Low-frequency noise is difficult to deal with by traditional porous material due to its inherent high acoustic impedance. This study seeks to extend the effective range of sound absorption to lower frequencies by filling a low density gas, such as helium, in the porous material. Compared with conventional air-filled absorption material, the helium-filled porous material has a much reduced chara...

An ultrasonic reflectivity method is proposed for measuring porosity and tortuosity of porous materials having a rigid frame. Porosity is the relative fraction by volume of the air contained within a material. Tortuosity is a geometrical parameter which intervenes in the description of the inertial effects between the fluid filled the porous material and its structure at high frequency range. I...

This paper studied Buckling analysis of porous truncated conical shell subjected to axial load. It is considered that a fluid undrained between porous material and the Porous material properties vary across the thickness of shell with a specific function also assumed that the edge of the shell is simply supported. The governing equations are based on the Sanders kinematics equations and the fir...

Porous silicon fabricated by partial electrochemical dissolution of bulk silicon, shows outstanding material properties. The nanostructure of the remaining Si-skeleton is used for specific optical devices, such as emitters and filters. The high internal surface of the material opens new opportunities for different types of microsensors and -actuators and microsystem concepts. The porous layers ...

The military’s dependence on fossil fuels for electric power production in isolated settings is both logistically and monetarily expensive. Currently, the Department of Defense is actively seeking alternative methods to produce electricity, thus decreasing dependence on fossil fuels and increasing combat power. We believe piezoelectric generators have the ability to contribute to military appli...

This paper describes an investigation into mechanical cross talk within 1-3 and 2-2 connectivity piezoelectric composite array configurations, comprising a matrix of active piezoelectric elements embedded within a passive, polymeric, material. One way to take full advantage of the reported sensitivity and bandwidth improvements from single crystal materials is to configure them as a piezoelectr...

Enhancing the output power of a nanogenerator is essential in applications as a sustainable power source for wireless sensors and microelectronics. We report here a novel approach that greatly enhances piezoelectric power generation by introducing a p-type polymer layer on a piezoelectric semiconducting thin film. Holes at the film surface greatly reduce the piezoelectric potential screening ef...