• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 110
  • 98
  • 20
  • 18
  • 4
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 306
  • 90
  • 80
  • 69
  • 58
  • 46
  • 38
  • 31
  • 29
  • 27
  • 26
  • 24
  • 24
  • 23
  • 22
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Improving the representation of the fragility of coastal structures

Jane, Robert January 2018 (has links)
Robust Flood Risk Analysis (FRA) is essential for effective flood risk management. The performance of any flood defence assets will heavily influence the estimate of an area's flood risk. It is therefore critical that the probability of a coastal flood defence asset incurring a structural failure when subjected to a particular loading i.e. its fragility is accurately quantified. The fragility representations of coastal defence assets presently adopted in UK National FRA (NaFRA) suffer three pertinent limitations. Firstly, assumptions relating to the modelling of the dependence structure of the variables that comprise the hydraulic load, including the water level, wave height and period, are restricted to a single loading variable. Consequently, due to the "system wide" nature of the analysis, a defence's conditional failure probability must also be expressed in terms of a single loading in the form of a fragility curve. For coastal defences the single loading is the overtopping discharge, an amalgamation of these basic loading variables. The prevalence of other failure initiation mechanisms may vary considerably for combinations of the basic loadings which give rise to equal overtopping discharges. Hence the univariate nature of the existing representations potentially restricts their ability to accurately assess an asset's structural vulnerability. Secondly, they only consider failure at least partially initiated through overtopping and thus neglect other pertinent initiation mechanisms acting in its absence. Thirdly, fragility representations have been derived for 61 generic assets (idealised forms of the defences found around the UK coast) each in five possible states of repair. The fragility representation associated with the generic asset and its state of repair deemed to most closely resemble a particular defence is adopted to describe its fragility. Any disparity in the parameters which influence the defence's structural vulnerability in the generic form of the asset and those observed in the field are also likely to further reduce the robustness of the existing fragility representations. In NaFRA coastal flood defence assets are broadly classified as vertical walls, beaches and embankments. The latter are typically found in sheltered locations where failure is water level driven and hence expressing failure probability conditionally on overtopping is admissible. Therefore new fragility representations for vertical wall and gravel beach assets which address the limitations of those presently adopted in NaFRA are derived. To achieve this aim it was necessary to propose new procedures for extracting information on the site and structural parameters characterising a defence's structural vulnerability from relevant resources (predominately beach profiles). In addition novel statistical approaches were put forward for capturing the uncertainties in the parameters on the basis of the site specific data obtained after implementation of the aforementioned procedures. A preliminary validation demonstrated the apparent reliability of these approaches. The pertinent initiation mechanisms behind the structural failure of each asset type were then identified before the state-of-the-art models for predicting the prevalence of these mechanisms during an event were evaluated. The Obhrai et al. (2008) re-formulation of the Bradbury (2000) barrier inertia model, which encapsulates all of the initiating mechanisms behind the structural failure of a beach, was reasoned as a more appropriate model for predicting the breach of a beach than that adopted in NaFRA. Failure initiated exclusively at the toe of a seawall was explicitly accounted for in the new formulations of the fragility representations using the predictors for sand and shingle beaches derived by Sutherland et al. (2007) and Powell & Lowe (1994). In order to assess whether the new formulations warrant a place in future FRAs they were derived for the relevant assets in Lyme Bay (UK). The inclusion of site specific information in the derivation of fragility representations resulted in a several orders of magnitude change in the Annual Failure Probabilities (AFPs) of the vertical wall assets. The assets deemed most vulnerable were amongst those assigned the lowest AFPs in the existing analysis. The site specific data indicated that the crest elevations assumed in NaFRA are reliable. Hence it appears the more accurate specification of asset geometry and in particular the inclusion of the beach elevation in the immediate vicinity of the structure in the overtopping calculation is responsible for the changes. The AFP was zero for many of the walls (≈ 77%) indicating other mechanism(s) occurring in the absence of any overtopping are likely to be responsible for failure. Toe scour was found to be the dominant failure mechanism at all of the assets at which it was considered a plausible cause of breach. Increases of at least an order of magnitude upon the AFP after the inclusion of site specific information in the fragility representations were observed at ≈ 86% of the walls. The AFPs assigned by the new site specific multivariate fragility representations to the beach assets were positively correlated with those prescribed by the existing representations. However, once the new representations were adopted there was substantially more variability in AFPs of the beach assets which had previously been deemed to be in identical states of repair. As part of the work, the new and existing fragility representations were validated at assets which had experienced failure or near-failure in the recent past, using the hydraulic loading conditions recorded during the event. No appraisal of the reliability of the new representations for beaches was possible due to an absence of any such events within Lyme Bay. Their AFPs suggest that armed with more information about an asset's geometry the new formulations are able to provide a more robust description of a beach's structural vulnerability. The results of the validation as well as the magnitude of the AFPs assigned by the new representations on the basis of field data suggest that the newly proposed representations provide the more realistic description of the structural vulnerability of seawalls. Any final conclusions regarding the robustness of the representations must be deferred until more failure data becomes available. The trade-off for the potentially more robust description of an asset's structural vulnerability was a substantial increase in the time required for the newly derived fragility representations to compute the failure probability associated with a hydraulic loading event. To combat this increase, (multivariate) generic versions of the new representations were derived using the structural specific data from the assets within Lyme Bay. Although there was generally good agreement in the failure probabilities assigned to the individual hydraulic loading events by the new generic representations there was evidence of systematic error. This error has the potential to bias flood risk estimates and thus requires investigation before the new generic representations are included in future FRAs. Given the disparity in the estimated structural vulnerability of the assets according to the existing fragility curves and the site-specific multivariate representations the new generic representations are likely to be more reliable than the existing fragility curves.
2

Seismic fragility estimates for reinforced concrete framed buildings

Ramamoorthy, Sathish Kumar 25 April 2007 (has links)
Gravity load designed (GLD) reinforced concrete (RC) buildings represent a common type of construction in the Mid-America Region. These buildings have limited lateral resistance and are susceptible to story mechanisms during earthquake loading. Fragility estimates are developed to assess the seismic vulnerability of GLD RC buildings in the Mid-America Region. Fragility is defined as the conditional probability of reaching or exceeding a performance level for a given earthquake intensity measure. Five sample buildings of various story heights (1, 2, 3, 6, and 10 stories) are used to represent generic RC frame buildings of 1 to 10 stories tall. A Bayesian methodology is used to develop probabilistic demand models to predict the maximum inter story drift given the spectral acceleration at the fundamental period of the building. The unknown parameters of the demand models are estimated using the simulated response data obtained from nonlinear time history analyses of the structural models for a suite of synthetic ground motions, developed for Memphis, Tennessee. Seismic structural capacity values are selected corresponding to the performance levels or damage states as specified in FEMA-356 and as computed by nonlinear pushover analyses. For the sample buildings, fragility estimates are developed using the predicted drift demands and structural capacity values. Confidence bounds are developed to represent the epistemic uncertainty inherent in the fragility estimates. In addition, bivariate fragility estimates, formulated as a function of spectral acceleration and the fundamental building period, are developed from the fragility estimates of the individual buildings. The bivariate fragilities can be used to quantify the seismic vulnerability of GLD RC frame buildings of 1 to 10 stories. Using the Bayesian approach, a framework is developed to update the analytical fragility estimates using observed damage data or experimental test data. As an illustration of the updating framework, the analytical bivariate fragility estimates for the sample buildings in the Mid-America Region are updated using the damage data obtained from 1994 Northridge, California earthquake. Furthermore, to investigate and demonstrate the increase in seismic performance of the GLD RC frame buildings, the columns of the 2 and 3 story buildings are retrofitted by column strengthening. Fragility estimates developed for the retrofitted buildings show the effectiveness of the retrofit technique by the improved seismic performance of GLD RC frame buildings.
3

Impossible and Necessary: The Problem of Luck and the Promise of Kindness

Lundquist, Caroline 03 October 2013 (has links)
My dissertation explores the promise of kindness as a response to the problem of luck which confronts both ancient and modern visions of the moral life. A rich articulation of kindness in the light of historical moral theory reveals that, far from being a trifling, merely and purely sentimental phenomenon, kindness involves many of the key ethical commitments that distinguish both Aristotelian ethics and Kantian morality. More importantly, at the level of individuals kindness has the power to mitigate the toll of bad luck on agents and to yield the types of judgments that dissolve the problem of moral luck. Where it finds expression at the institutional level kindness has tremendous ameliorative potential. I therefore contend that kindness is to be esteemed above all other modes of comportment; in a world that is not up to us, our greatest hope for flourishing lies in being kind and in remaining graciously open to the kindness of others.
4

Fragile robustness : principles and practice

Quinton-Tulloch, Mark January 2012 (has links)
Selective robustness is a key feature of biochemical networks, conferring a fitness benefit to organisms living in dynamic environments. The (in-)sensitivity of a network to external perturbations results from the interaction between network dynamics, design, and enzyme kinetics. In this work, we focus on the subtle interplay between robustness and fragility. We describe a quantitative method for defining the fragility and robustness of system fluxes and metabolite concentrations to perturbations in enzyme activity. We find that for many mathematical models of metabolic pathways, the robustness is captured by a broad distribution of the robustness coefficients and demonstrate that, unlike fragility, robustness is not a conserved process. Using a combination of existing in silico models and novel sets of models, designed to allow specific network features of interest to be studied in isolation, we examine the effect of various network properties on the robustness of such pathways. We discuss the question of how to measure, in a meaningful way, the robustness of a pathway as a whole, defining several summary metrics which, in combination, can be used to compare the robustness of different pathways. We show that networking increases robustness, but that robustness is affected differently by varying aspects of complexity. The effect of system control loops on robustness is analysed and we find that, in general, the addition of such regulation increases pathway robustness. The evolution of flux robustness is also examined. We show that robustness in metabolic pathways is unlikely to simply be a by-product of selection for other pathway traits, highlighting several trade-offs that result from the evolution of robust systems. Finally, we extend our definition of robustness, defining robustness coefficients for cellular properties other than flux or metabolite concentration, and to perturbations other than changes in enzyme activity. Using the effect of benzoic acid on glycolysis as a case study, we show how such robustness coefficients can be used to give novel insights from experimental data.
5

Pieces: A Critical Look at Life with Pediatric Cancer Through Clay

Schow, Marissa 01 January 2018 (has links)
Art has the power to bring together communities of people who have suffered from traumatic experiences, and allow them to heal, and overall dismantles the stigma associated with it. My work delves into the emotional side of living with pediatric cancer from the child’s perspective, particularly my own experiences as a brainstem tumor survivor, and the overall concerns of fragility. This paper explores these perspectives that are severely lacking throughout studies, while also taking a closer look at how artists, such as Frida Kahlo and Jamie Bates Slone, have used art to reflect on and express emotions concerning personal traumas. My thesis project demonstrates how art, or in my case clay, can emphasize the resiliency of young children in overcoming pediatric cancer, and fosters a greater understanding, by focusing on the hopeful side of the diagnosis, in those who may only recognize fragility.
6

FRAX predictions in upper extremity fracture and non-fracture patients

Seyok, Thany 11 October 2019 (has links)
Osteoporosis is the most common human bone disease and a growing public health problem. Worldwide, 9 million fractures due to osteoporosis occur annually. Fracture is the main burden of the disease and is linked with significant morbidity and mortality. A history of upper extremity fragility fracture is known to contribute to increased risk of subsequent fractures. In this study, we compared the estimated FRAX 10-year probability of major osteoporotic fracture and hip fracture between upper extremity (UE) fracture and non-fracture patients. In addition, we assessed differences in demographics and osteoporosis evaluation between the two groups, and we report the prevalence of lab abnormalities among UE fragility fracture patients evaluated in our fracture liaison service (FLS). A total of 243 patients from Brigham and Women’s Faulkner Hospital were recruited to participate in the study. UE fracture patients were recruited from our FLS, and UE non-fracture patients were recruited from the UE clinic. Overall 10-year probability of major osteoporotic and hip fracture was higher in upper extremity fracture patients than upper extremity non-fracture patients (19.23 versus 9.23, p <0.001 and 4.26 versus 1.54. p < 0.001 respectively). When excluding fragility fracture history, 10-year probability of major osteoporotic fracture and hip fracture were similar between upper extremity fracture and non-fracture patients (10.59 versus 9.23, p = 0.095 and 1.88 versus 1.54, p = 0.215 respectively). The proportion of osteoporosis evaluation via bone mineral density assessment was higher in upper extremity fracture patients compared to upper extremity non-fracture patients (p < 0.001). However, the proportion of upper extremity fracture patients on osteoporosis medication was low and not different than upper extremity non-fracture patients (p < 0.079). Our results highlight history of fragility fracture as an important driver in subsequent fracture risk. UE fracture and non-fracture patients harbor similar fracture clinical risk factors, with the exception of fracture history, and are similarly at risk for future hip fracture and major osteoporotic fracture. Our results suggest close osteoporosis evaluation of older upper extremity non-fracture patients is warranted.
7

Proliferation of Non-State Armed Groups and their impact on state fragility and insecurity in the Sahel Region of Africa / Proliferation of Non-State Armed Groups and their impact on state fragility and insecurity in the Sahel Region of Africa

Ofori-Ayeh, David January 2022 (has links)
in English The most potent threat to the security and stability of the state in some geographical regions after the cold war has been the proliferation of VNSA due largely to the declining capacities of states especially in the developing world. For a myriad of reasons, the modern nation-state seems incapable of performing its functions and fulfilling the obligations of the state to its citizens. Moreover, the state appears to have lost its monopoly on the use of force within its territory, a situation which has led to the prevalence of swathes of ungoverned territory with marginalized and aggrieved communities whose resentment against central authority find resonance with Non-State Armed Groups whose violent contestation of state authority has further contributed to state fragility and increased insecurity. The Sahel region is one that represents this dynamic in all of its dimensions.
8

A Probabilistic Deformation Demand Model and Fragility Estimates for Asymmetric Offshore Jacket Platforms

Fallon, Michael Brooks 14 March 2013 (has links)
Interest in evaluating the performance and safety of offshore oil and gas platforms has been expanding due to the growing world energy supply and recent offshore catastrophes. In order to accurately assess the reliability of an offshore platform, all relevant uncertainties must be properly accounted for. This necessitates the development of a probabilistic demand model that accounts for the relevant uncertainties and model errors. In this study, a probabilistic demand model is developed to assess the deformation demand on asymmetric offshore jacket platforms subject to wave and current loadings. The probabilistic model is constructed by adding correction terms and a model error to an existing deterministic deformation demand model. The correction terms are developed to capture the bias inherent in the deterministic model. The model error is developed to capture the accuracy of the model. The correction terms and model errors are estimated through a Bayesian approach using simulation data obtained from detailed dynamic analyses of a set of representative asymmetric offshore platform configurations. The proposed demand model provides accurate and unbiased estimates of the deformation demand on offshore jacket platforms. The developed probabilistic demand model is then used to assess the reliability of a typical offshore platform considering serviceability and ultimate performance levels. In addition, a sensitivity analysis is conducted to assess the effect of key parameters on the results of the analyses. The proposed demand model can be used to assess the reliability of different design options and for the reliability-based optimal design of offshore jacket platforms.
9

The fragile state of the European Union (EU): its battle for survival with the Member States

Fox, James January 2006 (has links)
Thesis (Masters)--Macquarie University, Division of Humanitites, Dept. of Politics, 2006. / Bibliography: p. 215-231. / The fragile state of the European Union (EU), its battle for survival with the Member States. -- The growth of the EU and the gradual transfer of powers from the Member States. -- The impact of the European Court of Justice. -- The formation of policy communities and multi-level governance. -- The Commission's sole right to initiate legislation and its reference to subsidiarity. -- The all-powerful Competition Directorate, which has an influential section of economic purists. -- The increased powers of the European Parliament and its shortcomings. -- The reluctance of national governments to adopt progressive attitudes and to let the Commission change its policies and procedures. -- The national contributions to the EU budget. -- The taxation differences between the various Member States. -- The EU constitution. -- The demographic development. -- Regional development and the structural funds. -- Competition policy. -- The Common Agricultural Policy. -- The Common Environment Policy. -- Economic and Monetary Union (EMU), the Euro, the Stability and Growth Pact (SGP) and the European Central Bank. -- Transport. -- The Common Energy Policy. -- The Area of Freedom, Security and Justice (AFSJ). / The European Union (EU) is partly supranational and partly inter-governmental. It is dependent on the concurrance of all its Member States for the important decisions required for the running of the EU. This causes an inherent instability in the EU. / Electronic reproduction. / 231 leaves
10

Melt Dynamics Correlated with Glass Topological Phases in dry Li- and Na- Borates

Skipper, Charles 24 October 2019 (has links)
No description available.

Page generated in 0.061 seconds