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

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 ($T_{eff}$), metallicity ([Fe/H]), surface gravity (log $g$) when derived from moderate low resolution (R=8000) spectra with S/N $\sim 100$. We calibrated $T_{eff}$ and [Fe/H] as functions of equivalent widths of spectral indices by means of the PCA regression. We derive log $g$, mass, radius, and age from the atmospheric parameters, Gaia parallaxes and evolutionary tracks. We obtained $T_{eff}$/[Fe/H]/log $g$ with precision of 97 K/0.06 dex/0.05 dex. We identify five solar analogs with $V\sim10.5$ (located at $\sim135$ pc): HIP 991, HIP 5811, HIP 69477, HIP 55619 and HIP 61835. Other six stars have $T_{eff}$ close to solar but slightly lower [Fe/H]. Our analogs show no evidence of reddening but for four stars, which present $E(B-V) \geq 0.06$ mag, translating to at least a 200 K decrease in photometric $T_{eff}$.Comment: Paper accepted. Fundamental parameters of the solar analogs are in Table