A 0.8 mm 3 wireless, ultrasonically powered, freefloating neural recording implant is presented. The device is comprised only of a 0.25 mm 2 recording IC and a single piezoceramic resonator that is used for both power harvesting and data transmission. Uplink data transmission is performed by analog amplitude modulation of the ultrasound echo. Using a 1.78 MHz main carrier, >35 kbps/mote equivalent uplink data rate is achieved. A technique to linearize the echo amplitude modulation is introduced, resulting in <1.2% static nonlinearity of the received signal over a ±10 mV input range. The IC dissipates 37.7 µW, while the neural recording front-end consumes 4 µW and achieves a noise floor of 5.3 µVrms in a 5 kHz bandwidth. This work improves sub-mm recording mote depth by >2.5x, resulting in the highest measured depth/volume ratio by ∼3x. Orthogonal subcarrier modulation enables simultaneous operation of multiple implants, using a single-element ultrasound external transducer. Dual-mote simultaneous power up and data transmission is demonstrated at a rate of 7 kS/s at the depth of 50 mm.

Current seismic codes are generally based on the use of response spectra in the computation of the seismic demand of structures. This study evaluates the use of energy concept in the determination of the seismic demand due to its potential to overcome the shortcomings found in the current response spectra-based methods. The emphasis of this study is placed on the computation of the input and plastic energy demand spectra directly derived from the energy-balance equation with respect to selected far-field ground motion obtained from Pacific Earthquake Engineering Research (PEER) database, soil classification according to National Earthquake Hazards Reduction Program (NEHRP) and characteristics of the structural behavior. The concept and methodology are described through extensive nonlinear time history analyses of single-degree-of-freedom (SDOF) systems. The proposed input and plastic energy demand spectra incorporate different soil types, elastic perfectly plastic constitutive model, 5% viscous damping ratio, different ductility levels, and varying seismic intensities.

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Summary Input energy is the principal component of the energy balance equation. It is beneficial to determine, through its components, how the recoverable and irrecoverable energies are distributed within the structural elements. Several equations and attenuation relations to define mass‐normalized input energy spectra exist in the literature. They are mainly proposed for elastic systems subjected to far‐fault EQs. There is a lack of experimental verification of these proposed spectra. In this paper, experimental assessment was performed to the existing spectra, and further improvements were accomplished. For this purpose, steel cantilever columns were tested on the shake table for two specific historical EQs coincidently having similar spectral acceleration values. Based on the experimental results, a three‐part mass‐normalized relative input energy spectrum was formulated including soil type, EQ (corner period, intensity, duration, spectral acceleration, and velocity), and structural behavioral characteristics (period and structural damping). The proposed input energy spectrum was experimentally calibrated and numerically validated for various EQs featuring near‐ and far‐field types. Analytical and experimental comparisons were made between the previously developed spectrum and the newly proposed one. The validation studies and the statistical evaluations exposed that the proposed spectrum yielded better agreement with the experimental and numerical results.