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Several previous studies have been dedicated to incorporating double defect modes of a phononic crystal (PnC) into piezoelectric energy harvesting (PEH) systems to broaden the bandwidth. However, these prior studies are limited to examining an identical configuration of the double defects. Therefore, this paper aims to propose a new design concept for PnCs that examines differently configured double defects for broadband elastic wave energy localization and harvesting. For example, a square-pill

This review paper addresses the critical need for structural prognostics and health management (SPHM) in aircraft maintenance, highlighting its role in identifying potential structural issues and proactively managing aircraft health. With a comprehensive assessment of various SPHM techniques, the paper contributes by comparing traditional and modern approaches, evaluating their limitations, and showcasing advancements in data-driven and model-based methodologies. It explores the implementation o

This paper proposes a one-dimensional, defect-introduced phononic crystal design for target frequency matching. A quarter-wave stack is used as a unit cell. The supercell-technique-based transfer matrix method enables the defect’s length to be explicitly derived; this generates a defect band at the target frequency in band-structure analysis. For the verification through time-harmonic analysis, the perturbation-theory-incorporated S-parameter method is used. The results show that the proposed de

This paper proposes an explicit solution for the design of a target-frequency-customized, one-dimensional phononic crystal (PNC) with a defect for piezoelectric energy harvesting under longitudinal waves. Due to the innate narrow bandwidth nature of the defect modes of a PNC at the target frequency, there is a great need to generate an electromechanically coupled defect band of a piezoelectric-defect-introduced PNC. This work considers the transfer matrix method which has been widely used in ana

Solenoid valves are widely used to control fluid flow in various mechanical systems. If the valves do not function properly, the mechanical systems can lose their ability to control the fluid flow. This paper describes a fault detection method that can monitor coil burnout under dynamic thermal loading. The method consists of three steps. First, an equivalent current model of the solenoid valves is derived from Kirchhoff's voltage law. Then, a predictive regression model is developed to describe

Abstract Significant prior research has explored elastic wave-energy localization via defect modes of phononic crystals (PnCs). The integration of defect-introduced PnCs and piezoelectric materials has paved the way for the development of new conceptual products for applications in energy harvesters, wave filters, and ultrasonic sensors. Recently, an attempt has been made to deviate from this paradigm and design an ultrasonic transducer that generates elastic waves. Unfortunately, previous work