@article{Mellinger2004,
  author    = {Mellinger, Axel},
  title     = {Unbiased iterative reconstruction of polarization and space-charge profiles from thermal-wave experiments},
  issn      = {0957-0233},
  year      = {2004},
  abstract  = {The thermal-wave technique or laser-intensity modulation method is an important tool for the non-destructive probing of space-charge and polarization profiles in electrets. Analysing the experimental data requires solving a Fredholm integral equation which is known to be an ill-conditioned problem. This paper presents an iterative approach that is capable of reconstructing inherently unsmooth distributions. The deviations from the true profiles are slightly smaller than those obtained with Tikhonov regularization, while the computational burden is not a limiting factor on modem personal computers. The optimum number of iterations is estimated using the randomized generalized cross- validation technique. Results are shown for a number of model distributions, as well as for experimental data from a layered polyvinylidene fluoride film sandwich},
  language  = {en}
}
@article{MellingerCamachoGonzalezGerhard2004,
  author    = {Mellinger, Axel and Camacho Gonz{\´a}lez, Francisco and Gerhard, Reimund},
  title     = {Photostimulated discharge in electret polymers : an alternative approach for investigating deep traps},
  year      = {2004},
  abstract  = {The stability of space charge in electrets such as polytetrafluoroethylene (PTFE), polyethylene terephthalate (PETP) and polypropylene (PP) under ultraviolet irradiation has been investigated using photostimulated discharge spectroscopy. While only weak discharge currents were observed in PTFE coated with semitransparent gold electrodes, up to 15 pA/cm(2) were found in PETP around the UV absorption edge near 310 nm. Space charge profiles obtained with the piezoelectrically generated pressure step method indicate that near-surface charges were almost completely removed. In PP foam, recent findings of a UV-reduced d(33) coefficient were confirmed for exposure times of up to 3.5 h, and a discharge peak at 200 urn could be assigned to the charges stored on the surfaces of the voids. The unique morphology and the (quasi-) piezoelectric properties of cellular PP make it a role model for the future investigation of charge storage in electrets},
  language  = {en}
}