25 research outputs found
An Efficient Beam Steerable Antenna Array Concept for Airborne Applications
Deployment of a satellite borne, steerable antenna array with higher directivity and gain in Low Earth Orbit makes sense to reduce ground station complexity and cost, while still maintaining a reasonable link budget. The implementation comprises a digitally beam steerable phased array antenna integrated with a complete system, comprising the antenna, hosting platform, ground station, and aircraft based satellite emulator to facilitate convenient aircraft based testing of the antenna array and ground-space communication link. This paper describes the design, development and initial successful interim testing of the various subsystems. A two element prototype used in this increases the signal-to-noise ratio (SNR) by 3 dB which is corresponding to more than 10 times better bit error rate (BER)
Theoretical research into directional stability of trailed tandem- type disk harrow
Received: August 27th, 2021 ; Accepted: October 6th, 2021 ; Published: October 7th, 2021 ; Correspondence: [email protected] is one of the methods of soil cultivation, provides its effective crumbling, loosening,
partial mixing and soil inversion. This ensures that crop residues on the soil surface are shredded
and intermixing with loosened soil particles. Since, in addition to crop stubble, weeds are also
counted as crop residues, soil disking, along with the use of herbicides, is often regarded as the most
effective method of controlling the weediness of the agricultural background. Despite the fact that
numerous studies on the disk harrow working process are available, insufficient attention has been
paid to the study of the stability of harrow machine-tractor units, especially trailed ones. The purpose
of this study is to establish the theoretical patterns that would provide for selecting the trailed disk
harrow parameters that ensure the desired directional stability of the implement, which, in its turn,
helps to achieve the desired qualitative performance of the disk harrowing machine-tractor unit. The
principles of the theory agricultural machine, analytical mechanics, higher mathematics, as well as
methods of PC-assisted numerical calculations have been used. According to the results of the study,
it has been established that sufficient directional stability of the trailed disk harrow can be ensured
if its working width B, the distance from the hitch point to the centre of resistance (parameter d) and
the operating speed are properly selected. Determining the above-mentioned parameters of the
disk harrow with the use of the obtained new analytical relations ensures achieving just their optimal
combination, which provides for the maximum field productivity of the harrow machine-tractor unit
with the satisfactory stability of disk harrow movement in the horizontal plane
Theoretical research into operation of rotary potato harvester
Received: May 25th, 2021 ; Accepted: June 22nd, 2021 ; Published: June 28th, 2021 ; Correspondence: [email protected] topic of the paper is the determination and justification of the rational design and
kinematic parameters of clod breaking tools in rotary potato harvesters with the aim of improving
their separating efficiency. A new mathematical model has been developed for the motion of a
soil particle on the working surfaces of the cone-shaped and cylindrical vanes in the rotary tool
of the new design developed by the authors. Differential equations have been generated for the
motion of a soil clod as a material particle from the moment of its arrival to the surface of the
vane until the moment of its departure from the said surface. As a result of the completed
investigations, relations have been established between the time of contact and absolute
displacement of the soil particle and the velocity of its departure from the rotor vane surface, on
the one hand, and the kinematic and design parameters of the rotor, on the other hand. For
example, when the machine translation velocity increases, the absolute displacement of the soil
particle within the interval from the time zero to the moment of its departure from the vane surface
increases from 0.59 m to 0.65 m, the velocity of soil particle departure from the vane surface -
from 1.61 m sâ1 to 1.81 m sâ1. The highest values of the absolute displacement of the soil particle
and the velocity of its departure from the vane surface are achieved at a machine translation
velocity of 2.0 m sâ1. The time of the contact between the material particle and the vane surface
decreases with the rise of the translation velocity. When the rotor rotation frequency varies within
the range from 20 minâ1 to 100 minâ1, the absolute velocity, with which the soil particle leaves
the vane surface, rises to 4 m sâ1. The duration of the contact between the material particle and
the vane reaches its maximum value of 0.33 s, when the rotor rotation frequency varies within
the range of 30â40 minâ1
Justification of parameters for novel rotary potato harvesting machine
Received: March 6th, 2021 ; Accepted: May 12th, 2021 ; Published: May 14th, 2021 ; Correspondence: [email protected] authors have set an aim in relation to the development of a novel rotary potato
harvesting machine design and the substantiation of rational design and process parameters for the
clod crushing tools in the machine in order to improve its separation capacity. A novel design solution
has been suggested for the process of crushing the two adjacent potato rows with the vanes of the
vertical rotor and the expediency of using the methods of crushing clods in the two adjacent potato
rows in advance has been justified. Also, the more rational placement of the clod crushing tools in the
potato harvesting machine has been suggested. Following the completed research, the geometrical
parameters of the vertical rotor have been substantiated, in particular, its diameter dŃ = 0.65â1.0 m and
height hzag = 0.27 m. Additionally, the process parameters have been substantiated for some other tools
crushing the clods, in particular, the angle of inclination of the shareâs working face, which has to be
equal to 10°, the elevator belt width bel = 1.05 m, the linear velocity of the belt Vp = 1.95 m s
â1
, the belt
agitation amplitude Đst = 18 mm. If the soil moisture content is equal to W = 18.4%, the soil separation
rate rises insignificantly, when the rotor diameter increases within the range of 0.65â1.0 m, moreover,
at Vm = 1.0 m s
â1
it varies within the range of 85.3â87.2%, at Vm = 1.5 m s
â1 â within the range of
87.0â92.7%, at Vm = 2.0 m s
â1 â within the range of 86.0â89.1%. The best performance is achieved at
a rotor rotation frequency of nŃ = 100 minâ1
and a translational velocity of Vm = 1.5 m s
â1
, in which
case the soil separation rate S is equal to 93.5%. The tuber damage rate Pb decreases from 4.2% to
1.5%, as the rotor diameter dŃ increases from 0.65 m to 1.0 m, the translational velocity of the machine
Vm â from 0.8 to 2.2 m s
â1
at the rotor rotation frequency nŃ = 50â100 minâ1
Extracellular DNA in blood: an index of <i>in vivo</i> inflammatory response
Increased concentration of cell-free DNA (cfDNA) in the circulating blood of humans and animals is a sign of inflammatory conditions and a distinctive characteristic of various pathophysiological processes in the body. The aim of the present study was to investigate the possible role of tumor necrosis factor (TNFα) in changes of cfDNA contents in peripheral blood as a response to experimentally induced systemic inflammation.We used 40 female hybrid mice (C57Bl/6xDBA/2) F1 at the age of 6-8 weeks. The concentration of cfDNA and its individual fractions was determined using a PicoGreen fluorescent dye. The dynamics of inflammatory process was evaluated after 4, 8, 11 and 24 hours following LPS injection. A significant increase in the blood plasma cfDNA levels was shown under the action of E. coli lipopolysaccharide (LPS), along with simultaneous decreased levels of cfDNA, associated with cell surface. The ratio of cell surface-bound cfDNA to the total cfDNA contents was reduced in dose-dependent manner as early as 4 hours after LPS injection to the animals, thus allowing us to consider this ratio a characteristic sign of netosis of neutrophilic granulocytes during the development of acute inflammation. The described effects are significantly suppressed with co-injection of recombinant TNFα neutralizing protein along with LPS, whereas increased intake of neutrophils in the tissues is determined by some other factors which are not directly related to the production of this cytokine.Based on the obtained data, we proposed a following hypothesis: induction of netosis by inflammatory stimuli causes an increase in the concentration of cfDNA in blood plasma not only due to de novo emerging extracellular DNA by neutrophil netosis, but also by the release of distinct cfDNA fraction that was previously firmly bound to cell membranes in multiple body tissues under the action of proteases released during netosis
Blood platelets in chronic graft-versus-host disease: association with Th1/Th2 ratio
As found in clinical and laboratory studies, platelets not only play a key role in the processes of coagulation and thrombosis, but are also able to actively participate in other pathophysiological processes, including the development of immune reactions. It has been shown that changes in the immune system leading to systemic lupus erythematosus (SLE) are often accompanied by changes in the number of platelets and their activity in the peripheral blood of SLE patients, which correlate with the severity of the clinical manifestations of the disease. Earlier we have studied the standard experimental model of SLE in detail, based on the induction of chronic graft-versus-host disease (cGVHD) in the semi-allogeneic system DBA/2 â (C57Bl/6 x DBA/2)F1. However, the participation of platelets in this immunopathological process has not been studied. There are no data in the literature on the behavior of platelets in cGVHD or on their relationship with the state of Th1/Th2 balance. It can been expected that the platelet count changes according to the development of cGVHD in the used experimental model by analogy with the development of SLE in humans.In the experiments, we used female mice of the DBA/2 strain and (C57Bl/6 Ă DBA/2)F1 hybrids. Chronic GVHD in a semi-allogeneic system was induced by injecting DBA/2 mouse splenocytes into B6D2F1 hybrid mice: 60-70 Ă 106 cells intravenously twice with an interval of 6 days. The studied parameters were evaluated three months after the start of the experiment and the formation of lupus-like glomerulonephritis in animals with Th2-dependent cGVHD variant.A decrease in the number of erythrocytes and hemoglobin, a decrease in hematocrit and a parallel increase in the number of reticulocytes in the blood of mice with cGVHD are in good agreement with our earlier conclusion that these animals have autoimmune hemolytic anemia. It was found that, platelets increase significantly with the development of cGVHD unlike other blood cells. Secondary thrombocytosis is observed in the case of the Th2-dependent variant of ŃGVHD in this model of SLE, while in the group with the Th1-dependent variant of ŃGVHD, the average number of platelets in the blood does not differ from the control group
The origin of second harmonic generation hotspots in chiral optical metamaterials [Invited]
Novel ways to detect the handedness in chiral optical metamaterials by means of the second harmonic generation (SHG) process have recently been proposed. However, the precise origin of the SHG emission has yet to be unambiguously established. In this paper, we present computational simulations of both the electric currents and the electromagnetic fields in chiral planar metamaterials, at the fundamental frequency (FF), and discuss the implications of our results on the characteristics of experimentally measured SHG. In particular, we show that the results of our numerical simulations are in good agreement with the experimental mapping of SHG sources. Thus, the SHG in these metamaterials can be attributed to a strong local enhancement of the electromagnetic fields at the FF, which depends on the particular structure of the patterned metamaterial
Nonlinear superchiral meta-surfaces: tuning chirality and disentangling non-reciprocity at the nanoscale.
Circularly polarized light is incident on a nanostructured chiral meta-surface. In the nanostructured unit cells whose chirality matches that of light, superchiral light is forming and strong optical second harmonic generation can be observed
Numerical integration of Sommerfeld integrals based on singularity extraction techniques and double exponential-type quadrature formulas
A direct integration algorithm for the evaluation of Sommerfeld integrals is presented. This algorithm does not require the deformation of the integration path to avoid spectral singularities. The integration is performed along the real axis only. The algorithm is based on the combination of an asymptotic extraction technique to remove the singularities and double-exponential quadrature rules to take the tail of the integral into account. Numerical examples confirm the validity of the proposed algorithm
KUL and EPFL cooperation on numerical integration of Sommerfeld integrals.
This paper reports the result of the cooperation between KUL and EPFL on the numerical integration of Sommerfeld integrals (SI). Each institution is well-known for developing specific techniques suited for the evaluation of SI: double-exponential quadrature rules to take the tail of the integral into account (EPFL) and an asymptotic extraction technique to remove the singularities (KUL). The combination of these two techniques results in a very promising algorithm, allowing to perform the integration along the real axis only. Several examples illustrate the algorithm efficiency