In spite of the extensive studies of zero-index metamaterials, the realization of zero impedance with finite phase velocity has not been explored. Here, we show that this extreme case, realized by elaborately-tuned paired resonators, can effectively enhance sensing and actuation. To explain the formation mechanism of the near-zero effective impedance with finite phase velocity by paired resonators at a target frequency, a theory using an equivalent model based on mechanical longitudinal waves is developed. If the frequency of the extreme property is further tuned at a Fabry–Pérot resonance frequency, highly efficient enhancement is possible. Experiments using a piezoceramic transducer (PZT) installed on the plate region bounded by two resonators confirm that the proposed extreme property mechanism highly enhances the sensing and actuation outputs of the transducer.

Youn-Kyung Choi, Seung Eun Baek, Kiyean Kim, Sung-Hun Kim, Seong-Sik Kim, Yong-Il Kim. Korean J Orthod 2025;55:487-94. https://doi.org/10.4041/kjod25.155

Using finite element method (FEM) analysis of a clear aligner (CA), this study aimed to investigate the effects of varying the edentulous space on canine distal bodily movement during space closure following maxillary first premolar extraction. FEM analysis was used to simulate distal canine bodily movement following maxillary first premolar extraction using CAs. Four CA designs for edentulous spaces were compared: no-pontic, full-pontic, half-pontic, and beam. Three-dimensional models of the tooth components and CA were created. The target was set at a 0.25-mm distal canine movement. Long-term tooth movement was simulated using an iterative calculation method. All the groups initially showed crown displacement, distal tipping, and distal rotation. Over time, the movement patterns differed in relation to the design. The no-pontic design exhibited the greatest displacement and tipping. The beam design exhibited the largest initial displacement but showed the lowest displacement and tipping thereafter. Full- and half-pontic designs yielded intermediate results. Significant force reduction was observed immediately after CA application, and was followed by a gradual decrease. The mean tooth-movement achievement rate was approximately 76.7%. The edentulous space design of the CA substantially affected tooth-movement behavior. An iterative simulation is necessary to evaluate longterm tooth-movement patterns. The beam design demonstrated optimal suitability for bodily movement with minimal tipping. For optimal results, additional setup or overcorrection may be necessary.

We propose a novel method to boost the power of a magnetostrictive patch transducer (MPT) for generating antisymmetric Lamb wave modes in a plate. Because an MPT installed on a plate mainly exerts in-plane deformation onto a test specimen, it cannot efficiently generate antisymmetric wave modes such as the lowest antisymmetric Lamb wave ( A ₀ ) mode, unlike the generation of symmetric wave modes. To achieve the high-power generation of antisymmetric modes, we propose an add-on passive boosting element which is referred to here as a detuned resonator. The resulting MPT can serve both as an actuator and a sensor. Here, we present the specific boosting resonator configuration, explain its operating mechanism, and verify its role in increasing the transducer power. A theoretical analysis and experimental validation are carried out.