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Publications

2020

Environmental and Economic Constraints on the Use of Lubricant Oils for Wind and Hydropower Generation: The Case of NATURGY

Authors
González Reyes, GA; Bayo Besteiro, S; Llobet, JV; Añel, JA;

Publication
SUSTAINABILITY

Abstract
Lubricant oil is an essential element in wind and hydropower generation. We present a lifecycle assessment (LCA) of the lubricant oils (mineral, synthetic and biodegradable) used in hydropower and wind power generation. The results are given in terms of energy used, associated emissions and costs. We find that, for the oil turbines and regulation systems considered here, biodegradable oil is a better option in terms of energy and CO2 equivalent emissions than mineral or synthetic oils, from production and recycling through to handling. However, synthetic and mineral oils are better options due to the potential risks associated with the use of biodegradable oil, generally when it comes into contact with water. There are also significant savings to be made in the operation of wind turbines when using an improved type of synthetic oil.

2020

The GRAVITY young stellar object survey: III. The dusty disk of RY Lup

Authors
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;

Publication
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

The Effect of a Linear Tuning between the Antigenic Stimulations of CD4(+) T Cells and CD4(+) Tregs

Authors
Yusuf, AA; Figueiredo, IP; Afsar, A; Burroughs, NJ; Pinto, AA; Oliveira, BMPM;

Publication
MATHEMATICS

Abstract
We study the equilibria of an Ordinary Differencial Equation (ODE) system where CD4+ effector or helper T cells and Regulatory T cells (Tregs) are present. T cells trigger an immune response in the presence of their specific antigen. Regulatory T cells (Tregs) play a role in limiting auto-immune diseases due to their immune-suppressive ability. Here, we present explicit exact formulas that give the relationship between the concentration of T cells, the concentration of Tregs, and the antigenic stimulation of T cells, when the system is at equilibria, stable or unstable. We found a parameter region of bistability, limited by two thresholds of antigenic stimulation of T cells (hysteresis). Moreover, there are values of the slope parameter of the tuning for which an isola-center bifurcation appears, and, for some other values, there is a transcritical bifurcation. We also present time evolutions of the ODE system.

2020

Minimizing Wind Power Curtailment Using a Continuous-Time Risk-Based Model of Generating Units and Bulk Energy Storage

Authors
Nikoobakht, A; Aghaei, J; Shafie Khah, M; Catalao, JPS;

Publication
IEEE TRANSACTIONS ON SMART GRID

Abstract
Wind power curtailment (WPC) occurs because of the non-correlation between wind power generation (WPG) and load, and also due to the fast sub-hourly variations of WPG. Recently, advances in energy storage technologies facilitate the use of bulk energy storage units (ESUs) to provide the ramping required to respond to fast sub-hourly variations of WPGs. To minimize the sub-hourly WPC probability, this paper addresses a generic continuous-time risk-based model for sub-hourly scheduling of energy generating units and bulk ESUs in the day-ahead unit commitment (UC) problem. Accordingly, the Bernstein polynomials are hosted to model the continuous-time risk-based UC problem with ESU constraints. Also, the proposed continuous-time risk-based model ensures that the generating units and ESUs track the sub-hourly variations of WPG, while the load and generation are balanced in each sub-hourly intervals. Finally, the performance of the proposed model is demonstrated by simulating the IEEE 24-bus Reliability and Modified IEEE 118-bus test systems.

2020

Emidio Garcia School Pilot description: A Robosteam Erasmus plus Project Activity based on a Challenge based Learning Approach

Authors
Camargo, C; Brancaliao, L; Goncalves, J; Lima, J; Ramos, M; Fernandes, L; Trovisco, M; Conde, M;

Publication
PROCEEDINGS OF THE 2020 IEEE GLOBAL ENGINEERING EDUCATION CONFERENCE (EDUCON 2020)

Abstract
In this paper it is described a Pilot that took place at Emidio Garcia School from Braganca, Portugal. The presented Pilot is based on a Challenge based Learning Approach, being an activity of the RoboSTEAM - Integrating STEAM and Computational Thinking development by using robotics and physical devices - ERASMUS+ Project. In the presented educational experiment it were used physical devices, being chosen the mBot robot, programmed using Scratch. The presented challenges had as research question a global problem that was Wildfires. Student had to propose and to develop solutions based on the use of robots to prevent and fight wildfires. The students that participated in the experiment were secondary school students, from Spain and Portugal, with their background in technology and arts respectively. Previously to the experiment the involved students filled a STEM semantic Survey and during the experiments their performance was evaluated.

2020

Emergency Landing Spot Detection for Unmanned Aerial Vehicle

Authors
Loureiro, G; Soares, L; Dias, A; Martins, A;

Publication
FOURTH IBERIAN ROBOTICS CONFERENCE: ADVANCES IN ROBOTICS, ROBOT 2019, VOL 2

Abstract
This paper addresses the topic of emergency landing spot detection for Unmanned Aerial Vehicles (UAVs). During operation, the vehicle is susceptible to faults and must be able to predict the land spot able to ensure that the UAV will be able to land without damages and injuries to humans and structures. A method was developed, based on geometric features extracted from Light Detection And Ranging (LIDAR) data. A simulation environment was developed in order to validate the effectiveness and the robustness of the proposed method.

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