Changes in doc/guide/pd/polydispersity.rst [d712a0f:29afc50] in sasmodels
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doc/guide/pd/polydispersity.rst
rd712a0f r29afc50 20 20 P(q) = \text{scale} \langle F^* F \rangle / V + \text{background} 21 21 22 where $F$ is the scattering amplitude and $\langle\cdot\rangle$ denotes an 23 average over the size distribution $f(x; \bar x, \sigma)$, giving 24 25 .. math:: 26 27 P(q) = \frac{\text{scale}}{V} \int_\mathbb{R} 28 f(x; \bar x, \sigma) F^2(q, x)\, dx + \text{background} 22 where $F$ is the scattering amplitude and $\langle\cdot\rangle$ denotes an 23 average over the size distribution. 29 24 30 25 Each distribution is characterized by a center value $\bar x$ or … … 46 41 with larger values of $N_\sigma$ required for heavier tailed distributions. 47 42 The scattering in general falls rapidly with $qr$ so the usual assumption 48 that $ f(r - 3\sigma_r)$ is tiny and therefore $f(r - 3\sigma_r)f(r - 3\sigma_r)$43 that $G(r - 3\sigma_r)$ is tiny and therefore $f(r - 3\sigma_r)G(r - 3\sigma_r)$ 49 44 will not contribute much to the average may not hold when particles are large. 50 45 This, too, will require increasing $N_\sigma$. … … 68 63 69 64 Additional distributions are under consideration. 70 71 .. note:: In 2009 IUPAC decided to introduce the new term 'dispersity' to replace72 the term 'polydispersity' (see `Pure Appl. Chem., (2009), 81(2),73 351-353 <http://media.iupac.org/publications/pac/2009/pdf/8102x0351.pdf>`_74 in order to make the terminology describing distributions of properties75 unambiguous. Throughout the SasView documentation we continue to use the76 term polydispersity because one of the consequences of the IUPAC change is77 that orientational polydispersity would not meet their new criteria (which78 requires dispersity to be dimensionless).79 65 80 66 Suggested Applications
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