Browsing by Author "Zhao, Qiang"

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    New Results on Selection Diversity over Fading Channels
    Zhao, Qiang (Virginia Tech, 2003-01-08)
    This thesis develops a mathematical framework for analyzing the average bit error rate performance of five different selection diversity combining schemes over slow, frequency non-selective Rayleigh, Nakagami-m and Ricean fading channels. Aside from the classical selection diversity, generalized selection combining and the "maximum output" selection methods, two new selection rules based on choosing the branch providing the largest magnitude of log-likelihood ratio for binary phase shift keying signals (with and without phase compensation in the selection process) are also investigated. The proposed analytical framework is sufficiently general to study the effects of dissimilar fading parameter and unequal mean received signal strengths across the independent diversity paths. The effect of branch correlation on the performance of a dual-diversity system is also studied. The accuracies of our analytical expressions have been validated by extensive Monte-Carlo simulation runs. The proposed selection schemes based on the log-likelihood ratio are attractive in the design of low-complexity rake receivers for wideband CDMA and ultra wideband communication systems.
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    Rapid Effect of Nitrogen Supply for Soybean at the Beginning Flowering Stage on Biomass and Sucrose Metabolism
    Zhou, Hongli; Yao, Xingdong; Zhao, Qiang; Zhang, Wei; Zhang, Bo; Xie, Futi (Springer Nature, 2019-10-29)
    Nitrogen application at the beginning flowering stage (R1 stage) increased the soybean grain yield, however, the rapid effect of enriched nitrogen at R1 growth stage on soybean dry matter accumulation and sugar metabolism is still unclear. Continuous high nitrogen (CHN), Continuous low nitrogen (CLN), Enriched nitrogen supply at R1 stage (ENS) treatments were applied on two soybean cultivars (Liaodoull, Liaodou14), to investigate the effect of enriched nitrogen on plant biomass accumulation and sucrose metabolism. After 12 h of ENS treatment, the root/shoot rate of both cultivars were lower than that of CLN, but at 24 h it was no significant difference between ENS and CLN. Enriched N at R1 stage, soybean kept a balance of sucrose synthesis and decomposition in leaf by affecting sucrose synthetase (SS) and sucrose phosphate synthase (SPS) activities. Under N limitation condition the plant dry matter accumulation supported root growth priority. Enriched N at R1 stage resulted in the rapid shoot biomass accumulation. In high yield cultivar, the shoot growth was priority to root growth, the common yield cultivar was on the contrary. Our result suggest that enrich N at R1 stage resulted in the accumulation of biomass in shoot rapidly.