Vector wavefields for weakly attenuating anisotropic media by the ray method

Geophysics ◽  
1992 ◽  
Vol 57 (1) ◽  
pp. 27-38 ◽  
Author(s):  
Dirk Gajewski ◽  
Ivan Pšenčík
Keyword(s):  
Seismic Waves ◽  
Three Dimensional ◽  
Anisotropic Media ◽  
Elastic Model ◽  
Complex Frequency ◽  
Three Dimensional Model ◽  
Elastic Parameters ◽  
Ray Method ◽  
Isotropic Constant ◽  
Reflectivity Method

The ray method is used to compute high‐frequency seismic vector wavefields in weakly attenuating layered anisotropic structures. The attenuating effects are introduced by substituting the real elastic parameters for perfectly elastic media by complex frequency dependent elastic parameters with small imaginary parts. The imaginary parts are formally considered to be of the order of [Formula: see text] for [Formula: see text]. Under this assumption, it is possible to work with real rays, only the eikonal is complex. The approximate computations based on this algorithm are only a few percent slower than those for perfectly elastic anisotropic media. The range of applicability of the weak attenuation concept is investigated by comparison of ray computations with results of the reflectivity method for an isotropic, constant gradient model. The study indicates that the region of applicability of the weak attenuation concept may be broader than expected. The combined effects of anisotropy and attenuation on the propagation of seismic waves in a three‐dimensional model of the uppermost crust with an anisotropic attenuating layer are then studied. The anisotropy as well as the attenuation are supposed to be caused by aligned partially liquid‐filled cracks. Hudson’s formulas to compute complex effective elastic parameters are used. Frequency responses and VSP synthetic seismograms for different degrees of viscosity of the liquid, and, thus, different degree of attenuation, show the effects of attenuation on the propagating waves. Nine‐component VSP vector wavefields are computed for two different source‐borehole directions along the strike of the cracks and 45 degrees off the strike of the cracks. The seismograms for the attenuating model are compared with seismograms for the corresponding perfectly elastic model.

scholarly journals DETERMINATION OF AZIMUTHAL ANISOTROPIC MEDIA ELASTIC PARAMETERS FROM MULTIWAVE AVOA DATA BY NONLINEAR OPTIMIZATION METHOD

2019 ◽  
pp. 14-26 ◽  
Author(s):  
T. V. Nefedkina ◽  
P. A. Lykhin ◽  
G. A. Dugarov
Keyword(s):  
Signal To Noise Ratio ◽  
Anisotropic Media ◽  
Optimization Method ◽  
Parameter Estimates ◽  
Reflection Coefficients ◽  
Elastic Parameters ◽  
Ray Method ◽  
Pp Wave ◽  
Hti Medium

In this paper, we investigate optimization algorithm of joint nonlinear AVOA inversion of PP+PS reflections in anisotropic media. Algorithm is based on the exact solution for PP and PS waves reflection coefficients in anisotropic HTI medium. The PP and PS wave’s reflections from the top of the anisotropic layer are examined. We use synthetic seismograms generated by ray method for the algorithm testing. We show that joint compressional and converted wave’s inversion allows increasing the robustness of the method and the accuracy of medium-parameter estimates. Coefficients of anisotropy are determined with better accuracy if signal-to-noise ratio is bigger than 5 for PP wave and bigger than 2 for PS wave.

Dynamic Analysis of Arch Dam Based on Observed Earthquake

2013 ◽  
Vol 438-439 ◽  
pp. 1542-1545
Author(s):  
Zheng Liu ◽  
Yong Gang Guo ◽  
Long Bang Qing
Keyword(s):  
Seismic Waves ◽  
Three Dimensional ◽  
Safety Evaluation ◽  
Arch Dam ◽  
Element Calculation ◽  
Dimensional Model ◽  
Acceleration Response ◽  
Three Dimensional Model ◽  
Water Interaction ◽  
Scientific Support

A three-dimensional model of dam-water-interaction system was built. Three different materials were used to model the dam, and the acceleration response of arch dam under the observed seismic waves was simulated. The results show that the dynamic reactions of the arch dam under observed earthquakes can well match the monitoring values, which means the established model of the arch dam is reliable. In the future, when great earthquakes happen, the stress strain situation of the key positions can be quickly obtained by the finite element calculation, which could provide scientific support for post-earthquake safety evaluation and decision-making.

scholarly journals A Nonlinear Elastic Model for Compressible Aluminum Alloys with Finite Element Implementation

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7351
Author(s):  
Aleksander Szwed ◽  
Marcin D. Gajewski
Keyword(s):  
Finite Element ◽  
Aluminum Alloys ◽  
Deformation Theory ◽  
Three Dimensional ◽  
Constitutive Relationship ◽  
Elastic Model ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Theory Of Plasticity ◽  
Nonlinear Elastic

In this paper, a three-dimensional model of nonlinear elastic material is proposed. The model is formulated in the framework of Green elasticity, which is based on the specific elastic energy potential. Equivalently, this model can be associated to the deformation theory of plasticity. The constitutive relationship, derived from the assumed specific energy, divides the material’s behavior into two stages: the first one starts with an initial almost linear stress–strain relation which, for higher strain, smoothly turns into the second stage of hardening. The proposed relation mimics the experimentally observed response of ductile metals, aluminum alloys in particular. In contrast to the classic deformation theory of plasticity or the plastic flow theory, the presented model can describe metal compressibility in both stages of behavior. The constitutive relationship is non-reversible expressing stress as a function of strain. Special attention is given to the calibration process, in which a one-dimensional analog of the three-dimensional model is used. Various options of calibration based on uniaxial stress test are extensively discussed. A finite element code is written and verified in order to validate the model. Solutions of selected problems, obtained via ABAQUS, confirm the correctness of the model and its usefulness in numerical simulations, especially for buckling.

scholarly journals Comparison of Hertzian and JKR theories with a finite element model in boundary lubrication conditions between a compression ring and a cylinder

2018 ◽  
Vol 188 ◽  
pp. 04009
Author(s):  
Kyriakos Grigoriadis ◽  
Anastasios Zavos ◽  
Pantelis G. Nikolakopoulos
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Combustion Engine ◽  
Three Dimensional ◽  
Element Model ◽  
Elastic Model ◽  
Three Dimensional Model ◽  
Dry Conditions ◽  
The Common ◽  
Lubrication Conditions

This study focuses on the creation of an isothermal elastic model to highlight, through stresses, the occurrence of plastic deformation in certain crank angles under extreme dry conditions inside an internal combustion engine. The stresses that are exported from this analysis are pointing out not only the necessity for an elastoplastic model to be created, but also the importance of predicting the correct friction coefficient, as pointed out by both the contact surface stress and those in depth of the two bodies in contact. A comparison between two coefficients of frictions and one frictionless case is conducted. The comparison between the finite element model and the adhesion mathematical model of Johnson, Kendall and Roberts (JKR), seals the importance of the interaction forces, acting on the common solid surface, in the pursuit of defining a propriate contact patch. Furthermore, a three-dimensional model is proposed for further investigation, highlighting the importance of modelling surface’s micro asperities for a solid stress analysis.

Three-Dimensional Model for Virtual Surgical Simulation, during Complex Skull Base Surgery and Aneurysm Surgery

Skull Base ◽  
2008 ◽  
Vol 18 (S 01) ◽  
Author(s):  
Akio Morita ◽  
Toshikazu Kimura ◽  
Shigeo Sora ◽  
Kengo Nishimura ◽  
Hisayuki Sugiyama ◽  
...  
Keyword(s):  
Skull Base ◽  
Surgical Simulation ◽  
Skull Base Surgery ◽  
Three Dimensional ◽  
Aneurysm Surgery ◽  
Dimensional Model ◽  
Three Dimensional Model

Digitalization system of ancient architecture decoration art based on neural network and image features

2020 ◽  
pp. 1-12
Author(s):  
Wu Xin ◽  
Qiu Daping
Keyword(s):  
Neural Network ◽  
Construction Industry ◽  
Three Dimensional ◽  
Performance Testing ◽  
Image Features ◽  
Three Dimensional Model ◽  
Performance Effect ◽  
Data Process ◽  
And Performance ◽  
Construction Mode

The inheritance and innovation of ancient architecture decoration art is an important way for the development of the construction industry. The data process of traditional ancient architecture decoration art is relatively backward, which leads to the obvious distortion of the digitalization of ancient architecture decoration art. In order to improve the digital effect of ancient architecture decoration art, based on neural network, this paper combines the image features to construct a neural network-based ancient architecture decoration art data system model, and graphically expresses the static construction mode and dynamic construction process of the architecture group. Based on this, three-dimensional model reconstruction and scene simulation experiments of architecture groups are realized. In order to verify the performance effect of the system proposed in this paper, it is verified through simulation and performance testing, and data visualization is performed through statistical methods. The result of the study shows that the digitalization effect of the ancient architecture decoration art proposed in this paper is good.

Phonetic iconicity in the evaluative morphology of a sample of Indo-European, Niger-Congo and Austronesian languages

2010 ◽  
Vol 3 (2) ◽  
pp. 156-180 ◽  
Author(s):  
Renáta Gregová ◽  
Lívia Körtvélyessy ◽  
Július Zimmermann
Keyword(s):  
Three Dimensional ◽  
Sound Symbolism ◽  
Three Dimensional Model ◽  
Austronesian Languages ◽  
Place Of Articulation ◽  
European Languages ◽  
Phonetic Symbolism ◽  
The Individual ◽  
Core Vocabulary

Universals Archive (Universal #1926) indicates a universal tendency for sound symbolism in reference to the expression of diminutives and augmentatives. The research ( Štekauer et al. 2009 ) carried out on European languages has not proved the tendency at all. Therefore, our research was extended to cover three language families – Indo-European, Niger-Congo and Austronesian. A three-step analysis examining different aspects of phonetic symbolism was carried out on a core vocabulary of 35 lexical items. A research sample was selected out of 60 languages. The evaluative markers were analyzed according to both phonetic classification of vowels and consonants and Ultan's and Niewenhuis' conclusions on the dominance of palatal and post-alveolar consonants in diminutive markers. Finally, the data obtained in our sample languages was evaluated by means of a three-dimensional model illustrating the place of articulation of the individual segments.

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