Spin rotation for ballistic electron transmission induced by spin-orbit interaction

We study spin dependent electron transmission through one- and two-dimensional curved waveguides and quantum dots with account of spin-orbit interaction. We prove that for a transmission through arbitrary structure there is no spin polarization provided that electron transmits in isolated energy subband and only two leads are attached to the structure. In particular there is no spin polarization in the one-dimensional wire for which spin dependent solution is found analytically. The solution demonstrates spin evolution as dependent on a length of wire. Numerical solution for transmission of electrons through the two-dimensional curved waveguides coincides with the solution for the one-dimensional wire if the energy of electron is within the first energy subband. In the vicinity of edges of the energy subbands there are sharp anomalies of spin flipping.Comment: 9 oages, 7 figure

Results of experimental investigations of a flexible active harrow with loosening teeth

ArticleSoil tillage processes significantly affect the growth of cultivated plants; therefore, improvement of various designs and combinations of ploughs is still an actual practical and scientific task. This paper presents investigations of the design of a soil tillage machine consisting of three plough bodies equipped from the lateral side with a module with a flexible active harrow driven by a support wheel. The technological process of tillage by this machine is carried out in such a way that the module of the flexible active harrow is installed at a certain depth of soil tillage. The purpose of this work is an experimental comparative investigation of the quality indicators of the work of a design of the soil tillage working body with a flexible active harrow having loosening teeth. In the process of comparative experimental investigations of the operation of ploughs with a standard flexible harrow and an experimental active harrow having loosening teeth, the soil lumpiness (characterising the quality of crumbling) and water permeability of the obtained soil structure were estimated. An experimental model of this working tool was tested under the production conditions, and it showed advantages of loosening and crumpling the soil compared to the conventional harrows. This can be explained by the fact that the harrow tines, freely mounted on the axes of its links, ensure their oscillatory movements when moving in two different planes, thereby creating conditions for more intense soil disintegration

Harrow with screw-type operating tools: optimisation of design and process parameters

Received: August 1st, 2022 ; Accepted: September 8th, 2022 ; Published: September 9th, 2022 ; Correspondence: [email protected] new design of the harrow with screw-type operating tools is presented in the paper. It describes the theoretical and experimental investigations carried out for the purpose of optimising the design and process parameters of the harrow with screw-type operating tools. Such optimisation will provide for improving the soil fertility, when burying chaff and other plant residues as organic fertilisers into the soil during its tillage. On the basis of the results obtained in the comprehensive experimental investigations, new regression relations have been generated. These relations provide for determining the proportion of the field surface, where the after harvesting residues have been completely buried in the soil with the harrow with screw-type operating tools. It has been established that the dominant effect on the relative amount of the field surface area S with completely worked-in plant residues is produced by the soil tillage depth h, then follows the factor of the screw-type operating device battery approach angle β. The pitch distance Т of the screw-type operating device has the smallest effect. The results of the completed research prove that increasing the pitch distance Т of the screw-type operating tool from 0.18 m to 0.26 m results in the decrease in the area S of the field surface with the plant residues buried in the soil by 1.4%. An increase in the approach angle β from 20° to 40° results in the increase in the field surface area S with the plant residues completely worked into the soil by 5.6%. Increasing the soil tillage depth from 0.08 m to 0.12 m results in the increase in the above-mentioned surface S by 7.1%. The simultaneous action of the factors of the tillage depth h and the approach angle β results in the percentage of the surface S rising from 72% to 82%

Experimental study of the distribution of the heights of sugar beet root crowns above the soil surface

ArticleThe results of experimental studies and operational tests of the sugar beet harvesting process carried out recently reveal that the latest models of beet harvesters produced in Europe and America cause considerable loss of the sugar-bearing mass. The source of this loss is mainly the poor topping of the crowns of standing sugar beet roots, more specifically the excessively low point at which the tops are cut off, which results in the straight out loss of sugar-bearing mass. Thus, there is need to search for such engineering solutions that would avoid both the loss of sugar-bearing mass and the presence of residual haulm on the roots. The aim of this study was to reduce the loss of sugar-bearing mass in the process of topping sugar beet root crowns. The results of this research into the distribution of the heights that root crowns protrude above the soil surface have confirmed the hypothesis that it follows the normal distribution. Based on the results, it has been established that this distribution has the following statistical parameters: mean deviation a = 20–30 mm, mathematical expectation m = 40...60 mm. The laboratory unit developed for this work and the field studies performed with it have provided sufficient evidence to develop a new system to automatically adjust the topping height on state-of-the-art root crop harvesters

Theoretical study of the conditions of the maximum allowable slipping of wheel tractors

Received: October 1st, 2022 ; Accepted: March 15th, 2023 ; Published: March 17th, 2023 ; Correspondence: [email protected] process of tractor wheels slipping is accompanied by two forms of ground deformation: displacement and shearing. From the point of view of preserving the structure of the soil environment, wheel slip should be limited to displacement only. The limit of soil strength [σo] at this deformation can be a standardizing parameter. In this article an analytical dependence is developed, which allows using the parameter [σo] to establish the maximum permissible level of slipping of wheeled tractors. Of the soil parameters, the specified dependence includes the coefficient of sliding friction between the particles of soil medium and the coefficient of wheel rolling resistance on a particular agrotechnical background. Theoretical studies have established that the greater the value of this coefficient, the smaller should be the maximum permissible value of tractor slipping with a more economical effect on the soil environment. Compared to a tractor with a nominal drawbar pull of 14 kN, the use of a heavier tractor with a drawbar pull of 30 kN is possible with higher values of maximum permissible towing. This result is due to the magnitude of the vertical load on the wheel of the heavier tractor, which gives it a greater friction force between the tire wheel and the ground and allows the same contacting traction force to be realized at a lower level of slipping. The results of mathematical modeling using the developed analytical relationships indicate that with increasing the value of the angle of placement (slope) of the tractor wheel to the longitudinal axis of symmetry, the maximum permissible level of its slipping should be less. This will help to reduce the value of deformation (longitudinal shift) of the soil by the tractor during its working movement. When using the ground shear strength limit [σo] у as a limiting parameter for increasing the pitch and height of the tractor tire, as well as the width of the tractor wheel tyre, the maximum permissible level of its towing is more than 15%, which is an undesirable fact

Electric circuit networks equivalent to chaotic quantum billiards

We formulate two types of electric RLC resonance network equivalent to quantum billiards. In the network of inductors grounded by capacitors squared resonant frequencies are eigenvalues of the quantum billiard. In the network of capacitors grounded by inductors squared resonant frequencies are given by inverse eigen values of the billiard. In both cases local voltages play role of the wave function of the quantum billiard. However as different from quantum billiards there is a heat power because of resistance of the inductors. In the equivalent chaotic billiards we derive the distribution of the heat power which well describes numerical statistics.Comment: 9 pages, 7 figure

Hall-like effect induced by spin-orbit interaction

The effect of spin-orbit interaction on electron transport properties of a cross-junction structure is studied. It is shown that it results in spin polarization of left and right outgoing electron waves. Consequently, incoming electron wave of a proper polarization induces voltage drop perpendicularly to the direct current flow between source and drain of the considered four-terminal cross-structure. The resulting Hall-like resistance is estimated to be of the order of 10^-3 - 10^-2 h/e^2 for technologically available structures. The effect becomes more pronounced in the vicinity of resonances where Hall-like resistance changes its sign as function of the Fermi energy.Comment: 4 pages (RevTeX), 4 figures, will appear in Phys. Rev. Let

Теоретическое определение силы счесывания ботвы сахарной свёклы с головки корнеплода

Beet tops harvesting is a complex task of the sugar beet growing industry which forms the qualitative indicators of root crops during their further digging out from the soil and determines the loss of tops and sugar-bearing mass. In the development of theoretical foundations of the optimal tops cutting from heads of sugar beet root by different types of topping working bodies should take into account forces which act at the same time and the rational cutting height. Theoretical researches having been carried out hitherto concerned only the detailed analytical description of the functioning of the new designs of topping working bodies and practically did not concern the general provisions of the separation tops from the head of root crop. The aim of this study is the theoretical determination of the forces that occur at the contact point of cutting working body of topper machines with root crops head of sugar beet root crop. When carrying out theoretical studies are used the methods of mathematics, theoretical mechanics, strength of materials, methods of programming and numerical calculations on PC. As a result, of the theoretical research new analytical dependencies of force describing the processes of crumpling and subsequently cutting of sugar beet heads by topping working body, depending on the size and shape of root crops heads and design parameters of topper have been obtained. As a result, of numerical calculations on PC critical level value of penetration of the cutting element of topping working body into root crops head of sugar beet and maximum value of cutting force at which ejection of root vegetables from the soil doesn’t take place, was defined. The obtained theoretical dependencies and values of normal reaction and cutting forces are the basis for the further working out of a mathematical model of dynamic interaction system of cutting working bodies with the heads of sugar bee