http://nopr.niscair.res.in/handle/123456789/14143 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/14184 Title: Characterization of dielectric dispersion and ionic conduction behaviour of acetonitrile at low frequencies <br/> <br/>Authors: Choudhary, Shobhna; Sengwa, R J <br/> <br/>Abstract: The complex dielectric function, ionic conductivity and impedance behaviour of acetonitrile have been investigated over the frequency range 20 Hz-1 MHz and at the temperatures 15, 30 and 45°C. The real part of complex dielectric function increases significantly with the decrease of frequency below 100 kHz, confirms the contribution of electrode polarization effect in the dielectric properties of acetonitrile at low frequencies. The real part of alternating current conductivity shows the direct current ionic conductivity plateau in the frequency range 1 kHz-1 MHz. The complex impedance plane plots have been used to separate the electrode polarization effect from the bulk acetonitrile properties. The values of temperature dependence electrode polarization relaxation time have been determined from the frequency which corresponds to the peaks observed in the dielectric loss tangent spectra. The activation energies of relaxation time, conductivity and viscosity have been evaluated from their Arrhenius plots, and discussed in relation to the ionic conduction mechanism in the pure liquid state of acetonitrile. <br/> <br/>Page(s): 411-414 http://nopr.niscair.res.in/handle/123456789/14183 Title: Effect of salinity on the dielectric properties of water <br/> <br/>Authors: Gadani, D H; Rana, V A; Bhatnagar, S P; Prajapati, A N; Vyas, A D <br/> <br/>Abstract: The complex permittivity <img src='http://www.niscair.res.in/jinfo/belongs.gif' border=0>=<img src='http://www.niscair.res.in/jinfo/belongs.gif' border=0>'-j<img src='http://www.niscair.res.in/jinfo/belongs.gif' border=0>" of distilled water and NaCl solutions of concentrations varying from 5000 to 35000 ppm have been measured in the frequency range from 200 MHz to 1.4 GHz using a Vector Network Analyzer (VNA). The complex permittivity of saline water collected from Kanyakumari sea bank has also been measured in this frequency range. It has been observed that the dielectric constant of water decreases slowly with increase in frequency from 200 MHz to 1.4 GHz for given salinity of water. At given frequency, the dielectric constant decreases slowly with increase in salinity from 5000 to 35000 ppm. The dielectric loss of distilled water increases with increase in frequency from 200 MHz to 1.4 GHz, but for saline water it decreases with increase in frequency, over this frequency range. The decrease in dielectric loss with increase in frequency is more for higher salinity in water. The variation of complex permittivity of water with salinity and frequency is calculated using the Stogryn equations[<i style="">IEEE Trans. On Microwave Theory and Techniques</i>, August 1971, pp. 733-736] as well as with the Klein and Swift [<i>IEEE Transactions on Antennas and Propagation</i>, Vol. AP-25, No.1, January 1977, pp. 104-111] equations, and the results are found to be in good agreement with corresponding experimental values. The variation of emissivity with variation of salinity calculated at fixed frequencies of 0.5, 0.9 and 1.4 GHz have also been presented in the paper, which is very much useful for remote sensing applications of oceans. <br/> <br/>Page(s): 405-410 http://nopr.niscair.res.in/handle/123456789/14182 Title: Optical and infrared properties of lithium diborate glasses doped with copper oxide: Effect of gamma irradiation <br/> <br/>Authors: El-Batal, Hatem A; El-Mandouh, Zeinab S; Zayed, Hamdia A; Marzouk, Samir Y; El-Komy, Gihan M; Hosny, Ahmed <br/> <br/>Abstract: A series of lithium diborate glasses containing successive CuO contents have been prepared by conventional melt annealing technique. Optical and infrared spectral properties have been measured before and after successive gamma irradiation to study the effect of gamma irradiation on the prepared glasses. Cu-doped samples show the same strong UV absorption as the undoped sample beside a characteristic broad visible band around 772 nm with marked splitting into four peaks at 614, 656, 774 and 1064 nm in higher CuO contents. Gamma irradiation of undoped lithium borate glass causes the generation of induced absorption bands but the introduction of CuO content causes some shielding behaviour towards successive gamma irradiation. Infrared absorption spectra of the undoped and CuO-doped glasses show characteristic vibrational absorption bands related to triangular and tetrahedral borate units. The addition of CuO in lithium borate glasses causes minor changes on the intensities of the IR bands but their numbers and positions are retained. The same limited effect is observed with gamma irradiation on the measured IR bands. <br/> <br/>Page(s): 398-404 http://nopr.niscair.res.in/handle/123456789/14181 Title: Thermoelastic properties of alkali halides at high temperatures <br/> <br/>Authors: Sunil, K; Sharma, B S <br/> <br/>Abstract: The thermoelastic properties of materials at high temperatures, specifically the thermal expansivity and the isothermal bulk modulus have been studied using the Anderson formula for thermal expansivity and the interatomic potential functions within the framework of the Born model. We have considered sixteen alkali halides with NaCl structure, and calculated their properties for a wide range of temperatures starting from room temperature up to their melting temperatures. Potential energy curves have been plotted and used to determine interatomic distances at the melting points. The results for interatomic distances, thermal expansivity and isothermal bulk modulus at different temperatures have been found to compare well with the available experimental data. The Hildebrand equation of state has been used to predict the pressure-volume-temperature relationship in case of NaCl using the Born-Mayer exponential potential function. The results,thus, obtained are found to present good agreement with the measured data. <br/> <br/>Page(s): 387-397