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Publications

2024

Time-predictable task-to-thread mapping in multi-core processors

Authors
Samadi, M; Royuela, S; Pinho, LM; Carvalho, T; Quinones, E;

Publication
JOURNAL OF SYSTEMS ARCHITECTURE

Abstract
The performance of time-predictable systems can be improved in multi-core processors using parallel programming models (e.g., OpenMP). However, schedulability analysis of parallel applications is a big challenge due to their sophisticated structure. The common drawbacks of current task-to-thread mapping approaches in OpenMP are that they (i) utilize a global queue in the mapping process, which may increase contention, (ii) do not apply heuristic techniques, which may reduce the predictability and performance of the system, and (iii) use basic analytical techniques, which may cause notable pessimism in the temporal conditions. Accordingly, this paper proposes a task-to-thread mapping method in multi-core processors based on the OpenMP framework. The mapping process is carried out through two phases: allocation and dispatching. Each thread has an allocation queue in order to minimize contention, and the allocation and dispatching processes are performed using several heuristic algorithms to enhance predictability. In the allocation phase, each task-part from the OpenMP DAG is allocated to one of the allocation queues, which includes both sibling and child task-parts. A suitable thread (i.e., allocation queue) is selected using one of the suggested heuristic allocation algorithms. In the dispatching phase, when a thread is idle, a task-part is selected from its allocation queue using one of the suggested heuristic dispatching algorithms and then dispatched to and executed by the thread. The performance of the proposed method is evaluated under different conditions (e.g., varying the number of tasks and the number of threads) in terms of application response time and overhead of the mapping process. The simulation results show that the proposed method surpasses the other methods, especially in the scenario that includes overhead of the mapping. In addition, a prototype implementation of the main heuristics is evaluated using two kernels from real-world applications, showing that the methods work better than LLVM's default scheduler in most of the configurations.

2024

Water Utility Service Quality Index: A customer-centred approach for assessing the quality of service in the water sector

Authors
Vilarinho, H; Pereira, MA; D'Inverno, G; Nóvoa, H; Camanho, AS;

Publication
SOCIO-ECONOMIC PLANNING SCIENCES

Abstract
This work delves into the crucial role of service quality in the water supply and sanitation sectur. Despite extensive research and implementation of quality management practices in this sector, a universally accepted definition of quality is still lacking, resulting in varikoza service quality assesunent procedures that are difficult to compam. To address this issue, the World Bank launched the Thility of the Future' (UoF) programme, aiming guide water service providers in their efforts to become future-focused utilities that offer reliable, safe, Inclusive, transparent, and resposesive services through best-fit practices. Building upon the Damework provided by the lof programme, this study proposes the Water Utility Service Quallity Index (WUSOI) composite Indicator that reflects the quality of service provided by water supply and sanitation utilities from a customer perspective. Based on Data Envelopment Analysis, the Benelli-of-the-Douht appenach is employed to assign weights for aggregating the indicators representing the diverse performance dimensions. The study operationalines the WUSOI to assess the quality of Purtuguese wholesale water and wastewater companies using data enflected by the national regulator of water and waste services. A Multiple Criteria Decision Analysis technique, the Deck of Cands method, is used to specify an indicator of transparency from the information made available by the regulated utilities. The results show the effectiveness of this tool for evaluating and measuring service quality at the company level. Additionally, the findings highlight areas for Improvement in the utilities' performance. By enabling companies and regulators to identify areas for improvement, the WUSOI can support the delivery of high-quality services to customers.

2024

Memristor-Based 1-Bit Reconfigurable Intelligent Surface for 6G Communications at D-Band

Authors
Elsaid, M; Inacio, SI; Salgado, HM; Pessoa, LM;

Publication
2024 INTERNATIONAL CONFERENCE ON ELECTROMAGNETICS IN ADVANCED APPLICATIONS, ICEAA 2024

Abstract
The Sub-THz and millimeter-wave bands have gained popularity, with the expectation that they will host the next generation of wireless communication systems. Furthermore, research on beam-steering characteristics provided by Programmable Electromagnetic Surfaces, such as Reflective Intelligent Surfaces (RISs), has garnered considerable attention as an enabling technology for 6G communications. Due to size limitations, RISs face challenges related to power consumption in the reconfigurable elements and their integration with unit cells operating at high frequencies. This paper discusses the design of a 1-bit reconfigurable unit cell at the D-band using non-volatile technology to minimize static power consumption. Simulation results show that the proposed unit cell performs well with a reflection loss of less than 1.3 dB in both reconfigurable states across a frequency band from 120 to 170 GHz. Moreover, the phase difference between the two states is maintained at 180 degrees +/- 20 degrees, with an operational bandwidth of approximately 16 GHz. The beamforming capabilities, with steering angles from -60 degrees to 60 degrees, of the 12x12 RIS, utilizing the proposed unit cell, have been demonstrated in terms of controlling the main beam radiation precisely to various angles with consistent performance at frequencies of 147GHz,152GHz, and 152.5 GHz.

2024

Socioeconomic impact of Brazilian electricity market liberalization: Forecasting and optimized tariff analysis

Authors
Silva, PF; da Costa, VBF; Dias, BH; Soares, TA; Bonatto, BD; Balestrassi, PP;

Publication
ENERGY

Abstract
-This article integrates forecasting methods with an optimized tariff model to assess the effectiveness of the schedule proposed by the Brazilian Association of Energy Traders, as outlined in the technical note NT n degrees 10/ 2022-SRM/ANEEL. This note discusses the regulatory measures to fully open the free energy market to all captive consumers by 2026. Several models, including Winters, SARIMA, ARIMA, and trend analysis were compared to determine the most suitable method for each input variable in the TAROT model, aiming to enhance forecasting accuracy. The results show that the new schedule proposed in the technical note successfully maintains the balance between the economic surplus of concessionaires and the socioeconomic welfare. Despite both approaches declining during the migration period of low-voltage consumers, their surpluses remain positive. However, there are negative effects on tariffs, impacting all consumer groups remaining in the regulated market, both high-voltage and low-voltage consumers. A key conclusion is that further regulatory changes are essential to mitigate additional increases in energy tariffs, aligning the proposed schedule with the reduction of legacy contracts.

2024

GAMAI, an AI-Powered Programming Exercise Gamifier Tool

Authors
Montella, R; De Vita, CG; Mellone, G; Ciricillo, T; Caramiello, D; Di Luccio, D; Kosta, S; Damasevicius, R; Maskeliunas, R; Queiros, R; Swacha, J;

Publication
ARTIFICIAL INTELLIGENCE IN EDUCATION: POSTERS AND LATE BREAKING RESULTS, WORKSHOPS AND TUTORIALS, INDUSTRY AND INNOVATION TRACKS, PRACTITIONERS, DOCTORAL CONSORTIUM AND BLUE SKY, AIED 2024, PT I

Abstract
This paper presents GAMAI, an AI-powered exercise gamifier, enriching the Framework for Gamified Programming Education (FGPE) ecosystem. Leveraging OpenAI APIs, GAMAI enables the teachers to leverage the storytelling approach to describe the gamified scenario. GAMAI decorates the natural language text with sentences needed by OpenAI APIs to contextualize the prompt. Once the gamified scenario has been generated, GAMAI automatically produces the exercise files for the FGPE AuthorKit editor. We present preliminary results in AI-assessed gamified exercise generation, showing that most generated exercises are ready to be used with none or minimum human effort needed.

2024

Exploring the dynamics of the Kelvin-Helmholtz instability in paraxial fluids of light

Authors
Ferreira, TD; Garwola, J; Silva, NA;

Publication
PHYSICAL REVIEW A

Abstract
Paraxial fluids of light have recently emerged as promising analog physical simulators of quantum fluids using laser propagation inside nonlinear optical media. In particular, recent works have explored the versatility of such systems for the observation of two-dimensional quantum-like turbulence regimes, dominated by quantized vortex formation and interaction that results in distinctive kinetic energy power laws and inverse energy cascades. In this manuscript, we explore a regime analog to Kelvin-Helmholtz instability to examine in further detail the qualitative dynamics involved in the transition from smooth laminar flow to turbulence at the interface of two fluids with distinct velocities. Both numerical and experimental results reveal the formation of a vortex sheet as expected, with a quantized number of vortices determined by initial conditions. Using an effective length transformation scale we get a deeper insight into the vortex formation phase, observing the appearance of characteristic power laws in the incompressible kinetic energy spectrum that are related to the single vortex structures. The results enclosed demonstrate the versatility of paraxial fluids of light and may set the stage for the future observation of distinct classes of phenomena recently predicted to occur in these systems, such as radiant instability and superradiance.

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