Stationary Zone Research Articles

Reactive Transport Modeling for Exploring the Potential of Water Quality Sensors to Estimate Hydrocarbon Levels in Groundwater

AbstractPetroleum products have contaminated groundwater with harmful organic compounds, such as benzene, toluene, ethylbenzene, and xylenes (BTEX). Collecting and analyzing polluted groundwater samples is expensive and undertaken infrequently. However, quick remedial action in case of unexpected events requires continuous monitoring. In‐situ water quality sensors (pH, EC, DO, ORP) may show correlations with the components of dissolved petroleum hydrocarbon (PHC) such as aromatics and non‐volatile mobile fractions. Correlations are prerequisite to ultimately develop real‐time prediction models. Since suitable field data sets are limited, we simulated the fate of hydrocarbons in groundwater under various realistic conditions using a reactive transport model as novel approach to explore when, where, and why correlations occur. A stationary oil source zone continuously dissolved at the top of a heterogeneous and shallow sandy aquifer over a two‐dimensional cross‐section. Our model considered transient conditions (fluctuating water table) and spatially uniform hydrogeochemical composition. We observed a strong correlation between PHCs and water quality sensors (rolling Spearman's correlation > |0.8|) at varying periods. These correlations are strongly affected by the location of observation wells, the aquifer's hydraulic conductivity, and the availability of calcite and oxide minerals, and other electron acceptors. DO and ORP are significant for the early detection of hydrocarbon contamination, whereas pH and EC are important features for the long‐term monitoring of hydrocarbons. Our findings lay the foundation for the subsequent development of a data analysis model to detect and estimate in real time PHC levels in groundwater using in‐situ water quality sensors.

Improved Temporary Traffic Control Guidance for Mobile Operations on Two-Lane Roadways

The objective of this research was to develop guidance for improving safety at mobile operations on two-lane roadways. One of the most significant hazards to workers performing mobile operations is unpredictable driver behavior around the operation (including poor passing decisions). Researchers observed 1,209 passing maneuvers at 17 different mobile operations in Texas and Minnesota, U.S., to better understand driver behavior around mobile operations. An analysis of the passing maneuver data showed that 449 passing maneuvers were made by drivers who were not first in the queue of vehicles behind the mobile operation. These passing maneuvers were considered undesirable because they indicate some degree of driver impatience. Researchers analyzed the amount of time each driver spent in the queue and found that nearly 50% of drivers who waited in the queue for 4 min or longer attempted an undesirable passing maneuver. This increased to nearly 85% when wait times exceed 6 min. As a result of the field studies, the researchers recommended that transportation agencies strive to avoid creating situations where drivers in queue must follow a mobile operation for several minutes without opportunities to pass. When these delays cannot be avoided, the work crew may need to pull over and allow vehicles to pass. If there are no suitable pullover locations, a stationary work zone with positive traffic control methods (e.g., flaggers, portable signals) should be considered.

On the contribution of the top and bottom walls in micro-pillar array columns and related high-aspect ratio chromatography systems

We report on a steady-state based, and hence highly accurate numerical modelling study of the effect of the top and bottom wall in the current generation of micro-pillar array columns. These have a mesoporous retention layer that not only covers the pillar walls but also the bottom wall. Our results show that the performance of these columns can in general not be improved by also covering the top wall with the same layer, despite the increased column symmetry this approach would offer. The reason for this is that the local species retardation caused by a retentive layer is much stronger than the pure flow arresting effect of an uncovered wall. At least, this has a crucial impact in high aspect-ratio systems such as micro-pillar array columns because these require a small inter-pillar distance to promote mass transfer together with a large channel depth to enable a sufficiently high flow rate. On the other hand, a notable improvement could be made if micro-pillar array would be produced without having a retentive layer at the bottom. At Péclet number Pe = 50 and aspect ratio AR = 5 for flow-channels, this gain amounts up to about 4.5 h-units at a zone retention factor k’’ = 2 and 1.75 h-units at k’’ = 16 (gain scales almost linearly with Pe).To verify these results, we also considered another high aspect-ratio system with a simplified geometry: the open-tubular channel with a flat-rectangular cross-section. This led to very similar observations, thus confirming the findings for the micro-pillar array.The results produced in the present study also allow us to conclude that the classic modelling paradigm adopted in chromatography, which is based on the independency and hence additivity of the hCm- and hCs-contributions, can lead to large modelling errors in chromatographic systems with a high aspect-ratio, even when their geometry is so simple as that of a straight open-tubular channel with constant cross-section. Indeed, when both zones are treated independently, the analysis misses how the vertical diffusion through the retentive layer helps suppressing the vertical gradients in the mobile zone. The diffusion through this layer occurs in a ratio of k’’Ds/Dm (Dm being the diffusion coefficient in mobile phase zone and Ds being the diffusion coefficient in stationary phase zone), such that at high retention factors this diffusion contribution even becomes the dominant one.

On the modelling of the effective longitudinal diffusion in bi-continuous chromatographic beds

We report on the possibility to extend to bi-continuous packings the two models for the effective longitudinal diffusion Deff, or B-term band broadening, recently proposed for discontinuous chromatographic beds. In bi-continuous packings, like monolithic columns, solutes experience a connected end-to-end pathway in both the mobile and stationary zones, as opposed to discontinuous packings, wherein the stationary adsorptive zone is distributed over a set of isolated elements. Since it is unclear whether a densely packed bed of spherical particles should be treated as a continuous or a bi-continuous medium, this extension is also crucial to fully understand the behaviour of packed particle beds. The proposed models for the effective longitudinal diffusion Deff originate from the adoption of the Two Zone Moment Analysis (TZMA) method by which Deff can be expressed as a linear combination of two essential quantities γm and γs, referred to as effective zone-diffusion factors. In the present work we propose two analytical models for γm and γs that now cover both the discontinuous and the bi-continuous case. To validate the theory, several bi-continuous packings are investigated, including the tetrahedral skeleton model (TSM), six different Triple Periodic Minimal Surface (TPMS) monoliths and randomly packed beds of spheres. For all of these, the models provide highly accurate results for Deff over a wide range of porosities and zone retention factors k″. The comparison with literature experimental data for both monolithic silica columns and columns packed with fully porous and porous-shell particles is also presented.

The Active Place Avoidance (APA) Test, an Effective, Versatile and Repeatable Spatial Learning Task for Mice.

Hippocampus-dependent spatial learning in rodents has been tested using a variety of methods. These include the Morris water maze (MWM), Y-maze, and novel object location (NOL) tasks. More recently, the active place avoidance (APA) task has been developed as an alternative to these more traditional approaches. In the APA task, mice must use spatial cues placed around a rotating arena to avoid a stationary shock zone. Due to the multiple parameters that can be adjusted, the APA task has been demonstrated to be a very versatile approach. It lends itself to being used longitudinally and repeatedly for the same cohort of mice. Here, we provide a detailed protocol to successfully conduct the APA task. We also highlight alternative APA approaches that can be used to examine different components of spatial learning. We describe the data collection and analysis processes. Critical steps during the APA task are discussed to increase the likelihood of successfully conducting the test. The APA task has several advantages over more traditional spatial navigation tests. It is appropriate to use with aged mice or those with disease phenotypes such as Alzheimer's disease. The complexity of the task can be easily altered, allowing a wide range of mouse strains to be tested. Further, the APA task is suitable for testing animals that have undergone surgery or experimental interventions that may have affected motor or neural function, such as stroke or traumatic brain injury.

Nonadditivity and Nonlinearity of Mobile and Stationary Zone Mass Transfer Resistances in Chromatography.

Using a two-zone moment analysis (TZMA) method based on Brenner's generalized dispersion theory for two-dimensional (2D) and three-dimensional (3D) periodic media, we investigated the mechanisms for dispersion in particulate media for liquid chromatography. This was done using a set of plate height data covering an unprecedented wide range of retention factors, diffusion coefficients, and velocities, all computed with unequaled accuracy. Applying Giddings' additivity test, based on alternatingly making the diffusion coefficient in the mobile and stationary zones infinitely large, the dispersion data clearly indicate a lack of additivity. Although this lack could be directly understood by identifying the existence of multiple parallel mass transfer paths, the additivity assumption interestingly overestimates the true C term band broadening (typically by more than 10%, depending on conditions and dimensionality of the system). However, Giddings originally asserted the occurrence of parallel paths would always lead to an underestimation of the dispersion. The origin of the lack of additivity is analyzed in detail and qualitatively explained. Finally, we also established a generic framework for the modeling of the effect of the reduced velocity and the retention coefficient on the C term in ordered chromatographic media. This led to the introduction of a new expression for the mobile zone mass transfer term, which, unlike the currently used literature expression, contains the complete k″ dependency.

Passive Soil Arching Effect in Aeolian Sand Backfills for Grillage Foundation.

The passive soil arching effect exists in many soil-grille interaction systems. Increasing mental grillage foundations are used for transmission lines in aeolian sand areas; thus, exploring the evolution mechanism of passive soil arching is crucial. This study investigates the evolution and influencing factors of passive soil arching through a series of tests using a trapdoor device and particle image velocimetry (PIV). The test results show that the evolution of the arching structure causes the aeolian sand deformation to gradually extend to the backfill surface and stationary zone, generating two triangular arching surfaces between the movable beams and sliding surface at the junction of the active and stationary zones. Cracks in the arching and sliding surfaces were connected to form a W-shaped shear band. The development of the soil pressure was divided into four arching structure stages. The different stages of the inner and outer arches of the bearing characteristics had strong differences. Taking the appearance of the first arch surface as the time point, the soil pressure changes abruptly and the inner and outer arches alternate to bear the as a major role. The beam spacing significantly affected the arching evolution. A smaller beam spacing formed an initial bending configuration with an inconspicuous arching structure and incomplete shear band. As the beam spacing increased, the arching shape changed from triangular to parabolic, sudden changes in the soil pressure were more pronounced, and the arch height increased. The relative density and water content had little impact on the arch shape and shear zone but significantly affected the arching strength, soil pressure transfer, and arching height. The medium and high relative densities and low water contents resulted in a stronger arching structure and greater arching height, while low relative densities and high water contents weakened the soil pressure transfer. The range values for the optimum beam spacing, relative density, and water contents are given based on the variation characteristics of the evaluated parameters (E, n) under different conditions.

Analysis of multi-particulate flow through the horizontal eccentric annulus considering the borehole cleaning

Multi-particulate flow CFD modelling is carried out while taking eccentricity into account considering drilling horizontal oil wells. The present work focuses on the effect of different cuttings sizes and their concentration on borehole cleaning. The carrier phase is a CMC-Bentonite solution which is a non-Newtonian fluid and the secondary phase is sand cuttings with different sizes. The RNG-k-ε turbulence mixture model is implemented along with the Eulerian-Eulerian multiphase model. The present CFD work has been validated with different experimental work and analytical results. The cutting size distribution in terms of volume fraction has been plotted along the various planes. Contours for volume fraction for different cutting size and inlet cuttings concentrations are also obtained. The increase in turbulence kinetic energy through increase inlet axial slurry velocity and drillpipe rotation (from v = 1 m/s, N = 50 rpm to v = 3.5 m/s, N = 100 rpm) is very effective in reducing cuttings accumulation for slurry A. The migration of cuttings from stationary zone to suspension zone is high for larger cuttings as compared to smaller cuttings from plane P2. The equivalent two-phase simulation for considered five-phase flow of slurry A has the similar cuttings distribution.

High-quality surface wave retrieval from vibrations generated by high-speed trains moving on viaducts

Short-time passive surface wave imaging of the shallow subsurface faces great challenges due to the lack of anthropogenic noise in areas far away from towns. Vibrations generated by high-speed trains (HST) are good complements because of its strong energy and broad frequency band. The processing scheme of surface wave imaging from HST vibrations has not been systematically studied. We propose an optimized workflow of high-quality surface wave imaging from HST vibrations. An HST signal selection method is used to automatically select the data during the HST running through the stationary phase zone of the survey line. The characteristic of sharp equidistant spectral lines in the frequency spectrum of HST signals will distort the virtual shot gather and the frequency domain normalization operation can suppress the distortion. The phase weighted stacking and the multi-channel correlation weighted stacking are applied to improve the signal-to-noise ratio of the virtual shot gather. The HST signal processing scheme is applied to field data with four survey lines and surface wave signals are better retrieved than using the conventional ambient noise processing scheme. The results demonstrate the advantage of our proposed workflow in real-world applications, which provides a tool of surface wave imaging from HST vibrations.

Dependence of effective permeability on pore pressure gradient at low flow rates in low-permeability limestone

Many researchers note a nonlinearity of flow in tight rock samples at low rates. The effects include changes in apparent permeability with pore pressure gradient and so-called threshold gradients, below which low flow or no flow occurs. It is believed that these effects may be related to the influence of adhesive layers with altered properties at the interfaces between liquid and solid phases. For low-permeable rocks, the estimation of reservoir permeability without taking into account the nonlinearity of the flow can lead to significant errors. An account of the flow nonlinearity also can downgrade the reservoir productivity estimation and may result in underestimation of stationary oil zone appearances. Conventional methods for studying fluid flows in porous rocks are poorly suited for studying their permeability when approaching zero flow rates because of the lack of accuracy. Such studies also require a special approach for the interpretation of the data obtained. At the same time, there is a lack of discussion of the appropriate experimental technique in the publications known. Our goal was to develop a technique suitable for studying the flow nonlinearity at extremely low flow rates. Using the developed experimental technique, we carried out three series of consecutive tests on three similar limestone core samples. The samples were taken from the aquifer; however, their porosity and permeability are similar to the typical parameters of a tight oil reservoir. During the test series, we observed the change in the deviation from the linear Darcy’s law over a long time. We realized that in the sample with the most pronounced deviation from linear flow, there was a most significant decrease in net permeability in the entire series. We believe that our method can provide more precise evaluation of the permeability of tight rocks at the near real flow rate.

Evaluating spatial and temporal variations in sub-field level crop water demands

Variable rate irrigation (VRI) requires accurate knowledge of crop water demands at the sub-field level. Existing VRI practices commonly use one or more variables like soil electrical conductivity, historical yields, and topographic maps to delineate variable rate zones. However, these data sets do not quantify within season variability in crop water demands. Crop coefficients are widely used to help estimate evapotranspiration (ET) at different stages of a crop’s growth cycle, and past research has shown how remotely sensed data can identify differences in crop coefficients at regional and field levels. However, the amount of spatial and temporal variation in crop coefficients at the sub-field level (i.e. within a single center pivot system) has not been widely researched. This study aims to compare sub-field ET estimates from two remote sensing platforms and quantify spatial and temporal variations in aggregated sub-field level ET. Vegetation indices and reference ET data were collected at Kansas State University’s Southwest Research Extension Center (SWREC) and two Water Technology Farms during the 2020 corn growing season. Weekly maps of the Normalized Difference Vegetation Index (NDVI) and the Soil Adjusted Vegetation Index (SAVI) from aerial imagery are combined with empirical equations from existing literature to estimate both basal and combined crop coefficients at a 1-meter resolution. These ET estimates are aggregated to a 30 m resolution and compared to the Landsat Provisional Actual ET dataset. Finally, actual ET estimates from aerial images were aggregated using k-means clustering and stationary variable speed zones to determine if there is enough variation in actual ET at the sub-field level to build variable rate irrigation schedules. An equivalence test demonstrated that the aerial imagery and Landsat data sources produce significantly different crop coefficient estimates. However, the two datasets were moderately correlated with Pearson’s product-moment correlation coefficients ranging from -0.95 to 0.86. Both the aerial imaging and Landsat datasets showed high variability in crop coefficients during the first 5-6 weeks after emergence, with these coefficients becoming more spatially uniform later in the growing season. These crop coefficients may help irrigators make more informed irrigation management decisions during the growing season. However, more research is needed to validate these remotely sensed ET estimates and integrate them into an irrigation decision support system.

Hydro-mechanical behaviour of soils during water-soil gushing in shield tunnels using MPM

Water-soil gushing has become the main risk affecting the safety of shield tunnels in water-rich sandy layers. In this paper, a two-phase single-point material point method (MPM) is used to simulate the evolution of gushing in shield tunnels and the hydro-mechanical responses of the surrounding soils. The method is validated by well-documented experiments. The influence of gushing on the surrounding soil can be divided into three zones: flow zone, disturbed zone, and stationary zone. Based on the development laws of the flow zone, the gushing process can be divided into three stages: the initial developing stage, the expansive developing stage, and the stable developing stage. Parametric analysis is carried out to investigate the effect of the gushing location, the buried depth of the tunnel, and the soil parameters. The lower the gushing location, the smaller the development rate of the gushing, but the greater the variation in soil stress. The shallower the tunnel depth for the gushing, the smaller the impact on deep layers, but the greater the influence on ground settlement. Increasing the friction angle can effectively reduce the area and the development rate of the flow zone.

Image Analysis of Particle Flow in Centrifugal Solar Particle Receiver

Abstract Particle solar receivers promise economical and operational advantages compared to the molten salt-based solar receivers. In this study, an experiment is designed to observe the particle flow characteristics in the Centrifugal Particle Solar Receiver. A set of experiments for various receiver rotational speeds and particle mass flowrates is conducted, and experimentally obtained raw results are post-processed by means of an Image Processing Routine based on 4BestEstimate algorithm. The axial advance of the particles in one receiver rotation, the particle film thickness, and the ratio of the length of the stationary zone to the receiver circumference is measured to be later used in the validation study of the discrete element method-based numerical model.

Exact analytical expressions for the band broadening in polydisperse 2-D multi-capillary columns with diffusional bridging

Using a recent generalization of the Aris dispersion method, we have derived exact analytical expressions for the long-time limit dispersion in 2-D multi-capillary packings with diffusional bridging (binary channel system). Both the plug flow and the parabolic flow case are considered. The expressions are mathematically exact over the entire range of possible values of the degree of polydispersity (σ), the retention equilibrium constant K and the diffusion coefficients in the mobile and stationary zone. They are validated by comparing them to the dispersion data obtained by numerically solving the partial differential equation describing the general advection-diffusion mass balance. A correlation coefficient of R2 > 0.99995 is obtained. The form of the obtained analytical expression shows the dispersion arising from the polydispersity effect in multi-capillary systems can be split in two contributions, one related to the actual velocity difference between the adjacent channels and one related to the fact that the average of the intra-capillary C-term band broadening is larger in any σ≠0-case than in the σ=0-case. When leaving the small σ-assumption, a new factor ((1- σ2)/(1+3σ2)2) emerges, common to both the solution for the plug flow and the parabolic case. The analysis shows the parabolic flow not only leads to a larger intra-capillary dispersion (σ=0) than the plug flow case as known from literature but is also more sensitive to the polydispersity effect (up to some 10 to 20%).

Substance Transfer in a Porous Medium with a Small Amount of Homogeneous Salt Modeling

The salt-transfer problem in a porous media with piecewise uniform salinity is numerically solved in this paper. There are two scenarios to consider: 1) a salt solution-saturated stationary zone; 2) a dry stratum with piecewise homogenous salinity. The distribution of substance concentration and the amount of adsorbed substance are determined based on the numerical solution of the problem. It has been found that substance adsorption has an effect on salt-transfer properties.

Research of ANSYS Autodyn capabilities in evaluating the landmine blast resistance of specialized armored vehicles

The object of research is the processes of pulse explosive loading in an explicit formulation for simulation of complex nonlinear dynamics of solids, gases, and their interactions. One of the most problematic areas of modern studies of nonlinear dynamic loads of materials using a numerical analysis is that such studies usually do not take into account the characteristic transition of the stationary deformation zone of the loaded material to the unsteady one and the front pressure and shockwave velocity variation by time. The work is aimed at developing a mathematical model of a pulsed load of materials by a shockwave, developing a mathematical apparatus for calculating the parameters of a shockwave, creating analytical dependences of the interaction of a shockwave with a loaded surface. A study of dynamic explosive loading using software based on an explicit method for solving the equations of continuum mechanics is proposed. In this work, the stress-state equation at a point of the material under pulsed load conditions was further developed, methods for determining the principal stresses and the invariant of the stress tensor, taking into account the pulsed nature of the load, were established. The character of the behavior of the shockwave formed as a result of the detonation of the explosive has been established. Analytical dependences of the interaction of a shockwave with a loaded surface are compiled. A mathematical apparatus has been developed for calculating such parameters of the shockwave as the detonation front pressure and its change in time and the velocity of the shockwave at the moment when it reaches the surface. Mathematical dependences have been developed and proposed, which, in contrast to the existing ones, make it possible to determine the current values of stresses and strains passing through the points of the actual stress curve, as well as the intensity of stresses and strains under pulse loading of metals. On the basis of theoretical and experimental studies of the parameters of body material deformation under the action of explosive loading, the mechanisms of destruction of the KrAZ «Shrek» and KrAZ «Fiona» (Ukraine) specialized armored vehicles body were clarified to establish the compliance of the declared landmine resistance of vehicles with the STANAG 4569 standardization agreement.

Local-scale phase velocity estimation using ambient seismic noise: comparison between passive seismic interferometry and conventional frequency–wavenumber methods

SUMMARYWe present a new processing scheme that uses passive seismic interferometry (PSI) followed by multichannel analysis of surface waves (MASW), which we call the 2-D PSI-MASW method, to obtain Rayleigh wave phase velocity dispersion (PVD) information. In this scheme, we first use the principles of PSI to form multidirectional cross-correlations (CCs) then project the CCs onto a 1-D virtual array and apply the phase-shift transform as in MASW processing. We compare PVD information obtained by this method with those of the conventional beam-power based frequency–wavenumber decomposition (CVFK) method using ambient seismic noise (ASN) data collected by local-scale 2-D arrays deployed at three selected sites in Bursa, Turkey. By analysing the ASN data from these sites, we show that similar multimodal PVD curves can be obtained with the two methods over a broad frequency range (∼2–23 Hz) within the wavenumber resolution and aliasing limits. However, in one of our sites where the 2-D array configuration has a considerable antisymmetry, we show that the 1-D virtual array used in the 2-D PSI-MASW method has a better array response function in terms of wavenumber resolution and suppression of side-lobes leading to superior mode resolution and separation than that of the CVFK method, which shows strong directional variations. Furthermore, unlike the CVFK method, the 2-D PSI-MASW method takes advantage of temporal stacking of CCs ensuring weak but coherent Rayleigh wave signals present in the ASN wavefield to be strengthened and has the potential for better extraction of PVD information. We conclude that by using a 2-D array with spatial coverage providing a wide range of directions and distances, reliable PVD information can be obtained even if the ASN sources are not concentrated in the stationary phase zones. Thus, we suggest that the 2-D PSI-MASW method is highly advantageous for the extraction of reliable PVD information owing to the multidirectional CCs provided by the 2-D array configurations. We also report that using only a single receiver line in the interferometric approach results in biased and/or incomplete PVD information due to the non-isotropic ASN source distribution at all three sites we analysed. In conclusion, our results clearly indicate that the 2-D PSI-MASW method can be used as complementary or alternative to the CVFK method to extract multimodal Rayleigh wave PVD information in local-scale seismological studies.

The Recreational Capacity of the Zones of the Ukrainian National Natural Parks

Purpose. To determine the recreational capacity of the territories of several National Natural Parks (NNPs) of Ukraine, as well as the recreational capacity of the tourist trails of these parks. Methods. The methodological basis of the study is based on a critical analysis of the current approaches to the assessment of a recreational facilities of the Ukrainian NNPs. Various published data sources as well as the data, regarding to the recreational renewal capacity of the territories of the NNPs acquired during own research was used. Results. The area of the reserved core that is larger than a one third of the entire area of the park may be seen in only few parks. Most of the NPPs have an insufficient size of the protected areas. This indicate an unstable and severely disturbed ecological conditions, which threatens the conservation of the biological diversity in these parks. That’s why the increase of the protected areas of these NNPs is highly advisable. In addition to all above, the area of the NNP special use zone should be smaller than the area of the regulated recreational area, which plays a certain environmental role; it can be decreased in a favor of the stationary recreational zone if needed. Unfortunately, these conditions are not met for the most of the studied NPPs. That’s why it is advisable to optimize the functional zoning of the NNPs, which will effectively protect the unique natural complexes and will let use them for the recreational purposes. The capacity, the degree of the resistance to the recreational loads, the level of improvement and the capacity of the tourist routes in each of the spoken NNPs were analyzed. The main criteria for choosing the studied NNPs were their representativeness or representation in terms of a variety of the accommodating regions, the availability of the data based on the physical and geographical characteristics, the length of the tourist routes and the statistcs of the visitors per year. The recreational capacity for the summer season of some NPPs of Ukraine was calculated, while taking into account the standards for each type of the natural complex for the zones of stationary and regulated recreation. Potentially, these zones may be expanded replacing the parts of the reserved special use zone. An assessment of the capacity of some tourist trails of the barely improved NPPs for an unstable and stable category of natural landscape complexes was given. Conclusions. The recreational potential of the researched Ukrainian NPPs is currently underutilized, but with the increase in the flow of the recreants, the recreational areas that are poorly equipped as well as the trails may lead to a deterioration in the state of the natural ecosystems. The functional zones of the stationary and of the regulated parts of the recreational areas of the NNPs may be expanded by migrating some types of the recreational activities to the special use zone of the parks. It is vital to expand the list of the recreational services for recreants, to strive the level of improvement of the tourist trails of the NNPs. If the natural healing resources are present on the territories of the NNPs, it is advisable to organize some centers for the sanatorium treatment, medical and socio-psychological rehabilitation, which will contribute to the creation and an improvement of the medical and the health infrastructure, the activation of recreational activities and the increase in the efficiency of the functioning of the NNP.

Особенности локализации деформации при термосиловой обработке

The paper considers the issues of ensuring the uniformity of strain of axisymmetric long-dimensional samples during thermal force processing (TFP), which is the simultaneous application of force and temperature effects for comprehensive improvement of geometric characteristics and physical and mechanical parameters of the workpiece material. This technology is used at various stages of technological processes of parts manufacturing, but its main task is to ensure the axis straightness and the specified distribution of residual technological stresses at the procuring stage. The disadvantage of TFP is that the axial deformation proceeds nonuniformly along the workpiece axis. The core process parameter is the deformation, the control of which is a key factor ensuring the TFP efficiency. The authors studied the plastic strain distribution over the sections of long-length workpieces with different deformation degrees. The study involved the assessment of strain uniformity over the workpiece sections, taking into account the stage of the stress-strain relation at the end of the loading cycle. Based on the concepts of plastic deformation as an auto-wave process, the authors selected the range of technological modes corresponding to the most uniform strain distribution along the workpiece axis with complete processing of the entire workpiece volume. This range corresponds to the stage of parabolic hardening of the plastic flow curve with the formation of the maximum number of stationary zones of localized plasticity. Rheological modeling allows identifying the control points that specify the boundaries of the plastic flow curve stages at various loading parameters, including temperature. To improve the reliability of determining the actual deformation under production conditions, the authors proposed modernizing the TFP process monitoring method by fixing the deformation on a limited workpiece section using the optical technique. The statistical analysis of the strain distribution over the sections for the samples confirms the correctness of this approach. The application of the proposed control method will ensure the most uniform distribution of plastic deformation due to the reliable enter of the workpiece deformation to the range of strain values corresponding to the stage of parabolic hardening of the plastic flow curve.

Multicriterial Optimization of the Composition of a Lubricant

In this paper, a study has been performed to reveal the effect of the composition of a three-component lubricant on the consumption thereof, on the wear rate of the wheels of the rolling stock, and on the friction coefficient of the wheel-rail tribocontact by means of a simplex-lattice design that provides a minimum wear rate of wheel flanges. The most promising components of the lubricant have been chosen taking into account tribotechnical requirements and economic and environmental aspects. A matrix of a simplex-lattice design with the variation range of variable factors is formed. Regression models of the output parameters have been obtained for different combinations of lubricant components. A stationary zone of the simplex that characterizes the rational composition of the lubricant components to provide an exact trade-off combination of the components is established. The efficiency of the developed composition of the proposed lubricant is confirmed by full-scale tests of the rolling stock on the pieces of the North Caucasus Railway by a 28.4% decrease in the wear intensity of wheel flanges.