Polymer particles having the same chemical makeup but different sizes would have their own special contributions to the generation of static charges,owing to the differences in catalyst residue and surface properties ...Polymer particles having the same chemical makeup but different sizes would have their own special contributions to the generation of static charges,owing to the differences in catalyst residue and surface properties among them.Experiments were performed in a gas-solid fluidized bed to determine the changes in the electrostatic charges with addition of various fine polyethylene particles,which were the same material as the coarse polyethylene particles,to better understand their role in influencing electrostatic charge generation/dissipation.By measuring the electrostatic potential at different bed axial heights,it was found that the electric field inside the bed was significantly influenced by the size of added fine polyethylene particles,mass fractions and catalyst residue.Consequently,an impact factor of fine particles(Fb) was proposed,which was the sum of particle diameter term and catalyst residue term.Within the experimental limits in this paper,after three kinds of fines with Fb all less than 1 were added in the fluidized bed,the electrostatic potential in the bed was just influenced slightly.However,the bed electrostatic potential changed significantly following the addition of the fines with the smallest particle diameter and highest residual catalyst content.While Fb of this kind of fines was less than 1,the static potential did not change much but even decreased slightly with the addition of fines.Once Fb of the fourth kind of fines was more than 1,the electrostatic potential in the bed increased greatly.With Fb of the fourth kind of fines increasing further,the electrostatic potential fell a little,and meanwhile it was found that a large amount of fine particles adhered to the column wall.展开更多
Investigations are directed to the development of high-power sources ofUWB （ultrawideband） radiation based on excitation of anterma arrays with bipolar voltage pulses. In the previously designed high-power UWB sourc...Investigations are directed to the development of high-power sources ofUWB （ultrawideband） radiation based on excitation of anterma arrays with bipolar voltage pulses. In the previously designed high-power UWB sources only one bipolar pulse former and different feeder systems for pulse distribution through the array elements were used. By means of this approach, a number of UWB sources were created with the bipolar voltage pulse length ranging from 0.2 to 2 ns and effective potential of radiation ranging from 0.4 to 3 MV. The approach has got a restriction related to the electrical breakdown in a bipolar voltage pulse former. A new approach to the creation of high-power UWB sources based on a multicharmel bipolar pulse former is suggested： the number of bipolar pulse formers is equal to the number of antennas in the array. The main problem in realization of this approach is a stable operation of bipolar pulse formers in order to ensure a coherent summation of radiated pulses in the far-field zone. The result of this work is the instability of-150 ps at the pulse length of 3 ns obtained in a one-channel bipolar pulse former indicating that the suggested approach is realizable.展开更多
文摘Polymer particles having the same chemical makeup but different sizes would have their own special contributions to the generation of static charges,owing to the differences in catalyst residue and surface properties among them.Experiments were performed in a gas-solid fluidized bed to determine the changes in the electrostatic charges with addition of various fine polyethylene particles,which were the same material as the coarse polyethylene particles,to better understand their role in influencing electrostatic charge generation/dissipation.By measuring the electrostatic potential at different bed axial heights,it was found that the electric field inside the bed was significantly influenced by the size of added fine polyethylene particles,mass fractions and catalyst residue.Consequently,an impact factor of fine particles(Fb) was proposed,which was the sum of particle diameter term and catalyst residue term.Within the experimental limits in this paper,after three kinds of fines with Fb all less than 1 were added in the fluidized bed,the electrostatic potential in the bed was just influenced slightly.However,the bed electrostatic potential changed significantly following the addition of the fines with the smallest particle diameter and highest residual catalyst content.While Fb of this kind of fines was less than 1,the static potential did not change much but even decreased slightly with the addition of fines.Once Fb of the fourth kind of fines was more than 1,the electrostatic potential in the bed increased greatly.With Fb of the fourth kind of fines increasing further,the electrostatic potential fell a little,and meanwhile it was found that a large amount of fine particles adhered to the column wall.
文摘Investigations are directed to the development of high-power sources ofUWB （ultrawideband） radiation based on excitation of anterma arrays with bipolar voltage pulses. In the previously designed high-power UWB sources only one bipolar pulse former and different feeder systems for pulse distribution through the array elements were used. By means of this approach, a number of UWB sources were created with the bipolar voltage pulse length ranging from 0.2 to 2 ns and effective potential of radiation ranging from 0.4 to 3 MV. The approach has got a restriction related to the electrical breakdown in a bipolar voltage pulse former. A new approach to the creation of high-power UWB sources based on a multicharmel bipolar pulse former is suggested： the number of bipolar pulse formers is equal to the number of antennas in the array. The main problem in realization of this approach is a stable operation of bipolar pulse formers in order to ensure a coherent summation of radiated pulses in the far-field zone. The result of this work is the instability of-150 ps at the pulse length of 3 ns obtained in a one-channel bipolar pulse former indicating that the suggested approach is realizable.
