2018
Authors
Migueis, VL; Freitas, A; Garcia, PJV; Silva, A;
Publication
DECISION SUPPORT SYSTEMS
Abstract
The early classification of university students according to their potential academic performance can be a useful strategy to mitigate failure, to promote the achievement of better results and to better manage resources in higher education institutions. This paper proposes a two-stage model, supported by data mining techniques, that uses the information available at the end of the first year of students' academic career (path) to predict their overall academic performance. Unlike most literature on educational data mining, academic success is inferred from both the average grade achieved and the time taken to conclude the degree. Furthermore, this study proposes to segment students based on the dichotomy between the evidence of failure or high performance at the beginning of the degree program, and the students' performance levels predicted by the model. A data set of 2459 students, spanning the years from 2003 to 2015, from a European Engineering School of a public research University, is used to validate the proposed methodology. The empirical results demonstrate the ability of the proposed model to predict the students' performance level with an accuracy above 95%, in an early stage of the students' academic path. It is found that random forests are superior to the other classification techniques that were considered (decision trees, support vector machines, naive Bayes, bagged trees and boosted trees). Together with the prediction model, the suggested segmentation framework represents a useful tool to delineate the optimum strategies to apply, in order to promote higher performance levels and mitigate academic failure, overall increasing the quality of the academic experience provided by a higher education institution.
2018
Authors
Rodrigues, JC; Freitas, A; Garcia, P; Maia, C; Pierre Favre, M;
Publication
2018 3RD INTERNATIONAL CONFERENCE OF THE PORTUGUESE SOCIETY FOR ENGINEERING EDUCATION (CISPEE)
Abstract
Doctoral programmes are facing several challenges in modern societies. The societal role of the University, funded by the state, requires it to: a) increase the offer and admission of third cycle students; b) to reach industry/companies expectations; c) to ensure reasonable employability prospects for the PhD candidates. With the current demography, most candidates can only find a job in industry/companies. Therefore, significant pressure is being put on doctoral programmes to include transferable skills in their curriculum. This paper presents a course "Fit for Industry?" aiming at filling this need. The course design methodology is presented in detail. It includes: a) the involvement of industry since its inception; b) the joint identification of a small number of key competencies to be addressed; c) the inclusion of assessment and feedback mechanisms in its design; d) an immersive and international dimension. It was found that the course had a profound impact on the candidates' perceptions of industry and valued by industry participants. Other stakeholders, such as PhD supervisors, also had a positive perception. The paper concludes with recommendations for those willing to replicate the course locally.
2018
Authors
Abuter, R; Amorim, A; Anugu, N; Bauböck, M; Benisty, M; Berger, JP; Blind, N; Bonnet, H; Brandner, W; Buron, A; Collin, C; Chapron, F; Clénet, Y; Du Foresto, VC; De Zeeuw, PT; Deen, C; Delplancke Ströbele, F; Dembet, R; Dexter, J; Duvert, G; Eckart, A; Eisenhauer, F; Finger, G; Schreiber, NMF; Fédou, P; Garcia, P; Lopez, RG; Gao, F; Gendron, E; Genzel, R; Gillessen, S; Gordo, P; Habibi, M; Haubois, X; Haug, M; Haußmann, F; Henning, T; Hippler, S; Horrobin, M; Hubert, Z; Hubin, N; Rosales, AJ; Jochum, L; Jocou, L; Kaufer, A; Kellner, S; Kendrew, S; Kervella, P; Kok, Y; Kulas, M; Lacour, S; Lapeyrère, V; Lazareff, B; Le Bouquin, JB; Léna, P; Lippa, M; Lenzen, R; Mérand, A; Müler, E; Neumann, U; Ott, T; Palanca, L; Paumard, T; Pasquini, L; Perraut, K; Perrin, G; Pfuhl, O; Plewa, PM; Rabien, S; Ramírez, A; Ramos, J; Rau, C; Rodríguez Coira, G; Rohloff, RR; Rousset, G; Sanchez Bermudez, J; Scheithauer, S; Schöller, M; Schuler, N; Spyromilio, J; Straub, O; Straubmeier, C; Sturm, E; Tacconi, LJ; Tristram, KRW; Vincent, F; Von Fellenberg, S; Wank, I; Waisberg, I; Widmann, F; Wieprecht, E; Wiest, M; Wiezorrek, E; Woillez, J; Yazici, S; Ziegler, D; Zins, G;
Publication
ASTRONOMY & ASTROPHYSICS
Abstract
The highly elliptical, 16-year-period orbit of the star S2 around the massive black hole candidate Sgr A* is a sensitive probe of the gravitational field in the Galactic centre. Near pericentre at 120 AU approximate to 1400 Schwarzschild radii, the star has an orbital speed of approximate to 7650 km s(-1), such that the first-order effects of Special and General Relativity have now become detectable with current capabilities. Over the past 26 years, we have monitored the radial velocity and motion on the sky of S2, mainly with the SINFONI and NACO adaptive optics instruments on the ESO Very Large Telescope, and since 2016 and leading up to the pericentre approach in May 2018, with the four-telescope interferometric beam-combiner instrument GRAVITY. From data up to and including pericentre, we robustly detect the combined gravitational redshift and relativistic transverse Doppler effect for S2 of z = Delta lambda/lambda approximate to 200 km s(-1)/c with different statistical analysis methods. When parameterising the post-Newtonian contribution from these effects by a factor f, with f = 0 and f = 1 corresponding to the Newtonian and general relativistic limits, respectively, we find from posterior fitting with different weighting schemes f = 0.90 +/- 0.09 vertical bar(stat) +/- 0.151 vertical bar(sys). The S2 data are inconsistent with pure Newtonian dynamics.
2018
Authors
Sanchez Bermudez, J; Weigelt, G; Bestenlehner, JM; Kervella, P; Brandner, W; Henning, T; Mueller, A; Perrin, G; Pott, JU; Scholler, M; van Boeke, R; Abuter, R; Accardo, M; Amorim, A; Anugu, N; Avila, G; Benisty, M; Berger, JP; Blind, N; Bonnet, H; Bourget, P; Brast, R; Buron, A; Cantalloube, F; Garatti, ACO; Cassaing, F; Chapron, F; Choquet, E; Clenet, Y; Collin, C; du Foresto, VC; de Wit, W; de Zeeuw, T; Deen, C; Delplancke Strobele, F; Dembet, R; Derie, F; Dexter, J; Duvert, G; Ebert, M; Eckart, A; Eisenhauer, F; Esselborn, M; Fedou, P; Garcia, PJV; Dabo, CEG; Lopez, RG; Gao, F; Gendron, E; Genzel, R; Gillessen, S; Haubois, X; Haug, M; Haussmann, F; Hippler, S; Horrobin, M; Huber, A; Hubert, Z; Hubin, N; Hummel, CA; Jakob, G; Jochum, L; Jocou, L; Karl, M; Kaufer, A; Kellner, S; Kendrew, S; Kern, L; Kiekebusch, M; Klein, R; Kolb, J; Kulas, M; Lacour, S; Lapeyrere, V; Lazareff, B; Le Bouquin, JB; Lena, P; Lenzen, R; Leveque, S; Lippa, M; Magnard, Y; Mehrgan, L; Mellein, M; Merand, A; Moreno Ventas, J; Moulin, T; Muller, E; Mueller, F; Neumann, U; Oberti, S; Ott, T; Pallanca, L; Panduro, J; Pasquini, L; Paumard, T; Percheron, I; Perraut, K; Petrucci, PO; Pfluger, A; Pfuhl, O; Duc, TP; Plewa, PM; Popovic, D; Rabien, S; Ramirez, A; Ramos, J; Rau, C; Riquelme, M; Rodriguez Coira, G; Rohloff, RR; Rosales, A; Rousset, G; Scheithauer, S; Schuhler, N; Spyromilio, J; Straub, O; Straubmeier, C; Sturm, E; Suarez, M; Tristram, KRW; Ventura, N; Vincent, F; Waisberg, I; Wank, I; Widmann, F; Wieprecht, E; Wiest, M; Wiezorrek, E; Wittkowski, M; Woillez, J; Wolff, B; Yazici, S; Ziegler, D; Zins, G;
Publication
ASTRONOMY & ASTROPHYSICS
Abstract
Context. eta Car is one of the most intriguing luminous blue variables in the Galaxy. Observations and models of the X-ray, ultraviolet, optical, and infrared emission suggest a central binary in a highly eccentric orbit with a 5.54 yr period residing in its core. 2D and 3D radiative transfer and hydrodynamic simulations predict a primary with a dense and slow stellar wind that interacts with the faster and lower density wind of the secondary. The wind-wind collision scenario suggests that the secondary's wind penetrates the primary's wind creating a low-density cavity in it, with dense walls where the two winds interact. However, the morphology of the cavity and its physical properties are not yet fully constrained. Aims. We aim to trace the inner similar to 5-50 au structure of eta Car's wind-wind interaction, as seen through Br gamma and, for the first time, through the He i 2s-2p line. Methods. We have used spectro-interferometric observations with the K-band beam-combiner GRAVITY at the VLTI. The analyses of the data include (i) parametrical model-fitting to the interferometric observables, (ii) a CMFGEN model of the source's spectrum, and (iii) interferometric image reconstruction. Results. Our geometrical modeling of the continuum data allows us to estimate its FWHM angular size close to 2 mas and an elongation ratio epsilon = 1.06 +/- 0.05 over a PA = 130 degrees +/- 20 degrees. Our CMFGEN modeling of the spectrum helped us to confirm that the role of the secondary should be taken into account to properly reproduce the observed Br gamma and He i lines. Chromatic images across the Br gamma line reveal a southeast arc-like feature, possibly associated to the hot post-shocked winds flowing along the cavity wall. The images of the He i 2s-2p line served to constrain the 20 mas (similar to 50 au) structure of the line-emitting region. The observed morphology of He i suggests that the secondary is responsible for the ionized material that produces the line profile. Both the Br gamma and the He i 2s-2p maps are consistent with previous hydrodynamical models of the colliding wind scenario. Future dedicated simulations together with an extensive interferometric campaign are necessary to refine our constraints on the wind and stellar parameters of the binary, which finally will help us predict the evolutionary path of eta Car.
2018
Authors
Boné, A; Amorim, A; Gordo, P; Hemprich, I; Kroes, G; Glauser, A; March, S; Raskin, G; Garcia, P;
Publication
SPACE TELESCOPES AND INSTRUMENTATION 2018: OPTICAL, INFRARED, AND MILLIMETER WAVE
Abstract
We present a solution to the challenges of interfacing the ELT's METIS to the telescope using a steerable hexapod structure. To guide the architectural choices, lumped physical models were derived from inverse kinematics in order to address the load distribution in each arm. Complete FE Analysis is carried on the optimal solutions of these models. The hexapod arms, which are high precision heavy duty linear actuators enduring forces in the excess of 30 tons, are designed using standard components whenever possible. An overall fully functional support structure design, satisfying the ESO/ELT and METIS requirements, is described.
2018
Authors
Sanchez Bermudez, J; Millour, F; Baron, F; van Boekel, R; Bourges, L; Duvert, G; Garcia, PJV; Gomes, N; Hofmann, KH; Henning, T; Isbell, JW; Lopez, B; Matter, A; Pott, JU; Schertl, D; Thiebaut, E; Weigelt, G; Young, J;
Publication
EXPERIMENTAL ASTRONOMY
Abstract
During the last two decades, the first generation of beam combiners at the Very Large Telescope Interferometer has proved the importance of optical interferometry for high-angular resolution astrophysical studies in the near- and mid-infrared. With the advent of 4-beam combiners at the VLTI, the u - v coverage per pointing increases significantly, providing an opportunity to use reconstructed images as powerful scientific tools. Therefore, interferometric imaging is already a key feature of the new generation of VLTI instruments, as well as for other interferometric facilities like CHARA and JWST. It is thus imperative to account for the current image reconstruction capabilities and their expected evolutions in the coming years. Here, we present a general overview of the current situation of optical interferometric image reconstruction with a focus on new wavelength-dependent information, highlighting its main advantages and limitations. As an Appendix we include several cookbooks describing the usage and installation of several state-of-the art image reconstruction packages. To illustrate the current capabilities of the software available to the community, we recovered chromatic images, from simulated MATISSE data, using the MCMC software SQUEEZE. With these images, we aim at showing the importance of selecting good regularization functions and their impact on the reconstruction.
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