Influence of dynamic properties of the process module on vertical vibrations of the wheel axis

Tractors are technological energy means used for general mechanization and automation of agricultural production, as well as for the transportation of finished raw materials. Tractors of traction class 8 must have high productivity and efficiency, in order to achieve the best results, in the shortest agrotechnical time.
 The need for the development of tractor designs of the 8th traction class is explained by current trends in the development of agriculture. The increase in the area of agricultural land sets manufacturers the task of increasing the speed of tillage, which entails an increase in the power and ergonomics of tractors.
 The necessary traction and layout characteristics of energy-saturated tractors of traction class 8 allow the implementation of articulated frames. The main task of the design is the development of a articulated frame with a cab rotation mechanism that will be able to fulfill the requirements for modern tractors of the 8th traction class.
 Purpose. Investigation of the forces of resistance to rotation of the articulated frame and the occurrence of a favorable moment for turning the cab using a model in the MATLAB Simulink environment.
 Methodology. Methods of mathematical modeling and analysis were used in the article.
 Results. The parameters showing the necessary forces for the rotation of the articulated frame and the occurrence of a favorable moment for turning the cab are obtained.
 Practical implications. The results obtained can be applied in the design of a tractor on a articulated frame with a cab rotation mechanism.

The dynamic effects of pair correlation functions (pcf) on spin relaxation by translational diffusion in infinite two-dimensional fluids are considered explicitly through a Smoluchowski equation, for the usual conditional probability, with appropriate boundary conditions, especially at the contact separation of the interacting pair of molecules. The solution of this equation by finite difference techniques permits the calculation of time correlation functions, spectral densities, and spin-relaxation rates associated with a dipolar relaxation mechanism between the spin-bearing molecules. Comparison of the two-dimensional spin-relaxation results obtained with different pcf is presented. The spectral densities and spin-relaxation rates are indeed found to be significantly altered by the pcf. For example, for a nonuniform pcf, the two-dimensional spectral densities, at (and above) the Larmor frequency ω0, are greater for translational correlation times τt that are an order of magnitude faster than τt=ω−10 which provides the maximum spectral density in bulk theory. This fast motion result is consistent with the two-dimensional dynamical results found by other techniques. Moreover for a nonuniform pcf and a single translational correlation time, two well-defined minima are found in the variation of the spin-lattice relaxation time with the diffusion coefficient. This could be very useful for interpreting the spin-relaxation data of diffusing complexes in clays, intercalation compounds, and bilayers.

The bird-lemming hypothesis postulates that breeding success of tundra-nesting geese and waders in Siberia follows the cyclic pattern of lemming populations, as a result of predators switching from lemmings to birds when the lemming population crashes. We present 50years of data on constant-effort catches of red knot Calidris canutus and curlew sandpiper C. ferruginea at an autumn migratory stopover site (Ottenby) at the Baltic Sea, supplemented with literature data on winter censuses of dark-bellied brent goose Branta b. bernicla and white-fronted goose Anser albifrons in northwestern Europe, and waders in Germany and Southern Africa. Number and proportion of juveniles in these bird populations (both our own and literature data) were compared with an index of predation pressure (calculated from the abundance of lemmings on the Taimyr peninsula), and climate indices for the North Eurasia and the North Atlantic regions. The index of predation pressure correlated significantly with the number of juveniles of red knot and curlew sandpiper, but not with number of adults. Also, this index correlated with the reproductive performance of geese and waders reported in the literature. Fourier analysis revealed a significant deviation from random noise with the maximum spectral density at the period length of 3years for number of juvenile red knots and curlew sandpipers captured at Ottenby, abundance of lemmings, reproduction in arctic fox Alopex lagopus, and reproductive performance in geese on the Siberian tundra. Also, the date of passage at Ottenby for adult red knot and curlew sandpiper showed a spectral density peak at a period length of 3years, the latter species also showing a peak at a period length of 5-6years. Passage dates for adult red knot and curlew sandpiper were earlier in years of high predation pressure compared with years of low predation pressure. The fluctuations in reproductive success of the studied Siberian goose and wader species appear to be primarily influenced by biotic factors in the breeding area, rather than by abiotic factors, such as climate oscillations. Annual variations in migratory arctic bird populations may have far reaching effects in habitats along their migration routes and in their wintering areas. We suggest a link between lemming cyclicity in the Northern Hemisphere and predation pressure on Southern Hemisphere benthos, in which the signal is carried between continents by long distance migrating waders.

Hyporheic exchange is key to buffer water quality and temperatures in streams and rivers, while also providing localized downwelling and upwelling microhabitats. In this research, the effect of geomorphological parameters on hyporheic exchange has been assessed from a physical standpoint: surface and subsurface flow fields, pressure distribution across the sediment/water interface and the residence time in the bed.First, we conduct a series of numerical simulations to systematically explore how the fractal properties of bedforms are related to hyporheic exchange.We compared the average interfacial flux and residence time distribution in the hyporheic zone with respect to the magnitude of the power spectrum and the fractal dimension of riverbeds. The results show that the average interfacial flux increases logarithmically with respect to the maximum spectral density whereas it increases exponentially with respect to fractal dimension.Second, we demonstrate how the Froude number affects the free-surface profile, total head over sediment bed and hyporheic flux. When the water surface is fixed,the vertical velocity profile from the bottom to the air-water interface follows the law of the wall so that the velocity at the air-water interface has the maximum value. On the contrary, in the free-surface case, the velocity at the interface no longer has the maximum value: the location having the maximum velocity moves closer to the sediment bed. This results in increasing velocity near the bed and larger head gradients, accordingly.Third,we investigate how boulder spacing and embeddedness affect the near-bed hydrodynamics and the surface-subsurface water exchange.When the embeddedness is small, the recirculation vortex is observed in both closely-packed and loosely-packed cases, but the size of vortex was smaller and less coherent in the closely-packed case. For these dense clusters, the inverse relationship between embeddedness and flux no longer holds. As embeddedness increases, the subsurface flowpaths move in the lateral direction, as the streamwise route is hindered by the submerged boulder. The average residence time therefore decreases as the embeddedness increases.Lastly, we propose a general artificial neural network for predicting the pressure field at the channel bottom using point velocities at different level. We constructed three different data-driven models with multivariate linear regression, local linear regression and artificial neural network. The input variable is velocity in x, y, and z directions and the target variable is pressure at the sediment bed. Our artificial neural network model produces consistent and accurate prediction performance under various conditions whereas other linear surrogate models such as linear multivariate regression and local linear multivariate regression significantly depend on input variable.As restoring streams and rivers has moved from aesthetics and form to a more holistic approach that includes processes, we hope our study can inform designs that benefit both structural and functional outcomes. Our results could inform a number of critical processes, such as biological filtering for example. It is possible to use our approach to predict hyporheic exchange and thus constrain the associated biogeochemical processing under different topographies. As river restoration projects become more holistic, geomorphological, biogeochemical and hydro-ecological aspects should also be considered.

Abstract. Problem. The publications analysis about the self-propelled scrapers use on sites of road and reclamation construction is showed that during the performance of working operations there is unacceptable wear of the tires tread as a result of the intensive sliding on the support surface. Over time, the pneumatic tires wear leads to decrease on the durability of the wheeled mover or tire failure as a result of the carcass rupture and the tread delamination. In its turn, the time factor of the tire tread wear depends directly on the duration of the scraper operating cycle, which implements the traction and transport modes. Goal. The life time increasing of the wheeled mover for the self-propelled scraper by reducing the tire tread wear. Methodology. Analytical methods for interaction process research of the pneumatic tires with support surface are used. Mathematical modeling methods were used to determine the time factor of the tire tread wear during scraping. Results. Dependencies for determining the duration of operating cycle components according to the elliptical scheme of scraping organization are presented. Based on the proposed mathematical model, such as takes into account the force, speed and time factors, the fractions of tire tread wear are determined by the components of the scraper operating cycle, which including its maneuvering in the face. It was found that most often the tire tread wear occurs when moving of the soil-loaded scraper. The presented calculation results of the tire life time according to the proposed method are showed the sufficient convergencewith the scraper performance attributes, taking into account only the abrasive mechanism of the tire tread wear. Originality. To determine the life time of pneumatic tires for the self-propelled scraper, as the most fully combined characteristic features of the traction and transport machine, it is proposed to use the preferred mechanism of tire tread wear – abrasive, as well as the deformation models of the pneumatic tire and support surface. Practical value. The use of the proposed method for calculating the tire tread wear will to make the life time forecast of the wheeled mover for the self-propelled scraper at the design stage and to determine the reasonable needs for material and technical means of this machine operation.

The article analyzes the causes of the phenomenon of circulating power in a closed power circuit "wheel propulsion – bearing surface" and kinematic misalignment of the driving wheels of an all-wheel drive vehicle under various conditions and modes of its movement. The methods of reducing the kinematic misalignment of the driving wheels are analyzed, their advantages and disadvantages are indicated. An improved algorithm for the functioning of a device for determining the slipping of tire tread elements along the support surface is proposed in order to reduce the kinematic misalignment of the driving wheels with the transmission locked.

Quasilinear models of oblique whistler-mode instabilities

Purpose of the study - a comparative quantitative evaluation of regional circulation state, the degree of reducing femoral and leg contractility, as well as gait disorders in male and female patients with coxarthrosis. Material and methods. The patients with stages 1, 2, and 3 coxarthrosis were examined. The mean age of female group was 47±0.7 years, that of male one - 37±1,4 years, the number of observations was 314 and 99 persons, respectively. Arterial blood pressure (ABP), locomotion rate and the increase in heart rate during walking were determined in the patients, as well as walking time parameters, distribution of foot part loading statically and dynamically (DiaSled-Scan complex), the maximum moment of strength of femoral and leg anterior and posterior muscle groups. Linear blood flow rate in magistral arteries was determined by Doppler ultrasonography. Laser Doppler flowmetry of skin anterior surface of the leg middle third, and the dorsal surface of both limb feet (BLF-21 device of Transonic Systems, uSA) was used for capillary blood flow evaluation. Results. More rapid age-related increase in ABP and decrease in capillary blood flow rate in limb skin integuments for Stage 2 and 3 of the disease were observed in female patients above 45 years. As for Stage 3 of the disease in female patients, the maximum load of the foot support (bearing) surface when standing and walking was reduced. Limb muscle strength in female patients is twice lower than that in male patients. As far as the disease progressed, more rapid decrease in the contractility of femoral muscles was noted compared to that of the leg. The compensatory increase in muscle strength of the leg was observed for Stage 1 of the disease and after the performed complex conservative treatment. Walking speed in the patients decreased with their age increasing, and the pulse value of locomotion increased with the disease stage increasing. Conclusion. More frequent involvement of the hip in women may be partially explained by the increase in the relative number of the gender representatives in the older age groups. Hypertension in female patients with coxarthrosis is a compensatory response related to microcirculation aggravation in limb tissues, the dynamometric parameters of femoral muscles in female patients are much lower, and the load of foot support surface is less.

The aim of the study is to show the results of complex shaking table experimental investigation focused on the response of two models of cylindrical steel tanks under mining tremors and moderate earthquakes, including the aspects of diagnosis of structural damage. Firstly, the impact and the sweep-sine tests have been carried out, so as to determine the dynamic properties of models filled with different levels of liquid. Then, the models have been subjected to seismic and paraseismic excitations. Finally, one fully filled structure has been tested after introducing two different types of damages, so as to verify the method of damage diagnosis. The results of the impact and the sweep-sine tests show that filling the models with liquid leads to substantial reduction in natural frequencies, due to gradually increasing overall mass. Moreover, the results of sweep-sine tests clearly indicate that the increase in the liquid level results in significant increase in the damping structural ratio, which is the effect of damping properties of liquid due to its sloshing. The results of seismic and paraseismic tests indicate that filling the tank with liquid leads initially to considerable reduction in values of acceleration (damping effect of liquid sloshing); however, beyond a certain level of water filling, this regularity is inverted and acceleration values increase (effect of increasing total mass of the structure). Moreover, comparison of the responses under mining tremors and moderate earthquakes indicate that the power amplification factor of the mining tremors may be larger than the seismic power amplification factor. Finally, the results of damage diagnosis of fully filled steel tank model indicate that the forms of the Fourier spectra, together with the frequency and power spectral density values, can be directly related to the specific type of structural damage. They show a decrease in the natural frequencies for the model with unscrewed support bolts (global type of damage), while cutting the welds (local type of damage) has resulted in significant increase in values of the power spectral density for higher vibration modes.

The present study was aimed to in vivo assess the blood flow oscillatory patterns in rat pial microvessels during 30 min bilateral common carotid artery occlusion (BCCAO) and 60 min reperfusion by laser speckle imaging (LSI). Pial microcirculation was visualized by fluorescence microscopy. The blood flow oscillations of single microvessels were recorded by LSI; spectral analysis was performed by Wavelet transform. Under baseline conditions, arterioles and venules were characterized by blood flow oscillations in the frequency ranges 0.005–0.0095 Hz, 0.0095–0.021 Hz, 0.021–0.052 Hz, 0.052–0.150 Hz and 0.150–0.500 Hz. Arterioles showed oscillations with the highest spectral density when compared with venules. Moreover, the frequency components in the ranges 0.052–0.150 Hz and 0.150–0.500 were predominant in the arteriolar total power spectrum; while, the frequency component in the range 0.150–0.500 Hz showed the highest spectral density in venules. After 30 min BCCAO, the arteriolar spectral density decreased compared to baseline; moreover, the arteriolar frequency component in the range 0.052–0.150 Hz significantly decreased in percent spectral density, while the frequency component in the range 0.150–0.500 Hz significantly increased in percent spectral density. However, an increase in arteriolar spectral density was detected at 60 min reperfusion compared to BCCAO values; consequently, an increase in percent spectral density of the frequency component in the range 0.052–0.150 Hz was observed, while the percent spectral density of the frequency component in the range 0.150–0.500 Hz significantly decreased. The remaining frequency components did not significantly change during hypoperfusion and reperfusion. The changes in blood flow during hypoperfusion/reperfusion caused tissue damage in the cortex and striatum of all animals. In conclusion, our data demonstrate that the frequency component in the range 0.052–0.150 Hz, related to myogenic activity, was significantly impaired by hypoperfusion and reperfusion, affecting cerebral blood flow distribution and causing tissue damage.

Tweek-atmospherics (tweeks), along with radio transmission by VLF radio stations, are used to study the lower ionosphere. Electromagnetic pulse radiation, which has been excited by the lightning discharges, has a maximum spectral density at extra low frequencies range (ELF, 300...3000 Hz) and very low frequencies (VLF, 3...30 kHz). The Earth-ionosphere cavity serves as a waveguide for electromagnetic waves in these frequency ranges. On the spectrogram of the tweek, the initial part is a linearly polarized broadband signal, and then a number of individual harmonics are observed. Their instantaneous frequencies decrease, asymptotically approaching approximately multiples of the cutoff frequencies of the waveguide. The single position method for lightning location and estimation of the ELF wave’s reflection heights in the lower ionosphere by tweeks has been implemented into the computational algorithm. The clusters with approximately the same azimuths and distances to sources which have been obtained during the same night have been identified upon the ensemble of tweek-atmospheric records. The data were accumulated at the Ukrainian Antarctic Station "Akademik Vernadsky" in 2019. The location of the receiving complex in the near-polar region makes it possible to register tweek sources in two world thunderstorm centers with geographic azimuths from –60° to 130°. The results of processing these data have been used by studying the correlation matrix and partial correlation coefficients to identify causal relationships between the three main parameters of the tweek, such as (1) the average azimuth of the arrival of tweeks in regard to the magnetic meridian, (2) the average distance to the center of the cluster of tweek sources (lightning discharges), and (3) the average number of tweek harmonics. The same correlation analysis was applied to two groups with distances to sources of 2.2...7.5 Mm and 7.6...9.5 Mm used for study in detail. It is shown that the partial correlation coefficients between the number of tweek harmonics and the difference of the magnetic azimuth from the magnetic east are 0.624 (for the entire range of distances), 0.696 (for far tweek sources) and 0.595 (for main middle range), so, they always exceed the values of 0.1% significance level. The correlation of tweek spectrum with the distance to the tweek source in the range of 2.2…7.5 Mm has been shown to be comparable in magnitude or to exceed the correlation of tweek spectrum with the magnetic azimuth. The elimination of this masking effect by calculating the partial correlation coefficients made it possible to reveal the magnetic azimuth dependences of the tweek spectra if tweek propagates in a region outside the geomagnetic equator. Thus, the effect of non-reciprocity of propagation of ELF – VLF waves in regard to the magnetic meridian in the east – west and west – east directions is found in the spectra of tweek-atmospherics. It results in an increased probability of detecting tweeks with higher harmonics if their directions of arrival are close to the geomagnetic east. It is also shown that this effect, as a result of increased attenuation during the propagation of ELF – VLF radiation from the west and weakened attenuation during propagation from the east, leads to a highly significant correlation (with probability level more than 99.9%) between the magnetic azimuths of tweeks and the lengths of their paths to the receiving station.

Subject and Purpose. Designers of the research radars intended for detecting manifestations of biological activity of living organisms may be interested in the noise characteristics shown by their oscillators at offsets about 10–2 Hz or even 10–3Hz from the carrier frequency. Unfortunately, the producing companies do not practice regular information on noise performance of their products at frequencies below 1 Hz. The present authors have set the goal of deriving an analytical expression for the spectral density of flicker noise which should allow radar engineers estimating the probable noise performance of low-noise oscillators over any frequency range. Methods and Methodology. A great number of writers considering spectral properties of flicker noise tend to support the assertion that its spectral density increases continuously with a decrease in frequency, following the power law 1/f . Meanwhile, the present authors assume availability of a certain frequencyfmbelow which the spectral density should most likely remain unchanged, even to as low as zero frequency. Also, there is a range of frequencies above which the spectral density of flicker noise remains constant and the total spectral density is determined solely by thermal noise. Results.The spectral density of noise follows the power law 1/f throughout the range fromfm and up to the point where thermal noise starts to overbalance the flicker noise. The authors have proposed an approximating function to describe the behavior of the averaged spectral density of noise from the oscillator within the entire frequency range. Conclusions. The results obtained shall allow radio system designers to make estimates of the probable noise performance of low-noise oscillators in any frequency range, using only known reference data provided by the manufacturer.

The methods of diagnosis of damage through measuring the changes in dynamic structural properties have been intensively studied for many years now. On the contrary to mechanical or aeronautical engineering, however, the practical application of the methods in the case of civil engineering structures meets a number of difficulties indicating the need for further research. This concerns in particular the need for the shaking table investigations since the results of such tests are very limited. Therefore, the aim of the present paper is to show the results of the shaking table study conduced on a model of two-storey steel frame building. The 1.56 m high model structure was constructed of columns with cross section of mm. Damage was defined as a reduction in stiffness and introduced by replacing the columns with elements having mm cross section. Seven different structural damage cases described by different number of columns with the reduced cross section were considered in the study. During the shaking table experiment the base of the structure was excited under the sweep-sine loading. The results of the study show a characteristic decrease in the natural frequencies with the progression of damage. This trend has been especially observed for the first natural frequency, for which the decrease in the frequency value has been found to be uniform. The results of further analysis show the scattered values of the structural damping ratios without showing any relation with the level of structural damage.

Stabilization of residual point defects at the finishing stages of noise diodes can be ensured by the selection of appropriate ignition modes and the environment of its conduct. The method and technology of reducing the concentration of point defects in the structure of p-n-transition, taking into account the content of impurities of secondary metals, oxygen and nitrogen is proposed. It has been established that the burning of readymade structures and diodes of noise generators in nitrogen environments at temperatures of 450…600 °С for (80 ± 3) min leads to an increase in spectral noise density and a significant (twice) reduction of its unevenness. The most important result of this burn is a reduction in the spread of the average values of the noise parameters studied: by 61.2 % in effective noise voltage; spectral density by 34.2 %; at the boundary frequency of the signal by 34.9 %; in non-linear density by 25.9 %. This improves the quality of random numerical sequences in information protection software systems.

Assessment of the level of vibration effects on the elements of technological and transportation vehicles is one of the most important approaches in ensuring their reliability and operational safety. The aim of the research is to develop a method for constructing mathematical models of technical objects, whose vibrational interactions are estimated by the dynamic responses of the connections of the elements between themselves and the supporting surfaces. The work uses approaches based on the development of methods of structural mathematical modeling and introduces the concepts of dynamic responses of characteristic points of mechanical oscillatory systems, transfer functions of constraint responses and their frequency characteristics. The research demonstrates features of the dynamic properties of systems and the possibility of the occurrence of new dynamic effects. As additional constraints, a motion transformation device is introduced. It is shown that the ratio of the dynamic responses of constraints on the object of protection and on the support surface can be chosen as a parameter of the dynamic state of the system. Analytical dependencies are obtained to determine the coefficient of response dynamism. Numerical modeling is performed within the scope of the model problem; Dynamic effects are revealed that reflects the properties of the system in the possibilities of creating zones of suppression of external influences when varying adjusting parameters. The possibilities of implementing such approaches are shown through a change in the ratio of spring stiffness in the "cascade".