Velocity Modulus Research Articles

Determination of Shear Wave Velocity Using Multi-channel Analysis of Surface Wave Method and Shear Modulus Estimation of Peat Soil at Western Johore

Shear wave velocity and shear modulus is common for geotechnical and geophysics engineer to the determine interaction of soil dynamic properties. Both of the dynamic properties were often related to dynamic loading such as earthquake, moving traffic, machineries and bomb blasting. The study was conducted at western part of Johore such as Parit Sulong and Pontian where deposition of peat soil were exists and recognised as problematic soils to the engineers. This study was carried out to determine the shear wave velocity of peat soil using Multi-channel Analysis of Surface Wave (MASW) method and estimation shear modulus of peat using empirical formula. To use the empirical formula, the density of peat soil was also needed thus using the peat sampler for every 0.5 meter depth to obtain the density. From the MASW test for both test sites, the shear velocity of peat at Parit Sulong is between 40 m/s and 55 m/s until depth of 1.5 m meanwhile at Pontian, the shear wave velocity between 21 m/s and 67 m/s until 2.5 m depth. Using shear velocity, shear modulus of peat were estimated for Parit Sulong are ranged between 1575kPa – 3514kPa and Pontian are ranged between 385kPa – 5117kPa. The shear velocity and shear modulus of peat are very low due to the unique characteristics of peat soils compared with other typical soil.

Galectin-3: A Link between Myocardial and Arterial Stiffening in Patients with Acute Decompensated Heart Failure?

BackgroundHeart failure is accompanied by abnormalities in ventricular-vascular interaction due to increased myocardial and arterial stiffness. Galectin-3 is a recently discovered biomarker that plays an important role in myocardial and vascular fibrosis and heart failure progression.ObjectivesThe aim of this study was to determine whether galectin-3 is correlated with arterial stiffening markers and impaired ventricular-arterial coupling in decompensated heart failure patients.MethodsA total of 79 inpatients with acute decompensated heart failure were evaluated. Serum galectin-3 was determined at baseline, and during admission, transthoracic echocardiography and measurements of vascular indices by Doppler ultrasonography were performed.ResultsElevated pulse wave velocity and low arterial carotid distensibility are associated with heart failure in patients with preserved ejection fraction (p = 0.04, p = 0.009). Pulse wave velocity, carotid distensibility and Young’s modulus did not correlate with serum galectin-3 levels. Conversely, raised galectin-3 levels correlated with an increased ventricular-arterial coupling ratio (Ea/Elv) p = 0.047, OR = 1.9, 95% CI (1.0‑3.6). Increased galectin-3 levels were associated with lower rates of left ventricular pressure rise in early systole (dp/dt) (p=0.018) and raised pulmonary artery pressure (p = 0.046). High galectin-3 levels (p = 0.038, HR = 3.07) and arterial pulmonary pressure (p = 0.007, HR = 1.06) were found to be independent risk factors for all-cause mortality and readmissions.ConclusionsThis study showed no significant correlation between serum galectin-3 levels and arterial stiffening markers. Instead, high galectin-3 levels predicted impaired ventricular-arterial coupling. Galectin-3 may be predictive of raised pulmonary artery pressures. Elevated galectin-3 levels correlate with severe systolic dysfunction and together with pulmonary hypertension are independent markers of outcome.

Analysis of motion of solid hydrogen tracer particles in oscillating superfluid flows

We have developed a relatively simple cryostat which allows us to image turbulent flows in superfluid helium at temperatures below 2 K, using frozen H2 particles. We analyze the statistics of the velocities of these solid tracers, which follow the turbulent flow generated by oscillating bodies. We have also studied one of the oscillators working in air at room temperature, and traced the flow with solid talcum particles for comparison. Images were recorded by a digital camera at 240 frames per second, while frequencies of the oscillators are between 20 to 45 Hz. The flow is characterized by a modified Reynolds number Reδ based on the viscous penetration depth δ. Software in a dedicated particle tracking velocimetry code allows us to compute the trajectories and velocities of tens of thousands of particles. We have obtained the number of particles for equally spaced intervals of the velocity modulus. For the oscillators in the superfluid, the probability of finding particles at higher velocities has an exponential decay. Within our resolution the statistics in the superfluid for oscillating objects with sharp borders is largely independent of Reδ, while the logarithmic decay at low velocities seems faster than for high velocities for rounded objects. On the other hand, for data taken in air the result is closer to a classical Gaussian distribution of velocities.

A kinetic theory approach to the dynamics of crowd evacuation from bounded domains

A mathematical model of the evacuation of a crowd from bounded domains is derived by a hybrid approach with kinetic and macro-features. Interactions at the micro-scale, which modify the velocity direction, are modeled by using tools of game theory and are transferred to the dynamics of collective behaviors. The velocity modulus is assumed to depend on the local density. The modeling approach considers dynamics caused by interactions of pedestrians not only with all the other pedestrians, but also with the geometry of the domain, such as walls and exits. Interactions with the boundary of the domain are non-local and described by games. Numerical simulations are developed to study evacuation time depending on the size of the exit zone, on the initial distribution of the crowd and on a parameter which weighs the unconscious attraction of the stream and the search for less crowded walking directions.

Acoustic phonon behavior of PbWO4 and BaWO4 probed by low temperature Brillouin spectroscopy

Temperature dependent acoustic phonon behavior of PbWO4 and BaWO4 using Brillouin spectroscopy has been explained for the first time. Low temperature Brillouin studies on PbWO4 and BaWO4 have been carried out from 320–20K. In PbWO4, we observe a change in acoustic phonon mode behavior around 180K. But in the case of BaWO4, we have observed two types of change in acoustic phonon mode behavior at 240K and 130K. The change in Brillouin shift ω and the slope dω/dT are the order parameter for all kinds of phase transitions. Since we do not see hysteresis on acoustic phonon mode behavior in the reverse temperature experiments, these second order phase transitions are not related to structural phase change and could be related to acoustic phonon coupled electronic transitions. In PbWO4, the temperature driven phase transition at 180K could be due to changes in the environment around the lead vacancy (VPb2−) changes the electronic states. In the case of BaWO4, the phase transition at 240K shows the decrease in penetration depth of WO3 impurity. So it becomes more metallic. The transition at 130K could be the same electronic transitions as that of PbWO4 as function of temperature. The sound velocity and elastic moduli of BaWO4 shows that it could be the prominent material for acousto-optic device applications.

Impact of change in pore-fill material on P-wave velocity

The problem of predicting the change in seismic velocities (P-wave and S-wave) upon the change in pore-fill material properties is commonly known as substitution. For isotropic rocks, P- and S-wave velocities are fundamentally linked to the effective P-wave and shear moduli. The change in the S-wave velocity or shear modulus upon fluid substitution can be predicted with Gassmann’s equations starting only with the initial S-wave velocity. However, predicting changes in P-wave velocity or the P-wave modulus requires knowledge of the initial P- and S-wave velocities. We initiated a rigorous derivation of the P-wave modulus for fluid and solid substitution in monomineralic isotropic rocks for cases in which an estimate of the S-wave velocity or shear modulus is not available. For the general case of solid substitution, the exact equation for the P-wave modulus depends on parameters that are usually unknown. However, for fluid substitution, fewer parameters are required. As Poisson’s ratio increases for the mineral in the rock frame, the dependence of exact substitution on these unknown parameters decreases. As a result, in the absence of shear velocity, P-wave modulus fluid substitution can, for example, be performed with higher confidence for rocks with a calcite or dolomite frame than it can for rocks with quartz frame. We evaluated a recipe for applying the new P-wave modulus fluid substitution. This improves on existing work and is recommended for practice.

Effective dynamic properties of random nanoporous materials with consideration of surface effects

The frequency-dependent dynamic effective properties (velocity, attenuation and elastic modulus) of nanoporous materials with randomly positioned spherical cavities are studied. The surface energy theory proposed by Huang and Wang (Handbook of micromechanics and nanomechanics. Pan Stanford Publishing Pte Ltd., Singapore, pp 303-348, 2013) is used to derive the non-traditional boundary condition on the surface of the nanocavity and further the scattering matrix of a single nanocavity. Then, the total wave field is obtained by considering the multiple scattering processes among the dispersive spherical cavities. The configuration average of the total wave field results in the coherent waves or the averaged waves. The numerical examples of the effective speed, the effective attenuation of the coherent waves and associated effective dynamic modulus of a nanoporous material are given and shown graphically. The effects of surface elasticity and the residual surface tension are both considered. Moreover, the influences of the non-symmetric parts of in-plane surface stress and the out-of-plane parts of the surface stress are also discussed based on the numerical examples.

Analysis of Residual Stresses in Steel Welded Parts Using Ultrasounds

<span><p><span style="font-family: Times New Roman; font-size: medium;" face="Times New Roman" size="3">Welding is an assembly process used in different industries. The residual stresses influences fatigue behavior, fracture strength, corrosion resistance and for these reasons knowing their values are important. During time, many destructive as well as nondestructive methods to evaluate residual stresses were developed. Stress is evaluated by inducing a sound wave with the frequency of several megahertz into the sample and measuring velocity related parameters. Besides stress which affects sound velocity there are many others characteristics of metals with same influence and for this reason sorting from different influences made the estimation difficult. On another hand ultrasonic technology has many wave modes to investigate materials including bulk wave (longitudinal and shear wave), surface wave (Rayleigh) every mode offering unique parameters for extracting information. Of the several characteristics that may be used to measure stress the most exploited seems to be sound velocity dependence on the elastic modulus. </span>Our research to estimate residual stress into steel welded parts is based on dependence between sound velocity and elastic modulus using longitudinal sound wave. To conduct the experiments was designed sample as a frame. The sample was loaded using adapted equipment and the results were used for FEA tools (SolidWorks SimulationXpress) to obtain the distribution of stresses and displacements. This approach allowed the location of points of interest to the investigation with ultrasound. The ultrasound investigation was made and presented in comparative tables<strong><span style="text-decoration: underline;">. </span></strong>It is found that the variation of the velocity of sound for the two charge states of the piece is, on average, 5.8 per thousand. Particular values of residual stress values are observed for the points corresponding with weld or fusion zone and heat-affected zone. The ultrasonic investigation permits the evaluation of bulk stress state of welded components with acceptable accuracy.</p>

Coupled hydro-mechanical response of saturated asphalt pavement under moving traffic load

Based on the Boit's theory, the governing equation was established to account for the response of moisture pavement. The analytical solutions were obtained through the expansion of Fourier series. Furthermore, the effects of parameters (i.e. hydraulic conductivity, traffic load velocity, drainage boundary and solid modulus) on dynamic response were investigated in terms of water-induced damage of pavement. Compared with the dry–elastic pavement, the negative normal stress in saturated asphalt pavement is concentrated beneath the traffic load, which may be a reason for a damage phenomenon in asphalt pavement. Hydraulic conductivity anisotropy plays a significant role in influencing the physical fields. Between vertical and horizontal hydraulic conductivity, the physical field almost depends on vertical hydraulic conductivity rather than horizontal hydraulic conductivity which just affects the horizontal pore-water velocity obviously. Moreover, the drained boundary evidently influences the seepage field of surface course with high permeability.

An Analysis of Consolidation Grouting Effect of Bedrock Based on its Acoustic Velocity Increase

Acoustic velocity is an important parameter to evaluate the mechanical properties of fractured rock masses. Based on the in situ acoustic velocity measurement data of ~20 hydropower stations in China, we assessed the acoustic velocity increase of rock masses as a result of consolidation grouting in different geological conditions, such as fault sites, weathered areas and excavation-induced damage zones. We established an empirical relationship between the acoustic velocity of rock masses before and after consolidation grouting, and examined the correlation between acoustic velocity and deformation modulus. A case study is presented about a foundation consolidation grouting project for an intake tower of Pubugou Hydropower Station. The results show that different types of rock masses possess distinct ranges for resultant acoustic velocity increase by consolidation grouting. Under a confidence interval of 95 %, the ranges of the increasing rate of acoustic velocity in a faulted zone, weathered zone, and excavation-induced damage zone are observed to be 12.7–43.1, 12.3–31.2, and 6.9–14.5 %, respectively. The acoustic velocity before grouting and its increasing rate can be used to predict the effectiveness of consolidation grouting.

Experimental characterization of granite damage using nonlinear ultrasonic techniques

In this paper, a nondestructive evaluation (NDE) technique based on the nonlinear second harmonic wave theory is developed and used to characterize damage of granite samples subjected to compressive loadings. The nonlinear parameter defined in the new NDE technique is measured and compared with two traditional parameters including ultrasonic pulse velocity and dynamic modulus. The nonlinear parameter is found to be much more sensitive to the damage development in granites than traditional parameters. It is shown that the increase of nonlinear parameter is close to an exponential trend with respect to the increased loading level, which also indicates a faster increase rate of the nonlinear parameter corresponding to the internal damage of granite samples. A practical damage index is thus defined based on the exponential increasing trend of the nonlinear parameter. The new damage index based on nonlinear parameter is found to have a positive correlation with the loading level. This observation suggests that the new damage index may become a valuable indicator of loading level (or correspondingly material degradation) of granites in the in situ NDE tests.

Molybdenum sound velocity and shear modulus softening under shock compression

We measured the longitudinal sound velocity in Mo shock compressed up to 4.4 Mbars on the Hugoniot. Its sound speed increases linearly with pressure up to 2.6 Mbars; the slope then decreases up to the melting pressure of ∼3.8 Mbars. This suggests a decrease of shear modulus before the melt. A linear extrapolation of our data to 1 bar agrees with the ambient sound speed. The results suggest that Mo remains in the bcc phase on the Hugoniot up to the melting pressure. There is no statistically significant evidence for a previously reported bcc→hcp phase transition on the Hugoniot.

Simulation and experimental study on the motion of non-reacting objects in the freeboard of a fluidized bed

The motion of a large non-reacting object in the freeboard of a bubbling fluidized bed was characterized experimentally and compared with Monte Carlo simulations. A tracking technique was developed to study the object motion both when it is immersed in the dense bed and in the freeboard. Monte Carlo simulations, based on the kinematic equations of the motion, and relying on a minimum set of experimental data, were used to obtain the relevant characteristics of the process.The non-reacting object motion in the freeboard is only affected by gravity and can be described as a ballistic motion, characterized by the initial velocity of the object, or ejection velocity. The ejection velocity modulus and angle were experimentally determined for several conditions, varying the gas velocity and the bed height. The results showed a good correlation between the ejection velocity and the bubble velocity. Probability distributions for the modulus and angle of the ejection velocity were obtained from the experimental data.The object lateral displacement and the time spent by the object in the freeboard were calculated using three parallel approaches, with different degrees of simplicity and accuracy, employing the Monte Carlo model. The results of the model were compared to the experimental results, showing a good agreement.

Genetics of wood quality attributes in Western Larch

Wood quality traits are important to balance the negative decline of wood quality associated with selection for growth attributes in gymnosperm breeding programs. Obtaining wood quality estimates quickly is crucial for successful incorporation in breeding programs. The aims of this paper are to: (1) Estimate genetic and phenotypic correlations between growth and wood quality attributes, (2) Estimate heritability of the studied traits, and (3) Assess the accuracy of in situ non-destructive tools as a representative of actual wood density. Wood density (X-ray densitometry), tree height, diameter, volume, resistance drilling, acoustic velocity, and dynamic modulus of elasticity were estimated, along with their genetic parameters, for 1,200, 20-year-old trees from 25 open-pollinated families. Individual tree level heritabilities for non-destructive evaluation attributes were moderate ( $$ {\widehat{h}}_i^2=0.37-0.42 $$ ), wood density and growth traits were lower ( $$ {\widehat{h}}_i^2=0.23-0.35 $$ ). Favorable genetic and phenotypic correlations between growth traits, wood density, and non-destructive evaluation traits were observed. A perfect genetic correlation was found between resistance drilling and wood density (rG = 1.00 ± 0.07), while acoustic velocity and dynamic modulus of elasticity showed weaker genetic correlations with wood density (rG = 0.25 ± 0.24; 0.46 ± 0.21, respectively). This study confirmed that resistance drilling is a reliable predictor of wood density in western larch, while the weak genetic correlations displayed by acoustic velocity and dynamic modulus of elasticity suggest limited dependability for their use as fast in situ wood density assessment methods in this species.

Nicotinamide mononucleotide supplementation reverses vascular endothelial dysfunction and large elastic artery stiffness in old mice (698.10)

Reduced bioavailability of nicotinamide adenine dinucleotide (NAD+), a cofactor for the deacetylase sirtuin1 (SIRT1), may contribute to age‐related vascular dysfunction via oxidative stress and reduced nitric oxide (NO). We hypothesized that boosting NAD+ with the precursor nicotinamide mononucleotide (NMN) might reverse these adverse effects of aging. Old (O: 26 mo, n=14) C57 male mice had impaired ex vivo carotid artery endothelium‐dependent dilation (EDD) to acetylcholine (ACh, 60 ± 5 vs. 82 ± 3%) and NO‐mediated EDD (max dilation to ACh ‐ max dilation to ACh + L‐NAME, 37 ± 4 vs. 69 ± 5%), and increased aortic pulse wave velocity (aPWV, 467 ± 18 vs. 359 ± 8 cm/s) and elastic modulus (EM, 5899 ± 731 vs. 3307 ± 288 kPa, all p<0.05) (indices of arterial stiffness) vs. young (Y; 6 mo, n=12). In O treated with NMN (300 mg/kg/d in drinking water, 8 w) (n=10), EDD (89 ± 3%), NO‐mediated EDD (61 ± 5%), aPWV (364 ± 14 cm/s) and EM (3694 ± 315 kPa) all were improved (p<0.05 vs. O). Aorta from O had reduced expression (WB) of SIRT1 (0.7 ± 0.1 vs. 1.0 ± 0.1 AU, p=0.05 vs. Y) and increased nitrotyrosine (NT) (oxidant modification) (8.7 ± 1.1 vs. 1.0 ± 0.3 AU, p<0.05 vs. Y). In O, NMN restored SIRT1 (1.1 ± 0.1 AU) and reduced NT (4.7 ± 0.7 AU) (both p<0.05 vs. O). Increasing NAD+ bioavailability may be a novel therapy for reversing age‐related vascular dysfunction by reducing oxidative stress and restoring NO signaling.Grant Funding Source: Supported by NIH AG013038 and AG000279

Ultrasonic Test on Recycled Concrete: Relationship among Ultrasonic Waves Velocity, Compressive Strength and Elastic Modulus

In this paper an experimental program has been carried out in order to compare compressive strength fc and elastic static modulus Ec of recycled concrete with ultrasonic waves velocity Vp, to establish the possibility of employing nondestructive ultrasonic tests to qualify recycled concrete. 9 mix of concrete with different substitution percentage of recycled aggregates instead of natural ones and 27 cylindrical samples have been made. At first ultrasonic tests have been carried out on cylindrical samples, later elastic static modulus Ec and compressive strength fc have been experimentally evaluated. The dynamic elastic modulus Ed has been determined in function of ultrasonic wave velocity Vp; furthermore the correlations among Ed, Ec, fc e Vp have been determined. It has been demonstrated that ultrasonic tests are suitable for evaluating different deformative and resisting concrete performances even when variations are small.

Statistical models for concrete containing wood chipping as partial replacement to fine aggregate

The properties of concrete containing wood chippings as partial replacement to fine aggregate are presented in this paper. Wood chipping was treated by water before mixing to prevent it from soaking the water meant for cement hydration. Fifteen trial mixes were prepared and cast using three water–cement ratios (0.37, 0.41 and 0.57) at different replacement levels of wood chippings. Fresh concrete properties tested included slump, unit weight and air content. Hardened concrete properties tested included compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, rebound hammer (RH) and ultrasonic pulse velocity (UPV). Several statistical models were developed to show the relationships between measured responses and variables and among measured responses. These models were validated using various model statistics. Test results show that disposal of wood chipping in concrete is feasible and appropriate. These models are providing a design mix aid of concrete containing wood chipping as partial replacement of fine aggregate.

Hydraulic and acoustic properties of the active Alpine Fault, New Zealand: Laboratory measurements on DFDP-1 drill core

We report on laboratory measurements of permeability and elastic wavespeed for a suite of samples obtained by drilling across the active Alpine Fault on the South Island of New Zealand, as part of the first phase of the Deep Fault Drilling Project (DFDP-1). We find that clay-rich cataclasite and principal slip zone (PSZ) samples exhibit low permeabilities (⩽10−18 m2), and that the permeability of hanging-wall cataclasites increases (from c. 10−18 m2 to 10−15 m2) with distance from the fault. Additionally, the PSZ exhibits a markedly lower P-wave velocity and Young's modulus relative to the wall rocks. Our laboratory data are in good agreement with in situ wireline logging measurements and are consistent with the identification of an alteration zone surrounding the PSZ defined by observations of core samples. The properties of this zone and the low permeability of the PSZ likely govern transient hydrologic processes during earthquake slip, including thermal pressurization and dilatancy strengthening.

Frontal cationic curing of epoxy resins in the presence of defoaming or expanding compounds

ABSTRACTThermal frontal polymerization was carried out with trimethylol propane triglycidyl ether using two different BF3‐amine complexes, B‐950 and B‐110 from Leepoxy, as initiators for cationic polymerization. The amounts of filler (kaolin or fumed silica), defoaming, or expansion agents were varied to study how the compositions affected the front velocity, expansion, and flexural modulus of the resulting epoxy resins. The polymer produced with B‐950 initiator showed higher modulus than the polymers produced with B‐110. Moreover, fumed silica created stronger materials than kaolin. The presence of BYK as a defoamer or an expansion agent such as the Expancel #80 was also able to affect significantly the mechanical properties. differential scanning calorimetry studies indicated that the conversion was complete and that kaolin and silica increased the rate of reaction. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40339.

Thermophysical and mechanical properties of granite and its effects on borehole stability in high temperature and three-dimensional stress.

When exploiting the deep resources, the surrounding rock readily undergoes the hole shrinkage, borehole collapse, and loss of circulation under high temperature and high pressure. A series of experiments were conducted to discuss the compressional wave velocity, triaxial strength, and permeability of granite cored from 3500 meters borehole under high temperature and three-dimensional stress. In light of the coupling of temperature, fluid, and stress, we get the thermo-fluid-solid model and governing equation. ANSYS-APDL was also used to stimulate the temperature influence on elastic modulus, Poisson ratio, uniaxial compressive strength, and permeability. In light of the results, we establish a temperature-fluid-stress model to illustrate the granite's stability. The compressional wave velocity and elastic modulus, decrease as the temperature rises, while poisson ratio and permeability of granite increase. The threshold pressure and temperature are 15 MPa and 200°C, respectively. The temperature affects the fracture pressure more than the collapse pressure, but both parameters rise with the increase of temperature. The coupling of thermo-fluid-solid, greatly impacting the borehole stability, proves to be a good method to analyze similar problems of other formations.