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Publicações

2019

Symphony: routing aware scheduling for DSME networks

Autores
Kurunathan, H; Severino, R; Koubaa, A; Tovar, E;

Publicação
SIGBED Review

Abstract
Deterministic Synchronous Multichannel Extension (DSME) is a prominent MAC behavior first introduced in IEEE 802.15.4e. It can avail deterministic and best effort Service using its multisuperframe structure. RPL is a routing protocol for wireless networks with low power consumption and generally susceptible to packet loss. These two standards were designed independently but with the common objective to satisfy the requirements of IoT devices in terms of limited energy, reliability and determinism. A combination of these two protocols can integrate real-time QoS demanding and largescale IoT networks. In this paper, we propose a new multi-channel, multi-timeslot scheduling algorithm called Symphony that provides QoS efficient schedules in DSME networks. In this paper we provide analytical and simulation based delay analysis for our approach against some state of the art algorithms. In this work, we show that integrating routing with DSME can improve reliability by 40 % and by using Symphony, we can reduce the network delay by 10-20% against the state of the art algorithms. © Copyright held by the authors.

2019

Experimental NFT hydroponics system with lower energy consumption

Autores
Ramos, C; Nobrega, L; Baras, K; Gomes, L;

Publicação
Proceedings of the 2019 5th Experiment at International Conference, exp.at 2019

Abstract
Precision agriculture nowadays has great importance as it brings together the knowledge acquired through traditional cultivation techniques with precision and technological automation. One of the inherent techniques of precision agriculture is hydroponics, with plants growing using aqueous solutions and without soil availability. Although NFT (Nutrient Film Technique) systems are already well-developed systems, there is a big difference between home projects and highly automated processes, which in turn require high investment values. Among other things, in this work, the aim was to study and developed algorithms that allow the efficient recirculation of water, allowing electricity savings to be around 40% compared to more traditional systems. © 2019 IEEE.

2019

Bi-Objective Optimization Model for Optimal Placement of Thyristor-Controlled Series Compensator Devices

Autores
Salehizadeh, MR; Koohbijari, MA; Nouri, H; Tascikaraoglu, A; Erdinc, O; Catalao, JPS;

Publicação
ENERGIES

Abstract
Exposure to extreme weather conditions increases power systems' vulnerability in front of high impact, low probability contingency occurrence. In the post-restructuring years, due to the increasing demand for energy, competition between electricity market players and increasing penetration of renewable resources, the provision of effective resiliency-based approaches has received more attention. In this paper, as the major contribution to current literature, a novel approach is proposed for resiliency improvement in a way that enables power system planners to manage several resilience metrics efficiently in a bi-objective optimization planning model simultaneously. For demonstration purposes, the proposed method is applied for optimal placement of the thyristor controlled series compensator (TCSC). Improvement of all considered resilience metrics regardless of their amount in a multi-criteria decision-making framework is novel in comparison to the other previous TCSC placement approaches. Without loss of generality, the developed resiliency improvement approach is applicable in any power system planning and operation problem. The simulation results on IEEE 30-bus and 118-bus test systems confirm the practicality and effectiveness of the developed approach. Simulation results show that by considering resilience metrics, the performance index, importance of curtailed consumers, congestion management cost, number of curtailed consumers, and amount of load loss are improved by 0.63%, 43.52%, 65.19%, 85.93%, and 85.94%, respectively.

2019

Spectral and thermal data as a proxy for leaf protective energy dissipation under kaolin application in grapevine cultivars

Autores
Tosin, R; Pocas, I; Cunha, M;

Publicação
OPEN AGRICULTURE

Abstract
The dynamic effects of kaolin clay particle film application on the temperature and spectral reflectance of leaves of two autochthonous cultivars (Touriga Nacional (TN, n=32) and Touriga Franca (TF, n=24)) were studied in the Douro wine region. The study was implemented in 2017, in conditions prone to multiple environmental stresses that include excessive light and temperature as well as water shortage. Light reflectance from kaolin-sprayed leaves was higher than the control (leaves without kaolin) on all dates. Kaolin's protective effect over leaves' temperatures was low on the 20 days after application and ceased about 60 days after its application. Differences between leaves with and without kaolin were explained by the normalized maximum leaf temperature (T_max_f_N), reflectance at 400 nm, 532 nm, and 737 nm, as assessed through TN data. The wavelengths of 532 nm and 737 nm are associated with plant physiological processes, which support the selection of these variables for assessing kaolin's effects on leaves. The application of principal component analysis to the TF data, based on these four variables (T_max_f_N and reflectances: 400, 532, 737 nm) selected for TN, explained 83.56% of data variability (considering two principal components), obtaining a clear differentiation between leaves with and without kaolin. The T_max_f_N and the reflectance at 532 nm were the variables with a greater contribution for explaining data variability. The results improve the understanding of the vines' response to kaolin throughout the grapevine cycle and support decisions about the re-application timing.

2019

The VirtualSign Channel for the Communication Between Deaf and Hearing Users

Autores
Oliveira, T; Escudeiro, N; Escudeiro, P; Rocha, E; Barbosa, FM;

Publicação
IEEE REVISTA IBEROAMERICANA DE TECNOLOGIAS DEL APRENDIZAJE-IEEE RITA

Abstract
Deaf students, who use sign language as their mother language, continuously experience difficulties to communicate with non-deaf in their daily lives. This is a severe handicap in education settings seriously jeopardizing deaf people chances to progress in their professional career. Deaf people's comprehension of texts is limited due to grammar differences between sign and oral languages. There is a need to improve the communication between deaf and non-deaf and to support deaf students in environments where they are unable to be accompanied by sign interpreters. This article details the improvements and current structure of the VirtualSign platform, a bidirectional sign language to text translation tool in development since 2015. The platform has two main components, sign to text and text to sign, that are both described. Translation from text to sign relies on a 3D avatar. Translation from sign to text relies on a set of data gloves and Kinect. In this paper we discuss the relevance of different types of data gloves. VirtualSign is being developed in cooperation with the deaf communities from six different European countries and Brazil. This solution to support deaf students in educational settings has received positive feedback on several tests and pilot experiments. Some planned improvements and future functionalities for the tool are also mentioned and detailed.

2019

Single-phase universal active power filter based on ac-dc-ac converter with eight controlled switches

Autores
Rodrigues, PLS; Jacobina, CB; de Freitas, NB;

Publicação
IET POWER ELECTRONICS

Abstract
This study presents an ac-dc-ac converter with eight controlled switches. The proposed topology is applied as a universal active power filter, compensating for disturbances in the grid voltage, voltage sags/swells, and harmonics generated by non-linear loads. The difference between the proposed and conventional solution is the addition of an uncontrolled leg (composed only of diodes) to increase the number of voltage levels, reducing harmonics and the average switching frequency. For performance comparisons, current total harmonic distortion (THD), voltage weighted THD, switching and conduction losses of the semiconductors, and average switching frequency were used as parameters. Control and pulse-width modulation techniques based on space vector approaches were developed to eliminate zero-crossing distortions caused by the use of the uncontrolled leg. Simulation and experimental results were presented for validation of the mathematical model.

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