本文针对电流比较仪微差补偿装置自动化水平低,精确度易受电阻精度影响等问题,设计了一种高准确度、校准方便且自动化水平高的电流比较仪电流比例有源微差补偿装置。该装置基于单片机的12位二进制有源微差补偿装置,采用附加16位数字模...本文针对电流比较仪微差补偿装置自动化水平低,精确度易受电阻精度影响等问题,设计了一种高准确度、校准方便且自动化水平高的电流比较仪电流比例有源微差补偿装置。该装置基于单片机的12位二进制有源微差补偿装置,采用附加16位数字模拟转换器(digital to analog converter,DAC)灵活修正补偿装置二进制比例误差,可有效提高电流比较仪的准确度,并将二进制分流比例理论分辨率提升至28位,该装置采用基于数字信号处理(digital signal processing,DSP)的嵌入式数字电路实现系统的控制和算法,并通过源表法对该装置进行实验。实验结果表明,有源微差补偿装置的误差为10^(-6),相对标准差为2×10^(-7)。该研究为提高电流比较仪的自动化水平和用补偿方式解决电阻误差提供了参考。展开更多
Advanced microfluidic technology was used to examine the microscopic viscous and inertial effects evolution of water flow in rock joints. The influence of void space on fluid flow behaviour in rock joints under differ...Advanced microfluidic technology was used to examine the microscopic viscous and inertial effects evolution of water flow in rock joints. The influence of void space on fluid flow behaviour in rock joints under different flow velocities was experimentally investigated at the micro scale. Using advanced fabrication technology of microfluidic device, micro flow channels of semicircular, triangular, rectangular and pentagonal cavities were fabricated to simulate different void space of rock joints, respectively. Using the fluorescence labelling approach, the trajectory of water flow was captured by the microscope digital camera when it passed over the cavity under different flow velocities. The flow tests show that the flow trajectory deviated towards the inside of the cavity at low flow velocities. With the increase in flow velocity, this degree of flow trajectory deviation decreased until there was no trajectory deviation for flow in the straight parallel channel. The flow trajectory deviation initially reduced from the void corner near the entrance. At the same time, a small eddy appeared near the void corner of the entrance. The size and intensity of the eddy increased with the flow velocity until it occupied the whole cavity domain. The gradual reduction of flow trajectory near the straight parallel channel and the growth of eddy inside the cavity reflect the evolution of microscopic viscous and inertial forces under different flow velocities.The eddy formed inside the cavity does not contribute to the total flow flux, but the running of the eddy consumes flow energy. This amount of pressure loss due to voids could contribute to the nonlinear deviation of fracture fluid flow from Darcy's law. This study contributes to the fundamental understanding of non-Darcy's flow occurrence in rock joints at the micro scale.展开更多
The bias stability of differential interferometric fiber optical gyroscope is analyzed.Thermal error causing long-term bias drift are reduced by putting the 90°splice in the middle of the fiber coil and applying ...The bias stability of differential interferometric fiber optical gyroscope is analyzed.Thermal error causing long-term bias drift are reduced by putting the 90°splice in the middle of the fiber coil and applying a wide spectrum light source.Also,a kind of novel optical differential processing,which is much more precise than the electronic differential processing,is proposed for reducing the residual nonreciprocal error in the final differential output.An experimental setup based on optical differential processing was built.An^100 fold reduction in the long-term bias drift is demonstrated experimentally compared with the primary differential interferometric fiber optical gyroscope.展开更多
文摘本文针对电流比较仪微差补偿装置自动化水平低,精确度易受电阻精度影响等问题,设计了一种高准确度、校准方便且自动化水平高的电流比较仪电流比例有源微差补偿装置。该装置基于单片机的12位二进制有源微差补偿装置,采用附加16位数字模拟转换器(digital to analog converter,DAC)灵活修正补偿装置二进制比例误差,可有效提高电流比较仪的准确度,并将二进制分流比例理论分辨率提升至28位,该装置采用基于数字信号处理(digital signal processing,DSP)的嵌入式数字电路实现系统的控制和算法,并通过源表法对该装置进行实验。实验结果表明,有源微差补偿装置的误差为10^(-6),相对标准差为2×10^(-7)。该研究为提高电流比较仪的自动化水平和用补偿方式解决电阻误差提供了参考。
基金support from the Australian Research Council-linkage Project
文摘Advanced microfluidic technology was used to examine the microscopic viscous and inertial effects evolution of water flow in rock joints. The influence of void space on fluid flow behaviour in rock joints under different flow velocities was experimentally investigated at the micro scale. Using advanced fabrication technology of microfluidic device, micro flow channels of semicircular, triangular, rectangular and pentagonal cavities were fabricated to simulate different void space of rock joints, respectively. Using the fluorescence labelling approach, the trajectory of water flow was captured by the microscope digital camera when it passed over the cavity under different flow velocities. The flow tests show that the flow trajectory deviated towards the inside of the cavity at low flow velocities. With the increase in flow velocity, this degree of flow trajectory deviation decreased until there was no trajectory deviation for flow in the straight parallel channel. The flow trajectory deviation initially reduced from the void corner near the entrance. At the same time, a small eddy appeared near the void corner of the entrance. The size and intensity of the eddy increased with the flow velocity until it occupied the whole cavity domain. The gradual reduction of flow trajectory near the straight parallel channel and the growth of eddy inside the cavity reflect the evolution of microscopic viscous and inertial forces under different flow velocities.The eddy formed inside the cavity does not contribute to the total flow flux, but the running of the eddy consumes flow energy. This amount of pressure loss due to voids could contribute to the nonlinear deviation of fracture fluid flow from Darcy's law. This study contributes to the fundamental understanding of non-Darcy's flow occurrence in rock joints at the micro scale.
基金supported by the National Natural Science Foundation of China(Grant No.61205077)
文摘The bias stability of differential interferometric fiber optical gyroscope is analyzed.Thermal error causing long-term bias drift are reduced by putting the 90°splice in the middle of the fiber coil and applying a wide spectrum light source.Also,a kind of novel optical differential processing,which is much more precise than the electronic differential processing,is proposed for reducing the residual nonreciprocal error in the final differential output.An experimental setup based on optical differential processing was built.An^100 fold reduction in the long-term bias drift is demonstrated experimentally compared with the primary differential interferometric fiber optical gyroscope.
