Damage process in glass fiber reinforced polymer specimens using acoustic emission technique with low frequency acquisition

The damage process in fiber-reinforced polymers (FRP) has been the subject of continuous studies in recent decades using different approaches. In particular, the acoustic emission technique has been proved to be a powerful tool in the monitoring of structures of this type of material due to the large acoustic activity captured when this material is loaded to rupture. The present work explores several indexes that were calculated from the experimental recording of acoustic emission signals, and their efficiency in describing the failure process in structures. One of these indexes, called c value, is originally proposed, and its sensibility it is compared with other classical parameters that are usually employed in the Acoustic Emission analysis. A 3-point bending test has been performed on a glass fiber reinforced polymer plate. Our own methodology was proposed to identify AE signals in semi-automatic manner. This methodology also allowed a faster analysis of the global parameters during the process data of the AE test. The global parameter evolution obtained from the acoustic emission data during the damage process could be considered as precursors of the more meaningful event and as an aid to understand in which way the structure is going to the collapse

Analysis of Acoustic Emission Activity during Progressive Failure in Heterogeneous Materials: Experimental and Numerical Investigation

This work focuses on an experimental and numerical investigation into monitoring damage in a cube-shaped concrete specimen under compression. Experimental monitoring uses acoustic emission (AE) signals acquired by two independent measurement apparatuses, and the same damage process is numerically simulated with the lattice discrete element method (LDEM). The results from the experiment and simulation are then compared in terms of their failure load, final configurations, and the evolution of global parameters based on AE signals, such as the b-value coefficient and the natural time approach. It is concluded that the results from the AE analysis present a significant sensitivity to the characteristics of the acquisition systems. However, natural time methods are more robust for determining such differences, indicating the same general tendency for all three data sets

Levantamento da qualidade das sementes de aveia preta (Avena strigosa) e azevém (Lolium multiflorum) no Rio Grande do Sul.

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Levantamento de dados sobre produção e mercado de sementes forrageiras de clima temperado na região da Campanha do Rio Grande do Sul.

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Long-Range Correlations and Natural Time Series Analyses from Acoustic Emission Signals

This work focuses on analyzing acoustic emission (AE) signals as a means to predict failure in structures. There are two main approaches that are considered: (i) long-range correlation analysis using both the Hurst (H) and the detrended fluctuation analysis (DFA) exponents, and (ii) natural time domain (NT) analysis. These methodologies are applied to the data that were collected from two application examples: a glass fiber-reinforced polymeric plate and a spaghetti bridge model, where both structures were subjected to increasing loads until collapse. A traditional (AE) signal analysis was also performed to reference the study of the other methods. The results indicate that the proposed methods yield reliable indication of failure in the studied structures

Efecto subletal del plaguicida spirotetramat sobre los lípidos totales del camarón de agua dulce Macrobrachium borellii

Para evaluar los riesgos ecotoxicológicos de los plaguicidas es necesario realizar ensayos en organismos sensibles. En este trabajo se estudió el efecto del plaguicida de nueva generación spirotetramat, un ácido tetrámico que inhibe la síntesis de lípidos, sobre el camarón Macrobrachium borellii. Los camarones fueron expuestos a concentraciones subletales del plaguicida spirotetramat (0,6 y 1,2 mg/L) durante 4 y 10 días. Para cada ensayo se agregó un grupo control. Los lípidos totales fueron extraídos y analizados. Se compararon las variaciones estacionales de invierno y verano con 4 días de exposición (1,2 mg/L) y no se observaron diferencias significativas entre los tratamientos (p<0,05). Sin embargo, en el ensayo de 4 días realizado en invierno se observó una disminución de los lípidos entre los camarones expuestos a 0,6 mg/L con respecto al control (p<0,05). Mientras que en el ensayo de 10 días se observó una tendencia al aumento en el contenido de lípidos en los camarones expuestos.Instituto de Limnología "Dr. Raúl A. Ringuelet

Evaluación de la sensibilidad del caracol manzana Pomacea canaliculata al plaguicida de última generación spirotetramat

El desarrollo de mecanismos de resistencia de los organismos plaga frente a los agrotóxicos ha incentivado el uso indiscriminado de los mismos provocando deterioro en los ecosistemas donde son aplicados. Esto ha llevado a la búsqueda de técnicas alternativas para el control de plagas como el uso de insecticidas de última generación, entre los cuales se destaca el spirotetramat. Este actúa inhibiendo la lipogénesis, afectando principalmente la reproducción y el crecimiento de los organismos. Debido a la escasa información disponible sobre el efecto de estos compuestos en especies no blanco, se calculó la sensibilidad del spirotetramat en el caracol de agua dulce Pomacea canaliculata. El valor de LC50 -96h fue 12,93 mg /l de STM. De acuerdo a este resultado P. canaliculata tendría una sensibilidad intermedia al plaguicida en relación a la de los organismos estudiados hasta el presente.Instituto de Limnología "Dr. Raúl A. Ringuelet

Qualidade de sementes de aveia preta (Avena strigosa Schreb.) e azevém (Lolium multiflorum Lam.) em função da origem genética dos lotes.

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