Ahmed Allam

Ahmed Allam
Massachusetts Institute of Technology | MIT · Media Laboratory

Doctor of Philosophy

About

23
Publications
2,000
Reads
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107
Citations
Additional affiliations
January 2009 - August 2010
Ain Shams University
Position
  • Student
January 2009 - August 2010
Ain Shams University
Position
  • Research Assistant

Publications

Publications (23)
Article
Full-text available
Ultrasonic waves can transfer power and data to sensors and devices deployed to traditionally inaccessible locations, such as inside the human body or deep in the ocean, eliminating the need for battery replacement. In ultrasonic power and data transfer systems, a piezoelectric transducer converts incident ultrasonic waves to useful electric power...
Article
Full-text available
Additive manufacturing of alloys enables low-volume production of functional metallic components with complex geometries. Ultrasonic testing can ensure the quality of these components and detect typical defects generated during laser powder bed fusion (LPBF). However, it is difficult to find a single ultrasonic inspection technique that can detect...
Article
Ultrasonic waves can be used to transfer power through sealed metallic enclosures when feedthrough wires are not a viable or desirable option. In this work, we present a complete system-level investigation of ultrasonic power transfer through metallic barriers via detailed experiments, analytical modeling, and numerical simulations for analyzing an...
Article
We investigate the use of phased array ultrasonic testing (PAUT) as an offsite non-destructive quality assurance technique for parts made by selective laser melting (SLM). SLM is a popular additive manufacturing (AM) approach for fabricating high-value metallic components with complex geometries. Slight variations in the laser power during fabricat...
Article
No PDF available ABSTRACT Acoustic waves are widely used for underwater communication and also investigated for power transfer owing to their low attenuation compared to electromagnetic waves. We investigate enhancing the performance of an underwater Acoustic Power Transfer (APT) system using Gradient-Index Phononic Crystals (GRIN-PCs). The GRIN-PC...
Article
Full-text available
We investigate the harvesting of sound waves by exploiting a 3D-printed gradient-index phononic crystal lens. The concept is demonstrated numerically and experimentally for focusing audio frequency range acoustic waves in air to enhance sound energy harvesting. A finite-element model is developed to design the unit cell dispersion properties and to...
Conference Paper
We explore the harvesting of acoustic waves by leveraging a 3D-printed gradient-index phononic crystal (GRIN-PC) lens design. The concept is demonstrated numerically and experimentally for audio frequency range acoustic waves in air. Unit cell design procedure to achieve the required refractive index profile and numerical simulations of the band st...
Article
Full-text available
A 3D-printed gradient-index phononic crystal structure based on air inclusions in a polymer is introduced to manipulate underwater acoustic waves. The proposed approach enables a simple configuration without heavy inclusions or geometrically complex unit cells to create the required refractive-index profile and focus incident plane waves propagatin...
Article
Acoustic power transfer (APT) for wireless electronic components has received growing attention as a viable approach to deliver power to remotely located small electronic devices. The design of an efficient APT system requires accurate models to describe its individual components as well as the interaction between them. Most of the analytical model...
Article
No PDF available ABSTRACT Metamaterial concepts are revolutionizing the way we tackle acoustic wave propagation control. For aqueous media, the realization of metamaterial and phononic crystal concepts using impedance contrast has been mainly limited to using heavy metallic rods which are often bulky and complicated to fabricate to achieve the requ...
Article
Full-text available
A spatially reversible and programmable piezoelectric metamaterial concept is introduced for the manipulation of surface acoustic waves to achieve on-demand wave mode conversion and reflection. The concept uses an array of inductive-shunted piezoelectric elements (with gradually varying inductors in space) attached to the surface of an elastic prop...
Thesis
Full-text available
Acoustic metamaterials (AMM) are artificial materials with engineered sub-wavelength structures that possess acoustic material properties which are not readily available in nature. The material properties of AMMs can be manipulated by embedding active elements inside their structure (active AMMs). This manipulation of properties is done by an exter...
Article
Full-text available
A class of active acoustic metamaterials (AMMs) with a fully controllable effective density in real-time is introduced, modeled and experimentally verified. The density of the developed AMM can be programmed to any value ranging from-100 kg/m 3 to 100 kg/m 3 passing by near zero density conditions. This is achievable for any frequency between 500 a...
Article
Full-text available
A two-dimensional active acoustic metamaterial with controllable anisotropic density is introduced. The material consists of composite lead–lead zirconate titanate plates clamped to an aluminum structure with air as the background fluid. The effective anisotropic density of the material is controlled, independently for two orthogonal directions, by...
Conference Paper
Full-text available
Mufflers are widely used to reduce the exhaust and intake noise of fluid machines for different applications. Every muffler has to be tailored carefully to the engine to which it is connected. One very important tool of muffler design is the measurement of its properties, acoustic performance and pressure drop. Introduction of flow is a key issue a...

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