Electric-field

Other methods have been sought to augment the depolarization of the membrane by cross-flow. For particles with a higher density than water, centrifugal force has been explored. For particles bearing an electric charge, an electric field has been investigated. 

Centrifugal Force. Robertson et al40 designed an apparatus in which the centrifugal force vector was perpendicular to the membrane surface but opposite (and parallel) to the flux vector. Solutions of casein and dextran (60,400 dal-tons) were passed over the membrane in laminar flow. When the apparatus was spun, centrifugal field strengths from 100 to 600g resulted in flux improvement factors of 3 to 16. 

At the critical voltage, regime (b), there is no concentration polarization because the electrophoretic transport is equal to the convective transport. In this regime, increasing the tangential velocity is expected to have no influence on the flux because fluid shear can only improve the transport of particles down a concentration gradient. In this case, there is no concentration gradient. 

PLATE 3. Multiple bulking brush discharges on powder bed (time exposure). (From Bartknecht in Industrial Dust Explosions, ASTM STP 958, p. 175) 

It was initially thought that these discharges only occur during bulking of coarse powders with diameter 1-10 mm, such as pellets [25], Later work demonstrated that this is not the case although the phenomenon is more frequently observed with coarse powders (6-3.1.1 and 6-4.2.1). 

Tests using vertical cylindrical silos have shown that the charge transferred by these discharges increases with silo diameter [161]. The maximum observed charge transfer Q varied with silo diameter D according to 

The minimum size of container for bulking brush discharges has not been established, but is probably about 1 m3. Their occurrence in such small containers might require coarse particles such as pellets and therefore represent a hazard only where flammable gas or hybrid mixtures are present. Assuming that the effective energy of the discharges is at the low end of the proposed 

1- 20 mJ range, the only significant feature vis-a-vis brush discharges is that no field-intensifying electrode is required to initiate the discharge. 

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These hazards are reduced drastically by desalting crude oils, a process which consists of coalescing and decanting the fine water droplets in a vessel by using an electric field of 0.7 to 1 kV/cm. 

Writing the electromagnetic field in terms of transverse electric (TE) and transverse magnetic (TM) components, the electric field has the form ... 

The equation (1) assumes the knowledge of the incident field E (r) which is the electrical field in the anomalous domain considering the flaw absent. This field must be computed before and one can imagine that small errors in estimation of this field may 2586... 

By using the method of the dyadic Green s function [4] and the adequate boundary conditions [5], the expressions of the electric field in the zone where the transducer is placed can be written as [2]... 

Electrical forerunners may be found out as the result of electrical field potential between two points (electrotelluric field on the earth surface) measurement. Usually the background potential is 10 mV and during the earthquake it equals to 70 mV. 

This electrical field potential is measured by means of portable millivoltmeter with high input resistance. The field registration is carried out in the mountain areas at the distance of 5 km and more, at the same time the minimal gradient value is about 10 mV/km. 

The effects of electric fields on monolayer domains graphically illustrates the repulsion between neighboring domains [236,237]. A model by Stone and McConnell for the hydrodynamic coupling between the monolayer and the subphase produces predictions of the rate of shape transitions [115,238]. 

This subject has a long history and important early papers include those by Deijaguin and Landau [29] (see Ref. 30) and Langmuir [31]. As noted by Langmuir in 1938, the total force acting on the planes can be regarded as the sum of a contribution from osmotic pressure, since the ion concentrations differ from those in the bulk, and a force due to the electric field. The total force must be constant across the gap and since the field, d /jdx is zero at the midpoint, the total force is given the net osmotic pressure at this point. If the solution is dilute, then... 

Rowell and co-workers [62-64] have developed an electrophoretic fingerprint to uniquely characterize the properties of charged colloidal particles. They present contour diagrams of the electrophoretic mobility as a function of the suspension pH and specific conductance, pX. These fingerprints illustrate anomalies and specific characteristics of the charged colloidal surface. A more sophisticated electroacoustic measurement provides the particle size distribution and potential in a polydisperse suspension. Not limited to dilute suspensions, in this experiment, one characterizes the sonic waves generated by the motion of particles in an alternating electric field. O Brien and co-workers have an excellent review of this technique [65]. 

Derive the expression for the electric field around a point dipole, Eq. VI-5, by treating the dipole as two charges separated by a distance d, then moving to distances X d. 

Mixing fatty acids with fatty bases can dissolve films as the resulting complexes become water-soluble however, in some cases the mixed Langmuir film is stabilized [128]. The application of an electric field to a mixed lipid monolayer can drive phase separation [129]. 

Semiconductors are poor conductors of electricity at low temperatures. Since the valence band is completely occupied, an applied electric field caimot change the total momentum of the valence electrons. This is a reflection of the Pauli principle. This would not be true for an electron that is excited into the conduction band. However, for a band gap of 1 eV or more, few electrons can be themially excited into the conduction band at ambient temperatures. Conversely, the electronic properties of semiconductors at ambient temperatures can be profoundly altered by the... 

The charge redistribution that occurs when a molecule is exposed to an electric field is characterized by a set of constants called polarizabilities. In a imifonn electric field F, a component of the dipole moment is... 

Consider the interaction of a neutral, dipolar molecule A with a neutral, S-state atom B. There are no electrostatic interactions because all the miiltipole moments of the atom are zero. However, the electric field of A distorts the charge distribution of B and induces miiltipole moments in B. The leading induction tenn is the interaction between the pennanent dipole moment of A and the dipole moment induced in B. The latter can be expressed in tenns of the polarizability of B, see equation (Al.S.g). and the dipole-mduced-dipole interaction is given by... 

In this fonn it is clear that k leads to an attenuation of the electric field amplitude with distance (i.e. absorption). 

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