Synthesis of a new self-supported Mgy(CuxNi0.6-xMn0.4)1-yFe2O4 oxygen carrier for chemical looping steam methane reforming process

Novel self-supported Mg_y(Cu_xNi_0.6-xMn_0.4)_1-yFe₂O₄ with (y = 0, 0.05, 0.1, 0.15, and x = 0, 0.15, 0.3, 0.45, 0.6) oxygen carriers (OCs) are synthesized through the co-precipitation method. The synthesized OCs’ properties are characterized by X-ray powder diffraction (XRD), Raman spectra, transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), and Thermogravimetric Analysis (TGA). The synthesized OCs are assessed in Chemical Looping Steam Methane Reforming (CL-SMR) process subject to different mesh sizes, reaction temperatures, Steam/Carbon (S/C) molar ratios, Mg concentrations, and Cu and Ni concentrations. The characterization of the OCs and process results indicate the contributive effect of Mg incorporation on the Cu_xNi_0.6-xMn_0.4Fe₂O₄ support structure. The redox results reveal that Mg_0.1(Cu_0.3Ni_0.3Mn_0.4)_0.9Fe₂O₄ OC is of the highest activity, even at low reduction temperatures. This OC exhibits the highest activity and stability with lowest coke deposition during 24 redox cycles at 650 °C and S/C = 2.5. The highest CH₄ conversion of about 99.4% and H₂ yield of about 84.4% are obtained.     

Molecular simulation of water and chloride ion diffusion in nanopores of alkali-activated aluminosilicate structures

In this paper, a molecular model is proposed to investigate sorption of water molecules and chloride ions in nanopores of alkali-activated binders (geopolymer) gels. The structure of water molecule and geopolymer matrix was optimised by molecular dynamics simulation, and sorption of water molecules and chloride ions was performed by Monte Carlo approach. Totally, four systems containing nanoscale geopolymer structure, 50 molecules of water and 0, 2, 5 or 7 chloride ions were investigated. The results showed that water molecules can be absorbed by nanopores and remain in the system where this absorption releases heat. Thermodynamic analysis showed that the water absorption is temperature-independent. Absorption of chloride ions was suggested to depend on chloride ion concentration. As concentration of chloride ions raises, more absorption occurs and as a result, heat release of absorption and possible degradation of geopolymer structure increases. The thermodynamic analysis showed that higher concentration of chloride ions may decrease Gibbs free energy and raise configurational entropy of the systems. It is proposed that by increasing the temperature, absorption of chloride ion by the geopolymer gel nanopores diminishes and more corrosion may occur in other parts/structures of the matrix.     

A delicate maneuver on conjugated rod-rod structures composed of poly(3-hexylthiophene) and polyaniline subtending patched-fibrillar,ringed-fibrillar,double-fibrillar and sandwiched configurations

Full-conjugated rod-rod structures comprising patched-fibrillar, ringed-fibrillar, and double-fibrillar configurations were designed from poly(3-hexylthiophene) (homo-P3HT) and polyaniline (PANI) nanorods in chloroform, p-xylene, and amyl acetate dilute solutions, respectively. Solvent quality, seeding effect, and constituent material were focused while characterizing the developed structures. By exacerbating the processing solvent quality from chloroform to p-xylene, a ringed-fibrillar configuration was detected instead of patched-fibrillar structure. In a poor solvent, double-fibrillar structures were acquired from homo-P3HT chains and PANI nanorods. Towards a poorer solvent, P3HT chains were capable of developing their own crystals by less sensing presence of PANI nanorods as seeds. In another experiment, by copolymerization of both P3HT and PANI with crystallizable PEG blocks, sandwiched rod-rod mixed-brush single crystals were developed. Molecular weight of neither P3HT nor PANI was effective on surface patterning of P3HT/PANI mixed-brushes. Via elevating crystallization temperature, PANI dispersed patterns became more delicate and their width decreased from 80 to 160 nm to 12–30 nm. P3HT backbones were tethered with a extended flat-on orientation onto the PEG substrate at either low or high crystallization temperatures. Beside sandwiched single crystals seeded with homo-PEG tiny crystals, slightly and highly curved half-ring crystals were also developed in the PEG-b-P3HT systems.

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Graphical abstract

     

Optimization of Split Keyboard Design for Touchscreen Devices

While many large touchscreen devices have a split keyboard option to enable two-thumb typing, there are significant differences in the design which affect users’ text entry rate. A mixed-integer programming model is developed to optimize key-to-thumb assignment with the objective of minimizing the expected time to type a character. Computer simulations are conducted to determine the optimal key dimension under different values of the Fitts’ law’s slope coefficient, typing error rate, and alternate-hand advantage phenomenon. The results show that text entry rate and the optimal key-to-thumb assignment depend on key dimensions, user’s speed-accuracy profile, and the level of alternate-hand advantage. The optimal keyboard is proposed. To validate the analytical findings, an empirical study is conducted with eighteen users and six different keyboards in terms of key dimensions and typing zone. Empirical results report between 7% and 18% improvement in the text entry rate over the other split keyboards tested.     

An Iterative Algebraic Geometric Approach for Identification of Switched ARX Models with Noise

The algebraic geometric (AG) approach has been used to identify switched auto regressive exogenous (SARX) models in hybrid systems, and it has several advantages over other SARX identification methods. This paper is focused on improving the estimation accuracy of the AG approach for systems corrupted with indispensable noises. A stochastic hybrid decoupling polynomial (SHDP) is constructed by reformulating the hybrid decoupling polynomial (HDP) used in the original AG method. An iterative scheme is developed to estimate parameters of the SHDP, which are used to calculate the SARX model parameters. This estimation involves linear regression with multiplicative noises, therefore a novel approach is proposed to solve this regression problem. Then, the parameters are recovered from the SHDP. Finally, all these steps for SARX model identification are summarized in an algorithm called the iterative algebraic geometric (IAG) approach. Simulations and experimental validation results are shown to demonstrate the effectiveness of and the improvement made by the proposed IAG method.     

A DASH-based HEVC multi-view video streaming system

Recent advancement in cameras and image processing technology has generated a paradigm shift from traditional 2D and 3D video to multi-view video (MVV) technology, while at the same time improving video quality and compression through standards such as high efficiency video coding (HEVC). In multi-view, cameras are placed in predetermined positions to capture the video from various views. Delivering such views with high quality over the Internet is a challenging prospect, as MVV traffic is several times larger than traditional video, since it consists of multiple video sequences, each captured from a different angle, requiring more bandwidth than single-view video to transmit MVV. In addition, the Internet is known to be prone to packet loss, delay, and bandwidth variation, which adversely affect MVV transmission. Another challenge is that end users’ devices have different capabilities in terms of computing power, display, and access link capacity, requiring MVV to be adapted to each user’s context. In this paper, we propose an HEVC multi-view system using Dynamic Adaptive Streaming over HTTP to overcome the above-mentioned challenges. Our system uses an adaptive mechanism to adjust the video bit rate to the variations of bandwidth in best effort networks. We also propose a novel scalable way for the multi-view video and depth content for 3D video in terms of the number of transmitted views. Our objective measurements show that our method of transmitting MVV content can maximize the perceptual quality of virtual views after the rendering and hence increase the user’s quality of experience.     

Optimization of arsenite removal by adsorption onto organically modified montmorillonite clay: Experimental & theoretical approaches

Arsenic is a critical contaminant for aqueous environments as it poses harmful health risks. To meet the stringent regulations regarding the presence of arsenic in aqueous solutions, the feasibility of montmorillonite clay modified with hexadecyltrimethyl ammonium chloride as the adsorbent was tested for the removal of arsenic ions from aqueous solutions. A scanning electron microscopy (SEM) study confirmed that the organically modified nanoclay (ONC) adsorbent had a porous structure with a vast adsorbent surface.The x-ray fluorescence (XRF) analysis proved the presence of carbon in the structure of the modified nanoclay that can be evidence for the creation of ONC. The x-ray diffraction (XRD) analysis results confirm the existence of four main groups of minerals, carbonate (Calcite), clay (Askmtyt and Kandyt), silicate (Quartz), and phyllosilicate (Kaolinite), in the ONC structure.The influence of various parameters such as solution pH, adsorbent dosage, initial arsenite concentration, and contact time on arsenic adsorption onto ONC was investigated. A 2⁵ full factorial central composite experimental design was applied. A central composite design under response surface methodology (RSM) was employed to investigate the effects of independent variables on arsenite removal and to determine the optimum condition. The experimental values were in a good fit with the ones predicted by the model. The optimal operating points (adsorbent dosage: 3.7 g L^?1, surfactant dosage: 3 g L^?1 and the contact time: 37.2min) giving maximum arsenite removal (95.95%) were found using Solver “Add-ins” in Microsoft Excel 2010.     

Disperse-within-disperse patterning on ternary/binary mixed-brush single crystals using polyaniline,polystyrene and poly(methyl methacrylate) grafts

Novel binary rod-coil and ternary rod-coil-coil mixed-brushes were designed using poly(ethylene glycol) (PEG)-b-poly(styrene) (PS), PEG-b-poly(methyl methacrylate) (PMMA), and PEG-b-polyaniline (PANI) block copolymers. In the current rod-coil mixed-brushes, the brush osmotic pressure did not absolutely affect the surface morphology, instead, the rigidity or flexibility of brushes was a dominant factor. The flexibility of coily PS brushes caused them to be easily entered into the system compared to the rod brushes with higher osmotic pressure, thereby they composed the matrix phase. In a similar growth condition but with packed pancake PMMA brushes, a more faise osmotic pressure was detected for PANI nanorods in the vicinity of PMMA brushes compared to PS ones. A higher faise osmotic pressure for PANI nanorods reflected the lower diameter dispersity and population of PANI nanorods in PEG-b-PMMA/PEG-b-PANI compared to PEG-b-PS/PEG-b-PANI. Via enhancing the amorphous brushes molecular weight, in a constant PANI nanorods molecular weight, the diameter dispersity and population of PANI nanorods increased. The PANI nanorods diameter in binary PS/PANI and PMMA/PANI mixed-brushes ranged in 6–10 nm. With elevating the crystallization temperature, no changes were detected in the morphology of rod-coil mixed-brush single crystals. In the novel ternary mixed-brushes with the amorphous PS and PMMA brushes and the PANI nanorods, the PANI nanorods were dispersed within both matrix (PS) and disperse (PMMA) phases. In these systems, the PANI diameters were 6 and 7 nm in PMMA disperses and 6–9 nm in PS matrix phase. The overall PANI nanorods population was in the range of 594–1392 for binary mixed-brushes. Furthermore, in ternary structures, the PANI overall populations were about 222 and 316 in PMMA and PS phases, respectively. Generally, in all binary and ternary mixed-brush systems, the amorphous brushes (PS and PMMA), due to their flexibility could be arranged in the vicinity of each other in a more facile manner compared to the PANI nanorods, they thus developed matrix phase.

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Graphical abstract The mixed-brush single crystals were carefully patterned with double rod-coil and triple rod-coil-coil grafted polymer chains

     

Artificial neural networks application to predict the compressive damage of lightweight geopolymer

In this work, compressive strength of lightweight geopolymers produced by fine fly ash and rice husk–bark ash together with palm oil clinker (POC) aggregates has been investigated experimentally and modeled based on artificial neural networks. Different specimens made from a mixture of fine fly ash and rice husk–bark ash with and without POC were subjected to compressive strength tests at 2, 7, and 28 days of curing. A model based on artificial neural networks for predicting the compressive strength of the specimens has been presented. To build the model, training and testing using experimental results from 144 specimens were conducted. The data used in the multilayer feed-forward neural networks models are arranged in a format of six input parameters that cover the quantity of fine POC particles, the quantity of coarse POC particles, the quantity of FA + RHBA mixture, the ratio of alkali activator to ashes mixture, the age of curing and the test trial number. According to these input parameters, in the neural networks model, the compressive strength of each specimen was predicted. The training and testing results in the neural networks model have shown a strong potential for predicting the compressive strength of the geopolymer specimens in the considered range.