Research on split and evolution of acoustic cavity resonance frequency of rotating loaded tire

The tire acoustic cavity resonance noise (TACRN) is known to contribute to audible noise in the passenger compartment of a vehicle. In order to reduce TACRN effectively, its mechanism needs to be grasped better. In this paper, the calculation formulas of tire acoustic cavity resonance frequency for four different conditions such as static unloaded tire, static loaded tire, rotating unloaded tire, and rotating loaded tire are analyzed and verified by the simulation and experiment. In particular, the resonance frequency formulas of static loaded tire introducing inflation pressure and rotating loaded tire are proposed and verified, respectively, in this paper. And the influence of tire inflation pressure, load, and running velocity on splitting frequency are studied. Some new findings are described and discussed; for example, the first-order resonance frequency may split into four resonance frequencies in most cases, and may split into three resonance frequencies in certain cases when a loaded tire is rotating. And the existing conditions for three and four resonance frequencies are also discussed.

Terahertz Sensing for R/S Chiral Ibuprofen via All-Dielectric Metasurface with Higher-Order Resonance

A terahertz (THz) all-dielectric metasurface with crescent cylinder arrays for chiral drug sensing has been demonstrated. Through the multipole expansion method, we theoretically found that breaking the symmetry of the metasurface can excite higher-order resonance modes and provide stronger anisotropy as well as enhanced sensitivity for the surroundings, which gives a better sensing performance than lower-order resonance. Based on the frequency shift and transmittance at higher-order resonance, we carried out the sensing experiments on (R)-(−)-ibuprofen and (S)-(+)-ibuprofen solution on the surface of this metasurface sensor. We were able to monitor the concentrations of ibuprofen solutions, and the maximum sensitivity reached 60.42 GHz/mg. Furthermore, we successfully distinguished different chiral molecules such as (R)-(−)-ibuprofen and (S)-(+)-ibuprofen in the 5 μL trace amount of samples. The maximum differentiation was 18.75 GHz/mg. Our analysis confirms the applicability of this crescent all-dielectric metasurface to enhanced sensing and detection of chiral molecules, which provides new paths for the identification of biomolecules in a trace amount.