1,333 research outputs found
A distributed scenario-based stochastic MPC for fault-tolerant microgrid energy management
This paper proposes a fault-tolerant energy management algorithm for microgrid systems composed of several agents. The method stems from the necessity to design an algorithm that takes explicitly into account the possibility of faults and their consequences to avoid solutions which are excessively conservative. A tree of possible fault scenarios is built in a completely distributed way by all the agents of the network; then the resulting optimization problem is solved through a distributed algorithm which not only does not require a high computational power for each agent, but keeps also private all local data and decision variables. The effectiveness of the proposed method is proved through simulation results
Functional Organization of Visual Cortex in the Owl Monkey
In this study, we compared the organization of orientation preference in visual areas V1, V2, and V3. Within these visual areas, we also
quantified the relationship between orientation preference and cytochrome oxidase (CO) staining patterns. V1 maps of orientation
preference contained both pinwheels and linear zones. The location of CO blobs did not relate in a systematic way to maps of orientation;
although, as in other primates, there were approximately twice as many pinwheels as CO blobs. V2 contained bands of high and low
orientation selectivity. The bands of high orientation selectivity were organized into pinwheels and linear zones, but iso-orientation
domains were twice as large as those in V1. Quantitative comparisons between bands containing high or low orientation selectivity and
CO dark and light bands suggested that at least four functional compartments exist in V2, CO dense bands with either high or low
orientation selectivity, and CO light bands with either high or low selectivity. We also demonstrated that two functional compartments
exist in V3, with zones of high orientation selectivity corresponding to CO dense areas and zones of low orientation selectivity corresponding
to CO pale areas. Together with previous findings, these results suggest that the modular organization of V1 is similar across
primates and indeed across most mammals. V2 organization in owl monkeys also appears similar to that of other simians but different
from that of prosimians and other mammals. Finally, V3 of owl monkeys shows a compartmental organization for orientation selectivity
that remains to be demonstrated in other primates
Testing Asteroseismic Radii of Dwarfs and Subgiants with Kepler and Gaia
We test asteroseismic radii of Kepler main-sequence and subgiant stars by
deriving their parallaxes which are compared with those of the first Gaia data
release. We compute radii based on the asteroseismic scaling relations as well
as by fitting observed oscillation frequencies to stellar models for a subset
of the sample, and test the impact of using effective temperatures from either
spectroscopy or the infrared flux method. An offset of 3%, showing no
dependency on any stellar parameters, is found between seismic parallaxes
derived from frequency modelling and those from Gaia. For parallaxes based on
radii from the scaling relations, a smaller offset is found on average;
however, the offset becomes temperature dependent which we interpret as
problems with the scaling relations at high stellar temperatures. Using the
hotter infrared flux method temperature scale, there is no indication that
radii from the scaling relations are inaccurate by more than about 5%. Taking
the radii and masses from the modelling of individual frequencies as reference
values, we seek to correct the scaling relations for the observed temperature
trend. This analysis indicates that the scaling relations systematically
overestimate radii and masses at high temperatures, and that they are accurate
to within 5% in radius and 13% in mass for main-sequence stars with
temperatures below 6400 K. However, further analysis is required to test the
validity of the corrections on a star-by-star basis and for more evolved stars.Comment: 12 pages, 9 figures. Accepted for publication in MNRA
Resilient Distributed MPC Algorithm for Microgrid Energy Management under Uncertainties
This paper proposes a resilient distributed energy management algorithm able to cope with different types of faults in a DC microgrid system. A distributed optimization method allows to solve the energy management problem without sharing any private data with the network and reducing the computational cost for each agent, with respect to the centralised case. A distributed MPC scheme based on distributed optimization is used to cope with uncertainty that characterizes the microgrid operation. In order to be resilient to faults that limit the amount of power available to consumers, we propose to adaptively store an amount of power in the storage systems to support the loads. A soft constraint on the minimum energy stored in each battery is introduced for feasibility and to cope with persistent faults. The effectiveness of the method is proved by extensive simulation results considering faults on three types of components: renewable generator, distribution grid and communication network
AGB subpopulations in the nearby globular cluster NGC 6397
It has been well established that Galactic Globular clusters (GCs) harbour
more than one stellar population, distinguishable by the anti-correlations of
light element abundances (C-N, Na-O, and Mg-Al). These studies have been
extended recently to the asymptotic giant branch (AGB). Here we investigate the
AGB of NGC 6397 for the first time. We have performed an abundance analysis of
high-resolution spectra of 47 RGB and 8 AGB stars, deriving Fe, Na, O, Mg and
Al abundances. We find that NGC 6397 shows no evidence of a deficit in Na-rich
AGB stars, as reported for some other GCs - the subpopulation ratios of the AGB
and RGB in NGC 6397 are identical, within uncertainties. This agrees with
expectations from stellar theory. This GC acts as a control for our earlier
work on the AGB of M 4 (with contrasting results), since the same tools and
methods were used.Comment: 10 pages, 7 figures, 8 tables (2 online-only). Accepted for
publication in MNRA
Occurrence of phytoplasma associated with sugarcane yellow leaf syndrome in three regions of São Paulo State, Brazil
Uma doença conhecida como sÃndrome do amarelecimento foliar da cana-de-açúcar ou amarelinho causou danos expressivos à cultura no estado de São Paulo, na década de noventa. A sÃndrome também foi registrada em outros paÃses e investigações sobre a etiologia evidenciaram a associação da doença com vÃrus e fitoplasma, de forma isolada ou simultânea. A doença é potencialmente importante e ocorre endemicamente no estado paulista, por esta razão o presente estudo buscou demonstrar a ocorrência do fitoplasma em três tradicionais regiões produtoras de cana, localizadas no estado de São Paulo, através da detecção molecular deste agente em plantas naturalmente infectadas. Para isto, plantas sintomáticas das variedades SP71-6163, SP71-6180 e SP89-1115 foram amostradas em Piracicaba, Jaú e Ribeirão Preto e a partir do tecido foliar foi extraÃdo o DNA total. PCR duplo foi processado com os "primers" P1/Tint-16F2n/R2 e os produtos foram analisados por eletroforese em gel de agarose. Amplificações de fragmentos de DNA de 1,2 kb evidenciaram a presença de fitoplasma em 36% das plantas sintomáticas e revelaram a sua ocorrência nas três regiões amostradas. Os resultados demonstraram a associação do fitoplasma com a doença e a importância de se manter uma atenta vigilância nos campos e viveiros, bem como buscar genótipos com bom nÃvel de resistência nos programas de melhoramento.Sugarcane yellow leaf syndrome caused serious damage to crops in the São Paulo State, Brazil, in the 1990's. The syndrome was also reported in other countries and investigations into the etiology revealed an association between the disease and virus and/or phytoplasma. The disease is potentially important and occurs endemically in that State, and for this reason the present study was conducted in order to demonstrate the occurrence of phytoplasma in three traditional sugarcane-producing areas, in São Paulo State, through molecular detection from naturally infected plants. Symptomatic plants belonging to varieties SP71-6163, SP71-6180 and SP89-1115 were sampled from Piracicaba, Jaú and Ribeirão Preto, and total DNA was extracted from foliar tissues. Nested PCR was conducted with primer pairs P1/Tint-16F2n/R2, and the amplified products were analyzed by electrophoresis on agarose gels. Amplified DNA fragments of 1.2 kb evidenced the presence of phytoplasma in 36% of symptomatic plants and revealed its occurrence in all sampled regions. The results demonstrated that phytoplasma is associated with the disease and that it is important to keep a safe inspection of nurseries and monitoring plants in the field, as well as to select sugarcane genotypes with a good level of resistance in breeding programs.Coordenação de Aperfeiçoamento de Pessoal NÃvel Superior - CAPE
- …