Study of Multiple Wave Reflections in Physical Models of Transmission Lines

2020 ◽  
Author(s):  
Sergey Kropotukhin ◽  
Yuri Patrakov ◽  
Vladislav Popovtsev ◽  
Sergey Yuferev
Keyword(s):  
Transmission Lines ◽  
Physical Models ◽  
Wave Reflections ◽  
Multiple Wave

An optical method for direct measurements of strain in a torsional Hopkinson-bar apparatus

1975 ◽  
Vol 10 (3) ◽  
pp. 172-179 ◽  
Author(s):  
M G Stevenson ◽  
J D Campbell
Keyword(s):  
Torsion Test ◽  
Hopkinson Bar ◽  
Gauge Length ◽  
Wave Reflections ◽  
Multiple Wave ◽  
Torsional Waves ◽  
Direct Measurements ◽  
Angular Velocities ◽  
Bar Test

A method has been developed to measure the related rotation of the flanges of a thin-walled tubular specimen during a torsion test. The method, which is based on the Moiré-fringe technique, is capable of use at the high rates of strain encountered during a Hopkinson-bar test, as well as at low rates of strain. In the application described, the specimen gauge length is very short, but the method could be used for specimens of considerably longer gauge length. Direct calibration of the system is easily carried out at low angular velocities. The method can then be used to measure directly the specimen strain during a Hopkinson-bar test, and thus to check the value derived from measuremets of torsional waves in the elastic bars. Results of such comparisons are given, and it is found that the values given by the two method agree well, the differnce being attributable largely to inaccuracies in the torque measurement. The new method permits the determination of specimen deformation during the later stages of the test when multiple wave reflections render the wave analysis iaccurate. In particular, it has been found that the specimen may be subjected to reversed plastic straining, so that the total plastic strain connot be determined from the permenent deformation at the end of the test.

Response spectra of earthquakes on very soft clay

1964 ◽  
Vol 54 (3) ◽  
pp. 855-866
Author(s):  
J. I. Bustamante
Keyword(s):  
Mexico City ◽  
Soft Clay ◽  
Response Spectra ◽  
Wave Reflections ◽  
General Shape ◽  
Dimensional Theory ◽  
Multiple Wave ◽  
One Dimensional ◽  
Velocity Spectra ◽  
The One

Abstract The response spectra of two strong and two mild earthquakes recorded on the thick lacustrine formation of Mexico City in 1961 and 1962 are presented. The velocity spectra of the two strong ones are compared with studies made independently by Jennings. Discrepancies there-with are explained in terms of wave reflections. A criterion to simplify data reduction and spectrum computations is supported by these comparisons. Velocity and pseudovelocity spectra are practically alike. The period corresponding to the maximum peak and the general shape of these curves agree closely with those predicted applying the one-dimensional theory of multiple wave reflections to the formations in question.

Comportement dynamique des lignes aériennes de transport d'électricité dû aux bris de câbles. I. Modélisation mathématique

1989 ◽  
Vol 16 (3) ◽  
pp. 335-353 ◽  
Author(s):  
Ghyslaine McClure ◽  
René Tinawi
Keyword(s):  
Mathematical Model ◽  
Dynamic Analysis ◽  
Transmission Lines ◽  
Nonlinear Dynamic ◽  
Nonlinear Dynamic Analysis ◽  
Physical Models ◽  
Element Analysis ◽  
Electric Transmission ◽  
Electric Transmission Lines ◽  
Supporting Structures

This paper presents a mathematical model for the nonlinear dynamic analysis of aerial electric transmission lines subjected to conductor breakage. The model uses existing finite elements and validated numerical techniques available in most commercial programs capable of handling nonlinear dynamic analysis. ADINA is used in this study. In comparison with other models, the novel approach presented here focusses on the discretization of the conductors as well as the supporting structures, specially near the breakage point. Dynamic interactions between all the structural components are therefore considered and comparisons with simpler models emphasize the importance of these interactions, the effects of geometric nonlinearities present in the conductors and in the supporting structures, and the contribution of higher modes.The mathematical model is validated with 7 of 56 tests conducted on reduced-scale physical models, reported in work done for the American Electric Power Research Institute.The results of the present study are very encouraging for designers interested in validating their design criteria for longitudinal dynamic loads by use of existing nonlinear dynamic finite element analysis packages. Key words: Nonlinear dynamic analysis, electric transmission lines, conductor breakage simulation.

Vapor Dynamics of Heat Pipe Start-Up

1991 ◽  
Vol 113 (4) ◽  
pp. 985-994 ◽  
Author(s):  
F. Issacci ◽  
I. Catton ◽  
N. M. Ghoniem
Keyword(s):  
Steady State ◽  
Nonlinear Filtering ◽  
Heat Fluxes ◽  
Vapor Flow ◽  
Wave Reflections ◽  
Local Pressure ◽  
Multiple Wave ◽  
Steady State Condition ◽  
Pressure Drops ◽  
Start Up

Vapor dynamics of heat pipes during the start-up phase of operation is analyzed. The vapor flow is modeled by a two-dimensional, compressible viscous flow in an enclosure with inflow and outflow boundary conditions. For high-input heat fluxes, a compression wave is created in the evaporator early in the operation. A nonlinear filtering technique, along with the centered difference scheme, is used to capture the shocklike wave and overcome the cell Reynolds number problem. Multiple wave reflections are observed in the evaporation and adiabatic regions. These wave reflections cause a significant increase in the local pressure and flow circulations, which grow with time. It is shown that the maximum and maximum-averaged pressure drops oscillate periodically because of the wave reflections. Although the pressure drops converge to a constant value at steady state, they are significantly higher than their steady-state value at the initiation of the process. The time for the vapor core to reach a steady-state condition was found to be on the order of seconds.

On Compensation of Wave Reflections in Transmission Lines and Applications to the Overvoltage Problem AC Motor Drives

2004 ◽  
Vol 49 (10) ◽  
pp. 1757-1762 ◽  
Author(s):  
R. Ortega ◽  
A. de Rinaldis ◽  
M.W. Spong ◽  
S. Lee ◽  
K. Nam
Keyword(s):  
Transmission Lines ◽  
Motor Drives ◽  
Wave Reflections ◽  
Ac Motor ◽  
Ac Motor Drives

Recent Radiative and Collisional Atomic Data of Astrophysical Interest

1988 ◽  
Vol 102 ◽  
pp. 129-132
Author(s):  
K.L. Baluja ◽  
K. Butler ◽  
J. Le Bourlot ◽  
C.J. Zeippen
Keyword(s):  
Mass Production ◽  
Bound States ◽  
Physical Models ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Atomic Data ◽  
Isoelectronic Sequence ◽  
Astrophysical Interest ◽  
Radiative Transitions ◽  
Forbidden Transitions

SummaryUsing sophisticated computer programs and elaborate physical models, accurate radiative and collisional atomic data of astrophysical interest have been or are being calculated. The cases treated include radiative transitions between bound states in the 2p4and 2s2p5configurations of many ions in the oxygen isoelectronic sequence, the photoionisation of the ground state of neutral iron, the electron impact excitation of the fine-structure forbidden transitions within the 3p3ground configuration of CℓIII, Ar IV and K V, and the mass-production of radiative data for ions in the oxygen and fluorine isoelectronic sequences, as part of the international Opacity Project.

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