Yiping Sun^1,2, Qiang Bai¹, Xuefeng Zhao¹, Meng Tao^1,*

CMES-Computer Modeling in Engineering & Sciences, Vol.130, No.2, pp. 1149-1170, 2022, DOI:10.32604/cmes.2022.017760 - 13 December 2021

Abstract A cavity viscoelastic structure has a good sound absorption performance and is often used as a reflective baffle or sound absorption cover in underwater acoustic structures. The acoustic performance field has become a key research direction worldwide. Because of the time-consuming shortcomings of the traditional numerical analysis method and the high cost of the experimental method for measuring the reflection coefficient to evaluate the acoustic performance of coatings, this innovative study predicted the reflection coefficient of a viscoelastic coating containing a cylindrical cavity based on an artificial neural network (ANN). First, the mapping relationship between… More >

Tetti Novalina Manik^1,2,*, Sulung Apria Nuki², Nur Aini Fauziyah¹, Mashuri¹, Mochamad Zainuri¹, Darminto^1,*

Journal of Renewable Materials, Vol.9, No.9, pp. 1647-1660, 2021, DOI:10.32604/jrm.2021.016089 - 23 April 2021

Abstract The performance of oil palm trunk wastes from Banjarbaru of South Kalimantan was improved with the help of chemical modification in a two-step treatment. The first was formalization with formaldehyde solution with varying pH, and the second was impregnation with melamine-formaldehyde resin under 5 bar pressure for an hour. In these processes, the samples were cured at 120°C for 10 min and then dried in an oven at (103 ± 2)°C in order to attain a moisture content of less than 6%. These treatments improved the physical properties (density, moisture content, and volume swelling), mechanical More > Graphic Abstract

Yipu Wang¹, Yonghua Wang^1,2,*, Zheming Liu¹, Huadong Yu¹, Jinkai Xu¹

Journal of Renewable Materials, Vol.9, No.5, pp. 923-941, 2021, DOI:10.32604/jrm.2021.014138 - 20 February 2021

Abstract Noise pollution is one of the contemporary environmental pollution, which seriously damages people’s green and healthy life. In order to further improve the low frequency sound absorption performance of microperforated panel (MPP), a new plastocene coupled microperforated plate (PCMPP) is proposed. The acoustic properties of PCMPP with different apertures and perforation ratio were measured by transfer function method and compared with that of conventional MPPs. It is found that when the aperture was 0.8 mm, the peak value of sound absorption coefficient of PCMPP decreased by 150 Hz compared with MPP. In a certain range,… More >

Ali Safari Variani¹, Ali Dastamoz¹, Sajad Zare², Ahmad Nikpey¹, Saeid Ahmadi^1,*

Sound & Vibration, Vol.54, No.1, pp. 43-55, 2020, DOI:10.32604/sv.2020.08636 - 01 March 2020

Abstract This work investigated multiple jet nozzles with various geometrical shape, number of exits, and material on reducing noise radiated from jet flows. Nozzles are categorized in two groups with few and many exit numbers, each with various exit shapes, slot and circular, and geometry. Firstly, nozzles are designed and then fabricated by a 3D printer, Form Labs, Form2USA, with polymeric resin. Also, the nozzle with the most noise reduction made of stainless steel. Noise and air thrust were measured at three air pressure gauges, 3, 5, 7 BAR and directions from nozzle apex, 30°, 90°,… More >

Yadong Zhang^{1, *}, Jiye Zhang²

FDMP-Fluid Dynamics & Materials Processing, Vol.16, No.1, pp. 105-120, 2020, DOI:10.32604/fdmp.2020.07959 - 01 February 2020

Abstract The object of research of this paper is the DSA380 high-speed pantograph. The near-field unsteady flow around the pantograph was investigated using large eddy simulation (LES) while the far-field aerodynamic noise was analysed in the frame of the Ffowcs Williams-Hawkings (FW-H) acoustic analogy. According to the results, the contact strip, base frame and knuckle are the main aerodynamic noise sources, with vortex shedding, flow separation and recombination around the pantograph being related key physical factors. The aerodynamic noise radiates outwards in the form of spherical waves when the distance of the noise receiving point is… More >