Direct synthesis of A2(Ti(1 − y)Zry)2O7 (A = Gd, Y) solid solutions by ball milling constituent oxides

Different compositions in two solid solutions, A₂(Ti_(1 − y)Zr_y)₂O₇ (A = Gd³⁺, Y³⁺), with high oxygen ion conductivity, have been successfully prepared at room temperature via mechano-chemical synthesis. Stoichiometric mixtures of the constituent oxides were milled in a planetary ball mill by using zirconia vials and balls. Chemical changes in the powder mixtures as a function of composition and milling time were followed by using X-ray diffraction showing that in all cases and after milling for 19 h, the powders consisted of a single phase. Powders were also examined by scanning electron microscopy (SEM) finding out that they basically consist of sub-micron size agglomerates and aggregates of nanoparticles.     

Stimuli-directed self-organized chiral superstructures for adaptive windows enabled by mesogen-functionalized graphene

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Edible films from mucilage of Cereus hildmannianus fruits: Development and characterization

Mucilages are heteropolysaccharides with rich monosaccharide composition. They are capable of forming films that are brittle and fragile, and in order to obtain flexible materials, plasticizers must be added. The present study aims to evaluate the physicochemical properties of mucilage‐based films produced with Cereus hildmannianus and different glycerol concentrations by the casting technique. Transparent and yellowish films were obtained by the addition of glycerol, which also improved handleability, evidenced by increased elongation, and reduced tensile strength and Young's modulus. Thermal gravimetric analysis and differential thermal analysis revealed that glycerol presence reduced the thermal stability, showing the influence of a plasticizer over the polymer structure. Water absorption capacity and contact angle were reduced with the increase of plasticizer concentration; on the other hand, the water vapor permeability increased, as expected, due to the hydrophilic nature of glycerol. The results indicated the potential application of C. hildmannianus mucilage as a promising material to produce edible films. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45223.     

Surface, kinetics and electrocatalytic properties of the Ti/(Ti + Ru + Ce)O2-system for the oxygen evolution reaction in alkaline medium

Ti-supported (Ti + Ru + Ce)O₂ electrodes, prepared at 450 °C, were characterised by XRD, open-circuit potential (E_oc), capacity data (C) and morphology factor (φ) determinations. XRD measurements showed mixed oxides present a low degree of crystallinity. E_oc-data and CV-spectra support surface electrochemistry of mixed oxides is governed by the Ru(III)/Ru(IV) redox couple. In situ surface characterisation revealed the active surface area increases on increasing nominal CeO₂-content. φ-Values remained in the 0.18-0.3 interval supporting the coatings have a low electrochemical porosity. Kinetics was studied recording polarisation and chronopotentiometric curves, which permitted to determine the Tafel slope and reaction order (with respect to OH⁻), in the low and high overpotential domains. Tafel slope data, b, presented a dependence on overpotential and oxide composition indicating the OER electrode mechanism depends on these variables. A unit reaction order with respect to OH⁻ was found for all electrode compositions investigated. The theoretical analysis of the electrode mechanism permitted to analyse the changes in the experimental Tafel slopes taking into account modifications in the apparent electronic transfer coefficient, α_ap. Analysis of the true and apparent electrocatalytic activities revealed the O₂-evolution reaction rate is affected by oxide composition due to morphologic effects.     

Superconducting wires of Cu-Nb3Sn: the liquid-phase sintering method

A new method aimed at obtaining Cu-Nb₃Sn wires in a simple and low cost way is introduced. A powder mixture of Cu-30 wt% (Nb-H)-0.3 wt% Al was degassed and heat treated (T=1200° C) under vacuum, leading to soft, highly dense Cu-Nb sintered samples. Tin diffusion and reaction resulted from external and internal processes. In the latter case cores of tin-rich alloy were used, but an intrinsic drawback related to the occurrence of hard -phase precipitates can be identified. The critical temperature, critical current density, and normal electrical resistivity at 19 K are analysed and correlated with the other parameters (e.g. reaction time and Cu/SC ratio).     

Reactive processing and evaluation of butadiene–styrene copolymer/polyaniline conductive blends

Blending is an important way to obtain materials based on intrinsically conductive polymers and conventional plastics and rubber materials. Much research has been carried out to determine the best performance of materials be used for electrostatic dissipation and electromagnetic interference shielding. Mechanical mixing, codissolution, and in situ polymerization have been used to prepare these materials. The method used depends on the host polymer and its thermal stability and acid attack resistance. Homogeneity and miscibility are properties that should be controlled during blend preparation. In this study, we prepared a conductive thermoplastic elastomer material based on butadiene–styrene copolymer (SBR) and polyaniline (PANI) doped with dodecylbenzene sulfonic acid (DBSA) and poly(styrene sulfonic acid) (PSS). PSS also acted as compatibilizer between PANI and SBR. PANI was doped by reactive processing with DBSA and PSS to produce the conductive complex PANI–DBSA–PSS. This complex was mixed with 90, 70, and 50% (w/w) SBR in a counterrotatory internal mixer. Conductivity tests, swelling studies, thermal analysis, and mechanical property and reflectivity testing were done, and the results show a strong dependence on PANI concentration and the ratio between PANI–DBSA and PSS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 681–685, 2006     

Local heuristic for the refinement of multi-path routing in wireless mesh networks

We consider wireless mesh networks and the problem of routing end-to-end traffic over multiple paths for the same origin–destination pair with minimal interference. We introduce a heuristic for path determination with two distinguishing characteristics. First, it works by refining an extant set of paths, determined previously by a single- or multi-path routing algorithm. Second, it is totally local, in the sense that it can be run by each of the origins on information that is available no farther than the node’s immediate neighborhood. We have conducted extensive computational experiments with the new heuristic, using AODV and OLSR, as well as their multi-path variants, as underlying routing methods. For two different CSMA settings (as implemented by 802.11) and one TDMA setting running a path-oriented link scheduling algorithm, we have demonstrated that the new heuristic is capable of improving the average throughput network-wide. When working from the paths generated by the multi-path routing algorithms, the heuristic is also capable to provide a more evenly distributed traffic pattern.     

REUSE: A combined routing and link scheduling mechanism for wireless mesh networks

Increasing the capacity of wireless mesh networks has motivated numerous studies. In this context, the cross-layer optimization techniques involving joint use of routing and link scheduling are able to provide better capacity improvements. Most works in the literature propose linear programming models to combine both mechanisms. However, this approach has high computational complexity and cannot be extended to large-scale networks. Alternatively, algorithmic solutions are less complex and can obtain capacity values close to the optimal. Thus, we propose the REUSE algorithm, which combines routing and link scheduling and aims to increase throughput capacity in wireless mesh networks. Through simulations, the performance of the proposal is compared to a developed linear programming model, which provides optimal results, and to other proposed mechanisms in the literature that also deal with the problem algorithmically. We observed higher values of capacity in favor of our proposal when compared to the benchmark algorithms.     

A NON‐GAUSSIAN FAMILY OF STATE‐SPACE MODELS WITH EXACT MARGINAL LIKELIHOOD

The Gaussian assumption generally employed in many state‐space models is usually not satisfied for real time series. Thus, in this work, a broad family of non‐Gaussian models is defined by integrating and expanding previous work in the literature. The expansion is obtained at two levels: at the observational level, it allows for many distributions not previously considered, and at the latent state level, it involves an expanded specification for the system evolution. The class retains analytical availability of the marginal likelihood function, uncommon outside Gaussianity. This expansion considerably increases the applicability of the models and solves many previously existing problems such as long‐term prediction, missing values and irregular temporal spacing. Inference about the state components can be performed because of the introduction of a new and exact smoothing procedure, in addition to filtered distributions. Inference for the hyperparameters is presented from the classical and Bayesian perspectives. The results seem to indicate competitive results of the models when compared with other non‐Gaussian state‐space models available. The methodology is applied to Gaussian and non‐Gaussian dynamic linear models with time‐varying means and variances and provides a computationally simple solution to inference in these models. The methodology is illustrated in a number of examples.