Changeset 6431056 in sasmodels


Ignore:
Timestamp:
Jan 30, 2017 12:00:42 PM (8 years ago)
Author:
smk78
Branches:
master, core_shell_microgels, costrafo411, magnetic_model, ticket-1257-vesicle-product, ticket_1156, ticket_1265_superball, ticket_822_more_unit_tests
Children:
cdcebf1
Parents:
3b9a526
Message:

Updated model docstrings for guinier_porod and unified_power_rg models
to explain relationship to one another, deficiency of unified_power_rg,
and add Hammouda references. (Relates to issue raised in email from
Jurrian, Jan 2017).

Location:
sasmodels/models
Files:
2 edited

Legend:

Unmodified
Added
Removed
  • sasmodels/models/guinier_porod.py

    ra807206 r6431056  
    44and dimensionality of scattering objects, including asymmetric objects 
    55such as rods or platelets, and shapes intermediate between spheres 
    6 and rods or between rods and platelets. 
     6and rods or between rods and platelets, and overcomes some of the  
     7deficiencies of the (Beaucage) Unified_Power_Rg model (see Hammouda, 2010). 
    78 
    89Definition 
     
    5960--------- 
    6061 
    61 A Guinier, G Fournet, *Small-Angle Scattering of X-Rays*, 
    62 John Wiley and Sons, New York, (1955) 
     62B Hammouda, *A new Guinier–Porod model*,  
     63*J. Appl. Cryst.*, (2010), 43, 716-719 
    6364 
    64 O Glatter, O Kratky, *Small-Angle X-Ray Scattering*, Academic Press (1982) 
    65 Check out Chapter 4 on Data Treatment, pages 155-156. 
     65B Hammouda, *Analysis of the Beaucage model*,  
     66*J. Appl. Cryst.*, (2010), 43, 1474–1478 
     67 
    6668""" 
    6769 
  • sasmodels/models/unified_power_Rg.py

    rb3f2a24 r6431056  
    33---------- 
    44 
    5 The Beaucage model employs the empirical multiple level unified 
    6 Exponential/Power-law fit method developed by G. Beaucage. Four functions 
    7 are included so that 1, 2, 3, or 4 levels can be used. In addition a 0 level 
    8 has been added which simply calculates 
     5This model employs the empirical multiple level unified Exponential/Power-law  
     6fit method developed by Beaucage. Four functions are included so that 1, 2, 3,  
     7or 4 levels can be used. In addition a 0 level has been added which simply  
     8calculates 
    99 
    1010.. math:: 
     
    1515many different types of particles, including fractal clusters, random coils 
    1616(Debye equation), ellipsoidal particles, etc. 
     17 
     18The model works best for *mass* fractal systems characterized by Porod exponents  
     19between 5/3 and 3. It should not be used for *surface* fractal systems. Hammouda  
     20(2010) has pointed out a deficiency in the way this model handles the  
     21transitioning between the Guinier and Porod regimes and which can create  
     22artefacts that appear as kinks in the fitted model function. 
     23 
     24Also see the Guinier_Porod model. 
    1725 
    1826The empirical fit function is: 
     
    5664 
    5765G Beaucage, *J. Appl. Cryst.*, 29 (1996) 134-146 
     66 
     67B Hammouda, *Analysis of the Beaucage model*,  
     68*J. Appl. Cryst.*, (2010), 43, 1474–1478 
    5869 
    5970""" 
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