ECRP: an energy-aware cluster-based routing protocol for wireless sensor networks

Energy conservation is the main issue in wireless sensor networks. Many existing clustering protocols have been proposed to balance the energy consumption and maximize the battery lifetime of sensor nodes. However, these protocols suffer from the excessive overhead due to repetitive clustering resulting in high-energy consumption. In this paper, we propose energy-aware cluster-based routing protocol (ECRP) in which not only the cluster head (CH) role rotates based on energy around all cluster members until the end of network functioning to avoid frequent re-clustering, but also it can adapt the network topology change. Further, ECRP introduces a multi-hop routing algorithm so that the energy consumption is minimized and balanced. As well, a fault-tolerant mechanism is proposed to cope up with the failure of CHs and relay nodes. We perform extensive simulations on the proposed protocol using different network scenarios. The simulation results demonstrate the superiority of ECRP compared with recent and relevant existing protocols in terms of main performance metrics.

     

Assignment and Scheduling in Flexible Job-Shops by Hierarchical Optimization

In this paper, we propose a new hierarchical method for the flexible job-shop scheduling problem (FJSP). This approach is mainly adapted to a job-shop problem (JSP) with high flexibility and is based on the decomposition of the problem in an assignment subproblem and a sequencing subproblem. For the first subproblem, we propose two methods: the first one is based successively on a heuristic approach and a local search; the second one, however, is based on a branch-and-bound algorithm. The quality of the assignment is evaluated by a lower bound. For the second subproblem we apply a hybrid genetic algorithm to deal with the sequencing problem. Computational tests are finally presented.     

Role of end-groups and catalyst in polyester cyclodepolymerization and cycle-chain equilibria

The influence of polyesters end-groups on cyclic oligoester formation is investigated using a series of hydroxy-, carboxy- and methylester-terminated aliphatic polyesters, in the presence of various ester interchange catalysts. The presence of hydroxy end-groups is the preponderant factor on cyclodepolymerization kinetics. This indicates that the main reaction is the intramolecular hydroxy–ester interchange reaction between hydroxy end-groups and ester functions in the chain. Carboxy-ester and ester–ester interchanges play a minor role, as the cycle-chain equilibrium is reached only very slowly when carboxy- or ester-terminated polyesters are reacted. High temperature and the presence of tin catalysts are also favorable factors, while, as expected, dilution shifts the equilibrium toward the formation of high yields of cyclic oligoesters. A mechanism is proposed, based on the reverse of the “coordination-insertion” mechanism established for the ring-opening polymerization of lactones.     

Zn–Ni/nano-TiO2 composite electrodeposits: surface modifications and protective properties

Zn–Ni composite coatings were obtained by electrochemical co-deposition of TiO₂ nano-particles (mean diameter 21 nm). Zn–Ni alloy coating was also produced under the same experimental conditions for comparison. The surface morphology, crystallographic structure, and the grain size of the deposits were investigated, along with the percentage of the embedded nano-particles in Zn–Ni matrix, as a function of concentration of TiO₂ nano-particles in the bath. As the titania incorporation percentage is increased, a grain refinement in the nanometer region was revealed followed enhanced microhardness values and an improvement of the content of the nickel in the alloy. Annealing of all coatings at 200 °C revealed the crystallization of the matrix accompanied by a decrease of microhardness followed by stability for 24 h. The corrosion behavior of Zn–Ni/nano-TiO₂ composite coatings with various amount of particle content was mainly studied by electrochemical impedance spectroscopy in 3 % NaCl. It was seen that Zn–Ni/nano-TiO₂ composite coatings exhibited higher corrosion resistances comparing to Zn–Ni alloy coating and corrosion protection improved with increasing nano-TiO₂ in coatings.     

Chemically induced graft copolymerization of 4-vinyl pyridine onto carboxymethyl chitosan

A novel super absorbent polymer was prepared by graft copolymerization of 4-vinyl pyridine (4VP) onto the chains of carboxymethyl chitosan in aqueous solution using potassium persulphate (KPS) as initiator. The effect of monomer and initiator concentration, reaction temperature, and time on the grafting yield has been investigated. The maximum grafting yield was achieved at [KPS] = 4 × 10⁻² mol/L, [M] = 2.5 mol/L at reaction temperature = 60 °C within reaction time = 3 h. The molecular structure of the graft copolymer was confirmed by FTIR, surface morphology before and after the polymerization was examined by SEM. Different analyses were done for the graft copolymer such as X-ray diffraction, solubility tests, and thermal analysis. Different applications were done on the graft copolymer such as swell ability in different pH solutions, dye, and metal uptake.     

Synthesis and characterization of new polyurethanes: influence of monomer composition

Different polyurethanes (PU) were synthesized from polycaprolactone diol, 1.6-hexamethylene diisocyanate and bis(2-hydroxyethyl)terephthalate, using a two- and one-step methods providing regular and random distributions of starting monomers in the polyurethane chains. Even with an identical molar monomer composition, the properties of obtained PU are different depending on the method of synthesis. The chemical structure of PU was characterized by ¹H and ¹³C NMR spectroscopy, as well as by FTIR and UV–Visible spectroscopy. The thermo-mechanical and hydrophilic properties of synthesized PU were also studied demonstrating the influence of aromatic ring in the macromolecular chain.     

Antibacterial activity of cationically modified cotton fabric with carboxymethyl chitosan

A water‐soluble carboxymethyl chitosan was prepared with a view to develop a multifunctional finish on cotton. Carboxymethyl chitosan (CMCTS) was synthesized by chemical reaction of chitosan with monochloroacetic acid under alkaline condition. The water soluble CMCTS was applied to cationized cotton with different concentrations. The treated fabrics were characterized through monitoring the textile physical properties and for the antibacterial activity against Escherichia coli DSMZ 498 and Micrococcus luteus ATCC 9341. The results obtained show that the physical properties of the treated fabrics are improved by increasing the CMCTS concentration, as well as the antibacterial activity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008