经验模态分解在切削振动信号分析中的应用

为了分析切削振动的变化规律及产生根源,采用在线监测的方法采集振动信号,提出了运用经验模态分解对振动信号进行分析的方法,构建了分段频率变化的仿真振动信号,分别对仿真振动信号进行短时傅里叶变换、小波变换和经验模态分解时频分析。结果表明,经验模态分解方法具有更高的时频分辨率,运用经验模态分解方法对实际振动信号进行分析,提取典型分量绘制希尔伯特幅值谱,能较好地反映振动信号的时频变化规律。经验模态分解适合对切削振动信号进行分析,但是需要对算法的模态混叠及计算效率低等不足进行完善。研究结果对非平稳信号的分析具有参考价值。     

循环流化床锅炉燃烧系统动态特性的分析

为了克服传统方法存在的分析相对误差率高和分析时间较长的问题,文章提出了一种新的基于经验模态分解的循环流化床锅炉燃烧系统动态特性分析方法。以循环床锅炉流动参数和热力参数为基础沿炉膛高度方向对炉膛区域进行划分,并构建循环床锅炉燃烧系统数学模型。根据建模结果,利用经验模态分解方法对热量信号进行分解,并对每一个IMF分量进行希尔伯特变换,得到希尔伯特谱。以希尔伯特谱为基础,分析主蒸汽压力、床温、燃烧系数等参数变化情况下,热量信号的阶跃响应,得到最终的燃烧系统动态特性分析结果。实验结果表明,该方法的热量信号去噪效果好,分析相对误差率平均值为3.6%,分析时间始终保持在0.6 s以下。     

蜗轮蜗杆减速机齿形变化故障特征提取方法

蜗轮蜗杆减速机蜗轮齿形变化故障诊断,提出一种新的振动信号特征检测方法。在诊断故障过程中,为提取故障信号的特征频率,给出经验模态分解与希尔伯特变换相结合的方法。     

基于经验模态分解的滚动轴承早期故障预警研究

滚动轴承是旋转机械中最常用的零部件之一。针对滚动轴承早期故障预警较差的问题,提出了一种基于经验模态分解(Empirical Mode Decomposition,简称EMD)的滚动轴承早期故障预警方法。该方法首先对轴承原始信号进行经验模态分解,得到一阶固有模态函数(Intrinsic Mode Function,简称IMF),然后对一阶IMF分量进行分析,提取反映轴承故障发展的特征指标。再采用局部均值法对特征指标进行处理,将特征局部均值与阈值比较,实现对滚动轴承早期故障的预警。最后利用滚动轴承试验数据对该方法进行了验证,结果表明,基于经验模态分解的滚动轴承早期故障预警方法能够有效地识别和预警滚动轴承早期故障。     

VMD敏感分量在风电机组主轴故障诊断中的应用

提出基于VMD敏感分量的风力发电机主轴故障诊断方法。利用变分模态分解分析风机主轴的振动信号,将其分解、评估、分析,选取包含信号特征的有效模态分量重构信号。然后提取重构信号的特征值,构成模态分析向量,凸显信号故障信息,结合VPMCD方法进行故障诊断。将所提方法应用于风电机组仿真实验,对主轴外圈、内圈和滚动体故障数据进行分析验证,结果表明该方法的有效性。     

振动信号分析技术在汽轮机故障诊断中的应用

分析汽轮机典型故障成因,提出了一种基于振动信号时—频联合分析技术的汽轮机故障诊断方法。分别基于专家经验和经验模态分解法对采集到的汽轮机振动信号进行时域、频域分析,提取了多个与汽轮机故障状态相关的特征量,然后搭建了基于深度信念网络的诊断模型,并依据在线振动监测数据完成了训练,最后测试各模型在测试集中的识别准确率。结果表明,该故障诊断方法的平均准确率可达95.12%,可以有效识别汽轮机的振动诱因。     

基于支持向量机的离心机振动信号采集及分析

为更准确地判断离心机工作状态，使用动态信号采集仪对离心机进行信号采集，并对数据进行预处理。使用支持向量机模型，提取离心机振动信号的时域和时频域信息作为其状态特征，使用主成分分析（PCA）降维技术得到低维、冗余信息较小、对状态信息表达一致的低维特征矩阵。将特征矩阵输入支持向量机进行分类识别，使用时域特征、时频域特征、时域+时频域特征作为输入，识别准确率可达90%。     

基于振动信号特征提取的糖机运行状态分析

针对甘蔗预处理设备在长期、高负荷运行时易出现损伤故障等问题,从实际应用出发,以糖机减速机为研究对象,确定振动监测点,搭建振动信号采集系统,分析信号信息熵指标,利用连续小波变换分析振动信号时频分布特征、Hlibert包络解调分析信号调制特征,使用经验模态分解提取糖机隐含调制和冲击成分,分析糖机运行状态。     

大型起重机械减速机振动信号降噪方法的研究

大型起重机械的减速机负荷重,是起重机主要出现故障的部位之一~([1,2])。针对大型起重机械减速机工况复杂以及振动信号噪声大的问题,采用适用于大型起重机械减速机的集合经验模式分解(EEMD)降噪方法,利用高斯白噪声频率均匀分布的特性,通过引入噪声作为辅助信号用来解决EMD中模态混叠的问题。此外,针对EEMD降噪方法中难以选取真实IMF分量的问题,选择基于相关系数的IMF分量选取方法,利用IMF与原始信号间的相关系数大小来选取真实的IMF分量。     

基于压缩感知理论和密度聚类算法的全回转推进器滚动轴承故障诊断

滚动轴承振动信号具有非线性、非平稳性等特性,且往往存在噪声干扰,信号特征难以提取,传统故障工况诊断方法受到应用限制。以全回转推进器为研究对象,提出一种基于压缩感知理论和密度聚类算法的滚动轴承故障诊断算法。首先,将振动信号分解,进行稀疏变换,得到稀疏域下的振动信号;其次,采用压缩感知理论进行信号重构,建立绝对值、偏斜度、方差以及裕度等特征指标;最后,采用密度聚类算法DBSCAN,将不同特征指标之间两两组合进行分析,成功区分了故障工况。为滚动轴承故障的无损化、智能化诊断提供了理论依据。     

Divergent patterns of engagement in Internet standardization: Japan,Korea and China

This article analyzes the engagement of Japanese, Korean and Chinese participants in the development of Internet standards at IETF on the basis of four quantitative metrics: attendance, patenting, authorship and leadership. The results are strikingly divergent. Japanese involvement in Internet standardization began early and Japan was, for many years, second only to the U.S. in terms of IETF participation. Though Japanese participation has declined since the early 2000s, Japan remains a major contributor to IETF standardization. Korean involvement in IETF has always been significant, but below the levels of Japan and major European countries. Korean participation in IETF has also declined over the past decade, and has been dominated by one firm, Samsung. Though meaningful Chinese involvement in IETF did not begin until the mid-2000s, it has rapidly expanded in recent years. Today, China is a major player in numerous areas of Internet standardization in terms of three metrics (participation, patenting and leadership), and is rapidly gaining in terms of document authorship as well. Most of China׳s recent IETF involvement can be attributed to Huawei, though other Chinese firms have recently begun to increase their participation in the organization. Thus, contrary to some views that China׳s engagement with standardization is primarily one of indigenous innovation and “catching up”, China׳s experience with IETF demonstrates deliberate and effective engagement with a major Western standards-development organization on its own terms.     

Whose Image is it Anyway?: Some Considerations of the Curricular Importance of Subject Image in Secondary School Design and Technology Education

This paper explores the idea that a sense of school subject image is a necessary feature of curriculum management and a potent force for change. The discussion centres on the view that all school subjects have an image and that if those intimately involved with the subject do not control the image then someone else does! In such circumstances the image is the product of past encounters and old euphemisms and is unlikely to hold the changed realities.The UK developments in Design and Technology education (the term Design and Technology is used to denote the school subject defined under this heading by the UK National Curriculum, 1995) have created something of an image problem which has interesting international parallels. Some of these problems are due to clearly discernible internal tensions and an ambiguous relationship with other subject areas.Through greater attention to subject image internal controversies might be acknowledged and resolved, relationships with other subject areas can be more meaningfully understood and practitioners can be helped to make sense of curriculum change.     

快速成形技术的应用及热点分析

基于快速成形技术的原理,展示了快速成形技术在快速模具制造、金属零件直接成形、反求工程等领域的广泛应用,总结了快速成形制造技术研究的热点,即研发新材料和新设备、提高成形精度、建立RPM的反求工程系统、建立成形技术的统一标准和扩大成形技术的应用领域。     

增强Linux系统安全性的措施

L inux系统的安全取决于系统管理员如何来管理它。本文探讨了一系列可以增强安全性的技巧与策略 ,包括 :系统安装原则、BIOS安全、口令安全策略、设计帐户自动注销功能、文件系统和日志安全策略、使用 SSH及 TCP-WRAPPERS,隐藏系统信息、删除所有特殊帐户、关闭控制台程序、限制系统中的 SUID/ SGID程序等。本文最后向 L inux系统管理员提出了一些安全管理方面的建议     

HSE走进中国石油

企业管理水平的好坏直接影响着企业的经济效益,运用HSE管理能提高企业管理水平,HSE管理模式将健康,安全,环境三者视为一个有机的整体。HSE管理认为人的安全是第一位的,人是创造财富的原动力,是企业的最大财产,HSE管理体系强调的是“蝴蝶效应”。     

CIS与现代企业管理美学

概括性介绍了 ＣＩＳ（Ｃｏｒｐｏｒａｔｅ Ｉｄｅｎｔｉｔｙ Ｓｙｓｔｅｍ）的三大基本组成，并阐述了它与现代企业管理密不可分的相互联系及所处的举足轻重的地位，指出导入ＣＩＳ是现代企业谋求发展的重要手段。     

Material power and normative conflict in global and local agrifood governance: The lessons of ‘Golden Rice’ in India

This special section aims to investigate the interaction of global and local forces in shaping agrifood governance. It starts from the recognition that a multitude of actors and norms shape today’s agrifood system. The resulting opaqueness of the systems makes it extremely difficult to understand and explain processes and outcomes of agrifood governance. Given the sustainability challenges facing the agrifood system, improvements in our understanding of what the interaction of global and local actors and norms means on the ground are urgently needed, however. The section, therefore, analyses agrifood governance in India across a selected group of cases. It does so by employing a systematic framework emphasizing the material and ideational dimensions of power and their interaction. The section has chosen India as the setting in which to analyze this interaction due to the crucial role the food demand and supply of this rising power plays in today’s agrifood system. This article provides the special sections’ analytical framework, which uses the interplay of material and ideational dimensions of power as a focal lens. In addition, the article applies this framework to an empirical study of the political conflict around GMO foods in India, specifically the case of ‘Golden Rice’.     

蒸汽热量计量应用的探析

研究了石油化工企业的燕汽计量情况,着重对蒸汽热量计量的合理性进行了分析,阐述了蒸汽热量计量的依据及计算方法,以及蒸气热量计量对节能降耗的重要意义.     

论传统旗袍文化与现代时装

中国的旗袍文化蕴含着非常丰富的文化内涵和设计思想,如今旗袍的普及受到一定的限制,只有经过改良,才可变局限性为可行性,才可使旗袍焕发青春,走向新时代。     

望峰岗矿井贯通测量技术分析

在深部开采矿井两井间贯通测量时,利用加测陀螺定向边和用四架法代替传统的三架法测量,分析了由起始边的方位角误差引起的支导线终点误差及由测角量边引起的导线终点的点位误差.