Measurement Of Propagation Velocity Research Articles

Evaluation of cortical bone strength using a quantitative ultrasound measurement device in dogs.

This study was performed to evaluate cortical bone strength in dogs using a quantitative ultrasound measurement device. In this study, 16 clinically healthy dogs with no lameness underwent measurement of the ultrasound propagation velocity of cortical bone (namely, speed of sound [SOS]) at the radius and tibia. Additionally, computed tomography examination with a calibration phantom was performed in 10 dogs. We calculated the bone mineral density (BMD) and Young's modulus from the computed tomography data using bone strength evaluation software. SOS, BMD, and Young's modulus were statistically compared between the radius and tibia. In addition, we examined the correlation between SOS and BMD and between SOS and Young's modulus. We also examined the correlation between SOS and age in the 13 dogs whose age was known. BMD and Young's modulus were not significantly different between the radius and tibia, but SOS was significantly different (P<0.05). Moreover, SOS and BMD showed a positive correlation in both radius and tibia. Similarly, SOS and Young's modulus showed a positive correlation. In addition, SOS and age showed a strong positive correlation (radius: r=0.77, P<0.05, tibia: r=0.83, P<0.05). Our finding that SOS of the radius and tibia cortical bone was correlated with BMD and Young's modulus indicates that quantitative ultrasound can be useful for evaluating cortical bone strength in dogs.

Shockwave velocimetry using wave-based image processing to measure anisotropic shock emission

Noninvasive optical measurements of the shockwave propagation velocity using multiple pulse illumination allow deducing the shockwave pressure amplitude through Hugoniot relations and an appropriate equation of state of the medium. This technique is particularly useful for spatially resolved measurements near the shockwave emission site. Due to diffraction, however, a shockwave front can significantly change its morphology, rendering precise velocity measurements non-trivial. As solution we propose a wave front evolution (WaFE) velocimetry technique, which applies Huygens principle. We take a shadowgraph of the wave front at subsequent times as initial condition for the acoustic Helmholtz equation and numerically propagate the fronts in time. From the instance of time, when two subsequently taken wave front shadows numerically interfere and form one sharp wave front, the local shock velocity is obtained and the local shock pressure amplitude measured. With artificial test images, it is shown that this technique has excellent sub-pixel accuracy, robustness to noise, and can work with low contrast images and even overlapping and interfering wave fronts. The software is made available freely and can be applied to general shock front velocity measurements. We apply WaFE to determine the anisotropic shockwave emission from an elongated laser-induced plasma in water from shadowgraphs of the shockwave front imaged four times onto the same camera frame using multiple pulse illumination at a repetition rate of 60 MHz. The direction dependence of attenuation of the shockwave pressure amplitude is measured at distances of 50–300 μm to the plasma.

Study of Hedge Ignition and Flame Propagation Characteristics of Unsymmetrical Dimethylhydrazine and Its Metamorphosed Mixtures in a Nitrogen Tetroxide Atmosphere

Unsymmetrical dimethylhydrazine (UDMH) is a common liquid propellant widely used in rocket engines and other applications. The safety of UDMH in service is affected by its slow oxidation during long-term storage to form impurities such as dimethylamine (DMA) and formaldehyde dimethylhydrazone (FDH). How these impurities affect combustion performance is not known, and in order to assess these effects, the present experiments investigated the combustion characteristics of self-igniting fuels and carried out ignition delay time measurements and flame propagation velocity measurements of pure UDMH and its denatured mixtures in a nitrogen tetroxide (NTO) atmosphere. This experiment was carried out to measure the delay time of hedge ignition of pure UDMH and qualitative analysis of its flame propagation properties under vacuum conditions at room temperature (T = 293 K). Ignition delay time measurements and flame propagation characterization were performed under the same experimental conditions for UDMH mixed with 1%, 5% and 10% FDH, UDMH mixed with 1%, 5% and 10% H2O, UDMH mixed with 1%, 5% and 10% DMA, as well as for UDMH mixed with the same proportions of the three substances (1%, 5% and 10%). The flame propagation characteristics were analyzed. The results showed that the incorporation of DMA, H2O and FDH in different proportions could inhibit the combustion of UDMH to varying degrees and prolong its ignition delay time. It is worth noting that the introduction of FDH had the least effect on it, and the least effect was observed at a concentration of 1%. In contrast, the effect of DMA on UDMH is more obvious, and the addition of H2O has the largest increase in the ignition delay time of UDMH. In the flame propagation experiment, the flame of the experimental group adding H2O can no longer fill the whole experimental window, while the other experimental groups can still make the window full of flame. Combined with the measurements of the ignition delay time, it can be seen that the moisture content has the greatest effect on the combustion characteristics.

Development of sweep frequency ultrasonic interferometer for high precision velocity measurement in liquids.

An ultrasonic interferometer with variable separation between the transducer and reflector is widely used for the measurement of ultrasonic propagation velocity in liquids. The inherent limitation of such an interferometer is due to the mechanical movement of its reflector for ultrasonic wavelength measurement in a liquid medium. It is observed that the ultrasonic velocity measurement precision is adversely affected at higher frequencies compared to lower ones. For instance, in our experimentation, a standard deviation of ±21.5m/s (±1.43%) was obtained for velocity measurement at 1.84MHz with the consideration of two consecutive maxima, which increases drastically to ±76.8m/s (±5.12%) at 9.4MHz. These measurements can significantly be improved by considering many maxima and averaging for wavelength estimation. However, it still requires design attention and improvement, particularly for higher frequencies. In this article, a sweep-frequency based ultrasonic interferometer design with a fixed separation for liquid characterization is proposed and described. This technique overcomes the limitations of mechanical movement systems and also provides a better and uniform precision for lower as well as higher frequencies. The functionality of the developed sweep frequency method was tested in water, carbon tetrachloride, ethylene glycol, and glycerol, which shows good agreement with literature values. The velocity measurement in double distilled water by the developed technique at 1Hz sweep resolution has shown an improved standard deviation of ±0.74m/s (±0.05%) at 9.4MHz.

ПРИМЕНЕНИЕ МЕТОДА С ИСПОЛЬЗОВАНИЕМ ИЗГИБНЫХ ВОЛН ДЛЯ ОБСЛЕДОВАНИЯ ПЛИТНЫХ И СТЕНОВЫХ КОНСТРУКЦИЙ

The paper considers the possibility of estimating the stiffness and strength characteristics of slab and wall structures by thickness based on the results of experimental studies of measurements of bending wave propagation velocities of different frequency ranges. Theoretical dispersion curves of bending wave velocities as a function of their lengths for plate structures of different characteristics at different thicknesses are constructed. Comparison of theoretical and experimental results for estimation of the state of materials by the thickness of slabs has been carried out. Experimental measurements of bending wave propagation velocities on the walls of an existing building in St. Petersburg have been carried out, and the primary assessment of masonry stiffness properties and control of the design wall thickness have been performed. The results of the studies confirmed the possibility of assessing the characteristic of the state of materials in the thickness of slab and wall structures by comparing experimental studies of bending wave propagation velocity measurements at different frequency ranges. The use of bending wave method also allows controlling the design thickness of slab, wall and lining at one-sided access

On the evolution of artificially maturated hydrocarbon source rocks

The elastic moduli are a function of properties that could vary between samples and change during maturation. Consequently, the effects of organic matter maturation on the elastic wave velocities of organic-rich rocks are challenging to describe. This work analyzes the isolated maturation effects on the organic content, pore volume, microstructure, and propagation velocities of elastic waves. To avoid any initial rock heterogeneity, we prepared a series of homogeneous samples from a unique outcrop block collected on the Eagle Ford formation with mineral composition initially determined using X-ray diffraction. From the initial set, four samples were held in their original condition and four were artificially maturated by hydropyrolysis until transformation rates were up to 95%. Then, the evolution of the sample properties was examined using an association of LECO TOC, Rock-Eval pyrolysis, vitrinite reflectance, mercury intrusion porosimetry (MIP), and ultrasonic pulse propagation. In addition, scanning electron microscopy images registered the microstructure evolution. To evaluate the effects of maturation on pore geometry and the organic matter elastic moduli, we analyze the relationship between the measured quantities using a rock physics inclusion model with the unmeasured properties taken as fitting parameters. The hydropyrolysis maturation increases the vitrinite reflectance from the initial 0.55% to 1.34% on the most matured sample. A total organic carbon reduction from 4.2% to 2.1% and a porosity increase from 9.2% to 21% are associated with observed maturation. The geochemical characterization on cleaned samples reveals an initial increment of soluble organic matter followed by a monotonical reduction related to oil migration out of bulk volume. The measurement of wave propagation velocities as a function of confining pressure displays an increasing pressure sensitivity with a downward trend in both velocity moduli. The petrophysical analysis indicates that the porosity increases through organic matter consumption and pore creation. The rock physics diagnoses indicate a decrease in the pore aspect ratio with an increase in the elastic modulus of the organic matter with maturation.

Finite velocity of ECG signal propagation: preliminary theory, results of a pilot experiment and consequences for medical diagnosis

A satisfactory model of the biopotentials propagating through the human body is essential for medical diagnostics, particularly for cardiovascular diseases. In our study, we develop the theory, that the propagation of biopotential of cardiac origin (ECG signal) may be treated as the propagation of low-frequency endogenous electromagnetic wave through the human body. We show that within this approach, the velocity of the ECG signal can be theoretically estimated, like for any other wave and physical medium, from the refraction index of the tissue in an appropriate frequency range. We confirm the theoretical predictions by the comparison with a direct measurement of the ECG signal propagation velocity and obtain mean velocity as low as v=1500 m/s. The results shed new light on our understanding of biopotential propagation through living tissue. This propagation depends on the frequency band of the signal and the transmittance of the tissue. This finding may improve the interpretation of the electric measurements, such as ECG and EEG when the frequency dependence of conductance and the phase shift introduced by the tissue is considered. We have shown, that the ECG propagation modifies the amplitude and phase of signal to a considerable extent. It may also improve the convergence of inverse problem in electrocardiographic imaging.

Precision and Accuracy of Pulse Propagation Velocity Measurement in Power Cables

The partial discharge (PD) measurement is an important method used in determining the condition of medium- and high-voltage cable insulation. Considering the propagation velocity of PD signals in power cables is necessary for determining the location of PD defects. However, the determination of velocity is not straightforward due to propagation-related attenuation and dispersion, which distorts the PD pulse waveform. This introduces a degree of uncertainty into the pulse velocity as well as the PD source locations determined based on that velocity, which is usually considered to be of constant value in PD analysis. This paper investigates the accuracy of the pulse propagation velocity measurement in power cables. Tests were performed on a medium voltage power cable in a laboratory setting using two sets of PD-specific measurement equipment: a high-frequency current transformer (HFCT) and an IEC 60270-compliant conventional measurement system. The propagation velocities and their statistical variability were determined using both devices to assess the uncertainty of the propagation velocity measurement. The results indicate that the measured velocity is slightly higher in the case of the HFCT and that the 50% peak threshold value should be used rather than the peak value of PD sensor response waveforms to increase the precision of velocity measurements.

Hugoniot Relation for a Bow-Shaped Detonation Wave Generated in RP Laser Propulsion

Repetitive-pulsed (RP) laser propulsion is expected to replace chemical propulsion systems because it can reduce launch costs. A laser-supported detonation wave (LSD) plays an important role in the thrust-generation process of RP laser propulsion. The LSD propagation mechanism has been studied. Nevertheless, the LSD propagation velocity measured in an earlier study was lower than the Chapman–Jouguet (CJ) velocity, which meant that Hugoniot analysis produced no solution. The findings suggest that the radial flow from the central axis of LSD exerts some effects, but it has not been evaluated quantitatively. Two-dimensional axisymmetric computational fluid dynamics (CFD) analysis using the measured propagation velocity was performed for this study to evaluate effects of the radial flow of a bow-shaped LSD. Results show that the ratios of the radial flow of mass, momentum, and enthalpy from the central axis can be calculated, respectively, as 0.82, 0.13, and 0.17. Additionally, the measured propagation velocity of a bow-shaped LSD was shown to be higher than the CJ velocity calculated using the two-dimensional axisymmetric CFD reproducing the experiment conditions.

Comprehensive use of the Gutenberg–Richter law and geotomography for improving seismic hazard evaluation in hard coal mines

Mining-induced seismicity occurs in numerous underground mines worldwide where extraction is conducted at great depths or in areas characterised by complex tectonic structure. It is accompanied by rock bursts, which result in the loss of working functionality and the possibility of accidents among personnel. The issue of a constant and reliable seismic hazard evaluation is of key significance for both the safety of miners and the stability of production. Research on its improvement is directed at developing new interpretive solutions and methods. The nature of the presented solution is the complex interpretation of seismological data that characterise rock mass seismicity and of underground measurement results in the form of a map presenting the longitudinal wave propagation velocity distribution in the rock surrounding the mined coal seam. The solution was tested in hard coal mines located in the Upper Silesian Coal Basin. The mines are equipped with a modern seismological system enabling the constant monitoring of seismicity together with hazard level evaluation as well as with seismic apparatus for conducting periodic measurements of the seismic wave propagation velocity before the mining face. Comprehensive seismic hazard evaluation criteria were determined based on the obtained results, involving the anomaly of the Gutenberg–Richter law “b” value and the maximum longitudinal seismic wave propagation velocity in the roof rock. The obtained experience and the result validation of this new comprehensive hazard evaluation method confirm its practical usefulness and indicate the directions of improvement for the solution in question.

Reference installation for measuring acoustic parameters of solids

The issues of providing working standards of the 1st category of metrological organizations of the country with regard to modern needs in the field of ultrasonic measurements in solids are considered. There is presented a modernized reference installation designed for precision measurements of propagation velocities of longitudinal and shear ultrasonic waves and damping coefficient of longitudinal ultrasonic waves in solids. Measurements of acoustic parameters of solid media are made by pulse-echo and resonance methods using contactless broadband capacitive methods of excitation and registration of ultrasonic waves. This installation is used as working standard of the 1st category in accordance with the state verification schedule for measuring instruments of the propagation velocities and damping coefficient of ultrasonic waves in solids. The technical means included in the installation (mechanical and electronic parts) have been improved, analog measuring means have been replaced with digital ones, methods for measuring acoustic parameters of solids based on the use of digital measuring means have been developed and the thickness range of installed ultrasonic measures has been expanded. The composition and main components of the reference installation, the used measurement methods and the principles of operation of the installation in various operating modes are described. The technical and metrological characteristics of the installation are given. Sources of measurement error (uncertainty) were analyzed. The field of application of the results is high-precision measurements of the acoustic characteristics of solid media, metrological ensuring of ultrasonic non-destructive testing and diagnostics.

Geotechnical characterization of an amphibolite from Baixada Santista-SP, Brazil

This work presents the results of the characterization of a sound to slightly weathered amphibolite, sampled at Baixada Santista, on the coast of the state of São Paulo, in the southeastern region of Brazil. Initially, petrographic analysis of material sheets were performed. Characterization tests were carried out to determine the physical indexes and to determine p-wave propagation velocity. For the mechanical characterization of these materials, uniaxial compression and point load tests were carried out in two different loading directions. The results of the micro petrographic analysis indicate that an average of 66% of the analysed minerals did not present weathering and 34% percent of the minerals are the result of weathering. The physical characterization results indicate (average values) of apparent porosity equal to 2.77%, apparent absorption capacity of 0.92% and apparent specific dry mass of 2.69 g/cm3. The results of p-wave propagation velocity measurements indicate a 2.63% reduction in the wave velocity of the ones measured on parallel direction to the ones on perpendicular direction. As for the mechanical characterization tests, there was an average value of uniaxial compressive strength equal to 77.40 MPa for samples loaded on the parallel direction and 92.96 MPa for samples loaded on the perpendicular direction (differences of about 20%). For the point load compression tests, an Is50 value of 2.44 MPa was obtained for the samples loaded on the direction parallel to the foliation and of 5.41 MPa for the samples loaded on the perpendicular direction (increase of about 121%). The UCS/Is50 ratio was determined for both loading directions, being equal to 17.2 and 31.7 for samples loaded on the parallel and perpendicular directions to the foliation, respectively.

Factors other than fibrosis that increase measured shear wave velocity.

Shear wave elastography (SWE) is now becoming an indispensable diagnostic tool in the routine examination of liver diseases. In particular, accuracy is required for shear wave propagation velocity measurement, which is directly related to diagnostic accuracy. It is generally accepted that the liver shear wave propagation velocity reflects the degree of fibrosis, but there are still few reports on other factors that increase the shear wave propagation velocity. In this study, we reviewed such factors in the literature and examined their mechanisms. Current SWE measures propagation velocity based on the assumption that the medium has a homogeneous structure, uniform density, and is purely elastic. Otherwise, the measurement is subject to error. The other (confounding) factors that we routinely experience are primarily: (1) Conditions that appear to increase the viscous component; and (2) Conditions that appear to increase tissue density. Clinically, the former includes acute hepatitis, congested liver, biliary obstruction, etc, and the latter includes diffuse infiltration of malignant cells, various storage diseases, tissue necrosis, etc. In any case, it is important to evaluate SWE in the context of the entire clinical picture.

Linear annular path damage probability distribution based ultrasonic guided wave method for position imaging and tracking of multi-damage on plate-like carbon fiber composite structure

Plate-like carbon fiber composite is an important component of the main bearing structure of spacecraft and high-speed trains, which has significant advantages in reducing the dead weight and energy consumption, and improving the carrying capacity. However, due to long-term exposure to complex service environments, material properties will be changed, these changes accumulated to a certain extent will lead to structural damage, threatening equipment operation and personal safety. To facilitate the attainment of mastering structural health states, this paper proposes a damage position imaging and tracking technology based on linear annular path damage probability distribution and ultrasonic guided wave for composite plate-like structures. Firstly, according to the dispersion curve, the propagation velocity characteristics of guided wave on composite structure are analyzed. Then, combined with the limited number of measured propagation velocities, the group velocity of the A0 mode in each direction is fitted. Based on the fitted velocity, the time-of-flight (TOF) map for all search points on each path can be pre-constructed. Subsequently, the damage TOFs and absolute TOF difference threshold are combined to obtain the annular damage probability distribution map of each sensing path. Ultimately, the total damage probability of the whole monitoring region is obtained by summing up the path damage probability, which can directly reflect the current damage position. Experimental results show that the proposed method has obvious advantages in imaging and tracking of single or multiple damage positions. It is hoped that the findings in this paper can provide new ideas for long-term damage state monitoring of the composite structures.

Abstract 13216: Evaluation of Left Ventricular Flow Propagation Velocity From Multi-Dimensional Cardiac Imaging

Introduction: The propagation velocity (Vp) during the left ventricular (LV) early diastole has been proposed as a marker of the diastolic function. However, the measurement of Vp is limited to one-dimensional data from Color M-mode (CMM) echocardiography and does not consider the spatiotemporal variation of Vp. Methods: We introduce a new method to evaluate the LV diastolic flow propagation from multi-dimensional cardiac flow imaging. The proposed method estimates the local and instantaneous flow propagation velocity (V prop ) by fitting the first order wave equation to the velocity gradients with weighted least-squares. The proposed method was validated using the synthetic vortex ring flow data. The method was applied to the LV flow data acquired with two-dimensional phase-contrast magnetic resonance imaging (pc-MRI) and 4D flow MRI. Results: The V prop estimated from multi-dimensional data has about 50% less error than the V prop from one-dimensional data. Fig. 1(a) shows the waveforms of the mitral inflow velocity, the IVPD, and the propagation intensity (I prop ) during the LV diastole of a normal filling patient. During early diastole, the timing of peak flow propagation coincides with the peak intraventricular pressure difference. Fig. 1(b) presents the fields of the blood flow velocity, the V prop , and the relative pressure from the timeframes indicated using the dotted lines in the waveform plots. The flow propagation towards the apex is mainly located at the front of the inflow jet and downstream of the vortex ring formed near mitral valve tips. Conclusions: This study introduces a novel propagation velocity measurement method for multi-dimensional cardiac flow imaging and demonstrated the V prop ’s spatial distribution temporal evolution.

Measurement of Ultrasound Propagation Velocity in Liquids Using an FPGA Module

The design and development of an ultrasonic device for the measurement of ultrasonic propagation velocity in liquids based on Field Programmable Gate Array (FPGA) architecture is described. The device was implemented using a DE0-Nano-SoC Development Kit FPGA development module, a 2x16 LCD Display, a 2-channel quadrature output optical encoder with push button, two ultrasonic transducers and an external module for interfacing with the transducers containing the circuits corresponding to the transmitter, receiver and amplifier. For the development, the Altera Integrated Development Environment (IDE) software called Quartus II was used, which allows the logical design and supports different HDL hardware description languages, such as Verilog and VHLD. Although the device was calibrated to measure the acoustic velocity of water in the range of 35°C to 40°C, due to its design characteristics it is feasible to extend its application to measure acoustic velocity in different liquids, delimiting the operation intervals. The device acquires 100 readings per second, calculates the average with polynomial adjustment and displays the value of the ultrasonic propagation velocity in the fluid with a resolution of 0.01 [m/s] with a refresh rate of one second.

Fully Coupled Three-Dimensional Simulation of Downward Flame Spread over Combustible Material.

Three-dimensional simulations of laminar flame propagating downwards the vertical surface of a rigid polyurethane slab heated by a radiative panel are presented and compared with the measurement data. The gas-phase model (ANSYS Fluent) allows for finite-rate volatile oxidation, soot formation and oxidation, emission, transfer, and absorption of thermal radiation. The solid-phase model Pyropolis considers heat transfer across the material layer and generation of combustible volatiles in thermal decomposition of the material. Kinetic model of material decomposition is derived to obey the microscale combustion calorimetry data for different heating rates. Transient behavior of propagating flame and pyrolysis zone, as well as spatial distributions of heat flux components, temperature, and mass burning rates over the specimen surface are examined. Variation of the thermal properties of the material during its thermal decomposition, as well as the specimen surface emissivity and reradiation are shown to be the important issues strongly affecting model predictions. Two distinct modes of counterflow flame spread, thermal and kinetic, are identified. In the thermal mode corresponding to fast chemistry in the gaseous flame, the flame propagation velocity is governed by the heating rate of the combustible material ahead of the flame front. Alternatively, in the kinetic mode, it is limited by the burning velocity of the volatile-air mixture forming ahead of the flame front. Simulation results are favorably compared with the measured propagation velocity.

Adaptation of the SonReb method to the mea-surement of the compressive strength of a two-layers concrete structure

The three most common building materials which most structures are built from are: timber, steel and Reinforcement Concrete (RC). Estimating the in-situ compressive strength is an imperative issue to evaluate the performance of in-situ concrete structures during their service life. Most codes and technical recommendations indicate that in-situ concrete strength should be estimated by means of cores, possibly supplemented by Non-Destructive tests. In this study a series of ultrasonic refraction measurements on a two layers slabs (mortar over concrete) are carried out in order to recover the velocity of the compression waves of each layer in view of combining the results with the rebound method in order to estimate the compressive strength of the mortar layer. Accuracy of measurements of compression wave propagation velocities and errors on the estimation of the compressive strength are investigated.

Multi-objective optimization to evaluate the compressive strength of concrete by combining non-destructive techniques

The compressive strength of concrete is one of the most important mechanical parameters in the evaluation of the mechanical performance of reinforced concrete structures. The recent methodology for the evaluation of the mechanical strength of concrete of an existing structure combines non-destructive testing (NDT) measurements, such as rebound measurement and ultrasonic wave propagation velocity measurement, with destructive measurements (sampling) in order to develop a conversion model, between mechanical strength and non-destructive measurements. The conversion model is then used to estimate the local value of the resistance at each location of the non-destructive measurements and thus to represent the spatial variability. The goal of this study is to propose a new methodology based on multi-objective optimization to predict the compressive strength of concrete and its variability based on NDT measurements. To this end, a large experimental and synthetic database of destructive and non-destructive tests was used. The conclusions drawn from the synthetic data will be compared with the results obtained on the real database in order to test the potential of the proposed methodology. This study shows the principle of the methodology and the first results of its effectiveness in predicting compressive strength and its variability.

Ultrasonic Monitoring of Part’s Height and Layer Thickness in Powder Bed Fusion

This paper presents a preliminary study on an in-situ ultrasonic measurement technique applied to monitoring part’s height and defect occurrence during the Laser Powder Bed Fusion process. Firstly the ultrasonic wave speed is determined for LPBF manufactured 100Cr6 samples with a pulse echo configuration and a 10Mhz ultrasonic wave. A measured propagation speed value, of 5660 ±100m/s in every direction confirms the isotropy of the obtained LPBF samples. Secondly, the ultrasonic pulse echo technique is used to monitor the part’s height evolution during the process based on the measured propagation velocity. This new method provides in-situ measurements showing that the actual remelted layer thickness value oscillates in the range of ± 30% of the theoretical layer thickness.