def k_small(self):
        """
        Small-angle driving force term: :math:`r'' = -k_{small} r`.

        Note: :math:`k_{small} = \\frac{k}{2{\\sigma_r^2}}`
        """
        return self.k * _np.sqrt(2/_np.pi) / self.sig_y
def k_small(self):
        """
        Small-angle driving force term: :math:`r'' = -k_{small} r`.

        Note: :math:`k_{small} = \\frac{k}{2{\\sigma_r^2}}`
        """
        return self.k * _np.sqrt(2/_np.pi) / self.sig_y
def k_small ( self ) : return self . k * _np . sqrt ( 2 / _np . pi ) / self . sig_y
Small-angle driving force term: :math:`r'' = -k_{small} r`.

        Note: :math:`k_{small} = \\frac{k}{2{\\sigma_r^2}}`
Small - angle driving force term : : math : r = - k_ { small } r .