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A Monte Carlo generator to simulate events of single-photon annihilation to hadrons at center-of-mass energies below 2 GeV is described. The generator is based on existing data on cross sections of various exclusive channels of e+e− annihilation obtained in scan and ISR experiments. It is extensively used in the software packages for analysis of experiments at the Novosibirsk e+e− colliders VEPP-2000 and VEPP-4M aimed at high-precision measurements of hadronic cross sections with different applications, e.g. to calculations of the hadronic vacuum polarization for the muon anomalous magnetic moment.

The results of experimental studies of fast dynamics (dependence of transmitted elastic wave amplitude and velocity on pump amplitude) of longitudinal and transverse elastic waves in a 3D-printed polyacrylonitrile-butadiene-styrene (ABS) sample are reported. The measurements are carried out using the echo-pulse method in the frequency range from 500 to 900 kHz. It is shown that the pump amplitude dependence of the wave velocity variation is stronger for longitudinal waves, while the dependence of the passing wave amplitude on the pump amplitude is stronger for transverse waves with different polarizations. Both cases demonstrate a nonlinear nature of the dependence. Based on the data on the velocity of longitudinal and transverse waves, the estimates of nonlinear changes in the elastic modulus are obtained.

This article discusses the quality of astronomical images under conditions of moderate small-scale turbulence and varying meso-scale airflows above the Baikal Astrophysical Observatory (BAO). We applied a Weather Research and Forecasting (WRF) Model, as well as statistical estimations of the Fried parameter from the differential motion of the solar images. The simulations were performed with a fairly high horizontal resolution within a large area of 1600 × 1600 km. A high horizontal resolution provides representative estimations of atmospheric characteristics and correct accounting of large-scale air advection. We considered the influence of atmospheric motions over the cold water area of Lake Baikal, as well as meso-scale vortex structures over rough terrain on solar image quality. A better understanding of structured turbulent small-scale motions and optical turbulence over rough terrain may help to develop advanced methods for diagnostics and prediction of image quality. For the first time, we have shown that the BAO is located at the periphery of a meso-scale atmospheric vortex structure with an anticyclonic direction of airflows in the daytime. An increase in image quality was associated with weakening airflows over Lake Baikal and a decrease in the intensity of wind speed fluctuations. Calculated spectra of atmospheric turbulence in the daytime were close to the classical form. At night and in the morning, the spectra had a steeper slope on small scales. Deformations of the spectra were due to the suppression of turbulence under stable stratification of the atmosphere. The characteristic horizontal scales of the transition from “−5/3” to ∼“−3” spectral slope were 2–2.5 km. The results obtained using the WRF model and analysis of optical turbulence strength (namely, the Fried parameter) indicated that the parameterization schemes used in the WRF model were accurate.

A low-order model of quadrupole sound sources in a turbulent jet has been developed using the acoustic analogy method. Multimicrophone acoustic measurements of jet sound radiation are used to estimate the model parameters and validate it. Based on measurements carried out in different zones of the sound field, estimates of the size of the effective localization region of sound sources are made and the boundaries of the zone of dominance of quadrupole sound radiation over pseudo-sound fluctuations are determined. The proposed model can be used in practical estimates of the spectral and correlation characteristics of the far and near sound field of the jet.

This article describes an original method for adaptive control of day length, illumination level, and the spectral composition of light in neonatal incubators. From a hardware point of view, the proposed method is based on the use of special glazing that produces smooth changes in transparency using an electric current (as an actuator), a neural controller (as a control unit), and light flux sensors (to generate feedback). The adaptive algorithm supports synchronization of priority control commands from medical staff with the current integral light flux falling on the outer surface of the incubator. The solutions proposed here can be used for more flexible control of environmental conditions in neonatal incubators.

A laser scanning vibrometer was used to measure the amplitudes and phases of the vibrational velocity of shear waves excited by a one-dimensional source in the form of a narrow rectangular bar in a gel-like medium. The vibrations of 26 plates reflecting the laser beam and located inside an optically transparent phantom along a segment with a length of 84.5 mm at a distance of 20 mm from the source were measured. The angular distributions of the amplitude and phase of shear waves at discrete frequencies from 59 to 500 Hz were measured in continuous mode. In pulsed mode, the vibrator excited a pulse in the medium with a duration of 1.5 periods of the 300 Hz frequency. The amplitudes and phases of shear waves were calculated by fast Fourier transform of the time profile of the vibration velocity of the plates with a duration of 50 ms. The angular amplitude distributions measured in the pulsed and continuous modes are qualitatively the same. At all frequencies, the distributions are symmetrical with respect to the vertical axis. The maximum oscillation amplitude is observed at angles close to ±45°. The velocity of shear waves, calculated from the measured phase distributions, increases from 2 to 2.5 m/s with a change in frequency from 50 to 500 Hz. It is shown that this velocity behavior is well described by a relaxation model of the medium with one relaxation time equal to 0.3 ms. Shear wave attenuation depends on frequency and exceeds 1 cm –1 for waves with frequencies above 250 Hz. The maximum attenuation per wavelength is observed near the relaxation frequency of the medium in the 300–400 Hz range. The results can be used to optimize devices for measuring the elasticity of soft tissues.

— We present the results of numerical simulation and experimental studies of the propagation of fle-xural elastic waves in a notched metal bar with a rectangular cross section that approximates the acoustic black hole effect. The sample is a notched bar; the depth of notches increases according to a power law with an exponent of 4/3. The experimental results and the results of numerical simulation confirm that such bars slow the propagation velocity of an elastic wave towards the end of the bar. It is demonstrated that flexural waves in such structures exhibit dispersion and their amplitude at the end of the bar for some eigenfrequencies is higher than that in a solid bar. The eigenmode shapes of a solid and notched bar are compared together with the distribution of the flexural wave amplitude along the bars. The frequency dependence of the flexural wave length is studied during wave propagation towards the end of the notched bar.

The propagation of flexural elastic waves in notched metal bars with a rectangular cross section with the depth of notches increasing by a power law has been studied by numerical modeling and experimental laser scanning vibrometry. Three types of notch arrangement have been considered: uniform and more frequent and sparse towards the end of a bar. Such structures exhibit the characteristics of an acoustic black hole. For all the studied samples, in the 10–100 kHz frequency range, an increase in amplitude and decrease in length of the flexural wave have been experimentally found as a wave approaches the end of a bar. It has been shown that there is a critical frequency, above which the modes exhibit a section with highly reduced amplitude of oscillations.

— The paper reports some results of experimental study on the effect of 3D-printing on the linear and nonlinear elastic properties of ABS polymer specimens manufactured in the form of thin filaments with 100% filling. The initial and 3D-printed ABD polymer specimens were studied by the static and Thurston–Bragger methods. Linear and nonlinear Young’s moduli and second-order nonlinear acoustic parameters were determined for several loading–unloading cycles of a specimen. It has been shown that the selected 3D-printing mode does not almost change the strength characteristics of ABS polymer, and its plastic characteristics even become slightly better. It has been revealed that mechanical loading has different effects on the nonlinear parameter of the initial and 3D-printed specimens. For the 3D-printed specimen, the nonlinear parameter is observed to decrease with increasing load.

The article presents the results of experimental studies of how 3D printing with 100% filling influences the elastic properties of PLA filament polymer samples. The static and Thurston–Brugger methods simultaneously measure the dependence of strain and the relative change in the velocity of elastic waves on the applied mechanical stress (up to failure) for the initial and 3D-printed samples of the PLA polymer. Based on the measurement results, the linear and nonlinear Young’s moduli and second-order acoustic nonlinear parameter are calculated. It has been established that 3D printing leads to a deterioration in the strength and plastic characteristics of PLA. A different behavior of the nonlinear parameters of the initial and 3D-printed PLA samples in the loading and unloading region was revealed, associated with a change in the internal structure of the sample caused by 3D printing.