Rheological State Research Articles

Forecasting the rheological state properties of self-compacting concrete mixes using the response surface methodology technique for sustainable structural concreting.

It is structurally pertinent to understudy the important roles the self-compacting concrete (SCC) yield stress and plastic viscosity play in maintaining the rheological state of the concrete to flow. It is also important to understand that different concrete mixes with varying proportions of fine to coarse aggregate ratio and their nominal sizes produce different and corresponding flow- and fill-abilities, which are functions of the yield stress/plastic viscosity state conditions of the studied concrete. These factors have necessitated the development of regression models, which propose optimal rheological state behavior of SCC to ensure a more sustainable concreting. In this research paper on forecasting the rheological state properties of self-compacting concrete (SCC) mixes by using the response surface methodology (RSM) technique, the influence of nominal sizes of the coarse aggregate has been studied in the concrete mixes, which produced experimental mix entries. A total of eighty-four (84) concrete mixes were collected, sorted and split into training and validation sets to model the plastic viscosity and the yield stress of the SCC. In the field applications, the influence of the sampling sizes on the rheological properties of the concrete cannot be overstretched due to the importance of flow consistency in SCC in order to achieve effective workability. The RSM is a symbolic regression analysis which has proven to exercise the capacity to propose highly performable engineering relationships. At the end of the model exercise, it was found that the RSM proposed a closed-form parametric relationship between the outputs (plastic viscosity and yield stress) and the studied independent variables (the concrete components). This expression can be applied in the design and production of SCC with performance accuracies of above 95% and 90%, respectively. Also, the RSM produced graphical prediction of the plastic viscosity and yield stress at the optimized state conditions with respect to the measured variables, which could be useful in monitoring the performance of the concrete in practice and its overtime assessment. Generally, the production of SCC for field applications are justified by the components in this study and experimental entries beyond which the parametric relations and their accuracies are to be reverified.

Evaluation of the Effect of C9 Petroleum Resin on Rheological Behavior, Microstructure, and Chemical Properties of Styrene–Butadiene–Styrene Modified Asphalt

Understanding the modification mechanism of C9 petroleum resin (C9PR) on styrene–butadiene–styrene (SBS) polymer modified asphalt properties is of significant importance. In this paper, dynamic shear rheometer (DSR), storage stability, fluorescence morphology (FM), scanning electron microscope (SEM), Fourier transform-infrared (FTIR) spectrometer, and molecular dynamic (MD) simulation were adopted to evaluate the rheological, chemical, and microstructure molecular motion state of C9PR and SBS composite modified asphalt at different aging states. The DSR storage results indicate that the addition of C9PR could improve the high-temperature property, storage stability, and temperature susceptibility. FM and SEM results indicate that the network microstructure was enhanced and the roughness between polymer resins and virgin asphalt was improved at the microscopic scale. The MD results indicate that the heterogeneity between C9PR and SBS modified asphalt was demonstrated, and the bonding energies were enhanced with the addition of C9PR. Moreover, the FTIR results indicate that new function groups were generated in addition to C9PR. In general, the addition of C9PR is a good approach to promote high-quality polymer modified asphalt (PMA) for pavement engineering.

Study on the Melt Rheological Characterization of Micro-Tube Gas-Assisted Extrusion Based on the Cross-Scale Viscoelastic Model.

In the micro-tube gas-assisted extrusion process, flow theories ignoring cross-scale viscoelastic variations fail to effectively characterize the rheological state of the melt. To investigate the impact of cross-scale viscoelastic variation on the quality of the micro-tube gas-assisted extrusion, a 3D multiphase flow extrusion model incorporating a double gas-assisted layer was developed. Subsequently, we modified the DCPP constitutive equations based on the cross-scale factor model. Both the traditional and gas-assisted extrusions were simulated under macroscale and cross-scale models using the Ansys Polyflow. Finally, using the established gas-assisted extrusion platform, extrusion experiments were conducted. The results indicate that, owing to the reduced melt viscosity under the cross-scale model, the deformation behavior of the melt is more pronounced than in the macroscale model. The cross-scale model's numerical results more closely match the experimental outcomes under the same parameters, thereby confirming the feasibility of the theoretical analysis and numerical simulation. Moreover, the predictive capability of the cross-scale model for the micro-tube gas-assisted extrusion is further validated through numerical and experimental analyses with varying parameters. It is demonstrated that the cross-scale viscoelastic variation is a critical factor that cannot be overlooked in the gas-assisted extrusion.

Regulation of rheological properties of soy protein isolate-beeswax based bigel inks for high-precision 3D printing

Bigel inks were developed for high-precision 3D food printing using soy protein isolate (SPI) hydrogel and beeswax oleogel. The ratio of hydrogel to oleogel played a crucial role in determining the rheology and moisture state of the inks. When the ratio of hydrogel to oleogel reached 7:3, the ink was softer and showed stronger shear-thinning properties, which resulted in better recoverability and stronger self-supportability. These were demonstrated by the lowest flow index (n value) of 0.135, the largest recovery viscosity of 10.920 × 105 mPa s, and the biggest yield stress (1034.200 Pa), complex modulus (G* of 6608.066 Pa), and gel strength (A value of 488.34 × 103 Pa s1/z). Additionally, the ink contained more semi-solid water (T22) and had a higher proportion of moisture freedom (A23). Consequently, the ink had a smooth extrusion while exhibiting strong mechanical properties and better structure stability. As a result, a hollow-rotating structure was achieved with a height of 20.05 mm, a gap diameter of 10.11 mm, and an inclination angle of 46.13° with precision beyond 99%. This was attributed to the presence of more β′ and β crystals with high oleogel content, which might protect the completeness of the SPI hydrogel network structure and prevent the aggregation of oleogel particles. In this turn, it improved the microstructure of the SPI-based bigel inks and made them more resistant to shearing during extrusion. This work provides a new insight into the application of SPI in personalized diets.

Effects of vibration on granular chute flow under low-gravity conditions

The essence of most geological hazards and industrial processes is gravity-driven flows of dense particles. In this research, we use the discrete element method to simulate the particle chute flow, and discuss the effect of vibration acceleration on the granular flow under different gravity conditions. The results indicate that vibration has a greater impact on the particle flow state under low-gravity environments and low inclination angles. The granular temperature (T) and inertia number (I) increase with increasing vibration acceleration. Vibration enhances the flowability of particles by changing the stress state and reducing the volume fraction of the granular system. This work reveals the rheological state of vibration-triggered particle flow on an inclined surface under different gravity environments.

Evaluation of tensile properties and cracking potential evolution of fly ash-cement mortar at early age based on digital image correlation method

The early-age tensile properties and shrinkage behaviors of mortar are important to investigate its early-age cracking potential. This study employs the digital image correlation method to quantify the tensile properties and shrinkage behaviors of fly ash-cement mortars at early age, aiming to reveal the effect of fly ash on the mortar's cracking potential evolution. Fresh mortars with varying fly ash (FA) contents (0%, 10%, 20%, 30%) undergo comprehensive tests, encompassing tensile strength, ultimate tensile strain, plastic shrinkage, mass loss, and damage assessment within 90–180 mins after casting. The results show that FA could enhance early-age ultimate tensile strain and extend the time for the mortar to maintain plasticity while reducing early-age shrinkage strain and mass loss. The mortar's cracking risk is potentially linked to its setting time. The rheological state of mortar gradually changed from plastic to non-plastic after initial setting, and the ultimate tensile strain stabilized, but the shrinkage strain increased rapidly, which resulted in a greater risk of shrinkage-induced cracking. Furthermore, after 180 mins of curing, the damage index of the fly ash-cement mortar (10% FA) was 1.6 times that of pure Portland cement mortar, whereas the damage indexes of the fly ash-cement mortars with 20% and 30% FA contents are approximately equivalent to 82% of the pure Portland cement mortar's damage index. This indicates that incorporating more than 20% fly ash is beneficial in reducing the risk of plastic shrinkage-induced cracking in mortar.

What controls the formation of vulcanian bombs? A case study from the 1 February 2014 eruption of Tungurahua (Ecuador)

Vulcanian eruptions are very common at many volcanoes around the world that erupt intermediate to silicic magmas. This type of eruption generates a wide variability of bombs and blocks preserving information onto the conduit processes that strongly control the dynamics of these events. After 84 years of repose, a new cycle of eruptive activity of Tungurahua volcano (Ecuador) started in October 1999, consisting of recurrent low-to-moderate explosive phases, which included sporadic stronger Strombolian to sub-Plinian pulses, as well as Vulcanian outbursts. The 1 February 2014 eruption was one of the most important Vulcanian events and was characterized by highly energetic explosions resulting from a plug conduit failure that generated a ∼ 9 km-high eruptive column and fallback pyroclastic density currents. Four different types of blocks and bombs were found in the deposits of the pyroclastic density currents: dense fragments (DB), breadcrust bombs (BCB), cauliflower bombs (CFB) and foliated, banded bombs (FB). All the different types of bombs have homogenous andesitic bulk-rock compositions but different, highly evolved matrix glass compositions ranging from rhyolitic for BCB to dacitic for CFB and DB, suggesting the occurrence of contrasting shallow crystallization processes within the conduit. The wide variability of the bombs in terms of patterns of surface cracks, external morphologies, internal density and vesicularity gradients records different conditions of formation from a same magma composition.The combination of morphological measurements, compositional data and textural analysis allow us (i) to infer the pre-eruption physical and rheological state of the conduit plug, (ii) to reconstruct the short-scale lateral and vertical gradients characterizing the plug, and (iii) to clarify the specific mechanism controlling the formation conditions of CFB, still poorly defined in the literature.

Characterization of aged bitumen recovered from in-situ polymer-modified HMA and WMA using advanced technologies

The growing attention of public opinion towards the environment has prompted, in the last decades, to find eco-sustainable and economic alternatives to the traditional productions of hot-mix asphalt (HMA). Under these auspices, the use of warm mix asphalt (WMA) technology applied to mixtures containing reclaimed asphalt (RA) has grown, also due to the well-proven advantages in terms of plant odor emissions and improved working conditions. In addition, it is now known that the mechanical performance of WMAs is completely comparable, even superior in some cases, to that of HMAs. However, to date, there is no comparison in terms of long-term performance of bitumens used in full-scale pavements laid with the two different technologies. Therefore, the aim of this research is to evaluate the oxidative and rheological state of four bitumens recovered from different layers of a full-scale pavement prepared with WMA and HMA technologies and set up a methodology tool set for investigating the physicochemical properties of bitumens. An in-depth laboratory investigation, carried out through physicochemical and rheological tests, has shown that the bitumens used in WMA mixtures are characterized by less oxidation than HMA ones (which are characterized by longer relaxation and glass transition times) and the Styrene-Butadiene-Styrene (SBS) polymers inside them are less degraded and still contribute positively to the rheological response even after five years in service, demonstrating the ability of the chemical additive to act as possible “sacrificial agent”, safeguarding the rheological characteristics of polymer modified bitumens (PMBs).

Matematyczne modele hydromechaniki przepływu wielofazowego o zmiennej masie

The paper discusses the mathematical model of hydromechanics of multiphase flows with varying mass. A multiphase flow is considered a continuum consisting of a set of a large number of different groups of particles. The derivation of motion equations and similarity criteria are given taking into account both the externally attached (or detached) mass and phase transitions within the medium. The equations of mass, momentum and energy transfer for individual phases and the medium as a whole are derived based on fundamental conservation laws. It was demonstrated that in the absence of sources (or flow-offs) of mass, momentum and energy, the known equations of single- and multi-phase flow hydromechanics follow as a special case from the obtained systems of motion equations and similarity criteria. The obtained motion equations are valid for the description of an ingredient of mixture and the medium as a whole, regardless of their physical and mechanical properties. Thermodynamic and rheological state equations, as well as expressions for heat flow, interfacial mass forces phase transitions, and heat exchange between phases can be used to close them. The implemented models make it possible to simulate both the stationary distribution of parameters along the wellbore during production and non-stationary processes that occur, for example, when the pump shaft speed changes during oil production. The developed approaches were implemented in the DataFlow software tool for analysis of the hydrodynamics of multiphase hydrocarbon flows, taking into account heat exchange with the rocks surrounding the well, and phase transitions in the fluid. Using the software package, test calculations were carried out to demonstrate the performance of the proposed and implemented models.

Anticipating gelation and vitrification with medium amplitude parallel superposition (MAPS) rheology and artificial neural networks

Anticipating qualitative changes in the rheological response of complex fluids (e.g., a gelation or vitrification transition) is an important capability for processing operations that utilize such materials in real-world environments. One class of complex fluids that exhibits distinct rheological states are soft glassy materials such as colloidal gels and clay dispersions, which can be well characterized by the soft glassy rheology (SGR) model. We first solve the model equations for the time-dependent, weakly nonlinear response of the SGR model. With this analytical solution, we show that the weak nonlinearities measured via medium amplitude parallel superposition (MAPS) rheology can be used to anticipate the rheological aging transitions in the linear response of soft glassy materials. This is a rheological version of a technique called structural health monitoring used widely in civil and aerospace engineering. We design and train artificial neural networks (ANNs) that are capable of quickly inferring the parameters of the SGR model from the results of sequential MAPS experiments. The combination of these data-rich experiments and machine learning tools to provide a surrogate for computationally expensive viscoelastic constitutive equations allows for rapid experimental characterization of the rheological state of soft glassy materials. We apply this technique to an aging dispersion of Laponite® clay particles approaching the gel point and demonstrate that a trained ANN can provide real-time detection of transitions in the nonlinear response well in advance of incipient changes in the linear viscoelastic response of the system.

Rheological state variables: A framework for viscosity parametrization in crystal-rich magmas

Igneous processes involve multiphase magmas, and the rate at which these processes operate is tightly controlled by multiphase rheology. The rheology of magmatic suspensions containing irregular-shaped crystals is complex, and this complexity is illustrated by the strong non-linear response to deformation and the lack of apparent self-similarity when comparing the results of experiments conducted under different shear conditions. Structural and empirical models have been developed to describe the experimental data. However, they are not predictive due to presence of several tuning parameters and their strong dependence on the flow variables and suspension characteristics. The current study proposes a state variable framework that restores self-similarity in the rheology of crystal-rich magmas. This framework only uses two rheological state variables and defines a universal rheological model to explain the relative viscosity of magmatic suspensions while considering microstructural changes such as crystals’ orientation, deformation, and comminution as well as shear-induced heterogeneities. We show that the viscosity of crystal-rich magmas as function of crystal content obeys the well-known monotonic and divergent behavior documented for suspensions of solid particles. This is achieved when the appropriate state of crystal dispersion is obtained using a unique product of the two rheological state variables. This theoretical approach, compared to empirical models, is as powerful for fitting, and can be also extrapolated beyond experimental data used in the fitting procedure. Hence, the state variable framework can be generalized to form a unified law with predictive power. At low shear rates, this framework is fully predictive as we can directly constrain both variables and their unique product. At high shear rates, one of the variables must be computed and measured independently. It is also shown that the proposed model can be used to detect the presence of anomalies, e.g., crystal breakage and shear-induced heterogeneities, in experimental data.

Forecasting landslides using community detection on geophysical satellite data.

As a result of extreme weather conditions, such as heavy precipitation, natural hillslopes can fail dramatically; these slope failures can occur on a dry day, due to time lags between rainfall and pore-water pressure change at depth, or even after days to years of slow motion. While the prefailure deformation is sometimes apparent in retrospect, it remains challenging to predict the sudden transition from gradual deformation (creep) to runaway failure. We use a network science method-multilayer modularity optimization-to investigate the spatiotemporal patterns of deformation in a region near the 2017 Mud Creek, California landslide. We transform satellite radar data from the study site into a spatially embedded network in which the nodes are patches of ground and the edges connect the nearest neighbors, with a series of layers representing consecutive transits of the satellite. Each edge is weighted by the product of the local slope (susceptibility to failure) measured from a digital elevation model and ground surface deformation (current rheological state) from interferometric synthetic aperture radar (InSAR). We use multilayer modularity optimization to identify strongly connected clusters of nodes (communities) and are able to identify both the location of Mud Creek and nearby creeping landslides which have not yet failed. We develop a metric, i.e., community persistence, to quantify patterns of ground deformation leading up to failure, and find that this metric increased from a baseline value in the weeks leading up to Mud Creek's failure. These methods hold promise as a technique for highlighting regions at risk of catastrophic failure.

The effects of differential shortening and competent blocks on the structural development of Andean fold-and-thrust belts at 32°-34°S: Insights from analogue models

Andean fold-and-thrust belts (FTBs) in the western border of South America show important along-strike variations in their structural style (thin- or thick-skinned) and shortening magnitudes, among others. These variations can arise from multiple factors, such as depth-to-detachment, geometry, and thickness of underlying basins, structural highs, the competence of the units involved in deformation, pre-orogenic structure of the basement, the rheological state of the upper crust or latitudinal gradients in shortening, among others. We carry out a set of new analogue models to understand how two of these factors affect the development and the geometry of the thrust systems within the Andean Principal Cordillera and adjacent fold-and-thrust belts at 32°-34°S (La Ramada and Aconcagua FTBs). In this contribution, we present the results of analogue modeling of doubly-vergent thrust systems with a built-in heterogeneity that allow us to evaluate the influence of differential shortening and presence of competent blocks (of relatively higher cohesion) in the generation, evolution, and structural setting of Andean FTBs. We highlight that despite the similar pattern of differential shortening in the models, the presence of the competent block has a significant influence on the structural configuration and leads to greater topographic uplift. Differential shortening plays a role in accommodating deformation, but when a competent block is present, the faults bounding the block control the deformation, producing a notable curvature of the FTBs. Summarizing, the presence of a competent block significantly influences the structural configuration within a doubly-vergent thrust system, emphasizing the role of inherited architecture in the orogenic growth of the Southern Central Andes.

The fractal scale-invariant structure of a temporal hierarchy in the relaxation and energy dissipation processes in a visco-elastic/capillary-porous medium

The phenomena of elastic aftereffects during loading/unloading of viscoelastic and capillary-porous bodies, relaxation of their stresses is accompanied by the energy accumulation and dissipation to be taken into account in the theory of oscillations which also considers the behavior of materials when the force is applied to them. The elastic aftereffect and stress relaxation forms ostensibly opposite energy processes. In the first case, under constant load deformation, the work increases in course of time, and in the second case, under constant load deformation, the work (energy) decreases. While researching on the energy dissipation in the conditions of oscillations application, i.e. within the frame of internal friction theories, one can find that some theories are based on the dependence of friction on the oscillations’ velocity, other ones establish the dependence of friction on the amplitude. Research papers are based on the hypothesis of M.M. Davydenkov, according to which the energy when subjected to oscillations depends on the amplitude and does not depend on the velocity. According to E.S. Sorokin, the theory of internal friction is poorly consistent with the theories describing the inherited properties of materials (viscoelastic and capillary-porous ones). A tendency is observed: the better a theory reflects hereditary properties, the worse this theory is adapted to describe energy losses due to oscillations.In this paper, an attempt has been made to harmonize both these theories and numerous experiments on the destruction of materials described in the academic literature. It turns out that in order to remove contradictions, it is necessary to take into account the dependence of body deformation changing in the course of time.It is shown that the hierarchy of times determining shear and bulk relaxation in viscoelastic/capillary-porous medium has a fractal (scale-invariant) structure. It was observed that the presence of time fractality eases the modeling of viscoelastic/capillary-porous bodies resulting in the universal relaxation function of a rather simple kind. In particular, for the scale-invariant distribution of relaxation characteristics medium, the application of algebraic relaxation law for viscoelastic/capillary-porous materials is possible: this resulting in rheological models and state equations with the derivatives of fractional order.

Influence of effective microorganisms on the rheology and fresh state properties of SCMs-based concrete for digital fabrication

A reduction in the cost and anthropogenic CO2 emissions of Portland cement production can be achieved by adding supplementary cementitious materials (SCMs) obtained from industrial origins, like fly ash, silica fume, slagments, and naturally available such as limestone and kaolinitic clay. Replacement of large quantities of cement with SCMs profoundly influences the fresh and mechanical characteristics of structural concrete. This study presents an experimental investigation to evaluate the influence of effective microorganisms (EM) on freshly mixed fly ash- and limestone calcined clay (LC2) cement-based fibre-reinforced printable concrete (FRPC). EM is a mixture of three different microorganisms: photosynthetic bacteria, lactic acid bacteria, and yeast. Its inclusion complements green concrete and is environmentally friendly for a sustainable environment. Four mixes (i.e., fly ash cement-based mix, LC2 cement-based mix, and both mixes induced by EM) were prepared and examined to achieve printable concrete of varying rheological properties, and tested for slump and slump flow, setting/open time, rheological characterisation of various parameters, and buildability performance. The findings from this study revealed that the SCMs and the EM considered exhibited satisfactory material rheological performance and other unique characteristics identified as critical early-age properties for suitable 3D printability. In addition, near zero slumps were displayed for all the mixes and the slump flows were in the range of 140 – 160 mm after standard small slump flow table impact agitation, implying remarkable and adequate results for printable concrete. The penetration, bleeding, and segregation was also reduced when compared with no SCM inclusion. Conclusively, good relationships between the fresh properties and buildability quantification are also presented.

Recycled strontium hexaferrite powder behavior in the magneto fluidized state in dependence of the chamber fill factor

The magnetic powders affected by external magnetic fields can be transferred in the pseudo fluidized state to intensify the process of permanent magnets production. The behavior of the fluidized fine strontium hexaferrite powder with an average particle size 0.93 μm obtained by recycling old electric engine stators was studied. Mutually perpendicular constant and alternating gradient magnetic fields were used to form the magneto fluidized bed from the powder. The rheology state of the magnetic powder can be controlled by the parameters of the electromagnetic fields. The powder was affected by a constant field with induction values from 3 mT to 43 mT and alternating gradient magnetic field with induction gradient values from 87 mT/m to 317 mT/m. The chamber bulk fill varied from 4% to 100%. To study the rheological state of the powder in the chamber, we used an inductive method – an inductive coil was put on the chamber and the moving powder particles induced the current in the coil. The values of the current allowed to estimate the mobility of the powder particles in the magneto fluidized bed. The paper presents the results of experimental studies how electromagnetic fields regimes influences on the rheology of the fluidized powder. Methods of choosing the fields regimes providing the rheological state optimal for the required technological process depending on the chamber fill factor are described.

Mapping the role of oral cavity physiological factors into the viscoelastic model of denture adhesives for numerical implementation.

Physiological parameters of the oral cavity have a profound impact on any restorative solutions designed for edentulous patients including denture adhesives. This study aims to mathematically quantify the influence of three such variables, namely: the temperature, pH, and the swelling of such adhesives under the influence of saliva on its mechanical behavior. The mathematical quantification is further aimed to implement a material model for such adhesives which considers the impact of such physiological factors. The denture adhesive is experimentally investigated by means of rheological steady state frequency sweep tests to obtain the relaxation spectrum of the material. The relaxation behavior is measured for a wide range of oral cavity temperatures and pH. Also, the adhesive is hydrated and upon swelling to different levels again tested to understand the impact of swelling on the mechanical behavior. The experimentally measured continuous relaxation spectrum is modeled as a viscoelastic material using a discrete set of points based on the Prony series discretization technique. The relaxation spectrums for various temperatures are compared and the possibility of a time-temperature superposition is explored for the model. Similarly, the measured values of Storage and loss modulus are investigated to understand the role of pH and swelling. The results in this study clearly indicated a horizontal shift in the relaxation behavior with increase in temperature. And hence, the time-temperature shift factor was calculated for the adhesive. The relaxation spectrum also showed a strong correlation with swelling of the adhesive and the pH. The influence of these two parameters were captured into the model based on the relaxation time parameter in the Prony series approach. Based on this study the impact of these parameters could be appreciated on the performance and mechanical behavior of denture adhesives and implemented into a Prony series based viscoelastic material model which can be used with numerical simulations.

Diagnostic method for the selection of regimes of electromagnetic effect on the particulate ferromagnetic material

The recycling of obsolete permanent magnets, the processing and reusing of the obtained powder for a new magnets production has both economic and environmental benefits. The processing of recycled magnetic slur to the particle size distribution required for the magnets production has a problem specific for fine magnetic powders – particle aggregation limiting the milling efficiency. One way of solving this problem is milling the magnetic material with the formation of the magneto fluidized bed. In the present work we study the behavior of the recycled from old electromotor stators strontium hexaferrite powders with average particle sizes 56.8 µm and 7.5 µm in the magneto fluidized bed formed by mutually perpendicular constant and alternating gradient magnetic fields. The desired state of the fluidized bed for milling is the one with the maximal particle motion intensity that prevents particle aggregation. The intensification of particle motion could be done by the increase of the alternating magnetic field gradient, but this also increases energy consumption of the process. In the present paper we propose using the inductive method for estimating rheological state of the strontium hexaferrite powder in the magneto fluidized bed. Such estimation allows finding the optimal parameters of electromagnetic fields forming the fluidized bed for the efficient powder milling process.

The effect of hyperbaric oxygenation on the state of blood rheology and hemostasis in children with inflammatory bowel diseases

Aim. To study the rheological properties of blood and platelet hemostasis in children with inflammatory bowel diseases before and after a course of hyperbaric oxygenation Materials and methods. Aggregation and deformability of erythrocytes, activation and aggregation of platelets were studied in 16 patients with Crohn's disease and 11 patients with ulcerative colitis age from 6 to 17 years. Similar indicators were studied after a course of hyperbaric oxygenation, carried out in a single-seat air-oxygen pressure chamber “BaroOx 1.0”. The course consisted of 5-8 daily sessions in the 1.3-1.4 ata during 40 minutes. Results. In pediatric patients with Crohn's disease and ulcerative colitis a significant violation of the rheological and hemostasiological properties of blood was revealed. After a course of hyperbaric oxygenation a significant decrease in the aggregation of erythrocytes, an increase in their deformability, and a decrease in the functional activity of platelets were noted. Conclusion. The use of hyperbaric oxygenation in children with inflammatory bowel diseases contributes to a significant correction of the rheological and hemostasiological properties of blood.

Results of the simulation of tracked vehicles ride considering the interaction with a deformable road

BACKGROUND: Tracked vehicles motion on a deformable road, which can be, for instance, cross-country terrain or field of various agricultural plants, is defined with various indicators. Depending on environment conditions, road surface properties etc., some of these indicators are chosen as main criteria of vehicles operational and technical performance assessment. Search of optimal parameters and operation modes of tracked vehicles demands using numerical modelling of considered processes.
 AIMS: Using imitational modelling, to obtain visual representation of influence of path unevenness, path microprofile, tracked vehicle velocity, its layout, nature of relation between particular unit assemblies, systems and their properties, physical and mechanical road properties regarding rheological approach to determination of them, state parameters of road material on change of tracked vehicles ride comfort indicators.
 METHODS: Results of simulation of ride comfort indicators for various tracked vehicles, obtained with the known earlier mathematical model, which considers design and technological properties of them as well as road surface state parameters, presented as physical and mechanical properties, based on a well-known rheological approach, are presented in the article. Agricultural tractors of different mass and the S-300 anti-aircraft missile systems, based on the 832M tracked chassis, are considered as tracked vehicles.
 RESULTS: Analysis of obtained relations, based on use of imitational modelling, revealed a set of patterns of tracked vehicles ride comfort indicators changing. It is defined that consideration of rheological characteristics and state parameters of a soil layer helps to improve simulation accuracy significantly. The obtained data shows the influence of velocity, mass and base length of tracked vehicles, offset of pressure center of caterpillar mover and other design parameters on growth of vertical and longitudinal-angular oscillations.
 CONCLUSIONS: The conducted study contributes to optimal development of tracked vehicles and assembling of different machine-tractor units, performing demanded technological operations in different conditions with specific road surface state parameters.