Band Gap Formation by Cylinder Arrays in an Acoustic Waveguide

2007 ◽  
Author(s):  
Liang-Wu Cai ◽  
David C. Calvo ◽  
Dalcio K. Dacol ◽  
Gregory J. Orris
Keyword(s):  
Acoustic Waves ◽  
Stop Band ◽  
Three Dimensional ◽  
Wave Number ◽  
Pass Band ◽  
Gap Formation ◽  
Numerical Examples ◽  
Cylinder Arrays ◽  
Horizontal Wave ◽  
Special Case

Scattering of acoustic waves by arrays of identical circular cylindrical scatterers in a horizontal waveguide is studied. Although three-dimensional in its geometry, the waveguide permits only a finite number of modes of acoustic wave propagating in different directions with respect to horizontal, and the number of these propagating modes increases as the frequency increases. The horizontal wave numbers of these modes span a range of frequency limited by the total wave number. Numerical examples are used to explore a special case in which the cylinder height equals the depth of the waveguide and in which the cylinders and the waveguide have pressure-release boundaries at both top and bottom surfaces. In such a special case, there is no coupling among the modes permitted by the waveguide and hence is the simplest case for such problems. It is observed that the combination of the modes generally decreases the wave-blocking effects of a stop band; and it is likely that a stop band in one waveguide mode might correspond to a pass band in a different mode. However, numerical examples also show that the main characteristics of a stop band are maintained, despite the multiple modes; and it is possible to extend the stop band by cascading cylinders arrays of different arrangement.

INVERSE ACOUSTIC SCATTERING PROBLEMS IN OCEAN ENVIRONMENTS

1999 ◽  
Vol 07 (02) ◽  
pp. 111-132 ◽  
Author(s):  
YONGZHI XU
Keyword(s):  
Acoustic Waves ◽  
Three Dimensional ◽  
Acoustic Scattering ◽  
Stratified Medium ◽  
Computational Results ◽  
Scattering Problems ◽  
Numerical Examples ◽  
Layered Waveguide ◽  
Shape Determination

This paper presents theoretical and computational results from our research on inverse scattering problems for acoustic waves in ocean environments. In particular, we discuss the determination of a three-dimensional (3-D) distributed inhomogeneity in a two-layered waveguide from scattered sound and the shape determination of an object in a stratified medium. Numerical examples are presented.

scholarly journals On the Solutions of Three-Dimensional Rational Difference Equation Systems

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
H. S. Alayachi ◽  
A. Q. Khan ◽  
M. S. M. Noorani
Keyword(s):  
Difference Equation ◽  
Mathematical Program ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Boundedness Of Solutions ◽  
Real Numbers ◽  
Third Order ◽  
Numerical Examples ◽  
Rational Difference Equation ◽  
Special Case

In this paper, we are interested in a technique for solving some nonlinear rational systems of difference equations of third order, in three-dimensional case as a special case of the following system: x n + 1 = y n z n − 1 / y n ± x n − 2 , y n + 1 = z n x n − 1 / z n ± y n − 2 ,  and  z n + 1 = x n y n − 1 / x n ± z n − 2 with initial conditions x − 2 , x − 1 , x 0 , y − 2 , y − 1 , y 0 , z − 2 , z − 1 ,  and  z 0 are nonzero real numbers. Moreover, we study some behavior of the systems such as the boundedness of solutions for such systems. Finally, we present some numerical examples by giving some numerical values for the initial values of each case. Some figures have been given to explain the behavior of the obtained solutions in the case of numerical examples by using the mathematical program MATLAB to confirm the obtained results.

Engineered Three-dimensional Colloidal Crystals Containing a Planar Defect

2005 ◽  
Vol 901 ◽  
Author(s):  
Pascal Massé ◽  
Beatrice Agricole ◽  
Elisabeth Sellier ◽  
Serge Ravaine
Keyword(s):  
Colloidal Particles ◽  
Near Infrared ◽  
Stop Band ◽  
Three Dimensional ◽  
Colloidal Crystals ◽  
Defect Mode ◽  
Middle Layer ◽  
Behenic Acid ◽  
Pass Band ◽  
Extrinsic Defect

AbstractWe have fabricated three-dimensional (3D) colloidal crystals containing a two-dimensional (2D) defect as the middle layer by the Langmuir-Blodgett (LB) technique. Either a homogeneous sheet made of hundreds layers of behenic acid or a single monolayer of silica colloidal particles of various sizes was inserted between two opal films of silica spheres. The presence of the extrinsic defect led to an impurity mode within the photonic stop band, which was observed as a pass band in the near-infrared (NIR) spectra. The position of this defect mode was found to vary periodically with the value of the ratio of the thickness of the defect layer to the diameter of the colloids of the upper and lower opals.

scholarly journals Experimental Study on Coherent Structures by Particles Suspended in Half-Zone Thermocapillary Liquid Bridges: Review

Fluids ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 105
Author(s):  
Ichiro Ueno
Keyword(s):  
Coherent Structures ◽  
Three Dimensional ◽  
Wave Number ◽  
Flow Structures ◽  
Liquid Bridges ◽  
Thermocapillary Effect ◽  
Particle Accumulation ◽  
Azimuthal Wave Number ◽  
Experimental Approaches ◽  
Particle Behaviour

Coherent structures by the particles suspended in the half-zone thermocapillary liquid bridges via experimental approaches are introduced. General knowledge on the particle accumulation structures (PAS) is described, and then the spatial–temporal behaviours of the particles forming the PAS are illustrated with the results of the two- and three-dimensional particle tracking. Variations of the coherent structures as functions of the intensity of the thermocapillary effect and the particle size are introduced by focusing on the PAS of the azimuthal wave number m=3. Correlation between the particle behaviour and the ordered flow structures known as the Kolmogorov–Arnold—Moser tori is discussed. Recent works on the PAS of m=1 are briefly introduced.

scholarly journals A Variance Gamma model for Rugby Union matches

2020 ◽  
Vol 17 (1) ◽  
pp. 67-75
Author(s):  
John Fry ◽  
Oliver Smart ◽  
Jean-Philippe Serbera ◽  
Bernhard Klar
Keyword(s):  
Three Dimensional ◽  
Rugby Union ◽  
Three Dimensional Model ◽  
Gamma Model ◽  
Variance Gamma ◽  
Poisson Models ◽  
History Of ◽  
Bonus Points ◽  
Variance Gamma Model ◽  
Special Case

Abstract Amid much recent interest we discuss a Variance Gamma model for Rugby Union matches (applications to other sports are possible). Our model emerges as a special case of the recently introduced Gamma Difference distribution though there is a rich history of applied work using the Variance Gamma distribution – particularly in finance. Restricting to this special case adds analytical tractability and computational ease. Our three-dimensional model extends classical two-dimensional Poisson models for soccer. Analytical results are obtained for match outcomes, total score and the awarding of bonus points. Model calibration is demonstrated using historical results, bookmakers’ data and tournament simulations.

Stability and instability of some nonlinear dispersive solitary waves in higher dimension

1996 ◽  
Vol 126 (1) ◽  
pp. 89-112 ◽  
Author(s):  
Anne de Bouard
Keyword(s):  
Solitary Waves ◽  
Acoustic Waves ◽  
Vries Equation ◽  
Three Dimensional ◽  
Higher Dimension ◽  
Ion Acoustic Waves ◽  
Stability And Instability ◽  
Ion Acoustic ◽  
De Vries ◽  
The Stability

We study the stability of positive radially symmetric solitary waves for a three dimensional generalisation of the Korteweg de Vries equation, which describes nonlinear ion-acoustic waves in a magnetised plasma, and for a generalisation in dimension two of the Benjamin–Bona–Mahony equation.

Novel Low-Pass Microwave Filter Based on Rectangular Ring DGS

2013 ◽  
Vol 273 ◽  
pp. 371-374
Author(s):  
Bao Ping Li ◽  
Yan Liang Zhang
Keyword(s):  
Stop Band ◽  
Center Frequency ◽  
Pass Band ◽  
Band Pass Filter ◽  
Defected Ground Structure ◽  
Ground Structure ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Compact Size ◽  
Low Pass

Due to the frequency response periodicity of distributed transmission line, microstrip band-pass filter usually produces parasitic pass-band and outputs harmonics away from the center frequency of main pass-band. Based on the study of rectangular ring defected ground structure, a 5-order microstrip LPF(low-pass filter) was designed using the single-pole band-stop and slow-wave characteristics of the rectangular ring DGS(Defected Ground Structure) and SISS(Step-Impedance Shunt Stub) structure. Compared with traditional LPF, this LPF presents the advantages of compact size, low insertion loss, broad stop-band and high steep. It also validates the requirements of miniaturization and high performance for filters.

Design and Simulation of Switched Capacitor Filter for Speed Change Parameter Converter

2013 ◽  
Vol 562-565 ◽  
pp. 1132-1136
Author(s):  
Xiao Wei Liu ◽  
Jian Yang ◽  
Song Chen ◽  
Liang Liu ◽  
Rui Zhang ◽  
...  
Keyword(s):  
Stop Band ◽  
Cutoff Frequency ◽  
Rapid Change ◽  
Pass Band ◽  
Cmos Process ◽  
Switched Capacitor ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass ◽  
The Time Domain

In this paper, we design a high-order switched capacitor filter for rapid change parameter converter. This design uses a structure which consists of three biquads filter sub-units. The design is a 6th-order SC elliptic low-pass filter, and the sample frequency is 250 kHz. By the MATLAB Simulink simulation, the system can meet the design requirements in the time domain. In this paper, the 6th-order switched capacitor elliptic low-pass filter was implemented under 0.5 um CMOS process and simulated in Cadence. The final simulation results show that the pass-band cutoff frequency is 10 kHz, and the maximum pass-band ripple is about 0.106 dB. The stop-band cutoff frequency is 20 kHz, and the minimum stop-band attenuation is 74.78 dB.

THREE‐DIMENSIONAL FILTERING WITH AN ARRAY OF SEISMOMETERS

Geophysics ◽  
1964 ◽  
Vol 29 (5) ◽  
pp. 693-713 ◽  
Author(s):  
John P. Burg
Keyword(s):  
Array Processing ◽  
Three Dimensional ◽  
Processing System ◽  
Seismic Signal ◽  
P Wave ◽  
Wave Number ◽  
Theoretical Problem ◽  
Least Mean Square ◽  
Optimum Frequency ◽  
Filtering Theory

The development of the Wiener linear least‐mean‐square‐error processing theory for seismic signal enhancement through use of a two‐dimensional array of seismometers leads to the theory of three‐dimensional filtering. The array processing system for this theory consists of applying individual frequency filters to the outputs of the seismometers in the array before summation. The basic design equations for the optimum frequency filters are derived from the Wiener multichannel theory. However, the development of the three‐dimensional frequency and vector‐wave‐number‐filtering theory results in a physical understanding of generalized linear array processing. The three‐dimensional filtering theory is illuminated by a theoretical problem of P‐wave enhancement in the presence of ambient seismic noise. An analysis of the results shows why optimum three‐dimensional filtering gives greater signal‐to‐noise ratio improvements than achieved by conventional array processing techniques.

Unsteady Lifting Surface Theory for a Rotating Cascade of Swept Blades

1989 ◽  
Author(s):  
Hidekazu Kodama ◽  
Masanobu Namba
Keyword(s):  
Three Dimensional ◽  
Acoustic Power ◽  
Aerodynamic Characteristics ◽  
Blade Loading ◽  
Surface Theory ◽  
Numerical Examples ◽  
Lifting Surface ◽  
Blade Flutter ◽  
Annular Cascade ◽  
Remarkable Reduction

A lifting surface theory is developed to predict the unsteady three-dimensional aerodynamic characteristics for a rotating subsonic annular cascade of swept blades. A discrete element method is used to solve the integral equation for the unsteady blade loading. Numerical examples are presented to demonstrate effects of the sweep on the blade flutter and on the acoustic field generated by interaction of rotating blades with a convected sinusoidal gust. It is found that increasing the sweep results in decrease of the aerodynamic work on vibrating blades and also remarkable reduction of the modal acoustic power of lower radial orders for both forward and backward sweeps.

Sign in / Sign up

Export Citation Format

Share Document