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Abstract

The paper presents the investigations aimed at the determination of the effect of time and wavelength of ultrasound field on the value of capillary suction time (CST), sludge thickening and dry matter of the excess sludge subjected to the process of stabilization. The investigations were carried out on the excess sludge which comes from communal waste treatment plant. The sludge was exposed to ultrasound field, using ultrasound generator with power of 1500 W, frequency of 20 kHz and amplitude 39.42 μm (which corresponded to the amplitude of 100%). Sonication of the sludge was carried out for different amplitudes and sonication times. The non-conditioned sludge and the sludge initially conditioned with ultrasound field were subjected to the process of stabilization in laboratory flasks (V = 0.5 dm3) for the period of 10 days. On each day, sludge thickening and dewatering capacities were determined. The sludge subjected to the effect of ultrasound field exhibited elevated levels of CST. However, the sonication time had positive effect on the increase in the degree of thickening for each of the amplitudes studied. Also, the process of stabilization positively affected final thickening and dewatering of the sludge.
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Abstract

This paper presents and analyses the results of a simulation of the acoustic field distribution in sectors of a 1024-element ring array, intended for the diagnosis of female breast tissue with the use of ultrasonic tomography. The array was tested for the possibility to equip an ultrasonic tomograph with an additional modality - conventional ultrasonic imaging with the use of individual fragments (sections) of the ring array. To determine the acoustic field for sectors of the ring array with a varying number of activated ultrasonic transducers, a combined sum of all acoustic fields created by each elementary transducer was calculated. By the use of MATLAB software, a unique algorithm was developed, for a numerical determination of the distribution of pressure of an ultrasonic wave on any surface or area of the medium generated by the concave curvilinear structure of rectangular ultrasound transducers with a geometric focus of the beam. The analysis of the obtained results of the acoustic field distribution inside the ultrasonic ring array used in tomography allows to conclude that the optimal number of transducers in a sector enabling to obtain ultrasound images using linear echographic scanning is 32 ≤ n ≤ 128, taking into account that due to an increased temporal resolution of ultrasonic imaging, this number should be as low as possible.
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