Dynamics of changes in stress autocorrelation functions of aluminum melt during ultrafast cooling
We present the results of the study of changes in liquid properties during ultrafast cooling. The molecular dynamics (MD) method is used, with aluminum melt as an example. Based on the changes in shear stress autocorrelation functions (SACF) with temperature in an ensemble of MD trajectories, we develop three approaches to the study of melt changes. In the first one, we investigate the asymptotic behavior of SACFs and a sharp increase in the melt viscosity, which is a conventional criterion. In the second approach, we present direct evidence of the transition of a metastable melt to a non-equilibrium state. In the third one, we show the appearance of transverse oscillations in a film of the melt. The most important observation is that all three phenomena occur in the same temperature range. On the basis of the current and the previous work, we conclude that there is a gap between the temperature of the splitting of the second peak of the pair correlation function and the temperature of the transition to a solid-like amorphous state. The splitting of the second peak occurs at a significantly higher temperature and this phenomenon is discussed.
Although the high-pressure phase diagram of carbon at extreme temperatures and pressures is in focus of theoretical and experimental dynamic compression studies, there still exist outstanding problems including disagreement between theoretical predictions and experiments. Using first-principles molecular dynamics simulations at high temperatures and pressures and employing large unit cells, we construct an accurate phase diagram of carbon using two-phase and Z-methods. In accord with previous simulations, a large positive slope of the melting line is observed for pressures from 0 to 200 GPa, whereas at pressures above 500 GPa a very small negative slope exists, which is in contrast to most of previous simulations and experiment. Our accurate results demonstrate the necessity for future dynamic compression experiments to clarify behavior of carbon at extreme conditions including its melting line.
The research deals with the construction, implementation and analysis of the model of the non-equilibrium financial market using econophysical approach and the theory of nonlinear oscillations. We used the scaled variation of supply and demand prices and elasticity of these two variables as dynamic variables in the simulation of the non-equilibrium financial market. View of the dynamic variables data was determined based on the strength of econophysical prerequisites using the model of hydrodynamic type. As a result, we found that the non-equilibrium market can be described with a good degree of accuracy with oscillator models with nonlinear rigidity and a self-oscillating system with inertial self-excitation. The most important states of model of oscillation non-equilibrium model of the market were found, including the appearance of chaos and its mechanisms. We have made the calculations of the correlation dimension for the financial time series. The results show that all observed time series have a clearly defined chaotic dynamic nature.
Due to their high durability and immobilization properties, cementitious materials have found a considerable application in the design and construction of radioactive waste repositories in the last decades. During cement paste production, organic additives are introduced to modify various properties of cement. The presence of such organic complexants may negatively affect the immobilizing properties of cement with respect to radionuclides. For better understanding and prediction of the effects of interactions between organic molecules and cementitious materials with radionuclides, we have developed several representative models consisting of three principal components: (i) calcium silicate hydrate (C-S-H) phase - the main binding phase of cement; (ii) gluconate, a simple well-described molecule, as a representative of organic additives; (iii) U(VI), as one of the most studied radionuclides of the actinide series. The C-S-H phase with low Ca/Si ratio (~0.83) typical for â€œlow-pHâ€ and degraded cement pastes has been selected for this modelling study. Structural, and energetic aspects of the sorption processes of uranyl, gluconate, and their mutual correlations on the surface of cement were quantitatively modeled by classical molecular dynamics (MD) and potential of mean force (PMF) calculations. The ternary surface complex formation between uranyl hydroxides and Ca2+ cations at the C-S-H aqueous interfaces is shown to have an important role in the overall sorption process. In the presence of gluconate, U(VI) sorption on C-S-H is facilitated by weakening the Ca2+ binding with the surface. Additionally, Na+ is proven to be an important competitor for certain surface sorption sites and can potentially affect the equilibrium properties of the interface.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.