Composite electrodes consisting of platinum particles and polyaniline nanowires as electrocatalysts for methanol oxidation

Polyaniline (PANI) with nanowire (PANI‐(NW)) network structure (mean diameter 10–20 nm) was successfully deposited on a stainless steel (SS) electrode by a galvanostatic process. Platinum particles were deposited into the PANI nanowire network structure to result the PANI(NW)‐Pt composite electrode. The PANI(NW)‐Pt electrode was used as electrocatalysts for the electrochemical oxidation of methanol. The PANI nanowires and PANI(NW)‐Pt nanocomposite were characterized by scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and UV–vis absorption spectroscopy. Nanowire morphology with an average diameter of 10–20 nm could be seen from scanning electron micrograph. Small amount (70 mμm) of spherical Pt particles could be deposited into the PANI(NW). Catalytic activity for the oxidation of methanol was studied by using cyclic voltammetry (CV). For comparative purposes, bulk Pt (deposited Pt on SS) and PANI nanowires based electrodes were tested. The PANI(NW)‐Pt nanocomposite electrode exhibited excellent catalytic activity for the electrooxidation of methanol in comparison to bulk Pt electrodes, which reveals that the PANI(NW)‐Pt nanocomposite electrodeis more promising for application in electrocatalyst as a support material. POLYM. COMPOS., 28:650–656, 2007. © 2007 Society of Plastics Engineers     

Cost analysis of a two unit repairable system subject to on-line preventive maintenance and/or repair

The purpose of this paper is to carry out the cost analysis of a two-unit repairable system subject to on-line preventive maintenance(PM) and repair. The policy adopted here is that the on-line PM work of the operating unit is undertaken followed by repair work of the failed unit(if any). All the random variables that. arise in the analysis are assumed to be independently and arbitrarily distributed. A mathematical model is developed using semi-regenerative phenomena and system of integral equations satisfied by various state probabilities corresponding to various initial conditions are obtained. An iterative numerical method is used to solve the system of integral equations. A cost function is built based on the expected number of various jobs completed by the server in [0, t].     

Analysis of a two-unit system subject to repair and preventive maintenance with non-linear revenue and costs

The cost-benefit analysis of a one-server two-identical-unit cold standby system subject to repair and preventive maintenance (PM) with non-linear revenue and costs is presented in this paper. Initially, one unit is in operation and the other is cold standby. When a unit fails, it is taken up for repair or waits for repair if the server is busy. The latter results in a system breakdown. If a unit returns from service (repair or PM) and the other unit is operating, the operating unit is taken up for PM. The revenue obtained by operating a unit for an uninterrupted interval of time is some function of the length of the interval. Similarly, the cost of a repair or PM action is a function of the length of the repair or PM time, respectively, for that action. With the help of regeneration point technique, the expected net revenue over an interval (0,t] is obtained. It is shown that the results for the special case when the revenue and cost function are linear agree with previously obtained results.     

Cost-benefit analysis of one-server two-unit imperfect switch system subject to multistage repairs

This paper deals with the cost-benefit analysis of 1-server 2-unit system with imperfect switch where repairs take place in stages. The repair times of the unit and of the switch are assumed to be arbitrarily distributed while the failure rates of units and of the switch are constants. Initally, one unit is switched on (switch is working at t = 0) and the other is kept as cold standby. The repair of the switch is given preference after completion of current repair of a unit. The analysis is carried out by regeneration point technique. Explicit expressions for the expected durations the server is busy in (0, t) with particular stages of repair of the unit and of the switch are obtained to carry out the cost-benefit analysis of the system.     

Graft copolymerization of polyacrylonitrile (PAN) onto polyester (PET) and simultaneous homopolymerization: A kinetic study. I

The kinetics of graft copolymerization of polyacrylonitrile (PAN) onto polyester (PET) and the simultaneous homopolymerization initiated by the potassium penoxomonosulfate (PMS)–ascorbic acid (H₂A) redox system were studied separately. Results on the graft copolymerization was adequately explained by a mechanism which also accounts for the reason for simultaneous homopolymerization. The observed homopolymerization results agreed with the proposal. Kinetic chain-length measurements on the graft copolymer and homopolymerization were used to evaluate the kinetic parameters. © 1995 John Wiley & Sons, Inc.