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Publicações

2021

The GRAVITY young stellar object survey: IV. The CO overtone emission in 51 Oph at sub-au scales

Autores
Koutoulaki, M; Lopez, RG; Natta, A; Fedriani, R; Garatti, ACO; Ray, TP; Coffey, D; Brandner, W; Dougados, C; Garcia, PJV; Klarmann, L; Labadie, L; Perraut, K; Sanchez Bermudez, J; Lin, CC; Amorim, A; Baubock, M; Benisty, M; Berger, JP; Buron, A; Caselli, P; Clenet, Y; du Foresto, VC; de Zeeuw, PT; Duvert, G; de Wit, W; Eckart, A; Eisenhauer, F; Filho, M; Gao, F; Gendron, E; Genzel, R; Gillessen, S; Grellmann, R; Habibi, M; Haubois, X; Haussmann, F; Henning, T; Hippler, S; Hubert, Z; Horrobin, M; Rosales, AJ; Jocou, L; Kervella, P; Kolb, J; Lacour, S; Le Bouquin, JB; Lena, P; Linz, H; Ott, T; Paumard, T; Perrin, G; Pfuhl, O; Ramirez Tannus, MC; Rau, C; Rousset, G; Scheithauer, S; Shangguan, J; Stadler, J; Straub, O; Straubmeier, C; Sturm, E; van Dishoeck, E; Vincent, F; von Fellenberg, S; Widmann, F; Wieprecht, E; Wiest, M; Wiezorrek, E; Yazici, S; Zins, G;

Publicação
ASTRONOMY & ASTROPHYSICS

Abstract
Context. 51 Oph is a Herbig Ae/Be star that exhibits strong near-infrared CO ro-vibrational emission at 2.3 mu m, most likely originating in the innermost regions of a circumstellar disc.Aims. We aim to obtain the physical and geometrical properties of the system by spatially resolving the circumstellar environment of the inner gaseous disc.Methods. We used the second-generation Very Large Telescope Interferometer instrument GRAVITY to spatially resolve the continuum and the CO overtone emission. We obtained data over 12 baselines with the auxiliary telescopes and derive visibilities, and the differential and closure phases as a function of wavelength. We used a simple local thermal equilibrium ring model of the CO emission to reproduce the spectrum and CO line displacements.Results. Our interferometric data show that the star is marginally resolved at our spatial resolution, with a radius of similar to 10.58 2.65R(circle dot). The K-band continuum emission from the disc is inclined by 63 degrees +/- 1 degrees, with a position angle of 116 degrees +/- 1 degrees, and 4 +/- 0.8 mas (0.5 +/- 0.1 au) across. The visibilities increase within the CO line emission, indicating that the CO is emitted within the dust-sublimation radius. By modelling the CO bandhead spectrum, we derive that the CO is emitted from a hot (T = 1900-2800 K) and dense (N-CO = (0.9-9) x 10(21) cm(-2)) gas. The analysis of the CO line displacement with respect to the continuum allows us to infer that the CO is emitted from a region 0.10 +/- 0.02 au across, well within the dust-sublimation radius. The inclination and position angle of the CO line emitting region is consistent with that of the dusty disc.Conclusions. Our spatially resolved interferometric observations confirm the CO ro-vibrational emission within the dust-free region of the inner disc. Conventional disc models exclude the presence of CO in the dust-depleted regions of Herbig AeBe stars. Ad hoc models of the innermost disc regions, that can compute the properties of the dust-free inner disc, are therefore required.

2021

A new model for location-allocation problem based on sectorization

Autores
Teymourifar, Aydin; Rodrigues, Ana Maria; Ferreira, José Soeiro;

Publicação
Engineering World

Abstract
Many models have been proposed for the location-allocation problem. In this study, based on sectorization concept, we propose a new single-objective model of this problem, in which, there is a set of customers to be assigned to distribution centres (DCs). In sectorization problems there are two important criteria as compactness and equilibrium, which can be defined as constraints as well as objective functions. In this study, the objective function is defined based on the equilibrium of distances in sectors. The concept of compactness is closely related to the accessibility of customers from DCs. As a new approach, instead of compactness, we define the accessibility of customers from DCs based on the covering radius concept. The interpretation of this definition in real life is explained. As another contribution, in the model, a method is used for the selection of DCs, and a comparison is made with another method from the literature, then the advantages of each are discussed. We generate benchmarks for the problem and we solve it with a solver available in Python’s Pulp library. Implemented codes are presented in brief.

2021

Preface

Autores
Gruschka N.; Antunes L.F.C.; Rannenberg K.; Drogkaris P.;

Publicação
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Abstract

2021

Hybrid stochastic/robust optimization model for resilient architecture of distribution networks against extreme weather conditions

Autores
Shahbazi, A; Aghaei, J; Pirouzi, S; Shafie khah, M; Catala, JPS;

Publicação
INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS

Abstract
This paper expresses the planning model of the backup distributed generation (DG) and lines hardening and tie lines in distribution networks according to resilient architecture (RA) strategy under natural disaster conditions such as earthquakes and floods. Indeed, the proposed deterministic problem of resilient distribution system planning considers the minimization of the daily investment, operation and resiliency (repair and load shedding) costs as objective functions subject to constraints of AC power flow equations, system operation limits, planning and operation model of backup DG and hardening and tie lines, as well as network reconfiguration formulation. The problem formulation is based on a mixed integer non-linear programming (MINLP) model, which is converted to a mixed integer linear programming (MILP) model on the basis of Benders decomposition (BD) approach using linearization approaches to achieve the optimal solution with the lower computational efforts and error. Besides, a hybrid stochastic/robust optimization (HSRO) based on the bounded uncertainty-based robust optimization (BURO) and a scenario-based stochastic optimization is used to model the uncertainties of load, energy price and availability of the network equipment under the extreme weather conditions. Finally, the proposed RA strategy is applied on 33-bus and 119-bus distribution test systems to investigate its capabilities in different case studies.

2021

Robotic grasping: from wrench space heuristics to deep learning policies

Autores
de Souza, JPC; Rocha, LF; Oliveira, PM; Moreira, AP; Boaventura Cunha, J;

Publicação
ROBOTICS AND COMPUTER-INTEGRATED MANUFACTURING

Abstract
The robotic grasping task persists as a modern industry problem that seeks autonomous, fast implementation, and efficient techniques. Domestic robots are also a reality demanding a delicate and accurate human-machine interaction, with precise robotic grasping and handling. From decades ago, with analytical heuristics, to recent days, with the new deep learning policies, grasping in complex scenarios is still the aim of several works' that propose distinctive approaches. In this context, this paper aims to cover recent methodologies' development and discuss them, showing state-of-the-art challenges and the gap to industrial applications deployment. Given the complexity of the related issue associated with the elaborated proposed methods, this paper formulates some fair and transparent definitions for results' assessment to provide researchers with a clear and standardised idea of the comparison between the new proposals.

2021

PLAY for LEARNING: Serious Games to Assist Learning of Basic Didactic Concepts: A Pilot Study

Autores
Rocha, T; Barroso, J;

Publicação
HCI (29)

Abstract
In this paper, the study of the design and implementation of a gamebased application for learning new basic concepts and/or re-learning these concepts within a cognitive rehabilitation perspective, is presented. Specifically, in this first version, the topics considered were: colours, animals, objects, and vehicles. The solution was developed to be usable and accessible to two user groups, children with special education needs and seniors in need of cognitive training and/or rehabilitation. The two main goals are: (1) to develop a game-based interface for the two specific user groups – children with special educational needs and seniors; (2) and, assess user engagement and acceptance. To achieve the first goal a universal design methodology was followed. For the later, we performed a preliminary usability assessment. Specifically, a Cognitive Walkthrough reinforced with a post-test semi-structured interviews was conducted. Overall results showed a good user engagement and acceptance. The gamebased solution seemed to facilitated children’ apprenticeship of basic contents and the helped in the cognitive rehabilitation by the seniors. The preliminary results indicated the solution could be used as an assistive tool, in a special education or in rehabilitation contexts, with tutors, teachers or clinicians; but also, in a more without obstruction and autonomous interaction, at home.

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