4,611 research outputs found
Distributed Energy Trading: The Multiple-Microgrid Case
In this paper, a distributed convex optimization framework is developed for
energy trading between islanded microgrids. More specifically, the problem
consists of several islanded microgrids that exchange energy flows by means of
an arbitrary topology. Due to scalability issues and in order to safeguard
local information on cost functions, a subgradient-based cost minimization
algorithm is proposed that converges to the optimal solution in a practical
number of iterations and with a limited communication overhead. Furthermore,
this approach allows for a very intuitive economics interpretation that
explains the algorithm iterations in terms of "supply--demand model" and
"market clearing". Numerical results are given in terms of convergence rate of
the algorithm and attained costs for different network topologies.Comment: 24 pages, 8 figures; new version answering reviewers' comments; the
paper is now accepted for publication in the IEEE Transactions on Industrial
Electronics; the paper is now publishe
On the Statistical Relationship between CME Speed and Soft X-ray Flux and Fluence of the Associated Flare
Both observation and theory reveal a close relationship between the
kinematics of coronal mass ejections (CMEs) and the thermal energy release
traced by the related soft X-ray (SXR) emission. The major problem of empirical
studies of this relationship is the distortion of the CME speed by the
projection effect in the coronagraphic measurements. We present a re-assessment
of the statistical relationship between CME velocities and SXR parameters,
using the SOHO/LASCO catalog and GOES whole Sun observations during the period
1996 to 2008. 49 events were identified where CMEs originated near the limb, at
central meridian distances between 70 and 85, and had a
reliably identified SXR burst, the parameters of which - peak flux and fluence
- could be determined with some confidence. We find similar correlations
between the logarithms of CME speed and of SXR peak flux and fluence as several
earlier studies, with correlation coefficients of 0.48 and 0.58, respectively.
Correlations are slightly improved over an unrestricted CME sample when only
limb events are used. However, a broad scatter persists. We derive the
parameters of the CME-SXR relationship and use them to predict ICME arrival
times at Earth. We show that the CME speed inferred from SXR fluence
measurements tends to perform better than SoHO/LASCO measurements in the
prediction of ICME arrival times near 1 AU. The estimation of the CME speed
from SXR observations can therefore make a valuable contribution to space
weather predictions.Comment: Solar Physics, in pres
Asynchronous online ADMM for consensus problems
In this paper, we consider the consensus problem where a set of nodes cooperate to minimize a global cost. In particular, we consider an online setting and propose an online algorithm based on the alternating direction method of multipliers. Besides, we take into account the asynchronous operation of the nodes. In this context, we prove that the algorithm attains sublinear regret on the objective. Finally, we assess numerically the performance of the algorithm in a distributed sparse regression problem
Design of a mixed reality workspace for an expressive humanoid robot
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (p. 25).The MIT Media Laboratory Robotic Life Group's Leonardo is a highly expressive robot used for, among other things, social learning and human-robot teamwork research. A mixed reality workspace was conceived to aid in experimentation and demonstration of human-robot interaction by providing a complex state space and several interaction possibilities. A box concept was selected for its ability to incorporate several interaction mechanisms while allowing for meaningful physical tasks. A first iteration of the system was completed, which was controllable primarily through serial communication with a computer, while providing minimal physical communication. For a second revision of the system, physical interaction devices were developed which could be actuated by either the robot or a human, so as to better explore social interaction. Further development of the project will yield a robust, flexible and expandable tool with which future robot social learning and teamwork research can be performed.by Javier G. Matamoros.S.B
Adoptando diferentes perspectivas de investigación sobre concepto de derivada
En este trabajo se aborda una trayectoria de investigaciones considerando el concepto de derivada. En primer lugar, se presentan investigaciones sobre el desarrollo de la comprensión del concepto y, posteriormente, investigaciones centradas en el aprendizaje de estudiantes para profesor de matemáticas de lo que se considera conocimiento adecuado para la enseñanza de dicho concepto. Esto conlleva, en cierto modo cierta transferencia del conocimiento en el sentido de que dichas investigaciones aportan información para el diseño de módulos de formación, permitiendo realizar investigaciones en el contexto de aula sobre el aprendizaje de los futuros profesores
Falta de transparencia formal de una cláusula suelo en un contrato de préstamo hipotecario: comentario a la STS 8 septiembre 2014 (RJ 2014, 4660)
Una cláusula suelo es abusiva por falta de transparencia formal cuando el consumidor no pudo razonablemente conocer, al tiempo de celebrar el contrato, la existencia y efectos de aquélla.A floor clause is abusive for lack of formal transparency when the consumer can not to know clearly, at the time of concluding the contract, the existence and effects of that clause
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