24,634 research outputs found
Potential impact of load curtailment on the day-ahead Iberian market : a preliminary analysis
ABSTRACT: Demand response (DR) in electricity markets may offer a variety of financial and operational benefits. Typically, customers respond to DR events by adopting curtailment and shifting strategies. This article focuses on the former strategy and assumes that consumers are encouraged to avoid consuming electricity during specific hours of a 24 h day, because the energy price is above a given threshold. It presents a study on the Iberian market, conducted with the help of an agent-based simulation tool, called MATREM. The results are very favorable to the adoption of the load curtailment strategy (as a consequence of the enrollment in different DR programs).info:eu-repo/semantics/publishedVersio
Particle Learning and Smoothing
Particle learning (PL) provides state filtering, sequential parameter
learning and smoothing in a general class of state space models. Our approach
extends existing particle methods by incorporating the estimation of static
parameters via a fully-adapted filter that utilizes conditional sufficient
statistics for parameters and/or states as particles. State smoothing in the
presence of parameter uncertainty is also solved as a by-product of PL. In a
number of examples, we show that PL outperforms existing particle filtering
alternatives and proves to be a competitor to MCMC.Comment: Published in at http://dx.doi.org/10.1214/10-STS325 the Statistical
Science (http://www.imstat.org/sts/) by the Institute of Mathematical
Statistics (http://www.imstat.org
GeMs/GSAOI observations of La Serena 94: an old and far open cluster inside the solar circle
Physical properties were derived for the candidate open cluster La Serena 94,
recently unveiled by the VVV collaboration. Thanks to the exquisite angular
resolution provided by GeMS/GSAOI, we could characterize this system in detail,
for the first time, with deep photometry in JHK - bands. Decontaminated
JHK diagrams reach about 5 mag below the cluster turnoff in H. The locus
of red clump giants in the colour - colour diagram, together with an extinction
law, was used to obtain an average extinction of . The
same stars were considered as standard - candles to derive the cluster
distance, kpc. Isochrones were matched to the cluster colour -
magnitude diagrams to determine its age, , and
metallicity, . A core radius of pc was
found by fitting King models to the radial density profile. By adding up the
visible stellar mass to an extrapolated mass function, the cluster mass was
estimated as M, consistent with an
integrated magnitude of and a tidal radius of
pc. The overall characteristics of La Serena 94 confirm that
it is an old open cluster located in the Crux spiral arm towards the fourth
Galactic quadrant and distant kpc from the Galactic centre. The
cluster distorted structure, mass segregation and age indicate that it is a
dynamically evolved stellar system.Comment: 16 pages, 24 figures, 2 Tables, accepted by MNRAS; corrected typo
Advantages and shortcomings of the utilization of recycled wastes as aggregates in structural concretes
Global material resources are quickly being drained by the demands of global economic development.
Simultaneously, the environmental impacts of the massive amounts of waste generated globally every
year are also growing exponentially. As such, the implementation of waste recycling through its utilization
as a component of a construction material, particularly one with a global demand as high as concrete,
is a strategy which acts in both planes: material efficiency and waste generation. This paper details the
results of a systematic review performed on the scientific literature that concerns the possibility of incorporating
recycled wastes as aggregates in structural ordinary Portland cement concretes. The available
literature suggests that a reduced number of wastes of recycled origin may, albeit in low quantities, be
used in structural OPC concretes. Furthermore, the presence of substances such as glass wastes or
alkali-rich cement fragments in recycled aggregates elevates the potential for expansions originated by
the occurrence, in these concretes, of the well known phenomenon known as alkali-silica reaction.
Moreover, the variety, quantity and the limits to the utilization of these wastes as aggregates in structural
concretes all suggest that a massification of the utilization of recycled aggregates in OPC concretes will
not take place. The investigation also found that, in light of the evidence showing that the performance
of alkali-activated binder concretes is less impacted by the shortcomings of recycled aggregates, recycled
wastes may be better suited for reutilization as aggregates in these concrete compositions.FCT - Fundação para a Ciência e Tecnologia, under the project SFRH/BD/111813/201
Sanitizing the fortress: protection of ant brood and nest material by worker antibiotics
Social groups are at particular risk for parasite infection, which is heightened in eusocial insects by the low genetic diversity of individuals within a colony. To combat this, adult ants have evolved a suite of defenses to protect each other, including the production of antimicrobial secretions. However, it is the brood in a colony that are most vulnerable to parasites because their individual defenses are limited, and the nest material in which ants live is also likely to be prone to colonization by potential parasites. Here, we investigate in two ant species whether adult workers use their antimicrobial secretions not only to protect each other but also to sanitize the vulnerable brood and nest material. We find that, in both leaf-cutting ants and weaver ants, the survival of the brood was reduced and the sporulation of parasitic fungi from them increased, when the workers nursing them lacked functional antimicrobial-producing glands. This was the case for both larvae that were experimentally treated with a fungal parasite (Metarhizium) and control larvae which developed infections of an opportunistic fungal parasite (Aspergillus). Similarly, fungi were more likely to grow on the nest material of both ant species if the glands of attending workers were blocked. The results show that the defense of brood and sanitization of nest material are important functions of the antimicrobial secretions of adult ants and that ubiquitous, opportunistic fungi may be a more important driver of the evolution of these defenses than rarer, specialist parasites
Instanton Corrected Non-Supersymmetric Attractors
We discuss non-supersymmetric attractors with an instanton correction in Type
IIA string theory compactified on a Calabi-Yau three-fold at large volume. For
a stable non-supersymmetric black hole, the attractor point must minimize the
effective black hole potential. We study the supersymmetric as well as
non-supersymmetric attractors for the D0-D4 system with instanton corrections.
We show that in simple models, like the STU model, the flat directions of the
mass matrix can be lifted by a suitable choice of the instanton parameters.Comment: Minor modifications, Corrected typos, 38 pages, 1 figur
Developing a site-conditions map for seismic hazard Assessment in Portugal
The evaluation of site effects on a broad scale is a critical issue for seismic hazard and risk assessment, land use planning and emergency planning. As characterization of site conditions based on the shear-wave velocity has become increasingly important, several methods have been proposed in the literature to estimate its average over the first thirty meters (Vs30) from more extensively available data. These methods include correlations with geologic-geographic defined units and topographic slope. In this paper we present the first steps towards the development of a site–conditions map for Portugal, based on a regional database of shear-wave velocity data, together with geological, geographic, and lithological information. We computed Vs30 for each database site and classified it according to the corresponding geological-lithological information using maps at the smallest scale available (usually 1:50000). We evaluated the consistency of Vs30 values within generalized-geological classes, and assessed the performance of expedient methodologies proposed in the literature
Aceleração do ganho genético para produtividade e outras características chaves para a competitividade da cultura de arroz irrigado.
São discutidas as características chaves visadas pelo melhoramento genético para uma maior competitividade agronômica e comercial do arroz: Produtividade, Alta capacidade de perfilhamento. Resistência ao acamamento das plantas. Resistência à toxidez por excesso de ferro no solo. Tolerância à herbicidas para controle de arroz vermelho e adaptação ao sistema de cultivo de arroz pré-germinado. Resistência à brusone. Tolerância aos estresse de temperatura baixa nas fases de germinação, emergência e vegetativa e vigor inicial de plântulas; Tolerância aos estresses de temperatura alta na fase reprodutiva; Qualidade de grãos.Palestra
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