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 X(4140)X(4140), X(4274)X(4274), X(4500)X(4500) and X(4700)X(4700)

We investigate the newly observed $X(4500)$ and $X(4700)$ based on the diquark-antidiquark configuration within the framework of QCD sum rules. Both of them may be interpreted as the $D$-wave $cs\bar{c}\bar{s}$ tetraquark states of $J^P = 0^+$, but with opposite color structures, which is remarkably similar to the result obtained in Ref.~\cite{Chen:2010ze} that the $X(4140)$ and $X(4274)$ can be both interpreted as the $S$-wave $cs\bar{c}\bar{s}$ tetraquark states of $J^P = 1^+$, also with opposite color structures. However, the extracted masses and these suggested assignments to these $X$ states do depend on these running quark masses where m_s (2 \mbox{ GeV}) = 95 \pm 5 MeV and $m_c (m_c) = 1.23 \pm 0.09$ GeV. As a byproduct, the masses of the hidden-bottom partner states of the $X(4500)$ and $X(4700)$ are extracted to be both around 10.64 GeV, which can be searched for in the $\Upsilon \phi$ invariant mass distribution.Comment: 6 pages, 4 figures. Accepted by Eur. Phys. J.

QCD sum rule Study of the d∗(2380)d^*(2380)

We systematically construct $I(J^P)=0(3^+)$ six-quark local interpolating currents without derivative operators. We discuss the best choice of operator, and select three $\Delta$-$\Delta$ like operators to perform QCD sum rule analyses to calculate the mass of the $d^*(2380)$. The mass extracted from this analysis is $M_{d^*} = 2.4\pm0.2$ GeV, consistent with the $d^*(2380)$ mass observed by the WASA detector at COSY. We also obtain a sum-rule lower mass bound $M_{d^*} > 2.25$ 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 $d^*(2380)$ 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

a1(1420)a_1(1420) resonance as a tetraquark state and its isospin partner

We systematically construct tetraquark currents of $I^GJ^{PC}=1^-1^{++}$ and classify them into types $\mathbf{A}$ (antisymmetric), $\mathbf{S}$ (symmetric) and $\mathbf{M}$ (mixed), based on flavor symmetries of diquarks and antidiquarks composing the tetra quark currents. We use tetraquark currents of type $\mathbf{M}$ to perform QCD sum rule analyses, and find a tetraquark current $\eta^M_{5\mu}$ with quark contents $q s\bar q \bar s$($q=u$ or $d$) leading to a mass of $1.44 \pm 0.08$ GeV consistent with the $a_1(1420)$ state recently observed by the COMPASS collaboration. Our results support tetraquark explanations for both $a_1(1420)$ and $f_1(1420)$, assuming that they are isospin partners. We also study their possible decay patterns. As tetraquark candidates, the possible decay modes of $a_1(1420)$ are $S$-wave $a_1(1420) \rightarrow K^*(892)K$ and $P$-wave $a_1(1420)\rightarrow f_0(980) \pi$ while the possible decay patterns of $f_1(1420)$ are $S$-wave $f_1(1420) \rightarrow K^*(892)K$ and $P$-wave $f_1(1420) \rightarrow a_0(980) \pi$. We speculate that $a_1(1420)$ is partly responsible for the large isospin violation in the $\eta(1405)\to f_0(980)\pi_0$ decay mode which is reported by BESIII collaboration in the $J/\psi\to\gamma 3\pi$ 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 A₂B₂X, A₂B₂XX\u27 and A₂B₂XX\u27X were assigned to 4-nitro-cumene, 4-ethyl-nitrobenzene and 4-nitro-toluene respectively. Basic spin wave functions were constructed for both the A₂B₂X and A₂B₂XX\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 A₂B₂. 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