http://nopr.niscair.res.in/handle/123456789/8610 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/8826 Title: Convective flow of two immiscible viscous fluids using Brinkman model <br/> <br/>Authors: Singh, Atul Kumar <br/> <br/>Abstract: Generalised Couette flow of two viscous, incompressible, immiscible fluids with heat transfer through two straight parallel horizontal walls is studied. A naturally permeable material of high porosity bound below the lower wall and the flow inside the porous medium is assumed to be of moderate permeability, modeled by Brinkman equation. Analytical solutions of the momentum and energy equations have been obtained for the flow domain by dividing it into three zones. Appropriate matching conditions of velocity and temperature have been used to link various flow regimes. The effects of inverse permeability parameter, Reynolds number and viscous parameter on velocity fields and temperature fields in various zones along with mass flow rate, skin-friction at the walls and rates of heat transfer have been presented. <br/> <br/>Page(s): 415-421 http://nopr.niscair.res.in/handle/123456789/8825 Title: Study of dielectric properties of <img src='/image/spc_char/alpha.gif' border=0> -alumina doped with MnO, CdO and MoO <br/> <br/>Authors: Farag, I S Ahmed; Battisha, I K; Rafaay, M M El <br/> <br/>Abstract: The dielectric constant (Ɛ),conductivity (<i style="">σ</i>) and activation energy (Eg) of <img src='/image/spc_char/alpha.gif' border=0> -alumina doped with different molar ratios ranging from 0.01 to 0.19 of manganese oxide (MnO), and from 0.01 to 0.16 for both molybdenum oxide (MoO) and cadmium oxide (CdO) were studied. The XRD patterns reveal clearly that the prepared samples, consist of only single phase (<img src='/image/spc_char/alpha.gif' border=0> -alumina phase).<b style=""> </b>The crystallite size and micro-strain of the investigated samples were calculated. The crystallite size increases with increasing dopant concentration. But the rate of the crystallite growth differs from one system to another. The value of e has been measured in a frequency range 42 Hz-5 MHz as a function of temperature ranging from 100 to 450°C. The possible explanations and the role of some impurities (mainly Mn, Mo and Cd) are analyzed. The value e of pure sample increases from 9.4 to 10.63 as a function of temperature at constant frequency 1 MHz. In this material, the value of e increases with increase of temperature due to space charge polarization and crystal defects, while it decreases as a function of frequency due to the scattering of charge carriers at high frequencies. From the plots of log σ as a function of the reciprocal of temperature at different frequencies, it has been shown that more than one straight line with different shapes are obtained, indicating different conduction mechanisms at 100 kHz and 1 MHz. An increase in the conductivity with increasing dopant concentration appeared and it could be related to the increase of the charge carriers, which are localized at ions or vacant sites. The activation energies for conduction in the high temperature region are calculated and found to be equal to 0.489, 0.457 and 0.459 eV for 0.01% of Mn, Mo and Cd, cations respectively at constant frequency of 100 kHz. The lower activation energy values for conduction in doped materials may be attributed to a larger charge carrier concentration in them compared to pure a-alumina.<b style=""> </b>The<b style=""> </b>XRD was elucidating to confirm that the obtained phase is a single <img src='/image/spc_char/alpha.gif' border=0> -alumina phase. <b style=""></b> <br/> <br/>Page(s): 446-458 http://nopr.niscair.res.in/handle/123456789/8824 Title: Gamma activity in some environmental samples in south Egypt <br/> <br/>Authors: Arabi, A M El <br/> <br/>Abstract: <smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="country-region"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place"> As a part of national survey to evaluate natural radioactivity in the environment, concentration levels of natural radioactivity have been analyzed from more than 108<b style=""> </b>environmental samples taken from <i style="">wadi Allaqi</i> area, south Egypt. The distribution of naturally occurring radionuclides of ²²⁶Ra, ²³²Th and ⁴⁰K in the samples (soil, granite, grass and water) have been measured using a high purity germanium detector. The specific activities in these samples, having a radium equivalent activity of less than 370 Bq.kg^-1, when evaluated for radiological effects show that all samples meet the external gamma-ray dose limitation of 1.5 mSv.y^-1. The data presented here will serve as a baseline survey for primordial radionuclide concentrations in igneous and sediment of the area. </smarttagtype></smarttagtype> <br/> <br/>Page(s): 422-426 http://nopr.niscair.res.in/handle/123456789/8823 Title: Spectroscopic and thermodynamic analysis of enolic form of 3-oxo-L-gulofuranolactone <br/> <br/>Authors: Srinivasan, S; Gunasekaran, S; Ponnambalam, U; Savarianandam, A; Gnanaprakasam, S; Natarajan, S <br/> <br/>Abstract: A qualitative analysis of the enolic form of 3-oxo-L-gulofuranolactone (ascorbic acid) has been made by a satisfactory vibrational band assignment using FTIR and FT Raman spectra. The calculated theoretical vibrational frequencies are compared with the experimental frequencies by employing the molecular mechanics method using MM3 force field. The observed frequencies are used to compute the thermodynamic functions, namely, the entropy, heat capacity and heats of formation using standard expressions, at one atmospheric pressure in the 298-398 K temperature range. <br/> <br/>Page(s): 459-462