Fitting isochrones to open cluster photometric data III. Estimating metallicities from UBV photometry

The metallicity is a critical parameter that affects the correct determination fundamental characteristics stellar cluster and has important implications in Galactic and Stellar evolution research. Fewer than 10 % of the 2174 currently catalog open clusters have their metallicity determined in the literature. In this work we present a method for estimating the metallicity of open clusters via non-subjective isochrone fitting using the cross-entropy global optimization algorithm applied to UBV photometric data. The free parameters distance, reddening, age, and metallicity simultaneously determined by the fitting method. The fitting procedure uses weights for the observational data based on the estimation of membership likelihood for each star, which considers the observational magnitude limit, the density profile of stars as a function of radius from the center of the cluster, and the density of stars in multi-dimensional magnitude space. We present results of [Fe/H] for nine well-studied open clusters based on 15 distinct UBV data sets. The [Fe/H] values obtained in the ten cases for which spectroscopic determinations were available in the literature agree, indicating that our method provides a good alternative to determining [Fe/H] by using an objective isochrone fitting. Our results show that the typical precision is about 0.1 dex

On a family of topological invariants similar to homotopy groups

The intimacy relation between smooth loops, which is a strong homotopy relation, is generalized to smooth maps defined on the n-cube, leading to a family of groups similar to the classical homotopy groups. The formal resemblance between the two families of groups is explored. Special attention is devoted to the role of these groups as topological invariants for manifolds and as tools for describing geometrical structures defined on manifolds such as bundles and connections

Image transfer through a chaotic channel by intensity correlations

The three-wave mixing processes in a second-order nonlinear medium can be used for imaging protocols, in which an object field is injected into the nonlinear medium together with a reference field and an image field is generated. When the reference field is chaotic, the image field is also chaotic and does not carry any information about the object. We show that a clear image of the object be extracted from the chaotic image field by measuring the spatial intensity correlations between this field and one Fourier component of the reference. We experimentally verify this imaging protocol in the case of frequency downconversion.Comment: 17 pages, 7 figure

Large Graph Analysis in the GMine System

Current applications have produced graphs on the order of hundreds of thousands of nodes and millions of edges. To take advantage of such graphs, one must be able to find patterns, outliers and communities. These tasks are better performed in an interactive environment, where human expertise can guide the process. For large graphs, though, there are some challenges: the excessive processing requirements are prohibitive, and drawing hundred-thousand nodes results in cluttered images hard to comprehend. To cope with these problems, we propose an innovative framework suited for any kind of tree-like graph visual design. GMine integrates (a) a representation for graphs organized as hierarchies of partitions - the concepts of SuperGraph and Graph-Tree; and (b) a graph summarization methodology - CEPS. Our graph representation deals with the problem of tracing the connection aspects of a graph hierarchy with sub linear complexity, allowing one to grasp the neighborhood of a single node or of a group of nodes in a single click. As a proof of concept, the visual environment of GMine is instantiated as a system in which large graphs can be investigated globally and locally

The Viana footbridge: construction and dynamic monitoring

A new moveable footbridge was recently built at the entrance of Marina Atlantico in the city of Viana do Castelo, Portugal. This paper presents a brief description of the global solution, with a special focus on the characterisation of the construction methods adopted. Particular consideration is given to the construction of the pivot pylon and the steel structure, showing how all the bridge components work together to ensure a safe working relationship with the marina, the river and users of the continuous bicycling and pedestrian pathway running across the closed bridge. The mechanical, hydraulic, electrical and navigational light systems play fundamental roles, especially during bridge opening and closing operations. Moreover, as this light footbridge is susceptible to vibrations due to human traffic, the paper also describes the dynamic tests performed during and after construction, including two ambient vibration tests, the measurement of cable-stay forces, and tests with groups of pedestrians used to evaluate induced vibration levels along with the monitoring of bridge accelerations over 4 months of use

Entrepreneurship as a career option: do temporary workers have the competencies, intention and willingness to become entrepreneurs?

This study analyses the entrepreneurial intentions and the willingness of temporary workers to consider entrepreneurship as a career option. Specifically, we analyse the self-perception of entrepreneurial competencies of a group of temporary workers. A total of 184 temporary workers participated in the study. We performed a multiple correspondence analysis (MCA) to identify profiles of entrepreneurial competencies according to temporary workers' entrepreneurial intention and willingness to consider entrepreneurship as a career option. We conclude that temporary workers do not always perceive themselves as having the necessary competencies to choose for entrepreneurship in their occupational paths. The self-perception of different levels of entrepreneurial competencies is also associated with different intentions and willingness to consider entrepreneurship as a career option. Finally, we provide insights for practice, which can be considered as a starting point for activities aiming to develop entrepreneurial competencies at the individual or organisational levels.info:eu-repo/semantics/submittedVersio

Continuous dynamic monitoring of bridges: different perspectives of application

This paper makes a brief characterisation of some aspects related with the extensive research activity of the Laboratory of Vibrations and Structural Monitoring (ViBest) of the Faculty of Engineering of the University of Porto (FEUP) in the field of Continuous Dynamic Monitoring of Bridges and Special Structures, selecting four examples where large high quality databases have been created since 2007, namely Infante D. Henrique bridge, Pedro e Ines footbride, FEUP Campus stress-ribbon footbridge and Trezoi railway bridge