Surface Layer Research Articles

Estimation of errors of the spectral method for measuring the concentration of water vapor and moisture reserves in the surface layer of the earth’s atmosphere

Estimation of errors of the spectral method for measuring the concentration of water vapor and moisture reserves in the surface layer of the earth’s atmosphere

Comparison of surface layers responses under heavy truck loadings on new and rehabilitated pavement with different interface bond conditions

The integrity and functionality of road pavements are vital for ensuring safe and efficient transportation networks. However, surface layers are prone to various forms of deterioration. This study investigates the responses of two pavement structures-one newly constructed and one rehabilitated-under traffic loading, through experimental tests conducted on an accelerated pavement testing facility (APT) and numerical simulations using the Viscoroute©2.0 software. Focus is placed on surface layer behavior, with an emphasis on understanding the behavior of interfaces between the asphalt layers. The findings show that the new pavement structure exhibits good bonding and continuous strain distribution, while the reinforced pavement structure exhibits partial sliding at the interface and strain discontinuity. For the new pavement structure, the strains are well predicted using a bonded interface, while for the rehabilitated pavement structure, the strains are predicted using a thin elastic interface layer with a low elastic modulus.

Modeling wear of different surface layers of agricultural tools in soil abrasive mass

Uniform quantitative measures have not been developed to identify the areas with the greatest intensification of tool wear. Therefore, this paper developed original approach to assess the wear of cutting elements by identifying the intensity of local volumetric wear. A tribological test was conducted under natural operating conditions in two soil types: sandy loam and loam. The specimens were mounted on a 9-tined cultivator with spring tines aggregated with an agricultural tractor. A method was developed to discretise the local volume changes of a component using surface scanning models developed from 3D scanning. The notion of the rake angle has been defined, allowing the assessment of changes in the shape of the element during wear. The practical usefulness of the developed method was verified on three types of surface layers, i.e. 38GSA steel, ELHARD70 deposited on it, and a G10 layer of carbide. For each of the tested variants, local volumetric consumption was defined based on the identification of the wear grid. These should be the basis for developing the technology of surface strengthening of elements. The work confirmed the complexity of the process of wear of working elements in natural soil conditions, presented in many research works. A different course of wear of the 38GSA steel and the Elhard 70 weld layer was shown, depending on the type of treated soil. In the case of samples made of G10 cemented carbide, the largest volumetric wear for heavy soil occurred outside the place of reinforcement application. The highest volumetric wear in the front zone was recorded for 38GSA steel in heavy soil. Wear results from the modelling are similar to those obtained from the experiment under natural conditions in light soil using the nominal model (CAD) and the actual friction surface.

Characteristics of Submesoscale Compensated/Reinforced Fronts in the Northern Bay of Bengal

AbstractFronts in the Bay of Bengal (BoB) are active and can potentially impact the regional dynamics such as temperature variability, salinity distribution and oceanic circulation. Based on the high resolution model output (LLC4320), this study investigates the characteristics of submesoscale fronts in the northern BoB and associated compensation/reinforcement effects. At sea surface, horizontal gradients of salinity and density are remarkable in the northern BoB, and they are nearly 3 times larger than temperature gradients. As the depth deepens, temperature gradients increase and become comparable to salinity gradients, while density gradients decrease a lot due to the increasing effects of compensation at subsurface. Statistical results show the dominance of salinity‐controlled fronts over temperature‐controlled fronts, and compensated fronts over reinforced fronts. The surface cooling/heating results in significant temporal variation of compensation at surface, but this variation is limited at subsurface by the blocking of the mixed layer base. The submesoscale‐selective feature of compensation is much more pronounced at subsurface layer than surface layer. From statistical analysis and idealized numerical model, we found the slump of salinity‐controlled compensated fronts are important in generating temperature inversion and maintaining barrier layer. This study validates the compensation theories originating from observations, and further illustrates the importance of subsurface compensated fronts using spatially continuous, regionally extended and longer‐term model output. The subsurface‐intensified submesoscale‐selective compensation is proved for the first time in this study.

B3LYP and B3PW computations of BaSnO3 and BaZrO3 perovskite (001) surfaces

By means of the B3LYP and B3PW hybrid exchange-correlation functionals, as it is included in the CRYSTAL computer code, we performed ab initio computations for BaSnO3 and BaZrO3 perovskite (001) surfaces. For BaSnO3 and BaZrO3 perovskite (001) surfaces, with a few exceptions, all atoms of the upper surface layer relax inwards, all atoms of the second surface layer relax outwards, and all third layer atoms, again, relax inwards. The relaxation of BaSnO3 and BaZrO3 (001) surface metal atoms for upper two surface layers, for both BaO and BO2-terminations, as a rule, are considerably larger than the relaxation of relevant oxygen atoms. The BaO (1.30 eV) and ZrO2-terminated (1.31 eV) BaZrO3 (001) surface energies are almost equal. The BaZrO3 perovskite BaO (4.82 eV) and ZrO2-terminated (4.48 eV) (001) surface Г-Г band gaps are reduced regarding the respective bulk Г-Г band gap value (4.93 eV). The B–O chemical bond populations in BaSnO3 and BaZrO3 perovskite bulk always are smaller than near their SnO2 and ZrO2-terminated (001) surfaces, respectively.

Developing sustainable steel slag-based aerated concrete: Effects of accelerated carbonation on performance and carbon emissions

This research undertakes an in-depth examination of the properties of carbonated steel-slag aerated concrete (CSSAC), the mineral composition and microstructure were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), life cycle assessment (LCA) also employed for evaluating its environmental impacts. Results revealed that a strength of 6.6 MPa and a dry density of 958 kg/m3 for CSSAC was achieved through carbonation curing, utilizing a 30 vol% CO2 concentration at ambient pressure for a duration of 24 h. Nonetheless, elements such as high water-solid ratio, cement content, and foaming agent content were found to negatively affect the strength development. Furthermore, the overuse of lime as a cement substitute formed a dense pore structure on the surface layer, consequently lowering CO2 sequestration efficiency. It was found that compressive strength was enhanced and water absorption was reduced by 66 % with calcium stearate, through effective pore structure optimization. Significantly, the carbon footprint of CSSAC stood at a minimal 0.0673 kg∙CO2∙eq/kg, achieving a substantial 73.36 % reduction when compared with its original carbon footprint. This adoption of carbonation curing effectively mitigated the carbon footprint of the product, offering actionable insights for the manufacturing of zero-carbon and even negative-carbon building materials.

Microplastic and ichthyoplankton in the Ukrainian waters of the Black Sea

The ability of planktonic and neustonic organisms to feed on microplastics and subsequently transfer it through the marine food web has been studied extensively. However, there are no studies on microplastic in the Northwestern Black Sea. The present study assesses the diversity and spatial distribution of microplastics and ichthyoplankton in two surface layers: 0-5cm (neuston surface layer; NL) and 5-20cm (hyponeuston layer; HL). The sampling was undertaken in June 2020 – October 2021 in the coastal (CW) and open (OW) waters of the Northwestern Black Sea. Microplastics was observed at all studied sites and was composed of fibres (75%) and fragments (25%). Black and red fibres were the most abundant type of fibre, and black particles dominated the fragments. Four types of polymers were identified by Raman spectroscopy: polyethylene, polyester, polyurethane, polypropylene. The concentration of microplastics near the coast significantly exceeded that of open waters; the average microplastics concentration in the CW reached 136±74 (±SE) and 46±30 particles.m-3 in the NL and HL, respectively, whereas it reached 18±3 and 2±0.8 particles.m-3 in the NL and HL of the OW, respectively. In the NL, ichthyoplankton was found only at 31% of the sites, and at only 24% of sites in the HL. In total, 6 species of fish were recorded. The most abundant species was the European anchovy, one of the main commercial species in the Black Sea. The ratio of microplastics to ichthyoplankton was 0.34 (or 1:2.87) for both layers, where ichthyoplankton was present. When considering all studied sites, the ratio of microplastics to ichthyoplankton was 1.07 (or 1:0.93). As ichthyoplankton is an ephemeral component of the neuston community, but microplastics is omnipresent, we may consider that comparable densities of microplastics:ichthyoplankton favour their interrelation, negative effect, and transport through the food web.

Remote sensing retrieval of surface soil moisture in Mu Us Sandy Land based on optical trapezoid model

Abstract Maowuosu sandland ecosystem is fragile, and moisture is a key factor restricting the growth and development of sandland plants and ecological construction in semi-arid areas. Therefore, this study constructed the eigenspace based on the data of the 4th period of 2016, fitted the dry and wet edge equations of the eigenspace, calculated the OPTRAM, and utilized the measured in situ soil moisture data from various depths during the corresponding period. The OPTRAM was regressed to construct a model for estimating soil moisture. This model was then subjected to a series of validation procedures to ensure its accuracy. The coefficients for the shortwave infrarouges conversion reflection coefficient (STR) - standardized differential vegetation index (NDVI) feature space dry and wet edge fits increased with the increase of the month, where the dry and the R2 for the wet side in September was 0.88 and 0.87, respectively. OPTRAM and the measured soil moisture content data in the surface layer were all correlated to some extent, with correlation coefficients above 0.45. The OPTRAM model is more accurate than other models in inverting in situ moisture content at the 0∼10 cm depths within this area.

Survival strategies of microalgae in response to fluctuating brine environments in Saroma-ko Lagoon sea ice, Hokkaido, Japan.

This study investigated the changes in sea ice temperature, microalgae species distribution, shape changes, and photosynthetic activity observed in the first-year ice that forms in winter in Saroma-ko Lagoon, Hokkaido, Japan. Temperatures at the bottom of the ice remained constant at -1.7°C, near the freezing point, while they varied between -6 and -1°C with diel fluctuations at the surface layer. Carefully collected algal samples showed high photosynthetic quantum yield and acclimation to the light intensities of individual ice layers; this indicates that the algal photosynthetic activity responds to dynamic changes in the ice environment, such as variations in temperature, salinity, and brine space. The algal communities consisted of more than 95% diatoms. Smaller algal cells were distributed in the upper layer of the sea ice compared to the lower layers. Chaetoceros sp., the dominant small-cell species, was evenly distributed throughout the layers. In contrast, Detonula confervacea, the dominant large-cell species, was unevenly distributed in the lower layer, with smaller colony size and cell volume in the upper layer. The shape differences observed in this species were thought to be a response to the changing environment within the first-year sea ice.

SYNTHESIS AND PHYSICO-CHEMICAL PROPERTIES OF A NEW COMPLEX FERRITE

The article discusses the synthesis of new complex ferrite, radiographic and electron microscopic studies. The phase of complex ferrites was synthesized by the method of high-temperature sol-gel synthesis. For the first time, the structure of CrKFe2O5 Composite ferrite was studied by X-ray phase analysis and scanning electron microscope methods, the syngony type, elementary cell parameters, radiographic and pycnometric densities, and elemental analysis were determined. A comparative analysis of the relationship between the parameters of the Crystal cell of primary substances and the parameters of the obtained complex ferrite Crystal cell was carried out. Micro-samples were taken from different parts of the crystallite obtained through a scanning electron microscope, the elemental composition of the crystals was analyzed, and the general type of layer of the complex ferrite surface was demonstrated. As a result, the fact that the compound consists of two phases, the clarity of its construction was determined by the topography and chemical composition of the compound. As a result, it was found that the newly synthesized complex ferrite corresponds to the Formula CrKFe2O5. The particle size of the compounds formed is large (between 200 μm, 20.0 μm, 5.00 μm and 2.00 μm).

Hierarchical Ti3C2Tx MXene@Honeycomb nanocomposite with high energy efficiency for solar water desalination

The utilization of solar-driven interfacial evaporation holds immense promise in enhancing energy efficiency and establishing sustainable methods for seawater desalination and water purification. While designing the materials to achieve high evaporation efficiency, the tuning of materials with porosity and surface chemistry is very crucial. Novel sustainable materials are of great importance for solar water desalination applications since clean water production is utmost important in the current era. There exists a lack of exploration in modifying the surface wettability states of solar evaporators to expedite the vapor generation rates. In this study, we showcase a hydrophilic Ti3C2Tx MXene-coated carbonized honeycomb (CHC) (Ti3C2Tx MXene@CHC) nanocomposite-based hexagonal-shaped evaporator surface. This is the first-time report on the effective utilization of hierarchical CHC for the preparation of solar absorber comprising of Ti3C2Tx MXene@CHC nanocomposite, particularly for the solar water desalination. The Ti3C2Tx MXene@CHC nanocomposite evaporator achieves an impressive water evaporation rate of 1.6 kg m−2 h−1 with 90% efficiency under 1 sun illumination. The augmented thickness of the water layer in the hydrophilic surface of the Ti3C2Tx MXene@CHC nanocomposite helps in facilitating the rapid escape of water molecules. The relatively elongated contact lines in the hydrophobic region simultaneously ensure substantial water evaporation, significantly enhancing the water desalination process. The Ti3C2Tx MXene@CHC nanocomposite exceeds stringent quality benchmarks, signaling its potential for solar water desalination.

Elucidating the time-dependent charge neutrality point modulation of polymer-coated graphene field-effect transistors in an ambient environment.

The charge neutrality point (CNP) is one of the essential parameters in the development of graphene field-effect transistors (GFETs). For GFET with an intrinsic graphene channel layer, the CNP is typically near-zero-volt gate voltage, implying that a well-balanced density of electrons and holes exists in the graphene channel layer. Fabricated GFET, however, typically exhibits CNP that is either positively or negatively shifted from the near-zero-volt gate voltage, implying that the graphene channel layer is unintentionally doped, leading to a unipolar GFET transfer characteristic. Furthermore, the CNP is also modulated in time, indicating that charges are dynamically induced in the graphene channel layer. In this work, understanding and mitigating the CNP shift were attempted by introducing passivation layers made of polyvinyl alcohol and polydimethylsiloxane onto the graphene channel layer. The CNP was found to be negatively shifted, recovered back to near-zero-volt gate voltage, and then positively shifted in time. By analyzing the charge density, carrier mobility, and correlation between the CNP and the charge density, it can be concluded that positive CNP shifts can be attributed to the charge trapping at the graphene/SiO2interface. The negative CNP shift, on the other hand, is caused by dipole coupling between dipoles in the polymer layer and carriers on the surface of the graphene layer. By gaining a deeper understanding of the intricate mechanisms governing the CNP shifts, an ambiently stable GFET suitable for next-generation electronics could be realized.

Improving microstructure and frictional wear behavior of plasma cladding FeCoCrNiMo high-entropy alloy layers by annealing treatment

The application of high-strength, wear-resistant materials for the restoration of large-scale coal development equipment is pivotal in ensuring efficient production and energy conservation within the industry. In this study, FeCoCrNiMo high-entropy alloy (HEA) cladding layers were fabricated on Q235 steel using plasma cladding techniques and subsequently subjected to annealing at 700°C, 800°C, 900°C, and 1000°C, respectively. The microstructural evolution, hardness, and wear resistance of the annealed cladding layers were thoroughly investigated. The results indicated that the microstructure of FeCoCrNiMo HEAs predominantly consisted of alternating eutectic formations of FCC, σ, and μ phases. The content of σ phase initially increased and then decreased with the increase of the annealing temperature. As the σ phase increased, both the microhardness and wear resistance were enhanced. Compared to HEA layers annealed at other temperatures, the HEA layer annealed at 900°C exhibited the highest hardness (700 HV). The wear mechanisms of the cladding layers were predominantly characterized by oxidative wear and adhesive wear. Notably, a stable oxide film was observed on the surface of the cladding layer treated at 900°C, with a wear rate as low as 1.27×10-7mm3N-1mm-1. This study provided a technological basis and theoretical support for the repair of coal equipment.

Effects of Sodium Chloride on PEMFC Durability at a Concentration Close to that of a Marine Environment

The marine application of proton exchange membrane fuel cells (PEMFCs) requires special attention due to sea salt aerosols and atmospheric pollutants, susceptible to degrade these systems and induce performance losses. To the best of our knowledge, this study is the first to identify the performance losses of PEMFCs due to sodium chloride (NaCl) pollution similar to that of the marine environment. A 641 h ageing test with a NaCl concentration in air of 120 μg.m‒3 was carried out on a five cells stack of 220 cm2. The results reveal a key mechanism for reversible performance loss, namely the deposition of salt particles in the channels and on the surface of the cathode gas diffusion layer (GDL). This can lead to the complete shutdown of a cell. Nonetheless, this contamination did not induce significant irreversible performance losses as the restarts of the stack cause the salt particles to dissolve. An overall degradation rate of 8 μV·h‒1, similar to that of the baseline without NaCl contamination, is observed.

Effect of concentration of aqueous alcohol solution and layer thickness on free convection due to local heating

This paper investigates the effect of point heating, ethyl alcohol concentration, and layer thickness on the convective behavior of the solution. Laser heating enhances heat and mass transfer at low energy costs. For the first time, the research determines boundaries of the transition to the chaotic behavior of the velocity field at a change in several parameters: the initial alcohol concentration and the initial thickness of the liquid layer. Simple estimated ratios are obtained to determine the critical value of the Bond number in a binary solution. The solution behavior is predominantly influenced by the solute Rayleigh and Marangoni numbers. A small alcohol concentration (about 10%) is shown to have a stabilizing effect on the velocity field. In the course of evolution, several flow patterns change sequentially, which is associated with changes in the gradient of surface tension, solution concentration and layer thickness with evaporation time.

Gold as a Promising Electrode Material for LiNbO3-on-Insulator (LNOI) SH-SAW Resonators: An Experimental Study.

The need for wideband radio frequency front ends (RFFEs) with next-generation wireless protocols highlights the importance of electromechanical coupling [Formula: see text]. The hetero acoustic layered (HAL) surface acoustic wave (SAW) resonator with aluminum (Al) electrodes has shown superior performance compared to conventional SAW devices. Despite gold (Au) having excellent conductivity and stable properties, its high acoustic absorption and low phase velocity have made it less favorable for electrodes. This work demonstrates that high-performance shear horizontal (SH)-SAW resonators can be fabricated on the lithium niobate-on-insulator (LNOI) platform using a setup specifically designed for an Au electrodes. Experimental validation shows that the device achieves a high quality factor (Q) over 870, excellent [Formula: see text] up to 40%, and operates around 765 MHz. Unwanted transverse spurious modes are suppressed through adequate electrode design, and the temperature stability of LNOI SH-SAW with Au electrodes is discussed. This study highlights gold's potential as an electrode material for high [Formula: see text], clean spectrum, and wideband applications.

Hyperslip velocity of melting ice sliding down inclined parallel ridges

A geometric and physical model for melting ice sliding over inclined superhydrophobic (SH) surfaces with parallel ridges is presented. By analyzing the micro-shear flows of molten liquid films between the ice layer and SH surfaces, the hyperslip velocities of melting ice sliding are investigated. The stick-slip boundary condition of the SH surface is used to establish the dual-series equations analytically, and the numerical solutions are implemented by truncating Fourier series and transforming the dual-series equations into linear algebraic equations to determine the hyperslip velocities of melting ice sliding. The numerical results indicate that the non-dimensional hyperslip velocities increase nonlinearly from near 0 to approximately 1.1 for longitudinal sliding and from near 0 to approximately 0.55 for transverse sliding with an increasing air groove ratio (a). The hyperslip velocities increase with increasing δ at the beginning initially (δ < 1), after which they tend toward asymptotic solutions as δ = 1. The hyperslip velocity ratio (Wh/Uh) shows that longitudinal ridges are at least twice as effective as transverse ridges in enhancing the ice hyperslip velocity, with the velocities accounting for more than 60% of the ice sliding velocities for arbitrary θ at a = 0.95 and δ = 0.1. The relative deviations between the numerical and asymptotic solutions are less than 5% at δ = 1, with the maximum relative deviation occurring at a = 0.65 for arbitrary θ.

Flow field characteristics and vibration responses of saddle-shaped membrane structures

Elastically mounted flexible membrane roofs exposed to flows are prone to vortex-induced vibrations and even aero-instability due to the strong fluid–structure interaction (FSI). This study is to investigate the FSI mechanism in the saddle-shaped membrane structure over a range of Reynolds numbers and wind directions in laminar flows, by bridging structural vibration responses and flow dynamics. The aeroelastic characteristics of membrane structures, including statistics of displacement responses, oscillation frequency, and oscillation damping ratios, were identified from the perspective of time and frequency domains. Simultaneously, the particle image velocimetry system was employed to visualize the flow features, including velocity vector, turbulence intensity, and vortex evolution in both space and time. The flow modes were further decomposed by proper orthogonal decomposition (POD) to capture the salient aspects of the flow. Three patterns of POD modes are identified, and the first mode plays the dominant role in POD modes. It showed that as the wind Reynolds number increases, the space between the shear layer and membrane surface would be narrowed, and resultantly the vortices turn out smaller in scale and closer in space. This trend leads to an increase in the frequency of vortex shedding and a stronger FSI effect. When the frequency of vortex shedding approaches the fundamental frequency of structures, the vibration of the membrane would be shifted from turbulent buffeting to vortex-induced resonance, featured with lock-in frequency, significant amplified displacement, and negative aerodynamic damping ratio.

Role of Initial Conditions and Meteorological Drought in Soil Moisture Drought Propagation: An Event‐Based Causal Analysis Over South Asia

AbstractThe role of meteorological droughts and initial conditions (land and atmosphere) in soil moisture drought (SMD) propagation are not yet fully understood. This work uses a drought event‐based causal framework to investigate the relative importance of meteorological drought (MD) duration and intensity and initial conditions that result in surface and rootzone SMD, considering their event‐level propagation time (PT) over South Asia. Initially, spatial variability of drought propagation is assessed by the Propagation Ratio (PR) computed based on MD counts that trigger SMD at various lags. PR depicts 2–3 months slower rootzone propagation than at surface. The gradual decrease in PR with increasing regional aridity indicates faster propagation over humid regions. The causal impact of initial conditions and MD parameters on propagating SMD are evaluated using normalized mutual information and a newly proposed normalized conditional mutual information. We found greater importance of triggering MD parameters followed by initial soil moisture condition on propagating SMD. This behavior is more evident for the surface layer propagation at shorter PT. There is a confounding effect of initial atmospheric conditions on drought propagation through initial soil moisture, depicting the significance of land‐atmosphere interactions prior to propagation. In the rootzone propagation, initial soil moisture has a greater influence on propagation, especially at longer PT, indicating the significance of soil moisture persistence. Stronger causal links obtained through the joint influence of MD parameters on SMD suggest the importance of accounting for MD duration and intensity simultaneously, which are not considered in drought index‐based propagation studies.

Influence of milling interventions on the geometry of wall-shaped structures in hybrid wire-arc direct energy deposition

The Hybrid Wire-Arc Direct Energy Deposition (Hybrid Wire-Arc DED) process integrates Wire-Arc Direct Energy Deposition (Wire-Arc DED) with machining (typically milling) interventions, offering the potential for creating intricate geometries and finished surfaces. However, if milling is employed as a hybrid intervention rather than as a final part-finishing process, the interplay between these processes remains under-investigated. This paper examines the influence of milling interventions on the geometry of a wall-shaped structure, quantified by the transverse cross-sectional width, built using a Hybrid Wire-Arc DED. Through experiments on mild steel, the underlying causes of observed wall-width variations are analyzed. Initial observations suggested that thermo-mechanical deformations from milling influence the width variations. However, evidence indicates the significant role of additional remelting cycles experienced by the milled surface layer during subsequent layer depositions. The study also reveals that the observed increase in wall width for each milling intervention occurs at approximately the same depth below the milled surface. A mechanistic explanation for this observation is given. Crucially, the findings suggest that unless milling is done at higher frequencies, like after each layer deposition, the resultant unevenness might render the Hybrid Wire-Arc DED process less efficient in terms of surface quality and dimensional accuracy than its non-hybrid counterpart.