基于改进BP网络的冷水机组故障诊断

采用常规神经网络进行冷水机组的故障检测与诊断,存在整体检测率低或完全无法检测的现象。为了提高冷水机组故障检测效率及诊断精度,本文提出了一种基于贝叶斯正则化的改进神经网络故障检测策略。由于BP神经网络存在泛化能力差的缺陷,对神经网络进行贝叶斯正则化,从而提高模型的检测效率。贝叶斯算法通过限制神经网络权值,使网络反应更加光滑,模型更精确。通过利用ASHRAE Project提供的数据对FDD(fault detection and diagnosis)策略进行验证,检测率明显提高。     

冷水机组多故障耦合研究

为了提高冷水机组的运行效率、设备可靠性和能源利用率,本研究将对冷水机组的多故障耦合进行检测和诊断。首先,本研究使用RP-1043(Research Promotion)项目的故障数据,对冷水机组几种典型故障数据进行分析对比。其次,本研究使用3种树模型对数据进行训练,发现随机森林在准确率和训练预测的效率上综合表现最好。使用随机森林模型,结合专家知识,对故障等级为1的冷水机组的运行数据进行特征选取,然后建立贝叶斯网络故障诊断模型。最后,使用该模型对实际故障案例进行诊断与分析,对比附加信息层对故障诊断的影响。结果表明,该模型仅使用故障特征节点便可以对故障进行有效的诊断,合理利用附加信息层可以进一步提高故障诊断的可靠性。     

基于单类支持向量机的冷水机组温度传感器故障检测

冷水机组系统中,温度传感器出现故障会严重影响机组工作效率及使用寿命。针对冷水机组温度传感器偏差故障,本文提出一种基于单类支持向量机(one-class support vector machine,OC-SVM)的故障检测方法,采用冷水机组正常数据建立OCSVM模型,通过十折交叉验证法获得模型优化参数。分别采用工程实测数据和实验数据(共4组)对该方法进行了验证,结果表明:基于OC-SVM的方法能有效检测出4组冷水机组的温度传感器偏差故障。其中对于螺杆式冷水机组(数据集Ⅰ)的故障检测效果明显,当冷冻水侧温度传感器偏差故障幅值绝对值大于1℃时,检测效率达到100%。     

基于EWMA-BN的冷水机组故障诊断策略

为提高冷水机组故障诊断的准确度,本文提出一种基于EWMA-BN的冷水机组故障诊断策略。EWMA-BN模型通过EWMA控制图进行故障检测,以其控制限为阈值将各性能指标的故障数据分为高、低、正常3种状态,通过概率统计获得条件概率表,将条件概率表和由专家知识获得的先验概率表输入BN进行故障诊断。利用实验数据从输入模型的证据节点数量、顺序及完整性等方面分析该模型的故障诊断特性。结果表明:EWMA-BN方法对冷水机组常见故障的诊断效果显著,后验概率值(故障诊断结果)均大于0.85,且输入模型的证据节点越多,故障诊断结果越准确,但证据节点输入模型的顺序对最终故障诊断结果无任何影响;对不确定、不完整信息的利用进一步提高了模型的故障诊断能力。采用ASHRAE Project提供的数据对EWMA-BN模型进行验证,故障诊断结果良好。     

小波消噪-HHT的四通阀故障诊断

提出一种基于小波阈值去噪和希尔伯特-黄变换(HHT)的故障诊断方法.先用小波变换实现信噪分离,然后对提纯的信号进行经验模式分解(EMD)和HHT,分析HHT边际谱,进行故障诊断.结果表明,该方法减少了噪声对EMD分解的干扰,能有效地突出故障特征频率成分,提高机械故障诊断率.此外,结果还验证了传感器安装在四通阀顶部能最及时有效地进行故障诊断.     

结合连续小波变换和多约束非负矩阵分解的故障特征提取方法

为了在故障早期从信噪比较低的振动信号中提取故障特征,提出了一种结合小波变换和多约束非负矩阵分解振动信号特征提取方法。首先,采用最小小波熵测量提取出最优时频系数矩阵。然后,根据故障特征在系数矩阵中的表现规律,采用基于稀疏性和光滑性约束的非负矩阵分解算法对小波系数矩阵进行非线性降维,从而提取信噪比较高的故障特征。最后,通过仿真数据和实际数据对该方法进行了验证,结果表明该方法能够在时域中提取出微弱的故障特征,实现机械状态的早期故障诊断。     

改进小波算法在机械故障诊断中的应用

小波变换具有优良的时频分析特性,适合于提取非平稳信号和时变信号,利用小波变换来提取机械设备的故障特征是当前的一个研究热点.但是由于小波滤波器的频响应特性不理想,因此直接对信号进行小波变换必定会产生一定的虚假频率,从而影响故障特征提取的准确性.针对小波变换产生混频的原因提出了一种改进的小波分解算法,仿真结果表明该方法能有效地消除混频现象,提高故障诊断的精度.     

基于统计学参数与SVM算法的核电风冷式冷水机组高压保护故障研究

采用传统的人工识别方法很难确定核电风冷式冷水机组高压保护故障是源于翅片脏堵还是源于散热不良。本文采用基于统计学参数和机器学习的分析方法对冷水机组高压保护进行分类研究,经数据预处理和模型选择,提出一种基于统计学参数与SVM(支持向量机)算法的核电风冷式冷水机组高压保护故障诊断方法,故障识别率达96%,达到了行业专家分析水平。     

基于关联规则分类的冷水机组故障诊断研究

鉴于现有基于数据驱动的故障诊断方法多以黑箱模型为主,诊断过程和结果难以解释的问题,本文提出一种基于关联规则分类的冷水机组故障诊断和故障作用机理解释的方法,在保证较好故障诊断精度的前提下,利用故障诊断模型中的规则库对诊断过程进行逆向分析,解析故障作用机理和模型的诊断过程,提升了基于数据驱动的故障诊断方法的可靠性。通过ASHRAE研究项目1043的实验数据对该方法进行验证。结果表明,基于关联规则分类的冷水机组故障诊断方法可以有效地识别7种典型冷水机组故障,平均故障诊断准确率高达90.84％。此外,提取的规则能够较好地吻合制冷原理及热力学相关知识,可用于故障作用机理分析与故障诊断的进一步研究。     

时间-小波能量谱在滚动轴承故障诊断中的应用

为滚动轴承故障诊断提供了一种新途径，针对滚动轴承故障振动信号的特点，构造脉冲响应小波，采用连续小波变换的方法来提取滚动轴承故障振动信号的特征，在此基础上提出了一种滚动轴承故障诊断方法：时间-小波能量谱自相关分析法。通过对滚动轴承具有外圈缺陷、内圈缺陷的情况下振动信号的分析，说明时间-小波能量谱自相关分析法不仅能检测到滚动轴承故障的存在，而且能有效地识别滚动轴承的故障模式。     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Study on Bond Ability of Arc-Spraying Coatings with Different Surface Pretreatment on Cast-Iron

Arc spraying coatings are widely used in various applications, but uncommon in cast iron substrate. Different surface pretreatment technology is tested on substrates of gray cast iron. Surface roughness and residual stress were measured by TR200 and X-ray diffraction analyzer. Influence of different surface pretreatment methods ( dry blasting and fusebond) on roughness and residual stress was analyzed. The arc-sprayed coatings of wire 3Cr13 (φ2mm) on gray cast iron substrate is studied. The microstructure and interface of bonding layer were observed by SEM. The bond strength was taken by tensile test. Results show that bond strength with grit blasting is higher than fuse-bond; it is feasible to make wire 3Cr13 coating with arc spraying on cast iron substrate roughened by grit blasting.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.     

Evaluation of fatigue life of steel using steel grain size

The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase.