Article

Sulla eccezionalita' delle onde di mutua influenza magneto-elastica

January 1973

Authors:

By reducing magneto-elasticity waves study to a first order system it is shown that discontinuity waves of magneto-elastic mutually influence are exceptional. It is also pointed out that the second derivative of two of three possible propagation velocities, generally undergoes a discontinuity across the wave front

On a magneto-elastic system with discontinuous coefficients and the propagation of a weak discontinuity

Article

Sep 1977

Andrea Donato

In questa nota si deduce un sistema di equazioni per la Magneto-elasticita' con deformazioni finite nel caso tridimensionale. Come applicazione si studia la propagazione di una discontinuita' debole nella ipotesi che i coefficienti delle equazioni risultano essi stessi discontinui. Tale ipotesi risulta verificata, ad es., quando si considerano due differenti mezzi magneto-elastici uno in contatto con l'altro

ResearchGate has not been able to resolve any references for this publication.

Article

Admittance of Rectangular Waveguide Radiating from a Conducting Cylinder

October 1988 · IEEE Transactions on Antennas and Propagation

Trevor S Bird

Theory and experiment are compared for the admittance presented to a rectangular waveguide which terminates at an arbitrary angle in the surface of a conducting cylinder. Two methods are described for calculating the admittance: a single-mode approximation from the modal solution and an alternative asymptotic solution. Using these methods, the effect of aperture orientation on admittance, and the ... [Show full abstract] results obtained are compared with the experiment. The single-mode approximation is in good agreement with experimental results for the case when the input waveguide supports the TE₁₀ mode only. The accuracy of the approximate formula for waveguide admittance was also verified. The admittance is shown to be weakly dependent on aperture orientation for moderately large cylinders

Article

Full-text available

Coupling reduction of antenna array elements using small interdigital capacitor loaded slots

January 2012 · Progress In Electromagnetics Research C

Adel B. Abdel-Rahman

Small size capacitor loaded ground plane slots are used to reduce the mutual coupling between elements in a microstrip antenna array design. The proposed compact slots are inserted between the adjacent E-plane coupled elements in the array to limit the propagation of surface waves between the elements of the array. In order to validate the feasibility of the proposed structure, a two-element ... [Show full abstract] array with 0.5λ o distance between centers of two patches is designed, fabricated, and measured. The measured results show a reduction in mutual coupling of 17 dB obtained between elements at the operation frequency.

Article

Spatial distribution of the electromagnetic radiation accompanying propagation of magnetostatic surf...

July 2000 · Technical Physics Letters

A model is proposed for description of the spatial distribution of electromagnetic waves (EMWs) generated during the propagation of magnetostatic surface waves (MSSWs) in a ferrite film (FF) magnetized by a transversely nonuniform field. The EMW radiation pattern calculated using this model has two lobes mutually symmetric relative to the FF plane. The lobes are tilted in the direction of MSSW ... [Show full abstract] propagation, the tilt increasing with the MSSW velocity approaching the velocity of EMW in the film. The calculated results are in good qualitative agreement with experiment.

Article

Population evolution in mutualistic Lotka–Volterra system with spatial diffusion

February 2014 · Physica A Statistical Mechanics and its Applications

We consider the population dynamics of two species described by the mutualistic Lotka–Volterra model with a +/+ interaction in the presence of spatial diffusions. The results demonstrate that diffusion does not affect the system’s stability but it brings two situations: one is a win–win situation where both species propagate with the same largest speed; in the other situation the aggressive ... [Show full abstract] species has two propagating wave fronts and the other species travels with a single slow wave front. Our model may help to understand the evolution of mutualism.

Article

Full-text available

Anomalous Interaction of Spatial Solitons in Photorefractive Media

April 1998 · Physical Review Letters

We investigate the interaction of mutually incoherent spatial solitons in photorefractive media with anisotropic nonlocal nonlinear response. We show that the photorefractive nonlinearity leads to an anomalous interaction between solitons. Theoretical and experimental results reveal that an incoherent soliton pair may experience both attractive and repulsive forces, depending on their mutual ... [Show full abstract] separation.

Article

Temporal coherence of acoustic rays and modes using the path integral approach

June 2012 · The Journal of the Acoustical Society of America

Tsih C Yang

Acoustic propagation can be described by rays and normal modes. Applying the path integral to refractive rays in three dimensional space, Dashen et al. [J. Acoust. Soc. Am. 77, 1716-1722 (1985)] derived the mutual coherence function of the acoustic field. For shallow water where sound interacts with boundaries, the acoustic field can be described by vertical modes and horizontal rays. Applying ... [Show full abstract] the path integral to the horizontal rays, one obtains the mutual coherence function of the normal modes. This paper applies this formulation to the derivation of the temporal coherence function of individual modes and also that of the acoustic field in the presence of linear internal waves. The effects of mode coupling due to internal waves on temporal coherence loss are illustrated with numerical calculations.

Chapter

Gain-Guided Diode-Laser Oscillators

January 1994

Nils W. Carlson

The distinction between diode-laser array oscillators, the subject of this chapter, as well as Chaps. 6 and 7, and diode-laser amplifiers, the subject of Chap. 8, is being made because of the difference in the mode-discrimination mechanisms. Laser oscillators will have both forward and backward propagating waves that provide feedback to the active region in the optical cavity; whereas laser ... [Show full abstract] amplifiers are injected with an external-traveling wave that determines the modal properties. Some or all elements of a laser-array oscillator are mutually coupled; however in amplifier arrays the coupling is predominantly unidirectional, with the direction being determined by the propagation direction of the dominant traveling wave, which typically originates from a single-mode oscillator section.

Article

Reduction of Mutual coupling in Microstrip Array Antenna using Polygonal Defected Ground Structure

April 2011 · The Applied Computational Electromagnetics Society Journal (ACES)

The surface wave propagation is a significant problem in microstrip array antennas. Several methods have been reported to suppress the propagation of surface wave such as defected ground structure (DGS). The main problem in DGS is to determine the shape of ground slot. In this paper, a new method is proposed in which the slot is assumed to be a polygon and its shape is obtained by enhanced ... [Show full abstract] genetic algorithm (GA) and ant colony optimization (ACO) to have an array antenna with good gain and the least amount of return loss and mutual coupling.

Article

A study of multiple scattering in bubbly liquids by many-body theory

February 2011 · Canadian Journal of Physics

In this paper it is suggested that acoustic-wave propagation in bubbly liquids can be easily studied using the diagram method in many-body theory. The merit of this method is that it allows convenient inclusion of any higher order bubble interactions. In particular consideration is given to a higher order correction due to the mutual interaction of bubbles. It is shown that under certain ... [Show full abstract] circumstances, this correction could be rather significant. Other higher order interactions are also briefly discussed.

Article

Full-text available

Spatial coherence property of a laser beam during acousto-optic diffraction

June 1999 · Journal of the Optical Society of America A

Chen-Wen Tarn

The spatial coherence property of a partially coherent light during the Bragg acousto-optic interaction is investigated. Starting from the wave equation, four coupled, parabolic equations that can describe the evolution and the propagation of mutual intensity functions of the diffracted light during the acousto-optic interaction are derived. A partially coherent light beam with arbitrary spatial ... [Show full abstract] profile and complex degree of spatial coherence is assumed to be incident on the Bragg acousto-optic cell. With the use of a statistical theory of linear systems, a general formalism of angular-correlation functions for zero-order and minus-one-order light can be derived. The corresponding mutual intensity and complex coherence factor functions are hence implemented numerically. From the solutions one can note that, through the acousto-optic interaction, the degrees of spatial coherence of the diffracted light beams are controllable by the intensity and the frequency of the sound wave.

Article

Formation Mechanisms of Vibration Band Gaps in Locally Resonant Periodic Structures

February 2019 · Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University

Detailed formation mechanisms of vibration band gaps in locally resonant periodic structures are investigated for the problem that the mechanism of the detailed formation process of vibration band gaps in locally resonant periodic structures is not clear and the investigation bases on a two-dimensional locally resonant periodic structure. Firstly, it bases on the dynamic theory that a basic ... [Show full abstract] theoretical hypothesis of the formation mechanism for the band gap of locally resonant periodic structures is proposed based on the modal superposition principle; Secondly, the detailed formation mechanism of vibration band gaps is further clarified according to the formation mechanism model of band gaps; Finally, the formation mechanism of vibration band gaps is verified by the interaction between the elastic wave and the structure during the formation of vibration band gaps in a typical two-dimensional locally resonant periodic structure. The result shows that there exist six types of generalized propagation modes of waves in the locally resonant periodic structure, while these generalized propagation modes are formed by the mutual transformation of the main modes and these main modes are generated by corresponding 12 modes based on the superposition principle. The vibration mode dominated by the main mode of the vibrator determines the formation of a vibration band gap by suppressing or releasing the generalized propagation mode. When the oscillator's main mode suppresses the generalized propagation mode of the wave, a generalized sub-band gap that can only suppress the corresponding propagation mode is formed. The influence mechanism of the band gap is further studied and an active design method of the band gap is proposed. This research not only perfects the basic theory of periodic structure, but also lays a theoretical foundation for the study of band gap theory of periodic structure and the active design of band gap characteristics, and also provides a new method for vibration reduction technology of engineering structures.

Article

Baroclinic instability in a three layer flow: A wave approach

November 1998 · Dynamics of Atmospheres and Oceans

Thierry Pichevin

The baroclinic instability of a three layer flow including a bottom slope is addressed analytically. The classical approach calculating the growth rate of the perturbation of a given basic state leads to very intricate results and does not permit a global view of the solution. In this paper, it is used only to derive very general results regarding the long wavelengths (in an infinitely wide ... [Show full abstract] channel): they are shown to be always unstable with a flat bottom, and to be stabilized by a bottom slope provided that the speed in the two lower layers are different. To solve the general problem, it is shown that instabilities can be characterized by interactions of Rossby waves propagating in each layer. Specifically, if each layer is isolated from the others, free topographic Rossby waves (due to the slope of the interfaces) can propagate therein. Coupling the layers then leads to wave interactions. These interactions are unstable when the Rossby waves propagate at the same absolute speed and mutually reinforce. This simple technique leads to a simple and general analysis, and enables a general survey of the parameter space. It is shown that the instabilities are mainly governed by two parameters: S=(−1/ϵ)(U3−U2)/(U2−U1) and c=(ρ3−ρ2)/(ρ2−ρ1). The interacting waves determine if the instability grows thanks to energy released from the upper interface, the lower interface, or both. Finally, since the analysis is carried out using topographic Rossby waves, the role of the bottom slope is quite simple to incorporate.