Over the past decade, RNA sequencing (RNA-seq) has become an indispensable tool for transcriptome-wide analysis of differential gene expression and differential splicing of mRNAs. However, as next-generation sequencing technologies have developed, so too has RNA-seq. Now, RNA-seq methods are available for studying many different aspects of RNA biology, including single-cell gene expression, translation (the translatome) and RNA structure (the structurome). Exciting new applications are being explored, such as spatial transcriptomics (spatialomics). Together with new long-read and direct RNA-seq technologies and better computational tools for data analysis, innovations in RNA-seq are contributing to a fuller understanding of RNA biology, from questions such as when and where transcription occurs to the folding and intermolecular interactions that govern RNA function.

RNA sequencing: the teenage years

Time-reassigned synchrosqueezing transform: The algorithm and its applications in mechanical signal processing

Foreword Chapter 1 Introduction to SHM (Daniel L Balageas) Chapter 2 Vibration-based techniques for SHM (Claus-Peter Fritzen) Chapter 3 Fiber-optics sensors (Alfredo Guemes and Jose M Menendez) Chapter 4 SHM with piezoelectric sensors (Philippe Guy and Thomas Monnier) Chapter 5 SHM using electrical resistance (Michelle Salvia and Jean-Christophe Abry) Chapter 6 Low frequency electromagnetic techniques (Michel B Lemistre) Chapter 7 Capacitive methods for SHM in civil engineering (Xavier Derobert and Jean Iaquinta) Short Bibliographies of the Contributors Index

/pdf/structural-health-monitoring-37wv1pwxci.pdf

Structural health monitoring

Ultrasonic guided wave (UGW) is one of the most commonly used technologies for non-destructive evaluation (NDE) and structural health monitoring (SHM) of structural components. Because of its excellent long-range diagnostic capability, this method is effective in detecting cracks, material loss, and fatigue-based defects in isotropic and anisotropic structures. The shape and orientation of structural defects are critical parameters during the investigation of crack propagation, assessment of damage severity, and prediction of remaining useful life (RUL) of structures. These parameters become even more important in cases where the crack intensity is associated with the safety of men, environment, and material, such as ship’s hull, aero-structures, rail tracks and subsea pipelines. This paper reviews the research literature on UGWs and their application in defect diagnosis and health monitoring of metallic structures. It has been observed that no significant research work has been convened to identify the shape and orientation of defects in plate-like structures. We also propose an experimental research work assisted by numerical simulations to investigate the response of UGWs upon interaction with cracks in different shapes and orientations. A framework for an empirical model may be considered to determine these structural flaws.

Structural Health Monitoring (SHM) and Determination of Surface Defects in Large Metallic Structures using Ultrasonic Guided Waves.

This review introduces several areas of importance in acoustic emission (AE) technology, starting from signal attenuation. Signal loss is a critical issue in any large-scale AE monitoring, but few systematic studies have appeared. Information on damping and attenuation has been gathered from metal, polymer, and composite fields to provide a useful method for AE monitoring. This is followed by discussion on source location, bridge monitoring, sensing and signal processing, and pressure vessels and tanks, then special applications are briefly covered. Here, useful information and valuable sources are identified with short comments indicating their significance. It is hoped that readers note developments in areas outside of their own specialty for possible cross-fertilization.

/pdf/review-on-structural-health-evaluation-with-acoustic-2yceo4jr7o.pdf

Review on Structural Health Evaluation with Acoustic Emission

Damping in miniature resonators is a consequence of many factors, one of which is due to interaction with the substrate to which the resonator is mounted. It is common practice to create a model of the resonator that includes a small segment of the substrate plate with a finite element (FE) software in conjunction with absorbing boundary elements. As an alternative to implementing absorbing boundary elements, semi-analytical methods have been developed in which such elements are replaced by analytical expressions for Lamb waves. This approach requires the specification of a harmonic load and the determination of the subsequent harmonic response at a point on the resonator. The modal frequency and damping can then be estimated from the computation of the frequency response function on a frequency grid. In this paper, the approach is demonstrated for single and double cantilever configurations on a plate in the case of plain strain. The influence of the number of selected Lamb modes, mesh density and the size of the modeled plate segment is investigated through parametric studies. Moreover, it is shown that the semi-analytical results are in good agreement with those from conventional transient finite element simulations.

Parametric studies for semi-analytical investigation of plate-mounted resonators

It is well known that guided ultrasonic waves are suitable to detect damages in composite plates. It has also been shown that these Lamb waves can be utilized to infer material properties through nondestructive measurements. More recently, it was shown that this may be used to determine regional inhomogeneity that is inherent to composite materials due to manufacturing imperfections. In this project, it is investigated whether automated processing of Lamb wave-based data is generally suitable to detect such imperfections. Woven prepreg and short-fiber composite panels are manufactured. A large set of nondestructive measurements are conducted to determine dispersion and attenuation characteristics for multiple regions across each panel. Automated signal processing is performed to extract characteristic features of the signal, which are in turn used to identify any differences within the panels. Moreover, it is studied which type of sensing technology, such as contact transducers, air-coupled transducers or a laser Doppler vibrometer are most suitable for this task. That is, ultrasound measurements with different actuator and sensor combinations are accompanied by additional transducer characterization measurements. Optimal frequency ranges for each transducer are determined in addition to studying potential effects of transducer orientation. Based on all findings, it can be concluded that detecting regional inhomogeneity remains challenging due to various compounding limitations, such as optimal transducer frequency ranges, human error and generally low signal-to-noise ratios in Lamb wave-based measurements, especially at longer propagation distances. In turn, the development of guided wave-based nondestructive evaluation methods require a holistic approach with careful considerations of the employed transducers.

Christoph Schaal

Papers

Parametric studies for semi-analytical investigation of plate-mounted resonators

On detecting regional inhomogeneity in composite plates using Lamb waves