Ramp-up experiments by means of lower hybrid wave on HT-7 superconducting tokamak have been performed and analyzed. A ramp-up rate of over 300 kA/s is obtained and a conversion efficiency of over 1.0% has been achieve...Ramp-up experiments by means of lower hybrid wave on HT-7 superconducting tokamak have been performed and analyzed. A ramp-up rate of over 300 kA/s is obtained and a conversion efficiency of over 1.0% has been achieved during the ramp-up phase. The study of the dependence of conversion efficiency on plasma density shows that the conversion efficiency is affected by the driven current, which is mainly dominated by the competition of impurity concentration with wave accessibility condition. In addition, the effect of current profile may play an important role in determining the conversion efficiency.展开更多
This paper presents a programmable gain amplifier（PGA） circuit with a digitally assisted DC offset cancellation（DCOC） scheme for a direct conversion WLAN receiver.Implemented in a standard 0.13-μm CMOS process,th...This paper presents a programmable gain amplifier（PGA） circuit with a digitally assisted DC offset cancellation（DCOC） scheme for a direct conversion WLAN receiver.Implemented in a standard 0.13-μm CMOS process,the PGA occupies 0.39 mm2 die area and dissipates 6.5 mW power from a 1.2 V power supply.By using a single loop single digital-to-analog converter（DAC） mixed signal DC offset cancellation topology,the minimum DCOC settling time achieved is as short as 1.6μs with the PGA gain ranging from -8 to 54 dB in a 2 dB step.The DCOC loop utilizes a segmented DAC structure to lower the design complexity without sacrificing accuracy and a digital control algorithm to dynamically set the DCOC loop to fast or normal response mode,making the PGA circuit in compliance with the targeted WLAN specifications.展开更多
The conversion from constant current(CC)to constant voltage(CV)is one of the key technologies of CC underwater observatory systems.A shunt regulator with high stability and high reliability is usually used.Application...The conversion from constant current(CC)to constant voltage(CV)is one of the key technologies of CC underwater observatory systems.A shunt regulator with high stability and high reliability is usually used.Applications,however,are limited by high heat dissipation and low efficiency.In this paper,with an improved shunt regulation method,a novel concept of stepless power reconfiguration(SPR)for the CC/CV module is proposed.In cases with stable or slowly changing load,two modes of CC/CV conversion are proposed to reduce unnecessary power loss of the shunt regulator while being able to retain any operatorpreset power margin in the system:(1)the manual SPR(MSPR)method based on single-loop control method;(2)the automatic SPR(ASPR)method based on inner-outer loop control method.The efficiency of the system is analyzed.How to select some key parameters of the system is discussed.Experimental results show that MSPR and ASPR are both effective and practical methods to reduce heat dissipation and improve the efficiency of the CC/CV module,while the high stability of the shunt regulator remains.展开更多
The computer program AMPS-1D（analysis of microelectronic and photonic structures） has been employed to simulate the performance of the a-Si：H/a-SiGe：H/a-SiGe：H triple-junction solar cell at the radiation of AM1.5...The computer program AMPS-1D（analysis of microelectronic and photonic structures） has been employed to simulate the performance of the a-Si：H/a-SiGe：H/a-SiGe：H triple-junction solar cell at the radiation of AM1.5G（100 mW/cm2/ and room temperature. Firstly, three sub-cells with band gaps of 1.8, 1.6 and 1.4 eV are simulated, respectively. The simulation results indicate that the density of defect states is an important factor, which affects the open circuit voltage and the filling factor of the solar cell. The two-step current matching method and the control variate method are employed in the simulation. The results show that the best solar cell performance would be achieved when the intrinsic layer thickness from top to bottom is set to be 70, 180 and 220 nm, respectively. We also optimize the tunnel-junction structure of the solar cell reasonably, the simulation results show that the open circuit voltage, filling factor and conversion efficiency are all improved and the S-shape current density–voltage curve disappears during optimizing the tunnel-junction structure. Besides, the diagram of the energy band and the carrier recombination rate are also analyzed. Finally, our simulation data are compared to the experimental data published in other literature. It is demonstrated that the numerical results agree with the experimental ones very well.展开更多
文摘Ramp-up experiments by means of lower hybrid wave on HT-7 superconducting tokamak have been performed and analyzed. A ramp-up rate of over 300 kA/s is obtained and a conversion efficiency of over 1.0% has been achieved during the ramp-up phase. The study of the dependence of conversion efficiency on plasma density shows that the conversion efficiency is affected by the driven current, which is mainly dominated by the competition of impurity concentration with wave accessibility condition. In addition, the effect of current profile may play an important role in determining the conversion efficiency.
文摘This paper presents a programmable gain amplifier（PGA） circuit with a digitally assisted DC offset cancellation（DCOC） scheme for a direct conversion WLAN receiver.Implemented in a standard 0.13-μm CMOS process,the PGA occupies 0.39 mm2 die area and dissipates 6.5 mW power from a 1.2 V power supply.By using a single loop single digital-to-analog converter（DAC） mixed signal DC offset cancellation topology,the minimum DCOC settling time achieved is as short as 1.6μs with the PGA gain ranging from -8 to 54 dB in a 2 dB step.The DCOC loop utilizes a segmented DAC structure to lower the design complexity without sacrificing accuracy and a digital control algorithm to dynamically set the DCOC loop to fast or normal response mode,making the PGA circuit in compliance with the targeted WLAN specifications.
基金Project supported by the National Natural Science Foundation of China(No.51979246)the Ningbo Science and Technology Innovation 2025 Major Special Project,China(No.2020Z075)。
文摘The conversion from constant current(CC)to constant voltage(CV)is one of the key technologies of CC underwater observatory systems.A shunt regulator with high stability and high reliability is usually used.Applications,however,are limited by high heat dissipation and low efficiency.In this paper,with an improved shunt regulation method,a novel concept of stepless power reconfiguration(SPR)for the CC/CV module is proposed.In cases with stable or slowly changing load,two modes of CC/CV conversion are proposed to reduce unnecessary power loss of the shunt regulator while being able to retain any operatorpreset power margin in the system:(1)the manual SPR(MSPR)method based on single-loop control method;(2)the automatic SPR(ASPR)method based on inner-outer loop control method.The efficiency of the system is analyzed.How to select some key parameters of the system is discussed.Experimental results show that MSPR and ASPR are both effective and practical methods to reduce heat dissipation and improve the efficiency of the CC/CV module,while the high stability of the shunt regulator remains.
基金Project supported by the National Natural Science Foundation of China(Nos.11274266,10990103)Science and Technology Projectof Yunnan University(No.2012CG008)the Key Project of Applied Basic Research Program of Yunnan Province of China(No.2013FA029)
文摘The computer program AMPS-1D（analysis of microelectronic and photonic structures） has been employed to simulate the performance of the a-Si：H/a-SiGe：H/a-SiGe：H triple-junction solar cell at the radiation of AM1.5G（100 mW/cm2/ and room temperature. Firstly, three sub-cells with band gaps of 1.8, 1.6 and 1.4 eV are simulated, respectively. The simulation results indicate that the density of defect states is an important factor, which affects the open circuit voltage and the filling factor of the solar cell. The two-step current matching method and the control variate method are employed in the simulation. The results show that the best solar cell performance would be achieved when the intrinsic layer thickness from top to bottom is set to be 70, 180 and 220 nm, respectively. We also optimize the tunnel-junction structure of the solar cell reasonably, the simulation results show that the open circuit voltage, filling factor and conversion efficiency are all improved and the S-shape current density–voltage curve disappears during optimizing the tunnel-junction structure. Besides, the diagram of the energy band and the carrier recombination rate are also analyzed. Finally, our simulation data are compared to the experimental data published in other literature. It is demonstrated that the numerical results agree with the experimental ones very well.
