Optimized Group Channel Assignment Using Computational Geometry over Wireless Mesh Networks

Wireless Mesh Networks (WMNs) are an evolving division in the field of wireless networks due to their ease of deployment and assured last mile connectivity. It sets out a favorable situation to guarantee the Internet connectivity to all the mobile and static nodes. A wireless environment is dynamic, heterogeneous, and unpredictable as the nodes communicate through the unguided links called channels. The number of nonoverlapping channels available is less than the number of mesh nodes; hence, the same channel will be shared among many nodes. This scarcity of the channels causes interference and degrades the performance of the network. In this paper, we have presented a group based channel assignment method to minimize the interference. We have formulated a mathematical model using Nonlinear Programming (NLP). The objective function defines the channel assignment strategy which eventually reduces the interference. We have adapted the cognitive model of Discrete Particle Swarm Optimization (DPSO), for solving the optimization function. The channel assignment problem is an NP hard problem; hence, we have taken the benefits of a stochastic approach to find a solution that is optimal or near optimal. Finally, we have performed simulations to investigate the efficiency of our proposed work

Transesterification of cyclic carbonates to Dimethyl Carbonate using solid oxide catalyst at ambient conditions: environmentally benign synthesis

Continuous synthesis at ambient conditions: Dimethyl carbonate (DMC) is an important methylating and carbonylating agent. Transesterification of cyclic carbonates using methanol for the synthesis of DMC is environmentally benign. CaO–ZnO catalysts, prepared by a wet impregnation method, are effective catalysts for the transesterification of ethylene carbonate using methanol in batch and in continuous reactors. Yields of ca. 84 % DMC can be achieved at ambient conditions

Structure, characterisation and dynamics of copper(I) complexes of 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine

Two mononuclear copper(I) complexes of a tripodal ligand, 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L), have been prepared, [CuL(ClO4)]·CH2Cl21 and [CuL(PPh3)]ClO42. A new route to L is also proposed. The crystal structures of both complexes have been determined. In 1 the perchlorate is bonded through one of its oxygens with a distance of 2.426(3)Å. In 2 the perchlorate ion is thermally disordered. A variable-temperature NMR study of both complexes revealed that the methylene carbon of 2 is chiral at low temperatures. Carbon monoxide formed a terminal adduct with 1

Ligand dynamics in tetracoordinate copper(I) complexes of bis(pyrazolyl)pyridine ligands †

Several mononuclear and a binuclear copper(I)–phosphine complex with a tridentate ligand, L [2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine] or L′ [2,6-bis(pyrazol-1-ylmethyl)pyridine], have been prepared and characterized. The crystal structure of [LCu(PPh2CH2CH2PPh2)CuL][ClO4]2 has been solved. All complexes exhibit interesting molecular dynamics which could be monitored by 1H NMR spectral characteristics arising from the methylene group of the ligand and also from the protons of the pyrazole part of the ligand in some cases. The complexes with unsymmetric phosphine ligands such as PPhnBu3–n with n = 1 or 2 revealed the presence of two conformations with differing populations as evidenced by temperature dependent 1H NMR spectral data. The thermodynamics of these transformations due to the fluxional character of the ligand, L, has been studied by computer simulations of the experimental spectra. The NMR spectral characteristics revealed that the methylene protons are diastereotropic

Supported imidazole as heterogeneous catalyst for the synthesis of cyclic carbonates from epoxides and CO2

Imidazole anchored onto a silica matrix, by means of a propyl linkage, is found to be an effective heterogeneous catalyst for the synthesis of cyclic carbonates from epoxides and CO2 in near quantitative yield. The versatility of this catalyst is demonstrated by using different substrates (epichlorohydrin, propylene oxide, butylene oxide and styrene oxide) for this cycloaddition reaction. These CO2 insertion reactions were typically carried out in the temperature range of 343 to 403 K at 0.6 MPa CO2 pressure under solvent-free conditions. Several spectroscopic methods were used to characterize the catalyst and study the integrity of the fresh and spent catalysts

[2,6-Bis(3,5-dimethylpyrazol-1-ylmethyl-κN²)pyridine-κN]bis(thiocyanato-N)copper(II)

The title compound, [Cu(NCS)₂(C₁₇H₂₁N₅)], displays a distorted square-pyramidal coordination geometry, where the basal plane is defined by the tridentate ligand and by one of the thiocyanate ions. The apical position is occupied by the other thiocyanate ion