25,757 research outputs found

    Operator for Describing Polarization States of a Photon

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    Based on the quantized electromagnetic field described by the Riemann-Silberstein complex vector FF, we construct the eigenvector set of F% F, which makes up an orthonormal and complete representation. In terms of % F we then introduce a new operator which can describe the relative ratio of the left-handed and right-handed polarization states of a polarized photon .In FsF^{\prime}s eigenvector basis the operator manifestly exhibits a behaviour which is similar to a phase difference between two orientations of polarization of a light beam in classical optics.Comment: This version (5 pages) will be published in the European Physical Journal

    Direction-of-Arrival Estimation Based on Sparse Recovery with Second-Order Statistics

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    Traditional direction-of-arrival (DOA) estimation techniques perform Nyquist-rate sampling of the received signals and as a result they require high storage. To reduce sampling ratio, we introduce level-crossing (LC) sampling which captures samples whenever the signal crosses predetermined reference levels, and the LC-based analog-to-digital converter (LC ADC) has been shown to efficiently sample certain classes of signals. In this paper, we focus on the DOA estimation problem by using second-order statistics based on the LC samplings recording on one sensor, along with the synchronous samplings of the another sensors, a sparse angle space scenario can be found by solving an ell1ell_1 minimization problem, giving the number of sources and their DOA's. The experimental results show that our proposed method, when compared with some existing norm-based constrained optimization compressive sensing (CS) algorithms, as well as subspace method, improves the DOA estimation performance, while using less samples when compared with Nyquist-rate sampling and reducing sensor activity especially for long time silence signal

    Polyadic Constacyclic Codes

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    For any given positive integer mm, a necessary and sufficient condition for the existence of Type I mm-adic constacyclic codes is given. Further, for any given integer ss, a necessary and sufficient condition for ss to be a multiplier of a Type I polyadic constacyclic code is given. As an application, some optimal codes from Type I polyadic constacyclic codes, including generalized Reed-Solomon codes and alternant MDS codes, are constructed.Comment: We provide complete solutions on two basic questions on polyadic constacyclic cdes, and construct some optimal codes from the polyadic constacyclic cde

    EEG signals analysis using multiscale entropy for depth of anesthesia monitoring during surgery through artificial neural networks

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    In order to build a reliable index to monitor the depth of anesthesia (DOA), many algorithms have been proposed in recent years, one of which is sample entropy (SampEn), a commonly used and important tool to measure the regularity of data series. However, SampEn only estimates the complexity of signals on one time scale. In this study, a new approach is introduced using multiscale entropy (MSE) considering the structure information over different time scales. The entropy values over different time scales calculated through MSE are applied as the input data to train an artificial neural network (ANN) model using bispectral index (BIS) or expert assessment of conscious level (EACL) as the target. To test the performance of the new index's sensitivity to artifacts, we compared the results before and after filtration by multivariate empirical mode decomposition (MEMD). The new approach via ANN is utilized in real EEG signals collected from 26 patients before and after filtering by MEMD, respectively; the results show that is a higher correlation between index from the proposed approach and the gold standard compared with SampEn. Moreover, the proposed approach is more structurally robust to noise and artifacts which indicates that it can be used for monitoring the DOA more accurately.This research was financially supported by the Center for Dynamical Biomarkers and Translational Medicine, National Central University, Taiwan, which is sponsored by Ministry of Science and Technology (Grant no. MOST103-2911-I-008-001). Also, it was supported by National Chung-Shan Institute of Science & Technology in Taiwan (Grant nos. CSIST-095-V301 and CSIST-095-V302) and National Natural Science Foundation of China (Grant no. 51475342)

    Fourth Generation Leptons and Muon g2g-2

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    We consider the contributions to gμ2g_\mu-2 from fourth generation heavy neutral and charged leptons, NN and EE, at the one-loop level. Diagrammatically, there are two types of contributions: boson-boson-NN, and EE-EE-boson in the loop diagram. In general, the effect from NN is suppressed by off-diagonal lepton mixing matrix elements. For EE, we consider flavor changing neutral couplings arising from various New Physics models, which are stringently constrained by μeγ\mu\to e\gamma. We assess how the existence of a fourth generation would affect these New Physics models.Comment: Minor changes, with references update

    Periodicities in Solar Coronal Mass Ejections

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    Mid-term quasi-periodicities in solar coronal mass ejections (CMEs) during the most recent solar maximum cycle 23 are reported here for the first time using the four-year data (February 5, 1999 to February 10, 2003) of the Large Angle Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO). In parallel, mid-term quasi-periodicities in solar X-ray flares (class >M5.0) from the Geosynchronous Operational Environment Satellites (GOES) and in daily averages of Ap index for geomagnetic disturbances from the World Data Center (WDC) at the International Association for Geomagnetism and Aeronomy (IAGA) are also examined for the same four-year time span. Several conceptual aspects of possible equatorially trapped Rossby-type waves at and beneath the solar photosphere are discussed.Comment: Accepted by MNRAS, 6 figure