53,581 research outputs found

    Chiral Structure of Vector and Axial-Vector Tetraquark Currents

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    We investigate the chiral structure of local vector and axial-vector tetraquark currents, and study their chiral transformation properties. We consider the charge-conjugation parity and classify all the isovector vector and axial-vector local tetraquark currents of quantum numbers I(G)J(PC)=1(-)1(-+), I(G)J(PC)=1(+)1(--), I(G)J(PC)=1(-)1(++) and I(G)J(PC)=1(+)1(+-). We find that there is a one to one correspondence among them. Using these currents, we perform QCD sum rule analyses. Our results suggest that there is a missing b1 state having I(G)J(PC)=1(+)1(+-) and a mass around 1.47-1.66 GeV.Comment: 27 pages, 8 figures, 3 tables, accepted by EPJC. arXiv admin note: text overlap with arXiv:1311.443

    Frictional interface crack-tip singular stress field in anisotropic

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    This study presents the asymptotic displacement and stress fields at the crack tip of frictional interface where slip can occur along the interface between two anisotropic composite laminates. The results show that real values corresponding to the order of stress singularities may exit at the crack tip of the frictional interface between two anisotropic layers. The order of stress singularity largely depends on the coefficient of friction within the interface and the material properties of anisotropic composite laminates such as fibre orientations

    Extracting Noun Phrases from Large-Scale Texts: A Hybrid Approach and Its Automatic Evaluation

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    To acquire noun phrases from running texts is useful for many applications, such as word grouping,terminology indexing, etc. The reported literatures adopt pure probabilistic approach, or pure rule-based noun phrases grammar to tackle this problem. In this paper, we apply a probabilistic chunker to deciding the implicit boundaries of constituents and utilize the linguistic knowledge to extract the noun phrases by a finite state mechanism. The test texts are SUSANNE Corpus and the results are evaluated by comparing the parse field of SUSANNE Corpus automatically. The results of this preliminary experiment are encouraging.Comment: 8 pages, Postscript file, Unix compressed, uuencode

    On Weak Topology for Optimal Control of Switched Nonlinear Systems

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    Optimal control of switched systems is challenging due to the discrete nature of the switching control input. The embedding-based approach addresses this challenge by solving a corresponding relaxed optimal control problem with only continuous inputs, and then projecting the relaxed solution back to obtain the optimal switching solution of the original problem. This paper presents a novel idea that views the embedding-based approach as a change of topology over the optimization space, resulting in a general procedure to construct a switched optimal control algorithm with guaranteed convergence to a local optimizer. Our result provides a unified topology based framework for the analysis and design of various embedding-based algorithms in solving the switched optimal control problem and includes many existing methods as special cases
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