72 research outputs found
A review of in-situ loading conditions for mathematical modelling of asymmetric wind turbine blades
This paper reviews generalized solutions to the classical beam moment equation for solving the deflexion and strain
fields of composite wind turbine blades. A generalized moment functional is presented to effectively model the moment
at any point on a blade/beam utilizing in-situ load cases. Models assume that the components are constructed from inplane
quasi-isotropic composite materials of an overall elastic modulus of 42 GPa. Exact solutions for the displacement
and strains for an adjusted aerofoil to that presented in the literature and compared with another defined by the
Joukowski transform. Models without stiffening ribs resulted in deflexions of the blades which exceeded the generally
acceptable design code criteria. Each of the models developed were rigorously validated via numerical (Runge-Kutta)
solutions of an identical differential equation used to derive the analytical models presented. The results obtained
from the robust design codes, written in the open source Computer Aided Software (CAS) Maxima, are shown to be
congruent with simulations using the ANSYS commercial finite element (FE) codes as well as experimental data. One
major implication of the theoretical treatment is that these solutions can now be used in design codes to maximize the
strength of analogues components, used in aerospace and most notably renewable energy sectors, while significantly
reducing their weight and hence cost. The most realistic in-situ loading conditions for a dynamic blade and stationary
blade are presented which are shown to be unique to the blade optimal tip speed ratio, blade dimensions and wind
speed
Analysis of the Gibbs sampler for hierarchical inverse problems
Many inverse problems arising in applications come from continuum models
where the unknown parameter is a field. In practice the unknown field is
discretized resulting in a problem in , with an understanding
that refining the discretization, that is increasing , will often be
desirable. In the context of Bayesian inversion this situation suggests the
importance of two issues: (i) defining hyper-parameters in such a way that they
are interpretable in the continuum limit and so that their
values may be compared between different discretization levels; (ii)
understanding the efficiency of algorithms for probing the posterior
distribution, as a function of large Here we address these two issues in
the context of linear inverse problems subject to additive Gaussian noise
within a hierarchical modelling framework based on a Gaussian prior for the
unknown field and an inverse-gamma prior for a hyper-parameter, namely the
amplitude of the prior variance. The structure of the model is such that the
Gibbs sampler can be easily implemented for probing the posterior distribution.
Subscribing to the dogma that one should think infinite-dimensionally before
implementing in finite dimensions, we present function space intuition and
provide rigorous theory showing that as increases, the component of the
Gibbs sampler for sampling the amplitude of the prior variance becomes
increasingly slower. We discuss a reparametrization of the prior variance that
is robust with respect to the increase in dimension; we give numerical
experiments which exhibit that our reparametrization prevents the slowing down.
Our intuition on the behaviour of the prior hyper-parameter, with and without
reparametrization, is sufficiently general to include a broad class of
nonlinear inverse problems as well as other families of hyper-priors.Comment: to appear, SIAM/ASA Journal on Uncertainty Quantificatio
Fall 2007 Visiting Speaker Series
Speakers include:
Andrew Herod, University of Georgia. Fighting Communism through Urban Planning: The AFL-CIO\u27s Housing Programs in Latin America and the Caribbean during the 1960sJan Bardsley, University of North Carolina at Chapel Hill. Princess, Geisha, Beauty Queen: Women and Democracy in Cold War JapanDonald N. Clark, Trinity University. The Two Koreas: Lessons from the Past, Hope for the Futurehttps://egrove.olemiss.edu/croft_spe/1000/thumbnail.jp
Vitamin K antagonists predispose to calciphylaxis in patients with end-stage renal disease.
BACKGROUND/AIMS: Calciphylaxis is associated with a poor prognosis in dialysis patients, and its pathogenesis remains incompletely understood. Although the use of vitamin K antagonists (VKA) has been implicated, previous reports are conflicting. We aimed to determine if vitamin K antagonists conferred an increased risk of calciphylaxis in patients on dialysis. METHODS: We performed a single-centre, retrospective cohort study of 2,234 patients receiving dialysis, and compared the characteristics of those with and without calciphylaxis. RESULTS: We identified 5 cases of calciphylaxis (all female) between January 2009 and December 2013. Overall, 142 patients (6.4%) were treated with VKA during the study period. Calciphylaxis was more common in the VKA group (4 of 142 patients, OR = 61, 95% CI 6.7-546, p = 0.0001). VKA was withdrawn in all cases and treatment instituted with sodium thiosulphate, cinacalcet and supportive measures. All patients recovered, although there was one sudden cerebrovascular death during follow-up. CONCLUSION: Treatment with VKA predisposes to the development of calciphylaxis.TFH is funded by the Cambridge BRC and NIHR.This is the accepted manuscript for a paper published in Nephron Clinical Practice, Vol. 129, No. 3, 2015, DOI:10.1159/00037144
Development and validation of a Hospital Frailty Risk Score focusing on older people in acute care settings using electronic hospital records: an observational study
Background Older people are increasing users of health care globally. We aimed to establish whether older people with characteristics of frailty and who are at risk of adverse health-care outcomes could be identified using routinely collected data. Methods A three-step approach was used to develop and validate a Hospital Frailty Risk Score from International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) diagnostic codes. First, we carried out a cluster analysis to identify a group of older people (â„75 years) admitted to hospital who had high resource use and diagnoses associated with frailty. Second, we created a Hospital Frailty Risk Score based on ICD-10 codes that characterised this group. Third, in separate cohorts, we tested how well the score predicted adverse outcomes and whether it identified similar groups as other frailty tools. Findings In the development cohort (n=22â139), older people with frailty diagnoses formed a distinct group and had higher non-elective hospital use (33·6 bed-days over 2 years compared with 23·0 bed-days for the group with the next highest number of bed-days). In the national validation cohort (n=1â013â590), compared with the 429â762 (42·4%) patients with the lowest risk scores, the 202â718 (20·0%) patients with the highest Hospital Frailty Risk Scores had increased odds of 30-day mortality (odds ratio 1·71, 95% CI 1·68â1·75), long hospital stay (6·03, 5·92â6·10), and 30-day readmission (1·48, 1·46â1·50). The c statistics (ie, model discrimination) between individuals for these three outcomes were 0·60, 0·68, and 0·56, respectively. The Hospital Frailty Risk Score showed fair overlap with dichotomised Fried and Rockwood scales (kappa scores 0·22, 95% CI 0·15â0·30 and 0·30, 0·22â0·38, respectively) and moderate agreement with the Rockwood Frailty Index (Pearson's correlation coefficient 0·41, 95% CI 0·38â0·47)
Team reasoning and the rational choice of payoff-dominant outcomes in games
Standard game theory cannot explain the selection of payoff-dominant outcomes that are best for all players in common-interest games. Theories of team reasoning can explain why such mutualistic cooperation is rational. They propose that teams can be agents and that individuals in teams can adopt a distinctive mode of reasoning that enables them to do their part in achieving Pareto-dominant outcomes. We show that it can be rational to play payoff-dominant outcomes, given that an agent group identifies. We compare team reasoning to other theories that have been proposed to explain how people can achieve payoff-dominant outcomes, especially with respect to rationality. Some authors have hoped that it would be possible to develop an argument that it is rational to group identify. We identify some largeâprobably insuperableâproblems with this project and sketch some more promising approaches, whereby the normativity of group identification rests on morality
Twenty-three unsolved problems in hydrology (UPH) â a community perspective
This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through on-line media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focussed on process-based understanding of hydrological variability and causality at all space and time scales.
Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come
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