http://nopr.niscair.res.in/handle/123456789/10384 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/10394 Title: Multivariable optimization of two-stage thermoelectric refrigerator driven by two-stage thermoelectric generator with external heat transfer <br/> <br/>Authors: Meng, Fankai; Chen, Lingen; Sun, Fengrui <br/> <br/>Abstract: The finite time thermodynamic model of a combined thermoelectric device, two-stage thermoelectric refrigerator driven by two-stage thermoelectric generator with heat transfer irreversibility is built by combining non-equilibrium thermodynamic theory with finite time thermodynamics theory. The solution procedure of optimal performance and the corresponding optimal variables are given and the cooling load and COP of the combined thermoelectric device are optimized. The control equation of the combined thermoelectric system is obtained. For fixed total number of thermoelectric elements and fixed total external thermal conductance of the device, the allocations of thermoelectric elements and thermal conductance are optimized for maximum cooling load and COP, respectively. The effects of the heat source temperature of the two-stage thermoelectric generator and the heat source (cooling space) temperature of the two-stage thermoelectric refrigerator on the optimal performance and optimal variables selection are analyzed by detailed numerical examples. The numerical simulation results show that the optimization is necessary and effective. By optimization, the performance is improved. When the two-stage thermoelectric generator works at a difference of 150 K, a cooling temperature difference of about 60 K could be reached. When the two-stage thermoelectric refrigerator works at a difference of 20 K, a COP of about 0.10 could be reached. These are considerable for application in a wide-scale for specific purposes <br/> <br/>Page(s): 731-742 Tue, 28 Sep 2010 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/10393 Title: Characterization of low pressure plasma-<i>dc</i> glow discharges (Ar, SF₆ and SF₆/He) for Si etching <br/> <br/>Authors: T Chiad, Bahaa; L Al-zubaydib, Thair; Khalaf, Mohammad K; I Khudiar, Ausama <br/> <br/>Abstract: Low-pressure plasma reactor which is generated for SF6, SF6/He and Ar gases discharges between two metal electrodes (planer –parallel) using <i style="">dc</i>-high voltage power supply of 2 kV has been proposed. Paschen’s curves show the breakdown voltage of gases as a function of the parameter <i>p*d</i> which is the product of the pressure in the chamber (<i>P</i>=6.5´10^-2-1.5´10^-1mbar) and the distance between the two electrodes (<i>d</i>=4.6 cm)<i>.</i> The minimum breakdown voltages were found 450 V at pressure of 1.35´10^-1mbar and 276 V at pressure of 4.3´10^-1mbar for SF₆and Ar, respectively. Current-voltage characteristics have been studied at different values of pressure (6.5´10^-2-1.5´10^-1mbar) and inter-electrodes spacing (3.4, 4.2, 4.6, 5 cm). The SF₆, SF₆/He and Ar gases discharges plasmas in Si etching have been discussed <br/> <br/>Page(s): 723-730 Tue, 28 Sep 2010 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/10392 Title: Density functional theory study of FTIR and FT-Raman spectra of 7-acetoxy-4-methyl coumarin <br/> <br/>Authors: Arivazhagana, M; Sambathkumarb, K; Jeyavijayanc, S <br/> <br/>Abstract: The solid phase FTIR and FT-Raman spectra of 7-acetoxy-4-methyl coumarin have been recorded in the regions 4000-50 cm⁻¹ and 3500-100 cm⁻¹, respectively. The spectra were interpreted with the aid of normal coordinate analysis following full structure optimization and force field calculation based on density functional theory using standard B3LYP/6-311+G** method and basis set. All the normal modes of vibrations are assigned and calculations of total energy distribution (TED) are also performed. <br/> <br/>Page(s): 716-722 Tue, 28 Sep 2010 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/10391 Title: Infrared, ESR and optical absorption studies of Cu²⁺ ions doped in TeO₂-ZnO-NaF glass system <br/> <br/>Authors: Kamalaker, V; Upender, G; Prasad, M; Chandra Mouli, V <br/> <br/>Abstract: Glasses of composition 80TeO₂-(20−<i style="">x</i>)ZnO-<i style="">x</i>NaF mol % were prepared by melt quenching technique and characterized by ESR, optical absorption and infrared spectroscopy. The IR spectra reveal that the glass consists of TeO₃, TeO₄, Te(O,F)₃and Te(O,F)₄ units as local structure of the glass network. The hydroxyl group concentration decreases with the increase of NaF content. From ESR spectra, it is found that the Cu²⁺ ions are in octahedral sites with tetragonal distortion with as ground state. From the ESR and optical absorption studies, molecular orbital coefficients were calculated and correlated with the structural variation of the glass system. From the optical absorption data, the optical band gap (<i>E</i>_opt) and Urbatch energy (Δ<i>E</i>) values were calculated. It is found that <i>E</i>_opt values increase with NaF content. The low Δ<i>E</i> values showed that the present glasses were highly homogenous and stable. <br/> <br/>Page(s): 709-715 Tue, 28 Sep 2010 22:58:59 GMT