This work addresses a strong need in accurate fatigue properties of glass- and carbon-fiber reinforced polymer–matrix composites. In particular, interlaminar shear fatigue properties of glass/epoxy ...and carbon/epoxy composite tape material systems used in aircraft fatigue-critical applications are needed. The interlaminar shear fatigue material properties, essential for the development of the analysis methods able to capture fatigue delamination failure onset in composite structures, are presented in this work. S–N curves are generated based on custom short-beam shear (SBS) fatigue tests. The custom SBS test configurations ensure a consistent interlaminar shear failure mode. This work extends the recently developed methodology, published in Composites Science and Technology to characterize nonlinear shear properties of composite materials using digital image correlation (DIC) and finite element analysis, to fatigue loading. Test data sets used to develop the fatigue properties, include approximately 20 glass/epoxy and 30 carbon/epoxy SBS coupons. All tests were run in load control at 0.1 load ratio. To better understand material behavior under cyclic loading, surface shear strain was monitored using the DIC technique. Accurate shear stress approximation resulted in similar S–N curve shapes for the glass-fiber and the carbon-fiber composites.
The research was conducted in the European northeast of Russia (Komi Republic), in the reclaimed quarries for mining construction sand in the middle taiga subzone, in the course of two decades after ...the forest reclamation (
Pinus sylvestris
) had been applied. The specific features of initial pedogenesis on substrates of different textures have been revealed. On sands and sandy loams, the dynamic soil sequence is composed by abralith (the 0-moment) → residual-calcareous humus psammozem (11th yr) → humus-raw-humus residual-calcareous podzolized humus gleyic psammozem (18th yr). On the loamy substrate, the following soil sequence is formed: abralith → humus residual-calcareous pelozem (3rd and 11th yr) → humus-raw-humus residual-calcareous eluviated gleyic pelozem (the 18th year). The formation of litter and humus-accumulative horizons are the leading soil forming processes. Their intensity is determined by the degree of plant community development. By the end of the second decade, the humus-accumulative horizon (0–20 cm thick) of sandy loamy soils accumulates up to 2.7 t/ha of organic carbon. Organic carbon pool in loamy soils reaches 6.3 t/ha. The stocks of soil nitrogen reach 0.1 and 0.4 t/ha, respectively. The rate of organic carbon accumulation in soil reaches 0.16 (sandy-loamy substrates) and 0.37 t/ha per year (loamy substrates). The organic matter of humus-accumulative horizons in the young soils of quarries is characterized by a higher content of water-soluble and labile components of humus and a low degree of condensation of humic acids as compared to the background soils. Initial pedogenesis on quarry substrata is characterized by an increase in the acidity of soil water extracts from pH 8.0 in abralith to pH 6.3–6.7 in the W horizon of the forming soils. The rate of acidification in loamy soils is lower than in sandy and sandy loamy soils. Carbonate leaching is confirmed by the absence of calcite and dolomite in the mineral composition of the upper W horizons of the forming soils, a decrease in the total content of calcium oxide from 4% in abralith to 2–3% in the W soil horizon and in the content of calcium carbonates (3 and <0.5%, respectively). In 18 years, weakly expressed features of eluviation, illuviation, and gleying appeared in the soil profiles.
The microstructure and phase transformations of copper atom doped ceramic BiNbO
4
synthesized at 950 and 1100°C were studied. According to XPA the samples in compact, pressed form crystallize in the ...α-BiNbO
4
structure irrespective of the synthesis temperature and in spite of the phase transformation α → β at 1040°C. The substances BiNb
1–
x
O
4–δ
∙
x
CuO (
x
≤ 0.04) are graphite-colored composites with visually expressed grain microstructure. Thermograms of the samples show near 900°C an endo effect associated with the decomposition of the copper (II) oxide and thermal effects due to reconstructive phase transformations of the type α → γ → β in BiNbO
4
. It was determined that copper oxide impurity in bismuth orthoniobate ceramic acts as a heat sink, which increases the temperature of the phase transition α → γ on heating of compact samples.
A theoretical model is devised to assess effects of surface roughness on dispersion interactions between macroscopic bodies, bounded by self-affine fractal surfaces and separated by a vacuum gap. The ...rough-surface profiles are described statistically by the saturation values of surface width and the correlation lengths; i.e., in terms of experimentally measurable quantities. The model devised takes into account the separation distance-dependent nature of dispersive interactions. The case of non-retarded van der Waals interactions, known to operate at smaller separation distances between the bodies, and that of retarded attractions, operative at larger separation length-scales, are treated separately in this work. Analytical formulae for the roughness corrections are deduced for the two aforementioned types of attractions. The model is employed to compute roughness corrections to interactions between an extended body, bounded by a self-affine surface, and: a) a point-like adherent; and b) a planar half-space. Furthermore, the roughness-induced corrections to dispersive interaction energies between half-spaces, both bounded by self-affine surfaces, are obtained under assumption that the corresponding surface profiles are not correlated. The predictions of the model are compared with some previously reported theoretical studies and available experimental data on the theme of dispersive adhesion between macroscopic bodies.
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•A theoretical model for roughness corrections to dispersion interaction energies is developed.•The cases of non-retarded and retarded interactions are considered.•Corrections to energies are obtained as functions of saturated surface width and correlation length.•The case of two interacting self-affine rough surfaces is considered.
Objective.
The aim of the work is to study the use of nanofluids as heat carriers to increase the efficiency of heat removal in energy facilities. To solve this problem, materials of domestic and ...foreign scientific articles, conferences and dissertations on the subject of nanofluids were analyzed. Numerous scientific publications, including those cited in the international databases Web of Science and Scopus, indicate that the topic of nanofluids is in the focus of modern science. However, despite a rather long period of fluid research, not all issues of this topic are sufficiently well covered and systematized, which opens up great opportunities for further research in this direction.
Method
. When achieving this goal, the areas of possible application of fluids, the mechanism of their synthesis, the features of their operation are considered, the advantages as a liquid coolant are indicated, and the disadvantages that prevent their widespread use are identified. Particular attention is paid to such issues as: synthesis of standardized nanofluids; ensuring their stable properties; the use of surfactants; increasing the pressure drop inside heat exchangers during operation of this coolant.
Result.
To eliminate the main drawback in the form of agglomeration of nanoparticles in the base fluid, it is proposed to use the oscillatory circulation of the coolant, which will also further intensify heat exchange from forced turbulence of the fluid.
Conclusion.
The results obtained can be used to improve the efficiency of heat and mass transfer devices with liquid coolant and systems based on them, as well as to reduce the weight and size parameters of such devices.
Lidar observations at Siberian Lidar Station (SLS) of the Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, in Tomsk (56.5° N; 85.0° E) showed the presence of ...stratospheric aerosol layers, descent of air masses, and deficit of ozone over the city during winter 2017–2018. Aura OMI/MLS data indicated that the total ozone (TO) content and NO
2
content in the stratosphere over northern Eurasia, as well as the temperature in the stratosphere, were significantly lower than normal in December 2017–January 2018. Analysis of back trajectories and integrated (over profile) TO showed that the dynamic disturbance of the Arctic stratosphere in December 2017 led to the extrusion of cold air masses with excessive reactive chlorine content (in view of NO
2
deficit) beyond the Arctic circle and their intrusion into the stratosphere of Tomsk. Seemingly, they were exposed to solar radiation in the stratosphere over Tomsk and, staying spatially isolated, became chemically disturbed. This state is similar to the state of the springtime Arctic stratosphere, where ozone is intensely destroyed until the final warming.
The effect of Fe and Mg-codoping on the crystal structure, optical and dielectric properties of bismuth tantalate-based pyrochlores has been studied. Samples of Bi2MgxFe1−xTa2O9.5−Δ (x ≤ 0.7) are ...characterized by a porous dendrite-like microstructure. Fe,Mg-codoped bismuth tantalate pyrochlores are thermally stable up to a temperature of 1140 °C (x = 1). The Bi2Mg0.5Fe0.5Ta2O9.5−Δ thermal expansion coefficient increases uniformly and weakly from 3.6 to 9.3 × 10−6 °C−1 (30–1050 °C). The unit cell parameter of solid solutions increases uniformly from 10.5009(1) Å (x = 0.3) up to 10.5225(7) Å (x = 0.7). The structural parameters of disordered pyrochlore are determined by the Rietveld method (sp. gr. Fd3¯m:2 (227), Z = 8). According to near edge X-ray absorption fine structure and X-ray photoelectron spectroscopy data, ions in solid solutions are in the charge states Bi (+3), Mg (+2), Fe (+3), Ta (+5-δ). The Mössbauer spectrum is represented by a symmetric doublet with parameters IS = 0.365 ± 0.0020 mm/s, QS = 0.604 ± 0.034 mm/s, related to Fe3+ ions in regular axial octahedral positions. The samples exhibit the properties of dielectrics. The permittivity and the tangent of dielectric losses at 20 °C increases with the growth of iron content in the samples in the range of 28.5–30.5 and 0.001 (1 MHz). The width of the band gap of the obtained materials for direct allowed electronic transitions is in the range of 2.16(5)–2.41(5) eV. The studied samples satisfy the condition of efficient conversion of solar energy into an electrical one and are promising as catalysts and light-absorbing elements for solar panels.
The article is dedicated to the search of ways of decreasing environmental damage from the quarry industry, generating crusher screening. Construction and technological reuse is offered as the most ...effective way of waste dump elimination. In this regard, screening of stone crushing are considered a valuable raw material component of high quality fine grain concretes, having mechanical, mechanical and physical as well as physical and chemical activity, which is effected in the processes of structure formation of concrete on its macro-, meso- and micronanolevels. The results of research of screening genesis, its characteristics, and its influence on the structure formation processes and the properties of fine grain concrete are presented. The suggestions for conditioning of screening with the view to increasing the efficiency of the concrete produced with their use and increasing the demand for screening in the construction market are validated.
Development of novel approaches for designing advanced energy storage devices generally requires a fundamental understanding of the atomic structure of and processes in constituent materials. ...Correspondingly, the modern-day frameworks for computational design of electrolyte materials extensively employ either quantum calculations or atomistic simulation methods, or often, a combination thereof. Within the frameworks of recently devised approaches, these two computational methods are augmented by advanced machine learning techniques. Here, we focus on the recent developments in electrolyte materials design, with the emphasis on the computational design of liquid electrolytes. A particular attention is paid to the recent progress in building a unified framework for large-scale and high-throughput screening of liquid electrolyte material systems for battery applications. We address the status quo in the area and present a perspective on essential further efforts that have to be undertaken to construct realistic paradigms for intelligent design of electrolyte materials by testing physical and chemical properties of large sets of candidate chemical compounds and their combinations. The issues of further improvements in quantum calculations and atomistic simulation are also briefly addressed in the context of energy storage device applications.
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