We prove a theorem on the existence of a nonzero periodic solution to a system of differential equations using the fixed-point method for a nonlinear operator defined on the product of two compact ...sets.
Abstract
The meteorological conditions in which organogenesis stages take place and hydrothermal regime can determine the phenotypic manifestation of quantitative signs, such as, for example, the ...activity of alpha-amylase. The purpose of our work was to determine what factors (temperature, precipitation, heterothermal coefficient) affect the enzyme activity, at what time of the vegetation, and in what way this influence is evident. The analysis of weather conditions and falling number (FN) for the period from 2011 to 2020 was carried out. Analysis of the FN value over 10 years showed that it can vary from 90 s to 429 s, and at that, the nature of its change is the same, regardless of whether we are considering one variety or the average value for a group of varieties. The correlation coefficient between the FN of a group of varieties and individual FN is 0.94-0.98. Generally, during the vegetation season, the alpha-amylase activity was influenced to a greater extent by the amount of precipitation than by temperature. This dependence is negative - an increase in precipitation leads to a decrease in the FN, and, consequently, to an increase in the enzyme activity. However, it was found that in different phases of ontogeny the influence of temperature and precipitation can be diametrically opposite.
This article discusses simulation of a circular interpolator developed according to the principle of differential analyzers on the basis of two coordinate electric servo drives with a stepper ...electric motor using the MATLAB/Simulink software during processing of the technological radius of workpiece. A simulation model has been obtained, including a model of a circular interpolator and models of two servo electric drives based on a stepper motor, which move, for example, along the
X
and
Y
coordinates of various coordinate machines with numerical control, using a stepper motor. The contour errors of servo electric drives when processing the radius of a circle were obtained, as well as graphs of transient processes of servo electric drives for various interpolation parameters. The resulting tracking errors are not only necessary for diagnosing the inertial properties of the electric drive, but also can be considered as a consequence of adjusting the control system as a whole.
—Restoration of the spherical surface of a steel 35L cone housing by mechanized surfacing in protective gas is proposed. The method employed does not involve heating of the part before or in the ...course of surfacing. The coating produced has the required thickness and chemical composition, with specified structure. The coating is strongly bound to the restored surface and is free of pores and cracks.
Abstract
This paper proposes a new approach to parametric identification of induction motor with error of speed sensor. The ordinary least squares (OLS) estimates are shown to be biased. Generalized ...total least squares (GTLS) with a singular covariance matrix of the error are propose for estimation of K parameters of induction motor. Identification of parameters takes place in 2 steps. At the first step, two K parameters are estimated using GTLS with a singular error matrix. At the second step, the remaining three K parameters are estimated. An equivalent augmented system is used to solve a biased normal system. Based on the simulation results, a comparison of the accuracy of the estimates of the proposed algorithm and ordinary least squares estimates is given.
Spectral and kinetic properties of extrinsic crossluminescence (CL) in SrF2:Ba (1%) and CaF2:Ba (1%) are compared with those of intrinsic CL in BaF2 and are analyzed taking into account EXAFS data ...obtained at the Ba LIII edge and results of first-principles calculations. The CL decay time was revealed to be longer in SrF2:Ba and CaF2:Ba compared to BaF2. This fact contradicts the expected acceleration of luminescence decay which could result from an increased overlap of wave functions in solid solutions due to shortening of the Ba-F distance obtained in both EXAFS measurements and first-principles calculations. This discrepancy is explained by the effect of migration and subsequent non-radiative decay of the Ba (5p) core holes in BaF2 and by decreasing of the probability of optical transitions between Ba (5p) states and the valence band in SrF2:Ba and CaF2:Ba predicted by first-principles calculations.
•The crossluminescence kinetics in SrF2:Ba and CaF2:Ba is slower than in BaF2.•Ba2+ ions substitute for host Ca2+(Sr2+) ions in the on-center positions.•The nearest Ba-F distances in SrF2:Ba and CaF2:Ba are shorter than in BaF2.•EXAFS data and first-principles calculations of the local structure agree well.•First-principles calculations explain slower luminescence decay in solid solutions.
Broad-band luminescence with maximum at 3.35eV has been revealed from new luminescence material CsTaF6 under VUV excitation. This luminescence was interpreted as emission of molecular type ...self-trapped excitons localized at the Ta F 6ˉ complexes. The energy of effective vibrational mode responsible for exciton-lattice coupling was determined to be equal to 45 meV (363 cm-1), which does not correspond to the energy of breathing mode of Ta F 6ˉ complex vibrations. The observed luminescence possesses thermal quenching with activation energy ∼58 meV.
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