Modified genetic algorithm as a new approach for solving the problem of 3d packaging

In this paper, we proposed one of the options for developing a new evolutionary heuristic approach for solving the three-dimensional packing problem called BPP (Bin packing problem), as applied to the variation of this problem with a single container and a set of boxes of various dimensions, called the SKP (Single knapsack problem), and The comparison of 11 basic evolutionary heuristic approaches to solving the problem of three-dimensional packing of BPP (Bin packing problem) variations SKP (Single knapsack problem) with the developed new evolutionary heuristic approach to solving BPP using modi cited genetic algorithm (MGA). By performing correlation and statistical analysis using 10 randomly created sets of input data for solving BPP, the effectiveness of MGAs was proved in comparison with 11 basic evolutionary algorithms for solving BPP. Thus, it was confirmed that MGA and similar algorithms can be effectively used to solve such logistic NP-difficult problems

Formation of regression model for analysis of complex systems using methodology of genetic algorithms

© 2020, Education and Upbringing Publishing. All rights reserved. This study presents the approach to analyze evolution of an arbitrary complex system whose behavior is characterized by a set of different time-dependent factors. The key requirement for these factors is that they must contain an information about the system only; it does not matter at all what the nature (physical, biological, social, economic, etc.) of a complex system is. Within the framework of the presented theoretical approach, the problem of searching for non-linear regression models that express the relationship between these factors for a complex system under study is solved. It will be shown that this problem can be solved using the methodology of genetic (evolutionary) algorithms. The resulting regression models make it possible to predict the most probable evolution of the considered system, as well as to determine the significance of some factors and, thereby, to formulate some recommendations to drive by this system. It will be shown that the presented theoretical approach can be used to analyze data (information) characterizing the educational process in the discipline ”Physics” in the secondary school, and to develop the strategies for improving academic performance in this discipline

Amorphous Ni<inf>50</inf>Ti<inf>50</inf> Alloy with Nanoporous Structure Generated by Ultrafast Isobaric Cooling

© 2020, Pleiades Publishing, Ltd. Abstract: Amorphous metallic foams are prospective materials due to unique combination of their mechanical and energy-absorption properties. In the present work, atomistic dynamics simulations are performed under isobaric conditions with the pressure p = 1.0 atm in order to study how cooling with extremely high rates (5 × 1013–5 × 1014 K/s) affects the formation of pores in amorphous titanium nickelide. For equilibrium liquid phase, vaporization temperature Tb and the equation of states in the form of ρ(T) are determined. It is found that the porosity of this amorphous solid does not depend on cooling at such high rates, whereas the pore morphology depends on the magnitude of the cooling rate. The obtained results will be in demand in study of mechanical properties of amorphous metallic foams with a nanoporous structure

Amorphous porous phase of nitinol generated by ultrafast isobaric cooling

© 2020 Trans Tech Publications Ltd, Switzerland Titanium nickelide (nitinol) is of great applied interest in various industries due to unique combination of its physical and mechanical characteristics. In the present work, we consider the possibility of obtaining nitinol with mesoporous structure by rapidly cooling the molten sample to room temperature. Based on molecular dynamics simulation data, it was shown that the rapid cooling of the nitinol melt leads to formation of a porous structure. It was shown that the inner pore wall is formed mainly by titanium atoms, which provide biocompatibility of nitinol. It was found that the porosity of nitinol weakly depends on the cooling rate, while the porosity increases linearly with decreasing melt density

A novel view on classification of glass-forming liquids and empirical viscosity model

In the last few decades, theoretical and experimental studies of glass-forming liquids have revealed presence of universal regularities in the viscosity-temperature data. In the present work, we propose a viscosity model for scaling description of experimental viscosity data. A feature of this model is presence of only two adjustable parameters and high accuracy of experimental data approximation by this model for a wide temperature range. The basis of the scaling description is an original temperature scale. Within this scaling description we obtain the transformed Angell plot, in which the area separating “fragile” and “strong” glass-formers emerges. The proposed scaling procedure make it possible to reconsider belonging some liquids to the type of “fragile” glass-formers. The obtained results form basis for development of a generalized scaling description of crystallization kinetics in supercooled liquids and glasses

Elastic properties and glass forming ability of the zr<inf>50</inf>cu<inf>40</inf>ag<inf>10</inf> metallic alloy

© 2020 Trans Tech Publications Ltd, Switzerland The elastic properties of the Zr50Cu40Ag10 metallic alloy, such as the bulk modulus B, the shear modulus G, the Young’s modulus E and the Poisson’s ratio σ, are investigated by molecular dynamics simulation in the temperature range T=250–2000 K and at an external pressure of p=1.0 bar. It is shown that the liquid–glass transition is accompanied by a considerable increase in the shear modulus G and the Young’s modulus E (by more than 50%). The temperature dependence of the Poisson’s ratio exhibits a sharp fall from typical values for metals of approximately 0.32– 0.33 to low values (close to zero), which are characteristic for brittle bulk metallic glasses. Non-monotonic temperature dependence of the longitudinal and transverse sound velocity near the liquid-glass transition is also observed. The glass forming ability of the alloy is evaluated in terms of the fragility index m. As found, its value is m≈64 for the Zr50Cu40Ag10 metallic glass, that is in a good agreement with the experimental data for the Zr-Cu-based metallic glasses

Electrocrystallization of Supercooled Water in Confinement

© 2020, Pleiades Publishing, Ltd. Abstract: The paper discusses the features of supercooled water thin film of width d = 3.97 nm contained by the perfect graphene layers and crystallizing under external stationary electric field. It was found that the electric field applied perpendicular to graphene layers impedes structural ordering, while the electric field applied in lateral direction contributes to formation of the cubic ice (Ic) phase, which is thermodynamically less stable compared to the hexagonal ice (Ih) phase. It is shown that the growth of the Ic crystalline phase occurs without formation of intermediate crystalline phases. It was found that the crystallization rate depends strongly on the magnitude of the applied electric field. In particular, the processes of full electrocrystallization of the system do not appear over simulation time scale (~40 ns) if the electric field of the magnitude less than 0.07 V/Å is applied

Mechanical response of mesoporous amorphous NiTi alloy to external deformations

The porous titanium nickelide is very popular in various industries due to a фunique combination of physical and mechanical properties such as shape memory effect, high corrosion resistance, and biocompatibility. The non-equilibrium molecular dynamics simulation was applied to study the influence of porosity degree on mechanical properties of porous amorphous titanium nickelide at uniaxial tension, uniaxial compression, and uniform shear. We have found that the porous amorphous alloy is characterized by a relatively large value of Young's modulus in comparison to its crystalline analogue. It has been found that the system with a percolated network of pores exhibits improved elastic characteristics associated with resistance to tensile and shear. The system containing isolated spherical pores is more resistant to compression and less resistant to tensile and shear. These results can be applied to develop and improve the methods for making amorphous metal foams

Direct evaluation of attachment and detachment rate factors of atoms in crystallizing supercooled liquids

Kinetic rate factors of crystallization have a direct effect on formation and growth of an ordered solid phase in supercooled liquids and glasses. Using the crystallizing Lennard-Jones liquid as an example, in the present work, we perform a direct quantitative estimation of values of the key crystallization kinetic rate factors-the rate g+ of particle attachments to a crystalline nucleus and the rate g- of particle detachments from a nucleus. We propose a numerical approach, according to which a statistical treatment of the results of molecular dynamics simulations was performed without using any model functions and/or fitting parameters. This approach allows one to accurately estimate the critical nucleus size nc. We find that for the growing nuclei, whose sizes are larger than the critical size nc, the dependence of these kinetic rate factors on the nucleus size n follows a power law. In the case of the subnucleation regime, when the nuclei are smaller than nc, the n-dependence of the quantity g+ is strongly determined by the inherent microscopic properties of a system, and this dependence cannot be described in the framework of any universal law (for example, a power law). It has been established that the dependence of the growth rate of a crystalline nucleus on its size goes into the stationary regime at the size n > 3nc particles