Dissertations / Theses on the topic 'Tree risk'
To see the other types of publications on this topic, follow the link: Tree risk.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Tree risk.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Limér, Christoffer, and Erik Kalmér. "Monte Carlo Tree Search for Risk." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297695.
Full textAbstract:
The idea of using artificial intelligence to evaluatemilitary strategies is relevant for a large number of governmentstoday. With programs like AlphaZero beating world championsin games of ever-increasing complexity, military adaptations areprobably not far away, if they are not in use already. Partof these programs’ recent success is due to a heuristic searchalgorithm called Monte Carlo Tree Search. In this project,we explored the possibility of using this algorithm to build aprogram capable of playing the strategy board game of Riskat a high level. The complexity and stochastic dynamic ofthe game demanded the use of chance nodes and aggressivegameplay limitations, known as action-pruning. By changing theconditions and game environment of the algorithm, we observedperformance differences, mainly simulation length considerablyimproved convergence. We suggest that the created program,optimized with correct algorithm parameters, has the potentialof playing Risk at a high level.Tanken att använda artificiell intelligensför att evaluera militära strategierär relevant för ett stortantal regeringar idag. När program så som AlphaZero slårvärldsmästare i allt mer komplexa spel bör militära tillämpningarinte ligga långt borta, om de inte redanär implementerade. Endel av programmens framgång kan härledas till dess användningav en heuristisk sökalgoritm, kallad Monte Carlo-Trädsökning. Idet här projektet, utforskade vi möjligheten att använda dennaalgoritm för att konstruera ett program, kapabel att spela detstrategiska brädspelet Risk på en hög nivå. Spelets komplexitetoch stokastiska natur krävde användning av så kallade ”chance-nodes” och en aggressiv användning av spelbegränsningar kändasom ”action-pruning”. Genom attändra villkoren och spelmiljönför algoritmen observerades prestandaförändringar, där konver-gensen i huvudsakökade vid begränsningar av möjliga val. Viföreslår att det skapade programmet, optimerat med korrektaalgoritmparametrar, har potentialen att spela Risk på en högnivå.
Kandidatexjobb i elektroteknik 2020, KTH, Stockholm
2
Sandqvist, Joakim, and Erik Byström. "A Framework For Analysing Investable Risk Premia Strategies." Thesis, KTH, Industriell ekonomi och organisation (Inst.), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-147547.
Full textAbstract:
The focus of this study is to map, classify and analyse how different risk premia strategies that are fully implementable, perform and are affected by different economic environments. The results are of interest for practitioners who currently invest in or are thinking about investing in risk premia strategies. The study also makes a theoretical contribution since there currently is a lack of publicised work on this subject. A combination of the statistical methods cluster tree, spanning tree and principal component analysis are used to first categorise the investigated risk premia strategies into different clusters based on their correlation characteristics and secondly to find the strategies’ most important return drivers. Lastly, an analysis of how the clusters of strategies perform in different macroeconomic environments, here represented by inflation and growth, is conducted. The results show that the three most important drivers for the investigated risk premia strategies are a crisis factor, an equity directional factor and an interest rate factor. These three components explained about 18 percent, 14 percent and 10 percent of the variation in the data, respectively. The results also show that all four clusters, despite containing different types of risk premia strategies, experienced positive total returns during all macroeconomic phases sampled in this study. These results can be seen as indicative of a lower macroeconomic sensitivity among the risk premia strategies and more of an “alpha-like” behaviour.Denna studie fokuserar på att kartlägga, klassificera och analysera hur riskpremie-strategier, som är fullt implementerbara, presterar och påverkas av olika makroekonomiska miljöer. Studiens resultat är av intresse för investerare som antingen redan investerar i riskpremiestrategier eller som funderar på att investera. Studien lämnar även ett teoretiskt bidrag eftersom det i dagsläget finns få publicerade verk som behandlar detta ämne. För att analysera strategierna har en kombination av de statistiska metoderna cluster tree, spanning tree och principal component analysis använts. Detta för att dels kategorisera riskpremie-strategierna i olika kluster, baserat på deras inbördes korrelation, men också för att finna de faktorer som driver riskpremiestrategiernas avkastning. Slutligen har också en analys över hur de olika strategierna presterar under olika makroekonomiska miljöer genomförts där de makroekonomiska miljöerna representeras av inflation- och tillväxtindikatorer. Resultaten visar att de tre viktigaste faktorerna som driver riskpremiestrategiernas avkastning är en krisfaktor, en aktiemarknadsfaktor och en räntefaktor. Dessa tre faktorer förklarar ungefär 18 procent, 14 procent och 10 procent av den undersökta datans totala varians. Resultaten visar också att alla fyra kluster, trots att de innehåller olika typer av riskpremiestrategier, genererade positiv avkastning under alla makroekonmiska faser som studerades. Detta resultat ses som ett tecken på en lägre makroekonomisk känslighet bland riskpremiestrategier och mer av ett alfabeteende.
3
Tejedor, Garavito Natalia. "Impact of climate change on extinction risk of montane tree species." Thesis, Bournemouth University, 2014. http://eprints.bournemouth.ac.uk/21485/.
Full textAbstract:
The potential impacts of climate change on many species worldwide remains unknown, especially in those tropical regions that are centers of endemism and are highly biodiverse. This thesis provides an insight into the extinction risk of selected tree species using different species distribution modelling techniques and reviewing the current conservation status on montane forest in the Tropical Andes. Starting with a global analysis, the potential impacts of climate change on montane ecoregions is investigated, by identifying those that are more vulnerable to the expected changes in temperature and precipitation, from global predictions under different climate change scenarios. It then gives an insight on the current and potential threats to biodiversity in the Andean region, including the identification of those that are most likely to be responsible for increasing the extinction risk of the species. With the use of the IUCN Red List Categories and Criteria, selected tree species were assessed to identify their extinction risk. Information on the species’ current distribution was collated and used to estimate their potential distribution under climate change, by using different modelling techniques. These results were used to reassess the species using the IUCN Red List and establish the changes in Red List Category. Lastly, it provides a discussion that integrates all the results obtained throughout the thesis, to explore the implications for conservation, in order to highlight the overriding importance of including threatened tree species to target conservation efforts in the region, while considering the uncertainties that surround predictions under climate change scenarios, modelling techniques and the use of the IUCN Red List.
4
Srivastava, Anurag. "Generalized Event Tree Algorithm and Software for Dam Safety Risk Analysis." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/32.
Full textAbstract:
ABSTRACT: Event tree analysis is a most commonly used method in dam safety risk analysis modeling. Available software tools for performing event tree analyses lack the flexibility to efficiently address many important factors in dam safety risk analysis. As a result of these practical limitations, spreadsheets have been used, sometimes including Visual Basic macros, to perform these analyses. However, this approach lacks generality and can require significant effort to apply to a specific dam or to modify the event tree structure. In response to these limitations, here a generalized event tree analysis tool, DAMRAE (DAM safety Risk Analysis Engine), has been developed. It includes a graphical interface for developing and populating an event tree, and a tool for calculating and post-processing an event tree risk model for dam safety risk assessment in a highly flexible manner. This thesis describes the underlying theoretical and computational logic employed in the current version of DAMRAE, and provides a detailed example of the calculations in the current version of DAMRAE for an application to a US Army Corps of Engineers (USACE) dam. The thesis closes with some conclusions about the capabilities of DAMRAE and a summary of plans for its further development.
5
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.
Full textAbstract:
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.
6
Adams, Henry D., Greg A. Barron-Gafford, Rebecca L. Minor, Alfonso A. Gardea, Lisa Patrick Bentley, Darin J. Law, David D. Breshears, Nate G. McDowell, and Travis E. Huxman. "Temperature response surfaces for mortality risk of tree species with future drought." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/626267.
Full textAbstract:
Widespread, high levels of tree mortality, termed forest die-off, associated with drought and rising temperatures, are disrupting forests worldwide. Drought will likely become more frequent with climate change, but even without more frequent drought, higher temperatures can exacerbate tree water stress. The temperature sensitivity of drought-induced mortality of tree species has been evaluated experimentally for only single-step changes in temperature (ambient compared to ambient + increase) rather than as a response surface (multiple levels of temperature increase), which constrains our ability to relate changes in the driver with the biological response. Here we show that time-to-mortality during drought for seedlings of two western United States tree species, Pinus edulis (Engelm.) and Pinus ponderosa (Douglas ex C. Lawson), declined in continuous proportion with increasing temperature spanning a 7.7 degrees C increase. Although P. edulis outlived P. ponderosa at all temperatures, both species had similar relative declines in time-to-mortality as temperature increased (5.2% per degrees C for P. edulis; 5.8% per. C for P. ponderosa). When combined with the non-linear frequency distribution of drought duration-many more short droughts than long droughts-these findings point to a progressive increase in mortality events with global change due to warming alone and independent of additional changes in future drought frequency distributions. As such, dire future forest recruitment patterns are projected assuming the calculated 7-9 seedling mortality events per species by 2100 under business-as-usual warming occur, congruent with additional vulnerability predicted for adult trees from stressors like pathogens and pests. Our progressive projection for increased mortality events was driven primarily by the non-linear shape of the drought duration frequency distribution, a common climate feature of drought-affected regions. These results illustrate profound benefits for reducing emissions of carbon to the atmosphere from anthropogenic sources and slowing warming as rapidly as possible to maximize forest persistence.
7
Bolin, Jakob, and Nico Palmroos. "Monte-Carlo Tree Search Used for Fortification in the Game of Risk." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297698.
Full textAbstract:
The strategy game Risk is a very popular boardgame, requiring little effort to learn but lots of skill to master.The aim of this project is to explore the fortification phase of thegame, where the player’s troops are moved between territories.Our method is based on adapting Monte Carlo tree search(MCTS) to Risk. To improve the troop movements, we proposetwo techniques, hierarchical search and progressive bias. Thesemethods, combined with other extensions of MCTS are thencompared against a baseline player of the game. Our results showthat hierarchical search improved the MCTS agent’s playingpower and the progressive bias have potential to improve theagent but needs further investigation.Strategispelet Risk är ett väldigt populärt brädspel som är lätt att lära sig men svårt att bemästra. Syftet med detta projekt är att utforska spelets befästningsfas, där spelarens trupper flyttas mellan territorier. Vår metod är baserad på en anpassning av Monte Carlo trädsökning (MCTS) till Risk. För att förbättra trupprörelserna föreslår vi två tekniker, ”hierarchical search” och ”progressive bias”. Dessa metoder, i kombination med andra tillägg av MCTS, jämförs sedan mot en standard agent i spelet. Våra resultat visar att hierarchical search förbättrade MCTS agentens spelstyrka och att progressivce bias har möjlighet att förbättra agenten men kräver fortsatt utforskning.
Kandidatexjobb i elektroteknik 2020, KTH, Stockholm
8
Metzroth, Kyle G. "A Comparison of Dynamic and Classical Event Tree Analysis for Nuclear Power Plant Probabilistic Safety/Risk Assessment." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306185445.
Full text
9
Osborn, Douglas M. "Seamless Level 2 / Level 3 Probabilistic Risk Assessment Using Dynamic Event Tree Analysis." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1372524956.
Full text
10
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.
Full textAbstract:
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
11
Lundström, Love, and Oscar Öhman. "Machine Learning in credit risk : Evaluation of supervised machine learning models predicting credit risk in the financial sector." Thesis, Umeå universitet, Institutionen för matematik och matematisk statistik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-164101.
Full textAbstract:
When banks lend money to another party they face a risk that the borrower will not fulfill its obligation towards the bank. This risk is called credit risk and it’s the largest risk banks faces. According to the Basel accord banks need to have a certain amount of capital requirements to protect themselves towards future financial crisis. This amount is calculated for each loan with an attached risk-weighted asset, RWA. The main parameters in RWA is probability of default and loss given default. Banks are today allowed to use their own internal models to calculate these parameters. Thus hold capital with no gained interest is a great cost, banks seek to find tools to better predict probability of default to lower the capital requirement. Machine learning and supervised algorithms such as Logistic regression, Neural network, Decision tree and Random Forest can be used to decide credit risk. By training algorithms on historical data with known results the parameter probability of default (PD) can be determined with a higher certainty degree compared to traditional models, leading to a lower capital requirement. On the given data set in this article Logistic regression seems to be the algorithm with highest accuracy of classifying customer into right category. However, it classifies a lot of people as false positive meaning the model thinks a customer will honour its obligation but in fact the customer defaults. Doing this comes with a great cost for the banks. Through implementing a cost function to minimize this error, we found that the Neural network has the lowest false positive rate and will therefore be the model that is best suited for this specific classification task.När banker lånar ut pengar till en annan part uppstår en risk i att låntagaren inte uppfyller sitt antagande mot banken. Denna risk kallas för kredit risk och är den största risken en bank står inför. Enligt Basel föreskrifterna måste en bank avsätta en viss summa kapital för varje lån de ger ut för att på så sätt skydda sig emot framtida finansiella kriser. Denna summa beräknas fram utifrån varje enskilt lån med tillhörande risk-vikt, RWA. De huvudsakliga parametrarna i RWA är sannolikheten att en kund ej kan betala tillbaka lånet samt summan som banken då förlorar. Idag kan banker använda sig av interna modeller för att estimera dessa parametrar. Då bundet kapital medför stora kostnader för banker, försöker de sträva efter att hitta bättre verktyg för att uppskatta sannolikheten att en kund fallerar för att på så sätt minska deras kapitalkrav. Därför har nu banker börjat titta på möjligheten att använda sig av maskininlärningsalgoritmer för att estimera dessa parametrar. Maskininlärningsalgoritmer såsom Logistisk regression, Neurala nätverk, Beslutsträd och Random forest, kan användas för att bestämma kreditrisk. Genom att träna algoritmer på historisk data med kända resultat kan parametern, chansen att en kund ej betalar tillbaka lånet (PD), bestämmas med en högre säkerhet än traditionella metoder. På den givna datan som denna uppsats bygger på visar det sig att Logistisk regression är den algoritm med högst träffsäkerhet att klassificera en kund till rätt kategori. Däremot klassifiserar denna algoritm många kunder som falsk positiv vilket betyder att den predikterar att många kunder kommer betala tillbaka sina lån men i själva verket inte betalar tillbaka lånet. Att göra detta medför en stor kostnad för bankerna. Genom att istället utvärdera modellerna med hjälp av att införa en kostnadsfunktion för att minska detta fel finner vi att Neurala nätverk har den lägsta falsk positiv ration och kommer därmed vara den model som är bäst lämpad att utföra just denna specifika klassifierings uppgift.
12
Rhodehamel, Edward Jeffery. "A microbiological decision tree approach for performing a hazard analysis and its relationship to microbiological risk analysis." Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-06062008-151500/.
Full text
13
Akashah, Farid Wajdi. "Quantitative fire risk assessment by combining deterministic fire models with automatic event tree analysis." Thesis, Ulster University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.536465.
Full textAbstract:
Risk assessment is an integral part of the decision making process within the built environment especially with the adoption of performance-based regulations in place of prescriptive-based regulations. This dissertation examines risk assessment methods, identifying problems within the current methods available. Specifically, this dissertation defines gaps in current quantitative risk assessment where there is a need for event tree analysis, a component of quantitative risk assessment, to be improved. The dissertation also examines agent-based modelling and some of its applications across different industries. Agent based modelling has lead to a development of a novel methodology to automate the process of producing event trees for fire risk assessment. The fire risk methodology provides the risk curve for a set of scenarios by developing a software package combining the use of a) deterministic models i.e. fire zone models, b) probabilistic models i.e. Monte Carlo model, and c) an agent-based model including uncertainty analysis. The present fire risk methodology has been applied to two case studies. The first case study involves the application of the methodology to assess the benefit of installing two different options of fire safety systems in a warehouse. The second case study is the application of the methodology to a two-storey dwelling house where its flexibility and its ability to perform uncertainty analysis is further examined. These applications of the methodology to the case studies show the methodology flexibility to be applied within different fire risk assessment domains. Finally, recommendations are made to further develop the methodology to include components such as structural risk assessment module and evacuation assessment module.
14
Haghighi, Mona. "Rule-based Risk Monitoring Systems for Complex Datasets." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6248.
Full textAbstract:
In this dissertation we present rule-based machine learning methods for solving problems with high-dimensional or complex datasets. We are applying decision tree methods on blood-based biomarkers and neuropsychological tests to predict Alzheimer’s disease in its early stages. We are also using tree-based methods to identify disparity in dementia related biomarkers among three female ethnic groups. In another part of this research, we tried to use rule-based methods to identify homogeneous subgroups of subjects who share the same risk patterns out of a heterogeneous population. Finally, we applied a network-based method to reduce the dimensionality of a clinical dataset, while capturing the interaction among variables. The results show that the proposed methods are efficient and easy to use in comparison to the current machine learning methods.
15
Picoco, Claudia. "Integrated Framework for Representing Recoveries Using the Dynamic Event Tree Approach." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu155550242815033.
Full text
16
Mark, Jennifer. "Applications of the IUCN Red List in evaluating global extinction risk of timber tree species." Thesis, Bournemouth University, 2018. http://eprints.bournemouth.ac.uk/30531/.
Full textAbstract:
Anthropogenic deforestation and habitat degradation are major pressures on biodiversity. The world’s wild-growth timber tree species additionally face pressure from unsustainable and illegal harvest practices. Despite the threats to these economically valuable species, our understanding of their extinction risk remains incomplete and outdated. In fact, many timber tree taxa are marketed under trade names only, making it difficult to identify those most at risk. An additional challenge is presented by limited data and the pressing need for rapid species assessment in order to inform conservation actions. However, the use of ‘big data’ is coming to the fore in ecological research, and offers a valuable chance to meet international assessment targets such as those of The Global Strategy for Plant Conservation (GSPC), which call for knowledge of the conservation status of all known plant species to guide conservation actions (GSPC Target 2), in addition to sustainable harvesting of all wild- sourced plant-based products (GSPC Target 12), by the year 2020 (CBD, 2012). This thesis therefore aimed to identify timber tree taxa in trade at the species level; to assess utility of occurrence records from the Global Biodiversity Information Facility (GBIF) in timber species range mapping; to assess current extinction risk of a priority subset of timber tree species by applying the IUCN Red List (Red List) of Threatened Species Categories and Criteria; and, lastly, to evaluate the uncertainty of these preliminary Red List assessments. Consolidation of open-access timber lists produced a ‘working list’ of 1,578 angiosperm timber taxa in trade. GBIF records were demonstrated to be a suitable low time-cost resource with which to estimate species extent of occurrence and prioritise range-restricted timber tree species for Red List assessment. In addition to GBIF datasets, Global Forest Change (GFC) satellite imagery was found to be a valuable resource for assessing timber tree species range size, habitat fragmentation, and population trends over time. Preliminary Red List assessments conducted for 324 timber tree species suggest that some 69% may be threatened with extinction if current rates of deforestation persist. Although GBIF and GFC ‘big data’ were found to introduce some uncertainty into timber tree Red List categorisations, quantitative comparison to assessments conducted using ‘expert’ datasets suggested that categorisations were not greatly impacted. Furthermore, these evaluations illustrated the scarcity and inaccessibility of more traditional sources of Red List assessment data for timber tree species. It is evident that if we are to meet GSPC and other conservation targets for timbers and other at-risk, poorly-known tree taxa, we must recognise that open-access ‘big data’ repositories represent a powerful opportunity for Red Listing.
17
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.
Full textAbstract:
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.
18
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.
Find full textAbstract:
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.
19
SALA, CRISTIAN. "TREE STABILITY ANALYSIS: EXPERIMENTAL PULLING TESTS AND ANALYTICAL INTERPRETATION." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2021. http://hdl.handle.net/10281/325901.
Full textAbstract:
Negli ultimi anni la società ha aumentato la considerazione dell'importanza del verde per la tutela del pianeta e per la salute delle persone. Nelle aree urbane, in particolare, la presenza di alberi aumenta notevolmente la qualità della vita dei cittadini sotto vari aspetti, ad esempio aumentando l'ombreggiamento e abbassando le temperature estive, riducendo gli inquinanti nell'aria, diminuendo lo stress e migliorando l'umore delle persone, ecc.
Tuttavia, gli alberi possono subire rotture biomeccaniche per ragioni meteorologiche, fitopatologiche e antropiche, provocando notevoli danni a cose e persone. Esistono, quindi, diversi metodi per valutare la stabilità degli alberi che possono consentire di prevederne la caduta ed evitare possibili danni, ma la materia è molto complessa e, allo stato attuale delle conoscenze, queste tipologie di valutazioni presentano alcuni limiti.
Negli ultimi anni il metodo principale utilizzato per valutare la stabilità delle radici di un albero è il SIM - Static Integrated Method (pulling test), perché spesso è l'unico conosciuto e attualmente non esistono altri metodi alternativi con la stessa affidabilità e ripetibilità, sebbene questo abbia alcune limitazioni, così come gli altri metodi.
Lo scopo di questo lavoro è stato, quindi, quello di cercare di migliorare il metodo di valutazione della stabilità radicale degli alberi, avvalendosi dell'esperienza lavorativa della società Agro Service, specializzata nella valutazione della stabilità degli alberi per clienti pubblici e privati.
Innanzitutto, per migliorare la valutazione della stabilità radicale è necessario osservare diverse prove di trazione (pulling test) e analizzarne i risultati. Quindi, con la collaborazione della società Agro Service, dall'anno 2017 al 2020 sono state effettuate quasi cento prove di trazione da utilizzare per questa ricerca. In questo lasso di tempo sono state realizzate altre prove di trazione, ma i relativi risultati non sono stati presi in considerazione per questo studio perché la qualità dei dati non era sufficientemente elevata.
Tutte le prove di trazione sono state eseguite con strumenti FAKOPP, che hanno permesso di raccogliere più punti della curva di ribaltamento in rapporto fra la rotazione della zolla radicale e la forza applicata. Dopo la normale fase di trazione fino alla rotazione di 0,2 °, come previsto dal metodo SIM, alcune prove sono state registrate anche nella successiva fase di scarico, per analizzare il comportamento del sistema albero-radici-suolo.
Nelle 11 diverse località in cui vengono effettuati i test in Lombardia e Liguria, sono stati prelevati 18 campioni di terreno per conoscere la granulometria di questi siti e la sua possibile influenza nell'ottenimento dei risultati delle prove.
Dall'osservazione delle caratteristiche dei dati dei test di trazione e delle anomalie matematiche del metodo tradizionale, è stata proposta criticamente un'equazione interpretativa più generale rispetto al classico approccio di Wessolly, al fine di migliorare la valutazione della stabilità radicale degli alberi, aumentando così la sicurezza nei luoghi pubblici e la possibilità di preservare gli alberi monumentali.
Successivamente questa nuova equazione proposta è stata validata da alcuni test di trazione sperimentali, consistenti in prove in scala reale, sia tradizionali sia fino allo sradicamento dell'albero, e prove in scala ridotta.
Infine viene riportato un lavoro sull'incremento della sicurezza di un albero con un approccio deterministico, svolto dallo stesso gruppo di lavoro di questo studio. Nonostante questo approccio possa essere riproposto solo per alberi di particolare pregio, ovvero alberi monumentali, per la sua complessità e per i suoi costi eccessivi, questo lavoro è risultato importante per iniziare ad approfondire il problema della stabilità degli alberi e per iniziare a sviluppare i successivi studi esposti in questa tesi.In recent years, society has increased the consideration of the importance of green areas for the protection of the planet and the health of people. In urban areas, in particular, the presence of trees significantly increases the quality of life of citizens under various aspects, i.e. greater shading and reduction of summer temperatures, reduction of pollutants in the air, reduction of stress and improvement of people's mood, etc. However, trees can suffer biomechanical breakages for meteorological, phytopathological and anthropic reasons, causing considerable damage to things and people. There are, therefore, different methods for evaluating the stability of trees that can make it possible to predict their fall and avoid damage, but the matter is very complex and, in the current state of knowledge, these evaluations have some limitations. In the last years the main method used to value the root stability of a tree is the SIM – Static Integrated Method (pulling test), because it’s often the only one known and currently there’re not other alternative methods with the same reliability and repeatability, although it has some limitations as other methods. The purpose of this work was, therefore, to try to improve the method of evaluating the root stability of trees, taking advantage of the work experience of the Agro Service society, specialized in tree stability evaluation for public and private customers. First of all, to improve root stability evaluation is necessary to observe several pulling tests and analyze their results. So, with the cooperation of Agro Service society, almost one hundred pulling tests are carried out since year 2017 to 2020 to be used for this research. More other pulling tests are carried out in this time frame, but relative results are not considered for this study because the data quality isn’t enough high. All the pulling tests are performed with FAKOPP instruments, that allowed to collect several points of the fitting overturning curve between root plate rotation and applied force. After the ordinary pulling phase until the rotation of 0,2°, as expected by the SIM, some of them are also recorded during the following unload phase, to analyze the behavior of tree-roots-soil system. In the 11 different places where tests are carried out around Lombardy and Liguria regions, 18 soil samples are picked up to know the granulometry of these sites and its possible influence in pulling test results. By the observation of the pulling tests data features and the mathematical anomalies of the ordinary method, a more general interpretative equation has been proposed critically compared to the classical Wessolly approach, in order to improve the evaluation of the root stability of the trees, increasing the public safety and the possibility to preserve monumental trees. So this new proposed equation has been validated by some experimental pulling tests, consisting in real scale tests, traditional ones and until failure of the tree, and scale tests. Finally, a work on increasing the safety of a tree with a deterministic approach is reported, wich was carried out by the same working group of this study. In spite of this approach can only be re-proposed for trees of particular value, i.e. monumental trees, due to its complexity and its excessive costs, this work was important to begin to deepen the topic of tree stability and from it we started to develop the following studies exposed in this thesis.
20
Ravindran, D. S. "Risk, store of wealth and land use choice : a socio-economic analysis of farmer adoption of woodlots in Karnataka, India." Thesis, Bangor University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389520.
Full text
21
Strazzabosco, L. "La sostenibilità degli interventi su alberi veterani: un protocollo per la valutazione integrata e la cura." Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3425281.
Full textAbstract:
The purpose of this study was to develop and implement a protocol for risk analysis and assessment of veteran trees in public places. One of the main objectives of the management plans of the historical sites is the preservation of the trees "founders". Many of the trees "founder" survivors are subjected to inappropriate management practices, which lowered their life expectancy and greatly reduced their biomechanical safety factor. The protocol developed for the assessment of these trees is based on two types of analysis: a biological assessment of tree health and well-being, and a new method for assessing the biomechanical stability of the tree ( OREBLA - a worksheet digital based tree modeling and evaluation system ).
The biological evaluation of tree health is a critical step to evaluate the ability of a veteran tree to react to management practices that lead to the reduction of the biomass. In particular, the metabolic activity of the root system is evaluated by measuring the starch content of the root that has been shown to be related to the response to tree management practices. OREBLA is an integrated tool biomechanical analysis, which includes a modeling of the tree structure based on the protocol EUROCODE for the evaluation of the safety factor of structures exposed to the wind . The evaluation is based on data dendrometric and diagnostic, non-invasive tools for the analysis of the trunk and limbs ( Sonic tomography and electrical ) , and also on an assessment of the risk of tree failure due to fracturing of the plate ( Pulling Test). The protocol was tested in the assessment of veterans 'founders' of the Park trees Revedin Bolasco in Castelfranco Veneto (Italy).Lo scopo dello studio è stato quello di sviluppare e implementare un protocollo per l'analisi del rischio e la valutazione di alberi veterani in luoghi aperti al pubblico. Uno dei principali obiettivi dei piani di gestione dei siti storici è la conservazione degli alberi " fondatori". Molti degli alberi "fondatore" superstiti sono sottoposti a pratiche gestionali inadeguate, che ha abbassato la loro speranza di vita e notevolmente ridotto il loro fattore di sicurezza biomeccanico. Il protocollo messo a punto per la valutazione di questi alberi si basa su due tipi di analisi: una valutazione biologica di salute degli alberi e il benessere e un nuovo metodo per la valutazione biomeccanica della stabilità dell'albero ( OREBLA - un foglio di lavoro digitale basato modellazione albero e sistema di valutazione ). La valutazione biologica di salute degli alberi è un passo fondamentale per valutare la capacità di un albero veterano di reagire alle pratiche di gestione che comportano la riduzione della biomassa. In particolare l'attività metabolica del sistema radicale viene valutata mediante la misurazione del contenuto di amido radice che è stato dimostrato essere correlata alla risposta albero alle pratiche di gestione. OREBLA è uno strumento integrato analisi biomeccanica , che comprende una modellazione della struttura ad albero basato sul protocollo EUROCODE per la valutazione del fattore di sicurezza di strutture esposta al vento. La valutazione si basa su dati dendrometriche e diagnostici, strumenti non invasivi, per il tronco e gli arti di analisi ( Sonic e tomografia elettrica), e anche su una valutazione del rischio di fallimento albero a causa della zolla fratturazione (Pulling Test). Il protocollo è stato testato nella valutazione degli alberi veterani " fondatori " del Parco Revedin Bolasco a Castelfranco Veneto ( Italia).
22
Singh, Anima Ph D. Massachusetts Institute of Technology. "Risk stratification of cardiovascular patients using a novel classification tree induction algorithm with non-symmetric entropy measures." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/64601.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 95-100).
Risk stratification allows clinicians to choose treatments consistent with a patient's risk profile. Risk stratification models that integrate information from several risk attributes can aid clinical decision making. One of the technical challenges in developing risk stratification models from medical data is the class imbalance problem. Typically the number of patients that experience a serious medical event is a small subset of the entire population. The goal of my thesis work is to develop automated tools to build risk stratification models that can handle unbalanced datasets and improve risk stratification. We propose a novel classification tree induction algorithm that uses non-symmetric entropy measures to construct classification trees. We apply our methods to the application of identifying patients at high risk of cardiovascular mortality. We tested our approach on a set of 4200 patients who had recently suffered from a non-ST-elevation acute coronary syndrome. When compared to classification tree models generated using other measures proposed in the literature, the tree models constructed using non-symmetric entropy had higher recall and precision. Our models significantly outperformed models generated using logistic regression - a standard method of developing multivariate risk stratification models in the literature.
by Anima Singh.
S.M.
23
Psota, Michal. "Softwarová podpora analýzy rizik." Master's thesis, Vysoké učení technické v Brně. Ústav soudního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-232747.
Full textAbstract:
This thesis focuses on the theoretical description of risk management options related to information technologies and describes methods used to risk analysis. Described methods are fault tree analysis, event tree analysis, FMEA, HAZOP and Markovov analysis. Practical part includes proposal and implementation of program that visualizes decision trees and determines probability of each tree item.
24
Srivastava, Anruag. "A Computational Framework for Dam Safety Risk Assessment with Uncertainty Analysis." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/1480.
Full textAbstract:
The growing application of risk analysis in dam safety, especially for the owners of large numbers of dams (e.g., U.S. Army Corps of Engineers), has motivated the development of a new tool (DAMRAE) for event tree based dam safety risk analysis. Various theoretical challenges were overcome in formulating the computational framework of DAMRAE and several new computational concepts were introduced. The concepts of Connectivity and Pedigree matrices are proposed to quantify the user-drawn event tree structures with proper accounting of interdependencies among the event tree branches. A generic calculation of Common-Cause Adjustment for the non-mutually exclusive failure modes is implemented along with introducing the new concepts of system response probability and consequence freezing. New output presentation formats such as cumulative risk estimate vs. initiating variable plots to analyze the increase of an incremental (annualized) risk estimate as a function of initiating variable are introduced. An additional consideration is given to the non-breach risk estimates in the risk modeling and new output formats such as non-breach F-N and F-$ charts are included as risk analysis outputs.
DAMRAE, a Visual Basic.NET based framework, provides a convenient platform to structure the risk assessment of a dam in its existing state and for alternatives or various stages of implementing a risk reduction plan. The second chapter of the dissertation presents the architectural framework of DAMRAE and describes the underlying theoretical and computational logic employed in the software. An example risk assessment is presented in the third chapter to demonstrate the DAMRAE functionalities.
In the fourth chapter, the DAMRAE framework is extended into DAMRAE-U to incorporate uncertainty analysis functionality. Various aspects and requirements reviewed for uncertainty analysis in the context of dam safety risk assessment and theoretical challenges overcome to develop the computational framework for DAMRAE-U are described in this chapter. The capabilities of DAMRAE-U are illustrated in the fifth chapter, which contains an example dam safety risk assessment with uncertainty analysis. The dissertation concludes with a summary of DAMRAE features and recommendations for further work in the sixth chapter.
25
Karabey, Bugra. "Attack Tree Based Information Technology Security Metric Integrating Enterprise Objectives With Vulnerabilities." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12614100/index.pdf.
Full textAbstract:
Security is one of the key concerns in the domain of Information Technology systems. Maintaining the confidentiality, integrity and availability of such systems, mandates a rigorous prior analysis of the security risks that confront these systems. In order to analyze, mitigate and recover from these risks a metrics based methodology is essential in prioritizing the response strategies to these risks and also this approach is required for resource allocation schedules to mitigate such risks. In addition to that the Enterprise Objectives must be focally integrated in the definition, impact calculation and prioritization stages of this analysis to come up with metrics that are useful both for the technical and managerial communities within an organization. Also this inclusion will act as a preliminary filter to overcome the real life scalability issues inherent with such threat modeling efforts. Within this study an attack tree based approach will be utilized to offer an IT Security Risk Evaluation Method and Metric called TEOREM (Tree based Enterprise Objectives Risk Evaluation Method and Metric) that integrates the Enterprise Objectives with the Information Asset vulnerability analysis within an organization. Applicability of the method has been analyzed within a real life setting and the findings are discussed as well within this study.
26
Mahboob, Qamar. "A Bayesian Network methodology for railway risk, safety and decision support." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-138087.
Full textAbstract:
For railways, risk analysis is carried out to identify hazardous situations and their consequences. Until recently, classical methods such as Fault Tree Analysis (FTA) and Event Tree Analysis (ETA) were applied in modelling the linear and logically deterministic aspects of railway risks, safety and reliability. However, it has been proven that modern railway systems are rather complex, involving multi-dependencies between system variables and uncertainties about these dependencies. For train derailment accidents, for instance, high train speed is a common cause of failure; slip and failure of brake applications are disjoint events; failure dependency exists between the train protection and warning system and driver errors; driver errors are time dependent and there is functional uncertainty in derailment conditions. Failing to incorporate these aspects of a complex system leads to wrong estimations of the risks and safety, and, consequently, to wrong management decisions. Furthermore, a complex railway system integrates various technologies and is operated in an environment where the behaviour and failure modes of the system are difficult to model using probabilistic techniques. Modelling and quantification of the railway risk and safety problems that involve dependencies and uncertainties such as mentioned above are complex tasks.
Importance measures are useful in the ranking of components, which are significant with respect to the risk, safety and reliability of a railway system. The computation of importance measures using FTA has limitation for complex railways. ALARP (As Low as Reasonably Possible) risk acceptance criteria are widely accepted as ’\'best practice’’ in the railways. According to the ALARP approach, a tolerable region exists between the regions of intolerable and negligible risks. In the tolerable region, risk is undertaken only if a benefit is desired. In this case, one needs to have additional criteria to identify the socio-economic benefits of adopting a safety measure for railway facilities. The Life Quality Index (LQI) is a rational way of establishing a relation between the financial resources utilized to improve the safety of an engineering system and the potential fatalities that can be avoided by safety improvement. This thesis shows the application of the LQI approach to quantifying the social benefits of a number of safety management plans for a railway facility.
We apply Bayesian Networks and influence diagrams, which are extensions of Bayesian Networks, to model and assess the life safety risks associated with railways. Bayesian Networks are directed acyclic probabilistic graphical models that handle the joint distribution of random variables in a compact and flexible way. In influence diagrams, problems of probabilistic inference and decision making – based on utility functions – can be combined and optimized, especially, for systems with many dependencies and uncertainties. The optimal decision, which maximizes the total benefits to society, is obtained.
In this thesis, the application of Bayesian Networks to the railway industry is investigated for the purpose of improving modelling and the analysis of risk, safety and reliability in railways. One example application and two real world applications are presented to show the usefulness and suitability of the Bayesian Networks for the quantitative risk assessment and risk-based decision support in reference to railways.
27
Giordani, Martina. "Probabilistic Risk Assessment for Contamination by Mineral Oil." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Find full textAbstract:
The research topic has as its main objective the modeling of the flow of contaminant (mineral oil) following a road accident involving a heavy transport vehicle carrying 24 tons of CHEMOL pesticide, produced by the company Chemia S.p.A. of Sant’Agostino (FE). The target area is the ex-cave Olmi, currently used as a flood retention basin in the town of Calderara di Reno (BO), N-E of Bologna's Marconi airport, which is the final destination of the vehicle.
Within this context, the thesis work concerned first of all the georeferencing and the study of an environmental report performed on the target area useful in the study of the hydrogeology of the soil and its stratigraphy. Subsequently, it was necessary to use the HSSM software to model the flow of contaminant in the soil. After this initial study, the Fault Tree (FTA) was built, the final event of which is the achievement of the target area, within a given time limit, a concentration higher than the limit given by the legislation.
The failure rate of each basic event, which leads to the realization of the final event, was evaluated using values derived from technical reports, with the exception of the event consisting in exceeding the concentration limit value in the target area. For the latter event, a Monte Carlo simulation was used, combining the values of hydraulic conductivity and initial concentration of contaminant, which were the values most affected by uncertainty. Finally, these values were entered into the aforementioned HSSM software to evaluate the results. The probability of failure of this basic event was obtained by having the software compile a number of times equal to that of the possible combinations.
The final calculation of the result, deriving from the constructed tree, was carried out using Boolean algebra, a method typically used in this probabilistic risk calculation technique. Below are elements relating to the techniques available for the removal of the pollutant.
28
Ng, Anthony Kwok-Lung. "Risk Assessment of Transformer Fire Protection in a Typical New Zealand High-Rise Building." Thesis, University of Canterbury. Civil Engineering, 2007. http://hdl.handle.net/10092/1223.
Full textAbstract:
Prescriptively, the requirement of fire safety protection systems for distribution substations is not provided in the compliance document for fire safety to the New Zealand Building Code. Therefore, the New Zealand Fire Service (NZFS) has proposed a list of fire safety protection requirements for distribution substations in a letter, dated 10th July 2002. A review by Nyman [1], has considered the fire safety requirements proposed by the NZFS and discussed the issues with a number of fire engineers over the last three years. Nyman concerned that one of the requirements regarding the four hour fire separation between the distribution substation and the interior spaces of the building may not be necessary when considering the risk exposure to the building occupants in different situations, such as the involvement of the sprinkler systems and the use of transformers with a lower fire hazard. Fire resistance rating (FRR) typically means the time duration for which passive fire protection system, such as fire barriers, fire walls and other fire rated building elements, can maintain its integrity, insulation and stability in a standard fire endurance test. Based on the literature review and discussions with industry experts, it is found that failure of the passive fire protection system in a real fire exposure could potentially occur earlier than the time indicated by the fire resistance rating derived from the standard test depending on the characteristics of the actual fire (heat release rate, fire load density and fire location) and the characteristics of the fire compartment (its geometric, ventilation conditions, opening definition, building services and equipment). Hence, it is known that a higher level of fire safety, such as 4 hour fire rated construction and use of sprinkler system, may significantly improve the fire risk to health of safety of occupants in the building; however, they could never eliminate the risk. This report presents a fire engineering Quantitative Risk Assessment (QRA) on a transformer fire initiating in a distribution substation inside a high-rise residential and commercial mixeduse building. It compares the fire safety protection requirements for distribution substations from the NZFS to other relevant documents worldwide: the regulatory standards in New Zealand, Australia and United States of America, as well as the non-regulatory guidelines from other stakeholders, such as electrical engineering organisation, insurance companies and electricity providers. This report also examines the characteristics of historical data for transformer fires in distribution substations both in New Zealand and United States of America buildings. Reliability of active fire safety protection systems, such as smoke detection systems and sprinkler systems is reviewed in this research. Based on the data analysis results, a fire risk estimate is determined using an Event Tree Analysis (ETA) for a total of 14 scenarios with different fire safety designs and transformer types for a distribution substation in a high-rise residential and commercial mixed-use building. In Scenario 1 to 10 scenarios, different combinations of fire safety systems are evaluated with the same type of transformer, Flammable liquid (mineral oil) insulated transformer. In Scenario 11 to Scenario 14, two particular fire safety designs are selected as a baseline for the analysis of transformer types. Two types of transformer with a low fire hazard are used to replace the flammable liquid (mineral oil) insulated transformer in a distribution substation. These are less flammable liquid (silicone oil) insulated transformers and dry type (dry air) transformers. The entire fire risk estimate is determined using the software package @Risk4.5. The results from the event tree analysis are used in the cost-benefit analysis. The cost-benefit ratios are measured based on the reduced fire risk exposures to the building occupants, with respect to the investment costs of the alternative cases, from its respective base case. The outcomes of the assessment show that the proposed four hour fire separation between the distribution substations and the interior spaces of the building, when no sprinkler systems are provided, is not considered to be the most cost-effective alternative to the life safety of occupants, where the cost-benefit ratio of this scenario is ranked fifth. The most cost-effective alternative is found to be the scenario with 30 minute fire separation and sprinkler system installed. In addition to the findings, replacing a flammable liquid insulated transformer with a less flammable liquid insulated transformer or a dry type transformer is generally considered to be economical alternatives. From the QRA analysis, it is concluded that 3 hour fire separation is considered to be appropriate for distribution substations, containing a flammable liquid insulated transformer and associated equipment, in non-sprinklered buildings. The fire ratings of the separation construction can be reduced to 30 minute FRR if sprinkler system is installed. This conclusion is also in agreement with the requirements of the National Fire Protection Association (NFPA).
29
Olandersson, Sandra, and Jeanette Fredsson. "Threats in Information Security : Beyond technical solutions. - Using Threat Tree Analysis." Thesis, Blekinge Tekniska Högskola, Institutionen för programvaruteknik och datavetenskap, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-3829.
Full textAbstract:
To be able to protect an organisation's resources, it is important to understand what there is to protect and what to protect it from. The first step is to try to analyse the security threats that exist against an organisation's resources to explore the risks. Threats have to be identified, for the organisation to protect its resources and find where the optimal placement against threats is. This thesis analysis whether it is possible to obtain a Threat Tree Analysis that is useful for developing an information security policy for the municipality in Ronneby, using the SS 62 77 99-1 standard. A co-operation between the technical solutions and the administrative security is necessary to achieve information security, together with ordinary common sense. True, each of these can help improve security, but none of them is a complete solution. Security is not a product - it is a process. Threat trees form the basis of understanding that process. In this thesis, we have been using a qualitative method. The analysis method is a case study at the Social Department, at the municipality in Ronneby. Through interviews it has come us to hand, that the organisation has not established an information security policy which should give the code of practice for how the work of information security will pursue within the organisation. The organisation does neither use a model for structuring threats nor a method for collecting threats against information today. Through the structure of possible threats, the personnel generates an understanding of the organisation and takes active part finding adequate threats within the Social Department. As users understand the importance of security, how to use it, and where to report suspected violations, they can do a great deal to reduce the risk to loose information. Important to remember is that the education is an ongoing process, new users need training and trained users need reminding, especially when new technologies or processes are introduced. Thus, Threat Tree Analysis is useful for continuing towards developing an information security policy according to SS 62 77 99-1 standard.För att kunna skydda en organisations resurser är det viktigt att förstå vad organisationen behöver skydda och vad den ska skydda det ifrån. Det första steget är att analysera hot mot organisationens resurser för att uppskatta riskerna. Hot måste identifieras för att organisationen ska kunna skydda sina resurser och hitta den optimala placeringen av åtgärder mot hot. Denna uppsatsen undersöker om det är möjligt att skapa en hotträdsanalys som är användbar för skapandet av en informationssäkerhetspolicy för Ronneby kommun, genom att använda standarden SS 62 77 99-1. Vi betonar i uppsatsen att ett samarbete mellan existerande tekniska lösningar och administrativ säkerhet är nödvändigt för att uppnå informationssäkerhet. Visst kan var och en av dessa hjälpa till att förbättra säkerheten, men ingen av dem är ensam den kompletta lösningen. Säkerhet är inte en produkt - det är en process. Hotträd formar grunden för en förståelse av den processen. I denna uppsats har vi använt en kvalitativ metod. Analysmetoden är en fallstudie på Socialförvaltningen i Ronneby kommun. Genom intervjuer har vi fått fram att organisationen inte har etablerat en informationssäkerhetspolicy, vilken ska ge riktlinjer för hur säkerhetsarbetet ska fullföljas inom organisationen. Organisationen använder varken en modell för att identifiera hot mot information eller en metod för att strukturera hoten. Genom strukturen av möjliga hot, genererar personalen en förståelse för organisationen och tar aktivt del i att identifiera hot mot Socialförvaltningen. Detta medför att alla användare förstår hur viktigt det är med säkerhet, vart de ska rapportera misstänkta händelser och de kan göra mycket för att minska risken att förlora information. Det är viktigt att komma ihåg att utbildning är en pågående process, nya användare behöver utbildning och utbildade användare behöver vidareutbildning, speciellt när nya tekniker eller processer introduceras. Därför är hotträdsanalysen en användbar modell för arbetet mot att skapa en informationssäkerhetspolicy enligt standarden SS 62 77 99-1.
Sandra Olandersson Blåbärsvägen 27 372 38 RONNEBY 0457 / 12084 Jeanette Fredsson Villa Viola 372 36 RONNEBY 0457 / 26616
30
Nusbaumer, Olivier P. M. "Analytical solutions of linked fault tree probabilistic risk assessments using binary decision diagrams with emphasis on nuclear safety applications /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17286.
Full text
31
Miller, Brian. "Development of a Chaid Decision Tree for Assessing Risk of Detecting Metabolic Syndrome in Adults, Age 20-39 Years." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1342752599.
Full text
32
Ericsson, Emil, and Eric Gregorson. "Quantitative Risk Assessment of Wave Energy Technology." Thesis, Uppsala universitet, Elektricitetslära, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-342033.
Full textAbstract:
European Commission (2011) aims to reduce the greenhouse gas emission sby 85-95% by 2050 in comparison to 1990’s levels. Wave energy could be an important step to archiving this goal. This report aims to develop a quantitative risk assessment for the Uppsala University's wave energy converter. Failure rates have been collected from various databases and reports and have been processed accordingly in order to implement them in the risk analysis. CAPEX, OPEX and possible downtime windows have been estimated. A fault tree analysis (FTA) has estimated the total unavailability, unreliability and downtime. Furthermore an economical assessment model using Monte Carlo and the unreliability data from the FTA has been developed, estimating the expected LCOE and OPEX/WEC for parks consisting of 20, 100, and 200 WECs (wave energy converters). The result show that the O-ring seal has the largest impact on both the unavailability, and the economy of the OPEX/WEC. Second biggest contributor is the translator bearing failure. The study also shows that the CAPEX cost has to be reduced to make the LCOE competitive in comparison to other renewable sources. A comparison between the system unavailability and unreliability has also been done in terms of different component parameters.
33
Aigner, Benjamin Lee. "Risk Assessment and Improving Brown Marmorated Stink Bug (Stål), Halyomorpha halys, Sampling in Virginia Soybean Systems." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/82742.
Full textAbstract:
Brown marmorated stink bug (BMSB), Halyomorpha halys (Stål), has become an important pest of soybean in the Mid-Atlantic US. To assess the influence of tree borders on BMSB infestations in soybean, twelve fields were sampled weekly using five 3-min visual counts of BMSB on tree of heaven (TOH) (Ailanthus altissima) and other host trees along a wooded border, on the adjacent soybean edge, 15 m and 30 m into the soybean field. At all locations, BMSB densities increased on TOH wooded borders in July, then, gradually moved into adjacent soybean borders later in the summer. BMSB did not move far from the field edge, with approximately half as many bugs being present at 15 m into the field and very few being detected 30 m into the field. These results validate the use of border sprays for BMSB control in soybean.
Additional studies conducted in 2013 and 2014 compared a visual plant inspection method with a standard sweep net strategy for sampling BMSB. Overall, the two methods were highly correlated with a correlation coefficient of R=0.83. Visual inspection appears to be an effective method for assessing BMSB populations in soybean.
One of the major factors affecting the distribution and establishment of invasive species is climate. The CLIMEX modeling software uses climatic and biological factors of species to predict the geographic risk for pest outbreaks. A climate simulation model was run with CLIMEX to determine the potential distribution of BMSB in Virginia based on temperature. To develop a more accurate model, factors like resource availability and source population would need to be considered.Master of Science in Life Sciences
34
Hošták, Martin. "Systém pro podporu managementu rizik." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2009. http://www.nusl.cz/ntk/nusl-236676.
Full textAbstract:
The thesis deals with project management body of knowledge with focus on a risk management. It explained the importance of risk management in software developing projects. Risk management cycle and used methodology is described. The core unit of second part is requirements analysis for risk management support system, description of the application via UML and implementation of application which was created in development environment NetBeans IDE 6.5 in Java language. Conclusion of my thesis contains a short summary and possible way of extension.
35
Shew, Cameron Hunter. "TRANSFERABILITY AND ROBUSTNESS OF PREDICTIVE MODELS TO PROACTIVELY ASSESS REAL-TIME FREEWAY CRASH RISK." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/863.
Full textAbstract:
This thesis describes the development and evaluation of real-time crash risk assessment models for four freeway corridors, US-101 NB (northbound) and SB (southbound) as well as I-880 NB and SB. Crash data for these freeway segments for the 16-month period from January 2010 through April 2011 are used to link historical crash occurrences with real-time traffic patterns observed through loop detector data.
The analysis techniques adopted for this study are logistic regression and classification trees, which are one of the most common data mining tools. The crash risk assessment models are developed based on a binary classification approach (crash and non-crash outcomes), with traffic parameters measured at surrounding vehicle detection station (VDS) locations as the independent variables. The classification performance assessment methodology accounts for rarity of crashes compared to non-crash cases in the sample instead of the more common pre-specified threshold-based classification.
Prior to development of the models, some of the data-related issues such as data cleaning and aggregation were addressed. Based on the modeling efforts, it was found that the turbulence in terms of speed variation is significantly associated with crash risk on the US-101 NB corridor. The models estimated with data from US-101 NB were evaluated based on their classification performance, not only on US-101 NB, but also on the other three freeways for transferability assessment. It was found that the predictive model derived from one freeway can be readily applied to other freeways, although the classification performance decreases. The models which transfer best to other roadways were found to be those that use the least number of VDSs–that is, using one upstream and downstream station rather than two or three.
The classification accuracy of the models is discussed in terms of how the models can be used for real-time crash risk assessment, which may be helpful to authorities for freeway segments with newly installed traffic surveillance apparatuses, since the real-time crash risk assessment models from nearby freeways with existing infrastructure would be able to provide a reasonable estimate of crash risk. These models can also be applied for developing and testing variable speed limits (VSLs) and ramp metering strategies that proactively attempt to reduce crash risk.
The robustness of the model output is assessed by location, time of day and day of week. The analysis shows that on some locations the models may require further learning due to higher than expected false positive (e.g., the I-680/I-280 interchange on US-101 NB) or false negative rates. The approach for post-processing the results from the model provides ideas to refine the model prior to or during the implementation.
36
Prinsloo, Christoffel Frederick. "Investigating the influence of individual value systems and risk propensities on decision-making quality in value clashing circumstances." Thesis, University of Pretoria, 2017. http://hdl.handle.net/2263/61270.
Full textAbstract:
This study investigated the influences of personal value systems and risk propensities on managerial decision-making quality during value clashes. The post-globalisation business landscape is impacted by role players of vastly differing personal attributes, hypothesised to have varying influences on decision-making behaviour. A deeper understanding of how these attributes impact decision-making quality will therefore enrich the literature and arm practitioners with improved decision-making skills.
A review of behavioural decision-making literature revealed three core approaches: the normative (prescriptive) perspective, focussed on decision analysis, the cognitive limitations perspective highlighting the boundaries of human cognition and the psychological (values/emotions/motivations) perspective allowing for ethical- or value-boundedness. The extant literature contributes little on the quality of decision-making exhibited by managers, or how to improve it. It also doesn’t consider variance in decision-making between groups defined by personal value and risk traits. This study therefore aimed to establish whether decision-making quality varied with variances in personal attributes, and whether an intervention would improve decision-making behaviour.
The research, conducted on a sample of 460 South African managers, established the demographics and value- and risk orientations of the participating group. Three value clashing scenarios, incorporating social-relational framing interventions, where introduced to gauge the decision-making behaviour of the test subjects. Decision-making quality was assessed through the integrative complexity measure and qualitative assessments were conducted on the decision motivation texts.
Decision-tree analyses, multiple regression analyses as well as T-tests comparing the decision-quality produced by individuals of opposing orientations, revealed a clear relationship between the value segments of self-enhancement and openness to change and higher quality decision-making. Social risk-taking was related to better decision-making and reframing the scenarios produced better decision-making quality responses, if the reframing was done harshly enough. The qualitative analysis supported these findings, but hinted at additional, context specific decision motivators.
This study contributed an integrated view of decision-making literature, tested the application of integrative complexity as a measure of decision quality and introduced new perspectives on how value orientations, risk proclivities and scenario framing relate to decision-making quality. Practitioners can apply this to assess individuals in terms of their decision-making abilities, and can improve decision-making quality in managers through scenario re-framing.Thesis (PhD)--University of Pretoria, 2017.
Gordon Institute of Business Science (GIBS)
PhD
Unrestricted
37
Mullett, Margaret. "Conducting a randomised experiment in eight English prisons : a participant observation study of testing the Sycamore Tree Programme." Thesis, University of Cambridge, 2016. https://www.repository.cam.ac.uk/handle/1810/275047.
Full textAbstract:
This dissertation is a participant observer’s account of implementing a multisite, randomised controlled trial within Her Majesty’s Prison Service. It adds to a scarce literature detailing the steps involved in implementing experiments in custodial settings by providing a candid account of the route from planning to successful implementation. The randomised controlled trial was designed to evaluate the effectiveness of the Sycamore Tree Programme. This programme’s goal is to teach prisoners the wider harm of crime and includes a face-to-face meeting between a victim of crime and the participating offenders. It derives its rehabilitative potential from restorative justice and seeks to foster hope that change is possible for offenders, thus aiding them to desist from crime. Its development and theoretical basis are described for the first time. In an in-depth narrative the dissertation details how at every stage strategies were developed to manage participant procurement, random assignment, maintaining treatment integrity, and preparing for final outcome measurements. The randomised controlled trial was designed to produce an individual experiment in eight prisons. These will be combined in a meta-analysis as well as analysed as a pooled sample. Overall the implementation process took close to two years and involved a charitable body, Her Majesty’s Prison Service, the National Offender Management Service, and two police forces. This work has demonstrated how the unstable nature of English prison populations and the risk-averse climate must be addressed when conducting experiments in that environment. It has also illustrated the gap between the rhetoric of evidence-based policy and the facilitation of research designed to seek that evidence. Nevertheless, developing trusting relationships and combining rapidly learnt skills with inherent abilities ensured that the evaluation methodology was supported and protected through the various challenges it met. Finally, the dissertation suggests conditions for closer collaboration between government executive bodies and researchers that might increase the number of experiments undertaken in prisons. It also aims to encourage researchers that prison experiments, although not easy, are feasible, defendable, and, above all, worthwhile.
38
Bakhsh, Kelarestaghi Kaveh. "A Risk Based Approach to Intelligent Transportation Systems Security." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/91421.
Full textAbstract:
Security threats to cyber-physical systems are targeting institutions and infrastructure around the world, and the frequency and severity of attacks are on the rise. Healthcare manufacturing, financial services, education, government, and transportation are among the industries that are the most lucrative targets for adversaries. Hacking is not just about companies, organizations, or banks; it also includes critical infrastructure. Wireless Sensors Networks, Vehicle-to-everything communication (V2X), Dynamic Message Signs (DMS), and Traffic Signal Controllers are among major Intelligent Transportation Systems (ITS) infrastructure that has already been attacked or remain vulnerable to hacking. ITS has been deployed with a focus on increasing efficiency and safety in the face of dramatic increases in travel demand. Although many studies have been performed and many security primitives have been proposed, there are significant concerns about flawless performance in a dynamic environment. A holistic security approach, in which all infrastructure performs within the satisfactory level of security remains undiscovered. Previously, hacking of road infrastructure was a rare event, however, in recent years, field devices such as DMS are hacked with higher frequency. The primary reason that transportation assets are vulnerable to cyber-attacks is due to their location. A more dramatic scenario occurs when hackers attempt to convey tampered instructions to the public.
Analyzing traveler behavior in response to the hacked messages sign on the basis of empirical data is a vital step toward operating a secure and reliable transportation system. There may be room for improvement by policymakers and program managers when considering critical infrastructure vulnerabilities. With cybersecurity issues escalating every day, road users' safety has been neglected. This dissertation overcomes these challenges and contributes to the nascent but growing literature of Intelligent Transportation System (ITS) security impact-oriented risk assessment in threefold.
• First, I employ a risk-based approach to conduct a threat assessment. This threat assessment performs a qualitative vulnerability-oriented threat analysis. The objective is to scrutinize safety, security, reliability, and operation issues that are prompted by a compromised Dynamic Message Signs (DMS).
• Second, I examine the impact of drivers' attitudes and behaviors on compliance, route diversion behavior, and speed change behavior, under a compromised DMS. We aim to assess the determinants that are likely to contribute to drivers' compliance with forged information. To this extent, this dissertation evaluates drivers' behavior under different unauthentic messages to assess in-depth the impact of an adversarial attack on the transportation network.
• Third, I evaluate distracted driving under different scenarios to assess the in-depth impact of an adversarial attack on the transportation network. To this extent, this dissertation examines factors that are contributing to the manual, visual, and cognitive distractions when drivers encountering fabricated advisory information at a compromised DMS.
The results of this dissertation support the original hypothesis and indicate that with respect to the forged information drivers tend to (1) change their planned route, (2) become involved in distracting activities, and (3) change their choice speed at the presence of a compromised DMS. The main findings of this dissertation are outlined below:
1. The DMS security vulnerabilities and predisposing conditions allow adversaries to compromise ITS functionality. The risk-based approach of this study delivers the impact-likelihood matrix, which maps the adverse impacts of the threat events onto a meaningful, visual, matrix. DMS hacking adverse impacts can be categorized mainly as high-risk and medium-risk clusters. The safety, operational (i.e., monetary losses) and behavioral impacts are associated with a high-risk cluster. While the security, reliability, efficiency, and operational (i.e., congestion) impacts are associated with the medium-risk cluster.
2. Tech friendly drivers are more likely to change their route under a compromised DMS. At the same time, while they are acquiring new information, they need to lowering their speed to respond to the higher information load. Under realistic-fabricated information, about 65% of the subjects would depart from their current route. The results indicate that females and subjects with a higher driving experience are more likely to change their route. In addition, those subjects who are more sensitive to the DMS's traffic-related messages and those who use DMS under congested traffic condition are more likely to divert. Interestingly, individuals with lower education level, Asians, those who live in urban areas, and those with trouble finding their direction in new routes are less likely to pick another route rather the one they planned for.
3. Regardless of the DMS hacking scenarios, drivers would engage in at least one of the distractive activities. Among the distractive activities, cognitive distraction has the highest impact on the distracted driving likelihood. Meaning, there is a high chance that drivers think of something other than driving, look at surrounding traffic and scenery, or talk to other passengers regarding the forged information they saw on the DMS. Drivers who rely and trust in technology, and those who check traffic condition before starting their trips tend to become distracted. In addition, the result identified that at the presence of bogus information, drivers tend to slow down or stop in order to react to the DMS. That is, they would either (1) become involved in activities through the means of their phone, (2) they would mind wander, look around, and talk to a passenger about the sign, and (3) search for extra information by means of their vehicle's radio or internet.
4. Females, black individuals, subjects with a disability, older, and those with high trust in DMS are less likely to ignore the fabricated messages. In contrary, white, those who drive long hours, and those who see driving as a tedious task are more likely to ignore the bogus messages. Drivers who comply with traffic regulations and have a good driving record are likely to slow down under the tampered messages. Furthermore, female drivers and those who live in rural areas are more likely to slow down under fabricated advisory information. Furthermore, this dissertation identifies that planning for alternative route and involvement in distractive activities cause speed variation behaviors under the compromised DMS.
This dissertation is the first to investigate the adverse impact of a compromised DMS on the road users and operators. I attempt to address the current gap in the literature by assessing and evaluating the impact of ITS security vulnerabilities. Broader impacts of this study include (1) to systematically raising awareness among policy-makers and engineers, (2) motivating further simulations and real-world experiments to investigate this matter further, (3) to systematically assessing the adverse impact of a security breach on transportation reliability and safety, and drivers' behavior, and (4) providing insights for system operators and decision-makers to prioritize the risk of a compromised DMS. Additionally, the outcome can be integrated with the nationwide connected vehicle and V2X implementations and security design.Doctor of Philosophy
Security threats are targeting institutions and infrastructure around the world, and the frequency and severity of security attacks are on the rise. Healthcare manufacturing, financial services, education, government, and transportation are among the industries that are the most lucrative targets for adversaries. Hacking is not just about companies, organizations, or banks; it also includes critical infrastructure. Intelligent Transportation Systems have been deployed with a focus on increasing efficiency and safety in the face of dramatic increases in traffic volume. Although many studies have been performed and many security primitives have been proposed, there are significant concerns about flawless performance in a dynamic environment. A holistic security approach, in which all infrastructure performs within the satisfactory level of security remains undiscovered. Previously, hacking of road infrastructure was a rare event, however, in recent years, field devices, such as dynamic message signs, are hacked with higher frequency. The primary reason that transportation assets are vulnerable to cyber-attacks is that of their location in public. A more dramatic scenario occurs when hackers attempt to convey tampered instructions to the public. Analyzing traveler behavior in response to the hacked messages sign on the basis of empirical data is a vital step toward operating a secure and reliable transportation system. This study is the first to investigate the adversarial impact of a compromised message sign on the road users and operators. I attempt to address the current gap in the literature by assessing and evaluating the impact of ITS security vulnerabilities.
39
Krejčířová, Magda. "Návrh na implementaci metodiky rozhodovacího stromu při investičním rozhodování ve firmě." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2007. http://www.nusl.cz/ntk/nusl-221421.
Full textAbstract:
This master's thesis concerns the use of the methodology of the decision tree in the investment decision making. The proposed decision model provides the best solution from the available options for the EXPECT-IT ltd. company. This thesis contains also a range of own proposals followed by their evaluation.
40
Lee, Ji Hyun. "A Regulatory Approach for Extending the Licensing Basis to Include Beyond Design Basis Events." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1370937698.
Full text
41
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.
Find full textAbstract:
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.
42
ABDUL, MAHDI NOOR. "Genetic variability Of the LCR, E6, E7 and L1 genes of the high risk HPV-31, HPV-58 and probable high risk HPV-66, HPV-53 and Phylogenetic analysis of the infected Italian women from urban area of Rome." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2009. http://hdl.handle.net/2108/214311.
Full textAbstract:
Sono stati descritti oltre 100 genotipi HPV, 18 dei quali classificati come ad alto rischio a causa della loro associazione con lo sviluppo del cancro alla cervice. La diversità genomica all’interno dello stesso genotipo di HPV-16 e 18 è stata sudiata in maniera estesa, mentre pochi dati sono stati prodotti per altri genotipi meno comuni ad alto rischio. Il presente studio investiga la variabilità nucleotidica e la filogenesi dei genotipi ad alto rischio HPV-31e HPV58 e i probabili genotipi ad alto rischio HPV53 e HPV66 in campioni raccolti in Italia, a Roma. A questo scopo, i geni L1, E6, E7 e LCR sono stati sequenziati in 33 campioni di HPV-31, 24 campioni di HPV-58, 30 campioni di HPV-53 e 24 campioni di HPV-66. Diverse varianti di questi tipi di HPV sono stati rilevate con la presenza delle corrispondenti lesioni citologiche, alcune delle quali sono state rilevate anche in altre parti del mondo. Inoltre, sono state determinate nuove varianti di tutti i genotipi esaminati. Sulla base delle sequenze E6, E7 e L1, sono stati descritte le varianti compresi i cambiamenti aminoacidici conservativi e non consecutivi e anche le sequenze LCR sono state analizzate per i siti di legame dei fattori di trascrizione. L’albero filogenetico è stato costruito studiando i geni L1 e L6; l’analisi filogenetica degli isolati di HPV31, HPV58, HPV53 e HPV66 non ha rilevato un “clustering” etnico o geografico come osservato precedentemente for HPV-16 e 18. In aggiunta, non c’era correlazione tra le varianti dei quattro genotipi e delle lesioni citologiche corrispondenti; questo è stato anche confermato calcolando la diversità genomica di L1, E6 e LCR per ogni genotipo e per il gene E6 in relazione alle lesione citologica. La diversità genetica è risultata molto simile e molto limitata in ciascun gene per tutte le lesioni genotipiche e citologiche.
L’elevato numero di nuove varianti rilevate può essere spiegato dai pochissimi studi che sono stati condotti ad oggi riguardanti la variabilità genetica di questi genotipi HPV meno prevalenti ad alto rischio. Benchè non potessimo condurre uno studio funzionale, ulteriori dati sono necessari per comprendere l’effetto possible di queste varianti sulla funzione proteica e la progressione della malattia.
La caratterizzazine genomica delle varianti di HPV è cruciale per capire la correlazione geografica intinseca e le differenze biologiche di questi virus e fornisce ulteriori informazioni agli studi sulla loro infettività e patogenicità.More than 100 HPV types have been described, 18 of which are classified as high-risk due to their association with the development of cervical cancer. The intratype genomic diversity of HPV-16 and -18 has been studied extensively, while little data have been generated for other less common high-risk types. The present study explores the nucleotide variability and phylogeny of the high-risk HPV-31and HPV58 and probable high-risk HPV53 and HPV66 in samples collected from Rome Italy. For this purpose, the L1, E6, E7 and LCR genes were sequenced from 33 samples HPV-31, 24 samples HPV-58, 30 samples HPV-53 and 24 samples HPV-66. Several variants of these HPV types were detected with the correspondent cytological lesions, some of which have been detected in other parts of the world. Furthermore, novel variants of all types examined were detected. Based on the E6, E7 and L1 sequences, variants were described comprising conservative and non-conservative amino acid changes, also the LCR have been analyzed for the transcription factors binding sites. Phylogenetic tree was constructed with respect to L1 and E6 gene; the phylogenetic analysis of HPV31, HPV58, HPV53, and HPV66 isolates did not reveal ethnic or geographical clustering as observed previously for HPV-16 and -18. In addition, there was no correlation between the HPV variants of the four genotypes and correspondent cytological lesion; this was confirmed by calculating the genomic diversity of L1, E6 and LCR for each genotype and for E6 gene in relation with the cytological lesion. The results of genetic diversity were similar and very limited in each gene for all the genotypes and cytological lesions. The high number of new variants detected can be explained by the very few studies that have been conducted to date concerning the genetic variability of these less prevalent high-risk HPV types. Although, we couldn’t perform a functional study, more data are needed to understand the possible effect of these variants on protein function and disease progression. The genomic characterization of HPV variants is crucial for understanding the intrinsic geographical relatedness and biological differences of these viruses and contributes further to studies on their infectivity and pathogenicity.
43
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/.
Full textAbstract:
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.
44
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.
Full text
45
Bucknor, Matthew D. "Modeling of Electrical Cable Failure in a Dynamic Assessment of Fire Risk." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1373996537.
Full text
46
Janošík, Petr. "Rozhodovací metody v managementu rizik." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2011. http://www.nusl.cz/ntk/nusl-236999.
Full textAbstract:
This thesis deals with the matter of risk managament in IT projects. It explains the importance of risk management in such projects and shows different ways and methods of managing and analyzing the risks. After explaining the basic concepts and the various phases of risk management the text focuses on two methods of risk analysis - the fault tree analysis of event tree analysis. Use of both methods is explained for both quantitative and qualitative analyses. The second half of the work includes the design of an application for the support of risk analysis employing the methods of fault tree analysis and event tree analysis. This is followed by a description of the implementation of the proposed system in a web environment using jQuery, Nette Framework and Dibi.
47
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.
Full textAbstract:
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.
48
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.
Full textAbstract:
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.
49
Dan, Gorton. "Aspects of Modeling Fraud Prevention of Online Financial Services." Doctoral thesis, KTH, Transportvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176298.
Full textAbstract:
Banking and online financial services are part of our critical infrastructure. As such, they comprise an Achilles heel in society and need to be protected accordingly. The last ten years have seen a steady shift from traditional show-off hacking towards cybercrime with great economic consequences for society. The different threats against online services are getting worse, and risk management with respect to denial-of-service attacks, phishing, and banking Trojans is now part of the agenda of most financial institutions. This trend is overseen by responsible authorities who step up their minimum requirements for risk management of financial services and, among other things, require regular risk assessment of current and emerging threats.For the financial institution, this situation creates a need to understand all parts of the incident response process of the online services, including the technology, sub-processes, and the resources working with online fraud prevention. The effectiveness of each countermeasure has traditionally been measured for one technology at a time, for example, leaving the fraud prevention manager with separate values for the effectiveness of authentication, intrusion detection, and fraud prevention. In this thesis, we address two problems with this situation. Firstly, there is a need for a tool which is able to model current countermeasures in light of emerging threats. Secondly, the development process of fraud detection is hampered by the lack of accessible data.In the main part of this thesis, we highlight the importance of looking at the “big risk picture” of the incident response process, and not just focusing on one technology at a time. In the first article, we present a tool which makes it possible to measure the effectiveness of the incident response process. We call this an incident response tree (IRT). In the second article, we present additional scenarios relevant for risk management of online financial services using IRTs. Furthermore, we introduce a complementary model which is inspired by existing models used for measuring credit risks. This enables us to compare different online services, using two measures, which we call Expected Fraud and Conditional Fraud Value at Risk. Finally, in the third article, we create a simulation tool which enables us to use scenario-specific results together with models like return of security investment, to support decisions about future security investments.In the second part of the thesis, we develop a method for producing realistic-looking data for testing fraud detection. In the fourth article, we introduce multi-agent based simulations together with social network analysis to create data which can be used to fine-tune fraud prevention, and in the fifth article, we continue this effort by adding a platform for testing fraud detection.Finansiella nättjänster är en del av vår kritiska infrastruktur. På så vis utgör de en akilleshäl i samhället och måste skyddas på erforderligt sätt. Under de senaste tio åren har det skett en förskjutning från traditionella dataintrång för att visa upp att man kan till en it-brottslighet med stora ekonomiska konsekvenser för samhället. De olika hoten mot nättjänster har blivit värre och riskhantering med avseende på överbelastningsattacker, nätfiske och banktrojaner är nu en del av dagordningen för finansiella institutioner. Denna trend övervakas av ansvariga myndigheter som efterhand ökar sina minimikrav för riskhantering och bland annat kräver regelbunden riskbedömning av befintliga och nya hot.För den finansiella institutionen skapar denna situation ett behov av att förstå alla delar av incidenthanteringsprocessen, inklusive dess teknik, delprocesser och de resurser som kan arbeta med bedrägeribekämpning. Traditionellt har varje motåtgärds effektivitet mätts, om möjligt, för en teknik i taget, vilket leder till att ansvariga för bedrägeribekämpning får separata värden för autentisering, intrångsdetektering och bedrägeridetektering.I denna avhandling har vi fokuserat på två problem med denna situation. För det första finns det ett behov av ett verktyg som kan modellera effektiviteten för institutionens samlade motåtgärder mot bakgrund av befintliga och nya hot. För det andra saknas det tillgång till data för forskning rörande bedrägeridetektering, vilket hämmar utvecklingen inom området.I huvuddelen av avhandlingen ligger tonvikten på att studera ”hela” incidenthanteringsprocessen istället för att fokusera på en teknik i taget. I den första artikeln presenterar vi ett verktyg som gör det möjligt att mäta effektiviteten i incidenthanteringsprocessen. Vi kallar detta verktyg för ”incident response tree” (IRT) eller ”incidenthanteringsträd”. I den andra artikeln presenterar vi ett flertal scenarier som är relevanta för riskhantering av finansiella nättjänster med hjälp av IRT. Vi utvecklar också en kompletterande modell som är inspirerad av befintliga modeller för att mäta kreditrisk. Med hjälp av scenarioberoende mått för ”förväntat bedrägeri” och ”value at risk”, har vi möjlighet att jämföra risker mellan olika nättjänster. Slutligen, i den tredje artikeln, skapar vi ett agentbaserat simuleringsverktyg som gör det möjligt att använda scenariospecifika resultat tillsammans med modeller som ”avkastning på säkerhetsinvesteringar” för att stödja beslut om framtida investeringar i motåtgärder.I den andra delen av avhandlingen utvecklar vi en metod för att generera syntetiskt data för test av bedrägeridetektering. I den fjärde artikeln presenterar vi ett agentbaserat simuleringsverktyg som med hjälp av bland annat ”sociala nätverksanalyser” kan användas för att generera syntetiskt data med realistiskt utseende. I den femte artikeln fortsätter vi detta arbete genom att lägga till en plattform för testning av bedrägeridetektering.
QC 20151103
50
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.
Full text