An apparatus for determining the secondary electron emission properties of nonconductors
The apparatus described allows the measurement of the secondary emission coefficient and the secondary electron energy distribution from nonconducting surfaces. The potential of the nonconducting surface is stabilized by a cathode very close to it. The use of an oscillatory primary beam allows a measurement of the secondary emission coefficient. The application of a sinusoidally modulated voltage sawtooth allows the determination of the emitted electron energy distribution and measures the potential of the emitting surface. The performance of the apparatus is demonstrated by results obtained from an amorphous magnesium oxide coating.
Conduction, breakdown, and other phenomena in dielectric liquids
The format of this year's chapter is essentially the same as last year's. In addition to major sections on conduction and breakdown, sections on the following topics are included: technology, fluid motion, electrostatics, and dielectric phenomena. The selection of subject matter in the dielectric phenomena section is based upon its direct or indirect connection with conduction or breakdown. Although the connection may seem obscure in some cases, those concerned will recognize the articles of interest to them. Relaxation behavior is generally excluded from this section, but subjects like opalescence and secondary electron emission are included, in addition to the obviously-important subject of electric field distribution.
Actuating Principle of Online Automatic Balancer with Counter Weight Driven by Magnetic Force
Kinematic precept of mass block in automatic balancer is proposed following the principle of online automatic dynamic balancing.By combination of electromagnet and permanent magnet,the magnetic circuit of the balancer with ring coil and rare earth permanent magnet is designed.Actuating process of the balancer is discussed and then a step drive voltage waveform is defined.For the high-speed grinding motorized spindle 170MD12Y16,the mechanical structure and dimensions of the balancer are schemed out.The electromagnetic simulations for the designed balancer are conducted and the better coil ampere-turns and reluctance adjusting ring thickness are then determined.The validity of simulation results is verified by a balancer driving experiment and the desired voltage value and its duration time are also determined.the designed balancer has a stable operation process without out-of-step and fluctuation around balanced position when the ampere-turns are considered as 1 kA,the reluctance adjusting ring thickness 0.2 mm,the driving voltage 12.4 V and the voltage duration time 120 ms.