Unfolding-based Partial Order Reduction

Partial order reduction (POR) and net unfoldings are two alternative methods to tackle state-space explosion caused by concurrency. In this paper, we propose the combination of both approaches in an effort to combine their strengths. We first define, for an abstract execution model, unfolding semantics parameterized over an arbitrary independence relation. Based on it, our main contribution is a novel stateless POR algorithm that explores at most one execution per Mazurkiewicz trace, and in general, can explore exponentially fewer, thus achieving a form of super-optimality. Furthermore, our unfolding-based POR copes with non-terminating executions and incorporates state-caching. Over benchmarks with busy-waits, among others, our experiments show a dramatic reduction in the number of executions when compared to a state-of-the-art DPOR.Comment: Long version of a paper with the same title appeared on the proceedings of CONCUR 201

Effects of carbon nanotubes/graphene nanoplatelets hybrid systems on the structure and properties of polyetherimide-based foams

Foams based on polyetherimide (PEI) with carbon nanotubes (CNT) and PEI with graphene nanoplatelets (GnP) combined with CNT were prepared by water vapor induced phase separation. Prior to foaming, variable amounts of only CNT(0.1–2.0wt%) or a combination of GnP(0.0–2.0 wt %) and CNT (0.0–2.0 wt %) for a total amount of CNT-GnP of 2.0 wt %, were dispersed in a solvent using high power sonication, added to the PEI solution, and intensively mixed. While the addition of increasingly higher amounts of only CNT led to foams with more heterogeneous cellular structures, the incorporation of GnP resulted in foams with ¿ner and more homogeneous cellular structures. GnP in combination with CNT effectively enhanced the thermal stability of foams by delaying thermal decomposition and mechanically-reinforced PEI. The addition of 1.0 wt % GnP in combination with 1.0 wt % CNT resulted in foams with extremely high electrical conductivity, which was related to the formation of an optimum conductive network by physical contact between GnP layers and CNT, enabling their use in electrostatic discharge (ESD) and electromagnetic interference (EMI) shielding applications. The experimental electrical conductivity values of foams containing only CNT ¿tted well to a percolative conduction model, with a percolation threshold of 0.06 vol % (0.1 wt %) CNTPostprint (published version

Effects of graphene nanoplatelets and cellular structure on the thermal conductivity of polysulfone nanocomposite foams

Polysulfone (PSU) foams containing 0–10 wt% graphene nanoplatelets (GnP) were prepared using two foaming methods. Alongside the analysis of the cellular structure, their thermal conductivity was measured and analyzed. The results showed that the presence of GnP can a ect the cellular structure of the foams prepared by both water vapor induced phase separation (WVIPS) and supercritical CO2 (scCO2) dissolution; however, the impact is greater in the case of foams prepared by WVIPS. In terms of thermal conductivity, the analysis showed an increasing trend by incrementing the amount of GnP and increasing relative density, with the tortuosity of the cellular structure, dependent on the used foaming method, relative density, and amount of GnP, playing a key role in the final value of thermal conductivity. The combination of all these factors showed the possibility of preparing PSU-GnP foams with enhanced thermal conductivity at lower GnP amount by carefully controlling the cellular structure and relative density, opening up their use in lightweight heat dissipatorsPostprint (published version

Polyetherimide foams filled with low content of graphene nanoplatelets prepared by scCO2 dissolution

Polyetherimide (PEI) foams with graphene nanoplatelets (GnP) were prepared by supercritical carbon dioxide (scCO2) dissolution. Foam precursors were prepared by melt-mixing PEI with variable amounts of ultrasonicated GnP (0.1–2.0 wt %) and foamed by one-step scCO2 foaming. While the addition of GnP did not significantly modify the cellular structure of the foams, melt-mixing and foaming induced a better dispersion of GnP throughout the foams. There were minor changes in the degradation behaviour of the foams with adding GnP. Although the residue resulting from burning increased with augmenting the amount of GnP, foams showed a slight acceleration in their primary stages of degradation with increasing GnP content. A clear increasing trend was observed for the normalized storage modulus of the foams with incrementing density. The electrical conductivity of the foams significantly improved by approximately six orders of magnitude with only adding 1.5 wt % of GnP, related to an improved dispersion of GnP through a combination of ultrasonication, melt-mixing and one-step foaming, leading to the formation of a more effective GnP conductive network. As a result of their final combined properties, PEI-GnP foams could find use in applications such as electrostatic discharge (ESD) or electromagnetic interference (EMI) shieldingPostprint (published version

Interdependent Compositions Employed in Sonic Ecosystems: Integrating the Listener in the Evolving Soundscape

A presente dissertação explora a integração de ouvintes na paisagem sonora em transformação enquanto compositores do ambiente sónico, no formato de instalações áudio.A investigação é motivada pela necessidade de promover e discutir a identidade do património aural da cidade do Porto e a sua crescente transformação.O desenho metodológico seguido é o practice-led research/research-led practice, e foca-se na compreensão e no desenvolvimento de ecossistemas sonoros e das relações interdependentes entre os agentes internos e externos do sistema.Os participantes exploram cartografias sonoras generativas, transformando iterativamente a natureza composicional das paisagens ao navegarem por motivos abrangentes ou focarem em elementos específicos da experiência.Palavras-chave: Identidade, Transformação, Ecossistema, Composição de Paisagens Sonoras, Interatividade.This dissertation explores the integration of listeners in the evolving soundscape as compositional agents of the sonic environment, presented as an audio installation.The investigation is motivated by the need to promote and discuss the sonic landscape identity of Porto and its rapid transformation. A method of practice-led research/research-led practice is followed, focusing on the development and understanding of sonic ecosystems and the interdependent relationships between its internal and external agents.Participants explore generative aural cartographies, transforming iteratively the nature of compositions by expanding into wider motifs or focusing on small and specific elements of the experience.Keywords: Identity, Transformation, Ecosystem, Soundscape Composition, Interactivity

Algoritmos adaptativos para controlo eficiente de bombas numa rede de distribuição de água

Modern cities have water distribution networks (WDN) that reliably meet the water demand of every individual household. These networks rely on pumps to move water from distant sources to the consumer. If inefficiently managed, this energy consuming process can become very costly. Using emerging computer power, simulation technologies and sensing devices, many techniques were developed that produce the most cost-efficient operational strategies. These methodologies rely on water consumption predictions to provide optimal pumping strategies. However, these predictions always contain errors, which may create control problems. Many efforts were made to develop progressively better predictions, some of which can change its parameters in real time. Nevertheless, these solutions still contain errors and cannot adapt appropriately to sudden changes in demand. To solve this problem, an adaptive controller that can efficiently update the pumping strategy based on monitored deviations of the predicted consumption is proposed. This methodology takes into account the tariffs of electricity over time and an optimal reference to continuously make the most cost-efficient updates in the pumping strategy. To validate the adaptive controller, two case studies were used: (i) a simple pump-reservoir network and (ii) the Richmond benchmark network. Both evaluations delivered positive results achieving the desired reliability while improving cost efficiency. The combination water consumption predictions and adaptive control methodologies provide a reliable and cost-efficient solution to operate a WDN automatically. This control model may become an essential feature in emerging water grids technology by closing the loop in the control system.Cidades modernas têm redes de distribuição de água que de forma confiável satisfazem as necessidades de água de todos os domicílios. Estas redes dependem de bombas para mover a água de fontes distantes ao consumidor. Se gerido de forma ineficiente, este processo consumidor de energia pode tornar-se muito dispendioso. Através de poder computacional emergente, tecnologias de simulação e sensores, muitas técnicas foram desenvolvidas para produzir as melhores estratégias de operação. Estas metodologias dependem de previsões do consumo de água para criar estratégias de bombeamento óptimas. Porém, estas previsões contêm sempre erros, que podem criar problemas de controlo. Muitos esforços foram feitos para desenvolver melhores previsões, algumas das quais podem mudar os seus parâmetros em tempo real. De qualquer forma, estas soluções ainda contem erros e não conseguem adaptar a mudanças drásticas de consumo. Para resolver este problema é proposto um controlo adaptativo capaz de eficientemente actualizar em tempo real a estratégia de bombeamento com base nos desvios monitorizados relativamente à previsão. Esta metodologia toma em consideração uma referência optimizada para continuamente fazer as actualizações mais eficientes à estratégia de bombeamento. Para validar o controlo adaptativo, dois casos de estudo foram explorados: (i) uma rede simples composta de uma bomba e um tanque, (ii) e a de rede de referência de Richmond. Ambas as avaliações entregaram resultados positivos melhorando a eficiência a nível de custo. A combinação de previsões de consumo de água com metodologias de controlo adaptativo providencia uma solução confiável e eficiente para controlo automático de redes de distribuição de água. Este modelo de controlo pode se tornar uma característica essencial na tecnologia emergente “water grids” fechando o ciclo de controlo no sistema.Mestrado em Engenharia Informátic

Corona discharges from grounded rods and 337/777 nm emissions of laboratory long sparks

Tesi en modalitat de compendi de publicacions, amb menció internacionalThis thesis presents an investigation on the signatures of corona discharges from grounded rods under thunderstorms and in the laboratory, with optical detections in the 337/777 nm wavelengths for high voltage sparks. This PhD project is contextualized in the European program: Science and Innovation with thunderstorms (SAINT), funded by the Horizon 2020 / Marie Sklodowska Curie Action (Grant agreement ID: 722337). Under conditions of electrification, charged clouds produce an enhancement of the electric field at the ground level. That, in turn, can lead to corona discharges that produce a space charge layer in the vicinity of grounded structures. The study of this phenomenon is useful for the understanding of lightning-related processes and attachment. In addition to the electrical current obtained from the discharges, another important variable is the optical signature generated by the plasma channels. Emissions in many spectra lines associated with reactions of streamers and leaders with the main components of the atmosphere are relevant for visual observations. This work presents a chapter for current literature review of the processes associated with lightning and the main concepts applied. Then, a detailed description of the instrumentation available for the tests carried out in the laboratory and in the field is provided. The first article of this compendium presents data obtained with experiments of a grounded rod under high background electric field in the laboratory and the field. A limited number of works in the literature have presented such data. An analysis correlating pulse frequency, electric field level and average wind speed is the main novelty of the article. A congress paper annexed in the thesis complements the findings comparing the discharges observed at two other experimental sites. The second article describes a compilation of results obtained in the laboratory for investigating optical signatures in two specific lines of the spectra (337 nm and 777 nm), the ones with stronger emissions in lightning-like events. There is special relevance of such experiments for supporting satellite-based observations of lightning by the Atmosphere-Space Interactions Monitor (ASIM) that perform optical measurements in the same wavelength ranges and the operational lightning imagers such as Geostationary Lightning Mapper (GLM) and the future Meteosat Third Generation Lightning Imager (MTG-LI). The conclusions are presented, together with the prospects for future work following the original results achieved with this PhD. This thesis ends with a detailed description of the dissemination activities (presentation at seminars and conferences, coauthored publications in journals and at conferences) and training activities received throughout this project. Finally, the appendix present additional developments and applications of the sensor developed during this doctorate, comprising experiments performed during a two-month internship at the Eindhoven University of Technology (TU/e), and one section with results for the use of photometers to determine the initiation of an upward leader. Such experiments are particularly interesting for understanding space charge production and in the validation of lightning rods. The concepts applied to the development of a corona discharge current sensor were patented together with Dena Desarrollos, the company where the investigations were carried out during this doctorate.Esta tesis presenta una investigación sobre las huellas de descargas de corona en pararrayos durante tormentas eléctricas y en el laboratorio, con detecciones ópticas en las longitudes de onda de 337/777 nm para descargas de alto voltaje. Este proyecto de doctorado se contextualiza en el programa europeo: Science and Innovation with thunderstorms (SAINT), financiado por la Acción Horizon 2020 / Marie Sklodowska Curie (Acuerdo de subvención ID: 722337). En condiciones de electrificación, las nubes cargadas producen un aumento del campo eléctrico a nivel del suelo. Eso, a su vez, puede ocasionar descargas de corona que producen una capa de carga espacial en las proximidades de las estructuras conectadas a tierra. El estudio de este fenómeno es útil para comprender los procesos y la conexión de los canales de los rayos. Además de la corriente eléctrica obtenida de las descargas, otra variable importante es la huella óptica (las señales ópticas a lo largo del tiempo) generada por los canales de plasma. Las emisiones en muchas líneas espectrales asociadas con reacciones de streamers y líderes con los componentes principales de la atmósfera son relevantes para las observaciones visuales. Este trabajo presenta un capítulo de revisión de la literatura actual sobre los procesos asociados a las descargas atmosféricas y los principales conceptos aplicados. A continuación, se realiza una descripción detallada de la instrumentación disponible para las pruebas realizadas en laboratorio y en campo. El primer artículo de este compendio presenta datos obtenidos con experimentos de una varilla puesta a tierra sujeta a un campo eléctrico de fondo elevado en laboratorio y en campo. Un número limitado de trabajos en la literatura han presentado dichos datos. Un análisis que correlaciona la frecuencia del pulso, el nivel del campo eléctrico y la velocidad media del viento es la principal novedad del artículo. Un artículo presentado en congreso adjunto a la tesis complementa los resultados y realiza una comparación de las descargas observadas en otros dos sitios experimentales. El segundo artículo presenta una recopilación de resultados obtenidos en el laboratorio para la investigación de la huella óptica en dos líneas específicas de los espectros (337 nm y 777 nm), las que tienen emisiones más intensas en los rayos. Existe una relevancia especial de dichos experimentos para respaldar las observaciones de rayos basadas en satélites por el Monitor de Interacciones Atmosfera-Espacio (ASIM) que realiza mediciones ópticas en los mismos rangos de longitud de onda y los generadores de imágenes de rayos operacionales como Geostationary Lightning Mapper (GLM) y el futuro Meteosat Third Generation Lightning Imager (MTG-LI). Se presentan las conclusiones, junto con las perspectivas de trabajo futuro siguiendo los resultados originales alcanzados con este doctorado. Esta tesis finaliza con una descripción detallada de las actividades de difusión (presentación en seminarios y congresos, publicaciones en coautoría en revistas y congresos) y actividades formativas recibidas a lo largo de este proyecto. Finalmente, el apéndice presenta desarrollos y aplicaciones adicionales del sensor desarrollado durante este doctorado, que comprende experimentos realizados durante período de prácticas de dos meses en la Universidad Tecnológica de Eindhoven (TU/e), y un apartado con resultados para el uso de fotómetros para determinar la iniciación de un líder ascendente. Estos experimentos son particularmente interesantes para comprender la producción de cargas espaciales y en la validación de pararrayos. Los conceptos aplicados al desarrollo del sensor de corriente de descarga corona fueron patentados junto con Dena Desarrollos, empresa donde se llevaron a cabo las investigaciones durante este doctorado.Postprint (published version

Chemical and biological characterization of the cytolytic protein enterolobin from seeds of enterolobium contortisiliqumm

Enterolobin, a 55 KDa haemolytic protein from Enterolobium contortisiliquum seeds, was purified and further characterized. Its partial amino acid sequence was determined by using both manual and automatic methods of sequence determination. A number of 271 residues could be placed by means of overlaps. A computational search of these overlapped peptides against the PM database revealed that some residues of one peptide had short sequence matches to the bacterial pore-forming aerolysins from Aeromonas hydrophyla and Aeromonas sobria and to colicin lb from Escherichia coli. A subsequent search for similar sequence patterns stored in the PROSITE database showed that the predicted cytolytic site of enterolobin and the aerolysins have similarities to the pattern of the tonB-dependent receptors of bacteria. This pattern occurs not only in these membrane receptor proteins, but also in colicins and other pore- formers and transport proteins. Hydropathy profile analyses made for aerolysins and the predicted cytolytic sites demonstrated their overall hydrophilic character with some short stretches of hydrophobic regions. Studies on the kinetics of haemolysis of normal red cells by enterolobin in the presence of possible effectors such as Ca(^2+), EDTA, galactose, choline, phosphatidylcholine, cholesterol, ricin and with trypsinised erythrocytes were performed. The analyses indicated that the membrane receptor for enterolobin was probably a protein, perhaps the band 3 anion-exchanger protein. Optical and electron microscopic observations of the effects of enterolobin and gold-enterolobin on the membranes of red cell and cancer cells were carried out, and revealed severely damaged membranes after contact with the cytolysin. Gold-enterolobin had a random distribution around holes on the red cell membrane. Bioassays showed that enterolobin was toxic to larvae of the insect Callosobruchus maculatus but not to those of Spodoptera litorallis. Assays of in vitro proteolysis using larval gut enzymes showed that only S. litorallis proteases could digest enterolobin. The mechanism of toxicity of enterolobin did not involve any damage to the microvillar membranes of the epithelial gut cells of C. maculatus as shown by electron microscopy