Solvent-free glycerolysis catalyzed by acetone powder of Nigella sativa seed lipase

The solvent-free glycerolysis of used sunflower oil catalyzed by acetone powder of Nigella sativa seeds was investigated. The highest partial acylglycerols yield was obtained at 60°C. The glycerolysis reactions, conducted at molar ratios of 1:1, 2:1, and 3:1 of oil to glycerol keeping the acetone powder content at 30% based on oil weight and the temperature at 60°C, approached equilibrium after 2 h. The highest partial acylglycerol content of the products was 66% (1:1 molar ratio) and 60% (2:1 molar ratio).     

Facilitation of water management in low Pt loaded PEM fuel cell by creating hydrophobic microporous layer with PTFE,FEP and PDMS polymers: Effect of polymer and carbon amounts

Microporous layers (MPLs) were prepared with different hydrophobic polymers to establish water management in polymer electrolyte membrane (PEM) fuel cells. Besides conventionally used polymers polytetrafluoroethylene (PTFE) and fluorinated ethylene propylene (FEP), two different molecular weights (MW) of polydimethylsiloxane (PDMS) polymer were used as hydrophobic materials in MPL. Membrane electrode assemblies (MEAs) having MPLs with low MW PDMS polymer exhibited the best fuel cell performance compared to the PTFE and FEP based ones. Thus it is concluded that PDMS polymer has a great potential to be used as hydrophobic material for MPL to reduce flooding phenomena in PEM fuel cell.     

Wavelet-based feature extraction and selection for classification of power system disturbances using support vector machines

This paper presents a new approach for the classification of the power system disturbances using support vector machines (SVMs). The proposed approach is carried out at three serial stages. Firstly, the features to be form the SVM classifier are obtained by using the wavelet transform and a few different feature extraction techniques. Secondly, the features exposing the best classification accuracy of these features are selected by a feature selection technique called as sequential forward selection. Thirdly, the best appropriate input vector for SVM classifier is rummaged. The input vector is started with the first best feature and incrementally added the chosen features. After the addition of each feature, the performance of the SVM is evaluated. The kernel and penalty parameters of the SVM are determined by cross-validation. The parameter set that gives the smallest misclassification error is retained. Finally, both the noisy and noiseless signals are applied to the classifier given above stages. Experimental results indicate that the proposed classifier is robust and has more high classification accuracy with regard to the other approaches in the literature for this problem.     

Transient response of PEM fuel cells with parallel and interdigitated flow field designs

Transient characteristics of proton exchange membrane (PEM) fuel cells with parallel and interdigitated flow fields upon changes in voltage load were investigated by applying a three-dimensional, two-phase model. Effects of channel to rib width ratios and cathode inlet flow rates on the transient response of PEM fuel cell were examined in detail. Current overshoot and undershoot occur because the time scale for the voltage change is much shorter than for the oxygen concentration changes. Therefore, the oxygen concentrations on the cathode diffusion layer-catalyst layer interface immediately after the voltage changes are essentially the same as before the voltage changes, which results in higher reaction rates causing overshoots when the voltage decreases or lower reaction rates causing undershoots when the voltage increases. The predictions also show that as the voltage decrease rate is reduced, the overshoot peak weakens and the response time shortens. Since the interdigitated flow field has higher oxygen concentrations on the cathode diffusion layer-catalyst layer interface due to the forced convection, the overshoot peaks and the undershoot valleys are all greater than for the parallel flow field. For both flow fields, larger channel to rib width ratios cause larger overshoots, smaller undershoots and longer response times.     

An inverse geometry design problem for optimization of single serpentine flow field of PEM fuel cell

The cathode flow-field design of a proton exchange membrane fuel cell (PEMFC) determines its reactant transport rates to the catalyst layer and removal rates of liquid water from the cell. This study optimizes the cathode flow field for a single serpentine PEM fuel cell with 5 channels using the heights of channels 2–5 as search parameters. This work describes an optimization approach that integrates the simplified conjugated-gradient scheme and a three-dimensional, two-phase, non-isothermal fuel cell model. The proposed optimal serpentine design, which is composed of three tapered channels (channels 2–4) and a final diverging channel (channel 5), increases cell output power by 11.9% over that of a cell with straight channels. These tapered channels enhance main channel flow and sub-rib convection, both increasing the local oxygen transport rate and, hence, local electrical current density. A diverging, final channel is preferred, conversely, to minimize reactant leakage to the outlet. The proposed combined approach is effective in optimizing the cathode flow-field design for a single serpentine PEMFC. The role of sub-rib convection on cell performance is demonstrated.     

Liquefaction/Solubilization of Low-Rank Turkish Coals by White-Rot Fungus (Phanerochaete chrysosporium)

Microbial coal liquefaction/solubilization of three low-rank Turkish coals (Bursa-Kestelek, Kütahya-Seyitömer and Mu?la-Yata?an lignite) was attempted by using a white-rot fungus (Phanerochaete chrysosporium DSM No. 6909); chemical compositions of the products were investigated. The lignite samples were oxidized by nitric acid under moderate conditions and then oxidized samples were placed on the agar medium of Phanerochaete chrysosporium. FTIR spectra of raw lignites, oxidized lignites and liquid products were recorded, and the acetone-soluble fractions of these samples were identified by GC-MS technique. Results show that the fungus affects the nitro and carboxyl/carbonyl groups in oxidized lignite sample, the liquid products obtained by microbial effects are the mixture of water-soluble compounds, and show limited organic solubility.     

Modeling convective drying of wet cake

This study analyzed convective drying of wastewater sludge cakes with three-dimensional cake structures probed using an X-ray micro-computerized tomography scanner (micro-CT), considering the development of cracks and cake morphology. The presence of artificial cracks on cake surface assist drying, but those occurred naturally cannot. The cake surface is noted far from saturation over drying. Moreover, the cracks transport easily moisture to cake surface, hence yielding high surface humidity (and rates) for drying. Comprehensive drying model has to incorporate real boundary conditions for success modeling.     

Composites of poly(2‐chloroaniline) and poly(o‐toluidine) with pumice and their application in the removal of chromium(VI) ions from aqueous solutions

Poly(2‐chloroaniline) (P2ClAn)/pumice (Pmc) and poly(o‐toluidine) (POT)/Pmc composites were synthesized via the chemical oxidative polymerization of 2‐chloroaniline and o‐toluidine in the presence of a dispersion of Pmc powders in water solvent with an (NH₄)₂S₂O₈ oxidant. The composites were characterized with Fourier transform infrared (FTIR) spectroscopy, thermo‐gravimetric/differential thermal analysis (TG‐DTA), and scanning electron microscopy devices. The presence of P2ClAn and POT in the structure of the composites was confirmed by FTIR. Theresults of analysis show strong interactions between the homopolymers and Pmc. The applicability of the P2ClAn/Pmc and POT/Pmc composites were investigated for the removal of Cr(VI) ions in water. Batch adsorption experiments were carried out as a function of pH, initial concentration, time, adsorbent dosage, and temperature. The batch sorption kinetics were tested, and the applicability of the Langmuir and Freundlich adsorption isotherms for this system was tested at 20 ± 1°C. An initial pH of 3.0 was most favorable for Cr(VI) removal by all adsorbents. The adsorption capacities obtained were 0.187 and 4.959 mmol/g of adsorbent for POT/Pmc and P2ClAn/Pmc from the Freundlich and Langmuir adsorption isotherms, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Effects of Reagent Concentrations on Advanced Oxidation of Amoxicillin by Photo-Fenton Treatment

The degradation and mineralization of amoxicillin in an aqueous solution was accomplished by using a photo-Fenton treatment. An ultraviolet light source with a 254-nm wavelength was used with hydrogen peroxide (H2O2) and iron(II). The effects of reagent concentrations on amoxicillin degradation and mineralization were investigated systematically by using the Box-Behnken statistical experiment design. Amoxicillin (10–200??mgL-1), H2O2 (10–500??mgL-1), and iron(II) (0–50??mgL-1) concentrations were considered independent variables; the percent amoxicillin degradation and the total organic carbon (TOC) removal (mineralization) were the objective functions to be maximized. Both H2O2 and iron(II) concentrations affected the extent of the amoxicillin degradation and mineralization. The amoxicillin degradation was completed within 2.5?min, and 53% mineralization took place within 60?min. The optimum H2O2∶Fe∶amoxicillin ratio that resulted in complete amoxicillin degradation and 53% mineralization was 100∶40∶105??mgL-1.