def solidsFluxPembNose(dp, db, emf, umf, us):
    """
    Calculates the solids entrainment flux for the surface of a bubbling bed
    with the bubble nose ejection model of Pemberton and Davidsion (Chem. Eng.
    Sci., 1986, 41, pp. 243-251). This model is suitable if there is a single
    bubble in the bed.

    Parameters
    ----------
    dp : float
        Particle diameter [m]
    db : float
        Bubble diameter [m]
    emf : float
        Void fraction at minimum fluidization [-]
    umf : float
        Minimum fluidization velocity [m/s]
    us : float
        Superficial gas velocity [m/s]

    Returns
    -------
    F0 : float
        Solids entrainment flux at the top of the bed [kg/m^2/s]
    """
    F0 = 3.0 * dp / db * (1 - emf) * (us - umf)
    return F0
