Showing papers by "Instituto Superior Técnico published in 2022"

Preserving Privacy of Smart Meter Data in a Smart Grid Environment

Abstract: The use of data from residential smart meters can help in the management and control of distribution grids. This provides significant benefits to electricity retailers as well as distribution system operators but raises important questions related to the privacy of consumers' information. In this article, an innovative differential privacy (DP) compliant algorithm is developed to ensure that the data from consumer's smart meters are protected. The effects of this novel algorithm on the operation of the distribution grid are thoroughly investigated not only from a consumer's electricity bill point of view but also from a power systems point of view. This method allows for an empirical investigation into the losses, power quality issues, and extra costs that such a privacy-preserving mechanism may introduce to the system. In addition, severalcost allocation mechanisms based on the cooperative game theory are used to ensure that the extra costs are divided among the participants in a fair, efficient, and equitable manner. Overall, the comprehensive results show that the approach provides privacy preservation in line with the consumer's preferences and does not lead to significant cost or loss increases for the energy retailer. In addition, the novel algorithm is computationally efficient and performs very well with a large number of consumers, thus demonstrating its scalability.

Adaptive Backstepping Control of a Quadcopter With Uncertain Vehicle Mass, Moment of Inertia, and Disturbances

Abstract: In this article, we propose a solution to the problem of path following for a quadcopter aircraft with unknown vehicle parameters (mass and moment of inertia) and external disturbances By employing the backstepping technique, the proposed adaptive control strategy guarantees the following: the quadcopter is globally steered toward, and kept within, an arbitrarily small neighborhood of a desired smooth path, achieving global uniformly ultimately boundedness; compared to trajectory tracking, a smoother convergence is obtained as the control actuation signals (thrust force and torque) are bounded with respect to the position error, and the designed timing law ensures that the desired path starts to move only when the vehicle gets close to the desired path; and a single adaptive control law can be used for accurate motion control of aerial vehicles with a wide range of inertial properties, without the need for retuning control gains or other parameters Moreover, the controller is also made robust to external constant and slowly time-varying disturbances through the design of disturbance estimators To demonstrate the effectiveness and performance of the proposed control strategies, simulation and experimental results are presented and analyzed

Modular flavour symmetries and modulus stabilisation

Abstract: A bstract We study the problem of modulus stabilisation in the framework of the modular symmetry approach to the flavour problem. By analysing simple UV-motivated CP-invariant potentials for the modulus τ we find that a class of these potentials has (non-fine-tuned) CP-breaking minima in the vicinity of the point of $$ {\mathrm{\mathbb{Z}}}_3^{ST} $$ ℤ 3 ST residual symmetry, τ ≃ e 2 πi /3 . Stabilising the modulus at these novel minima breaks spontaneously the CP symmetry and can naturally explain the mass hierarchies of charged leptons and possibly of quarks.

Technical and environmental potentialities of recycled steel fiber reinforced concrete for structural applications

Abstract: The use of recycled materials and industrial by-products as sustainable constituents of cement-based materials could be an environmentally and technically promising solution for application to structural elements. In the present work, the technical and environmental impact of using recycled steel fibers as an alternative to industrial steel fibers for concrete reinforcement was assessed at material level. Numerical simulations were performed to derive the post-cracking constitutive laws of the developed Recycled Steel Fiber Reinforced Concrete (RSFRC) and Industrial Steel Fiber Reinforced Concrete (ISFRC) by inverse analysis of experimental results obtained from three-point notched beam bending tests (3PNBBT), round panel tests supported in three points (RPT-3ps) and double edge wedge splitting tests (DEWST). These simulations were able of fitting with high accuracy the experimental results and consequently to derive the tensile stress-crack width relationships of RSFRC and ISFRC that was used to numerically simulate the bending response of a T-cross section steel RSFRC beam failing in shear. The environmental impact of the incorporation of RSF in concrete in comparison with ISFRC was evaluated using Life Cycle Assessment methodology . The reduction of the environmental impact of the production of RSFRC compared to ISFRC with the same concrete strength class is demonstrated.

Production of Environmentally Friendly Concrete Incorporating Bauxite Residue and Silica Fume

Abstract: Toward a sustainable approach, concrete consumption is confronted with new challenges to developing and implementing cleaner technology. Concrete production is associated with excessive use...

On the Robustness of Nominally Well-Posed Event-Triggered Controllers

Abstract: In this letter, we show that: 1) if the Krasovskii regularization of a hybrid system $\mathcal {H}$ has complete and discrete solutions, then $\mathcal {H}$ has solutions with arbitrarily small separation between jumps under the influence of admissible state perturbations; 2) if $\mathcal {H}$ is nominally well-posed and does not have complete discrete solutions, then it does not have solutions with vanishing time between jumps (such as Zeno solutions); 3) if, in addition, there exists a compact set $\mathcal {A}$ such that all maximal solutions to $\mathcal {H}$ from $\mathcal {A}$ are complete, discrete and remain in $\mathcal {A}$ , then all solutions converging to $\mathcal {A}$ have vanishing time between jumps. The results in this letter demonstrate that a good practice to avoid solutions with arbitrarily fast sampling in Event-Triggered Control (ETC) is to ensure that the closed-loop system is nominally well-posed and that it does not have complete discrete solutions.

Increased Excursions to Functional Networks in Schizophrenia in the Absence of Task

Abstract: Schizophrenia is a chronic psychotic disorder characterized by the disruption of thought processes, perception, cognition, and behaviors, for which there is still a lack of objective and quantitative biomarkers in brain activity. Using functional magnetic resonance imaging (fMRI) data from an open-source database, this study investigated differences between the dynamic exploration of resting-state networks in 71 schizophrenia patients and 74 healthy controls. Focusing on recurrent states of phase coherence in fMRI signals, brain activity was examined for intergroup differences through the lens of dynamical systems theory. Results showed reduced fractional occupancy and dwell time of a globally synchronized state in schizophrenia. Conversely, patients exhibited increased fractional occupancy, dwell time and limiting probability of being in states during which canonical functional networks-i.e., Limbic, Dorsal Attention and Somatomotor-synchronized in anti-phase with respect to the rest of the brain. In terms of state-to-state transitions, patients exhibited increased probability of switching to Limbic, Somatomotor and Visual networks, and reduced probability of remaining in states related to the Default Mode network, the Orbitofrontal network and the globally synchronized state. All results revealed medium to large effect sizes. Combined, these findings expose pronounced differences in the temporal expression of resting-state networks in schizophrenia patients, which may relate to the pathophysiology of this disorder. Overall, these results reinforce the utility of dynamical systems theory to extend current knowledge regarding disrupted brain dynamics in psychiatric disorders.