STRENGTH AND STIFFNESS OF REINFORCED CONCRETE BEAMS MADE ON EXPERIMENTAL COMPOSITION OF A CONCRETE GOODS PLANT

One of the options for optimization in the activities of the construction industry plants is the improvement of the composition of concrete mixtures, which requires control measures to assess indicators that ensure the reliability of operation of concrete and reinforced concrete structures. The strength of concrete in standard control cubes is at the same time the dominant parameter that determines the prospects of changes in production. The presented work presents the results of a comprehensive assessment of experimental concrete on cubes, prisms and reinforced concrete beams.

DEVELOPMENT OF A CIRCUITRY AND CONSTRUCTIVE-TECHNOLOGICAL BASIS FOR COSMIC CHIPS

The article considers the development of adaptive communication and control systems for space and civil purposes to ensure the reliability of operation and increase the accuracy of control. To ensure the resistance of CMOS BIS to ionizing radiation, methods of implementing the isolation unit, the design and technology of working transistors that ensure high stability of their characteris-tics are used.

REVIEW THERMOMETRIC METHODS CONTROL COMPRESSION STATOR CORE STATE OF POWERFUL TURBOGENERATORS

The article is devoted to the analysis of thermometric methods of control and diagnosis of the state of compression of the stator core of the turbogenerator (TG), which have found the greatest application. It is shown that ensuring effective and high-quality control of powerful electric machines, especially power plant generators, today is an integral part of ensuring the reliability and trouble-free operation of their work. As a result of the analysis, it is shown that ensuring high reliability of operation of the generating equipment is practically impossible without their equipping with modern means of control capable to work in real-time. Bibl. 34, fig. 4.

DEVELOPMENT OF A FICH PROTECTION DEVICE DESIGN

The water intake structure is a functional element of the water supply system, but it must also be a fish protection object. The following basic requirements are imposed on the devices of modern fish protection devices at water intakes: prevention of ingress and death of young fish and larvae, prevention of injury to young fish and larvae, removal of protected fish from water intake, reliability of operation under specific conditions and means. According to the principle of operation, the most effective is the active scheme, with the forced formation of the hydraulic flow structure. The design of a universal combined type device with the use of a jet generator as a flow-forming element that creates a reactive hydraulic movement designed to protect fish and juveniles with a body size of less than 15 mm is proposed.

Intelligent system for measuring the level and mass of liquid in fuel tanks and tanks during pitching and tilting

An overview of the existing methods for measuring the liquid level and their disadvantages in the case of surface vibrations is presented. A system for continuous measurement of the mass of liquids in fuel tanks and tanks during rolling and tilting of vehicles and ships, implemented in a level gauge based on intelligent sensors, is proposed. The sensors include a microcontroller with an individual calibration characteristic of the volume-level dependence, taking into account the shape of the tank or fuel tank, and nanosensors built into the intelligent sensor (ID) for measuring density, permittivity and ambient temperature. It is established that the actual metrological characteristics of the ID are significantly higher than the characteristics of traditional sensors. The number and dimensions of the plates of flat capacitors are justified and the scheme of their arrangement on the roof of the tanks is presented. The exclusion of movable elements increased the reliability of operation, simplified maintenance and design requirements of the measuring object. Analytical expressions for calculating the level and mass of the liquid, implemented by the microcontroller, are given. The use of the proposed measurement system with complex computational processing and taking into account corrections for temperature, density, humidity and permittivity of the liquid made it possible to increase the accuracy and stability of the level meter readings. Analytical expressions are derived that relate the liquid level and the output frequency of the generator from the composition of the level gauge.

Measuring system for monitoring the polydimensional deformation of superstructures of bridges and over-bridges

Bridges belong to critical structures. Therefore the geodetic monitoring of their stability should be performed during their operation. Correctly and qualitatively performed control over stability of the ready-built construction increases the term and the reliability of operation of the bridge and considerably increases the safety of its use. All over the world there is a tendency to increase the length of superstructures of bridges and to use widely the flexible constructions. This makes these structures even more sensitive to dynamic loads. Based on the concept of unfolding the laser beam in the horizontal plane, the methods and devices for measuring the polydimensional deformations of superstructures of bridges and over-bridges were developed. The article examines the methods and devices for measuring the polydimensional deformation of superstructures of bridges and over-bridges with the use of deployable optical laser systems for measuring the longitudinal deformation of superstructures and an ultrasonic sensor for measuring transverse deformation. The devices use lasers with continuous radiation of a beam of a certain wavelength. Optical collimators are arranged in series with the lasers. The spinner, for example, is an engine on the shaft of which there is a mirror or a prism with a reflecting face at an angle of 45° to the laser beam, or a rotating optical wedge, due to which the laser beam is deployed in a horizontal plane. All n sequentially arranged deformation sensors and an additional photodetector for the control of the deflection of the wire on which the ultrasonic sensor is installed, are made in the form of a line of elements of a certain length, and each photodetector has the same number of elements. Each element of the photodetector is made of a certain material that transmits a laser beam without any special interference. The devices can be used in the automated system of monitoring of the deformations of the bridge structure (ASDB), which will allow the quick control of their condition, displacements and deflections resulting from the external climatic influences, as well as the amplitude of oscillation of loads from the continuous traffic with non-cyclic long-term loading of superstructures of bridges and over-bridges.

Development of Accommodation System for Faults in Thrusters of Underwater Robots

The article discusses a solution to the problem of increasing the reliability of operation of underwater robots through the use of accommodation systems that compensate for the consequences of faults that appear in the thrusters. The following types of faults were considered: 1) a fault in the rotation speed sensor of thruster, causing error in its readings; 2) overheating of the motor or short-circuiting of several turns of the winding of its armature circuit, causing a change in the value of electrical resistance; 3) the appearance of an unknown external torque effect on the engine shaft, including when winding plants on the propeller. A new method for constructing accommodation systems is proposed, which contains three stages. At the first, the detection of emerging faults is carried out using the bank of diagnostic observers. Each observer is synthesized according to a special procedure in such a way that the residual formed by it is sensitive to the appearance of various combinations of possible faults. This allows to detect each specific fault. At the second stage, the values of sensor errors and deviations of the parameters of the thruster from their nominal values are estimated by additional variable structure observers. At the third stage, additional control signals for robot’s thrusters are formed. They ensure the stabilization of dynamic properties and quality indicators of thrusters in the event of faults. The results of mathematical modeling are presented, which have confirmed the operability and high efficiency of the synthesized accommodation system.

Decomposition model for examination and optimization of reliability of the basic structure of UES of Russia

The main provisions are outlined of the author’s model of electric energy systems and their associations (Unified Energy Systems of Russia, UPS), enabling to determine analytically the key parameters of reliability of operation of EES within generation facilities (generation adequacy) and trunk power grids (transmission reliability) subject to dislocation of generation facilities and electric loads, electric modes and reliability of operation of trunk power grids.For calculations of electric modes of operation of 750–220 kV power grids, Stott’s decomposition method is used involving simplification of the Jacobian matrix, the latter being divided into two independent subsystemsP → δ and Q → U, based on a weak functional link between P and Uand between Q and δ. When developing the model, much attention has been paid to improving the correctness in assessing the static and dynamic stability of the UES and taking into account these factors in the process of calculating the reliability of trunk power grids networks for each of the considered emergency situations. Special attention has been paid to improving the accuracy of estimates of economic losses (damage to the national economy) under various conditions of operation and recovery of UES: when working at low frequency, on actuation of automatic frequency load shedding (AFLS) devices and special load shedding automatics (SLSA), in case of sudden shutdowns, shutdowns with prior notice, and planned power supply restrictions. When forming the composition of consumers subject to restrictions, instead of the currently used proportional approach, the method of indefinite Laplace multipliers is used to reduce damage, based on taking into account the technological and economic response of various types of consumers to restrictions of their electrical loads. The calculations are concluded with an assessment of the annual average undersupply of electric energy and economic damage to consumers from disruptions of their power supply for the UES of Russia in 2017–2019, as a basis for optimizing the system reliability. It is shown that the probable annual average damage only in trunk grids of the UES of Russia amounts to as much as 1.2 percent of annual GDP, while its annual growth over the same period is estimated by the Ministry of Economic Development and the State Statistics Committee of the Russian Federation to be within 1.8%. Thus, due to the unreliability of the operation of only 750–220 kV main nets of UES, the national economy annually loses up to 2/3 of its annual growth.

Kriteriji za izbiro kakovostnih in zanesljivih UPS-ov v bolnišnicah

Uninterruptible Power Supply (UPS) management is one of the important factors in hospitals. With the help of UPSes, vital and critical electrical devices (especially in operating rooms and intensive care units) are not left without power in the event of a power outage. Therefore, when choosing these devices, it is important that they work reliably and that they have the longest possible period of operation. The article describes important criteria in the selection of UPS devices that affect the reliability of operation, which is especially important when updating equipment. The most important standards and methods for evaluating the reliability of operation and the calculation of MTBF (Mean Time Between Failures) in the case of UPS are presented, which indicate when the equipment needs to be replaced. As a result, the reliable functions of the UPS at three operating temperatures are given. We also calculated the values of the reliability function, where we checked the different qualities of the installed elements at two different operating temperatures.

Mathematical modeling of heat-trapping properties of a developed radiator surface in mechanical engineering

In this work the research of heat-removing properties of areas of extended surfaces, for example, of finned and needle radiators for assessment of efficiency of distribution of a thermal field and heat extraction is described. Also the description of the carried-out computational modeling is provided in the Fluent processor of universal program system of the final and element analysis Ansys. The relevance of the selected subject is confirmed by the fact that one of the most important and difficult tasks arising when developing the electronic equipment is a withdrawal of heat generated by it. At a current steady trend in reduction of dimensions of electronic devices this problem does not disappear, and opposite, becomes more and more sharp, and that is stronger, than device high power less its physical volume, and not only the efficiency of heat extraction, but also dimensions and, of course, reliability of operation of electronic devices depends on constructions of heat-removing elements. In work the conclusion is drawn that for a solution of a complex problem of assessment of efficiency of the heat sink for the purpose of decrease in temperature of heatterminated element, it is necessary to use electrothermal analogy.