2020
Autores
Bouarour, YI; Perraut, K; Menard, F; Brandner, W; Garatti, ACO; Caselli, P; van Dishoeck, E; Dougados, C; Garcia Lopez, R; Grellmann, R; Henning, T; Klarmann, L; Labadie, L; Natta, A; Sanchez Bermudez, J; Thi, WF; de Zeeuw, PT; Amorim, A; Baubock, M; Benisty, M; Berger, JP; Clenet, Y; du Foresto, VC; Duvert, G; Eckart, A; Eisenhauer, F; Eupen, F; Filho, M; Gao, F; Garcia, P; Gendron, E; Genzel, R; Gillessen, S; Jimenez Rosales, A; Jocou, L; Hippler, S; Horrobin, M; Hubert, Z; Kervella, P; Lacour, S; Le Bouquin, JB; Lena, P; Ott, T; Paumard, T; Perrin, G; Pfuhl, O; Rousset, G; Scheithauer, S; Shangguan, J; Stadler, J; Straub, O; Straubmeier, C; Sturm, E; Vincent, FH; von Fellenberg, SD; Widmann, F; Wiest, M;
Publicação
ASTRONOMY & ASTROPHYSICS
Abstract
Context. Studies of the dust distribution, composition, and evolution of protoplanetary disks provide clues for understanding planet formation. However, little is known about the innermost regions of disks where telluric planets are expected to form.Aims. We aim constrain the geometry of the inner disk of the T Tauri star RY Lup by combining spectro-photometric data and interferometric observations in the near-infrared (NIR) collected at the Very Large Telescope Interferometer. We use PIONIER data from the ESO archive and GRAVITY data that were obtained in June 2017 with the four 8m telescopes.Methods. We use a parametric disk model and the 3D radiative transfer code MCFOST to reproduce the spectral energy distribution (SED) and match the interferometric observations. MCFOST produces synthetic SEDs and intensity maps at different wavelengths from which we compute the modeled interferometric visibilities and closure phases through Fourier transform.Results. To match the SED from the blue to the millimetric range, our model requires a stellar luminosity of 2.5 L-circle dot, higher than any previously determined values. Such a high value is needed to accommodate the circumstellar extinction caused by the highly inclined disk, which has been neglected in previous studies. While using an effective temperature of 4800 K determined through high-resolution spectroscopy, we derive a stellar radius of 2.29 R-circle dot. These revised fundamental parameters, when combined with the mass estimates available (in the range 1.3-1.5 M-circle dot), lead to an age of 0.5-2.0 Ma for RY Lup, in better agreement with the age of the Lupus association than previous determinations. Our disk model (that has a transition disk geometry) nicely reproduces the interferometric GRAVITY data and is in good agreement with the PIONIER ones. We derive an inner rim location at 0.12 au from the central star. This model corresponds to an inclination of the inner disk of 50 degrees, which is in mild tension with previous determinations of a more inclined outer disk from SPHERE (70 degrees in NIR) and ALMA (67 5 degrees) images, but consistent with the inclination determination from the ALMA CO spectra (55 +/- 5 degrees). Increasing the inclination of the inner disk to 70 degrees leads to a higher line-of-sight extinction and therefore requires a higher stellar luminosity of 4.65 L-circle dot to match the observed flux levels. This luminosity would translate to a stellar radius of 3.13 R-circle dot, leading to an age of 2-3 Ma, and a stellarmass of about 2 M-circle dot, in disagreement with the observed dynamical mass estimate of 1.3-1.5 M-circle dot. Critically, this high-inclination inner disk model also fails to reproduce the visibilities observed with GRAVITY.Conclusions. The inner dust disk, as traced by the GRAVITY data, is located at a radius in agreement with the dust sublimation radius. An ambiguity remains regarding the respective orientations of the inner and outer disk, coplanar and mildly misaligned, respectively.As our datasets are not contemporary and the star is strongly variable, a deeper investigation will require a dedicated multi-technique observing campaign.
2020
Autores
Mansouri, SA; Ahmarinejad, A; Javadi, MS; Catalao, JPS;
Publicação
ENERGY
Abstract
The integrated use of electricity and natural gas has captured great attention over recent years, mainly due to the high efficiency and economic considerations. According to the energy hub design and operation, which allows using different energy carriers, it has turned into a critical topic. This paper develops a two-stage stochastic model for energy hub planning and operation. The uncertainties of the problem have arisen from the electric, heating, and cooling load demand forecasts, besides the intermittent output of the solar photovoltaic (PV) system. The scenarios of the uncertain parameters are generated using the Monte-Carlo simulation (MCS), and the backward scenario reduction technique is used to alleviate the number of generated scenarios. Furthermore, this paper investigates the effectiveness of demand response programs (DRPs). The presented model includes two stages, where at the first stage, the optimal energy hub design is carried out utilizing the particle swarm optimization (PSO) algorithm. In this respect, the capacity of the candidate assets has been considered continuous, enabling the planning entity to precisely design the energy hub. The problem of the optimal energy hub operation is introduced at the second stage of the model formulated as mixed-integer non-linear programming (MINLP). The proposed framework is simulated using a typical energy hub to verify its effectiveness and efficiency.
2020
Autores
Lisboa, IVMV; Barroso, JMP; Rocha, TdJV;
Publicação
Brazilian Journal of Development
Abstract
2020
Autores
Martins, A; Almeida, C; Lima, P; Viegas, D; Silva, J; Almeida, JM; Almeida, C; Ramos, S; Silva, E;
Publicação
GLOBAL OCEANS 2020: SINGAPORE - U.S. GULF COAST
Abstract
This paper presents an autonomous robotic system, IRIS, designed for lost fishing gear recovery. The vehicle was developed in the context of the NetTag project. This is a European Union project funded by EASME the Executive Agency for Small and Medium Enterprises addressing marine litter, and the reduction of quantity and impact of lost fishing gears in the ocean. NetTag intends to produce new technological devices for location and recovery of fishing gear and educational material about marine litter, raise awareness of fisheries industry and other stakeholders about the urgent need to combat marine litter and increase scientific knowledge on marine litter problematic, guaranteeing the engagement of fishers to adopt better practices to reduce and prevent marine litter derived from fisheries. The design of IRIS is presented in detail, addressing the mechanical design, hardware architecture, sensor system and navigation and control. Preliminary tests in tank and in controlled sea conditions are presented and ongoing developments on the recovery system are discussed.
2020
Autores
Pereira, J; Silva, FJG; Sá, JC; Bastos, JA;
Publicação
Lecture Notes in Networks and Systems
Abstract
The automotive industry is one of the most demanding sectors of the global market. The response capacity and flexibility of companies represent a key factor for their success. Applying Six Sigma, it was carried out an improvement project aiming at reducing the quantity of scrap on the most critical sector of a automotive components’ manufacturer achieving a better comprehension of the flows, process characteristics and different variables associated to the scrap generation, identifying the equipment responsible for that scrap and its type. Brain- storming sessions were performed, as well as the application of 5 Why’s and 5W2H techniques in order to fulfill the Ishikawa diagrams aiming at understanding possible root-causes for the scrap generation. A definition of the improvement actions has been developed. A reduction of 15% was achieve just in the machine identified as the main generator of scrap in these processes. © 2020, Springer Nature Switzerland AG.
2020
Autores
Jimenez Rosales, A; Dexter, J; Widmann, F; Baubock, M; Abuter, R; Amorim, A; Berger, JP; Bonnet, H; Brandner, W; Clenet, Y; de Zeeuw, PT; Eckart, A; Eisenhauer, F; Schreiber, NMF; Garcia, P; Gao, F; Gendron, E; Genzel, R; Gillessen, S; Habibi, M; Haubois, X; Heissel, G; Henning, T; Hippler, S; Horrobin, M; Jochum, L; Jocou, L; Kaufer, A; Kervella, P; Lacour, S; Lapeyrere, V; Le Bouquin, JB; Lena, P; Nowak, M; Ott, T; Paumard, T; Perraut, K; Perrin, G; Pfuhl, O; Rodriguez Coira, G; Shangguan, J; Scheithauer, S; Stadler, J; Straub, O; Straubmeier, C; Sturm, E; Tacconi, LJ; Vincent, F; von Fellenberg, S; Waisberg, I; Wieprecht, E; Wiezorrek, E; Woillez, J; Yazici, S; Zins, G;
Publicação
ASTRONOMY & ASTROPHYSICS
Abstract
We study the time-variable linear polarisation of Sgr A* during a bright near-infrared flare observed with the GRAVITY instrument on July 28, 2018. Motivated by the time evolution of both the observed astrometric and polarimetric signatures, we interpret the data in terms of the polarised emission of a compact region ("hotspot") orbiting a black hole in a fixed, background magnetic field geometry. We calculated a grid of general relativistic ray-tracing models, created mock observations by simulating the instrumental response, and compared predicted polarimetric quantities directly to the measurements. We take into account an improved instrument calibration that now includes the instrument's response as a function of time, and we explore a variety of idealised magnetic field configurations. We find that the linear polarisation angle rotates during the flare, which is consistent with previous results. The hotspot model can explain the observed evolution of the linear polarisation. In order to match the astrometric period of this flare, the near horizon magnetic field is required to have a significant poloidal component, which is associated with strong and dynamically important fields. The observed linear polarisation fraction of similar or equal to 30% is smaller than the one predicted by our model (similar or equal to 50%). The emission is likely beam depolarised, indicating that the flaring emission region resolves the magnetic field structure close to the black hole.
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