This work introduces an entirely new way to achieve highly directional sound beyond traditional techniques
Author: Curtis Paul Rasmussen
We collect information about the world through our senses, two of which, hearing and touch, are attuned to the mechanical vibrations travelling around us. Scientists and engineers have learned to control these acoustic waves, and in so doing they have opened new possibilities in how we interact with each other and the natural world. One area of rapid progress is acoustic metamaterials, which are architected structures that can shape sound waves in ways that go beyond what is possible with natural materials. Given the potential of these new materials, it is important to consider their limits and identify the underlying physical principles responsible for them. In this dissertation we examine limitations in the response of acoustic materials and devices due to passivity and time-reversal symmetry. An important constraint that arises due to time-reversal symmetry is reciprocity. Reciprocity must be broken to create devices that allow sound through in only one direction. This work explores acoustic nonreciprocity with particular attention to applications in surface acoustic wave devices and topological acoustic demonstrations. One way to achieve acoustic nonreciprocity is with fluid flow. Based on this technique, we present an acoustic Mach-Zehnder isolator and nonreciprocal leaky-wave antenna. A different but equally fundamental and important constraint in acoustics technology is the trade-off between the size, efficiency, and bandwidth of a small resonator. By considering arbitrary stored and radiated sound fields surrounding a compact source, we derive a theoretical lower bound on the quality factor of a passive acoustic radiator. This work discusses opportunities to overcome this constraint by considering active resonators. We experimentally demonstrate a three-fold bandwidth improvement to the passive case by synthesizing a non-Foster circuit load for a piezoelectric sonar transducer. By using a Green’s function approach and by connecting the physics of a disordered array to the statistical theory of random walks, we also explore the physics of near-zero-index materials, and leverage their unusual sound-matter interactions to enable robust and highly directive acoustic sources. This work introduces an entirely new way to achieve highly directional sound beyond traditional techniques
... 623–625 Two - photon spectroscopy , one - photon spectroscopy and , 327 Uniaxial stress effect on bound - exciton complexes ... 213 Time reversal symmetry , 110 broken , 661 Time reversal transformation , 658 Time reversal violation ...
Author: Robert A. Meyers
This comprehensive collection of articles emphasizes new discoveries and technology and also covers some long-standing areas of research in the field of physics. Topics covered include superconductivity, quantum optics, and laser cooling.
Scattering is the collision of two objects that results in a change of trajectory and energy. For example, in particle physics, such as electrons, photons, or neutrons are "scattered off" of a target specimen, resulting in a different energy and direction. In the field of electromagnetism, scattering is the random diffusion of electromagnetic radiation from air masses is an aid in the long-range sending of radio signals over geographic obstacles such as mountains. This type of scattering, applied to the field of acoustics, is the spreading of sound in many directions due to irregularities in the transmission medium. Volume I of Scattering will be devoted to basic theoretical ideas, approximation methods, numerical techniques and mathematical modeling. Volume II will be concerned with basic experimental techniques, technological practices, and comparisons with relevant theoretical work including seismology, medical applications, meteorological phenomena and astronomy. This reference will be used by researchers and graduate students in physics, applied physics, biophysics, chemical physics, medical physics, acoustics, geosciences, optics, mathematics, and engineering. This is the first encyclopedic-range work on the topic of scattering theory in quantum mechanics, elastodynamics, acoustics, and electromagnetics. It serves as a comprehensive interdisciplinary presentation of scattering and inverse scattering theory and applications in a wide range of scientific fields, with an emphasis, and details, up-to-date developments. Scattering also places an emphasis on the problems that are still in active current research. The first interdisciplinary reference source on scattering to gather all world expertise in this technique Covers the major aspects of scattering in a common language, helping to widening the knowledge of researchers across disciplines The list of editors, associate editors and contributors reads like an international Who's Who in the interdisciplinary field of scattering
( DE91-641735 ] 06 01039 N92-15945 Spontaneous symmetry breaking in N = 2 supergravity with matter ( DE91-639749 ] ... the super Schwarzian differential equation [ DE91-508301 ) 07 P1172 N92-16696 Upper bound SEU rate for devices in an ...
J Sound Vib mappings pl . and P occur to be uniformly close in planes are defined and from these several impact | 182 ... In symmetry breaking and period doubling pitchfork bifurcations , some new har- range interparticle interactions ...
AD - A095 056 GRA & I Broken Symmetry , Emergent Properties , Dissipative Structures , Life : Are They Related ? ... AD - B054 579L Fld / Gp 14/2 Carrier Localisation in Inversion Layers and Impurity Bands .
... devices using MHD , PIC , and CEM codes ( AIAA Paper 98-2926 ] 33 p2295 A98-32573 LUGNSLAND , JOHN W. Electromagnetic ... G. M. Time - reversal symmetry - breaking superconductivity in SrZRUOA 76 p3081 A98-38030 LUKE , P. A high ...
And Bhutto — by then, Pakistan's prime minister — wasted no time in getting Pakistan's bomb program under way. ... test is not practical, the team must rigorously calculate and test the reliability and predictability of the device.
The Bulletin of the Atomic Scientists is the premier public resource on scientific and technological developments that impact global security. Founded by Manhattan Project Scientists, the Bulletin's iconic "Doomsday Clock" stimulates solutions for a safer world.
Sections 1-2. Keyword Index.--Section 3. Personal author index.--Section 4. Corporate author index.-- Section 5. Contract/grant number index, NTIS order/report number index 1-E.--Section 6. NTIS order/report number index F-Z.
D. 1233-8 NOTION AN ECOLOGICAL MODEL OF CHILDREN'S EXPLORATION DEVELOPMENT : AN EXAMPLE OF THE LIMITS OF THE INDIVIDUAL ... p.1313-3 LEFT - RIGHT SYMMETRY IN NUCLEAR BETA DECAY ( POSITRON , POLARIZATION , ELECTROWEAK ) CHEMISTRY ...