Ammonia gas sensors: A comprehensive review.

The vehicle scanning method (VSM), an indirect approach for bridge measurement, has attracted intensive attention since it was proposed. By this method, a moving test vehicle is employed to detect ...

State-of-the-Art of Vehicle-Based Methods for Detecting Various Properties of Highway Bridges and Railway Tracks

Acoustic-elastic metamaterials and phononic crystals for energy harvesting: a review

Aiming at the problem of poor prediction performance of rolling bearing remaining useful life (RUL) with single performance degradation indicator, a novel based-performance degradation indicator RUL prediction model is established. Firstly, the vibration signal of rolling bearing is decomposed into some intrinsic scale components (ISCs) by piecewise cubic Hermite interpolating polynomial-local characteristic-scale decomposition (PCHIP-LCD), and the effective ISCs are selected to reconstruct signals based on kurtosis-correlation coefficient (K-C) criteria. Secondly, the multi-dimensional degradation feature set of reconstructed signals is extracted, and then the sensitive degradation indicator IICAMD is calculated by fusing the improved independent component analysis (IICA) and Mahalanobis Distance (MD). Thirdly, the false fluctuation of the IICAMD is repaired by using the gray regression model (GM) to obtain the health indicator (HI) of the rolling bearing, and the start prediction time (SPT) of the rolling bearing is determined according to the time mutation point of HI. Finally, generalized regression neural network (GRNN) model based on HI is constructed to predict the RUL of rolling bearing. The experimental results of two groups of different rolling bearing data-sets show that the proposed method achieves better performance in prediction accuracy and reliability.

A novel based-performance degradation indicator RUL prediction model and its application in rolling bearing.

Point-of-care (POC) testing devices are necessary to improve human life with many aspects both for developing and developed countries. Especially, the specific biomolecules, which are related to particular diseases, are the important targets for POC testing. Recently, many researchers are able to develop POC devices in various platforms and designs due to the discovery and development of new advanced technologies. In this review, recent developments of the POC devices for detecting biomolecules in each POC platform have been reviewed with the recent development strategies for detecting biomolecule with their advantages and challenges. The case study of the development of POC devices with the strategies for the new pandemic, Covid-19 has also been reviewed. Finally, the challenges and perspectives on the future advances of the POC for biomolecules are discussed.

Recent developments of point-of-care (POC) testing platform for biomolecules

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Peri-Elastodynamic Simulations of Guided Ultrasonic Lamb Waves in Smart Structure with Surface Mounted PZT

Peridynamic based elastodynamic computation tool named Peri-elastodynamics is proposed herein to simulate the three-dimensional (3D) Lamb wave modes in materials for the first time. Peri-elastodynamics is a nonlocal meshless approach which is a scale-independent generalized technique to visualize the acoustic and ultrasonic waves in plate-like structure, micro-electro-mechanical systems (MEMS) and nanodevices for their respective characterization. In this article, the characteristics of the fundamental Lamb wave modes are simulated in a sample plate-like structure. Lamb wave modes are generated using a surface mounted piezoelectric (PZT) transducer which is actuated from the top surface. The proposed generalized Peri-elastodynamics method is not only capable of simulating two dimensional (2D) in plane wave under plane strain condition formulated previously but also capable of accurately simulating the out of plane Symmetric and Antisymmetric Lamb wave modes in plate like structures in 3D. For structural health monitoring (SHM) of plate-like structures and nondestructive evaluation (NDE) of MEMS devices, it is necessary to simulate the 3D wave-damage interaction scenarios and visualize the different wave features due to damages. Hence, in addition, to simulating the guided ultrasonic wave modes in pristine material, Lamb waves were also simulated in a damaged plate. The accuracy of the proposed technique is verified by comparing the modes generated in the plate and the mode shapes across the thickness of the plate with theoretical wave analysis.

Peri-Elastodynamic Simulations of Guided Ultrasonic Waves in Plate-Like Structure with Surface Mounted PZT.

A Dirac-cone-like dispersion at the center of the Brillouin zone where the wave number $\stackrel{P\vec}{k}=0$ [L. Brillouin, Wave Propagation in Periodic Structures (Dover, New York, 1953)], is rare and only happens due to accidental degeneracy. At certain frequencies, the Dirac cone breaks the time-reversal symmetry of acoustic waves, which has not yet been fully explored. In this paper, even the simplest geometric microarchitecture of phononic crystals (PnCs) in a periodic structure can be modulated to obtain the accidental triple degeneracies that make a Dirac-like cone at the \ensuremath{\Gamma} point ($\stackrel{P\vec}{k}=0$). While doing so, it was observed that the frequency of a nondispersive "deaf" band obtained from any arbitrary periodic structure made of similar PnCs remains unaltered. Then, a deaf band based predictive modulation of the PnCs is realized, and multiple occurrences of the Dirac-like points are demonstrated. The claims are validated using a numerical and experimental study of a baseline periodic structure having a square array of cylindrical polyvinylchloride inclusions in an air matrix. Phenomena such as orthogonal wave transport, negative refraction, and wave vortex are verified to exist at the deaf band based engineered Dirac cone.

Deaf band based engineered Dirac cone in a periodic acoustic metamaterial: A numerical and experimental study

Exotic acoustical features, like acoustic transparency, ultrasonic beam focusing, acoustic band gap and super lensing capability using a single metamaterial architecture is unconventional and unprecedented in the literature, demonstrated herein. Conventional metamaterials can focus an ultrasonic beam at specific frequency which results into unwanted distortion of the output wave fields at neighboring sonic frequencies in the host medium. However, ultrasonic wave focusing by virtue of negative refraction and simultaneous transparency of the metamaterial at sonic frequencies are uncommon due to their frequency disparity. To circumvent this problem and to avoid the unwanted distortion of wave at sonic frequencies, metamaterial with an array of butterfly-shaped thin ring resonators are proposed to achieve the beam focusing at ultrasonic frequency (37.3 kHz) and keep the structure transparent to the sonic frequencies (<20 kHz). The butterfly metamaterial with local ring resonators or butterfly crystals (BC) were previously proposed to create wide band gaps (~7 kHz) at ultrasonic frequencies above 20 kHz. However, in this study a unique sub-wavelength scale wave focusing capability of the butterfly metamaterial utilizing the negative refraction phenomenon is demonstrated, while keeping the metamaterial block transparent to the propagating wave at lower sonic frequencies below the previously reported bandgaps.

https://iopscience.iop.org/article/10.1088/2399-6528/aaea82/pdf

Hossain Ahmed

Papers

Peri-Elastodynamic Simulations of Guided Ultrasonic Lamb Waves in Smart Structure with Surface Mounted PZT

Peri-Elastodynamic Simulations of Guided Ultrasonic Waves in Plate-Like Structure with Surface Mounted PZT.

Deaf band based engineered Dirac cone in a periodic acoustic metamaterial: A numerical and experimental study

Multifunction acoustic modulation by a multi-mode acoustic metamaterial architecture

Evidence of dissipative and growing nonlinearity in Lamb waves due to stress-relaxation and material degradation in composites.