scholarly journals Measurements of Normal Incidence Reflection Loss as a Function of Temperature at the Water-Castor Oil Interface

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3289
Author(s):  
Dong-Gyun Han ◽  
Him-Chan Seo ◽  
Sungho Cho ◽  
Jee Woong Choi
Keyword(s):  
Reflection Loss ◽  
Acoustic Impedance ◽  
Castor Oil ◽  
Arrival Time ◽  
Normal Incidence ◽  
Sound Speeds ◽  
Two Fluids ◽  
Reflection Model ◽  
Comparison Results ◽  
Model Predictions

Reflection loss at the water-castor oil interface as a function of temperature was measured in a direction normal to the interface using a 200-kHz acoustic signal. The acoustic impedance of water increases with temperature, whereas that of castor oil decreases. The measured reflection losses varied from 30 to 65 dB, and a sharp rising peak in reflection loss was observed at the temperature at which the acoustic impedance of water became equal to that of castor oil. This temperature is called the temperature of intromission in this paper. These measurements were compared with the model predictions based on a Rayleigh-reflection model using the measured sound speeds of both fluids. The sound speeds in water and castor oil as functions of temperature are the input parameters of the Rayleigh-reflection model, and were measured directly using an arrival time difference method in the temperature range of 5 to 30 °C. The comparison results imply that temperature is an important factor affecting the reflection at the interface separating the two fluids.

Classification of Iron Meteorites with High Frequency Ultrasonic Waves

2019 ◽  
Vol 24 (2) ◽  
pp. 277-284
Author(s):  
Dris El Abassi ◽  
Bouazza Faiz ◽  
Abderrahmane Ibhi ◽  
Idris Aboudaoud
Keyword(s):  
Phase Velocity ◽  
Acoustic Impedance ◽  
Nickel Content ◽  
Normal Incidence ◽  
Ultrasonic Pulse ◽  
Ultrasonic Waves ◽  
Iron Meteorites ◽  
Acoustic Transducer ◽  
Pulse Echo ◽  
Non Destructive

We present the results of an ultrasonic pulse-echo technique and its potential to classify iron meteorites into hexahedrites, octahedrites and ataxites by determining their acoustic impedance and phase velocity. Our technique has been adapted from those used in the field of ultrasonic non-destructive investigation of a variety of materials. The main advantage of our technique is that it does not need any preparation of the meteorites like cutting and etching and therefore is rapid, easy and non-destructive. In essence, a broadband acoustic transducer is used in a monostatic pulse-echo configuration which means that both the transducer and the meteorite sample are located in a water bath and adjusted in the way that the ultrasonic pulse shit the meteorite sample at normal incidence. Then the reflected pulses from the front and rear faces of the meteorite sample are measured with the emitting transducer, digitally recorded and processed to analyze the signal. After Fourier transforming the echoed pulses from the front and the rear face of the meteorite sample, the calculated reflection coefficients yield the phase velocity and the acoustic impedance. Our study investigates a variety of iron meteorites collected in Morocco and other countries and it helps to understand how the nickel content of these meteorites affects the acoustic impedance. It reveals that the acoustic impedance of iron meteorites increases with increasing nickel content, so that a further refinement of our technique might have the potential to classify iron meteorites directly and reliably into hexahedrites, octahedrites and ataxites without destroying them.

scholarly journals Correlation of IOP with Corneal Acoustic Impedance in Porcine Eye Model

2017 ◽  
Vol 2017 ◽  
pp. 1-6
Author(s):  
Jun Zhang ◽  
Yi Zhang ◽  
Yang Li ◽  
Ruimin Chen ◽  
K. Kirk Shung ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Linear Correlation ◽  
Acoustic Impedance ◽  
Mean Value ◽  
Reflection Model ◽  
Strong Linear Correlation ◽  
The Mean ◽  
Transducer Frequency ◽  
Transmission And Reflection

Purpose. The aim of this study is to correlate the intraocular pressure (IOP) change with the acoustic impedance of the cornea, in order to propose a noncontact and noninvasive method for IOP monitoring.Methods and Materials. A highly focused transducer (frequency 47-MHz; bandwidth 62%) was made to measure the echo from the anterior and posterior surfaces of intact porcine eyes, respectively. A multilayered transmission and reflection model was used to calculate the acoustic impedance. The linear relationship between acoustic impedance and intraocular pressure was analyzed by statistical method.Result.During pressure elevation from 10 mm Hg to 50 mm Hg, the mean acoustic impedance of the posterior cornea increased from 1.5393 to 1.5698 MRayl, which showed a strong linear correlation (R=0.9849;P=0.0022). Meanwhile, the mean value of the anterior cornea increased from 1.5399 to 1.5519 MRayl, and a less significant correlation was observed (R=0.7378;P=0.0025).Conclusion. This study revealed a linear correlation between intraocular pressure and acoustic impedance of the cornea, thus demonstrating a potentially important method to noninvasively measure the intraocular pressure in vivo.

scholarly journals Calibrating the Robertson’s Platoon Dispersion Model on a Coordinated Corridor with Advance Warning Flashers

2017 ◽  
Vol 2623 (1) ◽  
pp. 10-18
Author(s):  
Li Zhao ◽  
Laurence R. Rilett ◽  
Ernest Tufuor
Keyword(s):  
High Speed ◽  
Arrival Time ◽  
Dispersion Model ◽  
Urban Traffic ◽  
Smoothing Factor ◽  
Signal Coordination ◽  
Comparison Results ◽  
Time Coefficient ◽  
Dispersion Patterns ◽  
Platoon Dispersion

Platoon dispersion (PD) is the foundation of traffic signal coordination in an urban traffic network. PD describes the phenomenon by which vehicles depart from an upstream intersection as a platoon and begin to disperse before they arrive at the downstream intersection. Recently, advance warning flashers (AWFs) have been applied in many high-speed corridors. There is a need to update the traditional PD model to include the effect of AWFs. This paper examines the traffic flow dispersion patterns when an AWF is present and tests the hypothesis that the AWF will affect PD on a coordinated signal corridor. Platoon vehicles, which are not affected by the operation of the AWF, are used for comparison. Results show that when the AWF effect is included in the PD model, the smoothing factor F of the Robertson’s PD model ranges from 0.11 to 0.13. This range is smaller than the smoothing factor without the AWF effect. The platoon arrival time coefficient β ranges from 0.777 to 0.819 with the AWF effect. This is approximately the same as the default value of 0.8 in the TRANSYT simulation model. The PD coefficient α increases from an average of 0.11 with the AWF effect to an average of 0.24 without the AWF effect, which indicates an increase in roadway friction. It was concluded that AWFs increase the dispersion of the platoons, which might affect signal coordination.

Ocean Swell: How Much Do We Know

2017 ◽  
Author(s):  
Alexander V. Babanin ◽  
Haoyu Jiang
Keyword(s):  
Wave Amplitude ◽  
Arrival Time ◽  
Frequency Dispersion ◽  
Nonlinear Effects ◽  
Joint Analysis ◽  
Wave Forecast ◽  
Model Predictions ◽  
Forecast Models ◽  
Maritime Operations ◽  
Definition Of

Swell waves are present in more than 80% of ocean seas, and provide significant adverse impact on maritime operations. Their prediction by wave-forecast models, however, is poor, both in terms of wave amplitude and, particularly, arrival time. The very definition of ocean swell is ambiguous: while it is usually perceived as former wind-generated waves, in fact it may reconnect with the local wind through nonlinear interactions. The paper will bring together an overview of the complex swell problem. The visible swell attenuation is driven by a number of dissipative and non-dissipative processes. The dissipative phenomena include interaction with turbulence on the water and air sides, with adverse winds or currents. Non-dissipative contributions to the gradual decline of wave amplitude come from frequency dispersion, directional spreading, refraction by currents, and lateral diffraction of wave energy. The interactions with local winds/waves can, on the contrary, cause swell growth. Swell arrival time is the least understood and the most uncertain problem. Joint analysis of buoy observations and model reanalysis shows that swell can be tens of hours early or late by comparison with model predictions. Linear and nonlinear effects which can contribute to such biases are discussed.

Mapping lithofacies and pore‐fluid probabilities in a North Sea reservoir: Seismic inversions and statistical rock physics

Geophysics ◽  
2001 ◽  
Vol 66 (4) ◽  
pp. 988-1001 ◽  
Author(s):  
T. Mukerji ◽  
A. Jørstad ◽  
P. Avseth ◽  
G. Mavko ◽  
J. R. Granli
Keyword(s):  
North Sea ◽  
Seismic Data ◽  
Acoustic Impedance ◽  
Probability Distributions ◽  
Rock Physics ◽  
Normal Incidence ◽  
Seismic Inversion ◽  
Training Data ◽  
Well Log ◽  
Statistical Rock Physics

Reliably predicting lithologic and saturation heterogeneities is one of the key problems in reservoir characterization. In this study, we show how statistical rock physics techniques combined with seismic information can be used to classify reservoir lithologies and pore fluids. One of the innovations was to use a seismic impedance attribute (related to the [Formula: see text] ratio) that incorporates far‐offset data, but at the same time can be practically obtained using normal incidence inversion algorithms. The methods were applied to a North Sea turbidite system. We incorporated well log measurements with calibration from core data to estimate the near‐offset and far‐offset reflectivity and impedance attributes. Multivariate probability distributions were estimated from the data to identify the attribute clusters and their separability for different facies and fluid saturations. A training data was set up using Monte Carlo simulations based on the well log—derived probability distributions. Fluid substitution by Gassmann’s equation was used to extend the training data, thus accounting for pore fluid conditions not encountered in the well. Seismic inversion of near‐offset and far‐offset stacks gave us two 3‐D cubes of impedance attributes in the interwell region. The near‐offset stack approximates a zero‐offset section, giving an estimate of the normal incidence acoustic impedance. The far offset stack gives an estimate of a [Formula: see text]‐related elastic impedance attribute that is equivalent to the acoustic impedance for non‐normal incidence. These impedance attributes obtained from seismic inversion were then used with the training probability distribution functions to predict the probability of occurrence of the different lithofacies in the interwell region. Statistical classification techniques, as well as geostatistical indicator simulations were applied on the 3‐D seismic data cube. A Markov‐Bayes technique was used to update the probabilities obtained from the seismic data by taking into account the spatial correlation as estimated from the facies indicator variograms. The final results are spatial 3‐D maps of not only the most likely facies and pore fluids, but also their occurrence probabilities. A key ingredient in this study was the exploitation of physically based seismic‐to‐reservoir property transforms optimally combined with statistical techniques.

Dynamic Cylindrical Cavity Expansion of Compressible Strain-Hardening Materials

1991 ◽  
Vol 58 (2) ◽  
pp. 334-340 ◽  
Author(s):  
V. K. Luk ◽  
D. E. Amos
Keyword(s):  
Strain Hardening ◽  
Cylindrical Cavity ◽  
Normal Incidence ◽  
Cavity Expansion ◽  
Cylindrical Cavity Expansion ◽  
Model Predictions ◽  
Cylindrical Cavities ◽  
Compressible Materials ◽  
Aluminum Armor Plates ◽  
Good Agreement

We developed models for the dynamic expansion of cylindrical cavities from zero initial radii for compressible, elastic-plastic, rate-independent materials with powerlaw strain-hardening. Results from cavity-expansion models were used to derive perforation models to predict residual velocities and ballistic limits for rigid, conicalnose projectiles perforating strain-hardening target plates. We compared the numerical results from models for incompressible and compressible materials to show the effect of compressibility. To verify the models, we also compared the model predictions of residual velocities and ballistic limits with the data from terminal-ballistic experiments with tungsten projectiles impacting 5083-H131 aluminum armor plates at normal incidence. Very good agreement was obtained for impact velocities between 200 and 1,200 m/s and 12.7, 50.8, and 76.2-mm thick targets.

SEAFLOOR PROPERTIES DETERMINATION FROM ACOUSTIC BACKSCATTERING AT NORMAL INCIDENCE WITH A PARAMETRIC SOURCE

2000 ◽  
Vol 08 (02) ◽  
pp. 365-388 ◽  
Author(s):  
ANDREA CAITI
Keyword(s):  
Time Series ◽  
Surface Roughness ◽  
Wavelet Transform ◽  
Normal Incidence ◽  
P Wave ◽  
Sediment Layer ◽  
Time Frequency ◽  
Model Predictions ◽  
Parametric Sonar ◽  
Parametric Source

An inversion technique is proposed for the determination of the geoacoustic and morphological properties of the uppermost sediment layer. The methodology is based on the use of the backscattering acoustic return when the source is a parametric instrument steered at normal incidence with respect to the seafloor. The peculiarity of the parametric sonar (i.e., its narrow beam and the absence of sidelobes) allows for discriminating between the scattering effects due to surface roughness and those due to volume perturbations. The inversion procedure is based on the minimization of a discrepancy measure between data and model predictions. Model predictions are obtained as time series realization of a stochastic process, modeling the backscattering process with the Kirchoff approximation for surface scattering and the small perturbation theory for volume scattering. The BoRIS code is used to generate the time series predictions. It is important to note that the model is stochastic, i.e., the model predicted time series with the same nominal parameters may differ from one realization to another. However, by use of wavelet transform of the signals involved, and measuring the data-model discrepancy in a generalized time-frequency domain, the stochasticity of the problem is greatly reduced. In particular, the wavelet transform is insensitive to different model realizations obtained with the same set of parameters, and sensitive to changes in the parameters. By appropriately weighing the discrepancy in the wavelet domain, and exploiting the properties of the parametric source, it is possible to separately recover the parameters influencing the surface backscattering (acoustic impedance and surface roughness) and those influencing the volume backscattering (P-wave attenuation and volume inhomogeneity), avoiding ambiguities and nonuniqueness problems. The approach proposed requires, however, a precise calibration of the parametric sonar, in terms of source level and beam pattern. Comparison of inversion results with independently measured ground truth at three different sites in the Mediterranean Sea are reported.

scholarly journals Study of the Sound Absorption Properties of 3D-Printed Open-Porous ABS Material Structures

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1062 ◽  
Author(s):  
Martin Vasina ◽  
Katarina Monkova ◽  
Peter Pavol Monka ◽  
Drazan Kozak ◽  
Jozef Tkac
Keyword(s):  
Acoustic Impedance ◽  
Sound Absorption ◽  
Excitation Frequency ◽  
Acrylonitrile Butadiene Styrene ◽  
Noise Pollution ◽  
Normal Incidence ◽  
Material Structure ◽  
Absorption Properties ◽  
Impedance Tube ◽  
3D Printed

Noise pollution is a negative factor that affects our environment. It is, therefore, necessary to take appropriate measures to minimize it. This article deals with the sound absorption properties of open-porous Acrylonitrile Butadiene Styrene (ABS) material structures that were produced using 3D printing technology. The material’s ability to damp sound was evaluated based on the normal incidence sound absorption coefficient and the noise reduction coefficient, which were experimentally measured by the transfer function method using an acoustic impedance tube. The different factors that affect the sound absorption behavior of the studied ABS specimens are presented in this work. In this study, it was discovered that the sound absorption properties of the tested ABS samples are significantly influenced by many factors, namely by the type of 3D-printed, open-porous material structure, the excitation frequency, the sample thickness, and the air gap size behind the sound-absorbing materials inside the acoustic impedance tube.

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