With the aim of finding an optimal shape for a traffic noise absorber, we consider the boundary shape optimization problem of minimizing the total acoustic energy for a fixed frequency. The model is described by the boundary-value problem for the Helmholtz equation. All boundaries of the domain are supposed to be fixed except one part where the absorbing Robin boundary condition is imposed. The...

Radar absorbing materials, i.e. magnetite (Fe3O4) coated carbon fibers (MCCFs) were fabricated by electro-deposition technique. Black-colored single spinel phase Fe3O4 nanoparticles was easily synthesized by hydrothermal method using reduction of a Fe (III) - Triethanolamine complex in an aqueous alkaline solution at 60-80 ◦C. Uniform and compact Fe3O4 films were fabricated on nitric acid treat...

At present, a series of challenges are impeding large-scale application high temperature radar absorbing coatings (RACs), such as complex preparation raw material and complicated technology processing. In this paper, we designed experimentally demonstrated high-temperature metamaterial RAC (MRAC) with strong absorption thin thickness, which is composite coating layer metamaterial. To avoid mate...

This paper investigates the feasibility to use an electrodynamic loudspeaker to determine viscoelastic properties of sound-absorbing materials in the audible frequency range. The loudspeaker compresses the porous sample in a cavity, and a measurement of its electrical impedance allows one to determine the mechanical impedance of the sample: no additional sensors are required. Viscoelastic prope...