Multibubble standing wave patterns can be generated from a flat piezoceramic transducer element radiating into water. By adding a second transducer positioned at 90 degrees from the transducer generating the standing wave, a 3-dimensional volume of stable single bubbles can be established. Further, the addition of the second transducer stabilizes the bubble pattern so that individual bubbles may be studied. The size of the bubbles and the separation of the standing waves depend on the frequency of operation. Two transducers, operating at frequencies above 500 kHz, provided the most graphic results for the configuration used in this study. At these frequencies stable bubbles exhibit a bright sonoluminescence pattern. Whereas stable SBSL is well-known, stable MBSL has not been previously reported. This paper includes discussions of the acoustic responses, standing wave patterns, and pictorial results of the separation of individual bubble sonoluminescence in a multibubble sonoluminescence environment. 相似文献
The three-dimensional spin-1 Ising superlattice consisting of two different ferromagnetic materials with two different crystal fields Δ1 and Δ2 is considered in the mean field approximation. The phase diagrams are considered in the (t,d2) plane for different ranges of variation of d1(t=T/J,d1=Δ1/J, d2=Δ2/J are the reduced temperature and crystal fields respectively). The phase diagrams exhibit a variety of multicritical points and reentrant and double reentrant behaviours. They are found to depend qualitatively and/or quantitatively on the thicknesses of the materials in a supercell. This has direct consequences on the nature of the magnetic states of superlattices with different thicknesses. 相似文献
New aromatic compounds with a pyridazine core have been synthesized. Four electron‐withdrawing monomers have been easily prepared from simple condensation reactions and ring closure procedures. Optimized HOMO, LUMO, and bandgap energy levels have been obtained. The resulting conjugated polymers have been tested in organic solar cells. First studies have revealed power conversion efficiencies up to 0.5% for an active area of 1.0 cm2.
Based on a modified-Darcy-Maxwell model, two-dimensional, incompressible and heat transfer flow of two bounded layers, through electrified Maxwell fluids in porous media is performed. The driving force for the instability under an electric field, is an electrostatic force exerted on the free charges accumulated at the dividing interface. Normal mode analysis is considered to study the linear stability of the disturbances layers. The solutions of thelinearized equations of motion with the boundary conditions lead to an implicit dispersion relation between the growth rate and wave number. These equations are parameterized by Weber number, Reynolds number, Marangoni number, dimensionless conductivities, and dimensionless electric potentials. The case of long waves interfacial stability has been studied. The stability criteria are performed theoretically in which stability diagrams are obtained. Inthe limiting cases, some previously published results can be considered as particular cases of our results. It is found that the Reynolds number plays a destabilizing role in the stability criteria, while the damping influence is observed for the increasing of Marangoni number and Maxwell relaxation time. 相似文献
A substructuring technique is presented for transient dynamic analysis of systems composed of interconnected rigid and elastic bodies that undergo large angular displacements. Displacement of elastic bodies is represented by superposition of local linear elastic deformation on large displacement of body reference coordinate systems. Elastic bodies are thus represented by combined sets of reference and local elastic generalized coordinates. Modal analysis and substructuring of individual elastic components allow for elimination of insignificant modes. Equations of motion and constraint are formulated in terms of mixed sets of modal and reference generalized coordinates. Planar and spatial linkages with flexible elements are presented to illustrate use of the method developed. 相似文献
The Absolute Nodal Coordinate Formulation (ANCF) has been initiated in 1996 by Shabana (Computational Continuum Mechanics,
3rd edn., Cambridge: Cambridge University Press, 2008). It introduces large displacements of planar and spatial finite elements relative to the global reference frame without
using any local frame. A sub-family of beam, plate and cable finite elements with large deformations are proposed and employed
the 3D theory of continuum mechanics. In the ANCF, the nodal coordinates consist of absolute position coordinates and gradients
that can be used to define a unique rotation and deformation fields within the element. In contrast to other large deformation
formulations, the equations of motion contain constant mass matrices as well as zero centrifugal and Coriolis inertia forces.
The only nonlinear term is a vector of elastic forces. This investigation concerns a way to generate new finite element in
the ANCF for laminated composite plates. This formulation utilizes the assumption that the bonds between the laminae are thin
and shear is non-deformable. Consequently, the Equivalent Single Layer, ESL model, is implemented. In the ESL models, the
laminate is assumed to deform as a single layer, assuming a smooth variation of the displacement field across the thickness.
In this paper, the coupled electromechanical effect of Piezoelectric Laminated Plate is imposed within the ANCF thin plate
element, in such a way as to achieve the continuity of the gradients at the nodal points, and obtain a formulation that automatically
satisfies the principle of work and energy. Convergence and accuracy of the finite-element ANCF Piezoelectric Laminated Plate
is demonstrated in geometrically nonlinear static and dynamic test problems, as well as in linear analysis of natural frequencies.
The computer implementation and several numerical examples are presented in order to demonstrate the use of the formulation
developed in this paper. A comparison with the commercial finite element package COMSOL MULTIPHYSICS () is carried out with an excellent agreement. 相似文献
In this work, the field equations of the linear theory of thermoelasticity have been constructed in the context of a new consideration
of Fourier law of heat conduction with time-fractional order and three-phase lag. A uniqueness and reciprocity theorems are
proved. One-dimensional application for a half-space of elastic material in the presence of heat sources has been solved using
Laplace transform and state space techniques Ezzat (Canad J Phys Rev 86:1241–1250, 2008). According to the numerical results and its graphs, conclusion about the new theory has been established. 相似文献
The effect of an externally applied electric field on the stability of a thin fluid film over an inclined porous plane is analyzed using linear and non-linear stability analysis in the long wave limit. The principle aim of this study is to illustrate the influence of electric field on the non-linear stability of a thin liquid layer flow down incline substrate when the plane is porous. The driving force for the instability under an electric field is an electrostatic force exerted on the free charges accumulated at the dividing interface. The coupled non-linear evolution equations for the local film thickness and the interfacial charge for two-dimensional disturbances are derived to analyze the effect of long-wave instabilities. The method of multiple scales is applied to obtain approximate solutions and analyze the stability criteria. Numerical simulations of this system of non-linear evolution equations are performed. It is found that the permeability parameter as well as the inclination of the plane plays a destabilizing role in the stability criteria, while the damping influence is observed for increasing of the electrical conductivity in both linear and non-linear behavior. 相似文献
The present study is intended to study heat and mass transfer in a vertical annular cylinder embedded with saturated porous
medium. The inner surface of cylinder is maintained at uniform wall temperature and uniform wall concentration. The governing
partial differential equations are non-dimensionalised and solved by using finite element method (FEM). The porous medium
is discritised using triangular elements with uneven element size. Large number of smaller-sized elements are placed near
the walls of the annulus to capture the smallest variation in solution parameters. The results are reported for both aiding
and opposing flows. The effects of various non-dimensional numbers such as buoyancy ratio, Lewis number, Rayleigh number,
aspect ratio, etc on heat and mass transfer are discussed. The temperature and concentration profiles are presented. 相似文献