21,707 research outputs found
Optimal Control Realizations of Lagrangian Systems with Symmetry
A new relation among a class of optimal control systems and Lagrangian
systems with symmetry is discussed. It will be shown that a family of solutions
of optimal control systems whose control equation are obtained by means of a
group action are in correspondence with the solutions of a mechanical
Lagrangian system with symmetry. This result also explains the equivalence of
the class of Lagrangian systems with symmetry and optimal control problems
discussed in \cite{Bl98}, \cite{Bl00}.
The explicit realization of this correspondence is obtained by a judicious
use of Clebsch variables and Lin constraints, a technique originally developed
to provide simple realizations of Lagrangian systems with symmetry. It is
noteworthy to point out that this correspondence exchanges the role of state
and control variables for control systems with the configuration and Clebsch
variables for the corresponding Lagrangian system.
These results are illustrated with various simple applications
Investigating Fatigue Performance on the Foamed Asphalt Specimens Generated Using Different Foam Properties
An evaluation of fatigue resistance for foamed asphalt mixture is very demanding since the binder is not continuously distributed on the aggregate surface and this mixtures contains water, the content of which dramatically affects the mechanical properties. This paper discusses the results of laboratory fatigue testingon the foamed asphalt mixtures in which the specimens are generated using three different foamed bitumen properties. Foamed bitumen as the binder was produced at three different foaming water content (FWC) at a temperature of 180oC using a 70/100 pen. The aggregates were mechanically mixed with foamed bitumen using a Hobart mixer. The resulting mixtures were then compacted using a gyratory compactor to generatespecimen with diameter of 100 mm. The specimens were fatigue tested at various stress levels at a temperature of 20oC following a curing period of 3 days at 40oC. Overall, fatigue performance of foamed asphalt can be identified based upon both stress and strain for mixtures produced at FWC 1%, 5%, and 10%
A hierarchical Bayesian model to infer PL(Z) relations using Gaia parallaxes
Aims. We aim at creating a Bayesian model to infer the coefficients of PL or
PLZ relations that propagates uncertainties in the observables in a rigorous
and well founded way. Methods. We propose a directed acyclic graph to encode
the conditional probabilities of the inference model that will allow us to
infer probability distributions for the PL and PL(Z) relations. We evaluate the
model with several semi-synthetic data sets and apply it to a sample of 200
fundamental mode and first overtone mode RR Lyrae stars for which Gaia DR1
parallaxes and literature Ks-band mean magnitudes are available. We define and
test several hyperprior probabilities to verify their adequacy and check the
sensitivity of the solution with respect to the prior choice. Results. The main
conclusion of this work is the absolute necessity of incorporating the existing
correlations between the observed variables (periods, metallicities and
parallaxes) in the form of model priors in order to avoid systematically biased
results, especially in the case of non-negligible uncertainties in the
parallaxes. The tests with the semi-synthetic data based on the data set used
in Gaia Collaboration et al. (2017) reveal the significant impact that the
existing correlations between parallax, metallicity and periods have on the
inferred parameters. The relation coefficients obtained here have been
superseded by those presented in Muraveva et al. (2018a), that incorporates the
findings of this work and the more recent Gaia DR2 measurements.Comment: 14 pages, 12 figures. Submitted to A&
A Meeting with Native American Elders, Activists, Select Funders and Scholars
On June 20-21, 2003, the Marguerite Casey Foundation (MCF) brought together a group of Native people from across the country to participate in a consultative session designed to help the Foundation develop a comprehensive strategy to strengthen and support indigenous families and communities. With the help of CURL, a report was written up documenting the meeting
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