The T-gate stem height of In Al As/In Ga As In P-based high electron mobility transistor(HEMT) is increased from165 nm to 250 nm. The influences of increasing the gate stem height on the direct current(DC) and radio f...The T-gate stem height of In Al As/In Ga As In P-based high electron mobility transistor(HEMT) is increased from165 nm to 250 nm. The influences of increasing the gate stem height on the direct current(DC) and radio frequency(RF)performances of device are investigated. A 120-nm-long gate, 250-nm-high gate stem device exhibits a higher threshold voltage(Vth) of 60 m V than a 120-nm-long gate devices with a short gate stem, caused by more Pt distributions on the gate foot edges of the high Ti/Pt/Au gate. The Pt distribution in Schottky contact metal is found to increase with the gate stem height or the gate length increasing, and thus enhancing the Schottky barrier height and expanding the gate length,which can be due to the increased internal tensile stress of Pt. The more Pt distributions for the high gate stem device also lead to more obvious Pt sinking, which reduces the distance between the gate and the In Ga As channel so that the transconductance(gm) of the high gate stem device is 70 m S/mm larger than that of the short stem device. As for the RF performances,the gate extrinsic parasitic capacitance decreases and the intrinsic transconductance increases after the gate stem height has been increased, so the RF performances of device are obviously improved. The high gate stem device yields a maximum ft of 270 GHz and fmax of 460 GHz, while the short gate stem device has a maximum ft of 240 GHz and the fmax of 370 GHz.展开更多
Accurate and efficient estimation of forest growth and live biomass is a critical element in assessing potential responses to forest management and environmental change. The objective of this study was to develop mode...Accurate and efficient estimation of forest growth and live biomass is a critical element in assessing potential responses to forest management and environmental change. The objective of this study was to develop models to predict longleaf pine tree diameter at breast height （dbh） and merchantable stem volume （V） using data obtained from field measurements. We used longleaf pine tree data from 3,376 planted trees on 127 permanent plots located in the U.S. Gulf Coastal Plain region to fit equations to predict dbh and V as functions of tree height （H） and crown area （CA）. Prediction of dbh as a function of H improved when CA was added as an additional independent variable. Similarly, predic- tions of V based on H improved when CA was included. Incorporation of additional stand variables such as age, site index, dominant height, and stand density were also evaluated but resulted in only small improvements in model performance. For model testing we used data from planted and naturally-regenerated trees located inside and outside the geographic area used for model fitting. Our results suggest that the models are a robust alternative for dbh and V estimations when H and CA are known on planted stands with potential for naturally-regenerated stands, across a wide range of ages. We discuss the importance of these models for use with metrics derived from remote sensing data.展开更多
In order to mine gene loci associated with drought resistance and water use efficiency, and provide guidance for the breeding of drought-resistant wheat varieties, quantitative trait loci （QTLs） for plant height （P...In order to mine gene loci associated with drought resistance and water use efficiency, and provide guidance for the breeding of drought-resistant wheat varieties, quantitative trait loci （QTLs） for plant height （PH） and stem height （SH） of wheat were evaluated using a population of 302 recombinant inbred lines （RILs） derived from a cress between drought-tolerant cultivar Luohan 2 and water-sensitive cultivar Weimai 8 under different water regimes in six environments. Totally 17 additive QTLs for PH and SH were identified and distributed on chromosomes 2B, 3A, 3B, 4A, 5A, 5D, 6B, 7A and 7B, respectively, which explained 3.3% to 26.95% phenotypic variations, with additive effect of 1.919 6 to 5.382 8 cm. Among them, 14 QTLs, 24 times and 5 QTLs, 7 times were detected in three irrigation environments and three drought stress environments, respectively. Both the number of QTLs for PH and the times detected in drought stress environments were significantly less than those in irrigation environments. Of all the 17 QTLs for PH, 12 were detected only in irrigation environment, three QTLs were detected only in drought stress environment, and two QTLs were detected in both environments, suggesting that the expression of the genes is greatly influenced by en- vironmental condition. QPh-WL-7A. 3 detected between maker Xbarc049 and Xgwm273 on chromosome 7A in all the three drought stress environments, can enhance 2.481 5 - 3. 697 2 cm of PH, explain 8.6% - 10.0% additive effect, so it is useful for the genetic improvement of drought tolerance and molecular marker-assisted selection in wheat.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61434006)。
文摘The T-gate stem height of In Al As/In Ga As In P-based high electron mobility transistor(HEMT) is increased from165 nm to 250 nm. The influences of increasing the gate stem height on the direct current(DC) and radio frequency(RF)performances of device are investigated. A 120-nm-long gate, 250-nm-high gate stem device exhibits a higher threshold voltage(Vth) of 60 m V than a 120-nm-long gate devices with a short gate stem, caused by more Pt distributions on the gate foot edges of the high Ti/Pt/Au gate. The Pt distribution in Schottky contact metal is found to increase with the gate stem height or the gate length increasing, and thus enhancing the Schottky barrier height and expanding the gate length,which can be due to the increased internal tensile stress of Pt. The more Pt distributions for the high gate stem device also lead to more obvious Pt sinking, which reduces the distance between the gate and the In Ga As channel so that the transconductance(gm) of the high gate stem device is 70 m S/mm larger than that of the short stem device. As for the RF performances,the gate extrinsic parasitic capacitance decreases and the intrinsic transconductance increases after the gate stem height has been increased, so the RF performances of device are obviously improved. The high gate stem device yields a maximum ft of 270 GHz and fmax of 460 GHz, while the short gate stem device has a maximum ft of 240 GHz and the fmax of 370 GHz.
基金supported by the U.S.Department of Defense,through the Strategic Environmental Research and Development Program(SERDP)
文摘Accurate and efficient estimation of forest growth and live biomass is a critical element in assessing potential responses to forest management and environmental change. The objective of this study was to develop models to predict longleaf pine tree diameter at breast height （dbh） and merchantable stem volume （V） using data obtained from field measurements. We used longleaf pine tree data from 3,376 planted trees on 127 permanent plots located in the U.S. Gulf Coastal Plain region to fit equations to predict dbh and V as functions of tree height （H） and crown area （CA）. Prediction of dbh as a function of H improved when CA was added as an additional independent variable. Similarly, predic- tions of V based on H improved when CA was included. Incorporation of additional stand variables such as age, site index, dominant height, and stand density were also evaluated but resulted in only small improvements in model performance. For model testing we used data from planted and naturally-regenerated trees located inside and outside the geographic area used for model fitting. Our results suggest that the models are a robust alternative for dbh and V estimations when H and CA are known on planted stands with potential for naturally-regenerated stands, across a wide range of ages. We discuss the importance of these models for use with metrics derived from remote sensing data.
基金Supported by Scientific and Technological Development Plan of Jining Municipal Government(2013CB030102)Key Technological Project for Independent Innovation of Shandong Province(2014GJJS0201)
文摘In order to mine gene loci associated with drought resistance and water use efficiency, and provide guidance for the breeding of drought-resistant wheat varieties, quantitative trait loci （QTLs） for plant height （PH） and stem height （SH） of wheat were evaluated using a population of 302 recombinant inbred lines （RILs） derived from a cress between drought-tolerant cultivar Luohan 2 and water-sensitive cultivar Weimai 8 under different water regimes in six environments. Totally 17 additive QTLs for PH and SH were identified and distributed on chromosomes 2B, 3A, 3B, 4A, 5A, 5D, 6B, 7A and 7B, respectively, which explained 3.3% to 26.95% phenotypic variations, with additive effect of 1.919 6 to 5.382 8 cm. Among them, 14 QTLs, 24 times and 5 QTLs, 7 times were detected in three irrigation environments and three drought stress environments, respectively. Both the number of QTLs for PH and the times detected in drought stress environments were significantly less than those in irrigation environments. Of all the 17 QTLs for PH, 12 were detected only in irrigation environment, three QTLs were detected only in drought stress environment, and two QTLs were detected in both environments, suggesting that the expression of the genes is greatly influenced by en- vironmental condition. QPh-WL-7A. 3 detected between maker Xbarc049 and Xgwm273 on chromosome 7A in all the three drought stress environments, can enhance 2.481 5 - 3. 697 2 cm of PH, explain 8.6% - 10.0% additive effect, so it is useful for the genetic improvement of drought tolerance and molecular marker-assisted selection in wheat.
