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1
Hurdle, Emma Eileen. "System fault diagnosis using fault tree analysis." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/34678.
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Fault tree analysis is a method that describes all possible causes of a specified system state in terms of the state of the components within the system. Fault trees are commonly developed to analyse the adequacy of systems, from a reliability or safety point of view during the stages of design. The aim of the research presented in this thesis was to develop a method for diagnosing faults in systems using a model-based fault tree analysis approach, taking into consideration the potential for use on aircraft systems. Initial investigations have been conducted by developing four schemes that use coherent and non-coherent fault trees, the concepts of which are illustrated by applying the techniques to a simple system. These were used to consider aspects of system performance for each scheme at specified points in time. The results obtained were analysed and a critical appraisal of the findings carried out to determine the individual effectiveness of each scheme. A number of issues were highlighted from the first part of research, including the need to consider dynamics of the system to improve the method. The most effective scheme from the initial investigations was extended to take into account system dynamics through the development of a pattern recognition technique. Transient effects, including time history of flows and rate of change of fluid level were considered. The established method was then applied to a theoretical version of the BAE Systems fuel rig to investigate how the method could be utilised on a larger system. The fault detection was adapted to work with an increased number of fuel tanks and other components adding to the system complexity. The implications of expanding the method to larger systems such as a full aircraft fuel system were identified for the Nimrod MRA4.
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Beeson, Sally C. "Non coherent fault tree analysis." Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/6927.
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The aim of this thesis is to extend the current techniques available for the analysis of non-coherent fault trees. At present importance analysis of non-coherent systems is extremely limited. The majority of measures of importance that have been developed can only be used to analyse coherent fault trees. If these measures are used to analyse non-coherent fault trees the results obtained are inaccurate and misleading. Extensions for seven of the most commonly used measures of importance have been proposed to enable accurate analysis of non-coherent systems. The Binary Decision Diagram technique has been shown to provide an accurate and efficient means of analysing coherent fault trees. The application of this technique for the qualitative analysis of non-coherent fault trees has demonstrated the gains to be made in terms of efficiency and accuracy. Procedures for quantifying a non-coherent fault tree using this technique have been developed; these techniques enable significantly more efficient and accurate analysis than the conventional techniques for Fault Tree Analysis. Although the Binary Decision Diagram technique provides an efficient and accurate means of analysing coherent and non-coherent fault trees, large trees with many repeated events cannot always be analysed exactly. In such circumstances partial analysis must be performed if any conclusions regarding system safety and reliability are to be drawn. Culling techniques employed in conjuncfion with the Binary Decision Diagram method have been developed for the partial analysis of both coherent and non-coherent fault trees.
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Mason, Russell William. "Fault isolator tool for software fault tree analysis." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA294399.
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Sinnamon, Roslyn M. "Binary decision diagrams for fault tree analysis." Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/7424.
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This thesis develops a new approach to fault tree analysis, namely the Binary Decision Diagram (BDD) method. Conventional qualitative fault tree analysis techniques such as the "top-down" or "bottom-up" approaches are now so well developed that further refinement is unlikely to result in vast improvements in terms of their computational capability. The BDD method has exhibited potential gains to be made in terms of speed and efficiency in determining the minimal cut sets. Further, the nature of the binary decision diagram is such that it is more suited to Boolean manipulation. The BDD method has been programmed and successfully applied to a number of benchmark fault trees. The analysis capabilities of the technique have been extended such that all quantitative fault tree top event parameters, which can be determined by conventional Kinetic Tree Theory, can now be derived directly from the BDD. Parameters such as the top event probability, frequency of occurrence and expected number of occurrences can be calculated exactly using this method, removing the need for the approximations previously required. Thus the BDD method is proven to have advantages in terms of both accuracy and efficiency. Initiator/enabler event analysis and importance measures have been incorporated to extend this method into a full analysis procedure.
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Bäckström, Karl, and Andreas Linder. "Fault Tree Analysis of Quick Clay Slides." Thesis, KTH, Jord- och bergmekanik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-299065.
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Quick clay slides are quite rare but often leads to major consequences for the society. These type of slides are complex and the true causes leading to a slide is difficult to map since the evidence is destroyed during the slide. Because of this, different theories develop of the causes of the slide based on the same information. It is also problematic to back-calculate the sliding event because the commonly applied concept of perfectly plastic limite quilibrium cannot be applied on many of the landslides in quick clay. The objectives of this thesis were to construct a fault tree that facilitate risk identification and risk analysis of quick clay slides and to evaluate the applicability of the constructed fault tree, especially in the feasibility study and design phase. Uncertainties within the subject require a careful approach when dealing with quick clay. An implementation of a fault tree for quick clay slides in a risk management could reduce the risk of a slide and better understand the phenomenon. Two case studies were approached with the created fault tree and two advanced calculation methods that account for the special behaviour of quickclay. The use of a qualitative fault tree analysis in combination with calculation methods enables an evaluation of isolated singular events that in the end can lead to a quick clay slide. With the possibility to study isolated events, the implementation of more advanced calculation methods may be facilitated in an early stage to predict and prevent quick clay slides.Kvicklerskred är sällsynta men leder ofta till stor skada för samhället. Dessa skred är komplexa och orsaken till utlösandet av skredet är svårt att identifiera då bevisen förstörs under händelseförloppet. Detta leder till att olika teorier om orsaken av kvicklerskred kan variera från samma information. Det är också svårt att beräkna skredets omlopp i efterhand den vanliga beräkningsmetoden baseras på idealplastiska samband, något som inte går att applicera på kvicklera. Målet med denna studie var att konstruera ett felträd som underlättar riskidentifiering och riskanalyser av kvicklerskred. Målet var även att utvärdera användandet av felträdet i en byggnadsprocess, framförallt under förstudien och under projekteringsskedet. Osäkerheter inom området kräver en försiktig arbetsmetod när kvicklera finns i områden. Att använda sig av ett felträd för kvicklerskred i en riskhantering skulle kunna minska risken för ett skred och samtidigt öka systemförståelsen över fenomenet. Två fallstudier gjordes med det konstruerade felträdet, under dessa fältstudier gjordes även beräkningar med två avancerade beräkningsmetoder som tar hänsyn till det töjningsmjukande beteendet hos kvicklera. Användningav ett kvalitativt felträd i kombination med beräkningsmetoder möjligör en utvärdering av isolerade händelser som i slutändan kan leda till ett kvicklerskred. Möjligheten av att studera isolerade händelser kan underlätta en implementering av mer avancerade beräkningsmetoder i ett tidigt skede och på så vis förutse och förhindra kvicklerskred.
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Reid, William Samuel. "Software fault tree analysis of concurrent Ada processes." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA284979.
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Reay, Karen A. "Efficient fault tree analysis using binary decision diagrams." Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/7579.
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The Binary Decision Diagram (BDD) method has emerged as an alternative to conventional techniques for performing both qualitative and quantitative analysis of fault trees. BDDs are already proving to be of considerable use in reliability analysis, providing a more efficient means of analysing a system, without the need for the approximations previously used in the traditional approach of Kinetic Tree Theory. In order to implement this technique, a BDD must be constructed from the fault tree, according to some ordering of the fault tree variables. The selected variable ordering has a crucial effect on the resulting BDD size and the number of calculations required for its construction; a bad choice of ordering can lead to excessive calculations and a BDD many orders of magnitude larger than one obtained using an ordering more suited to the tree. Within this thesis a comparison is made of the effectiveness of several ordering schemes, some of which have not previously been investigated. Techniques are then developed for the efficient construction of BDDs from fault trees. The method of Faunet reduction is applied to a set of fault trees and is shown to significantly reduce the size of the resulting BDDs. The technique is then extended to incorporate an additional stage that results in further improvements in BDD size. A fault tree analysis strategy is proposed that increases the likelihood of obtaining a BDD for any given fault tree. This method implements simplification techniques, which are applied to the fault tree to obtain a set of concise and independent subtrees, equivalent to the original fault tree structure. BDDs are constructed for each subtree and the quantitative analysis is developed for the set of BDDs to obtain the top event parameters and the event criticality functions.
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Sihite, Josep Franklin. "Failure Analysis of Power Transformer Based on Fault Tree Analysis." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/180498.
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Wang, Yanjun. "Development of a computer-aided fault tree synthesis methodology for quantitative risk analysis in the chemical process industry." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1347.
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There has been growing public concern regarding the threat to people and
environment from industrial activities, thus more rigorous regulations. The investigation
of almost all the major accidents shows that we could have avoided those tragedies with
effective risk analysis and safety management programs. High-quality risk analysis is
absolutely necessary for sustainable development.
As a powerful and systematic tool, fault tree analysis (FTA) has been adapted to
the particular need of chemical process quantitative risk analysis (CPQRA) and found
great applications. However, the application of FTA in the chemical process industry
(CPI) is limited. One major barrier is the manual synthesis of fault trees. It requires a
thorough understanding of the process and is vulnerable to individual subjectivity. The
quality of FTA can be highly subjective and variable.
The availability of a computer-based FTA methodology will greatly benefit the
CPI. The primary objective of this research is to develop a computer-aided fault tree
synthesis methodology for CPQRA. The central idea is to capture the cause-and-effect
logic around each item of equipment directly into mini fault trees. Special fault tree
models have been developed to manage special features. Fault trees created by this
method are expected to be concise. A prototype computer program is provided to
illustrate the methodology. Ideally, FTA can be standardized through a computer
package that reads information contained in process block diagrams and provides
automatic aids to assist engineers in generating and analyzing fault trees.
Another important issue with regard to QRA is the large uncertainty associated
with available failure rate data. In the CPI, the ranges of failure rates observed could be
quite wide. Traditional reliability studies using point values of failure rates may result in
misleading conclusions. This dissertation discusses the uncertainty with failure rate data
and proposes a procedure to deal with data uncertainty in determining safety integrity
level (SIL) for a safety instrumented system (SIS). Efforts must be carried out to obtain
more accurate values of those data that might actually impact the estimation of SIL. This
procedure guides process hazard analysts toward a more accurate SIL estimation and
avoids misleading results due to data uncertainty.
10
Andersson, Johan. "Automated Fault Tree Generation from Requirement Structures." Thesis, Linköpings universitet, Fordonssystem, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-122471.
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The increasing complexity of today’s vehicles gives drivers help with everything from adaptive cruisecontrol to warning lights for low fuel level. But the increasing functionality also increases the risk offailures in the system. To prevent system failures, different safety analytic methods can be used, e.g.,fault trees and/or FMEA-tables. These methods are generally performed manually, and due to thegrowing system size the time spent on safety analysis is growing with increased risk of human errors. If the safety analysis can be automated, lots of time can be saved. This thesis investigates the possibility to generate fault trees from safety requirements as wellas which additional information, if any, that is needed for the generation. Safety requirements are requirements on the systems functionality that has to be fulfilled for the safety of the system to be guaranteed. This means that the safety of the truck, the driver, and the surroundings, depend on thefulfillment of those requirements. The requirements describing the system are structured in a graphusing contract theory. Contract theory defines the dependencies between requirements and connectsthem in a contract structure. To be able to automatically generate the fault tree for a system, information about the systems failure propagation is needed. For this a Bayesian network is used. The network is built from the contract structure and stores the propagation information in all the nodes of the network. This will result in a failure propagation network, which the fault tree generation will be generated from. The failure propagation network is used to see which combinations of faults in the system can violate thesafety goal, i.e., causing one or several hazards. The result of this will be the base of the fault tree. The automatic generation was tested on two different Scania systems, the fuel level displayand the dual circuit steering. Validation was done by comparing the automatically generated trees withmanually generated trees for the two systems showing that the proposed method works as intended. The case studies show that the automated fault tree generation works if the failure propagationinformation exists and can save a lot of time and also minimize the errors made by manuallygenerating the fault trees. The generated fault trees can also be used to validate written requirementsto by analyzing the fault trees created from them.
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Rutaganda, Remmy. "Automated Model-Based Reliability Prediction and Fault Tree Analysis." Thesis, Linköpings universitet, Institutionen för datavetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-67240.
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This work was undertaken as a final year project in Computer Engineering, within the Department of Computer and Information Science at Linköping University. At the Department of Computer and Information Science, work oriented at testing and analyzing applications is developed to provide solution approaches to problems that arise in system product development. One of the current applications being developed is the ‘Systemics Analyst’. The purpose of the application is to facilitate for system developers with an analysis tool permitting insights on system reliability, system critical components, how to improve the system and the consequences as well as risks of a system failure. The purpose of the present thesis was to enhance the ‘Systemics Analyst application’ by incorporating an ‘automated model-based reliability prediction’ and ‘fault tree analysis’ modules. This enables reliability prediction and fault tree analysis diagrams to be generated automatically from the data files and relieves the system developer from manual creation of the diagrams. The enhanced Systemics Analyst application managed to present the results in respective models using the new incorporated functionality. To accomplish the above tasks, ‘Systemics Analyst application’ was integrated with a library that handles automated model-based reliability prediction and fault tree analysis, which is described in this thesis. The reader will be guided through the steps that are performed to accomplish the tasks with illustrating figures, methods and code examples in order to provide a closer vision of the work performed.
12
Antony, Albin. "Fault tree analysis for automotive pressure sensor assembly lines." Diss., Online access via UMI:, 2006.
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Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Systems Science and Industrial Engineering Department, 2006.Includes bibliographical references.
13
Ridley, L. M. "Dependency modelling using fault-tree and cause-consequence analysis." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/7350.
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The technique of fault tree analysis is commonly used to assess the probability of failure of industrial systems. During the analysis of the fault tree the component failures are assumed to occur independently. When this condition is not satisfied alternative approaches such as the Markov method can be used. Constructing the Markov representation of a system is not such as intuitive process for engineers as fault tree construction since the state-transition diagram does not readily document the failure logic. In addition to this the size of the Markov diagram increases rapidly as the number of components in the system increases. This thesis presents the development of a new model which uses a combination of conventional fault tree methods with those of Markov methods to solve systems containing sequential or standby failures. New gates were developed in order to incorporate the dependent failures on the fault tree structure. The new assessment method was shown to efficiently solve these systems. With theses extended fault tree capabilities in place the technique was embedded within an optimisation framework to obtain the best system performance for systems containing standby failures. Sequential failures can be represented on a fault tree by using the Priority-And gate, however they can also be represented on a Cause-Consequence diagram. As with the fault tree analysis method, the Cause-Consequence Diagram method documents the failure logic of the system. In addition to this the Cause-Consequence Diagram produces the exact failure probability in a very efficient calculation procedure and has significant implications in terms of efficiency for static systems. Construction and analysis rules were devised for a cause-consequence diagram and used on systems containing independent and dependent failures.
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Taguchi, Genki. "Fault tree analysis of slurry and dewatered taiings management ??? a framework." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46292.
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Fault trees are used in reliability and risk analysis to develop the probability of occurrence of the top event, or failure mode. The top event results from a logical sequence, or combination, of lower level events using ???and??? and ???or??? logic. Probabilities for the basic events, i.e. the lowest level events identified, are calculated or estimated in order to calculate the probability for the top event.
This thesis develops a framework for fault tree analysis for failure of alternative tailings depositional schemes (slurry, thickened, paste and filtered). Failure is narrowly defined as the release of tailings to the environment. The following failure modes are evaluated for each of the depositional schemes: overtopping, static liquefaction, internal erosion, static slope instability and seismic slope instability. The fault trees are representative of potential failure sequences in the industry as a whole and not on site-specific conditions. Expert elicitation methods are used to select the likelihoods of the basic events.
Not all events in the fault trees are applicable to the range of depositional schemes, e.g. overtopping as a result of a large pool on slurry deposited tailings management facilities is not an event that will occur for filtered tailings. The outcome is that some of the events and parts of fault trees ???fall away??? as the tailings solids content increases. Apart from providing a visualization of the reduction in probability of occurrence of the top events for the failure modes, the results also provide a range of probabilities for the overall probability of failure for the range of tailings management options.
The framework is used to develop a site-specific likelihood of failure of the Bafokeng tailings facility. The result demonstrates that the fault tree framework can provide useful insights in both industry-wide and site-specific tailings management facility failure likelihoods.
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Needham, Donald Michael. "A formal approach to hazard decomposition in Software Fault Tree Analysis." Thesis, Monterey, California: Naval Postgraduate School, 1990. http://hdl.handle.net/10945/28230.
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As digital control systems are used in life-critical applications, assessment of the safety of these control systems becomes increasingly important. One means of formally performing this assessment is through fault tree analysis. Software Fault Tree Analysis (SFTA) starts with a system-level hazard that must be decomposed in a largely-human-intensive manner until specific modules of the software system are indicated. These modules can then be formally analyzed using statement templates. The focus of this thesis is to approach the decomposition of a system-level hazard from a formalized standpoint. Decomposition primarily proceeds along two distinct but interdependent dimensions, specificity of event and subsystem size. The Specificity-of-Event dimension breaks abstract or combined events into the specific system events that must be analyzed by the fault tree. The Subsystem-Size dimension deals with the scope of the hazard, and itemizes the subsystems where localized events may lead to the hazard. Decomposition templates are developed in this thesis to provide a framework for decomposing a system-level hazard to the point at which line-by-line code analysis can be conducted with existing statement templates. These templates serve as guides for conducting the decomposition, and ensure that as many as possible of all the applicable decomposition aspects are evaluated
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Ordonio, Robert Romero. "An automated tool to facilitate code translation for software fault tree analysis." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA273205.
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Alsaqqa, Obada. "Fuzzy Time-Delay Model in Fault-Tree Analysis for Critical Path Method." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429772426.
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Kevorkian, Christopher George. "UAS Risk Analysis using Bayesian Belief Networks: An Application to the VirginiaTech ESPAARO." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/73047.
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Small Unmanned Aerial Vehicles (SUAVs) are rapidly being adopted in the National Airspace (NAS) but experience a much higher failure rate than traditional aircraft. These SUAVs are quickly becoming complex enough to investigate alternative methods of failure analysis. This thesis proposes a method of expanding on the Fault Tree Analysis (FTA) method to a Bayesian Belief Network (BBN) model. FTA is demonstrated to be a special case of BBN and BBN can allow for more complex interactions between nodes than is allowed by FTA. A model can be investigated to determine the components to which failure is most sensitive and allow for redundancies or mitigations against those failures. The introduced method is then applied to the Virginia Tech ESPAARO SUAV.Master of Science
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Winter, Mathias William. "Software fault tree analysis of an automated control system device written in Ada." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA303377.
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Glaude, Robin Francoise. "Applicability of Uncertainty analysis to groundwater environmental risks through Fault Tree Analysis and Monte Carlo simulations." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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The Anthropocene epoch initiated by human in
uence on its Earth system (biosphere,
hydrosphere, ...) leads to an irreversible change: Global warming. Climate
change alters all existing natural processes, including the ones related to groundwater.
The present paper aims to study the occurrence's probability of two particular
groundwater risks: the generation of thermokarst lakes in permafrost environment
and its subsequent thermal consequences in the surroundings as well as seawater
intrusion inducing saltwater contamination in pumping wells. These processes are
dependent of physical parameters to which is attached uncertainty. Consequently,
two uncertainty analysis methods have been applied to determine the probability
of occurence of these undesired events: Fault Tree Analysis and Monte Carlo Simulation.
Beside the rough approximation performed to evaluate the probability of
thermokarst lake occurence (48%) and of talik development under these latter (73%)
by means of fault tree analysis, these high failure probabilities translate the urge to
slow down global warming due to the irreversible effect on permafrost environment,
meaning its thawing and releasing of trapped methane in the atmosphere. On the
other hand, Monte Carlo simulations have been performed to compare dfferent scenarii
related to seawater intrusion in Akrotiri aquifer in Cyprus. The results once
again translate the disastrous effect of climate change regarding the probability of
occurence of these unwanted events. Indeed, a failure probability around 6 times
greater (43%) is observed in the climate change scenario with respect to the reference
scenario (7%).
Uncertainty analysis is good methodology to apply to environmental concerns
to quantify the occurence's probability of these undesired events. This would urge
public authorities to perform decision making in order to avoid or reduce the failure's
probability of these groundwater issues that have irreversible consequences.
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Mauri, Guiseppe. "Integrating safety analysis techniques, supporting identification of common cause failures." Thesis, University of York, 2000. http://etheses.whiterose.ac.uk/10906/.
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Bhandaram, Abhinav. "Detecting Component Failures and Critical Components in Safety Critical Embedded Systems using Fault Tree Analysis." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1157555/.
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Component failures can result in catastrophic behaviors in safety critical embedded systems, sometimes resulting in loss of life. Component failures can be treated as off nominal behaviors (ONBs) with respect to the components and sub systems involved in an embedded system. A lot of research is being carried out to tackle the problem of ONBs. These approaches are mainly focused on the states (i.e., desired and undesired states of a system at a given point of time to detect ONBs). In this paper, an approach is discussed to detect component failures and critical components of an embedded system. The approach is based on fault tree analysis (FTA), applied to the requirements specification of embedded systems at design time to find out the relationship between individual component failures and overall system failure. FTA helps in determining both qualitative and quantitative relationship between component failures and system failure. Analyzing the system at design time helps in detecting component failures and critical components and helps in devising strategies to mitigate component failures at design time and improve overall safety and reliability of a system.
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Biteus, Jonas. "Fault Isolation in Distributed Embedded Systems." Doctoral thesis, Linköping : Vehicular Systems, Department of Electrical Engineering, Linköpings universitet, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8774.
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Bartlett, Lisa Marie. "Variable ordering heuristics for binary decision diagrams." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/10362.
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Fault tree analysis, FTA, is one of the most commonly used techniques for safety system assessment. Over the past five years the Binary Decision Diagram (BDD) methodology has been introduced which significantly aids the analysis of the fault tree diagram. The approach has been shown to improve both the efficiency of determining the minimal cut sets of the fault tree, and also the accuracy of the calculation procedure used to quantifY the top event parameters. To utilise the BDD technique the fault tree structure needs to be converted into the BDD format. Converting the fault tree is relatively straightforward but requires the basic events of the tree to be placed in an ordering. The ordering of the basic events is -critical to the resulting size of the BDD, and ultimately affects the performance and benefits of this technique. There are a number of variable ordering heuristics in the literature, however the performance of each depends on the tree structure being analysed. These heuristic approaches do not always yield a minimal BDD structure for all trees, some approaches generate orderings that are better for some trees but worse for others. Within this thesis three pattern recognition approaches, that of machine learning classifier systems, multi-layer perceptron networks and radial basis function neural networks, have been investigated to try and select a variable ordering heuristic for a given fault tree from a set of alternatives. In addition a completely new heuristic based on component structural importance measures has been suggested with significant improvement in producing the smallest BDD over those methods currently in the literature.
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Vestlund, Christian. "Threat Analysis on Vehicle Computer Systems." Thesis, Linköping University, Department of Computer and Information Science, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-53661.
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Vehicles have been around in our society for over a century, until recently they have been standalone systems. With increased amounts of initiatives to inter-network vehicles to avoid accidents and reduce environmental impact the view of a vehicle as a standalone system needs to be reconsidered. Networking and cooperation between vehicles requires that all systems and the information therein are trustworthy. Faulty or malicious vehicle systems are thus not limited to only affecting a single vehicle but also the entire network. The detection of anomalous behavior in a vehicle computer system is therefore of importance. To improve the vehicle systems we strive to achieve security awareness within the vehicle computer system. As a first step we will identify threats toward the vehicle computer system and what has been done to address them.
We perform a threat analysis consisting of fault trees and misuse cases to identify the threats. The fault trees provide away to connect the threats found with vehicle stakeholders' goals. The connection between stakeholder goals and threat highlights the need for threat mitigation.
Several research initiatives are discussed to find out what has been done to address the identified threats and to find the state of the research for security in vehicle computer system.
Lastly, an error model for the Controller Area Network (CAN) is proposed to model the consequences of threats applied to the CAN bus.
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Domis, Dominik [Verfasser]. "Integrating Fault Tree Analysis and Component-Oriented Model-Based Design of Embedded Systems / Dominik Domis." München : Verlag Dr. Hut, 2012. http://d-nb.info/1021072818/34.
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Fujino, Tomoyuki. "The development of a method for investigating construction site accidents using fuzzy fault tree analysis /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487848891514551.
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McGraw, Richard J. "Petri Net and Fault Tree analysis : combining two techniques for a software safety analysis on an embedded military application." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26162.
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Smith, Robin Lee. "Fault tree analysis and diagnostics development for PI-in-a-box with neurolab sleep and respiration experiment." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/46469.
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Zwack, Mathew R. "CONTRAST: A conceptual reliability growth approach for comparison of launch vehicle architectures." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53095.
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In 2004, the NASA Astronaut Office produced a memo regarding the safety of next generation launch vehicles. The memo requested that these vehicles have a probability of loss of crew of at most 1 in 1000 flights, which represents nearly an order of magnitude decrease from current vehicles. The goal of LOC of 1 in 1000 flights has since been adopted by the launch vehicle design community as a requirement for the safety of future vehicles. This research addresses the gap between current vehicles and future goals by improving the capture of vehicle architecture effects on reliability and safety.
Vehicle architecture pertains to the physical description of the vehicle itself, which includes manned or unmanned, number of stages, number of engines per stage, engine cycle types, redundancy, etc. During the operations phase of the vehicle life-cycle it is clear that each of these parameters will have an inherent effect on the reliability and safety of the vehicle. However, the vehicle architecture is typically determined during the early conceptual design phase when a baseline vehicle is selected. Unless a great amount of money and effort is spent, the architecture will remain relatively constant from conceptual design through operations. Due to the fact that the vehicle architecture is essentially “locked-in” during early design, it is expected that much of the vehicle's reliability potential will also be locked-in.
This observation leads to the conclusion that improvement of vehicle reliability and safety in the area of vehicle architecture must be completed during early design. Evaluation of the effects of different architecture decisions must be performed prior to baseline selection, which helps to identify a vehicle that is most likely to meet the reliability and safety requirements when it reaches operations. Although methods exist for evaluating reliability and safety during early design, weaknesses exist when trying to evaluate all architecture effects simultaneously.
The goal of this research was therefore to formulate and implement a method that is capable of quantitatively evaluating vehicle architecture effects on reliability and safety during early conceptual design. The ConcepTual Reliability Growth Approach for CompariSon of Launch Vehicle ArchiTectures (CONTRAST) was developed to meet this goal. Using the strengths of existing techniques a hybrid approach was developed, which utilizes a reliability growth projection to evaluate the vehicles. The growth models are first applied at the subsystem level and then a vehicle level projection is generated using a simple system level fault tree. This approach allows for the capture of all trades of interest at the subsystem level as well as many possible trades at the assembly level.
The CONTRAST method is first tested on an example problem, which compares the method output to actual data from the Space Transportation System (STS). This example problem illustrates the ability of the CONTRAST method to capture reliability growth trends seen during vehicle operations. It also serves as a validation for the development of the reliability growth model assumptions for future applications of the method.
The final chapter of the thesis applies the CONTRAST method to a relevant launch vehicle, the Space Launch System (SLS), which is currently under development.
Within the application problem, the output of the method is first used to check that the primary research objective has been met. Next, the output is compared to a state-of-the-art tool in order to demonstrate the ability of the CONTRAST method to alleviate one of the primary consequences of using existing techniques. The final section within this chapter presents an analysis of the booster and upper stage block upgrade options for the SLS vehicle. A study of the upgrade options was carried out because the CONTRAST method is uniquely suited to look at the effects of such strategies. The results from the study of SLS block upgrades give interesting observations regarding the desired development order and upgrade strategy. Ultimately this application problem demonstrates the merits of applying the CONTRAST method during early design. This approach provides the designer with more information in regard to the expected reliability of the vehicle, which will ultimately enable the selection of a vehicle baseline that is most likely to meet the future requirements.
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Bergström, Joakim, and Hampus Nilsson-Sundén. "Cost effective optimization of system safety and reliability." Thesis, Linköpings universitet, Fysik och elektroteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-119950.
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A method able to analyze and optimize subsystems could be useful to reduce project cost, increase subsystem reliability, improve overall aircraft safety and reduce subsystem weight. The earlier the optimization of development of an aircraft in the design phase can be performed, the better the yield of the optimization becomes. This master thesis was formed in order to construct an automatic analysis method, implementing a Matlab script, evaluating devices forming aircraft subsystems using a Genetic Algorithm. In addition to aircraft subsystems, the method constructed in the work is compatible with systems of various industries with minor modifications of the script.
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Primavera, Francesca. "Water Safety Plan and Fault Tree Analysis for the management and risk assessment of a drinking water supply system." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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This work of thesis studies the approach of the Water Safety Plan, that is applied to a part of the drinking water supply network managed by AIMAG S.p.A.
The Water Safety Plans have been introduced by the World Health Organization and have been identified as the most effective way to systematically guarantee the safety of the drinking water system, the quality of the water supplied, and the protection of the health of consumers. Through a preventive and qualitative analysis that includes risk assessment and management, the Water Safety Plans make it possible to guarantee over time the absence of potential physical, biological, and chemical hazards in the water available for consumption. The result obtained through the application of the Water Safety Plan involves the construction of a risk matrix, that allows the development of an improvement plan for the control of each hazard and associated risk (in priority scale). After that, the previously performed analysis is supported through the application of statistical and probabilistic techniques used in the reliability analysis to optimize the control activities based on a risk assessment. The first one is the Fault Tree Analysis, which is a deductive technique supported by Boolean algebra that focuses on a particular undesirable event and provides a method for identifying possible causes. In parallel with the application of the Fault Tree Analysis, the Monte Carlo method is applied, which is a computational method based on random sampling of certain variables to obtain numerical results. Finally, the result obtained through the application of both methodologies is the definition of the probability of failure of some nodes and internodes that are part of a portion of the drinking water supply network managed by AIMAG S.p.A.
At the end, the work of thesis lead to results which prove that the qualitative approach of the Water Safety Plans can be effective, especially if supported by different types of analysis.
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Levin, Pavel. "Computing Most Probable Sequences of State Transitions in Continuous-time Markov Systems." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/22918.
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Continuous-time Markov chains (CTMC's) form a convenient mathematical framework for analyzing random systems across many different disciplines. A specific research problem that is often of interest is to try to predict maximum probability sequences of state transitions given initial or boundary conditions. This work shows how to solve this problem exactly through an efficient dynamic programming algorithm. We demonstrate our approach through two different applications - ranking mutational pathways of HIV virus based on their probabilities, and determining the most probable failure sequences in complex fault-tolerant engineering systems. Even though CTMC's have been used extensively to realistically model many types of complex processes, it is often a standard practice to eventually simplify the model in order to perform the state evolution analysis. As we show here, simplifying approaches can lead to inaccurate and often misleading solutions. Therefore we expect our algorithm to find a wide range of applications across different domains.
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Belzer, Jessica A. "Unmanned Aircraft Systems in the National Airspace System: Establishing Equivalencyin Safety and Training Through a Fault Tree Analysis Approach." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1492778505498031.
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Riauke, Jelena. "SPEA2-based safety system multi-objective optimization." Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/5514.
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Safety systems are designed to prevent the occurrence of certain conditions and their future development into a hazardous situation. The consequence of the failure of a safety system of a potentially hazardous industrial system or process varies from minor inconvenience and cost to personal injury, significant economic loss and death. To minimise the likelihood of a hazardous situation, safety systems must be designed to maximise their availability. Therefore, the purpose of this thesis is to propose an effective safety system design optimization scheme. A multi-objective genetic algorithm has been adopted, where the criteria catered for includes unavailability, cost, spurious trip and maintenance down time. Analyses of individual system designs are carried out using the latest advantages of the fault tree analysis technique and the binary decision diagram approach (BDD). The improved strength Pareto evolutionary approach (SPEA2) is chosen to perform the system optimization resulting in the final design specifications. The practicality of the developed approach is demonstrated initially through application to a High Integrity Protection System (HIPS) and subsequently to test scalability using the more complex Firewater Deluge System (FDS). Computer code has been developed to carry out the analysis. The results for both systems are compared to those using a single objective optimization approach (GASSOP) and exhaustive search. The overall conclusions show a number of benefits of the SPEA2 based technique application to the safety system design optimization. It is common for safety systems to feature dependency relationships between its components. To enable the use of the fault tree analysis technique and the BDD approach for such systems, the Markov method is incorporated into the optimization process. The main types of dependency which can exist between the safety system component failures are identified. The Markov model generation algorithms are suggested for each type of dependency. The modified optimization tool is tested on the HIPS and FDS. Results comparison shows the benefit of using the modified technique for safety system optimization. Finally the effectiveness and application to general safety systems is discussed.
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Murtha, Justin Fortna. "An Evidence Theoretic Approach to Design of Reliable Low-Cost UAVs." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/33762.
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Small unmanned aerial vehicles (SUAVs) are plagued by alarmingly high failure rates. Because these systems are small and built at lower cost than full-scale aircraft, high quality components and redundant systems are often eschewed to keep production costs low. This thesis proposes a process to ``design in'' reliability in a cost-effective way. Fault Tree Analysis is used to evaluate a system's (un)reliability and Dempster-Shafer Theory (Evidence Theory) is used to deal with imprecise failure data. Three unique sensitivity analyses highlight the most cost-effective improvement for the system by either spending money to research a component and reduce uncertainty, swap a component for a higher quality alternative, or add redundancy to an existing component. A MATLAB$^{\circledR}$ toolbox has been developed to assist in practical design applications. Finally, a case study illustrates the proposed methods by improving the reliability of a new SUAV design: Virginia Tech's SPAARO UAV.Master of Science
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Aaron, Mandie. "An exploration of the applicability and utility of fault tree analysis to the diffusion of technological innovation in educational systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ59217.pdf.
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Kabir, Sohag, K. Aslansefat, I. Sorokos, Y. Papadopoulos, and Y. Gheraibia. "A Conceptual Framework to Incorporate Complex Basic Events in HiP-HOPS." Springer, 2019. http://hdl.handle.net/10454/17423.
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YesReliability evaluation for ensuring the uninterrupted system operation is an integral part of dependable system development. Model-based safety analysis (MBSA) techniques such as Hierarchically Performed Hazard Origin and Propagation Studies (HiP-HOPS) have made the reliability analysis process less expensive in terms of effort and time required. HiP-HOPS uses an analytical modelling approach for Fault tree analysis to automate the reliability analysis process, where each system component is associated with its failure rate or failure probability. However, such non-state-space analysis models are not capable of modelling more complex failure behaviour of component like failure/repair dependencies, e.g., spares, shared repair, imperfect coverage, etc. State-space based paradigms like Markov chain can model complex failure behaviour, but their use can lead to state-space explosion, thus undermining the overall analysis capacity. Therefore, to maintain the benefits of MBSA while not compromising on modelling capability, in this paper, we propose a conceptual framework to incorporate complex basic events in HiP-HOPS. The idea is demonstrated via an illustrative example.
DEIS H2020 Project under Grant 732242.
The full-text of this chapter will be released for public view at the end of the publisher embargo on 12 Oct 2021.
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BONFIETTI, GERSON. "Analise da confiabilidade do sistema de suprimento de energia eletrica de emergencia de um reator nuclear de pequeno porte." reponame:Repositório Institucional do IPEN, 2003. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11129.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Zornoza, Moreno Enrique. "Model-based approach for automatic generation of IEC-61025 standard compliant fault trees." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-40912.
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Reliability and safety of complex software-intensive systems are proved to be a crucial matter since most of these systems fulfil tasks, where a failure could lead to catastrophic consequences. For example, in space systems such as satellites, a failure could result in the loss of the satellite. Therefore, a certain level of reliability and safety must be assured for such systems to trust the services they provide. Standards set this level and put requirements for the analysis and assurance of these properties using documented evidence. In particular, European Cooperation for Space Standardization (ECSS) standards for space systems require Fault Tree Analysis(FTA) for identifying the causes of system failure and consequently safety hazards, as well as fault trees as evidence for the assurance of reliability and safety. In this thesis, we present a tool supported model-based approach to generate fault tree automatically from an existing system modelling and analysis toolset. CHESS is a system and dependability modelling toolset and integrates Concerto-FLA to enable the support of failure logic analysis. We proposed a model-based transformation from Concerto-FLA to fault tree model and implemented it as an Eclipse plugin in CHESS toolset. A case study is performed in the aerospace domain; more specifically we modelled Attitude Control System (ACS) and automatically generated IEC-61025-compliant fault trees.AMASS project
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CARVALHO, LUIZ S. "Frequencia de danos no nucleo por blecaute em reator nuclear de concepcao avancada." reponame:Repositório Institucional do IPEN, 2004. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11147.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Patil, Mayur. "Test Scenario Development Process and Software-in-the-Loop Testing for Automated Driving Systems." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1574794282029419.
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Marchello, Sara. "Analisi e valutazione dei rischi in edilizia con i metodi fault tree analysis (FTA) e failure mode and effect analysis (FMEA): il caso del rischio amianto." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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Il settore delle costruzioni è il comparto che ha subito più degli altri gli effetti negativi della crisi economica e di conseguenza è cambiata l’organizzazione al suo interno, sia nei rapporti di lavoro che nella sicurezza. Dai dati INAIL emerge un aspetto preoccupante: un incremento degli infortuni mortali e delle malattie professionali. Si può quindi affermare che non si muore solo in cantiere, ma anche a causa del lavoro.
In questo elaborato si fa riferimento alle malattie professionali causate dall’esposizione all’amianto; nello specifico si valuta il rischio di inalazione delle fibre di amianto durante la bonifica di una copertura realizzata in Eternit.
Si procede con una valutazione probabilistica del rischio, avvalendosi degli strumenti della Risk Analysis, Fault Tree Analysis (FTA) e Failure Mode and Effect Analysis (FMEA).
La valutazione del rischio attraverso la FTA si basa su un approccio di tipo backward, in cui partendo dal malfunzionamento del sistema, definito Top Event, si vanno a cercare le possibili cause scatenanti (eventi); al contrario, l’analisi FMEA si basa su un approccio di tipo forward, ovvero partendo da un set di eventi si procede in avanti per andare ad analizzare che tipo di malfunzionamento possono generare nel sistema.
Entrambi i metodi di analisi vengono applicati alle tre tecniche di bonifica, incapsulamento, confinamento e rimozione, analizzando per ciascuna le fasi operative, i macchinari e i prodotti da utilizzare, i DPI da indossare, valutando attentamente cosa occorre fare per operare in completa sicurezza.
Dallo studio emerge che i fattori principali associati al rischio amianto coinvolgono l’analisi e valutazione preliminare dello stato di fatto, l’utilizzo e la manutenzione dei DPI e dei macchinari e la supervisione durante le fasi salienti dei lavori. Si può quindi sostenere che formazione, informazione e addestramento dei lavoratori e un’analisi preventiva dell’opera sono alla base della sicurezza in cantiere.
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Nzekwe-Excel, Chinyere. "Development of an integrated framework for satisfaction assessment of construction project teams." Thesis, University of Wolverhampton, 2010. http://hdl.handle.net/2436/109166.
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With increasing competitive pressures in today‟s market, it has become critical for businesses to recognise the significance of satisfying their customers so as to ensure their economic stability. Various studies have emphasised on the need for customer focus and project satisfaction in the construction industry sector. The industry, however, has not fully embraced the practice of project satisfaction, which is grounded on meeting the needs of the customer. Though most research on project satisfaction has focussed on the client, it is essential that the satisfaction of the project delivery team and in the wider context, the stakeholders be considered. In this case, the client is the centre of gravity of the project team. In order to satisfy the project team, there are challenges in assessing their requirements. This necessitates the need to develop a unique and robust method for capturing and analysing the level of integrated project team satisfaction. In this research, the project delivery team and the stakeholders have been lumped together as an integrated project team. Therefore, integrated project team satisfaction entails recognising the client and project participants‟ requirements that guarantees project successful completion and acceptance by the team. In view of this, this research presents a framework, which has been developed to plug these needs and challenges. The framework, known as the Satisfaction Assessment Integrated Framework (SAIF) involves an integrated approach that considers the participants of a construction project as a tree structure, and each member of that tree as an intermediate or top element. Relationships and interactions of the elements, and how these affect the overall satisfaction levels of a single project, are analysed based on understanding their requirements and invoking modern satisfaction attainment theory. The framework includes a method for understanding and identifying the satisfaction attributes; multi-attribute analysis for prioritising the satisfaction attributes of the clients and project participants; fault tree analysis strategy for defining the satisfaction relationship in a particular project team; and an assessment scoring system (a combination of multi-attribute analysis, and failure mode and effects analysis methodical approach) that evaluates how much each member of the project team meets the requirements or satisfaction attributes of other participants. Hence, SAIF, a novel assessment methodology, investigates and identifies possible links and the influence of integrating the construction project team and their satisfaction attributes with the aim of improving their satisfaction levels as a team. Through the findings of this research, recommendations are made to further explore the implications of satisfying a given participant against dissatisfying the participant; and subsequently improve the satisfaction assessment process.
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Zhu, Weiqi, and ycqq929@gmail com. "An Investigation into Reliability Based Methods to Include Risk of Failure in Life Cycle Cost Analysis of Reinforced Concrete Bridge Rehabilitation." RMIT University. Civil, Environmental and Chemical Engineering, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080822.140447.
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Reliability based life cycle cost analysis is becoming an important consideration for decision-making in relation to bridge design, maintenance and rehabilitation. An optimal solution should ensure reliability during service life while minimizing the life cycle cost. Risk of failure is an important component in whole of life cycle cost for both new and existing structures. Research work presented here aimed to develop a methodology for evaluation of the risk of failure of reinforced concrete bridges to assist in decision making on rehabilitation. Methodology proposed here combines fault tree analysis and probabilistic time-dependent reliability analysis to achieve qualitative and quantitative assessment of the risk of failure. Various uncertainties are considered including the degradation of resistance due to initiation of a particular distress mechanism, increasing load effects, changes in resistance as a result of rehabilitation, environmental variables, material properties and model errors. It was shown that the proposed methodology has the ability to provide users two alternative approaches for qualitative or quantitative assessment of the risk of failure depending on availability of detailed data. This work will assist the managers of bridge infrastructures in making decisions in relation to optimization of rehabilitation options for aging bridges.
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Vargas, Carlos A. "Investigating construction falls using fault tree analysis and developing a prototype tool to reduce falls using expert system and computer assisted instrution methods /." The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu148795121493758.
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Durand, Marcus L. "The evaluation of methods for the prospective patient safety hazard analysis of ward-based oxygen therapy." Thesis, Cranfield University, 2009. http://dspace.lib.cranfield.ac.uk/handle/1826/4480.
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When even seemingly benign and routine processes fail in healthcare, people sometimes die. The profound effect on the patient’s families and the healthcare staff involved is clear (Vincent and Coulter, 2002), while further consequences are felt by the institution involved, both financially and by damage to reputation. The trend in healthcare for learning through experience of adverse events is no longer a viable philosophy (Department of Health,Sir Ian Carruthers OBE and Pauline Philip, 2006). In order to make progress towards preventative learning, three Prospective Hazard Analysis (PHA) methods used in other industries were evaluated for use in the area of ward based healthcare. Failure Modes and Effects Analysis (FMEA), Fault Tree Analysis (FTA) and Hazard and Operability Analysis (HAZOP) were compared to each other in terms of ease of use, information they provide and the manner in which it is presented. Their results were also compared to baseline data produced through empirical research. Oxygen Therapy was used in this research as an example of a common ward based therapy. The resulting analysis listed 186 hazards almost all of which could lead to death, especially if combined. FTA and FMEA provided better system coverage than HAZOP and identified more hazards than were contained in the initial hazard identification method common to both techniques. FMEA and HAZOP needed some modification before use, with HAZOP requiring the most extensive adjustment. FTA has a very useful graphical presentation and was the only method capable of displaying causal linkage, but required that hazards be translated into events for analysis. It was concluded that formal Prospective Hazard Analysis (PHA) was applicable to this area of healthcare and presented added value through a combination of detailed information on possible hazards and accurate risk assessment based on a combination of expert opinion and empirical data. This provides a mechanism for evidence based identification of hazard barriers and safeguards as well as a method for formal communication of results at any stage of an analysis. It may further provide a very valuable vehicle for documented learning through prospective analysis incorporating feedback from previous experience and adverse incidents. The clear definition of systems and processes that form part of these methods provides a valuable opportunity for learning and the enduring capture and dissemination of tacit knowledge that can be continually updated and used for the formulation of strategies for safety and quality improvement.
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da, Costa Rocha José. "A melhoria da disponibilidade do compensador estático da SE FTZ/CHESF através da análise da sua árvore de falhas." Universidade Federal de Pernambuco, 2008. https://repositorio.ufpe.br/handle/123456789/5267.
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Previous issue date: 2008Companhia Hidro Elétrica do São Francisco
Nos Sistemas Elétricos de Potência, os Compensadores Estáticos CE são equipamentos de elevada importância na regulação de tensão, tanto em regime permanente como em transitório, principalmente em sistemas onde os centros de carga estão localizados a grandes distâncias da geração. Esta dissertação, apresenta uma análise das causas de falha do Compensador Estático instalado na Subestação - SE de Fortaleza da Companhia Hidro Elétrica do São Francisco - CHESF, estado do Ceará, Brasil, com ênfase nas origens das falhas e em suas soluções, utilizando como ferramenta de análise a Árvore de Falhas deste Equipamento. Neste trabalho, encontramos a Árvore de Falhas do CE, composta por 62 eventos básicos, dos quais 20 apresentaram histórico suficiente para a análise paramétrica em um banco de dados de 22 anos. A partir das curvas de probabilidade de falha dos eventos básicos, elaborou-se um plano de ação com melhorias nos processos de manutenção, para viabilizar a elevação da disponibilidade do CE, com o objetivo de maximizar a remuneração da empresa Transmissora, no caso, a CHESF, e a confiabilidade do sistema de transmissão
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MONTOYA, CYNARA V. "Desenvolvimento de um sistema computacional de gerenciamento de riscos em processos de radioesterilizacao de tecidos biologicos." reponame:Repositório Institucional do IPEN, 2010. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9528.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Kabir, Sohag, M. Walker, Y. Papadopoulos, E. Rüde, and P. Securius. "Fuzzy temporal fault tree analysis of dynamic systems." 2016. http://hdl.handle.net/10454/17433.
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YesFault tree analysis (FTA) is a powerful technique that is widely used for evaluating system safety and reliability. It can be used to assess the effects of combinations of failures on system behaviour but is unable to capture sequence dependent dynamic behaviour. A number of extensions to fault trees have been proposed to overcome this limitation. Pandora, one such extension, introduces temporal gates and temporal laws to allow dynamic analysis of temporal fault trees (TFTs). It can be easily integrated in model-based design and analysis techniques. The quantitative evaluation of failure probability in Pandora TFTs is performed using exact probabilistic data about component failures. However, exact data can often be difficult to obtain. In this paper, we propose a method that combines expert elicitation and fuzzy set theory with Pandora TFTs to enable dynamic analysis of complex systems with limited or absent exact quantitative data. This gives Pandora the ability to perform quantitative analysis under uncertainty, which increases further its potential utility in the emerging field of model-based design and dependability analysis. The method has been demonstrated by applying it to a fault tolerant fuel distribution system of a ship, and the results are compared with the results obtained by other existing techniques.