def Tracer_AD_Pe(t_seconds, t_bar, C_bar, Pe):
    """Used by Solver_AD_Pe. All inputs and outputs are unitless. This is the
    model function, f(x, ...). It takes the independent variable as the
    first argument and the parameters to fit as separate remaining arguments.

    :param t_seconds: List of times
    :type t_seconds: float list
    :param t_bar: Average time spent in the reactor
    :type t_bar: float
    :param C_bar: Average concentration ((mass of tracer)/(volume of the reactor))
    :type C_bar: float
    :param Pe: The Peclet number for the reactor.
    :type Pe: float

    :return: The model concentration as a function of time
    :rtype: float list

    :Examples:

    >>> from aguaclara.research.environmental_processes_analysis import Tracer_AD_Pe
    >>> from aguaclara.core.units import unit_registry as u
    >>> Tracer_AD_Pe([1, 2, 3, 4, 5]*u.s, 5*u.s, 10*u.mg/u.L, 5)
    <Quantity([0.25833732 3.23793989 5.8349833  6.62508831 6.30783131], 'milligram / liter')>

    """
    return C_bar*E_Advective_Dispersion(t_seconds/t_bar, Pe)
Used by Solver_AD_Pe. All inputs and outputs are unitless. This is the
    model function, f(x, ...). It takes the independent variable as the
    first argument and the parameters to fit as separate remaining arguments.

    :param t_seconds: List of times
    :type t_seconds: float list
    :param t_bar: Average time spent in the reactor
    :type t_bar: float
    :param C_bar: Average concentration ((mass of tracer)/(volume of the reactor))
    :type C_bar: float
    :param Pe: The Peclet number for the reactor.
    :type Pe: float

    :return: The model concentration as a function of time
    :rtype: float list

    :Examples:

    >>> from aguaclara.research.environmental_processes_analysis import Tracer_AD_Pe
    >>> from aguaclara.core.units import unit_registry as u
    >>> Tracer_AD_Pe([1, 2, 3, 4, 5]*u.s, 5*u.s, 10*u.mg/u.L, 5)
    <Quantity([0.25833732 3.23793989 5.8349833  6.62508831 6.30783131], 'milligram / liter')>