Functionalization of Electrospun Titanium Oxide Nanofibers with Silver Nanoparticles: Strongly Effective Photocatalyst

In the present study, we are introducing silver-doped titanium oxide nanofibers produced by electrospinning technique. Calcination of dry nanofiber mats consisting of silver nitrate–titanium isopropoxide/PVAc in air at 600°C for 1 h leads to produce Ag-doped titania nanofibers. Two dyes have been invoked to check the photocatalytic ability of the produced nanofibers; methylene blue dihydrate and methyl red. The obtained results indicated that the silver-doped titanium oxide nanofibers can eliminate >92% of the methylene blue dye within 10 min only. In a case of methyl red, almost the dye was decayed (93%) within 3 h.     

One‐Pot Thioetherification of Aryl Halides Using Thiourea and Alkyl Bromides Catalyzed by Copper(I) Iodide Free from Foul‐Smelling Thiols in Wet Polyethylene Glycol (PEG 200)

In this article, we have developed a new protocol for the thioarylation of structurally diverse alkyl bromides such as benzyl, cinnamyl, n‐octyl, cyclohexyl, cyclopentyl, and tert‐butyl bromides with aryl iodides, bromides and an activated chloride using thiourea catalyzed by copper(I) iodide in wet polyethylene glycol (PEG 200) as an eco‐friendly medium in the presence of potassium carbonate at 80 and 100 °C under an inert atmosphere. The process is free from foul‐smelling thiols which makes this method more practical for the thioetherification of aryl halides. Another important feature of this method is the variety of alkyl bromides which are commercially available for the in situ generation of thiolate ions with respect to the existing protocols in which the less commercially available thiols are directly used for the preparation of arylthio ethers.     

Optimization of peroxidase-catalyzed oxidative coupling process for phenol removal from wastewater using response surface methodology

Hydroxylated aromatic compounds (HACs) are considered to be primary pollutants in a wide variety of industrial wastewaters. Horseradish peroxidase (HRP) is suitable for the removal of these toxic substances. However, development of a mathematical model and optimization of the HRP-based treatment considering the economical issues by novel methods is a necessity. In the present study, optimization of phenol removal from wastewater by horseradish peroxidase (HRP) was carried out using response surface methodology (RSM) and central composite design (CCD). As the initial experimental design, 2(4-1) half-fraction factorial design (H-FFD) is accomplished in triplicate at two levels to select the most significant factors and interactions in the phenol removal procedure. Temperature (degrees C), pH, concentration of enzyme (unit mL(-1)), and H202 (mM) were determined as the most effective independent variables. Finally, a fourfactor-five coded level CCD, 30 runs, was performed in order to fit a second-order polynomial function to the results and calculate the economically optimum conditions of the reaction. The goodness of the model was checked by different criteria including the coefficient of determination (R2 = 0.93), the corresponding analysis of variance ((Pmodel > F) < 0.0001) and parity plot (r = 0.96). These analyses indicated that the fitted model is appropriate for this enzymatic system. With the assumption that the minimum enzyme concentration was 0.26 unit mL(-1), the analysis of the response surface contour and surface plots defined the optimum conditions as follows: pH = 7.12, hydrogen peroxide concentration 1.72 mM, and 10 degrees C. This work improves phenol removal operation economically by applying minimum enzyme concentration and highest removal in comparison with previous studies.     

Synthesis of zirconium tungstate–zirconia core–shell composite particles

In this work, ZrW₂O₈–ZrO₂ core–shell composite particles were synthesized. ZrW₂O₈ that was used in the core is a material with negative coefficient of thermal expansion, and it was synthesized from a high-pH precursor based on use of tungstic acid and zirconium acetate. Shell layer was composed of ZrO₂ nanocrystallites and precipitated from an aqueous solution by urea hydrolysis. While volume of the shell was effectively controlled by the initial zirconium ion concentration in the solutions, the rate of precipitation was a function of the ratio of initial concentrations of urea to zirconium ions. It is hypothesized that isolation of the ZrW₂O₈ within a layer of ZrO₂, will be a key element in solving problems associated with reactivity of ZrW₂O₈ towards other components in sintering of ceramic–ceramic composites with tuned or zero thermal expansion coefficient.     

Three‐dimensional multiphase flow model to study channel flow dynamics of PEM fuel cells

A three‐dimensional multiphase flow model has been developed to study dynamics of a water droplet on the surface of the channel of proton exchange membrane fuel cell. Results are presented based on solving full Navier–Stokes equations for Newtonian liquids. The volume‐of‐fluid method is used to numerically determine the deformation of free surfaces. Water droplet and channel fluid properties determine whether the droplet deforms and remain stationary or disintegrate. We have shown the dependency of the water flooding to the flow rate and pressure drop in the channel has been introduced as a tool to determine water flooding in the channel. Copyright © 2010 John Wiley & Sons, Ltd.     

Influence of steel-concrete interface condition on galvanic corrosion currents in carbonated concrete

This paper presents specific experiments which were developed in order to assess galvanic currents in macrocell corrosion specimens involving active steel in carbonated concrete and passive steel in sound concrete. The influence of the steel-concrete interface condition on the galvanic current was also experimentally investigated. To focus on macrocell corrosion rate assessment, the initiation time of the corrosion process (concrete carbonation) was accelerated. FEM simulations were carried out in order to enhance the physical comprehension of these corrosion experiments. It was found that, in realistic condition, the electrical coupling of active and passive steel areas leads to high galvanic currents and consequently high corrosion levels according to RILEM recommendation. Moreover, steel-concrete interfacial defaults significantly increase the macrocell driving potential and, therefore, the galvanic corrosion current.     

The dual-edge alignment technique with improved spur reduction effects in ring oscillators

In this paper, the technique of dual-edge phase-alignment and its effects on ring oscillators are presented. This technique provides resetting of the built-up jitter at both rising and falling edges of a clean aligning signal named as the reference. Using signals and systems theory, the effect of the technique on the spurs due to the aligning reference signal is completely analyzed. We show that adding properly the dual-edge aligning feature to phase-aligned ring oscillators cause the spurs in the neighborhood of the carrier to disappear. First, the validity of the results obtained from the derived analytical equations is verified through simulations using MATLAB. Then a complete circuit considering realistic models for its components is simulated in TSMC RF CMOS 0.18um process using ADS for further validation.     

Pd-doped Co nanofibers immobilized on a chemically stable metallic bipolar plate as novel strategy for direct formic acid fuel cells

High contact resistance and corrosion are the main dilemma facing wide application of the metallic bipolar plates. In this study, deposition of thin film from Pd-decorated Co nanofibers on a silicon substrate is introduced as a novel strategy to produce functionalized metallic bipolar plate. The novel active metallic bipolar plate can be prepared by using simple, low cost, high yield and effective technique; electrospinning. The bimetallic nanofibrous film chemically bonds with the silicon substrate due to formation of silicon carbide which leads to merge the deeper nanofibers with the silicon surface. Accordingly, high current density (100 mA cm⁻¹) was obtained when the introduced covered silicon wafer was utilized as anode catalyst for formic acid electrooxidation. Because the bimetallic nanofibers are sheathed in a thin graphite shell, the introduced active bipolar plate reveals very good stability. Overall, the introduced study is opening a new avenue to prepare new class of functionalized metallic bipolar plates.     

Modeling and simulation of solar pond floor heating system

This paper presents the development of modeling, simulation and analysis of a solar pond floor heating system. The developed computer simulation has been used to study the potential of using such a system under climatic conditions in Jordan. It was found that the solar pond heating system could meet most of the winter season in Jordan with Solar fraction in the range 80–100% for at least 2 months of the season. It must be emphasized that the feasibility of such a system is its utilization in district heating and not for individual households due to the limiting economical factors of high capital cost of the solar pond for small domestic applications.