Veronese embedding and two–character sets

Two infinite families of two–character sets in PG(5,q) arising from the Veronese surface of PG(5,q) are constructed.     

Correlation equations for friction factors and convective coefficients in tubes containing bundles of internal, longitudinal fins

Finned tubes are commonly employed in tubular heat exchangers to augment the heat transfer rates between two dissimilar fluid streams. The goal of this study is two-fold: a) to determine the laminar, fully developed velocity and temperature fields for long, internal, longitudinal finned tubes; and b) to construct empirical correlation equations applicable for the asymptotic friction factor and the asymptotic Nusselt numbers as a function of the number of fins and the relative fin height in the bundle. Neither the fluid dynamics nor the heat transfer literature provides information for the second goal, which can be extremely useful to thermal engineers for the implementation of Computer-Aided Design (CAD) of internal, longitudinal finned tubes in heat exchange devices. Moreover, for the validity of the correlation equations, a seldom adopted criterion for the critical Reynolds number has also been introduced as an indispensable guideline to warrant laminar regimes. Received on 24 January 1997     

Interior-Point Solver for Large-Scale Quadratic Programming Problems with Bound Constraints

In this paper, we present an interior-point algorithm for large and sparse convex quadratic programming problems with bound constraints. The algorithm is based on the potential reduction method and the use of iterative techniques to solve the linear system arising at each iteration. The global convergence properties of the potential reduction method are reassessed in order to take into account the inexact solution of the inner system. We describe the iterative solver, based on the conjugate gradient method with a limited-memory incomplete Cholesky factorization as preconditioner. Furthermore, we discuss some adaptive strategies for the fill-in and accuracy requirements that we use in solving the linear systems in order to avoid unnecessary inner iterations when the iterates are far from the solution. Finally, we present the results of numerical experiments carried out to verify the effectiveness of the proposed strategies. We consider randomly generated sparse problems without a special structure. Also, we compare the proposed algorithm with the MOSEK solver. Research partially supported by the MIUR FIRB Project RBNE01WBBB “Large-Scale Nonlinear Optimization.”     

Spectrophotometric determination of fusicoccin

Fusicoccin incubated for 17 h in 6 M HCl at 37°C gives rise to a chromophoric system having an absorption maximum at 555 nm. A colorimetric method for the determination of pure fusicoccin and of fusicoccin in fermentation liquors and infected plant tissues is described. The method is useful for 50–800 μg of fusicoccin.     

New synthesis of condensed hydropyridazine derivatives V

The reactivity of pyrrole derivatives towards the semicarbazone of ω-bromoacetophenone has been reported. Substituents at position 1 of the pyrrole ring greatly affect the course of the reaction. 1,4,4a,4b,5,8,8a,8b-Octahydro-9H-pyrrolo[2,3-c:4,5-c′]dipyridazine derivative or α- and α,α-pyrrolyl derivatives were obtained depending on the substituents. The structures reported were assigned on the basis of satisfactory analytical and spectroscopic data.