source: sasview/src/sas/models/PolymerExclVolume.py @ 61f32d2b

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Last change on this file since 61f32d2b was 79492222, checked in by krzywon, 10 years ago

Changed the file and folder names to remove all SANS references.

  • Property mode set to 100644
File size: 4.0 KB
Line 
1#!/usr/bin/env python
2
3##############################################################################
4#       This software was developed by the University of Tennessee as part of the
5#       Distributed Data Analysis of Neutron Scattering Experiments (DANSE)
6#       project funded by the US National Science Foundation.
7#
8#       If you use DANSE applications to do scientific research that leads to
9#       publication, we ask that you acknowledge the use of the software with the
10#       following sentence:
11#
12#       "This work benefited from DANSE software developed under NSF award DMR-0520547."
13#
14#       copyright 2008, University of Tennessee
15##############################################################################
16from sas.models.BaseComponent import BaseComponent
17from scipy.special import gammainc,gamma
18import copy   
19import math
20   
21class PolymerExclVolume(BaseComponent):
22    """
23    Class that evaluates a PolymerExclVolModel model.
24    This file was auto-generated from ..\c_extensions\polyexclvol.h.
25    Refer to that file and the structure it contains
26    for details of the model.
27
28    List of default parameters:
29   
30    * scale           = 0.01
31    * rg              = 100.0 [A]
32    * m               = 3.0
33    * background      = 0.0 [1/cm]
34
35    """
36       
37    def __init__(self):
38        """ Initialization """
39       
40        # Initialize BaseComponent first, then sphere
41        BaseComponent.__init__(self)
42       
43        ## Name of the model
44        self.name = "PolymerExclVolume"
45        ## Model description
46        self.description =""" Compute the scattering intensity from polymers with excluded volume effects.
47                scale: scale factor times volume fraction,
48                or just volume fraction for absolute scale data
49                rg: radius of gyration
50                m = Porod exponent
51                background: incoherent background
52                """
53        ## Define parameters
54        self.params = {}
55        self.params['scale']        = 1.0
56        self.params['rg']           = 60.0
57        self.params['m']            = 3.0
58        self.params['background']   = 0.0
59
60       
61        ## Parameter details [units, min, max]
62        self.details = {}
63        self.details['scale'] = ['', None, None]
64        self.details['rg'] = ['[A]', None, None]
65        self.details['m'] = ['', None, None]
66        self.details['background'] = ['[1/cm]', None, None]
67
68        ## fittable parameters
69        self.fixed=[]
70       
71        ## non-fittable parameters
72        self.non_fittable=[]
73       
74        ## parameters with orientation
75        self.orientation_params =[]
76       
77    def _polymerexclvol(self, x):
78       
79        sc = self.params['scale']
80        rg = self.params['rg']
81        mm  = self.params['m']
82        bg = self.params['background']
83   
84        nu = 1.0 / mm
85   
86        Xx = x * x * rg * rg *(2.0 * nu + 1.0) * (2.0 * nu + 2.0) / 6.0
87        onu = 1.0 / nu
88        o2nu = 1.0 /(2.0 * nu)
89        Ps =(1.0 / (nu * pow(Xx,o2nu))) * (gamma(o2nu)*gammainc(o2nu,Xx) - \
90                        1.0 / pow(Xx,o2nu) * gamma(onu)*gammainc(onu,Xx))
91
92        if x == 0:
93            Ps = 1.0
94
95        return (sc * Ps + bg);
96
97    def run(self, x = 0.0):
98        """ Evaluate the model
99            @param x: input q-value (float or [float, float] as [r, theta])
100            @return: (guinier value)
101        """
102        if x.__class__.__name__ == 'list':
103            return self._polymerexclvol(x[0])
104        elif x.__class__.__name__ == 'tuple':
105            raise ValueError, "Tuples are not allowed as input to BaseComponent models"
106        else:
107            return self._polymerexclvol(x)
108   
109    def runXY(self, x = 0.0):
110        """ Evaluate the model
111            @param x: input q-value (float or [float, float] as [qx, qy])
112            @return: guinier value
113        """
114        if x.__class__.__name__ == 'list':
115            q = math.sqrt(x[0]**2 + x[1]**2)
116            return self._polymerexclvol(x)
117        elif x.__class__.__name__ == 'tuple':
118            raise ValueError, "Tuples are not allowed as input to BaseComponent models"
119        else:
120            return self._polymerexclvol(x)
121       
122
123   
124# End of file
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