Influence of reflected waves at the bonded boundary in double-layered thickness-shear resonator using α-quartz

2022 ◽  
Author(s):  
Taisei Noguchi ◽  
Yuji Ohashi ◽  
Masaya Omote ◽  
Yuui Yokota ◽  
Shunsuke Kurosawa ◽  
...  
Keyword(s):  
Acoustic Impedance ◽  
Density Ratio ◽  
Single Layer ◽  
Temperature Characteristic ◽  
Phase Matching ◽  
Total Amplitude ◽  
Reflected Waves ◽  
Electric Flux ◽  
Acoustic Losses ◽  
Thickness Shear

Abstract The influence of the reflected waves at the bonding boundary on the resonance waveform and temperature characteristics was investigated using α-quartz (QZ). The double-layered resonator specimen was fabricated using 129.55°Y- and 0°Y-cut QZ substrates with the thickness ratio x=0.520. The temperature characteristic at the range from 100°C to 300°C was deviated from the calculated values estimated by the equations considering thickness and electric flux density ratio proposed in the previous work, and the resonant waveform of the specimen was deteriorated as compared with that of single-layer resonators. In order to clarify these phenomena, the phase matching conditions and total amplitude in the specimen were examined. As a result, it was clarified that increase of the amplitude in the layer with lower acoustic impedance was affected to the temperature characteristic, and acoustic losses due to reflection / transmission at the bonding boundary was affected to the total amplitude of resonance.

Acoustic waves II

2004 ◽  
Author(s):  
Robert E. Newnham
Keyword(s):  
Acoustic Impedance ◽  
Acoustic Waves ◽  
Incident Beam ◽  
Normal Incidence ◽  
Reflection And Transmission ◽  
Reflected Waves ◽  
Transmission Coefficients ◽  
Plane Wave Incident ◽  
Incident Waves ◽  
Acoustic Losses

Acoustic impedance, acoustic losses, acoustic waves in piezoelectric solids, and surface waves are discussed in this chapter, along with a number of nonlinear acoustic phenomena. The reflection and transmission of acoustic waves across a boundary is governed by acoustic impedance. One of the most important boundary value problems in acoustics concerns a plane wave incident upon a planar surface, dividing one medium from another. In the general case of an anisotropic medium, the incident beam consists of three waves (one quasilongitudinal, two quasitransverse), each traveling at a different velocity. Each of the three incident waves will be refracted and reflected at the boundary. If the second medium is also anisotropic, each incident wave will generate three reflected waves and three refracted waves, a total of 27 waves in all. Wave propagation in a polycrystalline solid where there are many grain boundaries becomes very complicated. The simpler case of a pure longitudinally-polarized wave at normal incidence to the boundary provides insight into the more general problem. In this case the reflection and transmission coefficients are governed by the relatively simple acoustic impedance parameter (ρc)1/2 = ρv, where ρ is the density, c the stiffness coefficient, and v the phase velocity. The reflection coefficient R at the interface between medium I and medium II is The MKS unit for acoustic impedance is the Rayl (=kg/m2 s). Atypical value for a solid is about 107 rayls. In many acoustic applications it is desirable to reduce reflection by matching the acoustic impedance of the two media. Lithium tantalate transducers are well-matched to iron, for example. Sound transmission from the transducer to the medium can be enhanced with composite materials or with graded coupling layers. Backing materials are often selected to promote reflection. In this case acoustic impedances are mismatched. Tungsten and air are two commonly used backing materials. In an isotropic material the acoustic impedance is (ρc11)1/2 for longitudinal waves and (ρc44)1/2 for shear waves. For anisotropic materials the wave velocities and acoustic impedance change with direction as indicated earlier.

scholarly journals Phase matching of high-order harmonic generation in single-layer graphene

2020 ◽  
Author(s):  
Roberto Boyero-García ◽  
Óscar Zurrón-Cifuentes ◽  
Luis Plaja ◽  
Carlos Hernandez-Garcia
Keyword(s):  
Harmonic Generation ◽  
Single Layer ◽  
High Order ◽  
Single Layer Graphene ◽  
Phase Matching ◽  
High Order Harmonic Generation ◽  
Layer Graphene ◽  
High Order Harmonic

scholarly journals Multiple states and transport properties of double-diffusive convection turbulence

2020 ◽  
Vol 117 (26) ◽  
pp. 14676-14681 ◽  
Author(s):  
Yantao Yang ◽  
Wenyuan Chen ◽  
Roberto Verzicco ◽  
Detlef Lohse
Keyword(s):  
Large Range ◽  
Local Density ◽  
Density Ratio ◽  
Single Layer ◽  
Multiple Equilibrium ◽  
Double Diffusive Convection ◽  
Flow Parameters ◽  
Diffusive Convection ◽  
Sharp Interfaces ◽  
Double Diffusive

When fluid stratification is induced by the vertical gradients of two scalars with different diffusivities, double-diffusive convection (DDC) may occur and play a crucial role in mixing. Such a process exists in many natural and engineering environments. Especially in the ocean, DDC is omnipresent since the seawater density is affected by temperature and salinity. The most intriguing phenomenon caused by DDC is the thermohaline staircase, i.e., a stack of alternating well-mixed convection layers and sharp interfaces with very large gradients in both temperature and salinity. Here we investigate DDC and thermohaline staircases in the salt finger regime, which happens when warm saltier water lies above cold fresher water and is commonly observed in the (sub)tropic regions. By conducting direct numerical simulations over a large range of parameters, we reveal that multiple equilibrium states exist in fingering DDC and staircases even for the same control parameters. Different states can be established from different initial scalar distributions or different evolution histories of the flow parameters. Hysteresis appears during the transition from a staircase to a single salt finger interface. For the same local density ratio, salt finger interfaces in the single-layer state generate very different fluxes compared to those within staircases. However, the salinity flux for all salt finger interfaces follows the same dependence on the salinity Rayleigh number of the layer and can be described by an effective power law scaling. Our findings have direct applications to oceanic thermohaline staircases.

Bragg scattering of water waves by a doubly periodic seabed

1988 ◽  
Vol 192 ◽  
pp. 51-74 ◽  
Author(s):  
Mamoun Naciri ◽  
Chiang C. Mei
Keyword(s):  
Water Waves ◽  
Transverse Direction ◽  
Resonance Condition ◽  
Phase Matching ◽  
Two Dimensional ◽  
Bragg Scattering ◽  
Reflected Waves ◽  
One Dimensional ◽  
Resonant Reflection ◽  
Bed Waves

We extend the recent work on Bragg scattering of water waves by one-dimensional parallel bars of sinusoidal profile to two-dimensional, doubly sinusoidal bed waves. The resonance condition governing the phase matching between the incident, scattered and bed waves is now more complicated and a much richer variety of resonant reflection can occur. In particular, for one normally incident wave there can be two reflected waves forming a standing wave in the transverse direction. Solutions for a wide strip of bed waves are discussed for incident water waves satisfying approximately the Bragg resonance condition. Modifications for a two-dimensional array of hemispheroids are also given. Possible application to the design of submerged breakwaters is suggested.

Model‐based inversion of amplitude‐variations‐with‐offset data using a genetic algorithm

Geophysics ◽  
1995 ◽  
Vol 60 (4) ◽  
pp. 939-954 ◽  
Author(s):  
Subhashis Mallick
Keyword(s):  
Reflection Coefficient ◽  
Acoustic Impedance ◽  
Poisson’S Ratio ◽  
Input Data ◽  
Synthetic Data ◽  
Single Layer ◽  
P Wave ◽  
Poisson's Ratio ◽  
Reasonable Accuracy ◽  
Avo Inversion

I cast the inversion of amplitude‐variation‐with‐offset (AVO) data into the framework of Bayesian statistics. Under such a framework, the model parameters and the physics of the forward problem are used to generate synthetic data. These synthetic data are then matched with the observed data to obtain an a‐posteriori probability density (PPD) function in the model space. The genetic algorithm (GA) uses a directed random search technique to estimate the shape of the PPD. Unlike the classical inversion methods, GA does not depend upon the choice of an initial model and is well suited for the AVO inversion. For the single‐layer AVO inversion where the amplitudes from a single reflection event are inverted, GA estimates the normal incidence reflection coefficient [Formula: see text] and the contrast of the Poisson’s ratio (Δσ) to reasonable accuracy, even when the signal‐to‐noise ratio is poor. Comparisons of single‐layer amplitude inversion using synthetic data demonstrate that GA inversion obtains more accurate results than does the least‐squares fit to the approximate reflection coefficients as is usually practiced in the industry. In the multilayer AVO waveform inversion, all or a part of the prestack data are inverted. Inversion of this type is nonunique for the estimation of the absolute values of velocities, Poisson’s ratios, and densities. However, by applying simplified approximations to the P‐wave reflection coefficient, I verify that [Formula: see text], the contrast in the acoustic impedance (ΔA), and the gradient in the reflection coefficient (G), can be estimated from such an inversion. From the GA estimated values of [Formula: see text], ΔA, and G, and from reliable estimates of velocity and Poisson’s ratio at the start time of the input data, an inverted model can be generated. I apply this procedure to marine data and demonstrate that the the synthetics computed from such an inverted model match the input data to reasonable accuracy. Comparison of the log data from a nearby well shows that the GA inversion obtains both the low‐ and the high‐frequency trends (within the bandwidth of seismic resolution) of the P‐wave acoustic impedance. In addition to P‐wave acoustic impedance, GA also obtains an estimate of the Poisson’s ratio, an extremely important parameter for the direct detection of hydrocarbons from seismic data.

scholarly journals Use of Attributes on 3D Seismic Data for Studying Mishrif Formation in East Abu-Amoud Field, South-Eastern Iraq

2021 ◽  
pp. 4802-4809
Author(s):  
Mohammed H. Al-Aaraji ◽  
Hussein H. Karim
Keyword(s):  
Seismic Data ◽  
Acoustic Impedance ◽  
Seismic Attributes ◽  
3D Seismic ◽  
Seismic Section ◽  
Reflected Waves ◽  
South Eastern ◽  
Seismic Sections ◽  
Sonic Logs ◽  
3D Seismic Data

      The seismic method depends on the nature of the reflected waves from the interfaces between layers, which in turn depends on the density and velocity of the layer, and this is called acoustic impedance. The seismic sections of the East Abu-Amoud field that is located in Missan Province, south-eastern Iraq, were studied and interpreted for updating the structural picture of the major Mishrif Formation for the reservoir in the field. The Mishrif Formation is rich in petroleum in this area, with an area covering about 820 km2. The horizon was calibrated and defined on the seismic section with well logs data (well tops, check shot, sonic logs, and density logs) in the interpretation process to identify the upper and lower boundaries of the Formation.  Seismic attributes were used to study the formation, including instantaneous phase attributes and relative acoustic impedance on time slice of 3D seismic data . Also, relative acoustic impedance was utilized to study the top of the Mishrif Formation. Based on these seismic attributes, karst features of the formation were identified. In addition, the nature of the lithology in the study area and the change in porosity were determined through the relative acoustic impedance The overlap of the top of the Mishrif Formation with the bottom of the Khasib Formation was determined because the Mishrif Formation is considered as an unconformity surface.

Normal moveout coefficients for horizontally layered triclinic media

Geophysics ◽  
2017 ◽  
Vol 82 (4) ◽  
pp. WA119-WA145 ◽  
Author(s):  
Zvi Koren ◽  
Igor Ravve
Keyword(s):  
Elastic Properties ◽  
Error Term ◽  
Single Layer ◽  
Normal Incidence ◽  
Effective Model ◽  
Pure Mode ◽  
Effective Parameters ◽  
Reflected Waves ◽  
Layered Model ◽  
The Individual

Sedimentary layers affected by vertical compaction and strong lateral tectonic stresses are often characterized by low anisotropic symmetry (e.g., tilted orthorhombic [TOR]/monoclinic or even triclinic). Considering all types of pure-mode and converted waves, we derive the normal moveout (NMO) series coefficients of near normal-incidence reflected waves in arbitrarily anisotropic horizontally layered media, for a leading error term of order six. The NMO series can be either a function of the invariant horizontal slowness (slowness domain) or the surface offset (offset domain). The NMO series coefficients, referred to also as effective parameters, are associated with the corresponding azimuthally varying NMO velocity functions. We distinguish between local (single-layer) and global (overburden multilayer) effective parameters, which are related by forward and inverse Dix-type transforms. We derive the local effective parameters for an arbitrary anisotropic (triclinic) layer, which is the main contribution of this paper. With some additional geologic constraints, the local effective parameters can then be converted into the interval elastic properties. To demonstrate the applicability of our method, we consider a synthetic layered model in which each layer is characterized with TOR symmetry. The corresponding global effective model loses the symmetries of the individual layers and is characterized by triclinic symmetry.

scholarly journals Characterization of Thin Gas Hydrate Reservoir in Ulleung Basin with Stepwise Seismic Inversion

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4077
Author(s):  
Bo-Yeon Yi ◽  
Young-Ho Yoon ◽  
Young-Jun Kim ◽  
Gil-Young Kim ◽  
Yong-Hwan Joo ◽  
...  
Keyword(s):  
High Resolution ◽  
Acoustic Impedance ◽  
Single Layer ◽  
Seismic Inversion ◽  
Thin Layers ◽  
Ulleung Basin ◽  
Hydrate Reservoir ◽  
Maximum Resolution ◽  
Gas Hydrate Reservoir ◽  
The Individual

Natural gas hydrates (GHs) filling sand layer pores are the most promising GHs that can be produced via conventional mechanisms in deep-sea environments. However, the seismic tracking of such thin GH-bearing sand layers is subject to certain limitations. For example, because most GH-bearing sand layers are thin and sparsely interbedded with mud layers, conventional seismic data with a maximum resolution of ~10 m are of limited use for describing their spatial distribution. The 2010 Ulleung Basin drilling expedition identified a relatively good GH reservoir at the UBGH2-6 site. However, the individual GH-bearing sand layers at this site are thin and cannot therefore be reliably tracked using conventional seismic techniques. This study presents a new thin layer tracking method using stepwise seismic inversion and 3D seismic datasets with two different resolutions. The high-resolution acoustic impedance volume obtained is then used to trace thin layers that cannot be harnessed with conventional methods. Moreover, we estimate the high-resolution regional GH distribution based on GH saturation derived from acoustic impedance at UBGH2-6. The thin GH layers, previously viewed as a single layer because of limited resolution, are further subdivided, traced, and characterized in terms of lateral variation.

scholarly journals High-temperature behavior of housed piezoelectric resonators based on CTGS

2021 ◽  
Vol 10 (2) ◽  
pp. 271-279
Author(s):  
Michal Schulz ◽  
Rezvan Ghanavati ◽  
Fabian Kohler ◽  
Jürgen Wilde ◽  
Holger Fritze
Keyword(s):  
Resonance Frequency ◽  
Shear Mode ◽  
Stable Operation ◽  
Mechanical Stiffness ◽  
Temperature Changes ◽  
Resonance Behavior ◽  
Acoustic Losses ◽  
Thickness Shear

Abstract. A temperature sensor based on piezoelectric single crystals allowing stable operation in harsh environments such as extreme temperatures and highly reducing or oxidizing atmospheres is presented. The temperature dependence of the mechanical stiffness of thickness shear mode resonators is used to determine temperature changes. The sensor is based on catangasite (Ca3TaGa3Si2O14 – CTGS), a member of a langasite crystal family. CTGS exhibits an ordered crystal structure and low acoustic losses, even at 1000 ∘C. The resonance frequency and quality factor of unhoused and of housed CTGS resonators are measured up to about 1030 ∘C. A temperature coefficient of the resonance frequency of about 200 Hz K−1 for a 5 MHz device is found and enables determination of temperature changes as small as 0.04 K. Housed CTGS resonators do not show any significant change in the resonance behavior during a 30 d, long-term test at 711 ∘C.

Guided Wave Matching Layer Using a Quarter of Wavelength Technique

2016 ◽  
Vol 833 ◽  
pp. 59-68
Author(s):  
H.M. Ilham ◽  
M.N. Salim ◽  
R.B. Jenal ◽  
T. Hayashi
Keyword(s):  
Acoustic Impedance ◽  
Lamb Wave ◽  
Parent Material ◽  
Guided Wave ◽  
Aluminum Plate ◽  
Multiple Wave ◽  
Reflected Waves ◽  
Matching Layer ◽  
Quarter Wavelength ◽  
Wave Matching

Matching layers of acoustic impedance are intensively studied in ultrasonic transducers for the efficiency of wave transmission. Large impedance mismatch between the active element of piezo and parent material in long range ultrasonic is also expected to have the similar affects on the ratio of the transmitted and reflected waves which can cause high reflection at the interface that result acoustic wave ringing and indicate low transmitted energy for inspection over large areas. This simulation study present analysis of Lamb wave propagation through a single matching layer from a piezoelectric transducers. It explains transmitted waves into aluminum plate using different materials of matching plates at thickness of quarter wavelength. Four matching plates with close to the computed value of acoustic impedance had been used in FEM simulations to study effect of the matching layers on the transmitted Lamb wave in aluminum plate. The results indicated slightly different phenomenon of multiple wave reflections from the transmitted S0 and A0 modes at boundary of the matching layer.

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