DETERMINATION OF CONCRETE PROPERTIES DURING THE ASSESSMENT OF THE CONDITION OF FLAT REINFORCED CONCRETE STRUCTURES

Formulation of the problem. Operation of buildings and structures is based on periodic assessment of the condition of structures. The procedure for determining the strength of concrete by non-destructive methods requires a certain preparation of the concrete surface of the structure and sampling in order to calibrate the devices. During sampling, the samples may be damaged, in addition the surface of the cylinders does not meet the requirements for normalized test conditions. Part of the cores during selection is being destroyed, which reduces the representativeness of the results of determining the physical and mechanical properties of concrete. The purpose of the article is to find out the possibilities to increase the reliability of determining the physical and mechanical properties of concrete. Results. In the conditions of a real object, core samples were taken to study the concrete strength of the damaged area. Samples that did not meet the normalized parameters were prepared for testing using a repair mixture Mapegrout Thixotropic. Testing of the recovered core samples showed that the repair mixture adhered well to the surface of the core. The nature of the destruction in the restored and normalized samples is similar. Conclusions. Studies have shown that: the application of the existing method of determining the strength of concrete for slab structures limits the possibility of using core samples taken from structures; the use of Mapegrout Thixotropic repair mixture allows to carry out tests according to the normative method of damaged concrete samples or samples rejected due to size mismatch; reliable assessment of the deformable properties of concrete cores in many cases is impossible; the existing methodology needs to be improved or replaced by an alternative one; quantitative assessment of the rheological properties of the concrete mixture used for the manufacture of concrete structure is possible on the basis of comparing the deformable and strength characteristics of concrete structure, which requires formalization of the procedure and standardization.

DEVELOPMENT AND MODELLING OF HIGH SPREAD CONDUCTIVITY EARTH ELECTRODES FOR COMPLEX EARTHING ARRANGEMENTS

The analysis of methods for calculating the electrical characteristics of earth electrodes in case of emergency currents of industrial frequency flowing through the elements of earthing arrangements is carried out. A method for improving complex earthing arrangements of electrical installations by optimization of their design parameters is proposed. The proposed method consists in installing an artificial earth electrode with an increased contact area of its surface with the ground, which makes it possible to increase the conductivity of earthing spreading. The use of these electrodes on the territory of projected or operating electrical installations ensures that the values of the normalized parameters of earthing arrangements are brought to permissible values. The use of the method given in the calculations of earthing arrangements requires the replacement of volumetric earth electrodes with a set of linear vertical electrodes. The design model is substantiated by equivalent electrical characteristics relative to the two-layer model of the electrical structure of the earth. The equivalent model was obtained by a given approximation of the electrical characteristics of a set of straight electrodes in the process of increasing their number to the equivalent characteristics of the reference model. In turn, the determination of the characteristics of the reference model was carried out directly by solving the boundary value problem for the potential satisfying Laplace equation using finite difference method. Theoretical investigations using induced potential method and methods of calculation of branched electric circuits with distributed parameters for calculation of electric field and resistance of the complex non-equipotential earth electrode in the ground with two-layer structure have been carried out. The developed electrodes of increased spread conductivity are mounted as experimental samples and are involved in the formation of the electrical characteristics of the earthing arrangements.

NORMALIZED PARAMETERS OF A MAGNETORESISTIVE SENSOR IN BRIDGE CIRCUITS

Magnetoresistive sensors are considered as part of bridge circuits for measuring magnetic field strength and electric current value. Normalized or relative expressions are introduced to change the resistance of the sensor and the measured bridge voltage to increase the information content of the regime to provide the possibility of comparing the regimes of different sensors. To justify these expressions, a geometric interpretation of the bridge regimes, which leads to hyperbolic straight line geometry and a cross ratio of four points, is given. Upon a change in the sensor resistance, the bridge regime is quantified by the value of the cross ratio of four samples (three characteristic values and the current or real value) of voltage and resistance. The cross ratio, as a dimensionless value, is taken as a normalized expression for the bridge voltage and sensor resistance. Moreover, the cross ratio value is an invariant for voltage and resistance. The proposed approach considers linear and nonlinear dependences of measured voltage on sensor resistance from general positions.

Devising a method to parametrize the jacket style varieties through the modification of tіpological series structures

The study reported here has revealed the issue related to the inefficient scaling of the uniformity of jacket model designs in the processes involving a typical representative as a result of modification parameters uncertainty. A variant has been proposed to synchronize the critical points of silhouetted allowances by grouping the numeric series in the vector of choosing the value for an increase in the allowance according to the characteristics of style varieties. The influence of shape-forming segmentation on the formation of a classifier of the structural and technological solutions for a jacket has been determined. The built model to support modification vectors has made it possible to describe the sequence of procedures execution by the method of typical representation. The presence of one design category, the same structural parts, the uniformity of style simplifies the processes of choosing and selecting the most characteristic models of the jacket. It was found that the morphological combination of attributes of the physical appearance affects the adjustment of style preferences in a manufacturer’s products. The parameters for typical segmentation relative to the junction points of the structural zones of the optimized five-seam prototype design have been defined as the most influential vectors of jacket modification. A method for scaling the allowance for free fitting has been devised on the basis of data from empirical research. An adequate regression model has been derived for normalizing the silhouette allowance parameters. The constructed model makes it possible to scale silhouette structures by changing the increments at the corner points of the contour according to the prototype of gradation under an automated mode. Practical recommendations have been compiled on the parameters of zonal-modular modification of silhouette designs of jacket varieties: a linear character of the state silhouetted transformation relative to ASi1=5 cm. The normalized parameters for constructing functional and decorative parts have been proposed

Deformation of Steel-Reinforced Concrete Round Thin Slabs Taking into Account the Compliance of the Support Contour

The paper presents the governing equations of bending of nonlinearly deformable, axisymmetrically loaded round, thin reinforced concrete and steel concrete slabs, taking into account the work of a non-deformable and pliable support contour. Based on the results of theoretical and experimental studies, the stress-strain state of reinforced concrete and steel-concrete slabs under short-term and long-term loadings was estimated. The nature of stress state is revealed in the stages of cracking and destruction of plates. The work of the slabs in the field of elastic, elastoplastic and plastic stages of work is estimated. Using the method of limiting equilibrium, a method for calculating steel-concrete slabs for strength with normalized parameters.

Application of Field-of-View Optimized and Constrained Undistorted Single Shot (FOCUS) with Intravoxel Incoherent Motion (IVIM) in 3T in Locally Advanced Rectal Cancer

Purpose. To evaluate the efficacy of field-of-view (FOV) optimized and constrained undistorted single shot (FOCUS) with IVIM in 3T MRI in the grading of patients with locally advanced rectal cancer. Methods. From January 1st to December 31st, 2019, patients with locally advanced rectal cancer were retrieved. FOCUS DWI and FOCUS IVIM were obtained. Apparent diffusion coefficient (ADC) and IVIM parameters including mean true diffusion coefficient ( D ), pseudodiffusion coefficient associated with blood flow ( D ∗ ), and perfusion fraction ( f ) of the tumor parenchyma and normal rectal wall, as well as the normalized tumor parameters by corresponding normal intestinal wall parameters (ADCNOR, D NOR , D ∗ NOR , and f NOR ), were compared between the well/moderately differentiated and poorly differentiated groups by Student’s t -test. The relationship between the above parameters and the histologic grade was analyzed using Spearman’s correlation test, with the ROC curve generated. Results. Eighty-eight patients (aged 31 to 77 years old, mean = 56 ) were included for analysis. D tumor and f tumor were positively correlated with the tumor grade ( r = 0.483 , p < 0.001 and r = 0.610 , p < 0.001 , respectively). All the normalized parameters (ADCNOR, D NOR , D ∗ NOR , and f NOR ) were positively correlated with the tumor grade ( r = 0.267 , p = 0.007 ; r = 0.564 , p = 0.001 ; r = 0.414 , p = 0.005 ; and r = 0.605 , p < 0.001 , respectively). The best discriminative parameter was the f tumor value, and the area under the ROC curve was 0.927. With a cut-off value of 22.0%, f tumor had a sensitivity of 88.9% and a specificity of 100%. Conclusion. FOCUS IVIM-derived parameters and normalized parameters are useful for predicting the histologic grade in rectal cancer patients.

Vehicle diagnostic system of the car engine

Support of the established technical characteristics of engines is reached by its regular service and diagnostics in particular - existence of the diagnostic programs built in the onboard computer of the car which carry out constant control of the main parameters of the engine.Based on the algorithm of vibroacoustic diagnostics, a system of vibration and vibroacoustic diagnostics of the internal combustion engine (ICE) is proposed, which can be integrated into the intelligent environment of self - diagnostics of the car (Check - Engine). The algorithm takes into account the normalized parameters and criteria for assessing the vibration state: the absolute values of displacements, velocities and accelerations and their changes.For the self-diagnostic system, it is important to develop a classifier of engine states also to determine and / or predict the failure of its parts or units. Engine vibrations can be attributed to the following types: imbalance of the 1st and 2nd order of the engine; vibration associated with combustion in the engine; auxiliary units.The analysis of a vibroacoustic signal at work of the serviceable and faulty engine is carried out, influence of various elements of a design, placement of the gauge in horizontal and vertical directions is shown on it.

Aircraft noise in residential areas, problems of measuring and evaluation

The intensity of civil aircraft flights elevates with the increase in the number of passenger and cargo transportation by air. Aircraft noise in the residential area near airports grows up too despite the use of low-noise aircraft models by airlines. This causes an augmentation in the number of complaints of the population in these areas. The Russian Federation’s normative and methodological documents requirements in force relating to measurements and assessment of noise in residential areas, including «aircraft noise», were analyzed. Their requirements in terms of measuring and assessing noise in residential areas, including “aircraft noise”, testifies to the insufficiency and ambiguity of these requirements. The main disadvantages are the lack of a clear definition of which sound event is considered «aircraft noise» and the lack of requirements for the duration of the reference time interval of noise measurement. The foreign experience of measuring and evaluating aircraft noise, as well as the effects of such noise on the population, are considered. This made it possible to determine the necessary and sufficient parameters for noise control in residential areas, including «aircraft noise». There were proposed both a definition of «aircraft noise» and the necessary parameters for its assessment. The necessary duration of the reference time interval for the measurement of normalized parameters was justified. Method for the normalized noise parameters in residential areas measurement using the chronograms of sound levels A was proposed. The technical implementation of such a method is presented. Proposed a definition of «aircraft noise» and measuring normalized parameters in the 15-minute reference time interval for inclusion in regulatory and methodological documents will help to eliminate ambiguity in measurements and noise assessment in residential areas.

Increasing of on-board radar system reliability with use of failure detection and reconfiguration system

The paper considers the possibility of improving the reliability of the on-board radar system by implementation of failures detection and reconfiguration system, as well as predicting and searching of failure locations up to the specified depth of failure search in real time, failures prediction by introducing into the system of pre-failure states of normalized parameters of on-board radar system components. The reconfiguration methods or partially restoring of the antenna phased array by failures generation and loading them into the detection system and reconfiguration of amplitude-phase distributions of emitters or the matrix of a new amplitude-phase distribution in real time are considered. The block diagram, description and operating principle of the fault detection and reconfiguration system are presented. The algorithm of the failure detection and reconfiguration system is given.