Input Selection of Wavelet-Coupled Neural Network Models for Rainfall-Runoff Modelling

Water Resources Management - The use of wavelet-coupled data-driven models is increasing in the field of hydrological modelling. However, wavelet-coupled artificial neural network (ANN) models...     

Different Energy Saving Schemes in Wireless Sensor Networks: A Survey

Wireless Personal Communications - Wireless sensor networks (WSNs) are one of the very active research area. They have many applications like military, health care, environmental monitoring and...     

Preparation of compatible blends of poly(methyl methacrylate) used in dentistry with a reactive terpolymer containing maleic anhydride and their thermomechanical characterization

This study focuses on the preparation of compatible blends with the poly(methyl methacrylate) (PMMA) using a reactive terpolymer maleic anhydride–styrene–vinyl acetate (MA–St–VA). In the first series of experiments, binary blends of the PMMA and the MA–St–VA terpolymer have been prepared in tetrahydrofurane. The PMMA and the MA–St–VA terpolymer formed the compatible blends. The effects on thermomechanical properties of MA–St–VA terpolymer ratio in the blends were studied. The glass transition temperatures (T_g), thermal expansion coefficient (α), and other thermomechanical parameters for the blends have been established by TMA method and the compatibility of two polymers has been evaluated by these TMA parameters. The addition of MA–St–VA terpolymer to PMMA made a plasticizing effect on PMMA. This effect regularly changed with the increasing of the terpolymer in the blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 363–367, 2006     

Performance of fly ash based polymer gels for water reduction in enhanced oil recovery: Gelation kinetics and dynamic rheological studies

The complexity of well and reservoir conditions demands frequent redesigning of water plugging polymer gels during enhanced oil recovery (EOR). In the present study, we developed coal fly ash (CFA) based gels from polyacrylamide (PAM) polymer and polyethyleneimine (PEI) crosslinker for water control in mature oil fields. The CFA acts as an inorganic additive to fine-tune gelation performance and rheological properties of PAM/PEI gel system. Hence, effects of various CFA (0.5 to 2 wt%), PAM (2 to 8.47 wt%) and PEI (0.3 to 1.04 wt%) concentrations on gelation kinetics and dynamic rheology of pure PAM/PEI gel and PAM/PEI-CFA composite gels were studied at a representative reservoir temperature of 90 oC. Experimental results reveal that gelation time of pure PAM/PEI gel increases with increasing CFA addition. Further observation demonstrates that increasing PAM and PEI concentrations decreases the gelation times of PAM/PEI-CFA composite gels. Gelation time was found to be within 3-120 hours. Understanding the property of reaction order enables better prediction of gelation time. Dynamic rheological data show that viscoelastic moduli (G′ and G″) of various PAM/PEI-CFA composite gels improved better as compared to the pure PAM/PEI gel across the strain-sweep and frequency-sweep tests. SEM analysis of selected samples at 72 hours and 720 hours of gelation activity consolidated gelation kinetics and dynamic rheological results. These polymer gels are excellent candidates for sealing water thief zones in oil and gas reservoirs.     

Star poly(4-vinylpyridine)s using dendritic ATRP initiators: Synthesis,electrolyte property and performance in dye sensitized solar cell

The G0 and G1 polyurethane dendrimers terminated with 3–12 atom transfer radical polymerization (ATRP) initiators were prepared using single and dual functional ATRP reagents and their structures were confirmed using FT-IR, ¹H–NMR, HR-MS and SEC-MALLS techniques. 4-Vinylpyridine was polymerized using the G1 dendritic initiators to obtain six- and twelve-arm star poly(4-vinylpyridine)s (STAR-P1 and STAR-P2). The absolute molecular weight and PDI of star polymers were in the order of 10⁵ and 1.23–1.24 respectively. Hydrolysis leading to degradation of inner polyurethane core of the star polymers yielded more narrow dispersed poly(4-vinylpyridine) chains and the SEC-MALLS data of these chains confirm the accurate control on number of arms. Both of the polymers were doped with KI/I₂ along with N3-dye to work as efficient polymer electrolytes for dye sensitized solar cell (DSSC). The increment in the conductivity of doped STAR-P1 was very significant and reached 2.415 mS/m from 0.0066 mS/m of dopant salt. The current-voltage characteristics of these doped polymer electrolytes measured under simulated sun light with AM 1.5 at 40 mW/cm² yielded energy conversion efficiency (η) of 5.13% and 1.90% for STAR-P1 and STAR-P2 respectively and these values also significantly high compared to 1.09% corresponds to current-voltage curve of the device fabricated without the polymers.

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Graphical abstract Star poly(4-vinylpyridine)s were prepared using novel dendritic ATRP initiators and used as electrolytes for dye sensitized solar cell (DSSC); one of the cells showed 5.13% energy conversion efficiency.

     

A new cutting depth model with rapid calibration in abrasive water jet machining of titanium alloy

Titanium alloys are widely used in the aeronautical and engineering fields as they show an excellent trade-off between the mass and mechanical properties, but as hard materials, they are difficult to machine using cutting tools. The abrasive water jet affords a good solution to produce titanium parts, especially slim ones. To do so, there is a need to adopt a modelling approach for the depth milled. However, a general methodology that takes into account all the parameters leads to complex models based on a large number of experiments. The present article proposes a depth of cut model combined with a rapid calibration method. The case addressed is that of open rectangular pockets on a Ti-6AL-4V titanium alloy. The approach introduces the machine configuration notion considering that a given machine, pressure level and abrasive impose the abrasive flow rate needed in order to obtain an optimal material removal rate. For a chosen configuration, calibration of the model is performed from a series of elementary passes and just three pocket machining passes. The method is rapid and effective as the accuracy of the models obtained over a number of configurations was to within the order of 5%.     

The evaluation of some flexural properties of a denture base resin reinforced with various aesthetic fibers

This study was performed to determine whether some flexural properties of a denture base resin material could be improved through reinforcement with five types of aesthetic fibers at 3% concentration by weight and in 2, 4, and 6 mm length. Five specimens of similar dimensions were prepared for each of the test groups; base resin and the same resin with glass, rayon, polyester, nylon 6 and nylon 6,6 fibers in three different lengths. Flexural properties were evaluated by using a 3-point bending test. A visual examination was also made to determine mode of fracture of the specimens. The incorporation of different fibers in varying lengths had no significant effect on flexural strength of the resin. The specimens reinforced with nylon 6,6 fibers of 6 mm length showed the highest flexural strength. Young’s modulus and maximum load suggests that such reinforcement makes resin resistant to fracture.     

Gut Microbiota Extracellular Vesicles as Signaling Molecules Mediating Host-Microbiota Communications

Over the past decade, gut microbiota dysbiosis has been linked to many health disorders; however, the detailed mechanism of this correlation remains unclear. Gut microbiota can communicate with the host through immunological or metabolic signalling. Recently, microbiota-released extracellular vesicles (MEVs) have emerged as significant mediators in the intercellular signalling mechanism that could be an integral part of microbiota-host communications. MEVs are small membrane-bound vesicles that encase a broad spectrum of biologically active compounds (i.e., proteins, mRNA, miRNA, DNA, carbohydrates, and lipids), thus mediating the horizontal transfer of their cargo across intra- and intercellular space. In this study, we provide a comprehensive and in-depth discussion of the biogenesis of microbial-derived EVs, their classification and routes of production, as well as their role in inter-bacterial and inter-kingdom signaling.