Relating the ultrasonic and aerosol filtration properties of filters
Notice bibliographique
Résumé
Non-contact methods are useful to improve the quality control of particle filtration media.The purpose of this paper is to investigate the correlation between the filtration efficiency of a porous sheet and its ultrasonic properties obtained using a non-contact technique.An air-coupled ultrasonic technique is used to obtain rapid measurements without affecting the integrity of the material.High frequencies (from 0.1 to 2.5 MHz) are used to improve technique sensitivity, and transmitted waves are measured to probe the internal properties of the material.Measurements of transmission coefficient spectra (amplitude and phase) and the corresponding ultrasound velocity and attenuation coefficient at different frequencies are obtained for a set of filtration media with well-characterized properties.Results show that the ultrasonic properties of filtration media vary as a function of basis weight, and therefore filtration efficiency, for a given charge state.However, the effect of electrostatic charge on ultrasonic propagation is almost negligible, as expected.We conclude that ultrasonic transmission may provide a valuable tool for the continuous online monitoring of material quality during fabrication and as a method to tease apart mechanical and electrostatic contributions to particle filtration. Keywords Filtration efficiency, Air-coupled ultrasound, Air filters testingThe filtration of aerosolized particles is critical to respiratory protection, within the context of both occupational and public health, and to building ventilation systems 1,2 .The demand for better, consistent quality filters requires methods to quickly ensure homogeneity and reproducibility of the materials that make up these products.This may become increasingly important as new filtration materials and new manufacturing methods are developed.Currently, measurements of particle filtration efficiency and pressure resistance require slow, typically offline, and typically destructive approaches to filter testing.Given that, in most cases, these materials can present some degree of intrinsic heterogeneity, testing large portions of the produced filters can become a key issue.This leaves an opportunity for complementing standard testing with non-destructive, online techniques.Acoustic and ultrasonic techniques, encompassing both water and air-coupled approaches, have been used in the past to test different porous media, where ultrasonic and acoustic properties have been correlated with different material properties, including permeability, fluid filtration efficiency, tortuosity, porosity, and pore size.The relationship between permeability or fluid resistance and acoustic propagation in air saturated porous materials at audio frequencies is well understood and has been employed to characterize porous materials in different applications, especially for sound absorbers [3][4][5][6][7][8][9] .At the same time, fluid immersion ultrasonic techniques have also been used to study porous materials for fluid filtration-mainly filtration membranes-to determine membrane fouling during operation 10,11 and particle retention capability 12 .Closer to the application here studied, ultrasonic waves and air-coupled techniques have also been used to study the correlation between permeability, flux resistivity, porosity and tortuosity with ultrasound propagation features for different porous and filtration materials 5,[13][14][15][16][17][18][19] .It has recently been demonstrated that, by using air-coupled ultrasonic transducers [20][21][22] with high sensitivity, high center frequency (> 150 kHz), and large frequency band (fractional bandwidth at -20 dB > 50%), it is possible to transmit ultrasonic signals through a variety of filtration layers used in the fabrication of face masks with sufficient signal-to-noise ratio to extract valuable information 23 .In addition, it was demonstrated that ultrasonic propagation takes place in the air gaps, such that ultrasonic parameters are sensitive to effective pore size, tortuosity, and porosity.In addition, it was shown that the loss in the transmission coefficient increases with the face mask grade, ranging from cloth face masks to respirators.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,004 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,003 | 0,003 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,001 | 0,001 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,001 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,017 | 0,004 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».