Effects of acid modified biochar on potassium uptake, leaching and balance in an alternate wetting and drying paddy ecosystem.

Straw biochar amended soils reduce fertilizer losses and alleviate soil K-exhaustion, while decrease grain yield due to its high pH. H2SO4-modified biochar has been studied as a means to enhance the advantages of biochar and address yield decrease. However, little information is available on its effects on aboveground K uptake, soil K fixation, K leaching, and utilization in paddy rice systems, especially under water stress. A 3-year field experiment was conducted with two irrigation regimes (continuously flooded irrigation, ICF and alternate wetting and drying irrigation, IAWD) as main plots and 0 (control), 20 t ha-1 biochar (B20), and 20 t ha-1 acid-modified biochar (B20A-M) as subplots. The results showed that IAWD significantly decreased water percolation by 9.26 %-14.74 % but increased K leaching by 10.84 %-15.66 %. Compared to B0, B20 and B20A-M significantly increased K leaching by 32.40 % and 30.42 % in 2019, while decreased it by 11.60 %-14.01 % in 2020 and 2021. Both B20 and B20A-M significantly improved aboveground K uptake by 3.45 %-6.71 % throughout the three years. B20 reduced grain yield in 2019 and increased it in 2020 and 2021, while B20A-M increased grain yield throughout the three years. Apparent K balance (AKB) from pre-transplanting to post-harvest over the three years suggested that IAWD significantly increased the risk of soil K depletion but B20 and B20A-M significantly increased AKB, thereby addressing the depletion of it. IAWDB20A-M have a comparable AKB with ICFB20A-M, but had up to 18.3 % and 21.61 % higher AKB than IAWDB20 and ICFB20. Therefore, the use of H2SO4 modified biochar could produce higher grain yield with lower K leaching for addition in IAWD paddy systems, which is beneficial to mitigate soil K depletion and ensure a sustainable agricultural production.

Experimental study on rubber concrete filled steel tube members under pure bending.

The test of four rubber concrete filled steel tube (RuCFST) members, one concrete filled steel tube (CFST) member and one empty member were conducted under pure bending. The main parameters were the shear span ratio (λ) from 3 to 5, and the rubber replacing ratio (r) from 10% to 20%. The bending moment-strain curves, the bending moment-deflection curves and the bending moment-curvature curves were obtained. The failure modes of core rubber concrete were analyzed. The failure mode of RuCFST members was bending failure from the results. The cracks of rubber concrete were distributed evenly and sparsely, and the filling of rubber in core concrete prevented the development of cracks. The shear span ratio has little effect on the behavior of the tested specimens. While the rubber replacing ratio had little effect on the bending moment capacity, but had some influence on the bending stiffness of the tested specimens. After filling in rubber concrete, the bending moment capacity and the bending stiffness can be improved compared with the empty steel tube specimen.

Prediction of the Maturity of Greenhouse Grapes Based on Imaging Technology.

To predict grape maturity in solar greenhouses, a plant phenotype-monitoring platform (Phenofix, France) was used to obtain RGB images of grapes from expansion to maturity. Horizontal and longitudinal diameters, compactness, soluble solid content (SSC), titratable acid content, and the SSC/acid of grapes were measured and evaluated. The color values (R, G, B, H, S, and I) of the grape skin were determined and subjected to a back-propagation neural network algorithm (BPNN) to predict grape maturity. The results showed that the physical and chemical properties (PCP) of the three varieties of grapes changed significantly during the berry expansion stage and the color-changing maturity stage. According to the normalized rate of change of the PCP indicators, the ripening process of the three varieties of grapes could be divided into two stages: an immature stage (maturity coefficient Mc < 0.7) and a mature stage (after which color changes occurred) (0.7 ≤ Mc < 1). When predicting grape maturity based on the R, G, B, H, I, and S color values, the R, G, and I as well as G, H, and I performed well for Drunk Incense, Muscat Hamburg, and Xiang Yue grape maturity prediction. The GPI ranked in the top three (up to 0.87) when the above indicators were used in combination with BPNN to predict the grape Mc by single-factor and combined-factor analysis. The results showed that the prediction accuracy (RG and HI) of the two-factor combination was better for Drunk Incense, Muscat Hamburg, and Xiang Yue grapes (with recognition accuracies of 79.3%, 78.2%, and 79.4%, respectively), and all of the predictive values were higher than those of the single-factor predictions. Using a confusion matrix to compare the accuracy of the Mc's predictive ability under the two-factor combination method, the prediction accuracies were in the following order: Xiang Yue (88%) > Muscat Hamburg (81.3%) > Drunk Incense (76%). The results of this study provide an effective way to predict the ripeness of grapes in the greenhouse.

Dynamic response analysis of a whole steel frame solar greenhouse under wind loads.

In recent years, whole steel frame steel greenhouses have become increasingly prevalent. With the characteristics of large flexibility and small mass, whole steel frame steel greenhouses are sensitive to wind loads. However, studies on the safety of whole steel frame steel greenhouses under wind loads are still limited. In this study, a 10 m span whole steel frame solar greenhouse was taken as the research objective. Taking the Davenport spectrum as the target spectrum, the time history of the wind speed was simulated by the harmonic superposition method. The finite element model of the greenhouse structure was established using ANSYS software. The simulated wind pressure was applied on the greenhouse structure for dynamic response analysis. The dynamic response results were compared with the static analysis results under average wind load. The results showed that the greenhouse structure mainly bears bending stress under wind load. The bending stress, axial stress and displacement of the greenhouse skeleton under average wind loads are lower than those under instantaneous wind loads. It is necessary to consider the dynamic characteristics of wind loads in the design of solar greenhouses. A wind-induced vibration coefficient is obtained, which can be used to convert the dynamic load into the equivalent static load and improve its design efficiency.

Temperature Dependency on the Microscopic Mechanism in the Normal Direction of Wrought AZ31 Sheet under Dynamic Compressive Behavior.

In order to analyze the competitive relationship of different deformation mechanisms in wrought AZ31 magnesium alloy, the dynamic compressive experiments were conducted by a Split Hopkinson Pressure Bar (SHPB) apparatus and a resistance-heated furnace in the range of temperature between 20 and 350 °C at the strain rate of 1000 s-1. With the help of Electron Backscattered Diffraction (EBSD) observation, theoretical calculated Schmid Factor (SF), Critical Resolved Shear Stress (CRSS), and critical equivalent stress (σ0.2), the dynamic compressive deformation behavior and corresponding mechanism of wrought AZ31 magnesium alloy along the normal direction (ND) were revealed in the current study. The results demonstrate that the c-axis of grains are gradually reoriented parallel to the normal direction of wrought AZ31-ND sheet with the temperature increasing, except the dynamic recrystallization (DRX) mechanism was activated or grains grew up. The non-basal slip and 101¯2 tension twinning are respectively the predominant deformation mechanisms at lower temperatures (≤250 °C) and higher temperatures (≥250 °C). The predominant type of DRX mechanism of wrought AZ31-ND sheet is rotational dynamic recrystallization (RDRX), which is regarded as an obstacle for the kernel misorientation concentration region enhancement.

Microstructural Characteristics and Subsequent Soften Mechanical Response in Transverse Direction of Wrought AZ31 with Elevated Compression Temperature.

In order to investigate the effect of temperature on the microstructure evolution and mechanical response in the transverse direction of a wrought AZ31 (AZ31-TD) alloy under a high strain rate, the dynamic compression was conducted using Split Hopkinson Pressure Bar (SHPB) apparatus and a resistance-heated furnace under 1000 s-1 at 20-250 °C. By combining optical and EBSD observations, the microstructure's evolution was specifically analyzed. With the help of theoretically calculated Schmid Factors (SF) and Critical Resolved Shear Stress (CRSS), the activation and development deformation mechanisms are systematically discussed in the current study. The results demonstrated that the stress-strain curves are converted from a sigmoidal curve to a concave-down curve, which is caused by the preferentially and main deformation mechanism {101¯2} tension twinning gradually converting to simultaneously exist with the deformation mechanism of a non-basal slip at an elevated temperature, then completing with each other. Finally, the dynamic recrystallization (DRX) and non-basal slip are largely activated and enhanced by temperature elevated to weaken the {101¯2} tension twinning.