Cookies Policy
The website need some cookies and similar means to function. If you permit us, we will use those means to collect data on your visits for aggregated statistics to improve our service. Find out More
Accept Reject
  • Menu
Publications

2022

Towards the experimental observation of turbulent regimes and the associated energy cascades with paraxial fluids of light

Authors
Ferreira, TD; Rocha, V; Silva, D; Guerreiro, A; Silva, NA;

Publication
NEW JOURNAL OF PHYSICS

Abstract
The propagation of light in nonlinear optical media has been widely used as a tabletop platform for emulating quantum-like phenomena due to their similar theoretical description to quantum fluids. These fluids of light are often used to study two-dimensional phenomena involving superfluid-like flows, yet turbulent regimes still remain underexplored. In this work, we study the possibility of creating two-dimensional turbulent phenomena and probing their signatures in the kinetic energy spectrum. To that end, we emulate and disturb a fluid of light with an all-optical defect using the propagation of two beams in a photorefractive crystal. Our experimental results show that the superfluid regime of the fluid of light breaks down at a critical velocity at which the defect starts to exert a drag force on the fluid, in accordance with the theoretical and numerical predictions. Furthermore, in this dissipative regime, nonlinear perturbations are excited on the fluid that can decay into vortex structures and thus precede a turbulent state. Using the off-axis digital holography method, we reconstructed the complex description of the output fluids and calculated the incompressible component of the kinetic energy. With these states, we observed the expected power law that characterizes the generated turbulent vortex dipole structures. The findings enclosed in this manuscript align with the theoretical predictions for the vortex structures of two-dimensional quantum fluids and thus may pave the way to the observation of other distinct hallmarks of turbulent phenomena, such as distinct turbulent regimes and their associated power laws and energy cascades.

2022

Regional smart specialisation strategies and Universities' engagement: An exploratory study

Authors
Sónia Pereira; Aurora Teixeira;

Publication

Abstract

2022

NEWTR: a multipath routing for next hop destination in internet of things with artificial recurrent neural network (RNN)

Authors
Sumathi, AC; Javadpour, A; Pinto, P; Sangaiah, AK; Zhang, WZ; Khaniabadi, SM;

Publication
INTERNATIONAL JOURNAL OF MACHINE LEARNING AND CYBERNETICS

Abstract
Internet of Things (IoT) and Wireless Sensor Networks (WSN) are a set of low-cost wireless sensors that can collect, process and send environment's data. WSN nodes are battery powered, therefore energy management is a key factor for long live network. One way to prolong lifetime of network is to utilize routing protocols to manage energy consumption. To have an energy efficient protocol in environment interactions, we can apply ZigBee protocols. Among these Artificial Intelligence Interactions routing methods, Tree Routing (TR) that acts in the tree network topology is considered a simple routing protocol with low overhead for ZigBee. In a tree topology, every nodes can be recognized as a parent or child of another node and in this regard, there is no circling. The most important problem of TR is increasing the number of steps to get data to the destination. To solve this problem several algorithms were proposed that its focus is on fewer steps. In this research we present an artificial Intelligence Tree Routing based on RNN and ZigBee protocol in IoT environment. Simulation results show that NEWTR improve the network lifetime by 5.549% and decreases the energy consumption (EC) of the network by 5.817% as compared with AODV routing protocol.

2022

O eterno caso dos adjetivos temporais e aspetuais um contributo para a sua caracterização semântica

Authors
Ferreira, I; Cunha, LF; Leal, A; Silvano, P; Silva, F;

Publication
Linguística: Revista de Estudos Linguísticos da Universidade do Porto

Abstract
The aim of this paper is to analyze the semantic behavior of adjectives that have been designated as temporal and aspectual in the literature, regarding the readings they can display. For this purpose, sixteen of these adjectives were selected and fifty occurrences of each one were randomly chosen and investigated. Overall, we observed a significant variety of readings associated with all the adjectives under scrutiny, which to greater or lesser degrees can express temporal, aspectual, temporo-aspectual values, and readings of qualificative and relational adjectives. This diversity of possible readings raises problems for proposals that intend to classify this group of adjectives in a static manner (i.e., without considering the context).

2022

The multi-product inventory-routing problem with pickups and deliveries: Mitigating fluctuating demand via rolling horizon heuristics br

Authors
Neves Moreira, F; Almada Lobo, B; Guimaraes, L; Amorim, P;

Publication
TRANSPORTATION RESEARCH PART E-LOGISTICS AND TRANSPORTATION REVIEW

Abstract
In this paper, we explore the value of considering simultaneous pickups and deliveries inmulti-product inventory-routing problems both with deterministic and uncertain demand. Wepropose a multi-commodity, develop an exact branch-and-cut algorithm with patching heuristicsto efficiently tackle this problem, and provide insightful analyses based on optimal plans. Thesimplicity of the proposed approach is an important aspect, as it facilitates its usage in practice,opposed to complicated stochastic or probabilistic methods. The computational experimentssuggest that in the deterministic demand setting, pickups are mainly used to balance initialinventories, achieving an average total cost reduction of 1.1%, while transshipping 2.4% oftotal demand. Under uncertain demand, pickups are used extensively, achieving cost savings of up to 6.5% in specific settings. Overall, our sensitivity analysis shows that high inventory costsand high degrees of demand uncertainty drive the usage of pickups, which, counter-intuitively, are not desirable in every case

2022

Regression Analysis with the Distribution and Symmetric Distribution Model

Authors
Dias, S; Brito, P;

Publication
Analysis of Distributional Data

Abstract

  • 1024
  • 4496