Abstract

Abstract
E-learning at the University of Tras-os-Montes e Alto Douro (UTAD) is at a very early stage, with the total number of courses available being very low. This is due to the lack of teacher training, lack of technical support, lack of specific tools and lack of institutional support policies, among others. An exception to this is the existence of a platform for teaching support, named SIDE - side.utad.pt, developed at UTAD and which has been systematically used over the last decade. However, SIDE works more like a teaching management platform (e.g. student management, assessment schedules management, attendance management, schedules management, etc.) rather than as a platform for dissemination and management of online content and courses. Recently, we have elsewhere presented a model of a system that is capable of responding to the training needs identified at UTAD, and we have been using it at UTAD. Here, we present the perspectives of the students, using a survey with 23 questions based on a Likert scale, with a 5 points interval, with 1 being the lowest value (or dissatisfaction) and 5 being the maximum (or excellence) value, being the intermediate point considered satisfaction. The questions were grouped in 5 classes: platform, teaching, tests/exams, devices/hardware and global appreciation. The 78 validated answers and their results will be presented and discussed. For the first class, platform, it was concluded that most of the students consider the platform easy to use and that it adapts to the contents that are taught in the various curricular units of the different degrees of study, and that they feel comfortable using and working with the platform and that they recommended higher use by their teachers.

Abstract
This article presents a review of the numerical techniques employed in simulating plasmonic optical sensors based on metal-dielectric nanostructures, including examples, ranging from conventional D-type fiber sensors, to those based on photonic crystal D-type fibers and incorporating metamaterials, nanowires, among other new materials and components, results and applications. We start from the fundamental physical processes, such as optical and plasmonic mode coupling, and discuss the implementation of the numerical model, optical response customization and their impact in sensor performance. Finally, we examine future perspectives.

Abstract
Photovoltaic energy is one of the clean and efficient energies which has been developing quickly in the last years. As the penetration of solar plants is increasing in the electricity network, new problems have arisen in network operation. This paper models a high penetration factor of solar energy in the electricity network and investigates the impact of solar energy growth on both the generation schedule of different power plants and in the natural gas transmission network. Fuel management of gas power plants is modeled through simulation of the natural gas transmission network. To this end, an increase in the penetration of solar energy in the electricity network inevitably leads to a sudden increase in the output of gas fired units and a linear and integrated model with the electricity and the natural gas transmission networks has been presented to analyze both of them at the same time to better depict the impact of a high penetration of the solar energy in natural gas transmission grids. In this method, natural gas transmission network and Security Constrained Unit Commitment (SCUC) are presented in a single level program. Gas network constraints are linearized and added to the SCUC problem. The stress imposed on the gas network due to a sudden increase in the load of the electricity network is investigated. Conclusions are duly drawn.

Abstract
Viticulturists need to obtain the estimation of productivity map during the grape vine harvesting, to understand in detail the vineyard variability. An accurate productivity map will support the farmer to take more informed and accurate intervention in the vineyard in line with the precision viticulture concept. This work presents a novel solution to measure the productivity during vineyard harvesting operation realized by a grape harvesting machine. We propose 2D LIDAR sensor attached to low cost IoT module located inside the harvesting machine, to estimate the volume of grapes. Besides, it is proposed data methodology to process data collected and productivity map, considering GIS software, expecting to support the winemakers decisions. A PCD map is also used to validate the method developed by comparison. © Springer Nature Switzerland AG 2019.

Abstract
To properly validate wireless networking solutions we depend on experimentation. Simulation very often produces less accurate results due to the use of models that are simplifications of the real phenomena they try to model. Networking experimentation may offer limited repeatability and reproducibility. Being influenced by external random phenomena such as noise, interference, and multipath, real experiments are hardly repeatable. In addition, they are difficult to reproduce due to testbed operational constraints and availability. Without repeatability and reproducibility, the validation of the networking solution under evaluation is questionable. In this paper, we show how the Trace-based Simulation (TS) approach can be used to accurately repeat and reproduce real experiments and, consequently, introduce a paradigm shift when it comes to the evaluation of wireless networking solutions. We present an extensive evaluation of the TS approach using the Fed4FIRE+ w-iLab.2 testbed. The results show that it is possible to repeat and reproduce real experiments using Network Simulator 3 (ns-3) trace-based simulations with more accuracy than in pure simulation, with average accuracy gains above