活化腐植酸肥料对苹果幼树的生长和养分利用的影响

为研究活化腐植酸肥料的颗粒形态和用量对苹果幼树生长、土壤理化性质及肥料利用率的影响,通过苹果幼树盆栽试验,共设计了8个处理,包括不施肥(CK)、普通习惯施肥(CCF)、100%施用量的大颗粒活化腐植酸肥(SAF1)、80%施用量的大颗粒活化腐植酸肥(SAF2)、50%施用量的大颗粒活化腐植酸肥(SAF3)、100%施用量的粉末状活化腐植酸肥(PAF1)、80%施用量的粉末状活化腐植酸肥(PAF2)、50%施用量的粉末状活化腐植酸肥(PAF3)。考察了不同处理苹果幼树的株高、茎粗、叶绿素含量、光合特性、生物量、肥料利用率和土壤的速效养分等。结果表明,与CCF处理相比,SAF1、SAF2和PAF1处理的株高、茎粗、新梢长度、干物重、光合强度和土壤的速效养分显著增加,SAF3和PAF3处理的叶绿素、净光合速率、气孔导度、蒸腾速率、植株干重、硝态氮、有效磷和速效钾差异不显著。此外,SAF1处理的氮、磷和钾养分平均利用率分别为40.7%、20.6%和46.2%,相比PAF1处理分别提高了12.7%、32%和38.7%。在减少肥料用量的条件下,SAF2处理促进苹果幼树生长和提高土壤肥力的效果最佳,且显著优于普通肥料。因此,大颗粒活化腐植酸肥料在肥料减施、提高养分利用率、促进苹果幼树生长和增加土壤肥力方面的作用显著,其大面积推广应用的潜力巨大。

Predicting Glass Transition Temperature of Polyethylene/Graphene Nanocomposites by Molecular Dynamic Simulation

The glass transition temperature of polyethylene/graphene nanocomposites was investigated by molecular dynamic simulation. The specific volumes of three systems（polycthylene, polyethylene with a small graphene sheet and two small graphene sheets） were examined as a function of temperature. We found that the glass transition temperature decreases with increasing graphene. Then the van der Waals energy changes obviously with increasing graphene and the torsion energy also plays an important role in the glass transition of polymer. The radial distribution functions of the inter-molecular carbon atoms suggest the interaction between PE and graphene weakens with increasing graphene. These indicate that graphene can prompt the motion of chain segments of polymer and decrease the glass transition temperature （Tg） of polymer.