Regular monitoring of the D- and F-layers of ionosphere over Central Asia territory is being performed on the permanent basis starting year 2008 when one Very Low Frequency (VLF) receiver and two SuperSID receivers were provided to Uzbekistan IHY cite by Stanford University. The results obtained at Tashkent IHY (International Heliophysical Year) station are applied to earthquake electromagnetic precursors, lightning, and Solar flares and to ionospheric disturbances originating from gamma ray flares of Soft Gamma-Ray Repeaters. Regular monitoring of the D-layer of ionosphere over Central Asia territory has been performed on the permanent basis. Several Solar events are observed and the analysis has shown that there is simultaneous correlation between the times of change of amplitude of the waves and the Solar flares. Features of the lightning discharge generated by radio atmospherics are studied and its effectiveness in D-region ionosphere diagnostics is examined. We have mainly analyzed GPS derived TEC disturbances from two GPS stations located in Tashkent and Kitab, for possible earthquake ionospheric precursors. The solar and geomagnetic conditions were quiet during occurrence of the selected more than 30 earthquakes. We produced TEC time series over both sites and apply them to detect anomalous TEC signals preceding or accompanying the earthquakes. The results show anomalous enhancements which are examined in the earthquakes.

Success in cultivating cotton largely depends on the timing and quality of soil preparation for sowing and sowing, and the latter, in turn, depends on how it is carried out and on the perfect design of the machines. The aim of the study is to justify the shape of the ridges and the parameters of the moulder to the cotton seeder. The authors proposed a new technology for sowing with the simultaneous formation of ridges. The shape and parameters of the ridge are theoretically substantiated. When performing the shape of the ridge in the form of an isosceles trapezoid and, accordingly, with a height and width of the ridge surface of at least 100 mm and 160 mm, the seed bed is protected from flooding by rain streams. The design of the developed comb moulder to a cotton seeder for the implementation of the proposed technology is given. Theoretically substantiated the main parameters of the crest moulder. It was found that when the input edge of the moulder is 290-320 mm wide, the output edge is 160 mm, the angle of inclination of the side blade to the direction of movement is 20°, the length of the runner of the moulder is 203-215 mm, the height of the side blade is 100 mm and the angle of installation of the side blade to horizon 42-45° ensures highquality implementation of the technological process of formation of ridges. When sowing cotton seeds on the ridges with the simultaneous formation of the ridge, the seedlings of the plants increase, and the cotton yield increases compared to the smooth sowing method of 9.9%.

Ташкентский финансовый институт; к.ф.-м.н., доцент Д.А. Ходжаев, Ташкентский институт ирригации и мелиорации Аннотация. В работе приводятся численный метод и алгоритм решения задач динамики вязкоупругих тонкостенных элементов конструкций переменной толщины. Уравнения движения относительно прогибов описываются интегро-дифференциальными уравнениями (ИДУ) в частных производных. При помощи метода Бубнова-Галеркина, основанного на многочленной аппроксимации прогибов, задача сводится к исследованию системы обыкновенных ИДУ, где независимой переменной является время. Система ИДУ решается предложенным численным методом, на основе которого описан алгоритм численного решения и создана программа на алгоритмическом языке Delphi. Исследование нелинейных колебаний тонкостенных элементов конструкции с учетом переменной толщины в геометрической нелинейной постановке позволило выявить ряд механических эффектов. В зависимости от физико-механических и геометрических параметров рассмотренных вязкоупругих тонкостенных элементов конструкций даны рекомендации по использованию жесткости системы. Ключевые слова: тонкостенные конструкции; переменная толщина; вязкоупругость, неоднородность; метод Бубнова-Галеркина; интегро-дифференциальные уравнения Введение В прикладных задачах механики деформируемых систем приходится встречаться с процессами, при описании которых необходимо оперировать имеющими разрывы величинами, различными по своему физико-механическому содержанию. В последнее время стало появляться все больше работ, посвященных результатам исследований критического состояния, колебаний и напряженно-деформированного состояния (НДС) конструкций с физико-механическими особенностями разрывного типа, т. е. конструкций cо ступенчато-переменной толщиной, с армированиями, неоднородностями структуры, местными включениями в виде сосредоточенных масс и отверстий, либо пониженной жесткости в виде ребра с учетом изотропных и анизотропных свойств материала [1-7].

The problems of oscillations of a viscoelastic cylindrical panel with concentrated masses are investigated, based on the Kirchhoff-Love hypothesis in the geometrically nonlinear statement. The effect of the action of concentrated masses is introduced into the equation of motion of the cylindrical panel using the δ function. To solve integro-differential equations of nonlinear problems of the dynamics of viscoelastic systems, a numerical method is suggested. With the Bubnov–Galerkin method, based on a polynomial approximation of the deflection, in combination with the suggested numerical method, the problems of nonlinear oscillation of a viscoelastic cylindrical panel with concentrated masses were solved. Bubnov–Galerkin’s convergence was studied in all problems. The influence of the viscoelastic properties of the material and concentrated masses on the process of oscillations of a cylindrical panel is shown.

A method for dynamic calculation of a box-like structure, consisting of interconnected longitudinal and transverse plate and beam elements is developed. The problem is posed of spatial vibrations of the box-like structure of a building under dynamic impact determined by its base motion according to a sinusoidal law. It is assumed that the external load-bearing walls of the building, perpendicular to the direction of the seismic effect, work on transverse bending only. The interior panels, located in the direction of external impact, are subjected to tension-compression and shear in their planes. Equations of vibrations of the points of panels, box beams, boundary and initial conditions of the problem are given. In the areas of butt joints of panels, full contact conditions are set to ensure the equality of displacements and stresses. Within the framework of the finite difference method, a methodology was developed for dynamic calculation of box-like structures. Numerical results of stresses over time in the hazardous areas of the box were obtained. The laws of changes in the maximum stress values in characteristic sections of the panels are graphically presented as a function of time.

We discuss the problem of the dynamic stability of a viscoelastic cylindrical panel with concentrated masses in a geometrically nonlinear formulation that is based on the Kirchhoff-Love hypothesis. The effect of the action of concentrated masses is introduced into the equation of motion of a cylindrical panel using the Dirac δ-function. The problem is solved by the Bubnov-Galerkin method based on a polynomial approximation of deflections together with a numerical method based on the use of quadrature formulas. The choice of the Koltunov-Rzhanitsyn singular kernel is justified. Comparisons between the results obtained from different theories are presented. The Bubnov-Galerkin method convergence is investigated for all problems. The effect of the material viscoelastic properties and concentrated masses on the process of the dynamic stability of a cylindrical panel is shown.Introduction. During the intense development of the modern industry, a reduction in the materials consumption of machine structures is one of the main problems of the mechanical and civil engineering. For the purpose of material saving, the need arises to manufacture thin-walled structures. The thinner is the element and the more flexible it is, the more strongly its susceptibility to buckling and loss of stability is manifested. The latter is accompanied by a catastrophic development of deformations and, as a rule, by a structural failure. From this standpoint, in the production of lightweight, durable and reliable structures, it is reasonable to use the materials which make it possible not only to improve their operating characteristics but, in a number of cases, to create the structures unfeasible with traditional materials. Here, the calculation procedure and structural design involving the consideration of their actual properties are rather complicated. Today, the development of efficient solution algorithms for nonlinear problems of dynamic stability of shells, panels and plates is the most pressing issue.Plates, panels or shells with objects fixed as additional masses have found wide use due to high viscoelastic and strength properties. In the design of structural elements, the prediction of their dynamic characteristics depending on the shape, mass distribution, viscoelastic properties of the material, etc. is an urgent problem.Longitudinal and transverse ribs, cover straps, fasteners, device assemblies and subassemblies act mainly as additional masses [1,2]. In a theoretical consideration of this kind of problems, it is sometimes convenient to interpret connected elements as additional masses rigidly attached to systems and concentrated at points.Works dealing with vibrations and dynamic stability of elastic systems with concentrated masses are known [3][4][5][6][7][8] where problems were solved in a linear formulation. Thus, for example, work [9] deals with the investigations on the nonlinear vibrations and dynamic stability of elastic cylindrical panels and shells carrying concentrated masses. Similar problems of vibrations and dynamic...

Mathematical statement, methods and algorithms of solution of the problem of assessment of stress-strain state and dynamic behavior of earth structures are considered in this paper which account for structural features, elastic-plastic and non-linear-moisturing properties of soil under static and dynamic effects. The problem is considered within the limits of plane deformation. The stress-strain state and dynamic behaviour of certain structures under different effects are studied. Some results revealed in the investigation have considerable practical importance.

In modern engineering and construction, thin-walled plates and shells of variable thickness, subjected to various static and dynamic loads, are widely used as structural elements. Advances in the technology of manufacturing thin-walled structural elements of any shape made it possible to produce structures with predetermined patterns of thickness variation. Calculations of strength, vibration and stability of such structures play an important role in design of modern apparatuses, machines and structures. The paper considers nonlinear vibrations of viscoelastic orthotropic cylindrical panels of variable thickness under periodic loads. The equation of motion for cylindrical panels is based on the Kirchhoff-Love hypothesis in a geometrically nonlinear statement. Using the Bubnov-Galerkin method, based on a polynomial approximation of deflections, the problem is reduced to the study of a system of ordinary integro-differential partial differential equations, where time is an independent variable. The solution to the resulting system is found by a numerical method based on the feature elimination in the Koltunov-Rzhanitsyn kernel used in the calculations. The behavior of a cylindrical panel with a wide range of changes in physico-mechanical and geometrical parameters is investigated.