Measurements of the nonlinear parameter of a gel-like medium were carried out in an acoustical resonator fixed without slipping between two solid-state boundaries. A sample of thickness L is fixed on an oscillating plate (x = 0). The other plate of finite mass on the free surface of the sample (x = L) moves together with this surface. By changing the mass of the plate (x = L), it is possible to achieve additional static deformation of the resonator up to 65%. The dynamic method assumes measuring resonance curves at various static deformations. Nonlinear properties appear at deformations of more than 20%. The nonlinear parameter and shear modulus measured dynamically were compared to static measurements where the dependence becomes nonlinear at strains greater than 30%. The static values of the shear modulus and the nonlinear parameter correspond to the values obtained in the dynamic method within an error.

Since human muscles, particularly biceps, have an anisotropic structure associated with fibrous structure, it is important to study the muscle taking into account its anisotropy. We constructed a simple ultrasonic shaker to control the activity of the biceps. The device performs non-invasive control of the biceps state from the surface. A certain frequency of the tissue displacement caused by the vibrating indenter is chosen to excite shear waves inside the biceps. The displacement of the tissue then can be registered by means of the ultrasonic signal emitted from the probe that is firmly connected to the indenting surface. Both speed and frequency of the shear waves are smaller than the same properties of the ultrasound. The device is a rectangular ultrasonic probe attached to the front part of the movable vibrator plate. The vibrator with the help of the movable plate, leaning the front part of the bicep, excites shear waves in it. An ultrasound probe monitors the propagation of shear waves in the muscle in real time. Two-channel signal generator connected to the operating computer powers both the vibrator and the ultrasonic probe. Registration of ultrasound pulses received by the piezoelectric element is performed using an oscilloscope also connected to a computer. Thus, power signals are formed and evaluation is implemented in specially developed software. The probe has a form of an elongated rectangle which makes it possible to register the shear waves excited in two polarizations: along and perpendicular to the muscle fibers and measure the shear elasticity of the muscle taking into account its anisotropy. Measurements of biceps shear elasticity are carried out at various loads: static and variable. The processes of biceps relaxation are investigated. This will help to develop a method that will determine the effect of muscle load on its growth and damage .

The results of application of the ultrasonic (US) Doppler method for measuring the elasticity of skeletal muscles lying at a small depth (2–4 cm) from the skin surface are presented. The technique is based on calculating the speed of shear waves excited by a vibrator on the skin’s surface at frequencies of 150–250 Hz. The distribution of shear displacements in an elastic phantom, calculated by the finite element method, was compared with the results of measurements using a miniature accelerometer. The shear modulus of the elastic phantom, measured using the proposed technique, corresponds to values obtained from static measurements.

The results of studying the influence of undamped thermal waves on the process of nuclear fusion in a remote target are presented. These waves form on the reverse side of a metal target, which is subjected to a water jet in the cavitation state, and are characterized by strictly defined frequencies (in air, under normal conditions, and at different humidities, the minimum frequency of such a wave is $${{\omega }_{0}} \approx 75{\kern 1pt} - {\kern 1pt} 85$$ MHz). It is shown that, the action of such waves on a remote sample of deuterated polycrystalline titanium (a “nuclear” target) generates alpha particles, the emission direction of which agrees with the target geometry and orientation.

The physical mechanism of the generation, features of propagation and the possible use of undamped temperature waves are considered. The process of generation of these waves is related to the possibility of reversibility of local relaxation thermodynamic processes of heat transfer. In the course of experiments, it was shown that such waves can exist only at certain frequencies, depending on the relaxation time. The possibility of energy transfer using these waves over a long distance has been investigated. It is shown that using of these waves X-ray generation is possible, and effective stimulation of nuclear fusion in a TiD target located behind a thick metal screen which is remote from the wave source. In this work is also considered a possible physical mechanism for the realization of LENR reactions connected with the formation of coherent correlated states of interacting particles under the action of these temperature waves. (C) 2020 ISCMNS. All rights reserved. ISSN 2227-3123

Shear modulus in the biceps of volunteers was measured with standard ultrasound equipment, the at loads from 0 to 50 N. The measurements were carried out by shear wave elastography in the clinic according to the medical protocol. The volunteer held a sport weight of known mass to load the bicep. Shear wave was excited in the muscle at a given depth by an ultrasonic sensor. The shear wave velocity was recorded in the specific point, which was determined by the position of the sensor. The shear modulus of the muscle fibers measured by elastography increases from 10 to 60 kPa with the increase of the load and returns to 10 kPa 1 min after load is removed. The maps of the shear modulus distribution were measured in the areas around the points of the shear velocity measurements. Research was funded by the grant from the Russian Science Foundation (Project No. 19-72-00086).

Monitoring of the electrical equipment as a part of electrical power systems is necessary to ensure the reliability of electrical energy transmission and distribution. Operating modes of power substation transformers and autotransformers are under particular control due to their high functional significance. The most effective method is the real time detection and classification of abnormal operating modes in transformers. Our approach reveals defects of the transformer. The setup consists of a transformer surrounded by three Dialog M-110 microphones connected to a computer via two Orient AU01SW USB and one Creative Play! (SB1140) RET sound cards. The increase of voltage on one of the transformer windings leads to the increase of the amplitude of the magnetic induction in the transformer core up to the value that corresponds to the deep saturation. We recorded a signal from each microphone to a unique track applying Steinberg Cubase 5 and divided each record into two parts representing different modes, which allowed us to observe different spectra for each mode in each series with embedded «Spectrum Analyzer». We ignored a part of spectra beyond the frequency range of the microphones which was 50 – 16 000 Hz and observed the change in components at 250 Hz and 350 Hz. We witness the increase of harmonics in transformer with defect that miss in a signal, obtained for the normal transformer. The artificial neural networks classify the set of signals. The artificial convolutional neural networks (CNN) method is most popular for sound classification nowadays. Neural network algorithms together with our approach to the study of acoustic signals generated by transformer elements will provide an opportunity to obtain effective methods for timely detection of non-normative operating modes of transformer equipment. The results are applicable for new generation of high-speed automation systems of emergency response in electric power systems.

We applied a commercial ultrasonic clinical diagnostic system for studies of human biceps. The investigated area was visualized in B-mode at a frequency of 8 MHz. We selected 1 cm and 2.5 cm depths for shear wave excitation. On these depths, the focused ultrasonic wave caused the acoustical radiation force. Due to nonlinear mechanism of excitation, a shear wave arose. The results we have obtained show that the biceps have the shear moduli of the order of 10 kPa. The loaded biceps demonstrated the nonlinear behavior better pronounced for the volunteer with smaller body mass index (BMI). As the load on the biceps increases, the shear modulus measured along the muscle fibers grows. The observed growth was stronger for the shear modulus of the short head. The shear modulus, measured in the direction across the fibers of the biceps, does not depend on the magnitude of the applied load and remains at the unloaded value. In 1 minute after load is removed the biceps tend to relax and its shear moduli turn their initial values.

The features of the propagation of undamped thermal (temperature) waves in air are investigated. The presence of these waves is a consequence of solution of the heat equation taking into account the relaxation of local thermal perturbation. It is shown that such waves can exist only in media with a finite (nonzero) time of local thermal relaxation, and their frequencies are determined by this time. The time of relaxation in air depends on the gas composition, its temperature and increases with a decrease in pressure. Under normal conditions, the minimum frequency of undamped waves in air corresponds to 70–80 MHz. One of the methods for exciting these waves is associated with pulsed heating of the surface of a medium bordering air. Pulsed heating on account of the application of shock waves generated during water jet cavitation is used. It is shown for the first time that these waves with frequencies in the range of 70–500 MHz can propagate in air without damping over a distance of up to 2 m.

The problems of the existence, generation, propagation and registration of long-distant undamped thermal waves formed in pulse radiative processes have been theoretically analyzed and confirmed experimentally. These waves may be used for the analysis of short-time processes of interaction of particles or electromagnetic fields with different targets. Such undamped waves can only exist in environments with a finite (nonzero) time of local thermal relaxation and their frequencies are determined by this time. The results of successful experiments on the generation and registration of undamped thermal waves at a large distance (up to 2m) are also presented.

The common algorithm of shear waves excitation for diagnostical ultrasonic devices was modified for measurements in muscles. We measured the speed of shear waves, excited by a focused ultrasound at a frequency of 5 MHz in the muscles of the volunteers. Siemens Acuson S2000 was used for in vivo measurements. The suggested algorithm was tested on the muscle mimicking phantoms. The values of shear wave velocities in the same areas of studied phantoms at the same angles measured with Siemens Acuson S2000 system corresponded to the values obtained by Verasonics, where the region of shear wave excitation had a form of “blade” of thickness less than 0.5 mm, length and width of 1.5-2 mm. Due to this form of the region, the excited shear wave has propagated codirectional with the long side of the ultrasonic medical probe. Thus, the direction of propagation of the shear wave with respect to the phantom fibers, became dependent on the position of the probe. [The reported study was funded by RFBR and Moscow city Government according to the research project № 15-32-70016 «mol_а_mos», by RFBR according to the research project № 16-02-00719 а, and by Program for Sponsorship of Leading Scientific Schools (Grant NSh-7062.2016.2).]

We studied standing shear waves in anisotropic resonator represented by a rectangular parallelepiped (layer) fixed without slipping between two wooden plates of finite mass. The viscoelastic layer with edges of 70 mm x 40 mm x 15 mm was made of a gelatin-based composition with rubber bands inside. We placed the bands between the top and the bottom plate. Mechanical properties of the homogeneous gelatin-based material without the bands were carefully measured, prior to the experiment. The value of linear shear modulus was found to be several kilopascals, which is common for such soft solids. Stretching the rubber bands inside the layer leads to change of elastic properties of the resonator. Such effect could be noticed due to frequency response of the resonator and becomes dependent on the relative volume of the rubber bands, i.e. the ratio between the volume of the bands and the volume of the whole resonator. We carried out the experiment to confirm numerical model of the resonator with rubber bands inside that we previously suggested. The model based on finite elements method (FEM) was performed in MatLab. We cut the resonator in hundreds of right triangular prisms. Each prism was provided with viscoelastic properties of the layer except for the top prisms provided with the wooden plate properties and the prisms at the site of the rubber bands provided with the rubber properties. The boundary conditions on each prism satisfied the requirements that resonator is inseparable and all its boundaries but bottom are free. The bottom boundary was set to move horizontally with constant acceleration amplitude. We considered two configurations placing the rubber bands first down and then across the resonator. This gave us an opportunity to study anisotropic properties of the resonator. We showed that the experimental data corresponds to the results of numerical simulation.

We proposed a technique for measurements of the viscoelastic properties of soft tissues applying shear standing waves to the studied material. The technique is based on the resonator method developed and described in detail previously. In this method, the resonator was represented by the layer of studied material firmly connected between two parallel plates of finite mass. Accelerations of the plates could be measured by small and light uniaxial accelerometers. The vibrator forces one of the plates, while the layer forces the other. Arbitrary function generator powers the vibrator. Signals measured by accelerometers are evaluated in LabVIEW by a special algorithm, which is designed to maintain given acceleration amplitude on the vibrator and collect data for steady-state oscillations. Thus, we obtain the resonance curves in the range 1500 Hz, showing the fundamental resonance and several more further resonances. We compare the resonance curves with the model of nonlinear resonator considering the material relaxation times. In this model, the wave from the plate forced by the vibrator interacts with the wave reflected from the opposite plate and standing wave is excited. This standing wave on the fundamental frequency tends to have a node in the area of the plate forced by the vibrator, whereas antinode is near the plate forced by the layer. The fundamental frequency depends on the viscoelastic properties of studied material and mass of the plate forced by the layer. Since frequency dependence on the plate mass lets one perform series measurements, it makes suggested method robust. We tested our technique "ex vivo". Measured values of shear moduli and shear viscosity correspond to the values for corresponding tissues found in literature. The further investigation will adapt the technique for "in vivo" measurements. In that case a novel inexpensive noninvasive technique applicable to tissue state control in human body will appear.

The authors study reduction of longitudinal ultrasonic oscillations in sodium chlorate crystals within the temperature range of 78 - 525 K and relative amplitudes of oscillatory deformation of 10(-7) - 10(-5) according to the method of compound piezoelectric vibrator at the frequencies of approximate to 10(5) Hz.

New regularities in radiation defects formation in the space charge region were established for indium phosphide with application of the method of deep level transient spectroscopy. The given regulations differ markedly from the regulations in the neutral region. The authors develop physical models of these processes and their mathematical description. They also work out new concepts of the processes of radiation defects formation in indium phosphide based on taking into account charge states of defects and their recharge dynamics.

Standing shear waves in a resonator in the form of layer of gel-like medium placed between two rigid plates are studied. The bottom plate is fixed to the vibrator and oscillates in the horizontal direction with a preset amplitude. Two rubber threads attached to the upper plate can displace the plate by a specified value in the horizontal direction. The change in the tension of the threads creates an additional static deformation of the elastic layer resulting in the effective shear elasticity increase. The measured static stress-strain dependence of the elastic layer can be described by the cubic parabola. We measured the dependences of the resonance frequency on the static deformation of the layer. For static deformations of the layer less than 0.3 h (h—is the layer thickness), the resonance frequency increases linearly, that can be explained by a linear growth of the elastic force of rubber threads. In the deformation range of 0.3-1 h, an additional shift of the resonance frequency caused by the nonlinearity of a gel-like medium appears. The method allows the dynamic nonlinear parameter measurement in gel-like media at the low frequency range.