[Effects of residual film density and area on water accumulation infiltration amount of soil]. / æ®‹è†œå¯†åº¦åŠé¢ç§¯å¯¹åœŸå£¤æ°´åˆ†ç´¯ç§¯å ¥æ¸—é‡çš„å½±å“.

With continuous increases in the amount and duration of plastic film used, the residual film in farmland soil is accumulated and tended to be fragmented, which affects soil water infiltration. We carried out an experiment of one-dimensional vertical infiltration of soil moisture. We examined the effects of different residual film density and area on soil water cumulative infiltration under 21 experimental treatments with 5 residual film area levels (0.25, 0.5, 1, 2, 8 cm2) and 5 residual film density levels (0, 60, 180, 300, 420 kg·hm-2). The results showed that soil water infiltration rate was accelerated and the total infiltration amount was increased by adding a certain amount of residual film into the clay loam soil with bulk density of 1.53 g·cm-3. The total infiltration amount of different residual film area always appeared mutation or turning point when the single residual film area was 1 cm2. When the residual film area and density were larger or smaller than that, the cumulative infiltration amount would be significantly affected, with the treatment of 0.5 cm2 residual film area and 200 kg·hm-2 residual film density being obvious demarcation. When the residual film area was 0.25 cm2, the cumulative infiltration reached the maximum. When the residual film with a single area ≤0.25 cm2 was uniformly mixed into the soil, the slope of soil water cumulative infiltration curve was significantly different from that of other residual film treatments, forming a "new structure" soil with unique water infiltration characteristics.

Fabrication of Taper Free Micro-Holes Utilizing a Combined Rotating Helical Electrode and Short Voltage Pulse by ECM.

Fabrication of the injection nozzle micro-hole on the aero engine is a difficult problem in today's manufacturing industry. In addition to the size requirements, the nozzle micro-hole also requires no burr, no taper and no heat-affected zone. To solve the above problem, an ultra-short voltage pulse and a high-speed rotating helical electrode were used in electrochemical drilling (ECD) process. Firstly, a theoretical model of ECD with ultra-short voltage pulse was established to investigate the effects of many predominant parameters on machining accuracy, and the effect of rotating helical electrode on the gap flow field was analyzed. Secondly, sets of experiments were carried out to investigate the effects of many key parameters on machining accuracy and efficiency. Finally, the optimized parameters were applied to machine micro holes on 500 µm thickness of GH4169 plate, and micro-holes with the diameter of 186 µm with no taper were machined at the feed rate of 1.2 µm/s. It is proved that the proposed ECD process for fabricating micro-holes with no taper has a huge potential and broad application prospects.