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A Numerical Study on Piezoelectric Energy Harvesting by Combining Transverse Galloping and Parametric Instability Phenomena

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Journal of Marine Science and Application 2017年第4期16卷 465-472页

作者： Guilherme Rosa Franzini Rebeca Caramêz Saraiva Santos celso pupo pesce Escola PolitEnica University of SAO Paulo SAO Paulo SP 05508-030 Brazil

This paper aims to numerically investigate the effects of parametric instability on piezoelectric energy harvesting from the transverse galloping of a square prism. A two degrees-of-freedom reduced-order model for this problem is proposed and numerically integrated. A usual quasi-steady galloping model is applied, where the transverse force coefficient is adopted as a cubic polynomial function with respect to the angle of attack. Time-histories of nondimensional prism displacement, electric voltage and power dissipated at both the dashpot and the electrical resistance are obtained as functions of the reduced velocity. Both, oscillation amplitude and electric voltage, increased with the reduced velocity for all parametric excitation conditions tested. For low values of reduced velocity, 2:1 parametric excitation enhances the electric voltage. On the other hand, for higher reduced velocities, a 1:1 parametric excitation(i.e., the same as the natural frequency) enhances both oscillation amplitude and electric voltage. It has been also found that, depending on the parametric excitation frequency, the harvested electrical power can be amplified in 70% when compared to the case under no parametric excitation.

关键词： transverse galloping energy harvesting piezoelectricity parametric instability numerical simulations

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Effect of Molasses Addition at Ensiling on Ruminal In Situ Dry Matter and Nutrient Degradation of Whole-Plant Soybean Silage Harvested at Different Phenological Stages

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Agricultural Sciences 2022年第2期13卷 268-281页

作者： Lucas Ghedin Ghizzi Matheus Rebouças pupo celso Heinzen Jr. Tiago Antônio Del Valle Francisco Palma Rennó Luiz Felipe Ferraretto Department of Animal Nutrition and Animal Production University of Sao Paulo Pirassununga Brazil Department of Animal and Dairy Sciences University of Wisconsin Madison USA Federal University of Santa Maria Santa Maria Brazil

Whole-plant soybean ensiling has limitations and challenges that affect silage fermentation patterns and reduce ruminal nutrient degradation. Perhaps either the addition of molasses at ensiling or harvesting at different phenological stages has the potential to enhance whole-plant soybean silage (WSS) ruminal degradation. This experiment was a completely randomized design with a 3 × 2 factorial arrangement of treatments evaluating the effects of molasses (0 and 40 g/kg fresh forage) and phenological stage (R5: beginning seed, R6: full seed, and R7: beginning maturity) on ruminal in situ degradation. Molasses increased effective ruminal degradability (ERD) of dry matter (DM) regardless of the phenological stage and increased ERD of crude protein at R5 and R6. The addition of molasses at later phenological stages increased ERD of neutral detergent fiber (NDF). There was a molasses × phenological stage interaction effect with greater fractions A and B of NDF at R7 and R5, respectively, but lower undegraded NDF at R5 and R6 with molasses addition. Although the benefits of adding molasses were more pronounced in R5 and R6, adding molasses to whole-plant soybean at ensiling is recommended regardless of phenological stage. Increasing the proportion of digestible nutrients at harvesting either by harvesting at later phenological stages or the addition of molasses is a powerful strategy to manage ruminal degradation of DM and nutrients in WSS.

关键词： Additive In Situ Degradation Ruminal Degradation Parameters Legume Ensiling

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