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Polymeric materials enjoy widespread acceptance among electrical insulation design engineers due to their multi‐functional attributes (e.g., excellent dielectric properties, high strength to weight ratio, and ease of molding). However, charge accumulation at the high DC field, poor discharge resistance, low thermal conductivity, limited‐service temperature range, and inadequate stiffness have proven to be severe obstructions to far‐reaching utilization of these materials. To ensure the reliability of today's electrical power systems, novel dielectric materials with enhanced functionalities are essential. An idea that originated under the name of polymer nanocomposites (PNCs) is supposed to provide a viable solution to the challenges mentioned earlier. PNCs are made by mixing a small quantity of nanometer‐sized fillers into a polymer matrix and dispersing them uniformly. To effectively use PNCs in electrical insulation for power apparatus, extensive research into the physical and chemical phenomena associated with these new materials is required. This article aims to provide a comprehensive review of previous research on dielectric PNCs, including synthesis, electrical and nonelectrical characterization, and attendant issues from an electrical insulation standpoint.

Abstract. We study the nonlinear dynamics of normal field instability in a ferrofluid under the influence of a uniform magnetic field. In addition, a small normal sinusoidal magnetic field is superimposed on the system. An equation governing the evolution of small but finite amplitude is obtained. Applying the Melnikov method, it is shown that there exist transverse homoclinic orbits leading to chaotic motions.

Abstract. An asymptotic nonlinear theory of the two superposed magnetic fluids is presented taking into account the spatial as well as temporal effects. A generalized formulation of the evolution equation governing the amplitude is developed which leads to the nonlinear Klein-Gordon equation. The various stability criteria are derived from this equation. Obtained also are the bell shaped soliton and the kink solutions.

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Hydroxy-terminated polybutadiene (HTPB) prepolymer prepared by freeradical mechanism at Chemical Engineering Complex, Vikram Sarabhai Space Center, Thiruvananthapuram was reacted with toluene diisocyanate (TDI), a curative at varying stoichiometric ratios (r ϭ [NCO]/[OH]) equal to 0.7, 0.8, 0.9, 1.0, and 1.1 at a constant temperature of 70°C. The increased rate of viscosity of polyurethane networks formed was used to calculate the rate constant. Similarly, the rate of change of viscosity of curing networks at different r values (0.7-1.1) and temperature intervals (30 -70°C) was used to calculate activation energy. The results of the curing networks showed that the rate constant at r Ͼ 0.9 is constant and the rate of decrease of activation energy is lower at r Յ 1; thereafter, it becomes quite significant.

Abstract. The nonlinear wave propagation of capillary-gravity waves on the surface of a ferrofluid of finite depth is investigated by employing the method of multiple scales. The stability analysis reveals the existence of different regions of instability. We show that the nonlinear modulational instability cannot be suppressed by the application of a strong magnetic field, however strong it may be. The influence of the magnetic field is not only quite signficant but its effect is also different for different regions of stability.1. Introduction. The study of wave propagation in magnetic fluids has drawn considerable interest during the last few years. Zelazo and Melcher [ 1 ] (see also references [2]-[5]) examined theoretically as well as experimentally the plane wave propagation for two superposed magnetic fluids in the presence of a tangential magnetic field, and demonstrated that the magnetic field exerts a stabilizing influence on waves. In their investigation of the nonlinear evolution of wave packets on the surface of a magnetic fluid, Malik and Singh [6] showed that the wave train solution of constant amplitude is unstable against modulation if the product of the group velocity rate and the nonlinear interaction coefficient is negative. Furthermore, the magnetic field has a stabilizing influence on the modulational instability for small wavenumbers.