Annual ryegrass (Lolium rigidum Gaud) competition altered wheat grain quality: A study under elevated atmospheric CO2 levels and drought conditions

Annual ryegrass is one of the most serious, costly weeds of winter cropping systems in Australia. To determine whether its competition-mediated plant defence mechanisms effect on wheat grain quality, wheat (cv. Yitpi) and annual ryegrass were grown under two levels of CO2 (400 ppm; (a[CO2]) vs 700 ppm; (e[CO2]), two levels of water (well-watered vs drought) and two types of competition (wheat only; (W), and wheat × annual ryegrass; (W × R) with four replicates. The competition × [CO2] interaction had a significant effect on wheat grain protein content, where it was increased in W × R under both e[CO2] (+17%) and a[CO2] (+21%). Grain yield, total grain reducing power and phenolic content were significantly affected by [CO2] × drought × competition. In a summary, annual ryegrass competition significantly altered the wheat grain quality under both [CO2] levels (depending on the soil water level), while also decreasing the grain yield. © 2018 Elsevier Lt

Lower grain nitrogen content of wheat at elevated CO2 can be improved through post-anthesis NH4+ supplement

We test the hypothesis that reduction in grain N concentration under elevated CO2 concentration (e[CO2]) is associated with N types (NH4+ and NO3−) and their ratios. Wheat (Triticum aestivum L. cv. H45) was grown in a glasshouse under two CO2 concentrations (389 μmol mol−1 and 700 μmol mol−1), supplied with equal amount of N with different ratios of NH4+ and NO3−: (i) 100% NO3−–N; (ii) 50% NO3−–N and 50% NH4+–N; and (iii) 25% NO3−–N and 75% NH4+–N. Plant growth, N uptake and partitioning were measured during plant development. Plant biomass and grain yield was increased at e[CO2] when N was supplied as an equal proportion of NO3− and NH4+. Despite the yield increment, grain N concentration was not affected by e[CO2], in 50% NO3−–N treatment. In contrast, grain N concentration decreased in 100% NO3−–N and 25% NO3−–N treatments. In 50% NO3−–N treatment, N uptake during post-anthesis stage (from 69 to 141 days after planting) was significantly stimulated under e[CO2] compared to 100% NO3−–N and 25% NO3−–N treatments. We concluded that supplement of N in an equal proportion of NO3− and NH4+ which increases post-anthesis N uptake, avoid the reduction of grain N concentration under e[CO2]. © 2017 Elsevier Lt

MPC and energy storage based frequency regulation strategy for hybrid electric ships

Propulsion system of a hybrid electric ship is powered by the main engine and a motor coupled to the propeller shaft via a gearbox. The motor provides a power boost when the propulsion load is high and extracts excess power working as a generator at low loading conditions. The power boost comes from the auxiliary engine which is used to supply service loads as well. When excess power is taken out from the shaft it is delivered to the ship power system requiring the auxiliary engine to reduce its power. Consequently, auxiliary engine experiences frequent changes resulting in frequency sags or swells. In extreme conditions these could result in blackouts. In addition, changes in service loads could also lead to frequency deviations causing serious power quality issues. This paper proposes a novel model predictive control (MPC) based strategy to address this issue and thereby improve the power quality. The proposed strategy uses a battery energy storage system to absorb load changes and regulate the frequency of the ship power system. The same approach is tested with the PI controllers as well for performance comparisons. Simulation results are presented to verify the efficacy of the proposed frequency regulation strategy. © 2018 IEEE