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北疆棉花精准种植施肥指标量试验研究 被引量:1
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作者 周可法 孙莉 +2 位作者 张清 陈曦 王军 《干旱区资源与环境》 CSSCI CSCD 北大核心 2007年第3期149-152,共4页
建立在试验地土壤背景数据库的基础之上,将不同空间单元(时间空间和地理空间)的产量数据与其他多层数据叠合分析,以棉花生长模型、棉花营养平衡施肥专家系统为支持,提出了北疆棉花精准施肥的指标。采用精准施肥指标的试验结果表明:(1)... 建立在试验地土壤背景数据库的基础之上,将不同空间单元(时间空间和地理空间)的产量数据与其他多层数据叠合分析,以棉花生长模型、棉花营养平衡施肥专家系统为支持,提出了北疆棉花精准施肥的指标。采用精准施肥指标的试验结果表明:(1)与全部化肥一次足量深施比,667m2平均节约化肥费用22.5元,667m2增产10%左右;(2)与化肥和有机肥全部作基肥深施相比,前者比后者667m2平均节约化肥成本36元,籽棉增产10%-15%;(3)用滴灌专用肥进行的灌溉施肥,氮的利用率在70%左右,磷的利用率在31%-34%左右。这一结果基本接近国际水平(75%和35%)。 展开更多
关键词 棉花 精准种植 施肥指标 试验
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Time synchronization in communication networks based on the Beidou foundation enhancement system 被引量:7
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作者 LIU Hui ZHANG RuFei +1 位作者 LIU JingNan ZHANG Ming 《Science China(Technological Sciences)》 SCIE EI CAS CSCD 2016年第1期9-15,共7页
Communication networks rely on time synchronization information generated by base station equipment(either the Global Navigation Satellite System receiver or rubidium atomic clock) to enable wireless networking and co... Communication networks rely on time synchronization information generated by base station equipment(either the Global Navigation Satellite System receiver or rubidium atomic clock) to enable wireless networking and communications. Meanwhile, the time synchronization among base stations depends on the Network Time Protocol. With the development of mobile communication systems, the corresponding time synchronization accuracy has increased as well. In this case, the use of sparsely distributed-high-precision synchronization points to synchronize time for an entire network with high precision is a key problem and is the foundation of the enhanced network communication. The current receiver equipment for China's digital synchronous network typically includes dedicated multi-channel GPS receivers for communication; however, with the development of GPS by the USA, network security has been destabilized and reliability is low. Nonetheless, network time synchronization based on Beidou satellite navigation system timing devices is an inevitable development trend for China's digital communications network with the establishment of the independently developed BDS, especially the implementation and improvement of the Beidou foundation enhancement system. 展开更多
关键词 Beidou satellite navigation system precision timing time synchronization Beidou foundation enhancement system communication network time synchronization
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