The effect of hearing aids (HAs) and educational counseling (EC) or their combination on tinnitus is ambiguous. This study aimed to investigate whether the combined use of HAs and EC is more effective than EC alone on tinnitus relief.A total of 72 adults with chronic, bothersome tinnitus and coexisting sensorineural hearing loss completed at least 1-month and 3-month follow-up. After receiving EC and HA prescriptions, 21 participants selected to purchase HAs (i.e., the HA + EC group), whereas the remaining 51 refused to use HAs despite recommendations (i.e., the EC group). Tinnitus severity was measured by Tinnitus Handicap Inventory (THI), Tinnitus Evaluation Questionnaire (TEQ), and Visual Analog Scale (VAS) for loudness. The primary outcome measure was THI, and tinnitus relief was defined as a 20-point or more reduction in THI. A generalized linear mixed model was used to confirm that the heterogeneity in baseline characteristics between groups did not interfere with the results.The THI, TEQ, and VAS scores decreased significantly after treatments, and both groups yielded a similar trend of reduction. There were no significant differences in the incidence of tinnitus relief and time-to-event curves between the two groups. In addition, the length of follow-up did not affect treatment effectiveness.There was insufficient evidence to support the superiority of the combined use of HA and EC for tinnitus over EC with no device.
A crosstalk analysis model for optical network-on-chip based on WDM is proposed. The crosstalk noise and signal-to-noise-ratio of multiple wavelengths networks are analyzed. And a case study is presented to evaluate the proposed crosstalk model.
Surface acoustic wave (SAW) filters play a critical role as radio frequency components in the front-end module of electronic equipment. The conventional design methods of SAW filters heavily rely on researchers' experiences and extensive software simulations, thus requiring substantial computational expenses. Therefore, this work explores the machine learning techniques to speed up the design of ladder-type SAW filters. A novel approach is proposed by combining the convolutional neural network (CNN) and cuckoo search (CS) optimization method. The method utilizes neural networks as surrogate models, replacing simulation software to predict the performance of SAW filters. This substitution aims to reduce the time needed for the entire filter optimization process. The incorporation of CS optimization method avoids the reliance of the optimization process on the designer's experiences. A numerical example is provided to prove the efficiency of the proposed method.
In this paper, an active metamaterial (MM) absorber loaded with PIN diodes is proposed. By adjusting the bias currents of PIN diodes to change the value of the introduced equivalent resistance, the Q factors of multiple resonances of the whole structure are altered. Therefore, multiple broadband absorption states with moderate absorption performance at different frequencies are obtained. These states cover continuously tunable absorption frequencies in an ultrabroad frequency band. Bias circuits for PIN diodes are also specially designed to obtain polarization-insensitive absorption performance. Optimizing works were carried out by analyzing the operating mechanism based on the simulated field distribution and power loss distribution. The presented absorber covers an ultrawideband absorption bandwidth with a reflection coefficient below -10 dB from 0.78 GHz to 4.62 GHz (142.2% in relative bandwidth) by adjusting the PIN diodes. It is worth noting that the absorption bandwidth of the low-resistance state reaches 21.0% in the P band, which greatly improves performance in the low-frequency regime. The absorber shows good angular stability under oblique incident angles from 0° to 30°. In addition, the total thickness of the absorber is only 1/16 of the wavelength at the lowest operating frequency with an areal density of 2.06 kg/m2.
The finite-difference frequency-domain (FDFD) method is an effective method for numerical simulation of electromagnetic fields. It has great advantages in dealing with electromagnetic scattering problems of complex structures and complex media. This method can transform the frequency-domain Maxwell equations into a linear system for solution by difference operation on the spatial grid. However, high-precision differential calculations can result in more memory consumption and a decrease in computational speed. In previous reports, subgridding technique is often used to solve such problems, where mesh refinement is only performed in local areas, while coarse mesh partitioning is still used in other areas. However, the refinement area can only be manually set, lacking flexibility and accuracy. Therefore, we propose a novel FDFD method based on adaptive grids, which uses the cartesian tree-based hierarchical grids to discrete the spatial domain. It can automatically refine the local grids according to the geometrical characteristic of the model to improve the accuracy of specific areas, without significantly increasing the number of unknowns, and has strong flexibility while improving the calculation efficiency. In this study, we use two levels of grids for adaptive grids construction, with a mesh size ratio of 3:1. Using second-order interpolation to handle the transmission problem of electromagnetic field components at different grid boundaries. The simulation results show that the computation speed of the adaptive grids FDFD system is faster than that of structured grids.
Abstract Kirigami technique, a method to reconfigure structures via mechanical approaches, has received much attention in material science, due to its versatile and unconventional structural transformations. The counterparts in the electromagnetic metamaterial field has recently allowed for the tunable control of electromagnetic responses. However, they are limited to global tuning of absorption, chirality, etc., leaving much potential of controlling spatially varying distribution and therefore the optical wavefront unexploited. Here, the authors propose a class of kirigami‐based reconfigurable gradient metasurfaces through which the electromagnetic wavefront can be tuned over continuous‐state ranges by changing the meta‐structures from folded (compact) to unfolded (large surface) configurations. As the proof‐of‐concept, meta‐devices including switchable anomalous refractor and reconfigurable metalens are demonstrated both in simulations and experiments. Moreover, a new paradigm to mitigate chromatic dispersion is also realized by the kirigami‐based reconfigurable metalens, which is able to keep the focal length unchanged over a continuous frequency band by setting metalens with various folding states. Their approach provides a new alternative for designing reconfigurable gradient metasurface with additional mechanical properties and may have potential applications in advanced devices such as reconfigurable optical components and imaging system.
Active Acoustic Structure(AAS)proposed in recent years has been viewed as an encouraging approach to actively control sound radiation from vibrating structures.Analyzing the physical mechanism of AAS can offer some guidance to key issues e.g.design optimization,the arrangements of secondary sources and error sensors,and selecting objective function.In this paper,under minimization of the total sound power output,the physical mechanism of noise reduction is investigated by analyzing the sound power output change of primary and secondary structures and the distribution of sound intensity.The results show that there are three mechanisms in active control,which are energy restraint,energy absorption and energy un-absorption.For near field sound intensity distribution,the effect of active control is revealed by amplitude restraint and direction adjusting for sound intensity.Partial acoustic energy which is transferred into far field before control will flow to sound sources after control.
Metasurfaces, ultrathin two-dimensional version of metamaterials, have attracted tremendous attention due to their exotic capabilities to freely manipulate electromagnetic waves. By incorporating various tunable materials or elements into metasurface designs, reconfigurable metasurfaces and related metadevices with functionalities controlled by external stimuli can be realized, opening a new avenue to achieving dynamic manipulation of electromagnetic waves. Recently, based on the tunable metasurface concept, reconfigurable intelligent surfaces (RISs) have received significant attention and have been regarded as a promising emerging technology for future wireless communication due to their potential to enhance the capacity and coverage of wireless networks by smartly reconfiguring the wireless propagation environment. Here, in this article, we first focus on technical issues of RIS system implementation by reviewing the existing research contributions, paying special attention to designs in the microwave regime. Then, we showcase our recent attempts to practically demonstrate RIS systems in real-world applications, including deploying reflective RIS systems in indoor scenarios to enhance the wireless network coverage and utilizing intelligent omni-metasurfaces to improve both indoor and through-wall wireless communication quality. Finally, we give our own perspectives on possible future directions and existing challenges for RISs toward a truly commercial intelligent technology platform.
In this paper, metasurfaces with optical transparency is proposed to control either the propagation or the scattering of microwave. Specifically, we have designed a band-pass frequency selective surface (FSS) with a transmission window around 1.6 GHz and a coding metasurface for suppressing the backward scattering with broad working band from 7.8 to 15 GHz. The proposals provide new opportunities to tailor the microwave propagation and scattering with simultaneously high transmittance in visible frequencies, which could offer many benefits in practical uses, such as window and solar panel applications.
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