ABSTRACT
Conventional water immersion ultrasonic testing faces limitations due to factors such as environmental conditions, workpiece dimensions, corrosion, and resource wastage. Contact-based coupling methods, which employ coupling media or specific coupling structures, offer a convenient approach to coupling acoustic waves and reduce signal attenuation. However, these methods are time-sensitive and lack adaptability to uneven surfaces, particularly when dealing with workpieces featuring subtle undulations, resulting in significant signal decay. This paper presents an ultrasonic coupling method based on a flexible capillary water column array. By employing a stable and flexible water column array within the micro-channels as the coupling medium, stable contact-based transmission of ultrasonic signals is achieved. The influence of water column array unit dimensions and array structures is explored through theoretical analysis and experimentation, demonstrating lower energy attenuation compared to reductions in water column area. Notably, the tests revealed the method's adaptability at oblique angles below 20°, which surpasses the performance of submerged detection at similar angles. This research presents an innovative and stable approach for contact-based ultrasonic coupling testing, particularly in scenarios involving dynamic contact scanning between ultrasonic waves and workpieces.
ABSTRACT
Photodegradation of inderal in a photo-Fenton like system at near-neutral pH modified with catechin, a natural catecholate siderophore, was investigated under simulated sunlight. The main factors influencing the process, such as Fe(iii)-catechin complexes, pH, and catechin concentration were examined. Photodegradation of inderal was strongly dependent on pH, following the order pH 3.0 < 5.0 < 7.0 < 6.0. Formation of the Fe(iii)-catechin complex resulted in the stabilization of ferric iron and generation of ËOH under irradiation at near-neutral pH values. The removal of inderal was about 75% under optimal conditions (50 µmol L(-1) Fe(iii) and 200 µmol L(-1) catechin at pH 6.0). The photodegradation products of inderal were identified by LC-ESI-MS and GC-MS, and the photodegradation pathway was proposed. Iron in the Fe(iii)-catechin system was reused by simple addition of catechin to the reaction mixture. Results of this study suggest that the Fe(iii)-catechin complex may be used in the photo-Fenton like process, an advanced approach to the removal of organic pollutants at near-neutral pH.
