Transforming projection methods to solve steady incompressible flows

Abstract

Projection methods are known to be very effective in solving the unsteady flow problems. In this study the idea used in the SIMPLEC method is used to derive the general three- and the four-step projection methods. The concept used in the derivation of the projection methods is extended to obtain projection type methods for the solution of the steady flow problems directly, without resorting to a pseudo transient approach. The performance of the resulting three- and the four-step steady algorithms are compared with the well-known SIMPLE method in solving the steady flow problems on unstructured grids. The performance of the general three- and the four-step projection methods are also compared in solving the unsteady flow problems.     

Spectroelectrochemistry of pyrrole oligomers in the presence of acrylamide

Soluble pyrrole oligomers were characterized during electropolymerization of pyrrole in the presence of acrylamide (in acetonitrile) which stabilizes radical cations of pyrrole allowing the reaction to be followed by spectroscopic and spectroelectrochemical means. The role of the applied electrical conditions and the effect of the presence of acrylamide on the formation of pyrrole oligomers in solution, and on the resulting polymer on an electrode surface (both Pt and indium tin oxide), were investigated. The soluble and insoluble products were characterized using UV‐visible and FTIR spectroscopy, cyclic voltammetry and a four‐point probe technique. Polypyrrole and poly(pyrrole–acrylamide) free‐standing films had conductivity values of about 90 and 1 S cm^?1, respectively. Spectroscopic, cyclovoltammetric and conductivity results support the incorporation of acrylamide into intermediate species that may have useful application in industry. © 2002 Society of Chemical Industry     

Electrochemical and morphological study of the effect of polymerization conditions on poly(tetrathiophene) with emphasis on carbon fiber microelectrodes: A cyclic voltammetry and atomic force microscopy study

Electropolymerization of tetrathiophene was carried out in various solvents on carbon fiber microelectrodes and platinum electrodes. Acetonitrile, dichloroethane and propylene carbonate were investigated as solvent systems for film formation, and solvent effect as well as the effect of other experimental conditions (scan rate, supporting electrolyte) on the electropolymerization has been discussed on the basis of the electropolymerization mechanism. Surface morphology was investigated by atomic force microscopy (AFM). Carbon fiber electrodes were found to be an effective microelectrode system for the electropolymerization of tetrathiophene, which was compared with polyterthiophene growth on carbon fibers.     

Implementation of boundary conditions in pressure-based finite volume methods on unstructured grids

In this study, the implementation of boundary conditions for the Navier–Stokes and the energy equations, including the pressure and pressure correction equations, are presented in the context of finite volume formulation on cell-centered, colocated unstructured grids. The implementation of boundary conditions is formulated in terms of the contribution of boundary face of a cell to the coefficients of the discretized equation for either Dirichlet- or Neumann-type boundary conditions. Open boundaries through which the flow is not fully developed are also considered. In this case, a data reconstruction method is proposed for finding the boundary values of the variables at the correction stage. The validity of implementations is checked by comparing the results with some well-known benchmark problems.     

Inhibition of pyrite corrosion and photocorrosion by MEKF-R modified carbazoles

In this study natural iron sulfide (FeS₂) surface was coated by films of poly(N-vinylcarbazole) (PNVCz), poly(N-vinylcarbazole methylethylketoneformaldehyde resin) (P[NVCz-MEKF-R]), carbazole methylethylketone formaldehyde resin (Cz-MEKFR) and poly(carbazole methyl ethylketone formaldehyde resin) (P[Cz-MEKFR]). The corrosion, photocorrosion, and photoactivity characteristics of coated electrodes were investigated in potassium iodide/iodide (KI/I₂) redox electrolyte. The inhibition effect and photoactivity of Cz-MEKF-R, P[Cz-MEKF-R] P[NVCz-MEKFR] and PNVCz homopolymer coatings were compared. Coating performance was tested by polarization and electrochemical impedance (EIS) measurements. The photopotential and photocurrent values of bare and coated pyrite electrodes were obtained under illuminated conditions. The inhibition efficiencies were calculated from corrosion currents obtained by Tafel extrapolation from polarization curves.     

Synthesis of 2‐(9H‐carbazole‐9‐yl)ethyl methacrylate: Electrochemical impedance spectroscopic study of poly(2‐(9H‐carbazole‐9‐yl)ethyl methacrylate) on carbon fiber

In this contribution, 2‐(9H‐carbazol‐9‐yl) ethyl methacrylate (CzEMA) monomer was chemically synthesized. The monomer characterization was performed by FT‐IR, ¹H‐NMR, ¹³C‐NMR, and melting point analysis. The electropolymerization of CzEMA was studied onto carbon fiber microelectrodes (CFMEs) as an active electrode material in 0.1M sodium perchlorate (NaClO₄)/acetonitrile (ACN) solution. The electropolymerization experiments were done from 1 mM to 10 mM. The detailed characterization of the resulting electrocoated Poly (CzEMA)/CFME thin films was studied by various techniques, i.e., cyclic voltammetry (CV), Scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The effects of initial monomer concentrations (1, 3, 5, and 10 mM) during the preparation of modified electrodes were examined by EIS. Capacitive behaviors of modified CFMEs were defined via Nyquist, Bode‐magnitude, and Bode‐phase plots. Variation of capacitance values by initial monomer concentration and specific capacitance values are presented. The highest specific capacitance value electrocoated polymer thin film by CV method in the initial monomer concentration of 5 mM with a charge of 52.74 mC was obtained about 424.1 μF cm^?2. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Morphological and impedance studies on electropolymerized 3,4-(2,2-dibenzylpropylenedioxy)thiophene nanostructures on micron sized single carbon fiber

Micron sized single carbon fibers were cyclovoltammetrically coated with poly[3,4-(2,2-dibenzylpropylenedioxy)thiophene] resulting in a nanofiber network at the surface. The method provides conjugated polymer nanostructures covalently and uniformly bound to micron sized substrates. When the electropolymerization is carried out with different electrolytes in acetonitrile the dopant influences the structure of the coating layer what is proved by electrochemical impedance spectroscopy and electron microscopy. Electrodes based on poly[3,4-(2,2-dibenzylpropylenedioxy)thiophene] on single carbon fiber microelectrodes (SCFMEs) prepared in Bu₄NPF₆/ACN show the best capacitance performance due to their higher surface area. The improvement is attributed to the formed nanofiber network structure which results in a more efficient charge transport and collection.     

Determination of optimal hierarchical fuzzy controller parameters according to loading condition with ANN

This paper represents an artificial neural network (ANN) backpropagation algorithm is used to choose best coefficients of hierarchical fuzzy power system stabilizer (HFPSS). PSS is used for stability enhancement of a single machine infinite bus (SMIB) power system. ANN algorithm is used to predict load condition of the power system. And according to the predicted load condition ANN determinates choosing optimal parameters of the hierarchical fuzzy controller (HFC) to achieve better performance. Simulation results are compared with conventional PSS (CPSS) to show the effectiveness of the proposed controller. Also quantitative criterias of measuring performance is computed for 16 loading conditions.     

Poly(carbazole-co-acrylamide) electrocoated carbon fibers and their adhesion behavior to an epoxy resin matrix

The surface properties of original high strength and preoxidized high modulus carbon fibers were altered by electrocopolymerizing acryl amide and carbazole and therefore depositing a copolymer coating onto the fibers. Scanning electron microscopy and zeta-potential measurements confirmed the presence of a rough but dense and continuous electrocoating with a basic surface character. Therefore, good adhesion behavior between the electrocoated carbon fibers and an epoxy resin matrix should be expected. The interfacial adhesion was measured using the single fiber pull-out and single fiber indentation test. It was shown that only intermediate adhesion was present between the carbon fibers and the electrocoating, but superior adhesion between the coating and epoxy resin exists. The single fiber model composites always failed at the fiber/electrocoating interface. However, as shown by using the indentation test, the interfacial adhesion between fibers and electrocoating can be significantly improved if preoxidized fibers are used as substrate for electropolymerization. A very high tensile strength for the electrocoating can be expected as derived from the single fiber pull-out tests.