Abstract
The legal framework for the conduct of the work, derives from the Decree Law No. 28/2019 of February 15, combined with Ordinance 195/2020 of 13 August and the VAT Code, as well as the amendment to the proposal of Law No. 61/XIV, which postponed to 2022 the mandatory printing of the QR-Code on the invoice and documents fiscally relevant. The objective of the paper focuses on the presentation of a validation of a multidisciplinary and integrative approach, which was developed to analyze the impact on the different stakeholders, when introducing the QR-Code in the relevant tax documents in Portugal. The methodology used was Design Science Research. The paper's contributions are based on the presentation and validation of the Approach using survey design, with the aim of assessing its suitability and feasibility with the various stakeholders (Software Producers/Installers, Hauliers, Certified Accountants, Tax and Customs Authority, Taxpayers and Buyers). In this way, it was possible to assess the expectations of the stakeholders in face of the new legal framework, as well as the impact that these legislative changes will cause in an organizational context.

Abstract
Crop sustainability is essential for balancing economic development and environmental care, mainly in strong and very competitive regions in the agri-food sector, such as the Region of Murcia in Spain, considered to be the orchard of Europe, despite being a semi-arid area with an important scarcity of fresh water. In this region, farmers apply efficient techniques to minimize supplies and maximize quality and productivity; however, the effects of climate change and the degradation of significant natural environments, such as, the “Mar Menor”, the most extent saltwater lagoon of Europe, threatened by resources overexploitation, lead to the search of even better irrigation management techniques to avoid certain effects which could damage the quaternary aquifer connected to such lagoon. This paper describes the Irriman Platform, a system based on Cloud Computing techniques, which includes low-cost wireless data loggers, capable of acquiring data from a wide range of agronomic sensors, and a novel software architecture for safely storing and processing such information, making crop monitoring and irrigation management easier. The proposed platform helps agronomists to optimize irrigation procedures through a usable web-based tool which allows them to elaborate irrigation plans and to evaluate their effectiveness over crops. The system has been deployed in a large number of representative crops, located along near 50,000 ha of the surface, during several phenological cycles. Results demonstrate that the system enables crop monitoring and irrigation optimization, and makes interaction between farmers and agronomists easier.

Abstract
Marine polymers such as collagen, chitosan, and fucoidan can be combined to form ionic-linked hydrogel networks towards applications in tissue engineering (TE). The use of greener approaches (as determined by green metrics - E-factor), including the absence of external chemical cross-linking agents, has advantages regarding the potential cytotoxicity. By tailoring the formulation of such an ionic-linked hydrogel, it is possible to fine-tune scaffold biofunctionality. In this study, a comparative study of composite hydrogels was accomplished, seeking to understand the correlation between polymer characteristics and physical behaviour to develop the applicability of this technology in soft-to-hard TE. Parameters such as polymer concentration, molecular weight, polymer-biomaterials bonds, biomaterial structural architecture, pore size, and mechanical rheological properties were directly correlated to the hydrogel's formulation. The results highlight that the formulation with greatest potential was the 3-component hydrogel (H-12, followed by H-10, H-11), due to its superior mechanical properties, making it suitable for cartilage TE. This research offers a valuable perspective on hydrogel formulation and a new processing methodology, as well as how tailoring the hydrogel composition influences mechanical behaviour to support selecting the best composition for tissue engineering applications.

Abstract
Object recognition represents the ability of a system to identify objects, humans or animals in images. Within this domain, this work presents a comparative analysis among different classification methods aiming at Tactode tile recognition. The covered methods include: (i) machine learning with HOG and SVM; (ii) deep learning with CNNs such as VGG16, VGG19, ResNet152, MobileNetV2, SSD and YOLOv4; (iii) matching of handcrafted features with SIFT, SURF, BRISK and ORB; and (iv) template matching. A dataset was created to train learning-based methods (i and ii), and with respect to the other methods (iii and iv), a template dataset was used. To evaluate the performance of the recognition methods, two test datasets were built: tactode_small and tactode_big, which consisted of 288 and 12,000 images, holding 2784 and 96,000 regions of interest for classification, respectively. SSD and YOLOv4 were the worst methods for their domain, whereas ResNet152 and MobileNetV2 showed that they were strong recognition methods. SURF, ORB and BRISK demonstrated great recognition performance, while SIFT was the worst of this type of method. The methods based on template matching attained reasonable recognition results, falling behind most other methods. The top three methods of this study were: VGG16 with an accuracy of 99.96% and 99.95% for tactode_small and tactode_big, respectively; VGG19 with an accuracy of 99.96% and 99.68% for the same datasets; and HOG and SVM, which reached an accuracy of 99.93% for tactode_small and 99.86% for tactode_big, while at the same time presenting average execution times of 0.323 s and 0.232 s on the respective datasets, being the fastest method overall. This work demonstrated that VGG16 was the best choice for this case study, since it minimised the misclassifications for both test datasets.

Abstract
In this work, we reviewed the most important achievements of INESC TEC related to the fabrication of long-period fiber gratings using the electric arc technique. We focused on the fabrication setup, the type of fiber used, and the effect of the fabrication parameters on the gratings' transmission spectra. The theory was presented, as well as a discussion on the mechanisms responsible for the formation of the gratings, supported by the measurement of the temperature reached by the fiber during an electric arc discharge.

Abstract
The Symposium of Electrical and Computer Engineering (ECE), integrated in the 2021 edition of FEUP’s Doctoral Congress of Engineering is an important showcase for PhD research in this broad and vibrant area, and an opportunity for doctoral students to interact, to improve communications skills, and to gather feedback on their research work.