Sections Of Curve Research Articles

Characteristic conic connections and torsion-free principal connections

We study the relation between torsion tensors of principal connections on G-structures and characteristic conic connections on associated cone structures. We formulate sufficient conditions under which the existence of a characteristic conic connection implies the existence of a torsion-free principal connection. We verify these conditions for adjoint varieties of simple Lie algebras, excluding those of type Aℓ≠2 or Cℓ. As an application, we give a complete classification of the germs of minimal rational curves whose VMRT at a general point is such an adjoint variety: nontrivial ones come from lines on hyperplane sections of certain Grassmannians or minimal rational curves on wonderful group compactifications.

NEW PROCEDURE BASED ON OBTAINING THE AVERAGE DECELERATION FOR IMPROVING THE SPANISH NATIONAL INSPECTION OF TRACTOR SERVICE BRAKES

This study addresses the status and proposes key aspects relevant to refining of the procedure for the Spanish National Inspection of Vehicles relative to tractor service brakes, specifically focusing on obtaining the average deceleration. The current inspection method lacks a clear definition of the calculation process for average deceleration in the Spanish Official Manual of Procedures of Inspection of Vehicles. This lack of clarity results in varying outcomes and potential acceptance or rejection of the inspection based on the selected equipment and procedure. To address this issue, a comprehensive series of tests were conducted on different vehicles, using various equipment and calculation methods. The objective was to derive meaningful conclusions regarding the calculation method, measuring equipment, and other relevant factors. This study reveals the inadequacy of the current average deceleration calculation method as outlined in the official inspection manual. The findings highlight the crucial role of accurate equipment selection, appropriate calculation methods, and skilled personnel experience in ensuring reliable and consistent results. To address this, a new standardized procedure is proposed to streamline the process of obtaining the average deceleration in the inspection of tractor service brakes. The recommended procedure encompasses the use of a secure, well-defined track, clearly marked acceleration and braking points, a GPS decelerometer, a portable or on-track speedometer, and data processing that excludes the initial and final sections of the deceleration curve. Furthermore, this study highlights the need to update the acceptance thresholds for the inspection, as the current thresholds may no longer align with the proposed procedure. A revision of these thresholds is suggested to establish new criteria that are more appropriate and in line with the proposed method and for tractors manufactured after 01/01/2016. Keywords: Tractors, brake testing, vehicle inspection, road safety.

Magnetization processes features in the tapes of cobalt-based amorphous alloy

Studies of the amorphous cobalt-based soft magnetic alloy AMAG-172 (Co–Ni–Fe–Cr–Mn–Si–B) from different manufacturers have shown that in the as-quenched state there is nonuniformity of the magnetic characteristics, and therefore the level of internal stresses across the width of the tape produced by MSTATOR (Borovichi) significantly lower. However, similar to the tape produced by NIIMET (Kaluga), there is nonuniformity of the tape in thickness, which contributes to the formation of a bimodal field dependence of magnetic permeability.This may be a consequence of the non-uniform concentration along the width of the tape of hydrogen and oxygen atoms embedded in its surface during interaction with atmospheric vapor and the presence of temperature gradients during the manufacturing process. A stepwise shape of the initial sections of the magnetization curves in the region of the first maximum of magnetic permeability was discovered. The abrupt nature of the magnetization processes in the region of weak fields allows us to conclude that in the samples of tape produced by MSTATOR, the formation of the first maximum of the field dependence is associated with an independent magnetization reversal of the surface layer, while the main layer of the tape participates in the formation of the second maximum. The smoothed shape of the stepped initial section of the magnetization curve of samples produced by NIIMET corresponds to the gradual involvement of the main layer of the tape in the processes of magnetization and remagnetization. A comparison of the hysteresis loops of both parts of the tape, measured in the same magnetic field region, shows that the field shift of the hysteresis loops is associated with the interlayer interaction of the surface and volume of the tape, and the formation of asymmetric hysteresis loops occurs with the participation of the second layer with its gradual involvement in the processes of magnetization and magnetization reversal.

The Expression of the Force-Length Properties of the Gastrocnemius in Ice Hockey Players.

Leonard, C and Challis, JH. The expression of the force-length properties of the gastrocnemius in ice hockey players. J Strength Cond Res 38(9): 1635-1639, 2024-Although the force-length properties of muscles have an approximately parabolic shape, in vivo not all the force-length curve is necessarily used, only a portion of the curve is expressed (i.e., ascending, plateau, or descending regions of the force-length curve). The number of sarcomeres in series in a muscle fiber affects the expressed section of the force-length curve; this number can be influenced by the nature of activity the muscle experiences. It was hypothesized that the reduced range of motion ice skaters experience, because of the constraints imposed by the ice skates, that the gastrocnemii of a group of ice skaters will adapt and will more frequently express in vivo the plateau of the force-length curve compared with a nonspecifically trained population. Twelve NCAA Division I female ice hockey players volunteered for the study. Their maximum isometric ankle plantarflexion moments were recorded for 6 ankle angles and 3 knee angles. Exploiting the biarticularity of the gastrocnemius, the expressed sections of the subject's force-length curves were determined. Six subjects operated over the ascending limb, 5 operated over the plateau region, and 1 over the descending limb. This frequency of distribution for ice hockey players was statistically different to the distribution measured for 28 nonspecifically trained subjects from a previous study ( p < 0.0001). These results likely reflect morphological differences between the 2 groups for their gastrocnemii, potentially arising from the limited range of gastrocnemius length feasible in ice-skates. These results have implications for the specificity of their off-ice training for ice hockey players.

Reading between the rational sections: Global structures of 4d $\mathcal{N}=2$ KK theories

We study how the global structure of rank-one 4d \mathcal{N}=2𝒩=2 supersymmetric field theories is encoded into global aspects of the Seiberg-Witten elliptic fibration. Starting with the prototypical example of the \mathfrak{su}(2)𝔰𝔲(2) gauge theory, we distinguish between relative and absolute Seiberg-Witten curves. For instance, we discuss in detail the three distinct absolute curves for the SU(2)SU(2) and SO(3)_±SO(3)± 4d \mathcal{N}=2𝒩=2 gauge theories. We propose that the 11-form symmetry of an absolute theory is isomorphic to a torsion subgroup of the Mordell-Weil group of sections of the absolute curve, while the full defect group of the theory is encoded in the torsion sections of a so-called relative curve. We explicitly show that the relative and absolute curves are related by isogenies (that is, homomorphisms of elliptic curves) generated by torsion sections - hence, gauging a one-form symmetry corresponds to composing isogenies between Seiberg-Witten curves. We apply this approach to Kaluza-Klein (KK) 4d \mathcal{N}=2𝒩=2 theories that arise from toroidal compactifications of 5d and 6d SCFTs to four dimensions, uncovering an intricate pattern of 4d global structures obtained by gauging discrete 00-form and/or 11-form symmetries. Incidentally, we propose a 6d BPS quiver for the 6d M-string theory on \mathbb{R}^4× T^2ℝ4×T2.

Bond performance between hybrid fiber-reinforced concrete and BFRP bars under freeze-thaw cycle.

This study applied the pull-out test to examine the influence of freeze-thaw cycles and hybrid fiber incorporation on the bond performance between BFRP bars and hybrid fiber-reinforced concrete. The bond-slip curves were fitted by the existing bond-slip constitutive model, and then the bond strength was predicted by a BP neural network. The results indicated that the failure mode changed from pull-out to splitting for the BFRP bar ordinary concrete specimens when the freeze-thaw cycles exceeded 50, while only pull-out failure occurred for all BFRP bar hybrid fiber-reinforced concrete specimens. An increasing trend was shown on the peak slip, but a decreasing trend was shown on the bond stiffness and bond strength when freeze-thaw cycles increased. The bond strength could be increased significantly by the incorporation of basalt fiber (BF) and cellulose fiber (CF) under the same freezing and thawing conditions as compared to concrete specimens without fibers. The Malvar model and the Continuous Curve model performed best in fitting the ascending and descending sections of the bond-slip curves, respectively. The BP neural network also accurately predicted the bond strength, with relative errors of predicted bond strengths ranging from 3.75% to 13.7%, and 86% of them being less than 10%.

Study on the bond properties between basalt fiber-reinforced spontaneous combustion coal gangue concrete and BFRP bars

Microstructural characterization of spontaneous combustion coal gangue (SCCG), the hydration products and mechanism of spontaneous combustion coal gangue concrete (SCCGC) were discerned through microscopic analysis. The bond performance was assessed employing a central pull-out test on samples variably substituted with SCCG (0%, 25%, 50%, 75%, and 100%) and augmented with basalt fiber (BF) (0%, 0.1%, 0.15%, and 0.2%). The failure mode and bonding mechanism were also revealed by this test. The bond-slip curves were fitted by various bond-slip constitutive models and a suitable model was found for each section. As indicated by the results, SCCGC possessed a lower carbon content and higher Al and Si element contents. These elements would undergo secondary hydration reactions with CH, which could enhance the strength of the ITZ and the compactness of the bond interface between BFRP bars and concrete. The failure modes were splitting and pull-out. An inverse correlation was observed between bond strength and the increment in SCCG aggregate substitution, ranging from a decline of 2.6% to 23.1%. As the BF content increased, the bond strength and peak slip increased by 3.9% ∼ 19.7% and 4.0% ∼ 14.6%, respectively. Furthermore, the reinforcing effect of BF on bond strength increased from 3.9% ∼ 10.3% to 8.8% ∼ 19.7% as the SCCG replacement rate increased, which was noticeable. The Malvar model and the Continuous Curve model were the best fitting models for the ascending and descending sections of bond-slip curves, respectively, while the residual stage was well fitted by the Hao Qingduo model.

Mathematical models for the electric vehicle routing problem with time windows considering different aspects of the charging process

This paper addresses the electric vehicle routing problem with time windows (E-VRPTW), considering the battery’s state of charge (SoC\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$SoC$$\\end{document}) and the recharging process's linearity and non-linearity. We compare two proposed models: the first assumes a linear charging process, and the second evaluates the impact generated by including the non-linearity of the battery recharging process. The non-linear model considers the limitation of the state of charge and restricts the deep battery discharge during movement. Additionally, the effect of overload on the supplied energy process has been evaluated to extend the batteries' useful life. The models are tested on instances commonly used in the literature. The obtained results verify that including the non-linearity recharging process reduces the total time of the routes. Indeed, by accessing the upper sections of the recharge curve (>85%SoC\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$> 85\\% \\; SoC$$\\end{document}, the more significant degradation), autonomy is obtained to avoid unnecessary visits to stations. In addition, including the option to carry out a fast recharge could reduce the total time, even reducing the number of vehicles necessary to carry out the delivery tasks and the maximum time defined by each route.

SORBENTS BASED ON THE Ni,Fe-LAYERED DOUBLE HYDROXIDES AND ITS MAGNETIC NANOCOMPOSITES FOR DEACTIVATION AND PRECONCENTRATION OF Cs(I) AND Sr(II) IONS FROM AQUEOUS SOLUTIONS

The synthesis and comparative evaluation of the adsorption capacity in relation to Sr(II) and Cs(I) ions of the carbonate form of Ni(II)/­Fe(III)–layered double hydroxides (NiFe-LDH) and their nanocomposites was carried out. At first, Fe3O4 nanoparticles having a crystallite size of 20–50 nm were obtained by Fe(III) precursors. In the second step, Fe3O4 nanoparticles were embedded in NiFe-LDH matrix by the co-precipitation at hydrothermal conditions and subsequent condensation of the basic solution containing Fe3O4nanoparticles. The influence of the physicochemical parameters of the synthesized sorbents on the efficiency of magnetic solid phase extraction of these radionuclides from aqueous solutions was investigated. Their effectiveness in extracting Sr(II) and Cs(I) ions with a change in the pH of the aqueous medium was evaluated, as well as sorption isotherms on the obtained sorbents at pH0 4.5–5.0 were obtained, and their analysis and processing were carried out to establish the mechanism of sorption extraction at all le­vels of filling of the sorption layer with analytes. Equilibrium adsorption data were analyzed using Freundlich and Langmuir isotherm models. Of the models tested, Langmuir isotherm expressions were found to give better fit to the experimental data compared to the Freundlich model. The applicability of mathematical models for estimating the kinetic patterns of sorption of radionuclides on NiFe-LDH and their magnetic nanocomposites was analyzed. The adequacy of the Boyd and Morris – Weber diffusion models in the initial section (up to F = 0.4–0.6) of the kinetic curves is shown. Kinetically, the growth of effective diffusion coefficients and adsorption rate constants is observed in the series: Fe3O4&lt;NiFe-LDH&lt;Fe3O4@NiFe-LDH, and the pseudo-second-order kinetic model most accurately reflects the patterns of sorption of these radionuclides. Due to high sorption efficiency and manufacturability, the obtained sorbents are promising for water purification from radioactive pollutants.

Pattern recognition based on statistical methods combined with machine learning in railway switches

Railway switches are critical components in the rail system. Operation and maintenance tasks are essential to ensure proper functioning and avoid any failure that can cause delays, reducing operational safety. Data from condition monitoring systems requires advanced analysis tools. This paper presents the analysis of power output data of railway switches. A novel approach is proposed based on statistical analysis techniques combined with Machine Learning techniques to classify power curves by analyzing different sections of the power curves. These curves are studied statistically to classify them into normal and non-normal curves. Then, a dataset is generated with normal and non-normal labelled curves. Shapelets and k-Nearest Neighbour classification algorithms are applied to these data with good results (accuracy, sensitivity and specificity above 88% in each case). As a further analysis, a second dataset with the sectioned curves is done to detect non-normal curves without analyzing the complete curve. For this case study, k-Nearest Neighbour algorithm is able to classify with higher accuracy on the last section of the curve.

Method for selecting the damping characteristics of the pneumohydraulic suspension system of a wheeled vehicle

BACKGROUND: In the process of developing suspension systems for modern high-speed wheeled and tracked vehicles, having the selected optimal elastic characteristic curve of the suspension system, its unsatisfactory damping characteristic curve can have a significant negative impact on the overall operation of the suspension unit. Therefore, the search for a method for obtaining the optimal damping characteristic curve is a relevant task.&#x0D; AIMS: Description the method for selecting the damping characteristic curve of a single-level pneumohydraulic spring for a wheeled vehicle considering the motion along tracks with a harmonic profile and a rough cobblestone road.&#x0D; METHODS: The damping characteristic curve of the spring is selected using simulation mathematical modeling in the MATLAB/Simulink software, which makes it possible to take into account the nonlinearity of the suspension characteristics. In the process of building the characteristic curve, the limit values of the forces at the front wheels tires are fixed for the sections of the characteristic curve that operate with the valves of the pneumohydraulic spring turned off. Accelerations at the driver's seat and the pressure in the spring chamber are fixed for the sections of the characteristic curve that operate with the valves are turned on.&#x0D; RESULTS: The results of the selection of an optimized damping characteristic curve showed an improved contact of the wheels with the surface and an increase in the stability of the vehicle, a decrease in vibration accelerations at low disturbance frequencies.&#x0D; CONCLUSIONS: The practical value of the study lies in the possibility of using this method to develop suspension systems for new wheeled and tracked vehicles.

Self-Dual Matroids from Canonical Curves

Self-dual configurations of 2n points in a projective space of dimension n – 1 were studied by Coble, Dolgachev–Ortland, and Eisenbud–Popescu. We examine the self-dual matroids and self-dual valuated matroids defined by such configurations, with a focus on those arising from hyperplane sections of canonical curves. These objects are parametrized by the self-dual Grassmannian and its tropicalization. We tabulate all self-dual matroids up to rank 5 and investigate their realization spaces. Following Bath, Mukai, and Petrakiev, we explore algorithms for recovering a curve from the configuration. A detailed analysis is given for self-dual matroids arising from graph curves.

Temperature Resistance Properties of Unidirectional Laminated Cf/SiC-Al Prepared by PIP and Vacuum Pressure Infiltration.

Material used for aero-engine fan blade requires excellent mechanical properties at high temperature (300 °C). Continuous carbon-fiber-reinforced silicon carbide ceramic matrix composites (Cf/SiC) are necessary candidates in this field, possessing low density, high strength, high modulus, and excellent high-temperature resistance. However, during the preparation process of Cf/SiC, there were inevitably residual pores and defects inside, resulting in insufficient compressive strength and reliability. The vacuum pressure melting infiltration process was used to infiltrate low melting point and high wettability aluminum alloys into the porous Cf/SiC composite material prepared by the precursor impregnation cracking process, repairing the residual pore defects inside the body. The porosity of porous Cf/SiC decreased from 49.65% to 5.1% after aluminum alloy repair and strengthening. The mechanical properties of Cf/SiC-Al composite materials strengthened by aluminum alloy repair after heat treatment were studied. The tensile strength of the as-prepared Cf/SiC-Al was 166 ± 10 MPa, which were degraded by 13~22% after heat treatment. The nonlinear sections of stress-displacement curve of as-treated samples were shorter than that of as-prepared sample. The hardness of aluminum alloy matrix after 300 °C 1 h heat treatment was 58 Hv, which was not obviously reduced compared with the sample without heat treatment. The vacuum infiltration of aluminum alloy is expected to have guiding significance for repairing and strengthening internal defects in ceramic matrix composites.

IDENTIFICATION OF SEPARATION CURVES OF STRONGLY CONTRASTING ENVIRONMENTS USING COMPLEX ANALYSIS METHODS

When modeling mass transfer processes (for example, filtration) in porous media, there may be cases of the existence of highly permeable layers, which are separated from the corresponding studied parts by some curves that must be found (identified) in the process of solving the problem. When constructing a mathematical model of the corresponding physical process, we will consider a highly permeable medium as "ideally (theoretically infinitely) permeable." In this case, the desired curve can be considered an equipotential line. This work considers the stationary process of fluid movement in a homogeneous horizontal layer of infinitely large dimensions - a soil massif, which is limited by infinite sections of curves, in particular by the desired curve of theoretical water resistance and the horizontal axis, on which the local speed of movement is known. On the basis of the methods of conformal reflections and total images, an approach to the identification of the curve of the separation of media is proposed. The constructed algorithm is modified for solving nonlinear inverse boundary value problems on quasi-conformal mappings of curvilinear polygonal regions bounded by uncertain streamlines and equipotential lines. The feature of the method proposed is that the summary representation formulae allow to explicitly write the solution to the localized linear (main) part of the obtained system of equations. The unknown coefficients are determined here by solving a non-linear system generated solely by the boundary conditions and numerical analogues of the Cauchy–Riemann equations.

О ФОРМИРОВАНИИ МЕТОДИКИ ОПТИМИЗАЦИИ ПЛАНИРОВАНИЯ КАПИТАЛЬНОГО РЕМОНТА ЖИЛЫХ ЗДАНИЙ НА ЭТАПАХ ЭКСПЛУАТАЦИИ И РЕМОНТА

The sources available for research and analysis, including the current regulatory documents, contain a number of methods for determining and accounting for the physical wear of buildings and structures, however, many of them either contain too average data or contradict each other. This article discusses the developed approach to assessing the physical deterioration of residential buildings in terms of the frequency of restoration measures and major repairs. The necessity of improving the approach to monitoring the technical condition of residential buildings in order to optimize the costs of maintaining a working condition is described. The cases of various options for the application of decision-making policy in the field of operation of residential buildings are considered. A method for determining the dependence of the physical wear of a building on the service life is proposed. The cost of performing restoration work based on experimental data is estimated. The characteristic sections of the dependence curve "service life – physical wear" are determined with the analysis of factors and prerequisites for making managerial decisions regarding the capital construction object. Mathematical modeling is performed based on the data obtained. This allows developing recommendations regarding the timing and scope of restoration work during repairs at the operational stage.

Grinding limit and profile optimization in the high-incidence section of rail corrugation in mountainous city metro

As the most common and direct control method for rail corrugation, the rail grinding can effectively improve the service life of rails, but requires scientific theoretical guidance to achieve the efficient grinding. Therefore, it is necessary to formulate corresponding grinding limits and profile optimizations for different characteristics of rail corrugations. According to the on-site investigation of rail corrugation in the overlapping section of horizontal-vertical curves of the mountainous city metro, the corresponding dynamic model of vehicle-track system is constructed. Through the safety evaluation of the dynamic characteristics of the vehicle-track system, the safety limit of the rail corrugation grinding is preliminarily determined. Then, based on the wheel-rail friction-coupled vibration theory, the finite element model of the wheel-rail system is built. By exploring the wheel-rail friction-coupled vibration characteristics in the corrugated section with typical characteristics, the optimal limit of rail corrugation grinding is further confirmed. Finally, the treatment effects before and after rail grinding are compared using the profile optimization. Results show that when the corrugation wavelengths in the overlapping section are 30 mm, 40 mm, 50 mm, 60 mm, and 70 mm, the safety limits for rail corrugation grinding are 0.03 mm, 0.04 mm, 0.05 mm, 0.08 mm, and 0.15 mm. For the typical rail corrugation with the wavelength of 50 mm, the optimal limit of the rail corrugation grinding is 0.02 mm. Moreover, the earlier the rail corrugation is polished, the better the relative optimization effect is, but it is necessary to consider the grinding cost for targeted grinding.

Interfacial bonding performance of textile reinforced ECC and seawater sea-sand concrete under a dry-wet environment

In order to promote the application of cementitious composites in the marine environment, it is crucial to clarify the interfacial bonding properties of cementitious composites to concrete. Therefore, the interfacial bonding performance of a new cementitious composite, textile reinforced ECC (TRE), to seawater sea-sand concrete (SWSSC) in a chloride salt dry-wet environment was investigated by single shear test. The interface behavior was evaluated from the failure modes, average bond strength, load-slip curves, and fracture energy of TRE-SWSSC interface. The main research factors included the erosion environment, the thickness of TRE composite, and the dry-wet cycles. The study showed that the failure mode of specimens with a small thickness of TRE composite are mainly the fracture and sliding of matrix in the free length of TRE. The failure pattern of the TRE-SWSSC interface with 20 mm thickness changed from the fracture and sliding of matrix in bond length of TRE to that in free length of TRE with the increase of dry-wet cycles. And the failure of specimens in immersion environment was interfacial peeling. The average bond strength of TRE-SWSSC interface increased with the thickness of TRE. After 270 days of environmental action, the interfacial average bond strength in the dry-wet environment was 15.94 % higher than that in the immersion environment. The load-slip curves were smoother for specimens with smaller TRE thickness, and the descending section of the load-slip curves became steeper with the increase of TRE thickness. The interfacial fracture energies of the specimens with different TRE thicknesses showed different growing trend with the dry-wet cycles. With the increase of the dry-wet cycles, the interfacial fracture energy of the specimens with a TRE thickness of 10 mm gradually increased, but the interfacial fracture energy of the specimens with a TRE thickness of 20 mm gradually decreased.

Cause Analysis of Rail Corrugation Based on Stick-slip Characteristics

By analyzing the measured corrugation data, the cause of rail corrugation was discussed theoretically. Then, the vehicle-track coupling model was used to study the stick-slip characteristics of wheel-rail system. Finally, the cause of rail corrugation was explained by combining modal analysis and wheel-rail stick-slip relation. The transverse stick-slip curve on the inner rail-inner wheel of the leading wheelset presents a negative slope characteristic, which makes the inner wheel easy to slide on the inner rail surface and aggravates the wear of inner rail; there are also negative slope sections of the stick-slip curve on the outer rail-outer wheel of the trailing wheelset, but the adhesion coefficient is relatively large, indicating that the outer wheel will not slide obviously and the wear is relatively small. Meantime, with the increase of line curve radius, the negative slope phenomenon of stick-slip curves on the inner and outer rail sides shows a decreasing trend, which illustrates that the sliding wear of wheel is gradually reduced, and thus the occurrence probability of rail corrugation decreases. Combined with modal analysis, it can be seen that the coupling action of wheel discs bending vibration and inner rail bending-torsional vibration is the main cause of rail corrugation under the condition of wheel-rail system with stick-slip negative slope.

Исследование кинетики цементации кадмия в присутствии ПАВ

The aim of the paper is to study the kinetics of cadmium cementation with zinc powder in aqueous media in a continuous mode using an ion-selective cadmium electrode. Reduction of cadmium from aqueous solutions was carried out with zinc powder, with particle sizes from 63 to 200 μm. In a number of experiments, the influence of the cationic flocculant Besfloc K6645 on the cadmium cementation process was tested. The process was carried out in the temperature range from 30 to 50 °C with continuous stirring at 200 rpm with an overhead stirrer. Kinetic curves were recorded using a cadmium-selective electrode. The kinetic curves were conditionally divided into linear segments. Tangents were drawn to each section, which made it possible to determine the apparent rate constants using the first-order equation, as well as the mode coefficients using the Erofeev–Kolmogorov equation. An increase in temperature had a positive effect on cementation. The introduction of a flocculant into the electrolyte in the amount of 70 mg/L reduced the degree of cementation from two to three times over a period of 600 s. The data obtained made it possible to calculate the activation energies of the process rates on the linear sections of the kinetic curves, which amounted to approximately 46, 32 and 11–13 kJ/mol in the first, second, and third sections, respectively, for reduction without the addition of a flocculant, as well as 117–130 and 82–85 kJ/mol in the presence of Besfloc K6645 flocculant. It has been shown that in the presence of a flocculant, the activation energy increases, especially in the first section, which is characterized by a slow cementation rate. The study demonstrates the effect of the Besfloc K6645 additive on the duration of the initial section of the cementation kinetic curves.

ОЦЕНКА ЭФФЕКТИВНОСТИ ВВЕДЕНИЯ РЯДА ДОБАВОК В ОТРАБОТАННОЕ МОТОРОНОЕ МАСЛО ДЛЯ ЗАЩИТЫ СЕЛЬСКОХОЗЯЙСТВЕННОЙ ТЕХНИКИ В ПЕРИОД МЕЖСЕЗОННОГО ХРАНЕНИЯ

The search for effective conservation materials to protect agricultural machinery from atmospheric corrosion during off-season storage continues to be an urgent task. Compositions based on used engine synthetic oil with emulgin and paraffin additives at a concentration of 1–10 wt. % investigated for its solution. Preservative compositions were prepared by dissolving a multifunctional additive in used oil when heated. Corrosion and electrochemical tests were carried out on samples of steel St3, a protective film of the studied composition was formed within 15 minutes. The effectiveness of anti-corrosion protection of steel with these compositions was studied by gravimetric (tests in 0.5 M NaCl and a climatic chamber) and electrochemical methods. It is shown that in 0.5 M NaCl, the composition with paraffin at a maximum additive concentration of 10% provides a protective effect of more than 70%. The addition of emulgin at the same concentration is less effective. Paraffin-containing formulations provide protective effect values of over 90% in the absence of aggressive chloride ions under climate chamber conditions. The inhibition of the corrosion process under the films of the studied compositions occurs due to the shift of the corrosion potential to the anode region. The presence of the conservation composition does not change the mechanism of the corrosion process of steel in 0.5 M NaCl, since there is no sharp change in the Tafel slope coefficients of the cathode and anode sections of the polarization curves. According to impedance spectroscopy, it was found that the presence of paraffin in the film of used motor oil at a concentration of 5, 10 wt. % causes a decrease in the capacitance of the electrical double layer, as well as an increase in the charge transfer resistance in both the cathodic and anodic reactions. In addition, there is an increase in the diffusion resistance of the depolarizer oxidizer, which may indicate the effectiveness of shielding the metal surface. The results obtained showed the prospects for the use of compositions with paraffin for further research as a conservation material for the protection of agricultural machinery.