Radial Wave Velocity Research Articles

Lamina Influences on Tensile Strength of Shallow Marine Shales from Upper Ordovician, Western Ordos Basin.

To investigate the influence of the lamina effect on the tensile strength of shallow marine shales and improve the shortcomings of the existing Brazilian standard disc splitting method, the Lamina shale of the Upper Ordovician Wulalik Fm in the western margin of the Ordos Basin was selected as the experimental object. Based on the radial wave velocity anisotropy test, the direction of crustal stress was determined, and standard cores were drilled. The Brazilian standard disc splitting experiment on Lamina shale with different loading angles was designed and carried out. The influence of lamina on the tensile strength of shale was summarized, and an improved calculation method of tensile strength was proposed. The experimental results indicate that the presence of lamina makes the tensile strength of shallow marine shale exhibit significant anisotropy, and the fracture surface morphology of standard discs under different loading angles varies greatly. The overall failure characteristics can be classified into two types: linear and curved. When the loading angle is 0° or 90°, the fracture surface of the disc belongs to tensile failure (linear type), and the traditional splitting method has good applicability. When the loading angle is greater than 0° and less than 90°, the fracture surface of the disc belongs to tensile shear failure (curve type), and traditional splitting methods are not applicable. There is a difference in tensile strength between vertical and horizontal wells, and vertical wells should consider the comprehensive tensile strength of the rock matrix and lamina at a 90° loading angle. Horizontal wells should consider the tensile strength of the weak lamina plane with a loading angle of 0°. The improved Brazilian splitting method solves the problem of the traditional method, calculating lower tensile strength values when the loading angle is greater than 0° and less than 90°. This provides important basic data support for wellbore stability evaluation and reservoir stimulation transformation.

Study on Changes in Wave Velocity in Surrounding Tunnel Rock under Different High In-situ Stresses

Studies have indicated that in the tunnel’s surrounding rock, high in-situ stress influences the wave velocity changes. Under different ground stresses, an underground model system is used to study the propagation characteristics of the blasting seismic wave velocity. The electric spark was used to recreate explosive blasting by employing a model loading system to simulate gradient loading under high in-situ stress in the tunnel. The DH5983 dynamic signal analytical system was used to collect the vibration acceleration and calculate the average velocity. The average radial and axial wave velocities gradually increased with increasing in-situ stress, and the increase in the average radial wave velocity was greater than the axial wave velocity, according to the test results. The growth rate of the average wave velocity gradually slowed down under various high in-situ stressors, with that in the low in-situ stress stage being greater than in the high in-situ stress stage. A logarithmic growth trend is seen when the wave velocity gradually becomes constant. The average decay growth rate of the radial wave velocity was larger than the rate of axial velocity, which was approximately 1.5 times.

Pattern Recognition of Chemical Waves: Finding the Activation Energy of the Autocatalytic Step in the Belousov-Zhabotinsky Reaction.

The Belousov–Zhabotinsky (BZ) reaction is an example of a homogeneous, nonequilibrium reaction used commonly as a model for the study of biological structure and morphogenesis. We report the experimental effects of temperature on spontaneously nucleated trigger waves in a quasi-two-dimensional BZ reaction–diffusion system, conducted isothermally at temperatures between 9.9 and 43.3 °C. Novel application of filter-coupled circle finding and localized pattern analysis is shown to allow the highly accurate extraction of average radial wave velocity and nucleation period. Using this, it is possible to verify a strong Arrhenius dependence of average wave velocity with temperature, which is used to find the effective activation energy of the reaction in accordance with predictions elaborated from the widely used Oregonator model of the BZ reaction. On the basis of our experimental results and existing theoretical models, the value for activation energy of the important self-catalyzed step in the Oregonator model is determined to be 86.58 ± 4.86 kJ mol–1, within range of previous theoretical prediction.

Analysis of wave propagation in orthotropic microtubules embedded within elastic medium by Pasternak model

Microtubules are embedded within elastic medium in living cells, where they perform a wide variety of functions; in cell motility and division, in organelle transport, and in cell organization. Waves propagate along microtubules in performing their physiological functions, so, wave propagation along microtubules has been the topic of research in the past decade. In the present article, the wave propagation in microtubules embedded in the elastic medium has been investigated on the basis of orthotropic-Pasternak model. We considered microtubules as orthotropic elastic shell and its surrounding elastic matrix as Pasternak foundation. We found that the flexural rigidity of microtubules has been increased with the stiffening of the elastic medium. Moreover, we observed that due to the mechanical coupling of microtubules with the elastic medium, their radial wave velocity has increased considerably as compared to other two wave velocities, i.e., longitudinal wave velocity and torsional wave velocity. The effect of foundation parameters H and G is more pronounced on radial wave velocity, to a lesser extent on torsional wave velocity and least even negligible on longitudinal wave velocity.