def Bingham(x, ystress=1.0, eta_bg=0.1):
    """Bingham model

    Note:

    .. math::
       \sigma=\sigma_y+\eta_{bg}\cdot\dot\gamma

    Args:
        ystress: yield stress [Pa]

        eta_bg : Background viscosity [Pa s]

    Returns:
        stress : Shear Stress, [Pa]
    """
    return ystress + eta_bg * x