Joint gateway selection, transmission slot assignment, routing and power control for wireless mesh networks

Cataloged from PDF version of article.Wireless mesh networks (WMNs) provide cost effective solutions for setting up a communications network over a certain geographic area. In this paper, we study strategic problems of WMNs such as selecting the gateway nodes along with several operational problems such as routing, power control, and transmission slot assignment. Under the assumptions of the physical interference model and the tree-based routing restriction for traffic flow, a mixed integer linear programming (MILP) formulation is presented, in which the objective is to maximize the minimum service level provided at the nodes. A set of valid inequalities is derived and added to the model in an attempt to improve the solution quality. Since the MILP formulation becomes computationally infeasible for larger instances, we propose a heuristic method that is aimed at solving the problem in two stages. In the first stage, we devise a simple MILP problem that is concerned only with the selection of gateway nodes. In the second stage, the MILP problem in the original formulation is solved by fixing the gateway nodes from the first stage. Computational experiments are provided to evaluate the proposed models and the heuristic method. (C) 2013 Elsevier Ltd. All rights reserved

Use of an antibiotic growth promoter and two herbal natural feed additives with and without exogenous enzymes in wheat based broiler diets

No Abstract. South African Journal of Animal Science Vol. 35 (1) 2005: pp.61-7

Superhydrophobic and Omnidirectional Antifreflective Surfaces from Nanostructured Ormosil Colloids

Cataloged from PDF version of article.A large-area superhydrophobic and omnidirectional antireflective nanostructured organically modified silica coating has been designed and prepared. The coating mimics the self-cleaning property of superhydrophobic lotus leaves and omnidirectional broad band antireflectivity of moth compound eyes, simultaneously. Water contact and sliding angles of the coating are around 160 and 10, respectively. Coating improves the transmittance of the glass substrate around 4%, when coated on a single side of a glass, in visible and near-infrared region at normal incidence angles. At oblique incidence angles (up to 60) improvement in transmission reaches to around 8%. In addition, coatings are mechanically stable against impact of water droplets from considerable heights. We believe that our inexpensive and durable multifunctional coatings are suitable for stepping out of the laboratory to practical outdoor applications

Hidden Symmetries and their Consequences in t2gt_{2g} Cubic Perovskites

The five-band Hubbard model for a $d$ band with one electron per site is a model which has very interesting properties when the relevant ions are located at sites with high (e. g. cubic) symmetry. In that case, if the crystal field splitting is large one may consider excitations confined to the lowest threefold degenerate $t_{2g}$ orbital states. When the electron hopping matrix element ($t$) is much smaller than the on-site Coulomb interaction energy ($U$), the Hubbard model can be mapped onto the well-known effective Hamiltonian (at order $t^{2}/U$) derived by Kugel and Khomskii (KK). Recently we have shown that the KK Hamiltonian does not support long range spin order at any nonzero temperature due to several novel hidden symmetries that it possesses. Here we extend our theory to show that these symmetries also apply to the underlying three-band Hubbard model. Using these symmetries we develop a rigorous Mermin-Wagner construction, which shows that the three-band Hubbard model does not support spontaneous long-range spin order at any nonzero temperature and at any order in $t/U$ -- despite the three-dimensional lattice structure. Introduction of spin-orbit coupling does allow spin ordering, but even then the excitation spectrum is gapless due to a subtle continuous symmetry. Finally we showed that these hidden symmetries dramatically simplify the numerical exact diagonalization studies of finite clusters.Comment: 26 pages, 3 figures, 520 KB, submitted Phys. Rev.

Unusual Symmetries in the Kugel-Khomskii Hamiltonian

The Kugel-Khomskii Hamiltonian for cubic titanates describes spin and orbital superexchange interactions between $d^1$ ions having three-fold degenerate $t_{2g}$ orbitals. Since orbitals do not couple along "inactive" axes, perpendicular to the orbital planes, the total number of electrons in $|\alpha >$ orbitals in any such plane and the corresponding total spin are both conserved. A Mermin-Wagner construction shows that there is no long-range spin ordering at nonzero temperatures. Inclusion of spin-orbit coupling allows such ordering, but even then the excitation spectrum is gapless due to a continuous symmetry. Thus, the observed order and gap require more symmetry breaking terms.Comment: 4 pages (two column format with 2 figures), to appear in Phys. Rev. Lett. (submitted on Dec. 2002

Efficient energy storage in residential buildings integrated with RESHeat system

The Renewable Energy System for Residential Building Heating and Electricity Production (RESHeat) system has been realized for heating and cooling residential buildings. The main components of the RESHeat system are a heat pump, photovoltaic modules, sun-tracking solar collectors and photovoltaic/thermal modules, an under-ground thermal energy storage unit, and a ground heat exchanger. One of the main novelties of the RESHeat system is efficient ground regeneration due to the underground energy storage unit. During a heating season, a large amount of heat is taken from the ground. The underground energy storage unit allows the restoration of ground heating capability and the heat pump's coefficient of performance (COP) to be kept high as possible for consecutive years. The paper presents an energy analysis for a residential building that is a RESHeat system demo site, along with integrating the RESHeat system with the building. The experimentally validated components coupled with the building model to achieve the system performance in TRNSYS software. The results show that the yearly average COP of the heat pump is 4.85 due to the underground energy storage unit. The RESHeat system is able to fully cover the heating demand of the building using renewable energy sources and an efficient underground energy storage system

Competing Magnetic Phases on a "Kagome Staircase"

We present thermodynamic and neutron data on Ni_3V_2O_8, a spin-1 system on a kagome staircase. The extreme degeneracy of the kagome antiferromagnet is lifted to produce two incommensurate phases at finite T - one amplitude modulated, the other helical - plus a commensurate canted antiferromagnet for T ->0. The H-T phase diagram is described by a model of competing first and second neighbor interactions with smaller anisotropic terms. Ni_3V_2O_8 thus provides an elegant example of order from sub leading interactions in a highly frustrated systemComment: 4 pages, 3 figure

Coarse-grained model of entropic allostery

Many signaling functions in molecular biology require proteins to bind to substrates such as DNA in response to environmental signals such as the simultaneous binding to a small molecule. Examples are repressor proteins which may transmit information via a conformational change in response to the ligand binding. An alternative entropic mechanism of "allostery" suggests that the inducer ligand changes the intramolecular vibrational entropy, not just the mean static structure. We present a quantitative, coarse-grained model of entropic allostery, which suggests design rules for internal cohesive potentials in proteins employing this effect. It also addresses the issue of how the signal information to bind or unbind is transmitted through the protein. The model may be applicable to a wide range of repressors and also to signaling in trans-membrane proteins

Pressure-Induced Interlinking of Carbon Nanotubes

We predict new forms of carbon consisting of one and two dimensional networks of interlinked single wall carbon nanotubes, some of which are energetically more stable than van der Waals packing of the nanotubes on a hexagonal lattice. These interlinked nanotubes are further transformed with higher applied external pressures to more dense and complicated stable structures, in which curvature-induced carbon sp$^{3}$ re-hybridizations are formed. We also discuss the energetics of the bond formation between nanotubes and the electronic properties of these predicted novel structures.Comment: 4 pages, 4 postscript figures; To be appear in PR