Articles you may be interested inInfrared transparent frequency selective surface based on metallic meshes AIP Advances 4, 027112 (2014); 10.1063/1.4866292 Enhancing and broadening absorption properties of frequency selective surfaces absorbers using FeCoB-based thin filmFrequency selective surfaces as near-infrared electromagnetic filters for thermophotovoltaic spectral controlThe present study was undertaken in order to quantify absorption effects due to ohmic loss in frequency-selective surfaces ͑FSS͒ at infrared frequencies. The structures considered in this work act as electromagnetic filters, and as such, are of interest for use as thermophotovoltaic spectral control devices. For this application, absorption is of primary concern since it leads to reduced filter efficiency. This work focuses on the behavior of single-layer, free-standing FSS arrays comprised of circular apertures ͑holes͒ and circular loop apertures ͑rings͒. Numerical calculations of the transmission, reflection, and absorption characteristics of various arrays were carried out for wavelengths between 1 and 15 m using a commercial finite-element software package. Absorption effects were included using measured optical properties as input parameters to a surface impedance boundary condition. Analytical techniques were then employed to determine the absorption behavior in the static limit. An interesting result of this analysis is the fact that absorption at 15 m is predicted by the finite-element calculations to increase versus aperture radius ͑for fixed aperture separation͒, while in the static limit absorption was found ͑through the use of analytical techniques͒ to decrease. The results of the finite-element calculations were confirmed using another numerical method based on the periodic moment method. We are thus led to the conclusion that the qualitative relationship for absorption versus aperture radius must reverse for some frequency regime yet to be investigated.
In this article, the authors attempt to treat both strong m i s t i n g and slight twisting of fiber via a consistent asymptotic approach to the coupled-mode theory. In strong twisting, an admirably simple and useful asymptotic equation is derived in the form R f = const., which relates the minimum required twist rate 7 with the minimum allowable radius of curvature R In slight twisting an oscillatory pattern of the polarization behauior clearly reveals the advantageous feature of a twist-spun fiber, which is made by a prior spinning of the fiber before a twi3ting. 0 1995 John Wiley & Sons, Inc.
Received 11-30-94Microwave and Optical Technology Letters, 9/1,37-41 0 1995 John Wiley & Sons, Inc.
KEY TERMS Complex pemrittiuq naeasmments, complex permeability measurements, pariialb filled waveguide ABSTRACTA partially filled waveguide is presented to measure complex permittivity and permeability simultaneously at microwave frequency in this article.The mode-matching method is used to analyze the higher-order modes in the waveguide. Experimental results a p e well with theoretical results. 0 I995 John uliley & Sons, Inc.
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