http://nopr.niscair.res.in/handle/123456789/8222 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/8336 Title: Microwave dielectric relaxation study of poly (methyl methacrylate) and polysulphone in dilute solutions <br/> <br/>Authors: Tanwar, A; Gupta, K K; Singh, P J; Vijay, Y K <br/> <br/>Abstract: Dielectric relaxation studies of poly (methyl methacrylate) in dilute solutions of benzene and 1,4-dioxane and polysulphone in dilute solutions of 1,4-dioxane have been carried out at 8.92 GHz and temperatures 30, 40, 50, 60ºC, respectively. Average relaxation time τ ₀, and relaxation times corresponding to group rotation τ(1) _,segmental motion τ(2)and dipole moment <img src='/image/spc_char/micro.gif' border=0>have been determined. The results have been interpreted by the internal and hindered rotation of ester group and sulphone unit for PMMA and polysulphone, respectively. The study reveals the existence of both, the intramolecular and overall orientations in PMMA and polysulphone. Thermodynamic parameters, viz. free energy, enthalpy and entropy of activation have been calculated using the dielectric data. Thermodynamic parameters indicate existence of cooperative orientation in the molecule resulting from the dipole-dipole interaction. <br/> <br/>Page(s): 548-553 Wed, 28 Jun 2006 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/8335 Title: Effective heating in heavily doped semiconductor devices <br/> <br/>Authors: De, S S; Ghosh, A K; Ghosh, T K; Jana, D <br/> <br/>Abstract: A model has been developed to investigate the heat generation processes in semiconductor devices under heavily doped condition. The equilibrium between heat generation and heat dissipation by various mechanisms has been studied. The variations of heat dissipation with the change of carrier concentrations and the heat along the distance from the junction to the bulk have been estimated by numerical analyses. These are shown graphically with the results of an earlier work. <br/> <br/>Page(s): 543-547 Wed, 28 Jun 2006 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/8334 Title: Synthesis and characterization of certain nanomagnetic particles coated with citrate and dextran molecules <br/> <br/>Authors: Mehta, R V; Desai, Rucha; Bhatt, Prashant; Upadhyay, R V <br/> <br/>Abstract: Nanomagnetic particles of magnetite and Mn-Zn ferrites are synthesized and coated with dextran and citrate molecules. Particles are characterized by XRD, FTIR , TGA and magnetometry. FTIR as well as TGA shows that binding of citrate molecules on magnetite is stronger then in case of dextran on magnetite. In the case of Mn-Zn ferrite particles citrate ions are bound by physi- as well as- chemi-absorption. The calculated value of binding from TGA analysis agrees with that obtained from magnetometry analysis. <br/> <br/>Page(s): 537-542 Wed, 28 Jun 2006 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/8333 Title: Thermally stimulated processes: I-Mechanisms involved in the appearance of a thermoluminescence glow curve <br/> <br/>Authors: Prakash, Jai; Singh, P K; Dwivedi, D K <br/> <br/>Abstract: Mechanisms involved in the appearance of a thermoluminescence (TL) glow curve are re-investigated with an aim to establish a suitable model. A generalized equation has been developed which is found to be able to explain the intensity of TL glow curves of different systems. Suggested equation successfully represents the TL intensities of systems involving different order of kinetics including first order. The proposed model helps in the evaluation of the values of trap depth or activation energy, the frequency factor governing the release of electrons from their traps, the initial concentration of the trap centres, order of kinetics involved and extent of rates of retrapping and recombination. <br/> <br/>Page(s): 532-536 Wed, 28 Jun 2006 22:58:59 GMT