An approach for the development of protective coatings for the novel magnetostrictive material Tb0.3Dy0.7Fe1.92

A logical approach towards the development of protective metallic coatings for the newly developed pseudo-binary rare earth magnetostrictive material Tb_0.3Dy_0.7Fe_1.92 has been put forth. Based on the proposal, experimental trials were conducted on nickel-based coatings, produced by electrodeposition and electroless plating techniques. Direct current electrodeposition of nickel was conducted using both aqueous and non-aqueous plating baths. Non-aqueous electrodeposition produced adherent nickel deposits unlike aqueous electrodeposition and electroless plating methods. The main cause of poor coating adherence in aqueous electrodeposition and electroless plating has been identified as excessive hydrogen evolution. The physical disintegration of the substrate due to hydrogen embrittlement has been briefly addressed.     

Greedy Geometric Algorithms for Collection of Balls,with Applications to Geometric Approximation and Molecular Coarse‐Graining

Choosing balls that best approximate a 3D object is a non‐trivial problem. To answer it, we first address the inner approximation problem, which consists of approximating an object defined by a union of n balls with balls defining a region . This solution is further used to construct an outer approximation enclosing the initial shape, and an interpolated approximation sandwiched between the inner and outer approximations. The inner approximation problem is reduced to a geometric generalization of weighted max k‐cover, solved with the greedy strategy which achieves the classical lower bound. The outer approximation is reduced to exploiting the partition of the boundary of by the Apollonius Voronoi diagram of the balls defining the inner approximation. Implementation‐wise, we present robust software incorporating the calculation of the exact Delaunay triangulation of points with degree two algebraic coordinates, of the exact medial axis of a union of balls, and of a certified estimate of the volume of a union of balls. Application‐wise, we exhibit accurate coarse‐grain molecular models using a number of balls 20 times smaller than the number of atoms, a key requirement to simulate crowded cellular environments.     

Security risk assessment: Applying the concepts of fuzzy logic

Chemical process industries (CPI) handling hazardous chemicals in bulk can be attractive targets for deliberate adversarial actions by terrorists, criminals and disgruntled employees. It is therefore imperative to have comprehensive security risk management programme including effective security risk assessment techniques. In an earlier work, it has been shown that security risk assessment can be done by conducting threat and vulnerability analysis or by developing Security Risk Factor Table (SRFT). HAZOP type vulnerability assessment sheets can be developed that are scenario based. In SRFT model, important security risk bearing factors such as location, ownership, visibility, inventory, etc., have been used. In this paper, the earlier developed SRFT model has been modified using the concepts of fuzzy logic. In the modified SRFT model, two linguistic fuzzy scales (three-point and four-point) are devised based on trapezoidal fuzzy numbers. Human subjectivity of different experts associated with previous SRFT model is tackled by mapping their scores to the newly devised fuzzy scale. Finally, the fuzzy score thus obtained is defuzzyfied to get the results. A test case of a refinery is used to explain the method and compared with the earlier work.     

Positron lifetime studies and coincidence Doppler broadening spectroscopy of Al–6Mg–<Emphasis Type="Italic">x</Emphasis>Sc (<Emphasis Type="Italic">x</Emphasis> = 0 to 0.6 wt.%) alloy

Positron annihilation spectroscopy (PAS), comprising of both positron lifetime and coincidence Doppler broadening measurements, has been employed for studying the phase decomposition behaviour of scandium doped Al–6Mg alloys. Micro structural and age hardening studies have also been conducted to substantiate the explanation of the results of PAS. Samples with scandium concentration ranging from 0 to 0.6 wt.% have been studied. The measured positron lifetimes of undoped alloy reveal that GP zones are absent in the as-prepared Al–6Mg alloy. The observed positron lifetimes and the results of coincidence Doppler broadening measurements largely stem from the entrap of positrons at the interface between aluminium rich primary dendrites and the magnesium enriched interdendritic eutectic mixture of Mg₅Al₈ (β) and the primary solid solution of aluminium (α). The study also provides evidence of the formation of scandium vacancy complexes in Al–6Mg alloys doped with scandium upto a concentration of 0.2 wt.%. However such complex formation ceases to continue beyond 0.2 wt.% Sc; instead, the formation of fine coherent precipitates of Al₃Sc is recorded in the as prepared alloy containing 0.6 wt.% scandium. The positron annihilation studies coupled with CDBS have also corroborated with the fact that the fine coherent precipitates of Al₃Sc are formed upon annealing the Al–6Mg alloys doped with scandium of concentration 0.2 wt.% and above. Transmission electron microscopic studies have provided good evidence of precipitate formation in annealed Al–6Mg–Sc alloys. Elevated temperature annealing leads to dissociation of the scandium-vacancy complexes, thereby leading to the enhancement of the mobility of magnesium atoms. This has facilitated fresh nucleation and growth of Mg₅Al₈ precipitates in the above alloys at 673 K.     

Sol-Gel Derived Nanocrystalline Lanthanum Doped Lead Zirconate Titanate Thin Films Studied for Solitary Waves Propagation

Nanocrystalline PLZT thin films of composition Pb_1-xLa_xZr_0.52Ti_0.48 (x = 0, 2, 5%) were deposited on silicon substrates by sol-gel process using lead acetate trihydrate, lanthanum nitrate hydrate, zirconium propoxide and titanium propoxide as lead, lanthanum, zirconium and titanium precursor materials. Experimental studies have been made on solitary waves in 2 mol% lanthanum doped sol-gel derived lead zirconate titanate thin films. The solitary waves are generated under the influence of external alternating electric field, which has the same frequency as the external field. These solitary waves propagate through the thin film upto its boundary and then reflect back. The magnitude of the solitary waves attenuates as they move away from the electrodes and their phase reverses on reflection. For certain frequencies of the external electric field, solitary waves exhibit resonance effect. Distortion in hysteresis loops has been demonstrated on the basis of solitary waves propagation in the film having different electrode area.     

Formation of silver nanoparticles in poly(perfluorosulfonic) acid membrane

The formation of silver nanoparticles by chemical reduction of Ag+-loaded Nafion-117 membrane with NaBH4 was studied using radioactivity tagged ions. The counterion-exchange method (Ag(m)+ <--> Na(s)+) was used to obtain a membrane sample with a varying proportion of Ag+ ions. The X-ray elemental mapping across the thickness of the membrane by energy-dispersive X-ray spectrometer attached to the environmental scanning electron microscope (ESEM/EDAX) indicated that Na+ and Ag+ were uniformly distributed in the membrane samples before reduction. The average size of nanoparticles formed after reduction was found to be 15 +/- 3 nm, irrespective of the concentration of silver ions present in the membrane before reduction. Energy-dispersive X-ray fluorescence (EDXRF) analyses of the membrane samples, carried out before and after reduction, indicated that the Ag concentration on the membrane surface was considerably increased after reduction. EDXRF measurements of the membrane samples, obtained from reduction carried out in a dead end cell, indicated that Ag nanoparticles were formed only on the membrane surface exposed to NaBH4 solution. Reduction carried out with NaBH4 tagged with 22Na showed that the formation of Ag nanoparticles involved exchange of Ag+ ions from ion-exchange sites in the interior of the membrane with Na+ ions, followed by reduction of Ag+ ions with BH4- ions at the surface of membrane. The study of self-diffusion of water, Na+, and Cs+ ions in the membrane loaded with Ag nanoparticles indicated that formation of Ag nanoparticles did not affect the diffusional transport properties of the membrane. The ion-exchange capacity and water uptake capacity were also not affected by the formation of Ag nanoparticles in the membrane. The spatial distribution of Ag nanoparticles across the thickness of the membrane obtained by ESEM/EDAX showed that Ag nanoparticles were confined to a few-micrometer surface layer of the membrane. Based on these observations, an attempt has been made to explain the mechanism of the formation of Ag nanoparticles in the membrane.     

Cyberbullying detection on social multimedia using soft computing techniques: a meta-analysis

Multimedia Tools and Applications - Cyberbullying is to bully someone in the digital realm. It has become extremely detrimental as the social media and the internet have become more popular and...     

Identifying the role of fly ash properties for minimizing sulfate-heave in lime-stabilized soils

The paper describes a study carried out to examine the effects of fly ash in limiting damaging sulfate-heave (swelling) in lime-stabilized soils. This considered three clays with various sulfate levels; seven fly ashes covering a range of physical and chemical properties, and stored under different conditions (dry, stockpiled and ponded); and a typical quicklime. The initial part of the study examined the effects of fly ash (applied at levels of 6 to 24% by mass of dry soil) on compaction (in terms of density/moisture relationships) of the lime-stabilized soils (using 3.0% lime) to establish mix compositions and provide an insight to their resulting structure. This indicated that maximum dry density (MDD) and optimum moisture content (OMC) were influenced by the characteristics of fly ash (reducing and increasing respectively with increasing fly ash coarseness and loss-on-ignition (LoI; including that under wet storage)) and, depending on these, by the level of application. Tests for sulfate-heave were made following the BS EN 13286-49 volumetric swelling method. Fly ash gave systematic reductions in sulfate-heave with increasing application level up to 24% for the lime-stabilized soils tested. It was found that coarse, high LoI fly ashes, stored under wet conditions, were most effective in limiting the process, suggesting that the coarser structure obtained during compaction with these materials, i.e. lower MDD, is an important factor influencing this. The presence of high sulfate levels in fly ash reduced the effectiveness of the material in this role. The practical implications are considered and a nomogram relating fly ash fineness and application level, MDD and sulfate-swelling is developed, which demonstrates a possible methodology for material selection with regard to minimizing damage.     

Thermophilic biohydrogen production for commercial application: the whole picture

Hydrogen is a promising alternative to fossil fuel for a source of clean energy. Thermophilic biohydrogen production is beneficial for obtaining high H₂ production yield. This review recapitulates the basic metabolic pathways in bacteria for hydrogen production and the enzymes involved in various thermophilic hydrogen producing pathways in microorganisms. It also focuses on the current status of thermophilic biohydrogen production through fermentation of commercially viable substrates, such as agricultural residues. The use of metabolic engineering to attain certain physiological desirable characteristics in H₂‐producing microorganisms, culture conditions, and types of bioreactors to be used are reviewed. Major obstacles in industrial production of biohydrogen like low volumetric hydrogen production and its environmental impact are identified. The review has further identified current limitations in the commercial thermophilic hydrogen production and suggested methods like the use of heat exchangers and effluent recirculation to reduce the production cost. Copyright © 2015 John Wiley & Sons, Ltd.