In order to determine if heat treatments can be discerned by nondestructive ultrasonic testing, samples of SAE 1045 and SAE 4140 steels were subjected to the classical heat treatments of annealing, normalizing, quenching, and quenching and tempering, and their elastics constants, Young's, shear and Poisson's moduli, were monitored by ultrasound. Results show that the microstructural differences associated to the various heat treatments generate differences on the elastic constants that can be effectively discerned by the use of longitudinal and shear ultrasonic waves. Special attention is given to Poisson's modulus, since for its determination only times of flight of longitudinal and shear ultrasonic waves, and not the distance the waves travel, are required, which is of quite practical importance, since measurements are simplified and a fundamental source of error is eliminated. It is thus shown that the microstructural evolution of a steel part subjected to heat treatments can be monitored by this simple ultrasonic method.
The review highlights the various methods used for assessing environmental quality in Mediterranean coastal lagoons, with emphasis on benthic parameters and processes. The application of indices based on benthic macrofauna, extensively used in coastal areas, may fail in discerning between natural and anthropogenic pressures over naturally stressed coastal lagoons. Sediment can play an important regulatory role over the overlying water composition through the storage capacity for organic matter and pollutants, regeneration of nutrients or its buffering capacity. Descriptive classical measurements like sedimentary organic matter, Chlorophyll α and nutrient content are commonly included in monitoring efforts. However, other more complex indicators like primary production, sediment-water solute fluxes, solute sorption dynamics or microbial reaction rate determinations, have not been fully implemented for environmental quality assessment in coastal lagoons. These could offer crucial information on current and projected anthropogenic influence on ecosystem functioning. Irruption of novel techniques in benthic biogeochemistry like Excitation-Emission-Matrix (EEM) fluorescence for the study of dissolved organic matter dynamics shows high potential in combination with biological quality elements and other metabolic measurements for the evaluation of the environmental quality in coastal lagoons.
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