22,047 research outputs found
Recommended from our members
Cost Efficient Distributed Load Frequency Control in Power Systems
The introduction of new technologies and increased penetration of renewable resources is altering the power distribution landscape which now includes a larger numbers of micro-generators. The centralized strategies currently employed for performing frequency control in a cost efficient way need to be revisited and decentralized to conform with the increase of distributed generation in the grid. In this paper, the use of Multi-Agent and Multi-Objective Reinforcement Learning techniques to train models to perform cost efficient frequency control through decentralized decision making is proposed. More specifically, we cast the frequency control problem as a Markov Decision Process and propose the use of reward composition and action composition multi-objective techniques and compare the results between the two. Reward composition is achieved by increasing the dimensionality of the reward function, while action composition is achieved through linear combination of actions produced by multiple single objective models. The proposed framework is validated through comparing the observed dynamics with the acceptable limits enforced in the industry and the cost optimal setups
Molecular dynamics simulations of complex shaped particles using Minkowski operators
The Minkowski operators (addition and substraction of sets in vectorial
spaces) has been extensively used for Computer Graphics and Image Processing to
represent complex shapes. Here we propose to apply those mathematical concepts
to extend the Molecular Dynamics (MD) Methods for simulations with
complex-shaped particles. A new concept of Voronoi-Minkowski diagrams is
introduced to generate random packings of complex-shaped particles with tunable
particle roundness. By extending the classical concept of Verlet list we
achieve numerical efficiencies that do not grow quadratically with the body
number of sides. Simulations of dissipative granular materials under shear
demonstrate that the method complies with the first law of thermodynamics for
energy balance.Comment: Submitted to Phys. Rev.
Cooler and bigger than thought? Planetary host stellar parameters from the InfraRed Flux Method
Effective temperatures and radii for 92 planet-hosting stars as determined
from the InfraRed Flux Method (IRFM) are presented and compared with those
given by other authors using different approaches. The IRFM temperatures we
have derived are systematically lower than those determined from the
spectroscopic condition of excitation equilibrium, the mean difference being as
large as 110 K. They are, however, consistent with previous IRFM studies and
with the colors derived from Kurucz and MARCS model atmospheres. Comparison
with direct measurements of stellar diameters for 7 dwarf stars, which
approximately cover the range of temperatures of the planet-hosting stars,
suggest that the IRFM radii and temperatures are reliable in an absolute scale.
A better understanding of the fundamental properties of the stars with planets
will be achieved once this discrepancy between the IRFM and the spectroscopic
temperature scales is resolved.Comment: 15 pages, 4 figures. Accepted for publication in Ap
Ratcheting of granular materials
We investigate the quasi-static mechanical response of soils under cyclic
loading using a discrete model of randomly generated convex polygons. This
response exhibits a sequence of regimes, each one characterized by a linear
accumulation of plastic deformation with the number of cycles. At the grain
level, a quasi-periodic ratchet-like behavior is observed at the contacts,
which excludes the existence of an elastic regime. The study of this slow
dynamics allows to explore the role of friction in the permanent deformation of
unbound granular materials supporting railroads and streets.Comment: Changed content Submitted to Physical Review Letter
Measuring the transition to homogeneity with photometric redshift surveys
We study the possibility of detecting the transition to homogeneity using
photometric redshift catalogs. Our method is based on measuring the fractality
of the projected galaxy distribution, using angular distances, and relies only
on observable quantites. It thus provides a way to test the Cosmological
Principle in a model-independent unbiased way. We have tested our method on
different synthetic inhomogeneous catalogs, and shown that it is capable of
discriminating some fractal models with relatively large fractal dimensions, in
spite of the loss of information due to the radial projection. We have also
studied the influence of the redshift bin width, photometric redshift errors,
bias, non-linear clustering, and surveyed area, on the angular homogeneity
index H2 ({\theta}) in a {\Lambda}CDM cosmology. The level to which an upcoming
galaxy survey will be able to constrain the transition to homogeneity will
depend mainly on the total surveyed area and the compactness of the surveyed
region. In particular, a Dark Energy Survey (DES)-like survey should be able to
easily discriminate certain fractal models with fractal dimensions as large as
D2 = 2.95. We believe that this method will have relevant applications for
upcoming large photometric redshift surveys, such as DES or the Large Synoptic
Survey Telescope (LSST).Comment: 14 pages, 14 figure
Análisis y validación de modelos digitales de elevaciones mediante datos LIDAR
entre otras, siendo en muchas ocasiones uno de los factores determinantes de la calidad de sus estudios. En este
trabajo se realiza un análisis comparativo entre Modelos Digitales de Elevaciones (MDE) generados mediante diferentes
métodos de interpolación y uno obtenido mediante tecnología LIDAR. De esta forma, asumiendo este último
como verdad-terreno, se establece cual de los modelos interpolados representa con mayor fidelidad la superficie
terrestre.
Las técnicas de interpolación utilizadas han sido la lineal, splines, TIN y ANUDEM obteniendo un total de 4 MDEs
interpolados. El análisis de los errores en los diferentes modelos se ha llevado a cabo mediante tres procedimientos
1. Análisis de la distribución del error de las elevaciones en los MDEs interpolados.
2. Evaluación de los errores en varias capas de variables derivadas del MDE
3. Evaluación de los errores de localización de las redes de drenaje extraídas de los diferentes modelos respecto
a la red generada a partir del modelo LIDAR. Con respecto a la ubicación de la red de drenaje, se han estimado dos
tipos de error: error de omisión y error de comisión.Terrain modelling is an important task in many scientific areas such as climatology, hydrology among others, with
a deep influence on the quality of the results. In this work we make a comparative analysis of Digital Elevation Model
(DEM) generated by different interpolation algorithms with one obtained by LIDAR technology, assuming the later as
ground truth.
Four different interpolation algorithms have been used: linear splines, TIN and ANUDEM, that means a total of
four interpolated DEMs. The analysis of errors in the different models was carried out with three different procedures:
1. Error distribution analysis in the interpolated DEMs.
2. Error evaluation in terrain parameters derived from DEM.
3. Analysis of the positional errors in the extract
- …