Isothermal transient current studies in cellulose acetate films

Step voltage transient current studies have been made in cellulose acetate films as a function of filed and thickness. A logarithmic plot (Scherr-Montroll plot) of the transient current vs. time gives a knee at a time t_T, which is interpreted as the transit time of the charge carrier. The value of the carrier mobility has been estimated to be 3.9 × 10^?9 cm².V^?1.S^?1 in cellulose acetate film. The carrier mobility in iodine-doped (2% w/w) cellulose acetate film has also been determined from Scher-Montroll plot and is found to be 3.3 × 10^?7 cm².V^?1.S^?1.     

Axisymmetric static and dynamic buckling of orthotropic shallow spherical cap with circular hole

Nonlinear axisymmetric static and dynamic buckling of clamped isotropic and cylindrically orthotropic elastic cap with central circular hole have been investigated. The governing equations are expressed in terms of normal displacement ω and stress function ψ. The orthogonal point collocation method has been used in the space domain and Newmark-β scheme in the time domain. The cases of shallow cap with free hole and with a hole plugged by rigid central mass are considered. Analysis has been carried out for uniformly distributed load and a ring load at the hole. Dynamic load is taken as a step function load. Detailed new results for static and dynamic buckling loads have been presented for the isotropic and orthotropic cases.     

Retarding and antioxidant activity of 1-cyclohexylthio-2-mercaptobenzimidazole in the vulcanization of NR accelerated by thiocarbamyl sulfenamide

The effect of 1-cyclohexylthio-2-mercaptobenzimidazole (CMB) on the vulcanization of NR accelerated by N-oxydiethylene thiocarbamyl-N′-oxydiethylene sulfenamide (OTOS) has been studied. It is found that CMB delays the onset of cure and generates 2-mercaptobenzimidazole during vulcanization. The results indicate the retarding as well as antioxidant activity of CMB.     

Unsteady compressible 3-dimensional boundary-layer flow near an asymmetric stagnation point with mass transfer

The heat and mass transfer for unsteady laminar compressible boundary-layer flow, which is asymmetric with respect to a 3-dimensional stagnation point (i.e. for a jet incident at an angle on the body), have been studied. It is assumed that the free-stream velocity, wall temperature, and surface mass transfer vary arbitrarily with time and also that the gas has variable properties. The solution in the neighbourhood of the stagnation point has been obtained by series expansion in the longitudinal distance. The resulting partial differential equations have been solved numerically using an implicit finite-difference scheme. The results show that, in contrast with the symmetric flow, the maximum heat transfer does not occur at the stagnation point. The skin-friction and heat-transfer components due to asymmetric flow are only weakly affected by the mass transfer as compared to those components associated with symmetric flow. The variation of the wall temperature with time has a strong effect on the heat transfer component associated with the symmetric part of the flow. The skin friction and heat transfer are strongly affected by the variation of the density-viscosity product across the boundary layer. The skin friction responds more to the fluctuations of the free stream oscillating velocities than the heat transfer. The results have been compared with the available results and they are found to be in excellent agreement.     

The w-plane finite element method for the solution of scalar field problems in two dimensions

A simple, efficient finite element method has been presented for the solution of a variety of scalar field problems in two dimensions. It is based on the mapping of the physical problem domain into an ‘image’ domain in the w-plane. The governing equation(s) and the boundary conditions in the physical plane are also appropriately transformed into the w-plane. The processes of standard finite element analysis are then implemented to obtain a solution in the w-plane. The method has been explained in detail, with illustrative examples where appropriate; it has several important advantages over the standard finite element method, particularly for the solution of infinite or semi-infinite domain problems. The method has been demonstrated to be simple, efficient, economical and potentially capable of dealing with a large repartoire of two-dimensional problems, including non-homogeneity, nonlinearity, etc.     

Cyclic symmetry and the Shannon entropy

The authors have axiomatically characterized the Shannon entropy using cyclic symmetry.