Effects of polyethylene molecular structure on peroxide crosslinking of low density polyethylene

The effects of molecular structure on the dicumyl peroxide crosslinking of two low density polyethylenes have been studied. Peroxide efficiency was determined largely by the content of terminal vinyls in the two polymers. Differences in molecular weight distribution and branch content had comparatively little influence on the gel content but hot creep resistance of the vulcanized materials was affected. Scorching was affected, also, by the presence of vinyl unsaturations in the polymer.     

The fractional and harmonic p-indices for multiple authorship

A proposal is made so that the p-index (a composite performance index that can effectively combine size and quality of scientific papers) can be extended for bibliometric research assessment in cases where multiple authorship is taken into account. The fractional and harmonic p-indices are applied to some recent examples to show their usefulness.     

Variationally correct assumed strain field for the simple curved beam element

The classical curved beam element (the cubic-linear element) has been discredited for a long time because of poor performance. In a previous paper, the first author showed that the poor performance could be attributed to the inconsistency in the membrane strain field interpolations and that this could be improved by designing a new membrane strain field which met the consistency requirements. This paper shows that this formulation can be improved by re-constituting the ‘assumed’ strain field in a variationally correct manner.     

Effect of shear deformation on post-buckling behaviour of columns

The post-buckling behaviour of a cantilever column of variable moment of inertia with tip load is studied by means of a simple numerical iterative scheme. The governing equation of equilibrium is formulated using the axial and transverse displacement quantities, and applying linear constitutive and nonlinear kinematic relations. Numerical results obtained by numerical iterative procedure are presented in the form of curves showing the relation between non-dimensional tip-deflection and non-dimensional load for different values of shear correction factors and taper ratios.     

Non-linear beam vibration problems and simplifications in finite element models

When finite element formulations are used to study the non-linear vibration problems, some simplifications, which are not consistent with the governing variational principles, are commonly employed. Three such simplifications are critically reviewed here, through beam finite element models. The first one, equivalent/ quasi-linearisation technique is shown to have a reduced non-linear stiffness. The second, where in neglect of in plane displacements takes place, is seen to register an excessive non-linear stiffness. Thirdly, when both these simplifications are introduced together, they produce results closer to those of variationally correct ones,rather fortuitously. The objective of this paper is to highlight the necessity of formulating this class of problems in a variationally correct and consistent manner. Numerical computations are performed systematically, using two different beam finite element models for various commonly studied boundary conditions and suitable conclusions are drawn.     

The large amplitude vibration of hinged beams

The large amplitude free vibrations of a simply-supported beam with ends kept a constant distance apart is studied using the actual nonlinear equilibrium equations (i.e. specification of loads in terms of the deformed coordinates of the beam) and the exact nonlinear expression for curvature in addition to the nonlinearity arising from the axial force. A variable separable assumption, together with certain assumptions as to the behaviour of the time function defines an eigenvalue characteristic of the vibration. A numerically exact successive integration and iterative technique establishes the dependence of this quantity on the amplitude of vibrations. The hardening effect of nonlinearity is then interpreted in terms of the variation of this quantity with the amplitude of vibration. This new criteria to define nonlinearity, is compared with several existing in the literature. The present analysis allows the separation of the effects of stretching and large deflection equations on the nonlinear behaviour and the conclusion can be made, based on numerical evidence, that the predominant nonlinearity is due to stretching. The axial force at any station in the beam and the bending stress can also be computed in a numerically exact sense, at the point of maximum amplitude.     

An acoustic emission energy analysis and its use to study damage in laminated composites

A new technique which uses the output of a true RMS voltmeter to measure the acoustic emission energy output of a transducer is presented. To demonstrate its use in a typical case, this procedure is used to measure acoustic emission energy during tensile tests on [0°/±30°/90°]_s glass-epoxy laminate uniaxial and 10° off-axis tensile coupons. The test results were compared with numerical predictions of laminate response and acoustic emission energy. The experiments indicate that acoustic emission energy can be used to indicate the onset of ply and interlaminar failure.     

Kinetic experiments for evaluating the Nernst-Monod model for anode-respiring bacteria (ARB) in a biofilm anode

Anode-respiring bacteria (ARB) are able to transfer electrons from reduced substrates to a solid electrode. Previously, we developed a biofilm model based on the Nernst-Monod equation to describe the anode potential losses of ARB that transfer electrons through a solid conductive matrix. In this work, we develop an experimental setup to demonstrate how well the Nernst-Monod equation is able to represent anode potential losses in an ARB biofilm. We performed low-scan cyclic voltammetry (LSCV) throughout the growth phase of an ARB biofilm on a graphite electrode growing on acetate in continuous mode. The (j)V response of 9 LSCVs corresponded well to the Nernst-Monod equation, and the half-saturation potential (E(KA)) was -0.425 +/- 0.002 V vs Ag/AgCl at 30 degrees C (-0.155 +/- 0.002 V vs SHE). Anode-potential losses from the potential of acetate reached approximately 0.225 V at current density saturation, and this loss was determined by our microbial community's E(KA) value. The LSCVs at high current densities showed no significant deviation from the Nernst-Monod ideal shape, indicating that the conductivity of the biofilm matrix (kappa(bio)) was high enough (> or = 0.5 mS/cm) that potential loss did not affect the performance of the biofilm anode. Our results confirm the applicability of the Nernst-Monod equation for a conductive biofilm anode and give insights of the processes that dominate anode potential losses in microbial fuel cells.     

Synthesis and characterisation of CuS nanomaterials using hydrothermal route

Copper sulphide (CuS) nanomaterials with interesting morphology were synthesised using copper nitrate trihydrate, thiourea and water as a solvent by a simple hydrothermal route. A systematic investigation was carried out to investigate the effect of reaction time (5, 16 and 24?h) at 150°C on the morphology of the materials. Without the use of any template or additives, shape controlled synthesis of CuS nanocrystallites were achieved. The possible mechanism for the formation of the various nanostructures of CuS in this system is discussed. The prepared materials were characterised by X-ray diffraction, field emission scanning electron microscopy (FE-SEM) and DRS-UV–Vis absorption analysis. The UV–Vis spectrum shows that it is the promising material which can absorb in the visible region and hence could be used for photocatalytic applications. In addition, the electrochemical characteristic of the synthesised material was investigated by cyclic voltammetric analysis, which shows that CuS could be used for electrocatalytic applications.