Browsing by Subject "Energy transfer"

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    Enhancement and Field Test Evaluation of New Battery-Less Wireless Traffic Sensors
    (Center for Transportation Studies, 2011-10) Pruden, Sean; Vijayaraghavan, Krishna; Rajamani, Rajesh
    This project focused on the enhancement of a previous battery-less wireless traffic flow sensor so as to enable it to provide weigh-in-motion (WIM) measurements and provide enhanced telemetry distance. The sensor consists of a 6-feet-long device which is embedded in a slot in the road flush with the pavement. As a vehicle travels over the sensor, vibrations are induced in the sensor. Using piezoelectric elements, energy is harvested from the vibrations and used to power the electronics in the sensor for signal measurements and wireless transmission. The sensor’s performance was evaluated by embedding it in a slot in concrete pavement and driving various vehicles of known weight over it at a number of different speeds on different days. The sensor was found to meet the specification of 500 feet telemetry distance. It was able to provide WIM measurements with an accuracy of better than ±15% in the absence of vehicle suspension vibrations. However, much of the WIM data during the latter period of sensor testing was obtained in the presence of significant suspension vibrations. The project also evaluated the use of 4 consecutive WIM sensors in the road to remove the influence of suspension vibrations.
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    Supporting data for Intermolecular Forces Dictate Vibrational Energy Transfer in Plasmonic–Molecule Systems
    (2022-02-22) Yu, Ziwei; Frontiera, Renee; rrf@umn.edu; Frontiera, Renee
    These files contain data along with associated output from described analysis supporting all results reported in Yu, Z.; Frontiera, R. R. Intermolecular Forces Dictate Vibrational Energy Transfer in Plasmonic–Molecule Systems. ACS Nano, 2022, 16, 1, 847–854. Anti-Stokes and Stokes scattering from aromatic thiols adsorbed on gold nanoparticles are monitored with ultrafast surface-enhanced Raman spectroscopy (SERS). Vibration population ratio changing kinetics of the aromatic thiols is obtained by conducting peak fitting with the acquired ultrafast anti-Stokes and Stokes SERS spectra and performing Boltzmann analysis. The as-obtained kinetic traces are fitted with exponential decay convoluted with the instrument response function to extract the temporal increase and lifetime of the population ratio kinetics, which are found to be correlated with the molecular property in a fashion that molecules with a stronger intermolecular interaction experience less temporal population ratio increase and shorter excited vibrational state lifetime.