A.C.Hannon Interfere and Merge in Excel
page 4
convenience, but note that the values for these parameters cannot be set on this worksheet. Figure 3
shows as an example the QLIM worksheet for a tellurite glass [5].
The QLIM worksheet is followed by three worksheets named ALF, LIN and LIM. These three
worksheets contain copies of the final parameters in a format suitable for producing output files for use
in the ATLAS suite. On each of these worksheets the required data is surrounded by a border.
Probably the easiest way to get the numbers out of Excel is to select the required area and then copy
and paste it to some other application, such as Microsoft Notepad, from which they can more easily be
saved as a text file (for use by ATLAS on a VMS computer).
The three final worksheets (DCS2, INT and MERGE) are used for performing the calculations
and should not normally be modified at all.
5. Suggested procedure for using the Excel workbook
Once the data have been inserted in the workbook, using the method described above in
section 3, the following procedure is suggested for setting the parameters:
1. Start with the highest angle data.
2. Choose the re-normalising factors
i
to make each
()
α
ii
IQ oscillate about
()
IQ
i
S
.
3. If necessary set the straight line gradient
A
i
and intercept B
i
so that
()
iQ
i
oscillates about zero
over the full
Q-range likely to be used (perhaps 15 to 40 Å
-1
for LAD 150° detectors - see Figure 3).
4. Choose the
Q-limits. For the highest angle data (150° on LAD) the value of Q
min
is usually
somewhere between 10 and 15Å
-1
- below this value the highest angle data become inconsistent
with lower angle data due primarily to the Placzek effect (see figure 2 for example). The value of
Q
max
should be chosen to be the highest Q at which information can be discerned.
5. The above procedure should then be repeated for the next highest angle (90° on LAD), and so on
down to the lowest angle.
It is generally advisable to choose the
Q-limits to be where the slope is small (e.g. at the top of
a peak or at the bottom of a trough). This approach reduces the risk of obtaining significant steps in the
final merged
()
iQ at any of the Q-limits. The only limits where this consideration is not important are
the very highest
Q
max
and the very lowest Q
min
. Note that if Q
min
for a particular group is set higher
than
Q
max
then this has the effect of completely omitting that group from the final merged
()
iQ.
6. Using the parameters with the ATLAS suite
The weighting scheme used by the Excel workbook to merge the data simply involves ones
and zeros. This is to be contrasted with the MERGE program in the ATLAS suite which uses a more
sophisticated scheme based upon the incident flux corresponding to each data point (as determined by
the vanadium run). For this reason it is recommended that, once the Excel workbook has been used to
obtain a satisfactory set of parameters (
α
i
, A
i
, B
i
and the Q-limits), the final analysis is done using the
ATLAS suite. The parameter values can be entered into the calculations performed by the ATLAS suite
(55 páginas)
Manymanuals.com
Manymanuals.de
Manymanuals.fr
Manymanuals.it
Manymanuals.pl
Manymanuals.cz
Manymanuals.es
Manymanuals-pt.com
Comentários a estes Manuais