Dielectric properties of bionano-composites modified by fish scales

The presented work presents the results of studying the temperature dependences of the dielectric constant and the tangent of the dielectric loss angle of biocomposites modified with fish scales. It was found that with an increase in the volumetric content of the bio-filler, the dielectric constant of the biocomposites increases, and the tangent of the dielectric loss angle decreases. By varying the volumetric content of the bio-filler, it is possible to control the properties of biocomposites in the desired direction.

Numerical determination of the combustion rate of a gas suspension of coal dust in a propane-air mixture

The results of the numerical solution of the problem of the combustion rate of a coal-propane-air mixture are presented. The physical and mathematical formulation of the problem is based on the approaches of the dynamics of multiphase reacting media. The method for solving the problem is based on the algorithm for the decay of an arbitrary discontinuity. The dependences of the visible and normal combustion rate of the coal-propane-air mixture on the radius and the volumetric content of propane in the gas are obtained.

Jet mixing unit for introducing a light bulk substance into a liquid stream

For the oil spill emergency response, a ship system for supplying an active substance to the contaminated zone has been proposed. Various chemical compounds and substances, microorganisms can be used as active substances. To collect most of the oil spill, it was proposed to use a thermally split graphite sorbent. Its supply to the contaminated zone should be carried out in the form of a pulp. One of the key elements of the system is a mixer for introducing the sorbent into the water flow. This article presents the results of three stages of the study of the influence of the geometric parameters of the jet mixer on the average volumetric content of the sorbent in the pulp, the shape of the nozzle and flow of the working fluid. The necessity of mandatory use of a arch destruction device in a bunker with a light sorbent is noted.

Structure, density and viscosity of water

We analyzed the possibilities of the use of the cluster model of water to assess its viscosity. The Nemethy-Scheraga model was used in our study. In a simplified version, this model implies the presence of water cluster that are linked by hydrogen bonds as well as individual molecules (monomolecules) interacting only by van der Waals forces. The paper gives an estimation of average cluster size. Based on the experimental temperature dependences of viscosity and density, the content of monomolecules in water was approximately determined. In the first case, the ratio of the viscosity of water to monomolecules was estimated from the inverse Arrhenius temperature dependence of viscosity by considering experimental activation energy ~18.6 kJ mol–1 (0÷300C) and energy of dispersion interactions ~7.4 kJ mol–1. Then, the volumetric content of monomolecules was estimated by using the inverse Betchelor's formula, which relates the viscosity of the suspension (clusters) and dispersion medium (monomolecules) to their ratio. On the other hand, a similar estimation was performed based on the density of water, clusters that were considered similar to ice floes, and the estimated density of monomolecules. Both estimates showed that the volumetric content of water not bound into clusters does not exceed 9%. It was concluded that the structure of water most likely corresponds to the clathrate model, according to which some of the H2O molecules move into the middle of ice-like clusters, and vacancies are stabilized by H3O+–OH– pairs.

Durability of working bodies of soil-cultivating machines strengthened by composite electrolytic coatings (CEC)

The task of this work is to find the optimal ratio between the size of the particles of silicon carbide and their volumetric content in the nickel matrix to provide maximum characteristics of strength and wear resistance of the working bodies of soil-processing machines. The article investigates the processes of forming complex electrolytic coatings (CEC) on a nickel basis with particles of the filler of various sizes of silicon carbide (SIC). It has been established that the formation of a sicle size sicle and SiC5 is carried out on a vertical, and all other particles in a horizontal cathode. The volumetric content of SICnano and SiC5 particles in nickel reaches a maximum of about 10%, and SiC100 – 46 %. Cap with particle size 28/20 and 50/40 μm allow you to get the most wear-resistant coatings. In this case, the coating with particles 28/20 μm have higher wear resistance, but coating with particles 50/40 μm are more technological when they are formed. The size of the filler particles has a significant effect on the tribological characteristics of the CEP, namely wear resistance and friction coefficient. It has been established that the highest wear resistance and the smallest friction coefficients are characterized by coatings having as a filler of fractions 28/20 and 50/40 μm. Tribological studies show the promise and efficiency of the CEP to increase the wear resistance of the working bodies of soil-cultivating machines.

Effects of Rock Fragments on the Soil Physicochemical Properties and Vegetation on the Northeastern Tibetan Plateau

Stony soils are very widely distributed and contain abundant rock fragments (>2 mm), which impose major effects on soil properties and plant growth. However, the role of rock fragments is still often neglected, which can lead to an inadequate understanding of the interaction between plants and soil. Undisturbed soil columns were collected from three alpine grasslands on the Qilian Mountain, and the X-ray computed tomography method was applied to investigate the characteristics of rock fragments. The results showed there was significant difference in number density, volumetric content and surface area density of rock fragment among the three grasslands, and followed the order of alpine meadow > alpine steppe > alpine desert steppe. In addition, the soil organic carbon, total nitrogen, total phosphorus, available phosphorus, N-NH4+, and N-NO3− contents in fine earth all increased with increasing number density, volumetric content and surface area density but to different degrees. Furthermore, positive correlations were observed between the rock shape factor and belowground biomass (R2 = 0.531, p < 0.05), between the rock volumetric content and aboveground biomass (R2 = 0.527, p < 0.05), and between number density and Simpson’s index (R2 = 0.875, p < 0.05). Our findings suggest that within a certain range, the increase in rock fragment content is conducive to soil nutrient accumulation and soil water storage and circulation and changes plant features, which contributes to the growth of plants. In addition, rock fragments should be given more consideration when investigating the relationships between soil and vegetation and their response to climate change in future studies.

Numerical study of the effect of droplet coagulation on the dynamics of a two-fraction aerosol in an acoustic resonator

The study is devoted to the study of the effect of coagulation of dispersed phase droplets on aerosol oscillations in an acoustic resonator. The mathematical model of aerosol dynamics implements a continuous mathematical model of the dynamics of a multiphase medium, taking into account the velocity and thermal inhomogeneity of the mixture components. To describe the dynamics of the carrier medium, a two-dimensional unsteady system of Navier – Stokes equations for a compressible gas is used, written taking into account the interphase force interaction and interphase heat transfer. To describe the dynamics of the dispersed phase, a system of equations is solved for each of its fractions, including the continuity equation for the «average density» of the fraction, the equations for the conservation of the spatial components of the momentum and the equation for the conservation of thermal energy of the fraction of the dispersed phase of the gas suspension. The interphase force interaction included the Archimedes force, the force of the added masses and the force of aerodynamic drag. The heat exchange between the carrier medium - gas and each of the dispersed phase fractions was also taken into account. The mathematical model of the dynamics of a polydisperse aerosol was supplemented by a mathematical model of collisional aerosol coagulation. For the velocity components of the mixture components, uniform Dirichlet boundary conditions were specified. For the remaining functions of the dynamics of the multiphase mixture, homogeneous Neumann boundary conditions were specified. The equations were solved by the explicit McCormack method with a nonlinear correction scheme that allows obtaining a monotonic solution. As a result of numerical calculations, it was determined that a region with an increased content of coarse particles is formed in the vicinity of the oscillating piston. The coagulation process leads to a monotonic increase in the volumetric content of the fraction of coarse particles and a monotonic decrease in the volumetric content of fine particles.

SPECTRA OF THERMOSTIMULATED DEPOLARIZATION OF BIOCOMPOSITES WITH FILLERS OF BIOLOGICAL ORIGIN

The paper presents the results of studying the spectra of thermally stimulated depolarization of high-pressure polyethylene modified with fillers of biocomposites with fillers of biological origin - fish bone and fish scales. It was revealed that the stability and surface density of space charges can be controlled by varying the volumetric content of biological fillers. The optimal values of bio-fillers that contribute to the stability of the surface density of the studied biocomposites have been determined.

NONLENEAR DEFORMATION OF GRANULAR COMPOSITES

The model of nonlinear deformation of a layered material with physically nonlinear layers is proposed. The laminate is considered a two-component material with random layers. The basis is the stochastic differential equations of the physically nonlinear theory of elasticity L.P. Khoroshun. The solution to the problem of the stress-strain state and effective properties of the composite material is constructed by the averaging method. An algorithm for determining the effective deformable properties of a layered material with physically nonlinear layers has been developed. The solution of nonlinear equations taking into account their physical nonlinearity is constructed by an iterative method. The law of the relationship between macrostresses and macrostrains in a layered material and the dependence of average strains and stresses in its layers on macrostrains has been established. Curves of material deformation are plotted for different values of the volumetric content of its filler. The dependence of the effective deformative properties of the laminated material on the volumetric content of the filler has been studied. The effect of nonlinearity of layers on the deformation of a layered composite material is investigated. It was found that the nonlinearity of the layers significantly affects the effective deformative properties and the stress-strain state of laminated materials.