DEVICES FOR DETERMINING THE STRENGTH OF SNOW AND ICE FORMATIONS

В статье представлен анализ существующих средств определения прочности снежно-ледовых образований, выявлены их недостатки, преимущества и отличительные способности. Целью данной работы является разработка компактных средств измерения прочности компонентов дорожных покрытий и обеспечения контроля качества уплотнения полотна сооружаемых зимних дорог по глубине покрытия. Предложено техническое решение, которое позволяет достичь более высокого технического результата по сравнению с известными аналогами, который заключается в повышении точности измерений, упрощении фиксации шарового элемента в корпусе, обеспечении фиксации подвижных элементов при транспортировке и расширении функциональных возможностей за счет определения прочности на поверхности и по глубине снежного покрова с наконечниками разного профиля, а также позволяет снизить стоимость изготовления и трудоемкость работ при измерениях. Предложенный прибор (твердомер) позволяет расширить область применения, как для свежевыпавшего снега, так и для лежалого, за счёт применения разных нижних поверхностей профиля наконечников в виде конуса, цилиндра или шара. Шаровая поверхность увеличивает площадь соприкосновения нижней поверхности его со снежными образованиями для свежевыпавшего снега. Прибор спроектирован, изготовлен и позволяет определять прочностные свойства снежно-ледовых образований при выполнении научно-исследовательских работ. The article presents an analysis of the existing means for determining the strength of snow-ice formations, reveals their disadvantages, advantages and distinctive abilities. The purpose of this work is to develop compact means for measuring the strength of road pavement components and ensuring quality control of the compaction of the roadbed of winter roads under construction by the depth of the pavement. A technical solution is proposed that allows achieving a higher technical result in comparison with known analogues, which consists in increasing the measurement accuracy, simplifying the fixing of the ball element in the housing, ensuring the fixation of the moving elements during transportation and expanding the functionality by determining the strength on the surface and in depth snow cover with tips of different profiles, and also allows you to reduce the manufacturing cost and laboriousness of work during measurements. The proposed device (hardness tester) allows you to expand the field of application, both for freshly fallen snow, and for old, due to the use of different lower surfaces of the profile of the tips in the form of a cone, cylinder or ball. The spherical surface increases the contact area of ​​its lower surface with snow formations for freshly fallen snow. The device has been designed, manufactured and allows to determine the strength properties of snow-ice formations during scientific research.

Binaural Synthetic Aperture Imaging of the Field of Audition as the Head Rotates and Localisation Perception of Monophonic Sound Listened to through Headphones

A human listening to monophonic sound through headphones perceives the sound to emanate from a point inside the head at the auditory centre at effectively zero range. The extent to which this is predicted by synthetic-aperture calculation performed in response to head rotation is explored. The instantaneous angle between the auditory axis and the acoustic source, lambda, for the zero inter-aural time delay imposed by headphones is 90°. The lambda hyperbolic cone simplifies to the auditory median plane, which intersects a spherical surface centred on the auditory centre, along a prime meridian lambda circle. In a two-dimensional (2-D) synthetic-aperture computation, points of intersection of all lambda circles as the head rotates constitute solutions to the directions to acoustic sources. Geometrically, lambda circles cannot intersect at a point representing the auditory centre; nevertheless, 2-D synthetic aperture images for a pure turn of the head and for a pure lateral tilt yield solutions as pairs of points on opposite sides of the head. These can reasonably be interpreted to be perceived at the sums of the position vectors of the pairs of points on the acoustic image, i.e., at the auditory centre. But, a turn of the head on which a fixed lateral tilt of the auditory axis is concomitant (as in species of owl) yields a 2-D synthetic-aperture image without solution. However, extending a 2-D synthetic aperture calculation to a three-dimensional (3-D) calculation will generate a 3-D acoustic image of the field of audition that robustly yields the expected solution.

Research on the mathematical modelling of the starting torque of self-lubricating spherical plain bearings

The starting torque of self-lubricating spherical plain bearings (SSPBs) is a key parameter for evaluating the performance of bearings. Therefore, the starting torque of SSPBs should be controlled to within an allowable range. In this paper, the starting torque generation mechanism is analyzed, and the critical load for the separation of the liner from the outer spherical surface of the inner ring is determined. A mathematical model of the starting torque is established; the experimental and theoretical results of the starting torque are compared and analyzed, and then the accuracy of the mathematical model is evaluated by the deterministic coefficient R2. The research reveals that a critical load exists for the starting torque. Below the critical load, the starting torque is dependent on the outer spherical radius of the inner ring, bearing wrap angle, and liner parameters such as the compressive elastic modulus, friction coefficient, and precompression of the liner; however, the starting torque is independent of the radial load. Above the critical load, the starting torque is also dependent on the radial load. The research results provide a theoretical basis for the design and application of bearings.

New Approach to Three-Coordinate Milling of Large-Sized Surfaces of Second Order

The study introduces a new approach to precision machining of large-sized surfaces of second order on a three-coordinate horizontal milling machine. The new technology does not require the use of unique large-size boring lathes or five-axis milling machines. Three-axis horizontal milling machines do not need to be equipped with additional equipment that provides the workpiece with the missing rotational and translational movements relative to the machine table. The proposed technology is based on the use of a new approach that combines the geometric parameters of the second-order machined surface, the spherical surface of the cutting tool, i.e. cutter, and their position relative to the working table. The use of the developed technology will improve the efficiency and accuracy of machining the surface of second order, as well as simplify the control program and technological support due to the absence of movable equipment. The study gives an example of practical implementation and shows the possibility of independent control of the machined parabolic surface geometry using a three-coordinate horizontal milling machine.

ANALYTICAL DETERMINATION OF THE MICRORELIEF PARAMETERS FORMED AS A RESULT OF CENTERLESS GRINDING OF THE FULL SPHERE

При технологической подготовке операций чистовой и отделочной обработки деталей абразивными инструментами очень важными задачами являются прогнозирование ее результатов в зависимости от назначенных режимов и назначение режимов в зависимости от требуемого качества обработанных поверхностей. Имеющиеся многочисленные справочные материалы такого характера получены в лабораторных условиях, носят дискретный характер, не учитывают специфическую топографию поверхностей абразивных инструментов и множества других условий и поэтому недостаточно достоверны. На их основе возможно планировать технологический процесс только предварительно, а затем неизбежно требуется уточнять его параметры экспериментальным путем, что приводит к значительному удорожанию процесса подготовки производства. Наличие достоверной аналитической методики позволяет кратно снизить эти затраты, и поэтому она настоятельно необходима не только и даже не столько при выполнении научных исследований, сколько в реальном производстве. В статье аналитически определены параметры микрорельефа, образующегося в результате бесцентрового шлифования полной сферы. Уточнено влияние процесса выхаживания на формирование шероховатости сферы. Приведена методика расчета среднеарифметического отклонения микропрофиля сферической поверхности In the technological preparation of the operations of finishing processing of parts with abrasive tools, it is very important to predict its results depending on the assigned modes and the purpose of modes depending on the required quality of the processed surfaces. The available numerous reference materials of this nature were obtained in laboratory conditions, are discrete in nature, do not take into account the specific topography of the surfaces of abrasive tools and many other conditions, and therefore are not reliable enough. On their basis, it is possible to plan the technological process only in advance, and then inevitably it is necessary to refine its parameters experimentally, which leads to a significant increase in the cost of the production preparation process. The availability of a reliable analytical method allows you to multiply these costs, and therefore it is urgently needed not only and even not so much when performing scientific research, but in real production. In the article, we analytically determine the parameters of the microrelief formed as a result of centerless grinding of a full sphere. We determined the influence of the nursing process on the formation of the sphere roughness. We present a method for calculating the arithmetic mean deviation of the micro-profile of a spherical surface

Conditions for a pure toroidal dipole source

Recently, the physical significance of dynamic toroidal multipoles in the context of electrodynamics has been put under discussion. Indeed, the latter can be shown to arise simply from a Taylor series of the exact source (Cartesian) multipole moments. The split into elementary and toroidal parts was demonstrated to lead to an unphysical result were forbidden components of the momentum transform of the current could radiate into free space. In this contribution, we elaborate the conditions that a current distribution must necessarily satisfy to be considered a ‘pure’ toroidal dipole source. We demonstrate for the first time that symmetry prevents such current distribution to radiate as an elementary electric dipole moment, without leading to an unphysical result. Thus, while both elementary electric dipole and toroidal dipoles are indistinguishable outside the source, they display topologically distinct characteristics within the smallest spherical surface enclosing the source itself and have different physical origin. Based on our results, a pure ‘toroidal’ source can be designed. We believe the outcome of our investigations will help clarify further the formal meaning of the toroidal multipoles.

Deformation measurement by single spherical near-field intensity measurement for large reflector antenna

This paper presents a new method to obtain the deformation distribution on the main reflector of an antenna only by measuring the electric intensity on a spherical surface with the focal point as the center of the sphere, regardless of phase. Combining the differential geometry theory with geometric optics method, this paper has derived a deformation-intensity equation to relate the surface deformation to the intensity distribution of a spherical near-field directly. Based on the finite difference method (FDM) and Gauss-Seidel iteration, deformation has been calculated from intensity simulated by geometrical optics (GO) and physical optics (PO) methods, respectively, with relatively small errors, which prove the effectiveness of the equation proposed in this paper. By means of this method, it is possible to measure the deformation only by scanning the electric intensity of a single hemispherical near-field whose area is only about 1/15 of the aperture. The measurement only needs a plane wave at any frequency as the incident wave, which means that both the signals from the outer space satellite and the far-field artificial beacon could be used as the sources. The scanning can be realized no matter what attitude and elevation angle the antenna is in because the size and angle of the hemisphere are changeable.