Browsing by Subject "At resonance"

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    Analysis of double-negative materials with surface integral equations and the multilevel fast multipole algorithm
    (IEEE, 2011) Ergül O.; Gürel, Levent
    We present a fast and accurate analysis of double-negative materials (DNMs) with surface integral equations and the multilevel fast multipole algorithm (MLFMA). DNMs are commonly used as simplified models of metamaterials at resonance frequencies and are suitable to be formulated with surface integral equations. However, realistic metamaterials and their models are usually very large with respect to wavelength and their accurate solutions require fast algorithms, such as MLFMA. We consider iterative solutions of DNMs with MLFMA and we investigate the accuracy and efficiency of solutions when DNMs are formulated with two recently developed formulations, namely, the combined tangential formulation (CTF) and the electric and magnetic current combined-field integral equation (JMCFIE). Numerical results on canonical objects are consistent with previous results in the literature on ordinary objects. © 2011 IEEE.
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    A wideband and a Wide-Beamwidth acoustic transducer design for underwater acoustic communications
    (IEEE, 2007-05) Elmaslı, I. Ceren; Köymen, Hayrettin
    This paper is concerned with the design of an efficient, wideband and a wide-beamwidth resonant acoustic transducer for high frequency use. The general transducer structure which has two back-to-back quarter wave thick 1-3 composite ceramic elements at resonance frequency is introduced. The transducer is employed for both transmit and receive modes. Design of transmitting and receiving transducers are discussed. Several transfer functions are derived and their effective bandwidths are calculated. It is shown that the phase angle difference between two acoustic ports in receive mode can be processed at the electrical ports to maintain better throughput. The paper includes future works to be done. It is concluded that the proposed structure can be used for applications of spread spectrum schemes in underwater communications. ©2006 IEEE.