Charge relaxation

The rate of charge reiaxation may in some cases be increased by increasing the conductivity either of the charged medium or of the surroundings. Exam-pies inciude 

Increasing the relative humidity of the air to 45 to 60% can significantly reduce charging where rates of surface separation are relatively small and 

Resistivity /(S m) Relaxation Time T(S) Specific Chaige q/m (pC/kg) Level of ESD hazard 

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Law. S. E., Thompson, S. A., and Balachandran, W., Electroclamping forces for controlling bulk particulate flow charge relaxation effects, J. Electrostatics, 37 79-94 (1996)... 

Charge relaxation time The time required for a charge in a liquid or on a solid material to dissipate to 36.8 percent of its initial value when the material is grounded. 

Note that the investment cost of each distillation column can be expressed as a nonlinear fixed charge relaxation in which the nonlinearities are introduced due to the cost dependence on both the temperature and the column and the feed flow rate. 

Summary. The semiclassical Boltzmann-Langevin method is extended to calculations of higher cumulants of current. Rs efficiency is demonstrated for mesoscopic diffusive contacts and chaotic cavities. We show that in addition to a dispersion at the inverse RC time characteristic of charge relaxation, higher cumulants of noise have a low-frequency dispersion at the inverse dwell time of electrons in the system. 

Consider now the frequency dependence of the third cumulant. We will be interested in the case of a good conductor where the charge-relaxation time tq is much shorter than the dwell time td- Unlike the second cumulant of current, the third cumulant P3(wi,w2) in general exhibits a strong dispersion at wy2 1/td [11], For symmetry reasons, this dispersion vanishes for symmetric cavities and cavities with two tunnel or two ballistic contacts. The shape of P3(wi, w2) essentially depends on the parameters of the contacts. In particular, for a cavity with one tunnel and one ballistic contact with equal conductances Gl = Gr = G it exhibits a non-monotonic behavior as one goes from lv1 = uj2 = 0 to high frequencies. A relatively simple analytical expression for this case may be obtained if td 3> tq and one of the frequencies is zero ... 

Fig. 9. A rotation spectrum is produced by observing the motion of a cell in a rotating electric field of constant amplitude and plotting the rotation speed of the cell against frequency of the field. In solutions of low conductivity, the cell rotates in the opposite direction to the field (anti-field rotation) at low frequencies. This rotation reaches a peak when the field frequency corresponds to the charge relaxation time of the membrane. The position of this peak therefore contains information about membrane permittivity and conductivity. As the frequency increases further, the rate of cell spinning falls, becoming zero at about 1 MHz. Above this frequency, the cell starts to spin with the field (co-field rotation) and a second peak is reached. The frequency at which this peak occurs depends in practice mainly on the conductivity of the interior of the cell. It may be used for non-destructive determination of cytosolic electrolyte concentration.

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