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  • sasmodels/models/hollow_cylinder.py

    r2d81cfe r455aaa1  
    11r""" 
     2Definition 
     3---------- 
     4 
    25This model provides the form factor, $P(q)$, for a monodisperse hollow right 
    3 angle circular cylinder (rigid tube) where the form factor is normalized by the 
    4 volume of the tube (i.e. not by the external volume). 
     6angle circular cylinder (rigid tube) where the The inside and outside of the 
     7hollow cylinder are assumed to have the same SLD and the form factor is thus 
     8normalized by the volume of the tube (i.e. not by the total cylinder volume). 
    59 
    610.. math:: 
    … …  
    812    P(q) = \text{scale} \left<F^2\right>/V_\text{shell} + \text{background} 
    913 
    10 where the averaging $\left<\ldots\right>$ is applied only for the 1D calculation. 
     14where the averaging $\left<\ldots\right>$ is applied only for the 1D 
     15calculation. If Intensity is given on an absolute scale, the scale factor here 
     16is the volume fraction of the shell.  This differs from 
     17the :ref:`core-shell-cylinder` in that, in that case, scale is the volume 
     18fraction of the entire cylinder (core+shell). The application might be for a 
     19bilayer which wraps into a hollow tube and the volume fraction of material is 
     20all in the shell, whereas the :ref:`core-shell-cylinder` model might be used for 
     21a cylindrical micelle where the tails in the core have a different SLD than the 
     22headgroups (in the shell) and the volume fraction of material comes fromm the 
     23whole cyclinder.  NOTE: the hollow_cylinder represents a tube whereas the 
     24core_shell_cylinder includes a shell layer covering the ends (end caps) as well. 
    1125 
    12 The inside and outside of the hollow cylinder are assumed have the same SLD. 
    13  
    14 Definition 
    15 ---------- 
    1626 
    1727The 1D scattering intensity is calculated in the following way (Guinier, 1955) 
    … …  
    4858---------- 
    4959 
    50 L A Feigin and D I Svergun, *Structure Analysis by Small-Angle X-Ray and 
    51 Neutron Scattering*, Plenum Press, New York, (1987) 
     60.. [#] L A Feigin and D I Svergun, *Structure Analysis by Small-Angle X-Ray and 
     61   Neutron Scattering*, Plenum Press, New York, (1987) 
    5262 
    5363Authorship and Verification 
    … …  
    5565 
    5666* **Author:** NIST IGOR/DANSE **Date:** pre 2010 
    57 * **Last Modified by:** Richard Heenan **Date:** October 06, 2016 
    58    (reparametrised to use thickness, not outer radius) 
    59 * **Last Reviewed by:** Richard Heenan **Date:** October 06, 2016 
     67* **Last Modified by:** Paul Butler **Date:** September 06, 2018 
     68   (corrected VR calculation) 
     69* **Last Reviewed by:** Paul Butler **Date:** September 06, 2018 
    6070""" 
    6171 
    … …  
    120130    vol_total = pi*router*router*length 
    121131    vol_shell = vol_total - vol_core 
    122     return vol_shell, vol_total 
     132    return vol_total, vol_shell 
    123133 
    124134def random(): 
    … …  
    151161tests = [ 
    152162    [{}, 0.00005, 1764.926], 
    153     [{}, 'VR', 1.8], 
     163    [{}, 'VR', 0.55555556], 
    154164    [{}, 0.001, 1756.76], 
    155165    [{}, (qx, qy), 2.36885476192], 
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