On the coupling of resonance and Bragg scattering effects in three-dimensional locally resonant sonic materials

Ultrasonics ◽  
2013 ◽  
Vol 53 (7) ◽  
pp. 1332-1343 ◽  
Author(s):  
Bo Yuan ◽  
Victor F. Humphrey ◽  
Jihong Wen ◽  
Xisen Wen
Keyword(s):  
Three Dimensional ◽  
Bragg Scattering ◽  
Scattering Effects

scholarly journals the Interaction of Resonance And Bragg Scattering Effects for the Locally Resonant Phononic Crystal with Alternating Elastic and Fluid Matrices

2017 ◽  
Vol 42 (4) ◽  
pp. 725-733 ◽  
Author(s):  
Bo Yuan ◽  
Yong Chen ◽  
Min Jiang ◽  
Shuai Tang ◽  
Miao He ◽  
...  
Keyword(s):  
Phononic Crystal ◽  
Three Dimensional ◽  
Band Gaps ◽  
Acoustic Properties ◽  
Bragg Scattering ◽  
Wavelength Band ◽  
Local Resonance ◽  
Scattering Effects ◽  
Acoustic Speed ◽  
Sub Wavelength

Abstract Three-dimensional (3D) locally resonant phononic crystals (LRPCs) are studied with the aim of optimising the sub-wavelength band gaps of such composites. By analysing their effective acoustic properties, it has been found that the effective acoustic speed of the composite will drop to zero when local resonance arise, and will increase monotonically when Bragg scattering effects occur. Moreover, if the matrix is a low-shear-speed medium, local resonators can significantly reduce the effective acoustic speed of the composite and, therefore, lower the frequency where Bragg scattering effects occur. Hence, a specific LRPC with alternating elastic and fluid matrices is proposed, whose resonance and Bragg gaps are already close in frequency. The fluid matrix behaves as a wave filter, which prevents the shear waves from propagating in the composite. By using the layer-multiple-scattering theory, the coupling behaviour of local resonance and Bragg scattering band gaps has been investigated. Both gaps are enhanced when they move closer to each other. Finally, a gap-coupled case is obtained that displays a broad sub-wavelength band gap. Such proposal excels at the application of underwater acoustic materials since the arrangement of structure can be handily adjusted for tuning the frequency of coupled gap.

Electron crystallographic determination of the 3-D structure of staurolite at atomic resolution

1991 ◽  
Vol 49 ◽  
pp. 540-541
Author(s):  
Kenneth H. Downing ◽  
Hu Meisheng ◽  
Hans-Rudolf Went ◽  
Michael A. O'Keefe
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
High Resolution Electron Microscopy ◽  
Atomic Resolution ◽  
Dimensional Structure ◽  
Structure Information ◽  
Resolution Electron ◽  
Scattering Effects ◽  
High Resolution Images ◽  
Effects Of Radiation

With current advances in electron microscope design, high resolution electron microscopy has become routine, and point resolutions of better than 2Å have been obtained in images of many inorganic crystals. Although this resolution is sufficient to resolve interatomic spacings, interpretation generally requires comparison of experimental images with calculations. Since the images are two-dimensional representations of projections of the full three-dimensional structure, information is invariably lost in the overlapping images of atoms at various heights. The technique of electron crystallography, in which information from several views of a crystal is combined, has been developed to obtain three-dimensional information on proteins. The resolution in images of proteins is severely limited by effects of radiation damage. In principle, atomic-resolution, 3D reconstructions should be obtainable from specimens that are resistant to damage. The most serious problem would appear to be in obtaining high-resolution images from areas that are thin enough that dynamical scattering effects can be ignored.

scholarly journals Quantitative allocation of Bragg scattering effects in highly efficient OLEDs fabricated on periodically corrugated substrates

2013 ◽  
Vol 21 (14) ◽  
pp. 16319 ◽  
Author(s):  
C. Fuchs ◽  
T. Schwab ◽  
T. Roch ◽  
S. Eckardt ◽  
A. Lasagni ◽  
...  
Keyword(s):  
Bragg Scattering ◽  
Highly Efficient ◽  
Scattering Effects

scholarly journals Modeling acoustic waves with paraxial extrapolators

Geophysics ◽  
1990 ◽  
Vol 55 (3) ◽  
pp. 306-319 ◽  
Author(s):  
R. W. Graves ◽  
R. W. Clayton
Keyword(s):  
Acoustic Waves ◽  
Parallel Machines ◽  
Three Dimensional ◽  
Azimuthal Anisotropy ◽  
Splitting Technique ◽  
Active Storage ◽  
Transmission And Reflection Coefficients ◽  
Scattering Effects ◽  
Heterogeneous Models ◽  
The Media

Modeling by paraxial extrapolators is applicable to wave‐propagation problems in which most of the energy is traveling within a restricted angular cone about a principal axis of the problem. Using this technique, frequency‐domain finite‐difference solutions accurate for propagation angles out to 60° are readily generated for both two‐dimensional (2-D) and three‐dimensional (3-D) models. Solutions for 3-D problems are computed by applying the 2-D paraxial operators twice, once along the x‐axis and once along the y‐axis, at each extrapolation step. The azimuthal anisotropy inherent to this splitting technique is essentially eliminated by adding a phase‐correction operator to the extrapolation system. For heterogeneous models, scattering effects are incorporated by determining transmission and reflection coefficients at structural boundaries within the media. The direct forward‐scattered waves are modeled with a single pass of the extrapolation operator in the paraxial direction for each frequency. The first‐order backscattered energy is then modeled by extrapolation (in the opposite direction) of the reflected field determined on the first pass. Higher order scattering can be included by sweeping through the model with more passes. The chief advantages of the paraxial approach are (1) active storage is reduced by one dimension compared to solutions which must track both forward‐scattered and backscattered waves simultaneously; thus, realistic 3-D problems can fit on today’s computers, (2) the decomposition in frequency allows the technique to be implemented on highly parallel machines, (3) attenuation can be modeled as an arbitrary function of frequency, and (4) only a small number of frequencies are needed to produce movie‐like time slices.

Neutron diffraction studies of the actinide oxides I. Uranium dioxide and thorium dioxide at room temperature

1963 ◽  
Vol 274 (1356) ◽  
pp. 122-133 ◽  
Keyword(s):  
Room Temperature ◽  
Three Dimensional ◽  
Coherent Scattering ◽  
Systematic Errors ◽  
Fluorite Structure ◽  
Bragg Scattering ◽  
Thorium Dioxide ◽  
Structure Factors ◽  
Neutron Structure ◽  
Actinide Oxides

Three-dimensional neutron structure factors have been measured on single crystals grown from the melt and from solution. The Bragg reflexions divide into three groups, strong, medium and weak: the strong and medium reflexions are affected by extinction, which is particularly severe for solution-grown crystals, and the weak reflexions by double Bragg scattering. Least-squares analysis of experimental data corrected for these systematic errors confirms that the oxides have the fluorite structure at room temperature and gives precise values for the Debye-Waller factors of the heavy-metal and oxygen atoms and for the ratios of their nuclear coherent scattering amplitudes.

Neutron Scattering Measurements of the Staggered Magnetization of an Antiferromagnetic Epitaxial thin Film FeF2

1993 ◽  
Vol 313 ◽  
Author(s):  
D. P. Belanger ◽  
M. Lui ◽  
R. W. Erwin
Keyword(s):  
Thin Film ◽  
Neutron Scattering ◽  
Critical Behavior ◽  
Three Dimensional ◽  
Bragg Scattering ◽  
Double Crystal ◽  
Elastic Neutron ◽  
Antiferromagnetic Materials ◽  
Scattering Measurements ◽  
Multilayered Systems

ABSTRACTElastic neutron scattering measurements performed at the NIST reactor have been used to measure the staggered magnetization near the transition temperature in a thin antiferromagnetic epitaxial film of FeF2 of thickness 0.8μm and diameter 1cm grown on a diamagnetic (001) ZnF2substrate by MBE. The use of a thin film permits extinction-free Bragg intensities, something which has proven impossible in bulk crystals. The growth techniques yield sufficient crystal quality to observed resolution limited Magnetic Bragg scattering peaks and to approach the transition within a reduced temperature of |t| = 0.003. The structure quality of this sample has been characterized using X-ray double crystal diffraction with a measured rocking curve lin ewidth of less than 30 arc sec. The sample thickness, while small enough to eliminate extinction, is sufficiently large to assure three-dimensional Ising Model critical behavior. We indeed observe critical behavior consistent with theoretical predictions. The success of the thin film experiments demonstrates the possibilities of extinction-free Bragg scattering measurements in a variety of antiferromagnetic Materials, including multilayered systems.

Consideration of the Scattering Effects in the Glass As a Participating Medium Using the Discrete Ordinates Method

2001 ◽  
Author(s):  
S. Coutin Rodicio ◽  
B. Restrepo Torres
Keyword(s):  
Heat Flux ◽  
Radiative Heat ◽  
Three Dimensional ◽  
Discrete Ordinates ◽  
Radiative Heat Exchange ◽  
Scattering Medium ◽  
Discrete Ordinates Method ◽  
Radiant Intensity ◽  
Scattering Coefficients ◽  
Scattering Effects

Abstract Three-dimensional radiative heat exchange in a commercial type of glass as a participating medium is predicted using the discrete ordinates method. The radiative transfer equation (RTE) is analyzed for an absorbing, re-emitting, and scattering medium enclosed by gray walls. The main objective of this work is to formulate the RTE in a three-dimensional enclosure represented by a rectangular glass furnace where scattering effects are considered in the prediction of the radiant intensity, temperature distribution, incident and emitted energy, and heat flux at the glass surface. A comparative study is performed for glass under scattering and non-scattering conditions. The influence of scattering effects in the radiant intensity will provide further understanding of their impact in the glass thermal behavior. Additionally, the results of a parametric study on the glass for different scattering coefficients, surface heat flux, wall emissivity, and the forward scattering are discussed. The S4 approximation of the discrete ordinates method is employed in this model.

Separation of three-dimensional scattering effects in tilt-series Fourier ptychography

2015 ◽  
Vol 158 ◽  
pp. 1-7 ◽  
Author(s):  
Peng Li ◽  
Darren J. Batey ◽  
Tega B. Edo ◽  
John M. Rodenburg
Keyword(s):  
Three Dimensional ◽  
Scattering Effects ◽  
Tilt Series
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