The talk with present the key results of the IPCC Working Group III 5th assessment report. Concluding four years of intense scientific collaboration by hundreds of authors from around the world, the report responds to the request of the world's governments for a comprehensive, objective and policy neutral assessment of the current scientific knowledge on mitigating climate change. The report has been extensively reviewed by experts and governments to ensure quality and comprehensiveness.

Climate change 2014 - Mitigation of climate change

This article reviews acoustic microfiuidics: the use of acoustic fields, principally ultrasonics, for application in microfiuidics. Although acoustics is a classical field, its promising, and indeed perplexing, capabilities in powerfully manipulating both fluids and particles within those fluids on the microscale to nanoscale has revived interest in it. The bewildering state of the literature and ample jargon from decades of research is reorganized and presented in the context of models derived from first principles. This hopefully will make the area accessible for researchers with experience in materials science, fluid mechanics, or dynamics. The abundance of interesting phenomena arising from nonlinear interactions in ultrasound that easily appear at these small scales is considered, especially in surface acoustic wave devices that are simple to fabricate with planar lithography techniques common in microfluidics, along with the many applications in microfluidics and nanofluidics that appear through the literature.

/pdf/microscale-acoustofluidics-microfluidics-driven-via-5bet39j13p.pdf

Microscale acoustofluidics: Microfluidics driven via acoustics and ultrasonics

Renewable energy sources have gained much attention due to the recent energy crisis and the urge to get clean energy. Among the main options being studied, wind energy is a strong contender because of its reliability due to the maturity of the technology, good infrastructure and relative cost competitiveness. In order to harvest wind energy more efficiently, the size of wind turbines has become physically larger, making maintenance and repair works difficult. In order to improve safety considerations, to minimize down time, to lower the frequency of sudden breakdowns and associated huge maintenance and logistic costs and to provide reliable power generation, the wind turbines must be monitored from time to time to ensure that they are in good condition. Among all the monitoring systems, the structural health monitoring (SHM) system is of primary importance because it is the structure that provides the integrity of the system. SHM systems and the related non-destructive test and evaluation methods are discussed in this review. As many of the methods function on local damage, the types of damage that occur commonly in relation to wind turbines, as well as the damage hot spots, are also included in this review.

https://iopscience.iop.org/article/10.1088/0957-0233/19/12/122001/pdf

Structural health monitoring for a wind turbine system: a review of damage detection methods

The sensitivity method in finite element model updating: A tutorial

The sensitivity method in finite element model updating: A tutorial (vol 25, pg 2275, 2010)

Independent Component Analysis (ICA) is used for recovering the various independent sources exciting a system and to separate their contributions. In this paper, ICA is applied to vibrational and acoustic data measured on undamaged and damaged rolling bearings, where those data contains information about the vibration frequencies related to the defect, if present, to the rotation of the bearing, to its dynamic behaviour (resonance frequencies) and to random noise. The aim of the method is to separate those different contributions and to enhance only the one related to the vibration frequency associated to the defect in order to diagnose its presence. To improve the power of the method to identify the contribution of the bearing fault characteristic frequency, a pre-processing step is introduced based on Empirical Mode Decomposition (EMD), allowing to reconstruct multiple sets of time series from a single sensor data, called multiple intrinsic mode functions, which are then given as input to the ICA.

Rolling Bearing Diagnostics by means of EMD-Based Independent Component Analysis on Vibration and Acoustic Data

Continuous Scanning Laser Doppler Vibrometry (CSLDV) is a well-known technique within the structural dynamic community. However, the whole potentials of CSLDV for diagnostic purposes have not been fully exploited yet. This paper presents a time domain approach for identifying damages in structures. The method, which is based on a wavelet processing of vibration data collected by CSLDV, does not need any a-priori knowledge of the vibration behavior of the undamaged sample. Applications on real test cases are presented and discussed in the paper, demonstrating the promising performance of the approach as a non-destructive testing technique.

Continuous scanning laser Doppler vibrometry and wavelet processing for diagnostics: A time domain approach

Damping and loss factor assessment of high damped materials is a challenging task addressed in the past by several researchers, one of the most important is H. Oberst who defined a standard method to tackle the issue.

Damping Properties Assessment of Very Highly Compliant Sandwich Materials: Are Traditional Methods Really Too Old?

This paper presents an experimental study on acoustic attenuation of different types of face masks in use by the general population during the COVID-19 pandemic. In particular, measurements are performed on ten samples of masks, of which four are medical masks, three are respirators, and three are community masks. Breathability and Bacterial Filtration Efficiency (BFE) tests, in compliance to the standard characterization process of medical masks, are also carried out. The porosity on each layer composing the masks is measured by processing their scanning electron microscopy (SEM) images. The analysis of the results aims to establish if acoustic attenuation is correlated to any of these parameters. It emerges that porosity and breathability are strongly correlated to acoustic attenuation, while bacterial filtration efficiency is not.

/pdf/acoustic-attenuation-of-covid-19-face-masks-correlation-to-3pjvdf9z.pdf

Acoustic Attenuation of COVID-19 Face Masks: Correlation to Fibrous Material Porosity, Mask Breathability and Bacterial Filtration Efficiency

The acoustic emission characterization of gear systems is a key issue in several mechanical fields aiming at improving sound quality and diagnostic features. The possibility of identifying contribution of different vibro-acoustic sources would help on tackling that objective. A Time Domain Correlation method based on simultaneously collected acoustic and vibration data is exploited for separating the acoustic contribution coming from the different components of a three epicyclical gear electric motor. Two different approaches of the Scanning Laser Doppler Vibrometry are discussed for measuring vibration data: the Continuous Scan one, where the laser sweep continuously the surface under test simultaneously providing temporal and spatially sampled data, and the Standard Sequential Scan.

Milena Martarelli

Papers

Rolling Bearing Diagnostics by means of EMD-Based Independent Component Analysis on Vibration and Acoustic Data

Continuous scanning laser Doppler vibrometry and wavelet processing for diagnostics: A time domain approach

Damping Properties Assessment of Very Highly Compliant Sandwich Materials: Are Traditional Methods Really Too Old?

Acoustic Attenuation of COVID-19 Face Masks: Correlation to Fibrous Material Porosity, Mask Breathability and Bacterial Filtration Efficiency

Spatial Noise Component Identification Based on Different Vibro-Acoustic Data Sets