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Number of results: 6
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Abstract

The measured rate of release of intercellular protein from yeast cells by ultrasonication was applied for evaluating the effects of sonication reactor geometry on cell disruption rate and for validation of the simulation method. Disintegration of two strains of Saccharomyces cerevisiae has been investigated experimentally using a batch sonication reactor equipped with a horn type sonicator and an ultrasonic processor operating at the ultrasound frequency of 20 kHz. The results have shown that the rate of release of protein is directly proportional to the frequency of the emitter surface and the square of the amplitude of oscillations and strongly depends on the sonication reactor geometry. The model based on the Helmholtz equation has been used to predict spatial distribution of acoustic pressure in the sonication reactor. Effects of suspension volume, horn tip position, vessel diameter and amplitude of ultrasound waves on the spatial distribution of pressure amplitude have been simulated. A strong correlation between the rate of protein release and the magnitude of acoustic pressure and its spatial distribution has been observed. This shows that modeling of acoustic pressure is useful for optimization of sonication reactor geometry.
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Abstract

The paper presents and discusses a method of azimuth determination of ultrasonic echo arrival in air. The basis of the presented approach is the assumption that the received signal is a narrowband one. In this way, the direction of the signal arrival can be determined based on its phase shift using two receivers. When the distance between the receivers exceeds half of the wavelength of the received signal, a problem of ambiguity in determining the angle of arrival arises. To solve this, a method using multiple pairs of receivers was used. Its robustness and temperature dependence is analysed. The most important advantages of the presented approach are simplified computations and low hardware requirements. Experimental data made it possible to show that for strong echoes, the accuracy is higher than 0.5X. In the case of weak echos, it is reduced to about 2X. Because the method is based on phase shift measurement, the ultrasonic sonar that uses this method can be compact in size. Moreover, owing to the theoretical analysis, certain properties of the mutual location of the receivers were found and formally proved. They are crucial for determining proper receivers’ inter-distances.
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Abstract

The paper presents results of numerical calculations and experimental data on the directional pattern of two 38-element parametric arrays composed of ultrasound sources. Two types of antenna arrays are considered, namely with parallel and coaxial connections of ultrasonic transducers (elements). The results of selecting and functional testing of unit elements are described in this paper. It is found that in the coaxial element connection of the antenna array, the level of side lobes is higher than that in the parallel element connection.
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Abstract

The compactness of dimension stone blocks was previously controlled through various methods that were partially based on personal experiences, acoustic and visual observance of materials. With the development of technology, the ultrasonic pulse method is frequently used for the examination of stone test pieces and with an analysis of acquired data through the tomography method, the compactness is determined. The monolith stone blocks that are found at a site contain hidden discontinuities. The technique of data acquisition and the use of various instruments enable a good overview of the block interior. With an increased number of measurements, a suitable classification is prepared that helps reduce modification costs and increases the quality of stone blocks. The control methodology of compactness is based on the passage of longitudinal waves through the stone block without damaging the block during control. High differences in speed show irregularities in the material. With the observation system, we can prepare a tomography of the measured profiles that show us the locations of irregularities that should be observed more closely. During in situ measurements, the data for comparison with measured results are acquired. Determination of critical locations is of extreme importance before the processing of the block into smaller stone products or during the reconstruction of older stone elements or sculptures. The purpose of “in situ” measurements is to prepare a simple and fast method for the evaluation of materials compactness and for production work.
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Abstract

An emerging ultrasonic technology aims to control high-pressure industrial processes that use liquids at pressures up to 800 MPa. To control these processes it is necessary to know precisely physicochemical properties of the processed liquid (e.g., Camelina sativa oil) in the high-pressure range. In recent years, Camelina sativa oil gained a significant interest in food and biofuel industries. Unfortunately, only a very few data characterizing the high-pressure behavior of Camelina sativa oil is available. The aim of this paper is to investigate high pressure physicochemical properties of liquids on the example of Camelina sativa oil, using efficient ultrasonic techniques, i.e., speed of sound measurements supported by parallel measurements of density. It is worth noting that conventional low-pressure methods of measuring physicochemical properties of liquids fail at high pressures. The time of flight (TOF) between the two selected ultrasonic impulses was evaluated with a cross-correlation method. TOF measurements enabled for determination of the speed of sound with very high precision (of the order of picoseconds). Ultrasonic velocity and density measurements were performed for pressures 0.1–660 MPa, and temperatures 3–30XC. Isotherms of acoustic impedance Za, surface tension #27; and thermal conductivity k were subsequently evaluated. These physicochemical parameters of Camelina sativa oil are mainly influenced by changes in the pressure p, i.e., they increase about two times when the pressure increases from atmospheric pressure (0.1 MPa) to 660 MPa at 30XC. The results obtained in this study are novel and can be applied in food, and chemical industries.
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Abstract

Ultrasonic processing in the cavitation mode is used to produce the composite materials based on the metal matrix and reinforcing particles of micro- and nano-sizes. In such a case, the deagglomeration of aggregates and the uniform distribution of particles are the expected effects. Although the particles can not only fragment in the acoustic field, they also can coagulate, coarsen and precipitate. In this paper, a theoretical study of processes of deagglomeration and coagulation of particles in the liquid metal under ultrasonic treatment is made. The influence of various parameters of ultrasound and dispersion medium on the dynamics of particles in the acoustic field is considered on the basis of the proposed mathematical model. The criterion of leading process (coagulation or deagglomeration) has been proposed. The calculated results are compared with the experimental ones known from the scientific literature.
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