Wyniki wyszukiwania - BazTech

1

Adaptive trans-dimensional inversion of multimode dispersion curve based on slime mold algorithm

Wang Xin, Feng Xuan, Liu Qian, Bai Han, Dong Xuri, Wang TaiHan

Acta Geophysica

|

2024

|

Vol. 72, no. 1

233--245

EN

With the rise of low-cost and high-density observation system Distributed Acoustic Sensing (DAS), the effective utilization of high-mode surface wave becomes extremely important due to unique measuring method of DAS. To solve the interference of mode identification of dispersion curve and model dimension division on inversion results, we introduced the fitting degree of the dispersion curve, the model dimension, and the uncertainty estimation of the picked dispersion curve to construct a new objective function, and developed a strategy of adaptive trans-dimensional inversion of multimode dispersion curve based on slime mold algorithm (SMA). The research results show that our objective function can not only satisfy the fitting degree of dispersion curve, but also adaptively select the best model dimension, and does not depend on the mode identification of dispersion curve. Inversion strategy based on SMA algorithm has high flexibility, accuracy, stability, and practicality. Our method develops a new technology for dispersion curve inversion and provides a new idea for DAS system to realize low-cost and high-resolution city underground structure detection.

2

Seismic crust structure beneath the Aegean region in southwest Turkey from radial anisotropic inversion of Rayleigh and Love surface waves

Çakır Ö.

Acta Geophysica

|

2018

|

Vol. 66, no. 6

1303--1340

EN

The Turkish plate is covered by hundreds of accelerometer and broadband seismic stations with less than 50 km inter-station distance providing high-quality earthquake recordings within the last decade. We utilize part of these stations to extract the fundamental mode Rayleigh and Love surface wave phase and group velocity data in the period range 5–20 s to determine the crust structure beneath the Aegean region in southwest Turkey. The observed surface wave signals are interpreted using both single-station and two-station techniques. A tomographic inversion technique is employed to obtain the two-dimensional group velocity maps from the single-station group velocities. One-dimensional velocity–depth profiles under each twodimensional mesh point, which are jointly interpreted to acquire the three-dimensional image of the shear-wave velocities underneath the study area, are attained by utilizing the least-squares inversion technique, which is repeated for both Rayleigh and Love surface waves. The isotropic crust structure cannot jointly invert the observed Rayleigh and Love surface waves where the radial anisotropic crust better describes the observed surface wave data. The intrusive magmatic activity related to the northward subducting African plate under the Turkish plate results the crust structure deformations, which we think, causing the observed radial anisotropy throughout complex pattern of dykes and sills. The magma flow resulting in the mineral alignment within dykes and sills contributes to the observed anisotropy. Due to the existence of dykes, the radial anisotropy in the upper crust is generally negative, i.e., vertically polarized S-waves (Vsv) are faster than horizontally polarized S-waves (Vsh). Due to the existence of sills, the radial anisotropy in the middle-to-lower crust is generally positive, i.e., horizontally polarized S-waves (Vsh) are faster than vertically polarized S-waves (Vsv). Similar radial anisotropic results to those of the single-station analyses are obtained by the two-station analyses utilizing the cross-correlograms. The widespread volcanic and plutonic rocks in the region are consistent with the current seismic interpretations of the crustal deformations.

3

Application of Multichannel Analysis of Surface Waves to S-Phase Wave Anisotropy Estimation

Stan-Kłeczek I., Mendecki M. J.

Acta Geophysica

|

2016

|

Vol. 64, no. 5

1593--1604

EN

The Multichannel Analysis of Surface Waves (MASW) is an increasingly used technique for recognition of a shallow geological structure and estimation of geotechnical parameters, e.g., S-wave velocity, layer density, layer thickness, shear modulus, estimated P-wave velocity, and estimated Poisson ratio. MASW surveys were carried out in two limestone quarries in the southern part of Poland. The experimental areas are characterised by a simple geological structure: consolidated Triassic limestone. Measurement profiles were arranged as a shapely six-pointed star. For each survey line, 12 geophones with 2-meter (Deposit 1) and 3-meter (Deposit 2) spacing were applied. The research allowed to compare P- and S-wave velocity changes with the main crack systems in the studied rock masses.

4

Shallow Water Turbulent Surface Wave Striking an Adverse Slope

Bose S. K.

Acta Geophysica

|

2015

|

Vol. 63, no. 4

1090--1102

EN

The problem of a sinusoidal wave crest striking an adverse slope due to gradual elevation of the bed is relevant for coastal sea waves. Turbulence based RANS equations are used here under turbulence closure assumptions. Depth-averaging the equations of continuity and momentum, yield two differential equations for the surface elevation and the average forward velocity. After nondimensionalization, the two equations are converted in terms of elevation over the inclined bed and the discharge, where the latter is a function of the former satisfying a first order differential equation, while the elevation is given by a first order evolution equation which is treated by Lax-Wendroff discretization. Starting initially with a single sinusoidal crest, it is shown that as time progresses, the crest leans forwards, causing a jump in the crest upfront resulting in its roll over as a jet. Three cases show that jump becomes more prominent with increasing bed inclination.

5

Nonlinear surface elastic waves in materials

Rushchitsky J.

Vibrations in Physical Systems

|

2014

|

Vol. 26

33--40

EN

This paper is devoted to analysis of the surface nonlinear elastic harmonic waves of four types (Rayleigh and Stoneley harmonic waves within the framework of plane strain state; Love and Mozhaev harmonic wave within the framework of anti-plane strain state). The nonlinear model is based on introducing the Murnaghan elastic potential, which includes both geometrical and physical nonlinearities. Each type of surface waves is discussed in four steps: statement of the problem, nonlinear wave equations, approximate solution (first two approximations), so-me conclusions. A nonlinear analysis of waves required many novelties: new variants of the Murnaghan potential, new nonlinear wave equations and new nonlinear boundary conditions. The nonlinear wave equations were solved by the method of successive approximations. A new approach to analyze the boundary conditions is offered. Some new nonlinear wave effects are observed theoretically: a wave picture is reached by the 2nd harmonic and becomes changing in time of propagation, the wave numbers become depending on the initial amplitude.

6

Przegląd zastosowania metody interferometrii sejsmicznej

Czarny R.

Przegląd Górniczy

|

2014

|

T. 70, nr 7

84--91

PL

Artykuł w sposób przeglądowy przedstawia szerokie możliwości zastosowania interferometrii sejsmicznej. Metoda jest stosunkowo nowa, mając na uwadze pierwsze eksperymenty wykonane w 2001 roku, i aktualnie znajduje się w fazie dynamicznego rozwoju. W pracy omówiono jej zastosowanie w wielu zagadnieniach związanych z odwzorowaniem budowy wnętrza Ziemi oraz warstw przypowierzchniowych, a także zagadnień geoinżynierskich z np. monitorowania czynnych osuwisk. Przedstawione przykłady badań zostały opublikowane w uznanych czasopismach naukowych.

EN

The aim of this paper is to review the wide range of seismic interferometry applications. Despite the fact that only 10 years have passed since the first application was implemented in seismology, seismic interferometry is currently used in many issues beginning with analysis of the Earth´s deep interior and ending with the time-laps velocity changes at active landslides. The presented research results were published in leading scientific journals.

7

Surface waves in non-homogeneous, general magnetothermo, viscoelastic media of higher order

Sethi M., Gupta K. C., Rani M.

International Journal of Applied Mechanics and Engineering

|

2013

|

Vol. 18, no. 4

1221--1236

EN

The aim of the present paper is to investigate surface waves in a non-homogeneous, isotropic, visco-elastic solid medium of n-th order including the time rate of strain. The theory of generalised surface waves has firstly been developed and then it has been employed to investigate particular cases of waves, viz., Stoneley, Rayleigh and Love type. The wave velocity equations have been obtained for different cases and are in well agreement with the corresponding classical result, when the effects of viscosity, temperature, magnetism as well as nonhomogeneity of the material medium are ignored.

8

Surface waves in fibre-reinforced anisotropic solid elastic media under the influence of gravity

Sethi M., Gupta K. C., Gupta D., Manisha

International Journal of Applied Mechanics and Engineering

|

2013

|

Vol. 18, no. 1

177--188

EN

The aim of the present paper is to investigate surface waves in an anisotropic, elastic solid medium under the influence of gravity. First, a theory of generalised surface waves was developed and then it was employed to investigate particular cases of waves, viz., Stoneley and Rayleigh, Love type. The wave velocity equations were obtained for different cases and they are in well agreement with the corresponding classical result, when the effect of gravity, viscosity as well as parameters for fibre-reinforcement of the material medium are ignored.

9

Obraz falowy w miastach

Krynicki T., Kowalczyk S., Mieszkowski R., Wojas A.

Przegląd Geologiczny

|

2010

|

Vol. 58, nr 5

401-407

EN

The paper presents analysis of factors influencing intensity of surface waves recorded in urban areas and methodology worked out for their measurement. Several examples of records of surface waves induced by different sources of vibrations are presented. The results of measurements show omnipresence of such waves. The wave record was executed using three-component geophones. The results of measurements show that induced vibrations may represent some hazard for buildings situated in distance up to 150 metres from their source.

10

Unexpected properties of SH-waves in superconducting heterostructure

Drzewiecki A., Maruszewski B., Starosta R.

Vibrations in Physical Systems

|

2008

|

Vol. 23

109--114

EN

The paper provides confrontation of a surface wave of SH polarization propagating in a superconducting layer (type II superconductor) located in a superconducting halfspace of similar material properties. It was found that the wave in the determined heterostructure is distinguished by the properties significantly different from classical Love wave propagating in similar elastic structure. Among more important differences first of all should be mentioned occurrence of only one mode and changed direction of the inequality that determines allowable range of phase velocity of propagating wave. Both waves are subject to normal dispersion.

11

Viscous Damping of Surface Waves

Kholief I. A.

Mechanics and Mechanical Engineering

|

2005

|

Vol. 9, nr 2

111--114

EN

In this article, the viscous damping of surface waves in a layer of constant depth is determined. A viscous term is included in Bernoulli equation, which agrees with Navier-Stoke's equation as proved here. The X dependence of the amplitude of the damped wave is determined by similarity and Fourier transforms.

12

Obliczenia i pomiary parametrów akustycznych fal powierzchniowych w niobianie litu o orientacji 128° YX

Soluch W., Łysakowska M.

Elektronika : konstrukcje, technologie, zastosowania

|

2000

|

Vol. 41, nr 3

18-20

PL

Przedstawiono wyniki obliczeń i pomiarów parametrów akustycznych fal powierzchniowych w niobianie litu (LiNbO3) o orientacji 128° YX, który jest powrzechnie stosowany w produkcji filtrów z akustyczn a falą powierzchniową (AFP). Obliczenia przeprowadzono przy wykorzystaniu opracowanego wczesniej programu komputerowego, który został przystosowany do obliczeń przy uwzględnieniu skończonej grubości warstwy metalu naniesionej na podłoże piezoelektryczne. Do pomiaru parametrów AFP zastosowano metodę czwórniakowego rezonansu synchronicznego. Uzyskano bardzo dobrą zgodność wyników obliczeń i pomiarów,

EN

Results of calculations and measurements of SAW parameters in 128° YX cut lithium niobate, which is used in mass production of surface acoustic wave (SAW) filters, are presented. The calculations were performed by means of a computer program, which was adapted for calculations with finite thickness of a metal layer deposited on a piesoelectric substrate. A two port synchronous resonator method was used for SAW parameters measurements. Very good agreement was obtained between the results of calculations and measurements.

13

Filtr zaporowy z rezonatorami kwarcowymi na akustycznych falach powierzchniowych

Soluch W., Wróbel T.

Elektronika : konstrukcje, technologie, zastosowania

|

2000

|

Vol. 41, nr 5

9-10

PL

Przedstawiono filtr zaporowy na częstotliwości 135.76 MHz. Filtr ten składa się z trzech ogniw wszechprzepustowych LC i trzech rezonatorów kwarcowych na akustycznych falach powierzchniowych (AFP). Częstotliwości rezonatorów różnią się między sobą, dzięki czemu uzyskano szerokość pasma zaporowego równą 11 kHz na poziomie 30 dB. Szerokość pasma przepustowego wynosi około 1000 MHz.

EN

A notch filter for frequency 135.76 MHz is presented. The filter consists of three LC all--pass networks and three quartz surface accoustic wave (SAW) resonators. The resonators frequencies differ between each other, therefore the notch bandwidth is equal to 11 kHz at 30 dB level. The passband width is equal to about 1000 MHz.