20 research outputs found
Empirical correction techniques: analysis and applications to chaotically driven low-order atmospheric models
Contemporary tools for reducing model error in weather and climate forecasting models include empirical correction techniques. In this paper we explore the use of such techniques on low-order atmospheric models. We first present an iterative linear regression method for model correction that works efficiently when the reference truth is sampled at large time intervals, which is typical for real world applications. Furthermore we investigate two recently proposed empirical correction techniques on Lorenz models with constant forcing while the reference truth is given by a Lorenz system driven with chaotic forcing. Both methods indicate that the largest increase in predictability comes from correction terms that are close to the average value of the chaotic forcing
Development of a Methodology for Parametric Analysis of STOL Airpark Geo-Density
Vehicles designed for urban air mobility (UAM)or on-demand mobility (ODM) applications typically adopt an architecture enabling vertical takeoff and landing (VTOL) capabilities. UAM or ODM systems featuring these capabilities typically have a smaller ground footprint but are subject to a number of performance compromises that make sizing and optimizing the vehicles more challenging. These design challenges can be further compounded when additional environmental considerations are taken into account and in particular if electric propulsion is considered. Alternative architectures such as short takeoff and landing (STOL) and super-short takeoff and landing (SSTOL) vehicles are thus investigated because they present possible advantages in terms of energy efficiency, overall vehicle performance, and noise footprint. However, the larger ground footprint of the infrastructure necessary to operate these systems means that these systems may be more difficult to integrate into a urban and suburban environment. One objective of this research is to estimate the geo-density of airparks suitable for STOL and SSTOL operations based on vehicle performance and ground footprint parameters. In turn, this helps establish requirements for the field performances of STOL and
SSTOL vehicles to be considered for ODM and UAM applications. This research proposes and interactive and parametric design and trade-off analysis environment to help decision makers assess the suitability of candidate cities for STOL and SSTOL operations. Preliminary results for the Miami metropolitan area show that an average airpark geo-density of 1.66 airparks per
square mile can be achieved with a 300 foot long runway
Behavioral Modernity and the Cultural Transmission of Structured Information: The Semantic Axelrod Model
Cultural transmission models are coming to the fore in explaining increases
in the Paleolithic toolkit richness and diversity. During the later
Paleolithic, technologies increase not only in terms of diversity but also in
their complexity and interdependence. As Mesoudi and O'Brien (2008) have shown,
selection broadly favors social learning of information that is hierarchical
and structured, and multiple studies have demonstrated that teaching within a
social learning environment can increase fitness. We believe that teaching also
provides the scaffolding for transmission of more complex cultural traits.
Here, we introduce an extension of the Axelrod (1997} model of cultural
differentiation in which traits have prerequisite relationships, and where
social learning is dependent upon the ordering of those prerequisites. We
examine the resulting structure of cultural repertoires as learning
environments range from largely unstructured imitation, to structured teaching
of necessary prerequisites, and we find that in combination with individual
learning and innovation, high probabilities of teaching prerequisites leads to
richer cultural repertoires. Our results point to ways in which we can build
more comprehensive explanations of the archaeological record of the Paleolithic
as well as other cases of technological change.Comment: 24 pages, 7 figures. Submitted to "Learning Strategies and Cultural
Evolution during the Paleolithic", edited by Kenichi Aoki and Alex Mesoudi,
and presented at the 79th Annual Meeting of the Society for American
Archaeology, Austin TX. Revised 5/14/1