Sound intensity fluctuations resulting from mode coupling in shallow-water nonlinear internal waves
Sound intensity fluctuations resulting from mode coupling in shallow-water nonlinear internal waves
V.A. Grigorev, B.G. Katsnelson, J.F. Lynch
The analysis is carried out for the low frequency (300±30 Hz) intensity fluctuations of the sound pulses propagating in the shallow water waveguide in the presence of nonlinear internal waves (NIW) in the experiment Shallow Water 2006 (Atlantic shelf of USA). Signals were being received by vertical line array (distance to the source ~20 km). NIW train was placed entirely inside of an acoustic track during time period of the sound radiation. Angle between wave front of NIW and direction of an acoustic track was ~10°. Theoretical modeling of spectrum of fluctuations were obtained using theory of authors for the sound fluctuations due to mode coupling. The main feature of the theory is existence of the so called «predominating frequency», corresponding to the spectral component of maximal amplitude. Comparison of modeling results and experimental data allows us to interpret position of the maximum in the spectrum as predominating frequency. Contribution of horizontal refraction is discussed as well.
Show AbstractThe change of rheological properties of high viscosity of the structured oil when ultrasonic processing
The change of rheological properties of high viscosity of the structured oil when ultrasonic processing
I.N. Evdokimov , N.Yu. Eliseev, A.A. Fesan
In the course of the research was conducted short-term and long-term ultrasonic treatment samples of high viscosity structured oil content of asphaltenes 15-16%. The results of measurements and calculations for short ultrasonic processing of high-viscosity oil show that the rheological dependencies there are intervals of shear rate, showing a decrease or increase in viscosity. Prolonged ultrasonic treatment does not lead to qualitative changes in the colloid-dispersed structure. After ultrasonic treatment of the structured oil can be observed as positive effects (reduced viscosity) and negative effects (increase in viscosity, precipitation, clogging of the pore space of the reservoir). For each case (individual type of oil, reservoir conditions, the power source of ultrasound), it is necessary to determine the appropriate processing time for achieving maximum positive effect.
Show AbstractМоделирование и измерение поля мощного многоэлементного терапевтического излучателя в широком диапазоне интенсивностей вплоть до проявления эффекта насыщения в фокусе
Моделирование и измерение поля мощного многоэлементного терапевтического излучателя в широком диапазоне интенсивностей вплоть до проявления эффекта насыщения в фокусе
П.В Юлдашев, А. Максвелл, В. Крайдер, О.А. Сапожников, М. Бэйли, Л. Крам, В.А. Хохлова
Во многих современных приложениях мощного фокусированного ультразвука (HIFU) в неинвазивной хирургии, например, при гистотрипсии, возникает необходимость генерации мощных ультразвуковых полей с амплитудой ударного фронта в фокусе до 120 МПа на значительной глубине в ткани. Для экспериментального исследования возможности создания таких полей и генерации механических разрушений в ткани был создан прототип системы, состоящий из усилителя и излучателя с рабочей частотой 1 МГц. Излучатель состоит из семи отдельных элементов круглой формы, расположенных на сферической чашке диаметром 14.7 см и радиусом кривизны 14 см. Цель настоящей работы состояла в характеризации поля указанного излучателя в воде с помощью гидрофонных измерений и численного моделирования. Моделирование поля было выполнено на основе трехмерного уравнения Вестервельта с начальными условиями, полученными экспериментально методом акустической голографии. В эксперименте профили волны в фокусе были измерены оптоволоконным гидрофоном. Измерения проводились при различной амплитуде акустического давления на поверхности источника. Было показано, что результаты измерений и расчетов хорошо согласуются между собой. Найдены максимально достижимые значения для пиковых давлений и амплитуды ударного фронта. Таким образом, в работе было показано, что численное моделирование на основе трехмерного уравнения Вестервельта является важным инструментом для прогнозирования характеристик ультразвуковых полей, создаваемых мощными терапевтическими HIFU излучателями.
Show AbstractElastic Properties of Polymer Layer under Uniaxial Compression in Cylindrical Geometry
Elastic Properties of Polymer Layer under Uniaxial Compression in Cylindrical Geometry
T.B. Krit, V.G. Andreev, A.V. Shanin, I.I. Golubkova
We measured the linear and nonlinear elastic moduli of polymer material plastisol. The layer of material was polymerized between two coaxial solid cylinders with diameters 6-8 times greater than the thickness of the layer. During the polymerization process mechanical stresses arose within the material. Comparing the measured values of the elastic parameters of the material, polymerized between the cylinders, to the values measured in the material, polymerized between flat parallel plates, under uniaxial compression it became possible to evaluate these stresses. Measurements in the flat and cylindrical geometry have been carried out by the method of static shear deformations up to 0.4-0.6 of the layer thickness. Nonlinear effects are well pronounced under such deformations, which allows to estimate their contribution to the elastic properties exhibited by the material and measure the nonlinear Landau parameters. Shear strain was created by certain tension applied to one of the plastisol boundaries in plane geometry. The second boundary was fixed and could not move in the direction of shear deformation. However, bindings allowed this boundary to move in the direction perpendicular to the direction of shear deformation. The shear strain in a cylindrical geometry was created by the rotation of one of the cylinders applying a certain stress tangentially to the lateral surface. The pattern of stress-strain curves and the measured values of static shear modulus appeared to be significantly different in cylindrical geometry and planar geometry, whereas the thickness of plastisol was the same. Landau parameter A, measured in plane geometry with the uniaxial compression applied, was equal to -392 kPa.
Show AbstractPhotoacoustic investigations of the Gruneisen parameter for cadmium diphosphide in the field of commensurate-incommensurate phase transition
Photoacoustic investigations of the Gruneisen parameter for cadmium diphosphide in the field of commensurate-incommensurate phase transition
N.I. Odina, A.S. Polushko
The results of the experimental studies of the temperature dependence of the normalized Gruneisen parameter for cadmium diphosphide single crystal in the field of commensurate-incommensurate phase transition are presented. Measurements were made using laser photoacoustic method with harmonic excitation and piezoelectric registration in the temperatures interval of 280-330 K. Anomalies of the temperature dependence of the amplitude of the photoacoustic signal is proportional to the Gruneisen parameter were observed in the temperature range of 305-322 K. These anomalies are associated with the occurrence of phase transitions from commensurate to incommensurate phase. The estimation of the temperature dependence of the normalized Gruneisen parameter using literature data and comparison with experimental data were made.
Show AbstractApplication of ultrasound phased arrays with different number of elements for irradiation of tissue behind the ribs
Application of ultrasound phased arrays with different number of elements for irradiation of tissue behind the ribs
S.A. Ilyin, L.R. Gavrilov, V.A. Khokhlova
In many current medical applications of high intensity focused ultrasound it is necessary to take into account additional energy losses due to the presence of natural obstacles like ribs. In this study the feasibility of using phased arrays with different number of elements to reduce overheating ribs when focusing through the intercostal spaces was studied. Geometric approach to switch off the array elements that are in the shadow of ribs was used to minimize the exposure of the ribs to the ultrasound energy. The effect of the number of the array elements on the value of the power losses of the focused beam at the ribs and the level of intensity in the focal region behind the ribs was studied.
Show AbstractThe modification method of the microwave acoustic resonator spectroscopy of thin layers and films for measurements over a wide frequency range
The modification method of the microwave acoustic resonator spectroscopy of thin layers and films for measurements over a wide frequency range
S.G. Alekseev, I.M. Kotelyanskii, N.I. Polzikova, G.D. Mansfeld
The spectrum of the composite acoustic resonator (HBAR) is a multimode, and may contain several thousand resonance peaks. We have developed a set of programs that allows recording the spectrum scans with arbitrary frequency step within the whole frequency range of the network analyzer. Due to the high degree of automation of the processing of scans we obtain data on the parameters (frequency and width) of each resonance peak. Proposed method increases the accuracy of the previously known method of measuring the velocity of an acoustic wave (AW) of the material by comparing the spectra HBAR before and after developing the test layer. For the layers with the thickness of a few wavelengths the new method allows to obtain information about the velocity from only one AW spectrum.
Show AbstractInfluence of defect structure on the elastic properties of the D16 aluminum alloy
Influence of defect structure on the elastic properties of the D16 aluminum alloy
V.S. Kozlov, A.I. Korobov
The results of experimental studies of the influence of defect structure changes in a D16 polycrystalline aluminum alloy on its linear and nonlinear elastic properties are presented. The change of defect structure in the sample is caused by application of static cyclic stress (tension- compression - tension – compression) to it. Studies of the elastic properties of the test specimen during the application of variable loads were carried out using static, quasi-static and dynamic methods. Ultrasonic measurements were conducted using the pulse method. Investigation of nonlinear elastic properties of the test material were done using two methods: a dynamic spectral method according to the efficiency of generation of the second harmonic in the acoustic wavefield of finite amplitude at a frequency of 5 MHz and quasistatic method by measuring the change of velocity of acoustic waves in the sample as a function of the applied static pressure to it. Keywords: defects, nonclassic elastic nonlinearity, plastic deformation, spectral method, second harmonic.
Show AbstractMagnetoelastic interactions in the acoustic microwave resonator containing epitaxial ferromagnetic films on nonmagnetic substrate
Magnetoelastic interactions in the acoustic microwave resonator containing epitaxial ferromagnetic films on nonmagnetic substrate
N.I. Polzikova, S.G. Alekseev, I.M. Kotelyanskii, V.A. Luzanov, A.O. Raevskii
In this paper it is experimentally demonstrated that in the composite resonator structure with ferromagnetic and piezoelectric films magnetic oscillations can be excited and detected directly by means of an electroacoustic transducer of bulk acoustic waves. Excitation of nonuniform ferromagnetic resonance occurs at frequencies close to those of the magnetoelastic resonance in a magnetic material, and appears as a frequency rearrangement of the multimode resonator, which depends resonantly on the external magnetic field. The rearrangement for the resonator with the ZnO film and YIG in the whole intermodal interval 3.6 MHz was experimentally observed. The observed effect is of interest to: a) the practical application of a tunable frequency control elements and microwave filters, b) study the magnetic dynamics in ferromagnetic films, c) new applications of microwave acoustic resonators.
Show AbstractThe acoustical investigation of shear viscoelastic properties of colloidal suspensions of nanoparticles
The acoustical investigation of shear viscoelastic properties of colloidal suspensions of nanoparticles
Dembelova T.S., Tsyrenzhapova A.B, Makarova D.N., Damdinov B.B., Badmaev B.B.
A complex shear modulus of colloidal suspensions of silica nanoparticles in the liquid polymer PES-2 are measured depending on the angle of shear deformation using acoustical resonance method. A piezoelectric crystal with the resonance frequency of 73 kHz as vibrator is applied in study. The changing of the viscoelastic properties of the suspensions depending on the concentration and size of nanoparticles is shown according to the comparison with the base liquid.
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