Anharmonic Phonons in B.C.C. 4He

1972 ◽  
Vol 50 (11) ◽  
pp. 1152-1155 ◽  
Author(s):  
H. R. Glyde ◽  
F. C. Khanna
Keyword(s):  
Lattice Dynamics ◽  
Reasonable Agreement ◽  
Phonon Frequency ◽  
Frequency Dispersion ◽  
Dispersion Curves ◽  
Experimental Results ◽  
Matrix Approach ◽  
T Matrix

A T-matrix approach is used to calculate lattice dynamics of b.c.c. 4He. The phonon frequency dispersion curves and phonon group widths are in reasonable agreement with the experimental results of Osgood et al.

Lattice dynamics of heavy rare-gas solids

1969 ◽  
Vol 47 (6) ◽  
pp. 617-625 ◽  
Author(s):  
N. P. Gupta ◽  
R. K. Gupta
Keyword(s):  
Iterative Method ◽  
Specific Heat ◽  
Lattice Dynamics ◽  
Reasonable Agreement ◽  
Zero Point ◽  
Central Force ◽  
Experimental Results ◽  
Rare Gas ◽  
Buckingham Potential ◽  
Phonon Spectra

Phonon spectra, dispersion curves, and the specific heat of frozen argon, krypton, and xenon have been studied using a quasiharmonic central force rigid-atom model with interactions up to eighth neighbors. The effect of zero-point vibration is included by an iterative method and a modified Buckingham potential is used. There is reasonable agreement between theoretical and experimental results. A number of possibilities for the improvement of results have been discussed.

On b.c.c. 3He, a Highly Anharmonic Crystal

1971 ◽  
Vol 49 (6) ◽  
pp. 761-775 ◽  
Author(s):  
H. R. Glyde
Keyword(s):  
Elastic Constants ◽  
Lattice Dynamics ◽  
Phonon Frequency ◽  
Frequency Dispersion ◽  
Anharmonic Crystal ◽  
Self Consistent ◽  
Anharmonic Term ◽  
Single Method ◽  
The One ◽  
Anharmonic Crystals

The self consistent (SC) theory of lattice dynamics for highly anharmonic crystals is derived via expansion and selected re-summation of the one phonon Green function. Since perturbation treatments of weakly anharmonic crystals use the same expansion, the two cases can then be viewed as variations in a single method. The SC theory to lowest (SCH) and second (SC2) order and a re-order potential power series in which each coefficient appears averaged over the vibrational motion is derived.The SCH theory with the leading correction in the new series, the cubic anharmonic term, is applied to b.c.c. 3He. Phonon frequency dispersion curves, lifetimes, sound velocities, and elastic constants are computed. The phonons are well defined and the elastic constants and isotropy agree quite well with experiment. Although the cubic correction is significant, it suggests that the re-ordered series converges.

SPECIFIC HEATS AND DISPERSION CURVES FOR CsCl ON THE BASIS OF THE SHELL MODEL

1967 ◽  
Vol 45 (10) ◽  
pp. 3339-3346 ◽  
Author(s):  
G. P. Srivastava ◽  
B. Dayal
Keyword(s):  
Specific Heat ◽  
Shell Model ◽  
Lattice Dynamics ◽  
Cesium Chloride ◽  
Dispersion Curves ◽  
Experimental Results ◽  
Fair Agreement ◽  
Chloride Crystal ◽  
Specific Heats ◽  
Positive Ions

The shell model of Dick and Overhauser as developed by Cochran and Woods el al. has been applied to study theoretically the lattice dynamics of a cesium chloride crystal. The polarizabilities of both negative and positive ions have been taken into account in this treatment. The charges on the shells of the two ions come out to be of different magnitude. It is seen that the theoretical specific-heat variation with temperature based on this model is in fair agreement with experimental results in the range for which they have been obtained. The theoretical dispersion curves in the three symmetry directions are also given.

Unbalance Response of a Dual Rotor System: Theory and Experiment

1993 ◽  
Vol 115 (4) ◽  
pp. 427-435 ◽  
Author(s):  
K. Gupta ◽  
K. D. Gupta ◽  
K. Athre
Keyword(s):  
System Theory ◽  
Transfer Matrix ◽  
Mode Shape ◽  
Reasonable Agreement ◽  
Complex Variables ◽  
Rotor System ◽  
Experimental Results ◽  
Unbalance Response ◽  
Theoretical Results ◽  
Theory And Experiment

A dual rotor rig is developed and is briefly discussed. The rig is capable of simulating dynamically the two spool aeroengine, though it does not physically resemble the actual aeroengine configuration. Critical speeds, mode shape, and unbalance response are determined experimentally. An extended transfer matrix procedure in complex variables is developed for obtaining unbalance response of dual rotor system. Experimental results obtained are compared with theoretical results and are found to be in reasonable agreement.

Surface-Wave Simulation for the Continuously Moving Seismic Sources

2021 ◽  
Author(s):  
Yuefeng Yan ◽  
Chengyu Sun ◽  
Tengfei Lin ◽  
Jiao Wang ◽  
Jidong Yang ◽  
...  
Keyword(s):  
Rayleigh Waves ◽  
Frequency Dispersion ◽  
Dispersion Curves ◽  
Velocity Estimation ◽  
Surface Velocity ◽  
Seismic Sources ◽  
Near Surface ◽  
Moving Source ◽  
Source Data ◽  
Doppler Effects

Abstract In exploration and earthquake seismology, most sources used in subsurface structure imaging and rock property estimation are fixed in certain positions. Continuously moving seismic sources, such as vehicles and the metro, are one kind of important passive sources in ambient noise research. Commonly, seismic data acquisition and processing for moving sources are based on the assumption of simple point passive sources, and the dispersion curve inversion is applied to constrain near-surface velocity. This workflow neglects the Doppler effects. Considering the continuously moving properties of the sources, we first derive the analytical solution for the Rayleigh waves excited by heavy vehicles and then analyze their Doppler effects and dispersion curves. We observe that the moving source data have the Doppler effect when compared with the changes in the frequency of the source intensity, but this effect does not affect the frequency dispersion of Rayleigh waves. The dispersion curves computed for moving source records are consistent with the analytical dispersion solutions, which provide a theoretical foundation for velocity estimation using moving source data.

scholarly journals TSUNAMI GENERATION AND PROPAGATION

1972 ◽  
Vol 1 (13) ◽  
pp. 146
Author(s):  
Joseph L. Hammack ◽  
Frederic Raichlen
Keyword(s):  
Linear Theory ◽  
Source Region ◽  
Three Dimensional ◽  
Frequency Dispersion ◽  
Nonlinear Effects ◽  
Its Region ◽  
Experimental Results ◽  
Specific Class ◽  
Two Dimensional ◽  
Three Dimensional Models

A linear theory is presented for waves generated by an arbitrary bed deformation {in space and time) for a two-dimensional and a three -dimensional fluid domain of uniform depth. The resulting wave profile near the source is computed for both the two and three-dimensional models for a specific class of bed deformations; experimental results are presented for the two-dimensional model. The growth of nonlinear effects during wave propagation in an ocean of uniform depth and the corresponding limitations of the linear theory are investigated. A strategy is presented for determining wave behavior at large distances from the source where linear and nonlinear effects are of equal magnitude. The strategy is based on a matching technique which employs the linear theory in its region of applicability and an equation similar to that of Korteweg and deVries (KdV) in the region where nonlinearities are equal in magnitude to frequency dispersion. Comparison of the theoretical computations with the experimental results indicates that an equation of the KdV type is the proper model of wave behavior at large distances from the source region.

scholarly journals Spectral Fourier-microscopy of the periodic structures based on Ge2Sb2Te5

2021 ◽  
Vol 2103 (1) ◽  
pp. 012173
Author(s):  
A I Solomonov ◽  
S I Pavlov ◽  
P I Lazarenko ◽  
V V Kovalyuk ◽  
A D Golikov ◽  
...  
Keyword(s):  
Experimental Data ◽  
Reasonable Agreement ◽  
Angular Resolution ◽  
Periodic Structures ◽  
Diffraction Gratings ◽  
Dispersion Curves ◽  
Reflection Spectra ◽  
Waveguide Modes ◽  
Periodic Gratings

Abstract The method of spectral Fourier microscopy was used to study the reflection spectra with an angular resolution of submicron periodic gratings based on amorphous and crystalline Ge2Sb2Te5. The form of the dispersion curves of quasi-waveguide modes in the structures under study was established. The experimental data were compared with the calculations of dispersion curves in synthesized diffraction gratings. Reasonable agreement between theoretical and experimental data was obtained.

scholarly journals Self-consistent T-matrix approach to Bose-glass in one dimension

2016 ◽  
Vol 397 ◽  
pp. 11-19
Author(s):  
A.G. Yashenkin ◽  
O.I. Utesov ◽  
A.V. Sizanov ◽  
A.V. Syromyatnikov
Keyword(s):  
One Dimension ◽  
Matrix Approach ◽  
Self Consistent ◽  
Bose Glass ◽  
T Matrix
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