随机海洋环境下基于互相关函数和主成分分析的平台结构损伤辨识

为了确保海洋平台安全作业,及时辨识损伤以及进行损伤定位,海洋平台结构健康监测技术已成为学者研究关注的重要问题.针对某在役导管架平台,对平台在不同随机波浪激励下的动力响应分别进行了健康状态和损伤状态的数值模拟.在损伤辨识过程中,对结构不同位置的动力响应进行互相关分析,提取损伤敏感特征;利用主成分分析(principal ...     

基于事故树的海岛爆破飞石风险辨识

为帮助海岛爆破工程科学系统化的作业,运用事故树分析法对海岛爆破飞石事故的产生原因进行了分析,建立了爆破飞石事故树图,求出最小割集13个,最小径集8个,得到了基本事件的重要结构度值。结果表明:爆破方案审核不严、现场管理不当等问题是造成海岛爆破飞石事故的主要原因,针对这些基本事件提出了4点预防爆破飞石事故的对策措施,为今后的海岛工程爆破系统作业提供了决策支持。     

基于事故树的海岛爆破飞石风险辨识

为帮助海岛爆破工程科学系统化的作业,运用事故树分析法对海岛爆破飞石事故的产生原因进行了分析,建立了爆破飞石事故树图,求出最小割集13个,最小径集8个,得到了基本事件的重要结构度值。结果表明:爆破方案审核不严、现场管理不当等问题是造成海岛爆破飞石事故的主要原因,针对这些基本事件提出了4点预防爆破飞石事故的对策措施,为今后的海岛工程爆破系统作业提供了决策支持。     

大型蒸汽喷射泵真空系统基于模糊识别的故障诊断方法

针对大型蒸汽喷射泵真空系统的运行状态的工况识别和故障诊断问题，提出了征兆向量和模糊征兆向量的概念，在此基础上给出了一种蒸汽喷射泵真空系统工况和故障的模糊模式识别的方法，并对三种故障进行了诊断和验证。     

Anelastic relaxation processes due to hopping of interstitial oxygen in scandium

The anelastic spectrum of the solid solution Sc–O has been investigated on a polycrystalline sample from 360 to 570 K for oxygen concentrations varying between 0.024 and 0.91 at.% O, as estimated by electrical resistivity and intentional doping. Two relaxation processes appear at 430 and 520 K for the vibration frequency of 3.5 kHz; both peaks are stable with thermal cycling and their intensities increase with the oxygen content.

The process at lower temperature has been tentatively interpreted as due to the stress-induced hopping of oxygen atoms between the non equivalent tetrahedral and octahedral interstitial sites. A possible mechanism for the higher temperature process could be the dissolution/formation of interacting O–O pairs.     

A Kalman filter based strategy for linear structural system identification based on multiple static and dynamic test data

The problem of identification of stiffness, mass and damping properties of linear structural systems, based on multiple sets of measurement data originating from static and dynamic tests is considered. A strategy, within the framework of Kalman filter based dynamic state estimation, is proposed to tackle this problem. The static tests consists of measurement of response of the structure to slowly moving loads, and to static loads whose magnitude are varied incrementally; the dynamic tests involve measurement of a few elements of the frequency response function (FRF) matrix. These measurements are taken to be contaminated by additive Gaussian noise. An artificial independent variable τ$\tau$, that simultaneously parameterizes the point of application of the moving load, the magnitude of the incrementally varied static load and the driving frequency in the FRFs, is introduced. The state vector is taken to consist of system parameters to be identified. The fact that these parameters are independent of the variable τ$\tau$ is taken to constitute the set of ‘process’ equations. The measurement equations are derived based on the mechanics of the problem and, quantities, such as displacements and/or strains, are taken to be measured. A recursive algorithm that employs a linearization strategy based on Neumann’s expansion of structural static and dynamic stiffness matrices, and, which provides posterior estimates of the mean and covariance of the unknown system parameters, is developed. The satisfactory performance of the proposed approach is illustrated by considering the problem of the identification of the dynamic properties of an inhomogeneous beam and the axial rigidities of members of a truss structure.     

核主成分分析的高炉故障检测研究

由于高炉冶炼系统的复杂性,传统的故障检测方法在高炉故障检测中的应用效果不佳.同时,高炉冶炼过程中的数据具有明显的非线性特征,利用主成分分析(PCA)等线性多元统计方法也难以取得良好的故障检测效果.针对这种情况,提出了利用核主成分分析(KPCA)方法对高炉冶炼过程中的故障进行检测,以适应高炉的非线性特征,实现对高炉故障的快速检测.     

基于PCA的多变量控制系统的故障监测与诊断

 主元分析(PCA)是一种能够对过程生产进行监测和质量控制的有效方法,在保证数据信息丢失最少的情况下,大大降低了原始数据空间的维数．利用PCA分析建模可以消除变量间的非线性关联,降低噪声影响．通过对某食品厂蒸煮设备控制流程进行大量试验表明,PCA 故障诊断模型能够有效地对设备生产进行监测,并能较准确及时地诊断设备运行中发生的故障．     

时滞数据动态过程传感器故障诊断的改进方法

提出利用不断更新的时滞数据矩阵建立变化的动态主元模型对某些动态系统内的传感器故障进行检测，利用变量贡献图的样本平均对故障进行识别的方法．该方法克服了传统静态主元分析方法不适于分析具有动态特性的系统传感器故障的缺陷，而且改善了常用的基于时滞数据建立的动态主元分析法对于分析变量间关系不确定的动态系统存在的局限性．最后给出了3种方法的实验比照结果，验证了方法的有效性，     

Fluorescence properties of a novel side-chain polymer based on polyamic acid

The p-π conjugated polyamic acid (PAA) had been synthesized through 1,4-diaminoanthraquinone (DAAQ) and pyromellitic dianhydride (PMDA) under microwave irradiation. The graft PAAs were obtained by toluene-2,4-diisocyanate (TDI) derivatives having different straight-chain alkyl. The resulted graft polymers had good dissolution capabilities, film-forming capabilities and strong fluorescence. We investigated some factors influencing fluorescence performance on graft PAA and found that with increasing chain length of the straight-chain alkyl or increasing graft degree, the fluorescence intensity and quantum efficiency will be enhanced markedly.     

基于动态规划的动载荷时域识别方法研究

提出一种基于动态规划方程的动态载荷时域方法。首先从系统的状态空间方程出发,利用最小二乘法建立系统响应的实际测量值与识别值之间的目标函数。将Bellman最优化原理运用到目标函数的最小化当中,推导出动态优化载荷识别公式。通过一个多自由度数值算例对本方法进行验证,表明方法对含有噪声的动态载荷识别问题适应性强,具有较高的识别精度。     

About the measurement of dynamic mechanical properties of bi-layer systems

The bi-layer system has been well developed for many engineering structural components in the aircraft, automotive, microelectronics and modern space industries in the last few decades. Consequently, a good determination of its dynamic mechanical properties is important for an appropriate design of its industrial application. These studies are usually performed by a three-point bending test using a dynamic mechanical analyzer (DMA). In this work, we show that the three points bending test on a bi-layer system carried out with the test tool provided in a commercial DMA, for example the dynamic mechanical thermal analyzer (DMTA) Rheometric IV, can lead to erroneous results. Measurements on polymer-hard substrate bi-layer systems around the glass transition temperature of the polymer, T_g, give larger changes in elastic modulus and loss tangent than they are. This problem is not observed at temperatures lower than T_g. The design of new test tool and specimen geometry for the three points bending test is shown together with its application to the measurement of the dynamic elastic properties of a polyvinyl chloride (PVC)–aluminum bi-layer system.     

一种基于Triplet loss的齿轮箱复合故障识别方法

随着设备检测点的数量与采样频率的增加,机械健康监测进入了大数据时代.深度学习以其强大的自适应特征提取和分类能力也在机械大数据处理方面取得了丰硕的成果.在故障诊断领域,目前深度学习方法的研究对象均集中于单一故障,而复合故障却鲜有人涉足.复合故障因为其各类故障信号间有耦合,变化的工况(负载,转速)也会对信号产生较大影响...     

Viscoelastic monitoring of starch-based biomaterials in simulated physiological conditions

Dynamic mechanical analysis (DMA) was used to investigate the solid-state rheological behaviour in a starch-based thermoplastic aimed to be used in different biomedical applications. The tested samples were processed by different injection moulding procedures. The dry samples were immersed in a simulated physiological solution and the relevant viscoelastic parameters were monitored against time. The decrease of stiffness due to swelling can be followed in real time, being less pronounced for the composite sample with hydroxyapatite (HA). The temperature control of the liquid bath was found to be very good. Frequency scans were also performed in wet conditions in samples previously immersed during different times, indicating that DMA is a suitable method to control in-vitro the changes on the viscoelastic properties of biomaterials during degradation.     

Using a microcalorimeter to measure the Lamb shift in hydrogenic gold and uranium on cooled, decelerated ion beams

A precise determination of the Lamb shift from photons emitted by highly charged, one electron ions represents one of the most sensitive tests of QED in strong electromagnetic fields. Recent progress in the production and cooling of intense beams of fully stripped Au and U in the SIS/ESR synchrotron storage ring at GSI, Darmstadt has made it possible to obtain precision spectroscopy of these ions. A fully stripped beam of either Au⁷⁹⁺ or U⁹²⁺ ions is injected, stored and cooled in the ESR and interacts with an internal gas target. The capture of an electron and the subsequent population of a 2p or 3p state will lead to a decay by either Lyman or Balmer X-ray emission. Although measurements of the 1 s Lamb shift in U with Ge ionization detectors accurate to 3% have provided a test of QED for the high Z domain, the experimental errors (±13 eV) are about one order of magnitude larger than the accuracy theoreticians presently claim (±1 eV). We present the results from initial broad band experiments using NTD Ge microcalorimeters to measure the 2 s Lamb Shift in Au and U at the ESR. The broad band coverage of the microcalorimeter makes it possible to reduce the systematic uncertainties in the Doppler corrections while the high-energy resolution reduces the statistical error in the absolute energy calibration.     

Study on the instability of organic field-effect transistors based on fluorinated copper phthalocyanine

The effects of positive and negative gate-bias stress on organic field-effect transistors (OFET) based on tantalum (Ta)/tantalum pentoxide (Ta₂O₅)/fluorinated copper phthalocyanine (F₁₆CuPc) structure are investigated as a function of stress time and stress temperature. It is shown that gate-bias stress induces a parallel threshold voltage shift (ΔV_T) of OFETs without changes of field-effect mobility μ_EF and sub-threshold slope (ΔS). The ΔV_T is observed to be logarithmically dependent on time at high gate-bias appropriate to OFET operation. More importantly, the shift is directional, namely, be large shift under positive stress and almost do not move under negative stress. The threshold voltage shift is temperature dependent with activation energy of 0.51 eV. We concluded that threshold voltage shift of the OFET with F₁₆CuPc as active layer is due to charge trapping in the insulator in which trapped carriers have redistribution.     

Effect of stacking fault energy on the dynamic recrystallization during hot working of FCC metals: A study using processing maps

The influence of stacking fault energy (SFE) on the mechanism of dynamic recrystallization (DRX) during hot deformation of FCC metals is examined in the light of results from the power dissipation maps. The DRX domain for high SFE metals like Al and Ni occurred at homologous temperature below 0·7 and strain rates of 0·001 s⁻¹ while for low SFE metals like Cu and Pb the corresponding values are higher than 0·8 and 100 s⁻¹. The peak efficiencies of power dissipation are 50% and below 40% respectively. A simple model which considers the rate of interface formation (nucleation) involving dislocation generation and simultaneous recovery and the rate of interface migration (growth) occurring with the reduction in interface energy as the driving force, has been proposed to account for the effect of SFE on DRX. The calculations reveal that in high SFE metals, interface migration controls DRX while the interface formation is the controlling factor in low SFE metals. In the latter case, the occurrence of flow softening and oscillations could be accounted for by this model.     

基于动态正常模型和免疫计算的软件故障高精度处理

针对软件故障的检测、消除和修复的问题,用动态正常模型和免疫计算的方法进行了软件故障高精度处理的研究.动态的正常模型用来提高软件故障检测的精度,免疫计算用来提高软件系统对软件故障的免疫力和修复能力.用正常软件系统中所有组件的时空属性唯一确定了该系统的正常状态,设计了软件故障检测、消除与修复的免疫算法,包括自体/软件故障的检测算法、已知软件故障的识别算法、未知软件故障的识别算法、软件故障的消除算法和受损系统的修复算法.在时间属性正确的条件下,软件系统的正常模型大大提高了对软件故障的检测率(理论上可达到100%),降低了误检率.正常模型和免疫计算有助于从精度和智能两方面同时解决软件系统的安全性问题,为未来软件的设计与工程化提供有用的创新思路.     

Anelastic relaxation processes due oxygen in Nb–3.1 at.% Ti alloys

In the last 50 years several studies have been made to understand the relaxation mechanisms of the heavy interstitial atoms present in transition metals and their alloys. Internal friction measurements have been carried out in a Nb–Ti alloy containing 3.1 at.% of Ti produced by the Materials Department of Chemical Engineering Faculty of Lorena (Brazil), with several quantities of oxygen in solid solution using a torsion pendulum. These measurements have been performed by a torsion pendulum in the temperature range from 300 to 700 K with an oscillation frequency between 0.5 and 10 Hz. The experimental results show complex internal friction spectra that have been resolved, into a series of Debye peaks corresponding to different interactions. For each relaxation process it was possible to obtain the height and temperature of the peak, the activation energy and the relaxation time of the process.     

运用PCA的多变量实验系统控制限确定方法研究

鉴于目前大部分校准实验室在提高校准结果质量方面较少考虑校准用计量器具自身的性能对校准结果的影响.在对采用常规控制图的方法进行实验室校准过程控制研究的基础上,提出了应用于在多种稳定工作状态下的计量器具校准结果监控控制限设定的方法.方法通过对系统不同变量的历史数据进行分析,获取系统变量的经验分布,然后划分系统变量的状态范围,最后利用主成分分析法确定平方预测误差的控制极限.实验表明,方法有效保证了实验室校准结果的质量控制.