13,077 research outputs found
An ACO Algorithm for Effective Cluster Head Selection
This paper presents an effective algorithm for selecting cluster heads in
mobile ad hoc networks using ant colony optimization. A cluster in an ad hoc
network consists of a cluster head and cluster members which are at one hop
away from the cluster head. The cluster head allocates the resources to its
cluster members. Clustering in MANET is done to reduce the communication
overhead and thereby increase the network performance. A MANET can have many
clusters in it. This paper presents an algorithm which is a combination of the
four main clustering schemes- the ID based clustering, connectivity based,
probability based and the weighted approach. An Ant colony optimization based
approach is used to minimize the number of clusters in MANET. This can also be
considered as a minimum dominating set problem in graph theory. The algorithm
considers various parameters like the number of nodes, the transmission range
etc. Experimental results show that the proposed algorithm is an effective
methodology for finding out the minimum number of cluster heads.Comment: 7 pages, 5 figures, International Journal of Advances in Information
Technology (JAIT); ISSN: 1798-2340; Academy Publishers, Finlan
Understanding the internal structures of the , , and
We investigate the newly observed and based on the
diquark-antidiquark configuration within the framework of QCD sum rules. Both
of them may be interpreted as the -wave tetraquark states
of , but with opposite color structures, which is remarkably similar
to the result obtained in Ref.~\cite{Chen:2010ze} that the and
can be both interpreted as the -wave tetraquark
states of , also with opposite color structures. However, the
extracted masses and these suggested assignments to these states do depend
on these running quark masses where m_s (2 \mbox{ GeV}) = 95 \pm 5 MeV and
GeV. As a byproduct, the masses of the
hidden-bottom partner states of the and are extracted to be
both around 10.64 GeV, which can be searched for in the
invariant mass distribution.Comment: 6 pages, 4 figures. Accepted by Eur. Phys. J.
QCD sum rule Study of the
We systematically construct six-quark local interpolating
currents without derivative operators. We discuss the best choice of operator,
and select three - like operators to perform QCD sum rule
analyses to calculate the mass of the . The mass extracted from this
analysis is GeV, consistent with the mass
observed by the WASA detector at COSY. We also obtain a sum-rule lower mass
bound GeV. We also consider the effect of mixing of singlet
dibaryon fields with the same quantum numbers, and perform the QCD sum rule
analysis of the mixed interpolating current and extract the mass of the
and its lower mass bound. With optimized mixing parameters, we find
that the mixed current does not change the numerical result significantly.Comment: 9 pages, 4 figure
resonance as a tetraquark state and its isospin partner
We systematically construct tetraquark currents of and
classify them into types (antisymmetric), (symmetric)
and (mixed), based on flavor symmetries of diquarks and
antidiquarks composing the tetra quark currents. We use tetraquark currents of
type to perform QCD sum rule analyses, and find a tetraquark
current with quark contents ( or )
leading to a mass of GeV consistent with the state
recently observed by the COMPASS collaboration. Our results support tetraquark
explanations for both and , assuming that they are
isospin partners. We also study their possible decay patterns. As tetraquark
candidates, the possible decay modes of are -wave and -wave while
the possible decay patterns of are -wave and -wave . We speculate that
is partly responsible for the large isospin violation in the
decay mode which is reported by BESIII
collaboration in the process.Comment: 15 pages, 8 figures. Accepted by Phys. Rev.
Substituent effects on the magnetic resonance spectra of 1, 4-disubstituted benzenes
The Nuclear Magnetic Resonance spectra of five complete series of para-substituted benzenes have been investigated: the benzoic acids, benzonitriles, benzoyl chlorides, methyl benzoates and nitrobenzenes. Precise values of aromatic proton chemical shifts and coupling constants were obtained from LAOCOON3 computer analyses of the spectra. Using the relative internal chemical shift technique of Beachell and Beistel, excellent linear correlations among all five series were found. All substituents gave proton shifts which lay on the least-squares line, so it is concluded that all substituents are well behaved. Using the correlation plots the chemical shifts of the aromatic ring protons can be predicted to 0.01 ppm.
Highly resolved, first-order spectra were observed at 100 MHz for the 4-alkyl-nitrobenzenes. The group designations Aâ‚‚Bâ‚‚X, Aâ‚‚Bâ‚‚XX\u27 and Aâ‚‚Bâ‚‚XX\u27X were assigned to 4-nitro-cumene, 4-ethyl-nitrobenzene and 4-nitro-toluene respectively. Basic spin wave functions were constructed for both the Aâ‚‚Bâ‚‚X and Aâ‚‚Bâ‚‚XX\u27 systems and both diagonal and off-diagonal matrix elements were evaluted. No methyl-ring proton coupling was found for 4-t-butylnitrobenzene and ring proton spectrum was simply Aâ‚‚Bâ‚‚.
The perturbed valence bond model of Beistel has been used to rationalize substituent effects on the p.m.r. spectra of the para-substituted benzenes. This model assumes that the hybridization of the skeletal atoms can be perturbed from sp² to (sp²+Δp) or (sp²-Δp), depending on the directive abilities of the substituent. The perturbation influences the proton shift upfield relative to benzene when the proton is bonded to a carbon hybridized (sp²+Δp), and downfield for a carbon hybridized (sp²-Δp). Available carbon-13 shift data has proved consistent with the proposed model.
The directive abilities of the substituents decrease in the sequencer N(CH₃)₂, NH₂, OCH₃, OH, F, CH₃, C₂H₅ , H, C₃H₇, Cl, C₄H₉, Br, CN, COOCH₃, COCl, I and N0₂. That is according to the hybridization of the central atom, its relative nuclear charge and the principal quantum number of the valence electrons. The groups COH, CONH₂ and COCH₃ have not been included in the sequence since complete series were not studied. Files of spectral data and selected measurements suggest that these groups lie between CN and COOCH₃ in the order indicated --Abstract, pages iii-iv
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