Wonju Jeon

We propose a waveguide absorber (WGA) based on an acoustic black hole (ABH) to damp vibrations in plate structures. The proposed WGA is composed of a spiral ABH and a rod connecting it to the surface of the plate. The geometrical dimensions of the WGA are determined, such that it has a lower cut-on frequency than a given target range of frequencies, by using a recently developed impedance method for curved ABHs. We then optimize the location of attachment and direction of the WGA on a simply sup

We propose a metaliner that can insulate the duct noise for various grazing flow speeds with little flow resistance. The metaliner, whose unit cell consists of two different Helmholtz resonators with subwavelength scales, is placed underneath the duct. In order to predict sound insulation and absorption of metaliner in a duct with flow, an effective impedance model of the metaliner is established by considering the effect of flow. We present a design procedure for a metaliner with high transmiss

During the last decade, most of acoustic cloak research has been done within a theoretical framework in which the medium is at rest. However, such an acoustic cloak cannot preserve its unique properties or functions to make an object acoustically invisible in the presence of flow. In this study, we propose a theoretical framework to accurately investigate the effect of compressibility and non-uniformity in flow on the scattering pattern of acoustic cloak. In the formulation, the wave operator is

We present near-perfect sound absorption using a metasurface composed of meta-atoms (MAs) which are subwavelength Helmholtz resonators (HRs) with cavities non-uniformly partitioned by membranes. By embedding the membranes at different horizontal locations in the cavities, we break geometrical symmetry between the MAs so as to derive hybrid resonance between the MAs at our target frequency. The resonance frequency of each MA is determined by delicately adjusting the locations of the membranes, re

We propose a sound-absorbing nonplanar metasurface by considering locally different incidence angles along the metasurface. Perfect sound absorption is realized with the aid of hybrid resonance between two different subwavelength Helmhwoltz resonators comprising a unit cell. We theoretically investigate the effect of incidence angles on the sound absorption of the unit cells, and present a design method of the nonplanar metasurface that achieves perfect absorption by considering locally differen

Previous studies have explored the relationship between termite branch tunnel geometry and foraging efficiency in a model simulation in which foraging efficiency, γ, for two termite species, Coptotermes formosanus Shiraki and Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae), was investigated in response to two variables, the probability of tunnel branching (P(branch)) and the probability of tunnel branch termination (Pterm). It was found that simulated tunnel patterns based on empiri