水文条件对紫色土坡面土壤侵蚀及养分流失的影响

采用人工模拟降雨试验,研究水文条件对紫色土坡面土壤侵蚀及氮和磷养分流失的影响。试验处理包括2个施肥水平(低肥和高肥水平),4个水文条件(自由下渗、土壤水分饱和、壤中流、壤中流+降雨)和一个降雨强度(60 mm/h,历时60 min)。结果表明:壤中流+降雨和土壤水分饱和条件下的土壤侵蚀量分别是自由下渗条件下的3.1和1.7倍,同自由下渗相比,壤中流、壤中流+降雨和土壤水分饱和条件下,地表径流中NO3-N、HPO4-P的浓度和流失量有显著增加;低肥水平条件下,自由下渗、土壤水分饱和、壤中流和壤中流+降雨地表径流中,NO3-N的浓度分别是0.88、58.90、698.41和87.80 mg/L,对应水文条件下地表径流中,HPO4-P的浓度分别是0.252、0.322、0.811和0.383 mg/L,高肥水平条件下,径流中的NO3-N和HPO4-P的浓度也有相同的趋势;土壤水分饱和条件下,地表径流中NO3-N和HPO4-P的流失量分别是自由下渗条件下的27~39和1.3倍,壤中流+降雨条件下,地表径流中NO3-N和HPO4-P的流失量分别是自由下渗条件下的100~114和1.5~1.7倍,同时,壤中流+降雨和土壤...

High-Saturation-Power and High-Speed Ge-on-SOI p-i-n Photodetectors

Ge-on-silicon-on-insulator p-i-n photodetectors were fabricated using an ultralow-temperature Ge buffer by ultrahigh-vacuum chemical vapor deposition. For a detector of 70-mu m diameter, the 1-dB small-signal compression power was about 110.5 mW. The 3-dB bandwidth at 3-V reverse bias was 13.4 GHz.

Ge composition saturation behavior during low-temperature Si1-xGex growth by disilane and solid Ge molecular beam epitaxy

Ge composition dependence on the Ge cell temperature has been studied during the growth of Si1-xGex by disilane and solid Ge molecular beam epitaxy at a substrate temperature of 500 degrees C. It is found that the composition x increases and then saturates when the Ge cell temperature increases, which is different from the composition-dependent behavior in growth at high temperature as well as in growth by molecular beam epitaxy using disilane and germane. The enhanced hydrogen desorption from a Ge site alone cannot account for this abnormal composition-variation behavior. We attribute this behavior to the increase of rate constant of H desorption on a Si site when the Ge cell temperature increases.