1,721,154 research outputs found
L'insegnamento della matematica nella Riforma scolastica di Paolo Boselli del 1909
No full textA law involving science curricula, proposed about one century ago, is analysed and its modern and still
valid interpretation of science teaching and of the relationship between school education and the productive
world is highlighted
Statistical approach of the irreversible entropy variation
No full textThe constructal theory is based on the thought that flow architecture is a consequence of a principle of maximization of flow access, in time, and in flow configuration that is free to be realised. The principle of maxima for the variation of the entropy due to irreversibility represents a general principle of investigation for the stability of open systems, by which it is possible to predict some macroscopic shapes, originated by the spatial organisation, in Nature, both in living and in non-living objects. Its statistical meaning has recently been introduced. Here a statistical and dynamical interpretation for the entropy due to irreversibility is proposed as a foundation of the constructal theory
Transport processes and irreversible thermodynamics analysis in tumoral systems
No full textCells are chemical engines in which specific ordered chemical reactions occur. Cancer can be described as an open complex dynamic and self-organizing system. Entropy generation approach has been used to evaluate the biochemical and biophysical conditions of the stationary states for tumoral cells, in relation to the transport processes through their
membrane. The tumoral systems can assume all the values of volume, temperature, chemical reaction rate and the time of chemical reaction, in the range of stationary conditions. This range can be evaluated by the principle of extrema variation of the entropy generation.
Outside this range, cancer cannot develop and dies. The geometrical characteristics are fundamental in the growth of cancer. The fractal dimensions are discussed in this analysis and the geometry of cancer is related to the entropy generation. A possible anticancer thermodynamic approach has been suggested
Time, irreversibility and cosmological throttling
Full text linkIn 2011 Perlmutter, Schmidt, and Reiss discovered that the expansion of the
Universe is accelerating. This finding is contrary to the expectation that gravity should
slow this expansion. This discovery raises fundamental questions about dark energy, which
constitutes about three-fourths of the Universe’s mass-energy and is responsible for driving
this acceleration. In this paper, we propose a thermodynamic perspective based on a possible
cosmological Joule-Thomson effect, supported by the significant entropy content of the
Universe, primarily from black-body radiation. The evolution of entropy in an open system
involves exchanges with the environment and is characterised by two components: entropy
flow and internal entropy production. Understanding irreversible processes is essential
to grasping these dynamics, as they link order and disorder. This approach shifts our
understanding of thermodynamics, revealing that the creation of order is associated with
non-equilibrium conditions, while disorder often corresponds to stable equilibrium. This
perspective calls for a revaluation of how systems in Nature are analysed, emphasising the
intricate relationship between order, disorder and the definition of time
Maximum or minimum entropy generation for open systems?
No full textEntropy generation is analysed and obtained from the entropy balance for open systems, considering the lifetime of the natural real process. The Lagrangian approach is discussed in order to develop an analytical method to obtain the stationary states of the open irreversible systems. The stationary conditions of the open systems are obtained in relation to the entropy generation and its maximum principle. An analysis of both minimum and maximum entropy generation is proposed, suggesting that they are two different viewpoints of the same aspect: the first is related to the system, while the second is related to the interaction between the system and the environment
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