Intelligent computer simulation tools for HV circuit breakers and issues related to simulation
Intelligent simulation tools are developed within the Integrated Simulation and Evaluation Environment using Visual Studio C++ and object oriented programming. Such an environment should result in huge savings in time and cost for switchgear manufacturers. Conventional k-epsilon turbulence model has been modified to take into account of steep radial temperature gradient at the arc edge with much improved results. Investigations of computational convergence and the effects of initial conditions show that solutions independent of initial arc conditions with sufficient accuracy can be achieved with the Liverpool arc model.
A comparative study of turbulence models for SF6 arcs in a supersonic nozzle
A comparative study of the two most popular turbulence models, the Prandtl mixing length model and the K-epsilon model, has been carried out for turbulent SF6 arcs burning in a supersonic nozzle under direct current conditions. The computed radial temperature profiles are compared with those measured previously by Leseberg and Pietsch at currents of 100 A, 600 A and 1800 A, respectively. It has been found that the turbulence parameters of the K-epsilon model are dependent upon the arcing current while those of the Prandtl mixing length model are applicable for all the currents investigated. For turbulent SF6 arcs in a supersonic nozzle, consideration of the range of applicability of the turbulence parameters and the cost of computation have made the Prandtl mixing length model preferable to the K-epsilon model.
Melanocins A, B and C, new melanin synthesis inhibitors produced by Eupenicillium shearii. I. Taxonomy, fermentation, isolation and biological properties.
New melanin synthesis inhibitors, melanocins A, B and C, were isolated from the fermentation broth and mycelium extract of Eupenicillium shearii F80695. Melanocin A, an isocyanide compound, inhibited mushroom tyrosinase and melanin biosynthesis of B16 melanoma cells with IC50 value of 9.0 nM and MIC value of 0.9 microM, respectively. Melanocin A also inhibited growth of Streptomyces bikiniensis. While, the structurally very related but non-isocyanide compounds melanocins B and C did not show inhibitory activity in these assays. Melanocins A, B and C showed potent antioxidant activity with scavenging activity of DPPH radical and superoxide anion radical.