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Publications

2024

SWINN: Efficient nearest neighbor search in sliding windows using graphs

Authors
Mastelini, SM; Veloso, B; Halford, M; de Carvalho, ACPDF; Gama, J;

Publication
INFORMATION FUSION

Abstract
Nearest neighbor search (NNS) is one of the main concerns in data stream applications since similarity queries can be used in multiple scenarios. Online NNS is usually performed on a sliding window by lazily scanning every element currently stored in the window. This paper proposes Sliding Window-based Incremental Nearest Neighbors (SWINN), a graph-based online search index algorithm for speeding up NNS in potentially never-ending and dynamic data stream tasks. Our proposal broadens the application of online NNS-based solutions, as even moderately large data buffers become impractical to handle when a naive NNS strategy is selected. SWINN enables efficient handling of large data buffers by using an incremental strategy to build and update a search graph supporting any distance metric. Vertices can be added and removed from the search graph. To keep the graph reliable for search queries, lightweight graph maintenance routines are run. According to experimental results, SWINN is significantly faster than performing a naive complete scan of the data buffer while keeping competitive search recall values. We also apply SWINN to online classification and regression tasks and show that our proposal is effective against popular online machine learning algorithms.

2024

Combined mediterranean diet-based sustainable healthy diet and multicomponent training intervention impact on plasma biomarkers and metabolome in older adults

Authors
Sampaio, J; Pinto, J; Pizarro, A; Oliveira, B; Moreira, A; Padrao, P; Moreira, P; de Pinho, PG; Carvalho, J; Barros, R;

Publication
CLINICAL NUTRITION

Abstract
Background and aims: Healthy dietary patterns and exercise practices have been associated with improved metabolic and inflammatory profiles. However, studies regarding the combined effect of these interventions on plasma biomarkers and metabolome in older adults are sparser. The primary aim of this study was to investigate the impact of a combined Mediterranean Diet-based Sustainable Healthy Diet (SHD) and Multicomponent Training (MT) intervention on the plasma biomarkers and metabolome and how dietary intake and exercise could modulate these effects. Methods: SHD intervention included a weekly supply of Mediterranean Diet-based SHD food and four nutrition sessions involving a Mediterranean-Diet culinary workshop, and the exercise program included 50-min MT group sessions, held three times a week, lasting both 12 weeks. Plasma biomarkers were obtained through standard biochemical analysis. A proton (1H) 1 H) nuclear magnetic resonance (NMR) spectroscopy-based metabolomics approach was used to study the metabolome in blood plasma. Repeated measures ANOVA were performed and adjusted for confounders. Results: SHD + MT intervention significantly decreased HDL-C and calcium. SHD + MT showed some changes in common with the SHD and MT group, namely a significant decrease in citrate levels (p = 0.009 for SHD + MT; p = 0.037 for SHDT) and an increase in pyruvate (p < 0.001 for MT and SHD + MT). The SHD + MT group also revealed specific changes in the levels of some amino acids (decrease in alanine, glutamine and lysine: p = 0.026; p < 0.001; p = 0.038, respectively). Increases in formate (p = 0.025) and unsaturated lipids (p = 0.011) are consistent with changes in energy and lipoprotein metabolism. Conclusion: Our data show that a combined lifestyle intervention program, including a Mediterranean Diet-based SHD and MT, could modulate biomarker and metabolome and there seems to be a metabolic path associated to these interventions in older adults. Due to its wide-ranging relevance, it is pertinent to assess to what extent combined SHD and MT can contribute to better clinical profiles. (c) 2024 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

2024

Evaluation of Grid-Following Inverter Control Models for Fault Response and their Impact on Protection Devices

Authors
Rosero Morillo, VA; Gonzalez Longatt, F; Riquelme Dominguez, JM; Orduña, E;

Publication
2024 IEEE 22ND MEDITERRANEAN ELECTROTECHNICAL CONFERENCE, MELECON 2024

Abstract
This article focuses on evaluating how different current control models of grid-following inverters affect fault response. It analyzes two models: the conventional model, which includes positive sequence current control, and another that combines both positive and negative sequence control. The main goal was to determine the impact of these models on the fault current and voltage detected by protection devices and to highlight the importance of selecting an appropriate model for an effective protection scheme. This study is crucial for characterizing the fault response of Inverter-Interface Distributed Generators (IIDG) and understanding the implications of their inclusion in protection devices. By gaining a deeper understanding of these effects, the aim is to significantly contribute to the development of advanced strategies and technologies for the protection of energy distribution networks, especially in scenarios that incorporate IIDG.

2024

Wind farm layout optimization under uncertainty

Authors
Agra, A; Cerveira, A;

Publication
TOP

Abstract
Wind power is a major source of green energy production. However, the energy generation of wind power is highly affected by uncertainty. Here, we consider the problem of designing the cable network that interconnects the turbines to the substation in wind farms, aiming to minimize both the infrastructure cost and the cost of the energy losses during the wind farm's lifetime. Nonetheless, the energy losses depend on wind direction and speed, which are rarely known with certainty in real situations. Hence, the design of the network should consider these losses as uncertain parameters. We assume that the exact probability distribution of these parameters is unknown but belongs to an ambiguity set and propose a distributionally robust two-stage mixed integer model. The model is solved using a decomposition algorithm. Three enhancements are proposed given the computational difficulty in solving real problem instances. Computational results are reported based on real data.

2024

Battery Control for Node Capacity Increase for Electric Vehicle Charging Support

Authors
Ahmad, MW; Lucas, A; Carvalhosa, SMP;

Publication
ENERGIES

Abstract
The integration of electric vehicles (EVs) into the power grid poses significant challenges and opportunities for energy management systems. This is especially concerning for parking lots or private building condominiums in which refurbishing is not possible or is costly. This paper presents a real-time monitoring approach to EV charging dynamics with battery storage support over a 24 h period. By simulating EV demand, state of charge (SOC), and charging and discharging events, we provide insights into the operational strategies for energy storage systems to ensure maximum charging simultaneity factor through internal power enhancement. The study uses a time-series analysis of EV demand, contrasting it with the battery's SOC, to dynamically adjust charging and discharging actions within the constraints of the upstream infrastructure capacity. The model incorporates parameters such as maximum power capacity, energy storage capacity, and charging efficiencies, to reflect realistic conditions. Results indicate that real-time SOC monitoring, coupled with adaptive charging strategies, can mitigate peak demands and enhance the system's responsiveness to fluctuating loads. This paper emphasizes the critical role of real-time data analysis in the effective management of energy resources in existing parking lots and lays the groundwork for developing intelligent grid-supportive frameworks in the context of growing EV adoption.

2024

Empowering SMEs for the digital future: unveiling training needs and nurturing ecosystem support

Authors
Carvalho, T; Simoes, AC; Teles, V; Almeida, AH;

Publication
EUROPEAN JOURNAL OF ENGINEERING EDUCATION

Abstract
Previous studies show that digital transition brings several benefits and challenges for companies. Among those challenges, particularly for Small and Medium-sized Enterprises (SMEs), the main one is increased capacitation, from technical roles to management. Considering this, the main objective of this study is to identify the training needs and the ecosystem support in the face of the digital transition for Portuguese manufacturing SMEs.Semi-structured interviews were conducted with industry experts and company professionals in the automotive and textile sectors. It was concluded that all workers, from technical roles to middle and top management, need more digital capabilities and would benefit from training programmes. The most desired areas for training are data science, virtualisation skills, quality assurance, technical training, and soft skills. The preferred format is physical (or hybrid at most) during working hours and with theoretical training before on-the-job learning. Both industrial companies and experts believe in the value of involving external entities in the training of employees, with the three most referred entities being technology and interface centres, universities, and business associations.

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