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Last change
on this file since b532aa1 was
ec392464,
checked in by smk78, 10 years ago
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New ReST help files location for perspective help
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Property mode set to
100644
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File size:
1.2 KB
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[ec392464] | 1 | .. pr_help.rst |
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| 2 | |
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| 3 | .. This is a port of the original SasView html help file to ReSTructured text |
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| 4 | .. by S King, ISIS, during SasView CodeCamp-III in Feb 2015. |
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| 5 | |
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| 6 | .. |pi| unicode:: U+03C0 |
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| 7 | .. |chi| unicode:: U+03C7 |
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| 8 | |
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| 9 | P(r) Inversion Perspective |
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| 10 | ========================== |
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| 11 | |
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| 12 | The inversion approach is based on Moore, J. Appl. Cryst., (1980) 13, 168-175. |
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| 13 | |
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| 14 | P(r) is set to be equal to an expansion of base functions of the type |
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| 15 | phi_n(r) = 2 * r * sin(|pi| * n * r / D_max). |
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| 16 | |
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| 17 | The coefficient of each base function in the expansion is found by performing |
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| 18 | a least square fit with the following fit function: |
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| 19 | |
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| 20 | |chi| ^2 = sum_i[ I_meas(q_i) - I_th(q_i) ]^2 / error^2 + Reg_term |
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| 21 | |
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| 22 | where I_meas(q) is the measured scattering intensity and I_th(q) is the |
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| 23 | prediction from the Fourier transform of the P(r) expansion. |
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| 24 | |
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| 25 | The Reg_term term is a regularization term set to the second derivative |
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| 26 | d^2 P(r) / dr^2 integrated over r. It is used to produce a smooth P(r) output. |
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| 27 | |
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| 28 | The following are user inputs: |
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| 29 | |
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| 30 | * Number of terms: the number of base functions in the P(r) expansion. |
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| 31 | |
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| 32 | * Regularization constant: a multiplicative constant to set the size of |
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| 33 | the regularization term. |
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| 34 | |
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| 35 | * Maximum distance: the maximum distance between any two points in the |
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| 36 | system. |
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