Polytechnic Institute of Porto
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Congestion management in active distribution networks through demand response implementation
No full textDespite the positive contributions of controllable electric loads such as electric vehicles (EV) and heat pumps (HP) in providing demand-side flexibility, uncoordinated operation of these loads may lead to congestions at distribution networks. This paper aims to propose a market-based mechanism to alleviate distribution network congestions through a centralized coordinated home energy management system (HEMS). In this model, the distribution system operator (DSO) implements dynamic tariffs (DT) and daily power-based network tariffs (DPT) to manage congestions induced by EVs and HPs. In this framework, the HP and EV loads are directly controlled by the retail electricity provider (REP). As DT and DPT price signals target the aggregated nodal demand, the individual uncoordinated HEMS models operating under these price signals are unable to effectively alleviate congestion. A large number of flexible residential customers with EV and HP loads are modeled in this paper, and the REP schedules the consumption based on the comfort preferences of the customers through HEMS. The effectiveness of the market-based concept in managing the congestion is demonstrated by using the IEEE 33-bus distribution system with 706 residential customers. The case study results show that considering both pricing systems can considerably mitigate the overloading occurrences in distribution lines, while applying DTs without considering DPTs may lead to severe overloading occurrences at some periods.The present work was done and funded in the scope of the following projects: H2020 DREAM-GO Project (Marie Sklodowska-Curie grant agreement No 641794); AVIGAE Project (P2020 - 3401); UID/EEA/00760/2013 funded by FEDER, Spain funds through COMPETE program and by national funds through Fundação para a Ciência e a Tecnologia (FCT), Portugal; and SFRH/BD/94688/2013 (Mohammd Ali Fotouhi Ghazvini PhD grant).info:eu-repo/semantics/publishedVersio
Memory Bandwidth Regulation for Multiframe Task Sets
No full textTiming 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.info:eu-repo/semantics/publishedVersio
Techniques and Analysis for Mixed-criticality Scheduling with Mode-dependent Server Execution Budgets
No full textThis article appears as part of the ESWEEK-TECS special issue and was presented at the International Conference on Embedded Software (EMSOFT) 2019.In mixed-criticality systems, tasks of different criticality share system resources, mainly to reduce cost. Cost is
further reduced by using adaptive mode-based scheduling arrangements, such as Vestal’s model, to improve
resource efficiency, while guaranteeing schedulability of critical functionality. To simplify safety certification, servers are often used to provide temporal isolation between tasks. In its simplest form, a server is a
periodically recurring time window, in which some tasks are scheduled. A server’s computational requirements may greatly vary in different modes, although state-of-the-art techniques and schedulability tests do
not allow different budgets to be used by a server in different modes. This results in a single conservative
execution budget for all modes, increasing system cost.
The goal of this paper is to reduce the cost of mixed-criticality systems through three main contributions:
(i) a scheduling arrangement for uniprocessor systems employing fixed-priority scheduling within periodic
servers, whose budgets are dynamically adjusted at run-time in the event of a mode change, (ii) a new schedulability analysis for such systems, and (iii) heuristic algorithms for assigning budgets to servers in different
modes and ordering the execution of the servers. Experiments with synthetic task sets demonstrate considerable improvements (up to 52.8%) ininfo:eu-repo/semantics/publishedVersio
Lean Manufacturing: Implementation, Opportunities and Challenges
No full textThe paradigm of manufacturing is undergoing a major evolution throughout the world. The use of computers, the Internet and new challenges related to the Industry 4.0 have changed the way we engineer and manufacture products. Improving production with Lean Thinking is an evolution of a traditional approach in order to improve its processes to remain competitive in the global market.
Lean Manufacturing is a multidimensional approach that embraces a wide variety of management practices in a unified system. These practices contain, quality systems, team work, and supplier management, among others. Nowadays, other practices have been adopted such as human factors and ergonomics.
This book presents contributions of Lean Manufacturing applications in the world development and is intended to provide a comprehensive view of issues related to this area, with a specific focus on lean engineering principles; it is full of practical production examples of how Lean Thinking can be applied effectively to production systems.
This work was conceptualized for an audience of graduate students mainly; however, it can also be consulted by engineers and company managers who seek state-of-the-art applications on Lean Manufacturing within a wide diversity of scenarios and conditions.
The book, organized into 17 chapters, is intended to be an excellent source for dissemination of applied researches, lean concepts, and practices that have been successfully applied in the developing world domain. The book is also an excellent example of academy purpose with collaboration between different institutions from different countries that provide a global approach.info:eu-repo/semantics/publishedVersio
Poster Abstract: Multi-Drone Assisted Internet of Things Testbed Based on Bluetooth 5 Communications
No full textIn this paper, a multi-hop airborne system is built based on Bluetooth 5 connected autonomous drones to relay real-time data of
Internet of Things (IoT). A new lightweight Onboard Bluetooth
Transceiver (OBT) is developed for reliable drone-to-drone and
drone-to-ground communications. A graphical user interface is
presented to monitor real-time flight trajectory of the drones and
end-to-end data delivery. Outdoor experiments are conducted in
real world to test autonomous flight control of the drones and
received signal strength of the OBT communications.info:eu-repo/semantics/publishedVersio
MAC-PHY Cross-layer design for Secure Wireless Avionics Intra-Communications
No full textThis paper presents a framework for medium access control (MAC) and physical (PRY) cross-layer security design of wireless avionics intra-communications (WAICs). The paper explores the different options based on the latest results of MAC-PRY cross-layer design and the available standard technologies for WAICs. Particular emphasis is given to solutions based on multiple-input multiple-output (MIMO) systems and recent developments towards a wireless technology with ultra-low latency and high reliability in the context of 5G and machine-type traffic support. One major objective is to improve WAICs technology and thus match the real-time, reliability and safety critical performance of the internal aeronautics bus technologies (e.g., ARINC 664). The main identified vulnerabilities and potential solutions are explored, as well as their impact on system design complexity and feasibility for wireless networks on-board aircraft. The solutions are presented in the context of the European project SCOTT (secure connected trustable things) using the recently released reference architecture for trusted IoT systems. Other aspects of SCOTT such as trust, privacy, security classes, and safety are also discussed here for the aeronautics domain.info:eu-repo/semantics/publishedVersio
Mobile fog computing security: A user-oriented smart attack defense strategy based on DQL
No full textEach fog node interacts with data from multiple end-users in mobile fog computing (MFC) networks. Malicious users can use a variety of programmable wireless devices to launch different modes of smart attacks such as impersonation attack, jamming attack, and eavesdropping attack between fog servers and legitimate users. The existing research in MFC lacks in the contributions of defense of smart attack and also requires in the discussions of subjective decision making by participants. Therefore, we propose a smart attack defense scheme for authorized users in MFC in this paper. First, we construct a static zero-sum game model between smart attackers and legitimate users based on prospect theory. Second, the double Q-learning (DQL) is proposed to restrain the attack motive of smart attackers in the dynamic environment. The proposed DQL method generates the optimum defense choice of legitimate users against smart attacks so that they can efficiently determine whether to use only physical layer security (PLS) to avoid those smart attacks. We use our scheme to contrast with the basic schemes, i.e., Q-learning scheme, the Sarsa scheme, and the greedy strategy. Experiment results prove that the proposed scheme can enhance the utility of legitimate users, restrain the attack motive of smart attackers, and further provide better security protection in the MFC environment.info:eu-repo/semantics/publishedVersio
A Multi-Ray Analysis of LOS V2V Links for Multiple Antennas with Ground Reflection
No full textThis paper presents a vehicle-to-vehicle (V2V) geometric multi-ray tracing model for an improved line-of-sight (LOS) estimation. The model is especially suited for distributed antenna transceivers in the presence of ground reflections. The multiple antennas are assumed to be spaced regularly in horizontal and vertical directions over contiguous vehicles. The main focus of our study is the ability of the multiple antenna system to counteract or exploit, respectively, the destructive or constructive interference of multiple rays in the LOS channel component. This work is a complement to existing V2V channel models by providing more details on how ground reflections affect the LOS channel. The analysis is initially framed in the context of MIMO (multiple-input multiple-output) systems to investigate general aspects such as capacity limits and singular value distribution. The work then focuses on a scheme with single symbol repetition across the transmit antennas and two different strategies for signal combining at the receiver: maximum-ratio and equal-gain combining (MRC and EGC, respectively). These solutions are compared with a full diversity solution as well as with the information theoretical limits. An adaptive antenna selection mechanism is finally proposed that outperforms all other solutions. The paper shows both vertical and horizontal polarization results with corrected complex Fresnel reflection coefficients for lossy materials. Moreover, it is shown that multiple antenna design in V2V systems can be useful to counteract the destructive interference created by multiple rays on the LOS channel component.info:eu-repo/semantics/publishedVersio
Moving tissue spectral window to the deep‐ultraviolet via optical clearing
No full textThe optical immersion clearing technique has been successfully applied through the last 30 years in the visible to near infrared spectral range, and has proven to be a promising method to promote the application of optical technologies in clinical practice. To investigate its potential in the ultraviolet range, collimated transmittance spectra from 200 to 1000 nm were measured from colorectal muscle samples under treatment with glycerol-water solutions. The treatments created two new optical windows with transmittance efficiency peaks at 230 and 300 nm, with magnitude increasing with glycerol concentration in the treating solution. Such discovery opens the opportunity to develop clinical procedures to perform diagnosis or treatments in the ultraviolet.L.O. and V.T. have contributed equally to this work. The work was supported by the Portuguese grant FCTUID/
EQU/04730/2013. V.T. was supported by RF Governmental grant 14.W03.31.0023.info:eu-repo/semantics/publishedVersio
Nickel Oxide Nanoparticles Trigger Caspase- and Mitochondria-Dependent Apoptosis in the Yeast Saccharomyces cerevisiae
No full textThe expansion of the industrial use of nickel oxide (NiO) nanoparticles (NPs) raises concerns about their potential adverse effects. Our work aimed to investigate the mechanisms of toxicity induced by NiO NPs, using the yeast Saccharomyces cerevisiae as a cell model. Yeast cells exposed to NiO NPs exhibited typical hallmarks of regulated cell death (RCD) by apoptosis [loss of cell proliferation capacity (cell viability), exposure of phosphatidylserine at the outer cytoplasmic membrane leaflet, nuclear chromatin condensation, and DNA damage] in a process that required de novo protein synthesis. The execution of yeast cell death induced by NiO NPs is Yca1p metacaspase-dependent. NiO NPs also induced a decrease in the mitochondrial membrane potential and an increase in the frequency of respiratory-deficient mutants, which supports the involvement of mitochondria in the cell death process. Cells deficient in the apoptosis-inducing factor ( aif1Δ) displayed higher tolerance to NiO NPs, which reinforces the involvement of mitochondria in RCD by apoptosis. In summary, this study shows that NiO NPs induce caspase- and mitochondria-dependent apoptosis in yeast. Our results warn about the possible harmful effects associated with the use of NiO NPs.This work was performed in the framework of the financing by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of the UID/BIO/04469/2013 unit, COMPETE 2020 (POCI-01-0145-FEDER-006684), and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020Programa Operacional Regional do Norte and LAQV (UID/QUI/50006/2013-POCI/01/0145/FEDER/007265) with financial support from FCT/MEC through national funds and cofinanced by FEDER, under Partnership Agreement PT2020.
C.A.S. gratefully acknowledges the doctoral grant (SFRH/BD/101452/2014) from FCT.info:eu-repo/semantics/publishedVersio