Multifidelity prediction in wildfire spread simulation: Modeling, uncertainty quantification and sensitivity analysis

Wildfire behavior predictions typically suffer from significant uncertainty. However, wildfire modeling uncertainties remain largely unquantified in the literature, mainly due to computing constraints. New multifidelity techniques provide a promising opportunity to overcome these limitations. Therefore, this paper explores the applicability of multifidelity approaches to wildland fire spread prediction problems. Using a canonical simulation scenario, we assessed the performance of control variates Monte-Carlo (MC) and multilevel MC strategies, achieving speedups of up to 100x in comparison to a standard MC method. This improvement was leveraged to quantify aleatoric uncertainties and analyze the sensitivity of the fire rate of spread (RoS) to weather and fuel parameters using a full-physics fire model, namely the Wildland-Urban Interface Fire Dynamics Simulator (WFDS), at an affordable computation cost. The proposed methodology may also be used to analyze uncertainty in other relevant fire behavior metrics such as heat transfer, fuel consumption and smoke production indicators

Generalized averaged Gaussian quadrature and applications

A simple numerical method for constructing the optimal generalized averaged Gaussian quadrature formulas will be presented. These formulas exist in many cases in which real positive GaussKronrod formulas do not exist, and can be used as an adequate alternative in order to estimate the error of a Gaussian rule. We also investigate the conditions under which the optimal averaged Gaussian quadrature formulas and their truncated variants are internal

MS FT-2-2 7 Orthogonal polynomials and quadrature: Theory, computation, and applications

Quadrature rules find many applications in science and engineering. Their analysis is a classical area of applied mathematics and continues to attract considerable attention. This seminar brings together speakers with expertise in a large variety of quadrature rules. It is the aim of the seminar to provide an overview of recent developments in the analysis of quadrature rules. The computation of error estimates and novel applications also are described

Forest dynamics at regional scales: predictive models constrained with inventory data

Forest ecosystems store more carbon than the atmosphere and harbour the majority of the world's biodiversity, yet their response to changing climate is uncertain. Forest simulation models make landscape-level predictions of forest dynamics by scaling from key tree-level processes, but models typically have no climate dependency. In this thesis I demonstrate how large-scale national inventories combined with improvements in computational methods mean that models that incorporate the climate dependency of demographic processes may be parameterised at regional scales. In Chapter One I outline historical approaches to modelling forest dynamics and present a discussion of competing methods of parameterisation and model selection. In Chapter Two I present a model of individual tree mortality in the eastern United States which incorporates species, climatic and competitive effects parameterised using Markov Chain Monte Carlo methods. The remainder of the thesis concentrates on modelling Spanish forest dynamics, so in Chapter Three I present a brief introduction to Spanish forest ecology. In Chapter Four I examine how aboveground allometry - the scaling of tree height and crown shape - varies with climate and competition in Spain for 26 species. Hierarchical modelling suggests that scaling theories based on wood properties do not explain differences between species, but climatic factors, and in particular hydraulic limitations, do. In Chapter Five I parameterise a model of recruitment in Spanish forests using Approximate Bayesian Computation, a novel computational method which allows parameterisation of individual-based models without individual-based data, and demonstrate that it produces ecologically reasonable results. Chapter Six presents a forest dynamics model parameterised for the major native species in Spain and tests whether it is able to reproduce observed species-climate distributions. Finally, in Chapter Seven I discuss the main findings of the thesis and avenues for extending this research.This work was supported by a grant from Microsoft Research to the University of Cambridg

Recent Development of Hybrid Renewable Energy Systems

Abstract: The use of renewable energies continues to increase. However, the energy obtained from renewable resources is variable over time. The amount of energy produced from the renewable energy sources (RES) over time depends on the meteorological conditions of the region chosen, the season, the relief, etc. So, variable power and nonguaranteed energy produced by renewable sources implies intermittence of the grid. The key lies in supply sources integrated to a hybrid system (HS)

Characterising HIV-associated Mycobacterium tuberculosis blood stream infection

Despite the success of antiretroviral therapy roll-out, one-million people still die with HIV-infection annually. In high-burden settings, tuberculosis remains the most common proximal cause of hospital admission and death in people living with HIV. In post-mortem series, 90% of fatal HIV-associated tuberculosis is ‘disseminated’. This is a form of tuberculosis which has been poorly characterised and, despite the high associated-mortality, never been the subject of interventional trials to define optimal treatment strategies. This thesis contends that the mode of severe HIV-associated tuberculosis is blood stream infection. First it is argued with reference to historical literature that blood stream dissemination is part of the natural history of post-primary tuberculosis infection, and that HIV-associated M. tuberculosis blood stream infection (MTBBSI) can be conceived of as a reversion to, and exaggerated form of this natural history. Using data from a large cohort (n=571) of HIV-infected inpatients with CD4 cell count <350 cells/mm3 and a new TB diagnosis from Khayelitsha Hospital, South Africa (the KDHTB study), the extent and magnitude of MTBBSI is shown to be a major determinant of clinical phenotype and mortality risk. Systematic, quantitative markers of blood stream dissemination, including TB blood culture, urine-lipoarabinomannan (uLAM), and urine GeneXpert MTB/RIF testing (uXpert), can be combined into a ‘disseminated TB score. KDHTB patients have high prevalence of abnormal sodium and fluid balance, metabolic acidosis associated with acute kidney injury, hyperlactataemia, infiltrative liver and splenic pathology, and anaemia. Each of these pathophysiologies in turn correlates to disseminated TB score, and to risk of death, suggesting bacterial burden and MTBBSI are central to the pathophysiology of severe HIV-associated tuberculosis. An individual patient data meta-analysis, with 20 independent data sets comprising over 6000 patients, is used to establish the prevalence of TB blood culture positive disease amongst critically unwell HIV-infected inpatients. This shows that MTBBSI is more common than previous estimates suggest, is a strong independent association with mortality risk, and is also associated with specific increased risk of death if empirical treatment is delayed. The development of tools to identify and measure MTBBSI is described, including Xpert-ultra testing of blood, and the use of a novel dye, DMN-trehalose, to perform direct microscopy on patient blood samples. These techniques are used to provide the first description of the pharmacodynamics of MTBBSI, by serially quantifying blood bacilli load over the first 72-hours of standard TB therapy, in 28 patients with high predicted probability of bacteraemia. In this cohort, risk of mortality is related to several summary measures of MTBBSI dynamics in the first 72-hours of therapy, suggesting this approach can be used to define biomarkers of treatment response. In conclusion, MTBBSI is a highly-specific diagnosis responsible for substantial mortality in hospitalised people living with HIV. Interventions with strengthened bacteriocidal activity, focussed on reducing bacterial burden, are warranted for MTBBSI. Tools developed in this thesis, including potential pharmacodynamic biomarkers, should facilitate such trials

Safety and Reliability - Safe Societies in a Changing World

The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen

Social work with airports passengers

Social work at the airport is in to offer to passengers social services. The main methodological position is that people are under stress, which characterized by a particular set of characteristics in appearance and behavior. In such circumstances passenger attracts in his actions some attention. Only person whom he trusts can help him with the documents or psychologically