Surface Layer Research Articles

CORROSION RESISTANCE OF BRAKE DISCS AFTER NITRIDING

The article presents the work carried out to create a surface layer, ultimately on cast iron brake discs, by theZeroFlow method using regulated gas nitriding. The presented research is aimed at creating a nitrided layerwith corrosive wear resistance maintained at the stage of brake disc manufacture, waiting for sale of a newvehicle, and even during further exploitation. Examples of nitriding parameters enabling such treatment ofbrake discs made of flake cast iron are presented. The research also includes measurements of the roughnessof the working areas of brake discs before and after nitriding. The properties of the nitrided layers producedare assessed following microscopic observations and microhardness measurements using the Vickers method.The impact of nitrided layers on corrosive wear is also analyzed by observing the behavior of the surfaces ofthe tested discs in a corrosive environment in the so-called “corrosion experiment.”

Development and verification of material models in modeling of wave strain hardening and additive synthesis processes

BACKGROUND: The creation of competitive machine parts capable of withstanding standard and increased operational loads is an urgent task in mechanical engineering. Developing additive synthesis technologies together with strengthening technologies make it possible to create such products with high load-bearing capacity. However, to improve the efficiency of these technologies, it is necessary to create theoretical models of the processes taking place. The article presents the results of the first stage of creating complex theoretical models of the combined 3DMP process and wave strain hardening (WSH) required for designing technological processes for manufacturing engine parts and brake systems of automotive equipment. . AIMS: Creation and assessment of the adequacy of material models used in finite element modeling of additive synthesis processes with subsequent hardening. MATERIALS AND METHODS: Theoretical models of the material were created in the ANSYS software package, which allows for multidisciplinary calculations. The experimental data required for preparing the models were obtained by testing tensile samples manufactured using standardized methods. The hardness of materials was studied using a KB 30S automatic hardness tester. The adequacy of additive synthesis modeling was assessed based on the distribution of temperature fields. The adequacy of material models for the VDU process was assessed based on the sizes of individual plastic indentations and the distribution diagrams of the depth and degree of hardening in the surface layer. RESULTS: Theoretical models of the following materials were developed: steel, stainless steel, bronze alloy, titanium alloy, aluminum alloy. The theoretical data obtained from the modeling results have a high level of significance. The studies were conducted for various thermal (in the range from +20ºС to +800ºС) and deformation modes. Graphical results of theoretical and experimental studies allow us to obtain a qualitative assessment of the processes under study with the required accuracy. CONCLUSIONS: As a result of the assessment of the adequacy of the developed models, it was established that the discrepancy between the empirical and theoretical data does not exceed 7.4%. The obtained models of materials are statistically significant and can be correctly applied in further studies.

Features of the Structure and Dynamics of Water in the Northern Half of the Sea of Japan in Autumn-Winter Period According to Satellite Data and Ship Observation

The results of studies of the structure and dynamics of water in the zone of a large-scale cyclonic gyre in the northern half of the Sea of Japan are presented, where satellite IR images annually in the autumn-winter period most clearly show two areas of low temperatures, separated by the influx of warm Tsushima waters from Japan. The location of these thermal structures coincides with the location of the western and northern cyclonic gyres, which are inextricably linked with deep upwelling. During the autumn-winter periods 2019-2021 it has been established that deep upwelling in the northwestern part of the Sea of Japan extends from the bottom to the surface layer, focusing along the axial line passing through the Pervenets Rise and the Bersenev and Vasilkovsky ridges in the area of 42° N. between 132°E and 135.5° E. The western cyclonic gyre, located in the western part of the large-scale cyclonic gyre in the region of the considered deep upwelling, is a large topographic eddy. In the northern part of the large-scale cyclonic gyre, deep upwelling is confined to the continental clone, and the small northern cyclonic gyre is also located there. It is assumed that in the autumn-winter period the interaction of anticyclones that form vortex belts with cyclonic gyres leads to an increase in deep circulation. The peculiarity of the variability of the speed of deep currents - an increase from October to March, is probably due to the nature of the development of vertical and transverse horizontal circulation in the system of cyclonic gyres - vortex belts as a result of the intensification of deep upwelling with increased winds from the northern directions in winter.

Comparative Analysis of Tillage Practices on Soil Characteristics in Vertisol for Groundnut-based Cropping System

Tillage practices in groundnut-based Vertisol systems is essential for improving soil health and maximizing agricultural productivity. This study investigates the impact of tillage practices and cropping systems on soil physical and chemical properties in the Vertisol region of Karnataka during the 2022-23 Kharif and Rabi seasons. Conducted at the MARS, UAS, Dharwad, the experiment utilized a strip plot design, comparing minimum tillage with crop residue incorporation (M1) and conventional tillage without residue (M2) across four cropping systems. Findings revealed that minimum tillage significantly enhanced soil properties, demonstrating improved porosity (52.14%), maximum water holding capacity (55.97%) and soil aggregate stability (62.42%) while reducing bulk density (1.27 Mg m⁻³) at the surface layer. Among cropping systems, the groundnut + pigeon pea combination showed superior soil characteristics, with porosity at 50.88%, MWHC at 55.05%, and reduced bulk density of 1.31 Mg m⁻³ at 0-15 cm depth. Additionally, minimum tillage led to higher soil organic carbon (7.65 g kg⁻¹) and available NPK levels (315.8 kg ha⁻¹ N, 44.06 kg ha⁻¹ P, 324.53 kg ha⁻¹ K), particularly in the groundnut + pigeon pea system. These findings emphasize the efficacy of conservation agriculture techniques, reinforcing existing research that highlights how minimum tillage and leguminous cropping systems enhance soil health and foster sustainable farming practices. Such results are pivotal for promoting sustainable agricultural development, as they illustrate that implementing these practices can lead to significant improvements in soil vitality, crucial for boosting crop yields and ensuring ecological stability in Karnataka's Vertisol region.

Impact of Integrated Nutrient Management on Soil Micronutrients and Organic Matter Dynamics in Maize-mustard Crop Rotation in Himalayan Foothills

Aims: The purpose of this research is to investigate the effects of inorganic fertilizers and organic manures on availability of micronutrients and organic matter in soils of rainfed agriculture in foothills of Himalayas. Place and Duration of Study: Present study was conducted at Advance Centre for Rainfed Agriculture (ACRA), Rakh Dhiansar, Jammu from 2020 to 2022. Methodology: In a long-term field experiment, we investigated the effects of 10 treatments on soil micronutrients, organic matter and their correlation under rain fed agriculture. Randomized block design was used with three replications. Following are the treatments: T1 - Control, T2 - 100% RDF of N,P,K through chemicals, T3 - 50% RDF of N,P,K through chemicals, T4- 50% RD of N through crop residue, T5 - 50% RD of N through FYM, T6 -50% RDF of N,P,K through chemicals + 50% RDF of N through crop residues, T7- 50% RDF of N,P,K through chemicals + 50% RD of N through FYM, T8 - FYM @ 10 ton/ha, T9 - 100% RDF of N,P,K through chemicals + Zinc Sulphate @ 20kg/ha and T10 - Farmer practice (FYM @ 4 ton/ha + 40kg urea /ha). The micronutrients (Fe, Zn, Cu and Mn) showed maximum increase with the application of organic manures along with inorganic fertilizers over control in both surface and sub surface layers of the soil. However, in the sub-surface soil, there was less availability of these nutrients than the surface layer of the soil. The available Zn content was found maximum in the treatment T9 getting 100% NPK + ZnSO4 @ 20kg/ha over control. The treatment T8 with the application of FYM @ 10 ton/ha recorded highest content of soil organic matter in surface soil. Positive and significant correlations were observed between soil organic matter and the micronutrient content of the soil. The INM practices proved very beneficial for increasing the sustainability of soil.

Micro-structure and Macro-performance: Surface Layer Evolution of Concrete under Long-term Exposure in Harsh Plateau Climate

Micro-structure and Macro-performance: Surface Layer Evolution of Concrete under Long-term Exposure in Harsh Plateau Climate

A Novel UBM/SIS Composite Biological Scaffold for 2-Year Abdominal Defect Repairing and Strength Recovery in Canine Model.

Biological scaffolds are widely utilized in hernia treatment due to their exceptional pro-regenerative properties, which mitigate scar formation. However, serious complications occurred, caused by inflammatory response, premature degradation, and mechanical failure. Consequently, improvements of the biological scaffold are necessary to mitigate these risks. In this study, a novel biological scaffold integrating basement membrane-containing urinary bladder matrix (UBM) and small intestinal submucosa (SIS) is developed, and its safety and effectiveness are assessed in comparison to a commercial SIS (c-SIS) scaffold. The introduction of UBM as top surface layers significantly promotes cell adhesion, facilitating rapid formation of isolated regeneration zone. Proteomic analysis has demonstrated a more efficientdecellularization of the UBM/SIS scaffold, which subsequently mitigates inflammation in murine models, and promotes the polarization of macrophages toward the pro-healing M2 phenotype in a rat model of abdominal wall muscle defect. Furthermore, a two-year repair trial is conducted on a full-thickness abdominal wall muscle defect in canine model and confirmed that the UBM/SIS scaffold exhibits reduced seroma occurrences and enhanced tissue repair performances. Overall, the efficacyof this novel biological scaffold suggests its potential to minimize hernia recurrence in clinical practice and mitigatepatient suffering from severe inflammatory responses.

Effects of different sand fixation plantations on soil properties in the Hunshandake Sandy Land, Eastern Inner Mongolia, China.

Planting forests is an effective way to improve desertification. In order to elucidate the impacts of different vegetation types on soil development and restoration of degraded lands, we compared the properties of soils at different depths in three plantation forests in the Hunsandak Sandy Land in the Chinese agro-pastoral ecotone (Ulmus pumila, Pinus sylvestris var. mongolica, and Populus simonii). The results show that all three plantation forests were able to significantly improve the soil properties, and they resulted in soil nutrient enrichment in the surface layer. As the soil depth increased, the soil became progressively poorer in nutrients, the fine particle content decreased, and the bulk density and water content increased. The orders of the fractal dimension characterization and soil improvement effects of the different tree species were as follows: U. pumila > P. sylvestris var. mongolica > P. simonii. Compared with the bare sand, the soil bulk density under the U. pumila plantation was 19% lower; the soil water content was 74% higher; the soil organic matter, total N, P, and K were 336%, 207%, 106%, and 31% higher; the available N, P, and K were 41%, 125%, and 21% higher; and the clay and silt contents were 498% and 387% higher, respectively. The ranges of the soil fractal dimension were 1.67-2.08 for the bare sandy land and 2.14-2.32 for the planted forests. The soil fractal dimension was strongly correlated with the soil physicochemical properties, especially with the soil nutrients and fine particle content, which exhibited highly significant correlations (p < 0.01), and the correlation coefficients were all greater than 0.8. Therefore, we believe that U. pumila is a suitable sand-fixing plant species in this area. In addition, the soil fractal dimension can be used as an important reference index for characterizing soil properties in sandy areas.

A wideband and multibeam pattern reconfigurable antenna using partially reflecting surface

Abstract This paper presents a pattern reconfigurable antenna that accomplishes wideband and multibeam characteristics. The antenna design comprises a cross-slot radiator as the primary element and reconfigurable partially reflecting surface (PRS) layer placed above and below the cross-slot radiator. This configuration allows the antenna to adapt its radiation patterns effectively. The choice of the cross-slot radiator is based on its capability to offer wideband characteristics. The PRS layer consists of a precisely arranged array of 4×4 unit cells, incorporating PIN diodes into both the upper and lower PRS layers. The direction of radiation pattern can be changed by altering operating states of the PIN diodes on the PRS layer. The antenna operates in three distinct states, each exhibiting a unique radiation pattern. The antenna produces broadside, backward, and bidirectional radiation patterns. It demonstrates effective pattern reconfigurability across the frequency range of 3.10–3.86 GHz (21.71%), with a peak gain of 9.60 dBi. The simulated and measured results of the antenna are found to be in good agreement.

Effects of Particle Shape and Surface Structure on the Adsorption Properties of Polystyrene Microplastics

Model spherical polystyrene particles are studied to understand the interactions of microplastics with organic pollutants. Analysis of the experimental results presented in the literature is complicated since researchers use different types and concentrations of particles, durations of tests, etc. In addition, there is little information on the effect of the structure of the surface layer of polystyrene particles on the processes under study, and the question of the effect of the shape of polystyrene particles remains open. Here, we present the first results of a model experiment to study the effect of the shape and structure of the surface layer of polystyrene microspheres and non-spherical particles of 2 to 5 μm in size on the sorption properties in relation to model molecules of rhodamine B as a model organic pollutant. The properties of both the initial model polystyrene particles and the modified ones were studied by optical, transmission electron, and atomic force microscopy, as well as using the Brunauer–Emmett–Teller method (BET). The sorption process was studied by spectrophotometry, and the analysis of sorption curves was carried out using the Langmuir model. It is shown that the shape of polystyrene model particles does not have a significant effect on the sorption capacity. At the same time, the sorption processes of rhodamine B molecules are determined by the structure of the surface layer, which can be changed, for example, by exposing the polystyrene microspheres to N,N′-dimethylformamide.

CHEMICAL ATTRIBUTES AND SOIL CARBON AND NITROGEN STOCKS IN PASTURES IN THE MARANHÃO AMAZON

In the eastern Amazon region, converting forests into pastureland is a common practice that quickly leads to the degradation of these areas. This study aimed to evaluate the influence of different land uses in different evaluation periods on the chemical attributes, total contents, and carbon and nitrogen stocks of the soil in the Maranhão Amazon. The land use systems analyzed were: perennial pasture (PP), recovered pasture (RP), and secondary forest (SF). Trenches were opened in 2013 and 2019 in each use system in the 0.0-0.20 m and 0.20-0.40 m soil layers. The soil chemical attributes (pH, P, K, Ca, and Mg) and C and N contents and stocks were assessed. PP in the surface layer showed superior results compared to RP and SF, while the opposite behavior occurred in the subsurface. The chemical attributes of the soil decreased over the years evaluated, regardless of the layer and area. The chemical attributes of the soil, as well as the C and N contents and stocks, changed depending on the land use, layer, and year of sampling.

Membrane piezoelectric MDS-actuator with a flat double spiral of interacting electrodes

A schematic diagram and mathematical model of functioning of a new piezoelectric membrane (MDS) actuator with double spiral (DS) electrodes on the upper and/or lower surfaces of a thin piezoelectric layer with axisymmetric and periodic (with a small period) in radial coordinate mutual reversed electric polarization are presented. The polarization of the layer was realized as a result of connecting the polarizing electric voltage of the appropriate value to the outputs of the double spirals of the electrodes. The electrodes of each (upper and lower) double spiral of the MDS-actuator are made in the form of electrodeposited ribbon coatings on the surfaces of the piezoelectric layer in close proximity to each other (due to the small spiral pitch) to create high values of electric field strength along the lines of force in localized areas of the piezoelectric layer between them when an alternating or constant control electric voltage is connected to the electrodes, in particular, with positive and negative values of the electrical potentials. Importantly, the electric field force lines and, as a consequence, the polarization of the piezoelectric layer of the MDS actuator are oriented mainly along (i.e. towards or against) the radial coordinate of the membrane, in contrast to many conventional actuator schemes. The results of numerical modeling for a circular elastic membrane with piezoelectric actuators installed on its upper and lower surfaces confirmed the effectiveness of the proposed piezoelectric MDS-actuator when it functions according to the “bimorph” scheme, including the use of the proposed new structural element (section) – a piezoelectric “compression ring” MDS at various geometric and control parameters. The effect of a significant increase in the membrane deflection with installed piezoelectric MDS-actuators compared to the use of traditional homogeneous plate piezoelectric actuators of bimorph type for different conditions of the membrane fixation, in particular, stationary (rigid) fixation of its center is revealed. For a hybrid piezoelectric MDS-actuator including independent concentric round and circular (i.e. “compression ring”) sections, the non-monotonic nature and numerical analysis of the nonlinear dependence of the largest deflection at the center of a hinge-immobile membrane fixed at the edge on the ratio of the radii of its round and circular MDS sections were revealed. The cases in which the effect of the “compression ring” is manifested, i.e. when the maximum deflection of a membrane with the “compression ring” exceeds the best possible value of the deflection of this membrane without its use in the traditional “bimorph” scheme, are identified. The new piezoelectric MDS-actuator can be used in micromechanics, controlled optics, sensor technology, acoustics, in particular, in the manufacture of piezoelectric acoustic or sensor elements of membrane type, electromechanical transducers for vibration energy collection.

Nickel-based alloy efficient milling with ceramic tool and experimental verification in closed impeller

Nickel-based alloys are a class of materials that possess exceptional properties, including superior corrosion, oxidation, and fatigue resistance. They are increasingly utilized in high-performance critical components, particularly in the fields of aerospace engines and gas turbines. Nickel-based alloys pose significant challenges during machining due to their high cutting forces and work hardening, leading to low machining efficiency, severe tool wear, and subpar surface quality of the machined parts. To address these challenges, an orthogonal cutting experiment was conducted on GH4061 alloy to evaluate the machining performance by using monolithic ceramic milling tools. The optimal cutting parameters combination for dry cutting of nickel-based alloys was determined. The surface quality was tested and analyzed, including surface micro structure, residual stress, and surface roughness. The machining experiment was conducted on GH4061 closed impeller. The results demonstrated that high-speed cutting was more effective than low-speed cutting in improving the surface quality of the machined part. In the rough processing, monolithic ceramic milling tools was used to quickly remove the excess material. The adhesive and diffusion effects mainly contributing to the wear of the monolithic ceramic tool in GH4061 milling. Average surface roughness 1.41 μm can be obtained through dry milling using a monolithic ceramic tool with cutting speed 602.88 m/min, cutting depth 0.3 mm, cutting width 6 mm and feed per tooth 0.03 mm/z, along with metal removal rate 5184 mm3/min. High cutting speed will resulting in relatively low residual stress in the surface layer as well as a lower thickness of the surface alternation layer. Finally, a physical GH4061 closed impeller was machined to verify the proposed milling method.

Deflection characteristics of semi-rigid base asphalt pavement under traffic speed deflectometer loading

The three-dimensional viscoelastic finite element simulation and on-site validation was combined, so as to study the characteristics of the traffic speed deflection slope curve of the semi-rigid base asphalt pavement. Results show that there is an inert point in the deflection slope curve when only the surface or base structural state changes. With the loading center approaching transverse crack, the ‘three extreme values’ attribute transitions gradually to ‘single extreme value’. For the surface-base penetrating longitudinal crack caused by uneven subgrade settlement, the peak value of deflection slope curve increases significantly as the crack approaches the loading center, reaching an order of magnitude difference, and the attribute transforms from ‘three extreme values’ to ‘single extreme value’. Indicators characterizing the layered structural state were proposed, and the indicator change rules and applicability for the pavement with different surface and base layer thicknesses, under different deflectometer speeds, with or without cracks, were discussed.

Origin of Oxidation Variations in Ambient-Stable β-InSe.

Understanding and controlling the oxidation of layered materials remain critical issues in the final stages of their practical application in devices. Layered materials achieve a band gap by removing inversion symmetry. However, the oxidation process becomes complex, and the oxidation of these materials is not yet fully understood. As a representative example, InSe has attracted considerable attention due to its high charge mobility and Si-like band gap. However, conflicting observations such as oxidation by Se and In have been reported, including contrasting assessments of the oxidation susceptibility. In this study, we report in situ spectroscopy results detailing the origins of various oxidation pathways. We observed that at low defect densities the reduced reaction barrier of InSe due to Se vacancies leads to oxygen adsorption, while as defects increase, the lower electronegativity of In rises as a new pathway for oxidation. At low defect density, the bulk layer was more energetically favored for oxygen adsorption, allowing oxygen to diffuse to a depth sufficient to form pseudoheterojunctions and making the surface layer seemingly resistant to oxidation. Our results provide an answer to why the resulting diversity of optical responses is expected to increase as well as strategies to achieve gas stability.

Nanoindentation of nano-SiC/Si hybrid crystals and AlN, AlGaN, GaN, Ga&lt;sup&gt;2&lt;/sup&gt;O&lt;sup&gt;3&lt;/sup&gt; thin films on nano-SiC/Si

The review presents systematization and analysis of experimental data on nanoindentation (NI) of a whole class of new materials – wide-gap AlN, GaN, AlGaN and β-Ga2O3 heterostructures formed on a hybrid substrate of a new SiC/Si type, which were synthesized by the method of coordinated atom substitution. The deformational and mechanical properties of the investigated materials are described in detail. The methodology of the NI is described, and both advantages and disadvantages of the NI method were analyzed. The description of the apparatus to conduct the experiments on NI was given. The basic provisions of a new model for describing the deformation properties of a nanoscale rigid two-layer structure on a porous elastic base were proposed. The original method of visualization of residual (after mechanical interaction) deformation in transparent and translucent materials was described. Experimentally determined values of elastic moduli and hardness of SiC nanoscale layers on Si formed by the method of coordinated substitution on three main crystal planes of Si, namely (100), (110) and (111), and elastic moduli and characteristics (elastic modulus, hardness, strength) of surface layers of semiconductor heterostructures AlN/SiC/Si, AlGaN/SiC/Si, AlGaN/AlN/SiC/Si, GaN/SiC/Si and GaN/AlN/SiC/Si grown on SiC/Si hybrid substrates. The unique mechanical properties of a new material β-Ga2O3 formed on SiC layers grown on Si surfaces of orientations (100), (110) and (111) were described.

Computational analysis of a Cu3VS4-based solar cell with a V2O5 back surface layer

This study has described the development and computational evaluation of Cu3VS4 (CVS) based highly potential thin film solar cell where ZnS is exploited as the transparent layer and V2O5 as the back surface field (BSF) layer, respectively, to form the n-ZnS/p-Cu3VS4/p + -V2O5 hetero-junction. The investigation has highlighted the significant influence of the V2O5 BSF layer on the device performance. The standalone n-ZnS/p-Cu3VS4 device exhibits an open circuit voltage (VOC) of 0.87 V, a short circuit current (JSC) of 33.89 mA/cm2, a fill factor (FF) of 86.72%, and a power conversion efficiency (PCE) of 25.68%. The incorporation of the V2O5 BSF layer has enhanced the PCE to 28.33%, where VOC reached 0.94 V, JSC to 34.39 mA/cm2, and FF to 87.47%. This improvement in VOC has been attributed to the V2O5 BSF layer, leading to increased built-in potential and reduced surface recombination velocity at device interfaces. These findings suggest promising prospects for advancing high-efficiency CVS dual-heterojunction (DH) PV cells in the coming days.

Effect of Electrofriction Treatment on Microstructure, Corrosion Resistance and Wear Resistance of Cladding Coatings

In recent years, the issue of increasing the wear resistance of the working bodies of agricultural machinery designed for cutting and breaking the soil has received special attention. The surface layers of working bodies of agricultural machinery during operation are subjected to intensive abrasive wear, which leads to rapid wear of equipment and a reduction in its service life. The induction cladding method using materials such as Sormait-1 is widely used to increase the wear resistance of tool working surfaces. However, after coating, additional heat treatment is required to improve the physical and mechanical properties of the material and increase its durability. In electrofriction technology (EFT) hardening, the surfaces of the parts are subjected to melting under the influence of electric arcs. In this work, three types of surface treatment of L53 steel have been investigated: induction cladding using Sormait-1, electrofriction treatment, and a combination of induction cladding followed by electrofriction treatment. The microstructure was analyzed using optical microscopy and scanning electron microscopy. Erosion and abrasion tests were carried out in accordance with ASTM G65 and ASTM G76-04 international standards to evaluate the wear resistance of the materials under mechanical stress. A dendritic structure was formed after the induction cladding of the Sormait-1 material, but subsequent electrofriction treatment resulted in a reduction of this dendritic structure, which contributed to an increase in the hardness of the material. However, the highest hardness, reaching 965 HV, was recorded after electrofriction treatment of L53 steel. This is explained by needle martensite in the structure, which is formed as a result of quenching. Further, the influence of structural characteristics and hardness on erosion and abrasion wear resistance was examined. The analysis showed that the material microstructure and hardness have a decisive influence on the improvement of wear resistance, especially under conditions of intensive erosion and abrasive friction.

Effects of vertical forest stratification on precipitation material redistribution and ecosystem health of Pinus massoniana in the Three Gorges Reservoir area of China.

Vertical stratification of forest plays important roles in the local material balance and in maintaining forest health by distributing and redistributing precipitation materials through adsorption, fixation, and release. Differences in runoff nutrient concentrations among vertical layers are closely related to vertical stratification (factors such as the trunk, canopy, forest litter, and soil physical and chemical properties). Long-term forest observations revealed significant spatial differences in Pinus massoniana (Pinus massoniana Lamb.) forests in the Three Gorges Reservoir area. Pinus massoniana forests on downslopes were characterized by a dense canopy, green needles, and rich forest vegetation, while those on upslopes were characterized by low vegetation cover, dead trees, and decreases in the tree height, diameter at breast height, and volume per plant with increasing slope. By analyzing the soil at different sites, we found that the pH of the forest land soil differed significantly among different slope positions. Soil on upper slopes was significantly more acidic than soil on lower slopes, indicating that acidic substances were intercepted by filtration through the broad litter layer and the soil surface layer. This filtration process resulted in a normal rhizosphere environment suitable for the absorption of nutrients by vegetation on the lower slopes. In this way, downhill sites provided a good microenvironment for the growth of Pinus massoniana and other vegetation. Our results show that direct contact between needles and acid rain was not the main cause of root death. Instead, the redistribution of rainfall substances by forest spatial stratification caused changes in the soil microenvironment, which inhibited the absorption of nutrients by the roots of Pinus massoniana and the growth of understory plants in Pinus massoniana forests on upper slopes. These findings emphasize that increasing land cover with forests with vertical structural stratification plays an important role in woodland material redistribution and forest conservation.

Predictive Modeling and Adsorption Behavior, Kinetics, and Thermodynamic Studies of &lt;i&gt;Anthocleista grandiflora &lt;/i&gt;Leaf Extract for Corrosion Inhibition of Carbon Steel in Seawater

This study investigates the corrosion inhibition performance of Anthocleista grandiflora leaf (AGL) extract on carbon steel in seawater, considering the effects of temperature, immersion time, and inhibitor concentration. Predictive modeling, adsorption behavior, and the kinetics and thermodynamics of the inhibition process were examined. The weight loss technique,characterization techniques combined with response surface methodology (RSM), revealed that the AGL extract follows the Langmuir adsorption model, exhibiting physical adsorption with ΔG values between −16.24 to −15.49kJ/mol, indicating spontaneous and endothermic inhibition. The thermodynamic parameters entropy (−198.87 to −52.58 J/mol), enthalpy (20.42 to 53.42 kJ/mol), and activation energy (13.68 to 56.32 kJ/mol further support this. The corrosion reaction follows first-order kinetics, with the half-life decreasing as the rate constant and extract concentration increase.The SEM images revealed that the AGL extract formed a protective surface layer on the mild steel, effectively preventing pitting. This protective effect became more pronounced as the concentration of the extract increased. RSM optimization identified optimal conditions for maximum inhibition efficiency (98.70%) and corrosion rate (0.058 mm/y) at 800 ppm, 303 K, and 45 days, with a prediction accuracy of 95%, making it suitable for application in the oil and gas industry.