The article presents the results of testing samples of welded joints of polyethylene pipes for crack resistance at various temperatures. It is shown that in the weld zone a decrease in the stress intensity factor is observed up to 27% compared with the base material.

Keywords: Polymer, polyethylene, pipe, stretching, crack resistance, low temperatures, brittle failure, crack, welding, welded joint, fusion zone

In this article the comparative analysis of reinforcement of monolithic reinforced concrete plate under various conditions of calculation is made: without seismic actions, with design earthquake and with maximum design earthquake. It was found that taking into account the seismicity of 9 points without the use of methods of active seismic protection leads to an increase reinforcement to 28 % when taking into account the design earthquake and 81 % when calculating the maximum design earthquake. In addition, the analysis of the tool "Consumption of concrete and reinforcement" in the Lira-SAPR is made. The correction factor for the transition from theoretical to real reinforcement was obtained: it ranged from 2.4 to 3.0

Keywords: seismic impact, Lira-SAPR, maximum design earthquake calculation, frame calculation, slab, reinforced concrete, specific consumption of reinforcement

Durability of concrete, including fine-grained, with alternating cyclic temperature effect of the external environment is normalized according to GOST 26633 mark on frost resistance, and frost resistance criterion for all concrete in accordance with GOST 10060-2012 is the ratio of ultimate strength on compression of the main and control samples not less than 0.9 with a coefficient of variation of strength in the series, while for concrete road and airfield pavements is another additional criterion is the loss of mass. In the previous edition of GOST 10060, the ratio of the compressive strength of the main and control samples not less than 0.95 was adopted as the criterion of frost resistance for all concretes. GOST 31357 normalizes the indicator "frost resistance of the contact zone" for a number of mortars or fine-grained concretes obtained from dry building mixtures. This indicator characterizes the ability of the solution or fine-grained concrete to maintain the strength of adhesion to the concrete base after a certain number of freeze-thaw cycles. For the brand for frost resistance of the contact zone from Fkz25 to Fkz100, the number of cycles is taken, after which the decrease in the adhesion strength to the base does not exceed 20% according to GOST 31356, and in this case the coefficient of variation of the clutch values measured in the series is not taken into account. Due to the limited information on the change in the in-series coefficient of variation of strength after cyclic freezing-thawing, as well as the ratio of frost resistance by the criterion of compressive strength and adhesion strength to the base, the purpose of this study was to identify patterns of change in the in-series coefficient of variation of strength and adhesion strength to the base of fine-grained concretes obtained from dry building mixtures based on various Portland cements with the content of various redispersible polymer powders from 0 to 3%. The studies were carried out on the basis of 75 freeze-thaw cycles. This paper presents the results on the change in the coefficient of variation of strength after cyclic freezing-thawing and the ratio of frost resistance coefficients

Keywords: frost resistance of concrete, coefficient of variation of strength, coefficient of frost resistance, fine-grained concrete, dry mixes

The modeling of a hollow core slab in the finite element complex Ansys is considered. The construction of a 3D model is considered. Numerical modeling was carried out under static loading of the floor slab. The influence of material properties on the parameters of the stress state and deflection of the structure is investigated. Based on a numerical experiment, an approach to assessing the characteristics of a structure is constructed.

Keywords: hollow core slab, static analysis, modeling, FEM, Ansys, stress state, deflection

The article conentrates on the problem of synchronization the pseudo-noise sequence in direct sequence spread spectrum systems. Authors propose a method for transmitting information and synchronizing signals on a single carrier frequency, which allows data transmission in complex coditions in radio channel. A brief review of existing solutions for time synchronization direct sequence spread spectrum systems is carried out. The proposed solution is considered in terms of data transmission in broadband systems in the conditions of negative signal-to-noise ratio, while the limitations of the usage of this solution are also considered. A simulation of the scheme that implements the proposed synchronization method is carried out, and the requirements for the signal-to-noise ratio in the information and synchronization channels are determined. The proposed method can find application in systems with code division multiplexing, including modern IoT systems.

Keywords: time synchronization, direct sequence spread spectrum, broadband communication systems, Internet of Things, BER

Low-modulus inclusions in the form of entrained air or ash microspheres in the composition of fine-grained concrete practically do not affect the ratio of the ultimate strength in bending and compression during hardening of concrete under normal conditions. After 75 freezing-thawing cycles, the ratio of the flexural and compressive strengths of fine-grained concrete with ash microspheres did not change, and in concretes with involved air, the influence of factors such as the type and dosage of redispersible powder and the type of cement increased sharply. Low-modulus inclusions have practically no effect on the ratio between the initial elastic modulus and the compressive strength of fine-grained concrete during hardening under normal conditions. After 75 cycles of freezing and thawing in concrete with entrained air, the influence of such factors as the type and dosage of redispersible powder and the type of cement on the ratio of the initial elastic modulus to compressive strength increases sharply. The cyclic freezing-thawing does not affect on the ratio of module and strength in concretes with an ash microsphere. Regardless of the presence of low-modulus inclusions, there is no clear relationship between adhesion to a concrete base and flexural strength of fine-grained concrete. In concretes with entrained air, the increase in adhesion to the concrete base after 75 freezing-thawing cycles, depending on the type of cement and dosage of redispersible powder, was up to 82%, and for compositions with an ash microsphere, up to 62%. Regardless of the presence of low-modulus inclusions, after 75 freeze-thaw cycles, adhesion to the base corresponds to class C-1. With an increase in the dosage of redispersible powder from 0 to 3% in compositions with low-modulus inclusions, an increase in adhesion to the base was noted up to 62%.

Keywords: dry mortar mixes, redispersible polymer powders, low modulus inclusions, adhesion to the base, elastic modulus, tensile strength, freezing and thawing cycles

The article presents theoretical studies of the effect of various plasticizers on the mechanical properties of epoxy compositions. Based on this, the method of plasticization of the epoxy polymer ED-22 was chosen using the introduction of modified epoxy resin UP-563, which differs from the previously used modified compositions for repairing automotive vehicles in the field the simplicity of the availability of modifications in the field and as providing the widest range of changes in the properties of the epoxy composition for USAGE field. The scientific novelty lies in the justification for the creation of a new repair composition consisting of ED-22 epoxy-diane resin modified by UP-563 laproxil for the repair of hull and capacitive parts of automotive equipment in the field, which has increased vibration resistance. frost resistance and impact resistance.

Keywords: epoxy composition, epoxy resin, restoration, automotive engineering, body part, chemical modification, oligomer, polymer

In this paper, the previously obtained equation of motion in displacements is used to determine the frequencies and forms of free oscillations of the underground gas pipeline. The problem of solving this equation is reduced to finding the eigenvalues of the determinant, which are the squares of the natural frequencies of the cylindrical shell. Neglecting the secondary coefficients of the determinant and equating them to zero, the formula for the square of natural frequencies of an underground rectilinear thin-walled gas pipeline exposed to the action of internal working pressure and longitudinal force is obtained, taking into account the reaction of elastic resistance of the soil. Substituting the values for the wave numbers in the longitudinal and circumferential directions into the obtained formula, expressions for determining the frequencies according to the rod and shell theory are derived.Using these expressions, the dependence of the frequencies of free oscillations of the depth of the pipeline at fixed values of the pipe wall thickness, the coefficient of elastic resistance of the soil and the length parameter of the plot, for different values of internal pressure, the ratio of longitudinal compressive forces. When analyzing the results, it was found that with increasing depth of the pipeline, the frequency of free oscillations decreases, and at a certain depth, the frequency of free oscillations becomes equal to zero, this indicates a flattening of the cross section of the pipeline. Using the dynamic stability criterion, for which the frequency of free oscillations turns to zero, an expression is obtained that allows to determine the depth of the pipeline at which the stability loss of the second kind occurs.

Keywords: pipeline, frequency of free oscillations, depth of laying, coefficient of elastic resistance of soil, loss of stability

The article deals with the survey of transport and operational condition of the highway R224 " Samara-Orenburg in which it was found that the roadway surface is in poor condition due to the presence of transverse cracks, ruts and pits. In a survey of 5 existing culvert structures were identified unacceptable defects in the structure. Based on the foregoing, the specified section of road be repaired in accordance with GOST R 50597-2017 “roads and streets” . Currently, economical and mobile methods of inspection of road structures are of particular relevance. Conducting engineering surveys of the GPR system MIRA was determined the constructive layers of road clothes light. The decision on milling to a partial thickness of the pavement that runs recyclers WR 4200, with the subsequent device of asphaltgranulate type To

Keywords: pavement engineering, GPR applications, roads, surveys, MIRA GPR systempurposes of ensuring flexibility of production

In article the algorithm of calculation of systems with unilateral constraints with the replacement reactions of the supports on the force variables. The calculation algorithm is based on the finite element method in the form of the classical mixed method. The algorithm of search of version of the working constructive scheme is based on the modified "physically obvious" algorithm of design constructively nonlinear systems. The paper describes the features of the resolution system of the algorithm proposed by the authors and provides a flowchart. A comparative analysis with the algorithm of calculation of systems with unilateral constraints, proposed by the authors earlier, as well as some others. The efficiency of the algorithm is tested on numerical examples.The advantages of the proposed algorithm are: The vector of results includes the reaction of the support, which allows you to make a decision to change the design scheme; the calculation takes into account, as an additional loading factor, the size of the displasement in the realized one-way support, which increases the accuracy of the calculation.

Keywords: structural mechanics, single-sided supports, structural nonlinearity, the mixed form of the finite element method

The article discusses the current problems of calculating the distribution of water flow; the problems of current methods based on solving nonlinear equation systems are identified; proposes a new method for solving problems; analysis of the effectiveness of the proposed method; proposed a way to optimize the simulation calculations.

Keywords: waterways, water expenditures, modeling

We consider the problem of diagnosing breast cancer on the basis of combined thermometry. Diagnosis is carried out using two-dimensional generalized signs. Each such sign is formed on the basis of two one-dimensional. We propose an algorithm for the formation of sets of such features using tapering ellipses. On the basis of a set of such signs a classifier is built. By varying the semi-axes of the ellipses, the physician can control the sensitivity and specificity of the classifier. The doctor can fix the threshold value of specificity and achieve the maximum value of sensitivity. As a result of computational experiments, we built a family of 300 sets of two-dimensional signs and implemented a classifier customized by the doctor.

Keywords: combined thermometry, diagnostic algorithms, data analysis, algorithm sensitivity, algorithm specificity, logistic regression, custom classifier, breast screening, mammology

In this paper, we propose a method for expanding the functional range of image pre-processing systems (LUTs) and increasing sensitivity by reducing processing time. The main advantage of the implementation of preprocessing at FPSS is the implementation of spatio-temporal discrete-analog processing simultaneously with image formation. A disadvantage of the known methods for implementing image pre-processing systems is the low performance of the LDPE due to the fact that the processing is carried out step by step and the number of cycles is always the maximum regardless of the observation conditions. The purpose of the work is to expand the functional range of software and increase sensitivity, by reducing processing time. This goal was achieved by combining processing for the symmetric coefficients of the impulse response of a non-recursive filter. To assess the possibilities of improving the speed of the proposed processing method, noise suppression modeling on an X-ray image was simulated using low-pass filters with masks of size,,. Based on the difference between the original and processed images, it was concluded that the use of a mask is advisable. The use of a new processing method with a mask of dimension will allow to increase the performance by 2.778 times and, accordingly, the sensitivity of the software with 1.339 times.

Keywords: pre-processing, spatio-temporal, images, charge-coupled photosensitive devices, non-recursive filter

The technology of oil production includes a large number of processes in its cycle; extraction is one of the most energy-intensive processes before distillation of miscella. Analysis of automated extraction control methods determines the optimal process control method, which allows to improve the quality of miscella and save product consumption.

Keywords: automated, miscella, extraction, control, system, analysis, method, flow, solvent, quality

The generalized approach of statistical processing of results of fatigue tests of samples on the basis of a choice of numerical characteristics of parameter of static durability, processing of results of fatigue tests with use of methods of mathematical statistics, construction of a fatigue curve according to the linear regression analysis of mechanical characteristics of materials of designs and machines, definition of parameters of function of distribution of a limit of endurance by results of processing of diagrams of step change of loading is offered.

Keywords: Static strength, cyclic strength, reliability, mechanical properties of materials, endurance limit, mathematical statistics, linear regression analysis, method of step change of load, test planning