The Influence of Moss Colonization and Biochar Application on Evaporation Losses and Surface Crack in Shallow Carbonate–Derived Laterite During Dry–Wet Cycles

AimsSoil water deficit in karst mountain lands is becoming an issue of concern owing to porous, fissured, and soluble nature of underlying karst bedrock. It is important to identify feasible methods to facilitate soil water preservation in karst mountainous lands. This study aims to seek the possibility of combined utilization of moss colonization and biochar application to reduce evaporation losses in carbonate-derived laterite.MethodsThe treatments of the experiments at micro-lysimeter included four moss spore amounts (0, 30, 60, and 90 g·m−2) and four biochar application levels (0, 100, 400, and 700 g·m−3). The dynamics of moss coverage, characteristics of soil surface cracks and surface temperature field were identified. An empirical evaporation model considering the interactive effects of moss colonization and biochar application was proposed and assessed.ResultsMoss colonization reduced significantly the ratio of soil desiccation cracks. Relative cumulative evaporation decreased linearly with increasing moss coverage under four biochar application levels. Biochar application reduced critical moss coverage associated with inhibition of evaporation by 33.26%-44.34%. The empirical evaporation model enabled the calculation of soil evaporation losses under moss colonization and biochar application, with the R2 values ranging from 0.94 to 0.99.Conclusions Our result showed that the artificially cultivated moss, which was induced by moss spores and biochar, decreased soil evaporation by reducing soil surface cracks, increasing soil moisture and soil surface temperature.Moss colonization and biochar application has the potential to facilitate soil moisture conservation in karst mountain lands.

Influence of Exposed Electrode Thickness on Plasma Actuators Performance for Coupled Deicing and Flow Control Applications

Dielectric Barrier Discharge (DBD) plasma actuators are a popular topic of research within the active flow control field. Recently, these devices have gained interest for deicing and ice prevention applications and it has been proved they allow to perform simultaneously deicing and flow control. Studies have shown that the exposed electrode plays an important role on the surface temperature field of the plasma actuator. Thus, in the current study, by the first time, we investigate the influence of the exposed electrode thickness on the induced velocity flow field and surface temperature field. Three plasma actuators with different dielectric thicknesses (0.3 mm, 0.6 mm and 1.02 mm) were mounted with a thick exposed electrode (thickness of 0.8 mm). These three actuators with thick exposed electrode were experimentally studied and compared against other three plasma actuators with same dielectric thickness but with a thin exposed electrode (thickness of 80 μm). The DBD actuators were experimentally studied considering their electrical, mechanical and thermal behavior. The results are presented and discussed in order to understand the influence of the exposed electrode thickness on the mechanical and thermal plasma actuator performances.

Study on the Influence of Surface Temperature Field of Aluminum Alloy Etched by Laser Water Jet Composite Machining

This paper studies the compound effect of liquid medium and laser on the workpiece and analyses the law of material surface temperature change during the processing. Taking 7075-T6 aluminum alloy as the research object, the surface temperature field of aluminum alloy processed using water-jet-assisted laser machining under different process parameters was simulated using finite element software. In addition, the temperature field of the material surface was detected in real-time using the self-built water-jet-assisted laser machining temperature field detection system, and the processing results were observed and verified using an optical microscope, scanning electron microscope, and energy spectrum analyzer. The results show that when the water jet inflow angle is 45°, the heat-affected area of the material surface is the smallest, and the cooling effect of the temperature field of the material surface is better. Considering the liquidus melting point of 7075 aluminum alloys, it is concluded that the processing effect is better when the water jet velocity is 14 m·s−1, the laser power is 100 W, and the laser scanning speed is 1.2 mm·s−1. At this time, the quality of the tank is relatively good, there are no cracks in the bottom of the tank, and there is less slag accumulation. Compared with anhydrous laser etching, water-jet-assisted laser etching can reduce the problems of micro-cracks, molten slag, and the formation of a recast layer in laser etching and improve the quality of the workpiece, and the composition of the bottom slag does not change. This study provides theoretical guidance and application support for the selection and optimization of process parameters for water-jet-assisted laser etching of aluminum alloy and further enriches the heat transfer mechanism of multi-field coupling in the process of water-jet-assisted laser machining.