tailieunhanh - Introdution to Thermal Analysis Techniques and Applications Part 12

Tham khảo tài liệu 'introdution to thermal analysis techniques and applications part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 242 C3 Spreadsheet and database packages 15-101 The availability of powerful spreadsheet packages such as Microsoft Excel and Corel Qualm has virtually removed any necessity for the writing or use of dedicated software. Reich and co-workers have published a series of papers on the use of spreadsheets 4-6 and databases 7-9 for kinetic analyses of thermal analysis results These papers also show how the power of such packages continues Io improve C4 Algorithms Smoothing of data Whether data has been smoothed and the method. if any. used is seldom easy to ascertain Very smooth traces with little noise may indicate either excellent instrumentation or heavy smoothing. Various types of numerical filters are available. Savitsky-Golay 10 smoothing involves a least-squares convolution method and weighting factors are given 10 for from 5 Io 25-point polynomials. Where it Is important not to lose points horn the ends of the data set a modification developed by Gorry 111 can he used. Ebert Ct al I2 have published .1 spline smoothing program in Basic. Marchand and Marmet 13 have described a binomial filter and Bossian and Hardie 1I4 a robust filter. The application of some of these smoothing routines to a noisy DSC trace IS illustrated in Figure Cl. Numerical differentiation A DSC or DTA curve IS already an example of a differential measurement and so such curves are not usually differentiated further. If an integral measurement such as a TG curve has txren recorded then a DTG curve can be obtained by numerical differentiation Tile usual method is that of Savitsky and Golay 101 Data points must be at equally spaced time intervals. As an example of a 9-point convolution acting on point y4 with a normalising constant 110 of 60 dyi dt - 4 y - 3 y - 2 y - y y 2 y 3 yT 4 yt 60 At Peak integration Peak area determination see Figure C2 is usually done by numerical integration using either Simpson s rule or die trapezoidal rule For a large number of closely spaced points the trapezoidal

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