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  • Open Access

    ARTICLE

    Multiple Scattering Between Adjacent Sound Sources in Head-Related Transfer Function Measurement System

    Guangzheng Yu1,*, Yu Liu1,2, Bosun Xie1, Huali Zhou1

    Sound & Vibration, Vol.53, No.4, pp. 151-159, 2019, DOI:10.32604/sv.2019.04644

    Abstract To accelerate head-related transfer functions (HRTFs) measurement, two or more independent sound sources are usually employed in the measurement system. However, the multiple scattering between adjacent sound sources may influence the accuracy of measurement. On the other hand, the directivity of sound source could induce measurement error. Therefore, a model consisting of two spherical sound sources with approximate omni-directivity and a rigid-spherical head is proposed to evaluate the errors in HRTF measurement caused by multiple scattering between sources. An example of analysis using multipole re-expansion indicates that the error of ipsilateral HRTFs are within the bound of ± 1.0 dB… More >

  • Open Access

    REVIEW

    Adipose-derived mesenchymal stem/stromal cells: from the lab bench to the basic concepts for clinical translation

    Yesica Romina FRONTINI-LÓPEZ1, Aldana Daniela GOJANOVICH1, Diego MASONE1,2, Diego Martín BUSTOS1,3, Marina UHART1

    BIOCELL, Vol.42, No.3, pp. 67-78, 2018, DOI:10.32604/biocell.2018.07013

    Abstract In the last years, much work has shown that the most effective repair system of the body is represented by stem cells, which are defined as undifferentiated precursors that own unlimited or prolonged self-renewal ability, which also have the potential to transform themselves into various cell types through differentiation.All tissues that form the body contain many different types of somatic cells, along with stem cells that are called ‘mesenchymal stem (or stromal) cells’ (MSC). In certain circumstances, some of these MSC migrate to injured tissues to replace dead cells or to undergo differentiation to repair it.The discovery of MSC has… More >

  • Open Access

    ARTICLE

    Theoretical Study of the Energies of the Oscillating System with a Well- Distributed Mass of the Spring

    Yewan Ma, Hansen Chang, Zhaowang Wu, Yanyan Jiang, Juan Li, Xunchang Yin, Quanjin Liu, Lihua Zhang*

    Sound & Vibration, Vol.53, No.4, pp. 139-149, 2019, DOI:10.32604/sv.2019.04622

    Abstract The energy of a spring with a well-distributed mass ms is theoretically studied in this paper. The solution of the wave equation is derived in detail, and then the kinetic energy and potential energy of the spring are studied with the wave equation, as well as the kinetic energy of the oscillating mass M. The kinetic energy and potential energy of the spring, and total energy are numerically simulated for different ratios ms/M with considering the spring’s mass, which makes the property of energy of the oscillating system understood easily. More >

  • Open Access

    ARTICLE

    Lightweight Biobased Polyurethane Nanocomposite Foams Reinforced with Pineapple Leaf Nanofibers (PLNFs)

    Xiaojian Zhou1,2, Hui Wang1, Jun Zhang2, Zhifeng Zheng1, Guanben Du1,2,*

    Journal of Renewable Materials, Vol.6, No.1, pp. 68-74, 2018, DOI:10.7569/JRM.2017.634150

    Abstract Pineapple leaf nanofibers (PLNFs) extracted from pineapple leaf fiber were used for reinforcing biobased polyurethane foam (BPU). The dispersion performance of PLNF in the foaming mixture system, nanocomposite foaming behavior, cell morphology, cell size, density, compressive strength and dimensional stability were investigated. The viscosity of the mixtures increased with increasing the PLNF content. The addition of a tiny amount of PLNF did not influence the exothermic temperature of the foam system, but reduced the expansion and gel time of the nanocomposite foams. This reduced time was found to increase the production efficiency. Scanning electron microscopy (SEM) images showed that the… More >

  • Open Access

    ARTICLE

    Experimental and Numerical Investigation on the External Aerodynamic Noise of High-Speed Train

    Shijie Jiang*, Song Yang, Bohong Zhang, Bangchun Wen

    Sound & Vibration, Vol.53, No.4, pp. 129-138, 2019, DOI:10.32604/sv.2019.04048

    Abstract Aerodynamic noise is the dominant noise source of the high-speed train. It not only seriously affects the passenger comfort and people’s normal life along the railway line, but also may cause fatigue damage to the surrounding equipment and buildings. This manuscript carried out the simulation and experimental study on the external aerodynamic noise of high-speed train, in order to increase the understanding of the noise and hence to be better able to control it. The on-line tests were performed to verify that it is reasonable to simplify the high-speed train model. The turbulent air flow model was then developed, and… More >

  • Open Access

    ARTICLE

    Leak Detection of Gas Pipelines Based on Characteristics of Acoustic Leakage and Interfering Signals

    Lingya Meng1, *, Cuiwei Liu2, Liping Fang2, Yuxing Li2, Juntao Fu3

    Sound & Vibration, Vol.53, No.4, pp. 111-128, 2019, DOI:10.32604/sv.2019.03835

    Abstract When acoustic method is used in leak detection for natural gas pipelines, the external interferences including operation of compressor and valve, pipeline knocking, etc., should be distinguished with acoustic leakage signals to improve the accuracy and reduce false alarms. In this paper, the technologies of extracting characteristics of acoustic signals were summarized. The acoustic leakage signals and interfering signals were measured by experiments and the characteristics of time-domain, frequency-domain and time-frequency domain were extracted. The main characteristics of time-domain are mean value, root mean square value, kurtosis, skewness and correlation function, etc. The features in frequency domain were obtained by… More >

  • Open Access

    ARTICLE

    Influence of the Number of Loudspeakers on the Timbre in Horizontal and Mixed-Order Ambisoncis Reproduction

    Haiming Mai1, Bosun Xie1,2,*, Jianliang Jiang1, Dan Rao1, Yang Liu1

    Sound & Vibration, Vol.53, No.3, pp. 97-109, 2019, DOI:10.32604/sv.2019.04275

    Abstract Ambisonics is a series of flexible spatial sound reproduction systems based on spatial harmonics decomposition of sound field. Traditional horizontal and spatial Ambisonics reconstruct horizontal and spatial sound field with certain order of spatial harmonics, respectively. Both the Shannon-Nyquist spatial sampling frequency limit for accurately reconstructing sound field and the complexity of system increase with the increasing order of Ambisonics. Based on the fact that the horizontal localization resolution of human hearing is higher than vertical resolution, mixed-order Ambisonics (MOA) reconstructs horizontal sound field with higher order spatial harmonics, while reconstructs vertical sound field with lower order spatial harmonics, and… More >

  • Open Access

    ARTICLE

    Experimental and Numerical Study of Structural Identification Using Non-Linear Resonant Decay Method

    Mehdi Sarmast1,*, Hamed Ghafari2, Jan R. Wright3

    Sound & Vibration, Vol.53, No.3, pp. 75-95, 2019, DOI:10.32604/sv.2019.04193

    Abstract One of the practical approaches in identifying structures is the non-linear resonant decay method which identifies a non-linear dynamic system utilizing a model based on linear modal space containing the underlying linear system and a small number of extra terms that exhibit the non-linear effects. In this paper, the method is illustrated in a simulated system and an experimental structure. The main objective of the non-linear resonant decay method is to identify the non-linear dynamic systems based on the use of a multi-shaker excitation using appropriated excitation which is obtained from the force appropriation approach. The experimental application of the… More >

  • Open Access

    ARTICLE

    A Spring-Layer Model for a Bi-Layered Plate-Strip with Initial Stress Through Imperfect Contact Interface

    Ahmet Daşdemir*

    Sound & Vibration, Vol.53, No.3, pp. 65-74, 2019, DOI:10.32604/sv.2019.04087

    Abstract In this paper, we present our report on the forced vibration of a bi-layered plate-strip with initial stress resting on a rigid foundation induced by a time-harmonic force. The investigation is carried out according to the piecewise homogeneous body model with utilizing the three-dimensional linearized theory of elastic waves in initially stressed bodies (TLTEWISB). The materials of the body are chosen to be linearly elastic, homogeneous, and isotropic. The interface between the layers is assumed to be imperfect, and is simulated by the spring-layer model. A similar degree of imperfection on the interface is realized in the normal and tangential… More >

  • Open Access

    ARTICLE

    Effects of precipitation changes on the dynamics of sparse elm woodland in Northeastern China

    Yi TANG1,*, Carlos Alberto BUSSO2

    BIOCELL, Vol.42, No.2, pp. 61-66, 2018, DOI:10.32604/biocell.2018.07015

    Abstract Elm (Ulmus pumila L.) is the dominant tree species in the sparse elm woodland, the original vegetation in the Horqin Sandy Land. The effects of changes in precipitation on U. pumila trees have not been fully studied. We determined a dynamic model by considering the five stages in the U. pumila life cycle, i.e. seed, seedling, and juvenile, mature and over-mature tree stages. The effects of changes in precipitation on population density and age structure were then evaluated. Population density, after averaging all study developmental morphology stages, ranged from 16.67 individuals/m2 to 25.01 individuals/m2 under a mean annual precipitation (MAP)… More >

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