Calibration and optimal control for inaccurate predictive models
Calibration and optimal control for inaccurate predictive models
E. M. Churakov, P. V. Golubtsov
The problem of managing physical systems is considered. In such systems, there are various parameters: which we can control directly, which we can control indirectly through the first parameters and parameters that act as external disturbances of the system. The values of all variables come to us as sensor measurements, and the sensors, in turn, have measurement errors. In addition to perturbations and errors, there is another fundamental problem: We always know the model of a physical system inaccurately, this may be due to insufficient information or lack of a priori information about the type of model.
Show AbstractUsing Lasso-regression to select significant exogenous features in time series forecasting
Using Lasso-regression to select significant exogenous features in time series forecasting
A. I. Baliuk
It is proposed to make the preliminary processing of multidimensional time series and optimize the selection of exogenous variables using the least squares method with regularization, in order to use the obtained results in the SARIMAX model. The analysis of weather and atmospheric data of the Tver Oblast showed that the selection of significant exogenous features using Lasso-regression allows minimizing the forecast error and preventing model overfitting. The results obtained confirm that the correct choice of exogenous variables improves the quality of the predictive model.
Show AbstractA new technique for controlling scale discreteness in a differential mobile refractometer
A new technique for controlling scale discreteness in a differential mobile refractometer
A. D. Belyaev, V. V. Davydov
The necessity of developing a small-sized mobile refractometer for express control of the state of hydrocarbon media and a new method for determining their composition and concentration of components in case the medium is a mixture of two hydrocarbon media is substantiated. This method will allow for comprehensive control of hydrocarbon media at the sampling site and making an informed decision on their intended use without additional studies in a stationary laboratory. This will save time and resources when solving many problems related to the use of fuel (for example, for mobile objects, etc.). The new method is characterized by the speed of measurements and does not require special sample preparation. The error in measuring the refractive index is ± 0.0002, which is sufficient for reliable express control. The studies of hydrocarbon media and their mixtures confirmed the adequacy of the development and the reliability of determining the composition of the hydrocarbon mixture and the concentration of components.
Show AbstractInvestigation of the characteristics of rolled scale with magnetic properties to determine its effectiveness as an adsorbent
Investigation of the characteristics of rolled scale with magnetic properties to determine its effectiveness as an adsorbent
S. A. Kotov, Z. V. Naumova, T. S. Kudryavtseva, V. V. Davydov, O. I. Suchkova
One of the tasks of applied physics is to develop new methods for the use of condensed media, which are waste from various industries. In this case, several problems are solved, both related to ecology in its various applications, and to the production of various elements using physico-chemical processes. The paper considers rolling scale, which is formed in large quantities during the operation of metallurgical enterprises. One of the possible options for recycling rolled scale (recycling) is related to the possibility of its use as a sorbent in liquid purification and filtration systems. Morphological, chemical, and phase features of rolled scale are considered to determine its potential for sorption activity. Using spectral studies, a comparative analysis of magnetic and non-magnetic fractions was carried out, and differences in the content of iron-containing phases and impurity elements were revealed. It is established that the microstructure and composition of the material are determined by the conditions of its formation and directly affect the adsorption characteristics. The presence of magnetite and a porous structure contributes to the formation of an active surface for the deposition of chemically active elements on it, such as phosphorus, zinc and other dangerous elements that are not removed by mechanical filtration.
Show AbstractStructural properties of host galaxies of light-weight supermassive black holes based on new data from "Hubble" space telescope
Structural properties of host galaxies of light-weight supermassive black holes based on new data from "Hubble" space telescope
L. -. Osipova$^1$, K. -. Grishin$^2$, I. -. Chilingarian$^2$
In this paper, two-dimensional and one-dimensional photometric modeling of new Hubble Space Telescope data was performed for galaxies hosting intermediate-mass black holes (IMBHs), as well as for objects from an extended sample with black hole masses up to one million solar masses. Using the resulting models, the stellar mass of each galaxy bulge was estimated, and the positions of the galaxies were determined on the black hole mass–bulge mass scaling relation. The location of these galaxies on this relation provides constraints on black hole growth processes in the low-mass regime.
Show AbstractMethanol emission at 84.5 GHz in infrared dark clouds
Methanol emission at 84.5 GHz in infrared dark clouds
P. S. Sozinova, N. N. Shakhvorostova
We report observations of methanol emission at 84-GHz toward 32 infrared dark cloud (IRDC) sources at various evolutionary stages. Data were obtained using the 20-meter radiotelescope located in Onsala, Sweden, during 2019-2020. Among these 32 sources, the 5$_{-1}$---4$_{0} E$ methanol emission was detected in 24. These objects do not overlap with any previously observed 84-GHz sources, making all our detections novel. Based on our findings, five sources were identified in which emission of class I methanol masers was observed. Additionally, we compare the 84-GHz observations with previous 44-GHz measurements toward the same sources, revealing a correlation between emission at both frequencies and notable similarities in their spectral profiles.
Show AbstractNumerical modeling of vapor-liquid equilibria of ternary mixtures of hydrocarbons and carbon dioxide
Numerical modeling of vapor-liquid equilibria of ternary mixtures of hydrocarbons and carbon dioxide
D. V. Selezneva
In the oil and gas industry, carbon dioxide injection into the reservoir is considered a promising method for enhancing oil recovery: when dissolved in hydrocarbons, the viscosity of oil decreases and a swelling process occurs, which improves the efficiency of displacement. At certain values of pressure and temperature, a three-phase equilibrium can form in the system - two liquid phases (enriched in carbon dioxide and enriched in hydrocarbons) and a gas phase, which seriously complicates the use of classical iterative algorithms for calculating phase equilibria with stability tests. In this paper, the method of direct minimization of the Gibbs free energy at fixed values of pressure and temperature was used to determine the boundaries of the regions of two-phase and three-phase equilibrium; in addition, the viscosities of each phase were calculated using the Lorenz-Bray-Clark model, which made it possible to quantitatively estimate the decrease in the viscosity of the oil phase.
Show AbstractEstimation of Curium effect on neutron-physical characteristics of BN and VVER reactors under the homogeneous distribution
Estimation of Curium effect on neutron-physical characteristics of BN and VVER reactors under the homogeneous distribution
V. V. Hramkov, D. R. Aliev, V. O. Skulkin, A. A. Vorontsova, E. A. Gerdt, P. M. Aleksandrovich
The research aim is investigation of the curium affection on neutron-physical and thermophysical characteristics of VVER-1200 and BN-600. The fuel assemblies neutron-physical and thermophysical models have been created for the calculations to be made. Curium was added to the common fuel homogeneously in the proportions from 0,1 to 20 % as CmO2 oxide. Characteristics considered are: neutron multiplication factor, neutron spectrum, temperature distribution. A stronger effect on the reactivity is observed of the VVER-1200 model – Keff decreases by 3,85%. The maximum decrease of BN-600 neutron multiplication factor is 3%. Adding curium increases the neutron flux density of VVER-1200. Also curium does a considerable positive effect on the fast reactor’s reactivity, that creates a possibility of using Cm as a fuel. The maximum fuel temperature decreases by 500 grad, when curium is added.
Show AbstractOn the development of Kelvin-Helmholtz instability in the front region of an intense nonlinear acoustic wave in the atmosphere
On the development of Kelvin-Helmholtz instability in the front region of an intense nonlinear acoustic wave in the atmosphere
S. I. Kosyakov$^{1,2}$, S. N. Kulichkov$^{1,2}$, M. Z. Nafisovich$^1$
Currently, a significant effect of the expansion of the front region of intense nonlinear acoustic waves created in the atmosphere by pulsed point sources of various nature has not been fully explained – the recorded width of the front region is several orders of magnitude larger than it follows from theoretical concepts. To explain such a significant effect, a hypothesis has been put forward about the possibility of developing Kelvin-Helmholtz instability inside the front region of the wave with a shear flow caused by a mass velocity gradient in the front region itself. The paper substantiates the proposed hypothesis. For this purpose, direct (without using any semi-empirical models) numerical simulation of the Kelvin-Helmholtz instability inside a physically infinitesimal volume of air in the front region of an intense nonlinear acoustic wave is performed. The homogeneous plane motion of compressed air in a wave is considered. It is shown for the first time that the development of Kelvin-Helmholtz instability at different distances from the source should have geometric similarity due to the fact that the process develops in an ideal environment. It does not matter whether the width of the front area increases as the wave moves away from the source or it increases due to an increase in its energy.
Show AbstractThe method of "Large particles" in mathematical modeling of Kelvin–Helmholtz instability in air
The method of "Large particles" in mathematical modeling of Kelvin–Helmholtz instability in air
S. I. Kosyakov$^{1,2}$, S. N. Kulichkov$^{1,2}$, M. N. Zakirov$^1$
The application of the well–known "Large particles" method in mathematical modeling of the simplest type of shear flows - a two-dimensional unsteady plane mixing layer is considered. The results of direct numerical simulation of the Kelvin-Helmholtz instability development at the interface of two layers of air of different densities moving with a tangential velocity shift in a field of strong external acceleration are described. The reliability of the calculation results is confirmed by comparing them with analytical calculations, with the results of numerical solution of a similar problem, as well as with experimental data. Based on the results of calculations, a new functional dependence of the increase in the width of the mixing layer on time, external acceleration, the difference in the densities of the air layers and the velocity difference at the contact boundary is obtained. This dependence is obtained for large values of acceleration values, velocity differences, and density at the gap. It will be useful for predicting the expansion of mixing zones in various currents with a tangential velocity gap, which are ubiquitous both in technology and in the atmosphere – for example, at the initial section of the jet, at the initial stage of mixing in a cylindrical vortex, with the development of wavy clouds or instability of a clear sky in the atmosphere.
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