Insulator superconductor transition on solid inert gas substrates

We present observations of the insulator-superconductor transition in ultrathin films of Bi on solid xenon condensed on quartz and on Ge on quartz. The relative permeability $\epsilon_{r}$ ranges from 1.5 for Xe to 15 for Ge. Though we find screening effects as expected, the I-S transition is robust, and unmodified by the substrate. The resistance separatrix is found to be close to $h/4e^2$ and the crossover thickness close to 25 $\AA$ for all substrates. I-V studies and Aslamazov-Larkin analyses indicate superconductivity is inhomogeneous. The transition is best described in terms of a percolation model.Comment: Submitted to LT23 Proceeding

Effect of weld parameter on mechanical and metallurgical properties of dissimilar joints AA6082–AA6061 in T6 condition produced by FSW

The effect of processing parameters on the mechanical and metallurgical properties of dissimilarjoints of AA6082–AA6061 produced by friction stir welding was analysed in this study. Different FSW sampleswere produced by varying the welding speeds of the tool as 50 and 62 mm/min and by varying the alloypositioned on the advancing side of the tool. In all the experiments the rotating speed is fixed at 1600rpm. Allthe welds were produced perpendicularly to the rolling direction for both the alloys. Microhardness (HV) andtensile tests performed at room temperature were used to evaluate the mechanical properties of the joints. Inorder to analyse the microstructural evolution of the material, the weld’s cross-sections were observed opticallyand SEM observations were made of the fracture surfaces. The corrosion tests of base alloy and welded jointswere carried out in 3.5%NaCl solution at a room temperature. Corrosion current and potential were determinedusing potentiostatic polarization measurements. It was found that the corrosion rates of welded joints werehigher than that of base alloy

Kinetics of Aldehyde Oxidation on Platinum Anode In Aqueous Perchloric Acid & Sulphuric Acid

781-78

Analysis of Dual Phase Dual Stage Boost Converter for Photovoltaic Applications

In the previous two decades, the depletion of fossil fuels has led to applications with renewable energy sources. The approach for renewable energy application is to achieve eminent static boost ratio from with miniaturized ripple content in both current and voltage. The novel converter discussed in this paper is derived by combining the concept of interleaving and cascading of boost converters. The presented design has a dual phase boost converter followed by a stage of boost converter which as a whole acts like dual phase dual stage boost converter. The interleaving concept is utilized in dual phase boost converter to reduce the voltage current stress created in boosting process and its output is boosted by the dual stage boost converter which improves overall efficiency with respect to the existing systems. The converter is designed for a power rating of 200W with output voltage of 192V for an input voltage of 12V obtained from photovoltaic source at a switching frequency of 50KHz this illustrate the advantages over other existing converters . The different parameters of the proposed boost converter are contrasted with that of a conventional boost converter. Furthermore, the simulations results of the proposed converter are presented to validate the system design. The results exhibit that this converter achieves a predominant performance over other dc-dc boost converters by offering improved efficiency and voltage gain, while having lower input current ripple

Characteristics of Anodic Film on Aluminium in Borate Bath

88-9

Vortices and the mixed state of ultrathin Bi films

Current-voltage (I-V) characteristics of quench condensed, superconducting, ultrathin Bi films in a magnetic field are reported. These show hysteresis for all films, grown both with and without thin Ge underlayers. Films on Ge underlayers, close to superconductor-insulator transition, show a peak in the critical current, indicating a structural transformation of the vortex solid. These underlayers, used to make the films more homogeneous, are found to be more effective in pinning the vortices. The upper critical fields ($B_{c2}$) of these films are determined from the resistive transitions in perpendicular magnetic field. The temperature dependence of the upper critical field is found to differ significantly from Ginzburg-Landau theory, after modifications for disorder.Comment: Submitted to LT23 Proceeding