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Produção e Caracterização de Filme de a-C:H(N)
(Universidade Federal de São Carlos, 2018-10-03) Souza, Alan Roger Moreno; Rossino, Luciana Sgarbi; https://lattes.cnpq.br/0139027055418391; https://lattes.cnpq.br/8167885483299338
The great interest in using diamond-like carbon (DLC) thin films is justified by their remarkable properties. The DLC film may incorporate other atomic elements depending on the precursor gas and the deposition conditions of the films, which provide different optical and mechanical properties to the film. The incorporation of nitrogen in the DLC film (a-C:H(N)) causes the decrease in the amount of carbon atoms in the state of hybridization sp3 and decreases the internal tension of the film, thus increasing the adhesion of the film to the substrate. Therefore the deposition parameters were studied in order to avoid high internal stresses present in the films that impair its adhesion to the metallic substrate and promote properties of interest. The objective of this work was to produce and study the effect of nitrogen incorporation in DLC (a-C:H) films on their chemical, mechanical and structural properties. The a-C: H and a-C: H (N) films were deposited on glass substrates, titanium alloy (Ti6Al4V) and cobalt (WC-Co) carbide machining tool. The plasma-assisted vapor deposition technique (PECVD) using DC-pulsed source was used as the precursor methane gas with dilute argon, for the reproduction of a-C:H film, and nitrogen diluted in methane gas for the production and characterization of the aC:H(N) film. Studies on the physical cleaning, deposition of the interlayer film (a-Si), growth of a-C:H(N) film and study of the incorporation of nitrogen into the a-C:H film were made. For the characterizations, the techniques of visual evaluation, Fourier Transform Infrared Spectroscopy (FTIR), profilometry, dispersive energy spectroscopy (EDS) using scanning electron microscopy (SEM), Raman spectroscopy, photoelectron spectroscopy, X (XPS), nanoindentation and machining test. The results obtained were a-C:H and a-C:H(N) adherent films. The adhesion, deposition rate and mechanical and optical properties of DLC films are related to the following parameters: total gas flow, gas ratio, power, temperature and pre-treatments used, such as physical cleaning and deposition of silicon interlayer films. The physical cleaning of the substrate showed the best result when the concentration of the argon and hydrogen gases were made in equal proportions and with total gas pressure of approximately 2 Torr. The a-C:H film had a hydrogen concentration of 26.64%, hardness of 14 GPa and 39.1% of sp3 hybridization between carbons. With the characteristics described the film produced can be classified as a hard film of a-C:H, according to previous research (Robertson, 2002). For the a-C:H(N) films the increase in the amount of nitrogen incorporated into the film was observed with the increase in the N2 gas flow diluted during the treatment. The concentration increased from 2 to 8% when the proportion of nitrogen inserted during the treatment was increased, from 10 to 60%, respectively. It was observed the increase in the deposited film thickness when the nitrogen was inserted diluted concentrations of 10 to 40% in methane, but in nitrogen concentrations higher than 50 and 60%, the deposition rate decreased. The spectra obtained by FTIR showed C-C and C-H2 bonds with most sp3 bonds for the a-C:H film, while the presence of nitrogen bands was found for the a-C:H (N) film. For characterization by Raman spectroscopy, the change of the position of the G band to higher wave numbers denote the decrease of carbon with hybridized bonds sp3, this is due to the increase of the incorporation of nitrogen in the film. No significant change in film hardness was observed with different nitrogen incorporations. In the milling test, it was observed that, among the a-C:H(N) films produced, the film with a 20% dilution of nitrogen in methane provided a longer life for the cutting tool. The tool with no film deposition with a life of 6.2 minutes and the tool with a-C:H(N) film with 8.1 minutes of machining. However, the a-C:H film still had the best tool life with its total machining time of 9.2 minutes. The test specimen presented lower surface roughness for the tools with the deposition of DLC film when compared to the test body machined with the tool without deposition.
Previsibilidade em revoada de formigas-cortadeiras Atta sexdens rubropilosa Forel, 1908 (Hymenoptera, Formicidae) por meio de modelagem computacional
(Universidade Federal de São Carlos, 2018-10-03) Tallarico, Luís Carlos; Barbosa, Marcílio de Souza; https://lattes.cnpq.br/8917018101872409; Colato, Alexandre; https://lattes.cnpq.br/5460973924624757; https://lattes.cnpq.br/1842422940263874
The mating process of the leaf-cutting ants, genus Atta, represents a relevant event to be studied due to its biological interest. The mating coincides with the onset of the rainy season and the hottest period of the year, when, under very specific climatic conditions, winged males and females leave the adult colony for copulation, which occurs during flight, including between individuals from different colonies, aiming to increase the genetic variability of the population. The females then become the queens of new colonies that will be founded. The prediction of the mating period is important because it is fundamental information for monitoring the pest and for the planning of the application of methods for its control that enable: the reduction of the quantities and costs of the used inputs, the increase of the efficiency control agents and the reducing of the damage they can cause to the environment. It also facilitates the process of collecting these insects for use in experiments. The climatic conditions are an important factor for the definition of the period of the flock, however, there are few studies for the subject and there is no method or tool that uses mathematical modeling to predict its occurrence. The objective of this work was to estimate the mating period of leaf-cutting ant Atta sexdens rubropilosa occurs, based on climatic information and meteorological forecasts, through the construction of a computational model that involves data analysis and uses specific scoring functions, in an optimization process, that had its calibration based on the set of climatic data of a period and in the record of the respective dates in which the mating was observed. The optimization model was sufficiently sensitive and able to determine a maximum point, in terms of scoring, on the date on which the mating occurred.
Estudo do impacto da escolha do modelo para o controle de overdose na fase I dos ensaios clínicos
(Universidade Federal de São Carlos, 2018-10-03) Marins, Bruna Aparecida Barbosa; Cobre, Juliana; https://lattes.cnpq.br/1042802390444616; https://lattes.cnpq.br/6574049419922178
Escalation with overdose control proportional hazards is a Bayesian method with overdose control that estimates the maximum tolerated dose (MTD) assuming that the time a patient takes to show toxicity follows the proportional hazards model. In this work, we analyse the consequences of adopting a method based on the proportional hazard model when the time until toxicity follows the proportional survival model. In order to seek to answer if we would have an overestimate or an underestimate of MTD, simulations were performed in which we considered proportional odds survival data and application of the EWOC-PH method. As an extension of the EWOC-PH method, we propose the EWOC-POS method which assumes that time until toxicity follows the proportional odds survival model.