scholarly journals On the Accuracy of Asymptotic Solutions for TM Waves Diffracting on an Impedance Wedge

2014 ◽  
Vol 2014 ◽  
pp. 1-5
Author(s):  
Sonia Fu ◽  
Pierre Jacolot ◽  
Tommaso Balercia ◽  
Christian Rom ◽  
Jørgen B. Andersen ◽  
...  
Keyword(s):  
Electromagnetic Field ◽  
Boundary Conditions ◽  
The Other ◽  
Asymptotic Solutions ◽  
Electrical Conductor ◽  
Impedance Wedge ◽  
Uniform Theory Of Diffraction ◽  
Approximate Boundary Conditions ◽  
Perfect Electrical Conductor

The contribution focuses on the accuracy of two asymptotic solutions aimed at representing the electromagnetic field scattered by penetrable wedges. One is a heuristic manipulation of the solution for the perfect electrical conductor, and the other one is a more rigorous coefficient based on approximate boundary conditions. The results presented here extend those proposed by other authors by illustrating the accuracy of such solutions at the edge of validity of the uniform theory of diffraction. In particular, they show that the heuristic formulation can be freely applied in similar conditions, while the other might not always lead to accurate predictions.

Simulations of electric field at the initiation altitudes of sprites and halos generated by the thundercloud charge structure and lightning channels of causative return strokes

2021 ◽  
Author(s):  
Petr Kaspar ◽  
Ivana Kolmasova ◽  
Ondrej Santolik ◽  
Martin Popek ◽  
Pavel Spurny ◽  
...  
Keyword(s):  
Electromagnetic Field ◽  
Electric Field ◽  
Boundary Conditions ◽  
Free Space ◽  
Nonlinear Effects ◽  
Charge Structure ◽  
Transient Luminous Events ◽  
Lightning Channel ◽  
Free Parameters

<p><span>Sprites and halos are transient luminous events occurring above thunderclouds. They can be observed simultaneously or they can also appear individually. Circumstances leading to initiation of these events are still not completely understood. In order to clarify the role of lightning channels of causative lightning return strokes and the corresponding thundercloud charge structure, we have developed a new model of electric field amplitudes at halo/sprite altitudes. It consists of electrostatic and inductive components of the electromagnetic field generated by the lightning channel in free space at a height of 15 km. Above this altitude we solve Maxwell’s equations self-consistently including the nonlinear effects of heating and ionization/attachment of the electrons. At the same time, we investigate the role of a development of the thundercloud charge structure and related induced charges above the thundercloud. We show how these charges lead to the different distributions of the electric field at the initiation heights of the halos and sprites. We adjust free parameters of the model using observations of halos and sprites at the Nydek TLE observatory and using measurements of luminosity curves of the corresponding return strokes measured by an array of fast photometers. The latter measurements are also used to set the boundary conditions of the model.</span></p>

scholarly journals Memory Efficient Method for Electromagnetic Multi-Region Models Using Scattering Matrices

2018 ◽  
Vol 23 (4) ◽  
pp. 71 ◽  
Author(s):  
C. Custers ◽  
J. Jansen ◽  
E. Lomonova
Keyword(s):  
Electromagnetic Field ◽  
Boundary Conditions ◽  
Efficient Method ◽  
Maximum Size ◽  
Scattering Matrix ◽  
Matrix Approach ◽  
Matrix Formulation ◽  
Scattering Matrices ◽  
Memory Efficient

This paper describes the scattering matrix approach to obtain the solution to electromagnetic field quantities in harmonic multi-layer models. Using this approach, the boundary conditions are solved in such way that the maximum size of any matrix used during the computations is independent of the number of regions defined in the problem. As a result, the method is more memory efficient than classical methods used to solve the boundary conditions. Because electromagnetic sources can be located inside the regions of a configuration, the scattering matrix formulation is developed to incorporate these sources into the solving process. The method is applied to a 3D electromagnetic configuration for verification.

scholarly journals Some Non-Simple–Equilibrium Aspects in Axisymmetric Turbomachine Flow Theory

1969 ◽  
Author(s):  
H. J. Schroder
Keyword(s):  
Boundary Conditions ◽  
Axisymmetric Flow ◽  
Flow Theory ◽  
Flow Fields ◽  
The Other ◽  
Equilibrium Flow ◽  
Free Vortex ◽  
Difference Methods ◽  
Definite Difference ◽  
Insight Into

In turbomachines of non-free-vortex design the axisymmetric flow is mostly in a state of “disturbed equilibrium.” Methods of calculating flow fields of this kind were developed nearly 20 years ago. The examples chosen for their demonstration were rather intricate. Here, on the other hand, two very simple examples are produced which provide some insight into the — anything but self-evident — behavior of disturbed equilibrium flow. The examples serve to give some indication as to the use of definite difference methods, including the choice of boundary conditions, and a first attempt at taking incidence at the leading edges of the blades into account.

Rediscovering Leon Theremin

Tempo ◽  
1991 ◽  
pp. 18-23 ◽  
Author(s):  
Stephen Montague
Keyword(s):  
Electromagnetic Field ◽  
The Other ◽  
Electronic Instrument ◽  
Left Hand ◽  
Vertical Antenna ◽  
Right Hand ◽  
Concert Halls ◽  
The Right

In the early 1920s and 30s a strange electronic instrument found its way from Russia into some of the more fashionable ballrooms, night clubs, and concert halls in Europe and America. This exotic new invention, called the ‘theremin’ or ‘thereminvox’, caused a considerable stir. Part of the interest was its unusual sound (like a musical saw mated with a light soprano), but its most dramatic feature was that the performer never actually touched the instrument. He or she simply waved graceful hands near the two antennae (one set vertically, the other looped horizontally) to coax out seamless, melifluous melodies. The proximity of the right hand to the vertical antenna changed the ultrasonic electromagnetic field, thus changing the pitch over about a six-octave range. The left hand (or sometimes a foot pedal) controlled the volume. By gently shaking the right hand at the antenna a vibrato could be achieved, giving performances a little more musical (not to mention choreographic) interest. Fashionable women dressed in long gowns seemed to be favourite photographic subjects of the period as performers, as well as the inventor himself, poised ‘playing the rods’ in full dress tails, arms outstretched like a great conductor–or perhaps sorcerer.

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