100 research outputs found
Risk and vulnerability analysis in society’s proactive emergency management: Developing methods and improving practices
Risk and vulnerability analyses can play important roles in the society’s proactive emergency management. This thesis addresses two ways of improving the analysis of risk and vulnerability analysis in this context. First, by developing methods for risk and vulnerability analysis of technical infrastructure networks and emergency response systems. Secondly, by aiming to improve practises related to RVA through an evaluation of Swedish municipal RVAs and an empirical study of how various disaster characteristics affect people judgments of disaster seriousness. The research has to a large extent been carried out by using a design research approach developed in the thesis
Topological Performance Measures as Surrogates for Physical Flow Models for Risk and Vulnerability Analysis for Electric Power Systems
Critical infrastructure systems must be both robust and resilient in order to
ensure the functioning of society. To improve the performance of such systems,
we often use risk and vulnerability analysis to find and address system
weaknesses. A critical component of such analyses is the ability to accurately
determine the negative consequences of various types of failures in the system.
Numerous mathematical and simulation models exist which can be used to this
end. However, there are relatively few studies comparing the implications of
using different modeling approaches in the context of comprehensive risk
analysis of critical infrastructures. Thus in this paper, we suggest a
classification of these models, which span from simple topologically-oriented
models to advanced physical flow-based models. Here, we focus on electric power
systems and present a study aimed at understanding the tradeoffs between
simplicity and fidelity in models used in the context of risk analysis.
Specifically, the purpose of this paper is to compare performances measures
achieved with a spectrum of approaches typically used for risk and
vulnerability analysis of electric power systems and evaluate if more
simplified topological measures can be combined using statistical methods to be
used as a surrogate for physical flow models. The results of our work provide
guidance as to appropriate models or combination of models to use when
analyzing large-scale critical infrastructure systems, where simulation times
quickly become insurmountable when using more advanced models, severely
limiting the extent of analyses that can be performed
Ortho-to-para ratio of NH2. Herschel-HIFI observations of ortho- and para-NH2 rotational transitions towards W31C, W49N, W51 and G34.3+0.1
We have used the Herschel-HIFI instrument to observe both nuclear spin symmetries of amidogen (NH2) towards the high-mass star-forming regions W31C (G10.6-0.4), W49N (G43.2-0.1), W51 (G49.5-0.4) and G34.3+0.1. The aim is to investigate the ratio of nuclear spin types, the ortho-to-para ratio (OPR), of NH2. The excited NH2 transitions are used to construct radiative transfer models of the hot cores and surrounding envelopes in order to investigate the excitation and possible emission of the ground state rotational transitions of ortho-NH2 N_(K_a,K_c} J=1_(1,1) 3/2 - 0_(0,0) 1/2 and para-NH2 2_(1,2) 5/2 - 1_(0,1) 3/2$ used in the OPR calculations. Our best estimate of the average OPR in the envelopes lie above the high temperature limit of three for W49N, specifically 3.5 with formal errors of \pm0.1, but for W31C, W51, and G34.3+0.1 we find lower values of 2.5\pm0.1, 2.7\pm0.1, and 2.3\pm0.1, respectively. Such low values are strictly forbidden in thermodynamical equilibrium since the OPR is expected to increase above three at low temperatures. In the translucent interstellar gas towards W31C, where the excitation effects are low, we find similar values between 2.2\pm0.2 and 2.9\pm0.2. In contrast, we find an OPR of 3.4\pm0.1 in the dense and cold filament connected to W51, and also two lower limits of >4.2 and >5.0 in two other translucent gas components towards W31C and W49N. At low temperatures (T \lesssim 50 K) the OPR of H2 is <10^-1, far lower than the terrestrial laboratory normal value of three. In such a "para-enriched H2" gas, our astrochemical models can reproduce the variations of the observed OPR, both below and above the thermodynamical equilibrium value, by considering nuclear-spin gas-phase chemistry. The models suggest that values below three arise in regions with temperatures >20-25 K, depending on time, and values above three at lower temperatures
Efficacy and Safety of Nivolumab Alone or in Combination With Ipilimumab in Patients With Mucosal Melanoma: A Pooled Analysis
Winner-Take-All Politics in Europe? The Political Economy of Rising Inequality in Germany and Sweden
Challenging Varieties of Capitalism's Account of Business Interests: The New Social Market Initiative and German Employers' Quest for Liberalization, 2000-2014
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