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Chinese Journal of Aeronautics 2019年第3期32卷 627-638页

作者： Diyin TANG Jinrong CAO Jinsong YU School of Automation Science and Electrical Engineering Beihang University Collaborative Innovation Center of Advanced Aero-Engine

For critical engineering systems such as aircraft and aerospace vehicles, accurate remaining Useful Life(RUL) prediction not only means cost saving, but more importantly, is of great significance in ensuring system reliability and preventing disaster. RUL is affected not only by a system's intrinsic deterioration, but also by the operational conditions under which the system is operating. This paper proposes an RUL prediction approach to estimate the mean RUL of a continuously degrading system under dynamic operational conditions and subjected to condition monitoring at short equi-distant intervals. The dynamic nature of the operational conditions is described by a discrete-time Markov chain, and their influences on the degradation signal are quantified by degradation rates and signal jumps in the degradation model. The uniqueness of our proposed approach is formulating the RUL prediction problem in a semi-Markov decision process framework, by which the system mean RUL can be obtained through the solution to a limited number of equations. To extend the use of our proposed approach in real applications, different failure standards according to different operational conditions are also considered. The application and effectiveness of this approach are illustrated by a turbofan engine dataset and a comparison with existing results for the same dataset.

关键词： Condition-specific failure threshold Degradation modeling Dynamic operational conditions remaining useful life Semi-Markov decision process

remaining useful life prediction of lithium-ion batteries using a fusion method based on Wasserstein GAN

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The Journal of China Universities of Posts and Telecommunications 2020年第1期27卷 1-9页

作者： Zhou Wending Bao Shijian Xu Fangmin Zhao Chenglin School of Telecommunication Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China China International Engineering Consulting Corporation Beijing 100048China

Lithium-ion batteries are the main power supply equipment in many fields due to their advantages of no memory, high energy density, long cycle life and no pollution to the environment. Accurate prediction for the remaining useful life(RUL) of lithium-ion batteries can avoid serious economic and safety problems such as spontaneous combustion. At present, most of the RUL prediction studies ignore the lithium-ion battery capacity recovery phenomenon caused by the rest time between the charge and discharge cycles. In this paper, a fusion method based on Wasserstein generative adversarial network(GAN) is proposed. This method achieves a more reliable and accurate RUL prediction of lithium-ion batteries by combining the artificial neural network(ANN) model which takes the rest time between battery charging cycles into account and the empirical degradation models which provide the correct degradation trend. The weight of each model is calculated by the discriminator in the Wasserstein GAN model. Four data sets of lithium-ion battery provided by the National Aeronautics and Space Administration(NASA) Ames Research Center are used to prove the feasibility and accuracy of the proposed method.

关键词： remaining useful life lithium-ion battery battery capacity recovery fusion method Wasserstein generative adversarial network(GAN)

remaining Useful Life Prediction of Rolling Element Bearings Based on Different Degradation Stages and Particle Filter

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Transactions of Nanjing University of Aeronautics and Astronautics 2019年第3期36卷 432-441页

作者： LI Qing MA Bo LIU Jiameng Beijing Key Laboratory of High?End Mechanical Equipment Health Monitoring and Self?recovery Beijing University of Chemical Technology

A method is proposed to improve the accuracy of remaining useful life prediction for rolling element bearings,based on a state space model(SSM)with different degradation stages and a particle *** model is improved by a method based on the Paris formula and the Foreman formula allowing the establishment of different degradation *** remaining useful life of rolling element bearings can be predicted by the adjusted model with inputs of physical data and operating status *** late operating trend is predicted by the use of the particle filter *** rolling bearing full life experimental data validate the proposed ***,the prediction result is compared with the single SSM and the Gamma model,and the results indicate that the predicted accuracy of the proposed method is higher with better practicability.

关键词： different life stages of state space model remaining useful life prediction of rolling element bearing particle filter

Characteristics of remaining oil viscosity in water-and polymer-flooding reservoirs in Daqing Oilfield

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Science China Earth Sciences 2010年第12期53卷 72-83页

作者： XU ZhengShun,ZHANG JuHe,FENG ZiHui,FANG Wei & WANG FengLan Exploration and Development Research Institute,Daqing Oilfield Company Ltd.,Daqing 163712,China Exploration and Development Research Institute Daqing Oilfield Company Ltd. Daqing China

The experimental analysis of 21 crude oil samples shows a good correlation between high molecular-weight hydrocarbon components (C 40+) and ***-four remaining oil samples extracted from oil sands of oilfield development coring wells were analyzed by high-temperature gas chromatography (HTGC),for the relative abundance of C 21-,C 21-C 40 and C 40+ *** relationship between viscosity of crude oil and C 40+ (%) hydrocarbons abundance is used to expect the viscosity of remaining *** mobility characteristics of remaining oil,the properties of remaining oil,and the next displacement methods in reservoirs either water-flooded or polymer-flooded are studied with rock permeability,oil saturation of coring wells,*** experimental results show that the hydrocarbons composition,viscosity,and mobility of remaining oil from both polymer-flooding and water-flooding reservoirs are heterogeneous,especially the *** abundance of C 21- and C 21-C 40 hydrocarbons in polymer-flooding reservoirs is lower than that of water-flooding,but with more abundance of C 40+ *** is then suggested that polymer flooding must have driven more C 40- hydrocarbons out of reservoir,which resulted in relatively enriched C 40+,more viscous oils,and poorer *** oil in water-flooding reservoirs is dominated by moderate viscosity oil with some low viscosity oil,while polymer-flooding mainly contained moderate viscosity oil with some high viscosity *** each oilfield and reservoir,displacement methods of remaining oil,viscosity,and concentration by polymer-solution can be adjusted by current viscosity of remaining oil and mobility ratio in a favorable range.A new basis and methods are suggested for the further development and enhanced oil recovery of remaining oil.

关键词： remaining oil viscosity mobility ratio water-flooding polymer-flooding heterogeneity polymer-solution viscosity

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Methods for predicting the remaining useful life of equipment in consideration of the random failure threshold

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Journal of Systems Engineering and Electronics 2020年第2期31卷 415-431页

作者： WANG Zezhou CHEN Yunxiang CAI Zhongyi GAO Yangjun WANG Lili Equipment Management&UAV Engineering College Air Force Engineering UniversityXi’an 710051China

The value range of the failure threshold will generate an uncertain influence on the prediction results for the remaining useful life(RUL) of equipment. Most of the existing studies on the RUL prediction assume that the failure threshold is a fixed value,as they have difficulty in reflecting the random variation of the failure threshold. In connection with the inadequacies of the existing research, an in-depth analysis is carried out to study the effect of the random failure threshold(RFT) on the prediction results for the RUL. First, a nonlinear degradation model with unit-to-unit variability and measurement error is established based on the nonlinear Wiener process. Second, the expectation-maximization(EM) algorithm is used to solve the estimated values of the parameters of the prior degradation model, and the Bayesian method is used to iteratively update the posterior distribution of the random coefficients. Then, the effects of three types of RFT constraint conditions on the prediction results for the RUL are analyzed, and the probability density function(PDF) of the RUL is derived. Finally,the degradation data of aero-turbofan engines are used to verify the correctness and advantages of the method.

关键词： remaining useful life(RUL)prediction random failure threshold(RFT) nonlinear Wiener process measurement error unit-to-unit variability

Seismic hazard level reduction for existing buildings considering remaining building lifespans

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Earthquake Engineering and Engineering Vibration 2019年第3期18卷 649-661页

作者： Ji-Hun Park Division of Architecture and Urban Design Incheon National University

Seismic hazard levels lower than those for design of new buildings have been permitted for seismic evaluation and retrofi t of existing buildings due to the relatively short remaining lifespans. The seismic hazard reduction enables costeff ective seismic evaluation and retrofi t of existing buildings with limited structural capacity. The current study proposes seismic hazard reduction factors for Korea, one of low to moderate seismicity regions. The seismic hazard reduction factors are based on equal probabilities of non-exceedance within diff erent remaining building lifespans. A validation procedure is proposed to investigate equality of seismic risk in terms of ductility-based limit states using seismic fragility assessment of nonlinear SDOF systems, of which retrofi t demands are determined by the displacement coeffi cient method of ASCE 41-13 for diff erent target remaining building lifespans and corresponding reduced design earthquakes. Validation result shows that the use of seismic hazard reduction factors can be permitted in conjunction with appropriate lower bounds of the remaining building lifespans.

关键词： seismic hazard level existing building remaining building lifespan probability of limit state

remaining Useful Life Prediction of Turbofan Engine Using Hybrid Model Based on Autoencoder and Bidirectional Long Short-Term Memory

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Journal of Shanghai Jiaotong university(Science) 2018年第S1期23卷 85-94页

作者：宋亚石郭陈乐懿黄鑫沛夏唐斌 State Key Laboratory of Mechanical System and Vibration Department of Industrial EngineeringSchool of Mechanical Engineering Shanghai Jiao Tong University

Turbofan engine is a critical aircraft component with complex structure and high-reliability requirements. Effectively predicting the remaining useful life(RUL) of turbofan engines has essential significance for developing maintenance strategies and reducing maintenance costs. Considering the characteristics of large sample size and high dimension of monitoring data, a hybrid health condition prediction model integrating the advantages of autoencoder and bidirectional long short-term memory(BLSTM) is proposed to improve the prediction accuracy of RUL. Autoencoder is used as a feature extractor to compress condition monitoring data. BLSTM is designed to capture the bidirectional long-range dependencies of features. A hybrid deep learning prediction model of RUL is constructed. This model has been tested on a benchmark dataset. The results demonstrate that this autoencoder-BLSTM hybrid model has a better prediction accuracy than the existing methods, such as multi-layer perceptron(MLP), support vector regression(SVR), convolutional neural network(CNN) and long short-term memory(LSTM). The proposed model can provide strong support for the health management and maintenance strategy development of turbofan engines.

关键词： remaining useful life(RUL) autoencoder bidirectional long short-term memory(BLSTM) deep learning

Insight into the remaining high surface energy of atmospheric DBD plasma-treated polyethylene web after three months' aging

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Plasma Science and Technology 2019年第1期21卷 79-86页

作者：李花王正铎杨丽珍陈强 Laboratory of Plasma Physics & Materials Beijing Institute of Graphic Communication

In this paper, we report the modification of polyethylene(45 μm in thickness) webs through a roll-to-roll dielectric barrier discharge plasma treatment in an open atmospheric *** work differs from the normal adopted corona discharge treatment at an atmospheric pressure, in that three monomers: allylamine, acrylic acid, and ethanol, are inlet into the discharge zone by argon(Ar) carrier gas. As a comparison, Ar plasma treatment is also carried out. We focus on the aging properties of treated plastics in the open air. It is found that the modified webs can retain the surface energy as high as 50.0?±?1 mN m^(-1) for more than three months. After characterization of the as-prepared and aged samples by the surface roughness, the wettability, and the chemical structure, the mechanism of retaining high surface energy is then presumed. We think that the initial high surface energy just after plasma treatment is correlated to the grafted functional groups, while the over 50.0 mN m^(-1) remaining surface energy after three month aging is due to the stable concentrations of oxygen-contained and nitrogencontained groups by post-reaction on the surfaces.

关键词： aging atmospheric DBD treatment polyethylene surface energy remaining

remaining Useful Life Model and Assessment of Mechanical Products: A Brief Review and a Note on the State Space Model Method

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Chinese Journal of Mechanical Engineering 2019年第1期32卷 11-30页

作者： Yawei Hu Shujie Liu Huitian Lu Hongchao Zhang School of Mechanical Engineering Dalian University of Technology Department of Construction & Operations Management South Dakota State University Department of Industrial Engineering Texas Tech University

The remaining useful life(RUL) prediction of mechanical products has been widely studied for online system performance reliability, device remanufacturing, and product safety(safety awareness and safety improvement). These studies incorporated many di erent models, algorithms, and techniques for modeling and assessment. In this paper, methods of RUL assessment are summarized and expounded upon using two major methods: physics model based and data driven based methods. The advantages and disadvantages of each of these methods are deliberated and compared as well. Due to the intricacy of failure mechanism in system, and di culty in physics degradation observation, RUL assessment based on observations of performance variables turns into a science in evaluating the degradation. A modeling method from control systems, the state space model(SSM), as a first order hidden Markov, is presented. In the context of non-linear and non-Gaussian systems, the SSM methodology is capable of performing remaining life assessment by using Bayesian estimation(sequential Monte Carlo). Being e ective for non-linear and non-Gaussian dynamics, the methodology can perform the assessment recursively online for applications in CBM(condition based maintenance), PHM(prognostics and health management), remanufacturing, and system performance reliability. Finally, the discussion raises concerns regarding online sensing data for SSM modeling and assessment of RUL.

关键词： remaining useful life State space model Online assessment Bayesian estimation Particle filter Remanufacturing

remaining Oil Distribution Law and Potential Tapping Strategy of Horizontal Well Pattern in Narrow Oil Rim Reservoir with Gas Cap and Edge Water

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World Journal of Engineering and Technology 2019年第3期7卷 355-364页

作者： Xiaolin Zhu Zongbin Liu Xinran Wang Zhiqiang Meng Qin Zhu Tianjin Branch of CNOOC (China) Limited Tianjin China

For thin oil rim reservoir with gas cap and edge water, it is helpful to improve the development effect to find out the distribution law of remaining oil in this kind of reservoirs. For this reason, taking the narrow oil rim reservoir with gas cap and edge water of Oilfield A in Bohai Sea as a case, the main controlling factors, including reservoir structure, fault, gas cap energy, edge water energy and well pattern, affecting the distribution of residual oil in this kind of reservoir were analyzed by using the data of core, logging, paleogeomorphology and production. Then, the distribution law of remaining oil was summarized. Generally, the remaining oil distribution is mainly potato-shaped or strip-shaped in plane. Vertically, it depends on the energy of gas cap and edge water. For the reservoir with big gas gap and weak edge water, the remaining oil mainly lies in the bottom of oil column. And for the reservoir with small gas gap and strong edge water, the remaining oil mainly locates at the top of oil column. Aiming at different distribution modes of remaining oil, the corresponding potential tapping strategies of horizontal wells are put forward: in the late stage of development, for the reservoir with big gas gap and weak edge water, the remaining oil concentrates at the bottom of the oil column, and the position of horizontal well should be placed at the lower 1/3 to the lower 1/5 of the oil column;for the reservoir with small gas cap and strong edge water, the remaining oil locates at the top of the oil column, and the position of horizontal well should be put at the upper 1/5 to the upper 1/3 of the oil column height, vertically. Based on the study on remaining oil of Oilfield A, a potential tapping strategy of well pattern thickening and vertical position optimization of horizontal well was proposed. This strategy guided the efficient implementation of the comprehensive adjustment plan of the oilfield. Moreover, 18 infill development wells were implemented

关键词： Thin Oil Rim Reservoir with Gas Cap and Edge Water Horizontal Well Pattern remaining Oil Vertical Position Optimization Well Pattern Thickening