Targeted Adversarial Attacks on Deep Reinforcement Learning Policies via Model Checking

Deep Reinforcement Learning (RL) agents are susceptible to adversarial noise in their observations that can mislead their policies and decrease their performance. However, an adversary may be interested not only in decreasing the reward, but also in modifying specific temporal logic properties of the policy. This paper presents a metric that measures the exact impact of adversarial attacks against such properties. We use this metric to craft optimal adversarial attacks. Furthermore, we introduce a model checking method that allows us to verify the robustness of RL policies against adversarial attacks. Our empirical analysis confirms (1) the quality of our metric to craft adversarial attacks against temporal logic properties, and (2) that we are able to concisely assess a system's robustness against attacks.Comment: ICAART 2023 Paper (Technical Report

Laboratórios Abertos 2018

The Open Labs 2018 book is a collection of lectures and experiments that were made available to secondary and elementary schools that visited the Chemical Engineering Department of the Instituto Superior Técnico of the University of Lisbon during the week of February 5 to 9 2018. This initiative is part of the Science and Technology promotion promoted by the University for young people in the areas of Chemistry, Chemical Engineering and Materials Engineering. It aims to disseminate the importance of these matters in the construction of a more just, equalitarian and inclusive society, based on scientific knowledge that allows the development of a sustainable world in the future that is wanted for all. The Open Laboratories 2018 received about 2100 students and 200 teachers from secondary and basic education to participate in three different types of actions, depending on the schooling of the visitors: Open Laboratories for the students of the secondary education, the Open Labs Junior for the 3rd and 2nd cycle of basic education and the Kids Open Labs for 1st cycle students. They participated in a series of lectures, conversations around a film and interactive experiences. These activities were facilitated by IST Teachers, Non-Teachers and Students. The 2018 edition of the Open Labs of the Department of Chemical Engineering of the Technician took place in the amphitheaters of the South Tower and in the laboratories of the Chemistry Pavilion at the Instituto Superior Técnico.Fundação para a Ciência e a Tecnologia (FCT), Portugal (Project UID/QUI/00100/2013)

Defect analysis and alignment quantification of line arrays prepared by directed self-assembly of a block copolymer

Trabajo presentado al XXVIII Metrology, Inspection, and Process Control for Microlithography, celebrado en California (US) en 2014.Different linear patterns obtained from the directed self-assembly of the block copolymer (BCP) polystyrene-b-polyethylene oxide (PS-b-PEO) were analysed and compared. The hexagonal phase PS-b-PEO in a thin film exhibits linear pattern morphology, by conventional solvent annealing in an atmosphere saturated in chloroform. The surface energy of the silicon substrates was varied using surface functionalization of a self-assembly monolayer (SAM) and a polymer brush, chosen to investigate the influence of the surface energy on the self-assembly of the BCP. The linear patterns formed were analyzed with innovative image analysis software specifically developed in our laboratory to identify elements and defects of line arrays from block copolymer self-assembly. The technique starts by performing dimensional metrology to calculate the pitch size and estimate the linewidth of the lines. Secondly, the methodology allows identification and quantification of typical defects observable in BCP systems, such as turning points, disclination or branching points, break or lone points and end points. The defect density and the quantification of the alignment were estimated using our technique. The methodology presented here represents a step forward in dimensional metrology and defect analysis of BCP DSA systems and can be readily used to analyze other lithographic or non-lithographic patterns.The research leading to these results received funding from the European Union FP7 under the project LAMAND (grant agreement n° 245565), the Spanish MICIN under the project TAPHOR (contract nr. MAT2012-31392) and the Science Foundation Ireland under grant number 09/SIRG/I1615.Peer Reviewe

Scalable Safe Policy Improvement via Monte Carlo Tree Search

Algorithms for safely improving policies are important to deploy reinforcement learning approaches in real-world scenarios. In this work, we propose an algorithm, called MCTS-SPIBB, that computes safe policy improvement online using a Monte Carlo Tree Search based strategy. We theoretically prove that the policy generated by MCTS-SPIBB converges, as the number of simulations grows, to the optimal safely improved policy generated by Safe Policy Improvement with Baseline Bootstrapping (SPIBB), a popular algorithm based on policy iteration. Moreover, our empirical analysis performed on three standard benchmark domains shows that MCTS-SPIBB scales to significantly larger problems than SPIBB because it computes the policy online and locally, i.e., only in the states actually visited by the agent

Reduction of in-shell Brazil nut (Bertholletia excelsa H.B.K.) aflatoxin contamination by ozone gas application during storage

The susceptibility of the in-shell Brazil nut mycoflora and aflatoxins (AFLs) contamination to ozone (O3) gas during storage is reported. In-shell Brazil nuts obtained from retail market were submitted to O3 gas atmosphere at different concentrations immediately before to be stored. Samples were collected just after the gas exposure and every 30 days during the storage period to carry on mycological tests and AFLs analysis. A sensorial evaluation by descriptive quality analysis was carried out to check treated nuts sensory attributes according to consumer acceptance after gas exposure. The O3 treatment applied within 5 h at 31 mg/L was able to successfully inhibit the viability of fungi of the nut-contaminating microflora and so the toxigenic Aspergillus species from the day of application. AFLs were totally degraded in all samples whatever O3 concentration applied. No significant changes on sensory attributes were observed that could affect nut acceptability  after the O3 treatments and storage conditions applied in the present experiment. This procedure is tentatively applied at an Amazon State nut factory for checking its potential in mycotoxin risk contamination of in-shell Brazil nuts safeguarding under the Amazon region environment. Keywords: In-shell Brazil nut, Ozone, Mycoflora, Aflatoxin, Storage, Sensory evaluation

Study of the kinetics and mechanism of rapid self-assembly in block copolymer thin films during solvo-microwave annealing

Microwave annealing is an emerging technique for achieving ordered patterns of block copolymer films on substrates. Little is understood about the mechanisms of microphase separation during the microwave annealing process and how it promotes the microphase separation of the blocks. Here, we use controlled power microwave irradiation in the presence of tetrahydrofuran (THF) solvent, to achieve lateral microphase separation in high- lamellar-forming poly(styrene-b-lactic acid) PS-b-PLA. A highly ordered line pattern was formed within seconds on silicon, germanium and silicon on insulator (SOI) substrates. In-situ temperature measurement of the silicon substrate coupled to condition changes during "solvo-microwave" annealing allowed understanding of the processes to be attained. Our results suggest that the substrate has little effect on the ordering process and is essentially microwave transparent but rather, it is direct heating of the polar THF molecules that causes microphase separation. It is postulated that the rapid interaction of THF with microwaves and the resultant temperature increase to 55 degrees C within seconds causes an increase of the vapor pressure of the solvent from 19.8 to 70 kPa. This enriched vapor environment increases the plasticity of both PS and PLA chains and leads to the fast self-assembly kinetics. Comparing the patterns formed on silicon, germanium and silicon on insulator (SOI) and also an in situ temperature measurement of silicon in the oven confirms the significance of the solvent over the role of substrate heating during "solvo-microwave" annealing. Besides the short annealing time which has technological importance, the coherence length is on a micron scale and dewetting is not observed after annealing. The etched pattern (PLA was removed by an Ar/O-2 reactive ion etch) was transferred to the underlying silicon substrate fabricating sub-20 nm silicon nanowires over large areas demonstrating that the morphology is consistent both across and through the film

Avaliação do caldo de sorgo sacarino em diferentes aplicações de herbicidas.

Na cultura do sorgo sacarino, a utilização de herbicidas se mostra como uma ferramenta fitossanitária de extrema importância na condução da cultura. Entretanto, um dos principais problemas encontrados na cultura do sorgo sacarino é o manejo eficiente de plantas daninhas. O objetivo deste trabalho foi verificar os efeitos no peso do caldo e volume do caldo de plantas de sorgo sacarino submetidas a diferentes manejos de plantas daninhas, no Norte de Minas Gerais. O experimento foi conduzido na Fazenda Experimental da Embrapa Milho e Sorgo, localizada no município de Nova Porteirinha, MG. Os tratamentos foram dispostos em esquema de parcelas subdivididas. Nas parcelas foram alocados os cultivares de sorgo sacarino (BRS 501, BRS 504, BRS 506, BRS 508, BRS 509 e BRS 511), enquanto nas subparcelas foram alocados os tipos de manejo de plantas daninhas: 2,4-D (1209 g i.a ha-l), linuron (900 g i.a ha-l), atrazine (lOOOgi.a ha-1), bentazon (900 g i.a ha-l) e tembotrione (100 g i.a ha-1), além de tratamentos adicionais com capina (TCC) e sem capina (TSC). O delineamento experimental utilizado foi o de blocos casualizados, com quatro repetições. O herbicida Bentazon foi o mais positivo com relação à seletividade para as variedades de sorgo

Pós alternativos imunizantes na proteção de sementes armazenadas de guandú.

Edição dos resumos do 18º Congresso Brasileiro de Sementes, 2013, Florianópolis