163 research outputs found
Modeling dependent competing failure processes with degradation-shock dependence
No full textInternational audienceIn this paper, we develop a new reliability model for dependent competing failure processes (DCFPs), which accounts for degradation-shock dependence. This is a type of dependence where random shock processes are influenced by degradation processes. The degradation-shock dependence is modeled by assuming that the intensity function of the nonhomogeneous Poisson process describing the random shock processes is dependent on the degradation processes. The dependence effect is modeled with reference to a classification of the random shocks in three “zones” according to their magnitudes, damage zone, fatal zone, and safety zone, with different effects on the system’s failure behavior. To the best of the authors’ knowledge, this type of dependence has not yet been considered in reliability models. Monte Carlo simulation is used to calculate the system reliability. A realistic application is presented with regards to the dependent failure behavior of a sliding spool, which is subject to two dependent competing failure processes, wear and clamping stagnation. It is shown that the developed model is capable of describing the dependent competing failure behaviors and their dependence
An Interview with Deanna Fei, Author of A Thread of Sky
No full textDeanna Fei is author of A Thread of Sky (Penguin Press, 2010), a novel about three generations of women in a Chinese American family. Here, she talks with recent UC Irvine graduate Mengfei Chen.
Mengfei Chen: What were some of your inspirations in writing the book? How did it begin? What experiences informed your writing?
Deanna Fei: A Thread of Sky is the story of a family of Chinese American women who reunite for a tour of their ancestral home. It was inspired by a trip through China’s “must-sees” that I embarked on ten years ago with my mother, my sisters, my aunt and my grandmother — six strong-willed, complicated women herded together for two weeks on a package tour. I was struck by the dramatic possibilities of this set-up, as well as the questions it raised about home and identity, culture and authenticity, travel and migration, history and memory. The tour took place at the end of a year I’d spent studying Chinese at Beijing Normal University. I’d thought I was ready to move on to the next stage of my life: teaching in New York, studying creative writing. But a few years later, I hadn’t stopped thinking about that tour. I started scribbling notes, and the characters began taking on lives of their own, completely apart from their real-life counterparts, and soon I was writing a novel.
I knew that in order to write about my characters’ travels through China with the necessary depth and immediacy, I needed to return. This time, I went back on a Fulbright Grant, intending to stay for another year, researching contemporary Chinese history and soaking up modern life in Shanghai while making periodic trips to the cities on my characters’ itinerary. I became so immersed in my research and writing that my stay eventually stretched to three years, during which my understanding of China continually evolved — and I expect it always will
An Interview with Deanna Fei, Author of A Thread of Sky
No full textDeanna Fei is author of A Thread of Sky (Penguin Press, 2010), a novel about three generations of women in a Chinese American family. Here, she talks with recent UC Irvine graduate Mengfei Chen.
Mengfei Chen: What were some of your inspirations in writing the book? How did it begin? What experiences informed your writing?
Deanna Fei: A Thread of Sky is the story of a family of Chinese American women who reunite for a tour of their ancestral home. It was inspired by a trip through China’s “must-sees” that I embarked on ten years ago with my mother, my sisters, my aunt and my grandmother — six strong-willed, complicated women herded together for two weeks on a package tour. I was struck by the dramatic possibilities of this set-up, as well as the questions it raised about home and identity, culture and authenticity, travel and migration, history and memory. The tour took place at the end of a year I’d spent studying Chinese at Beijing Normal University. I’d thought I was ready to move on to the next stage of my life: teaching in New York, studying creative writing. But a few years later, I hadn’t stopped thinking about that tour. I started scribbling notes, and the characters began taking on lives of their own, completely apart from their real-life counterparts, and soon I was writing a novel.
I knew that in order to write about my characters’ travels through China with the necessary depth and immediacy, I needed to return. This time, I went back on a Fulbright Grant, intending to stay for another year, researching contemporary Chinese history and soaking up modern life in Shanghai while making periodic trips to the cities on my characters’ itinerary. I became so immersed in my research and writing that my stay eventually stretched to three years, during which my understanding of China continually evolved — and I expect it always will
A stochastic hybrid systems model of common-cause failures of degrading components
No full textCommon-Cause Failures (CCFs) are an important threat to safety critical systems. Most existing CCF models assume that the component failure behavior does not vary over time. Such an assumption is often challenged in practice due to the influence of various degradation mechanisms, e.g., wear, corrosion, fatigue, etc. In this paper, we develop a new model for CCFs considering components degradation. The model is developed in the mathematical framework of Stochastic Hybrid Systems (SHS). The CCFs are modeled as random shock processes that affect a group of components simultaneously and the components degradation processes are modeled by stochastic differential equations derived from physics-of-failures. The benefit of using the SHS model for CCFs is that the developed model is analytically solvable. The system reliability can, then, also be solved analytically in closed form. The proposed CCF modelling framework is demonstrated by a numerical example of a three-unit redundant system and, then, applied to an Auxiliary Feedwater Pump (AFP) system of a Nuclear Power Plant (NPP). A comparison to the Binomial Failure Rate (BFR) model of literature shows that by considering the components degradation processes, the proposed model can accurately describe the CCF effect on the reliability of a system with degrading components
A stochastic hybrid systems based framework for modeling dependent failure processes.
No full textIn this paper, we develop a framework to model and analyze systems that are subject to dependent, competing degradation processes and random shocks. The degradation processes are described by stochastic differential equations, whereas transitions between the system discrete states are triggered by random shocks. The modeling is, then, based on Stochastic Hybrid Systems (SHS), whose state space is comprised of a continuous state determined by stochastic differential equations and a discrete state driven by stochastic transitions and reset maps. A set of differential equations are derived to characterize the conditional moments of the state variables. System reliability and its lower bounds are estimated from these conditional moments, using the First Order Second Moment (FOSM) method and Markov inequality, respectively. The developed framework is applied to model three dependent failure processes from literature and a comparison is made to Monte Carlo simulations. The results demonstrate that the developed framework is able to yield an accurate estimation of reliability with less computational costs compared to traditional Monte Carlo-based methods
A Sequential Bayesian Approach for Remaining Useful Life Prediction of Dependent Competing Failure Processes
No full textA sequential Bayesian approach is presented for remaining useful life (RUL) prediction of dependent competing failure processes (DCFP). The DCFP considered comprises of soft failure processes due to degradation and hard failure processes due to random shocks, where dependency arises due to the abrupt changes to the degradation processes brought by the random shocks. In practice, random shock processes are often unobservable, which makes it difficult to accurately estimate the shock intensities and predict the RUL. In the proposed method, the problem is solved recursively in a two-stage framework: in the first stage, parameters related to the degradation processes are updated using particle filtering, based on the degradation data observed through condition monitoring; in the second stage, the intensities of the random shock processes are updated using the Metropolis-Hastings algorithm, considering the dependency between the degradation and shock processes, and the fact that no hard failure has occurred. The updated parameters are, then, used to predict the RUL of the system. Two numerical examples are considered for demonstration purposes and a real dataset from milling machines is used for application purposes. Results show that the proposed method can be used to accurately predict the RUL in DCFP conditions
Application of reliability technologies in civil aviation: Lessons learnt and perspectives
No full textWe consider reliability engineering in modern civil aviation industry, and the related engineering activities and methods. We consider reliability in a broad sense, referring to other system characteristics that are related to it, like availability, maintainability, safety and durability. We covered the entire lifecycle of the equipment, including reliability requirement identification, reliability analysis and design, verification and validation of reliability requirements (typically involved in the equipment design and development phase), quality assurance (which typically enters in the manufacturing phase), and fault diagnosis and prognosis and maintenance (which are connected to the operation phase). Lessons learnt from reliability engineering practices in civil aviation industry are given, which might serve as reference for reliability managers and engineers, also from other industries with high reliability requirements
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