State of research and development of small spacecraft with optical communication

The current state of scientific and technical research and development of small space vehicles using optical communication systems is considered. The problems standing in the way of creating intersatellite optical communication are discussed as well as the mutual position of satellites determination and it tracking. Scientific tasks for the implementation of the development of an optimal reliable control system for satellite communication are defined.

Experimental study of the resistance to the movement of trimaran vessels

The aim of the work is to develop a method for finding the resistance of a trimaran ship at the initial stages of design, depending on the geometric characteristics of the central hull, outriggers and their mutual position. The program of model tests in the experimental tank is characterized. Based on the analysis of the experimentally obtained data, the graphs of the resistance dependence on the Froude number for the trimaran ship model with the fore, central and stern arrangement of outriggers are presented. A graph of the outriggers’ location influence along the vessel length on its hydrodynamic resistance is also shown. A method for calculating the hydrodynamic resistance for a trimaran vessel at the stages of research design is proposed, which is an adjustment of a single-hull vessel model tests’ recalculation classical principle. One of the developed graphs of the residual drag coefficient dependence on the relative speed according to the Froude number for various central hull geometric characteristics of the vessel, outriggers and their relative position is presented. The analysis of serial model tests made it possible to establish the dependence of the trimaran ship resistance on the geometric characteristics of the central hull and outriggers, and their relative position relative to each other in this study. The method proposed in this work will make it possible to substantiate the best layout of outriggers when solving the problem of optimizing the design elements and characteristics of a trimaran at the research design stage.

Geometric Locations of Points Equally Distance from Two Given Geometric Figures. Part 4: Geometric Locations of Points Equally Remote from Two Spheres

The article deals with the geometric locations of points equidistant from two spheres. In all variants of the mutual position of the spheres, the geometric places of the points are two surfaces. When the centers of the spheres coincide with the locus of points equidistant from the spheres, there will be spheres equal to the half-sum and half-difference of the diameters of the original spheres. In three variants of the relative position of the initial spheres, one of the two surfaces of the geometric places of the points is a two-sheet hyperboloid of revolution. It is obtained when: 1) the spheres intersect, 2) the spheres touch, 3) the outer surfaces of the spheres are removed from each other. In the case of equal spheres, a two-sheeted hyperboloid of revolution degenerates into a two-sheeted plane, more precisely, it is a second-order degenerate surface with a second infinitely distant branch. The spheres intersect - the second locus of the points will be the ellipsoid of revolution. Spheres touch - the second locus of points - an ellipsoid of revolution, degenerated into a straight line, more precisely into a zero-quadric of the second order - a cylindrical surface with zero radius. The outer surfaces of the spheres are distant from each other - the second locus of points will be a two-sheet hyperboloid of revolution. The small sphere is located inside the large one - two coaxial confocal ellipsoids of revolution. In all variants of the mutual position of spheres of the same diameters, the common geometrical place of equidistant points is a plane (degenerate surface of the second order) passing through the middle of the segment perpendicular to it, connecting the centers of the original spheres. The second locus of points equidistant from two spheres of the same diameter can be either an ellipsoid of revolution (if the original spheres intersect), or a straight (cylindrical surface with zero radius) connecting the centers of the original spheres when the original spheres touch each other, or a two-sheet hyperboloid of revolution (if continue to increase the distance between the centers of the original spheres).

Mathematical solutions to the problem of creating basic decenter optical mirror models from the coma and astigmatism correction conditions

A serious drawback of reflective optics is a center without central screening that degrades the image quality. To eliminate it, rotations or displacements of mirrors are introduced, but there appear even-order non-elementary aberrations that must be corrected. The creation of compositions with decentered catoptric elements requires further development of the calculation and methodological base. The exact formulas are obtained for calculation of real rays from the astigmatism and coma correction conditions for the given angles of incidence of the main ray on the mirror surfaces and the “oblique” thickness d, that determines their mutual position. Based on the proposed formulas, a new method for parametric calculation of decentered mirror systems has been created, which allows one to compose algorithms and to design both basic models and complex mirror systems from off-axis mirrors. The development of new algorithms for two- and three-mirror off-center lenses will increase the accumulated potential of computational optics. The scope of the proposed technique can be expanded in terms of the number of components.

Evaluation of Selected Thermal Changes in Textile Materials Arising in the Wake of the Impact of Heat Radiation

The detection of changes in the morphological and chemical structure of four cotton/polyester blend fabrics and their constituent fibres caused by thermal radiation was the purpose of the study. Relatively short exposure times, i.e., 20 s, 25 s, 30 s and 40 s, of fabrics for an incident heat flux density of 10 kW/m2 were applied so that they did not cause changes visible to the naked eye. Such experimental conditions have been selected to resemble the ones that may occur during firefighting, rescue operations, some professional activities as well as during criminal events. The assumption that using the sequence of physicochemical methods, i.e., optical microscopy, scanning electron microscopy and FTIR spectroscopy, will make it possible to identify selected thermal changes in examined materials caused by a short-term temperature increase has been positively verified. Out of applied techniques, scanning electron microscopy showed the highest efficiency in tracking morphological changes in fibres occurring under the influence of heat radiation, while the FTIR method allows for the identification of thermal changes in the chemical structure of cotton fibres. Optical microscopic methods were also characterised by relatively high usefulness in the detection of thermal changes, especially in terms of the physical microstructure of PES fibres. The changes occurring in the fibres due to the action of heat radiation depend not only on the thermal behaviour of a particular type of fibre but also on the structural parameters of the examined textiles, i.e., porosity, and the mutual position of particular types of fibres in the three-dimensional structure of yarns and fabrics. Moreover, the studies revealed the presence of tiny, deformed balls at the ends of the thermoplastic fibres, visible on the surface of some original polyester-cotton textiles, caused by a singeing technological process, which should be taken into account during interpretation of analytical findings.

International cooperation of S. I. Subbotin Institute Geophysics, NAS of Ukraine for 2010—2020

The geological structure of the lithosphere of the main tectonic structures has been refined for the territory of Ukraine and adjacent regions of Slovakia, Poland, Romania, Russia, as well as Bulgaria, the Antarctic Peninsula (West Antarctica) and Southeast Asia, and new data have been obtained on geophysical impacts that can affect the environment. A geodynamic scenario has been developed for the formation of large-scale folding of the Fore- Dobrudzja Trough, the South Ukrainian monocline and the Ingul block of the Ukrainian Shield, caused by tectonic events associated with the closing of the Paleotethys and Neotethys oceans in the Mesozoic. In the Pripyat-Dnieper-Donets Basin, the structure of the earth’s crust and upper mantle can reflect different intensities of rifting, from its passive stage in the Dnieper Graben to active rifting in the Pripyat Trough. An analysis of the geoelectric structure of the Earth’s crust in the Ukrainian Eastern Carpathians indicates that seismic events occur mainly in resistive solid rock domainswhich surrounded by aseismic high conductive zones consisting of at least partially melted material. The present-day mutual position of the Ukrainian shield and Fennoscandia stabilized 1720—1660 Ma. The age, distribution, orientation and composition have been studied for the LatePalaeoproterozoicdykes in the Volyn, Ingul and Azov blocks of the Ukrainian Shield. Eastern Crimea and the Sorokin Trough are fragments of a tectonic wedge formed after the Paleocene. The geothermal conditions of the Intra-Carpathian region are due to subduction during the closure of the Pannonian sea basin and the collisional interaction of the Eurasian plate with the microplates system of this region. In Bulgaria, most earthquakes occur outside high-resistive domains. The tectonic stages are reconstructed for the formation of the northern part of the Antarctic Peninsula in the Mesozoic-Cenozoic. The relationship has been established between the geomagnetic field and climate change, with it being different for the Northern and Southern Hemispheres. The results have been obtained within the framework of 25 international projects and 6 temporary international target teams of S. I. Subbotin Institute of Geophysics, NAS of Ukraine consisting of researchers from 23 countries. The results are presented in 53 publications, 38 of which are indexed in the Web of Scienct database, and 32 papers are published in 20 international journals and special publications of 10 countries with different impact factors (from 0,101 to 4,214), whose average impact factor is 3,341, and the total one is 66,815.

The Off-Line Simulation on Measuring through Software PC-DMIS CAD++ V4.3

The article analyses and evaluates the ever-important topic of assessing geometric deviation of tolerated formations related to bases with the usage of coordinate measuring machines. The basic system for off-line simulation consists of the coordinate planes of a component’s coordinate system. At the beginning of the measurement, the coordinate system is created by the “3–2–1“alignment. Due to production deviations in real surfaces of the component, each measurement generates mutually different coordinate systems, which is well proven by the experiment on measuring with a coordinate measuring machine DEA Global Performance 12.22.10. An integral part of the article is also the quantification of geometric deviations of ideal tolerated formations related to bases, the estimate of the uncertainty of measurement arising from the placement of points in defining the base system, and the effect of such uncertainty upon the interval of satisfactory values in conformity with the STN EN ISO 14253-1 technical standard. The article also includes a proposal measure in order to ensure the reproducibility of defining the mutual position of coordinate systems.

An Electromagnetic Energy Harvester of Large-scale Bistable Motion by Application of Stochastic Resonance

Vibrational energy harvesting has attracted considerable research attention for electrical power collection from ambient vibrations. Thereby, this study firstly developed an electromagnetic energy harvester of large-scale bistable motion by application of stochastic resonance, to enhance energy harvesting efficiency at a broadly low frequency. The electromagnetic energy harvester is fabricated by a magnet-coil generator and an oblique-supported spring-mass system. In the beginning, a weighting function is originally proposed considering mutual position relationship of the magnet and coil, and a motion equation and an electromagnetic induction equation are simultaneously established considering both elastic spring recovery force and electromagnetic induction Lorentz force. Subsequently, numerical analysis is processed to resolve the simultaneous equations to obtain systematic response displacement and the induced voltage, and the numerical solutions are accurately consistent with the measuring results in validation experiments. Furthermore, a damping coefficient is identified considering the mutual effectiveness of the damping forces from the normal friction and electromagnetic induction, and the influence of electromagnetic induction damping on systematic response displacement is carefully discussed. Eventually, experimental results clarified that the stochastic resonance phenomenon actually occurred as a large-scale bistable motion, and it is further validated that power generation efficiency can be noticeably enhanced following amplitude amplifications of systematic response displacement.