Bidirectional Testing for Repairable Systems Reliability: Power Asymmetries, Panel of Control Charts, and Reliability Graphics

To a practitioner who chooses to be on the safe side, we offer an option between a cocktail of tests and a solo one-size-fits-all test as a needed antidote to power asymmetries. Two bidirectional tests are first established to empower a basic pair of tests as asymmetrical performances. Unsurprisingly, we’ve seen either bidirectional device championing in one alternative setting, but also being turned against the very setting altered with just one of the composed elements. Progressing by filtering out the bad and enhancing the good, we assemble a hybrid from the empowered pair to restore power symmetries that are thought to be automatic and required for quality assurance. Data elaborated by the maximum power-deficits certify that the hybrid, termed as the dual bidirectional test, is robust with essential quality assurance in addition to a user-friendly version for the practitioners conducting the work. To further substantiate the applicability of a p-value induced dual bidirectional test, we challenge the legendary Laplace test to a duel. The outcomes reveal some elaborate concerns associated with the defending champion while supporting the challenger as an all-purpose test and a safe bet for practitioners doing the applicable real-world case studies. We extend the statistical process control architecture to an all-in-one panel of coherent bidirectional control charts fit for group sequential testing and multisystem. The charting tools start with a basic pair of tests that are more complementary than competitive, and are bound together with a common set of control limits. Another unified control limits, partners of an empowered pair of tests, form a second bidirectional control chart. And, a series of novel group sequential control charts, centering on a hybrid of the empowered pair, characterize the test as the only tool possessing the unique feature of having proxies that are free of the system sample size and the sampling schemes. It is, therefore, capable of producing a one-size-fits-all control chart, to be considered in equipment performance assessments of repairable systems and, by extension, other applications. Moreover, we start the development by showing a simple dot-plot that cumulates all the dot-jumps up to each time-point of occurrences and leaves us an often mysterious but meaningful footprint to shed any light on. Its mystery lies in the sequence of the slopes and/or curvature associated with each corresponding hill edging up. We then launch elaborated graphics panels to gain a broad perspective on the data analysis to exchange information, support one another, share findings of reliability trends and the change-point(s) from both directions, and even interconnected with power asymmetries. A cocktail of bidirectional tests is a social lubricant in the saga of absorbing graphics to make it easier to collaborate on new and/or improved technologies in reliability engineering and, by extension, other applications

Decision-Making in Reuse of Highway Bridge Foundations

According to the 2019 National Bridge Inventory data from Federal Highway Administration, the average age of highway bridges in the U.S.A. is 45 years, with almost 43% of existing highway bridges being older than 50 years, and eight percent of all U.S. national highway bridges being in poor condition. Foundation and substructure of existing highway bridges (over land and water) may have significant functional values even after being under service for decades. Reusing an existing bridge foundation during the reconstruction of a bridge (e.g., major rehabilitation, retrofitting, replacement of superstructure and substructure, and addition/removal of a span) has the potential for significant savings on total cost and construction time. However, because of uncertainties in the evaluation of integrity, durability, and load-carrying capacity of an existing foundation, an inevitable level of risk is inherently associated with their reuse. This risk may weigh on potential benefits of reuse of a bridge foundation during the decision making. Therefore, developing a comprehensive framework and procedure for studying the feasibility of foundation reuse is an important step in the foundation reuse decision process. In particular, bridge owners need to have an estimation of various risks associated with available options during a reconstruction project (i.e., fully reuse, partial reuse, and no- reuse). In this dissertation, a decision-making framework is developed to evaluate the feasibility of reusing an existing foundation and substructure of highway bridges. This framework incorporates three factors including safety, cost, and environmental impacts of reusing an existing foundation and compares the available alternatives to find the most feasible alternative. Four general options in bridge reconstruction projects are defined. The time-dependent probability of failure, time-dependent consequences of failure, and subsequently time-dependent safety risk associated with available options are estimated using a comprehensive reliability-based approach. In the next step, bridge life-cycle costs of each of the options are estimated using deterministic and probabilistic approaches. Later, the environmental impacts of each option are estimated using Life-cycle Environmental Impact Assessment (LCIEA). The combination of results of risk analysis, bridge life-cycle costs analysis, and environmental impacts assessment of all options are used to compare the reuse attractiveness of four options. The comparison is conducted by implementing a pairwise comparison technique to incorporate three criteria of safety, life-cycle costs, and environmental impacts of each option. The final decision on the reuse of an existing bridge foundation is made using the Analytical Hierarchy Process (AHP). Finally, Oxford Valley Road Bridge over US-1 in Bucks County, PA is used as a case study to demonstrate application of the proposed framework

Nonlinear Dynamics

This volume covers a diverse collection of topics dealing with some of the fundamental concepts and applications embodied in the study of nonlinear dynamics. Each of the 15 chapters contained in this compendium generally fit into one of five topical areas: physics applications, nonlinear oscillators, electrical and mechanical systems, biological and behavioral applications or random processes. The authors of these chapters have contributed a stimulating cross section of new results, which provide a fertile spectrum of ideas that will inspire both seasoned researches and students

Un cadre holistique de la modélisation de la dégradation pour l’analyse de fiabilité et optimisation de la maintenance de systèmes de sécurité nucléaires

Components of nuclear safety systems are in general highly reliable, which leads to a difficulty in modeling their degradation and failure behaviors due to the limited amount of data available. Besides, the complexity of such modeling task is increased by the fact that these systems are often subject to multiple competing degradation processes and that these can be dependent under certain circumstances, and influenced by a number of external factors (e.g. temperature, stress, mechanical shocks, etc.). In this complicated problem setting, this PhD work aims to develop a holistic framework of models and computational methods for the reliability-based analysis and maintenance optimization of nuclear safety systems taking into account the available knowledge on the systems, degradation and failure behaviors, their dependencies, the external influencing factors and the associated uncertainties.The original scientific contributions of the work are: (1) For single components, we integrate random shocks into multi-state physics models for component reliability analysis, considering general dependencies between the degradation and two types of random shocks. (2) For multi-component systems (with a limited number of components):(a) a piecewise-deterministic Markov process modeling framework is developed to treat degradation dependency in a system whose degradation processes are modeled by physics-based models and multi-state models; (b) epistemic uncertainty due to incomplete or imprecise knowledge is considered and a finite-volume scheme is extended to assess the (fuzzy) system reliability; (c) the mean absolute deviation importance measures are extended for components with multiple dependent competing degradation processes and subject to maintenance; (d) the optimal maintenance policy considering epistemic uncertainty and degradation dependency is derived by combining finite-volume scheme, differential evolution and non-dominated sorting differential evolution; (e) the modeling framework of (a) is extended by including the impacts of random shocks on the dependent degradation processes.(3) For multi-component systems (with a large number of components), a reliability assessment method is proposed considering degradation dependency, by combining binary decision diagrams and Monte Carlo simulation to reduce computational costs.Composants de systèmes de sûreté nucléaire sont en général très fiable, ce qui conduit à une difficulté de modéliser leurs comportements de dégradation et d'échec en raison de la quantité limitée de données disponibles. Par ailleurs, la complexité de cette tâche de modélisation est augmentée par le fait que ces systèmes sont souvent l'objet de multiples processus concurrents de dégradation et que ceux-ci peut être dépendants dans certaines circonstances, et influencé par un certain nombre de facteurs externes (par exemple la température, le stress, les chocs mécaniques, etc.).Dans ce cadre de problème compliqué, ce travail de thèse vise à développer un cadre holistique de modèles et de méthodes de calcul pour l'analyse basée sur la fiabilité et la maintenance d'optimisation des systèmes de sûreté nucléaire en tenant compte des connaissances disponibles sur les systèmes, les comportements de dégradation et de défaillance, de leurs dépendances, les facteurs influençant externes et les incertitudes associées.Les contributions scientifiques originales dans la thèse sont:(1) Pour les composants simples, nous intégrons des chocs aléatoires dans les modèles de physique multi-états pour l'analyse de la fiabilité des composants qui envisagent dépendances générales entre la dégradation et de deux types de chocs aléatoires.(2) Pour les systèmes multi-composants (avec un nombre limité de composants):(a) un cadre de modélisation de processus de Markov déterministes par morceaux est développé pour traiter la dépendance de dégradation dans un système dont les processus de dégradation sont modélisées par des modèles basés sur la physique et des modèles multi-états; (b) l'incertitude épistémique à cause de la connaissance incomplète ou imprécise est considéré et une méthode volumes finis est prolongée pour évaluer la fiabilité (floue) du système; (c) les mesures d'importance de l'écart moyen absolu sont étendues pour les composants avec multiples processus concurrents dépendants de dégradation et soumis à l'entretien; (d) la politique optimale de maintenance compte tenu de l'incertitude épistémique et la dépendance de dégradation est dérivé en combinant schéma volumes finis, évolution différentielle et non-dominée de tri évolution différentielle; (e) le cadre de la modélisation de (a) est étendu en incluant les impacts des chocs aléatoires sur les processus dépendants de dégradation.(3) Pour les systèmes multi-composants (avec un grand nombre de composants), une méthode d'évaluation de la fiabilité est proposé considérant la dépendance dégradation en combinant des diagrammes de décision binaires et simulation de Monte Carlo pour réduire le coût de calcul

Multi-hazard resilience assessment of river-crossing bridges

Title from PDF of title page viewed December 7, 2020Dissertation advisors: ZhiQiang Chen and Majid Bani-YaghoubVitaIncludes bibliographical references (pages 216-233)Thesis (Ph.D.)--School of Computing and Engineering and Department of Mathematics and Statistics. University of Missouri--Kansas City, 2020Bridge structures are required to possess high reliability and robustness against the concurrent effect of extreme loads and environmental attacks. To achieve such interrelated goals, it is necessary to assess the system performance and resilience subjected to multi-hazard impacts and the beneficial effects of any retrofitting or hazard-countermeasure in a lifecycle context. The damaged bridge needs to be restored rapidly over its service life due to the significant economic losses and disruption to transportation networks. For river-crossing bridges, one of the essential hazard mitigation strategies is scour countermeasures. However, a quantitative understanding of the effects of SCs on bridge system resilience is not found. This dissertation presents a critical synthesis of the existing literature that provides relevant knowledge and a profound understanding of probabilistic multi-hazard assessment for bridge structures. Then, a finite element-based probabilistic framework is designed to assess the lifecycle resilience of reinforced concrete river-crossing bridges under seismic, flood-induced scour, and chloride-induced corrosion impacts, including the consideration of a typical scour countermeasure at variable service times. Based on the general performance-based approach, two probabilistic models are formulated, termed the mean-scour fragility analysis (MS-FA) model and the total-scour demand hazard analysis (TS-DHA) model, which produce straightforward functional curves and can be readily used to evaluate the seismic-scour multi-hazard effects. An integrated damage index is defined based on both local and system-level ductility demands to develop a demand hazard model and to estimate the damage-based residual functionality and recovery duration to quantify the lifecycle bridge resilience. Notably, the exceeding probability approach is designed to reveal how progressive and sudden hazards interact and result in resilience degradation and how scour countermeasures contribute to resilience enhancement. The outcomes of the numerical experiment reveal the positive and distinct effects of implementing SCs at different lifecycle intervals. More importantly, resilience time-series demonstrate arbitrary multi-modes and nonparametric patterns. Accordingly, a robust statistical distance-based approach is presented to determine the sequential evolution of time-varying multi-hazard resilience. The proposed framework would assist stakeholders and decision-makers in resilience patterns recognition, assessing the effectiveness of hazard mitigation strategies, and taking short- and long-term proactive intervention actions by specifying resilience thresholds.Introduction -- Probabilistic multi-hazard performance assessment and damage effects on bridges -- Lifecycle resilience quantification of bridges under multiple hazards -- Effect of scour countermeasure on resilience of river -crossing bridges -- Time-varying resilience quantification using nonparametric distance -- Conclusions and future work -- Appendice

Failure Diagnosis and Prognosis of Safety Critical Systems: Applications in Aerospace Industries

Many safety-critical systems such as aircraft, space crafts, and large power plants are required to operate in a reliable and efficient working condition without any performance degradation. As a result, fault diagnosis and prognosis (FDP) is a research topic of great interest in these systems. FDP systems attempt to use historical and current data of a system, which are collected from various measurements to detect faults, diagnose the types of possible failures, predict and manage failures in advance. This thesis deals with FDP of safety-critical systems. For this purpose, two critical systems including a multifunctional spoiler (MFS) and hydro-control value system are considered, and some challenging issues from the FDP are investigated. This research work consists of three general directions, i.e., monitoring, failure diagnosis, and prognosis. The proposed FDP methods are based on data-driven and model-based approaches. The main aim of the data-driven methods is to utilize measurement data from the system and forecast the remaining useful life (RUL) of the faulty components accurately and efficiently. In this regard, two dierent methods are developed. A modular FDP method based on a divide and conquer strategy is presented for the MFS system. The modular structure contains three components:1) fault diagnosis unit, 2) failure parameter estimation unit and 3) RUL unit. The fault diagnosis unit identifies types of faults based on an integration of neural network (NN) method and discrete wavelet transform (DWT) technique. Failure parameter estimation unit observes the failure parameter via a distributed neural network. Afterward, the RUL of the system is predicted by an adaptive Bayesian method. In another work, an innovative data-driven FDP method is developed for hydro-control valve systems. The idea is to use redundancy in multi-sensor data information and enhance the performance of the FDP system. Therefore, a combination of a feature selection method and support vector machine (SVM) method is applied to select proper sensors for monitoring of the hydro-valve system and isolate types of fault. Then, adaptive neuro-fuzzy inference systems (ANFIS) method is used to estimate the failure path. Similarly, an online Bayesian algorithm is implemented for forecasting RUL. Model-based methods employ high-delity physics-based model of a system for prognosis task. In this thesis, a novel model-based approach based on an integrated extended Kalman lter (EKF) and Bayesian method is introduced for the MFS system. To monitor the MFS system, a residual estimation method using EKF is performed to capture the progress of the failure. Later, a transformation is utilized to obtain a new measure to estimate the degradation path (DP). Moreover, the recursive Bayesian algorithm is invoked to predict the RUL. Finally, relative accuracy (RA) measure is utilized to assess the performance of the proposed methods

Piikarbidi-MOSFET:n kiihdytetty ikäännyttäminen ja prognostiikka

The reliability investigations in power semiconductor components have traditionally concentrated on statistical analysis of the failure data in order to set regular maintenance intervals to prevent failures in the field. A more recent discipline, prognostics, in turn attempts to evaluate the current state-of-health of the device online and to predict the remaining useful life by interpreting signals of degradation. The utilization of prognostics is valuable to businesses as it enables addressing the maintenance only to the products close to failure. In this thesis we studied prognostics from the physics-based perspective in two types of silicon carbide power MOSFETs, in 11 samples in total. The components were aged in a power cycling test system to produce data of the selected failure precursor, drain-source on-state resistance. For the prognostic analysis we developed a kernel\hyp{}smoothing\hyp{}based particle filter and applied it to joint state\hyp{}parameter estimation of a selected sample. The analysis results indicated satisfactory performance regarding the estimation of the states and the parameters but revealed significant deficiencies in the prediction performance of the remaining useful life. Although the work mainly focuses on studying the power MOSFET as single component it is important to observe it also as a part of a larger entity. Therefore, at the end of the work we propose design principles for a new test system where the power MOSFET operates in a DC-DC converter. The derived precepts are based on the insight of reliability data analysis and prognostics gained during the study.Tehopuolijohdekomponenttien luotettavuustutkimukset ovat perinteisesti keskittyneet vikadatan tilastolliseen analyysiin säännöllisten huoltovälien asettamiseksi, joilla ehkäistään kentällä tapahtuvia vikaantumisia. Prognostiikka on uudempi tiedonala, joka puolestaan pyrkii määrittämään laitteen käytönaikaisen terveydentilan ja ennustamaan jäljellä olevan elinajan tulkitsemalla signaaleja huononemista. Prognostiikan hyödyntäminen on arvokasta liiketoiminnalle, sillä se mahdollistaa huollon kohdistamisen ainostaan niille laitteille, jotka ovat lähellä vikaantumista. Tässä diplomityössä tutkimme prognostiikkaa fysiikkaan pohjautuvasta näkökulmasta kahdessa erityyppisessä piikarbiditeho-MOSFET:ssa, kokonaisuudessaan 11 näytteessä. Komponentit ikäännytettiin tehosyklaustestissä nielulähdepäälläoloresistanssidatan keräämiseksi, joka valittiin vikaantumisindikaattoriksi. Prognostista analyysia varten kehitimme ydinsilotukseen perustuvan partikkelisuodattimen, jota sovelsimme yhdistetyyn tilaparametriestimointiin valitussa näytteessä. Analyysin tulokset osoittivat tyydyttävää suorituskykyä tilan ja parametrien estimointissa mutta paljastivat merkittäviä puutteita jäljellä olevan eliniän ennustamisessa. Vaikka työ pääosin keskittyy teho-MOSFET:n tutkimiseen yksittäisenä komponenttina, on tärkeä huomioda se myös osana suurempaa kokonaisuutta. Tämän vuoksi työn lopussa esitetään suunnitteluperiaatteita uutta testausjärjestelmää varten, jossa teho-MOSFET toimii DC-DC -muuntimessa. Johdetut ohjenuorat pohjaavat työn aikana kertyneelle ymmärrykselle luotettavuusdatan analysoinnista ja prognostiikasta

Radiation Detectors Noise Spectroscopy

Kadmium telurid je velmi důležitý materiál jak základního, tak i aplikovaného výzkumu. Je to dáno zejména jeho výhodnými elektronickými, optickými a strukturními vlastnostmi, které ho předurčují pro náročné technické aplikace. Dnes se hlavně používá pro jeho vysoké rozlišení k detekci a X-záření. Hlavní výhodou detektorů na bázi CdTe je, že nepotřebují chlazení a mohou spolehlivě fungovat i při pokojové teplotě. To způsobuje efektivnější interakce fotonů než je tomu u Si nebo jiných polovodičových materiálů. Obsahem této práce byla analýza a interpretace výsledků získaných studiem šumových a transportních charakteristik CdTe vzorků. Měření ukázaly že odpor homogenní části CdTe krystalů mírně klesá při připojení elektrického pole na vzorku. Při změně teploty navíc dochází k odlišné reakci u CdTe typu p a n. Právě těmto efektům je v práci věnována pozornost. Pomocí šumové spektroskopie bylo zjištěno, že při nízkých frekvencích je u vzorků dominantní šum typu 1/f, zatímco při vyšších frekvencích je sledován generačně-rekombinační šum a tepelný šum. Všechny měřené vzorky vykazovaly mnohem vyšší hodnotu šumu na nízkých frekvencích než udává Hoogeova rovnice. Byly nalezeny a popsány zdroje nadbytečného šumu.Cadmium Telluride is a material of great importance in the fields of both fundamental research and technical applications, because of its structural, optical, electronic and photoelectronic properties. Today the main application of Cadmium Telluride is in high resolution detection of -rays and X–rays. The main advantage of radiation detectors manufactured on CdTe base is that they need no cooling and can operate at the room temperature and there is a more effective interaction of photons in CdTe than in either Si or Ge. The transport and noise characteristics of CdTe samples were studied. The measurements show that the bulk resistance of CdTe single crystals decreases very slowly when the external electric field is applied. n-type samples and p-type samples show different response on the temperature changes. These effects were analyzed. The noise measurements show that dominant noise at low frequencies is type of 1/f noise. At higher frequencies generation-recombination and thermal noise were apparent. All the studied samples have very high value of low frequency noise, much higher than it should have been according to Hooge’s formula. The sources of excess noise were investigated.