789 research outputs found
Exact one-loop results for in 3-3-1 models
We investigate the decays , with
in a general class of 3-3-1 models with heavy exotic leptons with arbitrary
electric charges. We present full and exact analytical results keeping external
lepton masses. As a by product, we perform numerical comparisons between exact
results and approximate ones where the external lepton masses are neglected. As
expected, we found that branching fractions can reach the current experimental
limits if mixings and mass differences of the exotic leptons are large enough.
We also found unexpectedly that, depending on the parameter values, there can
be huge destructive interference between the gauge and Higgs contributions when
the gauge bosons connecting the Standard Model leptons to the exotic leptons
are light enough. This mechanism should be taken into account when using
experimental constraints on the branching fractions to exclude the parameter
space of the model.Comment: 27 pages, 5 figures, 4 tables; additional explanation on input
parameters; matches journal versio
Electronic structure of Zr-Ni-Sn systems: role of clustering and nanostructures in Half-Heusler and Heusler limits
Half-Heusler and Heusler compounds have been of great interest for several
decades for thermoelectric, magnetic, half-metallic and many other interesting
properties. Among these systems, Zr-Ni-Sn compounds are interesting
thermoelectrics which can go from semiconducting half-Heusler (HH) limit,
ZrNiSn, to metallic Heusler (FH) limit, ZrNiSn. Recently Makogo et al. [J.
Am. Chem. Soc. 133, 18843 (2011)] found that dramatic improvement in the
thermoelectric power factor of HH can be achieved by putting excess Ni into the
system. This was attributed to an energy filtering mechanism due to the
formation of FH nanostructures in the HH matrix. Using density functional
theory we have investigated clustering and nanostructure formation in
HHFH systems near the HH and FH ends and found that excess Ni atoms
in HH tend to stay close to each other and form nanoclusters of FH. On the
other hand, there is competing interaction between Ni-vacancies in FH which
prevent them from forming HH nano clusters. Effects of nano inclusions on the
electronic structure at both HH and FH ends will be discussed.Comment: Published in J. Phys.: Condens. Matte
VQ-Based Written Language Identification
Humans can recognize different types of written languages by their grammars and vocabularies. However, computers see everything as numbers. We present a computational algorithm for machine classification of written languages using the method of vector quantization. For a language document, each word is converted to a sequence of numbers and forms as a vector of numerical values according to its characters. This collection of vectors is then represented by a codebook that contains a number of template vectors for classification. The proposed method is more effective for machine learning than the n-gram based method, which has been widely used for written language identification. Experimental results of classifying a set of five closely roman-typed scripts show the promising application of the proposed method.Griffith Sciences, School of Information and Communication TechnologyNo Full Tex
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