We develop a new method for deriving a geometric separator for a set of grid points. Our separator has a linear structure, which can effectively partition a grid graph. For example, we prove that for a grid graph G with a set of n points P in a two-dimensional grid, there is a separator with at most 1.129 √ n points in P that partitions G into two disconnected grid graphs each with at most 2n 3...

G. A. Dirac characterized chordal graphs as those in which minimal vertex separators always induce complete subgraphs. I generalize a traditional (2-)vertex separator to a k-vertex separator — meaning a set S of vertices whose removal puts k independent vertices into k separate components. Generalizing Dirac’s theorem, the {P5, 2P3}-free chordal graphs are the graphs in which minimal k-separato...

For undirected graphs G (V, E) and G0 (V0 , E0), say that G is a region intersection graph over G0 if there is a family of connected subsets {Ru ⊆ V0 : u ∈ V} of G0 such that {u , v} ∈ E ⇐⇒ Ru ∩ Rv , ∅. We show if G0 excludes the complete graph Kh as a minor for some h > 1, then every region intersection graph G over G0 with m edges has a balanced separator with at most ch √ m nodes, where ch i...

The characteristics of fluid flow and phase separation in an oil-water separator were numerically analysed as part of the work presented herein. Simulations were performed for different velocities and droplet diameters, and the way this parameters can influence the separator geometry was studied. The simulations were carried out using the software package Fluent 6.2, which is designed for numer...

A permutation σ ∈ Sn is a k-separator if all of its patterns of length k are distinct. Let F (k) denote the maximal length of a k-separator. Hegarty (2013) showed that k + ⌊√ 2k − 1 ⌋ − 1 6 F (k) 6 k + ⌊√ 2k − 3 ⌋ , and conjectured that F (k) = k + ⌊√ 2k − 1 ⌋ − 1. This paper will strengthen the upper bound to prove the conjecture for all sufficiently large k (in particular, for all k > 320801).

Separators in graphs are instrumental in the design of algorithms, having proven to be the key technical tool in approximation algorithms for many optimization problems. In the geometric setting, this naturally translates into the study of separators in the intersection graphs of geometric objects. Recently a number of new separator theorems have been proven for the case of geometric objects in...

A graph is called threshold if there exists a real number b and real numbers aj associated with its vertices w, such that ims a, < b holds iff S is a stable (independent) set of vertices. The vector (a ,..., a; b) associated to a threshold graph is called an integral separator if ai + a > b + 1 for every edge (w,, wj). A simple algorithm is presented to determine for a given threshold graph its...

This article studied static deflection, natural frequency and nonlinear vibration of a clamped-clamped microbeam under discontinues electrostatic actuation. The electrostatic actuation was induced by applying AC-DC voltage between the microbeam and electrode plate. In contrast to previous works, it was assumed that length of the electrode plate was smaller than that of the microbeam. In additio...

The ion-optical characteristics of the separator should meet the requirements of the antiproton beam, the parameters of which are given in Table 1. The magnetic bending power is 13 Tm; the transverse acceptance is 240 mm mrad; the momentum acceptance is 6 %. These parameters require magnets with large aperture, especially in the horizontal plane (up to 400 mm). The ion optics of the antiproton ...

The TRIμP facility, under construction at KVI, requires the production and separation of short-lived and rare isotopes. Direct reactions, fragmentation and fusionevaporation reactions in normal and inverse kinematics are foreseen to produce nuclides of interest with a variety of heavy-ion beams from the superconducting cyclotron AGOR. For this purpose, we have designed, constructed and commissi...