Homogeneous Layer Research Articles

The Influence of Hydroxyapatite Crystals on the Viscoelastic Behavior of Poly(vinyl alcohol) Braid Systems.

Composites of poly(vinyl alcohol) (PVA) in the shape of braids, in combination with crystals of hydroxyapatite (HAp), were analyzed to perceive the influence of this bioceramic on both the quasi-static and viscoelastic behavior under tensile loading. Analyses involving energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) allowed us to conclude that the production of a homogeneous layer of HAp on the braiding surface and the calcium/phosphate atomic ratio were comparable to those of natural bone. The maximum degradation temperature established by thermogravimetric analysis (TGA) showed a modest decrease with the addition of HAp. By adding HAp to PVA braids, an increase in the glass transition temperature (Tg) is noticed, as demonstrated by dynamic mechanical analysis (DMA) and differential thermal analysis (DTA). The PVA/HAp composite braids' peaks were validated by Fourier transform infrared (FTIR) spectroscopy to be in good agreement with common PVA and HAp patterns. PVA/HAp braids, a solution often used in the textile industry, showed superior overall mechanical characteristics in monotonic tensile tests. Creep and relaxation testing showed that adding HAp to the eight and six-braided yarn architectures was beneficial. By exhibiting good mechanical performance and most likely increased biological qualities that accompany conventional care for bone applications in the fracture healing field, particularly multifragmentary ones, these arrangements can be applied as a fibrous fixation system.

Field of a directional low-frequency acoustic emitter in the boundary layer of the atmosphere

Due to the fact that many wave emitters that a person is able to perceive belong to low-frequency ones, studies of sound fields created by such emitters are relevant. Thanks to the results obtained, it becomes possible to understand in which directions and with what power the sound field created by them will propagate, form practical recommendations for choosing the zone most suitable for observing them, solve inverse problems to determine their location. As a result of the analysis of existing models used to describe acoustic emitters, it was found that the most adequate models are those that take into account the directionality of sound sources. Among them, the parametric model proposed by G.N. Kuznetsov and A.N. Stepanov deserves special attention, which was used in the work. As a model representation of the atmosphere, a system of homogeneous layers was chosen, in one of which the source is located. For the selected models of the source and medium, the boundary value problem of finding the potential of the field created by the source is set, exact and approximate relations are obtained that can be used to solve direct and inverse problems associated with a multipole emitter. The influence of such factors as the height and frequency of the source, as well as the horizontal distance between the source and receiver on the amplitude component of the field has been studied.

Theoretical magnetotelluric response of stratiform earth consisting of alternative homogeneous and transitional layers

Abstract The magnetotelluric (MT) responses are explicitly solved for a stratiform earth containing multiple transitional layers in which the conductivity varies linearly with depth. In the model under consideration, any one homogeneous layer with constant conductivity or transitional one may be absent in the geometry. The traditional one-dimensional (1D) models with sharp boundaries will be obtained if all the transitional layers are absent in the geometry, while a special 1D model consisting of a sequence of contiguous transitional layers may be obtained if all the homogeneous layers (except the basement layer) are removed from the geometry. The tangential electric and magnetic fields as well as the surface impedance are analytically expressed by Airy functions. The analytical formula is validated in three theoretical examples by comparing with the results from available codes. The apparent resistivity and impedance phase on the surface of three different transitional models are illustrated to analysis the influence of the transitional layers on MT responses. The new formula provides an alternative way to obtain the analytic MT responses for the special layered earth.

Ni/CeZr deposition on metallic mesh supports for CO2 methanation. Adherence and morphology

Structured supports suitable for highly demanding reactions in heat and mass transfer such as the Sabatier reaction were synthesised. The use of a metallic mesh as the support is promising. In this work, a treatment strategy for the metallic substrate and deposition of the support and the catalytic phase was proposed to obtain a thin, homogeneous, and crack-free layer that avoid the attack of the metallic substrate under the reaction conditions. The metallic surface of the meshes was thermally pre-treated under different conditions to generate roughness. A layer of Ce and Zr oxides was deposited from Nyacol® to generate the catalyst support that act, at the same time, as a barrier between the reaction atmosphere and the surface of the meshes. Subsequently, nickel was deposited as an active phase by impregnation. The elimination of the excess was studied by air blowing and centrifugation. The morphology, phase structure and adhesion of the layer were investigated by SEM, EDX and adherence test. The results showed that the load and the adhesion of the layer were affected by the mesh size and the conditions of the excess removal as well as the concentration of the slurry. The adhesion of the active phase was excellent under severe conditions.

2-D seismic wave propagation using the distributional finite-difference method: further developments and potential for global seismology

SUMMARY We present a time-domain distributional finite-difference scheme based on the Lebedev staggered grid for the numerical simulation of wave propagation in acoustic and elastic media. The central aspect of the proposed method is the representation of the stresses and displacements with different sets of B-splines functions organized according to the staggered grid. The distributional finite-difference approach allows domain-decomposition, heterogeneity of the medium, curvilinear mesh, anisotropy, non-conformal interfaces, discontinuous grid and fluid–solid interfaces. Numerical examples show that the proposed scheme is suitable to model wave propagation through the Earth, where sharp interfaces separate large, relatively homogeneous layers. A few domains or elements are sufficient to represent the Earth’s internal structure without relying on advanced meshing techniques. We compare seismograms obtained with the proposed scheme and the spectral element method, and we show that our approach offers superior accuracy, reduced memory usage, and comparable efficiency.

Low-cost micron-sized silicon/carbon anode prepared by a facile ball-milling method for Li-ion batteries

Commercially, Si nanoparticles (nano Si) are blended with graphite to construct high-capacity Si/C anodes. However, this strategy falls short because of the high cost of nano Si, serious pollution due to the use of organic solvent, and weak physical-electrical connection between graphite and Si. Herein, using low-cost micron-sized Si (μSi) and graphite as the raw materials, we proposed a facial ball-milling method to construct high-performance Si/C anode (μSi/C@CH) in which milled Si particles are protected both by graphite matrix and homogeneous chitosan-derived carbon layer. It is shown that the N and O atoms not only tend to coordinate with Li+, generating uniformly-distributed Li+ transport channels, but also improve the electrical conductivity of the anode materials. As a result, μSi/C@CH shows high cycling stability (376.7 mAh g-1 at 0.5 A g-1 after 500 cycles) and good rate capability of 120.2 mAh g-1 at 5 A g-1. This dual protection strategy facilitates the practical application of Si/C materials in high-energy density Li ion batteries (LIBs).

Electrolyte Engineering with Tamed Electrode Interphases for High-Voltage Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) hold great promise for next-generation grid-scale energy storage. However, the highly instable electrolyte/electrode interphases threaten the long-term cycling of high-energy SIBs. In particular, the instable cathode electrolyte interphase (CEI) at high voltage causes persistent electrolyte decomposition, transition metal dissolution, and fast capacity fade. Here, this work proposes a balanced principle for the molecular design of SIB electrolytes that enables an ultra-thin, homogeneous, and robust CEI layer by coupling an intrinsically oxidation-stable succinonitrile solvent with moderately solvating carbonates. The proposed electrolyte not only shows limited anodic decomposition thus leading to a thin CEI,but also suppresses dissolution of CEI components at high voltage. Consequently, the tamed electrolyte/electrode interphases enable extremely stable cycling of Na3V2O2(PO4)2F (NVOPF) cathodes with outstanding capacity retention (>90%) over 3000 cycles (8 months) at 1 C with a high charging voltage of 4.3 V. Further, the NVOPF||hard carbon full cell shows stable cycling over 500 cycles at 1 C with a high average Coulombic efficiency (CE) of 99.6%. The electrolyte also endows high-voltage operation of SIBs with great temperature adaptability from -25 to 60°C, shedding light on the essence of fundamental electrolyte design for SIBs operating under harsh conditions.

Seismic Failure Mechanisms of Concrete Pile Groups in Layered Soft Soil Profiles

So far, little attention has been paid to the investigation on the seismic failure mechanisms of flexible concrete pile groups embedded in the layered soft soil profiles considering the material non-linearities of soil and concrete piles. The purpose of this study is to investigate seismic failure mechanism models of flexible concrete piles with varied groups in silt layered loose sand profiles under horizontal strong ground motions. Three-dimensional finite element models of the pile–soil interaction systems, which include nonlinearities of soil and concrete piles as well as coupling interactions between the piles and soil, were created for Models I, II, and III of the soil domains, encompassing 1x1, 2x2, and 3x3 flexible pile groups with diameters of 0.80 m and 1.0 m. Model I consists of a homogenous sand layer and a bedrock, Models II and III are composed of a five-layered domain with homogeneous sand and silt soil layers of different thicknesses. The linear elastic perfectly plastic constitutive model with a Mohr–Coulomb failure criterion is considered to represent the behavior of the soil layers, and the Concrete Damage Plasticity (CDP) model is used for the nonlinear behavior of the concrete piles. The interactions between the soil and the pile surfaces are modeled by defining tangential and normal contact behaviors. The models were analyzed for the scaled acceleration records of the 1999 Düzce and Kocaeli earthquakes, considering peak ground accelerations of 0.25 g, 0.50 g, and 0.75 g. The numerical results indicated that failure mechanisms of flexible concrete groups occur near the silt layers, and the silt layers have led to a significant increase in the spread area of the damaged zone and the number of damaged elements.

Geotechnical seismic isolation based on high-damping polyurethane: centrifuge modelling

Geotechnical seismic isolation (GSI) is a new category of low-damage resilient design methods that are in direct contact with geomaterials and of which the isolation mechanism primarily involves geotechnics. Various materials have been explored for placing around the foundation system in layer form to facilitate the beneficial effects of dynamic soil-foundation-structure interaction, as one of the GSI mechanisms. To reduce the thickness of the GSI foundation layer and to ensure uniformity of its material properties, the use of a thin and homogeneous layer of high-damping polyurethane (HDPU) was investigated in this study via centrifuge modelling. HDPU sheets were installed in three different configurations at the interface between the structural foundation and surrounding soils for realising GSI. It was found that using HDPU for GSI can provide excellent seismic isolation effects in all three configurations. The average rates of structural demand reduction amongst the eight earthquake events ranged from 35 to 80%. A clear correlation between the period-lengthening ratio and the demand reduction percentage can be observed amongst the three GSI configurations. One of the configurations with HDPU around the periphery of the foundation only is particularly suitable for retrofitting existing structures and does not require making changes to the structural systems or architectural features.

Effect of Vicia villosa protein isolate-based edible coating incorporated with ZnO nanoparticles on the shelf-life of chicken breast meat during cold storage

In this study, Vicia villosa protein isolate (VVPI), with a high and valuable protein source, was used to create an edible coating containing ZnO nanoparticles (ZnO NPs) to investigate the effect of active coating on the quality of chicken breast fillets during refrigerated storage. The results showed a low growth rate in total viable count (TVC) and lactic acid bacteria (LAB) in coated samples. Moreover, as ZnO NPs concentration increased, thiobarbituric acid reactive substances (TBARS) decreased in the coated samples. In addition, the acid value and total volatile basic nitrogen (TVB-N) in the coated samples were significantly lower than the control group. Fourier transform infrared (FTIR) spectrum confirmed the chemical interactions of the coating components. Scanning electron microscopy (SEM) showed a homogeneous layer of coating on the surface of the coated chicken meat. Organoleptic indicators including color, smell, texture and overall acceptability were acceptable in all coated samples. These findings showed that the coating based on protein isolate containing ZnO NPs has a good potential to increase the safety and shelf life of chicken meat.

NON-STATIONARY WAVES IN A FUNCTIONALLY GRADED VISCOELASTIC PLANE-PARALLEL LAYER2

The propagation of nonstationary disturbances in a plane-parallel layer of infinite extent, which arise as a result of normal dynamic loading of one of its surfaces when the other surface is stationary, is investigated. The material of the layer is assumed to be functionally graded and, at the same time, viscoelastic. The hereditary properties of such a material are taken into account using linear integral Boltzmann–Volterra relations with regular kernels in the form of partial sums of the Prony's series. The peculiarity of this work is that here the parameters of the relaxation kernels are considered continuous functions of the transverse coordinate in the same way as other physical and mechanical characteristics. A method was used for the study, which consists in replacing a functionally graded material with an approximating layered homogeneous structure with continuity conditions at the contact of homogeneous layers. The solution of the nonstationary dynamic linear viscoelasticity problem for a package of plane homogeneous viscoelastic layers is presented in a special form, which greatly simplifies its numerical implementation, especially with a large number of layers with different hereditary properties. This made it possible to successfully apply this method and carry out a series of calculations using an efficient algorithm. Transient wave processes are investigated in the case when the parameters of a functionally graded material are non-monotonic functions of the transverse coordinate, symmetrical with respect to the middle surface of the layer. A comparison of transient wave processes for different types of these functions is carried out. The convergence of the calculation results with an increase in the number of approximating homogeneous layers with a continuous dependence of the external load on time is confirmed. The significant influence of both heterogeneity and viscosity of the material on nonstationary wave processes has been established.

Silybum marianum Extract: A green inhibitor for Iron Metal Corrosion and Bacterial Growth in Fresh and Marine Media

Egyptian Silybum marianum ethanolic-hexane crude extract efficiency was investigated as an inhibitor of bacterial growth and iron steel corrosion in fresh water and marine environment media. Iron steel corrosion inhibition rate was quantitatively measured by two methods: one as a concentration of iron released in the medium over time intervals at different inhibitor ratios against the control using Inductive Coupled Plasma Mass Spectrometry (ICP-MS), and the second was relative weight loss method. Meanwhile, the development of the adsorption layer of the inhibitor on the surface of the iron steel specimen was monitored qualitatively using scanning electron microscopy. The adsorption of the extract constituents was found to obey Langmuir adsorption isotherm. Bacterial growth inhibition was examined using a well-diffusion method. After three days, the percentage of corrosion inhibition in fresh and marine media was 95% and 91%, respectively at the ratio of 1.5 mg/mL of the crude extract, and a homogeneous adsorption layer was observed on the surface of the iron specimen. The same dose was enough to inhibit bacterial growth in both media. Natural ecofriendly inhibitor extracted from a wild native Egyptian plant was found to be anticorrosion and at the same time antibacterial in both fresh and marine water media.

Investigation of perovskite layer growth from solution on textured substrates

Surface textures are indispensable to minimize optical losses in perovskite-based solar cells. However, the solution-processing of perovskite layers is often not compatible with textured substrates, and little is known about the film growth thereon. This study aims to elucidate the growth process of perovskite layers from solution on textured substrates and to identify the texture features ensuring compatibility with perovskite solution-processing. Using nanoimprint-lithography we prepared three different periodically as well as randomly textured glass substrates for spin-coated perovskite solar cells, of which one was duplicated from a commercially available texture. During the perovskite crystallization process, a time-resolved in situ photoluminescence measurement was conducted. The photoluminescence signal was not found to substantially alter using textured substrates with texture heights around 500 nm. Optical absorptance spectroscopy and scanning electron microscopic imaging were applied to investigate the growth, crystal structure, and optical properties of solution-processed perovskite on top of different textures. We find that periodic textures with height around 500 nm enable homogeneous solution-processed perovskite layers with optimized optical performance. In contrast, texture heights of several micrometers lead to macroscopic holes in the perovskite film. The results of this study will help to find optimum optical textures for high-efficiency perovskite single-junction and perovskite-silicon tandem solar cells.

Modeling carbon dioxide and methane adsorption on illite and calcite: enhancing the simplified local density model through crystal structure modifications.

The simplified local density (SLD) model has been frequently utilized to describe gas adsorption in porous media. The common assumptions associated with the SLD model are the graphene slit and uniform distribution of atoms. However, these fail to depict the heterogeneous surface of minerals. In this study, the original SLD model was modified by substituting mineral crystal structures for the homogeneous carbon layer when building the slit. The modified model may capture the heterogeneity-induced variation of the fluid-pore interaction potential and adsorbed phase density near the mineral surface. The calculated adsorption isotherms of methane and carbon dioxide on illite and calcite surfaces at 330.15 K were compared with literature experiment data to validate the modified SLD model. For the simulation of gas adsorption isotherms, the modified model predictions agree reasonably well with the previously reported experiment results using the gravimetric method. The calculated density profile in the slit indicates the monolayer adsorption behavior of CH4 and CO2. Based on more precise interaction potentials, the number of regression parameters was reduced to two, and the physical meaning of the model parameters was clarified. Therefore, for estimating hydrocarbon storage in reservoirs, the modified SLD model could be used as an efficient alternative to time-consuming molecular simulation methods.

ПОЧВООБРАБАТЫВАЮЩИЕ ФРЕЗЫ ДЛЯ ОСНОВНОЙ ОБРАБОТКИ ПОЧВЫ И ВОССТАНОВЛЕНИЯ ЗАДЕРНЕННЫХ УГОДИЙ

Milling is one of the most effective methods of processing of heavy over-compacted soils, recultivation of blackened lands and development of virgin and fallow lands. As a result of intensive loosening and mixing of the soil, the mineralization process accelerates. When choosing the type of milling unit and its operating modes, the depth of the humus horizon, the type and density of the soil, the thickness of the sod, the presence of shrubs, stones, stumps, hummocks, the microrelief of the soil, the contamination with rhizomatous and other weeds are taken into account. (Research purpose) The research purpose is analyzing the used tillage cutters for basic tillage and the returning of blackened lands into circulation. (Materials and methods) Considered the design features of tillage cutters used in basic tillage and in blackened areas. Systematized data about them. (Results and discussion) It was determined that various designs of cutters make it possible to effectively grind blackened and compacted soil, destroy above-ground vegetation, and level the surface soil layer. It was found that effective processing of blackened lands includes grinding the sod and embedding it in the soil to a depth of 20-25 centimeters, creating a loose homogeneous fertile soil layer. (Conclusions) Milling allows high-quality processing of heavy, including blackened soils. The technological operation of milling provides shredding of weeds, uniform processing of fields and leveling of the surface layer, increasing the air permeability and infiltration properties of soils, reducing the time to prepare for pre-sowing treatment by combining several technological operations when using combined cutters.

Interfacial assembly and rheology of multi-responsive glycyrrhizic acid at liquid interfaces.

Glycyrrhizic acid (GA), a naturally derived food-grade saponin molecule, is a promising alternative to synthetic surfactants for stabilizing multiphase systems including emulsions and foams, due to its biological activity and surface-active properties. Understanding the interfacial behavior of GA, particularly in relation to its complex self-assembly behaviors in water induced by multiple environmental stimuli, is crucial to its application in multiphase systems. In this study, we comprehensively investigate the interfacial structure and rheological properties of GA systems, as a function of pH and temperature, through Langmuir-Blodgett films combined with atomic force microscopy, interfacial particle tracking, adsorption kinetics, stress-relaxation behavior and interfacial dilatational rheology. The variation of solution pH provokes pronounced changes in the interfacial properties of GA. At pH 2 and 4, GA fibril aggregates/fibrils adsorb rapidly, followed by rearrangement into large lamellar and rod-like structures, forming a loose and heterogeneous fibrous network at the interface, which exhibit a stretchable gel-like behavior. In contrast, GA at pH 6 and 8, featuring micelles or monomers in solutions, adsorb slowly to the interface and re-assemble partially into small micelle-like or irregular structures, which lead to a dense and homogeneous interfacial layer with stiffer glassy-like responses. With successively elevated temperature, the GA structures (pH 4) at the interface break into smaller fragments and further adsorption is promoted. Upon cooling, the interfacial tension of GA further decreases and a highly elastic interfacial layer may be formed. The diverse GA assemblies in bulk solution impart them with rich and intriguing interfacial behaviors, which may provide valuable mechanistic insights for the development of novel edible soft matter stabilized by GA.

Influence of thermal boundary layer on thermophysical properties of construction materials

The paper considers the influence of thermal boundary layer on the thermal conductivity coefficient of building materials. The influence of thermal boundary layer on the thermal characteristics is shown on the example of cellular materials such as foam concrete, gas silicate and vacuum-powder thermal insulation materials.New ideas about regularities and mechanism of action of such factors as pore size, thickness and composition of interstitial partitions on thermal conductivity of porous materials are proposed. The thermal characteristics of porous systems were analyzed using the theory of similarity (calculation of Grasgoff, Rayleigh, and Prandtl criteria). Calculation of these criteria showed that in cellular materials with pore diameter up to 4 mm the convective component does not influence the heat transfer coefficient. The thermal boundary layer, a low-moving thin layer of gas adsorbed on the inner surface of the pore, has a great influence on the heat transfer processes in the pore. The paper considers the structure of the thermal boundary layer from the approach of the electrical surface properties of the pore and the gas in it. It is shown that the structure of the thermal boundary layer depends on the surface charges of the solid phase and gas. In the environment of air or oxygen denser and more homogeneous in structure thermal boundary layer will have materials, which pore walls will have an effective positive charge, and the thermal boundary layer of materials with a large negative surface charge will be loose, inhomogeneous. In hydrogen medium, on the contrary, materials with an effective negative charge will have a denser and more homogeneous thermal boundary layer structure.

An MPM-Based Phase-Field Simulation of Plating and Stripping of Lithium with a Solid Electrolyte Interphase

A methodology for performing phase-field simulations of plating and stripping in the presence of a solid electrolyte interphase (SEI) is presented and applied to a lithium metal electrode. Material point method (MPM) simulations are performed assuming a homogeneous SEI layer and are compared with experiment. Results are consistent with experiment for two electrolytes and confirm the dominance of the SEI layer in determining cell impedance. Notably, in some instances, the SEI potential drop greatly affected activation overpotential, differing from the applied potential. To accurately depict stripping current vs potential for SEI-free systems, the model considered non-ideal electrolyte effects: concentration-dependent salt activity coefficient, salt diffusion coefficient, and electrolyte conductivity. Conversely, systems with SEI layers displayed minimal non-ideal concentration-related electrolyte effects due to impedance originating primarily from the SEI. In plating scenarios, low SEI salt concentration negated the need for non-ideal SEI effects. However, for stripping, non-ideal salt-concentration dependent SEI effects were crucial in reproducing experimental behavior, owing to high salt concentration at the electrode/SEI interface.

Ultrafast, in situ transformation of a protective layer on lithium-rich manganese-based layered oxides for high-performance Li-ion batteries

We successfully used ultrafast high-temperature heating to create a homogeneous surface layer with a mixed-phase oxygen-vacancy composition on the cathode material, preserving the inherent layered structure within the cathode particles.

Comparative evaluation of remineralization potential of four different remineralization agents on human enamel: An in vitro study.

The study aimed to assess the remineralizing potential of four different commercially available agents using a Scanning Electron Microscope (SEM), energy dispersive X-ray (EDX) analysis, and Vickers Microhardness (VMH) Test. Forty-four specimens (n = 11 per group) were prepared from extracted teeth. A window of 6 mm × 4 mm was made on all the specimens that represented three zones, namely, sound enamel, demineralized enamel, and remineralized enamel. The zone for demineralized enamel was subjected to four different remineralizing agents; casein phosphopeptide-amorphous calcium phosphate fluoride (CPP-ACPF), tricalcium phosphate fluoride (TCP-F), calcium sucrose phosphate (CSP), and self-assembling peptide (P11-4). Remineralization (REM) was assessed using VMH; the structural changes were assessed using SEM that was analyzed using EDX analysis. The specimens were subjected to a newer regimen of demineralization. One-way ANOVA followed by post hoc Tukey test was used with a level of significance at P ≤ 0.05. There were no significant differences in VMH between the groups for sound enamel (P = 0.472) and demineralized enamel (P = 0.116). VMH was statistically significantly more for P11-4 and the least for CPP-ACPF (P = 0.011). A post hoc analysis revealed higher VMH for P11-4 compared to CPP-ACPF (P = 0.014) and TCP-F (P = 0.035). SEM showed a homogeneous layer of minerals for all groups except CPP-ACPF. TCP-F reported a higher degree of REM, followed by P11-4 as assessed using EDX analysis. Self-assembling peptide (P11-4) exhibited a higher degree of REM than other remineralizing agents followed by CSP.