APPLICATION OF OPTICAL DIFFRACTOMETRY FOR THE ERROR MONITORING OF MANUFACTURING OF PRECISION OPTICAL ELEMENTS

The work is devoted to an experimental study of the effectiveness of the method for measuring errors in manufacturing of computer-generated synthesized holograms using specialized marks. Each mark represents two aligned diffraction gratings with the same duty cycle and period, the first of which is formed before writing, and the second is formed in the process of forming the structure of the hologram. To determine the writing error, the method of optical diffractometry was used. The results of an experimental study of dependence of diffraction efficiency of the mark on the mutual displacement of parts of the microgratings are presented. The error manufacturing of a synthesized hologram arising during long-term writing of a diffractive optical element has been simulated experimentally.

ВИВЧЕННЯ ПРОЦЕСУ ОДНОВІСНОГО РОЗТЯГУ ТРИКОТАЖУ ПЕРЕПЛЕТЕННЯ ЛАСТИК РІЗНИХ РАПОРТІВ

Study of the process of deformation of rib knits, which occurs due to the application of tensile forces in the course direction. Methodology. During the study, methods of theoretical analysis, a camera, a stretching frame, Microsoft Excel software and Autodesk AutoCAD were used. Findings. For producing rib knit samples, a 10th class flat-bed knitting machine PVRK was used. Samples of knitwear were made with repeatable unit patterns of 1x1, 2x2, 3x3, 4x4, 5x5 and 6x6 from bamboo yarn of linear density 29x2 tex, woolen yarn 32x2 tex, half-woolen yarn 31x2 tex and Polyacrylonitrile yarn 32x2 tex. To carry out uniaxial stretching of knitted fabric samples along the line of stitch rows, a stretching frame was used. After fixing the opposite ends of the sample on the needle set of the frame holders, the distance between them gradually increased with an interval of 20 mm. At each stage of stretching, the samples were photographed together with a calibration ruler. Sample photos imported into Autodesk AutoCAD software. After calibration, for each state of stretching of the sample, such characteristics were determined as: the average value of the width of the repeatable unit pattern, the average value of the width of the convex part of the pattern, as well as the visible section of its concave part. The study showed that at the first stages of stretching, there is a mutual displacement of the sections of the pattern, belonging to different layers of knitwear and a decrease in the twisting of the sections of the smooth surface. Further application of the tensile force leads to a more uniform deformation of the ivestigated structural parts of the pattern. Scientific novelty. The change in the geometric characteristics of rib knits with various repeatable units patterns made from various types of raw materials is experimentally determined. Practical value. The characteristics of knitwear, obtained in the course of the study, were used to form a database necessary for the construction of three-dimensional models of rib knits with bamboo, woolen, semi-woolen, and polyacrylonitrile yarns.

Structural Deformation of a Running Wind Tunnel Measured By Optical Scanning

Nowadays, the development of wind tunnels for the study of various aerodynamic phenomena is actively developing. It is possible to generate a highly laminar flow only under the condition of structural stability of the construction parts of the wind tunnel under the action of sharp pressure drops. The aim of this research is to investigate the deformation and displacement of the structural parts of the developed wind tunnel capacity of 55 kW depending on the velocity of the generated airflow. To estimate the amount of deformation and mutual displacement of the structural elements of the wind tunnel depending on the airflow velocity, we used the ARAMIS optical system.

TWISTING RIGIDITY OF REINFORCED CONCRETE ELEMENTS OF I–BEAM SECTION WITH INCLINED CRACKS

The article shows that to determine the torsional stiffness of the element, you must first cut the reinforcement at the site of the inclined crack. After dissecting the reinforcement, the mutual displacement of the crack edges should be determined. This problem is the main and most difficult in the general problem of determining the torsional stiffness of elements with both normal and inclined cracks. The article is devoted to the solution of this most difficult part of the problem ‒ the determination of the mutual displacement of the banks of the inclined crack of the I-beam element. According to the proposed method, the real element with an inclined crack is replaced by an element with different stiffness in sections. Within an inclined crack, the element has a real slope equal to the slope of the inclined crack. In the area behind the apex of the inclined crack, it is hypothesized that the cross-sectional height of the element varies from a height equal to the height of the zone above the crack to the full cross-sectional height. And change of height occurs according to the law of a straight line. This line is inclined at some angle to the horizontal. It is shown that if we take the angle of inclination of this line equal to 45 degrees, the results are quite accurate. The equivalent section height is defined as the average value between the height above the inclined crack and the total section height. The equivalent torsional stiffness of the element on the section of the sloping line is taken equal to the stiffness of the element with a conditionally constant stiffness at a constant height equal to the equivalent. It is also shown that the calculation according to the proposed method differs from the calculation of an element with a normal crack only in that in the left part in the case of an inclined crack there is a section with a real slope of the section. The rest of the problem is identical. The comparison of calculations by the proposed method with the calculation data in the Lear program using volumetric finite elements is given. The comparison showed a good match of the data.

ON THE ESSENCE, THE PLACE, THE PART AND CHARACTER OF THE TASKS WITH PARAMETERS IN THE GEOMETRY COURSES OF THE INSTITUTIONS OF GENERAL SECONDARY EDUCATION

The so-called tasks with parameters for a long time now have become an integral part as of the every to some extent profound course of algebra or of algebra and the beginnings of cultures at the institutions of general secondary education, as of the corresponding tasks of the State Final Attestation in Mathematics and the External independent assessment in mathematics. And it isn’t accidental because in the most often cases the solution of the task with a parameter turns for the student into a small investigation by his own. The realization of such investigation favors the formation of the creative practical-oriented personality. Simultaneously we must state that, despite of the existence of a lot of the high scientific and methodical level created corresponding training books, it is difficult just now to find in the methodical literature the clear answers to the natural questions of what is meant on the whole by the task with parameter (or with parameters) and its solution. At the same time, in the courses of geometry of the institutions of general secondary education to the tasks with parameters it is given next to nothing consideration. But in fact such tasks in the courses are present, their importance for the proper construction of the courses can be exaggerated. In the paper the problems of what must be understand by the task with the parameter or with the parameters and by its solution are analyzed. The essence, the part and the place of the tasks with parameters in the geometry courses of institutions of general secondary education are elucidated. Euclidean geometry as an axiomatic theory investigates the sets that in their overwhelming majority represent by themselves the mathematical abstructions of the spatial forms of the surrounding, some relations between such set and quantities that characterize such sets and relations. In the contrast to the courses of algebra, in the geometrical courses the part of parameters may be played by all of the three mentioned components. Geometrical figures can change by the size and by the form. Changing by the size bring us to the concept of the scalar quantity. Changing by the form are considered in the tasks of paving and, for example, in the tasks of finding the amount and the types of symmetries of geometrical figure in dependence of its form. The part of the parameter-relation can be played by different variants of mutual displacement of the given figures in Euclidean plane or in Euclidean space. According to their content, different geometrical tasks with parameters are considered in the work. The task of the existence of geometrical figures, the tasks, conserning the character of some geometrical places of points, the tasks of tracing with the help of a compass and a ruler are among them.

Композиционный радиопоглощающий материал на основе резистивных квадратов

On the basis of the solution of the diffraction problem, the effective permittivity of the composite material consisting of alternating planar lattices of resistive squares displaced relative to each other and located in the dielectric layer is calculated. It is shown that the dispersion has a relaxation character. It is shown that it is possible to vary the dispersion characteristic over a wide range by varying the parameters of the structure. It is shown that the mutual displacement of lattices significantly changes the dispersion of the dielectric constant of the structure. The ratio of the wavelength to the period of the structure is estimated, at which the homogenization procedure is adequate.

Using ARAMIS system for measurement of structural stability of running wind tunnel

Wind tunnels are popularly used to study various aerodynamic phenomena. Their design significantly influences the quality of the created airflow. During the flow generation, the construction parts of the wind tunnel to get deformed due to pressure variations. This phenomenon significantly complicates the creation of high-level laminar flow and worsens the results of experimental studies. The main purpose of this work is to investigate the effect of a sharp change in flow velocity on the structural stability of parts of a wind tunnel with a capacity of 55 kW. For experimental studies, we used the ARAMIS optical measurement system. Using it, we estimated the amount of deformation and mutual displacement of parts of the running wind tunnel at a flow rate of 76 m·s-1.

Underground pipeline stresses caused by damage near anchor mounting

The article considers the issues of underground pipeline strength, which are operated in geological or technogenic complication conditions (movements of indigenous soil in the tectonic fault zone, mutual displacements and rotations of rock blocks, etc.). The work aims at studying of a mobility limitation effect of a pipeline anchorage imposed on the stress state in the pipe wall in the site of a local damage foundation. The pipeline static was investigated in a geometrically linear formulation, modeling it with a tubular cross-section, and with a momentless cylindrical shell for straight issues. The interaction of the pipe with a dense base through soil backfill was described by the hypothesis of Winkler's elastic layer. The deformation of the anchored pipe caused by base local continuity disturbances was studied, which was modeled by the given jumps of longitudinal displacement and the block angle of rotation. This approach makes it possible to evaluate the strength of long underground communications not on the external load from the ground, which is usually unknown, but according to the observed parameters of riverside movements. The limiting state of the pipeline under the internal pressure of the transported product and under additional loading from kinematic perturbation was investigated by the energy theory of strength. The authors formulated boundary value problems for differential tensile-compression equations and torsion of a straight bar with discontinuous right-hand sides. On the basis of analytical solutions to the problems, the effect of normal separation crack damage, foundation blocks convergence and their turn around the axis of the pipe on the stress-strain state of the pipeline was studied. Plots of displacement distribution, angles of rotation and equivalent stresses of von Mises are constructed depending on the magnitude and direction of the mutual displacement and reversal of the riverside at different distances from the anchor to the base defect. It has been found that overlapping anchors in the form of anchorage leads to a significant increase in the equivalent stresses in the pipe. It has also been found that for pipes under internal pressure, the approximation of the base blocks is more dangerous than their divergence.

Effects of Bifidobacterium bifidum in Mice Infected with Citrobacter rodentium

In vitro and in vivo studies suggest that selected Bifidobacterium bifidum strains sustain intestinal homeostasis. This study aimed to examine whether the administration of B. bifidum MIMBb75 (BB75) attenuates Citrobacter rodentium infection, a murine model for enteric infection and inflammatory bowel disease in humans. C57Bl6/J mice were randomized to receive BB75 daily starting before or after C. rodentium infection. BB75 load and infection kinetics were monitored. On day 10 post-infection (p.i.), histological parameters of the large intestine were assessed. Barrier integrity was evaluated by pathogen translocation to secondary organs and in vivo permeability test. Fecal C. rodentium load peaked at 1010 CFU/g at day 10 p.i., with clearance at day 24 p.i., regardless of probiotic treatment. BB75 administration resulted in 107 cells/g of feces with no effect of timing of administration. BB75 treatment did not attenuate C. rodentium-induced crypt hyperplasia nor inflammation. C. rodentium and BB75 can co-exist in the gut with no mutual displacement. However, BB75 cannot counteract C. rodentium pathology. Our findings provide insight for the understanding of probiotics behavior and their clinical relevance in intestinal inflammation.

Внутреннее трение на границах зерен, содержащих протяженные поры

A model of internal friction at a grain boundary containing equidistant parallel cylindrical pores is presented. Variable shear stress induces a mutual displacement of the interfacial regions matched at the segments between pores depending on their position. The values of scattered energy at each segment and total internal friction are determined. The temperature dependence of the internal friction has a form of a wide peak.