Repositório RCAAP

Most recurrent real-time applications can be modeled as a set of sequential code segments (or blocks) that must be (repeatedly) executed in a specific order. This paper provides a schedulability analysis for such systems modeled as a set of parallel DAG tasks executed under any limited-preemptive global job-level fixed priority scheduling policy. More precisely, we derive response-time bounds for a set of jobs subject to precedence constraints, release jitter, and execution-time uncertainty, which enables support for a wide variety of parallel, limited-preemptive execution models (e.g., periodic DAG tasks, transactional tasks, generalized multi-frame tasks, etc.). Our analysis explores the space of all possible schedules using a powerful new state abstraction and state-pruning technique. An empirical evaluation shows the analysis to identify between 10 to 90 percentage points more schedulable task sets than the state-of-the-art schedulability test for limited-preemptive sporadic DAG tasks. It scales to systems of up to 64 cores with 20 DAG tasks. Moreover, while our analysis is almost as accurate as the state-of-the-art exact schedulability test based on model checking (for sequential non-preemptive tasks), it is three orders of magnitude faster and hence capable of analyzing task sets with more than 60 tasks on 8 cores in a few seconds.

This work presents different approaches to calculate CPRO for set-associative caches. The PCB-ECB approach uses PCBs of the task under analysis and ECBs of all other tasks in the system to provide sound estimates of CPRO for set-associative caches. The resilienceP analysis then removes some of the pessimism in the PCB-ECB approach by considering the resilience of PCBs during CPRO calculations. We show that using the state-of-the-art (SoA) resilience analysis to calculate resilience of PCBs may result in underestimating the CPRO tasks may suffer. Finally, we have also presented a multi-set alike resilienceP analysis that highlights the pessimism in the resilienceP analysis and provides some insights on how it can be removed.

The advent of multi-core platforms in critical realtime domains such as the avionics, automotive and railways to achieve higher and higher computing performances has turned the view on thermal concerns of the underlying chip die while it is still mandatory to meet all the temporal constraints. As a matter of fact, high chip temperature may not only degrade system performance and reliability, but it may also damage the chip permanently. We propose a methodology to address this problem, based on fixed task-to-core mapping and per-core analysis to derive a sound system model without feedback loops. To this end, it is important to have a better and deeper understanding of the existing thermal models in the literature. This is the main contribution of this research.

In order to communicate, cores of a multi-core platform traditionally relied on shared busses. However, with the increasing number of computation nodes integrated in multi- and many-core platforms, Network-on-Chips (NoCs) emerged as a new alternative communication medium in Systems-on-Chips (SoCs). Hoplite-RT is a new NoC design that was recently proposed. Hoplite-RT is a compact design easy to analyze and with a low-cost implementation that was specifically tailored for FPGA. In this work, we introduce priority-based routing to Hoplite-RT and change the network topology so as to improve its timing behavior, i.e., its Worst-Case Traversal Time (WCTT).

Timing analysis of safety-critical real-time embedded systems should be free of both optimistic and pessimistic aspects. The multiframe model was devised to eliminate the pessimism in the schedulability analysis of systems with tasks whose worst-case execution times vary from job to job, according to known patterns. However, this model is optimistic and unsafe for multicores with shared memory controllers, since it ignores memory contention, and existing approaches to stall analysis based on memory regulation are very pessimistic if straightforwardly applied. This paper remedies this by adapting existing stall analyses for memory-regulated systems of conventional Liu-and-Layland tasks to the multiframe model. Experimental evaluations with synthetic task sets (and different task and memory budget assignment heuristics) show up to 85% higher scheduling success ratio for our analysis, compared to the frameagnostic analysis, enabling higher platform utilisation without compromising safety. We also explore implementation aspects, such as how to speed up the analysis and how to trade off accuracy with tractability.

This work explores the impact of antenna heights and polarization on overwater links during the cycle of tidal variations. We focus our attention on links of short-to-medium-range distances with antenna heights near-to-the-water-surface. The typical use-case for such a scenario is an overwater, water quality monitoring wireless sensor network. The radio propagation is simulated using a featured two-ray model that considers the relative permittivity of the water surface and the antenna polarization. The results show that the performance of overwater links may be better with lower antennas than higher antennas as well as with one polarization or the other, intuitively, during part of the tidal cycle.

This book describes the Optical Immersion Clearing method and its application to acquire information with importance for clinical practice and various fields of biomedical engineering. The method has proved to be a reliable means of increasing tissue transparency, allowing the investigator or surgeon to reach deeper tissue layers for improved imaging and laser surgery. This result is obtained by partial replacement of tissue water with an active optical clearing agent (OCA) that has a higher refractive index and is a better match for the refractive index of other tissue components. Natural tissue scattering is thereby reduced. An exponential increase in research using this method has occurred in recent years, and new applications have emerged, both in clinical practice and in some areas of biomedical engineering. Recent research has revealed that treating ex vivo tissues with solutions containing active OCAs in different concentrations produces experimental data to characterize drug delivery or to discriminate between normal and pathological tissues. The obtained drug diffusion properties are of interest for the pharmaceutical and organ preservation industry. Similar data can be estimated with particular interest for food preservation. The free water content evaluation is also of great interest since it facilitates the characterization of tissues to discriminate pathologies. An interesting new application that is presented in the book regards the creation of two optical windows in the ultraviolet spectral range through the application of the immersion method. These induced transparency windows open the possibility to diagnose and treat pathologies with ultraviolet light. This book presents photographs from the tissues we have studied and figures that represent the experimental setups used. Graphs and tables are also included to show the numerical results obtained in the sequential calculations performed.

This paper presents the analysis of the statistics of latency and information theoretic capacity of an adaptive link with retransmission-spatial diversity in a scenario with co-channel interference. The paper focuses specifically on the delay of the wireless transmission component, measured from the instant a packet at the head of the queue is first transmitted until it is correctly received by the destination (considering retransmissions). The objective is to evaluate the ability of temporal and spatial diversity tools to achieve ultra-low values of latency as desired in future 5G and machine-to-machine (M2M) networks with real-time requirements. It is assumed that the source transmits information towards the destination in a Rayleigh fading spatially correlated channel. In case the instantaneous signal-to-interference-plus-noise (SINR) ratio has not surpassed a predetermined reception threshold, then the source engages in a persistent retransmission protocol. All the copies of the original transmission and subsequent retransmissions are stored in memory and processed at the destination using maximum ratio combining (MRC) to obtain a more reliable copy of the signal (a scheme also called retransmission diversity). The retransmission scheme stops once the instantaneous post-processing SINR achieves the desired target threshold. This persistent retransmission scheme can also be regarded as a security mechanism against interference jamming attacks. Since retransmissions are assumed to take place in a short time interval in order to achieve very low values of latency, they are modelled with statistical temporal correlation, which is explicitly introduced in the embedded Gaussian channel distribution model. Results suggest that retransmission diversity can provide good latency results in moderate to high values of SINR. However, at low SINR, a combination with other diversity sources will be necessary to achieve the desired target value.

This paper presents the derivation new expressions for the statistics of a Chi-square distribution with $n$ degrees of freedom and where n is an even number. The complex Gaussian components of the chi-square distribution are modelled with a linear correlated model using different statistics (multi-rate) for each component. We focus on the specific expressions for the probability density function (PDF) and complementary cumulative density function (CCDF). Unlike previous approaches, we use a frequency domain interpretation that allows us to derive a closed form expression for the characteristic function (CF) as an inverse polynomial equation. Using the roots of this polynomial equation, it is possible to decompose the CF as a partial fraction expansion (PFE). This allows us to obtain a simple expression for both the PDF and CCDF by simply using the inverse Fourier transform of PFE decomposition of the CF. The statistics derived here have a much lower complexity than the expressions obtained from conventional non-frequency domain methods at the expense of the complexity of the polynomial root solution scheme. In scenarios where the average statistics of the components do not change over some periods of time, the proposed expressions provide the lowest possible complexity, as the polynomial rooting process needs to be conducted only once and potentially offline.

The very particular characteristics of electricity markets, require deep studies of the interactions between the involved players. MASCEM is a market simulator developed to allow studying electricity market negotiations. This paper presents a new proposal for the definition of MASCEM players’ strategies to negotiate in the market. The proposed methodology is implemented as a multiagent system, using reinforcement learning algorithms to provide players with the capabilities to perceive the changes in the environment, while adapting their bids formulation according to their needs, using a set of different techniques that are at their disposal. This paper also presents a methodology to define players’ models based on the historic of their past actions, interpreting how their choices are affected by past experience, and competition.

O mundo do trabalho é cada vez mais imprevisível, complexo e instável, o que coloca crescentes desafios às organizações e às pessoas que nelas trabalham. Às organizações exige-se o aumento da sua competitividade e da sua agilidade para responder às constantes mudanças. Simultaneamente, aos colaboradores exigem-se cada vez mais competências de modo a contribuírem para o sucesso organizacional. No equilíbrio entre os interesses das organizações e o bem-estar e produtividade dos colaboradores, situamos a inteligência emocional e o engagement no trabalho. Se por um lado a inteligência emocional tem sido apontada como preditora do engagement no trabalho, é sabido que este está associado tanto ao bem-estar do indivíduo como ao sucesso organizacional. O objetivo principal da presente investigação é analisar a relação entre a inteligência emocional e o engagement no trabalho. Pretende-se também analisar a associação entre variáveis sociodemográficas e profissionais com a inteligência emocional e com o engagement no trabalho. Participaram no estudo 161 colaboradores de três empresas de diferentes sectores de atividade que responderam à escala de avaliação das emoções (EAE; Schutte et al., 1998) e ao questionário de engagement no trabalho (UWES; Schaufeli et Bakker, 2004). O principal resultado encontrado permite-nos concluir que existe uma relação positiva entre a inteligência emocional e o engagement no trabalho, e que as habilitações literárias se relacionam positivamente com a inteligência emocional. Constata-se ainda que a inteligência emocional foi capaz de predizer 29% da variância do engagement no trabalho. Estes resultados apontam para importantes implicações para a prática, pois contribui para dotar as organizações de conhecimento orientador do desenvolvimento de políticas de recursos humanos que conjugam os interesses da organização com o bem-estar dos seus colaboradores.

O objetivo primordial desta dissertação é o estudo do regime das secções nas cooperativas agrícolas polivalentes e multissectoriais portuguesas. Especificamente, pretende-se saber se as diferentes secções das cooperativas agrícolas polivalentes e multissectoriais têm contabilidade separada. Para o efeito, fizemos uma revisão ao estado da arte e reflexão sobre a matéria escrita. As cooperativas apresentam-se como uma das famílias da economia social, setor que tem um papel preponderante na economia. Especificamente, as cooperativas agrícolas são um ramo do setor cooperativo com características próprias e, por isso, torna-se pertinente fazer um estudo jurídico e contabilístico das especificidades impostas às cooperativas agrícolas polivalentes e multissetoriais, particularizando as secções. A metodologia utilizada é qualitativa, baseando-se num estudo de caso múltiplo, através do estudo de fenómenos. Através deste método pudemos validar se, as cooperativas agrícolas polivalentes estudadas cumprem os normativos jurídicos e contabilísticos. Verificámos que existem lacunas nos estatutos e relatórios de contas das cooperativas, nomeadamente no referente às secções. Conclui-se que as cooperativas agrícolas deveriam estar enquadradas num sistema contabilístico mais apropriado às suas especificidades.

Deterministic Synchronous Multichannel Extension (DSME) is a prominent MAC behavior of IEEE 802.15.4e can avail deterministic service using its multisuperframe structure. RPL is a routing protocol for wireless networks with low power consumption and generally susceptible to packet loss. A combination of these two protocols can integrate real-time QoS demanding and large-scale IoT networks. In this paper, we propose an architecture to integrate routing with DSME. We also show a simulation result by which we improve reliability by 40 % using routing.

In this work, a thorough analysis based on the two-ray model in the presence of tides is performed. The study aims to provide a tool to guide the deployment of near-surface overwater wireless sensor networks, and thus improve its overall link quality regardless of the variations of the tides. We consider realistic parameters, such as the distance between the nodes and the tide-levels range taken from the mouth of the Douro river, Porto and the Seixal Bay, Lisbon. In future works, we will complement the theoretical analysis with network level simulations and an extended experimental campaign.

An important element in urban traffic management is the Intersection Management (IM) that deals with traffic lights signaling (either real or virtual). Intersections are vulnerable to traffic congestion and accidents. Therefore, this paper investigates a synchronous intersection management protocol for mixed autonomous and humandriven vehicles in the context of decentralized traffic management.

This paper presents a demo of an extension developed to support an existing programming abstraction for IoT: mT-Res. mT-Res is an extension of the T-Res programming abstraction, which allows users to write applications using a web framework without low level knowledge of resources. The paper describes an automated mechanism for allocate resources to such applications and adapt to changes in those resources.

Deep learning based communication using autoencoder have revolutionized the design of physical layer in wireless communication. In this paper, we propose an adversarial autoencoder to mitigate vulnerability of autoencoder against adversarial attacks. Results confirm the effectiveness of adversarial training by reducing block error rate(BLER) from 90 percent to 56 percent.

Safety-critical systems commonly face unpredictable and hostile environments, with emergent behaviors and with a growing number of external, malicious attackers. These are risk factors that should be taken into account during these systems design phases, but that is not always possible due to the overall complexity of the interaction between the systems and its external operational environment. Cyber-Physical Systems (CPS) are notable examples of practical implementations of safety-critical systems. Being able to guarantee that safetycritical CPS do not fail upon operation can easily become a huge challenge, depending on how complex the system is. Among the most promising approaches to reduce the complexity of designing safety-critical CPS are Runtime Monitoring (RM) (Watterson and Heffernan 2017) and Runtime Verification (RV) (Bartocci Et al. 2018), where monitors are generated and orchestrated in a software architecture that can be coupled to the target system, observe it during its execution, and identify aspects that were not foreseen during design phase, or that could not be proved to be absent via static verification methods. Monitors can be used to verify the correct functioning of a system by analyzing direct (and/or indirect) aspects of it. This can be especially useful when considering a security-oriented point of view, where monitors can identify possible security attacks to a system when exposed to the events taking place or the patterns of data being processed.

This work presents different approaches to calculate CPRO for set-associative caches. The PCB-ECB approach uses PCBs of the task under analysis and ECBs of all other tasks in the system to provide sound estimates of CPRO for set-associative caches. The resilienceP analysis then removes some of the pessimism in the PCB-ECB approach by considering the resilience of PCBs during CPRO calculations. We show that using the state-of-the-art (SoA) resilience analysis to calculate resilience of PCBs may result in underestimating the CPRO tasks may suffer. Finally, we have also presented a multi-set alike resilienceP analysis that highlights the pessimism in the resilienceP analysis and provides some insights on how it can be removed.

The quest for comfort and practicality is commonplace in contemporary society, but such benefits are still not offered satisfactorily to all. Among these, special attention is given to people with Disabilities, who often do not enjoy the latest technologies in applications and automated systems because they do not have their needs covered by these technologies (Domingo 2012). The aim of this work was to develop an automation system that would increase the level of inclusion. Tis work also propose a low cost residential automated system, developed using electronic waste, open hardware and open software, to increase the application of the system. There were used platforms of easy access, and easy replication, aiming at the dissemination of technology (Trihinas, Pallis, and Dikaiakos 2018). Among these platforms, it is possible to highlight the Google Assistant (Chatterjee, n.d.). All the platforms used helps the development of an Internet of Things (IOT) system, with multiple capabilities. Finally, functional tests were performed of three physical modules to control a door, a set of sockets and some lamps, using RFID, cellular and voice cards for its activation.