基于多重分形谱参数的刀具磨损状态特征提取

鉴于多重分形理论在精细刻画系统非线性现象和过程方面具有独特优势,提出了基于多重分形理论的刀具磨损状态特征提取方法.首先估计去噪后的刀具磨损声发射信号多重分形谱,验证其标度不变性和自相似性;然后在此基础上研究了刀具磨损多重分形谱参数α0、Δα和f(αmin)随磨损量变化情况,并通过散点图描述三种特征参数表征刀具磨损阶段的有效性;最后结合切削条件讨论特征f(αmin)与切削速度的关联性.研究结果表明:多重分形谱参数与磨损阶段之间具有较强的关联性,进而提出了基于多重分形谱参数进行刀具磨损状态特征提取的新方法.     

半连续Ag纳米薄膜显微图像的多重分形谱研究

多重分形谱是分形理论中最基本的一个数学概念,也是分形理论应用中最重要的一个方面。在解决实际问题中多重分形谱主要用来描述物理量不均匀的随机概率分布,通过对半连续Ag纳米薄膜显微图像结构形貌的分析和处理,以及通过薄膜显微图像多灰度概率测度进行多重分形谱分析,用多重分形谱描述随薄膜厚度变化的Ag颗粒的空间分布的不均匀性。实验结果表明,多重分形谱是一种有意义的表征参数,能够从多分形角度对薄膜中Ag厚度的空间分布均匀性和尺寸分布进行定量化的分析和解释。     

基于多重分形谱的行人检测

为了克服传统行人检测方法计算复杂度高、耗时长的问题,提出一种基于多重分形谱的行人检测方法.采用多重分形理论分析行人图像并计算对应多重分形谱,提取多重分形谱特征,选取支持向量机(support vector machine,SVM)二值分类器实现行人滑窗检测.将本文算法应用于INRIA数据库中,并与基于HOG、HOGNMF特征的算法进行比较.实验结果表明:本文算法检测率为86.59%,虚警率为7.75%,有较高的检测率和较低的虚警率.     

分形多重相关方差X线颅颌影像边缘检测

针对X线颅颌影像片边缘检测十分困难的问题,提出一种基于多重相关方差的计算多重分形谱的算法.构建一个X线图像的五邻域多重相关空间,定义图像的多重分形谱的概率测度,对数字X线头影侧位片进行多重分形性质的分析.通过图像的多重分形谱与权重因子相关性的分析,进一步判定线形区间及适当的权重因子,得到X线头影片图像的多重分形的线性区间,验证X线头影片图像的多重分形的几何性质,实现对X线头影侧位片的整体轮廓的边缘提取.该算法具有保持和加强图像的局部特性,突出图像的细微处的特点,克服了多重分形谱对噪声敏感的缺点,能有效抑制图像中的噪声.     

冲击破坏过程微震波形多重分形及其时变响应特征

采用多重分形理论研究了冲击破坏过程不同阶段微震波形的多重分形及其时变响应特征,提出了将最大多重分维数D_(maxq),多重分形谱参数Δα和Δf(α)作为煤矿微震波形多重分形特征量.研究表明:冲击诱发微震波形的多重分形特征明显强于冲击前后的常规微震波形;D_(maxq)和Δα能够反映微震波形的非均匀性和波动程度,D_(maxq)和Δα越大,微震波形的非均匀性和波动性越强,多重分形特征越明显;Δf(α)是反映微震波形信号中大小峰值所占比例的度量,Δf(α)越小表示微震波形中大峰值所占比例越大,即微震波能量越大.冲击破坏前微震波形多重分形特征量D_(maxq),Δα和Δf(α)的时变响应具有明显的规律性,当D_(maxq)或Δα超过其下临界值并持续增加接近其上临界值时,或当Δf(α)小于其上临界值并持续降低接近其下临界值时,特别是当上述3种时变响应特征同时发生时,极易发生大的冲击破坏事件;微震波形多重分形特征量D_(maxq),Δα和Δf(α)的时变响应特征能够作为有效的前兆信息对冲击地压进行监测预警.     

滑坡活动空间分布的多重分形特征及其预测意义

根据分形理论,研究了西藏樟木地区滑坡活动空间分布的多重分形特征。结果表明,不同时段滑坡活动空间分布的多重分形指数谱能够很好地描述滑坡活动的不确定性和随机性特征。滑坡活动的多重分形提供的信息对认识滑坡应力场的不均匀程度和滑系统从稳态向非稳态的转化过程有重要的意义。     

连云港市大气污染物浓度变化的多重分形分析

以2002-2005年连云港市不同功能区大气SO2,NO2和PM10的日监测数据为基础,运用多重分形分析方法对各污染物的时间演变特征进行了研究.结果表明,3种大气污染物的序列数据在不同城市功能区均表现出多重分形特征,且以SO2的多重分形性最强,PM10的多重分形性最弱.分析各污染物的多重分形谱发现,SO2变化的奇异性在工业区和商业及居民生活区有逐年发展的趋势;NO2变化的奇异性在各功能区基本相当,但工业区NO2发生剧烈变化的几率相对较小;PM10在各功能区均表现出下降的趋势,但港口服务区PM10波动变化的奇异性要强于其它功能区.研究结果对于连云港大气环境系统动力学过程的理解和环保决策的制定具有参考价值.     

多重分形谱在集成电路动态电流故障诊断中的应用

系统阐述了多重分形的概念和多重分形谱的小波模极大值计算方法,提出了一种新的基于动态电流IDDT多重分形谱分析的集成电路故障诊断方法.该方法利用多重分形分析方法有效地提取信号的几何结构特征信息,利用动态电流的多重分形谱分析来进行集成电路的故障诊断.使用Hspice电路仿真验证了该方法的可行性和有效性.     

MF-DFA方法与成矿元素分布特征——以大尹格庄金矿为例

在采用Jarque-Bera统计量和Augmented Dickey-Fuller检验法,分别进行正态和稳定性检验的基础上,运用多重分形消除趋势波动分析方法(MF-DFA)和多重分形谱分析方法,研究了山东大尹格庄金矿-290m中段多钻孔Au元素的长程相关性和多重分形特征,并分析多重分形谱曲线的宽度差异和对称性.结果显示:消除二阶多项式非线性趋势后,趋势波动函数Fq(s)与尺度s具有较好幂律关系,广义Hurst指数h(q)是随q的非线性函数,h(2)值均小于1但大于0.5,即具有长程相关性,表明在特定的地质背景下该矿体的发育相对稳定,其与大尹格庄金矿的地质事实相吻合.多重分形谱曲线为非对称状且各有不同,表明该地区的Au元素品位序列具有明显多重分形特征,其多重分形谱函数的形态差异为矿化强度的识别提供依据,从而可为进一步判定矿床富集程度、圈定有利成矿靶区提供指导.     

交通时间序列分形测量方法研究

为了研究交通数据的分形特征,引入一种新的分形测量方法,分析了2006年8月1日0时11分到8月10日14时11分的北京玉泉营高速路的交通流量时间序列.计算结果发现交通时间序列在不同的标度区间具有不同的分形维数.进一步借助多重分形谱的宽度和极大值对交通时间序列进行研究,结果发现,多重分形谱宽度为0.603 1、极大值为0.966 4.因此,交通流量具有明显多重分形特性,这将为多重分形在交通时间序列分析的非线性研究提供重要的理论基础.     

A power-quality monitoring and assessment system for high-speed railways based on train-network-data center integration

In recent years, with the rapid development of high-speed railways (HSRs), power interruptions or disturbances in traction power supply systems have become increasingly dangerous. However, it is often impossible to detect these faults immediately through single-point monitoring or collecting data after accidents. To coordinate the power quality data of both traction power supply systems (TPSSs) and high-speed trains (HSTs), a monitoring and assessing system is proposed to access the power quality issues on HSRs. By integrating train monitoring, traction substation monitoring and data center, this monitoring system not only realizes the real-time monitoring of operational behaviors for both TPSSs and HSTs, but also conducts a comprehensive assessment of operational quality for train-network systems. Based on a large number of monitoring data, the field measurements show that this real-time monitoring system is effective for monitoring and evaluating a traction-network system.

     

高铁运行经过地下站台的气动风场研究

为了研究高速列车运行经过地下车站时的气动效应,为地下高铁站设计提供参考,以某地下高铁站为背景,采用数值模拟的计算方法,建立了站前隧道-地下车站-列车的数值模型。运用滑移网格的计算方法,对列车运行经过地下车站的情况进行模拟。列车运行时速选定200、250、300和350 km/h,站台上布置25个测点进行监测,研究列车运行时速和站台位置两种因素对站台上气动风场的影响。结果表示:(1)站台上的气动效应随列车运行时速越高变化越大;(2)列车经过地下站台后还会产生不可忽视的尾波;(3)站台上气动风场波动值最高的位置是站台入口处。     

客车滚动轴承故障树分析

本文根据南昌车辆段1990年1月至1991年3月客车滚动轴承的检修统计,采用故障树分析法分析了客车滚动轴承的常见故障及原因。指出,引起客车滚动轴承故障的主要原因,是使用的2724(2726)型轴承承载能力偏低。建议在选用承载能力大的轴承型号的同时,采用状态监测及故障诊断技术对滚动轴承实行状态维修。     

An improved algorithm for fluid-structure interaction of high-speed trains under crosswind

Based on the train-track coupling dynamics and high-speed train aerodynamics, this paper deals with an improved algorithm for fluid-structure interaction of high-speed trains. In the algorithm, the data communication between fluid solver and structure solver is avoided by inserting the program of train-track coupling dynamics into fluid dynamics program, and the relaxation factor concerning the load boundary of the fluid-structure interface is introduced to improve the fluctuation and convergence of aerodynamic forces. With this method, the fluid-structure dynamics of a high-speed train are simulated under the condition that the velocity of crosswind is 13.8 m/s and the train speed is 350 km/h. When the relaxation factor equals 0.5, the fluctuation of aerodynamic forces is lower and its convergence is faster than in other cases. The side force and lateral displacement of the head train are compared between off-line simulation and co-simulation. Simulation results show that the fluid-structure interaction has a significant influence on the aerodynamics and attitude of the head train under crosswind conditions. In addition, the security indexes of the head train worsen after the fluid-structure interaction calculation. Therefore, the fluid-structure interaction calculation is necessary for high-speed trains.

     

Study on the critical diameter of the subway tunnel based on the pressure variation

When the subway train operates at a speed higher than 100 km/h,the corresponding aerodynamic issue becomes severe.To meet the future requirement for the speedup of subway trains,a research on the critical diameters of the subway tunnel for trains operating at 120 and 140 km/h has been performed based on passengers’aural discomfort caused by rail tunnel pressure variation.A three-dimensional computational fluid dynamic approach has been adopted for analysis.Meanwhile,trains with different airtight indices are considered and the pressure variations inside and outside the trains are both under investigation.Based on the corresponding criteria for different airtight indices,critical tunnel diameters for trains running at different speeds have been determined.This study would aid in the tunnel section design for future high-speed subway trains.     

高速铁路地下三岔口隧道压力变化数值模拟

为了研究高速铁路地下三岔口隧道内的空气动力学压力场,给出列车穿越地下车站时压力变化的三维黏性流场数值模拟过程.研究结果表明:列车从双线隧道过渡到单线隧道时,双线隧道内同一个测点的最大压力要大于列车从单线隧道过渡到双线隧道时产生的压力;而列车从双线隧道过渡到单线隧道时单线隧道内同一个测点的最大压力要小于列车从单线隧道过渡到双线隧道时产生的压力.其次,在过渡段内,隧道横断面越大,最大压力值越小,且与列车的运行方向无关.当列车会车于过渡段中部时,隧道内压力变化的最大值明显比单线隧道穿越过渡段时的要大很多,但不会达到2倍.     

基于嵌入式技术的机房监控系统设计

针对目前机房环境监控功能单一、缺乏集中管理等缺点,设计了基于嵌入式技术的机房监控系统.该系统由数据采集模块、监控单元和监控中心三部分组成.数据采集模块采集机房内各参数,监控单元实时监控各数据采集模块的运行状态并实时进行处理,监控中心显示各种参数和设备的运行状态.实践表明,该系统运行状态良好,具有推广应用价值.     

Numerical investigation of piled raft foundation in mitigating embankment vibrations induced by high-speed trains

A three-dimensional dynamic finite element model of track-ballast-embankment and piled raft foundation system is established. Dynamic response of a railway embankment to a high-speed train is simulated for two cases: soft ground improved by piled raft foundation, and untreated soft ground. The obtained results are compared both in time domain and frequency domain to evaluate the effectiveness of the ground improvement in mitigating the embankment vibrations induced by high-speed trains. The results show that ground improving methods can significantly reduce the embankment vibrations at all considered train speeds(36-432 km/h). The ground response to a moving load is dictated largely by the relationship between load speed and characteristic value of wave velocities of the ground medium. At low speeds, the ground response from a moving load is essentially quasi-static. That is, the displacements fields are essential the static fields under the load simply moving with it. For the soft ground, the displacement on the ballast surface is large at all observed train speeds. For the model case where the ground is improved by piled raft foundation, the peak displacement is reduced at all considered train speeds compared with the case without ground improvement. Based on the effect of energy-dissipating of ballast-embankment-ground system with damping, the train-induced vibration waves moving in ballast and embankment are trapped and dissipated, and thus the vibration amplitudes of dynamic displacement outside the embankment are significantly reduced. But for the vibration amplitude of dynamic velocity, the vibration waves in embankment are absorbed or reflected back, and the velocity amplitudes at the ballast and embankment surface are enhanced. For the change of the vibration character of embankment and ballast, the bearing capacity and dynamic character are improved. Therefore, both of the static and dynamic displacements are reduced by ground improvement; the dynamic velocity of ballast and embankment increases with the increase of train speed and its vibration noise is another issue of concern that should be carefully evaluated because it is associated with the running safety and comfort of high-speed trains.     

铁道信号微机监测系统中的转辙机状态监测回路分析

针对广深准高速铁路信号设备的实时监测,开发研制了采用PLC为采集机的GSWJ 98型微机监测系统;该系统的转辙机动作电流监测回路,通过转辙机动作电流监测铁路线上的重要设备道岔的运行状态,为设备的维护和检修提供依据,保证准高速路列车行驶安全.从硬件、软件两个方面分析了转辙机监测回路的原理及实现.