Spectral coupled mode approach to three‐dimensional propagation and reverberation in two‐dimensional, range‐dependent environments

2005 ◽  
Vol 118 (3) ◽  
pp. 1935-1935
Author(s):  
Wenyu Luo ◽  
Henrik Schmidt
Keyword(s):  
Three Dimensional ◽  
Two Dimensional ◽  
Coupled Mode ◽  
Dimensional Range

A THREE-DIMENSIONAL AZIMUTHAL WIDE-ANGLE MODEL FOR THE PARABOLIC WAVE EQUATION

1999 ◽  
Vol 07 (04) ◽  
pp. 269-286 ◽  
Author(s):  
CHIFANG CHEN ◽  
YING-TSONG LIN ◽  
DING LEE
Keyword(s):  
Wave Equation ◽  
Prediction Models ◽  
Three Dimensional ◽  
3D Models ◽  
Theoretical Development ◽  
Wide Angle ◽  
Two Dimensional ◽  
Narrow Angle ◽  
Propagation Prediction ◽  
Dimensional Range

In predicting wave propagations in either direction, the size of the angle of propagation plays an important role; thus, the concept of wide-angle is introduced. Most existing acoustic propagation prediction models do have the capability of treating the wide-angle but the treatment, in practice, is vertical. This is desirable for solving two-dimensional (range and depth) problems. In extending the two-dimensional treatment to 3 dimensions, even though the wide-angle capability is maintained in most 3D models, it is still vertical. Owing to the need of a wide-angle capability in the azimuth direction, this paper formulates an azimuthal wide-angle wave equation whose theoretical development is presented. An illustrative example is included to demonstrate the need for such azimuthal wide-angle capability. Also, a comparison is shown between results using narrow-angle and wide-angle equations separately.

Coordinated Nodding of a Two-Dimensional Lidar for Dense Three-Dimensional Range Measurements

2018 ◽  
Vol 3 (4) ◽  
pp. 4108-4115 ◽  
Author(s):  
Anindya Harchowdhury ◽  
Lindsay Kleeman ◽  
Leena Vachhani
Keyword(s):  
Three Dimensional ◽  
Two Dimensional ◽  
Range Measurements ◽  
Dimensional Range

A three-dimensional coupled-mode model for the acoustic field in a two-dimensional waveguide with perfectly reflecting boundaries

2016 ◽  
Vol 25 (12) ◽  
pp. 124309 ◽  
Author(s):  
Wen-Yu Luo ◽  
Xiao-Lin Yu ◽  
Xue-Feng Yang ◽  
Ze-Zhong Zhang ◽  
Ren-He Zhang
Keyword(s):  
Acoustic Field ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Coupled Mode ◽  
Reflecting Boundaries

DEPENDENCE OF THE AXIAL WAVE ON RANGE AND SOUND-SPEED PROFILE PROPERTIES IN A RANGE-INDEPENDENT OCEAN

2005 ◽  
Vol 13 (02) ◽  
pp. 259-278 ◽  
Author(s):  
NATALIE S. GRIGORIEVA ◽  
GREGORY M. FRIDMAN
Keyword(s):  
Numerical Simulation ◽  
Sound Speed ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Speed Profile ◽  
Wave Fields ◽  
Sound Speed Profile ◽  
Average Profile ◽  
Ducted Propagation ◽  
Dimensional Range

For ducted propagation in a waveguide when the source and receiver are placed closely to the depth of the waveguide axis, there exist cusped caustics repeatedly along the axis. In neighborhoods of these cusped caustics, the interference of the wave fields that correspond to near-axial rays occurs. This results in the formation of a coherent structure (the axial wave) that propagates along the waveguide axis like a wave. In this paper the integral representation of the axial wave obtained before for an arbitrary waveguide in a two-dimensional range-independent medium is generalized to a three-dimensional range-independent medium. Through numerical simulation, the dependencies of the axial wave on range, sound-speed profile properties, and geometry of the experiment are studied for two sound-speed profiles: the average profile from the AET experiment and the Munk canonical profile. The sound source frequency is taken equal to 75 Hz; the propagation range is up to 3250 km. The strong difference between shapes of the axial wave for the average profile from the AET experiment and the Munk canonical profile is shown for all the examined models.

scholarly journals Total Dielectric Function Approach to the Electron Boltzmann Equation for Scattering from a Two-Dimensional Coupled Mode System

VLSI Design ◽  
1998 ◽  
Vol 6 (1-4) ◽  
pp. 69-72
Author(s):  
B. A. Sanborn
Keyword(s):  
Boltzmann Equation ◽  
Dielectric Function ◽  
Three Dimensional ◽  
Collision Term ◽  
Two Dimensional ◽  
Coupled Mode ◽  
Low Field ◽  
Electron Boltzmann Equation ◽  
General Method ◽  
Dynamical Screening

The nonequilibrium total dielectric function lends itself to a simple and general method for calculating the inelastic collision term in the electron Boltzmann equation for scattering from a coupled mode system. Useful applications include scattering from plasmon-polar phonon hybrid modes in modulation doped semiconductor structures. This paper presents numerical methods for including inelastic scattering at momentum-dependent hybrid phonon frequencies in the low-field Boltzmann equation for two-dimensional electrons coupled to bulk phonons. Results for electron mobility in GaAs show that the influence of mode coupling and dynamical screening on electron scattering from polar optical phonons is stronger for two dimensional electrons than was previously found for the three dimensional case.

High Resolution Microscopy of Multi-Layered Biological Crystals

1982 ◽  
Vol 40 ◽  
pp. 80-83
Author(s):  
H.A. Cohen ◽  
T.W. Jeng ◽  
W. Chiu
Keyword(s):  
High Resolution ◽  
Low Dose ◽  
Three Dimensional ◽  
Data Interpretation ◽  
Two Dimensional ◽  
Biological Objects ◽  
Density Maps ◽  
Density Map ◽  
Complex Crystal ◽  
High Resolution Microscopy

This tutorial will discuss the methodology of low dose electron diffraction and imaging of crystalline biological objects, the problems of data interpretation for two-dimensional projected density maps of glucose embedded protein crystals, the factors to be considered in combining tilt data from three-dimensional crystals, and finally, the prospects of achieving a high resolution three-dimensional density map of a biological crystal. This methodology will be illustrated using two proteins under investigation in our laboratory, the T4 DNA helix destabilizing protein gp32*I and the crotoxin complex crystal.

Instrumentation For Quantitative Microscopy

1977 ◽  
Vol 35 ◽  
pp. 206-209
Author(s):  
B. Ralph ◽  
A.R. Jones
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Automatic Data ◽  
Phase Volume Fraction ◽  
Statistical Confidence ◽  
Resultant Data ◽  
Automatic Data Collection ◽  
Third Dimension ◽  
Evolution Of Microstructure

In all fields of microscopy there is an increasing interest in the quantification of microstructure. This interest may stem from a desire to establish quality control parameters or may have a more fundamental requirement involving the derivation of parameters which partially or completely define the three dimensional nature of the microstructure. This latter categorey of study may arise from an interest in the evolution of microstructure or from a desire to generate detailed property/microstructure relationships. In the more fundamental studies some convolution of two-dimensional data into the third dimension (stereological analysis) will be necessary.In some cases the two-dimensional data may be acquired relatively easily without recourse to automatic data collection and further, it may prove possible to perform the data reduction and analysis relatively easily. In such cases the only recourse to machines may well be in establishing the statistical confidence of the resultant data. Such relatively straightforward studies tend to result from acquiring data on the whole assemblage of features making up the microstructure. In this field data mode, when parameters such as phase volume fraction, mean size etc. are sought, the main case for resorting to automation is in order to perform repetitive analyses since each analysis is relatively easily performed.

A linearity test for thick specimens imaged by HVEM over a 180° angular range

1991 ◽  
Vol 49 ◽  
pp. 552-553
Author(s):  
Yu Liu
Keyword(s):  
Phase Contrast ◽  
Three Dimensional ◽  
Angular Range ◽  
Two Dimensional ◽  
Back Projection ◽  
Line Integral ◽  
Exponential Law ◽  
Transmission Electron ◽  
Absorption Law ◽  
Linearity Test

The image obtained in a transmission electron microscope is the two-dimensional projection of a three-dimensional (3D) object. The 3D reconstruction of the object can be calculated from a series of projections by back-projection, but this algorithm assumes that the image is linearly related to a line integral of the object function. However, there are two kinds of contrast in electron microscopy, scattering and phase contrast, of which only the latter is linear with the optical density (OD) in the micrograph. Therefore the OD can be used as a measure of the projection only for thin specimens where phase contrast dominates the image. For thick specimens, where scattering contrast predominates, an exponential absorption law holds, and a logarithm of OD must be used. However, for large thicknesses, the simple exponential law might break down due to multiple and inelastic scattering.

An Image Reconstruction System Applied to High Voltage Microscopy

1975 ◽  
Vol 33 ◽  
pp. 292-293
Author(s):  
D. E. Johnson
Keyword(s):  
High Voltage ◽  
Prior Information ◽  
Block Diagram ◽  
Three Dimensional ◽  
Real Space ◽  
Two Dimensional ◽  
Efficient Manner ◽  
Fourier Methods ◽  
Tilt Series ◽  
Methods Of Reconstruction

Increased specimen penetration; the principle advantage of high voltage microscopy, is accompanied by an increased need to utilize information on three dimensional specimen structure available in the form of two dimensional projections (i.e. micrographs). We are engaged in a program to develop methods which allow the maximum use of information contained in a through tilt series of micrographs to determine three dimensional speciman structure.In general, we are dealing with structures lacking in symmetry and with projections available from only a limited span of angles (±60°). For these reasons, we must make maximum use of any prior information available about the specimen. To do this in the most efficient manner, we have concentrated on iterative, real space methods rather than Fourier methods of reconstruction. The particular iterative algorithm we have developed is given in detail in ref. 3. A block diagram of the complete reconstruction system is shown in fig. 1.

Computer Assisted Image Reconstruction of Oligomer Structure

1976 ◽  
Vol 34 ◽  
pp. 472-473
Author(s):  
A.M. Jones ◽  
A. Max Fiskin
Keyword(s):  
Three Dimensional ◽  
Depth Of Field ◽  
Computer Assisted ◽  
Projection Data ◽  
Two Dimensional ◽  
Single Particles ◽  
Dimensional Reconstruction ◽  
Computer Assisted Image ◽  
The Fourier Transform ◽  
Space Approach

If the tilt of a specimen can be varied either by the strategy of observing identical particles orientated randomly or by use of a eucentric goniometer stage, three dimensional reconstruction procedures are available (l). If the specimens, such as small protein aggregates, lack periodicity, direct space methods compete favorably in ease of implementation with reconstruction by the Fourier (transform) space approach (2). Regardless of method, reconstruction is possible because useful specimen thicknesses are always much less than the depth of field in an electron microscope. Thus electron images record the amount of stain in columns of the object normal to the recording plates. For single particles, practical considerations dictate that the specimen be tilted precisely about a single axis. In so doing a reconstructed image is achieved serially from two-dimensional sections which in turn are generated by a series of back-to-front lines of projection data.

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