反映曲轴轴承磨损故障的频带能量作为故障特征参数。试验结果表明,该方法提取的故障特征参数能敏感地反映曲轴轴承的磨损状态,可作为诊断曲轴轴承故障的重要特征量。     

高速动车组低频周期性晃动问题分析与诊断

高速动车组同一车厢的两个转向架同相蛇行运动频率与车体固有上心滚摆频率接近时,车体因共振而出现低频周期性晃动,不仅影响乘坐舒适性,还会造成脱轨.本文根据低频周期性晃车成因,提出一种以车体横向加速度为研究对象的诊断方法.首先设置车体横向加速度阈值,对超阈值处延拓获得可能存在问题区段,然后利用集合经验模态分解法对这些区段车体...