Showing papers by "Deen Dayal Upadhyay Gorakhpur University published in 1979"

Propagation of magnetogasdynamic spherical shock waves in an exponential medium

Abstract: In this paper propagation of magnetogasdynamic spherical shock waves is considered in an exponentially increasing medium. The shock wave moves with variable velocity and the total energy of the wave is variable. It is shown that the magnetic field changes the flow velocity, density and pressure.

Glass transition temperatures of copolyphosphates

Abstract: Values of glass transition temperature (T g ) for several samples of sodium copolyphosphates were determined by DSC measurements. Their dependence on a number of factors has been considered. Contrary to the observations ofEisenberg et al.T g does not depend entirely on the ratio of the cation charge, $$\bar q$$ , and the inter-nuclear distance between the cation and the chain anion,a. For a particular kind of copolyphosphate it depends remarkably on the conditions of formation viz. the temperature of the melt quenched to form the glass and the time duration for which the melt remained as such before being quenched. When the temperature of the melt is kept constant and the time duration varied,T g registers an increase with increase in time. Keeping the time constant and raising the temperature once again results in an increase in the value ofT g . The values ofT g are also found to depend on the size and the atomic weight of the cation, other than sodium;T g increases with its size and its atomic weight. With a few exceptionsT g is also found to increase with increase in the value of the number-average molecular weight.

Frictional coefficient-11 (evaluation of degree of coupling, efficiency of energy conversion and membrane parameters)

Abstract: Frictional coefficients between membrane matrix and permeants have been evaluated for ThO2/DMF system. The degrees of coupling ′q′ and the maximum value of the efficiencies of electrokinetic energy conversion, νmax, for both the modes of conversion, viz., electro-osmotic flow and streaming potential have been calculated from these coefficients and the results have been found to be in accordance with non-equilibrium thermodynamic theories. The values of frictional coefficients have also been used for characterising the membrane, viz., in determining the equivalent pore radii and the number of pores.

On the anisotropic behaviour of ion-exchange membranes

Abstract: Directional dependence of solvodynamic transport, electroosmotic transport and current-voltage characteristics across a Zeokarb 225 membrane in Na+, Ba++ and Al−++ forms has been investigated. Results show that membranes are isotropic with respect to solvodynamic permeability and current-voltage characteristics but become strongly anisotropic with respect to electroosmotic permeation. Irreversible thermodynamic analysis of the data indicates that straight phenomenological coefficients are independent of direction of flow whereas, cross-phenomenological coefficients are strongly direction dependent.

On the streaming potential across a cation-exchange membrane

Abstract: Electrical potentials developed during streaming of methanol, water and their mixtures through a Zeokarb 225 (Al+++ form) membrane have been investigated. Build-up of streaming potential with time has been examined and discussed. Results indicate that dependence of streaming potential on applied pressure difference is non-linear and shows sign reversals. An attempt has been made to explain the results in terms of changes in the structure of electrical double layer at the membrane-permeant interface under the action of streaming pressure.

Thermal analysis of copolyphosphates

Abstract: DTA and TG were carried out on a number of sodium-containing copolyphosphates. The DTA curves were characteristic of long-chain polyphosphates and were similar in nature. All of them showed a sharp exothermic peak indicating crystallization temperature (Tc) followed by a sharp endothermic peak giving the value of melting temperature (Tm). TG curves showed weight loss occurring in two stages, the first one beginning at 50°C (loss of absorbed moisture) and the second one in the range 300-500°C (corresponding toTc). The values ofTm andTc appeared to decrease with increase in molecular weight. This could be due to the presence of crystallizable comonomer units in the copolyphosphate glasses.Tc andTm also appeared to increase with increase in the atomic weight of the cation other than sodium.