Zusammenfassung
Fourier series analysis is utilised to quantitatively evaluate the
linearity limits and characterise the non-linearity of the perturbation-response
relationship, in the frequency domain, for dynamic surface properties
of 2 % (w/w) aqueous solutions of poly(sodium 4-styrenesulfonate).
Under condition of periodic oscillations with different amplitudes
at the same frequency (i.e., at single-line spectrum), the total
harmonic distortion (THD) parameter shows the existence of a linearity
range in the relationship between an imposed change of interfacial
area and the ensuing surface tension response. Experiments at two-line
spectrum, both with harmonic and with non-harmonic tones, also convey
information about the linearity of the response. Under linearity
approximation, results reveal that the magnitude of the surface dilational
modulus can be determined even under periodic oscillations with a
non-monochromatic spectrum, by taking just the proper components
of the Fourier series. (c) 2004 Elsevier B.V all rights reserved.
Nutzer