基于α稳定分布的往复压缩机故障诊断方法

针对往复压缩机信号具有典型的非高斯脉冲特性,提出了一种基于α稳定分布模型的往复压缩机故障诊断方法.通过该方法估计了往复压缩机在气阀正常、阀片有缺口、阀片断裂和弹簧损坏4种状态下的信号分布参数,提取了估计参数下各状态的分数低阶统计量特征.结果表明:α稳定分布可以有效表征往复压缩机气阀信号状态,为其故障诊断提供了一种有效方...     

往复压缩机气阀振动信号的二阶循环谱特征提取

往复压缩机气阀振动信号具有典型的循环平稳性,循环平稳理论正是处理这类信号的有效工具,在研究二阶循环自相关及其傅里叶谱理论的基础上,对其主要特性进行了信号仿真研究,并将其应用到往复压缩机故障特征提取中,对2D12往复压缩机气阀在正常阀片和有缺口故障阀片两种状态下的实验数据进行了分析,结果表明二阶循环谱能够准确、有效地提取出往复压缩机气阀故障特征。     

基于图的拉普拉斯矩阵的塑料编织机轴承故障诊断研究

针对时域故障信号难以诊断的问题,提出基于图的拉普拉斯矩阵变换的注塑编织机轴承故障诊断方法。通过拉普拉斯矩阵变换将时域信号转化为图域,将时域的快速傅立叶变换思想引入图信号处理中,将转化所得图信号进行图像的傅立叶变换(GFT)得到故障振动信号的阶次图,根据所得阶次计算故障振动信号的故障频率,由此进行轴承的故障诊断。经仿真及实例分析结果表明:相比将时域信号直接进行快速傅里叶变换的故障诊断方法,本实验方法故障识别能力更强。     

往复压缩机故障诊断技术研究

按照机械故障诊断的技术路线,结合往复压缩机故障特点,分别就诊断信号选择、故障档的建立、状态识别技术的应用等过程中一些具体问题展开了较深入的研究,提出采用阀腔脉动压力作为诊断信号,通过计算机仿真建立故障档,将模糊诊断与人工神经网络结合等新观点,这些观点将有利于推进往复压缩机诊断技术的发展。     

基于灰度-梯度共生矩阵的往复压缩机气阀故障诊断方法研究

提出基于灰度-梯度共生矩阵的气阀故障图像特征提取方法,以不同故障气阀阀片的平滑伪威格纳-维尔分布图为研究对象,通过提取图像中的纹理特征信息计算其纹理特征参数,由结果可知,不同的故障图像对应不同的特征参量,从而实现了往复压缩机气阀故障的定量诊断。     

基于近似熵的往复压缩机气阀故障复杂性测度分析

针对往复压缩机气阀故障诊断及特征样本提取存在困难,结合近似熵在度量时间序列复杂性方面具有的优势及缺陷,提出适于近似熵分析的分阶段数据划分方法,将其用于分析往复压缩机气阀振动信号与气缸压力信号。结果表明,分阶段的气缸压力信号的近似熵比整体样本数据及气阀振动信号更具一致性,并且具有明显的分类效果,能够有效识别气阀故障状态。     

浅谈往复压缩机环形气阀的故障机理及诊断

在化工生产中,往复压缩机是常用的生产机械,其故障发生率也比较高,根据经验,最易发生故障的零部件有气阀、活塞环、填料函以及一些连接件的摩擦副等。往复压缩机有60%以上的故障发生在气阀上,能够及时发现气阀故障对往复压缩机故障诊断是相当重要的。     

基于经验模态分解的注射机轴承故障诊断

针对注射机轴承信号进行故障诊断易受到工作环境中其他噪声影响的问题,提出一种基于经验模态分解(EMD)结合快速傅立叶变换(FFT)对轴承振动信号提取故障特征的方法。对振动信号使用EMD算法以完成信噪分离,选取出高信噪比分量进行FFT算法变换,通过频谱图分析轴承故障位置。结果表明:使用变分模态分解算法对含有较大噪声的仿真信号和强背景噪声下注射机轴承故障信号有较好的降噪效果,通过FFT能准确诊断注射机轴承是否出现故障,二者结合达到很好的故障诊断效果,去噪效果明显,为其他旋转机械的故障诊断提供了参考。     

浅谈往复压缩机环形气阀的故障机理及诊断

在化工生产中，往复压缩机是常用的生产机械，其故障发生率也比较高，根据经验，最易发生故障的零部件有气阀、活塞环、填料函以及一些连接件的摩擦副等。往复压缩机有60％以上的故障发生在气阀上，能够及时发现气阀故障对往复压缩机故障诊断是相当重要的。     

时频分析在透平压缩机振动故障诊断中的研究与应用

设备故障诊断近年来已发展成为一门新兴学科。振动故障诊断是常见的应用于透平压缩机的故障诊断方法。针对上海焦化有限公司空气透平压缩机的故障振动信号,提取故障特征,对振动谱图进行时频分析,对故障形式进行分析判断。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.