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Abstract ：
A denoising method of the improved neighboring coefficients and the undecimated multiwavelet transform is proposed, Hilbert-Huang time-frequency analysis is applied as the post-processing method. The proposed method is applied to the incipient fault diagnosis of planetary gearboxes. In the planetary gearbox, the fault response is quite weak; the vibration is obviously non-stationary and evidently nonlinear; low-frequency characteristics are easily immersed in heavy noise. Therefore, the existing fault diagnosis theory and technology for traditional fixed-shaft gearboxes fail to solve the difficulty in the planetary gearbox fault diagnosis. The undecimated multiwavelet transform has the shift-invariant property in time domain, which can effectively weaken the Gibbs phenomena in the neighborhood of the discontinuities. The improved neighboring coefficients can select variant sizes of neighboring window and flexible thresholds at different decomposition levels, which can correctly extract the incipient fault features in the non-stationary signals. Hilbert-Huang time-frequency analysis can intuitively represent the non-stationary and nonlinear features of the collected signals. Experiments indicate that the proposed method can correctly extract the weak fault features caused by the incipient pitting defects in the planetary gearbox. © 2013 Journal of Mechanical Engineering.
Keyword ：
Incipient fault diagnosis Multiwavelet Neighboring coefficients Planetary gearboxes Time frequency analysis
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| GB/T 7714 | Sun, Hailiang , Zi, Yanyang , Yuan, Jing et al. Undecimated multiwavelet and Hilbert-Huang time-frequency analysis and its application in the incipient fault diagnosis of planetary gearboxes [J]. | Jixie Gongcheng Xuebao/Journal of Mechanical Engineering , 2013 , 49 (3) : 56-62 . |
| MLA | Sun, Hailiang et al. "Undecimated multiwavelet and Hilbert-Huang time-frequency analysis and its application in the incipient fault diagnosis of planetary gearboxes" . | Jixie Gongcheng Xuebao/Journal of Mechanical Engineering 49 . 3 (2013) : 56-62 . |
| APA | Sun, Hailiang , Zi, Yanyang , Yuan, Jing , He, Zhengjia , Li, Kang , Chen, Xuejun . Undecimated multiwavelet and Hilbert-Huang time-frequency analysis and its application in the incipient fault diagnosis of planetary gearboxes . | Jixie Gongcheng Xuebao/Journal of Mechanical Engineering , 2013 , 49 (3) , 56-62 . |
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Abstract ：
工业锅炉采用鳍片管时,《蒸汽锅炉安全技术监察规程》以及各种设计计算资料,都只要求校核各部位温度不超过所用材料的许用温度即可,并不考虑温差应力造成的强度失效和低周疲劳破坏.文章通过建立鳍片管温差应力计算数学模型,提出一种工业锅炉鳍片管温差应力和低周疲劳强度校核计算方法和结构尺寸设计公式,此前未见报道.通过计算分析,得出了只要鳍片高度大于厚度,鳍片管的最高温度只在鳍端发生;温差应力满足强度要求时,不会发生低周疲劳破坏.
Keyword ：
低周疲劳 工业锅炉 鳍片管 温差应力
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| GB/T 7714 | 张少军 , 屠若男 , 杨沛胥 et al. 工业锅炉鳍片管温差应力计算及结构设计 [J]. | 工业锅炉 , 2006 , (6) : 1-6,13 . |
| MLA | 张少军 et al. "工业锅炉鳍片管温差应力计算及结构设计" . | 工业锅炉 6 (2006) : 1-6,13 . |
| APA | 张少军 , 屠若男 , 杨沛胥 , 雷振华 , 陈学俊 . 工业锅炉鳍片管温差应力计算及结构设计 . | 工业锅炉 , 2006 , (6) , 1-6,13 . |
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Abstract ：
从理想的单气泡运动物理模型和离散正交小波与统计相结合的信号处理技术研究了泡状流压力波动的机理与多尺度时频规律,得到以下结论:泡状流的压力波动主要来源于气泡的运动和诱导湍流及液相湍流,其中在低流速下前者产生的压力波动幅度大于后两者;存在一个临界频率,低于该频率压力信号均方根随频率的增加而增加,高于该频率压力信号均方根随频率的增加而减小;发生流型转变时压力信号的时频特征发生明显改变,最大均方根出现在更低的频率区.
Keyword ：
多尺度分析 泡状流 压力波动
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| GB/T 7714 | 白博峰 , 陈学俊 . 垂直上升管泡状流压力波动的多尺度分析 [J]. | 工程热物理学报 , 2004 , (3) : 427-430 . |
| MLA | 白博峰 et al. "垂直上升管泡状流压力波动的多尺度分析" . | 工程热物理学报 3 (2004) : 427-430 . |
| APA | 白博峰 , 陈学俊 . 垂直上升管泡状流压力波动的多尺度分析 . | 工程热物理学报 , 2004 , (3) , 427-430 . |
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Abstract ：
In order to better understand the heat transfer characteristics of supercritical fluids, with the CFD software FLUENT 6.0, a numerical study has been conducted for the developing laminar heat transfer of water in a smooth vertical tube in the absence of gravity in the range of Reynolds number, Re-in=100-2000, inlet fluid temperature T-in=600-700K and pressure P=23-30MPa. The results show that under supercritical pressure, when inlet Re number is small, because of the heat transfer at the wall, the fluid temperature maybe reaches the pseudo-critical temperature. When this happens, the temperature gradient varies violently both in radial and axial directions; in the radial direction, there is a local maximum of Pr number; and a local maximum for heat transfer coefficient appears.
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| GB/T 7714 | Xu, F , Guo, LJ , Bai, BF et al. Numerical study of laminar beat transfer in pipe under supercritical pressure [C] . 2004 : 28-33 . |
| MLA | Xu, F et al. "Numerical study of laminar beat transfer in pipe under supercritical pressure" . (2004) : 28-33 . |
| APA | Xu, F , Guo, LJ , Bai, BF , Mao, YF , Duan, JZ , Chen, XJ . Numerical study of laminar beat transfer in pipe under supercritical pressure . (2004) : 28-33 . |
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Abstract ：
通过对差压波动信号的详细分析,明确了液塞头和液塞尾到达和离开传感器测压点的时刻与差压信号特征点之间的物理关系,提出了采用差压波动信号分析技术获得液塞速度、液塞长度和液塞频率的计算公式.采用该方法,在室内长24 m、内径0.054 m试验架上以空气-水、空气-柴油和空气-68#机械油为介质进行了实际测试,经过和文献中数据以及经验公式对比,验证了该测试方法的正确性.
Keyword ：
差压 长度 段塞流 频率 速度
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| GB/T 7714 | 何利民 , 郭烈锦 , 陈学俊 . 水平管道段塞流特征参数试验研究 [J]. | 化学工程 , 2003 , (4) : 37-41 . |
| MLA | 何利民 et al. "水平管道段塞流特征参数试验研究" . | 化学工程 4 (2003) : 37-41 . |
| APA | 何利民 , 郭烈锦 , 陈学俊 . 水平管道段塞流特征参数试验研究 . | 化学工程 , 2003 , (4) , 37-41 . |
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Abstract ：
压力波动是两相流动的固有特性,研究波动规律对实现两相流动的智能监测有重要意义.本文采用统计学原理和确定性混沌学中的分形理论,对垂直上升空气水两相流的壁面静压力波动过程进行了研究,分析了表观液速对统计特征和分形特征的影响规律,首次发现环状流内高气速时压力波动的分维数大于1.5.
Keyword ：
波动 分形 两相流 压力
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| GB/T 7714 | 白博峰 , 郭烈锦 , 陈学俊 . 气液两相流压力波动特性 [J]. | 水动力学研究与进展A辑 , 2003 , (4) : 476-482 . |
| MLA | 白博峰 et al. "气液两相流压力波动特性" . | 水动力学研究与进展A辑 4 (2003) : 476-482 . |
| APA | 白博峰 , 郭烈锦 , 陈学俊 . 气液两相流压力波动特性 . | 水动力学研究与进展A辑 , 2003 , (4) , 476-482 . |
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Abstract ：
分析了压力波动信号互相关求液塞速度存在的不足,引入了差压波动分析法,明确了液塞到达和离开上、下游测压点的时刻与差压波动信号起峰点及落峰点位置的关系;分析了电导探针信号、差压信号和压力信号互相关所求得的相关速度的含义,指出差压互相关得到的是液塞运动速度,电导探针信号互相关得到的是液塞速度与液膜段界面波速度的平均值,压力信号互相关得到的相关速度具有随机性;明确了差压信号脉冲宽度为液塞从传感器上游测压点运动到下游测压点的时间间隔,脉冲宽度与液塞速度的乘积为液塞长度与差压传感器间距之和.最后,按照上述方法分类,把空气-水、柴油和机械油的试验数据的分析结果与文献中报道的液塞速度和长度数据进行了对比,结果吻合得很好.
Keyword ：
差压 段塞流 互相关 气液两相流 液塞长度 液塞速度
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| GB/T 7714 | 何利民 , 郭烈锦 , 陈学俊 . 测量水平管道液塞速度和长度的差压波动分析法 [J]. | 化工学报 , 2003 , (2) : 192-198 . |
| MLA | 何利民 et al. "测量水平管道液塞速度和长度的差压波动分析法" . | 化工学报 2 (2003) : 192-198 . |
| APA | 何利民 , 郭烈锦 , 陈学俊 . 测量水平管道液塞速度和长度的差压波动分析法 . | 化工学报 , 2003 , (2) , 192-198 . |
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Abstract ：
Thermochemical gasification of biomass has been identified as a possible system for producing renewable hydrogen. A continuous tubular supercritical water gasification system is under development that can be used for solution or slurry materials gasification without drying. A unique feature of this system is its ability to realize the overall high-pressure continuous reaction by operating the valves. By the use of this system, designed for temperatures up to 923.15 K and pressures up to 35 MPa, glucose, as a model compound of biomass, was gasified in supercritical water at a series of temperature and pressure during different resident times to form a product gas composed of H-2, CO, CH4, CO2, and a small amount Of C2H4 and C2H6. Glucose at low concentrations (ca. 0.1 M) can be completely gasified in 923.15 K, 25 MPa, and 3.6 min resident time and no char or tar was observed. Consequently, we adopted these conditions as baseline reaction conditions for the following glucose concentration, alkali addition and reactor tube diameter effect studies. The raw biomass feedstock of sawdust with some CMC was also gasified in this system, the gasification efficiency in excess of 95% was reached. (C) 2002 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.
Keyword ：
biomass hydrogen production supercritical water
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| GB/T 7714 | Hao, XH , Guo, LJ , Mao, X et al. Hydrogen production from glucose used as a model compound of biomass gasified in supercritical water [J]. | INTERNATIONAL JOURNAL OF HYDROGEN ENERGY , 2003 , 28 (1) : 55-64 . |
| MLA | Hao, XH et al. "Hydrogen production from glucose used as a model compound of biomass gasified in supercritical water" . | INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 28 . 1 (2003) : 55-64 . |
| APA | Hao, XH , Guo, LJ , Mao, X , Zhang, XM , Chen, XJ . Hydrogen production from glucose used as a model compound of biomass gasified in supercritical water . | INTERNATIONAL JOURNAL OF HYDROGEN ENERGY , 2003 , 28 (1) , 55-64 . |
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Abstract ：
两相流的压差波动过程包含了关于流动的大量信息,是实现流动监测与控制的重要研究内容.该文研究了U形管垂直上升段空气-水两相流压差波动过程的统计和分形特征,着重分析了压差波动过程的均值、均方根、分维数随折算气速和液速的变化规律.结果表明这些特征参数都与流型有密切的联系,但据此识别流型缺乏实用性.均方根在低液速下随气速的变化体现了流型的转变,高液速时则不明显.相关研究根据概率密度分布函数识别流型的方法不具有普适性.实验发现环状流区高气速时的压差波动分维数大于1.5,在其它流型内都小于1.5.同时,折算液速的大小强烈影响压差波动的混沌特性.
Keyword ：
波动 分维数 两相流 统计分析 压差
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| GB/T 7714 | 白博峰 , 郭烈锦 , 陈学俊 . 空气-水两相流压差波动研究 [J]. | 中国电机工程学报 , 2002 , (3) : 22-26 . |
| MLA | 白博峰 et al. "空气-水两相流压差波动研究" . | 中国电机工程学报 3 (2002) : 22-26 . |
| APA | 白博峰 , 郭烈锦 , 陈学俊 . 空气-水两相流压差波动研究 . | 中国电机工程学报 , 2002 , (3) , 22-26 . |
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Abstract ：
利用室外大型多相流试验环道进行了段塞流的清管通球特性试验.以空气、水为试验介质,在多种气液流量下测量了管道中不同位置处的压力、压差,并记录了清管通球过程中管道入口的流量变化.分析试验结果发现:清管球进入管道后会引起气液流量变化,并会使管道中流体的流动出现短暂停滞,管道中各点的压力会逐次达到一个远远超过稳态的高压力值;清管球的运动速度,球前、后的压差是气液混合速度和距管道入口距离的函数.
Keyword ：
段塞流 清管 试验
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| GB/T 7714 | 何利民 , 郭烈锦 , 陈学俊 . 通球清管过程中微起伏管内的段塞流特性试验研究 [J]. | 西安交通大学学报 , 2002 , (7) : 674-678 . |
| MLA | 何利民 et al. "通球清管过程中微起伏管内的段塞流特性试验研究" . | 西安交通大学学报 7 (2002) : 674-678 . |
| APA | 何利民 , 郭烈锦 , 陈学俊 . 通球清管过程中微起伏管内的段塞流特性试验研究 . | 西安交通大学学报 , 2002 , (7) , 674-678 . |
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