A family of memristor‐based reactance‐less oscillators

In this paper, we present for the first time a family of memristor‐based reactance‐less oscillators (MRLOs). The proposed oscillators require no reactive components, that is, inductors or capacitors, rather, the ‘resistance storage’ property of memristor is exploited to generate the oscillation. Different types of MRLO family are presented, and for each type, closed form expressions are derived for the oscillation condition, oscillation frequency, and range of oscillation. Derived equations are further verified using transient circuit simulations. A comparison between different MRLO types is also discussed. In addition, detailed fabrication steps of a memristor device and experimental results for the first MRLO physical realization are presented. Copyright © 2013 John Wiley & Sons, Ltd.     

One-step electrosynthesis of MnO2/rGO nanocomposite and its enhanced electrochemical performance

We present a facile one-step electrochemical approach to generate MnO₂/rGO nanocomposite from a mixture of Mn₃O₄ and graphene oxide (GO). The electrochemical conversion of Mn₃O₄ into MnO₂ through potential cycling is expedited in the presence of GO while the GO is reduced into reduced graphene oxide (rGO). The MnO₂ nanoparticles are evenly distributed on the rGO nanosheets and act as the spacer to prevent rGO nanosheets from restacking. This unique structure provides high electroactive surface area (1173?m² g^?1) that improves ions diffusion within the MnO₂/rGO structure. As a result, the MnO₂/rGO nanocomposite exhibits high specific capacitance of 473?F?g^?1 at 0.25?A?g^?1, which is remarkably higher (3 times) than the Mn₃O₄/GO prior conversion. In addition, the electrosynthesized nanocomposite shows higher conductivity and excellent potential cycling stability of 95% at 2000 cycles.     

The stability of MIS solar cells and evaluation by C–V characteristics

To test the stability of MIS solar cell structures, we investigated the I–V and C–V characteristics during tests under illumination and dark conditions. The MIS solar cells were prepared using two different techniques to produce two types of oxide layer. Under illumination, the tested devices suffer from degradation. The rate of degradation was higher for cells with a thinner oxide layer. The cells with a thicker oxide layer exhibited a partial recovery for the open circuit voltage after storage in the dark. The degradation is due to the photo-neutralization of effective charges at the oxide–semiconductor interface. This mechanism leads to instability in the cell performance through changes in the barrier height. The C–V measurement confirms this result.     

The electroreduction (polarographically) of uranyl ion in nitric acid and nitric acid-methanol mixture media

The polarographic reduction of uranyl ion in nitric acid solution are found to be one electron reduction mechanism at lower acid concentration (0.1 M HNO₃) and two electron mechanism at high acid concentration (2M HNO₃). Methanol shifted the half wave potentials to more negative values and increased the free energy.The free energies of reduction of U(VI) to U(V) in these mixed solvents are inversely proportional to both the dielectric constants and Gutman's Acceptor number of methanol. The U(V) is stable at pH 3, but its dismutation increased at lower and higher pH's than pH 3.     

Performance Characteristics of a Suspended‐Catalyst Oscillatory Membrane Photocatalytic Reactor

The performance characteristics of an oscillatory membrane photocatalytic reactor were investigated using dye degradation over a suspended ZnO catalyst as a model reaction. Both flat‐surface membranes and ones with transverse turbulence promoters (TP) were used. Application of oscillatory motion can be effective in enhancing the performance of suspended‐catalyst membrane photocatalytic reactors. The eddy formation and vortex shedding when using membranes with TP gave rise to several synergistic effects by providing effective removal of catalyst deposits from the membrane surface, which enhanced the flux and increased the suspended‐catalyst fraction in solution, which consequently enhanced the reaction rate. The effective mixing in the reaction channel minimized particles sedimentation and agglomeration which further enhanced the catalyst suspension and increased its effective reaction area. The specific energy consumption favorably compared to a membrane cross‐flow filtration system.     

Modeling and mapping dynamic vulnerability to better assess WUI evacuation performance

Wildland‐urban interface (WUI) fire incidents are likely to become more severe and will affect more and more people. Given their scale and complexity, WUI incidents require a multidomain approach to assess their impact and the effectiveness of any mitigation efforts. The authors recently produced a specification for a simulation framework that quantifies evacuation performance during WUI incidents including inputs from three core domains: fire development, pedestrian performance and vehicular traffic [26]. This framework could produce new insights by simulating evolving conditions of WUI incidents based on developments and interactions between the core components. Thus, it aims to overcome known limitations of previous approaches (eg, static assessment, single domain approaches, or lack of projection), as well as to provide explanatory insights into the outcomes produced by the simulation. The proposed framework would also advance geo‐spatial mapping of WUI incidents. The concept of dynamic vulnerability, , is at the core of the framework and is enabled by the integrated simulation framework and the emergent conditions predicted. This allows users to construct richer incident narratives from the perspective of specific locations or subpopulations, and also makes fewer simplifying assumptions regarding interactions between the three core domains.     

Study on poly (ethylene-co-vinyl acetate), acrylonitrile butadiene copolymer,and their blend reinforced with carbon black using position annihilation lifetime spectroscopy

Positron annihilation lifetime spectroscopy (PALS) have been used to investigate the effect of filling each of poly (ethylene-co-vinyl acetate) (EVA), acrylonitrile butadiene rubber (NBR), and their blend (50/50wt-%) with different concentrations of high-abrasion furnace (HAF) (0–60?phr). PALS is characterised by the free-volume parameters (V_h and F %), which is a measure of the size and fraction of free-volume holes in the composites. The results show that the variation in V_h and F % of free-volume holes depends on the chemical structure and the degree of crystallinity of each polymer. The NBR has a smaller size (127.78?ų) and lower fraction (4.18%) of free-volume holes than the corresponding free-volume holes (177.48?ų and 7.03%) in EVA. The size of the free-volume holes increases in EVA with increasing HAF content up to 20 phr in polymer matrix while it decreases in NBR. The fractions (F %) of free-volume holes decrease due to the reduction in positronium formation in polymer and positron trapping at polymer interface. The results also show an inverse correlation between free-volume parameters (V_h and F %) and tensile strength value, and a direct correlation with elongation at break as a function of HAF content in EVA and NBR. The electrical properties are negatively correlated with lifetime of free positron, τ₂, and positively with its relative intensity (I₂).     

Interfacial phenomena and droplet size of particle stabilized emulsions in oscillatory shear

Production of particle stabilized oil in water emulsions has been investigated both theoretically and experimentally under oscillatory shear conditions using different stabilizing particles (SPs). The investigation included analysis of the interaction between particles interfacial stability and droplets breakage and coalescence. For hydrophobic SPs, droplets maintained their sizes as determined by torque balance (TB) without significant breakage or coalescence. For the more hydrophilic SPs, larger droplets formed that broke by eddies in the inertial subrange. At higher fluid shear stresses, loss of the SPs occurred during droplet formation leading to near bare droplet surface and coalescence to much larger sizes with subsequent fragmentation by capillary instabilities. The final droplet size in both cases was very different from TB model predictions. A modeling approach is proposed that combined both TB and droplet breakage and coalescence mechanisms. Comparison between the experimental results and the models predictions showed satisfactory agreement. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2902–2911, 2016     

Liquid‐Solid Mass Transfer Behavior of a Stirred‐Tank Reactor with a Fixed Bed at Its Bottom

The mass transfer behavior of a new batch stirred tank with a fixed bed of Raschig rings at the bottom was studied using diffusion‐controlled dissolution of copper in acidified dichromate. Variables studied, amongst others, were the impeller rotation speed, Raschig ring diameter, fixed‐bed height, and impeller geometry. The rate of mass transfer from the fixed bed to the solution increased with increasing impeller rotation speed, decreasing particle size, and decreasing bed height. The axial‐flow turbine is more efficient in increasing the rate of mass transfer than the radial‐flow turbine. The presented reactor is especially useful for conducting diffusion‐controlled liquid‐solid catalytic reactions involving reactants that need to be dispersed first, such as sparingly soluble solid particles.