The mass-front velocities of granular flows results from the joint action of particle size gradations and the underlying surfaces.However,because of the complexity of friction during flow movement,details such as the ...The mass-front velocities of granular flows results from the joint action of particle size gradations and the underlying surfaces.However,because of the complexity of friction during flow movement,details such as the slope-toe impedance effects and momentum-transfer mechanisms have not been completely explained by theoretical analyses,numerical simulations,or field investigations.To study the mass-front velocity of dry granular flows influenced by the angle of the slope to the runout plane and particle size gradations we conducted model experiments that recorded the motion of rapid and long-runout rockslides or avalanches.Flume tests were conducted using slope angles of 25°,35°,45°,and 55° and three particle size gradations.The resulting mass-front motions consisted of three stages:acceleration,velocity maintenance,and deceleration.The existing methods of velocity prediction could not explain the slowing effect of the slope toe or the momentum-transfer steady velocity stage.When the slope angle increased from 25° to 55°,the mass-front velocities dropped significantly to between 44.4% and59.6% of the peak velocities and energy lossesincreased from 69.1% to 83.7% of the initial,respectively.The velocity maintenance stages occurred after the slope-toe and mass-front velocity fluctuations.During this stage,travel distances increased as the angles increased,but the average velocity was greatest at 45°.At a slope angle of 45°,as the median particle size increased,energy loss around the slope toe decreased,the efficiency of momentum transfer increased,and the distance of the velocity maintenance stage increased.We presented an improved average velocity formula for granular flow and a geometrical model of the energy along the flow line.展开更多
The power/energy losses reduction in distribution systems is an important issue during planning and operation, with important technical and economical implications. Thus, the energy losses minimization implies not onl...The power/energy losses reduction in distribution systems is an important issue during planning and operation, with important technical and economical implications. Thus, the energy losses minimization implies not only the technical improvement of the network, through its renewal with the introduction of the technological innovations in the equipment and circuit components as well as the optimal planning of the design and development of the network, but also requires the use of the methods and software tools to facilitate the operation process. The paper presents a strategy for power / energy saving which is replacement of the 6 kV voltage level with 20 kV voltage level. In this line, different urban distribution networks were analyzed using fuzzy techniques for load modeling.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.41272297,41401195)the Applied Basic Research Fund of the Science and Technology Department of Sichuan Province (2014JY0121)the Key Research Fund of the Education Department of Sichuan Province (14ZA0095)
文摘The mass-front velocities of granular flows results from the joint action of particle size gradations and the underlying surfaces.However,because of the complexity of friction during flow movement,details such as the slope-toe impedance effects and momentum-transfer mechanisms have not been completely explained by theoretical analyses,numerical simulations,or field investigations.To study the mass-front velocity of dry granular flows influenced by the angle of the slope to the runout plane and particle size gradations we conducted model experiments that recorded the motion of rapid and long-runout rockslides or avalanches.Flume tests were conducted using slope angles of 25°,35°,45°,and 55° and three particle size gradations.The resulting mass-front motions consisted of three stages:acceleration,velocity maintenance,and deceleration.The existing methods of velocity prediction could not explain the slowing effect of the slope toe or the momentum-transfer steady velocity stage.When the slope angle increased from 25° to 55°,the mass-front velocities dropped significantly to between 44.4% and59.6% of the peak velocities and energy lossesincreased from 69.1% to 83.7% of the initial,respectively.The velocity maintenance stages occurred after the slope-toe and mass-front velocity fluctuations.During this stage,travel distances increased as the angles increased,but the average velocity was greatest at 45°.At a slope angle of 45°,as the median particle size increased,energy loss around the slope toe decreased,the efficiency of momentum transfer increased,and the distance of the velocity maintenance stage increased.We presented an improved average velocity formula for granular flow and a geometrical model of the energy along the flow line.
文摘The power/energy losses reduction in distribution systems is an important issue during planning and operation, with important technical and economical implications. Thus, the energy losses minimization implies not only the technical improvement of the network, through its renewal with the introduction of the technological innovations in the equipment and circuit components as well as the optimal planning of the design and development of the network, but also requires the use of the methods and software tools to facilitate the operation process. The paper presents a strategy for power / energy saving which is replacement of the 6 kV voltage level with 20 kV voltage level. In this line, different urban distribution networks were analyzed using fuzzy techniques for load modeling.
