Systems With Lumped Constants

The following paper is aimed at finding the effects of ultrasound on adsorption/desorption processes. Experiments concerning the ultrasonic power input indicate that particles absorb ultrasonic energy effectively if they are in resonance with the ultrasound. The ultrasonic energy is dissipated into heat. Hence, desorption processes are promoted. Desorption experiments at different frequencies show that neither particle oscillations nor cavitation effects are responsible for ultrasonically enhanced desorption processes for an adsorption system with surface diffusion as the rate-limiting step. Measured ultrasonic power distributions show that the ultrasonic field inside the adsorber is very inhomogeneous. With the temperature distribution inside the adsorber, the courses of concentration of ultrasonically enhanced desorption experiments can be explained by a hot-water desorption model. Thus, simulations substantiate the experimental results that thermal effects are responsible for ultrasonically enhanced desorption with the applied adsorption system.

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“…18 kHz). During propagation, it is attenuated by absorption in the propagation medium, , by cavitation bubbles, by particles, and at interfaces …”

Section: Theoretical Sectionmentioning

confidence: 99%

Effect of Ultrasound on Adsorption and Desorption Processes

Breitbach

Bathen

Schmidt–Traub

2003

Ind. Eng. Chem. Res.

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“…However, transducer response varies according to the material that it is in contact with, so that a substantially different response is observed for two transducers in contact compared to a transducer in contact with a biological sample. This issue is more of a problem in ultrasonic characterization of biological materials compared to engineering materials because the acoustic impedance mismatch between transducer and biological material is so much greater than between transducer and a material such as steel (10,12). Any frequency-dependent effects imposed on this acoustic impedance mismatch can then significantly affect the shape of the waveform and cause transit times determined from different pairs of points in reference and transmitted waveforms to vary.…”

Section: Resultsmentioning

confidence: 99%

“…In Figure 2a, reference and transmitted waveforms are lined up where the signal has clearly started, and a transit time of 10.1 µs is measured, from which a velocity of 1490 ms -1 is determined. This point represents the beginning of the main part of the energy associated with the pulse (10,11) and is referred to as the signal velocity. As remarked by Povey (ref 1, p. 24), the first dip in the waveform is frequently used in commercial instruments for determinations of velocity.…”

Section: Resultsmentioning

confidence: 99%

“…A technique typically used to ascertain the ultrasonic velocity in a food material is to measure the propagation of a short ultrasonic pulse through the food specimen (1,10). This pulse is constituted from the superposition of acoustic excitations spanning a continuous range of frequencies, with a width in frequency that is inversely proportional to the pulse length in time.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of Ultrasonic Velocities in Dispersive and Nondispersive Food Materials

Cobus

Ross

Scanlon

et al. 2007

J. Agric. Food Chem.

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Ultrasonic techniques are increasingly being used to evaluate the properties of food materials. Interpretation of the structure and dynamics on the basis of measured ultrasonic parameters requires rigorous definition of ultrasonic parameters such as velocity, especially since many food materials can display considerable dispersive behavior (changes in velocity with frequency). Agar gel (2% w/v) and agar gel (2% w/v) with a regular array of bubbles (8% volume fraction) were chosen as nondispersive and dispersive materials, respectively. Frequency and time domain techniques were used to analyze velocities. Signal, phase, and group velocities were identical in the agar gel and were indistinguishable from those of water (1500 m s(-1)), indicating the predominant effect of the bulk modulus of the water they contain on the longitudinal modulus of the gel. In contrast, the inclusion of the bubbles in the agar gel led to strongly dispersive behavior, with group velocities varying by 1000 m s(-1) above and below the 1500 m s(-1) of the agar gel without bubbles, depending on frequency. The addition of bubbles also led to strong attenuation in the agar gel with a peak occurring at a frequency associated with a band gap arising from destructive interference of sound waves. The results show that care must be taken when comparing ultrasonic parameters derived from experiments on food materials performed at different frequencies or with different ultrasonic techniques.

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“…The presented method for pressure reflection coefficient estimation shares a similar idea for measurements, where the sound energy reflected from a fixed, known geometric target is used as a reference for estimation of the unknown sound energy reflected from the investigated surface. The pressure reflection coefficient

is defined as shown in Equation ( 2 ) [ 19 ]

and it can be interpreted as a temporal ratio of the RMS value of the reflected sound pressure wave

with respect to the RMS value of the incident sound pressure wave

. Due to the methodology applied in this study, the reflection coefficient will be considered.…”

Section: Theoretical Background Of the Proposed Methodsmentioning

confidence: 99%

A Study of a Parametric Method for the Snow Reflection Coefficient Estimation Using Air-Coupled Ultrasonic Waves

Herman

Gudra

Opieliński

et al. 2020

Sensors

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In this paper, a method for estimating snow pressure reflection coefficient based on non-contact ultrasound examination is described. A constant frequency and air-coupled ultrasound pulses were used in this study, which incorporates a parametric method for reflected energy estimation. The experimental part was carried out in situ in the Antarctic, where the snow parameters were measured along with meteorological data. The proposed method represents a promising alternative for estimating the snow-water equivalent, since it uses a parametric approach, which does not require measurements of absolute values for acoustic pressure.

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Systems With Lumped Constants

Cited by 6 publications

References 10 publications

Effect of Ultrasound on Adsorption and Desorption Processes

Effect of Ultrasound on Adsorption and Desorption Processes

Comparison of Ultrasonic Velocities in Dispersive and Nondispersive Food Materials

A Study of a Parametric Method for the Snow Reflection Coefficient Estimation Using Air-Coupled Ultrasonic Waves

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