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The study of local stability of thermal engines modeled as an
endoreversible Curzon and Ahlborn cycle is shown. It is assumed a non-linear
heat transfer for heat fluxes in the system (engine + environments). A semisum
of two expressions of the efficiency found in the literature of finite time thermodynamics
for the maximum power output regime is considered in order to make the
analysis. Expression of variables for local stability and power output is found
even graphic results for important parameters in the analysis of stability, and
a phase plane portrait is shown.
We have determined a value for the 1S0 neutron-neutron scattering length (ann). The scattering length result is presented for the extended-soft-core (ESC04) interaction. The value obtained in the present work is ann = -18.6249 fm. The method of solution of the radial Schr?dinger equation with nonlocal potential for nucleonnucleon pairs is described and the result is consistent with previous determinations of ann = -18.63 ± 0.10 (statistical) ± 0.44 (systematic) ± 0.30 (theoretical) fm. The nonlocal potentials are of the central, spin-spin, spin-or-bital, and tensor type. The analysis from the ESC04 interaction is done at energies 0 ￡ Tlab ￡ 350 MeV. We compare the present result with experimental S-wave phase shifts analysis and agreement is found.
An analysis of the Stirling and Ericsson cycles from the point of view of the finite time thermodynamics is made by assuming the existence of internal irreversibilities in an engine modeled by these cycles, and the ideal gas as working substance is considered. Expressions of efficiency in both regimes maximum power output and maximum ecological function are also shown. Appropriate variables are introduced so that the objective functions, namely power output, ecological function and efficiency can be functions of the reservoirs temperatures ratio and certain “measurable” parameters as a thermal conductance, the general constant of gases and the compression ratio of the cycle. Several results from the finite time thermodynamics literature are used, so that the developed methodology leads directly to appropriate expressions of the objective functions in order to simplify the optimization process.