Compressible axially symmetric laminar boundary layer flow in the stagnation region of a blunt body in the presence of magnetic field

Summary In this paper, the steady laminar viscous hypersonic flow of an electrically conducting fluid in the region of the stagnation point of an insulating blunt body in the presence of a radial magnetic field is studied by similarity solution approach, taking into account the variation of the product of density and viscosity across the boundary layer. The two coupled non-linear ordinary differential equations are solved simultaneously using Runge-Kutta-Gill method. It has been found that the effect of the variation of the product of density and viscosity on skin friction coefficient and Nusselt number is appreciable. The skin friction coefficient increases but Nusselt number decreases as the magnetic field or the total enthalpy at the wall increases.

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Kompressible axialsymmetrische laminare Grenzschichtströmung in der Nähe des Staupunktes eines stumpfen Körpers unter Einwirkung eines Magnetfeldes

Zusammenfassung In dieser Arbeit wird die stationäre laminare viskose Überschallströmung einer elektrisch leitenden Flüssigkeit in der Nähe des Staupunktes eines isolierten stumpfen Körpers unter Einwirkung eines Magnetfeldes studiert unter Berücksichtigung der Veränderlichkeit des Produktes Dichte—Zähigkeit über die Grenzschicht. Die zwei gekoppelten nichtlinearen Gleichungen wurden mit Hilfe des Verfahrens von Runge-Kutta-Gill gelöst. Es zeigte sich, daß der Einfluß der Ortsabhängigkeit des Produktes Dichte—Zähigkeit auf den örtlichen Reibungsbeiwert und die Nusselt-Zahl keineswegs gering ist. Mit Zunahme des Magnetfeldes, oder der totalen Enthalpie an der Wand, nimmt der örtliche Reibungsbeiwert zu, die Nusselt-Zahl jedoch ab.

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With 3 Figures     

Wear characteristics and bearing performance of aluminium-mica particulate composite material

Some tribological properties of a mica-dispersed Al-4%Cu-1.5%Mg alloy cast by a conventional foundry technique are reported. The effect of mica dispersion on the wear rate and journal bearing performance of the matrix alloy was studied under different pressures and under different interface friction conditions. The dispersion of mica was found (a) to increase the wear rate of the base alloy, (b) to decrease the temperature rise during wear and (c) to improve the ability of the alloy to resist seizure.     

Symmetry and the Shannon entropy

Some equivalent systems of postulates characterizing the Shannon entropy of a finite discrete complete probability distribution are proposed.     

DC Electrical Resistivity and Magnetic Property of Single-Phase α-Fe2O3 Nanopowder Synthesized by a Simple Chemical Method

Nanocrystalline pure α-Fe₂O₃ powder, with an average particle size of 35 nm, has been synthesized by using an aqueous solution-based synthetic route. DC electrical resistivity of the synthesized material was measured with respect to temperature by the two-probe method from 28° to 225°C. Room temperature resistivity of the nanopowder was ∼10⁸Ω·cm. Magnetic hysteresis measurement revealed that the synthesized α-Fe₂O₃ nanopowder exhibited ferromagnetic behavior at room temperature. The hysteretic features are high saturation magnetization of 5.1 emu/g, high remanence of 2.2 emu/g, and coercivity of 200.5 Oe.     

Rheological behavior and morphological and interfacial properties of PLA/TPE blends

Rheological and interfacial tension data were employed to predict the morphology and thermal and mechanical properties of noncompatibilized and compatibilized poly(lactic acid) (PLA)/thermoplastic elastomer (TPE) blends. PLA was melt blended with thermoplastic polyurethane (TPU) and ethylene elastomer (EE) and compatibilized by ethylene–butyl acrylate–glycidyl methacrylate (EBG) in an internal mixer chamber. Both TPU and EE TPEs have higher viscosities than PLA, and the interfacial properties evaluated have revealed better adhesion between domains of PLA–TPU. The efficiency of the compatibilizer agent EBG depended on the TPE type inferred by modifications in the scanning electron microscopy images of PLA/TPE blends and by the Izod impact strength (improved by 23%). The EBG was more effective in the PLA/TPU blend. The TPEs and EBG did not affect the PLA thermal stability, and no thermal event was observed in the usual PLA extrusion and injection temperature range. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47962.     

Synthesis and characterization of highly acetylated sago starch

This study was carried out to understand and establish the changes in physicochemical parameters of sago starch after acetylation. Highly substituted starch acetate was prepared by reaction with native sago starch and acetic anhydride in organic solvent. Their formation was confirmed by the titrimetric analysis and FT‐IR. The presence of absorption band in FT‐IR at 1748 cm⁻¹ confirmed the carbonyl group attachment. The thermal behavior of native and acetyl substituted sago starch was investigated using thermo gravimetric analysis (TGA) and DSC. The results reveal that highly substituted starch acetate was more thermally stable as compared to native form. The XRD patterns showed loss of crystalline nature and its transformation into amorphous form. The SEM study suggested that the smooth surfaces of starch granules were changed into fibrous form after acetylation.