eeTMFO/GA: a secure and energy efficient cluster head selection in wireless sensor networks

Telecommunication Systems - Proliferation of technologies in wireless sensor networks is grabbing huge attention across scientific community due to its vast coverage in real life applications. It...     

Effect of vinyl acetate content on the photovoltaic-encapsulation performance of ethylene vinyl acetate under accelerated ultra-violet aging

The vinyl acetate (VA) content in ethylene vinyl acetate (EVA) can significantly affect its performance as an encapsulant in photovoltaic modules under field conditions. EVA films of varying VA content (18, 24, 33, and 40%) have been prepared using twin screw extruder with the necessary additives and subsequently cured at 150 °C. All the EVA films have been subjected to UV radiation at a wavelength of 340 nm for 1000 and 2000 h to simulate accelerated field aging. The effects of accelerated aging on the gel content, mechanical properties, transmittance, Fourier transform infra-red (FTIR) spectra, thermal stability, degree of crystallinity, and yellowness have been studied. The observations made in this study of UV aging up to 2000 h suggests that the optimum range of VA content in EVA should be between 18 and 33% by weight. VA content beyond 40% degrades almost all properties needed for an encapsulate material after aging of only 2000 h. VA content of around 18% is the most stable under UV aging conditions but has a slightly lower value of transmittance for the unaged sample although the difference in transmittance between different specimens decreases with UV aging. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48268.     

Mesophase behaviour of polyhedral particles

Translational and orientational excluded-volume fields encoded in particles with anisotropic shapes can lead to purely entropy-driven assembly of morphologies with specific order and symmetry. To elucidate this complex correlation, we carried out detailed Monte Carlo simulations of six convex space-filling polyhedrons, namely, truncated octahedrons, rhombic dodecahedrons, hexagonal prisms, cubes, gyrobifastigiums and triangular prisms. Simulations predict the formation of various new liquid-crystalline and plastic-crystalline phases at intermediate volume fractions. By correlating these findings with particle anisotropy and rotational symmetry, simple guidelines for predicting phase behaviour of polyhedral particles are proposed: high rotational symmetry is in general conducive to mesophase formation, with low anisotropy favouring plastic-solid behaviour and intermediate anisotropy (or high uniaxial anisotropy) favouring liquid-crystalline behaviour. It is also found that dynamical disorder is crucial in defining mesophase behaviour, and that the apparent kinetic barrier for the liquid-mesophase transition is much lower for liquid crystals (orientational order) than for plastic solids (translational order).     

Direct Correlation Between Adhesion Promotion and Coupling Reaction at Immiscible Polymer-Polymer Interfaces

Hugh Brown has shown that interfacial entanglements govern adhesion between two polymers. We demonstrate this for three systems by adding interfacial chains via chemical coupling. The adhesion between polypropylene (PP)/amorphous polyamide (aPA) was reinforced by the coupling reaction of maleic anhydride grafted PP (PP-g-MA) and the primary amine groups on aPA; huge increases in adhesion were observed. A good correlation between critical fracture toughness, G_c, and PP-g-MA concentration squared follows Brown's crazing mechanism. For a polystyrene (PS)/aPA interface reinforced by the coupling reaction of poly(styrene-r-maleic anhydride) (PS-r-MA)/aPA only modest adhesion increases in G_c were observed through the whole PS-r-MA concentration range. This different behavior of G_c vs. functional polymer concentration is believed to be caused by segregation of the formed graft copolymers at the interface. The relationship between G_c and the extent of coupling was studied quantitatively with a model PS/PMMA system. The interface was reinforced by the coupling reaction of 0-10% PS-NH₂/PMMA-anh. G_c was measured with the asymmetric dual cantilever beam test (ADCB) and the amount of copolymer formed at the interface was determined by a fluorescence labeling technique. G_c is low and is linear in block copolymer interfacial coverage (Σ), indicating a chain scission mechanism. Reasonable agreement was achieved between experiment and theoretical prediction based on the energy to break C-C bonds.     

Real-time management of berth allocation with stochastic arrival and handling times

In this research we study the berth allocation problem (BAP) in real time as disruptions occur. In practice, the actual arrival times and handling times of the vessels deviate from their expected or estimated values, which can disrupt the original berthing plan and possibly make it infeasible. We consider a given baseline berthing schedule, and solve the BAP on a rolling planning horizon with the objective to minimize the total realized cost of the updated berthing schedule, as the actual arrival and handling time data is revealed in real time. The uncertainty in the data is modeled by making appropriate assumptions about the probability distributions of the uncertain parameters based on past data. We present an optimization-based recovery algorithm based on set partitioning and a smart greedy algorithm to reassign vessels in the event of disruption. Our research problem derives from the real-world issues faced by the Saqr port, Ras Al Khaimah, UAE, where the berthing plans are regularly disrupted owing to a high degree of uncertainty in information. A simulation study is carried out to assess the solution performance and efficiency of the proposed algorithms, in which the baseline schedule is the solution of the deterministic BAP without accounting for any uncertainty. Results indicate that the proposed reactive approaches can significantly reduce the total realized cost of berthing the vessels as compared to the ongoing practice at the port.     

Continuous enzymatic polymerization of phenol in a liquid-solid circulating fluidized bed

A liquid-solid circulating fluidized bed (LSCFB) system consisting of 3.8 cm I.D. and 4 m high riser and 12 cm I.D. and 3.5 m high down-comer was investigated in this study for the continuous polymerization of phenol. Approximately 8.5 kg immobilized particles containing soybean seed hull peroxidase enzymes were applied in the LSCFB system. The continuous enzymatic polymerization was carried out in the riser section by introducing phenol and hydrogen peroxide at the entrance of the riser. Under optimized hydrodynamic conditions and by keeping the molar concentration ratio of phenol to H₂O₂ of 1:2, 54% conversion of phenol was achieved. The down-comer of the LSCFB was utilized for the regeneration of the coated immobilized enzyme particles. The effect of the superficial liquid velocity and an initial substrate concentration was studied. Our experimental results show that an enzymatic reaction and the regeneration of the biocatalysts can be carried out simultaneously and independently in the LSCFB system. Furthermore, this work opens the possibilities for many bioprocesses where the deactivation of the biocatalysts is a major problem and the regeneration of the biocatalysts is required.     

A Library of Thiazolidin-4-one Derivatives as Protein Tyrosine Phosphatase 1B (PTP1B) Inhibitors: An Attempt To Discover Novel Antidiabetic Agents

Protein tyrosine phosphatase 1B (PTP1B) is an important target for the treatment of diabetes. A series of thiazolidin-4-one derivatives 8 – 22 was designed, synthesized and investigated as PTP1B inhibitors. The new molecules inhibited PTP1B with IC₅₀ values in the micromolar range. 5-(Furan-2-ylmethylene)-2-(4-nitrophenylimino)thiazolidin-4-one ( 17 ) exhibited potency with a competitive type of enzyme inhibition. structure–activity relationship studies revealed various structural facets important for the potency of these analogues. The findings revealed a requirement for a nitro group-including hydrophobic heteroaryl ring for PTP1B inhibition. Molecular docking studies afforded good correlation with experimental results. H-bonding and π–π interactions were responsible for optimal binding and effective stabilization of virtual protein-ligand complexes. Furthermore, in-silico pharmacokinetic properties of test compounds predicted their drug-like characteristics for potential oral use as antidiabetic agents.Additionally, a binding site model demonstrating crucial pharmacophoric characteristics influencing potency and binding affinity of inhibitors has been proposed, which can be employed in the design of future potential PTP1B inhibitors.     

High-efficiency solid-state dye-sensitized solar cells based on TiO(2)-coated ZnO nanowire arrays

Replacing the liquid electrolytes in dye-sensitized solar cells (DSCs) with solid-state hole-transporting materials (HTMs) may solve the packaging challenge and improve the long-term stability of DSCs. The efficiencies of such solid-state DSCs (ss-DSCs), however, have been far below the efficiencies of their counterparts that use liquid electrolytes, primarily due to the challenges in filling HTMs into thick enough sensitized films based on sintered TiO(2) nanoparticles. Here we report fabrication of high-efficiency ss-DSCs using multilayer TiO(2)-coated ZnO nanowire arrays as the photoanodes. The straight channel between the vertically aligned nanostructures combined with a newly developed multistep HTM filling process allows us to effectively fill sensitized films as thick as 50 μm with the HTMs. The resulting ss-DSCs yield an average power conversion efficiency of 5.65%.     

Efficient machining of complex-shaped seal slots for turbomachinery

Complex sealing arrangement in turbomachinery can increase turbine efficiency by reducing leakage of high-pressure cooling flows into the hot gas path. While die-sinking EDM is widely used to machine straight seal slots, electrode preparation and wear make it less efficient for complex shapes. This paper presents research on optimisation of a variant of EDM milling using process control and fluid dynamics simulation to exploit optimal machining conditions. The analysis demonstrates a stable process to machine complex shaped slots by focusing on the key requirements for large-scale turbomachinery component manufacture, namely productivity, surface integrity and process monitoring.     

Direct Correlation Between Adhesion Promotion and Coupling Reaction at Immiscible Polymer-Polymer Interfaces

Hugh Brown has shown that interfacial entanglements govern adhesion between two polymers. We demonstrate this for three systems by adding interfacial chains via chemical coupling. The adhesion between polypropylene (PP)/amorphous polyamide (aPA) was reinforced by the coupling reaction of maleic anhydride grafted PP (PP-g-MA) and the primary amine groups on aPA; huge increases in adhesion were observed. A good correlation between critical fracture toughness, G _c , and PP-g-MA concentration squared follows Brown's crazing mechanism. For a polystyrene (PS)/aPA interface reinforced by the coupling reaction of poly(styrene-r-maleic anhydride) (PS-r-MA)/aPA only modest adhesion increases in G _c were observed through the whole PS-r-MA concentration range. This different behavior of G _c vs. functional polymer concentration is believed to be caused by segregation of the formed graft copolymers at the interface. The relationship between G _c and the extent of coupling was studied quantitatively with a model PS/PMMA system. The interface was reinforced by the coupling reaction of 0–10% PS-NH₂/PMMA-anh. G _c was measured with the asymmetric dual cantilever beam test (ADCB) and the amount of copolymer formed at the interface was determined by a fluorescence labeling technique. G _c is low and is linear in block copolymer interfacial coverage (Σ), indicating a chain scission mechanism. Reasonable agreement was achieved between experiment and theoretical prediction based on the energy to break C–C bonds.