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Developing individual tree-based models for estimating aboveground biomass of five key coniferous species in China 被引量:5
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作者 Weisheng Zeng Liyong Fu +3 位作者 Ming Xu Xuejun Wang zhenxiong chen Shunbin Yao 《Journal of Forestry Research》 SCIE CAS CSCD 2018年第5期1251-1261,共11页
Estimating individual tree biomass is critical to forest carbon accounting and ecosystem service modeling.In this study,we developed one-(tree diameter only) and two-variable(tree diameter and height) biomass equa... Estimating individual tree biomass is critical to forest carbon accounting and ecosystem service modeling.In this study,we developed one-(tree diameter only) and two-variable(tree diameter and height) biomass equations,biomass conversion factor(BCF) models,and an integrated simultaneous equation system(ISES) to estimate the aboveground biomass for five conifer species in China,i.e.,Cunninghamia lanceolata(Lamb.) Hook.,Pinus massoniana Lamb.,P.yunnanensis Faranch,P.tabulaeformis Carr.and P.elliottii Engelm.,based on the field measurement data of aboveground biomass and stem volumes from 1055 destructive sample trees across the country.We found that all three methods,including the one-and two-variable equations,could adequately estimate aboveground biomass with a mean prediction error less than 5%,except for Pinus yunnanensis which yielded an error of about 6%.The BCF method was slightly poorer than the biomass equation and the ISES methods.The average coefficients of determination(R^2) were 0.944,0.938 and 0.943 and the mean prediction errors were 4.26,4.49 and 4.29% for the biomass equation method,the BCF method and the ISES method,respectively.The ISES method was the best approach for estimating aboveground biomass,which not only had high accuracy but also could estimate stocking volumes simultaneously that was compatible with aboveground biomass.In addition,we found that it is possible to develop a species-invariant one-variable allometric model for estimating aboveground biomass of all the five coniferous species.The model had an exponent parameter of 7/3 and the intercept parameter a_0 could be estimated indirectly from stem basic density(a_0= 0.294 q). 展开更多
关键词 Biomass models Allometric equations Biomass conversion factor Error-in-variable simultaneous equations
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A BFSK and OOK IF demodulation circuit with 2.8 μs settling time and re-configurable image rejection functions for MICS/BCC applications 被引量:1
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作者 Tongqiang Gao zhenxiong chen +2 位作者 Siqi Zhao Haigang Yang Xinxia Cai 《Journal of Semiconductors》 EI CAS CSCD 2018年第7期104-109,共6页
A BFSK and OOK IF base-band circuit is provided to implement the low-IF RF receivers for a dualband MICS/BCC network controller. In order to transfer the massive vital data immediately, the IF circuit is comprised of ... A BFSK and OOK IF base-band circuit is provided to implement the low-IF RF receivers for a dualband MICS/BCC network controller. In order to transfer the massive vital data immediately, the IF circuit is comprised of the fast-settling feed-forward programmable gain amplifier(PGA), a Gm-C complex filter, the fixed gain amplifier(FGA) and a 4-input "quadratic sum" demodulator. A novel auto-switched coarse gain-setting method is adopted in the PGA to enhance the reaction speed and narrow the output signal range. Also the PGA does not suffer the same stability constraint as open-loop topologies. The complex filter fulfills the function of image rejection,in which the center frequency and bandwidth can be adjusted individually. The FGA is used to ameliorate the linearity and the 'quadratic sum' demodulator can reduce the overall power consumption. The designed IF circuit is fabricated with SMIC 0.18 μm CMOS process. The chip area is about 5.36 mm^2. Measurement results are given to verify the design goals. 展开更多
关键词 low-IF receiver VGA complex filter MICS BCC
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