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In this work we simulated the ultrasonic response of the aluminium/adhesive/aluminium multilayer using the theoretical reflection coefficient. This investigation is based on monitoring the evolution of the amplitude of the theoretical reflection coefficient as a function of the frequency and thickness of the aluminium layer in a first step and as a function of the frequency and thickness of the adhesive layer in a second step. Based on the mode doubling of the aluminium, we found the criteria to be met for such an ultrasonic characterisation of the bonding quality to be validated.

Several methods have been made to characterize the concrete during solidification and for this we proceed as way that we can collect non-overlapping ultrasonic signal that is when we choose vessels with well defined walls. Our work highlights the changes of the signals transmitted through the solidification of cement paste according to incidence angles. The work in question demonstrates the existence of a critical angle in this way the transmitted waves are strongly attenuated. This method is based on the determination of the FFT of signals collected during solidification cement and juxtaposed to form graphs being treated. Our method showed the presence of strong attenuations around well-defined angles.

International audience; Overseas fi sh is either directly treated on boats before being frozen or directly frozen, then treated in the factory after being unloaded. At the factory, the thawing of that fi sh is an essential step in its transformation and treatment; the quality of the texture is directly related to the quality of thawing. During this ABSTRACT Introduction. Fish quality is traditionally controlled by chemical and microbiological analysis. The non-destructive control presents an enormous professional interest thanks to the technical contribution and precision of the analysis to which it leads. This paper presents the results obtained from a characterisation of fi sh thawing process by the ultrasonic technique, with monitoring thermal processing from frozen to defrosted states. Material and methods. The study was carried out on fi sh type red drum and salmon cut into fi llets of 15 mm thickness. After being frozen at-20°C, the sample is enclosed in a plexiglas vessel with parallel walls at the ambient temperature 30°C and excited in perpendicular incidence at 0.5 MHz by an ultrasonic pulser-receiver Sofranel 5052PR. the technique of measurement consists to study the signals refl ected by fi sh during its thawing , the specifi c techniques of signal processing are implemented to deduce informations characterizing the state of fi sh and its thawing process by examining the evolution of the position echoes refl ected by the sample and the viscoelastic parameters of fi sh during its thawing. Results. The obtained results show a relationship between the thermal state of fi sh and its acoustic properties , which allowed to deduce the optimal time of the fi rst thawing in order to restrict the growth of microbial fl ora. For salmon, the results show a decrease of 36% of the time of the second thawing and an increase of 10.88% of the phase velocity, with a decrease of 65.5% of the peak-to-peak voltage of the signal refl ected, thus a decrease of the acoustic impedance. Conclusions. This study shows an optimal time and an evolution rate of thawing specifi c to each type of fi sh and a correlation between the acoustic behavior of fi sh and its thermal state which approves that this technique of ultrasonic monitoring can substitute the control using the destructive chemical analysis in order to monitor the thawing process and to know whether a fi sh has suffered an accidental thawing.

International audience; During the experiments carried out in the laboratory on the monitoring and study of fish thawing by ultrasonic technique. We had difficulties in detecting the begining of the thawing which is the main criterion of fish quality control. To correct the problem we use the singular value decomposition (s.v.d.) method which is a mathematical tool.This allowed us to show by the ultrasonic technique the thawing start for cod which is a fish that had an average fat content. The results were good with a central frequency transducer equal to 500 kHz. However for salmon which is a fish that had a high content of fat; and for centrals frequencies transducers above 500 kHz the observed results were not very good.

In this present work, our objective is to study the feasibility of the control of the maturity of orange fruit by the ultrasonic echo pulse method with immersion in water. This study relates to two varieties of orange (Navel and Mandarin) which are the most harvested particularly in the region of Souss-Massa-Drâa in Morocco. Contrary to the works already published in this field, we worked in the high frequencies by the means of a focusing transducer with 20MHz as a central frequency. By taking into account the strong attenuation of the ultrasounds in the texture of fruits and vegetables, we limited our study only to the characterization of the external layer called the flavedo characterized by its very small thickness. The use of the high frequencies will allow us a characterization of high resolution of the orange peel with a high space resolution. This control is based mainly on the measure of the ultrasonic parameters eventually velocity and attenuation in order to check the aptitude of this ultrasonic method to detect the degree of maturity of the fruit without passing by penetrometric and biochemical measurements which are mostly correlated with human perception concerning the firmness of the fruit but they are generally destructives.

International audience; The objective of this work is to characterize the fermentation of yogurt based on an ultrasonic technique. Conventionally, the acidity of the yogurt is measured by a pH meter to determine the progress of fermentation. However, the pH meter should be cleaned and calibrated for each measurement and, therefore, this method is not practical. In this regard, ultrasonic techniques are fast, non-invasive and inexpensive. The measurement of ultrasonic parameters such as amplitude and time-of-flight of the echoes backscattered by samples of yogurt were able to provid information on the phases of the fermentation and so on the state of yogurt over time. The major contribution of this work is the detection with high precision the moment when the fermentation process should end to stop the growth of bacteria.

National audience; Dans cet article, les performances de l'huile de Soja (HS) et de l'huile de Soja Partiellement Hydrogénée (HSPH) ont été analysées pour évaluer la dégradation de la qualité de l'huile sous l'effet de la thermo-oxydation en utilisant des techniques ultrasonores. La stabilité de HS et HSPH est caractérisée par les changements physiques et chimiques : La vitesse et l'atténuation ultrasonores, le taux des acides gras libres (AGL), le pourcentage des composants polaires (CP), et l'analyse des acides gras. Les huiles ont été frites 8h par jour à 180°C durant 4 jours consécutifs. Les mesures ultrasonores ont été prises pendant que l'huile est refroidie de 50 à 30°C. Il a été trouvé que les paramètres ultrasonores sont en corrélation avec les mesures du contenu des acides gras libres et du pourcentage des composants polaires. La performance de HSPH est significativement mieux que celle de HS suivant la vitesse ultrasonore. En conséquence les techniques ultrasonores peuvent être utilisées pour évaluer la qualité de l'huile de friture.

National audience; Généralement, le pH-mètre est l'outil expérimental utilisé pour déterminer l'état d'avancement de la fermentation du yaourt en mesurant son acidité. Toutefois, cette méthode n'est pas pratique, vu qu'elle n'est pas rapide et qu'elle demande une expertise. Dans cette étude, nous avons contrôlé la fermentation du lait dans production du yaourt par une technique ultrasonore. Le changement du pH pendant la fermentation du yaourt est évalué et comparé avec des mesures ultrasonores. Les variations de l'amplitude des ondes ultrasonores illustrent plus clairement la signature d'évolution du yaourt. Les expériences montrent que les mesures d'analyse telles que le pH ou d'acidité pourraient être remplacé par cette technique ultrasonore.

L'hydratation du ciment entraîne de nombreuses complexes réactions chimiques entre l'eau et les particules anhydres constituant le ciment. Par conséquence, il se produit des grands changements de l'état rhéologique et mécanique de la pâte de ciment : le mélange ciment/eau se transforme de l'état fluide visqueux à l'état viscoélastique puis à l'état élastique solide. La technique ultrasonore non destructive et non invasive, basée sur l'analyse et le traitement des signaux ultrasonores réfléchis par une pâte de ciment, et permettant de suivre en temps réel l'évolution de l'état rhéologique et mécanique des pâtes de ciment à travers la détermination du module de coefficient de réflexion et la vitesse de phase.

International audience; The durability of mortar structures is affected by chemical and mechanical factors, such as abrasion, temperature variation..., the Degradation of mortar structures located under flowing water in their structure or high humidity atmospheres. In this study we presented a method for ultrasonic non-destructive characterization in mortar to follow the evolution of the signals back scattered by mortar structures for different size of sand, Samples were manufactured using same water/cement ration (w/c) 0.65, and cement/sand ration (c/s) 0.5. The processing of the ultrasound wave has been chosen to follow the hardening of mortar and to understand the mechanisms driving to the degradation of mortar in relation with microstructure.