Phononic Crystals and Thermal Effects

In this work, we demonstrate a comprehensive theoretical study of one-dimensional perfect and defect phononic crystals. In our study, we investigate the elastic and shear waves with the influences of thermal effects. The numerical calculations based on the transfer matrix method (TMM) and Bloch theory are presented, where the TMM is obtained by applying the continuity conditions between two consecutive sub-cells. Also, we show that by introducing a defect layer in the perfect periodic structures (defect phononic crystals), we obtain localization modes within the band structure. These localized modes can be implemented in many applications such as impedance matching, collimation, and focusing in acoustic imaging applications. Then, we investigate the influences of the incident angle and material types on the number and intensity of the localized modes in both cases of perfect/defect crystals. In addition, we have observed that the temperature has a great effect on the wave localization phenomena in phononic band gap structures. Such effects can change the thermal properties of the PnCs structure such as thermal conductivity, and it can also control the thermal emission, which is contributed by phonons in many engineering structures

One-dimensional phononic crystals that incorporate a defective piezoelectric/piezomagnetic as a new sensor

In this paper, we have studied the propagation and localization of acoustic waves in a one-dimensional (1D) phononic crystal at the effects of both electric and magnetic fields. We focused on the sensing and measuring the electric and magnetic fields by adjusting the position of the transmitted peak (defect mode) inside the two piezoelectric/piezomagnetic defect layers (0.7 PMN-0.3PT/Terfenol-D). The defect mode is shifted towards the lower frequencies by applying electric and magnetic fields and towards the higher frequencies by opposing the field’s direction. The bigger the value of the applied field is the greater movement in the peak position is. In addition, our results revealed that the magnetic field has a bigger influence than the electric field on the position of the defect mode. Moreover, we studied such movement of the defect mode position by applying the electric and magnetic field simultaneously. These results can be used to improve and enhance piezoelectric and piezomagnetic energy harvesters

Thermal properties of one-dimensional piezoelectric phononic crystal

By using the transfer matrix method, we theoretically studied the propagation of a longitudinal acoustic wave in a one-dimensional phononic crystal (PnC) that contains a piezoelectric material as a defect layer. A pass band can be generated and controlled in the middle of the band gap. The pass band position is tuned by applying an external electric field. The position of the pass band inside the band gap is tuned by the changing of temperature. We introduce a comparison between temperature effects on two piezoelectric materials, PZT-5H and 0.7 PMN-0.3PT inside a PnC structure. Moreover, the pass band is shifted towards high or low frequencies by temperature decrement or increment, respectively. The simulated results provide a valuable guidance for PnC applications such as acoustic switch and temperature sensor

Experimental and numerical evidence of using a Phononic membrane with the coupling of Fano resonant modes as a highly sensitive temperature sensor

In this article, we present numerically and experimentally a tunable phononic membrane as an efficient temperature sensor based on the generation of slow modes (sharp resonance modes) in microcavities. The Phononic membrane is periodically perforated with subwavelength slits (apertures) to produce tunable modes in these cavities (mode corresponding to a cavity resonance). By emerging the silicon membrane in water, a coupling effect between acoustic waves through the slits occurs, which leads to multiple-wave interferences like Fabry Perot resonators. Besides, this design could secure the phenomenon of ultrasonic opacity through the perforated silicon membrane. Where a deep and large attenuation band with a relative bandwidth of 31 % and at the central frequency of 0.9 MHz is observed in the amplitude transmission spectra of the phononic membrane. Secondly, by modifying the temperature of the water, the position of the bandwidth is tuned, since, we could achieve high sensitivity of 2400 Hz °C-1 for a temperature change of 10–20 °C, which is considered a promising result for many important applications such as temperature sensors and biosensors

One-Dimensional Phononic Crystals: A Simplified Platform for Effective Detection of Heavy Metals in Water with High Sensitivity

Recently, the pollution of fresh water with heavy metals due to technological and industrial breakthroughs has reached record levels. Therefore, monitoring these metals in fresh water has become essentially urgent. Meanwhile, the conventional periodic one-dimensional phononic crystals can provide a novel platform for detecting the pollution of heavy metals in fresh water with high sensitivity. A simplified design of a defective, one-dimensional phononic crystals (1D-PnC) structure is introduced in this paper. The sensor is designed from a lead-epoxy multilayer with a central defect layer filled with an aqueous solution from cadmium bromide (CdBr2). The formation of a resonant peak through the transmittance spectrum is highly expected. This study primarily aims to monitor and detect the concentration of cadmium bromide in pure water based on shifting the position of this resonant peak. Notably, any change in cadmium bromide concentration can affect the acoustic properties of cadmium bromide directly. The transfer matrix method has been used to calculate the transmission spectra of the incident acoustic wave. The numerical findings are mainly based on the optimization of the cadmium bromide layer thickness, lead layer thickness, epoxy layer thickness, and the number of periods to investigate the most optimum sensor performance. The introduced sensor in this study has provided a remarkably high sensitivity (S = 1904.25 Hz) within a concentration range of (0–10,000 ppm). The proposed sensor provides a quality factor (QF), a resolution, and a figure of merit of 1398.51752, 48,875,750 Hz, and 4.12088 × 10−5 (/ppm), respectively. Accordingly, this sensor can be a potentially robust base for a promising platform to detect small concentrations of heavy metal ions in fresh water

Merosin deficient congenital muscular dystrophy: Clinical, neuroimaging and immunohistochemical study of 8 Egyptian pediatric patients

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Monitoring and simulation of the fuel irradiation behavior in nuclear reactors based on phononic crystal structure

Abstract We have presented in the current work a novel idea for simulating the irradiation behaviors of the nuclear fuel pellets in nuclear reactors by using a one-dimensional defective phononic crystal (1D-DPnC) design was presented. The transmission spectra of the incident mechanical waves were considered basic data for expressing the characteristics of different nuclear fuel-pellets. Herein, the density, sound speed, and Young’s modulus of the fuel-pellets represent the key parameters that are influenced by the irradiation behaviors of these pallets. Mixed plutonium–uranium oxide (MOX) nuclear fuel is considered the main fuel in the present study. In addition, a comparison is performed for this fuel with other types of nuclear fuels. Moreover, the mechanical properties of these MOX-pellets are dependent on the porosity, the ratio of oxygen-to-metal (O/M), and the plutonium (Pu-content). The theoretical treatments depend on the transfers matrix method to compute the transmission spectra through the 1D-DPnC. The numerical findings provided that the MOX-pellet has the highest performance compared to other fuel pellets and with sensitivity equal to 59.388 × 103 Hz s/m. It was also reported that the effects of the percentage of the O/M and Pu- content in MOX had a minor effect in a comparison with the impact of porosity. The theoretical simulation agreed extremely with the experimental data reported for these nuclear fuels. Because of the close relationship between sound speed and density, this sensor can be utilized to monitor the porosity, O/M, Pu-content, and density of fuel-pellets as a quick and non-destructive evaluation technique in a nuclear fuel fabrication laboratory. This article has proven theoretically that MOX fuel produced from nuclear waste of uranium dioxide and plutonium dioxide gives excellent results compared to other types of nuclear fuels, and this agrees with experimental researches. Thus, it may contribute in preserving the environment from nuclear waste, and this can be considered a novel kind of purification of environmental pollution treatment