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Search Results: 1 - 10 of 9971 matches for " acoustic field "
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Research Into the Influence of the Acoustic Field on the Efficiency of Removing Aerosols
Laura Stukait?,Ina Tetsman,Vladas Vekteris
Science – Future of Lithuania , 2012,
Abstract: The paper presents the methods for reducing harmful aerosols from galvanic baths polluting the environment under conditions when air flow helps in forming an acoustic field above the bath. The findings show that the level of air humidy is the lowest when aerosols are removed with the help of a side exhauster. Side effects on acoustic coagulation may occur. Aerosol coagulates when elevated above the liquid and returns to liquid not dispersed in the evironment. The article introduces active suckers in accordance to their form and effectiveness collecting pollutants. The dependence of humidity on temperature is analyzed under the impact of external factors such as sucking, blowing and sucking or blowing, sucking and an acoustic field. The paper also discusses data on the dependence of sound pressure and looks at the level of frequency distribution.Article in Lithuanian
Power Estimation of Acoustic Sources by Sensor Array Processing  [PDF]
Joseph Lardiès, Hua Ma, Marc Berthillier
Open Journal of Acoustics (OJA) , 2013, DOI: 10.4236/oja.2013.32A001
Abstract: A constant problem is to localize a number of acoustic sources, to separate their individual signals and to estimate their strengths in a propagation medium. An acoustic receiving array with signal processing algorithms is then used. The most widely used algorithm is the conventional beamforming algorithm but it has a very low resolution and high sidelobes that may cause a signal leakage problem. Several new signal processors for arrays of sensors are derived to evaluate the strengths of acoustic signals arriving at an array of sensors. In particular, we present the covariance vector estimator and the pseudoinverse of the array manifold matrix estimator. The covariance vector estimator uses only the correlations between sensors and the pseudoinverse of the array manifold matrix estimator operates with the minimum eigenvalues of the covariance matrix. Numerical and experimental results are presented.
Research on the Influence of an Acoustic Field on Particle Cohesion in Liquid
Ramūnas Vilki?ius,Andrius Styra,Vladas Vekteris
Science – Future of Lithuania , 2012,
Abstract: Iron is one of the most common natural elements. When iron concentration in water is more than 0,3 mg/l, it causes the formation of rust drain tag or changes the colour of the fabric during washing. Thus, the use of the acoustic field to improve water quality is a very relevant topic. Acoustic oscillations are currently widely used in various industrial sectors, including water treatment, metallurgy, chemical and food industry, equipment manufacturing and medicine. When materials are affected by acoustic fields, physical-chemical processes begin. Acoustic fields cause material dispersion, emulsification, coagulation and degassing (gas removal) as well as influence the crystallization and melting processes. Acoustic vibrations may also cause various chemical transformations such as oxidation, polymerization processes and depolymerisation. The utilization of acoustics to enhance water oxidation and precipitation of coarse impurities further extends the scope of the use of this physical method.Article in Lithuanian
Diffraction of a Plane Acoustic Wave from a Finite Soft (Rigid) Cone in Axial Irradiation  [PDF]
Dozyslav B. Kuryliak, Zinoviy T. Nazarchuk, Victor O. Lysechko
Open Journal of Acoustics (OJA) , 2015, DOI: 10.4236/oja.2015.54015
Abstract: The problem of diffraction of a plane acoustic wave by a finite soft (rigid) cone is investigated. This one is formulated as a mixed boundary value problem for the three-dimensional Helmholtz equation with Dirichlet (Neumann) boundary condition on the cone surface. The diffracted field is sought as expansion of unknown velocity potential in series of eigenfunctions for each region of the existence of sound pressure. The solution of the problem then is reduced to the infinite set of linear algebraic equations (ISLAE) of the first kind by means of mode matching technique and orthogonality properties of the Legendre functions. The main part of asymptotic of ISLAE matrix element determined for large indexes identifies the convolution type operator amenable to explicit inversion. This analytical treatment allows one to transform the initial diffraction problem into the ISLAE of the second kind that can be readily solved by the reduction method with desired accuracy depending on a number of truncation. All these determine the analytical regularization method for solution of wave diffraction problems for conical scatterers. The boundary transition to soft (rigid) disc is considered. The directivity factors, scattering cross sections, and far-field diffraction patterns are investigated in both soft and rigid cases whereas the main attention in the near-field is focused on the rigid case. The numerically obtained results are compared with those known for the disc.
Numerical Simulation of Near-Field Seismoacoustic Probing of a Layer Inclusion in a Homogeneous Infinite Medium  [PDF]
Yury Mikhailovich Zaslavsky, Vladislav Yuryevich Zaslavsky
Journal of Modern Physics (JMP) , 2010, DOI: 10.4236/jmp.2010.12017
Abstract: Spatial distribution of acoustic and elastic waves generated by an elementary vibration source at seismic profiling frequencies in an infinite medium close to a layer inclusion, i.e., an extended layer, is numerically simulated. Point dipole radiation in a homogeneous infinite medium separated by a liquid layer of different medium density or acoustic wave velocity is considered. Transverse elastic SH-waves excited by an oscillating power source in a solid medium also located close to the layer of different propagation velocity than the velocity of the vicinity are analyzed. Formulae for the spatial distribution of the wave field amplitude are derived and computer graphics of field distribution images is presented. Wave reflection, penetration deep into the layer inclusion, and transmittance through it are examined. Results of the analysis can be applied to seismoacoustic probing of geologic environment by the near field of a harmonic vibration source.
Theoretical and numerical investigations of the acoustic field excited by submarine explosion
海底爆破辐射声场的理论及数值研究

Tang Li-Guo,Xu Xiao-Mei,Liu Sheng-Xing,
汤立国
,许肖梅,刘胜兴

物理学报 , 2008,
Abstract: This paper simulates and analyzes numerically the dispersion characteristics of the waves propagating in the shallow-ocean overlying a semi-infinite elastic solid. The analytical solution of the acoustic field in the shallow-ocean, excited by an explosive point source in the solid bottom, is derived by using the theories for sound propagation in liquid and solid. The time-domain waveforms of transient acoustic field are simulated with the above analytical solution. The dispersion characteristics of the transient acoustic field are analyzed by using the smoothed pseudo Wigner-Ville distribution.
Acoustic beam modeling of ultrasonic transducers and arrays using the impulse response and the discrete representation methods
Franco, Ediguer E.;Andrade, Marco A. B.;Adamowski, Julio C.;Buiochi, Flávio;
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2011, DOI: 10.1590/S1678-58782011000400004
Abstract: the impulse response of the velocity potential and the discrete representation methods were used in order to model the acoustic field radiated by ultrasonic transducers and arrays. the first method deals with the calculation of the exact impulse response, in which solutions are possible only for simple geometries, such as the circular piston. the second method is an approximated solution based on the discretization of the acoustic aperture in small elementary areas, each of them radiating a spherical wave. by using circular transducers, which can be considered circular pistons, many simulations comparing the methods were carried out. the relation between the computational cost and the precision was analyzed, thus establishing the time and space discretization levels. the simulations were made using the matlab software and the results were compared to experimental measurements showing good agreement. the experimental results were obtained using a scanning system. the acoustic field radiated from a 1 mhz circular transducer was measured as well as a 3.5 mhz array of 16 elements both immersed in water. the acoustic field radiated by the array was simulated and measured with focalization on a radius of 30 mm with deflections of 0o and 20o.
Lateral field excitation properties of langasite single crystal

Ma Ting-Feng,Zhang Chao,Feng Guan-Ping,Jiang Xiao-Ning,

中国物理 B , 2010,
Abstract: In this work, bulk acoustic wave propagation properties of langasite single crystal excited by lateral electric field have been investigated. Three important crystal cuts have been identified for different operational modes of lateral field excitation (LFE) on langasite substrate, namely the (yxl)65circ (pure-LFE mode), (yxl)45circ (quasi-LFE mode), and (yxl)0circ (pseudo-LFE mode). Devices on langasite substrate with the above cuts were fabricated and tested, and the experimental results agree well with the theoretical analysis. It is found that a pure thickness shear mode exists in the (yxl)65circ langasite LFE device with the bare side facing liquid, and no spurious mode is found due to its moderately large piezoelectric coupling factor. In addition, (yxl)0circ langasite LFE device is also found suitable for liquid phase sensing applications.
Análisis de propagación de onda acústica en océanos estratificados mediante el método de modos normales
M. Quino-Cerdán,V. S. Rabinovich
Latin-American Journal of Physics Education , 2009,
Abstract: The normal-mode theory is presented for the transmission of sound from a stationary source in a homogeneous airlayer into an arbitrarily stratified ocean. Transmission loss calculations are performed for a Pekeris-type shallow-waterenvironment consisting of a water layer over a uniform solid seabed. Numerical results are presented to illustrate theacoustic field behavior depending on the distance between transmitter and receiver.
Regularities in discrete hierarchy seismo-acoustic mode in a geophysical field
Kamel Baddari,Anatoly D. Frolov
Annals of Geophysics , 2010, DOI: 10.4401/ag-4725
Abstract: Some regularities in seismo acoustic mode have been studied during the preparation and development of dynamic events generated during the deformation at different scales in a geophysical field. The time-space behavior of certain auto similarity parameters: the slope of the recurrence plot c, the fractal dimension of the hypocenters set D, the relationship D-3c and the crack concentration parameter Ksr in laboratory and field experiments in Algerian seismoactive zone have been analyzed as well. Precursory stage and local failure evolution in rock samples and in natural conditions were studied. It is shown that the regularities in the behavior of the parameters under study do not qualitatively depend on the dimension of the object being loaded. The quoted examples above speak of inhomogeneity and self-similarity of seismicity distribution in space-time. This suggests that the evolution of cracking process at different scales, from rock samples to Earth crust, is controlled by the same physical mechanism. The further development of these studies consolidates the physical basis of the prediction of the dynamic events.
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