Remaining useful life estimation based on Wiener degradation processes with random failure threshold

Remaining useful life(RUL) estimation based on condition monitoring data is central to condition based maintenance(CBM). In the current methods about the Wiener process based RUL estimation, the randomness of the failure threshold has not been studied thoroughly. In this work, by using the truncated normal distribution to model random failure threshold(RFT), an analytical and closed-form RUL distribution based on the current observed data was derived considering the posterior distribution of the drift parameter. Then, the Bayesian method was used to update the prior estimation of failure threshold. To solve the uncertainty of the censored in situ data of failure threshold, the expectation maximization(EM) algorithm is used to calculate the posteriori estimation of failure threshold. Numerical examples show that considering the randomness of the failure threshold and updating the prior information of RFT could improve the accuracy of real time RUL estimation.

Real time remaining useful life prediction based on nonlinear Wiener based degradation processes with measurement errors

Real time remaining useful life(RUL) prediction based on condition monitoring is an essential part in condition based maintenance(CBM). In the current methods about the real time RUL prediction of the nonlinear degradation process, the measurement error is not considered and forecasting uncertainty is large. Therefore, an approximate analytical RUL distribution in a closed-form of a nonlinear Wiener based degradation process with measurement errors was proposed. The maximum likelihood estimation approach was used to estimate the unknown fixed parameters in the proposed model. When the newly observed data are available, the random parameter is updated by the Bayesian method to make the estimation adapt to the item's individual characteristic and reduce the uncertainty of the estimation. The simulation results show that considering measurement errors in the degradation process can significantly improve the accuracy of real time RUL prediction.

Residual life estimation based on bivariate Wiener degradation process with measurement errors

An adaptive method of residual life estimation for deteriorated products with two performance characteristics (PCs) was proposed, which was sharply different from existing work that only utilized one-dimensional degradation data. Once new degradation information was available, the residual life of the product being monitored could be estimated in an adaptive manner. Here, it was assumed that the degradation of each PC over time was governed by a Wiener degradation process and the dependency between them was characterized by the Frank copula function. A bivariate Wiener process model with measurement errors was used to model the degradation measurements. A two-stage method and the Markov chain Monte Carlo (MCMC) method were combined to estimate the unknown parameters in sequence. Results from a numerical example about fatigue cracks show that the proposed method is valid as the relative error is small.

Life cycle inventory analysis of CO_2 and SO_2 emission of imperial smelting process for Pb-Zn smelter

Based on the principle of life cycle assessment, CO2 and SO2 emission of Imperial Smelting Process in a certain zinc-lead smelter was analyzed by life cycle inventory method. According to the system expansion and substitution method, the environmental impacts of co-products were allocated among the main products of zinc, lead and sulfuric acid. The related impacts were assessed by use of Global Warming Potential （GWP） and Acidification Potential （ACP）. The results show that the GWP index from 1998 to 2000 is 11.53, 11.65, 10.93 tCO2-eq/tZn respectively, the ACP index decreases from 14.88 kgSO2-eq/tZn in 1998 to 10.99 kgSO2-eq/tZn in 2000. Power and electricity generation, followed by smelting and zinc distillation, are mainly responsible for GWP. Sintering individually affects ACP. Reduction in greenhouse gas emissions of the ISP may come from energy conservation measures rather than from technological developments. And recycling more secondary Pb and Zn materials effectively treated by ISP, and reducing the amount of primary metal are the main ways to put SO2 emission under control.

A Statistical Analysis of Intensities Estimation on the Modeling of Non-Life Insurance Claim Counting Process

This study presents an estimation approach to non-life insurance claim counts relating to a specified time. The objective of this study is to estimate the parameters in non-life insurance claim counting process, including the homogeneous Poisson process (HPP) and the non-homogeneous Poisson process (NHPP) with a bell-shaped intensity. We use the estimating function, the zero mean martingale (ZMM) as a procedure of parameter estimation in the insurance claim counting process. Then, Λ(t) , the compensator of is proposed for the number of claims in the time interval . We present situations through a simulation study of both processes on the time interval . Some examples of the situations in the simulation study are depicted by a sample path relating to its compensator Λ(t). In addition, an example of the claim counting process illustrates the result of the compensator estimate misspecification.

System Safety Management of Whole Life Cycle of Chemical Process Unit

Guaranteeing the safety performance of chemical process units is the premise for the safety production of chemical enterprises.Only to have the system safety management of the whole life cycle of the process units can operate the process systems under the state of controllable risk.

Degradation process assessment of prestressed concrete continuous bridges in life-cycle

To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance assessment of concrete bridges was proposed.The existing assessment methods were firstly introduced and compared.Some essential mechanics problems involved in the degradation process,such as the deterioration of materials properties,the reduction of sectional areas and the variation of overall structural performance caused by the first two problems,were investigated and solved.A computer program named CBDAS(Concrete Bridge Durability Analysis System) was written to perform the above-metioned approach.Finally,the degradation process of a prestressed concrete continuous bridge under chloride penetration was discussed.The results show that the concrete normal stress for serviceability limit state exceeds the threshold value after 60 a,but the various performance indicators at ultimate limit state are consistently in the allowable level during service life.Therefore,in the case of prestressed concrete bridges,the serviceability limit state is more possible to have durability problems in life-cycle;however,the performance indicators at ultimate limit state can satisfy the requirements.

Feature Based Machining Process Planning Modeling and Integration for Life Cycle Engineering

Machining process data is the core of computer aided process planning application systems.It is also provides essen- tial content for product life cycle engineering.The character of CAPP that supports product LCE and virtual manufacturing is an- alyzed.The structure and content of machining process data concerning green manufacturing is also examined.A logic model of Machining Process Data has been built based on an object oriented approach,using UML technology and a physical model of machin- ing process data that utilizes XML technology.To realize the integration of design and process,an approach based on graph-based volume decomposition was apposed.Instead,to solve the problem of generation in the machining process,case-based reasoning and rule-based reasoning have been applied synthetically.Finally,the integration framework and interface that deal with the CAPP integration with CAD,CAM,PDM,and ERP are discussed.

INVESTIGATIONS ON LASER SHOCK-PROCESSING (LSP) TO IMPROVE FATIGUE LIFE OF SMALL HOLE IN AIRCRAFT STRUCTURES

Laser shock-processing (LSP) is of particular advantage for improving fa-tigue behavior of small holes and blind holes. Because there are not good accessibility andpassage, these holes cannot be treated by shot peening or cold extrusion. The fatigue livesof aircraft aluminum alloy 2024-T62 are increased greatly by means of optimization oflaser shocking parameters. With 95 % confidence, the mean fatigue life of LSP specimensis 4. 35~7, 75 times larger than that of the un-shocked ones.

基于溃决机理的堰塞湖溃决快速风险评估方法研究

堰塞湖发生后极易形成溃决灾害链,亟需构建基于有限数据包的溃决快速定量风险评估方法。通过快速获取堰塞湖影响区域的三维地理信息,构建溃决-致灾的快速定量评估模型。基于堰塞湖坝体颗粒级配组成,实现精细化、简单化的稳定性快速评价;基于冲蚀特性和崩塌过程溃决机理,实现溃口流量变化过程分析与洪水演进过程模拟(1 h内);基于极限学习机网络模型建立风险人口与生命损失的函数,实现了生命损失评估预警,明晰了溃决-致灾的灾害链效应。将其应用于唐家山堰塞湖实例发现:研究方法能够较好地预警溃决灾害链;开挖引流槽可降低堰塞湖的溃口峰值流量、最大流速、溃口宽度和溃决库容,但无法防止溃决发生;若不开挖引流槽,溃决库容将达到3.14×10^(8) m^(3),溃口峰值流量达到9343.35 m^(3)/s,溃口顶宽增大到151.6 m,开挖引流槽可使溃口峰值流量减少12.6%,溃决库容减少36.5%,降低了堰塞湖的溃决风险;当提前预警时间超过2 h后,及时疏散下游淹没范围内的居民可使生命损失率降低为0。研究方法可实现堰塞湖应急处置时的快速定量风险评估,并为其应急处置决策提供技术支撑。

轴向荷载作用下小规格拉铆钉和普通螺栓疲劳性能对比研究

拉铆钉因其良好的防松动、抗疲劳和防腐性能以及较强的环境适应性等特点而被广泛应用于航空航天、轨道交通、桥梁建筑等领域。为解决光伏支架中螺栓连接易发生疲劳的问题,现研究一种国产新型拉铆钉的轴向疲劳性能,用以代替普通螺栓连接进而提高光伏支架的疲劳寿命。对LMY8和LMY10小规格拉铆钉及同规格的普通螺栓进行了轴向荷载作用下的静力试验和疲劳试验,并利用ABAQUS软件进行了拉铆钉铆接过程的模拟,利用FE-Safe软件对拉铆钉疲劳寿命进行了模拟。研究结果表明:在同样条件下,铆钉的疲劳性能优于普通螺栓的疲劳性能;拉铆钉在轴向荷载作用下的疲劳断口位于套环和锁紧环槽啮合的第一圈螺纹处,此处应力集中是拉铆钉发生疲劳失效的主要原因;拉铆钉的疲劳寿命会随着最小荷载的增大而提高,随最大荷载的增大而降低;由疲劳云图可知,拉铆钉在承受轴向循环荷载作用时,铆钉头部下方R角过渡处也会产生较大的应力,此区域也是易发生疲劳失效的部位。

A Bayesian Inference of Non-Life Insurance Based on Claim Counting Process with Periodic Claim Intensity

The aim of this study is to propose an estimation approach to non-life insurance claim counts related to the insurance claim counting process, including the non-homogeneous Poisson process (NHPP) with a bell-shaped intensity and a beta-shaped intensity. The estimating function, such as the zero mean martingale (ZMM), is used as a procedure for parameter estimation of the insurance claim counting process, and the parameters of model claim intensity are estimated by the Bayesian method. Then,Λ(t), the compensator of N(t) is proposed for the number of claims in a time interval (0,t]. Given the process over the time interval (0,t]., the situations are presented through a simulation study and some examples of these situations are also depicted by a sample path relating N(t) to its compensatorΛ(t).

基于加速退化试验的漏电信号调理电路性能退化及可靠性研究

在电子电路服役过程中,元器件退化会引起电路输出特性变化,降低电子电路的可靠性。漏电信号调理电路作为一种电子电路,其可靠性直接决定了漏电断路器的可靠性。以漏电信号调理电路为研究对象,首先基于灵敏度分析方法确定影响电路性能退化的关键元器件,并对漏电信号调理电路进行了以温度为加速应力、动作电流值为退化特征量的恒定应力加速退化试验;其次根据不同温度应力下的试验数据建立基于Wiener过程的漏电信号调理电路性能退化模型,并利用极大似然估计法求取退化模型的未知参数,进而得出寿命预测的概率密度函数和可靠度函数;最后利用阿伦尼斯(Arrhenius)方程外推出正常应力下漏电信号调理电路的预测寿命。相关结论可为不同电子电路的寿命预测及可靠度分析提供支撑。

氯氧镁水泥混凝土中涂层钢筋的锈蚀劣化模型研究

为了推进钢筋氯氧镁水泥混凝土(magnesium oxychloride cement reinforced concrete,MOCRC)在西部地区的深度应用,设计模拟西部地区盐渍土环境、气候环境的室内加速破坏试验,研究涂层在多因素破坏试验环境下对钢筋的保护效果。利用电化学工作站测试试件的极化曲线和腐蚀电流密度,选用腐蚀电流密度作为Wiener随机退化过程的退化指标,建立随机退化过程的可靠度函数预测模型。结果表明:涂层在多因素试验环境下对钢筋的保护效果弱于纯浸泡试验环境下对钢筋的保护效果;通过可靠度函数寿命预测模型能够确定,MOCRC在不同浓度2%、4%、6%、8%氯化钠盐溶液室内多因素加速破坏试验环境下达到中等腐蚀破坏的时间分别为4000、3500、1400、400d。

基于两阶段随机维纳过程的机车车轮剩余寿命预测

为探究机车车轮退化过程中呈现的两阶段特征问题,提出一种基于两阶段维纳过程的车轮剩余寿命预测方法。利用两阶段维纳过程模型建立车轮轮缘退化模型,通过随机化漂移系数表征车轮退化过程中存在的个体差异;利用期望最大化(expectation maximum,EM)算法及贝叶斯理论实现了退化模型参数的离线估计与在线更新;通过Schwarz信息准则(Schwarz information criterion,SIC)判断并找到车轮退化过程中存在的变点;最后通过某机车车轮实测轮缘退化数据进行了实例验证。结果表明:与单阶段退化模型相比,考虑存在变点的两阶段退化模型更符合现场实际且在车轮80%寿命分位点处预测精度提升了9.42%。剩余寿命预测结果可以为车轮镟修周期的优化提供一定的理论依据。

食用菌预制菜的工艺配方研究及保质期预测

为丰富食用菌预制菜产品种类并解决预制菜储藏和运输的问题,通过运用高温反压式杀菌技术和加速破坏性试验(accelerated shelf-life testing,ASLT),开发出了一种复配型食用菌预制菜配方,并预测了其常温储藏保质期。采用3种食用菌为主要原料制作食用菌配方预制菜,加入猪五花肉、胡萝卜等配料,通过单因素和正交试验优化了其配方组成,获得了感官接受度较高的配方。配方组成为杏鲍菇200 g、香菇150 g、黑木耳50 g、猪五花肉70 g、胡萝卜30 g、香辣酱15 g、食盐1.2 g、蚝油1 g。该配方产品通过真空包装、高温反压式杀菌(121℃,20 min)和加速破坏性试验,预测在20℃下的保质期为195.4 d,满足常温储藏要求。通过对食用菌预制菜生产工艺的研究,证明了常温储藏食用菌预制菜的可行性。

基于AHP-模糊评价分析法的社区老年人售药机设计研究

为了提升社区生活环境中老年人用户售药机的使用体验,以及解决老年人在自主购药中的问题,在注重城市社区生活环境背景的同时,更加科学合理地对售药机设计方案进行创新。聚焦传统售药机的使用需求和使用习惯,以及现有老年人售药机存在的问题,运用AHP层次分析法将相对应的设计因素进行归纳总结,从操作、造型、人机和老年人需求4个方面构建社区老年人售药机的多层级分析模型,并归纳计算影响因素评价指标的权重;最后通过模糊综合评价分析法对设计方案进行评价,以判断设计方案是否具有可行性。将AHP与模糊评价分析法结合,使主观的设计需求转为客观准确的分析,并且通过模糊评价分析法验证结果的合理性,为老年人售药机提供有效客观的设计方法。通过对社区老年人售药机的分析和设计,提出了AHP-模糊评价分析法的集成模型应用于老年人售药机设计的可行性。

典型生物质发酵制取燃料乙醇环境影响分析

结合生命周期评价方法与层次分析方法对杨木、玉米秸秆、甘蔗渣3种典型纤维素生物质的发酵制取燃料乙醇工艺进行环境影响评价。针对酸化、富营养化、全球变暖、化石能源消耗、光化学污染、人体毒性6种环境类型进行分析对比,并选取3个不同视角分析生物质发酵工艺所带来的环境影响。结果表明:农业阶段和生产阶段所产生的温室效应在全生命周期过程中占比最高;全球性视角下,全球变暖影响占比较高;区域性和局地性视角下,工艺的酸化影响最严重。

再生水回用对典型污水处理工艺生态效应的影响

再生水回用是降低水污染、改善水环境、提高水资源利用率的重要途径,但这一过程同步增加了药剂和能源的消耗,以及温室气体排放等。研究再生水回用对典型污水处理工艺的生态效应影响,可为污水处理策略的全过程优化提供支持。文中采用生命周期评价法,从元素资源消耗(ADPE)、化石燃料消耗(ADPF)、臭氧层耗竭(ODP)、全球变暖(GWP)、酸化(AP)、富营养化(EP)、淡水生态毒性(FAETP)、陆地生态毒性(TETP)和人类毒性(HTP)9种环境效应,对比分析了常规污水处理工艺AAO和再生水处理工艺AAO+MBR的生态效应。结果表明,AAO+MBR工艺对EP的削减效果是AAO工艺的1.1倍,污水处理效果优于单独使用厌氧/缺氧/好氧(AAO)工艺;AAO+膜生物反应器(MBR)工艺对ADPE、ADPF、ODP、GWP、AP、FAETP、TETP、HTP的负面影响均高于AAO工艺;进一步在20%、40%、60%、80%和100%不同再生水回用率情景下比较AAO工艺和AAO+MBR工艺对9种环境效应的影响,发现再生水回用率显著影响ADPE、ADPF、FAETP、ODP,当再生水回用率为100%时,对环境影响下降45%~100%;对AP、GWP、TETP、HTP的影响较小,当再生水回用率为100%时,对环境影响下降17%~25%;对EP影响则不显著,随着再生水回用率变化,EP基本保持不变。研究可为污水处理决策优化提供支持。