3,557 research outputs found
Edge Selection in Bilinear Dynamical Networks
In large-scale networks, agents (e.g., sensors and actuators) and links
(e.g., couplings and communication links) can fail or be (cyber-)attacked. In
this paper, we focus on continuous-time bilinear networks, where additive
disturbances model attack/uncertainty on agents/states (a.k.a. node
disturbances) and multiplicative disturbances model attack/uncertainty on
couplings between agents/states (a.k.a. link disturbances). We then investigate
a network robustness notion in terms of the underlying digraph of the network,
and structure of exogenous uncertainties/attacks. Specifically, we define the
robustness measure using the H2-norm of the network and calculate it in terms
of the reachability Gramian of the bilinear system. The main result shows that
under certain conditions, the measure is supermodular over the set of all
possible attacked links. The supermodular property facilitates the efficient
solution finding of the optimization problem. We conclude the paper with a few
examples illustrating how different structures can make the system more or less
vulnerable to malicious attacks on links and present our concluding remarks.Comment: 6 pages, 2 figure
Liquid crystal phase and waterlike anomalies in a core-softened shoulder-dumbbells system
Using molecular dynamics we investigate the thermodynamics, dynamics and
structure of 250 diatomic molecules interacting by a core-softened potential.
This system exhibits thermodynamics, dynamics and structural anomalies: a
maximum in density-temperature plane at constante pressure and maximum and
minimum points in the diffusivity and translational order parameter against
density at constant temperature. Starting with very dense systems and
decreasing density the mobility at low temperatures first increases, reach a
maximum, then decreases, reach a minimum and finally increases. In the
pressure-temperature phase diagram the line of maximum translational order
parameter is located outside the line of diffusivity extrema that is enclosing
the temperature of maximum density line. We compare our results with the
monomeric system showing that the anisotropy due to the dumbbell leads to a
much larger solid phase and to the appearance of a liquid crystal phase. the
double ranged thermodynamic and dynamic anomalies.Comment: 14 pages, 5 figure
The vernacular house between the Cávado and the Ave, Portugal
Publicado em "Vernacular heritage and earthen architecture : contributions for sustainable development", ISBN 978-1-138-00083-4With acknowledged authenticity and cultural heritage value, rural vernacular construction of Entre-Douro-e-Minho represents the results of the centuries-old relation between men and available natural resources. Abandoned or victim of armful interventions, this unique heritage acquired economi- cal value by the growing interest on rural environment and life. It represents a mean to economical and social boosting of these depressed areas, but at the same time exposing them to the threatening lack of knowledge and property speculation. In order to protect and prevent future damages to this fragile herit- age, it’s fundamental the study and identification of its identity and technical-constructive key features. This paper presents the results of a fieldwork study performed between the Cávado and Ave rivers, which aimed to identify morfo-typologies, materials and construction techniques of the existent schist heritage. The data collected aims to contribute to its preservation and to assist technicians in future rehabilitation projects in the area
Ant-Balanced multiple traveling salesmen: ACO-BmTSP
A new algorithm based on the ant colony optimization (ACO) method for the multiple traveling salesman problem (mTSP) is presented and defined as ACO-BmTSP. This paper addresses the problem of solving the mTSP while considering several salesmen and keeping both the total travel cost at the minimum and the tours balanced. Eleven different problems with several variants were analyzed to validate the method. The 20 variants considered three to twenty salesmen regarding 11 to 783 cities. The results were compared with best-known solutions (BKSs) in the literature. Computational experiments showed that a total of eight final results were better than those of the BKSs, and the others were quite promising, showing that with few adaptations, it will be possible to obtain better results than those of the BKSs. Although the ACO metaheuristic does not guarantee that the best solution will be found, it is essential in problems with non-deterministic polynomial time complexity resolution or when used as an initial bound solution in an integer programming formulation. Computational experiments on a wide range of benchmark problems within an acceptable time limit showed that compared with four existing algorithms, the proposed algorithm presented better results for several problems than the other algorithms did.info:eu-repo/semantics/publishedVersio
Ageing profiling of craft beers: a sensorial and chemical overview
One of the main differences between craft and commercial beers is the presence of active yeast in the bottle, which can have high impact on beer stability during shelflife. For this reason, sensory and chemical beer profiling during storage is of upmost importance when focusing quality control. This study investigated the changes that occur during the storage/ageing of four different craft beers and two commercial beers, which were used for comparison. Sensory analysis of capped and corked beers was performed overtime accompanied by sampling for minor volatiles analysis. Craft beers showed an aromatic profile more intense than the commercial beers and kept the profile similar after six months, as well as the commercial beers. Fruity, floral and caramel were among the main descriptors found for the beers studied, and maintained their intensity during the analysis time. Minor compounds analysis was coherent with the aromatic profiles obtained, as well as those portrayed in the literature, however most of the main ageing markers reported were not found in the beers studied. Among the minor volatiles studied esters concentration varied differently depending on beer type and alcohols, fatty acids, carbonyl compounds and pyrazines concentrations increased for all beers. However, variations on minor volatiles composition had low impact on sensorial perception. The results allowed to conclude that the craft beers maintained the sensory quality as a commercial beer, over a six month period, with the benefit of having more intense flavors and aromas when compared to the commercial beers studied.info:eu-repo/semantics/publishedVersio
Plant growth-promoting bacteria in phytoremediation of metal-polluted soils:Current knowledge and future directions
Faint solar analogs: at the limit of no reddening
The flux distribution of solar analogs is required for calculating the
spectral albedo of Solar System bodies such as asteroids and trans-Neptunian
objects. Ideally a solar analog should be comparably faint as the target of
interest, but only few analogs fainter than V = 9 were identified so far. Only
atmospheric parameters equal to solar guarantee a flux distribution equal to
solar as well, while only photometric colors equal to solar do not. Reddening
is also a factor to consider when selecting faint analog candidates. We
implement the methodology for identifying faint analogs at the limit of
precision allowed by current spectroscopic surveys. We quantify the precision
attainable for the atmospheric parameters effective temperature (),
metallicity ([Fe/H]), surface gravity (log ) when derived from moderate low
resolution (R=8000) spectra with S/N . We calibrated and
[Fe/H] as functions of equivalent widths of spectral indices by means of the
PCA regression. We derive log , mass, radius, and age from the atmospheric
parameters, Gaia parallaxes and evolutionary tracks. We obtained
/[Fe/H]/log with precision of 97 K/0.06 dex/0.05 dex. We identify
five solar analogs with (located at pc): HIP 991, HIP
5811, HIP 69477, HIP 55619 and HIP 61835. Other six stars have close
to solar but slightly lower [Fe/H]. Our analogs show no evidence of reddening
but for four stars, which present mag, translating to at
least a 200 K decrease in photometric .Comment: Paper accepted. Fundamental parameters of the solar analogs are in
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