ALBERT

Description: This paper focuses on the twist defects and the control strategy in the process of four-roll bending for aluminum alloy Z-section profiles with large cross-section. A 3D finite element model (3D-FEM) of roll bending process has been developed, on the premise of the curvature radius of the profile, the particularly pronounced twist defects characteristic of 7075-O aluminum alloy Z-section profiles were studied by FE method. The simulation results showed that the effective control of the twist defects of the profile could be realized by adjusting the side roller so that the exit guide roll was higher than the entrance one (the side rolls presented an asymmetric loading mode with respect to the main rolls) and increasing the radius of upper roll. Corresponding experimental tests were carried out to verify the accuracy of the numerical analysis. The experimental results indicated that control strategies based on finite element analysis (FEA) had a significant inhibitory function on twist defects in the actual roll bending process.

Description: With rapid urbanization in China, the phenomenon of urban sprawl has become prominent and has severely challenged sustainable urbanization and ecological civilization. Aiming to understand the impact of urban sprawl on the urban environment, this study calculates the eco-efficiency of 264 prefecture-level cities in China from 2003 to 2016 by using a super-efficiency data envelopment analysis model. Then, we establish a panel Tobit model and threshold regression model to empirically test the impact of urban sprawl on eco-efficiency and the threshold effect of the urban scale. The results show that urban sprawl hinders the improvement of urban eco-efficiency, especially in Eastern China, but relatively weak or even insignificant effects are observed in Central and Western China. Additionally, a threshold effect of urban sprawl on eco-efficiency can be found. When the city scale is small, urban sprawl seriously hinders the improvement of eco-efficiency. As the city scale gradually expands, the negative effect of urban sprawl on eco-efficiency first decreases, then the restraining effect is gradually strengthened. Our research findings can aid urban development in cities with different scales to reduce the negative effect of urban sprawl on the urban environment.

Description: Hydrological recovery is the basis for restoring the structure and function of wetlands in semiarid and arid areas of China. Selecting an appropriate hydrological recovery mode may be helpful for improving the effectiveness of wetland restoration. We conducted pot experiments to study the effects of the flooding frequency, duration, depth, and occurrence time on the height, biomass, ion contents, and photosynthetic physiology of Phragmites australis in degraded saline–alkaline marsh in the West Songnen Plain, China. At the end of the growing season, we found that the biomass, photosynthetic parameters, and water use efficiency (WUE) of the leaves increased, whereas the Na+ concentration decreased, and the K+ content remained unchanged under an increased flooding frequency treatment. As the flooding depth increased, the plant height increased, but there were no differences in the photosynthetic parameters, biomass, and WUE under flooding at 5 cm and 10 cm. Under different flooding duration treatments, the plant height and biomass were greater, but the photosynthetic parameters and Na+ and K+ contents were lower under a flooding duration of three months. The flooding occurrence time had little effect on the growth of P. australis. Our results indicate that the flooding frequency and duration had greater effects than the flooding depth and occurrence time in the hydrological recovery model for P. australis restoration. The biomass accumulated by P. australis was related to lower Na+ contents and the maintenance of a high K+/Na+ contents, and WUE increased by adjusting photosynthesis under a moderate flooding frequency and duration. These results have important implications for the restoration of degraded semiarid wetlands with man-made channel systems in conditions with limited freshwater resources.

Description: Automatic transport can improve the operational efficiency in plant factory production and reduce the use of labor. However, a determination of a plant factory automation operation mode should comprehensively consider the economic strength of the enterprise, operation objects and operation mode, production scale, technical strength, labor costs, and other factors. In this study, a logistics transport system comprising a set of cultivation units was developed for plant factories, using a mode based on shelf-end delivery without power inside the shelf. Moreover, an analysis was conducted on four modes of common transportation methods for the cultivation units for vertical cultivation in plant factories. The results showed that, when comparing the progressive transport type and warehousing/reciprocating transport type for cultivation units, the transport productivity of the former is higher than that of the latter, and the difference in the two transport productivities is proportional to the capacity for cultivation units in each layer. When the capacities for cultivation units in each layer are 20 and 40, the transport productivity of the former is 115–200% and 130–250% higher than that of the latter, respectively. Moreover, the logistics transport system developed herein reaches an input (output) transport productivity of 330 (270) cultivation units h−1.