200nm gate-length GaAs-based InAlAs/InGaAs MHEMTs are fabricated by MBE epitaxial material and EBL （electron beam lithography） technology. Ti/Pt/Au is evaporated to form gate metals. A T-shaped gate is produced usin...200nm gate-length GaAs-based InAlAs/InGaAs MHEMTs are fabricated by MBE epitaxial material and EBL （electron beam lithography） technology. Ti/Pt/Au is evaporated to form gate metals. A T-shaped gate is produced using a novel PMMA/PMGI/PMMA trilayer resist structure to decrease parasitic capacitance and parasitic resistance of the gate. Excellent DC and RF performances are obtained and the transconductance （gm） ,maximum saturation drain current density （Joss）, threshold voltage （ VT）, current cut-off frequency （fT） , and maximum oscillation frequency （fmax） of InAlAs/ InGaAs MHEMTs are 510mS/mm,605mA/mm, -1.8V, 110GHz, and 72GHz, respectively.展开更多
Carbon fiber reinforced polymer (CFRP) bars were prestressed for the structural strengthening of 8 T-shaped rein-forced concrete (RC) beams of a 21-year-old bridge in China. The ultimate bearing capacity of the existi...Carbon fiber reinforced polymer (CFRP) bars were prestressed for the structural strengthening of 8 T-shaped rein-forced concrete (RC) beams of a 21-year-old bridge in China. The ultimate bearing capacity of the existing bridge after retrofit was discussed on the basis of concrete structures theory. The flexural strengths of RC beams strengthened with CFRP bars were controlled by the failure of concrete in compression and a prestressing method was applied in the retrofit. The field construction processes of strengthening with CFRP bars-including grouting cracks, cutting groove, grouting epoxy and embedding CFRP bars, surface treating, banding with the U-type CFRP sheets, releasing external prestressed steel tendons-were introduced in detail. In order to evaluate the effectiveness of this strengthening method, field tests using vehicles as live load were applied before and after the retrofit. The test results of deflection and concrete strain of the T-shaped beams with and without strengthening show that the capacity of the repaired bridge, including the bending strength and stiffness, is enhanced. The measurements of crack width also indicate that this strengthening method can enhance the durability of bridges. Therefore, the proposed strengthening technology is feasible and effective.展开更多
基金the State Key Development Program for Basic Research of China(No.G2002CB311901)the Equipment Investigation Program in Advance(No.61501050401C)the Dean Fund of the Institute of Microelectronics,Chinese Academy of Sciences(No.O6SB124004)~~
文摘200nm gate-length GaAs-based InAlAs/InGaAs MHEMTs are fabricated by MBE epitaxial material and EBL （electron beam lithography） technology. Ti/Pt/Au is evaporated to form gate metals. A T-shaped gate is produced using a novel PMMA/PMGI/PMMA trilayer resist structure to decrease parasitic capacitance and parasitic resistance of the gate. Excellent DC and RF performances are obtained and the transconductance （gm） ,maximum saturation drain current density （Joss）, threshold voltage （ VT）, current cut-off frequency （fT） , and maximum oscillation frequency （fmax） of InAlAs/ InGaAs MHEMTs are 510mS/mm,605mA/mm, -1.8V, 110GHz, and 72GHz, respectively.
基金supported by the National Hi-Tech Research and Development (863) Program of China (No. 2007AA04Z437)the National Natural Science Foundation of China (No. 50808158)the Zhejiang Provincial Natural Science Foundation of China (No. Y107049)
文摘Carbon fiber reinforced polymer (CFRP) bars were prestressed for the structural strengthening of 8 T-shaped rein-forced concrete (RC) beams of a 21-year-old bridge in China. The ultimate bearing capacity of the existing bridge after retrofit was discussed on the basis of concrete structures theory. The flexural strengths of RC beams strengthened with CFRP bars were controlled by the failure of concrete in compression and a prestressing method was applied in the retrofit. The field construction processes of strengthening with CFRP bars-including grouting cracks, cutting groove, grouting epoxy and embedding CFRP bars, surface treating, banding with the U-type CFRP sheets, releasing external prestressed steel tendons-were introduced in detail. In order to evaluate the effectiveness of this strengthening method, field tests using vehicles as live load were applied before and after the retrofit. The test results of deflection and concrete strain of the T-shaped beams with and without strengthening show that the capacity of the repaired bridge, including the bending strength and stiffness, is enhanced. The measurements of crack width also indicate that this strengthening method can enhance the durability of bridges. Therefore, the proposed strengthening technology is feasible and effective.
