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Publications

2026

Enhancing multi-agent deep reinforcement learning for flexible job-shop scheduling through constraint programming

Authors
Jesus, A; Corrêa, A; Vieira, M; Marques, C; Silva, C; Moniz, S;

Publication
COMPUTERS & OPERATIONS RESEARCH

Abstract
This paper introduces PRISMA, a hybrid multi-agent Deep Reinforcement Learning (DRL) framework for solving the Flexible Job-shop Scheduling Problem (FJSP). It uses Constraint Programming (CP) solutions to pretrain decentralized policies and to guide exploration during training. Although DRL can generate fast solutions for large combinatorial problems, it often fails to match the quality of optimization methods, motivating the integration with hybrid frameworks. The growing interest in embedding domain knowledge into learning algorithms has produced several hybrid formulations, yet their potential remains underexplored, particularly in multi-agent settings. PRISMA combines supervised and reinforcement learning within a multi-agent framework, where CP solutions are used to (i) learn expert decisions through imitation learning, and (ii) train an auxiliary network that guides DRL training via reward shaping. A shared graph network is adopted for transferring system-level knowledge into machine-level observations, enabling fast and consistent inference from enriched local embed-dings. To the best of our knowledge, PRISMA introduces the first expert-derived guidance mechanism for the FJSP and is among the earliest to apply imitation learning within a multi-agent formulation. By combining both modules, it strengthens the bridge between optimization and learning-based methods, where such dual integrations remain scarce. Experimental results show faster convergence and higher solution quality than state-ofthe-art DRL models. PRISMA achieves an average optimality gap of 6.74%, corresponding to a 50% relative improvement over the single-agent baseline, while reducing inference time. These findings reinforce the value of merging optimization accuracy with the flexibility of multi-agent DRL for efficient scheduling.

2026

Data Consistency as a Model-Dependent Property in Data-Driven Modelling

Authors
Rocha, C;

Publication

Abstract
Real-world datasets used in data-driven modelling are often affected by inconsistencies arising from discrepancies between recorded observations and actual system behaviour. Conventional approaches to data filtering and quality assessment rely primarily on statistical criteria and treat consistency as an intrinsic property of the dataset. However, such approaches may fail to identify observations that are statistically plausible yet incompatible with the structural assumptions underlying the model.This work introduces a model-dependent perspective on data consistency, in which the validity of observations is defined relative to the model used to interpret the data rather than to distributional properties alone. Within this framework, residuals are interpreted not merely as noise, but as indicators of incompatibility between observed data and model-defined behaviour.Importantly, inconsistencies may arise not only from anomalies in the target variable, but also from incorrect, incomplete, or misaligned representations of explanatory variables, even when observed outputs remain statistically valid. By formalising data consistency as a model-dependent property, this work challenges the conventional separation between data preprocessing and modelling, and reframes data filtering as part of the interpretation of model-data relations.The proposed framework provides a conceptual basis for integrating data consistency into data-driven modelling processes, with implications for data interpretation, representation, and validation in systems operating under imperfect real-world data conditions.

2026

Applied Dynamic System Theory for Coordination Assessment of Whole-Body Center of Mass During Different Countermovements

Authors
Rodrigues, C; Correia, MV; Abrantes, JMCS; Rodrigues, MAB; Nadal, J;

Publication
SENSORS

Abstract
This study applies phase plane analysis of medio-lateral, anteroposterior, and vertical directions for the coordination assessment of whole-body (WB) center of mass (COM) movement during the impulse phase of a standard maximum vertical jump (MVJ) with long, short, and no countermovement (CM). A video system and force platform were used, with the amplitudes of WB COM excursion obtained from image-based motion capture at each anatomical direction, and the 2D and 3D mean radial distance were compared under long, short, and no CM conditions. The estimate of the population mean length was used as a measure of distribution concentration, and the Rayleigh statistical test for circular data was applied with the sample distribution critical value. Watson's U2 goodness-of-fit test for the von Mises distribution was used with the mean direction and concentration factor. The applied metrics led to the detection of shared and specific features in the global and phase plane analysis of WB COM movement coordination in the medio-lateral, anteroposterior, and vertical directions during long, short, and no CM conditions in relation to MVJ performance assessed from ground reaction force (GRF) through the force platform. Thus, long, short, and no CM impulses share lower amplitudes of WB COM excursion in the medio-lateral direction and mean radial distance to its mean, whereas the anteroposterior and vertical excursion of WB COM, along with the 2D transversal and 3D spatial length of the WB COM path, present as potential predictors of MVJ performance, with distinct behavior in long CM compared to short and no CM. Additionally, the applied workflow on generalized phase plane analysis led to the detection, through complementary metrics, of the anatomical WB COM movement directions with higher coordination based on phase concentration tests at 5% significance, in line with MVJ performance under different CM conditions.

2026

Predictive Energy-Based Temporal Optimisation of Irrigation Systems under Time-of-Use Tariffs and PV Integration

Authors
Rocha, C; Brito, JN; Fernandes, R;

Publication

Abstract
Irrigation systems are a major source of energy consumption in agriculture, primarily due to water pumping. Increasing electricity price variability and renewable integration make energy-efficient irrigation operation challenging.This work proposes an energy-aware irrigation scheduling framework that combines predictive energy modelling with tariff-based optimisation. Rather than relying on explicit price forecasts, the approach uses relative cost representations derived from time-of-use tariffs, enabling robust scheduling under uncertain pricing conditions.Energy consumption is modelled as a function of aggregated system operation and embedded within a mixed-integer optimisation framework that determines irrigation schedules while satisfying agronomic, hydraulic, and operational constraints, including photovoltaic (PV) integration.The framework is evaluated using real-world data from a vineyard and an olive grove under varying demand, tariff, PV, and flexibility conditions. Results show substantial cost reductions without modifying irrigation demand. Benefits increase with tariff differentiation and system flexibility, while PV integration provides additional gains. In more flexible systems, scheduling may also reduce total energy consumption.Overall, irrigation scheduling emerges as an effective demand-side flexibility mechanism, improving both economic performance and energy efficiency.

2026

RIoT Digital Twin: Modeling, Deployment, and Optimization of Reconfigurable IoT System With OpticalRadio Wireless Integration

Authors
Abdellatif, AA; Silva, S; Baltazar, E; Oliveira, B; Qiu, SH; Bocus, MJ; Eder, K; Piechocki, RJ; Almeida, NT; Fontes, H;

Publication
IEEE OPEN JOURNAL OF THE COMMUNICATIONS SOCIETY

Abstract
This paper proposes an optimized Reconfigurable Internet of Things (RIoT) framework that integrates optical and radio wireless technologies with a focus on energy efficiency, scalability, and adaptability. To address the inherent complexity of hybrid optical-radio environments, a high-fidelity Digital Twin (DT) is developed within the Network Simulator 3 (NS-3) platform. The DT models deploy subsystems of the RIoT architecture, including Radio Frequency (RF) communication, Optical Wireless Communication (OWC), and energy harvesting and consumption mechanisms that enable autonomous operation. Real-time energy and power measurements from target hardware platforms are also incorporated to ensure accurate representation of physical behavior and enable runtime analysis and optimization. Building on this foundation, a proactive cross-layer optimization strategy is devised to balance energy efficiency and quality of service (QoS). The strategy dynamically reconfigures RIoT nodes by adapting transmission rates, wake/sleep scheduling, and access technology selection. Results demonstrate that the proposed framework, combining digital twin technology, hybrid optical-radio integration, and data-driven energy modeling, substantially enhances the performance, resilience, and sustainability of 6G IoT networks.

2026

Bridging Streaming Continual Learning via In-Context Large Tabular Models

Authors
Lourenço, A; Gama, J; Xing, EP; Marreiros, G;

Publication
StreamingCL@AAAI

Abstract
In streaming scenarios, models must learn continuously, adapting to concept drifts without erasing previously acquired knowledge. However, existing research communities address these challenges in isolation. Continual Learning (CL) focuses on long-term retention and mitigating catastrophic forgetting, often without strict real-time constraints. Stream Learning (SL) emphasizes rapid, efficient adaptation to high-frequency data streams, but typically neglects forgetting. Recent efforts have tried to combine these paradigms, yet no clear algorithmic overlap exists. We argue that large in-context tabular models (LTMs) provide a natural bridge for Streaming Continual Learning (SCL). In our view, unbounded streams should be summarized on-the-fly into compact sketches that can be consumed by LTMs. This recovers the classical SL motivation of compressing massive streams with fixed-size guarantees, while simultaneously aligning with the experience-replay desiderata of CL. To clarify this bridge, we show how the SL and CL communities implicitly adopt a divide-to-conquer strategy to manage the tension between plasticity (performing well on the current distribution) and stability (retaining past knowledge), while also imposing a minimal complexity constraint that motivates diversification (avoiding redundancy in what is stored) and retrieval (re-prioritizing past information when needed). Within this perspective, we propose structuring SCL with LTMs around two core principles of data selection for in-context learning: (1) distribution matching, which balances plasticity and stability, and (2) distribution compression, which controls memory size through diversification and retrieval mechanisms. © 2026 Copyright for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).

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