A service system is studied, in which, upon completion of servicing of each application, instant control of the quality of its service is carried out. In case of unsatisfactory quality, the application is sent for repeated services, which are carried out until the quality is considered satisfactory. A semi-Markov process of system functioning is constructed, and the stationary distribution of the embedded Markov chain is found. Analogues of the Pollaczek — Khinchin formula for generating functions of the stationary probabilities are obtained. The system stationary characteristics depending on the probability of quality service are determined: the stationary distribution of the queue over time, the average stationary duration of stay in a state, the average number of requests in the queue and system, the average duration of the request stay in the queue and system.

Results of studies on influence of the intensity of the appearance of users simultaneously using ToF-cameras in the field of view on the probability of incorrect construction of a depth map are presented. The process of users appearing in the field of view is described by a spatial point Poisson distributed process with a given intensity. Simulation results using the Intel RealSense D455 camera are presented. Calculations are performed of the shooting region area where ToF-cameras can create mutual interference during multi-camera shooting. The duration of the signal is also evaluated, and the shutter speed of the deep chamber is determined. Based on the data obtained, the probability of incorrectly constructing a depth map is estimated and a graph of its dependence on the intensity of the appearance of users in the visibility area was constructed. Results of an experiment to determine the dependence of the amount of interference on the distance of intersecting cameras from the object are presented.

Results of choosing a component base for the development of a phosphor composition are presented. The influence of the composition of the phosphor coating on the characteristics of the LED light source is considered. Models of white LEDs are created and research tests of their lighting and colorimetric characteristics are carried out. Proposed phosphor compositions make it possible to achieve luminous efficiency values of the order of 200 lm/W.

The possibility of using a multifunctional system for non-contact measurement of multiphase flow parameters in offshore fields, based on radioisotope radiation technology, is considered. The current equipment of offshore production with sensors, data analysis and automatic control systems is analyzed, and an insufficient number of measured parameters is revealed. The possibility of improving this multifunctional system by upgrading it based on an analysis of the risks and difficulties of offshore production in the Arctic zone is studied.

A test procedure developed on a Brookfield rotational viscometer for determining and calculating the basic rheological properties of two-component grease substance containing a frame structure is presented, using the standard Litol 24 lubricant as an example. The measurements are performed using the geometry standard for liquid lubricants, near the surface of the spindle (inner cylinder with radius Ri), in a narrow volume of liquid lubricant with a gap value (Ra - Ri) where Ra is the radius of the boundary along which the destruction of the grease’s frames occurred and fluid flow is observed. A method is proposed for calculating the yield strength and dynamic viscosity of a grease containing a frame structure. The developed methodology is verified. New data are obtained on the rheological properties of plastic binders based on Litol, Solidol, and electrical grease with the addition of graphene, molybdenum and copper.

A method for modeling a two-component composite material is considered to describe the anisotropy of thermal conductivity of its two-dimensionally oriented structure. The method consists of modeling the structure of the composite under study and subsequent calculation of its thermal conductivity using design relationships that are based on the well-known electrothermal analogy. In the method under consideration, the structure of a real composite is modeled by an elementary cell, which is a cube with edges of unit length. The final system of equations for calculating two-dimensionally oriented thermal conductivity is presented, an example is given, and an estimate of the expected accuracy of thermal conductivity prediction is given.

Results of a study on the use of absorption spectral analysis of light-curing radiopaque materials „Omichrome“ to evaluate their optical properties are presented. Application of this method is associated with the ability to quantitatively determine the elemental composition of a substance, high selectivity, simple preparation of dental samples under study, accuracy and sensitivity. Using spectrophotometer for experimental measurements, the spectral dependences of the absorption coefficient of the analyzed materials on the radiation wavelength were obtained over the entire measured range. The maximum and minimum values of the absorption coefficient of the materials were defined.

Results of experiments on the formation of submillimeter-diameter channels with a large aspect ratio (~100) in polymethyl methacrylate due to selected laser beam focusing parameters and the average power of a high-frequency pumped CO laser are presented. A comparative analysis of the possibilities of forming channels in polymethyl methacrylate using radiation from CO and CO2 lasers with high-frequency pumping is performed. Submillimeter channels with high aspect ratio can be used to create microfluidic chips.

A geometric representation of a random process is proposed. New vectors of the derivative of the envelope and the speed of rotation of the envelope vector are introduced in the graphical interpretation of the random process. Expressions for the envelope derivative and angular velocity have similar structures and are orthogonal projections of the same vector. The logarithmic derivative of the envelope and the derivative of the phase of a random process also have similar structures, close and even coinciding probabilistic characteristics. For a narrow-band Gaussian random process, a simple connection between their correlation functions is established.