http://nopr.niscair.res.in/handle/123456789/1818 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/1902 Title: Effect of horizontal thermal gradient on ferroconvection <br/> <br/>Authors: Vaidyanathan, G; Sekar, R; Hemalatha, R <br/> <br/>Abstract: The effect of horizontal thermal gradient on ferro convective instability of a single component system subjected to two dimensional magnetic field has been studied. The fluid layer is assumed to be bounded by free boundaries. The exact solution of constitutive equation is derived using linear theory. Wide range of values of the ratio of horizontal and vertical temperature gradient have been considered. Normally, the magnetization parameter M₁ is very large and is taken to be 1000. The system is found to stabilize through stationary mode only. It has also been seen that the oscillatory instability is not possible. <br/> <br/>Page(s): 477-483 Sat, 28 Jun 2008 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/1899 Title: Dielectric dispersion and relaxation of mixtures of 1-propanol and phenol at lower microwave frequencies <br/> <br/>Authors: Vyas, A D; Rana, V A; Bhatnagar, S P; Vashisth, V M <br/> <br/>Abstract: Complex permittivity of 1-propanol, phenol and mixtures of 1-propanol + phenol over wide range of concentration are measured over the frequency range 30MHz to 3.0 GHz using Vector Network Analyzer (VNA). Open ended co-axial probe technique suggested by Wei and Sridhar [Rev Sci Instr, 60 (9) (1989) 304] is used to obtain dielectric constant. The measured values of ε’ and ε” are fitted to Debye equation to obtain dielectric parameters. Obtained values of relaxation time of liquid mixtures are plotted against the concentration of one of the components of the liquid mixtures. Non-linear variation of relaxation time with concentration has been interpreted in terms of molecular interaction among the molecular species of different kinds in liquid mixtures. <br/> <br/>Page(s): 521-525 Sat, 28 Jun 2008 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/1898 Title: Ionic conduction and dielectric dispersion study on chain dynamics of poly(vinyl pyrrolidone)–glycerol blends <br/> <br/>Authors: Sengwa, R J; Sankhla, Sonu <br/> <br/>Abstract: Dielectric behaviour of glass-former polymer blends i.e. poly(vinyl pyrrolidone) (PVP) (average molecular weight Mw= 24000, 40000 and 360000 g mol-1) with glycerol (Gly) up to 30 wt % PVP has been investigated in the frequency range 20 Hz-1 MHz at 25ºC. The frequency dependent complex dielectric constant of the PVP-Gly blends indicates the relaxation process caused by the micro-Brownian chain motion of the PVP in the frequency range 10 kHz-1 MHz. The values of dielectric relaxation strength and relaxation time for this process were determined to explore the concentration and chain length effect on the relaxation process. The ac conductivity values were found corresponding to dc conductivity at frequencies lower than 10 kHz. The loss part of electric modulus exhibits a peak in the frequency range 10 kHz - 40 kHz, which corresponds to the ionic conductivity relaxation. The complex impedance plane plots of PVP-Gly blends confirm the contribution of the electrode surface polarization effect on the dielectric constant values at frequencies lower than 200 Hz. Further, the results of the dielectric dispersion of the PVP–Gly blends were compared with the dielectric dispersion of poly(vinyl pyrrolidone)–ethylene glycol oligomers (PVP–EGOs) blends [Shinyashiki et al., 2006] to confirm the effect of number of hydroxyl groups of the solvent molecules on the heterogeneous hydrogen bond complex formation in these blends. <br/> <br/>Page(s): 513-520 Sat, 28 Jun 2008 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/1897 Title: Growth and characterization of struvite crystals <br/> <br/>Authors: Chauhan, Chetan K; Joseph, K C; Parekh, B B; Joshi, M J <br/> <br/>Abstract: Struvite or ammonium magnesium phosphate hexahydrate (AMP) containing urinary stones are infection stones associated with urea splitting organisms, which are more common in women. Struvite crystals having different morphologies were grown by single diffusion gel growth technique in silica gel. The crystals were characterized by powder XRD, FT-IR, TGA and dielectric study. Kinetic and thermodynamic parameters were evaluated from thermogram. Dielectric study showed that the value of dielectric constant is found to decrease as the frequency increased. The ac resistivity and ac conductivity were also evaluated at different frequency. <br/> <br/>Page(s): 507-512 Sat, 28 Jun 2008 22:58:59 GMT