Mass accretion rates from multi-band photometry in the Carina Nebula: the case of Trumpler 14

We present a study of the mass accretion rates of pre-Main Sequence (PMS) stars in the cluster Trumpler 14 (Tr14) in the Carina Nebula. Using optical multi-band photometry we were able to identify 356 PMS stars showing H-alpha excess emission with equivalent width EW(H-alpha)>20\AA. We interpret this observational feature as indication that these objects are still actively accreting gas from their circumstellar medium. From a comparison of the HR diagram with PMS evolutionary models we derive ages and masses of the PMS stars. We find that most of the PMS objects are younger than 10 Myr with a median age of ~3 Myr. Surprisingly, we also find that ~20% of the mass accreting objects are older than 10 Myr. For each PMS star in Trumpler 14 we determine the mass accretion rate ($\dot{M}_{acc}$) and discuss its dependence on mass and age. We finally combine the optical photometry with near-IR observations to build the spectral energy distribution (SED) for each PMS star in Tr14. The analysis of the SEDs suggests the presence of transitional discs in which a large amount of gas is still present and sustains accretion onto the PMS object at ages older than 10 Myr. Our results, discussed in light of recent recent discoveries with Herschel of transitional discs containing a massive gas component around the relatively old PSM stars TW Hydrae, 49 Ceti, and HD 95086, support a new scenario in which old and evolved debris discs still host a significant amount of gas.Comment: 12 pages, 13 figures, accepted for publication on A&

Automated Design of Elevator Systems: Experimenting with Constraint-Based Approaches

System configuration and design is a well-established topic in AI. While many successful applications exists, there are still areas of manufacturing where AI techniques find little or no application. We focus on one such area, namely building and installation of elevator systems, for which we are developing an automated design and configuration tool. The questions that we address in this paper are: (i) What are the best ways to encode some subtasks of elevator design into constraint-based representations? (ii) What are the best tools available to solve the encodings? We contribute an empirical analysis to address these questions in our domain of interest, as well as the complete set of benchmarks to foster further researc

High homogeneity solenoidal magnet for cesium frequency standard

In Cs frequency standards a zone of highly uniform magnetic flux density, lower in value of 0.1 T, is required. The magnetic homogeneity value is tied to the overall accuracy of the standard and, for an accuracy of 10-14, a design value 1 p.p.m. is required. For this purpose a resistive solenoid 700 mm long with a bore radius of 32.5 mm has been designed and built. This paper reports the design process, the measurements on the manufactured magnet and the shimming strategy used to reach the homogeneity target

Comparative study of some dynamic properties of liquids and grains in the classroom

Visando entender as diferenças entre as propriedades dinâmicas dos materiais granulares e as propriedades dinâmicas dos líquidos, foram realizados experimentos usando água e grãos de arroz e açúcar. Os experimentos requerem poucos recursos e foram pensados para que possam ser desenvolvidos com facilidade na sala de aula ou num laboratório de ensino. Os resultados mostraram que o fluxo de grãos difere significativamente do fluxo de líquidos.In order to understand the differences in the dynamic properties between granular materials and liquids, experiments using water, rice and sugar grains were performed. The experiments require few material resources and were thought so as to be easily made in a classroom or in a teaching laboratory. The results showed that grain's flow differs significantly from that of liquids.Banco Santande

On the impact of the stem electrical impedance in neural network algorithms for plant monitoring applications

Smart agriculture offers an environmental-friendly path with respect to unsustainable farming that depletes the nutrients in the soil leading to a persistent degradation of ecosystems caused by population growth. Artificial Intelligence (AI) can help mitigate this issue by predicting plant health status to reduce the use of chemicals and optimize water usage. This paper proposes a custom framework to train neural networks and a comparison among different models to point out the impact and the importance of the stem electrical impedance in addition to environmental parameters for plant monitoring applications. In particular, the paper demonstrates how stem electrical impedance improves the accuracy of the proposed neural network application for plant status classification. The data set is composed of electrical impedance spectra and environmental data acquired on four tobacco plants for a two-month-long experiment. In this paper, we describe the acquisition system architecture, the feature composition of the data set, a general overview of the developed framework, and the training of the neural networks showing the different results considering both the stem impedance and the environmental parameters

Monitoring the Distribution, Abundance, and Movements of Birds Near Vancouver International Airport

The Vancouver International Airport (YVR) is Canada’s second-busiest civil airport and is located on the Fraser River delta—the staging and wintering ground for millions of birds representing many taxonomic groups. Consequently, YVR experiences one of the highest bird-strike rates of any airport in Canada. Since 1994, LGL Limited has investigated and monitored avian ecology as it relates to existing and potential hazards to air-traffic safety at YVR. A formalized monitoring program is on-going. The distribution, abundance, and flight patterns of birds are recorded and summarized by individual species or by taxonomic group. Monthly and semiannual reports present information that depict changes in the local bird community regarding spatial, temporal, and behavioural factors. A multi-year database permits the comparison of these factors during a present period to past highs, lows, and averages. Data analyses are complex, but have been streamlined through the development and application of database programming developed specifically for this project. Using this, and other information such as habitat mapping and bird-strike statistics, “hazard maps” are generated. Together with the remainder of the reports, these maps provide the Wildlife Control Program with an objective view of bird hazards at YVR. Among other uses, this information can guide control efforts and gauge the effectiveness of bird control over time

Monitoring the Distribution, Abundance, and Movements of Birds Near Vancouver International Airport

The Vancouver International Airport (YVR) is Canada’s second-busiest civil airport and is located on the Fraser River delta—the staging and wintering ground for millions of birds representing many taxonomic groups. Consequently, YVR experiences one of the highest bird-strike rates of any airport in Canada. Since 1994, LGL Limited has investigated and monitored avian ecology as it relates to existing and potential hazards to air-traffic safety at YVR. A formalized monitoring program is on-going. The distribution, abundance, and flight patterns of birds are recorded and summarized by individual species or by taxonomic group. Monthly and semiannual reports present information that depict changes in the local bird community regarding spatial, temporal, and behavioural factors. A multi-year database permits the comparison of these factors during a present period to past highs, lows, and averages. Data analyses are complex, but have been streamlined through the development and application of database programming developed specifically for this project. Using this, and other information such as habitat mapping and bird-strike statistics, “hazard maps” are generated. Together with the remainder of the reports, these maps provide the Wildlife Control Program with an objective view of bird hazards at YVR. Among other uses, this information can guide control efforts and gauge the effectiveness of bird control over time

Simulation of a molecular QCA wire

Molecular Quantum Dot Cellular Automata (MQCA) are among the most promising emerging technologies for the expected theoretical operating frequencies (THz), the high device densities and the non-cryogenic working temperature. In this work we simulated a molecular QCA wire, based on a molecule synthesized ad-hoc for this technology. The results discussed are obtained by means of iterative steps of ab-initio calculations