Determining the optimal maintenance action for a deteriorating repairable system

This paper develops a decision model for risk management of the deterioration of a repairable system. When a failure occurs in a deteriorating system, an optimal maintenance decision that includes the possibility of system replacement, as compared to mere deterioration reduction, should be made. There are many uncertainties associated with deterioration, however, so the decision may require a probabilistic analysis. Here, a well-known nonhomogeneous Poisson process with a power law intensity function is used to model the uncertain behavior of the deteriorating system. A Bayesian statistical approach is adopted to allow for the uncertainty of the parameters of the power law intensity function, which imposes a conjugate prior distribution of the parameters. A power law maintenance cost function and the failure cost are analyzed to determine the magnitude of failure risk reduction by minimizing the expected cost incurred from the maintenance action and future failures. A numerical example is given.     

基于快速引导滤波改进的暗原色先验去雾算法

针对目前单幅雾霾降质图像存在大面积天空域,导致暗原色失效复原图像失真以及去雾时间复杂度高的问题.提出一种基于暗原色先验和快速引导滤波的去雾方法,针对存在高亮天空域图像多尺度滤波采用自适应阈值分割得到天空域,在天空域求取精确大气光值,再将天空域和非天空域透射率有效归一化,最后采用暗通道图作为引导图快速引导滤波精细化透射率,最大限度保留边缘细节的同时有效降低时间复杂度.实验结果表明,该方法可以有效处理天空域,保持色彩和细节信息,在算法实时性上有明显优势.     

The effect of prior ferrite formation on bainite and martensite transformation kinetics in advanced high-strength steels

Most advanced high-strength steel products contain complex phases, including ferrite, bainite and martensite, which form successively during elaboration. It is essential to understand the effect of prior ferrite transformation on the subsequent bainite and martensite transformation kinetics to achieve precise control of the final microstructure. Nevertheless, the effect of the interface between the prior formed ferrite and the residual austenite (α/γ), together with the related chemical heterogeneity at the interface, on the subsequent phase transformations has been studied only rarely, and remains unclear. This study pays particular attention to the effect of the α/γ interface and its related concentration gradients on bainite and martensite transformation. It is shown that the interface and its related concentration gradients can play a very significant role on the subsequent bainite or martensite transformation kinetics: it retards bainite transformation whereas it accelerates martensite transformation. It is revealed from microprobe wavelength-dispersive spectrometry analysis and model calculations that there are both manganese and carbon gradients in front of the α/γ interface at the end of the ferrite transformation holding. The subsequent bainite transformation kinetics is controlled by the competition between the acceleration effect of the interface boundary itself and the retardation effect of the higher alloying concentration near the interface. Martensite transformation should initiate at the pre-existing dislocations in the center of the residual austenite grains, where the C and Mn contents are the lowest. A simple martensite transformation kinetics model taking into account C heterogeneity is proposed that can describe well the martensite transformation kinetics following the prior ferrite transformation.     

Ashes Thrown to the Wind: The Elusive Nature of Transgression

Transgression is not absolute. What constitutes a transgression is forever in flux, being redefined with the mores of society. The potential for transgression also does not halt with the completion of a building. David Littlefield examines the temporal character of transgression in relation to lived-in buildings, and the manner in which transgression lodges itself between a building and an idea. Here transgression is a byproduct of the occupiers rather than their makers, sometimes to the extent that a building can take on unbearably horrific associations.     

基于Bayes方法的小子样可靠性分析

少量数据的可靠性分析与评定一直是工程实践中的技术难题之一。Bayes方法可以融合多种验前信息,并结合现场数据,从而对少量数据作出有效的参数估计。针对多种验前信息的综合应用问题,引入支持向量机(support vectormachine,SVM)理论对不同来源的信息在验前分布中的权重分配策略进行研究,提出一种新的信息融合思路。并在此基础上,提出基于Bayes理论的威布尔分布的小样本参数估计方法。最后,运用实例对Bayes方法和传统的参数估计方法进行对比分析。     

一阶双重线性时间序列模型的参数估计

本文利用Gibbs抽样法求一阶双重时间序列模型的参数的估计.推出了模型中两个未知参数的Gibbs抽样迭代步骤,并对模型进行了模拟计算,给出了模拟计算的结果.     

非均匀环境下利用杂波脊信息的杂波滤除方法研究

该文针对空时自适应检测训练样本中含有干扰目标会导致目标检测性能下降的问题,提出一种利用杂波脊先验信息滤除杂波的方法,使目标检测不受训练样本中干扰目标的影响,并且提高了小样本情况下的检测性能。利用机载雷达地杂波在角度多普勒空间的分布特点,结合杂波2维高斯功率谱密度模型,构造杂波协方差矩阵用于滤除对目标有遮蔽影响区域内的杂波。模型参数的设定充分结合了环境先验信息,使参数设定快速准确。通过仿真数据和MCARM实测数据的仿真实验,结果表明在训练样本被干扰目标污染和小样本情况下,利用杂波脊信息的杂波滤除方法均能有效滤除杂波,检测性能高于传统的自适应检测方法。     

青海某复杂铜铅锌多金属矿石选矿工艺研究

针对青海某铜铅锌多金属硫化矿石易浮难分、有用矿物嵌布粒度极不均匀的特点,采用铜、铅、锌依次优先浮选工艺流程及特别研制的新型捕收剂YK1-11和新型抑制剂YK3-09对其进行选矿试验,并在选铅时采取反浮精选措施,获得了铜品位和铜回收率分别为18.02%和57.50%的铜精矿、铅品位和铅回收率分别为51.43%和33.20%的铅精矿、锌品位和锌回收率分别为45.83%和48.95%的锌精矿以及Pb+Zn品位为69.99%,铅、锌回收率分别为42.56%和34.05%铅锌混合精矿,并使矿石中的伴生银得到了有效富集,为合理开发利用该矿石提供了依据。     

无先验信息时去除两基站交叉定位中的假定位

在采用无源定位获取辐射源的位置信息的各种方法中,测向交叉定位方法是应用最多且较简便的一种方法．但在多个辐射源的情况下该方法在空间定位上存在假定位问题。本文在无先验信息的条件下,利用两站的测向结果进行信号分离,然后利用信号的相关性去除两基站测向交叉定位中的假定位。计算机模拟结果验证了本文的方法可以去除两基站测向交叉定位中的假定位。     

Can the Prior Cathodic Polarisation Treatment Remove the Air-Formed Surface Film and Is It Necessary for the Potentiodynamic Polarisation Test?

This paper clarifies two issues related to the prior cathodic polarisation treatment(PCPT) for the potentiodynamic polarisation test: whether PCPT can(1) remove the air-formed surface film and(2) affect the polarisation test results. X-ray photoelectron spectroscopy analyses of fluoride ion-labelled samples show that PCPT cannot remove the surface film completely due to the low reaction rate. Potentiodynamic polarisation tests demonstrate that PCPT with proper operating parameters,-1.0 V SCE for 5 min with subsequent open circuit potential(OCP) stabilisation in this study, is necessary because it can improve the test reproducibility without affecting the corrosion parameters by unifying the initial surface state. However, PCPT with lower potentials, longer time or no OCP stabilisation has significant effects on the electrochemical corrosion parameters due to the hydrogen absorption under the conditions of this study.