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Publications

2020

The multi-period vehicle routing problem with refueling decisions: Traveling further to decrease fuel cost?

Authors
Neves Moreira, F; Amorim Lopes, M; Amorim, P;

Publication
TRANSPORTATION RESEARCH PART E-LOGISTICS AND TRANSPORTATION REVIEW

Abstract
Most vehicle routing approaches disregard the need to refuel fleets. However, planners search for opportunities to refuel at lower prices even if, counter-intuitively, distant fuel stations need to be visited. We propose a novel mathematical formulation and develop branch-and-cut and matheuristic algorithms to efficiently tackle this problem. Results indicate that, to minimize costs, detour distances may increase up to 6 percentage points when fuel stations with lower prices are farther away from the depot. For practice, these insights imply that current policies disregarding station location and/or fuel prices along with "myopic" planning horizons may lead to sub-optimal decisions.

2020

Embedded Fiber Sensors to Monitor Temperature and Strain of Polymeric Parts Fabricated by Additive Manufacturing and Reinforced with NiTi Wires

Authors
Nascimento, M; Inacio, P; Paixao, T; Camacho, E; Novais, S; Santos, TG; Braz Fernandes, FMB; Pinto, JL;

Publication
SENSORS

Abstract
This paper focuses on three main issues regarding Material Extrusion (MEX) Additive Manufacturing (AM) of thermoplastic composites reinforced by pre-functionalized continuous Nickel-Titanium (NiTi) wires: (i) Evaluation of the effect of the MEX process on the properties of the pre-functionalized NiTi, (ii) evaluation of the mechanical and thermal behavior of the composite material during usage, (iii) the inspection of the parts by Non-Destructive Testing (NDT). For this purpose, an optical fiber sensing network, based on fiber Bragg grating and a cascaded optical fiber sensor, was successfully embedded during the 3D printing of a polylactic acid (PLA) matrix reinforced by NiTi wires. Thermal and mechanical perturbations were successfully registered as a consequence of thermal and mechanical stimuli. During a heating/cooling cycle, a maximum contraction of approximate to 100 mu m was detected by the cascaded sensor in the PLA material at the end of the heating step (induced by Joule effect) of NiTi wires and a thermal perturbation associated with the structural transformation of austenite to R-phase was observed during the natural cooling step, near 33.0 degrees C. Regarding tensile cycling tests, higher increases in temperature arose when the applied force ranged between 0.7 and 1.1 kN, reaching a maximum temperature variation of 9.5 +/- 0.1 degrees C. During the unload step, a slope change in the temperature behavior was detected, which is associated with the material transformation of the NiTi wire (martensite to austenite). The embedded optical sensing methodology presented here proved to be an effective and precise tool to identify structural transformations regarding the specific application as a Non-Destructive Testing for AM.

2020

Lipofuscin-Type Pigment as a Marker of Colorectal Cancer

Authors
Carvalho, S; Carneiro, I; Henrique, R; Tuchin, V; Oliveira, L;

Publication
ELECTRONICS

Abstract
The study of the optical properties of biological tissues for a wide spectral range is necessary for the development and planning of noninvasive optical methods to be used in clinical practice. In this study, we propose a new method to calculate almost all optical properties of tissues as a function of wavelength directly from spectral measurements. Using this method, and with the exception of the reduced scattering coefficient, which was obtained by traditional simulation methods, all the other optical properties were calculated in a simple and fast manner for human and pathological colorectal tissues. The obtained results are in good agreement with previous published data, both in magnitude and in wavelength dependence. Since this method is based on spectral measurements and not on discrete-wavelength experimental data, the calculated optical properties contain spectral signatures that correspond to major tissue chromophores such as DNA and hemoglobin. Analysis of the absorption bands of hemoglobin in the wavelength dependence of the absorption spectra of normal and pathological colorectal mucosa allowed to identify differentiated accumulation of a pigment in these tissues. The increased content of this pigment in the pathological mucosa may be used for the future development of noninvasive diagnostic methods for colorectal cancer detection.

2020

Tackling unsupervised multi-source domain adaptation with optimism and consistency

Authors
Pernes, D; Cardoso, JS;

Publication
CoRR

Abstract

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.

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