Generation characteristics of vacuum discharge plasma are very important for the applied research of metal plasma. The vacuum discharge electrode configuration and the cathode material affect the generation characteri...Generation characteristics of vacuum discharge plasma are very important for the applied research of metal plasma. The vacuum discharge electrode configuration and the cathode material affect the generation characteristics of the metal plasma which consists of metal ions coming from cathode and generated by vacuum discharge. In this research, the generation characteristics of the metal plasma generated by vacuum discharge are discussed for four patterns of electrode configurations, i.e. cone-mesh electrode setup, cone-cross line electrode setup, cone-line electrode setup and cone-ring electrode setup. Characteristics of the metal plasma, such as elec- tron density, electron temperature, space potential, ion energy, are measured by the probe method for discussing the impacts of different electrode configurations on the density of generated metal plasma. Moreover, the diffusion velocities of the metal plasma are measured for cathode materials of Pb, Al, and Cu, respectively. The experimental results indicate that the plasma generated by the discharge of cone-ring electrode configuration possesses the maximum density and the metal plasma generated by the Al cathode possesses the fastest diffusion velocity and the highest kinetic energy.展开更多
An experimental system of AC arc discharge in water was designed with pole-pole electrodes and a peak voltage of 1500 V and a test circuit was set up using virtual instrument technology. The mechanism of an AC plasma ...An experimental system of AC arc discharge in water was designed with pole-pole electrodes and a peak voltage of 1500 V and a test circuit was set up using virtual instrument technology. The mechanism of an AC plasma arc generated in water was analyzed. The voltage- current characteristic of the AC plasma are was obtained from the waveform. The temperature characteristic was tested with a spectrum diagnosis system, and the effect of different electrode materials on the striking voltage and peak current was analyzed. The results show that when a power supply of 6 kW is applied on electrodes with a gap of 2 mm in water, the striking voltage is from 900 V to 1300 V, the arc voltage is from 40 V to 100 V, the arc current is from 2 A to 7 A, and the zero rest period is from 1 ms to 2 ms. In addition, the arc voltage and current are different for electrodes in aluminum, copper and stainless steel. The arc voltage is lower and the current is higher for an aluminum electrode than those for copper and stainless steel ones. The highest temperature of the arc is 7643 K.展开更多
The different physical states of saturated sand, including shear elasticity, positive dilatancy, and negative dilatancy (preliminary negative dilatancy, secondary negative dilatancy and reversal negative dilatancy) ar...The different physical states of saturated sand, including shear elasticity, positive dilatancy, and negative dilatancy (preliminary negative dilatancy, secondary negative dilatancy and reversal negative dilatancy) are revealed based on the pore water pressure response of saturated sand in undrained dynamic torsional tests of thin cylinder samples and also checked by the drained cyclic triaxial tests under a given mean effective normal stress. According to the effective stress path of different physical states under the undrained cyclic torsional tests the physical state transformation surface, stress history boundary and yield surface are determined, and the state boundary surface is also determined by the range of effective frictional stress state movement. Based on the moving yield surface without rotation, and the expanding stress history boundary surface relevant to the stress path variations under different physical states in 3D stress space, a physical state model is proposed to provide a new approach to calculating the transient pore water pressure under the undrained condition, and the volume strain of dilatation under drained condition in this paper.展开更多
文摘Generation characteristics of vacuum discharge plasma are very important for the applied research of metal plasma. The vacuum discharge electrode configuration and the cathode material affect the generation characteristics of the metal plasma which consists of metal ions coming from cathode and generated by vacuum discharge. In this research, the generation characteristics of the metal plasma generated by vacuum discharge are discussed for four patterns of electrode configurations, i.e. cone-mesh electrode setup, cone-cross line electrode setup, cone-line electrode setup and cone-ring electrode setup. Characteristics of the metal plasma, such as elec- tron density, electron temperature, space potential, ion energy, are measured by the probe method for discussing the impacts of different electrode configurations on the density of generated metal plasma. Moreover, the diffusion velocities of the metal plasma are measured for cathode materials of Pb, Al, and Cu, respectively. The experimental results indicate that the plasma generated by the discharge of cone-ring electrode configuration possesses the maximum density and the metal plasma generated by the Al cathode possesses the fastest diffusion velocity and the highest kinetic energy.
基金supported by National Natural Science Foundation of China (No. 50777014)
文摘An experimental system of AC arc discharge in water was designed with pole-pole electrodes and a peak voltage of 1500 V and a test circuit was set up using virtual instrument technology. The mechanism of an AC plasma arc generated in water was analyzed. The voltage- current characteristic of the AC plasma are was obtained from the waveform. The temperature characteristic was tested with a spectrum diagnosis system, and the effect of different electrode materials on the striking voltage and peak current was analyzed. The results show that when a power supply of 6 kW is applied on electrodes with a gap of 2 mm in water, the striking voltage is from 900 V to 1300 V, the arc voltage is from 40 V to 100 V, the arc current is from 2 A to 7 A, and the zero rest period is from 1 ms to 2 ms. In addition, the arc voltage and current are different for electrodes in aluminum, copper and stainless steel. The arc voltage is lower and the current is higher for an aluminum electrode than those for copper and stainless steel ones. The highest temperature of the arc is 7643 K.
基金Project supported by the National Natural Science Foundation of China (No.10172071) the Natural Science Foundation of Shaanxi Province.
文摘The different physical states of saturated sand, including shear elasticity, positive dilatancy, and negative dilatancy (preliminary negative dilatancy, secondary negative dilatancy and reversal negative dilatancy) are revealed based on the pore water pressure response of saturated sand in undrained dynamic torsional tests of thin cylinder samples and also checked by the drained cyclic triaxial tests under a given mean effective normal stress. According to the effective stress path of different physical states under the undrained cyclic torsional tests the physical state transformation surface, stress history boundary and yield surface are determined, and the state boundary surface is also determined by the range of effective frictional stress state movement. Based on the moving yield surface without rotation, and the expanding stress history boundary surface relevant to the stress path variations under different physical states in 3D stress space, a physical state model is proposed to provide a new approach to calculating the transient pore water pressure under the undrained condition, and the volume strain of dilatation under drained condition in this paper.
