Electric-field-induced resistive

A qualitative, physical description of the longitudinal and transverse optical phonons is illustrated in Fig. 1.6. Kittel [22] phenomenologically explains the fact that ft)Lo > oio as follows. The local electric field induces polarization of the surrounding atoms in the opposite direction to that of the longitudinal mode but in the same direction as the transverse mode. This polarization causes an increasing resistance to the longitudinal vibration relative to the transverse one (see also Ref. [33]). 

Fig. 5.13 shows the equivalent circuit for the electrochemical dynamics. The total current I consists of three components, the double layer charging current Ic, the diffusion current In, and the electric field-induced migration current Im- Here C denotes the double layer capacitance, Ri is the ohmic resistance of the oxidized PPy layer, and i 2 denotes the resistance of the reduced PPy layer, the PVDF (electrol3de) layer, and the contacts. Zd and Zm represent the diffusion dynamics and the migration dynamics, respectively. 

An electrical field in the form of an external stimulus offers numerous advantages (e.g., availability of equipment). This form of an external stimulus also allows for precise control over the magnitude of the current, the duration of electrical pulses, and the interval between pulses. Poly(vinyl alcohol) (PVA) is one of the well-known electroactive polymers with good thermal stability, chemical resistance, water permeability, and biocompatibility. Xia et al. demonstrated electric-field induced actuation of PVA microfibers (Fig. 5.4.5) [17]. 

In a d.c. system the current distribution through the cross-section of a current-canying conductor is uniform as it consists of only the resistance. In an a.c. system the inductive effect caused by the induced-electric field causes skin and proximity effects. These effects play a complex role in determining the current distribution through the cross-section of a conductor. In an a.c. system, the inductance of a conductor varies with the depth of the conductor due to the skin effect. This inductance is further affected by the presence of another current-carrying conductor in the vicinity (the proximity effect). Thus, the impedance and the current distribution (density) through the cross-section of the conductor vaiy. Both these factors on an a.c. system tend to increase the effective... 

We then study experimentally the effect of an inert electrolyte solution and show that ion motion forces an applied electrical potential in the dark to drop near the substrate electrode, thus reinforcing the effects of the distributed resistance. Overall, the 2 conduction and valence bands (whose spatial gradients reflect the electric field) remain approximately flat both at equilibrium and under illumination therefore, charge transfer occurs primarily by diffusion rather than by field-induced drift [4,40-42]. Recent numerical simulations [43,44] and modeling of photogenerated trapped charges [45] show that in an illuminated DSSC there may be, in fact, a very small bulk electric field of about 0.1-3 mV/pm, but this is not expected to have much influence. 

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