Symmetry Relations for Trajectories of a Brownian Motor

A Brownian Motor is a nanoscale or molecular device that combines the effects of thermal noise, spatial or temporal asymmetry, and directionless input energy to drive directed motion. Because of the input energy, Brownian motors function away from thermodynamic equilibrium and concepts such as linear response theory, fluctuation dissipation relations, and detailed balance do not apply. The {\em generalized} fluctuation-dissipation relation, however, states that even under strongly thermodynamically non-equilibrium conditions the ratio of the probability of a transition to the probability of the time-reverse of that transition is the exponent of the change in the internal energy of the system due to the transition. Here, we derive an extension of the generalized fluctuation dissipation theorem for a Brownian motor for the ratio between the probability for the motor to take a forward step and the probability to take a backward step

Molecular random walks and invariance group of the Bogolyubov equation

Statistics of molecular random walks in a fluid is considered with the help of the Bogolyubov equation for generating functional of distribution functions. An invariance group of solutions to this equation as functions of the fluid density is discovered. It results in many exact relations between probability distribution of the path of a test particle and its irreducible correlations with the fluid. As the consequence, significant restrictions do arise on possible shapes of the path distribution. In particular, the hypothetical Gaussian form of its long-range asymptotic proves to be forbidden (even in the Boltzmann-Grad limit). Instead, a diffusive asymptotic is allowed which possesses power-law long tail (cut off by ballistic flight length).Comment: 23 pages, no figures, LaTeX AMSART, author's translation from Russian of the paper accepted to the TMPh (``Theoretical and mathematical physics''

Experience of Pseudospark Switch Operation in Pulse Power Applications

The paper demonstrates the results of TDI1-200k/25SN-P pseudospark switch (PSS) developed by Russian company "Pulsed Technologies Ltd" application. PSS was used in pulsed power unit intended for electric-discharge fracture of rocks and concrete blocks and splitting off from monolith. The pulsed power unit has a pulse current generator with the capacity of 560 [mu]F, stored energy of up to 63 kJ, operating voltage of up to15 kV, current pulse amplitude of up to 200 kA and pulse duration more than 200 [mu]sec. The study also shows the current waveforms determined in the short-circuit experiment of the pulse current generator and in the experiments of the electric-discharge fragmentation of concrete at the charging voltage of 13 kV. PSS was operated in ringing single-pulse mode with the exceedance of more than two maximum permissible parameters: current pulse amplitude, current pulse duration and maximum pulse energy. Internal electrode erosion of PSS is shown and possible reasons of asymmetric current feed are discussed

Метод для расчётных оценок характеристик безопасности железнодорожной автоматики

The problem of quantitative analysis of safety of microelectronic and microprocessor systems of railway automation and telemechanics is considered. The problem remains relevant, since the subject of safety analysis is rarely occurring, but extremely dangerous events. The risk and significance of failure are selected as the main safety features of these systems. The way to identify a failure was chosen according to MILSTD‑1629A standard, as the most adequate.Calculated expressions for significance of a failure are proposed. The probability of a dangerous failure is calculated by the method of model analysis. It is proposed to calculate the probability of a failure further developing into an accident using scenario analysis methods by constructing event trees. Calculated ratios for ratings of violations are suggested, allowing to compare dangerous failures and emergency sequences developed from a failure. The risk assessment of operation of railway automation systems was selected not related to economic categories, and thus convenient for rationing. It is based on probabilistic concepts of the nature of risk and is calculated using the methods of probability theory. The developed design ratios and models make it possible to analyze performance of the functions of train traffic safety systems by methods common to control systems, at the same time reflecting the features of operation of railway automation.Рассматривается проблема количественного анализа безопасности микроэлектронных и микропроцессорных систем железнодорожной автоматики и телемеханики. Проблема остаётся актуальной, так как предметом анализа безопасности являются редко происходящие, но очень опасные события. В качестве основных характеристик безопасности выбраны риск и значимость отказа. Определение значимости отказа выбрано по стандарту MIL-STD‑1629A как наиболее адекватное.Приведены расчётные выражения для значимости отказа. Вероятность возникновения опасного отказа получена методом модельного анализа. Вероятность перерастания отказа в аварию предлагается рассчитывать методами сценарного анализа путём построения древа событий. Приведены расчётные соотношения для рейтингов нарушений, позволяющие сравнивать опасные отказы и аварийные последовательности, в которые отказ может перерасти. Оценка риска эксплуатации систем железнодорожной автоматики выбрана не связанной с экономическими категориями, удобная для нормирования. Она основана на вероятностных представлениях о природе риска и рассчитывается методами теории вероятности. Разработанные расчётные соотношения и модели позволяют анализировать выполнение функций систем обеспечения безопасности движения поездов методами, общими для систем управления, но вместе с тем отражающими особенности работы железнодорожной автоматики

"Flora of Russia" on iNaturalist: a dataset

The "Flora of Russia" project on iNaturalist brought together professional scientists and amateur naturalists from all over the country. Over 10,000 people were involved in the data collection. Within 20 months, the participants accumulated 750,143 photo observations of 6,857 species of the Russian flora. This constitutes the largest dataset of open spatial data on the country’s biodiversity and a leading source of data on the current state of the national flor

Minimal Work Principle and its Limits for Classical Systems

The minimal work principle asserts that work done on a thermally isolated equilibrium system, is minimal for the slowest (adiabatic) realization of a given process. This principle, one of the formulations of the second law, is operationally well-defined for any finite (few particle) Hamiltonian system. Within classical Hamiltonian mechanics, we show that the principle is valid for a system of which the observable of work is an ergodic function. For non-ergodic systems the principle may or may not hold, depending on additional conditions. Examples displaying the limits of the principle are presented and their direct experimental realizations are discussed.Comment: 4 + epsilon pages, 1 figure, revte

Вероятностный метод нормирования ЭМС железнодорожной автоматики

[For the English abstract and full text of the article please see the attached PDF-File (English version follows Russian version)].ABSTRACT The scientific and technical problem of rationing of noise immunity level and rigidity of tests of railway automation and telemechanics is considered. The problem remains topical in connection with the widespread introduction of microprocessor and computer automation systems that ensure train traffic safety. The task is to find the norms of noise immunity on the basis of taking into account the probabilistic nature of the level of interference and the level of noise immunity of the hardware element base. The «load-stability» method was used to obtain equations for determining the normalized value of noise immunity. The norms calculated by the proposed method allow optimizing rigidity of tests and associated design solutions. Keywords: railway, automation and telemechanics systems, electromagnetic compatibility, rationing, probabilistic approach, test methods, probability of failure, train traffic safety.Текст аннотации на англ. языке и полный текст статьи на англ. языке находится в прилагаемом файле ПДФ (англ. версия следует после русской версии).Рассматривается научно-техническая проблема нормирования уровня помехоустойчивости и жёсткости испытаний железнодорожной автоматики и телемеханики. Проблема остается актуальной в связи с широким внедрением микропроцессорных и компьютерных систем автоматики, обеспечивающих безопасность движения поездов. Поставлена задача найти нормы помехоустойчивости на основе учёта вероятностного характера уровня помех и уровня помехоустойчивости элементной базы аппаратуры. Методом «нагрузка-устойчивость» получены уравнения для определения нормируемого значения помехозащищенности. Рассчитанные по предлагаемой методике нормы позволяют оптимизировать жёсткость испытаний и сопутствующие им конструкторские решения

Classical and Thermodynamic work fluctuations

We have studied the nature of classical work ($W_{c}$) and thermodynamic work ($W$) fluctuations in systems driven out of equilibrium both in transient and time periodic steady state. As the observation time of trajectory increases, we show that the number of trajectories which exhibit excursions away from the typical behaviour i.e., $W_{c}<0$, $W<\Delta F$ and dissipated heat $Q<0$ decreases as anticipated for macroscopic time scales. Analytical expressions for such trajectories are obtained. Trajectory for which $W_{c}<0$ may not correspond to $W<\Delta F$ or $Q<0$. The applicability of steady state fluctuation theorems are discussed in our linear as well as nonlinear models.Comment: Based on the talk presented by Mamata Sahoo at the Condensed Matter Days-Aug. 2008 held at Viswavarati University, Kolkata. 19 pages, 8 figure

Stochastic deformation of a thermodynamic symplectic structure

A stochastic deformation of a thermodynamic symplectic structure is studied. The stochastic deformation procedure is analogous to the deformation of an algebra of observables like deformation quantization, but for an imaginary deformation parameter (the Planck constant). Gauge symmetries of thermodynamics and corresponding stochastic mechanics, which describes fluctuations of a thermodynamic system, are revealed and gauge fields are introduced. A physical interpretation to the gauge transformations and gauge fields is given. An application of the formalism to a description of systems with distributed parameters in a local thermodynamic equilibrium is considered.Comment: 22 pages, revtex preprint style; some notations changed and references added; some formulas and comments adde

New mechanism of solution of the kTkT-problem in magnetobiology

The effect of ultralow-frequency or static magnetic and electric fields on biological processes is of huge interest for researchers due to the resonant change of the intensity of biochemical reactions although the energy in such fields is small. A simplified model to study the effect of the weak magnetic and electrical fields on fluctuation of the random ionic currents in blood and to solve the $k_BT$ problem in magnetobiology is suggested. The analytic expression for the kinetic energy of the molecules dissolved in certain liquid media is obtained. The values of the magnetic field leading to resonant effects in capillaries are estimated. The numerical estimates showed that the resonant values of the energy of molecular in the capillaries and aorta are different: under identical conditions a molecule of the aorta gets $10^{-9}$ times less energy than the molecules in blood capillaries. So the capillaries are very sensitive to the resonant effect, with an approach to the resonant value of the magnetic field strength, the average energy of the molecule localized in the capillary is increased by several orders of magnitude as compared to its thermal energy, this value of the energy is sufficient for the deterioration of the chemical bonds.Comment: 10 pages, Accepted to the Journal Central European Journal of Physic