Effective pattern discovery for text mining

Many data mining techniques have been proposed for mining useful patterns in text documents. However, how to effectively use and update discovered patterns is still an open research issue, especially in the domain of text mining. Since most existing text mining methods adopted term-based approaches, they all suffer from the problems of polysemy and synonymy. Over the years, people have often held the hypothesis that pattern (or phrase) based approaches should perform better than the term-based ones, but many experiments did not support this hypothesis. This paper presents an innovative technique, effective pattern discovery which includes the processes of pattern deploying and pattern evolving, to improve the effectiveness of using and updating discovered patterns for finding relevant and interesting information. Substantial experiments on RCV1 data collection and TREC topics demonstrate that the proposed solution achieves encouraging performance

Aqua­[2-(2-pyridylmethyl­imino­meth­yl)phenolato]nickel(II) nitrate monohydrate

In the title compound, [Ni(C13H11N2O)(H2O)]NO3·H2O, the Ni(II) ion is coordinated by one O atom and two N atoms of the Schiff base ligand and the O atom from a water mol­ecule, forming a slightly distorted square-planar geometry. A one-dimensional double-chain structure is formed along [001] by O⋯H—O hydrogen bonds and the Ni⋯O [2.617 (3) Å] inter­actions

{2,2′-[Pyridine-3,4-diylbis(nitrilo­methyl­idyne)]diphenolato}zinc(II)

The title compound, [Zn(C19H13N3O2)], has been synthesized by the reaction of Zn(ClO4)2·6H2O and the tetra­dentate Schiff base ligand 2,2′-[pyridine-3,4-diylbis(nitrilo­methyl­idyne)]diphenol (L). The coordination geometry of the ZnII ion is slightly distorted square-planar, formed by two N atoms and two O atoms from the L ligand

Fast antijamming timing acquisition using multilayer synchronization sequence

Pseudonoise (PN) sequences are widely used as preamble sequences to establish timing synchronization in military wireless communication systems. At the receiver, searching and detection techniques, such as the full parallel search (FPS) and the serial search (SS), are usually adopted to acquire correct timing position. However, the synchronization sequence has to be very long to combat jamming that reduces the signal-to-noise ratio (SNR) to an extremely low level. In this adverse scenario, the FPS scheme becomes too complex to implement, whereas the SS method suffers from the drawback of long mean acquisition time (MAT). In this paper, a fast timing acquisition method is proposed, using the multilayer synchronization sequence based on cyclical codes. Specifically, the transmitted preamble is the Kronecker product of Bose–Chaudhuri-Hocquenghem (BCH) codewords and PN sequences. At the receiver, the cyclical nature of BCH codes is exploited to test only a part of the entire sequence, resulting in shorter acquisition time. The algorithm is evaluated using the metrics of MAT and detection probability (DP). Theoretical expressions of MAT and DP are derived from the constant false-alarm rate (CFAR) criterion. Theoretical analysis and simulation results show that our proposed scheme dramatically reduces the acquisition time while achieving similar DP performance and maintaining a reasonably low real-time hardware implementation complexity, in comparison with the SS schem

Universal Thermoelectric Effect of Dirac Fermions in Graphene

We numerically study the thermoelectric transports of Dirac fermions in graphene in the presence of a strong magnetic field and disorder. We find that the thermoelectric transport coefficients demonstrate universal behavior depending on the ratio between the temperature and the width of the disorder-broadened Landau levels(LLs). The transverse thermoelectric conductivity $\alpha_{xy}$ reaches a universal quantum value at the center of each LL in the high temperature regime, and it has a linear temperature dependence at low temperatures. The calculated Nernst signal has a peak at the central LL with heights of the order of $k_B/e$, and changes sign near other LLs, while the thermopower has an opposite behavior, in good agreement with experimental data. The validity of the generalized Mott relation between the thermoelectric and electrical transport coefficients is verified in a wide range of temperatures.Comment: 4 pages, 4 figures, published versio