55 research outputs found
Q-based design equations for resonant metamaterials and experimental validation
Practical design parameters of resonant metamaterials, such as loss tangent,
are derived in terms of the quality factor of the resonant effective medium
permeability or permittivity. Through electromagnetic simulations of loop-based
resonant particles, it is also shown that the of the effective medium
response is essentially equal to the of an individual resonant particle.
Thus, by measuring the of a single fabricated metamaterial particle, the
effective permeability or permittivity of a metamaterial can be calculated
simply and accurately without requiring complex simulations, fabrication, or
measurements. Experimental validation shows that the complex permeability
analytically estimated from the measured of a single fabricated
self-resonant loop agrees with the complex permeability extracted from
parameter measurements of a metamaterial slab to better than 20%. This
equivalence reduces the design of a metamaterial to meet a given loss
constraint to the simpler problem of the design of a resonant particle to meet
a specific constraint. This analysis also yields simple analytical
expressions for estimating the loss tangent of a planar loop magnetic
metamaterial due to ohmic losses. It is shown that
is a strong lower bound for magnetic loss tangents for frequencies not too far
from 1 GHz. The ohmic loss of the metamaterial varies inversely with the
electrical size of the metamaterial particle, indicating that there is a loss
penalty for reducing the particle size at a fixed frequency
Full-wave simulations of electromagnetic cloaking structures
Based on a coordinate transformation approach, Pendry {\it et al.} have
reported electromagnetically anisotropic and inhomogeneous shells that, in
theory, completely shield an interior structure of arbitrary size from
electromagnetic fields without perturbing the external fields. We report
full-wave simulations of the cylindrical version of this cloaking structure
using ideal and nonideal (but physically realizable) electromagnetic parameters
in an effort to understand the challenges of realizing such a structure in
practice. The simulations indicate that the performance of the electromagnetic
cloaking structure is not especially sensitive to modest permittivity and
permeability variations. This is in contrast to other applications of
engineered electromagnetic materials, such as subwavelength focusing using
negative refractive index materials. The cloaking performance degrades smoothly
with increasing loss, and effective low-reflection shielding can be achieved
with a cylindrical shell composed of an eight (homogeneous) layer approximation
of the ideal continuous medium
Stochastic Fuzzy Algorithms for Impairment of Assets Management
The present paper aims to analyze the impairment of tangible assets with the help of artificial intelligence. Stochastic fuzzy numbers have been introduced with a dual purpose: on one hand to estimate the cash flows generated by tangible assets exploitation and, on the other hand, to ensure the value ranges stratifications that define these cash flows. Estimation of cash flows using stochastic fuzzy numbers was based on cash flows generated by tangible assets in previous periods of operation. Also, based on the Lagrange multipliers, were introduced: the objective function of minimizing the standard deviations from the recorded value of the cash flows generated by the tangible assets, as well as the constraints caused by the impairment of tangible assets identification according to which the cash flows values must be equal to the annual value of the invested capital. Within the determination of the impairment value and stratification of the value ranges determined by the cash flows using stochastic fuzzy numbers, the impairment of assets risk was identified. Information provided by impairment of assets but also the impairment risks, is the basis of the decision-making measures taken to mitigate the impact of accumulated impairment losses on company’s financial performance
Phase Conjugation and Negative Refraction Using Nonlinear Active Metamaterials
We present experimental demonstration of phase conjugation using nonlinear
metamaterial elements. Active split-ring resonators loaded with varactor diodes
are demonstrated theoretically to act as phase-conjugating or time-reversing
discrete elements when parametrically pumped and illuminated with appropriate
frequencies. The metamaterial elements were fabricated and shown experimentally
to produce a time reversed signal. Measurements confirm that a discrete array
of phase-conjugating elements act as a negatively-refracting time reversal RF
lens only 0.12 thick
USE OF SEXUAL PHEROMONES FOR MONITORING THE POPULATION OF THE PEST DELIA ANTIQUA (onion fly)
There were synthesized and tested: 2 variants for the Delia antiqua pheromone. The attack produced by the onion fly larvae in the onion culture was below 2%. In the climatic conditions of the year 2019, adults from generation 1 were captured in June, decades 1 and 2. The pheromonal variant V1 V1 - D (dipropyl disulfide) captured a greater number of adults, 57, 1%, compared to the control V2 - E (2 ø ethanol). - 42.9% of the total captured. Comparative study of the experiments carried out, setting up, experiments and testing of variants
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