Experimental investigation of lift enhancement by suction-assisted delayed separation of the boundary layer on NACA 0012 airfoil

In the aerodynamic industry, one of the major problems of interest is the lift enhancement without any increase in the drag. In this paper, an attempt is made to increase the lift coefficient by delayed boundary layer separation using suction at various points, also the study is carried out to identify the optimum location for suction which provides maximum lift augmentation. The experiment is conducted with selected suction pressures of 60, 70, 80, 90?kN/m² at different locations in the range of 40–75% of the chord length of the airfoil. Among the selected pressures, the lowest one at the 70% length provides maximum performance. The critical Reynolds number occurs at around 95% of the length instead of 45% of the length when the same experiment is conducted without suction. The suction also assists in the heat transfer enhancement over the airfoil surface.     

Experimental Investigations on Microstructure,Properties and Workability Behavior of Zinc Oxide Reinforced Al–Si–Mg Matrix Composites

Silicon - Al-Si based alloy matrix composites are now broadly utilized by the industrial sectors like automobile, structural, aerospace and more practical industrial applications due to its...     

Crystalline selenite substituted carbonated hydroxyapatite nanorods: Synthesis,characterization, evaluation of bioactivity and cytotoxicity

Synthesis of pure and selenite substituted hydroxyapatites (HAP and Se‐HAP with 0.02–0.10 Se) by sol–gel method and evaluation of their morphological features, nature of functional groups, phase purity, in vitro bioactivity and cytotoxicity are addressed. Spectral studies confirm the incorporation of selenite into the HAP lattice, accompanied by an increase in CO₃^2? content to maintain the charge imbalance following replacement of P⁵⁺ with Se⁴⁺, thus making the formation of selenite substituted carbonated HAP. Selenite substitution in the HAP lattice has led to a higher crystallinity and increased the crystallite size. The morphology of HAP is changed from sphere to rod‐like structure upon substitution by selenite and the size of the rod is increased with an increase in the selenite content. Among the Se‐HAPs, a better in vitro bioactivity and cell viability are observed for 0.02 Se‐HAP and 0.04 Se‐HAP while the trend is reversed when the extent of selenite substitution becomes higher.     

Copolymerization of styrene with an α‐olefin via atom transfer radical polymerization

This investigation reports the preparation of styrene–α‐olefinic random copolymers, using 1‐octene as an α‐olefin, via atom transfer radical polymerization. Atom transfer radical copolymerization of styrene with 1‐octene was successfully carried out using phenylethyl bromide as initiator and CuBr as catalyst in combination with N, N, N′, N″, N″‐pentamethyldiethylenetriamine as ligand. The copolymers had controlled molecular weight, narrow dispersity and well‐defined end groups with significant 1‐octene incorporation in the polymer. Incorporation of 1‐octene in the copolymers was confirmed using ¹H NMR and matrix‐assisted laser desorption ionization time‐of‐flight mass spectroscopy. An increase in 1‐octene content in the monomer feed led to an increase in the level of incorporation of the α‐olefin in the copolymer. An increase in the concentration of 1‐octene led to a decrease in the rate of polymerization and an increase in dispersity. The glass transition temperature of the copolymer gradually decreased as the incorporation of 1‐octene increased. Copyright © 2011 Society of Chemical Industry     

A constrained binary knapsack approximation for shortest path network interdiction

A modified shortest path network interdiction model is approximated in this work by a constrained binary knapsack which uses aggregated arc maximum flow as the objective function coefficient. In the modified shortest path network interdiction problem, an attacker selects a path of highest non-detection probability on a network with multiple origins and multiple available targets. A defender allocates a limited number of resources within the geographic region of the network to reduce the maximum network non-detection probability between all origin-target pairs by reducing arc non-detection probabilities and where path non-detection probability is modeled as a product of all arc non-detection probabilities on that path. Traditional decomposition methods to solve the shortest path network interdiction problem are sensitive to problem size and network/regional complexity. The goal of this paper is to develop a method for approximating the regional allocation of defense resources that maintains accuracy while reducing both computational effort and the sensitivity of computation time to network/regional properties. Statistical and spatial analysis methods are utilized to verify approximation performance of the knapsack method in two real-world networks.     

Temperature dependent growth and optical properties of SnO<Subscript>2</Subscript> nanowires and nanobelts

SnO₂ nanowires and nanobelts have been grown by the thermal evaporation of Sn powders. The growth of nanowires and nanobelts has been investigated at different temperatures (750–1000°C). The field emission scanning electron microscopic and transmission electron microscopic studies revealed the growth of nanowires and nano-belts at different growth temperatures. The growth mechanisms of the formation of the nanostructures have also been discussed. X-ray diffraction patterns showed that the nanowires and nanobelts are highly crystalline with tetragonal rutile phase. UV-visible absorption spectrum showed the bulk bandgap value (∼ 3–6 eV) of SnO₂. Photoluminescence spectra demonstrated a Stokes-shifted emission in the wavelength range 558–588 nm. The Raman and Fourier transform infrared spectra revealed the formation of stoichiometric SnO₂ at different growth temperatures.     

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.     

In situ synthesised TiO2 ‐chitosan‐chondroitin 4–sulphate nanocomposites for bone implant applications

The artificial materials for bone implant applications are gaining more importance in the recent years. The series titania‐chitosan‐chondroitin 4–sulphate nanocomposites of three different concentrations (2:1:x, where x ‐ 0.125, 0.25, 0.5) have been synthesised by in situ sol–gel method and characterised by various techniques. The particle size of the nanocomposites ranges from 30–50 nm. The bioactivity, swelling nature, and the antimicrobial nature of the nanocomposites were investigated. The swelling ability and bioactivity of the composites is significantly greater and they possess high zone of inhibition against the microorganisms such as Staphylococcus aureus and Escherichia coli. The cell viability of the nanocomposites were evaluated by using MG‐63 and observed the composites possess high cell viability at low concentration. The excellent bioactivity and biocompatibility makes these nanocomposites a promising biomaterial for bone implant applications.Inspec keywords: titanium compounds, filled polymers, nanocomposites, bone, orthopaedics, biomedical materials, sol‐gel processing, nanofabrication, particle size, swelling, microorganisms, cellular biophysics, nanomedicine, prostheticsOther keywords: in situ synthesised TiO₂ ‐chitosan‐chondroitin 4‐sulphate nanocomposites, bone implant applications, artificial materials, in situ sol‐gel method, particle size, swelling nature, antimicrobial nature, microorganisms, Staphylococcus aureus, Escherichia coli, cell viability, MG‐63, biomaterial, size 30 nm to 50 nm, TiO₂