Advanced flow measurement and active flow control need the development of new type devices and systems.Micro-electro-mechanical systems(MEMS) technologies become the important and feasible approach for micro transduce...Advanced flow measurement and active flow control need the development of new type devices and systems.Micro-electro-mechanical systems(MEMS) technologies become the important and feasible approach for micro transducers fabrication.This paper introduces research works of MEMS/NEMS Lab in flow measurement sensors and active flow control actuators.Micro sensors include the flexible thermal sensor array,capacitive shear stress sensor and high sensitivity pressure sensor.Micro actuators are the balloon actuator and synthetic jet actuator respectively.Through wind tunnel test,these micro transducers achieve the goals of shear stress and pressure distribution measurement,boundary layer separation control,lift enhancement,etc.And unmanned aerial vehicle(UAV) flight test verifies the ability of maneuver control of micro actuator.In the future work,micro sensor and actuator can be combined into a closed-loop control system to construct aerodynamic smart skin system for aircraft.展开更多
Today reliability is one of the serious requirements of electronic systems. The numbers of system failures, repair cost, guarantee, etc. are estimated by reliability estimation. In this paper reliability of a switchin...Today reliability is one of the serious requirements of electronic systems. The numbers of system failures, repair cost, guarantee, etc. are estimated by reliability estimation. In this paper reliability of a switching power supply, which is used for personal computers, is evaluated. It will show that the most of failure rates depends on power circuit because of more stresses and dissipations. Derating effect of devices on the failure rate is discussed. A prototype power supply＇s waveforms are used for stress detection and calculation of dissipations.展开更多
Pressure effect on the electrical conductivity of San Carlos olivine was investigated by the newly installed electrical conductivity measurement system at China University of Geosciences. Electrical conductivity of Sa...Pressure effect on the electrical conductivity of San Carlos olivine was investigated by the newly installed electrical conductivity measurement system at China University of Geosciences. Electrical conductivity of San Carlos olivine aggregates was measured up to 12 GPa and 1475 K using the Walker-type multi-anvil apparatus equipped with eight WC cubes as the second-stage anvils. The pressure generation against applied load for the experimental assemblage was examined by phase transition of Bi, quartz, forsterite under different P-T conditions. To check the data validity of this new system, electrical conductivities of the serpentinites and talc samples were measured. The results are consistent with the published data of the same samples. Electrical conductivity （σ） of the San Carlos olivine aggregates and temperature （T） satisfy the Arrhenian formula： σ=σ0exp[-（△E＋P△V）/kT]. The pre-exponential factor （σ0）, activation energy （AE） and activation volume （AV） yield value of 7.74 S/m, 0.85 eV and 0.94 cm^3/mol, respectively. Electrical conductivities of the San Carlos olivine aggregates decline with increasing pressure at same temperatures. The negative pressure effect can be interpreted by strain energy model of defect energy together with the lattice deformation. In addition, the electrical conductivity-depth 1-D profile of the upper mantle was constructed based on our results and some assumptions. The calculated profile is concordant with the geophysical observation at the depth of 180-350 km beneath Europe, which indicates that the upper mantle beneath Europe might be dry.展开更多
基金National Natural Science Foundation of China (No. 90305017No. 50775188No. 51105317)
文摘Advanced flow measurement and active flow control need the development of new type devices and systems.Micro-electro-mechanical systems(MEMS) technologies become the important and feasible approach for micro transducers fabrication.This paper introduces research works of MEMS/NEMS Lab in flow measurement sensors and active flow control actuators.Micro sensors include the flexible thermal sensor array,capacitive shear stress sensor and high sensitivity pressure sensor.Micro actuators are the balloon actuator and synthetic jet actuator respectively.Through wind tunnel test,these micro transducers achieve the goals of shear stress and pressure distribution measurement,boundary layer separation control,lift enhancement,etc.And unmanned aerial vehicle(UAV) flight test verifies the ability of maneuver control of micro actuator.In the future work,micro sensor and actuator can be combined into a closed-loop control system to construct aerodynamic smart skin system for aircraft.
文摘Today reliability is one of the serious requirements of electronic systems. The numbers of system failures, repair cost, guarantee, etc. are estimated by reliability estimation. In this paper reliability of a switching power supply, which is used for personal computers, is evaluated. It will show that the most of failure rates depends on power circuit because of more stresses and dissipations. Derating effect of devices on the failure rate is discussed. A prototype power supply＇s waveforms are used for stress detection and calculation of dissipations.
基金supported by the National Natural Science Foundation of China (Grant No. 41472040)the Fundamental Research Funds for the Central Universities (Grant Nos. G1323531510, CUGL150801)the MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (Grant No. MSFGPMR201408)
文摘Pressure effect on the electrical conductivity of San Carlos olivine was investigated by the newly installed electrical conductivity measurement system at China University of Geosciences. Electrical conductivity of San Carlos olivine aggregates was measured up to 12 GPa and 1475 K using the Walker-type multi-anvil apparatus equipped with eight WC cubes as the second-stage anvils. The pressure generation against applied load for the experimental assemblage was examined by phase transition of Bi, quartz, forsterite under different P-T conditions. To check the data validity of this new system, electrical conductivities of the serpentinites and talc samples were measured. The results are consistent with the published data of the same samples. Electrical conductivity （σ） of the San Carlos olivine aggregates and temperature （T） satisfy the Arrhenian formula： σ=σ0exp[-（△E＋P△V）/kT]. The pre-exponential factor （σ0）, activation energy （AE） and activation volume （AV） yield value of 7.74 S/m, 0.85 eV and 0.94 cm^3/mol, respectively. Electrical conductivities of the San Carlos olivine aggregates decline with increasing pressure at same temperatures. The negative pressure effect can be interpreted by strain energy model of defect energy together with the lattice deformation. In addition, the electrical conductivity-depth 1-D profile of the upper mantle was constructed based on our results and some assumptions. The calculated profile is concordant with the geophysical observation at the depth of 180-350 km beneath Europe, which indicates that the upper mantle beneath Europe might be dry.
