Let F be a flock of the quadratic cone Q: X 2=X1X3 , in PG(3, q), q even, and let 6t : X0 =xt X1 + t X2 +zt X3 , t # Fq , be the q planes defining the flock F. A flock is equivalent to a herd of ovals in PG(2, q), q even, and to a flock generalized quadrangle of order (q, q). We show that if the herd contains a monomial oval, this oval is the Segre oval. This implies a result on the existence o...

A spatial analysis of ground-water yields has been performed that expands upon previous work by Drew and others (1999) in which the spatial continuity of 939 water well yields within the Pinardville quadrangle, New Hampshire, has been associated with the fracture properties of the crystalline basement rocks. This expanded analysis was performed on updated and new geologic map data, new fracture...

The Lahontan Mountains quadrangle is located 11 km east of Fallon, Nevada at the southeastern margin of the Carson Sink (Fig. 1). Principal physiographic features include the Lahontan Mountains, collectively consisting of Sehoo, Eetza, Salt Wells, and Rainbow mountains. This quadrangle is part of the greater Lake Lahontan area that in part occupied the southern Carson Desert, previously mapped ...

In this paper we study geometric, algebraic, and computational aspects of flexibility and infinitesimal flexibility of Kokotsakis meshes. A Kokotsakis mesh is a mesh that consists of a face in the middle and a certain band of faces attached to the middle face by its perimeter. In particular any (3×3)-mesh made of quadrangles is a Kokotsakis mesh. We express the infinitesimal flexibility conditi...

Generalized n-gons were introduced by Tits in a famous work on triality [20] of 1959, in order to propose an axiomatic and combinatorial treatment for semisimple algebraic groups (including Chevalley groups and groups of Lie type) of relative rank 2. They are the central rank 2 incidence geometries, and the atoms of the more general “Tits-buildings.” If the number of elements of a generalized n...

Penttila and Williford constructed a 4-class association scheme from generalized quadrangle with doubly subtended subquadrangle. We show that an appropriate parameters satisfying some assumption about maximal cliques must be the Penttila–Williford scheme.