This paper presents investigations on reflectarray antennas using non-periodic element distributions. The study involves the analysis and design of two reflectarrays based quasi-periodic lattices with rectangular pentagonal profiles, whose performance is compared equivalent comprised regular grids elements. characterization these performed a tailored technique for periodical quasi-periodical gr...

We provide a new modus operandi for the computation of the nucleolus in cooperative games with transferable utility. Using the concept of dual game we extend the theory of characterization sets. Dually essential and if the game is monotonic dually saturated coalitions determine both the core and the nucleolus whenever the core is non-empty. We show how these two sets are related to the existing...

succinctly restate their position that the English past tense is governed by two competing mechanisms, identified as 'words and rules', and taken as examples of distinct procedural and declarative systems. Their mechanisms work separately, so that only one or the other is responsible for yielding a particular past tense form. To produce the past tense of keep, words and rules race to generate a...

Completeness for metric spaces is traditionally presented in terms of convergence of Cauchy sequences, and for uniform spaces in terms of Cauchy filters. Somewhat more abstractly, a uniform space is complete if and only if it is closed in every uniform space in which it is embedded, and so isomorphic to any space in which it is densely embedded. This is the approach to completeness used in the ...

A graph G is dually chordal if there is a spanning tree T of G such that any maximal clique of G induces a subtree in T . This paper investigates the Colourability problem on dually chordal graphs. It will show that it is NP-complete in case of four colours and solvable in linear time with a simple algorithm in case of three colours. In addition, it will be shown that a dually chordal graph is ...

An earlier paper describes a program to prove the Kepler conjecture on sphere packings. This paper carries out the second step of that program. A sphere packing leads to a decomposition of R into polyhedra. The polyhedra are divided into two classes. The first class of polyhedra, called quasi-regular tetrahedra, have density at most that of a regular tetrahedron. The polyhedra in the remaining ...