Application of AVAZ inversion algorithm based on exact formulas to a wide-azimuth seismic survey data

Results of applying of nonlinear AVAZ inversion optimization algorithm to data from 3D wide-azimuth seismic survey in the Republic of Serbia are presented. The algorithm is based on exact reflection coefficients formulas for PP reflection from anisotropic medium. We compare it with a conventional algorithm based on Ruger linear approximation of P-wave reflection from a boundary between isotropic and anisotropic (HTI) media. Maps of fracture orientation and anisotropy degree are more detailed in the case of using AVAZ inversion based on exact formulas. The results are in general accordance with the FMI well data, which indicates reliable performance of the algorithm.

TESTING OF AN OPTIMIZATION ALGORITHM FOR AVAZ INVERSION ON SYNTHETIC DATASET

In the paper, we study an optimization algorithm for a nonlinear AVAZ inversion of PP reflections from an anisotropic media. The algorithm is based on the exact formulas for PP wave reflection coefficient for an anisotropic HTI medium and could be applied in the case of strong-contrast boundary and various anisotropy degree. Algorithm testing on synthetic dataset for radial survey system shows that estimation of anisotropy parameters γ , δ and HTI medium symmetry axis is robust in the case of signal to noise ratio ≥ 5. For estimation of parameter ε far offset data is needed.

Exploring the micromechanical behaviour of sand-rubber mixtures using X-ray micro-tomography

The micromechanical behaviour of sand-rubber mixtures (SRMs) under monotonic triaxial shear were investigated using X-ray micro-tomography. The localisation of sand particle rotations that occurred in a pure sand sample under shear was inhibited in the sand mixed with 30% rubber grains by mass. Meanwhile, the SRMs exhibited an evolution of sand-sand contact coordination number that is not negatively correlated with sample porosity, dramatically different from that was observed in pure sands. Substantially increasing anisotropy degree of sand-rubber contacts compared with minor changes of sandsand contact fabric was observed, implying the increasingly important role of sand-rubber contacts in the transmission of deviatoric loads as the shear of SRMs progressed.

Original title: Zur Abschatzung der Anizotropie. Polish title: O szacowaniu anizotropii. English Title: On assessment of anisotropy degree

In continuous medium physics, crystal physics and related fields, the properties of the studied objects are described by means of Euclidean tensors of various orders. The symmetry and asymmetry of the described physical properties are manifested by changing these tensors as a result of subjecting them to rotation in the original physical space. If the tensor does not change with any rotation, it is called isotropic (odd-order hemitropic). Otherwise, the tensor is anisotropic. For some practical problems, it is useful to have some overall index of anisotropy by which tensors can be compared. Here, a novelty measure of anisotropy degree of any order Euclidean tensor is proposed, basing on the concept of tensor orbit.

SIMULATION OF REINFORCEMENT DEGREE OF NANOCOMPOSITES ELASTOMER/2D-NANOFILLER

Three schemes of modeling of reinforcement degree of nanocomposites polymer/2D-nanofiller with elastomeric matrix were proposed, differing principally from used ones earlier. These schemes do not used nominal characteristics of nanofiller (its modulus of elasticity, anisotropy degree), yet allow to obtain real (effective) values of these parameters. It has been shown, that modulus of elasticity of 2D-nanofiller aggregates in polymer matrix of nanocomposite is a function of stiffness of the indicated matrix. The other analogous model assumes the dependence of modulus of elasticity of 2D-nanofiller on its aggregation degree in polymer matrix, expressed by number of nanofiller separate platelets per one aggregate (“packet” or tactoid). The combination of these approaches allows to predict the real degree of nanofiller anisotropy and then reinforcement degree of nanocomposite. One more scheme uses the structure of nanofiller aggregates, characterized by its fractal dimension, for modeling of reinforcement degree of nanocomposites. The obtained real modulus of elasticity of 2D-nanofiller is in 5 orders of value smaller relatively to its nominal magnitude. The application of real (effective) characteristics of nanofiller allows to simulate reinforcement degree of nanocomposite within the framework of simple mixtures rule. Nanocomposites elastomer/2D-nanofiller are enough conservative systems, for which real anisotropy degree and structure of nanofiller aggregates do not depend on its content. This circumstance simplifies perceptibly prediction of mechanical properties of these nanocomposites.

Anısotropy Property of Dıfferent Types of Wood

The norm of elastic constant tensor and the norms of the irreducible parts of the elastic constants of different types of wood. The relation of the scalar parts norms and the other parts norms and the anisotropy of these woods is presented. The norm ratios are used as a criterion to present the anisotropy degree of the properties of these woods

Experimental Study on the Effect of Gas Pressure on Ultrasonic Velocity and Anisotropy of Anthracite

To research the elasticity of gas-bearing coal fluid-solid two-phase medium with seismic exploration method is critical to the prevention of gas disasters. To investigate the elasticity, the ultrasonic elastic test of anthracite samples under different gas pressures was carried out and the ultrasonic velocity and anisotropy of the samples were analyzed in this study. The results show that the velocities (P- and S-waves) decrease in turn in the strike, dip, and vertical directions. However, a negative linear correlation is proved to exist between ultrasonic velocity and gas pressure. With the increase of gas pressure, the anisotropy degree of both the P-wave and the S-wave of the samples decreases but the declining degree of the P-wave is greater than that of the S-wave. In addition, the decrease in velocity and the anisotropy degree of the P-wave is greater than that of the S-wave, indicating that the P-wave is more sensitive to gas pressure changes in terms of velocity and its anisotropy degree.

Co-carbonization of single coking coal and pyrolytic extracts from datong long-flame coal

Using modified coal as the raw material to produce coke is a novel method to improve the quality of coke during the process of coal blend coking. In this work, the activated components from low-rank coal were used as a common modifier for coal modification process. The properties of co-carbonization coke were studied. The pyrolytic extracts of Chinese Datong long-flame coal (DTLFPE) were used as the additive, while Jinjian gas coal and Zhongwei lean coal were used as the basic coals. The influence of the addition of DTLFPE on coke’s micro-strength, optical texture index (OTI), microstructure and coke reactivity were studied. The results showed that DTLFPE exhibited a significant impact on the performance of Zhongwei lean coal coke. The micro-strength and the OTI index of each coke significantly improved due to the addition of DTLFPE, which meant that their anisotropy degree was enhanced. The addition of DTLFPE also decreased the porosity of Jinjian gas coal coke, and improved the melting ability of the particles in Zhongwei lean coal coke. The DTLFPE was found to be a very suitable modifier for single coking coal, whereas moderate amounts of additives exhibited positive effects on improving the quality of coke.

Standardized Compliance Matrices for General Anisotropic Materials and a Simple Measure of Anisotropy Degree Based on Shear-Extension Coupling Coefficient

The compliance matrix for a general anisotropic material is usually expressed in an arbitrarily chosen coordinate system, which brings some confusion or inconvenience in identifying independent elastic material constants and comparing elastic properties between different materials. In this paper, a unique stiffest orientation-based standardized compliance matrix is established, and 18 independent elastic material constants are clearly shown. During the searching process for the stiffest orientation, it is interesting to find from our theoretical analysis and an example that a material with isotropic tensile stiffness does not definitely possess isotropic elasticity. Therefore, the ratio between the maximum and minimum tensile stiffnesses, although widely used, is not a correct measure of anisotropy degree. Alternatively, a simple and correct measure of anisotropy degree based on the maximum shear-extension coupling coefficient in all orientations is proposed. However, for a two-dimensional constitutive relation, both the stiffness ratio and the shear-extension coupling coefficient can be adopted as proper measures of anisotropy degree.