  The Curzon-Ahlborn (CA) cycle is a paradigmatic model of endoreversible heat
engines, which yields the so-called CA efficiency as the efficiency at maximum
power. Due to the arbitrariness of the relationship between the steady
temperature and the time taken for the isothermal process of the CA cycle, the
constructions of the CA cycle on the thermodynamic plane are not unique. Here,
we give some of the detailed constructions of the CA cycle on the thermodynamic
plane, using an ideal gas as a working substance. It is shown that these
constructions are equal to each other in the maximum power regime in the sense
that they achieve the best trade-off between the work and the inverse
cycle-time, known as the Pareto front in multi-objective optimization problems.
