4,631 research outputs found
Multi-Agent Reinforcement Learning using Centralized Critics in Collaborative Environments
No full textAgents trained through single-agent reinforcement learning methods such as self-play can provide a good level of performance in multi-agent settings and even in fully cooperative environments. However, most of the time, training multiple agents together using single-agent self-play yields poor results as each agent tries to learn how to perform their task while their teammates are also learning. Thus, training models to reach an optimal behaviour in such situations becomes a challenging, if not impossible issue to overcome. One possible solution to deal with this problem is to facilitate a centralized training process in which the policies of all agents are evaluated by a centralized critic that has access to the observations and actions of all the agents in the environment. By using this approach, the environment becomes stationary and the agents learn in a similar way to using a single-agent algorithm in settings where only one agent needs to be trained. In this paper, we test whether by using a multi-agent reinforcement learning algorithm with centralized critics, as opposed to single-agent ones, we would obtain an agent that generalizes better to new partners in a collaborative environment such as Overcooked, where coordination is critical for good performance. The results display a similar performance between the two algorithms when evaluated through self-play and slightly better or worse results when paired with the human model, representing a mediocre agent, depending on the map. Thus, the multi-agent, centralized critics algorithm used in this study did not train agents that generalize better to new partners. However, the training metrics clearly indicate that the centralized critics method makes the agents learn and converge twice as fast as its single-agent version.https://github.com/andrei-07/rp-overcooked-centralized-critics Link to GitHub repositoryCSE3000 Research ProjectComputer Science and Engineerin
Andrei Tarkovsky:
No full textThe author studies the originality of the film language of Andrei Tarkovsky, one of the great filmmakers of the twentieth century. For this purpose he considers the symbolic, poetic, technical and mystical elements of Tarkovsky’s seven films. Beyond the standard critics, he builds an unitary language for the interpretation of a work reputedly tight.El autor estudia la originalidad del lenguaje cinematográfico de Andrei Tarkovsky, uno de los grandes directores de cine del siglo XX. Para este propósito considera los aspectos simbólicos, poéticos, técnicos y místicos de sus siete películas. Desecha el formato de ficha crítica y construye un lenguaje unitario para la interpretación de una obra reputada como hermética
Application of 2H and 18O Isotopes for Tracing Municipal Solid Waste Landfill Contamination of Groundwater. Two Italian Case Histories
No full textGroundwater contamination due to municipal solid waste landfills leachate is a serious
environmental threat. During recent years, the use of stable isotopes as environmental tracers
to identify groundwater contamination phenomena has found application to environmental engineering.
Deuterium (2H) and oxygen (18O) isotopes have successfully used to identify groundwater
contamination phenomena if submitted to interactions with municipal solid waste landfills leachate,
with a significant organic amount. The paper shows two case studies, in central and southern Italy,
where potential contamination phenomenon of groundwater under municipal solid waste landfills
occurred. In both cases, isotope compositions referred to 2H and 18O highlight a δ2H enrichment for
some groundwater samples taken in wells, located near leachate storage wells. The δ2H enrichment is
probably caused by methanogenesis phenomena, during which the bacteria use preferentially the
hydrogen “lighter” isotope (1H), and the remaining enriched the “heavier” isotope (2H). The study
of the isotope composition variation, combined with the spatial trend of some analytes (Fe, Mn, Ni)
concentrations, allowed to identify interaction phenomena between the municipal solid waste
landfills leachate and groundwater in both case histories. Therefore, these results confirm the
effectiveness of 2H isotopes application as environmental tracer of groundwater contamination
phenomena due to mixing with municipal solid waste landfills leachate
História e Documentário no Cinema de Andrei Tarkóvski
No full textIn the article, the author discuses the Cinematic history and documentary of Andrei Tarkóvski
Isotope-Based Early-Warning Model for Monitoring Groundwater–Leachate Contamination Phenomena: First Quantitative Assessments
No full textGroundwater contamination due to municipal solid waste landfills’ leachate is a serious environmental threat. Deuterium (2H) and oxygen (18O) isotopes have been successfully applied to identify groundwater contamination processes, due to interactions with municipal solid waste landfills’ leachate, including significant organic amounts. A parameter influencing the isotope content of deuterium and oxygen18 is the deuterium excess (d or d-excess). This paper presents a d-isotope-based model, defined early-warning model, depending on the assessment of the deuterium excess variations in groundwater samples. The isotopic results are corroborated with the trace elements’ concentrations (Fe, Mn, Ni, Co and Zn), suggesting that the methanogenic activity diminished under trace element limitation. This model provides the determination of an index, F, as the percentage variation of d-excess, which makes it possible to define an alert level system to assess and check groundwater contamination by leachate. The procedure shows that values of F index higher than 1.1 highlight possible contamination phenomena of groundwater due to leachate and, therefore, actions by the municipal solid waste landfill management are required. This early-warning model is presented by the application to a case study in Central Italy in order to evaluate innovative aspects and opportunities to optimize the model. The application of the procedure to the case study highlighted anomalous values of the F index for the samples AD16 (Fmax = 2.069) and AD13 (Fmax = 1.366) in January, April, July and October surveys as well as the boundary values (1 ≤ F ≤ 1.1) for samples AD73 (F = 1.229) and AD68 (F = 1.219) in the April survey. The proposed model can be a useful management tool for monitoring the potential contamination process of groundwater due to the presence of landfills with municipal solid waste, including a significant organic component
Hydrogeochemistry and groundwater quality assessment in a municipal solid waste landfill (central Italy)
No full textMunicipal solid waste landfills leachate can cause serious environmental issues for groundwater quality. Therefore, the application of environmental tracing methods to identify groundwater contamination by municipal solid waste landfills leachate is significant. Hydrogeochemical evaluations to trace municipal solid waste landfills leachate are usually carried out. The study was carried out at a landfill in central Italy (Umbria). Samples of leachate and groundwater have been analyzed to evaluate the impact of leachates on groundwater through the comparison of their hydrogeochemical nature. Parameters like pH, Temperature (T), Electrical Conductivity (EC), redox potential (Eh) and Chemical Oxygen Demand (COD) were also measured in situ using digital instruments. Hydrogeochemical data (Na+, K+, Mg2+, Ca2+, SO42−, HCO3−, Cl−, NO3−), ionic ratios and geochemical correlations were used to confirm the processes that govern the chemistry of the spring water and to identify leachate contamination phenomena. In fact, the main geochemical diagrams (Langelier-Ludwig, Piper, Schoeller) confirm the leachate contamination in a groundwater sample. In particular, the Piper diagram shows that a sample is in Na+ – Cl- – HCO3- mixing zone, indicating a possible influence of the leachate on groundwater chemistry. As a matter of fact, some correlations between major elements, such as Cl- versus Na+ and Cl- versus HCO3-, confirm that the leachate in this study area is highly enriched in Cl- and HCO3- due to wastes dissolution and degradation processes. Further, the assessment of K+/Mg2+ ratio also confirms the presence of a sample heavily impacted from leachate contamination. These results indicate that also one basic hydrogeochemical study can be useful for fingerprinting the leachate pollution for groundwater samples
Andrei Tarkovsky:: devolver a la naturaleza sus enigmas
No full textThe author studies the originality of the film language of Andrei Tarkovsky, one of the great filmmakers of the twentieth century. For this purpose he considers the symbolic, poetic, technical and mystical elements of Tarkovsky’s seven films. Beyond the standard critics, he builds an unitary language for the interpretation of a work reputedly tight.El autor estudia la originalidad del lenguaje cinematográfico de Andrei Tarkovsky, uno de los grandes directores de cine del siglo XX. Para este propósito considera los aspectos simbólicos, poéticos, técnicos y místicos de sus siete películas. Desecha el formato de ficha crítica y construye un lenguaje unitario para la interpretación de una obra reputada como hermética
Fotografia ca apropiere și distanțare la Andrei Codrescu / Photography as distance and nearness to Andrei Codrescu
No full textThe present study is part of a PhD thesis titled “Space in Andrei Codrescu’s prose – between reality and imaginary”, analysing the religious space, the virtual space, the photo studio, the American space and the library, as reflected in the above mentioned writer’s prose. The chapter dedicated to the photo studio depicts the manner in which the professional environment of the writer’s parents and close relatives influence the perception of the Self and of the Other, passing from the hypostasis of photographed subject to that of photographer “withtheeyes”, starting from the postmodern statement: “I am a camera”. Our study presents the travel literature of the author, “Ay, Cuba!” and “Prof pe drum” (Road Scholar), the last one also an autobiographical volume, illustrated by photos as a completion of the text. We also discuss the transformation of Road Scholar into a documentary, well received by the critics. The second part of our study presents the text written by Andrei Codrescu for several photobooks, as Walker Evans’ “Cuba” and “Signs”, David Graham’s “Land of the free: What makes Americans different” and others. If, in thefirst part of the study, Andrei Codrescu needs the production of a photo camera to deepen the understanding of the words, we discover him in the second part as a verbalising agent helping the rounding and the guiding of a Weltanschauung for other viewers, the public of the images from the photo books
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