Three-Dimensional Numerical Theory for Impedance Eduction in Normal Incidence Tubes

2016 ◽  
Author(s):  
Willie R. Watson ◽  
Michael G. Jones
Keyword(s):  
Three Dimensional ◽  
Normal Incidence ◽  
Numerical Theory

scholarly journals Numerical Study of Hall Thruster Plume and Sputtering Erosion

2012 ◽  
Vol 2012 ◽  
pp. 1-16 ◽  
Author(s):  
Li Yan ◽  
Ping-Yang Wang ◽  
Yang-Hua Ou ◽  
Xiao-Lu Kang
Keyword(s):  
Electric Propulsion ◽  
Numerical Study ◽  
Three Dimensional ◽  
Direct Simulation Monte Carlo ◽  
Normal Incidence ◽  
Heavy Ion ◽  
Calculation Model ◽  
Hall Thruster ◽  
Yield Model ◽  
Sputtering Yield

Potential sputtering erosion caused by the interactions between spacecraft and plasma plume of Hall thrusters is a concern for electric propulsion. In this study, calculation model of Hall thruster’s plume and sputtering erosion is presented. The model is based on three dimensional hybrid particle-in-cell and direct simulation Monte Carlo method (PIC/DSMC method) which is integrated with plume-wall sputtering yield model. For low-energy heavy-ion sputtering in Hall thruster plume, the Matsunami formula for the normal incidence sputtering yield and the Yamamura angular dependence of sputtering yield are used. The validation of the simulation model is realized through comparing plume results with the measured data. Then, SPT-70’s sputtering erosion on satellite surfaces is assessed and effect of mass flow rate on sputtering erosion is analyzed.

Three‐dimensional primary zero‐offset reflections

Geophysics ◽  
1993 ◽  
Vol 58 (5) ◽  
pp. 692-702 ◽  
Author(s):  
Peter Hubral ◽  
Jorg Schleicher ◽  
Martin Tygel
Keyword(s):  
Ray Tracing ◽  
Large Scale ◽  
Initial Conditions ◽  
Fresnel Zone ◽  
Three Dimensional ◽  
Normal Incidence ◽  
Careful Analysis ◽  
Point Sources ◽  
Dynamic Ray Tracing ◽  
Zero Offset

Zero‐offset reflections resulting from point sources are often computed on a large scale in three‐dimensional (3-D) laterally inhomogeneous isotropic media with the help of ray theory. The geometrical‐spreading factor and the number of caustics that determine the shape of the reflected pulse are then generally obtained by integrating the so‐called dynamic ray‐tracing system down and up to the two‐way normal incidence ray. Assuming that this ray is already known, we show that one integration of the dynamic ray‐tracing system in a downward direction with only the initial condition of a point source at the earth’s surface is in fact sufficient to obtain both results. To establish the Fresnel zone of the zero‐offset reflection upon the reflector requires the same single downward integration. By performing a second downward integration (using the initial conditions of a plane wave at the earth’s surface) the complete Fresnel volume around the two‐way normal ray can be found. This should be known to ascertain the validity of the computed zero‐offset event. A careful analysis of the problem as performed here shows that round‐trip integrations of the dynamic ray‐tracing system following the actually propagating wavefront along the two‐way normal ray need never be considered. In fact some useful quantities related to the two‐way normal ray (e.g., the normal‐moveout velocity) require only one single integration in one specific direction only. Finally, a two‐point ray tracing for normal rays can be derived from one‐way dynamic ray tracing.

INTERVAL VELOCITIES FROM SURFACE MEASUREMENTS IN THE THREE‐DIMENSIONAL PLANE LAYER CASE

Geophysics ◽  
1976 ◽  
Vol 41 (2) ◽  
pp. 233-242 ◽  
Author(s):  
Peter Hubral
Keyword(s):  
Three Dimensional ◽  
Normal Incidence ◽  
Plane Layer ◽  
Three Dimensions ◽  
Seismic Parameters ◽  
Interval Velocity ◽  
Common Depth Point ◽  
Measured Time ◽  
Surface Measurements ◽  
Interval Velocities

The basic requirements to recover plane layers of constant interval velocity, arbitrary dip and strike from common depth point (CDP) recordings are the following four quantities related to the primary event of each reflector at the common midpoint of a CDP profile: a) Two‐way normal time b) Normal moveout velocity within one arbitrary CDP profile c) Time slope of normally reflected rays within the profile d) Time slope of normally reflected rays in some other direction. The solution of the inverse problem is obtained directly. The moveout velocity is expressed in terms of seismic parameters along the normal incidence path in three dimensions and the direction of the profile within the free surface. A formula connecting dip and strike of the emerging normal ray with the measured time gradients is given and discussed. The method includes, as a special case, the Dix formulas for plane parallel layers.

scholarly journals Design of hybrid narrow-band plasmonic absorber based on chalcogenide phase change material in the infrared spectrum

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Israel Alves Oliveira ◽  
Igor Leonardo Gomes de Souza ◽  
Vitaly Felix Rodriguez-Esquerre
Keyword(s):  
Phase Change ◽  
Electromagnetic Waves ◽  
Phase Change Materials ◽  
Empirical Relation ◽  
Three Dimensional ◽  
Normal Incidence ◽  
Resonant Absorption ◽  
Nanophotonic Devices ◽  
Intermediate Phases ◽  
Infrared Spectral

AbstractStructures absorbing electromagnetic waves in the infrared spectral region are important optical components in key areas such as biosensors, infrared images, thermal emitters, and special attention is required for reconfigurable devices. We propose a three-dimensional metal-dielectric plasmonic absorber with a layer of PCM’s (Phase Change Materials). The phase shift effects of PCMs are numerically analyzed, and it is possible to obtain a shifting control of the resonant absorption peaks between the amorphous and crystalline states using the Lorentz–Lorenz relation. By using this empirical relation, we analyzed the peak absorption shift at intermediate phases between the amorphous and the crystalline. The geometric parameters of the structure with the PCM layer in the semi-crystalline state were adjusted to exhibit strong absorption for normal incidence. The effects of the oblique incidence on the absorption for the TM and TE polarization modes were also analyzed. Our results demonstrate that PCMs have great potential for reconfigurable nanophotonic devices.

Remote detection of the pitch and orientation of a reflective diffraction grating: an optical strain gauge

2005 ◽  
Vol 461 (2053) ◽  
pp. 179-188 ◽  
Author(s):  
R. D. Alcock ◽  
C. D. Creasey ◽  
P. Wileman ◽  
N. A. Halliwell ◽  
J. M. Coupland
Keyword(s):  
Diffraction Grating ◽  
Angular Position ◽  
Three Dimensional ◽  
Normal Incidence ◽  
Surface Strain ◽  
Contact Method ◽  
Dimensional Theory ◽  
Optical Strain ◽  
Micro Machine ◽  
Hostile Environments

Measurement of surface strain in hostile environments remains a significant metrology challenge. An elegantly simple non–contact method is to measure the change in pitch of a reflective diffraction grating bonded to the surface of interest. The grating is probed with a laser beam and the change in angular position of diffracted orders is detected as the pitch changes due to surface strain. Robust application of this technique has not been possible due to assumptions such as near–normal incidence, which were necessary in predicting the angular position of diffracted orders from the existing two–dimensional theory. This paper introduces a new three–dimensional theory of diffraction, which obviates the need for these assumptions. Importantly, the theory shows that the angular position of orders can be determined for arbitrary orientation of the grating relative to the incident probe beam. This latter development is critical for success in a practical application. It is now possible to micro–machine reflective gratings directly into a surface or surface coating and thus avoid problems with creep in the bonding material. Together with the new theory, this idea now has the potential to revolutionize how strain will be measured in the future.

HOLOGRAPHIC LEED: A REVIEW OF RECENT PROGRESS

1997 ◽  
Vol 04 (05) ◽  
pp. 991-1001 ◽  
Author(s):  
D. K. SALDIN ◽  
X. CHEN ◽  
J. A. VAMVAKAS ◽  
M. OTT ◽  
H. WEDLER ◽  
...  
Keyword(s):  
Recent Progress ◽  
Three Dimensional ◽  
Scattered Wave ◽  
Normal Incidence ◽  
Long Range Order ◽  
Computer Reconstruction ◽  
Diffraction Patterns ◽  
Basic Ideas ◽  
Wave Kernel ◽  
Potential Object

We review the basic ideas of holographic LEED, and the latest progress in the field. We compare several proposed computer reconstruction schemes. Using experimental diffuse LEED data from O/Ni(001) and K/Ni(001) surfaces, we show that the capability now exists for filtering out the effects on the diffraction patterns of possible long-range order amongst the adsorbates, thus making holographic LEED much more analogous to photoelectron holography. Inclusion of a scattered-wave kernel to compensate for the variation of the magnitude of the reference wave at the positions of potential object-wave sources enables the reconstruction of a fully three-dimensional image of substrate atoms in the immediate vicinity of atomic adsorbates from a set of just normal-incidence diffuse LEED patterns.

scholarly journals Solar EUV Photoelectric Observations from Skylab

1974 ◽  
Vol 57 ◽  
pp. 497-500
Author(s):  
E. M. Reeves ◽  
P. V. Foukal ◽  
M. C. E. Huber ◽  
R. W. Noyes ◽  
E. J. Schmahl ◽  
...  
Keyword(s):  
Solar Atmosphere ◽  
Extreme Ultraviolet ◽  
Three Dimensional ◽  
Active Regions ◽  
Normal Incidence ◽  
Ionic Species ◽  
Ultraviolet Region ◽  
Spatial Image ◽  
Lyman Continuum ◽  
Solar Blind

Most of the atomic species originating in the solar atmosphere between the upper chromosphere and the corona have their strong characteristic wavelengths in the extreme ultraviolet region of the spectrum. A simple normal-incidence spectrometer system with solar blind detectors such as the Harvard instrument operating between approximately 250 Å and 1350 Å is ideally suited for observing in this most interesting range of the solar atmosphere where the temperature rises outward from 104 to 3 × 106 K. The temperature range represented by the various atomic and ionic species in the extreme ultraviolet is associated with many types of solar structure, prominences and filaments, the supergranulation cells and network, active regions and their associated loop structures and other features. Simultaneous observations in lines of different characteristic temperatures provide a three-dimensional probe of the solar atmosphere. In the instrument, the principal polychromatic position observes the Lyman continuum, Lα, C II, C III, O IV, O VI, and Mg x with seven detectors simultaneously from the same spatial image element, 5″ in size. Approximately 60 additional polychromatic positions are used routinely to carry out specific observing programs, for example, covering several lines of a given stage of ionization, observing lines or continuum from specific species of interest such as helium in prominences, comparing combinations of lines from a given ionic species such as O v where the relative intensities give a rather direct measurement of the density at a given temperature, or measuring differing positions in the Lyman continuum providing intensity measurements which can be interpreted in terms of the departure from ionization equilibrium.

Effect of Finite Width on Heat Transfer and Fluid Flow about an Inclined Rectangular Plate

1979 ◽  
Vol 101 (2) ◽  
pp. 199-204 ◽  
Author(s):  
E. M. Sparrow ◽  
J. W. Ramsey ◽  
E. A. Mass
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Transfer Coefficient ◽  
Angle Of Attack ◽  
Three Dimensional ◽  
Normal Incidence ◽  
Finite Width ◽  
Number Range ◽  
Narrow Plate

Wind tunnel experiments were performed to study the heat transfer and fluid flow characteristics for finite-width rectangular plates inclined at various angles of attack to an oncoming airflow. Plates having ratios of spanwise width to streamwise length of 0.4 and 2.5 were employed, and the angle of attack was varied from 90 deg (normal incidence) to 25 deg. The Reynolds number range extended from about 20,000 to 90,000. The naphthalene sublimation technique was used in the transfer coefficient determinations, and the fluid flow patterns adjacent to the plate were made visible by the oil/lampblack technique. The flow field was found to be highly complex and three dimensional, with stronger three-dimensional effects in evidence for the narrow plate. A stagnation zone, centered in the plate cross section at normal incidence, moved forward and ultimately disappeared as the plate was inclined at smaller angles of attack. The dimensionless heat (mass) transfer coefficient, expressed in terms of the Colburn j-factor, varied as the square root of the Reynolds number for all angles of attack, both for the narrow and the wider plates. For the wider plate, the transfer coefficients are completely independent of the angle of attack in the range investigated, while for the narrow plate there is an overall variation of twenty percent. An algebraically simple correlation of all the results, accurate to ± 10 percent, is given to facilitate their use in applications such as the wind-related heat loss from flat plate solar collectors.

Diffraction of a pulse by a resistive half-plane. II. Oblique incidence

1960 ◽  
Vol 255 (1283) ◽  
pp. 550-557 ◽  
Keyword(s):  
Half Plane ◽  
Oblique Incidence ◽  
Three Dimensional ◽  
Normal Incidence ◽  
Dimensional Problem

The three-dimensional problem which arises when a plane pulse is incident obliquely at the edge of a resistive half-plane is discussed, and the relations between this case and that of normal incidence (described in part I) are given.

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