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Sectoral M-EBG Antenna with Multipolarization Capabilities for Wimax Base Stations
Mohamad Hajj;Regis Chantalat;Michele Lalande;Bernard Jecko
PIER C , 2011, DOI: 10.2528/PIERC11020501
Abstract: A novel multipolarized sectoral antenna on a metallic electromagnetic band gap (M-EBG) surface is investigated. The M-EBG structure behaves as a partially reflecting surface (PRS) and enhances the directivity of a simple radiating source. The use of metallic structures offers a new approach to industrial partners in order to reduce costs and to facilitate design techniques. By using double layers of M-EBG structure working on orthogonal polarizations as a superstrate with a single patch feeding by two ports, multipolarization operation is achieved. This antenna provides vertical, horizontal, 0°/90°and circular polarizations with a sectoral radiation pattern in the azimuth plane. M-EBG antennas with sectoral pattern are usually designed only for vertical polarization. In order to verify the results a Bipolar M-EBG Sectoral antenna prototype for WIMAX application~[5.15-5.35] GHz is realized and measured. Finally, we study the possibility to generate circular polarization.
Rich-club vs rich-multipolarization phenomena in weighted networks  [PDF]
M. Angeles Serrano
Physics , 2008, DOI: 10.1103/PhysRevE.78.026101
Abstract: Large scale hierarchies characterize complex networks in different domains. Elements at their top, usually the most central or influential, may show multipolarization or tend to club forming tightly interconnected communities. The rich-club phenomenon quantified this tendency based on unweighted network representations. Here, we define this metric for weighted networks and discuss the appropriate normalization which preserves nodes' strengths and discounts structural strength-strength correlations if present. We find that in some real networks the results given by the weighted rich-club coefficient can be in sharp contrast to the ones in the unweighted approach. We also discuss that the scanning of the weighted subgraphs formed by the high-strength hubs is able to unveil features contrary to the average: the formation of local alliances in rich-multipolarized environments, or a lack of cohesion even in the presence of rich-club ordering. Beyond structure, this analysis matters for understanding correctly functionalities and dynamical processes relying on hub interconnectedness.
Multifrequency and IUE Campaigns on Blazars  [PDF]
Laura Maraschi
Physics , 1998,
Abstract: The IUE contribution to the understanding of the blazar phenomenon has been of fundamental importance. Here I review the progress obtained with the latest multifrequency campaigns performed with IUE on two prototype objects, the BL Lac PKS 2155-304 and the highly polarized, superluminal quasar 3C 279.
Multifrequency spin resonance in diamond  [PDF]
Lilian Childress,Jean McIntyre
Physics , 2010, DOI: 10.1103/PhysRevA.82.033839
Abstract: Magnetic resonance techniques provide a powerful tool for controlling spin systems, with applications ranging from quantum information processing to medical imaging. Nevertheless, the behavior of a spin system under strong excitation remains a rich dynamical problem. In this paper, we examine spin resonance of the nitrogen-vacancy center in diamond under conditions outside the regime where the usual rotating wave approximation applies, focusing on effects of multifrequency excitation and excitation with orientation parallel to the spin quantization axis. Strong-field phenomena such as multiphoton transitions and coherent destruction of tunneling are observed in the spectra and analyzed via numerical and analytic theory. In addition to illustrating the response of a spin system to strong multifrequency excitation, these observations may inform techniques for manipulating electron-nuclear spin quantum registers.
The multifrequency Siberian Radioheliograph  [PDF]
S. V. Lesovoi,A. T. Altyntsev,E. F. Ivanov,A. V. Gubin
Physics , 2012, DOI: 10.1007/s11207-012-0008-7
Abstract: The 10-antenna prototype of the multifrequency Siberian radioheliograph is described. The prototype consists of four parts: antennas with broadband front-ends, analog back-ends, digital receivers and a correlator. The prototype antennas are mounted on the outermost stations of the Siberian Solar Radio Telescope (SSRT) array. A signal from each antenna is transmitted to a workroom by an analog fiber optical link, laid in an underground tunnel. After mixing, all signals are digitized and processed by digital receivers before the data are transmitted to the correlator. The digital receivers and the correlator are accessible by the LAN. The frequency range of the prototype is from 4 to 8 GHz. Currently the frequency switching observing mode is used. The prototype data include both circular polarizations at a number of frequencies given by a list. This prototype is the first stage of the multifrequency Siberian radioheliograph development. It is assumed that the radioheliograph will consist of 96 antennas and will occupy stations of the West-East-South subarray of the SSRT. The radioheliograph will be fully constructed in autumn of 2012. We plan to reach the brightness temperature sensitivity about 100 K for the snapshot image, a spatial resolution up to 13 arcseconds at 8 GHz and polarization measurement accuracy about a few percent. First results with the 10-antenna prototype are presented of observations of solar microwave bursts. The prototype abilities to estimate source size and locations at different frequencies are discussed.
Multifrequency broadband tapered plasmonic nanoantennas  [PDF]
I. S. Maksymov,A. R. Davoyan,C. Simovski,P. Belov,Yu. S. Kivshar
Physics , 2011, DOI: 10.1016/j.optcom.2011.11.050
Abstract: We suggest a novel multifrequency broadband plasmonic Yagi-Uda-type nanoantenna equipped with an array of tapered directors. Each director can be used for the excitation of the antenna by nanoemitters matched spectrally with the director resonant frequency and placed in the director near-field region. Multifrequency op- eration of nanoantennas provides tremendous opportunities for broadband emission enhancement, spectroscopy and sensing. By the principle of reciprocity, the same tapered nanoantenna architecture can be used both as a transmitter and/or as a receiver, thus being useful for creating a broadband wireless communication system.
语言族的L可识性、L半可识性与L强可识性  [PDF]
雷忠学
科学通报 , 1986,
Abstract: 郭聿琦等建立和讨论了语言族的半可识性和强可识性,给出了积分语言族可识的充要条件。本文建立和讨论了语言族的L可识性、L半可识性和L强可识性,给出了L积分语言族的L可识、L半可识和L强可识的充分条件。
Multifrequency tympanometry in infants  [cached]
Moraes, Tamyne Ferreira Duarte,Macedo, Camila de Cássia,Feniman, Mariza Ribeiro
International Archives of Otorhinolaryngology , 2012,
Abstract: Introduction: The use of conventional tympanometry is not sufficiently sensitive to detect all cases of middle ear changes, and this hinders accurate diagnosis. Objective: To characterize acoustic immittance measures of infants from 0 to 3 months of age using multifrequency tympanometry in a prospective study. Method: 54 infants from 0 to 3 months of age were evaluated. The inclusion criteria included absence of respiratory infections during the evaluation, presence of transient evoked otoacoustic emissions, and absence of risk indicators for hearing loss. The subjects were evaluated by an audiologic interview, a visual inspection of the ear canal, and measures of acoustic immittance at the frequencies of 226 Hz, 678 Hz, and 1,000 Hz. Tympanometric records of the occlusion effect, tympanometric curve type, tympanometric peak pressure, equivalent ear canal volume, and peak compensated static acoustic admittance were collected. Results: The results indicated the presence of an occlusion effect (2.88% at 226 Hz, 4.81% at 678 Hz and 3.85% at 1,000 Hz), predominance of a tympanometric curve with a single peak (65.35% at 226 Hz, 81.82% at 678 Hz, and 77.00% at 1,000 Hz), and tympanometric peak pressure ranging from -155 to 180 daPa. Further, the equivalent ear canal volume increased with the frequency of the probe (0.64 mL at 226 Hz, 1.63 mho at 678 Hz, and 2.59 mmho at 1,000 Hz) and the peak compensated static acoustic admittance values increased with an increase in frequency (0.51 mL at 226 Hz, 0.55 mmho at 678 Hz and 1.20 mmho at 1,000 Hz). 93.06% of the tympanograms were classified as normal at 226 Hz, 81.82% at 678 Hz, and 77.00 % at 1,000 Hz, respectively. Conclusion: Taken together, these results demonstrated that utilizing these evaluations made it possible to characterize the acoustic immittance measures of infants.
Anharmonicity in multifrequency atomic force microscopy  [PDF]
Sergio Santos,Victor Barcons
Physics , 2014,
Abstract: In multifrequency atomic force microscopy higher eigenmodes are externally excited to enhance resolution and contrast while simultaneously increasing the number of experimental observables with the use of gentle forces. Here, the implications of externally exciting multiple frequencies are discussed in terms of cantilever anharmonicity, fundamental period and the onset of subharmonic and superharmonic components. Cantilever anharmonicity is shown to affect and control both the observables, that is, the monitored amplitudes and phases, and the main expressions quantified via these observables, that is, the virial and energy transfer expressions which form the basis of the theory.
《海森伯传》译者引言  [PDF]
戈革
物理 , 2004,
Abstract: ?《海森伯传》译者引言
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