Pair Of Transducers Research Articles

Transferring power and data simultaneously of different direction in ultrasonic contactless power transfer system

Ultrasonic contactless power transfer (UCPT) technology is a new kind of contactless power transfer (CPT) technology, which can be used to transfer power to loads in enclosed metal containers. In this paper, an UCPT system of transferring power and data simultaneously of different direction using only one pair of transducer is proposed. In the proposed system, power is transferred from the transmitting side to receiving side, and data is transferred in reverse direction simultaneously, from receiving side to transmitting side. The proposed system consists of power transfer channel and data backward transfer channel. The power transfer channel is modeled and the data backward transfer channel is analyzed in detail. 2ASK technology is used in data transfer channel. To show the effectiveness of the proposed system, an experimental setup is built. For power transfer channel, the output power is up to 40 W, and for data transfer channel, the data transfer rate is up to 1.6 kbps in ideal situation. When transferring a picture, the data transfer rate is 1.43 kbps and the output voltage is 5V which are realized at the same time.

High-frame-rate A-mode ultrasound for calibration-free cuffless carotid pressure: feasibility study using lower body negative pressure intervention

Purpose Existing technologies to measure central blood pressure (CBP) intrinsically depend on peripheral pressure or calibration models derived from it. Pharmacological or physiological interventions yielding different central and peripheral responses compromise the accuracy of such methods. We present a high-frame-rate ultrasound technology for cuffless and calibration-free evaluation of BP from the carotid artery. The system uses a pair of single-element ultrasound transducers to capture the arterial diameter and local pulse wave velocity (PWV) for the evaluation of beat-by-beat BP employing a novel biomechanical model. Materials and methods System’s functionality assessment was conducted on eight male subjects (26 ± 4 years, normotensive and no history of cardiovascular risks) by perturbing pressure via short-term moderate lower body negative pressure (LBNP) intervention (−40 mmHg for 1 min). The ability of the system to capture dynamic responses of carotid pressure to LBNP was investigated and compared against the responses of peripheral pressure measured using a continuous BP monitor. Results While the carotid pressure manifested trends similar to finger measurements during LBNP, the system also captured the differential carotid-to-peripheral pressure response, which corroborates the literature. The carotid diastolic and mean pressures agreed with the finger pressures (limits-of-agreement within ±7 mmHg) and exhibited acceptable uncertainty (mean absolute errors were 2.4 ± 3.5 and 2.6 ± 4.0 mmHg, respectively). Concurrent to the literature, the carotid systolic and pulse pressures (PPs) were significantly lower than those of the finger pressures by 11.1 ± 9.4 and 11.3 ± 8.2 mmHg, respectively (p < .0001). Conclusions The study demonstrated the method’s potential for providing cuffless and calibration-free pressure measurements while reliably capturing the physiological aspects, such as PP amplification and dynamic pressure responses to intervention.

Li-Ion Cell Safety Monitoring Using Mechanical Parameters: Part I. Normal Battery Operation

The normal operation of a 18650 lithium-ion cells has been monitored using rectangular rosette strain gauge and a pair of piezoelectric transducers. The sensors for mechanical measurements provide information about the cell deformation mechanism and electrodes structure during the cycling. The strain gauge signal revealed three type of mechanical processes. The predominant deformation pattern during galvanostatic discharge process is an isotropic cylindrical shrinkage relevant to the extraction of lithium ions from the graphite negative electrode. In the case of low-rate discharge in cyclic voltammetry mode, the deformation pattern changes to spherical growth when the state of charge falls below 40. In contrast, the thermal shrinkage and growth of the cell corresponds to simple decrease of the cell diameter with much smaller hysteresis effect. The ultrasound interrogation is able to detect repeatable progressive change of the acoustic waveform transferred across the cell in direction of the jellyroll diameter, which depends on the state of charge and does not undergo any significant changes at different cycling rates. The impact of the state of health under 2 h—rated charge/discharge cycling at 25 °C reveals slow progressive drift of the strain and acoustic signals corresponding to the growth of the cell size.

Measurement of Pipe and Fluid Properties With a Matrix Array-Based Ultrasonic Clamp-On Flow Meter.

Current ultrasonic clamp-on flow meters consist of a pair of single-element transducers that are carefully positioned before use. This positioning process consists of manually finding the distance between the transducer elements, along the pipe axis, for which maximum signal-to-noise ratio (SNR) is achieved. This distance depends on the sound speed, thickness, and diameter of the pipe and on the sound speed of the liquid. However, these parameters are either known with low accuracy or completely unknown during positioning, making it a manual and troublesome process. Furthermore, even when sensor positioning is done properly, uncertainty about the mentioned parameters, and therefore on the path of the acoustic beams, limits the final accuracy of flow measurements. In this research, we address these issues using an ultrasonic clamp-on flow meter consisting of two matrix arrays, which enables the measurement of pipe and liquid parameters by the flow meter itself. Automatic parameter extraction, combined with the beam-steering capabilities of transducer arrays, yields a sensor capable of compensating for pipe imperfections. Three parameter extraction procedures are presented. In contrast to similar literature, the procedures proposed here do not require that the medium be submerged nor do they require a priori information about it. First, axial Lamb waves are excited along the pipe wall and recorded with one of the arrays. A dispersion curve-fitting algorithm is used to extract bulk sound speeds and wall thickness of the pipe from the measured dispersion curves. Second, circumferential Lamb waves are excited, measured, and corrected for dispersion to extract the pipe diameter. Third, pulse-echo measurements provide the sound speed of the liquid. The effectiveness of the first two procedures has been evaluated using simulated and measured data of stainless steel and aluminum pipes, and the feasibility of the third procedure has been evaluated using simulated data.

Sound field optimization and particle trapping of confocal ultrasonic transducer

The nonlinear effect of high-intensity sound waves produces the acoustic radiation force (ARF), which are used for acoustic levitation and manipulation practical. With no special requirement for the physical and chemical properties of the controlled objects, acoustic levitation owns a promising application prospect. The common levitation scheme includes the standing-wave system and phased-array levitation system. The standing-wave system has poor performance in the aspects of the degree of spatial freedom, the ARF along the non-axial direction, and the levitation stability. The phased-array system requires a complex control system and a high production cost. Here, we propose a single-side acoustic levitation system based on the paired confocal focused transducers. By driving the transducer pairs with reverse phase mode, two anti-phase focused spherical waves interfere with each other, resulting in constant sound pressure of 0 Pa at the focus. The resulting potential well can achieve stable particle capturing and levitating. First, we verifed the theoretical feasibility of the system according to Huygens' principle. Then, using the finite element method, we analyzed the influences of structural and driving parameters on the sound field distribution, such as the angle between the transducer axis and the central axis of the structure and the excitation phase modes. Finally, we demonstrated the particle trappings under two kinds of excitation phase modes of the levitation system experimentally. The results show that, 1) the intensity of the dominating potential well reaches a strongest value when the structural angle is 45°; 2) as the excitation phases are 0, 0, π, and π, the sound field owns three potential wells which can capture three clusters of quartz sands, the primary potential well is stronger than the secondary one; 3) as the excitation phases are 0, π/2, π, and 3π/2, the sound field owns one potential well and captures one cluster of quartz sands. The isosurface of wave intensity around the potential well is more comprehensive than in the previous phase mode. The four-phase excitation improves the levitation stability better. The proposed levitation scheme can realize stable single- or multi-position capture of high-density objects in the fluid. Moreover, it has the advantages of low cost and a high degree of freedom.

Sound field construction and particle trapping based on confocal transducer pairs

The nonlinear effect of high-intensity sound waves produces the acoustic radiation force (ARF),which makes acoustic levitation and manipulation practical.Acoustic levitation has no special needs for the physical and chemical properties of the controlled objects and is hence a promising application prospect.The commonly used levitation schemes include the standing-wave and phased-array levitation systems.The standing-wave system is poor at spatial freedom,ARF along the non-axial direction,and levitation stability.The phased-array system requires a complex control system and a high production cost.Here,we propose a single-side acoustic levitation system based on confocal-focused transducers.By driving pairs of transducers with reverse phase mode,two anti-phase focused spherical waves interfere with each other,resulting in constant sound pressure of 0 Pa at the focus.The resulting potential well can achieve stable particle capture and levitation.First,we analyzed the theoretical feasibility of the system according to Huygens'principle.Then,depending on the finite element method,we studied the influence of structural and driving parameters on the sound field distribution,such as the angle between the transducer axis and the central axis of the structure and the excitation phase modes.Finally,we demonstrated the particle trapping and thus verified the potential though distribution under two kinds of excitation phase modes of the levitation system experimentally.We found these results as follows.The strength of the dominating potential well reaches the strongest as the structural angle is 45º.As the excitation phases are 0,0,π,π,the sound field owns three potential wells which capture three clusters of quartz sands;the primary potential well is stronger than the secondary one.As the excitation phases are 0,π/2,π,and 3π/2,the sound field owns one potential well and captures one cluster of quartz sands.The isosurface of wave intensity around the potential well is more comprehensive than in the previous phase mode.The four-phase excitation improves the levitation stability better.The proposed levitation scheme can realize stable single-or multi-position capture of high-density objects in the fluid.Moreover,it has the advantages of low cost and a high degree of freedom.

Lung Ultrasound for Imaging of B-Lines in Dogs and Cats-A Prospective Study Investigating Agreement between Three Types of Transducers and the Accuracy in Diagnosing Cardiogenic Pulmonary Edema, Pneumonia and Lung Neoplasia.

Simple SummaryThe high usefulness of thorax ultrasound examination in diagnosing lower respiratory tract diseases is well-evidenced in both human and veterinary medicine. However, the type of transducer (microconvex, linear, and phased array) which is most effective in the examination of dogs and cats remains unknown. In this study we examined dogs and cats using the three types of transducers and we assessed how consistent they were in detecting and quantifying B-lines. Moreover, we developed a method that allowed to quantitatively evaluate the occurrence of B-lines in cardiogenic pulmonary edema (CPE), pneumonia and lung neoplasm, referred to as the lung ultrasound score (LUSscore). Our results indicate that microconvex and linear transducers can be used interchangeably. LUSscore may help distinguish between lung neoplasms (lower values) and CPE or pneumonia (higher values) in dogs, and between CPE (higher values) and pneumonia or lung neoplasms (lower values) in cats.Transthoracic heart and lung ultrasound (LUS) was performed in 200 dogs and cats with dyspnea to evaluate the agreement between the results obtained using three types of transducers (microconvex, linear, and phased array) and to determine the accuracy of LUS in discriminating between three conditions commonly causing dyspnea in companion animals: cardiogenic pulmonary edema (CPE), pneumonia, and lung neoplasm. The agreement beyond chance was assessed using the weighted Cohen’s kappa coefficient (κw). The highest values of κw (>0.9) were observed for the pair of microconvex and linear transducers. To quantify B-lines the lung ultrasound score (LUSscore) was developed as a sum of points describing the occurrence of B-lines for each of 8 standardized thoracic locations. The accuracy of LUSscore was determined using the area under ROC curve (AUROC). In dogs AUROC of LUSscore was 75.9% (CI 95%: 65.0% to 86.8%) for distinguishing between lung neoplasms and the two other causes of dyspnea. In cats AUROC of LUSscore was 83.6% (CI 95%: 75.2% to 92.0%) for distinguishing between CPE and the two other causes of dyspnea. The study shows that results obtained with microconvex and linear transducers are highly consistent and these two transducers can be used interchangeably. Moreover, the LUSscore may help identify dogs with lung neoplasms and cats with CPE, however its diagnostic accuracy is only fair to moderate.

Elastic Properties Measurement Using Guided Acoustic Waves.

Nondestructive evaluation of elastic properties plays a critical role in condition monitoring of thin structures such as sheets, plates or tubes. Recent research has shown that elastic properties of such structures can be determined with remarkable accuracy by utilizing the dispersive nature of guided acoustic waves propagating in them. However, existing techniques largely require complicated and expensive equipment or involve accurate measurement of an additional quantity, rendering them impractical for industrial use. In this work, we present a new approach that requires only a pair of piezoelectric transducers used to measure the group velocities ratio of fundamental guided wave modes. A numerical model based on the spectral collocation method is used to fit the measured data by solving a bound-constrained nonlinear least squares optimization problem. We verify our approach on both simulated and experimental data and achieve accuracies similar to those reported by other authors. The high accuracy and simple measurement setup of our approach makes it eminently suitable for use in industrial environments.

Investigation of transcranial ultrasound delivery via Lamb wave mode conversion leveraging a transducer pair

Cranial Lamb waves have been recently proposed for the non-invasive identification of the mechanical properties of the cranial bone, the evaluation of its acoustic radiation characteristics, and the estimation of the elastic and transmission properties of cranial sutures. Few works have focused on the so-called Lamb mode conversion phenomenon for transcranial ultrasound delivery, in which an attempt was made to control the focal point within the brain for incident acoustic beams beyond the critical angle. In our study, we further investigate this problem by overcoming some of the limitations of previous works, which are mainly related to the use of simplified geometries and material properties. To this end, we experimentally and numerically investigate leaky Lamb waves in immersed cranial bones by adopting a two-step strategy. In the first step, the dispersion properties of leaky Lamb waves are retrieved in the 0–500 kHz range along the mechanical properties of the cranial bone layers. The material data are then used to determine, via numerical simulations, the range of frequencies in which Lamb mode conversion can be effectively exploited for transcranial focusing purposes. Finally, we experimentally validate the numerical findings by means of an immersed setup that utilizes a pair of ultrasonic transducers.

Ultrasonic S-wave responses of single rock joints filled with wet bentonite clay

Clay minerals are prevalent in rock discontinuities and have significant effects on mechanical, hydraulic and seismic properties of rock masses. Understanding seismic behaviours across individual clay-rich rock joints is of great importance in the fields of geology and earth sciences. However, the wave responses of individual clay-rich rock joints have not been well understood until now. This paper reports a laboratory investigation of ultrasonic S-wave propagation and attenuation across single rock joints filled with bentonite clays with varying degree of water saturation. In this study, a series of acoustic measurements were conducted on specimens of the bentonite clay-filled rock joint using a self-developed ultrasonic pulse-transmission test system that equipped with a S-wave transducer pair with a dominant frequency of 250 kHz. Based on the obtained laboratory data, the wave velocity, transmission ratio and the time-frequency-energy distribution of the S-waves transmitted through the bentonite clay-filled joint were calculated and evaluated. The experimental results show that the degree of water saturation of the bentonite clay greatly affects S-wave responses of the filled rock joint. In particular, an increase in the degree of saturation causes a nonlinear decrease in S-wave velocity. In addition, as the water saturation of the bentonite clay increases, the wave attenuation decreases; the minimum wave attenuation is reached at a saturation degree of 71.4% and then the attenuation increases slightly. Additionally, with the increase of the water saturation, the magnitudes of the S-wave energy transmitted across the bentonite clay-filled joint firstly increases and then decreases. The S-wave energy is mostly stored in the frequency range of 150 - 300 kHz regardless of the degree of water saturation of the bentonite clay. This finding indicates that the frequency partition of the transmitted S-waves rarely changes with the changing water saturation. The present work could not only compensate for the lack of laboratory-based research on wave behaviours across clay-rich rock joints but also provides insights into the interpretation of acoustic data from field tests for detecting, characterizing and monitoring rock discontinuities.

Non-invasive ultrasonic inspection of sludge accumulation in a pipe

Sludge accumulated inside a fluid-flowing pipe used in a chemical or semiconductor processing factory should be periodically removed to avoid flow blockage that increases undesirable pressure inside the pipe. Accordingly, it is common practice to periodically dismantle a pipe system, clean up the accumulate sludge, and reassemble. Therefore, an accurate estimation of sludge accumulation in the pipe is important to minimize the halting time of a chemical process using the system. Considering the lack of a practically efficient, non-invasive method to estimate the severity of sludge accumulation without interrupting the on-going chemical process, we propose an ultrasonic, non-invasive, real-time inspection method using a pair of ultrasonic wedge transducers installed circumferentially on the outer wall of a pipe at the same axial coordinate. To detect lowly accumulated sludge, an ultrasonic wave path from a transmitting transducer via a test pipe with accumulated sludge to a receiving transducer is carefully designed. The severity of sludge accumulation can then be determined by the amplitude of the longitudinal wave picked up by another transducer installed on the other side of the wall. We performed a series of experiments with steel and PVC pipes that are partially filled with water and sludge of different heights. The experimental results confirmed the effectiveness and practical viability of the proposed inspection method.

Acoustophoretic patterning of microparticles in a microfluidic chamber driven by standing Lamb waves

The contactless manipulation of microparticles and cells by using acoustic forces is important in many applications. However, multi-band acoustophoresis has been rarely investigated in the literature. In this Letter, we propose a microscale acoustofluidic system that has multiple orders of available Lamb modes for the acoustic trapping of microparticles at various frequencies. In our device, standing Lamb waves (SLWs) of specific orders can be selectively excited in a 300-μm-thick piezoelectric lithium-niobate (LiNbO3) crystal plate by a pair of interdigitated transducers (IDTs) at the corresponding frequency. We demonstrate the acoustophoretic trapping and patterning of 7-μm particles in a single acoustofluidic device with multiple available actuating frequencies. The approach to the proposed design and the working mechanisms are explained by using thin plate and a full-wave models that solve the dispersion relations and coupling fields of the piezoelectric SLW acoustofluidic system, respectively. Furthermore, we experimentally show that the stable and tight trapping of particles in the chamber can be achieved independently along two mutually orthogonal directions. This provides the essential ground for planar manipulations of microparticles and cells based on the proposed device. The results here can trigger more innovative designs and applications of acoustofluidic devices for microparticle manipulation and microfluidic mixing, with multi-frequency channels and a wide span of different actuating frequencies in one system.

The effect of phase modulation in dual-frequency excited standing surface acoustic wave (SSAW) on microparticle manipulation

Standing surface acoustic wave (SSAW) in a microfluidic channel generated from a pair of interdigital transducers (IDTs) has already shown its capability of particle accumulation at the pressure node and its potential in biomedical research. Manipulation of cells or microparticles to the desired position precisely is an important issue of this technology. Using the phase modulation in the dual-frequency excitation, the fundamental and third harmonic of the same IDTs simultaneously with the initial phase difference between them and the power ratio of the fundamental wave to the third harmonic of 85%, the positions of three pressure nodes of the SSAW in the microchannel moves at different rates because of changes to the synthesized waveform and resultant acoustic radiation force. Meanwhile, percentages of microparticles at each pressure node also vary with the initial phase. Experimental measurement of green fluorescent microspheres in a diameter of 4 µm in a 300 µm-microchannel driven by SSAW at 6.2 and 17.7 MHz simultaneously has a good correlation with the numerical prediction (R2 = 0.967 and 0.89 for the position of each pressure node and the percentage of microspheres accumulated at each pressure node in the range of initial phase from 0° to 360°, respectively, where R is the correlation coefficient). This proposed method could provide more tunability for SSAW-based microparticle manipulation with few changes to the setup of lab-on-a-chip system.

WEB-ORIENTED COMPONENT SYSTEM FOR CONTROL OF PIPELINES BY ULTRASOUND DIRECTED WAVES

The paper presents the development of an approach to control the presence of inclusions inside steel pipelines of small, medium and large diameters by ultrasonic guided acoustic symmetric and antisymmetric modes of zero or first order. The approach created as a control system with distributed parameters. The distributed parameters of the control system are ultrasonic primary transducers and transmitters of the radio signal received by the primary transducers. Due to the peculiarities of the propagation of directional ultrasonic waves at a distance from several meters to tens of meters, one pair of primary transducers can control a significant part of the dangerous or potentially dangerous section of the pipeline. The dangerous section can be determined by geodetic measurements or by design documentation, such as air transitions or technological knees. The results of changing the propagation parameters of ultrasonic directional wave modes depending on the changes in the physical and mechanical parameters of the boundary to the walls of the pipelines are presented. It is found that symmetric and asymmetric modes react differently to changes in the environment, which allows to increase control accuracy and determining type of the environment (liquid or solid). The results are presented in the form of graphs and tables. The paper proposes to create a system based on a component approach, in order to unify parts of the system. It allows to realize the possibility of building it from parts of different manufacturers to increase its versatility and adaptation to the economic capabilities of the customer of such a control system. The components of the control system are the subsystems of primary ultrasonic transducers, information transmission and storage and processing. The paper presents an analysis of the transmission subsystem and proposes a wireless hierarchical structure taking into account the peculiarities of its operation at long distances and within settlements with a high level of radio signal noise. The data storage and processing component offered a software solution based on the Apache free license, which implements a file distribution system with high requirements for its data security and performance. The peculiarities of the proposed software solution, which allows the analysis of results using web technologies, have been analysed.

Surface acoustic wave assisted depinning of magnetic domain walls

We investigate the effects of high frequency strain on the depinning of magnetic domain walls in perpendicular anisotropy materials. Micron wide stripes of [Co(0.3 nm)/Pt(0.6 nm)]5 are patterned between a pair of identical inter-digital transducers that generate high frequency (114.8 MHz) standing surface acoustic waves. We use magneto-optical Kerr effect microscopy to characterize the thermally-assisted depinning of domain walls at defect sites within the strips. Our results show that the excitation of the domain walls with surface acoustic waves results in an increase in their depinning probabilities by approximately a factor of 10. Our data are consistent with a model in which the magnetoelastic anisotropies induced by the acoustic waves modulate the energy barriers that pin the domain walls. These results suggest an alternative route to domain wall depinning in thin films and nanostructures and are relevant to the development of racetrack memories, where domain wall pinning can result in reduced velocities and non-deterministic motion.

Hand Gesture Detection and Recognition Using Spectrogram and Image Processing Technique with a Single Pair of Ultrasonic Transducers

This paper presents an effective signal processing scheme of hand gesture recognition with a superior accuracy rate of judging identical and dissimilar hand gestures. This scheme is implemented with the air sonar possessing a pair of cost-effective ultrasonic emitter and receiver along with signal processing circuitry. Through the circuitry, the Doppler signals of hand gestures are obtained and processed with the developed algorithm for recognition. Four different hand gestures of push motion, wrist motion from flexion to extension, pinch out, and hand rotation are investigated. To judge the starting time of hand gesture occurrence, the technique based on continuous short-period analysis is proposed. It could identify the starting time of the hand gesture with small-scale motion and avoid faulty judgment while no hand in front of the sonar. Fusing the short-time Fourier transform spectrogram of hand gesture to the image processing techniques of corner feature detection, feature descriptors, and Hamming-distance matching are the first-time, to our knowledge, employed to recognize hand gestures. The results show that the number of matching points is an effective parameter for classifying hand gestures. Based on the experimental data, the proposed scheme could achieve an accuracy rate of 99.8% for the hand gesture recognition.

Study on flow field and measurement characteristics of a small-bore ultrasonic gas flow meter

A new structure is proposed for a DN25-type ultrasonic gas flow meter with a V-shape double sound channel arrangement. The flow field characteristics are analyzed including velocity curves for the four channel lines, velocity profiles for different cross-sections of the flow meter, and streamlines of the transducer channel sections. The metering characteristics of the flowmeter are measured using a Venturi nozzle device. When the pipeline flow rate is less than 2.26 m/s, the pipe installation does not have a significant effect on the velocity profile and the velocity in the channel lines. However, the error in the low-flow region is large, and the flow distortion directly affects the measurement accuracy. When an ultrasonic gas flow meter with an accuracy class of 1.5 is used with pipes containing a single or double bend upstream, the linear error doubles, low-flow error becomes a negative deviation, and reference error in the low-flow region becomes approximately 700%–949%. The installation structure of the first pair of transducers also affects the signal propagation of the transducers behind it. Therefore, it is critical to process the ultrasonic signal according to the flow field distribution and adopt different weighted algorithms to obtain accurate pipeline flow rates to improve the measurement accuracy of the ultrasonic flow meter.

Development of a steady-state microthrust measurement stand for microspacecrafts

A null-displacement thrust stand based on torsional pendulum configuration has been developed to characterize the steady-state microthrust for microspacecrafts. A pair of elastic transducers are applied to constrain the rotation of pendulum arm, so that the stand can maintain static with a small deflection under the loading thrust. The thrust can be obtained according to its linear relationship with the displacement difference with respect to the deflection, which can be detected by a laser displacement sensor. The thrust calibration is implemented via an electromagnetic coil collocated with a pair of permanent magnetic sheets. The repeatability, response time, position drift, noise, resolution and measuring range of the stand are analyzed. The stand features the resolution of 0.1 mN and the maximum available thrust of 2.7 N. Exhibiting the uncertainty less than 12.36%, both steady-state and throttleable thrusts produced by a laser-augmented combustion micromotor are characterized utilizing this stand.

A New Acoustic-Based Approach for Assessing Induced Adulteration in Bovine Milk.

Milk is an important dietary requirement for many populations due to its high nutritional value. However, increased demand has also made it prone to fraudulent activity. In this sense, scientists have sought to develop simple, low-cost, and portable techniques to achieve quality control of milk in industry and farms as well. This work proposes a new instrumentation system based on acoustic propagation and advanced signal processing techniques to identify milk adulteration by industrial contaminants. A pair of transmitter-receiver low-cost piezoelectric transducers, configured in a pitch-catch mode, propagated acoustic waves in the bovine milk samples contaminated with 0.5% of sodium bicarbonate, urea, and hydrogen peroxide. Signal processing approaches such as chromatic technique and statistical indexes like the correlation coefficient, Euclidian norm and cross-correlation square difference were applied to identify the contaminants. According to the presented results, CCSD and RMSD metrics presented more effectiveness to perform the identification of milk contaminants. However, CCSD was 2.28 × 105 more sensitivity to distinguish adulteration in relation to RMSD. For chromatic clustering technique, the major selectivity was observed between the contamination performed by sodium bicarbonate and urea. Therefore, results indicate that the proposed approach can be an effective and quick alternative to assess the milk condition and classify its contaminants.

Correlating ultrasonic pulse velocity and compression resistance of dry concretes at 54 kHz and 500 kHz

Nondestructive tests applying ultrasound in concrete is used for more than halfcentury. However, the difficulties in making transit time measurement in heterogeneous media have limited the spread use of these applications. The objective of this work is to present a metrological protocol to determine the correlation between the compressive strength of concrete specimens with about 1 year of cure with their respective longitudinal ultrasonic pulse velocity (UPV). From excitation signals sent through a tunable square wave using the direct transmission method, two pairs of transducers with central frequencies of 54 kHz and 500 kHz were used. UPV is determined by the relation between the length and the propagation time of flight the waveform travels within the concrete test specimens. The pieces were constructed according to ABNT NBR 5738:2015 (Concrete – Procedure for molding and curing of concrete specimens) and tested for compression according to ABNT NBR 5739:2007 (Cylindrical specimen compression test – Method of the test). The preliminary results obtained discloses a coherent increase in UPV and concrete strength. Moreover, the highest frequency leads to higher UPV. With the findings presented in this paper, it is possible to define a dual-frequency nondestructive ultrasound method to evaluate concrete resistance more reliable than the traditional approach.