Universidade Federal da Fronteira Sul RESUMO:No mês de junho de 2014, a sequência de oito dias de chuvas ininterruptas promoveu uma série de transtornos (inundações, deslizamentos de terra, interdição de estradas) à parte da população dos estados do Rio Grande do Sul, Santa Catarina e Paraná. O trabalho objetiva identificar a ocorrência de eventos acumulados intensos de precipitação na região do alto Uruguai gaúcho, bem como seus mecanismos sinóticos responsáveis por esses acumulados de chuva. Dados diários de precipitação foram acumulados em grupos de cinco dias (pêntadas), perfazendo o total de 73 pêntadas anuais, no decorrer dos 53 anos da série . A aplicação do percentil 99 ao conjunto de dados determinou o valor do acumulado intenso (157,4 mm). Com base nesse valor foram calculadas a Frequência Absoluta, Frequência Relativa e o Tempo de Retorno desses acumulados intensos. Os resultados demonstraram que, dos dez eventos acumulados mais intensos, 70% ocorreram entre as pêntadas 30 e 47. Os eventos dos anos de 2014 e 1992 foram os mais intensos, acumulando, respectivamente, 366,7mm e 328,0mm. Os resultados demonstraram que os acumulados pluviométricos intensos entre 200 e 250 mm possuem um tempo de retorno de cerca de cinco anos.Já a análise sinótica desses eventos revelou que tais eventos são consequência da formação de frentes estacionárias e semiestacionárias com duração mínima de 36 horas. Nos eventos de maior intensidade, o tempo de permanência do sistema frontal e estacionário foi de 120 horas, para 2014 e, 32 horas para 1992. Dessa forma, verifica-se que eventos acumulados intensos têm sido frequentes no decorrer dos 53 anos da série, podendo, estes, estarem relacionados às mudanças climáticas, sobretudo pela intensificação dos casos nos últimos anos (1992 e 2014).Palavras-chave: pêntadas, eventos intensos, testes estatísticos, cartas sinóticas. RAINS IN RIO GRANDE DO SUL: A STUDY OF INTENSE RAINFALL ACCUMULATED IN THE UPPER URUGUAY GAUCHO.ABSTRACT: During June of 2014, eight days of continuous rainfall promoted a number of disorders (floods, landslides, road interdiction) to the population of the states of Rio Grande do Sul, Santa Catarina and Paraná. This study aims to identify the occurrence of accumulated intense precipitation events in the upper Uruguay Gaucho region as well as its synoptic mechanisms responsible for these accumulated rain. Daily precipitation data was accumulated in groups of five days (pentads), totaling 73 pentads per year, over the 53 years of the series (1961 -2014). The value of accumulated intense rainfall (157.4mm) was determined by applying the 99th percentile in the dataset. Based on this value, the time of return and the absolute and relative frequencies were calculated. The results showed that 70% of the ten most intense events occurred between 30th and 47th pentads. The events during the years of 2014 and 1992 were the most intense, respectively accumulating 366.7mm and 328.0mm. The
The search for renewable and sustainable fuels is becoming increasingly more important. As a result, the use of biomass as an energy source is one of the most promising methods in the reduction of energy dependence on non-renewable fossil fuels. In order to reduce the amount of solvent used during direct transesterification, this study has aimed at producing biodiesel from microalgae (Chlorella vulgaris) biomass using enzymatic catalysis (Novozym 435) and pressurized fluid (propane). The effects of pressure (3000 to 8000 kPa), temperature (323.15 to 353.15 K), and exposure time (1 to 8 h) have been studied through the experimental design for esters conversion. The newly investigated system showed consistency through the experimental design technique, evaluating the effect of significant variables such as time, temperature, and pressure in the process. The good conversions yielded have been achieved using mild temperature and higher pressure conditions, demonstrating that this process has great potential for obtaining biodiesel from microalgae biomass.
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