The use of a separate receiving antenna at different frequencies in parametric acoustic systems is associated with the irreversibility of nonlinear processes underlying its principle of operation. The paper considers the results of experimental and theoretical studies to assess the influence of external elements on the amplitude-frequency response of a piezoceramic acoustic antenna. The structural scheme of the experimental setup is considered. It is shown that parallel connection of an external inductance to a piezoelectric element allows shifting the antiresonance frequency of an acoustic antenna, which leads to an increase in both the signal amplitude at the antenna output and an increase in the complex resistance module at the operating frequency.
Keywords: acoustic antenna, the sensitivity of the receiving antenna, the amplitude-frequency characteristic, the modulus of the complex resistance
In this paper proposed a statistical model of the optoacoustic transformation in the moving liquid medium using nanoparticles for a noninvasive blood analysis system. Since to increase the accuracy of measurements should take into account the probabilistic nature of the distribution of nanoscale objects as contrast agents in the blood stream in the human cardiovascular system. To determine the statistical characteristics of the component of the sound signal formed by a conglomerate of nanoscale objects using Monte Carlo simulation. Main static characteristics were calculated and the density distribution of the probability of the normalized amplitude of the sound signal was determined for a series of numerical experiments.
Keywords: optoacoustics, optoacoustic effect, flow cytometry, acoustic signal, carbon nanotubes, laser sound excitation, statistical analysis
Application for monitoring ice conditions devices based on nonlinear acoustics using parametric radiating antenna takes into consideration such characteristics of the formation of the acoustic field, as having both low-frequency difference frequency formed as a result of the nonlinear interaction of two close by the value of the pump waves, and, in fact, high-frequency radiation source pump waves Development of instruments for acoustic monitoring ice conditions require consideration of all possible real oceanographic situations in which they will operate. The article discusses the results of the development of a system for monitoring the panorama of ice conditions in the parametric mode sonar. The analysis of the formation and propagation of the probing signals into acoustic channel parametric meter ice thickness is formulated the principle of measuring the thickness of the reflection (scattering) of the acoustic signals from a locally stratified system with blurred boundaries. Mathematical modeling of the acoustic channel power meter ice thickness and "windows of transparency" on the basis of the calculation of the critical angles of incidence and refraction. The conclusion of the feasibility of using as reference signals of shear waves.
Keywords: ice monitoring acoustic antenna, the critical angle , the transparency window
This study analyses fractal characteristics of open-loop and closed-loop control mechanisms for different conditions of the sensor control. The stabilogram acquired using three types of the sensor control: open eyes (OE), closed eyes (CE) and visual artificial feedback (VAF). To determine the difference in control mechanisms for different condition of sensor control we have applied the method, offered by Collins J.J. and De Luca C.J. This method is based on the calculation of the Hurst exponent. We did not reveal significant differences (p>0,05) for control mechanisms between OE and CE parameters. However, there were significant differences for control mechanisms between VAF and OE parameters. We revealed that VAF reinforces open-loop and closed loop control mechanisms in anteroposterior directions, as well as VAF reinforces closed-loop control mechanisms in mediolateral directions. It may be important, in a rehabilitation setting, to identify which one of the two components of postural control (open loop or closed loop) needs more reinforcement in a particular patient, and consequently design an optimized device to improve postural balance.
Keywords: fractal analysis, Hurst exponent, open-loop, closed-loop, artificial feedback, analysis of stabilogram, postural control
Briefly discussed the theoretical model of the spectrum of RR intervals and its changes depending on the processes taking place. Made a device for measuring cardiointervalogramms (CIG). Obtained from the renting of data, of varying duration and frequency shall be recorded for further processing. The analysis revealed that the resulting spectrum satisfies the conditions considered in the theoretical model, and can be further analyzed with fractal characteristics. Such an analysis is of great importance in the diagnosis of the patient directly to the duration of the therapeutic procedure for the optimization of both time and intensity exerted influence.
Keywords: CIG; fractal series; the spectrum of RR intervals
To study complex sonar systems, the method of decomposition was suggested. The peculiarities of the method applied to the sonar systems were considered. A four-level hierarchy of decomposition subsystems is proposed. A scheme of the first level of semantic decomposition was presented. Controlled modules allowed to build adaptive systems were described.
Keywords: decomposition, hydro speaker systems, hierarchy of subsystems
Now nanotechnologies are one of perspective methods of diagnostics in medical practice. Nanoparticles can be used as contrast agents for medical ultrasonic introscopy due to their adhesion to tumor cells and bacteria. The mathematical model of the laser excitation of acoustic signals in a liquid medium with the presence of the nanotubes was developed and numerically studied. Increasing of the level of photo acoustic signal was shown.
Keywords: Opt acoustic effect, nanotubes, and model