RESUMOO objetivo deste trabalho foi avaliar os efeitos da temperatura e da luz na germinação de sementes de capim-arroz, em diferentes períodos de armazenamento após a dispersão. O trabalho foi dividido em dois estudos: no primeiro avaliou-se o efeito de três temperaturas (15, 25 e 35 oC) e duas condições de luz (presença e ausência) na porcentagem de germinação, comprimento de hipocótilo e comprimento de radícula; e, no segundo, avaliouse o efeito de três temperaturas (15, 25 e 35 oC) no índice de velocidade de germinação e na velocidade de germinação. As sementes foram coletadas em campo logo após o início da dispersão natural. Os estudos foram conduzidos aos 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330 e 360 dias após a colheita das sementes. Aos 30 dias após a colheita não houve germinação, independentemente das condições de luz e temperatura. A partir de 60 dias após a colheita, as sementes germinaram tanto na presença quanto na ausência de luz. A ausência de luz promoveu o aumento no comprimento de hipocótilo, independentemente da temperatura. Sob condição de temperatura de 15 oC e ausência de luz, as sementes apresentaram maior comprimento de radícula. O incremento da temperatura proporcionou aumento no índice de velocidade de germinação e na velocidade de germinação das sementes. O entendimento dos fatores que afetam a germinação do capim-arroz contribui para o desenvolvimento de práticas de manejo cultural dessa importante espécie daninha que interfere em algumas culturas, incluindo a soja cultivada em rotação com o arroz irrigado.

ABSTRACTThe objective of this research was to evaluate the effects of temperature and light on germination of barnyardgrass in different periods of seed storage after dispersal. The research was divided into two studies: in the first it was evaluated the effect of three temperatures (15, 25 and 35 °C) and two light conditions (presence and absence), on germination percentage, hypocotyl length and radicle length; and, in the second, it was evaluated the effect of three temperatures (15, 25 and 35 oC) on the germination speed index and germination speed. The seeds were collected in the field shortly after the start of natural seed dispersal. The studies were performed at 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330 and 360 days after seed harvest. At 30 days after seed harvest, there was no germination regardless of light conditions and temperature. At 60 days after seed harvest, the seeds germinated both in the presence and absence of light. The absence of light increased hypocotyl length, regardless of temperature. Under 15 oC temperature condition and absence of light, the seeds showed higher radicle length. The increase in temperature caused an increase on the germination speed index and germination speed of the seeds. The knowledge of factors that affect barnyardgrass germination contribute to develop crop management practices of this important weed that interferes in some crops, including the soybean grown in rotation with rice paddy.

A new generation of composite pressure vessels for large scale market applications has been studied in this work. The vessels consist on a thermoplastic liner wrapped with a filament winding glass fibre reinforced polymer matrix structure. A high density polyethylene (HDPE) was selected as liner and a thermosetting resin was used as matrices in the glass reinforced filament wound laminate. The Abaqus 6.5.1 FEM package were used to predict the mechanical behaviour of pressure vessels with capacity of approximately of 0,068 m³ (68 l) for a 0.6 MPa (6 bar) pressure service condition according to the requirements of the prEN 13923 standard, namely, the minimum internal burst pressure. The Tsai-Wu and Von Mises criteria were used to predict composite laminate and thermoplastic liner failures, respectively, considering the elasto-plastic behaviour of the HDPE liner and the laminae properties deducted from micromechanical models for composite laminates. Finally, prototype pressure vessels were produced in the defined conditions to be submitted to pressure tests. The comparison between the FEM simulations and experimental results are discussed in the present paper.