Sampling-based Synthesis of Controllers for Multiple Agents under Signal Temporal Logic Specifications

openL’ampia applicazione dei robot nelle industrie e nella società ha portato alla necessità di prescrivere complessi compiti di alto livello ad agenti autonomi. Signal Temporal Logic (STL) è una logica temporale che consente di esprimere requisiti spazio-temporali e quantificare il livello di soddisfazione delle preferenze. Quando si pianifica considerando specifiche STL, la sfida principale è generare traiettorie che soddisfino le formule logiche e seguire le traiettorie così ottenute. Il progetto propone una soluzione per il problema di pianificazione del movimento di multipli agenti autonomi, soggetti a specifiche STL accoppiate. Partendo da uno scenario in cui sono coinvolti solo due agenti, un algoritmo basato sul campionamento, Coupled STL_RRT*, è progettato. L’approccio proposto, basato su RRT*, costruisce in modo distribuito due alberi nel dominio del tempo e dello stato accoppiati. Per ogni sistema dinamico, data una posizione iniziale, la strategia sviluppata trova la traiettoria probabilisticamente ottimale in termini di una funzione di costo che dipende dagli input di controllo richiesti. Prima di aggiungere nuovi stati all’albero corrispondente, l’algoritmo controlla se la formula logica non viene violata, assicurando quindi che la traiettoria finale, variabile nel tempo, soddisfi le specifiche spazio-temporali. La dinamica dell’agente autonomo è presa direttamente in considerazione e il concetto di raggiungibilità viene sfruttato per ottenere traiettorie ammissibili rispetto ai vincoli dinamici. L’algoritmo è quindi simulato, considerando un ambiente con ostacoli statici e diversi requisiti STL, specificati dall’utente. L’approccio viene poi esteso al caso di sistemi multi-agente con più di tre agenti. Come nel caso precedente, l’algoritmo costruisce un albero spazio-temporale per ciascun agente, assicurando che la traiettoria finale soddisfi i requisiti STL. La soluzione proposta è poi verificata in scenari simulati, considerando sistemi con 4 o 6 agenti.The wide application of robots in industries and society has brought the need to prescribe complex high-level tasks to autonomous agents. Signal Temporal Logic (STL) is a temporal logic that allows to express desired spatio-temporal requirements, while quantifying the satisfaction of the preferences. When planning under STL specifications, the main challenge is to generate trajectories that satisfy the logical formulas and to track those trajectories. The project proposes a solution for the motion planning problem of multiple autonomous agents, subject to coupled STL specifications. Starting from a scenario where only two agents are involved, a sampling-based algorithm, Coupled STL_RRT*, is designed. The proposed RRT*-based approach builds two trees in the coupled time and state domain in a distributed manner. For each dynamical system, given an initial position, the developed strategy finds a probabilistic optimal trajectory in terms of a cost function that depends on the required control inputs. Before adding new states to the corresponding tree, the algorithm checks if the logical formula is not violated, hence ensuring that the final time-varying trajectory satisfies the spatio-temporal specifications. The dynamics of the autonomous agent is directly taken into account and reachability is exploited to obtain a trajectory that is feasible with respect to the dynamic constraints. The algorithm is then simulated, considering an environment with static obstacles and different STL requirements, specified by the user. The approach is then extended to the case of multi-agent systems with more than three agents. As in the previous case, the algorithm builds a spatiotemporal tree for each agent, ensuring that the final trajectory satisfies the STL requirements. The proposed solution is then verified in simulated scenarios, considering 4-agents and 6-agents systems

Irmãs em conflito: música e texto em Elektra (1909) de Richard Strauss

Este artigo analisa a primeira conversa de Chrysothemis com sua irmã (“Elektra!/Ich kann nicht sitzen und ins Dunkel starren”), na ópera Elektra (1909) de Richard Strauss e Hugo von Hofmannsthal. O artigo identifica uma tensão entre música e texto na caracterização da personagem Chrysothemis: enquanto o texto de Hofmannsthal tende a aproximar as irmãs ao utilizar imagens que aludem à herança familiar comum a ambas, a música de Strauss – por meio de mudanças de estilo e desenvolvimento harmônico-melódico – apresenta as irmãs em polos diametralmente opostos diante da tragédia familiar. O artigo também investiga a ontologia dos leitmotifs de Klytämnestra, cuja utilização perspectival diagnostica uma desigualdade de poder entre Elektra e Chrysothemis em relação à orquestra.This paper undertakes a careful musical and lyrical analysis of Chrysothemis’ first interaction with her sister (“Elektra!/Ich kann nicht sitzen und ins Dunkel starren”) in Richard Strauss and Hugo von Hofmannsthal’s 1909 opera Elektra. The paper’s fundamental claim is that Chrysothemis is portrayed differently by Strauss and Hofmannsthal: where the text brings the sisters together by means of a cross-pollination of images that emphasizes their shared heritage as daughters of Klytämnestra, the music – through abrupt shifts in style, melodic development, and harmony – prefers to present the sisters in diametrically opposing poles with respect to the family tragedy. By way of exploring the tensions between music and text in Elektra, the paper also investigates the ontological status of Klytämnestra’s leitmotifs as they come into view and argues that proper classification of their role – as well as an understanding of leitmotivic perspectivism – is essential in diagnosing an imbalance of power between Elektra and Chrysothemis vis-à-vis the orchestra

THE HYPOTHETICAL IMPLEMENTATION OF PRESUIT AND PRETRIAL DISCOVERY IN CIVIL LITIGATION IN BRAZIL

When analyzing quantitative data from the common law and civil law family systems of justice, the first striking comparative difference that draws attention is the number of cases solved in the early stages in the common law systems. In both England and the United States (USA) there is a high degree of efficiency in settling cases even before the trial stage. Although there is no such thing as Anglo-American law, especially given the distinctions that the English and North American models have shown in recent decades, the instruments used in the civil justice systems of these two countries are fertile ground for the study of possible solutions to be implemented in Brazil. This article presents the mentioned solutions of the so called Anglo-American system and elaborates a proposal for reforms able to introduce such methods in the Brazilian procedural system

Geopolymer based brake pads

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From Macroplastic to Microplastic Litter: Occurrence, Composition, Source Identification and Interaction with Aquatic Organisms. Experiences from the Adriatic Sea

Marine litter is human-created waste that has been discharged into the coastal or marine environment. “Marine debris” is defined as anthropogenic, manufactured, or processed solid material discarded, disposed of, or abandoned in the environment, including all materials discarded into the sea, on the shore, or brought indirectly to the sea by rivers, sewage, storm water, waves, or winds. A large fraction of marine debris is made up of plastic items. Plastic marine debris has become one of the most prevalent pollution related problems affecting the marine environment globally. The widespread challenge of managing marine litter is a useful illustration of the global and transboundary nature of many marine environmental problems. At a global level, plastic litter constitutes 83–87% of all marine litter. Land-based sources are estimated to be responsible for approximately 80% of marine litter. The largest portion of plastic associated with marine pollution is often linked to the contribution from terrestrial sources associated with accidental or deliberate spills as well as inefficient waste management systems in heavily anthropized coastal regions. This chapter is intended to serve as a catalyst for further discussion to explore the potential for developing a Mediterranean regional framework for addressing marine litter

Fish, Corumbataí and Jacaré-Pepira river basins, São Paulo State, Brazil

Fish were studied in two river basins (Corumbataí and Jacaré-Pepira) subjected to strong human pressure, in the interior of the State of São Paulo, southeastern Brazil. In the Corumbataí basin, four sites were sampled: Cabeça river, Lapa stream, Passa-Cinco river, and Corumbataí river; in the Jacaré-Pepira basin, three sites were sampled: Tamanduá stream, Jacaré-Pepira river, and Água Branca stream. A total of 4,050 specimens belonging to 48 species and 13 families were caught and analyzed

Biological effects monitoring of a thermomechanical cleaned cuttings discharge from the Johan Sverdrup installation

Prosjektleder Steven BrooksThe following study describes an integrated biological effects monitoring programme using field transplanted mussels to determine the potential effects of thermomechanical cleaned cuttings (TCC) discharged from the Johan Sverdrup installation in the North Sea. Chemical body burden (PAHs, metals) and a suite of biological effects markers were measured in mussels positioned at strategic locations in the Johan Sverdrup field for 6-7 weeks and compared to two reference locations and a day zero (T0) group. The biomarkers measured in the mussels included: condition index (CI); stress on stress (SoS); micronuclei (MN); lysosomal membrane stability (LMS); metallothionein (MT) and gill and digestive gland histology. Based on oceanographic parameters, the DREAM model was employed to predict, and then later confirm, the direction of the TCC plume during the discharge period. Exposure to the TCC was limited to a 3-day window at the end of the mussel exposure but this was considered representative of the sporadic nature of the TCC discharge. PAH body burden in mussels was low in all mussel groups positioned at the Johan Sverdrup installation, although slightly above the reference and day zero mussel groups. Metal concentrations were either on or below the lower limit of the Norwegian classification scale for metal concentrations in mussel tissue indicating insignificant risk. Overall, the biomarker responses were considered low and did not differentiate significantly between the mussel groups. The Principal Component Analysis (PCA) showed no clear association between the chemical and biological responses in mussels and proximity to the Johan Sverdrup installation. The short duration of exposure to the TCC discharge may be partly responsible for the lack of chemical accumulation and biological response observed.EquinorpublishedVersio