Unsteady mixed convection flow of a thermomicropolar fluid on a long thin vertical cylinder

The unsteady laminar mixed convection boundary layer flow of a thermomicropolar fluid over a long thin vertical cylinder has been studied when the free stream velocity varies with time. The coupled nonlinear partial differential equations with three independent variables governing the flow have been solved numerically using an implicit finite difference scheme in combination with the quasilinearization technique. The results show that the buoyancy, curvature and suction parameters, in general, enhance the skin friction, heat transfer and gradient of microrotation, but the effect of injection is just opposite. The skin friction and heat transfer for the micropolar fluid are considerably less than those for the Newtonian fluids. The effect of microrotation parameter is appreciable only on the microrotation gradient. The effect of the Prandtl number is appreciable on the skin friction, heat transfer and gradient of microtation.     

Forced convection along a longitudinal cylinder embedded in a saturated porous medium

The thermal boundary layer along an isothermal cylinder in a porous 3edium is studied numerically by a finite difference scheme and also using the method of extended perturbation series. The series in terms of the transverse curvature parameter ξ extended to seven terms and is subsequently improved by applying the Shanks transformation twice and thrice, respectively. Results for heat transfer characteristics are found in very good agreement.     

Effect of Alumina Reactivity on the Densification and Properties of Al2O3–Cr2O3 Refractories

Alumina‐chrome (Al₂O₃–Cr₂O₃) refractories with Al₂O₃:Cr₂O₃ molar ratio 1:1 were synthesized in the temperature range of 1400–1700°C by conventional solid–oxide reaction route. The effect of different aluminas (viz., hydrated and calcined) on the densification, microstructure, and properties of Al₂O₃–Cr₂O₃ refractories was investigated without changing the Cr₂O₃ source. The starting materials were analyzed to determine the chemical composition, mineralogy, density, surface area, and particle size. Sintered materials were characterized in terms of densification, phase assemblage, and mechanical strength at room temperature and at higher temperatures. Microstructural evolution at different sintering temperature was correlated with sintering characteristics. It can be concluded that the Al₂O₃–Cr₂O₃ refractories prepared with hydrated alumina as Al₂O₃ source show better densification and hot mechanical strength than corresponding calcined variety.     

High‐strength biodegradable poly(vinyl alcohol)/fly ash composite films

We prepared biodegradable composite films of poly(vinyl alcohol) (PVA) and fly ash (FA) spanning 5, 10, 15, 20, and 25 wt % concentrations by casting aqueous solutions. The tensile strengths of the composite films were increased proportionally via the addition of FA. The strength of the film was enhanced by 193% with 20% FA compared to the neat PVA control. Further addition of FA deviated from the linear trend. The moduli of the composites also increased proportionally with FA addition to 212% at 20 wt % FA addition compared to the control. The percentage strain at break exponentially decreased with the addition of FA. In the dynamic mechanical behavior, the storage and loss moduli both increased with FA content. The tan δ peaks corresponding to the glass‐transition temperature shifted 5–10°C higher above the control sample (73°C). This shift was attributed to a reduction in the mobility of PVA segments because they were anchored by the FA surface. The reductions in mobility manifested in strong interfacial interactions were indicative of hydrogen bonding. Broadening and reduction in the intensities of the stretching and bending peaks of ? OH, ? CH and ? C?O of PVA in the Fourier transform infrared spectra were observed. This suggested that hydrogen bonding was active between the functional groups in the FA and PVA chains. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Crystallography of solid–liquid interface and evolution of texture during directional solidification of Tb0.3Dy0.7Fe1.95 alloy

The effect of growth texture on the magnetostriction of ternary Tb_0.3Dy_0.7Fe_1.95 was studied by conducting unidirectional solidification experiments using a zoning set-up. Detailed texture evolutions were studied using X-ray diffraction on samples obtained by varying growth rates from 18 to 72 cm/h, under a temperature gradient of 100 °C/cm. The estimated texture co-efficient and pole figures of the samples indicate that during the onset of the solidification, <110> and <331>/‘rotated <110>’ texture components nucleate and grow in all the samples. However, as the solidification progresses, <112> texture component becomes dominant at higher growth rate. This results in an improvement of magnetostriction from 1000 to 1300 microstrains for samples grown at growth rates of 18 and 72 cm/h respectively. The transition of preferred growth direction occurs through intermediate orientations <123>. An attempt has been made in this paper to explain the occurrence of different growth texture by considering the stability of growing interface, its planar packing fraction and atomic stacking sequence of several low index planes.     

Indole‐based polymer and its silver nanocomposite as advanced antibacterial agents: synthetic path,kinetics of polymerization and applications

Atom transfer radical polymerization of 1‐allylindole‐3‐carbaldehyde (AIC) was studied by employing 2‐bromoisobutyryl bromide as initiator in toluene. It led to controlled radical polymerization of AIC, with an increase of molecular weight along with the conversion of the monomer, and a relatively narrow molar mass distribution was obtained, as determined by gel permeation chromatography. The living nature of poly(1‐allylindole‐3‐carbaldehyde) (PAIC) was confirmed by the chain extension polymerization whereas ¹H NMR analysis showed that the major population of PAIC retained the chain‐end functional group. PAIC and its silver nanocomposite were found to be biologically active against some tested bacterial pathogens. Minimum inhibitory concentration tests revealed that PAIC exhibited antibacterial activity against Staphylococcus aureus, Proteus mirabilis and Klebsiella pneumonae whereas PAIC/Ag nanocomposite showed antibacterial activity against Enterococcus faecalis and K. pneumonae. © 2012 Society of Chemical Industry     

Robust observer based control for plasma glucose regulation in type 1 diabetes patient using attractive ellipsoid method

This paper deals with the design of robust observer based output feedback control law for the stabilisation of an uncertain nonlinear system and subsequently apply the developed method for the regulation of plasma glucose concentration in Type 1 diabetes (T1D) patients. The principal objective behind the proposed design is to deal with the issues of intra‐patient parametric variation and non‐availability of all state variables for measurement. The proposed control technique for the T1D patient model is based on the attractive ellipsoid method (AEM). The observer and controller conditions are obtained in terms of linear matrix inequality (LMI), thus allowing to compute easily both the observer and controller gains. The closed‐loop response obtained using the designed controller avoids adverse situations of hypoglycemia and post‐prandial hyperglycemia under uncertain conditions. Further to validate the robustness of the design, closed‐loop simulations of random 200 virtual T1D patients considering parameters within the considered ranges are presented. The results indicate that hypoglycemia and post‐prandial hyperglycemia are significantly reduced in the presence of bounded (±30% ) parametric variability and uncertain exogenous meal disturbance.Inspec keywords: medical control systems, observers, uncertain systems, nonlinear control systems, robust control, control system synthesis, linear matrix inequalities, feedback, sugar, closed loop systems, diseasesOther keywords: virtual T1D patients, type 1 diabetes patients, closed‐loop simulations, uncertain conditions, post‐prandial hyperglycemia, designed controller, closed‐loop response, controller gains, linear matrix inequality, controller conditions, T1D patient model, control technique, intra‐patient parametric variation, principal objective, plasma glucose concentration, uncertain nonlinear system, robust observer based output feedback control law, attractive ellipsoid method, plasma glucose regulation     

Dynamic process modelling of iron ore sintering

A mathematical model was developed for the iron ore sintering process considering all the major thermochemical phenomena in the system, assuming both the static and moving bed configurations. The model predicted a large number of parameters pertinent to the sintering process including the temperatures of the gas and solid, concentration of various species, amount of solid melted etc. The results were tested against the data existing in literature, and a limited number of pot tests conducted in a pilot plant. Despite high complexity of the problem, the agreement between the experimental and simulated data was reasonably good.