Critical Behavior of a 2D Spin-Pseudospin Model in a Strong Exchange Limit

We study the 2D static spin-pseudospin model equivalent to the dilute frustrated antiferromagnetic Ising model with charge impurities. We present the results of classical Monte Carlo simulation on a square lattice with periodic boundary conditions in a “strong” exchange limit. In the framework of the finite-size scaling theory we obtained the static critical exponents for the specific heat α and the correlation length ν for a wide range of the local density–density interaction parameter ∆ and charge density n. It was shown that the system exhibits non-universal critical behavior depending on these parameters. © 2020 Polish Academy of Sciences. All rights reserved.Russian Foundation for Basic Research, RFBR: 18-32-00837/18Ministry of Education and Science of the Russian Federation, Minobrnauka: 2277, 5719Government Council on Grants, Russian FederationThe research was supported by the Government of the Russian Federation, Program 02.A03.21.0006 and by the Ministry of Education and Science of the Russian Federation, projects No. 2277 and 5719 by RFBR according to the research project No. 18-32-00837/18, scholarship of the president of the Russian Federation No. SP-2278.2019.1

Unconventional phase separation in the model 2D spin-pseudospin system

The competition of charge and spin orderings is a challenging problem for strongly correlated systems, in particular, for high-Tc cuprates. We addressed a simplified static 2D spin-pseudospin model which takes into account both conventional spin exchange coupling and the on-site and inter-site charge correlations. Classical Monte-Carlo calculations for large square lattices show that homogeneous ground state antiferromagnetic solutions found in a mean-field approximation are unstable with respect to phase separation into the charge and spin subsystems behaving like immiscible quantum liquids. In this case, with lowering of a temperature one can observe two sequential phase transitions: first, antiferromagnetic ordering in the spin subsystem diluted by randomly distributed charges, then, the charge condensation in the charge droplets. The inhomogeneous droplet phase reduces the energy of the system and changes the diagram of the ground states. On the other hand, the ground state energy of charge-ordered state in a mean-field approximation exactly matches the numerical Monte-Carlo calculations. The doped charges in this case are distributed randomly over a system in the whole temperature range. Various thermodynamic properties of the 2D spin-pseudospin system are studied by Monte-Carlo simulation. © 2018 The Authors, published by EDP Sciences.The work is supported by Act 211 Government of the Russian Federation, agreement No 02.A03.21.0006 and by the Ministry of Education and Science, projects 2277 and 5719

The influence of local correlations on the phase states in the model of semi-hard-core bosons on a square lattice

The work considers a model of charged "semi-hard-core" bosons on a square lattice with a possible filling number at each node, ranging from 0 to 2. Temperature phase diagrams of the model are obtained using numerical Monte Carlo quantum simulation methods, and the influence of local charge correlations is examined. Comparison with results from mean-field methods shows that local charge correlations contribute to an increased role of quantum fluctuations in the formation of phase states.Comment: 5 pages, 2 figure

Energy supply of athletes’ muscles at the performance of standardized loads

Research of energy supply of athletes’ muscles activity under various conditions helps to find out the power, capacity and mobility in its constituent. Objective: to evaluate aerobic lactate and alactate influence in the body power supply during standard training tests. Materials and methods: 30 athletes were included in the study and were examined by the following tests: the Wingate-test and Increasing test with the treadmill. Results: Wingate-test of energy consumption performance showed 154,8±4,37 kJ/min. It was taken for aerobic capacity 46,2±1,56 kJ/min, lactate - 50,6±1,8 kJ/min, alactate - 4,5±1,5 kJ/min of them. During the increasing test the body energy consumptions total amount compiled 682,3±32,62 kJ/min over rest level. There is no any statistically proved differences (p=0,82) between the quantity energy characteristics of lactate and alactate body capacity, and they are approximately less in 14 times compare to aerobic body capacity(596,2±30,67 kJ/min). Conclusions: Wingate-test studies indicated there is approximately equal constituents in energy consumptions: 32,6% aerobic, 35,7% lactate and 31,7% alactate, respectively. Lactate ability level in its prevalence shows statistical significant differences (

Phase diagrams of a 2D Ising spin-pseudospin model

We consider the competition of magnetic and charge ordering in high-Tc cuprates within the framework of the simplified static 2D spin-pseudospin model. This model is equivalent to the 2D dilute antiferromagnetic (AFM) Ising model with charged impurities. We present the mean-field results for the system under study and make a brief comparison with classical Monte Carlo (MC) calculations. Numerical simulations show that the cases of strong exchange and strong charge correlation differ qualitatively. For a strong exchange, the AFM phase is unstable with respect to the phase separation (PS) into the charge and spin subsystems, which behave like immiscible quantum liquids. An analytical expression was obtained for the PS temperature.Comment: 14 pages, 3 figure

Food security against the background of unsustainably developing Russian economy: Price aspect

The paper considers food security from the perspective of the development of Russia’s economy in the form of a mixed economic model. Prices and incomes are an overriding concern in this process. The authors analyze the intricate nature of price in terms of consumer-producer interactions. Consideration is being given to views of reputed economists on price that involve different aspects of its nature. Features peculiar to the generation of the contemporary consumer’s aggregate income and purchasing behavior at different periods of time, i.e. from 1991 to 1999 and from 2000 to 2016, are shown. It ought to be noted that efforts towards food security are being made against the background of high inflation, the complicated system of end consumer incomes (e.g. money income, income in kind, and shadow income), and the existing mentality inherent in the nation

Assessing the Efficiency of Biogas Plants: The National and Foreign Experience

The issue of recycling waste from the main production is experiencing growing relevance and importance in the context of sustainable development and environmental protection. In today’s world, where environmental issues and conservation of natural resources are becoming extremely important, manufacturers and consumers are faced with the need to find new innovative approaches to waste management and reducing the negative impact of industrial processes on the environment. Therefore, the use of biogas plants is one of the promising solutions in this direction. These plants play an important role in reducing greenhouse gas emissions, using agricultural waste, improving the production cycle, and contributing to more sustainable and environmentally friendly production processes. This article reveals the importance of biogas plants as an innovative solution for addressing the issues of organic waste recycling along with creating more sustainable production. The article discusses the topical issue of assessing the efficiency of biogas plants, based on both domestic and foreign experience. The analysis of the efficiency of biogas plants is carried out on the basis of a comparison of domestic and international experience. Thus, the authors determine that in order to ensure a comprehensive assessment of the efficiency of biogas plants, it is necessary to thoroughly analyze technical parameters, technological solutions, economic aspects, and environmental indicators. The proposed multi-criteria approach will allow to obtain an exhaustive and objective assessment of the functioning of biogas plants, taking into account most of the key aspects of their efficiency. This will make it possible to determine the optimal areas for improving these plants in order to achieve the highest possible level of productivity and consistency of their operation. Further on, this approach will contribute to making sound managerial decisions and thus achieving a common goal in the modern energy paradigm. The authors propose to assess the efficiency of biogas plants by building a model based on fuzzy logic methods. This approach allows to take into account the ambiguity and uncertainty of incoming information, which gives the possibility to agree on different criteria and parameters, taking into account their unpredictability and dependence on many factors. The results of this model help in choosing the optimal biogas plant that meets the conditions and requirements of today

Phase Separation in the Ground State of the Model 2D Spin-Pseudospin System

We addressed a simplified static 2D spin-pseudospin model which takes into account both conventional Heisenberg spin exchange coupling and the on-site and inter-site charge correlations. Classical Monte-Carlo calculations for large square lattices show that homogeneous ground state solutions found in a mean-field approximation are unstable with respect to phase separation with the charge and spin subsystems behaving like immiscible quantum liquids. For instance, with lowering the temperature one can observe two sequential phase transitions: first, antiferromagnetic ordering in the spin subsystem diluted by randomly distributed charges, then, the charge condensation in the charge droplets. Thermodynamic properties and phase diagram of the 2D spin-pseudospin system are studied by Monte-Carlo simulation with a special attention given to the role played by the on-site correlation

Monte Carlo Simulation of a Model Cuprate

We develop a classical Monte Carlo algorithm based on a quasi-classical approximation for a pseudospin S = 1 Hamiltonian in real space to construct a phase diagram of a model cuprate with a high Tc. A model description takes into account both local and nonlocal correlations, Heisenberg spin-exchange interaction, correlated single-particle, and two-particle transport. We formulate a state selection algorithm for a given parameterization of the wave function in order to ensure a uniform distribution of states in the phase space. The simulation results show a qualitative agreement with the experimental phase diagrams. © 2021 Institute of Physics Publishing. All rights reserved.The research was supported by the Ministry of Education and Science of the Russian Federation, project FEUZ-2020-0054, and by scholarship of the president of the Russian Federation No. SP-2278.2019.1

Competition of Spin and Charge Orders in a Model Cuprate

We present results of the mean-field analysis of the competition between charge and spin orders in a model cuprate. Phase diagrams and temperature dependencies of the charge and magnetic order parameters are calculated for varying doping given different values of the on-site correlation parameter, inter-site density–density coupling, and spin exchange integral. © 2016, Springer Science+Business Media New York