Anomalous Ultrasonic Attenuation in Aqueous NaCl Solutions

Pal, Barnana; Kundu, Sourav

doi:10.13189/ujc.2013.010304

Cited by 4 publications

(2 citation statements)

References 29 publications

(54 reference statements)

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“…Still, the common experience is that, though velocity values obtained are in good agreement with each other, attenuation values show wide variation and deviates much from theoretical calculations. To be specific, we consider the data available in the literature for pure water [2,3,[5][6][7][8]. These are presented in Table-1.…”

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confidence: 99%

Pulse-echo method cannot measure wave attenuation accurately

Pal

2015

Ultrasonics

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A number of techniques with different degrees of accuracies have been devised for the measurement of acoustic wave attenuation in solids and liquids. Still, a wide variation is observed in the attenuation values in different materials reported in the literature. Present numerical study based on a 'propagating wave' model analysis clearly shows that the attenuation constant obtained from exponential fitting of the echo heights in pulse-echo method differs from the exact value of intrinsic attenuation in the medium, even in the ideal situation of plane wave propagation without diffraction, dispersion or scattering.Keywords: Pulse-echo technique, Attenuation measurement, Propagating wave model.Since the discovery of piezoelectric transducers, Pulse-echo method [1] has become the most popular experimental technique for the determination of acoustic velocity and attenuation in solids and liquids. Accurate measurement of attenuation becomes difficult due to reasons like diffraction, scattering and divergence of the ultrasonic beam. Efforts have been given to estimate relevant correction factors [1] and technical development as well [2][3][4]. Still, the common experience is that, though velocity values obtained are in good agreement with each other, attenuation values show wide variation and deviates much from theoretical calculations. To be specific, we consider the data available in the literature for pure water [2,3,[5][6][7][8]. These are presented in Table-1. A recent work by R Martinez et. al. [7] reports a comparison between the through-transmission and pulse-echo techniques for measuring attenuation in tri-distilled water at 25 o C and 19.8 o C. They observed high variation in the value of α measured at short distances from the transducer whereas at long distances measurements in the two methods produce comparable data but, the value differs widely from other reported values. Secondly, their result shows higher wave amplitude for pulse-echo method at far zone and attenuation value obtained from through transmission method is found to be a little higher than that obtained by pulse-echo method. P K Dubey et. al.[3] developed a high resolution technique based on very accurate measurement of echo amplitudes in pulse-echo set up and obtained a value for attenuation in distilled water at 34 o C comparable to the result reported by J M M Pinkerton [5]. In this communication we present a 'propagating-wave ' model approach [9] to analyze the pulse-echo response and from numerical calculation we show that the attenuation constant (α m ) obtained from an exponential fitting of the observed echo amplitudes deviates from the exponential decay constant (α) of the freely propagating wave.

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confidence: 99%

Pulse-echo method cannot measure wave attenuation accurately

Pal

2015

Ultrasonics

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“…The solute acts as scatterers in this measurement; that is, when the concentration of NaCl is high enough, ion clusters are created, and the effective cluster size also increases. [27,28]. We adjusted the NaCl concentration heuristically to acquire sufficient amplitude of flow signals.…”

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confidence: 99%

Image-Free Ultrasound Blood-Flow Monitoring Circuit System with Automatic Range-Gate Positioning Scheme: A Pilot Study

Park¹,

2021

Applied Sciences

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This work proposes a proof-of-concept ultrasound blood-flow-monitoring circuit system using a single-element transducer. The circuit system consists of a single-element ultrasonic transducer, an analog interface circuit, and a field-programmable gate array (FPGA). Since the system uses a single-element transducer, an ultrasound image cannot be reconstructed unless scanning with mechanical movement is used. An ultrasound blood-flow monitor basically needs to acquire a Doppler sample volume by positioning a range gate at a vessel region on a scanline. Most recent single-transducer-based ultrasound pulsed-wave Doppler devices rely on a manual adjustment of the range gate to acquire Doppler sample volumes. However, the manual adjustment of the range gate depends on the user’s experience, and it can be time consuming if a transducer is not properly positioned. Thus, automatic range-gate-positioning is more desirable for image-free pulsed-wave Doppler devices. This work proposes a circuit system which includes a new automatic range-gate-positioning scheme. It blindly tracks the position of a blood vessel on a scanline by using the accumulation of Doppler amplitude deviations and a hysteresis slicing function. The proposed range-gate-positioning scheme has been implemented in an FPGA for real-time operation and is based on addition-only computations, except for filter parts to reduce the complexity of computation in the hardware. The proposed blood-flow-monitoring circuit system has been implemented with discrete commercial chips for proof-of-concept purposes. It uses a center frequency of 2 MHz and a system-clock frequency of 20 MHz. The FPGA only utilizes 5.6% of slice look-up-tables (LUTs) for implementation of the range-gate-positioning scheme. For measurements, the circuit system was utilized to interrogate a customized flow phantom model, which included two vessel-mimicking channels. The circuit system successfully acquired Doppler sample volumes by positioning a range gate on a fluid channel. In addition, the estimated Doppler shift frequency shows a good agreement with the theoretical value.

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