Non-uniform slot injection (suction) or wall enthalpy into a steady nonsimilar compressible laminar boundary layer

Summary Steady two-dimensional and axisymmetric compressible nonsimilar laminar boundary-layer flows with non-uniform slot injection (or suction) and non-uniform wall enthalpy have been studied from the starting point of the streamwise co-ordinate to the exact point of separation. The effect of different free stream Mach number has also been considered. The finite discontinuities arising at the leading and trailing edges of the slot for the uniform slot injection (suction) or wall enthalpy are removed by choosing appropriate non-uniform slot injection (suction) or wall enthalpy. The difficulties arising at the starting point of the streamwise co-ordinate, at the edges of the slot and at the point of separation are overcome by applying the method of quasilinear implicit finite difference scheme with an appropriate selection of finer step size along the streamwise direction. It is observed that the non-uniform slot injection moves the point of separation downstream but the non-uniform slot suction has the reverse effect. The increase of Mach number shifts the point of separation upstream due to the adverse pressure gradient. The increase of total enthalpy at the wall causes the separation to occur earlier while cooling delays it. The non-uniform total enthalpy at the wall (i.e., the cooling or heating of the wall in a slot) along the streamwise co-ordinate has very little effect on the skin friction and thus on the point of separation.     

Mot d'adieu de la rédactrice en chef.

Upon the occassion of the last issue under his responsibility, the outgoing editor of the Canadian Journal of Behavioural Science expresses his gratitude to editorial committee members, collaborators and advisors who have contributed to the success of the journal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tensile and Fracture Properties of Cast and Forged Composite Synthesized by Addition of Al-Si Alloy to Magnesium

Cast Mg-Al-Si composites synthesized by addition of Al-Si alloy containing 10, 15, and 20 wt pct of Si, in molten magnesium, to generate particles of Mg₂Si by reaction between silicon and magnesium during stir casting has opened up the possibility to control the size of these particles. The microstructure of the cast composite consists of relatively dark polyhedral phase of Mg₂Si and bright phase of β-Al₁₂Mg₁₇ along the boundary between dendrites of α-Mg solid solution. After hot forging at 350 °C, the microstructure has changed to relatively smaller sizes of β-Al₁₂Mg₁₇ and Mg₂Si particles apart from larger grains surrounded by smaller grains due to dynamic recovery and recrystallization. Some of the Mg₂Si particles crack during forging. In both the cast and forged composite, the Brinell hardness increases rapidly with increasing volume fraction of Mg₂Si, but the hardness is higher in forged composites by about 100 BHN. Yield strength in cast composites improves over that of the cast alloy, but there is a marginal increase in yield strength with increasing Mg₂Si content. In forged composites, there is significant improvement in yield strength with increasing Mg₂Si particles and also over those observed in their cast counterpart. In cast composites, ultimate tensile strength (UTS) decreases with increasing Mg₂Si content possibly due to increased casting defects such as porosity and segregation, which increases with increasing Mg₂Si content and may counteract the strengthening effect of Mg₂Si content. However, in forged composite, UTS increases with increasing Mg₂Si content until 5.25 vol pct due to elimination of segregation and lowering of porosity, but at higher Mg₂Si content of 7 vol pct, UTS decreases, possibly due to extensive cracking of Mg₂Si particles. On forging, the ductility decreases in forged alloy and composites possibly due to the remaining strain and the forged microstructure. The initiation fracture toughness, J _IC , decreases drastically in cast composites from that of Mg-9 wt pct. alloy designated as MA alloy due to the presence Mg₂Si particles. Thereafter, J _IC does not appear to be very sensitive to the increasing presence of Mg₂Si particles. There is drastic reduction of J _IC on forging of the alloy, which was attributed to the remaining strain and forged microstructure, and it is further lowered in the composites because of cracking of Mg₂Si particles. The ratio of the tearing modulus to the elastic modulus in cast composites shows a lower ratio, which decreases with increasing Mg₂Si content. The ratio decreases comparatively more on forging of cast MA alloy than those observed in forged composites.     

A ferromagnetic resonance study of as-quenched and annealed amorphous Fe78Cr2B12Si8

Ferromagnetic resonance (FMR) studies of as-quenched and annealed amorphous Fe₇₈Cr₂B₁₂Si₈ are presented. For short annealing times (30 min) and low annealing temperatures (473 K) the resonant field,H ₁, and the FMR line width, H, are essentially constant. This can be explained in terms of a combination of effects due to magnetic anisotropy and the in homogeneous demagnetization due to stress relief in the sample. For larger annealing times or higher annealing temperatures,H ₁ and H increase due to the percipitation of crystallites in the amorphous structure. X-ray diffraction, selected area electron diffraction patterns and transmission electron micrographs are consistent with this interpretation.     

Buckling of Laminated Composite Rectangular Plates

The present study estimates the critical/buckling loads of laminated composite rectangular plates under in-plane uniaxial and biaxial loadings. The formulation is based on the first-order shear deformation theory and von-Karman-type nonlinearity. Chebyshev series is used for spatial discretisation and quadratic extrapolation is used for linearization. An incremental iterative approach is used for estimation of the critical load. Different combinations of simply supported, clamped and free boundary conditions are considered. The effects of plate aspect ratio, lamination scheme, number of layers and material properties on the critical loads are studied.     

Studies on the Physico-chemical Properties of the Starch of Euryale ferox

The physico-chemical properties of starch isolated from the seeds of Euryale ferox have been investigated mainly by methylation studies, periodate experiments, absorption measurements, and viscosity measurements. Starch was fractionated into amylose and amylopectin by precipitation technique. The average length of unit chain in amylose and amylopectin was found to be 22 and 380 glucose units, respectively. Starch contains 25% amylose as determined by potentiometric titrations. Other properties of starch, amylose and amylopectin have been described in the present paper.     

Composition of the seed oil of sterculia foetida,Linn

Summary Sterculia foetida oil has been found to contain 71.8% of sterculic acid and minor proportions of oleic, linoleic, and saturated acids. The saturated component consists mostly of myristic and palmitic acids. The oil consists of traces of tristearin (0.8%) and a major quantity of tristerculin (31.4%) together with different amounts of the glycerides of the type GS₂U, GSU₂, and GU₃ of other fatty acids.     

Studies on the reactions between thiocarbamyl sulfenamide and 2-(iminodithio)benzothiazole accelerator system in the early stage of vulcanization of NR

Investigations on the interactions of the synergistic pair of accelerators comprising of thiocarbamyl sulfenamide and 2-(iminodithio)benzothiazole have been carried out through hplc. N-cyclopentamethylene thiocarbamyl-N'-oxydiethylene sulfenamide, N-oxydiethylenethiocarbamyl-N'-cyclopentamethylene sulfenamide (OTCS), 2-morpholinodithiobenzothiazole, and 2-piperidinodithiobenzothiazole (PDB) have been selected as the reactants which, when suitably combined, provide most effective accelerator systems capable of generating heat and age resistant vulcanizates. The OTCS–PDB system has been found to yield vulcanizates which exhibit the greatest crosslink density, scorch safety, and highest modulus and tensile strength. An attempt has been made to explain the higher activity of the binary systems studied as compared to that obtained from comparable thiocarbamyl sulfenamide plus dibenzothiazyl disulfide system. Zin–dithiocarbamates have been found to influence the curing reactions depending upon the composition of the mixed accelerators. Cyclohexyl thiophthalimide, a versatile cure retarder, reacts with the accelerators to yield cyclohexyl thiomorpholine and cyclohexyl thiopiperidine, as the case may, which also have a profound effect upon cure retardation as noticed in the present investigation.     

Application of flyash instead of activated carbon for oxalic acid removal

Flyash, a waste product from thermal power plants, has been used as an adsorbent for the removal of oxalic acid. The adsorption process follows first-order kinetics and the equilibrium is attained within 30 min in the concentration range studied (0.01-0.1M). The adsorption obeys both the Freundlich and Langmuir isotherms and the constants have also been reported for flyash and activated carbon. At low concentrations, the increase in pH with flyash is comparatively more than for activated carbon. There seems to be a good scope for the use of flyash in place of activated carbon as an adsorbent for oxalic acid removal.     

Dielectric behavior of the constituents of the natural resin shellac

The dielectric relaxation data of the constituents of natural resin shellac have been analyzed by the Cole–Cole method at temperatures between 10° and 90°C in the frequency range of 50 Hz to 500 kHz. The functional groups present in hard and soft lac appeared to be responsible for the dielectric properties exhibited by shellac below and above its glass transition and melting temperature, respectively. A combination of 70% hard lac and 30% soft lac was found to exhibit the dielectric properties of shellac satisfactorily.