Background and Motivation After the discovery of piezoelectric effect in 1880,various piezoelectric devices have been designed and fabricated,such as resonators,filters,transducers,actuators and sensors *** the develo...
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Background and Motivation After the discovery of piezoelectric effect in 1880,various piezoelectric devices have been designed and fabricated,such as resonators,filters,transducers,actuators and sensors *** the developments of techniques,high temperature sensors are desired in many tech *** materials that are operational at elevated temperatures without failure are
<正>Background,Motivation and Objective In oil well operations,cement sheath is located between the casing and formation to provide zonal isolation through the life of a *** of cement sheath integrity is vital for a...
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<正>Background,Motivation and Objective In oil well operations,cement sheath is located between the casing and formation to provide zonal isolation through the life of a *** of cement sheath integrity is vital for a long-term wellbore *** of this
In analogy to photonic crystals, phononic crystals may exhibit complete band gaps in their transmission spectra where the propagation of acoustic or elastic waves is strictly forbidden in all directions. The complete ...
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In analogy to photonic crystals, phononic crystals may exhibit complete band gaps in their transmission spectra where the propagation of acoustic or elastic waves is strictly forbidden in all directions. The complete band gaps could be engineered to provide a vibrationless environment for high precision mechanical systems in given frequency ranges. Understanding the full band structures is expected to lead to the design of new generations of sound shields, filters, transducers, refractive devices such as acoustic lenses and acoustic interferometers, etc. By breaking the periodicity of the systems, it is possible to create highly localized defect or guided modes within the acoustic band gaps, which are analogous to localized modes in a photonic crystal and to localized impurity states in a semiconductor. This makes the phononic crystals potential candidates for the design of elastic or acoustic wave guides. In the case of solid/solid systems, the existence of full band gaps and localized defect modes and the possibility of guiding waves have been investigated theoretically using the different methods. In the present paper, this boundary element method is extended to the calculation of the defect states in two-dimensional phononic crystals. We consider a 2D phononic crystal consisting of a square array. Both scatterers and matrix are homogeneous, isotropic and linear elastic solids. Due to the periodicity of the system, we can restrict our attention to a supercell. For the solid/solid system, when the binary components perfectly contact, the boundary conditions along the interface are that the displacements and the stresses are *** addition, the periodicity of the structures implies that any field quantity(e.g. the displacement, stress, pressure and their derivatives) should obey the following Bloch theorem. The Bloch theorem allows us to solve the problem in a supercell. We bulid the boundary integral equations of the matrix and every scatter. Then the boun
The weakly compressible viscoelastic medium permeated with micro-bubbles has strong dispersive because of *** effective sound speed which can be obtained by effective medium method is very small at low frequency *** o...
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ISBN:
(纸本)9781467348140
The weakly compressible viscoelastic medium permeated with micro-bubbles has strong dispersive because of *** effective sound speed which can be obtained by effective medium method is very small at low frequency *** on the acoustic wave equations and boundary conditions,a method is applied to analyze the reduction of underwater structure-borne noise generated by an axially symmetric ring force on the interior of cylindrical *** structure-borne noise reduction is simulated for the baffle layer of slightly compressible porous *** effects of porosity,thickness,damping and shear modulus of matrix are *** simulations have confirmed that the underwater structure-borne noise can be reduced effectively by the porous *** work is helpful for designing the underwater noise control material.
Numerical modeling for a sandwich dipole well logging transmitting transducer is conducted in this *** characteristics for the first-order bending vibration of the sandwich transducer within different fluid loads are ...
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ISBN:
(纸本)9781467348140
Numerical modeling for a sandwich dipole well logging transmitting transducer is conducted in this *** characteristics for the first-order bending vibration of the sandwich transducer within different fluid loads are numerically *** is found that the resonant frequency and transmitting voltage response level are affected by the density,acoustic velocity and acoustic impedance of the fluid *** numerical results were preliminarily vahdated by our *** numerical analyses may provide useful suggestion for both the simulation design of logging transducer and the acoustic logging applications.
A novel in-plane mode rotary ultrasonic motor is designed in this *** Langevin type bending vibrators are placed separately around the ring shaped stator and used to excite an in-plane vibration mode of the ring *** t...
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ISBN:
(纸本)9781467348140
A novel in-plane mode rotary ultrasonic motor is designed in this *** Langevin type bending vibrators are placed separately around the ring shaped stator and used to excite an in-plane vibration mode of the ring *** tapered rotors are assembled to the inner ring of the stator and clamped together by screw nut.A thin cylindrical supporting is placed under the stator ring,which makes the motor more stable and convenient to *** ultrasonic motor has no bearings,which is good at operating in cryogenic and vacuum environment.
Wavefields excited by a dipole source with ampUtude mismatch are investigated through a 3D finite difference *** is revealed that the directional patterns of a dipole source mainly depend on the source frequency and t...
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ISBN:
(纸本)9781467348140
Wavefields excited by a dipole source with ampUtude mismatch are investigated through a 3D finite difference *** is revealed that the directional patterns of a dipole source mainly depend on the source frequency and the ampUtude ratio of the two monopoles combining the transmitter.A mismatched dipole will not generate the non-dipole components in the borehole as long as the dipole receivers are ideally *** both the transmitter and receivers are mismatched,the Stoneley mode with strong amplitudes appears in the in-line and cross-line components of the cross-dipole sonic logging *** would probably lead to incorrect evaluations of shear velocity and azimuthal anisotropy of the formation.
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