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We consider a periodic boundary value problem for a nonlocal Ginzburg–Landau equation in its weakly dissipative version. The existence, stability, and local bifurcations of one-mode periodic solutions are studied. It is shown that in a neighborhood of one-mode periodic solutions there may exist a three-dimensional local attractor filled with spatially inhomogeneous time-periodic solutions. Asymptotic formulas for these solutions are obtained. The results are based on using and developing methods of the theory of infinite-dimensional dynamical systems. In a special version of the partial integro-differential equation considered, we study the existence of a global attractor. Solution in the form of series are obtained for this version of the nonlinear boundary value problem.

In the paper, the influence of replacement of natural lead with lead-208 as a coolant and fast reactor reflector on its neutron-physical parameters is considered. The possibility of significantly increasing the mean prompt neutron lifetime by using lead-208 is shown. It is proposed to place a layer containing a neutron absorber over the core in its reflector to control the reactor reactivity. It is shown that when using lead-208, the efficiency of this layer is noticeably higher, and the Doppler effect is enhanced than when using natural lead.

The paper considers the effects produced by arranging a lead cavity in the central part of a lead-cooled fast reactor core. It is shown that the most favorable effect from the presence of an inner lead cavity at the center of the core can be obtained when radiogenic lead with a dominant 208Pb isotope content is used as the material of the cavity, coolant, and neutron reflector. This is explained by the extremely low neutron absorption of 208Pb in a wide range of neutron energies. If the thickness of the 208Pb inner cavity is chosen properly, then a spectral region with the prevailing share of resonance, epithermal, and thermal neutrons is created in the cavity. This results in a sharp increase in the mean prompt neutron lifetime (by few orders of magnitude) and enhancement of the stabilizing Doppler effect. The neutron migration from the inner cavity to the reactor core is able to intensify the fission chain reaction (FCR) and contribute positively to reactor reactivity. In addition, the high flux of slowed neutrons in the inner 208Pb-cavity makes it possible to expect efficient transmutation of long-lived fission products.

We consider a boundary-value problem for a quasilinear partial differential equation describing tube oscillations under the action of a fluid flow. We show that the well-known Landau—Hopf scenario of transition to turbulence is realized in the considered evolution boundary-value problem with a suitable choice of the governing parameter. To study the problem, we use the theory of infinite-dimensional dynamical systems. In particular, we use the method of integral manifolds, normal forms, and also asymptotic methods of analysis.

In the FRAGM experiment at the heavy-ion accelerator $$-$$ accumulator complex ITEP $$-$$ TWA, yields of cumulative charged $$\pi$$ mesons have been measured in a fragmentation of carbon ions with the energy of 3.2 GeV/nucleon on a beryllium target. The momentum spectra of $$\pi$$ mesons cover four orders of the invariant cross section magnitude. They demonstrate the exponential fall with increasing energy. The measured inverse slope parameter is compared with similar measurements in nucleon–nucleus interactions and ion–ion collisions at lower energies. The energy dependence of the ratio of the yields of negative to positive $$\pi$$ mesons is presented. This dependence is discussed in a connection with Coulomb and isotopic effects. The obtained data are compared with predictions of several ion–ion interaction models.

The electromagnetic calorimeter is an important part of the MPD detector, which helps to study properties of the dense nuclear matter produced in heavy-ion collisions at NICA. The high-granularity electromagnetic calorimeter (ECal) is optimized to measure the spatial coordinates and energy of photons and electrons. The production of the calorimeter modules started this year. This report presents the methods and results of the testing and calibration of the ECal modules. A technique for measuring assemblies of calorimeter modules on cosmic muons was developed, which allows calibrating a large number of modules in a wide dynamic range during a limited time. Periodic quality control measurements and determination of the main physical parameters of modules were proposed to be carried out with an electron beam at various energies. For this purpose, the electron beam of S-25R Pakhra synchrotron of the Lebedev Physics Institute has been proposed. A secondary electron channel was commissioned on the bremsstrahlung photon beam and transported to the calibration area. Simulation programs for the beam and cosmic tests were developed. The experimental results in comparison with simulated data are presented and discussed.

This article proposes a principle for making combined ac windings with a set of terminals and a magnetic motion force (MMF) with polarities p1 and p2. Equations are derived for the MMF and the phase turns of the combined winding. The force and the turns create co- and counterrotating MMF harmonics with p1 and p2. Cases of making a combined winding with corotating MMF harmonics of different polarities are considered in detail. The main correlations for the distribution of conductors in slots are provided. The spatial patterns of corotating MMF harmonics with p1 = 5 and p = 3 are presented. A concrete modification of combined two-phase winding is proposed.

The influence of numerical aperture of the Linnik interferometer optical system on the interferogram contrast was investigated. It was shown that the numerical aperture growth leads to effective coherence length decreasing. The modeling and full-scale experiments results were presented.

Signals with quadrature amplitude modulation (QAM) is widely used for high-speed transmission of information in many radio systems and, in particular, in digital television systems. In the receiver, which is part of the transceiver equipment of such systems, there is a block for the formation of reference oscillations and a clock synchronization block. Due to hardware instabilities and propagation conditions, phase and clock errors may occur, which cause additional errors during demodulation of the received signal, and which can significantly impair the noise immunity of the reception. The paper investigates the effect of phase and clock synchronization errors on the noise immunity of coherent reception of QAM signals. Using the methods of statistical radio engineering, the parameters of the distributions of processes in the receiver are obtained and the probability of bit error is estimated. The dependences of the probability of bit error on the magnitude of the phase error in the formation of the reference oscillations and on the relative displacement of the clock moments, as well as on the signal-to-noise ratio, are obtained. It is shown that these errors can greatly reduce the noise immunity of the reception, and with an increase in the positioning of the signals, this effect increases. If we assume that the admissible reception energy loss is 0.5 dB due to each of these errors, then the allowable phase error is from ~3° at M = 4 to ~1° at M = 64, and the allowable clock synchronization error, respectively, is from ~5% at M = 4 to ~2% at M = 64. To provide more stringent requirements for the magnitude of losses, the requirements for the indicated errors increase significantly.

The purpose of the paper is to highlight the possibilities of using a low-frequency electrostatic field in clinical practice. On the basis of available literature data and their own clinical observations authors summarize information concerning various aspects of the use of low-frequency electrostatic field in clinical practice, and gives a description of this method of treatment.

Quadrature amplitude modulation (QAM) is used for high-speed information transmission in many radio systems and, in particular, in DVB-S and DVB-S2/S2X digital satellite television systems. A receiver included as a part of the transmitting equipment of such systems has a block for the formation of quadrature oscillations used as a reference for signal demodulation. Due to hardware instabilities, amplitude and phase errors may occur, which leads to quadratures imbalance. These inaccuracies cause additional errors in the received signal demodulation. This can significantly degrade the noise immunity of the reception. The paper investigates the influence of amplitude and phase errors in the formation of quadrature oscillations (imbalance of quadratures) on the noise immunity of coherent reception of QAM signals. Using the methods of statistical radio engineering the parameters of the distributions of processes in the receiver are obtained, and the probability of a bit error is estimated. The dependences of the bit error probability on the amplitude unbalance factor, on the phase error of quadrature formation and on signal-to-noise ratio are obtained. It is shown that the amplitude imbalance of the quadratures leads to a significant decrease in the noise immunity of QAM signals reception at M ≥ 16. The acceptable amplitude deviation in this case can be considered to be equal to 5%. At M= 4, the amplitude imbalance in a wide range of values practically does not affect the noise immunity. The phase imbalance of quadratures markedly affects the noise immunity of coherent reception of QAM signals. The permissible phase error is no more than 0.05 rad (3 degrees). As the signals positionality increases, this influence also increases.

The convergence of bound-state calculations performed via the oscillator basis expansions by means of locating $$S$$ -matrix poles for bound states within the HORSE and SS-HORSE approaches is examined. The convergence in question is studied both in the case of a sharp truncation of the potential matrix in the harmonic-oscillator space and in the case of smoothed matrix elements of the potential. As a result, a new method of extrapolation to the case of the infinite-dimensional model space is proposed. This method makes it possible to predict, on the basis of variational calculations, binding energies and asymptotic normalization coefficients for bound states to a high accuracy and to estimate the uncertainties of these predictions.

A comparative study of Raman spectra excited by laser radiation λL = 632.8 nm and 488 nm of natural crystals of 2H-MoS2 and nanocrystallites MoS2 (C) containing 0.5 and 1.0 wt.% Carbon additives. A detailed numerical analysis of the shape of observed D and G bands was performed. The complication of the spectra of graphite-like and diamond-like structures with the appearance of additional spectral components at 1440-1500 cm-1 and 1230-1270 cm-1 as a result of doubling the size of the corresponding elementary quasi-cells are analyzed. It is shown that the frequencies of D-bands of diamond-like nanostructures 1297 ÷ 1302 cm-1 don’t depend on λL in contrast to the change in the frequencies of the G (k)-bands. A significant effect of 632.8 nm resonant radiation on the electronic states and properties of MoS2 (C) NC was established. The strengthening of the D bands of the diamond-like structure and the ordering of the graphite structure with increasing carbon content in MoS2 (C) nanocrystals have been established. The change of spectral positions of D, G, and G (k) bands at strengthening the degree of disordering of a diamond- and graphite-like structures is considered. The influence of laser radiation on carbon structures is discussed.

The article discusses the relationship between the calculated reactivity ρ = 1 – 1/keff obtained from steady-state calculations and its measured analog. In VVER reactors, the measured reactivity is determined from the readings of a reactivity meter that processes IC current using the inverse point kinetics equation. In the article, a relation is established between the reactivity obtained from steady-state calculations and readings of a reactivity meter using the solutions of adjoint problems. By examples of measurements of the efficiency of emergency rods in VVER reactors, it is shown that the approach considered in the article is useful.

The paper analyzes a principal capability to transmute neptunium, the main component of transuranium radiowastes (TRW), in lead-cooled fast BREST-type reactor. High-energy neutron spectrum of the BREST-type fast reactor makes it possible either to eliminate neptunium in fission reactions or convert neptunium to plutonium with large fraction of 238Pu in radiative neutron capture reactions. According to the IAEA regulatory documents, plutonium containing above 80% 238Pu is regarded as an unsuitable material for manufacturing of nuclear explosive devices. Besides, good neutron-multiplying properties of 238Pu and 239Pu can prolong substantially the reactor core lifetime. Thus, introduction of neptunium into fresh fuel composition can eliminate the largest TRW fraction, strengthen regime of nuclear non-proliferation, produce some additional amount of thermal energy and prolong the reactor core lifetime.

Using statistical radioengineering methods, we analyzed the noise immunity of the receiving of the signals with multiposition quadrature amplitude modulation (M-QAM) in the presence of noise and relayed interference in the radio channel. It is shown that the reception quality of signals with M-QAM is susceptible to the influence of such interference, and this effect increases as the positioning of the signals increases. It is also established that the noise immunity for the reception of M-QAM signals is significantly better against the background of relayed interference than that of similarly positioned M-PSK signals.

We present the results of the ground-based microwave measurements of evolution of the vertical ozone content in the middle atmosphere above Nizhny Novgorod (56°20' N, 44° E) in the winter of 2017–2018. The results are compared with the satellite-based sensing data obtained using the MLS instrument onboard the Aura satellite and the ERA5 reanalysis data. In particular, the degree of the dependence of the stratospheric-ozone content on the position of the polar-vortex boundary with respect to the observation point at different altitudes is established. It is recorded that in January 2018 the vortex approached the city of Nizhny Novgorod and the boundary of the vortex up to its collapse (February 12), oscillated above the city, so that different altitude levels alternately appeared inside or outside the vortex. Such dynamics of the vortex most noticeably affected the evolution of the stratospheric maximum of the ozone content, whose position followed variation in the vortex boundary and quasiperiodically varied in the altitude range 30–35 km. The results of the ground-based microwave sensing give on the average a lower relative ozone content than the MLS data with a maximum systematic difference of about 0.8 ppm at the altitudes 38–39 km. Nevertheless, we recorded a more distinct response of the ozone content to a change in the structure of the vortex above Nizhny Novgorod than that in the case of using the satellite and reanalysis data.

Turbulent flow of thermoviscous liquid is studied in a three-dimensional region with periodicity in two directions. Flow characteristics are described in the terms of equation for turbulent kinetic energy: this allows to differentiate contributions from different components related to generation, transport, and dissipation of turbulent kinetic energy. Those terms can be calculated from averaging the moments of different order. The previous studies demonstrated that thermoviscous liquid flow occurs through several stages of evolution, including the unsteady turbulence. This allows discussing the problem of mathematical rigorous statement and applicability of different methods for averaging. Existence of spatial periodicity allow using a combined spatial-time averaging for different values on the interval of steady turbulence. Results are presented as a set of Z—t-diagrams. Besides, the paper presents analysis of flow development on the basis of direct visualization of velocity and temperature.

Spatially inhomogeneous structures of light waves are used as a mechanism of compacting information in optical and fiber-optic communication systems. In this paper, we consider a mathematical model of an optical radiation generator with a nonlinear delayed feedback loop and a stretching (compression) operator of the spatial coordinates of the light wave in a plane orthogonal to the radiation direction. It is shown that the presence of a delay in the feedback loop can lead to the generation of stable periodic spatially inhomogeneous oscillations. In the space of the main parameters of the generator, the spaces of generation of stable spatially non-uniform oscillations are constructed, the mechanism of their occurrence is studied, and approximate asymptotic formulas are constructed.

—This article discusses the results of parallel measurements with two-coordinate position-sensitive He3 detectors with a delay line, which are installed on REFLEX and GRAINS neutron spectrometers of the IBR-2 pulsed reactor with the simultaneous use of three data acquisition systems: DeLiDAQ-1, DeLiDAQ-2, and a system based on the N6730 digitizer produced by CAEN.

Subject of Research. Fiber optic measurement systems are widely used in various industries. Most of these systems are fiber optic devices for detecting physical quantities. The development and creation of a measurement system for determination of the location and bends of extended objects in 3D space are actual at the moment. We propose the implementation of the sensitive part of the fiber optic measurement system based on seven single-mode fibers with an array of fiber Bragg gratings fixed to each other. Method. The method for determining the position and bends of extended objects in space is based on finding the level of axial deformation (compression, tension) of the fiber Bragg gratings during bending, and provides the calculation of the curvature direction and magnitude. Further reconstruction of the curve in space is realized by solving a system of differential equations with given initial conditions containing Frenet-Serre formulas. Main Results. The paper presents experiment results on writing fiber Bragg grating arrays into single-mode optical fibers, taking into account the features of the optical scheme and the source spectrum. The design and prototype of the fiber optic measurement system are developed. The results on the reconstruction of the shape based on experimental data are obtained. Practical Relevance. A special feature of this system is the fiber Bragg grating arrays formed in a wide range of wavelengths. Each Bragg grating corresponds to its own reflection wavelength, providing a sensitive part 1 m long. The geometry of the structure is based on seven fiber-optic armored microcables twisted with a given lay length during manufacturing, and provides the measurement of the kink value and direction.

The wide spread of various radio systems with phase shift keying, including multi-position (MPSK), is due to their high noise immunity and ease of construction of the transmitting and receiving parts of the equipment. In real equipment, additional differential (relative) encoding is used when implementing transmitter and receiver circuits and, accordingly, DMPSK signals are used. One of the ways to receive such signals is to use an autocorrelation demodulator built on a quadrature scheme. The paper studies the noise immunity of an autocorrelation demodulator of signals with differential phase shift keying in the presence of Gaussian noise, Rayleigh fades and harmonic interference in the radio channel. The statistical parameters of signals and interference in the inphase and quadrature channels of the autocorrelation demodulator are determined. For M = 2 and 4, analytical formulas are obtained for the probability of a symbolic error, conditional on the random phase of harmonic. It is verified that the formula at M = 2 without harmonic interference reduces to an expression known from the literature. The values of the unconditional probabilities of symbolic errors are obtained by numerical averaging. It is shown that at a low level of harmonic interference, Rayleigh fading has a dominant effect. With a large level of interference, the additional energy loss can be several decibels, and at M = 4 these losses are significantly greater than at M = 2.

A low-dissipation numerical method based on a combination of Godunov’s method and a piecewise parabolic method on a local stencil is presented. The construction of the method is described in detail. The method is tested using a one-dimensional problem of breakdown of a discontinuity. The results of a numerical simulation of collision of two relativistic gas spheres are given.

The paper studies turbulent mixing in thermoviscous fluid flow in a 3D cubic domain which is extended periodically in two directions (X and Y). The flow turbulization develops under the impact of two-dimensional chaotic disturbances at mass average Reynolds number Re1 = 4704. The vortex field structure is discussed in terms of an isosurface of Q-criterion and local enstrophy ζ1. For the advanced stages of flow evolution, the study considers Eulerian correlation coefficients for velocity fluctuations (auto-correlation functions) and the cross-correlations of pressure and temperature. The Eulerian correlation coefficient is split for analysis of correlation characteristics in periodicity and wall-normal directions. The integral scale is evaluated depending on the distance to the walls. The flow analysis is performed in the terms of viscous scale. The mesh resolution is evaluated for the flow regions corresponding to the logarithmic boundary layer and the near-wall thermal layers.

We describe the mathematical tools of the optimal estimation method for retrieval of tropospheric temperature profiles (0–10 km) from radiometric data with the desired profiles parameterized in the form of expansion over empirical orthogonal functions obtained by a singular analysis of the covariance matrix of the radiosonde measurement data. It is shown that within the framework of such an approach one can use a high-resolution altitude grid for a relatively small dimensionality of the inverse problem. This permits one to properly analyze the statistics of radiosonde measurements and, at the same time, retrieve the temperature profiles without using a large computing power. We have conducted test retrievals of temperature using a large ensemble of simulated noisy spectra of atmospheric self-radiation based on the statistics of radiosonde temperature measurements above Nizhny Novgorod. It is found that the r.m.s. error of temperature retrieval from spectra in frequency ranges 50–55 GHz, 55–59 GHz, and 50–59 GHz varies within the ranges 0.5–2.7 K (at altitudes of 0–10 km), 0.3–1 K (at altitudes of 0–2 km), and 0.3–2.8 K (at altitudes of 0–10 km), respectively. The optimal number of empirical orthogonal functions (dimensionality of the problem) is 6–8 in the case of the 50–55 GHz spectra, 8 in the case of the 55–59 GHz spectra, and 10 in the case of the 50–59 GHz spectra.

An approach to the simulation of reciprocal space maps corresponding to the maps obtained experimentally by the triple crystal X-ray diffractometry (TXD) is proposed. A specific feature of the approach is the use of spectral angular distribution diagrams of X-ray radiation, which allows one to visualize the two-dimensional pattern of the spectral angular “composition” of an X-ray beam after its interaction with each element of the scheme and thus to take into account the contribution of the hardware function of the experimental setup. The algorithms developed allow calculations for a wide class of radiation sources (from an X‑ray tube with any material of the anode to a synchrotron radiation source) and X-ray optical elements (slits, X-ray mirrors of monochromators, and analyzers). The results of simulation are compared with the experimental data for dispersive diffraction geometry, which confirms the adequacy of the proposed approach and its applicability to the simulation of a diffraction pattern corresponding to a real experiment in the triple crystal scheme.

The article presents the results of numerical simulation of the experiments conducted during the physical start-up of unit 1 of the Novovoronezh II NPP. The list of measured parameters includes the critical concentration of boric acid and the scram efficiency. The calculations were performed using both the RAINBOW-TPP code intended for the combined neutronics and thermal-hydraulic calculation of the reactor facility and precision neutronics Monte Carlo codes. The scram efficiency was defined from steady-state calculations and using the inverse kinetics equation solution method based on numerical simulation of the neutron flux at the location of the ionization chambers. The results of the numerical simulation of the scram efficiency were compared with the measured data defined in the course of the physical start-up.

The causes of the occurrence and development of random non-cyclic vibroactivity of gas turbine units (GTUs) in an isolated energy area with an industrial load have been analyzed. It has been found that torsional vibrations of the rotating GTU parts first occur, causing radial oscillation at frequencies close to the first natural frequency of rotating masses (11.8 Hz). This further leads to the manifestation of resonance phenomena in certain modes, a sharp increase in the GTU gear oscillation level, and the shutdown of all operating GTUs with the complete blackout of the energy area. The main cause of the occurrence of subsynchronous torsional oscillations of the GTUs is the load shedding by large asynchronous motors connected through thyristor variable frequency drives (VFDs). Load shedding leads to the VFD input current amplitude fluctuations, which, in turn, cause oscillations of the GTU load current and shaft torque. Field tests have shown that the modulation of the amplitude of the fundamental harmonic of the non-sinusoidal waveform during load shedding may reach 40 % of the rated value. The lists of top-priority and long-term organizational and technical measures are given, the implementation of which will prevent the occurrence of subsynchronous torsional oscillations of the GTUs and contribute to the reliable power supply to the energy area consumers.

We review the recent results obtained by the KEDR experiment in the charmonium energy range. They include the measurements of $J/\psi$ meson total and partial widths and exclusive branching fractions, study of $D^+$ and $D^0$ meson masses and R between 1.8 and 7.0 GeV.

Probability density functions of Gaussian laser beam irradiance measured after propagation over 7km atmospheric path in comparison with various theoretical models are presented. The initial laser beam diameter at the e-2 intensity level was about 6 mm, the receiving aperture size was 14.4 cm. The experimental observations were performed in a wide range of turbulence strengths. The cases of weak, moderate, and strong intensity fluctuation regimes have been analyzed. Different receiving aperture radiuses were considered. The chi-square metric was used to estimate the agreement between the experimental and different theoretical statistics. The fractional gamma distribution has shown the best results for probability density distributions of apertures with sizes about 1 cm and 4 cm under strong turbulence conditions. The aperture averaging effect results in excluding near-zero irradiance values, which are typically observed on-axis at strong turbulence and high value of scintillation index which qualitatively transforms the observed statistics, so that experimental probability density functions can be well approximated by the fractional gamma distribution. With the increase of the aperture size, a further transformation of the statistics was observed. The statistics of experimental data for moderate and weak fluctuation regimes approached the lognormal and gamma distributions.

Quadrature amplitude modulation (QAM) signals are widely used in modern information transmission systems. The quality of the receiver of such signals is significantly reduced if non-fluctuation interference is present in the communication channel. Narrow-band (harmonic) interference with the frequency of the useful signal is especially dangerous. The aim of this work is to develop and study an adaptive algorithm for suppressing such interference when receiving QAM signals. The algorithm is based on a non-recursive digital filter with adjustable weights. It uses known information about the shape of the phase pulse of the signal. The efficiency of the algorithm is investigated by the method of computer simulation. When checking the performance of the algorithm, the spectrum of the signal and noise, the amplitude-frequency characteristic of the adaptive filter and the change in its shape over time were estimated. For 4-QAM and 16-QAM signals, the dependences of the bit error probability on the intensity of harmonic interference and on the signal-to-noise ratio are obtained. It is shown that the adaptive filter effectively suppresses harmonic interference with a relative intensity µ> 0.2 when receiving a 4-QAM signal. The energy advantage is 2 dB or more. When receiving QAM signals with M ≥16, which also have amplitude modulation, the algorithm remains operational, but the efficiency of using this adaptive filter is much lower. The energy advantage does not exceed 0.5 dB.

The paper introduces a method for adaptive deductive synthesis of state models, of complex objects, with multilevel variable structures. The method makes it possible to predict the state of objects using the data coming from them. The data from the objects are collected with sensors installed on them. Multilevel knowledge graphs (KG) are used to describe the observed objects. The new adaptive synthesis method develops previously proposed inductive and deductive synthesis methods, allowing the context to be taken into account when predicting the states of the monitored objects based on the data obtained from them. The article proposes the algorithm for the suggested method and presents its computational complexity analysis. The software system, based on the proposed method, and the algorithm for multilevel adaptive synthesis of the object models developed, are described in the article. The effectiveness of the proposed method is shown in the results from modeling the states of telecommunication networks of cable television operators.

The quasifree $\overrightarrow{\gamma} d\to\pi^0n(p)$ photon beam asymmetry, $\Sigma$, has been measured at photon energies, $E_\gamma$, from 390 to 610 MeV, corresponding to center of mass energy from 1.271 to 1.424 GeV, for the first time. The data were collected in the A2 hall of the MAMI electron beam facility with the Crystal Ball and TAPS calorimeters covering pion center-of-mass angles from 49 to 148$^\circ$. In this kinematic region, polarization observables are sensitive to contributions from the $\Delta (1232)$ and $N(1440)$ resonances. The extracted values of $\Sigma$ have been compared to predictions based on partial-wave analyses (PWAs) of the existing pion photoproduction database. Our comparison includes the SAID, MAID, and Bonn-Gatchina analyses; while a revised SAID fit, including the new $\Sigma$ measurements, has also been performed. In addition, isospin symmetry is examined as a way to predict $\pi^0n$ photoproduction observables, based on fits to published data in the channels $\pi^0p$, $\pi^+n$, and $\pi^-p$., Comment: 11 pages, 9 figures, 5 tables; fixed 2 glitches

Differential cross sections for the production of nuclear fragments at an angle of 3.5° in the fragmentation of 2-GeV/nucleon carbon ions on a beryllium target were measured in the FRAGM experiment performed at the ITEP-TWA heavy-ion accelerator-accumulator complex. The predictions of four Monte Carlo models of ion-ion interactions (BC, INCL, LAQGSM, and QMD) were tested on the basis of a comparison with the momentum spectra of fragments. Successes and drawbacks of these models are discussed. The energy spectra of protons and 3He nuclei in the cumulative region in the projectile rest frame are well described by an exponential dependence, which make it possible to estimate temperature parameters of their emission source.

We present the results of microwave observations of atmospheric radiation in the ozone line in the case of ionospheric perturbation by powerful high-frequency radio emission from the “Sura” facility in September 2016. The atmospheric-radiation spectrum in the ozone line was measured by the method of the ground-based microwave radiometry. The state of the lower ionosphere was simultaneously diagnosed in the altitude range 50–130 km using the method of resonant scattering of radio waves by the artificial periodic irregularities of ionospheric plasma. A decrease in the intensity of the microwave atmospheric radiation in the ozone line was observed. The results of measurements of the amplitude and phase of the signal scattered by artificial periodic irregularities demonstrated a perturbation of the parameters of the lower ionosphere when it was heated by high-frequency radiation.

Structure vibration under the influence of unsteady hydrodynamic forces caused by the flow around their surfaces can adversely affect durability and rupture life. Reducing the adverse effects of hydrodynamic forces is currently possible with the help of linked CFD and vibration calculations. However, for an adequate description of the associated processes one should use calculation models and approaches specific to the hydro-vibration problem. To justify and validate such approaches, an experimental model was developed and a series of structure excitation tests in water flow was carried out.The model comprises two cylinders installed sequentially in water crossflow. Vibration levels, pressure and velocity fluctuations were measured in the tests as a functions of the flow velocity. The application of different non-intrusive measurement techniques was possible due to relatively simple test model construction which may be used for cross-validation and experimental uncertainty quantification.Flow-structure interaction, caused by synchronization effect of the flow separation frequency (or it’s spectral components) and eigenfrequency of cylinder, was analyzed based on simultaneously measured data. The tests performed gave the information about dynamical characteristics of the flow and vibration parameters of cantilevered cylinders. The experimental results are used for identification of required accuracy of hydrodynamic forces calculation by CFD and validation of oneand two-way linked methods for flow excitation frequency calculation.

The dynamics of a nanomagnet coupled to a Josephson junction has been studied. Although a magnetic field induced by the superconducting current in the Josephson junction is very weak, an applied voltage can generate the nonlinear dynamics of the nanomagnet, which gives a number of interesting phenomena. It has been shown that a ferromagnetic resonance can occur when the frequency of Josephson oscillations becomes equal to the eigenfrequency of the magnetic system. It has been demonstrated that the easy axis of the nanomagnet is reoriented at an increase in the Josephson-to-magnetic energy ratio, as well as in the coupling parameter between the Josephson current and the magnetic moment and in the frequency of Josephson oscillations. It has been shown that a current pulse can turn the magnetic moment of the nanomagnet, which opens new prospects for the application of this system in superconducting spintronics.

A new method for extrapolating bound-state energies obtained in a harmonic-oscillator basis is proposed. This method also makes it possible to calculate asymptotic normalization coefficients. A theoretical validation of the method is presented along with its application to a model problem.

The article proposed a method for modeling and analyzing the high-frequency properties of multi-valley semiconductors, in particular, GaN, AlN and InN. The model is applied to state-of-the-art, promising and relevant materials GaN, AlN and InN, which are now known under the generic name III-nitrides. The method is distinguished by the economical use of computational resources without significant loss of accuracy and the possibility of using both for dynamic tasks over time and variables in the space of fields. The proposed approach is based on solving a system of differential equations, which are known as relaxation equations and are derived from the Boltzmann kinetic equation in the relaxation time approximation by averaging over k-space. In English literature, this method is known as the "method of moments." In contrast to the traditional system of equations for the concentration of carriers, their momentum and energy, here, instead of the energy relaxation equation, the equation for electron temperature is used as a measure of the energy of only chaotic motion. The second significant difference is that the relaxation times are not determined as integral values from the static characteristics of the material, but through averaging the quantum-mechanical scattering rates commonly used in the Monte Carlo method for certain types of scattering. The averaging was performed over the Maxwell distribution function in the electron temperature approximation, as a result of which various mechanisms of carrier scattering through their specific relaxation times are taken into account. Since the system of equations used includes equations in partial derivatives with respect to time and coordinates, it makes it possible to investigate the characteristic manifestations of the impulse properties of the materials under consideration, namely, the time effect of the “overshoot” of drift velocity and the spatial “ballistic transport” of carriers. For the first time, the use of the Fourier transformation of the impulse dependence of the carrier drift velocity to calculate the maximum frequencies inherent in a semiconductor is considered. A connection was found between the shape of the spectral characteristic of the drift velocity and the scattering mechanisms that prevail in a given electric field. The properties of III-nitrides in the frequency domain in a strong electric field are analyzed and compared with existing methods for estimating cut-off frequencies. It is shown that the limiting frequencies increase with increasing electric field strength and amount to hundreds of gigahertz, and for aluminum nitride it exceeds one thousand gigahertz. This is due, apparently, to the greatest for him inter-valley distances and, accordingly, with a weakened inter-valley scattering. The analysis of the spatial manifestation of the splash effect shows the possibility of an almost collisionless, ballistic flight of electrons in a strong field at distances up to hundredths and tenths of a micrometer. Ref. 15, fig. 10, tabl. 1.

A model of distributed information carriers in the form of stable spatially inhomogeneous structures in optical and fiber-optic communication systems is considered. We study the conditions for the occurrence of such stable spatially inhomogeneous structures of the light wave of the generator of optical radiation. The formation of inhomogeneous structures that occur in a plane orthogonal to the direction of wave propagation is provided by a thin layer of nonlinear medium and a two-dimensional lagging feedback loop with the rotation operator of the spatial coordinates of the light wave in the emission plane of the optical generator. In the space of the main parameters of the generator (a control parameter, the angle of rotation of the spatial coordinates, the magnitude of the delay), the areas of generation of stable spatially inhomogeneous structures are constructed, the mechanisms of their occurrence are analyzed.

Shear and membrane locking phenomena are fundamental issues of shell finite element models. A family of refined shell elements for laminated structures has been developed in the framework of Carrera Unified Formulation, including hierarchical elements based on higher-order Legendre polynomial expansions. These hierarchical elements were reported to be relatively less prone to locking phenomena, yet an exhaustive evaluation of them regarding the mitigation of shear and membrane locking on laminated shells is still essential. In the present article, numerically efficient integration schemes for hierarchical elements, including also reduced and selective integration procedures, are discussed and evaluated through single-element p-version finite element models. Both shear and membrane locking are assessed quantitatively through the estimation of strain energy components. The numerical results show that the fully integrated hierarchical shell elements can overcome the shear and membrane locking effectively when a sufficiently high polynomial degree is reached. Reduced and selective integration schemes can help with the mitigation of locking on lower-order hierarchical shell elements.

The energy and spectral advantages of signals with phase shift keying predetermined their widespread use in modern digital navigation, communications and television systems. The use of such signals is the base of communication standards of DVB-S, DVB-S2 / S2X, GLONASS, CDMA, WiFi IEEE 802.11 and others. To increase the capacity of radio channels, multiple phase shift keying (MPSK) is applied. This increases the number of possible phase states of the signal and, thus, the information capacity of the channel symbol. However, such an increase greatly affects the noise immunity of MPSK signal reception. In the article the noise immunity of receiving signals with multiple phase shift keying in the presence of noise and phase-shift interference is analyzed by the methods of statistical radio engineering. The dependencies of bit error probability on the signal-to-noise ratio, on the interference intensity, on the relative transmission speed of the interference, and on its detuning relative to the center frequency of the spectrum of the useful signal are calculated. It is shown that signals with multiple phase shift keying are very strongly influenced by phase-shift interference, and this influence increases with increasing signal positionality. The degree of reduction of the noise immunity of the reception depends on the magnitude of the relative transmission rate of the interference and its intensity. The damaging effect of the phase-shift interference is most pronounced when it hits the main lobe of the signal spectrum. As the relative transmission rate increases, the interference becomes more broadband and pseudo-noise, and it affects even with very large frequency detuning somewhat decreasing in the region of the main lobe of the signal spectrum. This decrease seems natural, since the analyzed algorithm for receiving MPSK signals is optimal for the effects of noise interference.