Collisions of Two-Phase Liquid Droplets in a Heated Gas Medium

The paper presents the experimental research findings for the integral characteristics of processes developing when two-phase liquid droplets collide in a heated gas medium. The experiments were conducted in a closed heat exchange chamber space filled with air. The gas medium was heated to 400–500 °C by an induction system. In the experiments, the size of initial droplets, their velocities and impact angles were varied in the ranges typical of industrial applications. The main varied parameter was the percentage of vapor (volume of bubbles) in the droplet (up to 90% of the liquid volume). The droplet collision regimes (coalescence, bounce, breakup, disruption), size and number of secondary fragments, as well as the relative volume fraction of vapor bubbles in them were recorded. Differences in the collision regimes and in the distribution of secondary fragments by size were identified. The areas of liquid surface before and after the initial droplet breakup were determined. Conditions were outlined in which vapor bubbles had a significant and, on the contrary, fairly weak effect on the interaction regimes of two-phase droplets.

Non-destructive 3D microscopy in the study of patterns of biological adaptation among fossil and recent Homo

We apply non-destructive volumetric technique for evaluation of vascular net density in compact bone. Segmentation of Haversian canals and accurate estimation of their relative volume fraction gives the opportunity to estimate the density and capacity of the vascular system of the bone tissue in a proxy way. Radiological images of dorsal compact of medial and distal phalanges were studied (Neanderthals from Altai and Europe; CroMagnons; recent humans of Arctic and African origin). Results. High vascularization of compact clearly demonstrates that European Neanderthals and the majority of AMH were adapted to the Glacial Age. But Kostenki 14 (Eastern Europe) and Strashnaya 4 (Altai) have features in common with humans of recent tropic origin. Specimens of Neanderthals which lived in Altai region where glaciers never occurred are more diverse. Hypothetically the milder climate favored the existence of a wider adaptive norm reflecting patterns of former environments. Somewhat ambiguous morphological patterns of Denisova 9 and Okladnikov 2, 5 may reflect various episodes of Neanderthal migration to Siberia and their hybridization with people of tropical ancestry, most probably the early AMH. Chagyrskaya Neanderthal demonstrates a hyper-cold adaptation. Conclusion. Diversity in microstructural patterns of the Pleistocene people’s skeletal system gives evidence that both Neanderthals and CroMagnons were polymorphic in their adaptive reactions and presumably included both warm and cold adapted forms.

Analysis of CFRP Laminates Properties under Different Layup Structure using Finite Element Analysis

In order to study the effect of the layup structure on the static strength and low-velocity impact strength of carbon fiber/epoxy composite (CFRP) laminates, theoretical simulation analysis under different laying angles have been carried out. In this study, Finite Element Analysis (FEA) models for different CFRP laminate specimens are created using ANSYS Workbench by changing the relative volume fraction of 0°, 45° and 90° plies in each specimen and their relative location. The FEA results revealed that the increase of relative volume of 90° ply will improve the impact the impact resistance performance, while the increase of relative volume of 45° ply will take the opposite effect. Moreover, when the relative volume fraction of 0°, 45° and 90° plies are the same, the strength performance of the laminate cannot be improved by changing the thickness of the outermost layer. The study illustrated the significant effects of different stacking sequences and laying angles on the tensile and flexural failure mechanisms in composite laminates, leading to some suggestions to improve the design of composite laminates.

EFFECTIVENESS OF USE OF NANO FILLERS OF DIFFERENT TYPES IN POLYMERIC COMPOSITES

The paper provides a theoretical analysis of the effectiveness of using different types of nanofillers to produce high-strength polymer composites. Three basic types of nanoscale inorganic nanofillers were selected: dispersed nanoparticles (0D-nanofillers), carbon nanotubes and nanofibers (1D-nanofillers), and organoclay, graphene, etc. (2D-fillers). The relative modulus of elasticity, i.e. the degree of amplification, is used as the main criterion for the effectiveness of nanofillers. Within the framework of the percolation model, the amplification levels of nanocomposites for different types of nanofillers are determined depending on the relative volume fraction of nanofillers and interfacial regions. It is shown that interfacial regions in polymer nanocomposites are treated as a reinforcing element of the nanocomposite structure. To describe the surface structure of nanofiller particles, an effective value of the fractal dimension is used, which serves as a determining factor for the relative proportion of interfacial regions. At a condition that the fractal dimension of the structural framework of nanofiller particles cannot exceed the fractal dimension of the enclosing Euclidean space, the relative proportion of interfacial regions and, through it, the maximum degree of filling for the types of nanofillers under consideration are determined. The results of the theoretical evaluation of the maximum limit value of the fractal dimension of nanofiller particles carried out in this work show that the formation of a bulk frame of particles is possible only for anisotropic nanofillers, and dispersed particles form chains that do not change the structure of the polymer matrix in comparison with the matrix polymer. It is also found that for each type of nanofiller, there is a limit maximum degree of filling, which ultimately determines the limit maximum degree of amplification of the nanocomposite. These results allow us to conclude that the most effective for creating structural polymer nanocomposites is a dispersed nanofiller.

Influence of Polymer Modification on the Microstructure of Shielding Concrete

In this paper an analysis of the influence of polymer modification on the microstructure, shielding properties against neutrons, and compressive strength of heavy-weight magnetite concrete is carried out. The modifications involve the addition of acrylic or epoxy dispersions as well as micro- or/and macrofibers. A computer image analysis method is used to evaluate the microstructure of concretes and parameters of pore structure are calculated; these parameters include relative volume fraction, relative specific surface area, and pore arrangement ratios, including a proprietary ratio based on Voronoi tessellation. An assessment of significance of differences between stereological parameters of reference concrete and polymer modified concretes, as well as the impact of polymer form (dispersion or fibers) on shielding properties and compressive strength is carried out using Student’s t-test. The results show that except for the effect of the addition of both polypropylene micro- and macrofibers on the relative volume of pores, all other modifications result in statistically significant changes in the values of stereological parameters. Nevertheless, it is shown that neither polymer dispersions nor fibers have a statistically significant impact on shielding properties, but that they do influence compressive strength.

Theory of Holographic Formation in Multicomponent Photopolymer-Based Nanocomposites-=SUP=-*-=/SUP=-

The derivation of the three-component (monomer, chemically neutral component, and polymer) photopolymerization model from general thermodynamic considerations is presented. This model, together with another previously published one, are subject to a numerical solution for the case of a two-component one-dimensional diffusion (polymer component being steady). The divergence of results of work for both models was compared based on the average speed of the root-mean-square deviation in the spatial spectrum domain for relative volume fraction functions for all three components. Such a comparison was performed for 81 pairs of initial relative amount of neutral component and effective diffusion coefficient. The results of the work may serve as a good guide for the choice of parameters of experiments, which are aimed to verify the correctness of the modified theory. Keywords: photopolymerization, photoformer, holographic grating, multicomponent diffusion, polymer, holography.

Thermoplasmonic of Single Au@SiO2 and SiO2@Au Core Shell Nanoparticles in Deionized Water and Poly-vinylpyrrolidoneMatrix

Metal nanoparticles can serve as an efficient nano-heat source with confinement photothermal effects. Thermo-plasmonic technology allows researchers to control the temperature at a nanoscale due to the possibility of precise light propagation. The response of opto-thermal generation of single gold-silica core-shell nanoparticle immersed in water and Poly-vinylpyrrolidone surrounding media is theoretically investigated. Two lasers (CW and fs pulses) at the plasmonic resonance (532 nm) are utilized. For this purpose, finite element method is used via COMSOL multiphysics to find a numerical computation of absorption cross section for the proposed core –shell NP in different media. Thermo-plasmonic response for both lasers is studied. The heat profile of different nanostructures is estimated. The results revealed that the temperature distribution profile was varied due to changing in the relative volume fraction between the core and the shell of nanoparticle.

Thermoplasmonic of Single Au@SiO2 and SiO2@Au Core Shell Nanoparticles in Deionized Water and Poly-vinylpyrrolidoneMatrix

Metal nanoparticles can serve as an efficient nano-heat source with confinement photothermal effects. Thermo-plasmonic technology allows researchers to control the temperature at a nanoscale due to the possibility of precise light propagation. The response of opto-thermal generation of single gold-silica core-shell nanoparticle immersed in water and Poly-vinylpyrrolidone surrounding media is theoretically investigated. Two lasers (CW and fs pulses) at the plasmonic resonance (532 nm) are utilized. For this purpose, finite element method is used via COMSOL multiphysics to find a numerical computation of absorption cross section for the proposed core –shell NP in different media. Thermo-plasmonic response for both lasers is studied. The heat profile of different nanostructures is estimated. The results revealed that the temperature distribution profile was varied due to changing in the relative volume fraction between the core and the shell of nanoparticle.

UV-induced vesicle to micelle transition: a mechanistic study

The morphology of self-assembled block copolymer aggregates is highly dependent on the relative volume fraction of the hydrophobic block.

Effect of nano BiPb-2212 phase addition on BiPb-2223 phase properties

BiPb-2212 phase in nanoscale was added to BiPb-2223 phase with a general stoichiometry of (Bi[Formula: see text]Pb[Formula: see text]Sr[Formula: see text]Ca[Formula: see text]Cu[Formula: see text]O[Formula: see text]/Bi[Formula: see text]Pb[Formula: see text]Sr[Formula: see text]Ca[Formula: see text]Cu[Formula: see text]O[Formula: see text], 0.0 [Formula: see text] x [Formula: see text] 2.5 wt.%. All samples were prepared by the standard solid-state reaction method. The prepared nano BiPb-2212 phase was characterized by X-ray powder diffraction (XRD) and transmission electron microscope (TEM). The prepared samples were characterized by XRD and the scanning electron microscope (SEM). XRD analysis indicated that the sample with x = 1.5 wt.% has the highest relative volume fraction for BiPb-2223 phase. Samples were examined by electrical resistivity and I–V measurements. There is no significant change in the superconducting transition temperature [Formula: see text] for all samples. The highest critical current density [Formula: see text] was recorded for the sample with x = 1.5 wt.%. The normalized excess conductivity [Formula: see text] was calculated according to Aslamazov–Larkin (AL) model. Four different fluctuating regions were recorded as the temperature decreased. The coherence length along the c-axis at 0 K [Formula: see text], interlayer coupling strength s, Fermi velocity [Formula: see text] of the carriers and Fermi energy [Formula: see text] were calculated for both samples with x = 0.0 wt.% and 1.5 wt.%.