| 1. |
- Bagriy, Ihor Dmytrovych, et al.
(författare)
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Development and implementation of monitoring of corrosion processes of hydrogen degasation in embrillation zones during the operation of gas pipeline
- 2023
-
Ingår i: Environmental and Energy Challenges of the XXI Century. Global Projects. Ways of Implementation. - Kyiv : Institute of Geological Sciences of the National Academy of Sciences of Ukraine. - 9789667896874 ; , s. 254-286
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Bokkapitel (refereegranskat)abstract
- Pipelines for oil and gas create significant risks of destruction in the systems of industrial and main transportation of hydrocarbons in the presence of corrosion-embrittlement of metal. According to many researchers one of the main reasons for this process is in the area of hydrogen anomalies. It occurs under insulating coating. Insulating coating on the pipeline is peeled off from the metal in such places. Microcracks and pores appear; then moisture spreads to outer surface of the pipe and causes corrosion processes — embrittlement. In addition, it is not excluded that corrosion is intensified due to electrochemical processes and due to undercurrents of gaseous diffusion of hydrogen gas from the mantle strata formed in the areas of the pipeline location. Hydrogen is extremely permeable gas. It leads to swelling, insulation peeling off and defects expanding. The situation creates possibility for moisture penetration to the pipes surface. It also directly affects strength of the metal causing corrosion, cracking and embrittlement. Results of the studies show that embrittlement processes take place mostly in the areas where pipelines pass through oil and gas-bearing structures. In such places hydrogen exits are recorded.
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| 2. |
- Bagriy, Ihor Dmytrovych, et al.
(författare)
-
Gas dynamic phenomena (gdf) and causes of accidents at mines
- 2023
-
Ingår i: Environmental and Energy Challenges of the XXI Century. Global Projects. Ways of Implementation. - Kyiv : Institute of Geological Sciences of the National Academy of Sciences of Ukraine. ; , s. 238-253
-
Bokkapitel (refereegranskat)abstract
- There is a problem of development and implementation of prospecting technology to ensure protection of mining products and prevent disasters during the of coal deposits. It is especially relevant now when issue of environmental protection and improving labor safety in coal mines is very acute. Development of safe search technology for coal deposits is proposed by the authors. It will allow early monitoring to identify places of possible manifestations of gas-dynamic phenomena and make operational decisions for their elimination. The technology is based on application of exploratory gas-geochemical methods for mapping places of accumulation of gas-hydrogen accumulations and their areas. It together with a complex of geological-geophysical method allows to identify areas of possible emergency processes in development zones of mine fields. Feasibility of using search technology to justify use of laying anticipatory degassing wells to prevent uncontrolled explosive processes and technical disasters was proved on large array of conducted field work of planar and profile surveys. The proposed technology was tested on numerous mining sites in the process of exploratory and ecological research in development zones of active and exhausted mine fields.
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| 3. |
- Bagriy, Ihor Dmytrovych, et al.
(författare)
-
Justification of global natural, environmental and hydrological conditions of green hydrogen generation, accumulation and logistics ways
- 2023
-
Ingår i: Environmental and Energy Challenges of the XXI Century. Global Projects. Ways of Implementation. - Kyiv : Institute of Geological Sciences of the National Academy of Sciences of Ukraine. - 9789667896874 ; , s. 26-95
-
Bokkapitel (refereegranskat)abstract
- The implementation of global energy projectsfor comprehensive solutions to the developmentof energy from renewable sources has all thenecessary conditions for the production, accumulationand transportation of green hydrogenin the south-west of the Odesa region, within theboundaries of the Izmail administrative districtand is timed to the floodplain of the Danube River.
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| 4. |
- Bagriy, Ihor Dmytrovych, et al.
(författare)
-
Scientific justification of spatial distribution of hydrogen anomalies in the nearsurface layer of traditional and untraditional oil and gas-bearing structures and implementation of hydrogen search technology
- 2023
-
Ingår i: Environmental and Energy Challenges of the XXI Century. Global Projects. Ways of Implementation. - Kyiv : Institute of Geological Sciences of the National Academy of Sciences of Ukraine. - 9789667896874 ; , s. 96-237
-
Bokkapitel (refereegranskat)abstract
- Long-term results of research on mapping of oil and gas-bearing areas on traditional and non-traditional objects (mine fields, shelf areas, astroblems) made it possible to create a database of system criteria for search technology of structural-thermo-atmospheric-hydrologic geochemical research (STAHGR). It is an integral part of methodological solutions complex.There hydrogen was used as the main constituent element of explosives for the first time insearch practice. There are of hydrogen concentrations obtained in the process of research into the mapping features of the oil and gas capacity of traditional and non-traditional HC (hydrocarbons). Their spectrum of research includes H2-hydrogen. Analysis of data results made it possible to single out anomalous single values in areas and in productive areas (in the absence of background) and to conduct detailed, multi-scale studies for the purpose of planar mapping on prospecting works and environmental impacts of gas dynamic phenomena (GDF) during the development of coal massifs.
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| 5. |
- Broman, Göran, et al.
(författare)
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Instability of water jet : Aerodynamically induced acoustic and capillary waves
- 2012
-
Ingår i: Acoustical Physics. - : MAIK NAUKA/INTERPERIODICA/SPRINGER. - 1063-7710 .- 1562-6865. ; 58:5, s. 537-541
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Tidskriftsartikel (refereegranskat)abstract
- High-speed water jet cutting has important industrial applications. To further improve the cutting performance it is critical to understand the theory behind the onset of instability of the jet. In this paper, instability of a water jet flowing out from a nozzle into ambient air is studied. Capillary forces and compressibility of the liquid caused by gas bubbles are taken into account, since these factors have shown to be important in previous experimental studies. A new dispersion equation, generalizing the analogous Rayleigh equation, is derived. It is shown how instability develops because of aerodynamic forces that appear at the streamlining of an initial irregularity of the equilibrium shape of the cross-section of the jet and how instability increases with increased concentration of gas bubbles. It is also shown how resonance phenomena are responsible for strong instability. On the basis of the theoretical explanations given, conditions for stable operation are indicated.
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| 6. |
- Broman, Göran, et al.
(författare)
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Submerged Landau jet : exact solutions, their meaning and application
- 2010
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Ingår i: Physics Uspekhi. - : TURPION LTD. - 1063-7869 .- 1468-4780. ; 53:1, s. 91-98
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Forskningsöversikt (refereegranskat)abstract
- Exact hydrodynamic solutions generalizing the Landau submerged jet solution are reviewed. It is shown how exact inviscid solutions can be obtained and how boundary layer viscosity can be included by introducing parabolic coordinates. The use of exact solutions in applied hydrodynamics and acoustics is discussed. A historical perspective on the discovery of a class of exact solutions and on the analysis of their physical meaning is presented.
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| 7. |
- Demin, I.Yu., et al.
(författare)
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The numerical simulation of propagation of intensive acoustic noise
- 2013
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Ingår i: Proceedings of Meetings on Acoustics. - San Francisco : ASA. - 1939-800X.
-
Konferensbidrag (refereegranskat)abstract
- The propagation of intensive acoustic noise is of fundamental interest in nonlinear acoustics. Some of the simplest models describing such phenomena are generalized Burgers’ equations for finite amplitude sound waves. An important problem in this field is to find the wave’s behavior far from the emitting source for stochastic initial waveforms. The method of numerical solution of generalized Burgers equation proposed is step-by-step calculation supported on using Fast Fourier Transform of the considered signal. The general idea is to keep only Fourier image of concerned signal and update it recursively (in space). For simulating the wave evolution we used 4096 (212) point realizations and took averaging over 1000 realizations. Also the object of the present study is a numerical analysis of the spectral and bispectral functions of the intense random signals propagating in nondispersive nonlinear media. The possibility of recovering the input spectrum from the measured spectrum and bispectrum at the output of the nonlinear medium is discusses. The analytical estimations are supported by numerical simulation. For two different types of primary spectrum evolution of jet noise were numerically simulates at a short distance and assayed bispectrum and a spectrum analysis of the signals.
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| 8. |
- Dubkov, Alexander, et al.
(författare)
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Probability characteristics of nonlinear dynamical systems driven by delta -pulse noise
- 2016
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - : American Physical Society. - 1539-3755 .- 1550-2376. ; 93:6
-
Tidskriftsartikel (refereegranskat)abstract
- For a nonlinear dynamical system described by the first-order differential equation with Poisson white noise having exponentially distributed amplitudes of δ pulses, some exact results for the stationary probability density function are derived from the Kolmogorov-Feller equation using the inverse differential operator. Specifically, we examine the "effect of normalization" of non-Gaussian noise by a linear system and the steady-state probability density function of particle velocity in the medium with Coulomb friction. Next, the general formulas for the probability distribution of the system perturbed by a non-Poisson δ-pulse train are derived using an analysis of system trajectories between stimuli. As an example, overdamped particle motion in the bistable quadratic-cubic potential under the action of the periodic δ-pulse train is analyzed in detail. The probability density function and the mean value of the particle position together with average characteristics of the first switching time from one stable state to another are found in the framework of the fast relaxation approximation. © 2016 American Physical Society.
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| 9. |
- Dvoesherstov, M.Yu., et al.
(författare)
-
Numerical and experimental analysis of the parameters of an electroacoustic thin-film microwave resonator
- 2013
-
Ingår i: Acoustical Physics. - : Pleiades Publishing, Ltd.. - 1063-7710 .- 1562-6865. ; 59:5, s. 513-520
-
Tidskriftsartikel (refereegranskat)abstract
- The results of numerical and experimental analysis of the parameters of a singlefrequency micro wave thinfilm electroacoustic resonator based on an (0001)AlN piezofilm with an acoustic reflector operat ing at a frequency of 10 GHz are presented. The effect of the reflector design on the resonator characteristics is considered. Using the modified Butterworth–Van Dyke model, it was shown that the ohmic resistance of electrodes and entrance paths substantially decreases the Qfactor at the resonance frequency of series and the acoustic losses in the resonator deteriorate the Qfactor at the parallel resonance frequency
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| 10. |
- Enflo, Bengt, et al.
(författare)
-
Nonlinear standing waves in a closed tub
- 2002
-
Konferensbidrag (refereegranskat)abstract
- Simplified nonlinear evolution equations describing nonsteady-state forced vibrations in an acoustic resonator having one closed end and the other end periodically oscillating are derived. An approach is used based on a nonlinear functional equation. This approach is shown to be equivalent to the version of the successive approximation method developed in 1964 by Chester. It is explained how the acoustic field in the cavity is described as a sum of counterpropagating waves with no cross-interaction. The nonlinear Q-factor and the nonlinear frequency response of the resonator are calculated for steady-state oscillations of both inviscid and dissipative media. The general expression for the mean intensity of the acoustic wave in terms of the characteristic value of a Mathieu function is derived. Some results from a perturbation calculation of the wave profile are given.
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| 11. |
- Enflo, Bengt, et al.
(författare)
-
Nonlinear Standing Waves in a Layer Excited by the Periodic Motion of its Boundary
- 2002
-
Konferensbidrag (refereegranskat)abstract
- Simplified nonlinear evolution equations describing nonsteady-state forced vibrations in an acoustic resonator having one closed end and the other end periodically oscillating are derived. An approach is used based on a nonlinear functional equation. This approach is shown to be equivalent to the version of the successive approximation method developed in 1964 by Chester. It is explained how the acoustic field in the cavity is described as a sum of counterpropagating waves with no cross-interaction. The nonlinear Q-factor and the nonlinear frequency response of the resonator are calculated for steady-state oscillations of both inviscid and dissipative media. The general expression for the mean intensity of the acoustic wave in terms of the characteristic value of a Mathieu function is derived. The process of development of a standing wave is described analytically for three different types of periodic motion of the wall: harmonic excitation, sawtooth-shaped motion and "inverse saw motion".
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| 12. |
- Enflo, Bengt Olof, et al.
(författare)
-
Resonant properties of a nonlinear dissipative layer excited by a vibrating boundary : Q-factor and frequency response
- 2005
-
Ingår i: Journal of the Acoustical Society of America. - MELVILLE : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 117:2, s. 601-612
-
Tidskriftsartikel (refereegranskat)abstract
- Simplified nonlinear evolution equations describing non-steady-state forced vibrations in an acoustic resonator having one closed end and the other end periodically oscillating are derived. An approach based on a nonlinear functional equation is used. The nonlinear Q-factor and the nonlinear frequency response of the resonator are calculated for steady-state oscillations of both inviscid and dissipative media. The general expression for the mean intensity of the acoustic wave in terms of the characteristic value of a Mathieu function is derived. The process of development of a standing wave is described analytically on the base of exact nonlinear solutions for different laws of periodic motion of the wall. For harmonic excitation the wave profiles are described by Mathieu functions, and their mean energy characteristics by the corresponding eigenvalues. The sawtooth-shaped motion of the boundary leads to a similar process of evolution of the profile, but the solution has a very simple form. Some possibilities to enhance the Q-factor of a nonlinear system by suppression of nonlinear energy losses are discussed.
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| 13. |
- Enflo, Bengt O., et al.
(författare)
-
Standing and propagating waves in cubically nonlinear media
- 2006
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Ingår i: Mathematical Modeling of Wave Phenomena. - MELVILLE, NY : AMER INST PHYSICS. - 0735403252 ; , s. 187-195, s. 187-195
-
Konferensbidrag (refereegranskat)abstract
- The paper has three parts. In the first part a cubically nonlinear equation is derived for a transverse finite-amplitude wave in an isotropic solid. The cubic nonlinearity is expressed in terms of elastic constants. In the second part a simplified approach for a resonator filled by a cubically nonlinear medium results in functional equations. The frequency response shows the dependence of the amplitude of the resonance on the difference between one of the resonator's eigenfrequencies and the driving frequency. The frequency response curves are plotted for different values of the dissipation and differ very much for quadratic and cubic nonlinearities. In the third part a propagating N-wave is studied, which fulfils a modified Burgers' equation with a cubic nonlinearity. Approximate solutions to this equation are found for new parts of the wave profile.
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| 14. |
- Enflo, Bengt O., et al.
(författare)
-
Standing waves in quadratic and cubic nonlinear resonators : Q-factor and frequency response
- 2006
-
Ingår i: Innovations in Nonlinear Acoustics. - MELVILLE, NY : AMER INST PHYSICS. - 0735403309 ; , s. 457-460
-
Konferensbidrag (refereegranskat)abstract
- High-Q acoustic resonators are used to significantly increase the wave energy volume density. For high-intensity waves the magnitude of Q-factor is determined not only by the design of the resonator, but by the strength of internal field as well. Methods to calculate the Q-factor and both the spatio-temporal and spectral structure of this field are described. Results are given for quadratic and cubic nonlinear resonators demonstrating quite different physical properties.
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| 15. |
- Gazizov, Rafail, et al.
(författare)
-
Effect of resonant absorption in viscous and dry vibrating contact : Mathematical models and theory connected with slow dynamics and friction welding
- 2014
-
Ingår i: Communications in nonlinear science & numerical simulation. - : Elsevier. - 1007-5704 .- 1878-7274. ; 19:2, s. 337-344
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Tidskriftsartikel (refereegranskat)abstract
- Process of heating of thin layer located between two vibrating surfaces is studied. Energy loss goes on due to viscous or dry friction. Optimal quantities of shear viscosity and friction corresponding to maximum energy loss are determined. Resonant behavior of loss must be taken into account in the description of "slow dynamics" of rocks and materials exposed to high-intensity seismic or acoustic irradiation as well as in various technologies. Bonding of materials by linear friction welding, widely used in propulsion engineering, can exemplify such a technology.
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| 16. |
- Gray, Amber, et al.
(författare)
-
An Intense Wave in Defective Media Containing Both Quadratic and Modular Nonlinearities : Shock Waves, Harmonics, and Nondestructive Testing
- 2018
-
Ingår i: Acoustical Physics. - : Pleiades Publishing. - 1063-7710 .- 1562-6865. ; 64:4, s. 402-407
-
Tidskriftsartikel (refereegranskat)abstract
- The observed nonclassical power-law dependence of the amplitude of the second harmonic wave on the amplitude of a harmonic pump wave is explained as a phenomenon associated with two types of nonlinearity in a structurally inhomogeneous medium. An approach to solving the inverse problem of determining the nonlinearity parameters and the exponent in the above-mentioned dependence is demonstrated. To describe the effects of strongly pronounced nonlinearity, equations containing a double nonlinearity and generalizing the Hopf and Burgers equations are proposed. The possibility of their exact linearization is demonstrated. The profiles, spectral composition, and average wave intensity in such doubly nonlinear media are calculated. The shape of the shock front is found, and its width is estimated. The wave energy losses that depend on both nonlinearity parameters—quadratic and modular—are calculated. © 2018, Pleiades Publishing, Ltd.
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| 17. |
- Gurbatov, S. N., et al.
(författare)
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On the Inverse Problems of Nonlinear Acoustics and Acoustic Turbulence
- 2015
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Ingår i: Radiophysics and Quantum Electronics. - : Springer Science+Business Media B.V.. - 0033-8443 .- 1573-9120. ; 58:7, s. 463-476
-
Tidskriftsartikel (refereegranskat)abstract
- We consider the problem of retrieval of the radiated acoustic signal parameters from the measured wave field in some cross section of the nonlinear medium. The possibilities of solving regular and statistical inverse problems are discussed on the basis of the solution of the Burgers equation for zero and infinitesimal viscosities.
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| 18. |
- Gurbatov, S. N., et al.
(författare)
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Transformation of High-Frequency Noise in the Field of a Shockwave
- 2018
-
Ingår i: Acoustical Physics. - : PLEIADES PUBLISHING INC. - 1063-7710 .- 1562-6865. ; 64:5, s. 555-562
-
Tidskriftsartikel (refereegranskat)abstract
- We study the interaction of noise and regular signals with a front whose steepness increases or decreases owing to nonlinear distortion of the profile of an intense pumping wave. Projective transformation is used, which is a result of one of the Burgers equation symmetries. Signal interaction with the pumping wave at its leading edge results in an increase in signal amplitude, a decrease in its time scale, an increase in the signal evolution rate, and earlier merging of discontinuities. At the trailing edge, an increase in signal amplitude, an increase in the time scale, and deceleration of the evolution rate occur. Formulas are obtained that describe the transformation of the spectrum and the correlation function of noise. Laws of the change in noise energy for both small and large Reynolds numbers are found. We study the interaction of weak noise with a nonstationary shock front in a medium with a finite viscosity. It is shown that, owing to competition between amplification at the shock front and high-frequency attenuation, the dependence on the noise intensity on distance has a nonmonotonic character, and at large distances, the intensity tends to zero, while the correlation time tends to a finite value.
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| 19. |
- Gusev, V.A., et al.
(författare)
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Intensification of the impact of high-intensity focused ultrasound (HIFU) with special spatiotemporal modulation
- 2013
-
Ingår i: Acoustical Physics. - : Springer. - 1063-7710 .- 1562-6865. ; 59:1, s. 45-50
-
Tidskriftsartikel (refereegranskat)abstract
- The principle of forming a special form of powerful acoustic signals is proposed, which makes it possible to ensure precise spatiotemporal beam focusing. The introduction of a transverse-coordinate-dependent local wave frequency is suggested, due to which the equality of the formation lengths of a discontinuity for all rays is achieved. This thereby ensures an increase in nonlinear absorption; as a result, the temperature and radiation action of focused ultrasound on the medium increase.
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| 20. |
- Gusev, V. A., et al.
(författare)
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Nonlinear sound in a gas-saturated sediment layer
- 2015
-
Ingår i: Acoustical Physics. - : Maik Nauka/Interperiodica. - 1063-7710 .- 1562-6865. ; 61:2, s. 152-164
-
Tidskriftsartikel (refereegranskat)abstract
- Wave propagation in a near-bottom layer containing gas bubbles is analyzed. Evolution equations are derived for intense acoustic waves and wave beams in a medium with an inhomogeneous bubble distribution. The field of an intense beam along the axis of the focusing sound channel is calculated. The coefficients of reflection and passage of sound from a homogeneous medium into a bubble layer and back again are calculated. It is shown that the near-bottom layer can effectively trap rays incident on it and ensure a waveguide propagation character. The presence of bubbles increases both the interval of angles at which the wave penetrates the layer and the interval of angles at which rays undergo total internal reflection and do not depart the layer. The acoustic field in the layer from a point source is calculated.
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| 21. |
- Gusev, V.A., et al.
(författare)
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The Field of Radiative Forces and the Acoustic Streaming in a Liquid Layer on a Solid Half-Space
- 2010
-
Ingår i: Acoustical Physics. - : Pleiades Publishing. - 1063-7710 .- 1562-6865. ; 56:6, s. 861-870
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Tidskriftsartikel (refereegranskat)abstract
- The acoustic field and the field of radiative forces that are formed in a liquid layer on a solid substrate are calculated for the case of wave propagation along the interface. The calculations take into account the effects produced by surface tension, viscous stresses at the boundary, and attenuation in the liquid volume on the field characteristics. The dispersion equations and the velocities of wave propagation are determined. The radiative forces acting on a liquid volume element in a standing wave are calculated. The structure of streaming is studied. The effect of streaming on small size particles is considered, and the possibilities of ordered structure formation from them are discussed.
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| 22. |
- Haller, Kristian, et al.
(författare)
-
Slow variations of mechanical and electrical properties of dielectrics and nonlinear phenomena at ultrasonic irradiation
- 2010
-
Ingår i: Acoustical Physics. - : Pleiades Publishing. - 1063-7710 .- 1562-6865. ; 56:5, s. 660-664
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Tidskriftsartikel (refereegranskat)abstract
- The interconnection between variations of elasticity and dielectric permittivity of mesoscopic solid systems under exposure to ultrasound is experimentally observed. A phenomenological theory generalizing Debye’s approach for polar fluids is developed to explain the measured data. The substitution of acoustic measurements by dielectric ones not only simplifies the procedure, but offers new possibilities to remotely evaluate the mechanical properties of materials and natural media.
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| 23. |
- Hedberg, Claes, et al.
(författare)
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Collisions, mutual losses and annihilation of pulses in a modular nonlinear medium
- 2017
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Ingår i: Nonlinear dynamics. - : Springer Netherlands. - 0924-090X .- 1573-269X. ; 90:3, s. 2083-2091
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Tidskriftsartikel (refereegranskat)abstract
- One of the most important sections of nonlinear wave theory is related to the collisions of single pulses. These often exhibit corpuscular properties. For example, it is well known that solitons described by the Korteweg–de Vries equation and a few other conservative model equations exhibit properties of elastic particles, while shock waves described by dissipative models like Burgers’ equation stick together as absolutely inelastic particles when colliding. The interactions of single pulses in media with modular nonlinearity considered here reveal new physical features that are still poorly understood. There is an analogy between the single pulses collision and the interaction of clots of chemical reactants, such as fuel and oxidant, where the smaller component disappears and the larger one decreases after a reaction. At equal “masses” both clots can be annihilated. In this work various interactions of two and three pulses are considered. The conditions for which a complete annihilation of the pulses occurs are indicated. © 2017 The Author(s)
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| 24. |
- Hedberg, Claes, et al.
(författare)
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Dissipative and hysteresis loops as images of irreversible processes in nonlinear acoustic fields
- 2011
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Ingår i: Journal of Applied Physics. - : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 110:5
-
Tidskriftsartikel (refereegranskat)abstract
- Irreversible processes taking place during nonlinear acoustic wave propagation are considered using a representation by loops in a thermodynamic parameter space. For viscous and heat conducting media, the loops are constructed for quasi-harmonic and sawtooth waves and the descriptive equations are formulated. The linear and nonlinear absorptions are compared. For relaxing media, the processes are frequency-dependent. The loops broadens, narrows, and bends. The linear and nonlinear relaxation losses of wave energy are shown. Residual stresses and irreversible strains appear for hysteretic media, and here, a generalization of Rayleigh loops is pictured which takes into account the nonlinearly frequency-dependent hereditary properties. These describe the dynamic behavior, for which new equations are derived.
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| 25. |
- Hedberg, Claes, et al.
(författare)
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Interaction between low and high-frequency Modes in a Nonlinear System : Gas-Filled Cylinder Covered by a movable Piston
- 2003
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Ingår i: Nonlinear dynamics. - Dordrecht : Kluwer. - 0924-090X .- 1573-269X. ; 32:4, s. 405-416
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Tidskriftsartikel (refereegranskat)abstract
- A simple mechanical system containing a low-frequency vibration mode and set of high-frequency acoustic modes is considered. The frequency response is calculated. Nonlinear behaviour and interaction between modes is described by system of functional equations. Two types of nonlinearities are taken into account. The first one is caused by the finite displacement of a movable boundary, and the second one is the volume nonlinearity of gas. New mathematical models based on nonlinear equations are suggested. Some examples of nonlinear phenomena are discussed on the base of derived solutions.
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| 26. |
- Hedberg, Claes, et al.
(författare)
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Nonlinear acoustics of structurally complex materials described by non-analytic nonlinearities
- 2018
-
Ingår i: 25th International Congress on Sound and Vibration 2018, ICSV 2018. - : International Institute of Acoustics and Vibration, IIAV. - 9781510868458 ; , s. 1993-1998
-
Konferensbidrag (refereegranskat)abstract
- Everybody is accustomed to that nonlinear effects amplify with increasing amplitude or intensity of a wave. When the amplitude becomes small, the nonlinearity disappears and the wave enters a linear regime. Instead, we shall consider here so-called strong nonlinearity of the first type (according to a classification introduced earlier by the authors) where the effects of nonlinearity do not disappear even for infinitesimal amplitudes. Among these nonlinearities are modular (M) and quadratically-cubic (QC). When these nonlinearities are included in partial differential equations, they form new mathematical models describing new physical effects. Such equations have been proposed over the past few years and a review of these models is given here. They are interesting because of two reasons: (i) the equations admit exact analytic solutions, and (ii) the solutions describe real physical phenomena. Among them are M- and QC-equations of Hopf, Burgers, Korteveg-de Vries, Khokhlov-Zabolotskaya and Ostrovsky-Vakhnenko types. Media with non-analytic nonlinearities exist among composites, meta-materials, and inhomogeneous and multiphase systems. Some of the physical phenomena manifested in such media are described, e.g. stable shock fronts of compression and rarefaction in QC-media. The last cannot exist in usual media and the periodic wave consists of a series of trapezoidal teeth, rather than usual triangular. In an M-nonlinear medium collision, mutual losses and annihilation of pulses are studied. These pulses exhibit corpuscular properties and, in contrast to solitons (elastic particles) and shock waves (absolutely inelastic collisions), they behave like clots of chemical reagents (fuel and oxidizer). As result of an reaction, the smaller component disappears, and the larger decreases. At equal "masses", these clots disappear or annihilate. In M-media a new stable wave - a modular soliton - exists. Other interesting physical phenomena occur for focused waves in M-media and a review of these is also included in the presentation. Copyright © (2018) by International Institute of Acoustics & Vibration.All rights reserved.
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| 27. |
- Hedberg, Claes, et al.
(författare)
-
Pulse response of a nonlinear layer
- 2001
-
Ingår i: Journal of the Acoustical Society of America. - 0001-4966 .- 1520-8524. ; 110:5, s. 2340-2350
-
Tidskriftsartikel (refereegranskat)abstract
- A simple analytical theory is developed for the description of non-steady state response of a thin nonlinear layer, which differs markedly in its linear properties from the surrounding medium. Such a layer can model the behavior of real inhomogeneities like a cloud of gas bubbles in a liquid, a crack or split plane in a solid, or the contact between two slightly tighted rough surfaces. Both weakly nonlinear pulse and harmonic responses are calculated and the general properties of the spectral and temporal structure of the scattered field are discussed. The exact strongly nonlinear solutions are derived for a special type of stress-strain relationship corresponding to the behavior of real condensed media under strong load. Profiles and spectra shown are in conformity with experimental results. The pulse response on the short delta-pulse shaped incident wave is calculated for arbitrary nonlinear properties of the layer. The possibilities to apply the sets of data on measured characteristics of pulse response in the solution of inverse problems are briefly discussed.
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| 28. |
- Hedberg, Claes, et al.
(författare)
-
Standing Waves In Quadratic And Cubic Nonlinear Resonators : Q-Factor And Frequency Response
- 2005
-
Konferensbidrag (refereegranskat)abstract
- High-Q acoustic resonators are used to significantly increase the wave energy volume density. For high-intensity waves the magnitude of Q-factor is determined not only by the design of the resonator, but by the strength of internal field as well. Methods to calculate the Q-factor and both the spatio-temporal and spectral structure of this field are described. Results are given for quadratic and cubic nonlinear resonators demonstrating quite different physical properties.
|
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| 29. |
- Hedberg, Claes, et al.
(författare)
-
Wave motion in a medium with a cubic nonlinearity
- 2006
-
Konferensbidrag (refereegranskat)abstract
- An example of wave motion in a medium with a cubic nonlinearity is a transverse finite amplitude wave in an isotropic solid. The corresponding cubically nonlinear wave equation is derived with the nonlinearity expressed in terms of elastic constants. This nonlinear wave equation with dissipation is studied for standing and propagating waves. For standing waves in a resonator a simplified approach results in functional equations, from which frequency response curves are derived. These curves show the dependence of the amplitude on the difference between one of the resonator's ekgenfrequencies and the driving frequency. The frequency response curves are plotted for different values of the dissipation and are very different for quadratic and cubic nonlinearities. In the propagating wave case an N-wave evolution is studied, described by a modified Burgers' equation with a cubic nonlinearity. Approximate solutions to this equation are found for parts of the wave profile not studied in detail before.
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| 30. |
- Ibragimov, Nail H., et al.
(författare)
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Group analysis of evolutionary integro-differential equations describing nonlinear waves : General model
- 2011
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Ingår i: Journal of Physics A. - : IOP publishing. - 1751-8113 .- 1751-8121. ; 44:31
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Tidskriftsartikel (refereegranskat)abstract
- The paper deals with an evolutionary integro-differential equation describing nonlinear waves. Particular choice of the kernel in the integral leads to well-known equations such as the Khokhlov-Zabolotskaya equation, the Kadomtsev-Petviashvili equation and others. Since solutions of these equations describe many physical phenomena, analysis of the general model studied in the paper equation is important. One of the methods for obtaining solutions differential equations is provided by the Lie group analysis. However, this method is not applicable to integro-differential equations. Therefore we discuss new approaches developed in modern group analysis and apply them to the general model considered in the present paper. Reduced equations and exact solutions are also presented.
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| 31. |
- Ibragimov, Nail H., et al.
(författare)
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Principle of an a priori use of symmetries in the theory of nonlinear waves.
- 2004
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Ingår i: Acoustical Physics. - 1063-7710 .- 1562-6865. ; 50:4, s. 406-419
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Tidskriftsartikel (refereegranskat)abstract
- The principle of an a priori use of symmetries is proposed as a new approach to solving nonlinear problems on the basis of a reasonable complication of mathematical models. This approach often provides additional symmetries, and hence opens possibilities to find new analytical solutions. The potentialities of the proposed approach are illustrated by applying to problems of nonlinear acoustics.
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| 32. |
- Lebedev-Stepanov, P.V., et al.
(författare)
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Acoustic Flows in a Fluid Layer on a Vibrating Substrate
- 2013
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Ingår i: Acoustical Physics. - : Pleiades Publishing, Ltd.. - 1063-7710 .- 1562-6865. ; 59:6, s. 640-643
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Tidskriftsartikel (refereegranskat)abstract
- The field of radiation forces in a fluid layer on a solid substrate is calculated. This field is formed during propagation of surface capillary wave along a free surface. The wave is excited by substrate vibrations as a result of instability development. The structure of acoustic flows is studied. Their effect on small size particles and the possibilities of generating ordered structures from these particles are discussed.
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| 33. |
- Lebedev-Stepanov, P. V., et al.
(författare)
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Acoustic microfluidics : Capillary waves and vortex flows in the cylindrical volume of a fluid drop
- 2015
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Ingår i: Acoustical Physics. - 1063-7710 .- 1562-6865. ; 61:2, s. 173-177
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Tidskriftsartikel (refereegranskat)abstract
- We calculate the field of radiation forces in a cylindrical fluid layer on a solid substrate formed as a result of the action on a fluid of a capillary wave propagating from the axis along a free surface. We study the structure of acoustic flows excited by the radiation forces. We discuss the action of flows on small-sized particles and the possibilities of these particles to form ordered structures. © 2015, Pleiades Publishing, Ltd.
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| 34. |
- Meyer, Peter A., et al.
(författare)
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Data publication with the structural biology data grid supports live analysis
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Access to experimental X-ray diffraction image data is fundamental for validation and reproduction of macromolecular models and indispensable for development of structural biology processing methods. Here, we established a diffraction data publication and dissemination system, Structural Biology Data Grid (SBDG; data. sbgrid. org), to preserve primary experimental data sets that support scientific publications. Data sets are accessible to researchers through a community driven data grid, which facilitates global data access. Our analysis of a pilot collection of crystallographic data sets demonstrates that the information archived by SBDG is sufficient to reprocess data to statistics that meet or exceed the quality of the original published structures. SBDG has extended its services to the entire community and is used to develop support for other types of biomedical data sets. It is anticipated that access to the experimental data sets will enhance the paradigm shift in the community towards a much more dynamic body of continuously improving data analysis.
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| 35. |
- Mfoumou, Etienne, et al.
(författare)
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Acoustical measurement accompanying tensile test : new modality for non-destructive testing and characterization of sheet materials
- 2006
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Ingår i: 13th International Congress on Sound and Vibration 2006. - Vienna : Vienna University of Technology, Austria. - 9781627481502
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Konferensbidrag (refereegranskat)abstract
- A series of uniaxial tensile tests was performed for sheet materials like paperboard, polyethylene and packing layered composites. These sheets can be considered as membranes. In parallel with a tensile test, the natural frequency was measured through an acoustical excitation. Firstly, it was shown both theoretically and experimentally that, at a given load, the frequency is sensitive to the local deviation in the standard thickness or to the presence of cracks inside the material. It means that this acoustic measurement can be used as one of the methods of damage assessment, or nondestructive testing in general. Secondly, the resonance frequency shift was continuously monitored for increasing strain on polyethylene and paperboard, and the curves obtained were compared to the stress-strain curves for material characterization. They were not the same and showed a non-monotonic stiffness variation for the polyethylene. It was shown that the resonance frequency shift measurement can successfully replace the stress-strain curve for material characterization under tensile test. During a long time under load an irreversible plastic deformation of the sample takes place, and the frequency shift can also serve as a new method for evaluating the residual strain of the material.
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| 36. |
- Mikhailov, S. G., et al.
(författare)
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A Simple Bimodular Nonlinear Element
- 2018
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Ingår i: Acoustical Physics. - : Pleiades Publishing. - 1063-7710 .- 1562-6865. ; 64:3, s. 293-298
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the dynamics of an artificial nonlinear element representing a flexible membrane with oscillation limiters and a static pressing force. Such an element has the property of “bimodularity” and demonstrates “modular” nonlinearity. We have constructed a mathematical model that describes these oscillations. Their shapes have been calculated. We follow the analogy with a classical object—Galileo’s pendulum. We demonstrate that for a low-frequency excitation of the membrane, the level of the harmonics in the spectrum is higher than in the vicinity of the resonance frequency. We have established a strong dependence of the level of the harmonics on the magnitude of the pressing force for a weak perturbation. We propose a design scheme for a device in the quasi-static approximation possessing the property of bimodularity. We perform an experiment that confirms its operability. We show a qualitative coincidence of the experimental results and calculations when detecting an amplitude-modulated signal. © 2018, Pleiades Publishing, Ltd.
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| 37. |
- Mikhailov, S. G., et al.
(författare)
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A simple nonlinear element model
- 2017
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Ingår i: Acoustical Physics. - : MAIK NAUKA/INTERPERIODICA/SPRINGER. - 1063-7710 .- 1562-6865. ; 63:3, s. 270-274
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Tidskriftsartikel (refereegranskat)abstract
- We study experimentally the behavior of a nonlinear element, a light plate pressed to the opening in the cavity of an acoustic resonator. Measurements of field oscillations inside and outside the cavity have shown that for large amplitudes, they become essentially anharmonic. The time dependences of displacement of the plate with increasing amplitude of the exciting voltage demonstrates a gradual change in the shape of vibrations from harmonic to half-period oscillation. A constant component appears in the cavity: rarefaction or outflow of the medium through the orifice. We construct a theory for nonlinear oscillations of a plate taking into account its different elastic reactions to compression and rarefaction with allowance for monopole radiation by the small-wave-size plate or radiation of a plane wave by the plate. We calculate the amplitudes of the harmonics and solve the problem of low-frequency stationary noise acting on the plate. We obtain expressions for the correlation function and mean power at the output given a normal random process at the input.
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| 38. |
- Nefedov, N. N., et al.
(författare)
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On Front Motion in a Burgers-Type Equation with Quadratic and Modular Nonlinearity and Nonlinear Amplification
- 2018
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Ingår i: Doklady. Mathematics. - : MAIK NAUKA/INTERPERIODICA/SPRINGER. - 1064-5624 .- 1531-8362. ; 97:1, s. 99-103
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Tidskriftsartikel (refereegranskat)abstract
- A singularly perturbed initial-boundary value problem for a parabolic equation known in applications as a Burgers-type or reaction-diffusion-advection equation is considered. An asymptotic approximation of solutions with a moving front is constructed in the case of modular and quadratic nonlinearity and nonlinear amplification. The influence exerted by nonlinear amplification on front propagation and blowing- up is determined. The front localization and the blowing-up time are estimated.
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| 39. |
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| 40. |
- Rudenko, Oleg, et al.
(författare)
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A new equation and exact solutions describing focal fields in media with modular nonlinearity
- 2017
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Ingår i: Nonlinear dynamics. - : Springer Netherlands. - 0924-090X .- 1573-269X. ; 89:3, s. 1905-1913
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Tidskriftsartikel (refereegranskat)abstract
- Brand-new equations which can be regarded as modifications of Khokhlov–Zabolotskaya–Kuznetsov or Ostrovsky–Vakhnenko equations are suggested. These equations are quite general in that they describe the nonlinear wave dynamics in media with modular nonlinearity. Such media exist among composites, meta-materials, inhomogeneous and multiphase systems. These new models are interesting because of two reasons: (1) the equations admit exact analytic solutions and (2) the solutions describe real physical phenomena. The equations model nonlinear focusing of wave beams. It is shown that inside the focal zone a stationary waveform exists. Steady-state profiles are constructed by the matching of functions describing the positive and negative branches of exact solutions of an equation of Klein–Gordon type. Such profiles have been observed many times during experiments and numerical studies. The non-stationary waves can contain singularities of two types: discontinuity of the wave and of its derivative. These singularities are eliminated by introducing dissipative terms into the equations—thereby increasing their order. © 2017 The Author(s)
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| 41. |
- Rudenko, Oleg
(författare)
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A nonlinear screen as an element for sound absorption and frequency conversion systems
- 2016
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Ingår i: Acoustical Physics. - : Maik Nauka/Interperiodica. - 1063-7710 .- 1562-6865. ; 62:1, s. 46-50
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Tidskriftsartikel (refereegranskat)abstract
- The paper discusses a model for a screen with dissipative and nonlinear elastic properties that can be used in acoustic sound absorption and frequency conversion systems. Calculation and estimation schemes are explained that are necessary for understanding the functional capabilities of the device. Examples of the nonlinear elements in the screen and promising applications are described.
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| 42. |
- Rudenko, Oleg, et al.
(författare)
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Absorption of intense regular and noise waves in relaxing media
- 2014
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Ingår i: Acoustical Physics. - : Maik Nauka/Springer. - 1063-7710 .- 1562-6865. ; 60:5, s. 499-505
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Tidskriftsartikel (refereegranskat)abstract
- An integro-differential equation is written down that contains terms responsible for nonlinear absorption, visco-heat-conducting dissipation, and relaxation processes in a medium. A general integral expression is obtained for calculating energy losses of the wave with arbitrary characteristics-intensity, profile (frequency spectrum), and kernel describing the internal dynamics of the medium. It is shown that for weak waves, the general integral leads to well-known results of a linear approximation. Profiles of stationary solutions are constructed both for an exponential relaxation kernel and for other types of kernels. Energy losses at the front of week shock waves are calculated. General integral formulas are obtained for energy losses of intense noise, which are determined by the form of the kernel, the structure of the noise correlation function, and the mean square of the derivative of realization of a random process
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| 43. |
- Rudenko, Oleg, et al.
(författare)
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Blood flow dynamics under venipuncture and viscosity estimation from pressure and flow variations
- 2013
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Ingår i: Acoustical Physics. - : MAIK NAUKA/INTERPERIODICA/SPRINGER. - 1063-7710 .- 1562-6865. ; 59:1, s. 109-114
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Tidskriftsartikel (refereegranskat)abstract
- We have calculated the nonstationary flow of a viscous liquid in a narrow tube under the action of pressure variations with time. Such a flow accompanies venipuncture the procedure of taking a sample from a vein with a hypodermic needle. We show how the changes in the flow characterstics during venipuncture make it possible to actively estimate viscosity. This method is "nonperturbative" for blood in the sense that the measurement process weakly affects the measured quantity. It may find application in medicine.
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| 44. |
- Rudenko, Oleg, et al.
(författare)
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Control of the Self-Assembly Processes in a Droplet of a Colloidal Solution by an Acoustic Field
- 2010
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Ingår i: Acoustical Physics. - : Pleiades Publishing. - 1063-7710 .- 1562-6865. ; 56:6, s. 935-941
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Tidskriftsartikel (refereegranskat)abstract
- The formation of structured films consisting of ensembles of micro- or nanoparticles and possessing preset functional characteristics is studied both experimentally and theoretically. The films are obtained by drying out droplets of colloidal solutions on a solid substrate under the acoustic effect produced by a standing SAW field.
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| 45. |
- Rudenko, Oleg, et al.
(författare)
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Diffraction of high-intensity field in focal region as dynamics of nonlinear system with low-frequency dispersion
- 2015
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Ingår i: Acoustical Physics. - 1063-7710 .- 1562-6865. ; 61:1, s. 28-36
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Tidskriftsartikel (refereegranskat)abstract
- The stationary profile in the focal region of a focused nonlinear acoustic wave is described. Three models following from the Khokhlov-Zabolotskaya (KZ) equation with three independent variables are used: (i) the simplified one-dimensional Ostrovsky-Vakhnenko equation, (ii) the system of equations for paraxial series expansion of the acoustic field in powers of transverse coordinates, and (iii) the KZ equation reduced to two independent variables. The structure of the last equation is analogous to the Westervelt equation. Linearization through the Legendre transformation and reduction to the well-studied Euler-Tricomi equation is shown. At high intensities the stationary profiles are periodic sequences of arc sections having singularities of derivative in their matching points. The occurrence of arc profiles was pointed out by Makov. These appear in different nonlinear systems with low-frequency dispersion. Profiles containing discontinuities (shock fronts) change their form while passing through the focal region and are non-stationary waves. The numerical estimations of maximum pressure and intensity in the focus agree with computer calculations and experimental measurements. © 2015, Pleiades Publishing, Ltd.
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| 46. |
- Rudenko, Oleg, et al.
(författare)
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Enhancements of energy and Q-factor of a nonlinear resonator with increase in its losses
- 2002
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Ingår i: Doklady Akademii Nauk. - : MAIK Nauka/Interperiodica Publishing, Russia. - 0869-5652. ; 383:1, s. 330-333
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Tidskriftsartikel (refereegranskat)abstract
- A phenomenon that is paradoxical at first sight is studied: an appropriately-organized energy outflow from a resonator cavity results not in the attenuation of nonlinear vibrations but in their noticeable enhancement. An increase in the resonator Q-factor and in the energy accumulated in it is well pronounced when the frequencies of the higher harmonics generated in a nonlinear medium are close to the natural frequencies of the resonator. An important example of a nonlinear system with the necessary properties is an acoustic resonator with selective losses.
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| 47. |
- Rudenko, Oleg
(författare)
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Equation admitting linearization and describing waves in dissipative media with modular, quadratic, and quadratically cubic nonlinearities
- 2016
-
Ingår i: Doklady Mathematics. - : Maik Nauka/Interperiodica. - 1064-5624. ; 94:3, s. 703-707
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Tidskriftsartikel (refereegranskat)abstract
- A second-order partial differential equation admitting exact linearization is discussed. It contains terms with nonlinearities of three types—modular, quadratic, and quadratically cubic—which can be present jointly or separately. The model describes nonlinear phenomena, some of which have been studied, while others call for further consideration. As an example, individual manifestations of modular nonlinearity are discussed. They lead to the formation of singularities of two types, namely, discontinuities in a function and discontinuities in its derivative, which are eliminated by dissipative smoothing. The dynamics of shock fronts is studied. The collision of two single pulses of different polarity is described. The process reveals new properties other than those of elastic collisions of conservative solitons and inelastic collisions of dissipative shock waves.
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| 48. |
- Rudenko, Oleg, et al.
(författare)
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Evolution of weak noise and regular waves on dissipative shock fronts described by the Burgers model
- 2018
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Ingår i: Wave motion. - : Elsevier B.V.. - 0165-2125 .- 1878-433X. ; 82, s. 20-29
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Tidskriftsartikel (refereegranskat)abstract
- The interaction of weak noise and regular signals with a shock wave having a finite width is studied in the framework of the Burgers equation model. The temporal realization of the random process located behind the front approaches it at supersonic speed. In the process of moving to the front, the intensity of noise decreases and the correlation time increases. In the central region of the shock front, noise reveals non-trivial behaviour. For large acoustic Reynolds numbers the average intensity can increase and reach a maximum value at a definite distance. The behaviour of statistical characteristics is studied using linearized Burgers equation with variable coefficients reducible to an autonomous equation. This model allows one to take into account not only the finite width of the front, but the attenuation and diverse character of initial profiles and spectra as well. Analytical solutions of this equation are derived. Interaction of regular signals of complex shape with the front is studied by numerical methods. Some illustrative examples of ongoing processes are given. Among possible applications, the controlling the spectra of signals, in particular, noise suppression by irradiating it with shocks or sawtooth waves can be mentioned. © 2018 Elsevier B.V.
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| 49. |
- Rudenko, Oleg
(författare)
-
Exact solutions of an integro-differential equation with quadratically cubic nonlinearity
- 2016
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Ingår i: Doklady. Mathematics. - : Maik Nauka/Interperiodica. - 1064-5624 .- 1531-8362. ; 94:1, s. 468-471
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Tidskriftsartikel (refereegranskat)abstract
- Exact solutions of a nonlinear integro-differential equation with quadratically cubic nonlinear term are found. The equation governs, in particular, stationary shock wave propagation in relaxing media. For the exponential kernel the shapes of both compression and rarefaction shocks having a finite width of the front are calculated. For media with limited "memorizing time" the difference relation permitting the construction of wave profile by the mapping method is derived. The initial equation is rather general. It governs the evolution of nonlinear waves in real distributed systems, for example, in biological tissues, structurally inhomogeneous media and in some meta-materials.
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| 50. |
- Rudenko, Oleg
(författare)
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«exotic» models of high-intensity wave physics : Linearizing equations, exactly solvable problems and non-analytic nonlinearities
- 2018
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Ingår i: Izvestiya Vysshikh Uchebnykh Zavedeniy. Prikladnaya Nelineynaya Dinamika. - : Saratov State University. - 0869-6632. ; 26:3, s. 7-34
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Tidskriftsartikel (refereegranskat)abstract
- Topic and aim. A brief review of publications and discussion of some mathematical models are presented, which, in the author's opinion, are well-known only to a few specialists. These models are not well studied, despite their universality and practical significance. Since the results were published at different times and in different journals, it is useful to summarize them in one article. The goal is to form a general idea of the subject for the readers and to interest them with mathematical, physical or applied details described in the cited references. Investigated models. Higher-order dissipative models are discussed. Precisely linearizable equations containing nonanalytic nonlinearities -quadratically-cubic (QC) and modular (M) -are considered. Equations like Burgers, KdV, KZ, Ostrovsky-Vakhnenko, inhomogeneous and nonlinear integro-differential equations are analyzed. Results. The appearance of dissipative oscillations near the shock front is explained. The formation in the QC-medium of compression and rarefaction shocks, which are stable only for certain parameters of the «jump», as well as the formation of periodic trapezoidal sawtooth waves and self-similar N-pulse signals are described. Collisions of single pulses in the M-medium are discussed, revealing new corpuscular properties (mutual absorption and annihilation). Collisions are similar to inter-actions of clusters of chemically reacting substances, for example, fuel and oxidizer. The features of the behavior of «modular» solitons are described. The phenomenon of nonlinear wave resonance in media with QC-, Q-and M-nonlinearities is studied. Precisely linearizable inhomogeneous equations with external sources are used. The shift of maximum of resonance curves relative to the linear position, which is determined by the equality of velocities of freely propagating and forced waves, is indicated. Simplified models for diffracting beams obtained by projecting 3D equations onto the beam axis are analyzed. Strongly nonlinear waves in systems with holonomic constraints are discussed. Integro-differential equations with relaxation type kernel, and the possibility of reducing them to differential and differential-difference equations are considered. Discussion. The material is outlined on a popular level. Apparently, these studies can be continued if the readers find them interesting enough. © 2018 Saratov State University. All rights reserved.
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