Effect of the Time and Temperature of Isothermal Quenching on Microstructure and Mechanical Properties of Bainitic Gray Cast Iron

Metal Science and Heat Treatment - Mechanical properties of copper-alloyed bainitic gray cast iron are studied after isothermal quenching for bainite at different temperatures and holds. The...     

Green synthesis of zinc oxide nanoparticles using tomato (Lycopersicon esculentum) extract and its photovoltaic application

With an increasing awareness of green and clean energy, zinc oxide-based solar cells were found to be suitable candidates for cost-effective and environmentally friendly energy conversion devices. In this paper, we have reported the green synthesis of zinc oxide nanoparticles (ZnONPs) by thermal method and under microwave irradiation using the aqueous extract of tomatoes as non-toxic and ecofriendly reducing material. The synthesised ZnONPs were characterised by UV–visible spectroscopy (UV–vis), infra-red spectroscopy, particle size analyser, scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction study (XRD). A series of ZnO nanocomposites with titanium dioxide nanoparticles (TiO₂) and graphene oxide (GO) were prepared for photovoltaic application. Structural and morphological studies of these nanocomposites were carried out using UV–vis, SEM, XRD and AFM. The current–voltage measurements of the nanocomposites demonstrated enhanced power conversion efficiency of 6.18% in case of ZnO/GO/ TiO₂ nanocomposite.     

Preparation of MgO nano-rods with strong catalytic activity via hydrated basic magnesium carbonates

MgO nano-rods of several microns in length and 50–100 nm in width were prepared by calcining nesquehonite phase, obtained by simple precipitation using (NH₄)₂CO₃ under ambient condition. The MgO nano-rod with reasonably high surface area (75–120 m² g⁻¹) exhibits strong activity in solvent-free base catalyzed Claisen-Schmidt condensation giving 99% conversion in 2 h and is easily recyclable with no significant change in catalytic activity. Presence of numerous basic sites of different strengths (surface hydroxyl groups, low coordinate O²⁻ sites) is attributed to the observed effect.     

Synthesis and characterization of proton exchange poly (phenylenebenzophenone)s membranes grafted with propane sulfonic acid on pendant phenyl groups

A series of poly(phenylenebenzophenone)s with sulfonic acid groups via long alkyl side chains, SPPBPs, were successfully prepared as proton exchange membranes for fuel cells. The new monomer, 1,4-dichloro-2,5 diphenylenemethoxybenzophenone (PMBP) was synthesized by the Friedel–Crafts reaction of tetrachloroterephthalate with anisole and copolymerized with 1,4-dichloro-2,5-diphenylenebenzophenone (PBP) to prepare poly(phenylenebenzophenone)s copolymers containing dimethoxy groups (sPPMBP). After converting the methoxy group to the reactive hydroxyl group, the resulting side-chain-type sulfonated copolymers (SPPBP) were obtained by a sulfopropylation reaction. These SPPBP series membranes showed high proton conductivity in the range of 98.4–162.1 mS/cm 80 °C under 90% hydrated conditions. SPPBP-40 (IEC = 2.45 meq./g) showed comparable higher proton conductivity (162.1 mS/cm) than Nafion 211 (130.2 mS/cm) in the 90% hydrated state. The membranes were studied by ¹H NMR spectroscopy, thermo-gravimetric analysis, ionic exchange capacity, water uptake, and proton conductivity. Also surface morphologies were assessed by atomic force microscope (AFM).     

On hypersingular surface integrals in the symmetric Galerkin boundary element method: application to heat conduction in exponentially graded materials

A symmetric Galerkin formulation and implementation for heat conduction in a three‐dimensional functionally graded material is presented. The Green's function of the graded problem, in which the thermal conductivity varies exponentially in one co‐ordinate, is used to develop a boundary‐only formulation without any domain discretization. The main task is the evaluation of hypersingular and singular integrals, which is carried out using a direct ‘limit to the boundary’ approach. However, due to complexity of the Green's function for graded materials, the usual direct limit procedures have to be modified, incorporating Taylor expansions to obtain expressions that can be integrated analytically. Several test examples are provided to verify the numerical implementation. The results of test calculations are in good agreement with exact solutions and corresponding finite element method simulations. Copyright © 2004 John Wiley & Sons, Ltd.     

Robust multi‐objective blood glucose control in Type‐1 diabetic patient

In this study, an automatic robust multi‐objective controller has been proposed for blood glucose (BG) regulation in Type‐1 Diabetic Mellitus (T1DM) patient through subcutaneous route. The main objective of this work is to control the BG level in T1DM patient in the presence of unannounced meal disturbances and other external noises with a minimum amount of insulin infusion rate. The multi‐objective output‐feedback controller with H_∞, H₂ and pole‐placement constraints has been designed using linear matrix inequality technique. The designed controller for subcutaneous insulin delivery was tested on in silico adult and adolescent subjects of UVa/Padova T1DM metabolic simulator. The experimental results show that the closed‐loop system tracks the reference BG level very well and does not show any hypoglycaemia effect even during the long gap of a meal at night both for in silico adults and adolescent. In the presence of 50 gm meal disturbance, average adult experience normoglycaemia 92% of the total simulation time and hypoglycaemia 0% of total simulation time. The robustness of the controller has been tested in the presence of irregular meals and insulin pump noise and error. The controller yielded robust performance with a lesser amount of insulin infusion rate than the other designed controllers reported earlier.Inspec keywords: robust control, patient treatment, diseases, closed loop systems, patient monitoring, biochemistry, medical control systems, blood, organic compoundsOther keywords: robust multiobjective blood glucose control, automatic robust multiobjective controller, blood glucose regulation, Type‐1 Diabetic Mellitus patient, BG level, T1DM patient, insulin infusion rate, multiobjective output‐feedback controller, pole‐placement constraints, linear matrix inequality technique, subcutaneous insulin delivery, total simulation time, insulin pump noise, adolescent subjects, meal disturbance, normoglycaemia 92, in silico adults, UVa‐Padova T1DM metabolic simulator, closed‐loop system, hypoglycaemia effect     

The role of interfacial friction on the shock wave propagation in stratified gas-liquid flow inside pressure tubes

The admission of the interfacial friction factor in the analysis of the shock wave propagation in the horizontal two-phase stratified flow systems is observed to weaken the shock wave travelling through the phases. A quasi-steady energy balance alludes the importance of the inclusion of the frictional loss in the shock wave phenomena in the horizontal two-phase flows. Finally the problem is dealt with a fuel bundle placed inside the pressure tube, as in a CANDU system to demonstrate experimentally the adverse effect of the pressure transients inside the fuel bundles during a LOCA (loss of coolant accident).     

Synthesis and characterization of block copolymer and comparative study with random copolymer via superacid–catalyzed reaction

The grafted block copolymer based polymer electrolyte membrane (PEM) was successfully synthesized by the superacid-catalyzed polyhydroxyalkylation reaction from biphenyl, 2,2′-biphenol and isatin and the performance of the block copolymer were compared in conjunction with the random copolymer. These polymers have all carbon-carbon structure on polymer backbone without ether linkage. The bromoalkylsulfone potassium salt was prepared from 1,3-propane sultone and potassium bromide. Particularly, the attached alkyl sulfone groups were afforded better stability due to less reactivity towards nucleophilic substitution reaction. Moreover, the block copolymer exhibited better proton conductivity (76.84 mS/cm under 90% relative humidity at 80 ^°C), water resistivity, chemical, and thermal stability compared to the random copolymer, because block copolymer membranes showed good hydrophilic/hydrophobic phase separation and wide ionic channels. The structures of the resultant PEMs were confirmed by ¹H NMR spectroscopy and thermogravimetric analysis (TGA). These membranes were studied by proton conductivity, water uptake (WU), and ion exchange capacity (IEC). Fenton test was attended by Fenton's reagent (4 ppm Fe²⁺, 3% H₂O₂) for confirmation of the polymer degradation and the surface morphology of membranes was also analyzed by atomic force microscope.     

Studies of sulfonated poly(phenylene)-block-poly(ethersulfone) for proton exchange membrane fuel cell

The polymers were prepared by nickel catalyzed carbon–carbon coupling reaction of 1,4-dichloro-2,5-dibenzoylbenzene (DCDBB) and sulfone oligomer. DCDBB was synthesized from oxidation reaction of 2,5-dichloro-p-xylene and followed by Friedel–Craft reaction with benzene. DCDBB monomer had good reactivity in polymerization by electron withdrawing group as benzophenone. Sulfone group of oligomer had improving flexibility and solubility. Post sulfonation was carried out to add sulfonic acid groups by using chlorosulfuric acid. These polymers were presumably stable against nucleophilic attack by hydrogen peroxide, hydroxide anion, and radical generated by proton exchange membrane fuel cell operation system. The number of sulfonic acid groups were controlled by varying the mole ratio of 1,4-dichloro-2,5-dibenzoylbenzene in synthesized polymer. A series of membranes were studied by ¹H NMR spectroscopy, thermo-gravimetric analysis, ion exchange capacity, water uptake, and proton conductivity. Also surface morphologies were assessed by atomic force microscope (AFM).     

Investigation into the Microstructure and Mechanical Properties of Thin Wall Austempered Gray Cast Iron (TWAGI)

The main aim of this investigation is to assess the mechanical properties of thin wall (3 mm thickness) copper alloyed gray cast iron. Thin wall alloyed gray cast iron specimens are subjected to austempering heat treatment at six different temperatures for four different time periods. As a result, these samples develop an ausferrite matrix with excellent mechanical properties. The resulting microstructures have been evaluated and characterized by means of optical microscope and scanning electron microscope (SEM) and X-Ray diffraction analysis. The hardness and tensile properties of all these specimens are determined and correlated with the microstructure. The hardness, tensile strength and ductility initially increase, and thereafter it decreases on longer periods of austempering. On the other hand, hardness and tensile strength decreases with increasing austempering temperature, while ductility increases.