Entropy Pump Research Articles

Power Conversion and Its Efficiency in Thermoelectric Materials

The basic principles of thermoelectrics rely on the coupling of entropy and electric charge. However, the long-standing dispute of energetics versus entropy has long paralysed the field. Herein, it is shown that treating entropy and electric charge in a symmetric manner enables a simple transport equation to be obtained and the power conversion and its efficiency to be deduced for a single thermoelectric material apart from a device. The material’s performance in both generator mode (thermo-electric) and entropy pump mode (electro-thermal) are discussed on a single voltage-electrical current curve, which is presented in a generalized manner by relating it to the electrically open-circuit voltage and the electrically closed-circuited electrical current. The electrical and thermal power in entropy pump mode are related to the maximum electrical power in generator mode, which depends on the material’s power factor. Particular working points on the material’s voltage-electrical current curve are deduced, namely, the electrical open circuit, electrical short circuit, maximum electrical power, maximum power conversion efficiency, and entropy conductivity inversion. Optimizing a thermoelectric material for different working points is discussed with respect to its figure-of-merit and power factor. The importance of the results to state-of-the-art and emerging materials is emphasized.

ON THE PHYSICAL MEANING OF THE COEFFICIENT OF FRICTION UNDER CONDITIONS OF ABNORMALLY LOW FRICTION AND WEAR

The theoretical studies of tribosystems (TS) operating under conditions of abnormally low friction and wear are given. On the basis of the analysis of the mechanisms of dissipation of external energy, as factors of friction reduction in different areas of nature, the role of the wave component of friction force is clarified. Under certain thermodynamic conditions, a sufficiently large wave component of the friction force is formed in the TS, which significantly reduces the molecular-mechanical. The wave component Fw of the friction force Ffr is the «entropy pump» that converts the non-compensated external friction into the internal friction and accumulates the internal energy in the elastic-plastic layer of the rheological model of Shvedov tribosystem construction. The physical meaning of the friction coefficient for TS operating under conditions of normal mechanochemical wear and abnormally low friction and wear has been determined. It is determined that the main cause of the tribosystems transition to abnormally low friction and wear is the rheological properties of the tribosystem surface layer. In an anomalous-low friction and wear mode tribosystem, an equilibrium and inverse change of some insignificant amount of energy without work is possible. TS heat dissipation in this case approaches zero. When the external friction conditions change, the degree of excitation of tribosystem n, which depends on the number of mechanical quanta, changes. Any change in the tribosystem that puts it off balance, according to Le Chatelier principle, initiates in it processes that try to return it to its original position. For these processes in the developed model is responsible module of canonical energy distribution, which is regulated by microgeometry of the surface layer of TS. It is established that the condition of achieving abnormally low friction and wear is the equality of robots that perform external and internal forces in terms of contact interaction. Structural-energy approach to contact interaction allowed to establish the physical meaning of the coefficient of friction, which generally characterizes the work of external and internal forces in the path of friction tribosystems.

A Silicon PUF Based Entropy Pump

The security level of many cryptographic protocols and secure systems is determined by the strength of the cryptographic keys, which can be measured by entropy. Finding an entropy source that can generate secure keys with high entropy is a very challenging problem and it is normally associated with high cost. Instead of looking for a low-cost entropy source, we study in this article how to improve the entropy generated by a low-entropy source. Unlike the existing approaches based on hash function or cryptographic protocols, our solution leverages the intrinsic randomness in physical properties such as silicon physical unclonable functions (PUFs). Silicon PUF is a piece of circuitry that can capture certain intrinsic on-chip variations that were introduced during the chip fabrication process. It is generally believed that such variations are random and unpredictable. In this article, we demonstrate that the silicon PUF can be used as an effective entropy pump to boost low-entropy keys. Our approach is based on a recently developed highly flexible ring oscillator (RO) PUF. When we use the low-entropy key to configure the RO PUF, we find that the corresponding PUF response exhibits higher entropy, which means that the key's entropy has been improved. We implement our design on Nexys 4 Artix-7 FPGA board and demonstrate that the configurable PUF structure can successfully enhance the entropy of input keys. Compared to the other entropy enhancement methods, our PUF based entropy pump has the lowest hardware cost. Moreover, we apply this in a password enhancement application to provide robust high entropy passwords that can resist attacks such as the pre-compute attack.

Brownian motion surviving in the unstable cubic potential and the role of Maxwell's demon.

The trajectories of an overdamped particle in a highly unstable potential diverge so rapidly, that the variance of position grows much faster than its mean. A description of the dynamics by moments is therefore not informative. Instead, we propose and analyze local directly measurable characteristics, which overcome this limitation. We discuss the most probable particle position (position of the maximum of the probability density) and the local uncertainty in an unstable cubic potential, V(x)∼x^{3}, both in the transient regime and in the long-time limit. The maximum shifts against the acting force as a function of time and temperature. Simultaneously, the local uncertainty does not increase faster than the observable shift. In the long-time limit, the probability density naturally attains a quasistationary form. We interpret this process as a stabilization via the measurement-feedback mechanism, the Maxwell demon, which works as an entropy pump. The rules for measurement and feedback naturally arise from the basic properties of the unstable dynamics. All reported effects are inherent in any unstable system. Their detailed understanding will stimulate the development of stochastic engines and amplifiers and, later, their quantum counterparts.

Perspectives from energetic-thermodynamic analysis of land use systems: Perspektiven der energetisch-thermodynamischen analyse von landnutzungssystemen

Intensive agricultural production leads to degradation of the environment and consequently to decrease of quality of agricultural products. Therefore, there is a need to develop a universal environmental index, which could give information about the ‘environmental quality’ of agricultural products. From the physical point of view environmental degradation can be linked with the concept of entropy and therefore the main goal of the project is: to develop a new method, based on thermodynamics theory of ecosystems, for evaluation of the environmental degradation caused by the intensification of agriculture and to support and ensure ecological and sustainable public policies for agricultural land use. In this project the Pimental theory of eco-energetic analysis of ecosystems will be used. For the analysis and balance of entropy of agricultural ecosystems in relation to the referenced (natural) ecosystem, the concept of ‘entropy pump’ will be used. The overproduction of entropy (not balanced by the ‘entropy pump’ and caused by additional anthropogenic energy added into the ecosystem) causes the environmental changes (mainly soil degradation). Thus, the entropy can be used as a parameter to develop an index of both environmental degradation or environmental sustainability.

Thermodynamics and ecology

How to apply thermodynamic methods and concepts to ecology, how to describe the ecosystem's behaviour in terms of physics (and particularly, thermodynamics), what kind of physical criteria can be used for estimation of anthropogenic impact on ecosystems? — I try to answer these questions in this manuscript. From the viewpoint of thermodynamics, any ecosystem is an open system far from thermodynamic equilibrium, in which entropy production is balanced by the outflow of entropy to the environment. I suggest the ‘entropy pump’ hypothesis: the climatic, hydrological, soil and other environmental conditions are organised in such a way that only a natural ecosystem which is specific for these conditions can be in the dynamic equilibrium (steady-state). In the framework of this hypothesis I can calculate the entropy production for the ecosystem under anthropogenic stress. This approach was applied to the analysis of crop production in Hungary in the 1980s. Considering systems far from thermodynamic equilibrium we can prove that the so-called exergy is a functional of a dissipative function, which is undertaken along the trajectory from a thermodynamic equilibrium to a dynamic one. It was shown there is a close connection between the measure of additional information (Kullback's measure) and exergy.

Increasing entropy of biological systems.

FOLLOWING the recent correspondence between Wool-house1 and Popper2 concerning the apparently low entropy of biological systems, Campbell3 suggests that this low entropy can be achieved by an entropy pump, which he describes and then identifies with the mechanism of natural selection. The purpose of this communication is to propose a very different role for natural selection, which is still controlled by natural selection.

Entropy and evolution.

CAMPBELL'S expressed aim1 is “to describe the entropy pump whereby the species of living matter not only prevent a drop into a position of greater positive entropy at each generation, but may in fact acquire more negentropy as their reproduction continues”. This is attempted by recourse to the example of a codfish laying a million eggs the entropy content of whose genomes shows a normal distribution about a mean value in accordance with the second law of thermodynamics. On one tail of this distribution curve will be a small percentage of eggs with an entropy content equal to or less than that of the parents. There follows the crucial sentence: “These remarkable ones are most likely to grow up and repeat the reproductive process”. What follows in Campbell's communication is unexceptionable provided that this sentence is true. But what is the evidence that those eggs which are “most likely to grow and repeat the reproductive process” are those whose genomes have a lower entropy content than those of the parents ? It is at this point that the author merely evades one of the most important questions at issue in the earlier correspondence2–4. The genome may be regarded as a series of DNA molecules functioning as templates. The thermodynamic entropy content of these molecules is a function of the arrangement of the atoms, conventionally expressed as k. log D where k is the Boltzmann constant and D is a measure of the atomic disorder. A single alteration in the relative positions of adjacent nucleotide bases could convert a crucial part of the genome code to nonsense so that its capacity to support development was lost, but this could occur without an increase, indeed even with a decrease, in the thermodynamic entropy content of the genome molecules5. Stated in a more general way, this is the problem of the relationship between the amount of developmentally meaningful organization in the genome (we will call this the information content) and its entropy content. There are two problems here: first, the definition and quantization of the information content of the genome and, second, the nature of its relationship to the thermodynamic entropy content. One avenue of enquiry which offers hope in this situation would seem to be the information theory analogy.

Biological entropy pump.

THE recent exchange between Woolhouse1 and Popper2 presents the enigma of the low entropy content of living systems. The means whereby their rapid decay into the inert state of “equilibrium” is avoided are serious problems to the theoretical biologist. It is, of course, to Schrodinger3 that we owe the classic analysis of biological entropy. It was the source of negentropy which Schrodinger was unable to discover, as the recent discussion indicates. That from, one generation to the next, a complex coding and decoding can occur without net loss of negentropy is problem enough, but in the large sequence of generations through geological time, we see that, if anything, the informational system becomes fuller and the organization of many species more improbable. It is my purpose here to show what I believe to be the answer to this seeming paradox and to describe the “entropy pump” whereby the species of living matter not only prevent a drop into a position of greater positive entropy at each generation, but may in fact acquire more negentropy as their reproduction continues. This will involve only principles widely known and easily defended.