http://nopr.niscair.res.in/handle/123456789/2618 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/2672 Title: Dielectric studies of methyl methacrylate and butyl methacrylate with primary alcohols using time domain reflectometry <br/> <br/>Authors: Khan, F Liakath Ali; Sivagurunathan, P; Kamil, S Raja Mohamed; Mehrotra, S C <br/> <br/>Abstract: Using time domain reflectometry (TDR), dielectric relaxation studies have been carried out for alkyl methacrylates (methyl methacrylate and butyl methacrylate) with primary alcohols (methanol, ethanol, 1-hexanol, 1-nonanol and 1-dodecanol) mixtures over the frequency range 10 MHz-20 GHz at 303K. Static permittivity (Ɛ o), dielectric constant at high frequency (Ɛ) and relaxation time () were found through dielectric measurements for different concentration of each system. The Kirkwood correlation factor and the excess inverse relaxation time were determined and discussed to yield information on the molecular structure and dynamics of the mixture. The values of the static permittivity, relaxation time and the Kirkwood correlation factor decrease with increased concentration of alkyl methacrylate in alcohol. <br/> <br/>Page(s): 754-758 Wed, 29 Aug 2007 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/2671 Title: Dielectric study of spin coated nano-thick BaZrxTi₁₋xO₃ film <br/> <br/>Authors: Rout, S K; Badapanda, T; Panigrahi, S <br/> <br/>Abstract: Barium zirconium titanate thin films are attractive candidates for dynamic random access memories and tunable microwave devices. Barium zirconate titanate Ba(ZrxTi₁₋x) O₃ (BZT, y = 0.0, 0.2, 0.4) ceramics have been prepared by a sol-gel process. X-ray diffraction studies confirmed that the films of BZT are in crystalline form and of single phase. The SEM study shows that the films of homogeneous microstructure and Zr content strongly influence the grain size of the film. The grain size decreased and the microstructure became dense when Zr was substituted for Ti. The room temperature dielectric study shows that the permittivity as well as dielectric loss tangent decreases with increase in Zr content in the film. The ac conductivity was evaluated from dielectric data and was found to be decrease with increase in Zr concentration. <br/> <br/>Page(s): 749-753 Wed, 29 Aug 2007 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/2670 Title: Evaluation of thermal performance of heat exchanger unit for parabolic solar cooker for off-place cooking <br/> <br/>Authors: Murty, V V S; Gupta, A; Mandloi, N; Shukla, A <br/> <br/>Abstract: Different types of solar cookers developed for cooking are box type and concentrator type solar cookers. A parabolic concentrator type solar cooker has a wide range of applications like baking, roasting and distillation due to its unique property of producing a practically higher temperature of nearly 250°C and hence, it provides inconvenience to the user due to high amount of glare. The main objective of the present study is to incline cylindrical heat transfer fluid column as a heat transfer medium. The thermal performance of a parabolic solar cooker depends on inclined heat exchanger system of mild steel tube of length 157.5 cm and an internal radius 2.07 cm with heat transfer fluid (oil) of density 1075 kg/m³. Experiments are conducted for cooking of food at a normal day. The results show that inclined convective heat exchanger system can be used for off-place cooking. The optimization of the system design parameters is under investigation. <br/> <br/>Page(s): 745-748 Wed, 29 Aug 2007 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/2669 Title: Synthesis and characterization of BaTiO₃ and LiNbO₃ ceramic powders <br/> <br/>Authors: Sreenivasulu, A; Prasad, T N V K V; Buddhudu, S <br/> <br/>Abstract: The optimization of the sintering temperatures of dielectric materials such as barium titanate (BaTiO₃) and lithium niobate (LiNbO₃) in the form of pelletted ceramics has been reported. The optimized temperature for BaTiO₃ is 950ºC and in the case of LiNbO₃, it is 900ºC based on the temperature optimization studies carried out in the temperature range 800-1000ºC. The crystallanity nature has symmetrically been analyzed through the XRD and FTIR spectral measurements. Crystallization nature of the materials has been found to be tetragonal based on the XRD data results. Such tetragonal crystalline natured dielectric materials are of technological importance and significant relevance in the progress of wide variety of opto-electronic materials. <br/> <br/>Page(s): 741-744 Wed, 29 Aug 2007 22:58:59 GMT