Introduction. When milling complex-profile surfaces of parts, the selection of tool trajectories and orientations affect the roughness parameters. However, in the studies devoted to the formation of trajectories, recommendations to provide the quality of microgeometry of surfaces were not taken into account. Moreover, when writing programs for CNC equipment in CAM systems, the limitations of cutting modes were determined exclusively using a geometric approach. It did not take into account the influence of the orientation angles of the sphero-cylindrical tool relative to the normal plane on the quality of surface treatment, namely on roughness. The work was aimed at the creation of the methodology for selecting the limiting values of the orientation angles of a sphero-cylindrical tool to optimize the process of machining spatially complex surfaces.  The  tasks  included  achieving  the  minimum  values  of  the  amplitude  roughness  parameter  Rz and determining the effectiveness of various machining paths.

Materials and Methods.  Methods  of  correlation  and  regression  analysis  were  used,  the  results  were  compared  and generalized. The least-squares method was applied to estimate the parameters of the regression equation. The DMU 50 ecoline  processing  center  was  used  for  the experimental  studies.  Roughness  was  measured  on  a  Surfcam  1800  D profilometer. The material of the samples was steel 12X18N10T. The material of the tool was hard alloy 1620 Sandvik with PVD coating (physical vapor deposition, the closest domestic analogue is T15K6).

Results. It has been shown in detail how roughness parameters Rz depend on the angle of inclination and the diameter of the tool. Twenty examples were summarized in a table. Natural regression coefficients were calculated using linear and hyperbolic models. It was found that the diameter of the tool had a greater effect on the formation of roughness parameter Rz than the angle of inclination. For a detailed description of the influence features, the coefficients of multiple, partial, paired correlation and multiple determination were compared. The limitations associated with the angles of inclination of the  tool  when  processing  complex  surfaces  were  determined.  A  scheme  for  calculating  the  angle  of  the  normal  was visualized, which included the selected step along the axis to determine the lengths of the segments of the broken curve. The profilograms of surfaces obtained with different shaping trajectories were given in the form of drawings. This allowed us to conclude that milling from top to bottom is unsuitable when the tool is tilted 5°– 35°. A map has been compiled by which it is possible to judge the roughness, knowing the type of milling and the inclination angle (from 5° to 80 °). The dependence of the roughness parameter on the processing speed and the use of coolant was represented graphically. The calculated parameters for determining the optimal angle of inclination of the tool were tabulated. Their analysis proved the adequacy of the proposed method of preparing control information.

Discussion and Conclusion. The presented technique made it possible to determine the optimal values of the orientation angles of the sphero-cylindrical tool, taking into account the cutting speed and the minimum possible amplitude roughness parameter Rz. The pattern of feeding fz = 0.4 mm/tooth for surface areas with a total angle of 5°– 50°was considered. In this case, processing along trajectories in the passing, opposite and bottom-top directions, provided roughness in the range of 3–6 µm according to parameter Rz. The top-down toolpath is not recommended for use in final operations due to the significant height of parameter Rz.

Introduction. In recent years, one of the main trends in the field of testing road structures has become field study of their large-scale models at the accelerated load facility (ALF). It can significantly reduce the cost of selecting the most economical  and  durable  pavement  designs.  However,  the  results  obtained  on  the ALF  are  often  relative,  since  they practically do not correlate with the results of laboratory and field tests on real objects. This study is aimed at a comprehensive investigation of the response of a road structure to a dynamic load, the establishment of patterns of fatigue failure of asphalt concrete layers during the accelerated testing and full-scale tests on real objects.

Materials and Methods. During testing, an accelerated load facility was used, located on the territory of the ShanDong Transport University. When conducting field tests, a dynamic loading unit with a falling weight FWD Primax 1500 was used, which recorded the deflection bowl on the surface of the structure under study. To record the dynamic response in the arrangement of the road structure, a complex of strain gauge sensors was used, which made it possible to register both compressive stresses and tensile strains in different layers. The results obtained under natural conditions were compared to the results obtained on the mathematical FEM model.

Results. The research results have shown that the thickness of the lower coating layer is the main factor affecting the amount of vertical deformation of the pavement, which must be taken into account at the design stage of the pavement structure. Thus, with a thickness of the upper layer of the base of 10 cm, the vertical deformation was 100 µm, and with a thickness of 20 cm – 55  µm,  provided  that  the  overall strength of the structure was ensured. The number of load application cycles on the ALF had a minimal effect on the selected asphalt concrete samples during split tensile tests.

Discussion and Conclusion. The adequacy of the results obtained in the course of accelerated testing of road structures was shown through a comprehensive comparison of numerical simulation data and full-scale tests, and the adequacy of the applied calculation methods was validated. The results of the study can be further applied in the road industry to develop and improve the regulatory framework for the design of non-rigid pavement under conditions of increased loads and heavy traffic.

Introduction. The task of analyzing the stability of plates and shells under creep conditions is critical for structural elements made of materials with the property of aging, which are under the action of long-term loads, since the loss of stability can occur abruptly and long before the exhaustion of the strength resource of the material. Currently, the issues of joint consideration of geometric nonlinearity and creep in the problems of buckling plates remain poorly studied, existing software systems do not provide such calculations. The objective of this work is to develop an algorithm for calculating the stability of rectangular plates with initial deflection, which are subjected to loads in the middle plane, taking into account geometric nonlinearity and creep.

Materials and Methods. When obtaining the resolving equations, the geometric and static equations of the theory of flexible elastic plates were taken as the basis. Physical equations were derived from the assumption that total strains were equal to the sum of elastic strains and creep deformations. Finally, the problem was reduced to a system of two differential equations, in which the desired functions were the stress and deflection functions. The resulting system of equations was solved numerically using the finite-difference method in combination with the method of successive approximations and the Euler method. As the boundary conditions for the stress function, the frame analogy was used, as in the case of a plane problem of elasticity theory.

Results. The solution to the problem for a plate compressed in one direction by a uniformly distributed load has been presented. The nature of the growth of displacements at different load rates and initial deflection was studied. It has been established that when the vertical displacements reach values comparable to the thickness of the plate, their growth rate begins to decay even at a load greater than the long-term critical one.

Discussion and Conclusion. The results of stability analysis using the developed algorithm show that the growth of plate deflection under the considered boundary conditions is limited, stability loss is not observed at any load values not exceeding the instantaneous critical one. This indicates the possibility of long-term safe operation of such structures with a load less than instant critical one.

Introduction. The performance and reliability of gerotor hydraulic machines depend on the geometry of the cycloidal gearing  profile.  The  existing  methods  of  calculating  and  optimizing  the  profile  parameters  are  cumbersome,  multicriteria and difficult for practical application. Therefore, the problem of creating the methodology for calculating the parameters of the gerotor machine profile suitable for engineering calculations at the stage of conceptual design is a challenge. In this regard, the objective of this work was to modernize the methodology for designing the geometry of the profiles of the end section  of  hypocycloidal  gears  used  in  gerotor  hydraulic  machines,  and  to  analyze  the possibilities of their optimization during preliminary design. In  the  course  of  the  study,  the  Mathcad  computer mathematics  system  was  used; numerical  experiments  were  carried out to study the influence of geometric profile parameters  on  the  performance  and  operability  of  the  gerotor  hydraulic  machine,  based  on  the  data  obtained  and analyzed; recommendations for the design of optimal profiles of the end section of gerotor hydraulic machines were developed.

Materials and Methods. Materials included known methods of profile parameters calculation, based on application of classical  formulas  of  hypocycloidal  equidistant  used  for  outlining  profiles  of  teeth  of  working  elements  of gerotor machines. The basic research method was modeling the gerotor machine profile using Mathcad computer mathematics system. Calculated data were obtained for the selected ranges of varying parameters, processed through the univariate regression analysis.

Results. An algorithm for analyzing the tooth profile smoothness was developed. Two target parameters were defined: the cross-sectional area of the end profile, which affects the productivity; the smallest reduced radius of contact that determines operability  of  the  working  body.  A  technique  for  calculating  the  target  parameters  at  the  early  stage  of design was proposed. A number of optimal values of profile parameters according to the criteria of productivity and operability of gerotor machine was obtained. The dependences providing the optimum values of profile parameters at the stage of designing were constructed.

Discussion and Conclusion. The developed methodology makes it possible to obtain an assessment of the performance and operability of the gerotor hydraulic machine at the design stage of the working body. The research results can be used  in  mechanical  engineering  when  designing  gerotor  hydraulic  machines  in  order  to  improve  their  technical  and operational characteristics.

Introduction.  Long-stroke  movements  in  automated pneumatic  drives  account  for  a  significant  number  of  executive movements  in  coordinate  tables,  automated  warehouses,  cutting  machines,  etc. Long-stroke  movements  degrade  the dynamic quality and positioning of the drive. This is due to the friction of the piston and the nonlinear characteristics of the compressed gas flow in significant volumes of the pressure and drain cavities of the cylinder. Thus, it seems promising to create an automated position pneumatic actuator for long-stroke movements. This will increase the productivity of processes  while  providing  the  declared  accuracy.  The  objective  of  the  work  is  to  obtain  a  mathematical  model  and dependences of the critical parameters of the proposed automated position long-stroke pneumatic drive of fabrication system in the areas of acceleration, steady-speed movement, deceleration, and braking.

Materials and Methods. The basis for calculations and modeling was the scheme of two trajectories of movement from point A to point E, taking into account the forces expended on these processes. The optimal displacement was determined using the Portnyagin’s principle (i.e., optimal performance). Proportional drive control was presented as a method of achieving the result. For long-stroke drive movements, schematic solution and design scheme were visualized in detail (presented as drawings). An original jet sensor with an internal pneumatic connection and a pneumo-mechanic discrete-proportional device for the control loop performance were proposed. The mathematical model included the movement and braking of the piston, the balance of mass flow, the pressure at points, and the control loop. The system of equations was solved by the Runge — Kutta method in the SimInTech software product. Based on the results of the study of a generalized mathematical model, the dependences of changes in the kinematic, power and pneumatic properties of the drive were constructed in real time during a typical positioning cycle. The information was summarized and presented as a set of graphs.

Results. The mathematical model was formed according to a set of calculations. It took into account the dependences characteristic of the movement of the piston of the pneumatic cylinder. The balance of mass flow was investigated by the equations of gas flow during compression in the chamber, through distributors and throttles, in the discharge and drain cavities and in the control device. Inequalities describing the pressures at the points and the control loop were considered. A complex mathematical model was solved in the SimInTech software environment by the Runge — Kutta method with a variable integration step. A fragment of the program was selected as one of the illustrations. It showed that the software used the following indicators for calculations: target and reduced coordinates; absolute gas constant; coefficients of spring stiffness, resistance, adiabatic and viscous friction in the piston; compressor pressure; mass of the moving parts of the pneumatic actuator; strength of external resistances; diameters of the pipeline, the pneumatic cylinder piston and the braking device; length of the stroke of the cylinder piston; area of piston cavities and throttles; length of the pipeline and its internal volume. Thus, the program manipulated a significant set of data, which made it possible to obtain meaningful and adequate results. The relationship of blocks and diagrams used in solving the model was schematically shown. We are talking about graphs of movements, areas, pressures, velocities and temperatures. Blocks with the program text and intended for integration were used. Thus, a mathematical model of an automated pneumatic drive of the fabrication system and the dependences of the basic parameters of its operation were obtained. The graphs indicated that the operating mechanism of the pneumatic actuator properly followed the proposed trajectory.

Discussion and Conclusion. The research results allowed us to consider several stages of long-stroke movement of the drive, to determine the time frame of these processes (from 0 to 0.65s), as well as changes in pressure and speed of movement  of  the  pneumatic cylinder  carriage  recorded  in  these  intervals.  There  were  five  such  stages:  acceleration, steady-speed movement, deceleration, movement with positioning speed, and braking. Further research will focus on optimizing the system to reduce the duration and maintain accurate positioning under external influences.

Introduction. In  recent  decades,  knowledge  about  DNA  has  been  increasingly  used  to  solve  biological  problems (calculations using DNA, long-term storage of information). Principally, we are talking about cases when it is required to select artificial nucleotide sequences. Special programs are used to create them. However, existing generators do not take into account the physicochemical properties of DNA and do not allow obtaining sequences with a pronounced “non-biological” structure. In fact, they generate sequences by distributing nucleotides randomly. The objective of this work is to create a generator of quasirandom sequences with a special nucleotide structure. It should take into account some physicochemical features of nucleotide structures, and it will be involved in storing non-biological information in DNA.

Materials and Methods. A new GATCGGenerator software for generating quasirandom sequences of nucleotides was described. It was presented as SaaS (from “software as a service”), which provided its availability from various devices and platforms. The program generated sequences of a certain structure taking into account the guanine-cytosine (GC) composition and the content of dinucleotides. The performance of the new program algorithm was presented. The requirements for the generated nucleotide sequences were set using a chat in Telegram, the interaction with the user was clearly shown. The differences between the input parameters and the specific nucleotide structures obtained as a result of the program were determined and generalized. Also, the time costs of generating sequences for different input data were given in comparison. Short sequences differing in type, length, GC composition and dinucleotide content were studied. The tabular form shows how the input and output parameters are correlated in this case.

Results. The developed software was compared to existing nucleotide sequence generators. It has been established that the generated sequences differ in structure from the known DNA sequences of living organisms, which means that they can be used as auxiliary or masking oligonucleotides suitable for molecular biological manipulations (e.g., amplification reactions), as well as for storing non-biological information (images, texts, etc.) in DNA molecules. The proposed solution makes it possible to form specific sequences from 20 to 5 000 nucleotides long with a given number of dinucleotides and without homopolymer fragments. More stringent generation conditions remove known limitations and provide the creation of quasirandom sequences of nucleotides according to specified input parameters. In addition to the number and length of sequences, it is possible to determine the GC composition, the content of dinucleotides, and the nature of the nucleic  acid  (DNA  or  RNA)  in  advance.  Examples  of  short  sequences  differing  in  length,  GC  composition  and dinucleotide content are given. The obtained 30-nucleotide sequences were tested. The absence of 100 % homology with known DNA sequences of living organisms was established. The maximum coincidence was observed for the generated sequences with a length of 25 nucleotides (similarity of about 80 %). Thus, it has been proved that GATCGGenerator can generate non-biological nucleotide sequences with high efficiency.

Discussion and Conclusion. The new generator provides the creation of nucleotide sequences in silico with a given GC composition. The solution makes it possible to exclude homopolymer fragments, which improves qualitatively the physicochemical stability of sequences.

Introduction. Perianal fistula rapidly develops an abscess, requiring surgical decompression. However, simple cases must be managed. However, for patients with renal insufficiency, MRI with contrast is contraindicated. It is proposed to use diffusion-weighted images that can diagnose anal fistulae, showing areas of high signal intensity (inflammatory tissues). The aim is to determine sensitivity of diffusion-weighted image combined with T2 turbo inversion recovery magnitude and as an alternative technique to contrast-enhanced MRI using clinical examination as a reference.

Materials and Methods. Study included fifty patients with a clinical diagnosis of perianal fistula. MRI sequences were T2 turbo inversion recovery magnitude in oblique coronal and axial planes, diffusion-weighted image, and T1 weighted image turbo spin echo (fat suppression) pre- and post-administration of contrast agents in oblique axial planes. Three radiologists evaluated the MR imaging data using a questionnaire of parameters that necessitated a binary response, “yes” or “no” answer.

Results. Diffusion-weighted image combined with axial T2 turbo inversion recovery magnitude sequence had 96.7 %. All  raters  agreed  that  it  is  sensitive  enough  to  correctly  identify  perianal  fistula  with  a  moderate  Kappa  agreement (k = 0.586)  and  p-value<0.001.  The  mean  value  of  rater's  responses  was  76.7 %  represents  sensitivity  of  diffusion-weighted  images  + T2  turbo inversion recovery  magnitude  as  an  alternative  technique  to  T1-enhanced  contrast  with moderate (k = 0.553) agreement between raters and P-value<0.001.

Discussion and Conclusion. Diffusion-weighted images and T2 turbo inversion recovery magnitude sequences exhibit comparable efficacy to T1-enhanced contrast sequences in detecting perianal fistula. This may be an option for patients with renal impairment who cannot receive an MRI contrast.

Introduction. The analysis of approaches to tracking the human body identified problems when capturing movements in a three-dimensional coordinate system. The prospects of motion capture systems based on computer vision are noted. In existing  studies  on  markerless  motion  capture  systems,  positioning  is  considered  only  in  two-dimensional  space. Therefore, the research objective is to increase the accuracy of determining the coordinates of the human body in three-dimensional  coordinates  through  developing  a  motion  capture  method  based  on  computer  vision  and  triangulation algorithms.

Materials and Methods.  A  method  of  motion  capture  was  presented,  including  calibration  of  several  cameras  and formalization of procedures for detecting a person in a frame using a convolutional neural network. Based on the skeletal points obtained from the neural network, a three-dimensional reconstruction of the human body model was carried out using various triangulation algorithms.

Results. Experimental studies have been carried out comparing four triangulation algorithms: direct linear transfer, linear least squares method, L2 triangulation, and polynomial methods. The optimal triangulation algorithm (polynomial) was determined, providing an error of no more than 2.5 pixels or 1.67 centimeters.

Discussion and Conclusion. The shortcomings of existing motion capture systems were revealed. The proposed method was aimed at improving the accuracy of motion capture in three-dimensional coordinates using computer vision. The results obtained were integrated into the human body positioning software in three-dimensional coordinates for use in virtual simulators, motion capture systems and remote monitoring.

Introduction.  Environmental  problems  arising  in  shallow  waters  and  caused  by  both  natural  and  man-made  factors annually do significant damage to aquatic systems and coastal territories. It is possible to identify these problems in a timely manner, as well as ways to eliminate them, using modern computing systems. But earlier studies have shown that the resources of computing systems using only a central processor are not enough to solve large scientific problems, in particular, to predict major environmental accidents, assess the damage caused by them, and determine the possibilities of their elimination. For these purposes, it is proposed to use models of the computing system and decomposition of the computational domain to develop an algorithm for parallel-pipeline calculations. The research objective was to create a model of a parallel-conveyor computational process for solving a system of grid equations by a modified alternating-triangular iterative method using the decomposition of a three-dimensional uniform computational grid that takes into account technical characteristics of the equipment used for calculations.

Materials and Methods. Mathematical models of the computer system and computational grid were developed. The decomposition model of the computational domain was made taking into account the characteristics of a heterogeneous system. A parallel-pipeline method for solving a system of grid equations by a modified alternating-triangular iterative method was proposed.

Results. A program was written in the CUDA C language that implemented a parallel-pipeline method for solving a system of grid equations by a modified alternating-triangular iterative method. The experiments performed showed that with an increase in the number of threads, the computation time decreased, and when decomposing the computational grid, it was rational to split into fragments along coordinate  z  by a value not exceeding 10. The results of the experiments proved the efficiency of the developed parallel-pipeline method.

Discussion and Conclusion. As a result of the research, a model of a parallel-pipeline computing process was developed using  the  example  of  one  of  the  most  time-consuming  stages  of  solving  a  system  of  grid  equations  by  a  modified alternating-triangular  iterative  method.  Its  construction  was  based  on  decomposition  models  of  a  three-dimensional uniform  computational  grid,  which  took  into  account  the  technical  characteristics  of  the  equipment  used  in  the calculations. This program can provide you for the acceleration of the calculation process and even loading of program flows  in  time.  The  conducted  numerical  experiments  validated  the  mathematical  model  of  decomposition  of  the computational domain.