3,874 research outputs found

    Broadband and small-size 3-DB ring coupler

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    A topology for a 3-dB broadband and small-size ring coupler is proposed. It consists of fully distributed Composite Right-/Left-Handed phase shifters and a Lange coupler. For the fabricated coupler, the frequency bandwidth is one octave, centered on 1.5 GHz, while the footprint area is 25% compared to the conventional ring coupler topology. The experimental results are in good agreement with the expected ones, obtained by electromagnetic simulation

    Experimental results obtained on a new circuit topology of a broadband and low spurious frequency doubler

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    A CRLH (Composite Right-/Left-Handed) based distributed frequency multiplier circuit topology is proposed. It is demonstrated that using fully-distributed CRLH based unit cells, low spurious output spectrum and flat output power level may be obtained for a large frequency bandwidth. To validate the proposed frequency multiplier, a frequency doubler is designed and fabricated. The experimental results have shown that the conversion losses on the output second harmonic is less than 9 dB and 7 dB, for input power level of -1 dBm and 5 dBm, respectively, within an input frequency bandwidth from 4 GHz to 6 GHz. In the same frequency bandwidth, due to the CRLH based circuit topology, the first and third output harmonics are well filtered

    The neural correlates of orienting to walking direction in 6-month-old infants: an ERP study

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    The ability to detect social signals represents a first step to enter our social world. Behavioral evidence has demonstrated that 6‐month‐old infants are able to orient their attention toward the position indicated by walking direction, showing faster orienting responses toward stimuli cued by the direction of motion than toward uncued stimuli. The present study investigated the neural mechanisms underpinning this attentional priming effect by using a spatial cueing paradigm and recording EEG (Geodesic System 128 channels) from 6‐month‐old infants. Infants were presented with a central point‐light walker followed by a single peripheral target. The target appeared randomly at a position either congruent or incongruent with the walking direction of the cue. We examined infants' target‐locked event‐related potential (ERP) responses and we used cortical source analysis to explore which brain regions gave rise to the ERP responses. The P1 component and saccade latencies toward the peripheral target were modulated by the congruency between the walking direction of the cue and the position of the target. Infants' saccade latencies were faster in response to targets appearing at congruent spatial locations. The P1 component was larger in response to congruent than to incongruent targets and a similar congruency effect was found with cortical source analysis in the parahippocampal gyrus and the anterior fusiform gyrus. Overall, these findings suggest that a type of biological motion like the one of a vertebrate walking on the legs can trigger covert orienting of attention in 6‐month‐old infants, enabling enhancement of neural activity related to visual processing of potentially relevant information as well as a facilitation of oculomotor responses to stimuli appearing at the attended location

    Recherche des bosons de Higgs neutres d'un modÚle à deux doublets avec le détecteur ALEPH au LEP

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    Design optimization of meta-material transmission lines for linear and non-linear microwave signal processing

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    The possibility to use CRLH (Composite Right-/Left-Handed) cells to realize both distributed wide-band filters for linear signal processing and non-linear devices like frequency doublers is investigated analytically and numerically. Full-wave electromagnetic simulations are performed for the filtering structure by means of a commercial software package and confirm the validity of the analytic results. Numerical results for CRLH NLTL (Non-Linear Transmission Line) obtained by using the Microwave Office are discussed, providing design considerations about the synthesis of such a component

    Pattern Avoidance in Poset Permutations

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    We extend the concept of pattern avoidance in permutations on a totally ordered set to pattern avoidance in permutations on partially ordered sets. The number of permutations on PP that avoid the pattern π\pi is denoted AvP(π)Av_P(\pi). We extend a proof of Simion and Schmidt to show that AvP(132)≀AvP(123)Av_P(132) \leq Av_P(123) for any poset PP, and we exactly classify the posets for which equality holds.Comment: 13 pages, 1 figure; v2: corrected typos; v3: corrected typos and improved formatting; v4: to appear in Order; v5: corrected typos; v6: updated author email addresse

    Geometric combinatorial algebras: cyclohedron and simplex

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    In this paper we report on results of our investigation into the algebraic structure supported by the combinatorial geometry of the cyclohedron. Our new graded algebra structures lie between two well known Hopf algebras: the Malvenuto-Reutenauer algebra of permutations and the Loday-Ronco algebra of binary trees. Connecting algebra maps arise from a new generalization of the Tonks projection from the permutohedron to the associahedron, which we discover via the viewpoint of the graph associahedra of Carr and Devadoss. At the same time that viewpoint allows exciting geometrical insights into the multiplicative structure of the algebras involved. Extending the Tonks projection also reveals a new graded algebra structure on the simplices. Finally this latter is extended to a new graded Hopf algebra (one-sided) with basis all the faces of the simplices.Comment: 23 figures, new expanded section about Hopf algebra of simplices, with journal correction
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