scholarly journals Application of Nonredundant Sampling Representations of Electromagnetic Fields to NF-FF Transformation Techniques

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Ovidio M. Bucci ◽  
Claudio Gennarelli
Keyword(s):  
Electromagnetic Fields ◽  
Experimental Results ◽  
Measurement Time ◽  
Optimal Sampling ◽  
Unified Theory ◽  
Transformation Techniques ◽  
Rotational Surface ◽  
Probe Response ◽  
Remarkable Reduction

An overview of the application of the band-limitation properties and nonredundant sampling representations of electromagnetic fields to NF-FF transformations is presented. The progresses achieved by applying them to data acquired on conventional NF scanning surfaces are discussed, outlining the remarkable reduction in the number of needed NF samples and measurement time. An optimal sampling interpolation expansion for reconstructing the probe response on a rotational scanning surface from a non-redundant number of its samples is also discussed. A unified theory of the NF-FF transformations with spiral scannings, which allow a remarkable reduction of the measurement time, is then reviewed by describing a sampling representation of the voltage on a quite arbitrary rotational surface from its nonredundant samples collected on a proper spiral wrapping it. Some numerical and experimental results assessing the effectiveness of the considered NF-FF transformations are shown too.

scholarly journals Near-Field to Far-Field Transformation Techniques with Spiral Scannings: A Comprehensive Review

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Renato Cicchetti ◽  
Francesco D’Agostino ◽  
Flaminio Ferrara ◽  
Claudio Gennarelli ◽  
Rocco Guerriero ◽  
...  
Keyword(s):  
Communication Systems ◽  
Near Field ◽  
Theoretical Background ◽  
Wireless Communication Systems ◽  
Far Field ◽  
Unified Theory ◽  
Transformation Techniques ◽  
Positioning Systems ◽  
Rotational Surface ◽  
Spiral Scanning

An overview of the near-field-far-field (NF-FF) transformation techniques with innovative spiral scannings, useful to derive the radiation patterns of the antennas commonly employed in the modern wireless communication systems, is provided in this paper. The theoretical background and the development of a unified theory of the spiral scannings for quasi-spherical and nonspherical antennas are described, and an optimal sampling interpolation expansion to evaluate the probe response on a quite arbitrary rotational surface from a nonredundant number of its samples, collected along a proper spiral wrapping it, is presented. This unified theory can be applied to spirals wrapping the conventional scanning surfaces and makes it possible to accurately reconstruct the NF data required by the NF-FF transformation employing the corresponding classical scanning. A remarkable reduction of the measurement time is so achieved, due to the use of continuous and synchronized movements of the positioning systems and to the reduced number of needed NF measurements. Some numerical and experimental results relevant to the spherical spiral scanning case when dealing with quasi-planar and electrically long antennas are shown.

Unified Field Theory

1950 ◽  
Vol 2 ◽  
pp. 427-439 ◽  
Author(s):  
Max Wyman
Keyword(s):  
Field Theory ◽  
Variational Principle ◽  
Electromagnetic Fields ◽  
Linear Connection ◽  
Hamiltonian Function ◽  
Unified Theory ◽  
Unified Field Theory ◽  
Field Equations ◽  
Unified Field

Introduction. In a recent unified theory originated by Einstein and Straus [l], the gravitational and electromagnetic fields are represented by a single nonsymmetric tensor gy which is a function of four coordinates xr(r = 1, 2, 3, 4). In addition a non-symmetric linear connection Γjki is assumed for the space and a Hamiltonian function is defined in terms of gij and Γjki. By means of a variational principle in which the gij and Γjki are allowed to vary independently the field equations are obtained and can be written(0.1)(0.2)(0.3)(0.4)

CONTROLLABILITY OF ELECTROMAGNETICALLY INDUCED TRANSPARENCY IN A DOPPLER BROADENED FOUR-LEVEL ATOMIC SYSTEM

2013 ◽  
Vol 27 (11) ◽  
pp. 1350037 ◽  
Author(s):  
SOMIA ABD-ELNABI ◽  
K. I. OSMAN
Keyword(s):  
Density Matrix ◽  
Electromagnetic Fields ◽  
Atomic System ◽  
Electromagnetically Induced Transparency ◽  
Experimental Results ◽  
Doppler Broadening ◽  
Matrix Elements ◽  
Nonradiative Decay ◽  
Induced Transparency ◽  
Good Agreement

The influence of Doppler broadening on a four-level N-type atomic system has been investigated in the presence of spontaneous generating coherence. The atomic system interacting with three electromagnetic fields and includes the nonradiative decay, the effect of co- and counter-propagation of the fields is considered. The probe susceptibility behaviors can be modified by Doppler broadening via nonperturbative treatments of the density matrix elements solution in the absence and presence of the spontaneous generating coherence. Some interesting features are enhanced for the spectral behaviors and controllability of electromagnetically induced transparency, which were found to be in good agreement to some experimental results without including Zeeman sublevels to the system.

A Unified Theory of Cavitation Damage

1963 ◽  
Vol 85 (3) ◽  
pp. 365-373 ◽  
Author(s):  
A. Thiruvengadam
Keyword(s):  
Yield Stress ◽  
Strain Energy ◽  
Functional Relationship ◽  
Present Theory ◽  
Experimental Results ◽  
Unified Theory ◽  
Cavitation Damage ◽  
Dynamic Yield ◽  
Critical Cavitation ◽  
Damage Number

The Cavitation Damage Number proposed by the author has been modified to incorporate the concept of strain-energy instead of the dynamic yield stress of the material. The correlation between the Cavitation Damage Number and the Number of Cavities has been extended to different materials and different sizes. A third nondimensional number known as the Inception of Damage Number has been derived and correlated with the critical cavitation parameter. Detailed investigations in the threshold zone indicate the validity of the functional relationship between the critical cavitation parameter and the Inception of Damage Number. In this paper, the part played by each parameter is analyzed and some of the experimental results arrived at by earlier investigators are explained in the light of the present theory.

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