Nanocasting of Mesoporous In‐TM (TM = Co,Fe, Mn) Oxides: Towards 3D Diluted‐Oxide Magnetic Semiconductor Architectures

Transition metal (Co, Fe, Mn)‐doped In₂O_3?y mesoporous oxides are synthesized by nanocasting using mesoporous silica as hard templates. 3D ordered mesoporous replicas are obtained after silica removal in the case of the In‐Co and In‐Fe oxide powders. During the conversion of metal nitrates into the target mixed oxides, Co, Fe, and Mn ions enter the lattice of the In₂O₃ bixbyite phase via isovalent or heterovalent cation substitution, leading to a reduction in the cell parameter. In turn, non‐negligible amounts of oxygen vacancies are also present, as evidenced from Rietveld refinements of the X‐ray diffraction patterns. In addition to (In_1?xTM_x)₂O_3?y, minor amounts of Co₃O₄, α‐Fe₂O₃, and Mn_xO_y phases are also detected, which originate from the remaining TM cations not forming part of the bixbyite lattice. The resulting TM‐doped In₂O_3?y mesoporous materials show a ferromagnetic response at room temperature, superimposed on a paramagnetic background. Conversely, undoped In₂O_3?y exhibits a mixed diamagnetic‐ferromagnetic behavior with much smaller magnetization. The influence of the oxygen vacancies and the doping elements on the magnetic properties of these materials is discussed. Due to their 3D mesostructural geometrical arrangement and their room‐temperature ferromagnetic behavior, mesoporous oxide‐diluted magnetic semiconductors may become smart materials for the implementation of advanced components in spintronic nanodevices.     

An Improved NER Methodology to the Portuguese Language

Mobile Networks and Applications - The text mining process typically involves the application of natural language processing (NLP) techniques, in order to obtain important information and extract...     

New Drug‐Structure‐Directing Agent Concept: Inherent Pharmacological Activity Combined with Templating Solid and Hollow‐Shell Mesostructured Silica Nanoparticles

One of the major challenges in medicine is the delivery and control of drug release over time. Current approaches take advantage of mesostructured silica nanoparticles (MSNs) as carriers but suffer several problems including complex synthesis that requires sequential steps for (1) removal of surfactants and (2) functionalization of MSNs to allow upload of the drugs. Here, a novel solution is presented to these restrictions: the design of drug‐structure‐directing agents (DSDAs) with dual inherent pharmacological activity and ability to direct the formation of solid and hollow‐shell MSNs. Pharmacologically active DSDAs obtained by amidation of drugs with fatty acids are allowed to form micelles, around which the inorganic species self‐assembled to form MSNs. Since the DSDAs direct the formation of MSNs, the steps to remove surfactants, functionalization, and drug upload are not required. The MSNs thus prepared provide sustained release of the drug over more than six months, as well as rapid cellular internalization by both physiological and tumoral human colon cells without affecting cell viability. Moreover, the gradual intracellular release of both, the active drug and lipid moiety with potential nutraceutical properties is proved. MSN particles designed with this approach are promising vehicles for controlled and sustained intra‐or extracellular drug‐delivery.     

Measurements of horizontal three‐phase solid‐liquid‐gas slug flow: Influence of hydrate‐like particles on hydrodynamics

Gas hydrate formation is a main flow assurance concern in oil and gas production. Understanding the effects of the introduction of solid particles in the slug flow is essential to improve the efficiency and safety of multiphase production. The purpose of the present work is the experimental characterization of solid‐liquid‐gas slug flow with the presence of dispersed hydrate‐like particles. Experimental tests were carried out with inert polyethylene particles of 0.5‐mm diameter with density similar to gas hydrates (938 kg/m³). The test section comprised a 26‐mm ID, 9‐m length horizontal duct of transparent Plexiglas. High Speed Imaging and resistivity sensors was used to analyze the slug flow unit cell behavior due to the introduction of the solid particles and to measure the unit cell translational velocity, the slug flow frequency, the bubble and slug lengths, and the phase fractions. Two distinct concentrations of solid particles were tested (6 and 8 g/dm³). © 2018 American Institute of Chemical Engineers AIChE J, 64: 2864–2880, 2018     

Synthesis and ex-situ evaluation of quaternized polysulfone as an anion exchange ionomer for AEM technologies

Anion exchange ionomer (AEI) is a critical component used on anion exchange membrane fuel cell (AEMFC) and alkaline water electrolyzer (AWE). In this work, quaternized polysulfone with different functionalization degree were used as an ionomer to evaluate the performance in the oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR), both implied in the operation of AEMFC and AWE. The synthesized ionomer exhibited a better performance in both reactions in comparison to the commercial AEI Aemion®. PSf-130 exhibited better performance, since IEC and surface area increases twice regarding the same parameters in the PSf-60. The PSf-130 conductivity increases three times regarding the value exhibited by PSf-60. Finally, the J_lim and J_k increases 67% and 100% for ORR. On the other hand, the same catalytic parameter increased 44% and 35% for HOR comparing both polysulfone-based ionomers. The Tafel slope values do not showed drastically changes for different ionomers indicating the same rate determining step (RDS) and the same mechanism in both reactions for all the ionomers.     

Evolution of Mineralogical Phases by 27Al and 29Si NMR in MK‐Ca(OH)2 System Cured at 60°C

The evolution of the metastable phases in metakaolin/Ca(OH)₂ systems cured at high temperatures, remains mostly unknown, newer techniques may now help to establish both the kinetic mechanism of the pozzolanic reaction and the thermodynamic stability of the main hydrated hexagonal phases: Stratlingite (C₂ASH₈) and tetra calcium aluminate hydrate (C₄AH₁₃). For this reason this work examines the kinetics of the pozzolanic reaction in the MK/Ca(OH)₂ system over 123 d at 60°C using nuclear magnetic resonance spectroscopy (²⁷Al and ²⁹Si NMR). The results obtained by ²⁷Al and ²⁹Si NMR show that during the first 30 h, the metastable phases C₂ASH₈ and C₄AH₁₃, coexist with the cubic phase (C₃ASH₆) obtained directly from the pozzolanic reaction. The gel C–S–H is clearly identified after 21 h of reaction, whereas at shorter times the C–S–H bands overlap those with the unreacted metakaolin ones. After 123 d of pozzolanic reaction, the first signs of the cubic phase are detected, a consequence of the conversion reaction of the metastable phases, and a phenomenon not previously identified.     

Matching a system behavior with a known set of models: A quadratic optimization‐based adaptive solution

The matching process between a time‐domain external behavior of a lumped single‐input single‐output dynamical system and a known set of linear continuous time‐invariant models is tackled in this paper. The proposed online solution is based on an adaptive structure detector, which in finite time locates in the known set of models the one corresponding to the observed external behavior; the detector results from the solution of a constrained quadratic optimization problem. The problem is expressed in terms of the time‐domain activity of a family of discriminating filters and is solved via a normalized gradient algorithm, which avoids mismatching due to the presence of structural zeros in the filters and can take into account band‐limited high‐frequency measurement noise. A failure detection problem concerning a simulated servomechanism is included in order to illustrate the proposed solution. Copyright © 2008 John Wiley & Sons, Ltd.     

Adaptive quaternion control of a 3-DOF inertial stabilised platforms

ABSTRACT

Inertial stabilised platforms are increasingly popular with a large range of products available mainstream. Most items are controlled using popular algorithms that sometimes do not offer best achievable performances. Present paper proposes an advanced control which aims at improving these latter. The exposed solution is based on quaternion representation and self-adapts to the characteristics of the payload it tries to stabilise. Proposed control law ensures the stability of the system whatever the required orientation path is. Although only simulation has been performed to check the performances of such control, results look very promising compared to non-adaptive controls and may help to construct more polyvalent and efficient gimbals which would further facilitate their expansion. Proposed control law can also be applied, as is, to every system that shares the same quaternion-based rotational dynamics.     

Use of recycled copper slag for blended cements

Copper slag is a by‐product generated during smelting to extract copper metal from the ore. The copper slag obtained may exhibit pozzolanic activity and may therefore be used in the manufacture of addition‐containing cements. In this paper the effect of the incorporation of the copper slag in cement is measured. Blends of copper slag with Portland cement generally possess properties equivalent to Portland cement containing fly ash, but very different to the silica fume incorporation. Copper slag and fly ash reduce the heat of hydration more effectively than silica fume in mortars. The replacement of 30% cement by copper slag reduces the flexural and compressive strength in a similar way to fly ash; however, after 28 days, the reduction is less than the percentage of substitution. Hydrated calcium aluminate phases were analysed using scanning electron microscopy (SEM) and X‐ray diffraction (XRD) techniques. The pozzolanic activity of copper slag is similar to that of fly ash and higher than silica fume. In the presence of low water/cement ratios, certain pozzolanic materials produce a very compact cement paste that limits the space available for hydration products, a determining factor in the formation of hydrated calcium aluminates. SEM was found to be a useful analytical technique when aluminates are formed and can be clearly detected by XRD. Copyright © 2008 Society of Chemical Industry     

Optimization, Modeling, and Online Monitoring of the Enzymatic Extraction of Banana Juice

This article focuses on the optimization, modeling, and online monitoring of banana juice production through an enzymatic method. In order to perform this task, a batch reactor was designed with automatic control over the temperature and the agitation speed as well as online monitoring of torque. The experiments were carried out with the Musa AAA Cavendish banana variety (Enano gigante), the main variety planted in Mexico. Three different ripening stages were evaluated. Optimization of juice extraction was evaluated as a function of the pulp/water relationship and the concentration of the enzyme complex. The results showed that the adding of water had no influence on the extraction of banana juice, and the optimal enzyme concentration per kilogram of banana pulp was found. Based on a fuzzy logic approach, it was possible to relate the initial torque with the ripeness stage. Furthermore, an observable dynamical model based on ordinary differential equations and fuzzy logic is presented. With this model, the relationship between the torque dynamic and the instant juice yield was found to depend on the amount of enzyme, the temperature, and the maturity stage of the banana used. In addition, a principal components analysis was used to classify and to relate the final juice characteristics (e.g., L, a, and b colorimetric components) to the processing conditions and the final appreciation of a group of sensorial panelists. Additionally, a robust observer was designed and implemented to filter the noise present in the torque signal and to predict the instant juice yield.