Complex two-unit system with preventive maintenance

A two-unit warm standby redundant system with repair and preventive maintenance is considered. The pdf of the life time of a unit while in standby is assumed to be Erlangian. The pdfs of all the other random variables are arbitrary. Identifying suitable regeneration points, expressions for the Laplace transforms of the availability and reliability of the system are derived.     

Investigation of twin-wall structure at the nanometre scale using atomic force microscopy

The structure of twin walls and their interaction with defects has important implications for the behaviour of a variety of materials including ferroelectric, ferroelastic, co-elastic and superconducting crystals. Here, we present a method for investigating the structure of twin walls with nanometre-scale resolution. In this method, the surface topography measured using atomic force microscopy is compared with candidate displacement fields, and this allows for the determination of the twin-wall thickness and other structural features. Moreover, analysis of both complete area images and individual line-scan profiles provides essential information about local mechanisms of twin-wall broadening, which cannot be obtained by existing experimental methods. The method is demonstrated in the ferroelectric material PbTiO(3), and it is shown that the accumulation of point defects is responsible for significant broadening of the twin walls. Such defects are of interest because they contribute to the twin-wall kinetics and hysteresis.     

A novel method of unburned hydrocarbons and NOx gases capture from vehicular exhaust using natural biosorbent

Automobile emissions are composed of NO_x and unburned hydrocarbon that contribute significantly to major environmental and health issues. In this study, encapsulated Moringa oleifera beads (EMBs) were synthesized using Moringa oleifera pod powder that was cross-linked with calcium alginate and used as a biosorbent for reducing the emission gas concentrations from the single-cylinder diesel engine. The breakthrough curve was attained from single and double stage of fixed bed column by the influence of temperature ranging from (80°C–120°C) ± 5°C with a feed flow rate varying from 8 to 10 kg hr^–1 and bed height varying from 15 to 30 cm. Based on the experimental results, the maximum biosorption capacity (q_o) was found to be 14.45 and 123.51 mg g^–1 for HC and NO_x, respectively, and was obtained at 80°C–90°C with double stage of BH–30cm under flow rate of 8 kg hr^–1. Further, breakthrough curves were investigated, and the experimental data were fitted using well-established models like Thomas, Yoon–Nelson, and Wang models. In addition, mass transfer models like Weber–Morris and Boyd were investigated to identify the rate-limiting step of the overall biosorption process.     

Fabrication of a novel SnO2:Al/ZnO:F bi-layer for opto-electronic applications

Single layered aluminium doped tin oxide (ATO), fluorine doped zinc oxide (FZO) and bi-layered ATO/FZO thin films were deposited onto preheated glass substrates (T_s = 340 ± 5 °C) using a low-cost and simplified spray pyrolysis technique. The structural, optical, electrical and surface morphological properties of the bi-layered ATO/FZO thin films were studied and compared with that of the single layered films. The average optical transmittance of the bi-layer film in the visible range was found to be around 80 %. The bi-layered ATO/FZO films possessed both better transmittance in the visible range and sharp absorption edge, the unique desirable features of ATO and FZO films, respectively. The optical band gap (E_g) value of the bi-layer coating (3.22 eV) was found to lie between the E_g values of single layered ATO (3.71 eV) and FZO (3.20 eV) films. Sheet resistance values of ATO and FZO single layer films were 3.47 and 11.2 kΩ/sq., respectively. The bi-layered ATO/FZO thin films exhibited a sheet resistance of 4.42 kΩ/sq. which was very much close to that of ATO films and three times less than that of FZO film. The AFM images showed the good packing density and homogeneity of the surface of the bi-layer films. The annealing studies clearly showed that the ATO over layer remarkably improved the thermal stability of the bi-layered film.     

Synthesis,Characterization and Wire Electric Erosion Behaviour of AA7178-10 wt.% ZrB2 Composite

Silicon - In this work, AA7178-10 wt.% ZrB2 Metal Matrix Composite was produced using stir casting route and the mechanical properties of the composites were studied. The microstructure and...     

Effect of mean stress (stress ratio) and aging on fatigue-crack growth in a metastable beta titanium alloy, Ti-10V-2Fe-3Al

The effect of mean stress, or the stress ratio (R), on the fatigue-crack growth (FCG) behavior of α-aged and ω-aged microstructures of the beta titanium alloy Ti-10V-2Fe-3Al was investigated. While the mean stress had a negligible effect on the FCG behavior of the α-aged microstructure, a strong effect was observed in the ω-aged microstructure. In particular, the values of the threshold stress-intensity range (ΔK _th ) exhibited a strong dependence on R in the ω-aged microstructure, while this dependence was weak in the α-aged microstructure. These effects seem to arise primarily from fracture-surface roughness-induced crack closure. The crack closure levels for the α-aged microstructure were found to be very low compared to those for the ω-aged microstructure. Transmission electron microscopy and scanning electron microscopy studies of microstructures and fracture surfaces were performed to gain insight into the deformation characteristics and crack propagation mechanisms, respectively, in these microstructures. The microstructure-induced differences in FCG behavior are rationalized in terms of the effect of aging on slip and crack closure.     

Synthesis and Evaluation of a Nonsteroidal Anti-inflammatory Polymeric Prodrug for Sustained and Site-Specific Delivery

A new polymerizable drug derivative of diclofenac sodium was synthesized and characterized in terms of melting point, elemental analysis, and infrared spectroscopy. It was then polymerized to obtain a new polymeric prodrug. The prodrug was evaluated for its viscosity, drug content, and in vitro drug release behavior at pH 1.2 and 7.2. The in vitro studies showed that the drug release takes place predominantly at the higher pH and in a sustained manner, as hypothesized. Stability at room temperature, bioavailability, and ulcer-inducing effect of the polymeric prodrug were also studied. The investigations showed complete drug absorption from the polymeric prodrug with a statistically significant decrease in ulcer scoring effect, thus showing its potential for site-specific and sustained drug delivery.     

Failure mode transition in ceramics under dynamic multiaxial compression

An experimental technique based on the Kolsky pressure bar has been developed to investigate the behavior of ceramics under dynamic multiaxial compression. Experimental results for aluminum nitride (AlN), together with data available in the literature, indicate that a Mohr-Coulomb criterion and the Johnson–Holmquist model fit the experimental data for failure in a brittle manner, whereas the ceramic material exhibited pressure insensitive plastic flow at high pressures. A failure surface is constructed which represents the material failure behavior, including brittle failure, brittle/ductile transition and plastic flow, under various pressures. The effect of various material properties on the failure behavior was investigated. The Poisson's ratio is found to be a measure of brittleness for ceramic materials with low spall strength under shock wave loading conditions. Lower value of Poisson's ratio indicates that the material will fail in a brittle manner through axial splitting even under uniaxial strain loading; whereas materials with higher Poisson's ratio may be expected to deform plastically beyond the Hugoniot Elastic Limit (HEL). The applicability of the proposed failure surface to a range of ceramics is explored and the limitations of the model are outlined. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mechanical,ablative, and thermal properties of cenosphere‐filled ceramic/phenolic composites

This study mainly deals with cenosphere‐filled phenolic resin‐based composite that is prepared using ceramic‐ceramic fiber as reinforcement by traditional hand layup technique. The effect of cenosphere at various percentage is investigated on the mechanical, ablative, and thermal properties of the filled composites. Mechanical investigation revealed that the addition of microsized cenosphere up to 10% concentration increased the tensile strength of the composite. It is also observed that the addition of cenosphere increased the compressive strength and impact resistance of the composites. Thermogravimetric analysis (TGA) and ablative test revealed that the addition of cenosphere not only decreased both linear and mass ablative rates but also increased the upper working temperature of the filled ceramic/phenolic composites. POLYM. COMPOS., 37:1906–1913, 2016. © 2015 Society of Plastics Engineers     

Perovskite-based electrocatalyst discovery and design using word embeddings from retrained SciBERT language model

With the ever-increasing volume of scientific literature, there is a strong need to develop methods that allow rigorous information identification. In this contribution, a state-of-the-art natural language processing (NLP) model was used to select perovskite materials for electrocatalytic applications from literature. This was accomplished by obtaining word embeddings for perovskite materials from the NLP model and subsequently designing downstream tasks to discover perovskite-based electrocatalyst materials. However, embeddings could be obtained only for materials available in the literature. Consequently, a novel methodology was devised to generate embeddings for newly designed materials. Results from the analysis showed that the computed embeddings could be used to rank materials for their suitability for electrocatalytic applications. Further, the word embeddings were also employed as features in predicting the electrocatalytic activity of perovskite-based electrocatalysts. The analysis demonstrated that the fidelity of regression models increased when the embeddings were used as features.