Kinetics of oxygen evolution at α-Fe2O3 photoanodes: a study by photoelectrochemical impedance spectroscopy

Photoelectrochemical Impedance Spectroscopy (PEIS) has been used to characterize the kinetics of electron transfer and recombination taking place during oxygen evolution at illuminated polycrystalline α-Fe(2)O(3) electrodes prepared by aerosol-assisted chemical vapour deposition from a ferrocene precursor. The PEIS results were analysed using a phenomenological approach since the mechanism of the oxygen evolution reaction is not known a priori. The results indicate that the photocurrent onset potential is strongly affected by Fermi level pinning since the rate constant for surface recombination is almost constant in this potential region. The phenomenological rate constant for electron transfer was found to increase with potential, suggesting that the potential drop in the Helmholtz layer influences the activation energy for the oxygen evolution process. The PEIS analysis also shows that the limiting factor determining the performance of the α-Fe(2)O(3) photoanode is electron-hole recombination in the bulk of the oxide.     

Formation of lithium fluoride/metal nanocomposites for energy storage through solid state reduction of metal fluorides

In order to utilize high energy metal fluoride electrode materials as direct replacement electrode materials for lithium ion batteries in the future, a methodology to prelithiate the cathode or anode must be developed. Herein, we introduce the use of a solid state Li₃N route to achieve the lithiation and mechanoreduction of metal fluoride based nanocomposites. The resulting prelithiation was found to be effective with the formation of xLiF:Me structures of very fine nanodimensions analogous to what is found by electrochemical lithiation. Physical and electrochemical properties of these nanocomposites for the bismuth and iron lithium fluoride systems are reported.     

Electrochemical Initiated C‐N Coupling of 3‐Methylcatechol and n‐Hexylamine in a Flow Cell Monitored with ESI‐MS

The electrochemical initiated heterocoupling of 3‐methylcatechol and n‐hexylamine was investigated. The oxidation of 3‐methylcatechol was performed in an electrochemical flow cell with glassy carbon as the working electrode. As a result, the two‐electron, two‐proton oxidised chinone intermediate undergoes a C‐N coupling reaction in the presence of an amine (Michael addition). This mono coupling product can undergo a second two‐electron, two‐proton oxidation depending on acidic or basic conditions and substrate ratios. This flow cell was coupled on‐line with electrospray ionisation mass spectrometry to identify the possible coupling products. Higher substrate concentrations were performed off‐line as first scale‐up experiments in a two‐step procedure.     

Copper-catalyzed four-component synthesis of imidazo[1,2-a]pyridines via sequential reductive amination,condensation, and cyclization

A novel and efficient four-component approach for the synthesis of 2,3-disubstituted imidazo[1,2-a]pyridines is described. The copper-catalyzed reductive amination of 2-bromopyridine by sodium azide followed by sequential condensation and cyclization with aldehydes and isocyanides afforded the corresponding imidazo[1,2-a]pyridines in good yields.     

Investigation on total and instantaneous energy balance of bio-alternative fuels on an SI internal combustion engine

This paper investigates the effect of some biofuels on thermal balance and performance characteristics of a single-cylinder, four-stroke SI internal combustion engine. In this study, total and instantaneous energy balance of an air-cooled, small-scale engine using various biofuels is investigated. An experimental study is carried out on gasoline engine to validate the numerical calculations. Bio-alternative fuels which include methanol, ethanol and 2-ethanol–gasoline-blended fuels consisting of E85, E15 are examined numerically. Results indicate that methanol is the most effective fuel in aspect of power generation. Ethanol, E85, E15 and gasoline are placed in next positions, respectively. Break specific fuel consumption shows totally reversed trend. It is evaluated that by increasing engine speed, heat transfer to brake power ratio decreases and lower percentage of energy in form of heat transfer is lost. The least heat transfer to brake power ratio among studied fuel is related to methanol which approves it as the most efficient biofuel. Based on instantaneous in-cylinder energy balance analysis, at the end of combustion and during expansion stroke, instantaneous brake work of fuels outpaces each other at around 40° crank angle aTDC.

     

On the time transformation of mixed integer optimal control problems using a consistent fixed integer control function

Nonlinear control systems with instantly changing dynamical behavior can be modeled by introducing an additional control function that is integer valued in contrast to a control function that is allowed to have continuous values. The discretization of a mixed integer optimal control problem (MIOCP) leads to a non differentiable optimization problem and the non differentiability is caused by the integer values. The paper is about a time transformation method that is used to transform a MIOCP with integer dependent constraints into an ordinary optimal control problem. Differentiability is achieved by replacing a variable integer control function with a fixed integer control function and a variable time allows to change the sequence of active integer values. In contrast to other contributions, so called control consistent fixed integer control functions are taken into account here. It is shown that these control consistent fixed integer control functions allow a better accuracy in the resulting trajectories, in particular in the computed switching times. The method is verified on analytical and numerical examples.     

Controlled and scalable torsional actuation of twisted nylon 6 fiber

Large‐scale torsional actuation occurs in twisted fibers and yarns as a result of volume change induced electrochemically, thermally, photonically, and other means. A quantitative relationship between torsional actuation (stroke and torque) and volume change is here introduced. The analysis is based on experimental investigation of the effects of fiber diameter and inserted twist on the torsional stroke and torque measured when heating and cooling nylon 6 fibers over the temperature range of 26–62 °C. The results show that the torsional stroke depends only on the amount of twist inserted into the fiber and is independent of fiber diameter. The torque generated is larger in fibers with more inserted twist and with larger diameters. These results are successfully modeled using a single‐helix approximation of the twisted fiber structure. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1278–1286