207 research outputs found
Path-integral analysis of fluctuation theorems for general Langevin processes
We examine classical, transient fluctuation theorems within the unifying
framework of Langevin dynamics. We explicitly distinguish between the effects
of non-conservative forces that violate detailed balance, and non-autonomous
dynamics arising from the variation of an external parameter. When both these
sources of nonequilibrium behavior are present, there naturally arise two
distinct fluctuation theorems.Comment: 24 pages, one figur
Efficiency of using dump trucks BELAZ-75180
A comparative analysis of operational characteristics when using a different type of chassis of BELAZ-75180 mining dump trucks was performed. It is shown that the choice of the type and means of mining transport is determined by several factors, and, first of all, the characteristics of the cargo being transported, the distance of transportation, speed of flights, and the leverage for the given period. The power of vehicles and the performance of a mining dump truck depend on the scale of work (cargo turnover). The dependence of energy consumption during transport work on a quarry on the average size of pieces of rock is disclosed. The analysis of the dependence of the number of backup dump trucks on their number operating in a specific period is given. As a result of the analysis of operational characteristics, it was found that the chassis type of the BELAZ-75180 mining dump truck significantly affects its performance. © Published under licence by IOP Publishing Ltd
Analysis of the operational characteristics of the main units of BelAZ vehicles in a coal mine
A comparative analysis of the operational characteristics of the main components of BELAZ mining vehicles has been carried out. It is shown that the choice of type and means of career transport is determined by a number of factors and, first of all, by the characteristics of the transported cargo, the distance of transportation, the scale of work and the pace of their development. The power of vehicles depends on the scale of work (freight turnover), and the pace of mining operations determines the requirements for the operational reliability of career vehicles. The dependence of the dump truck failure parameter on the service life is disclosed. The analysis of the state of metal structures of structural elements of the dump truck BELAZ-7530 based on the method of non-destructive testing is given. As a result of the analysis of thermal imaging and measurements of the thickness of the walls of the motor housing, it was established that the amount of wear depends on the heating temperature of the metal structures. © Published under licence by IOP Publishing Ltd
Duality and fluctuation relations for statistics of currents on cyclic graphs
We consider stochastic motion of a particle on a cyclic graph with
arbitrarily periodic time dependent kinetic rates. We demonstrate duality
relations for statistics of currents in this model and in its continuous
version of a diffusion in one dimension. Our duality relations are valid beyond
detailed balance constraints and lead to exact expressions that relate
statistics of currents induced by dual driving protocols. We also show that
previously known no-pumping theorems and some of the fluctuation relations,
when they are applied to cyclic graphs or to one dimensional diffusion, are
special consequences of our duality.Comment: 2 figure, 6 pages (In twocolumn). Accepted by JSTA
Fluctuating work in coherent quantum systems: proposals and limitations
One of the most important goals in quantum thermodynamics is to demonstrate
advantages of thermodynamic protocols over their classical counterparts. For
that, it is necessary to (i) develop theoretical tools and experimental set-ups
to deal with quantum coherence in thermodynamic contexts, and to (ii) elucidate
which properties are genuinely quantum in a thermodynamic process. In this
short review, we discuss proposals to define and measure work fluctuations that
allow to capture quantum interference phenomena. We also discuss fundamental
limitations arising due to measurement back-action, as well as connections
between work distributions and quantum contextuality. We hope the different
results summarised here motivate further research on the role of quantum
phenomena in thermodynamics.Comment: As a chapter of: F. Binder, L. A. Correa, C. Gogolin, J. Anders, and
G. Adesso (eds.), "Thermodynamics in the quantum regime - Recent Progress and
Outlook", (Springer International Publishing). Second version: Misspell in
the title correcte
Methodology of Corrosion Testing of Nuclear and Fusion Reactors’ Materals Using TGA/DSC and MS Complex Techniques
Nowadays, nuclear power is the best that humanity has for the production and supply for cheap electric and thermal energy. The development of nuclear power takes place in a rigid competitive struggle, both with the traditional technologies of electricity production, and with alternative (renewable) sources
Fluctuation theorems for stochastic dynamics
Fluctuation theorems make use of time reversal to make predictions about
entropy production in many-body systems far from thermal equilibrium. Here we
review the wide variety of distinct, but interconnected, relations that have
been derived and investigated theoretically and experimentally. Significantly,
we demonstrate, in the context of Markovian stochastic dynamics, how these
different fluctuation theorems arise from a simple fundamental time-reversal
symmetry of a certain class of observables. Appealing to the notion of Gibbs
entropy allows for a microscopic definition of entropy production in terms of
these observables. We work with the master equation approach, which leads to a
mathematically straightforward proof and provides direct insight into the
probabilistic meaning of the quantities involved. Finally, we point to some
experiments that elucidate the practical significance of fluctuation relations.Comment: 48 pages, 2 figures. v2: minor changes for consistency with published
versio
Recurrent rhinovirus detections in children following a rhinovirus-induced wheezing exacerbation: A retrospective study
Introduction: It is unclear if children with a rhinovirus (RV)-induced wheezing exacerbation are more susceptible to viruses longitudinally, and whether a parental history of asthma and/or allergy impacts their susceptibility. The objective of this study was to determine if RV, RV-A and RV-C related wheezing exacerbations in children were associated with prior or subsequent viral detections and investigate the role of parental history of asthma and allergy. Materials and methods: Children presenting to hospital with acute wheeze were prospectively recruited and tested for respiratory viruses. Data on viruses detected in other respiratory samples (May 1997 to December 2012) were collected from hospital microbiology records and additional RV testing was performed on stored hospital respiratory samples (September 2009 to December 2012). A positive parental history was defined as either parent with self-reported asthma and/or allergy. Results: At recruitment, RV was detected in 69.2% of samples from children with an acute wheezing episode (n=373, 0–16 years of age), with RV-C the most common virus (65.5%). Children with a history of parental asthma and/or allergy and RV at recruitment had a 14-fold increased incidence rate ratio (IRR) of subsequent RV detection (IRR 14.0, 95% CI 1.9–104.1; p=0.01) compared with children without RV at recruitment. Children without this parental history had a reduced incident rate ratio for samples assessed during this time (IRR 0.5, 95% CI 0.3–0.9; p=0.03). Conclusion: Children with a parental history of asthma and/or allergy may become more susceptible to recurrent symptomatic RV infections
Explanation of the Gibbs paradox within the framework of quantum thermodynamics
The issue of the Gibbs paradox is that when considering mixing of two gases
within classical thermodynamics, the entropy of mixing appears to be a
discontinuous function of the difference between the gases: it is finite for
whatever small difference, but vanishes for identical gases. The resolution
offered in the literature, with help of quantum mixing entropy, was later shown
to be unsatisfactory precisely where it sought to resolve the paradox.
Macroscopic thermodynamics, classical or quantum, is unsuitable for explaining
the paradox, since it does not deal explicitly with the difference between the
gases. The proper approach employs quantum thermodynamics, which deals with
finite quantum systems coupled to a large bath and a macroscopic work source.
Within quantum thermodynamics, entropy generally looses its dominant place and
the target of the paradox is naturally shifted to the decrease of the maximally
available work before and after mixing (mixing ergotropy). In contrast to
entropy this is an unambiguous quantity. For almost identical gases the mixing
ergotropy continuously goes to zero, thus resolving the paradox. In this
approach the concept of ``difference between the gases'' gets a clear
operational meaning related to the possibilities of controlling the involved
quantum states. Difficulties which prevent resolutions of the paradox in its
entropic formulation do not arise here. The mixing ergotropy has several
counter-intuitive features. It can increase when less precise operations are
allowed. In the quantum situation (in contrast to the classical one) the mixing
ergotropy can also increase when decreasing the degree of mixing between the
gases, or when decreasing their distinguishability. These points go against a
direct association of physical irreversibility with lack of information.Comment: Published version. New title. 17 pages Revte
THERMOELECTRIC PROPERTIES OF HOT-PRESSED p-TYPE Mg2Si0.3Sn0.7 SOLID SOLUTION
It is shown that thermoelectric energy conversion which gives the possibility for utilizing a low potential heat is one of the ways for adoption of energy-saving technologies; and semiconductor materials with p-type and n-type conductivities having high thermoelectric figure of merit are necessary for operation of thermoelectric generators. The paper deals with possibility of usage of the p-Mg2Si0.3Sn0.7 solid solution (with a nanostructured modification) as a couple for the well studied thermoelectric material based on n-Mg2Si-Mg2Sn. A technological scheme for fabrication of heavily doped Mg2Si0.3Sn0.7 solid solution of p-type by hot pressing from nanopowder is developed. The given technology has made it possible to reduce duration of a homogeneous material fabrication and has improved its physical and chemical properties. The samples were made by three ways: direct fusion for polycrystals fabrication; hot pressing from microparticles; nanostructuring, i.e. hot pressing from nanoparticles. By X-ray diffraction it is shown that sizes of structural elements in the fabricated samples are about 40 nm. The probe technique is used for measurement of electric conductivity and Seebeck coefficient. The stationary absolute method is used for measurement of thermal conductivity. Thermoelectric figure of merit is defined by measured values of kinetic coefficients in the temperatures range of 77 – 800 K. It was demonstrated, that electric conductivity, Seebeck coefficient and the power factor do not depend practically on a way of solid solution preparation. Thermal conductivity of samples pressed from nanoparticles has appeared to be higher, than of samples, obtained by direct fusion; i.e. in this case nanostructuring has not led to increase of thermoelectric figure of merit. The conclusion is drawn, that polycrystalline semiconductor Mg2Si0.3Sn0.7 can be used as a p-branch for a thermoelectric generator though nanostructuring has not led to the figure of merit growth. The assumption is made, that thermoelectric figure of merit improvement can be expected at the further reduction of the nanograins size
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