Equivariant Perturbation in Gomory and Johnson's Infinite Group Problem. I. The One-Dimensional Case

We give an algorithm for testing the extremality of minimal valid functions for Gomory and Johnson's infinite group problem that are piecewise linear (possibly discontinuous) with rational breakpoints. This is the first set of necessary and sufficient conditions that can be tested algorithmically for deciding extremality in this important class of minimal valid functions. We also present an extreme function that is a piecewise linear function with some irrational breakpoints, whose extremality follows from a new principle.Comment: 38 pages, 10 figure

Proton magnetometer survey at the Menelaion and environs

Two short seasons of geophysical survey with a proton magnetometer were carried out at the Menelaion and its environs during the excavation seasons in 1974 and 1975 with a view to locating buried structures or other features in the following areas: close to the Mycenaean site, between this site and the Menelaion shrine, around the Menelaion shrine itself, the North Hill and the Chapel site. This report presents the results of the survey of these areas in 1975 which are shown in FIG. J.1. The geological environment and topography of the Menelaion plateau and environs are described elsewhere in this volume

Predicting wind turbine blade loads using vorticity transport and RANS methodologies

Two computational methods, one based on the solution of the vorticity transport equa- tion, and a second based on the solution of the Reynolds-Averaged Navier-Stokes equa- tions, have been used to simulate the aerodynamic performance of a horizontal axis wind turbine. Comparisons have been made against data obtained during Phase VI of the NREL Unsteady Aerodynamics Experimental and against existing numerical data for a range of wind conditions. The Reynolds-Averaged Navier-Stokes method demonstrates the potential to predict accurately the flow around the blades and the distribution of aero- dynamic loads developed on them. The Vorticity Transport Model possesses a consid- erable advantage in those situtations where the accurate, but computationally efficient, modelling of the structure of the wake and the associated induced velocity is critical, but where the prediction of blade loads can be achieved with sufficient accuracy using a lifting-line model augmented by incorporating a semi-empirical stall delay model. The largest benefits can be extracted when the two methods are used to complement each other in order to understand better the physical mechanisms governing the aerodynamic performance of wind turbines

The family "Thelypteridaceae" in Europe

Thelypteridaceae are mainly tropical ferns, the total number of species is about one thousand. The five European species represent five different groups, each of which has recently been accorded generic status. Thelypteris palustris Schott (including three varieties) extends throughout north temperate regions, with a closely allied species south of the equator; chromosome number n=35. Phaegopteris connectilis (Michx) Watt (triploid with base number 30) and Oreopteris limbosperma (All.) Holub (n=34) are members of small genera confined to north temperate regions. Stegnogramma pozoi (Lag.) K. Iwats. (n=36) represents a genus of 12-15 species, mainly in Africa and Asia, with one in Mexico. Christella dentata (Forsk.) Brownsey & Jermy is a wide-ranging and variable tetraploid species of a pantropic genus (c. 60 spp) the centre of distribution of wich appears to be Burma-Assam (base number 36).The genus Cyclosurus (s. str.) comprises a small pantropic group of species with grow (like Thelypteris) in open permanently swampy ground; I belive Cyclosorus and Thelypteris to be closely related genera. Stegnogramma is related to Sphaerostephanos which (in arrangement of Holttum) is the most diversified genus in the Old World with c. 140 spp. in Malesia . Christella is probably also related to Sphaerostephanos though less nearly than Stegnogramma.Las Thelypteridaceae son helechos principalmente tropicales, comprende aproximadamente mil especies. Las cinco especies europeas representan cinco grupos diferentes cada uno de los cuales ha recibido recientemente un estatus genérico. Thelypteris palustris Schott (incluyendo tres variedades) se extiende por las regiones templadas del norte, con un conjunto de especies próximas al sur del ecuador; el número cromosómico es n=35. Phegopteris connectilis (Michx) Watt (triploide con número básico 30) y Oreopteris limbosperma (All.) Holub (n=34), son miembros de pequeños géneros confinados a las regiones templadas del norte.Stegnogramma pozoi (Lag.) K. Iwats. (n=36) representa un género de 12-15 especies principalmente de Africa y Asia con una en Méjico. Christe lla dentata (Forsk.) Brownsey & Jermy es una variable especie tetraploide de amplia distribución cuyo género pantropical (cerca de 60 especies) parece tener su centro de distribución en Burma-Assam (número básico 36).El género Cyclosorus (s. str.) comprende un pequeño grupo de especies pantropicales que viven en llanuras permanentemente pantanosas. Creemos que Cyclosorus y Thelypteris son géneros muy emparentados. Stegnogramma está relacionado con Sphaerostephanos, el cual (en la ordenación de Holttum) es el género más diversificado en el viejo mundo con cerca de 140 especies en Malasia Christella esta tambien relacionada,probablemente, con Sphaerostephanos aunque su proximidad es menor que la mantenida con Stegnogramma

On the type of triangle groups

We prove a conjecture of R. Schwartz about the type of some complex hyperbolic triangle groups.Comment: 10 pages, 3 figure

Frequency dependence of partial discharge initiation voltages with embedded electrodes

Partial discharge initiation voltages of a dielectric insulation material exposed to ac voltages show little dependence on frequency in the power frequency range. This results after significant voltage conditioning at the measured frequencies with samples configured for embedded electrodes. Comparison to previously published results is made.Center for Electromechanic