Zakhidov E.A., Kokhkharov A.M., Kuvondikov V.O., Nematov Sh.K., Tazhibaev I.I. «A Low-Frequency Photoacoustic Spectrometer with an RGB Light-Emitting Diode for Evaluating Photosynthetic Activity in Plant Leaves» Акустический журнал, 65, № 1, с. pp. 90-95 (2019)

A photoacoustic spectrometer based on a three-colored light-emitting diode (with peak emission wavelengths of 465, 525, and 640 nm) designed to determine the intensity of photosynthesis in different deep layers of plant leaves is described. The physical properties of the photoacoustic signal were studied at different wavelengths and light modulation frequencies. It was shown that the proposed spectrometer can be employed for quantitative evaluation of heat dissipation and photochemical assimilation of the absorbed light energy in this medium.

Мингалев О.В., Хабарова О.В., Малова Х.В., Мингалев И.В., Кислов Р.А., Мельник М.Н., Сецко П.В., Зеленый Л.М., Zank G.P. «Моделирование ускорения протонов в магнитном острове в складке гелиосферного токового слоя» Астрономический вестник. Исследования Солнечной системы, 53, № 1, с. 34-60 (2019)

Пересечения гелиосферного токового слоя (ГТС) на орбите Земли часто ассоциируются с наблюдением анизотропных пучков высокоэнергичных протонов, ускоренных до энергий от сотен кэВ до нескольких МэВ и выше. Недавно обнаружилась связь между этим явлением и присутствием маломасштабных магнитных островов (МО) вблизи пересоединяющихся токовых слоев. В работе предложен механизм набора энергии предускоренными протонами при колебаниях множественных магнитных островов внутри складки пересоединяющегося ГТС. Разработана модель электромагнитного поля колеблющегося трехмерного МО с характерным размером ∼0.001 а.е., на который налетают протоны, ускоренные ранее в процессе магнитного пересоединения до энергий порядка от кэВ до десятков кэВ. Численные расчеты продемонстрировали, что возникающие продольные индукционные электрические поля способны дополнительно ускорять падающие на МО протоны. Показано, что существует локальная “ускорительная” область внутри острова, в которой приобретение энергии частицами наиболее эффективно, в результате чего их средние энергии вылета составляют от сотен кэВ до 2 МэВ и выше. Вне этой области ускорение частиц практически отсутствует. Показано, что набранные частицами энергии существенно зависят от начальных фаз и места попадания в МО, но слабо зависят от величин начальных энергий. Таким образом, низкоэнергичные частицы могут ускоряться эффективнее, чем высокоэнергичные, а на вылете из МО всеми частицами может достигаться общая предельная энергия. Обнаружено также, что направления скоростей вылета имеют сильную пространственную анизотропию. Полученные результаты согласуются с наблюдениями в плазме солнечного ветра.

Zhai J.X., Chen C. «Low-loss Floating Electrode Unidirectional Transducer for SAW Sensor» Акустический журнал, 65, № 2, с. pp. 178-184 (2019)

Two types of interdigital transducer (IDT) structures of SAW devices have been investigated; one type consists in a classical single electrode transducer where the unit cell has two electrodes, and the other type has a design of floating electrode unidirectional transducer (FEUDT) where the unit cell has six electrodes per period. By taking the Fourier transform of the corresponding time response, the insertion loss (IL) of the SAW device with FEUDT is calculated as –2.6 (forward) and –20.5 dB (backward). At the same time, the device with conventional IDT exhibits an IL value of –8.4 (forward) and –7.8 dB (backward). It turns out that the design of a novel FEUDT type SAW device can efficiently reduce the insertion loss of the SAW device.

Dai Yuxiang, Yan Shouguo, Zhang Bixing «Acoustic Field Excited by Single Force with Arbitrary Direction in Semi-Infinite Elastic Space» Акустический журнал, 65, № 3, с. pp. 235-245 (2019)

In this paper, the acoustic field excited by a single force with arbitrary direction in a semi-infinite elastic space is studied and its mathematical expressions are obtained. It shows that there are many complex behaviors when the elastic wave reaches the free boundary. The numerical simulation shows that there are several kinds of waves in the semi-infinite elastic space: direct P wave, direct SV wave, SP wave propagating along the free surface which can generate Head wave and Rayleigh wave. The forming mechanism of the SP wave and Rayleigh wave is specially studied. The waveforms at the observation point on the free surface of the semi-infinite space contain only direct P wave and direct SV wave when the SV wave incident angle is within the critical reflection angle. However, if the incident angle from the source to the observation point is exceeding to the critical reflection angle, not only direct P and direct SV wave but also the SP wave and Rayleigh wave are all be generated. It is focused on the relationships of the direction of single force to the excitation intensity of each wave. The relationship of each wave packet to the single force and observation direction is obtained and analyzed.

Yang Liu, Huang Jun, Yi Mingxu, Zhang Chaopu, Xiao Qian «A numerical study of the effects of design parameters on the acoustics noise of a high efficiency propeller» Акустический журнал, 63, № 6, с. pp. 699-710 (2017)

A numerical study of a high efficiency propeller in the aerodynamic noise generation is carried out. Based on RANS, three-dimensional numerical simulation is performed to obtain the aerodynamic performance of the propeller. The result of the aerodynamic analysis is given as input of the acoustic calculation. The sound is calculated using the Farassat 1A, which is derived from Ffowcs Williams–Hawkings equation, and compared with the data of wind tunnel. The propeller is modified for noise reduction by changing its geometrical parameters such as diameter, chord width and pitch angle. The trend of variation between aerodynamic analysis data and acoustic calculation result are compared and discussed for different modification tasks. Meaningful conclusions are drawn on the noise reduction of propeller.

Li Suobin, Dou Yihua, Chen Tianning, Wan Zhiguo, Ju Luyan, Zhang Fan, Cui Xiao Xiao «Forming Low-Frequency Complete Vibration Bandgaps in a thin Nonmetallic Elastic Metamaterial Plate» Акустический журнал, 65, № 3, с. pp. 322-333 (2019)

Low-frequency vibration-bandgaps in elastic metamaterials open new possibilities to minimize low-frequency vibration and noise. Unfortunately, fabricating a complete vibration bandgap for low frequencies still represents a challenging engineering task. In this paper, a new type of a low-frequency complete vibration bandgap in a thin non-metal elastic metamaterial plate is introduced and investigated numerically. The proposed elastic metamaterial plate consists of decoupling-resonators, which are deposited on a 2D, locally resonant phononic-crystal plate, made of an array of rubber fillers, which are embedded in a nonmetallic plate. The dispersion relationship, the power-transmission spectrum, and the displacement fields for the eigenmode are calculated using the finite element method. It is shown that coupling between the local resonance mode of the decoupling-resonators and the Lamb-wave mode of the epoxy plate, consistent with the modal superposition principle, is responsible for the formation of vibration bandgaps. Moreover, the equivalent spring-mass system for the coupling-resonators can be decoupled by introducing a rubber filler. In addition, both longitudinal and the transverse elastic wave bandgaps can be tuned to the same low-frequency range. As a result, a novel kind of low-frequency complete vibration bandgap, which can damp a low-frequency elastic wave, is produced. Furthermore, the effects of the decoupling-resonators on the vibration bandgap are investigated. It is now possible that an elastic metamaterial plate can be dampen with complete low-frequency vibration bandgaps, which can potentially be used for commercial noise and vibration reduction.

Li H.X., Tao C.H., Goloshubin G., Liu C., Shi S.H., Huang G.N., Zhang H., Zhang J., Zhang X.F. «A Modified Biot/Squirt Model of Sound Propagation in Water-Saturated Sedment» Акустический журнал, 64, № 4, с. pp. 453-458 (2018)

A modified Biot/Squirt flow model was developed. The difference between MBISQ and BISQ models is the expression for the porosity differential. Numerical analysis shows that the acoustic dispersion predicted by MBISQ is much higher than by BISQ. Investigations of the effects of permeability, viscosity, and squirt flow length on velocity and attenuation indicate that the behavior of MBISQ agrees with that of the BISQ model. The result of sediment acoustic inversion based on MBISQ was more reasonable than the result of BISQ model.

Li H.X., Tao C.H., Goloshubin G., Liu C., Shi S.H., Huang G.N., Zhang H., Zhang J., Zhang X.F. «A Modified Biot/Squirt Model of Sound Propagation in Water-Saturated Sedment» Акустический журнал, 64, № 4, с. pp. 453-458 (2018)

A modified Biot/Squirt flow model was developed. The difference between MBISQ and BISQ models is the expression for the porosity differential. Numerical analysis shows that the acoustic dispersion predicted by MBISQ is much higher than by BISQ. Investigations of the effects of permeability, viscosity, and squirt flow length on velocity and attenuation indicate that the behavior of MBISQ agrees with that of the BISQ model. The result of sediment acoustic inversion based on MBISQ was more reasonable than the result of BISQ model.

Zhang Kang «An Analytical Inverse Approach to Design GRIN Lenses» Акустический журнал, 64, № 6, с. pp. 684-691 (2018)

An analytical inverse method to design lenses of isotropic inhomogeneous refractive index (RI) distribution is presented, where the wave ray propagation is described by the eikonal equation. We show that some particular RI distributions can be obtained by the angles of incidence and emergence when the rays pass through the surfaces of the lenses. This method is applied to design lenses that perfectly focus rays or bend them to arbitrary angles. In addition, gradient refractive index (GRIN) devices are proposed, able to generate self-bending acoustic beams and obtain illusion shadows of arbitrary objects. The ray tracing and finite elements method simulation results indicate the validity of the method. The method may have potential applications in designing acoustic and optic GRIN devices for controlling energy flux, such as medical imaging, therapeutic ultrasound, acoustic levitation, energy isolation, acoustic and optic camouflaging, etc.

Su Ting, Zhang Shi, Li Dayu, Yao Dingjie «Combined Sign Coherent Factor and Delay Multiply and Sum Beamformer for Plane Wave Imaging» Акустический журнал, 64, № 3, с. pp. 379-386 (2018)

Plane wave imaging is a relatively new technique in ultrasound imaging. However, in traditional methods, the coherent information of different emissions and different elements are not considered. In fact, the sign coherent factor (SCF) can improve the lateral resolution of the imaging greatly. In addition, the delay multiply and sum (DMAS) beamformer is mainly based on the spatial correlation of background scattering signals, it has higher contrast and resolution, but suffers from energy loss at great depths. In this paper, combining the advantages of SCF and DMAS, the sign coherent factor delay multiply and sum (SCF-DMAS) beamformer for plane wave imaging is proposed. Unlike the traditional plane wave imaging, the proposed SCF-DMAS beamformer is based on the 2-D echo data set, which improves the imaging speed greatly. Finally, we simulated the point targets and the cyst phantom to evaluate the performance of proposed method. Compared with the traditional plane wave imaging, the lateral resolution of SCF-DMAS beamformer improves greatly for the point targets, and for the cyst phantom the contrast ratio (CR) and contrast-to-noise ratio (CNR) increased by 96.97 and by 79.98% respectively without reducing the frame rate.

Li J., Liu C.J., Zhang W.J. «Pressure potential and stability analysis in an acoustical noncontact transportation» Акустический журнал, 63, № 1, с. pp. 125-131 (2017)

Near field acoustic traveling wave is one of the most popular principles in noncontact manipulations and transportations. The stability behavior is a key factor in the industrial applications of acoustical noncontact transportation. We present here an in-depth analysis of the transportation stability of a planar object levitated in near field acoustic traveling waves. To more accurately describe the pressure distributions on the radiation surface, a 3D nonlinear traveling wave model is presented. A closed form solution is derived based on the pressure potential to quantitatively calculate the restoring forces and moments under small disturbances. The physical explanations of the effects of fluid inertia and the effects of non-uniform pressure distributions are provided in detail. It is found that a vibration rail with tapered cross section provides more stable transportation than a rail with rectangular cross section. The present study sheds light on the issue of quantitative evaluation of stability in acoustic traveling waves and proposes three main factors that influence the stability: (a) vibration shape, (b) pressure distribution and (c) restoring force/moment. It helps to provide a better understanding of the physics behind the near field acoustic transportation and provide useful design and optimization tools for industrial applications.

Li H.X., Tao C.H., Goloshubin G., Liu C., Shi S.H., Huang G.N., Zhang H., Zhang J., Zhang X.F. «A Modified Biot/Squirt Model of Sound Propagation in Water-Saturated Sedment» Акустический журнал, 64, № 4, с. pp. 453-458 (2018)

A modified Biot/Squirt flow model was developed. The difference between MBISQ and BISQ models is the expression for the porosity differential. Numerical analysis shows that the acoustic dispersion predicted by MBISQ is much higher than by BISQ. Investigations of the effects of permeability, viscosity, and squirt flow length on velocity and attenuation indicate that the behavior of MBISQ agrees with that of the BISQ model. The result of sediment acoustic inversion based on MBISQ was more reasonable than the result of BISQ model.

Cao Yonggang, Chen Qian, Zheng Huifeng, Lu Lidong, Wang Yuebing, Zhu Jiang «Study on the Mechanism of Ultrasonic Power Measurement Sensor based on Pyroelectric Effect» Акустический журнал, 64, № 6, с. pp. 789-795 (2018)

PVDF pyroelectric sensor has been widely applied in many fields, such as intruder alarm. Nowadays, this sensor shows a potential for ultrasonic power measurement. However, the transformation mechanism between the acoustic and pyroelectric signals has not been particularly studied until now. In this paper, a physical model was introduced for theoretical study of the mechanism of energy transformations. In addition, a simulation program based on finite-element analysis method was built up for analyzing the ultrasound propagation characteristics and the temperature rise on the PVDF, as well it predicted the waveform and amplitude of the generated pyroelectric signal. Besides that, a PVDF pyroelectric sensor was fabricated and used for acoustic power measurement experiment. Finally, the experiment and simulation results were compared, confirming that the physical model is suitable for pyroelectric sensor characteristics analysis. It can also provide useful suggestions for the design and fabrication of PVDF pyroelectric sensors with high sensitivity.

Ma Huayuan, Long Yuan, Zhong Mingshou, Li Xinghua, Xie Quanmin «Study on Ground Vibration Mode of Physical Explosion of High Pressure Natural Gas Pipeline» Акустический журнал, 65, № 5, с. pp. 583-592 (2019)

In this paper, an explosion experiment was carried out on the OD1219mm-X90-12Mpa natural gas pipeline to study the vibration hazard. Based on a series of experiments, the spatial distribution of the vibration energy was studied. The vibration distribution field was drawn by interpolation method based on re-harmonic equation and it was found that the field was non-circular symmetry. Through in-depth research, it was preliminarily proved that the vibration field had interference characteristics, which was caused by the special vibration source of the pipeline explosion. There was a significant difference in the frequency components between the interference strengthened region and the weakened region. The results shown that the strengthening effect of the interference in the 90° and 30° direction should be taken into account when evaluating the damage scope of the explosion accident. Research provided reference for safety design of parallel pipelines and buildings.

Wang Q., Zhou B., Chen Y., Quan H. «Subarray Beam-space Adaptive Beamforming Combined with Array Shape Estimation based on Non-Acoustic Sensor» Акустический журнал, 65, № 2, с. pp. 226-233 (2019)

To address the issue of serious decline in performance of the array signal processing caused by the towed array shape distortion during maneuvering, this paper presents a new method of subarray beam-space adaptive beamforming combined with an array shape estimation method based on non-acoustic sensor. Firstly, the array shape through the approximate circular arc structure of the array segment between the adjacent sensor during maneuvering is preliminary calculated. Next, the final estimated array shape through a smooth processing method on the entire array shape by means of a calibration method using spline interpolation technique is achieved. This method is able to estimate the array shape in real time. The array steering vector based on the real-time estimation of the array shape is updated, using a subarray beam-space adaptive beamforming (SBABF) to reduce the demand of the number of the snapshots. And the beam-space covariance matrix converges fast within a few snapshots. The SBABF method combined with array shape estimation (AE-SBABF) was verified by simulation data and sea trial data processing results. During maneuvering, the AE-SBABF can not only improve the array processing gain of the target effectively, but also solve the left/right ambiguity problem well.

Zhou Fulin, Wang Bin, Fan Jun, Peng Zilong «Theoretical and Numerical Studies on in vacuo Structural Admittance of an Infinite, Coated Cylindrical Shell» Акустический журнал, 65, № 1, с. pp. 14-22 (2019)

Studying the interaction of sound with a coated cylindrical shell immersed in water is essential for improving existing underwater target detection and classification algorithms. According to the impedance theory of sound scattering, in vacuo structural admittance describes the relationship between the sonar-induced forces and the resulting vibration on the surface, which can be used to solve the problem of the acoustic scattering and radiation. In this work, we investigate numerically and theoretically the structural admittance of a coated cylindrical shell. Analytical expressions of the structural admittance are derived for different external forces: a plane acoustic wave, a normal point force, and a random noise field. The structural admittance is also numerically evaluated. The results show that the structural admittance is independent of exterior medium and fluid loading. According to the impedance theory of sound scattering, the scattered field of a coated cylindrical shell is calculated by combining the structural-, acoustic-, and internal-admittance matrices. Because of the non-local property of structural surface admittance, we build an algebraic model of a coated object by nonlinear curve fitting and study a local approximation of the structural admittance. We also find that simplifying the large matrices is useful for research on structural vibrations. Thus, this work presents a systematic study of the acoustic scattering characteristics of structural admittance of an infinite, coated cylindrical shell.

Wu Delin, Dai Yuyu, Chen Hao, Zhou Yinqiu, Fu Lin, Wang Xiuming «Mode analysis of trilaminar bender bar transducers using an approximation method» Акустический журнал, 63, № 5, с. pp. 617-624 (2017)

Based on the vibration theory of a thin plate, an analytical treatment of the trilaminar bender bar with piezoelectric elements and inert substrate of various lengths is presented for mode analysis. Resonance frequency and effective electromechanical coupling coefficient are calculated by this method. The impacts of the geometries of the bender bar on the performance of its fundamental and third-order flexural mode are investigated in detail under rigid boundary conditions. It is shown that resonance frequency is extremely sensitive to the thickness of inert substrate. Moreover, the effective electromechanical coupling coefficient has peaks as the length of piezoelectric elements varies. The peaks are achieved when the length of piezoelectric elements equals the length between two nodes having zero strains in the x-direction. The trilaminar bender bar will be effectively excited when the strains on the piezoelectric element are in the same phase, which is important to disclose the vibration mechanisms of this kind of transducer. Also, analytical results are compared with the ones of numerical simulation. The results suggest that effective electromechanical coupling coefficient shares similar patterns with electrical conductance, which can be used to characterize transducer performance to a certain extent. It also demonstrates that the analytical treatment provides an efficient alternative way for optimizing the bender bar transducer design.

Cao Yonggang, Chen Qian, Zheng Huifeng, Lu Lidong, Wang Yuebing, Zhu Jiang «Study on the Mechanism of Ultrasonic Power Measurement Sensor based on Pyroelectric Effect» Акустический журнал, 64, № 6, с. pp. 789-795 (2018)

PVDF pyroelectric sensor has been widely applied in many fields, such as intruder alarm. Nowadays, this sensor shows a potential for ultrasonic power measurement. However, the transformation mechanism between the acoustic and pyroelectric signals has not been particularly studied until now. In this paper, a physical model was introduced for theoretical study of the mechanism of energy transformations. In addition, a simulation program based on finite-element analysis method was built up for analyzing the ultrasound propagation characteristics and the temperature rise on the PVDF, as well it predicted the waveform and amplitude of the generated pyroelectric signal. Besides that, a PVDF pyroelectric sensor was fabricated and used for acoustic power measurement experiment. Finally, the experiment and simulation results were compared, confirming that the physical model is suitable for pyroelectric sensor characteristics analysis. It can also provide useful suggestions for the design and fabrication of PVDF pyroelectric sensors with high sensitivity.

Li Baolei, Li Tinghua, Wu Jun, Hui Ming, Yuan Gang, Zhu Yongsheng «An arbitrary-shaped acoustic cloak with merits beyond the internal and external cloaks» Акустический журнал, 63, № 1, с. pp. 45-53 (2017)

Based on transformation acoustics, an arbitrary-shaped acoustic cloak capable of functioning as an information exchange-enabling internal cloak and a movement-allowing external cloak is presented. The general expressions of material parameters for the acoustic cloaks with arbitrarily conformal or non-conformal boundaries are derived, and then the performances of developed cloaks are validated by full-wave simulations. Finally, the different characteristics of the linear and nonlinear transformations-based cloaks are compared and analyzed. The proposed cloak could lead to wider applications beyond that of normal cloaks, since it effectively compensates the insufficiencies of traditional internal and external cloaks. Besides, this work also provides a new method to design bifunctional device and suggests an alternative way to make a large object invisible.

Zou Ming-Song, Wu You-Sheng, Liu Jian-De, Liu Shu-Xiao «A Mixed Analytical-Numerical Method for the Vibro-Acoustic Analysis of an Underwater Ring-Stiffened Cylindrical Shell Containing Substructures» Акустический журнал, 64, № 5, с. pp. 596-604 (2018)

A new sono-elastic substructure method is proposed in this paper to improve the computational efficiency of the hull-substructure coupled and fluid-structure interacted vibration and acoustic radiation of a submerged cylindrical-shell-type vehicle. The typical part of the vehicle structure is divided into the main hull and the internal substructures. The fluid-structure interaction problem of the main hull is solved by an analytical method based on the simplified model of a single-hull ring-stiffened cylindrical shell simply supported at both ends. Meanwhile, the substructures are numerically modeled through the Finite Element Method, with the condensed dynamic stiffness matrices of them obtained via the Superelement Method of Modal Synthesis. The main hull and the internal substructures are then integrated according to the boundary compatibility conditions at the connecting parts. Thus, a Mixed Analytical-Numerical Substructure (MANS) method is formulated. The applicability of this method is validated by two numerical examples as well as the test results of a large-scale submerged structural model. It is shown that the MANS method is suitable for the prediction of vibration and acoustic radiation of typical cylindrical-shell-type submerged structures in the medium frequency region.