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

The Problem of Supply of Coal for the New Steel Plants

WITH depletion of the lower ash, good coking coals occurring in the ripper seams of the Jharia coal field, which were the principal sources of supply of coking coals for the steel plants in the private sector, atte-ntion was focussed on the need for beneficiation of the higher ash Jharia coals. Three commercial coal washing plants (185 tons/hr. total capacity) were installed in recent years for supplying washed coal to the existing steel plants

The size requirement of Blast Furnace Coke (1)

THE exact specification for the physical characteristics of blast furnace coke remains controversial even today. But the advantage of using coke of consistent quality and is closely graded size has been generally recognised. Greater emphasis is being given on the size distribution of the coke rather than on the strength of the coke as assessed by conventional tests. It is believed that after the coke has been charged in the furnace, its strength is probably of less consequence, the size consistency being the dominant factor

Some aspects of preparation of Coal for Coking (11)

THE plans for India's industrial expansion envisage manifold increase in all branches of engineering indus-tries with a concomrnittant increase in the production and consumption of all quality of coals. Although India has fairly large reserves of inferior grades of coals, her resources of coking coals, including the washable reserves, are by no means plentiful. To meet the demand of increasing production of steel for the succ- essive Five Year plans, the consumption of coking coal will he stepped up inauy tines. This will result in even a quicker rate of depletion of the dwindling reserves of cobing Coals. There can, therefore, be no difference of opinion about the need for restricting the use of metall-urgical coals for coking purpose alone and for the adop-tion of suitable means for the beneficiation of the high ash coals. The installation of the coal washing plants, both in the private as well as public sectors, and the projects of erecting more washeries are concrete steps towards this objective, but much still remains to be done, and it has to be admitted that the magnitude of the problem has not yet been fully realised

Correlations among some Physical Properties of Coke - a Statistical Study

VARIOUS tests are employed in different countries for assessing the physical properties of coke. While the Shatter and the B.S. Abrasion tests are in general use in the United Kingdom, European practice is to employ the Alicuni test.In the U.S.A., the Haven test is employed in addition to a Shatter test similar to that of the U.K. The Indian steel plants carry out the Shatter.Micum and Haven tests. One of these plants uses a modified form of the original Breslau test in place of the standard Micum test1

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