Particles sorting phenomena

Bachelard describes how each simple substance actually received a substmcture. And the characteristic thing was that this substructure revealed itself as having a totally different essence from the essence of the phenomenon being studied. In explaining the chemical nature of an element by an organization of electric particles [... ] [a] sort of non-chemistry constituted itself to sustain chemistry (Bachelard 1968, 52). 

Seen from the theoretical analysis and the real accident, the mixture composed by gas and small coal has an obvious effect of sorting after coal and gas outburst. The closer to the outburst hole, the larger particle of small coal deposited on the floor of roadway priority. Generally speaking. For any pile of small coal in the roadway after coal and gas outburst, there is a lot of tiny coal on the surface. But at the bottom of this pile of small coal there is usually many big blocks of coal. At the place which is closer to the outburst hole the diameter of particle is larger relatively. On the contrary, the diameter of particle is smaller. All those phenomenon show that the bigger coal sink faster than the smaller coal. 

Let us mention that dielectrophoresis has also found wide application in manipulation and sorting of particles and biological cells. Together with standard electrophoresis, it is perhaps the most often used electrokinetic phenomenon with practical applications in mind. Even particle separation can be achieved by using microelectrode arrays [55]. Based on the dielectrophoresis phenomenon, a new technique has recently become available for particle or cell separation, namely the dielectrophoresis/gravitational field-flow fractionation (DEP/G-FFF). In DEP/ G-FFF, the relative positions and velocities of unequal particles or cells are controlled by the dielectric properties of the colloid and the frequency of the applied field. The method has been applied to model polystyrene beads, but, most interestingly, to suspensions of different biological cells [56]. 

This equation is valid for relatively low flow velocities at which there is no detachment of the layer of adherent particles, and for relatively small particles (diameter up to 10 jjm), for which the free-fall velocity is so low as to be insignificant. The decrease in concentration of such particles as the air passes through the vent drift of the mine [248] takes place as a result of particle adhesion, not free settling. The greater the flow velocity, the less the change in dust concentration as it passes away from the source of dust formation since at higher velocities the layer of adherent particles may be detached and the dust converted into a suspended state. In the present case this phenomenon is undesirable since adhesion gives a sort of filtration of the air stream. 

Normally neutrons only exist within the atomic nucleus and hence a nuclear reaction of some sort must be used in order to produce a beam of neutrons for neutron diffraction. Chadwick first produced neutrons by the interactions in beryllium of alpha particles from the decay of natural polonium. The first experimental demonstrations of the phenomenon of neutron diffraction were performed in 1936 and these also used radioactive sources. However, the neutron flux available from the decay of a radioactive source is very weak, and since neutron scattering is an intensity-limited technique, all neutron diffraction... 

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