Based on SEM/EDS analysis, an oxygen content of approx.

The carbon fibres produced from the four-stage oxidation were examined using SEM/EDS. According to FTIR spectra, two indices were expressed to follow the dehydrogenations and cyclizations (nitrile groups) and the band intensity of carbonyl groups to follow the oxidation. Acrylic fibres of homopolymer PAN are subjected to thermo-oxidative treatment following a four-stage or a two-stage isothermal programme, and the resulting oxidized fibres are pyrolyzed up to 1000 ☌ for 30 min or they are flash-pyrolyzed at 1000 ☌ for 5 min, and the shrinkage and weight loss are determined. oxidation/stabilization, carbonization/pyrolysis and electrochemical modification processes and their role for applications. Also referred as Shift FFT in some other applications.A unique consideration is intended, concerning the creation of functional groups during the production of carbon fibres from polyacrylonitrile, i.e. If selected, after forward Fourier transform the two parts of spectrum will be rearranged so that the lower frequency components are in the center the opposite rearrangement of spectrum will be done before inverse transform if any. Also referred as Normalize in some other applications. If your original data is real, you may want to additionally multiply the result by 2 to get the true amplitudes of real signal. Transform direction (here Inverse also equals to Backward)ĭivide forward transform result by number of points N (see formulas table). If your data is purely real, select imaginary item If the sampling interval is varying or real and/or imaginary data contains empty cells in the middle, the result of discrete Fourier transform will be incorrect.Ĭolumns with real and imaginary components of data. Note that using of discrete Fourier transform implies that the samples in your original data are equally spaced in time/frequency, i.e. You can set sampling interval manually in Sampling Interval field. MagicPlot calculates sampling interval as a difference between second and first values in Sampling column. Sampling interval of original data Δ t is used to compute the data in resulting sampling column. XN - anchor point x-coordinates yN - anchor point y-coordinatesĪ - area (integral) dx - half width at halfĪs for original Gaussian: a - amplitude dx - half width at halfĪs for original Lorentzian: a - amplitude dx - half width at half

It means that changing the first parameter compensates changing of the second one so that the fitting algorithm cannot select between them. If two parameters are linked the corresponding matrix value will be close to 1. The values lie in range -1…1, diagonal elements are always 1. This matrix shows if the parameters are linked. Here α is the matrix of partial derivatives of fit function with respect to parameters β m and β n which is also used by fitting algorithm to compute parameters for next iteration. This statistic is always smaller than R 2, can decrease as you add new fit curves or introduce parameters, and even be negative for poorly fitting models. This is a biased estimate of the population R 2, and will never decrease if additional fit parameters (fit curves) are added, even if they are irrelevant.Īdjusted R 2 (or degrees of freedom adjusted R-square) is a slightly modified version of R 2, designed to penalize for the excess number of fit parameters which do not add to the explanatory power of the regression. R 2 will be equal to one if fit is perfect, and to zero otherwise.

Root mean square of the error (Root MSE).

The advantage of the reduced chi-squared is that it already normalizes for the number of data points and model (fit function) complexity. This value is minimized during the fit to find the optimal fit function parameters. Not used by fit algorithm, only for comparison. This is the total number of unlocked parameters of fit curves which are summarized to fit. Only parameters with unset Lock checkbox are taken into account. This is the number of data points inside specified fit Interval.įor peak-like functions (Gauss, Lorentz) these parameters are amplitude, position and half width at half maximum.

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