منابع مشابه
The unlikely Carnot efficiency.
The efficiency of an heat engine is traditionally defined as the ratio of its average output work over its average input heat. Its highest possible value was discovered by Carnot in 1824 and is a cornerstone concept in thermodynamics. It led to the discovery of the second law and to the definition of the Kelvin temperature scale. Small-scale engines operate in the presence of highly fluctuating...
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Publications are increasingly (often wrongly) being used as research outputs. Furthermore, ‘impacts’ of such publications are often (wrongly as well) measured using ‘citations’. Popular metric, like the ‘Hirsch index’, or ‘h-index’ is used as yardstick for judging the quality of individual researchers. However, there are many controversies around it, whether it is a good yardstick, which could ...
متن کاملStochastic pumping of heat: approaching the Carnot efficiency.
Random noise can generate a unidirectional heat current across asymmetric nano-objects in the absence (or against) a temperature gradient. We present a minimal model for a molecular-level stochastic heat pump that may operate arbitrarily close to the Carnot efficiency. The model consists a fluctuating molecular unit coupled to two solids characterized by distinct phonon spectral properties. Hea...
متن کاملEfficiency at maximum power of low-dissipation Carnot engines.
We study the efficiency at maximum power, η*, of engines performing finite-time Carnot cycles between a hot and a cold reservoir at temperatures Th and Tc, respectively. For engines reaching Carnot efficiency ηC=1-Tc/Th in the reversible limit (long cycle time, zero dissipation), we find in the limit of low dissipation that η* is bounded from above by ηC/(2-ηC) and from below by ηC/2. These bou...
متن کاملEfficiency statistics at all times: Carnot limit at finite power.
We derive the statistics of the efficiency under the assumption that thermodynamic fluxes fluctuate with normal law, parametrizing it in terms of time, macroscopic efficiency, and a coupling parameter ζ. It has a peculiar behavior: no moments, one sub-, and one super-Carnot maxima corresponding to reverse operating regimes (engine or pump), the most probable efficiency decreasing in time. The l...
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ژورنال
عنوان ژورنال: Nature Communications
سال: 2014
ISSN: 2041-1723
DOI: 10.1038/ncomms5721