From 7949d382be66df4920eb4a35e4938d11ffe99587 Mon Sep 17 00:00:00 2001
From: "Joachim Wuttke (h)" <j.wuttke@fz-juelich.de>
Date: Sat, 16 Apr 2016 10:39:41 +0200
Subject: [PATCH] correct description of Ripple1 computation
---
Core/FormFactors/FormFactorRipple1.cpp | 31 +++++++++++++-------------
Doc/UserManual/FormFactors.tex | 12 +++++-----
2 files changed, 22 insertions(+), 21 deletions(-)
diff --git a/Core/FormFactors/FormFactorRipple1.cpp b/Core/FormFactors/FormFactorRipple1.cpp
index 8e4e0203415..010f7f5436f 100644
--- a/Core/FormFactors/FormFactorRipple1.cpp
+++ b/Core/FormFactors/FormFactorRipple1.cpp
@@ -21,14 +21,14 @@
#include <cmath>
-using namespace BornAgain;
+static complex_t I(0.,1.);
FormFactorRipple1::FormFactorRipple1(double length, double width, double height)
: m_width(width)
, m_height(height)
, m_length(length)
{
- setName(FFRipple1Type);
+ setName(BornAgain::FFRipple1Type);
check_initialization();
init_parameters();
@@ -57,9 +57,9 @@ bool FormFactorRipple1::check_initialization() const
void FormFactorRipple1::init_parameters()
{
clearParameterPool();
- registerParameter(Width, &m_width, AttLimits::n_positive());
- registerParameter(Height, &m_height, AttLimits::n_positive());
- registerParameter(Length, &m_length, AttLimits::n_positive());
+ registerParameter(BornAgain::Width, &m_width, AttLimits::n_positive());
+ registerParameter(BornAgain::Height, &m_height, AttLimits::n_positive());
+ registerParameter(BornAgain::Length, &m_length, AttLimits::n_positive());
}
FormFactorRipple1 *FormFactorRipple1::clone() const
@@ -80,9 +80,9 @@ double FormFactorRipple1::getRadius() const
//! Integrand for complex formfactor.
complex_t FormFactorRipple1::Integrand(double Z) const
{
- complex_t iqZ = complex_t(0.0, 1.0)*m_q.z()*Z;
+ complex_t iqZ = I*m_q.z()*Z;
complex_t aa = std::acos(2.0*Z/m_height - 1.0);
- return std::exp(iqZ)*aa*MathFunctions::sinc(aa*m_q.y()*m_width/(Units::PI2));
+ return std::exp(iqZ)*aa*MathFunctions::sinc( aa*m_q.y()*m_width/(Units::PI2) );
}
//! Complex formfactor.
@@ -90,17 +90,18 @@ complex_t FormFactorRipple1::evaluate_for_q(const cvector_t& q) const
{
m_q = q;
complex_t factor = m_length*MathFunctions::sinc(m_q.x()*m_length*0.5)*m_width/Units::PI;
- complex_t aaa = m_q.y()*m_width/(Units::PI2);
- complex_t aaa2 = aaa*aaa;
// analytical expressions for some particular cases
- if (0.0==m_q.y() && 0.0==m_q.z())
- return factor*Units::PID2*m_height;
- else if (0.0==m_q.z() && 1.0 == aaa2)
- return factor*Units::PID4*m_height;
- else if (0.0==m_q.z())
+ if ( m_q.z()==0. ) {
+ if( m_q.y()==0. )
+ return factor*Units::PID2*m_height;
+ complex_t aaa = m_q.y()*m_width/(Units::PI2);
+ complex_t aaa2 = aaa*aaa;
+ if ( aaa2==1. )
+ return factor*Units::PID4*m_height;
return factor*Units::PID2*m_height*MathFunctions::sinc(m_q.y()*m_width*0.5)/(1.0-aaa2);
-
+ }
+
// numerical integration otherwise
complex_t integral = mP_integrator->integrate(0, m_height);
return factor*integral;
diff --git a/Doc/UserManual/FormFactors.tex b/Doc/UserManual/FormFactors.tex
index be96875cc26..275a32c664d 100644
--- a/Doc/UserManual/FormFactors.tex
+++ b/Doc/UserManual/FormFactors.tex
@@ -1302,19 +1302,19 @@ with the parameters
\item \texttt{height}, $H$.
\end{itemize}
-The ripple is modelled as a surface $z=f(y)$ with
+The ripple is modelled as a surface
\begin{equation*}
- f(z) = \frac{H}{2}\left[ 1 + \cos\frac{2\pi y}{W} \right].
+ Z(y) = \frac{H}{2}\left[ 1 + \cos\frac{2\pi y}{W} \right].
\end{equation*}
\paragraph{Form factor, volume, horizontal section}\strut\\
-Using the inverse profile $y=\pm f^{-1}(z)$ with
+Using the inverse profile
\begin{equation*}
- f^{-1}(z) = \frac{W}{2\pi}\text{arccos}\left( \frac{2z}{H}-1 \right),
+ Y(z) = \frac{W}{2\pi}\text{arccos}\left( \frac{2z}{H}-1 \right),
\end{equation*}
the form factor is computed by numeric integration:
\begin{equation*}
-F =\frac{LW}{\pi} \sinc\left(\frac{q_xL}{2}\right)
- \int_0^H\!\d z\,\e^{iq_zz}\, f^{-1}(z)\sinc\left[\frac{q_yW}{2\pi} f^{-1}(z)\right].
+F = L \sinc\left(\frac{q_xL}{2}\right)
+ \int_0^H\!\d z\,\e^{iq_zz}\, 2Y(z)\sinc\left(q_y Y(z)\right).
\end{equation*}
\begin{equation*}
V = \dfrac{L W H}{2},
--
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