Emergent trends in the device development for neural prosthetics have focused on establishing stimulus localization, improving longevity through immune compatibility, reducing energy requirements, and embedding active control in the devices. Ultrasound stimulation can singlehandedly address several of these challenges. Ultrasonic stimulus of neurons has been studied extensively from 100 kHz to 10 MHz, with high penetration but less localization. In this paper, a chipscale device consisting of piezoelectric Aluminum Nitride ultrasonic transducers was engineered to deliver gigahertz (GHz) ultrasonic stimulus to the human neural cells. These devices provide a path towards complementary metal oxide semiconductor (CMOS) integration towards fully controllable neural devices. At GHz frequencies, ultrasonic wavelengths in water are a few microns and have an absorption depth of 10–20
We revisit the longstanding problem of grid sensitivity, i.e., the lack of grid convergence in largeeddy simulations (LES) of the stable boundary layer. We use a comprehensive set of LES of the wellknown Global Energy and Water Cycle Experiment Atmospheric Boundary Layer Study 1 (GABLS1) case with varying grid spacings between 12.5 m and 1 m to investigate several physical processes and numerical features that are possible causes of grid sensitivity. Our results demonstrate that there are two resolution regimes in which grid sensitivity manifests differently. We find that changing the numerical advection schemes and the subgridscale models alters the simulation results, but the options tested do not fully address the gridsensitivity issue. Moreover, sensitivity runs suggest that the surface boundary condition and the interaction of the surface with the nearsurface flow, as well as the mixing with the free atmosphere, are unlikely to be the causes of the observed grid sensitivity. One interesting finding is that the grid sensitivity in the fine gridspacing regime (grid spacings
 Award ID(s):
 1853354
 NSFPAR ID:
 10361801
 Publisher / Repository:
 Springer Science + Business Media
 Date Published:
 Journal Name:
 BoundaryLayer Meteorology
 Volume:
 182
 Issue:
 2
 ISSN:
 00068314
 Page Range / eLocation ID:
 p. 251273
 Format(s):
 Medium: X
 Sponsoring Org:
 National Science Foundation
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