Variation of cavity gas pressure in slopes with weak intercalation under seismic load

This study discussed how cavity gas pressure affects the stability of rock mass with fractures under well controlled laboratory experiments.Suddenly-created void space created and the induced gas pressures have been the focus of active researches because they are associated with fast movement of large-scale landslides.A shaking table experiment was set up to mimic weak-intercalated rock slope under seismic loads.Excessive cavity gas pressure would be produced in weak spots upon a sudden vibration load.The drastically elevated gas pressure is believed to be responsible for the creation of cavities surrounding the tension fracture.With dissipation of the excessive cavity gas pressure,the fractures are in unbounded closed-state.This observation explains that the slope body would be split and loosened under several aftershocks,and with the expanding of the cracks,the slope failure eventually occurred.The research of the mechanism of cavity gas pressure could provide a novel insight into the formation mechanism of landslides under seismic load and has implications for the disaster prevention and control theory for the slope stability evaluation.

Innovation Ultrasonic Assistant Soldering in Electronics

Innovative approaches in ultrasonic assistant soldering consists of increasing the activity of cavitation and accelerating difiusion processes at the interface between the solder and the soldering material.Besides that,it improves the effectiveness of cavitation processes in melts by saturating gas cavities with diameters that are smaller than the resonant sizes of cavitation germs.Gas saturation of liquids and melts raises level of cavitation pressure by 20-25%,that intensifies US processing of cleaning,soldering and metallization.Modelling diffusion process showed that the US activation increased the concentration of diffusing elements of Zn and Al in the interface depth by 15-20% on average,and the combined activation by the US and electric field increased it by 30-45%.Furthemore,as the energy quantity adsorbed by melt increases,increased amplitude and frequency of US vibrations induces concentration rise.The heat energy was also boosted by combining the activation of the melt-soldered material system with US vibrations energy and high current pulses.This allows for a faster increase in soldering temperature,as well as improved solder wettability.

RESEARCH ON THE BASE CAVITY OF A SUB-LAUNCHED PROJECTILE

The finite volume method based on a multiphase model is adopted to solve the Reynolds-Averaged Navier-Stokes （RANS） equations,which takes into account the effects of fluid compressibility,viscosity,gravity,medium mixture and energy transfer of water and combustion gas.The program Fluent User Define Function （UDF） module combined with the dynamic mesh method is employed to simulate the coupling flow field of combustion gas,water field and trajectory of projectile.The results show that the volume of gas cavity at the bottom of projectile and tail pressure will fluctuate after bottom of the projectile leaving the launch tube.The cause of the fluctuation is analyzed and its effects on the trajectory of projectile are presented.The numerical and experimental results agree well with each other.