28,404 research outputs found
Using qualitative models to define sustainable management for the commons in data poor conditions
Acknowledgments This work was funded by the University of Aberdeen and Scottish Natural Heritage (SNH) and their support is gratefully acknowledged. We thank MASTS (the Marine Alliance for Science and Technology for Scotland) for their role in funding this work and B. Leyshon and F. Manson (SNH) for fruitful discussion.Peer reviewedPostprin
Evaluation of Ares-I Control System Robustness to Uncertain Aerodynamics and Flex Dynamics
This paper discusses the application of robust control theory to evaluate robustness of the Ares-I control systems. Three techniques for estimating upper and lower bounds of uncertain parameters which yield stable closed-loop response are used here: (1) Monte Carlo analysis, (2) mu analysis, and (3) characteristic frequency response analysis. All three methods are used to evaluate stability envelopes of the Ares-I control systems with uncertain aerodynamics and flex dynamics. The results show that characteristic frequency response analysis is the most effective of these methods for assessing robustness
Theoretical Examination of the Lithium Depletion Boundary
We explore the sensitivity in open cluster ages obtained by the lithium
depletion boundary (LDB) technique to the stellar model input physics. The LDB
age technique is limited to open clusters with ages ranging from 20 to 200 Myr.
Effective 1-sig errors in the LDB technique due to uncertain input physics are
roughly 3% at the oldest age increasing to 8% at the youngest age. Bolometric
correction uncertainties add an additional 10 to 6% error to the LDB age
technique for old and young clusters, respectively. Rotation rates matching the
observed fastest rotators in the Pleiades affect LDB ages by less than 2%. The
range of rotation rates in an open cluster are expected to ``smear'' the LDB
location by only 0.02 mag for a Pleiades age cluster increasing to 0.06 mag for
a 20 Myr cluster. Thus, the observational error of locating the LDB (~7-10%)
and the bolometric correction uncertainty currently dominate the error in LDB
ages. For our base case, we formally derive a LDB age of 148 +- 19 Myr for the
Pleiades, where the error includes 8, 3, and 9% contributions from
observational, theoretical, and bolometric correction sources, respectively. A
maximally plausible 0.3 magnitude shift in the I-band bolometric correction to
reconcile main sequence isochrone fits with the observed (V-I) color for the
low mass Pleiades members results in an age of 126 +- 11 Myr, where the error
includes observational and theoretical errors only. Upper main-sequence-fitting
ages that do not include convective core overshoot for the Pleiades (~75 Myr)
are ruled out by the LDB age technique.Comment: 35 pages, 9 figures, accepted Ap
Enhancing Energy Production with Exascale HPC Methods
High Performance Computing (HPC) resources have become the key actor for achieving more ambitious challenges in many disciplines. In this step beyond, an explosion on the available parallelism and the use of special purpose
processors are crucial. With such a goal, the HPC4E project applies new exascale HPC techniques to energy industry simulations, customizing them if necessary, and going beyond the state-of-the-art in the required HPC exascale
simulations for different energy sources. In this paper, a general overview of these methods is presented as well as some specific preliminary results.The research leading to these results has received funding from the European Union's Horizon 2020 Programme (2014-2020) under the HPC4E Project (www.hpc4e.eu), grant agreement n° 689772, the Spanish Ministry of
Economy and Competitiveness under the CODEC2 project (TIN2015-63562-R), and
from the Brazilian Ministry of Science, Technology and Innovation through Rede
Nacional de Pesquisa (RNP). Computer time on Endeavour cluster is provided by the
Intel Corporation, which enabled us to obtain the presented experimental results in
uncertainty quantification in seismic imagingPostprint (author's final draft
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