ESOA modified unsaturated polyester hybrid networks: A new perspective

Hybrid polymer networks based on unsaturated polyester (UPE) and epoxidized soybean oil acrylate (ESOA) were synthesized by reactive blending through free radical addition polymerization reaction. ESOA was prepared by acrylation of epoxidized soybean oil (ESO). The physical, mechanical, thermal and electrical properties of the cured blends were compared with the neat resin. ESOA resin bearing reactive functional groups showed good miscibility and compatibility with the UPE resin. The co‐cured resin showed substantial upgrading in the toughness, impact resistance, thermal properties, and downgrading brittleness up to the addition of 20 wt % of ESOA content. The muddled phase structure was corroborated by Fourier transform infrared spectroscopy, scanning electron microscope, and transmission electron microscopy and proved the formation of excellent hybrid polymer network. An improvement in overall properties has been achieved without seriously affecting any other properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44345.     

Development of numerical linear algebra algorithms in dynamic fixed‐point format: a case study of Lanczos tridiagonalization

Proper range and precision analysis play an important role in the development of fixed‐point algorithms for embedded system applications. Numerical linear algebra algorithms used to find singular value decomposition of symmetric matrices are suitable for signal and image‐processing applications. These algorithms have not been attempted much in fixed‐point arithmetic. The reason is wide dynamic range of data and vulnerability of the algorithms to round‐off errors. For any real‐time application, the range of the input matrix may change frequently. This poses difficulty for constant and variable fixed‐point formats to decide on integer wordlengths during float‐to‐fixed conversion process because these formats involve determination of integer wordlengths before the compilation of the program. Thus, these formats may not guarantee to avoid overflow for all ranges of input matrices. To circumvent this problem, a novel dynamic fixed‐point format has been proposed to compute integer wordlengths adaptively during runtime. Lanczos algorithm with partial orthogonalization, which is a tridiagonalization step in computation of singular value decomposition of symmetric matrices, has been taken up as a case study. The fixed‐point Lanczos algorithm is tested for matrices with different dimensions and condition numbers along with image covariance matrix. The accuracy of fixed‐point Lanczos algorithm in three different formats has been compared on the basis of signal‐to‐quantization‐noise‐ratio, number of accurate fractional bits, orthogonality and factorization errors. Results show that dynamic fixed‐point format either outperforms or performs on par with constant and variable formats. Determination of fractional wordlengths requires minimization of hardware cost subject to accuracy constraint. In this context, we propose an analytical framework for deriving mean‐square‐error or quantization noise power among Lanczos vectors, which can serve as an accuracy constraint for wordlength optimization. Error is found to propagate through different arithmetic operations and finally accumulate in the last Lanczos vector. It is observed that variable and dynamic fixed‐point formats produce vectors with lesser round‐off error than constant format. All the three fixed‐point formats of Lanczos algorithm have been synthesized on Virtex 7 field‐programmable gate array using Vivado high‐level synthesis design tool. A comparative study of resource usage and power consumption is carried out. Copyright © 2015 John Wiley & Sons, Ltd.     

Crystallization behavior and morphology of polylactic acid (PLA) with aromatic sulfonate derivative

This article provides a detailed investigation of crystallization behavior and morphology of polylactic acid (PLA) in the presence of a nucleating agent: potassium salt of 5‐dimethyl sulfoisothalate, an aromatic sulfonate derivative (Lak‐301). Isothermal crystallization kinetics of PLA melt mixed with Lak at concentrations of 0.25–1 wt % was investigated at a range of crystallization temperature, 140–150 °C. To gain further insight on the effect of Lak, nonisothermal differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD), polarized optical microscope (POM), heat deflection temperature (HDT), and rheology were also performed. At 0.25 wt % Lak, crystallinity of PLA increased from 10% to 45%, and in 1 wt % Lak, maximum crystallinity of 50% was achieved. With 1 wt % Lak, crystallization half time reduced to 1.8 min from 61 min for neat PLA at 140 °C. The isothermal crystallization kinetics was analyzed using Avrami model. Values of the Avrami exponent for PLA with Lak were mainly in the range of 3 indicating a three dimensional crystal growth is favored. Crystallization rate was found to increase with increase in Lak content. Observation from POM confirmed that the presence of Lak in the PLA matrix significantly increased the nucleation density. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43673.     

Towards the design of hybrid QCA tiles targeting high fault tolerance

The increasing fabrication cost of CMOS-based computing devices and the ever-approaching limits of their fabrication have led to the search for feasible options with high device density and low power waste. Quantum-dot cellular automata (QCA) is an emerging technology with such potential to match the design target beyond the limits of state-of-the-art CMOS. But nanotechnologies, like QCA are extremely susceptible to various forms of flaws and variations during fabrication at nano scale. Thus, the exploration of ingenious fault tolerant structure around QCA is gaining high importance. This work targets a new robust QCA tile structure hybridizing rotated and non-rotated cell together resulting lesser kink energy. Different QCA logic primitives (majority/minority logic, fanout tiles, etc.) are made using such hybrid cell structure. The functional characterization using the kink energy and the polarization level of such QCA structures under different cell defects have been thoroughly investigated. The results suggest that the proposed QCA logic primitives have achieved high fault tolerance of 97.43 %. Also, 100 % fault tolerance can be ascertained if the proposed logic circuit drives the correct output with the application of \(\langle \)001, 011\(\rangle \) as a primitive test vector only. A comparative performance of the proposed logic over existing structure makes it more reliable.     

Effect of chemical treatment on newspaper fibers reinforced polymer poly(vinyl chloride) composites

Natural fibers used as reinforcement in composite materials present specific mechanical properties, which are comparable to glass fibers. In addition, they have the advantage of being renewable and recyclable. However, their main drawback is their inherent susceptibility to moisture expansion, which has the effect of inducing a decrease in mechanical properties, and of debonding in the composite. In this study, lignocellulosic fibers from newspapers were modified with acetic anhydride, NaOH, and KMnO₄ in order to enhance the interfacial adhesion between poly(viny lchloride) (PVC) matrix and the newspaper fibers. Composites samples were prepared with different treated fibers at the same loading (20 wt%). X‐ray and scanning electron microscopy (SEM) were used to characterize the fiber's surfaces. The mechanical, morphological, and thermal properties of PVC/newspaper composites were also studied. Moreover, the maximum improvement in the mechanical properties (tensile strength) was obtained for the permanganate treated PVC/newspaper composites. J. VINYL ADDIT. TECHNOL., 22:173–181, 2016. © 2014 Society of Plastics Engineers     

Microstructure and Wear Behavior of Single layer (CrN) and Multilayered (SiN/CrN) Coatings on Particulate Filled Aluminum Alloy Composites

This article presents the slurry erosive wear behavior of single and multilayer coatings on granite powder reinforced aluminum alloy composites for hydro-turbine blade material. The composites were fabricated by stir casting technique with different weight fraction (0, 2, 4, 6wt.%) of granite powder in 1050 aluminum alloy. In this study, the slurry jet erosive performance of uncoated, single layer and multilayer coating granite powder filled alloy composites in a slurry jet wear test was conducted for four different operating parameters such as filler content (0-6wt.%), impact velocity (10-25 m/s), impingement angle (30-75 ⁰) and erodent discharge (160-280 gm), respectively. The slurry erosion rate was a maximum at 0wt.% granite powder reinforcement in uncoated, single layer and multilayer coating samples such as: 0.0203 gm/kg, 0.00981 gm/kg and 0.00756 gm/kg, respectively at impact velocity of 25 m/sec. Taguchi’s orthogonal array (L ₁₆) was applied to study the experimental results of the uncoated and coated alloy composites. A correlation was derived from the results of the Taguchi experimental design and a proposed predictive equation for estimation of slurry erosion rate of these composites. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were conducted to analyze the topography of the eroded surface of uncoated and coated granite powder reinforced aluminum alloy composites.     

Influence of Six Nitrification Inhibitors on Methane Production in a Flooded Alluvial Soil

The influence of six nitrification inhibitors (NI) on CH₄ production in an alluvial soil under flooded condition was studied in a laboratory incubation experiment. The inhibition of CH₄ production followed the order of sodium azide > dicyandiamide (DCD) > pyridine > aminopurine > ammonium thiosulfate > thiourea. Inhibition of CH₄ production in DCD-amended soils was related to a high redox potential, low pH, low Fe²⁺ and lower readily mineralizable carbon content as well as lower population of methanogenic bacteria and their activity. In the presence of higher levels of urea N (40 g), the inhibitory effect of DCD was only partially alleviated. Results indicate that several NIs can differentially regulate CH₄ production in a flooded alluvial soil.     

Neural Mechanisms of Affective Interference in Schizotypy.

Negatively valenced stimuli foster cognitive impairment in schizotypy and schizophrenia. To identify relevant brain mechanisms, the authors had 16 positive-schizotypy and 16 control participants perform an emotional Stroop task, judging the ink color of negative and neutral words during functional magnetic resonance imaging (fMRI) of regional brain activity. Schizotypy individuals showed increased right and decreased left activity in dorsolateral prefrontal cortex, indicating a deficit in maintenance of attentional set in the presence of negative emotional distractors. They also showed abnormal activity in ventral limbic areas, including decreased activity in nucleus accumbens and increased activity in hippocampus and amygdala, a circuit involved in the integration of cognitive and affective processes. These results indicate that aspects of emotion-cognition processes and the brain mechanisms that implement them are similar in schizotypy and schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Synthesis and properties of graphene and graphene/carbon nanotube-reinforced soft magnetic FeCo alloy composites by spark plasma sintering

The effect of the addition of graphene nanoplatelets (GNP) and graphene nanoplatelet/carbon nanotube (GNT) mixtures on the mechanical and magnetic properties of spark plasma sintered soft magnetic FeCo alloys was studied. Three different volume fractions (0.5, 1 and 2 vol%) of GNPs and GNTs were investigated. Ball milling was used to disperse the GNPs in monolithic FeCo powder, while magnetic stirring and ultrasonic agitation were used to prepare hybrid GNT prior to ball milling. The highest saturation induction (B _sat) of 2.39 T was observed in the 1 vol% GNP composite. An increase in the volume fraction of the ordered nanocrystalline structure was found to reduce the coercivity (H _c) of the composites. The addition of CNTs to the GNP composite prevented grain growth, leading to grain refinement. An 18 % increase in hardness was observed in the 1 vol% GNP composite as compared to the as-received FeCo alloy. A reduction in tensile strength was observed in all of the composite materials, except for the 0.5 vol% GNT composite, for which a value of 643 MPa was observed. Raman spectroscopy indicated a reduction in the defect density of the GNPs after adding CNTs.     

Utilization of Chemically Synthesized Fine Powders of SiC/Al2O3 Composites for Sintering

Fine powders of (Al₂O₃)_100–x(SiC)_x (0 ≤ x ≤ 50) composites were prepared by chemical route (named as pyrophoric technique) to achieve a uniform mixture of SiC in an alumina matrix. The chemically synthesized fine SiC/Al₂O₃ composite powders were sintered to form composites at 1450°C which is well below the sintering temperature of SiC. Sintering was performed in an argon atmosphere. Highly dense SiC/Al₂O₃ microstructures were achieved. An improvement in bulk density and hardness has been achieved for SiC/Al₂O₃ composites with 20 wt% of SiC. Hexagonal-shaped grains have been obtained in (Al₂O₃)₅₀(SiC)₅₀ composite with well-connected grain boundaries. The peak position of alumina in SiC/Al₂O₃ composites shifts toward lower wavenumbers in Fourier transform infrared spectroscopy and higher wavenumbers in Raman spectroscopy due to the incorporation of SiC in the composites. The optical band gap decreases with the addition of SiC and the composite behaves more like a semiconductor rather than an insulator. These properties make SiC/Al₂O₃ composites attractive for various industrial applications.