Quasistatic approximation

In the problem of pulse diffraction on waveguide junctions, the quasistatic approximation is feasible if the diffraction length of the light beam is much shorter than the characteristic length of the pulse variation owing to the mentioned above MD, FTNR and SS effects which influence the pulse envelope. Then the results obtained for stationary light beam can be used in the analysis of the non-stationary beam self-focusing. 

It is seen that longitudinal dependences of the variation in the pulse duration plotted for 2 of the same modulus but different signs are approximately symmetrical with respect to the curve obtained in the quasistatic approximation. Hence, at normal GVD, the pulse duration is shorter than the initial one as a result of the self-focusing effect until, owing to GVD, this duration continuously increases to its initial value (denoted by asterisks) and then exceeds it. The size of the region within which the pulse compression is observed at decreases with increasing 2 - In turn,... 

The SPR can be simply formalized, in a first approach, by solving Laplace s equation in tlie case of a single conducting sphere surrounded by a homogeneous transparent medium, with tlie appropriate continuity relations at the metal-dielectric interface and assuming tliat the sphere radius is much lower than the wavelength (quasistatic approximation). The homogeneous local electric field inside the particle, E, then writes... 

A general discussion of the circumstances in which it is permissible to adopt the quasistatic approximation is provided by Happel and Brenner (H9, pp. 52-55). 

Consider a semiconductor film placed in the fringe field that exists above a piezoelectric crystal such as LiNbOj, which carries a surface acoustic Rayleigh wave. The geometry is shown in Fig. 16. One can use the quasistatic approximation for the traveling wave because the wave travels with the sound velocity which is nearly static when compared with the light veloc-... 

In reality, aqueous films stabilized with ionic surfactant, without electrolyte, also rupture, especially at surfactant concentrations below the cmc. The latter fact cannot be explained in the framework of the quasistatic approximation (117—119) this is still an open problem in the theory of li(juid-film stability. 

Simplify this equation by using the quasistatic approximation and taking T = T + Tp where T, Tq. Integrate this equation with the appropriate boundary condition at r = 0 to obtain... 

We developed earlier in (39) the relationship between free and trapped carrier density when the system rests at equilibrium. Equation (69) has a different meaning in that it states that equilibrium will be maintained for any time variation during kinetic measurements. Equation (69) is termed the quasistatic approximation and it was introduced to account for the properties of measured time constants in DSC [51 ]. 

Equation (79) implies that the system of Fig. 11 can be treated with the dynamic equations of a single level, but with kinetic coefficients (lifetime, diffusion coefficient) that depend on the steady state. The essence of the quasistatic approximation is to describe the kinetic factors associated to trapping and detrapping in terms of occupation of free and localized states. The quasistatic approximation is explained in more detail in [51, 52, 150, 151]. It has been widely used to describe experimental results of DSCs. 

However, it should be remembered that the time of interest is determined by the frequency displacement from line centre, Aoj. It is therefore possible that the wings of the line profile have to be calculated by the quasistatic approximation while the profile near the line centre is described by the impact approximation. 

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