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Automation of hyperfine interaction parameters analysis using machine learning techniques
2026 - SILVA, CRYSTIAN W. C. da; CARBONARI, ARTUR W.; OTUBO, LARISSA
The time-differential perturbed angular correlation (TDPAC) spectra often exhibit complex interactions between multiple hyperfine fields, making it difficult to isolate individual parameter contributions and accurately model the system. This study introduces a Python-based software designed to efficiently process files containing hyperfine parameters, which are essential for analyzing results obtained from fitting TDPAC spectra. The primary objective is to investigate hyperfine interactions in a variety of materials. The software organizes hyperfine parameters measured at different temperatures according to their respective sites and thermal regimes, enabling the automatic separation of behaviors associated with heating and cooling cycles. During the exploratory data analysis, unsupervised machine learning techniques, such as cluster analysis and Principal Component Analysis (PCA), are employed. These techniques facilitate the identification of cluster formation as a function of temperature, enabling the examination of correlations among parameters and the resulting groupings. In addition, the software implements a rule-based decision tree to automatically assign the most appropriate correlation coefficient to each pair of variables, taking into account the statistical characteristics of the dataset. This methodology represents a comprehensive and adaptable approach for the statistical analysis of TDPAC data.
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Analysis of iodine-126 contamination in the production of iodine-125 at the IEA-R1 reactor for brachytherapy applications
2026 - MEDEIROS, ILCA M. M. A.; MOURA, JOAO A.; MEDEIROS, JOSE A. G. de; KOKA, ANA C. S. S.; ANGELOCCI, LUCAS V.; ROSTELATO, MARIA E. C. M.; ZEITUNI, CARLOS A.
This work developed a method to determine the contamination rates of iodine-126 (126I) in the sodium iodide (NaI) solution used in the production of iodine-125 (125I) seeds for brachytherapy. The production of 125I is carried out at the IEA-R1 Reactor of the Nuclear and Energy Research Institute (IPEN-CNEN/SP) by irradiation with natural xenon. For the radionuclide analysis, a High-Purity Germanium (HPGe) radiation detector (ORTEC model GEM-C5970-B, coaxial detection system and beryllium window, nominal efficiency of 43% at 1333 keV of cobalt-60) was used, in which the activity of 125I was determined by the sum-peak method and the activity of 126I by an efficiency curve using a 166mHo calibration source (A = (1832 ± 2) Bq, T1/2 = 1.20 × 103 years and reference date: Feb 23rd 2024). The results demonstrated the predictions of 125I production in the IEA-R1 Reactor with 126I contamination levels below 0.005%, meeting the production requirements for clinical use.
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Upper to lower bainite transition in a high-carbon low alloy steel
2026 - SOUZA, SAMUEL da S. de; MANFRINATO, MARCOS D.; MORAES, NATHANAEL W. S.; CENTENO, DANY M. A.; GOLDENSTEIN, HELIO
The transition from upper-to-lower bainite in carbon steels is a complex process yet not fully explored. This study examines such transition in a 0.7C, 0.74Mn, 0.61Si, 0.2Cr (wt%) low-alloy steel using a comprehensive approach that integrates dilatometry, scanning electron microscopy (SEM), ex-situ HEXRD, and microhardness testing. Microhardness and dislocation density were found strongly coupled, both increasing with decreasing austempering temperature and presenting changing trends at approximately 350°C and 300°C. Likewise, an Arrhenius plot derived from the curves of transformed fraction as a function of austempering temperature presented the same behaviour. These turning points are considered, respectively, the onset and the end of the transitional interval between upper and lower bainite. Furthermore, SEM analyses confirmed a progressive change in morphology, from coarse upper bainite at high temperatures (400°C), to a mixture of upper and lower bainite in the transitional range, and finally to exclusively fine lower bainite at low temperatures (275°C). The results support that the upper-to-lower bainite transition is not a discrete step but a continuum and offer insights into the interplay between bainite morphology, overall transformation kinetics, and microhardness, which are critical for optimizing heat treatments routes.
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Exsolução de nanopartículas de Ni0 em CeO2 para produção de hidrogênio via reforma a vapor do etanol
2025 - VEIGA, EMERSON L. S.; RODRIGUES, JULIA P.; PAULA, DRYADE F. de; FIGUEIREDO, STEFANY S.; PIAZZOLLA, FERNANDO; FONSECA, FABIO C.
Este estudo demonstra o desenvolvimento de catalisadores de CeO₂ com nanopartículas de Ni⁰ geradas por exsolução, para produção de hidrogênio via reforma a vapor de etanol. O material Ce₀.₉Ni₀.₁O₂–δ foi sintetizado pelo método hidrotermal assistido por micro-ondas, calcinado (500 °C) e reduzido em diferentes temperaturas (600 °C e 800 °C). A difratometria de raios X confirmou inserção de Ni²⁺ na estrutura e formação de Ni⁰ após redução. Micrografias revelaram partículas entre 20–30 nm para a amostra calcinada e o surgimento de pontos claros indicando Ni⁰ na superfície das amostras reduzidas. Testes catalíticos (600 °C, 18 h, H₂O:etanol=3:1) mostraram >90% conversão de etanol e ~70% H₂ para amostra reduzida a 600 °C, contra ~80% conversão e ~63% H₂ para a reduzida a 800 °C. A menor atividade a 800 °C deve-se à redução da área superficial. Além disso, a produção de CO sugere inibição da reação de deslocamento gás-água nas condições reacionais.