Abstract
This fly’s incredible hearing is a curiosity to those developing better hearing aids
Ormia ochracea’s sense of directional hearing is second to none in the animal kingdom.
But, according to new University of Toronto Scarborough research, what makes its hearing so incredible may also complicate efforts in using it as a model for new technology, including hearing aids.
“These flies have highly specialized ears that provide the most acute directional hearing of any animal,” says Andrew Mason, a professor of biology at University of Toronto Scarborough. “The mechanism that makes their hearing so exceptional has even led to a range of bio-inspired technology, like the mini directional microphones used in hearing aids.”
Ormia is a small, yellow, nocturnal fly native to the southern United States and Mexico. The female uses its exceptional hearing to locate the songs of male crickets, where it deposits its larvae. The larvae then burrow inside the cricket, eating it alive in the process.
For more information, please visit https://www.sciencedaily.com/releases/2017/05/170515111136.htm
Sensing the nanoscale with visible light and the fundamentals of disordered waves
We cannot see atoms with the naked eye because they are so small relative to the wavelength of light. This is an instance of a general rule in optics—light is insensitive to features which are much smaller than the optical wavelength. However, a new experiment appearing in Science shows that features that are even 100 times smaller than the wavelength can still be sensed by light.
Hanan Sheinfux and Dr Yaakov Lumer, from the group of Prof. Moti Segev at the Technion–Technical Institute of Israel, carried out this study in collaboration with Dr Guy Ankonina and Prof. Guy Bartal (Technion) and Prof. Azriel Genack (City University of New York).
Their work examines a stack of nanometrically thin layers—each layer is on average 20,000 times thinner than a sheet of paper. The exact thickness of the layers is purposely random, and ordinarily this nanometric disorder should bear no physical importance. But this experiment shows that even a 2-nm (~6 atoms) thickness increase to one single layer somewhere inside the structure can be sensed if light illuminates the structure at a very specific angle of incidence. Furthermore, the combined effect of all the random variations in all of the layers manifests an important physical phenomenon called Anderson localization, but in a regime where it was believed to have vanishingly small effects.
For more information, please visit https://www.sciencedaily.com/releases/2017/06/170601151918.htm
Turbulent boundary layer excitation and cavity noise
The turbulent boundary layer (TBL)-induced vibration in transport vehicles, particularly in aircraft, can be an important source of interior noise and its simulation is still an open research challenge. Therefore, the focus of this project is the investigation of cavity noise as a result of flow excitation over a lightweight flexible structure connected to a cavity and noise transmission through the structure. The work is predominantly numerical based on a stochastic reconstruction of the wall pressure field. In this context, we are working on a new mathematical model for TBL excitation in vibro-acoustic problems. Such a model is built on a two-dimensional Butterworth filter, whose orders allow to modify the shape of the TBL and possibly to adapt it to different flow configurations.
For more information, please visit http://www.mech.kuleuven.be/en/research/mod/research/vibroacoustics
Exterior time domain vibro-acoustic analysis with model order reduction
To be able to use high-fidelity, time-domain, exterior vibro-acoustics models, model order reduction is a promising technique. This research topic focuses on deriving a time stable reduced order model based on finite elements with the inclusion of a boundary that approximates the Sommerfeld radiation condition. Also, it investigates the inclusion of these models in different contexts, such as virtual sensing, structural health monitoring, and sound auralization.
For more information, please visit http://www.mech.kuleuven.be/en/research/mod/research/vibroacoustics
Aeroacoustic numerical and experimental characterization of the absorption and transmission phenomena of the acoustic field in confined subsonic flow application
Validation and improvements of a recently developed time domain impedance formulation are based on recursive convolution. This formulation has been implemented in an in-house time-domain Runge–Kutta Discontinuous Galerkin (RKDG) linearized Euler equations (LEE) solver. The idea is to validate the performance of the implemented boundary condition in the presence of a finite thickness boundary layer over a lined wall, avoiding the use of the ill-posed Ingard–Myers condition and its more complex well-posed formulation.
For more information, please visit http://www.mech.kuleuven.be/en/research/mod/research/aero-acoustics
Investigating the mechanics of sound propagation through hot exhaust jets with cross-flow
Low-frequency noise near open cycle gas turbines (single cycle gas turbines) is an ongoing problem for communities near these plants. The excess levels low-frequency noise on a community can cause the following effects: audible low-frequency rumble, beating sensation in the chest, nausea, and acoustic excitation in structures with low resonant frequency, such as glass structures. This is not only a domestic issue but also a global issue. It is hypothesized that the low-frequency noise affecting neighboring communities are due to the hot turbulent exhaust gasses and laminar cross-winds. It is known that the shear layer, counter rotating vortex pairs, and horse shoe vortices that are generated from this type flow scenario can affect the propagation of sound with effects such as refraction, diffraction, and scattering. This project will further investigate the effects of this fluid flow mechanism on the propagation of low-frequency sound from the turbine itself. The investigation will be conducted experimentally at the University of Adelaide and computationally with a commercial CFD package (FLUENT).
For more information, please visit https://mecheng.adelaide.edu.au/avc/projects/projectabstract.php?UID=73
An investigation of the behavior of a three-tether point-absorbing wave energy converter
Ocean waves are a huge resource of renewable energy with a great potential to be captured and employed for electricity generation and water desalination. Australia is among the most attractive locations for harvesting wave power, with an estimated potential that is five times more than the average electricity consumption of the whole country.
Despite the fact that there are more than 200 different wave energy converters (WECs) in various stages of development, the WEC technology is still in its pre-commercial phase. Many concepts of extracting energy from ocean waves have been realized, but none of them have demonstrated their advantage over others. Therefore, the current project will investigate a behavior of a three-tether submerged point-absorbing WEC that utilizes several motion modes to extract energy from ocean waves. The main objective of this study is to use numerical modeling and experimental tools to estimate energy delivery which can be expected from this type of WEC.
For more information, please visit https://mecheng.adelaide.edu.au/avc/projects/projectabstract.php?UID=82
Vibration and wave energy transfer, capture, and dissipation in multistable systems
The transitions among stable states in structural, mechanical, or material systems can be both a source of potential and a concern. For instance, applications of vibration energy harvesting may be propelled by exploiting such dynamic transitions for large mechanical-to-electrical energy capture, while slender aerostructures may be greatly harmed should such dynamic behaviors fatigue airframe components. Yet, the strong nonlinearities exhibited in multistable structural dynamics makes them difficult to understand and faithfully predict.
To address this challenge, we are creating analytical approaches to accurately predict and explore the steady-state, transient, and stochastic dynamics of multistable systems. The approaches enable new insight on susceptibility and robustness of such structural systems by way of energy-based quantifiers. The efforts within this LSVR research initiative are supported by several organizations, including The Ohio State University Center for Automotive Research, the Defense Advanced Research Projects Agency (DARPA), the US Air Force Research Laboratory, and the American Society of Mechanical Engineers Haythornthwaite Young Investigator Award.
For more information, please visit https://lsvr.osu.edu/research