82 research outputs found
Implementation of simultaneous performance of two technological operations with different machine-and-tractor units
Received: January 25th, 2022 ; Accepted: April 6th, 2022 ; Published: April 18th, 2022 ; Correspondence: [email protected] gap between two technological operations should be minimal in the production
environment. For this, special combined (multi-operational) machine-and-tractor units (MTU)
are used. Their agricultural machines have sequentially installed working devices for various
technological purposes. In the absence of such MTUs, single-operation units are used. Such units
more often have different working widths. For their simultaneous operation in the same field, the
first unit (for example, a sowing unit) must have a wider width than the second one (for example,
a rolling one). In practice, the opposite case occurs more often when the first unit's working width
is less than the second unit's working width. As a result, the first machine-and-tractor unit delays
the work of the second one. This article aims to develop the algorithm for the simultaneous
operation of two machine-and-tractor units of different field performance. The first of them
(a sowing unit) has a working width of 3.6 m, and the second (a rolling one) is 6.1 m. As a result,
the following has been established using the example of processing a field of 80 hectares: the
second unit should start its work (i.e., rolling the crops) when the first one (sowing) has sown a
certain area. According to the formula proposed in the article, the size of this area is 44 hectares.
Under natural working conditions, the second unit (rolling) started its work after the first (sowing)
unit has sown 44 hectares of the field area. As a result, both units have completed the entire area
with a half-hour gap, i.e., practically simultaneously and without delay from each other
Helicoidal instability of a scroll vortex in three-dimensional reaction-diffusion systems
We study the dynamics of scroll vortices in excitable reaction-diffusion
systems analytically and numerically. We demonstrate that intrinsic
three-dimensional instability of a straight scroll leads to the formation of
helicoidal structures. This behavior originates from the competition between
the scroll curvature and unstable core dynamics. We show that the obtained
instability persists even beyond the meander core instability of
two-dimensional spiral wave.Comment: 4 pages, 5 figures, revte
Новый подход к выбору способа механической обработки грунта в условиях юга Украины
At a choice of an optimum way of machining of soil each land owner pursues one main aim - creation an optimum arable layer for cultivation of crops. Cultivation of soil finds the display in three systems: moldboard tillage, moldboardless tillage and no-till. The ad-vantages and shortcomings are inherent in each system. The right choice will provide preservation and improvement of physical and chemical properties and increase of fertility of soil, and it is one of the most important problems in the production of agricultural crops. The purpose of researches is improvement of quality of mechanical cultivation of soil, decrease in power expenses as a result of use of the boardless-subsoiler implement which can carry out at the same time two operations: loosening of surface layer of soil and decompaction of its lower layer. Scientists of university developed and patented soil-cultivating working body which carries out the moldboardless tillage of upper layer with a simultaneous decompaction of the lower layer by means of subsoiler. The offered boardless-subsoiler implement by loosening the top layer of soil and decompaction of the lower horizon, allows to keep crop residues on a surface of a tilled field and to loosen the lower layers of soil, providing the necessary water-air regime. Mechanical cultivation of the soil this boardless-subsoiler implement respond to criteria of quality of soil cultivation. Extent of crushing of the soil is lie in limits of necessary value, the sizes of structural units of the soil is 8-10mm. Forming of a necessary equilibrium condition of the soil on a depth of cultivation supports good germination of a root system and to increase in productivity of the grown-up cultures. Such processing most meets the agrotechnical requirements at growing crops such as
sunflower, corn, sugar beet. The offered way of soil cultivation provides fuel savings of up to 10 kg per hectare due to reduction of number of operations. The energy intensity of technology process decreases to 50% due to reduction of number of technology operations for the preparation of the soil
Universal Scaling of Wave Propagation Failure in Arrays of Coupled Nonlinear Cells
We study the onset of the propagation failure of wave fronts in systems of
coupled cells. We introduce a new method to analyze the scaling of the critical
external field at which fronts cease to propagate, as a function of
intercellular coupling. We find the universal scaling of the field throughout
the range of couplings, and show that the field becomes exponentially small for
large couplings. Our method is generic and applicable to a wide class of
cellular dynamics in chemical, biological, and engineering systems. We confirm
our results by direct numerical simulations.Comment: 4 pages, 3 figures, RevTe
Effect of the Predecessor and the Nitrogen Rate on Productivity and Essential Oil Content of Coriander (Coriandrum sativum L.) in Southeast Bulgaria
Received: May 31st, 2022 ; Accepted: August 13th, 2022 ; Published: September 19th, 2022 ;
Correspondence: [email protected] (Coriandrum sativum L.) is one of the most important essential oil crops on
a global scale. Coriander productivity is determined by the genotype, the environmental factors,
as well the agronomic practices. A field experiment was conducted in Southeast Bulgaria during
three vegetation seasons (2015, 2016, and 2017). The present study aimed at analysing the
influence of two crop predecessors (winter wheat and sunflower) and four nitrogen (N) levels (0,
40, 80, and 120 kg ha-1
). Productivity elements, seed yield, and seed essential oil content of
coriander (cv. Mesten drebnoploden) were under evaluation. The results obtained showed that
winter wheat was a more suitable predecessor of coriander in comparison to sunflower. The
highest results regarding the number of umbels per plant, the umbel’s diameter, the number of
umbellets per umbel, the number of seeds per umbel, the seed weight per plant, the 1,000 seed
mass, as well as the seed yield for the rate of 80 kg ha-1 of N were recorded. The highest essential
oil content after applying 120 kg ha-1 of N was established. Increasing the N level from 0 to
120 kg ha-1 led to a positive and significant effect on essential oil yield. No significant differences
between the N rates of 80 and 120 kg ha-1 were recorded. The received results contributed for the
evaluatation of the optimum nitrogen level, as well as for the determination of a more suitable
predecessor of coriander in order to obtain the highest yield of better quality in the region of
Southeast Bulgaria
-kinks in strongly ac driven sine-Gordon systems
We demonstrate that -kinks exist in non-parametrically ac driven
sine-Gordon systems if the ac drive is sufficiently fast. It is found that, at
a critical value of the drive amplitude, there are two stable and two unstable
equilibria in the sine-Gordon phase. The pairwise symmetry of these equilibria
implies the existence of a one-parameter family of -kink solutions in the
reduced system. In the dissipative case of the ac driven sine-Gordon systems,
corresponding to Josephson junctions, the velocity is selected by the balance
between the perturbations. The results are derived from a perturbation analysis
and verified by direct numerical simulations.Comment: 4 pages, 2 figures, revte
Theory of spiral wave dynamics in weakly excitable media: asymptotic reduction to a kinematic model and applications
In a weakly excitable medium, characterized by a large threshold stimulus,
the free end of an isolated broken plane wave (wave tip) can either rotate
(steadily or unsteadily) around a large excitable core, thereby producing a
spiral pattern, or retract causing the wave to vanish at boundaries. An
asymptotic analysis of spiral motion and retraction is carried out in this
weakly excitable large core regime starting from the free-boundary limit of the
reaction-diffusion models, valid when the excited region is delimited by a thin
interface. The wave description is shown to naturally split between the tip
region and a far region that are smoothly matched on an intermediate scale.
This separation allows us to rigorously derive an equation of motion for the
wave tip, with the large scale motion of the spiral wavefront slaved to the
tip. This kinematic description provides both a physical picture and exact
predictions for a wide range of wave behavior, including: (i) steady rotation
(frequency and core radius), (ii) exact treatment of the meandering instability
in the free-boundary limit with the prediction that the frequency of unstable
motion is half the primary steady frequency (iii) drift under external actions
(external field with application to axisymmetric scroll ring motion in
three-dimensions, and spatial or/and time-dependent variation of excitability),
and (iv) the dynamics of multi-armed spiral waves with the new prediction that
steadily rotating waves with two or more arms are linearly unstable. Numerical
simulations of FitzHug-Nagumo kinetics are used to test several aspects of our
results. In addition, we discuss the semi-quantitative extension of this theory
to finite cores and pinpoint mathematical subtleties related to the thin
interface limit of singly diffusive reaction-diffusion models
Parametrically forced sine-Gordon equation and domain walls dynamics in ferromagnets
A parametrically forced sine-Gordon equation with a fast periodic {\em
mean-zero} forcing is considered. It is shown that -kinks represent a
class of solitary-wave solutions of the equation. This result is applied to
quasi-one-dimensional ferromagnets with an easy plane anisotropy, in a rapidly
oscillating magnetic field. In this case the -kink solution we have
introduced corresponds to the uniform ``true'' domain wall motion, since the
magnetization directions on opposite sides of the wall are anti-parallel. In
contrast to previous work, no additional anisotropy is required to obtain a
true domain wall. Numerical simulations showed good qualitative agreement with
the theory.Comment: 3 pages, 1 figure, revte
Scroll waves in isotropic excitable media : linear instabilities, bifurcations and restabilized states
Scroll waves are three-dimensional analogs of spiral waves. The linear
stability spectrum of untwisted and twisted scroll waves is computed for a
two-variable reaction-diffusion model of an excitable medium. Different bands
of modes are seen to be unstable in different regions of parameter space. The
corresponding bifurcations and bifurcated states are characterized by
performing direct numerical simulations. In addition, computations of the
adjoint linear stability operator eigenmodes are also performed and serve to
obtain a number of matrix elements characterizing the long-wavelength
deformations of scroll waves.Comment: 30 pages 16 figures, submitted to Phys. Rev.
Imbibition in Disordered Media
The physics of liquids in porous media gives rise to many interesting
phenomena, including imbibition where a viscous fluid displaces a less viscous
one. Here we discuss the theoretical and experimental progress made in recent
years in this field. The emphasis is on an interfacial description, akin to the
focus of a statistical physics approach. Coarse-grained equations of motion
have been recently presented in the literature. These contain terms that take
into account the pertinent features of imbibition: non-locality and the
quenched noise that arises from the random environment, fluctuations of the
fluid flow and capillary forces. The theoretical progress has highlighted the
presence of intrinsic length-scales that invalidate scale invariance often
assumed to be present in kinetic roughening processes such as that of a
two-phase boundary in liquid penetration. Another important fact is that the
macroscopic fluid flow, the kinetic roughening properties, and the effective
noise in the problem are all coupled. Many possible deviations from simple
scaling behaviour exist, and we outline the experimental evidence. Finally,
prospects for further work, both theoretical and experimental, are discussed.Comment: Review article, to appear in Advances in Physics, 53 pages LaTe
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