Charl Ras

A study of the role of forceful behaviour in evacuations via microscopic modelling of evacuation drills

N Andrés-Thió, C Ras, M Bolger, V Lemiale

Journal article  |  2021  |  Safety Science

This paper reports on the microscopic modelling of evacuation drills through merging corridors carried out to gain further insight..

Computational complexity of the 2-connected Steiner network problem in the ℓp plane

CJ Ras, M Brazil, DA Thomas

Journal article  |  2021  |  Theoretical Computer Science

The geometric 2-connected Steiner network problem asks for a shortest bridgeless network spanning a given set of terminals in the ..

Early prediction of macrocrack location in concrete, rocks and other granular composite materials

Antoinette Tordesillas, Sanath Kahagalage, Charl Ras, Michal Nitka, Jacek Tejchman

Journal article  |  2020  |  SCIENTIFIC REPORTS

Heterogeneous quasibrittle composites like concrete, ceramics and rocks comprise grains held together by bonds. The question on wh..

Computing Skeletons for Rectilinearly Convex Obstacles in the Rectilinear Plane

M Volz, M Brazil, C Ras, D Thomas

Journal article  |  2020  |  Journal of Optimization Theory and Applications

We introduce the concept of an obstacle skeleton, which is a set of line segments inside a polygonal obstacle ω that can be used i..

Coupled Evolution of Preferential Paths for Force and Damage in the Pre-failure Regime in Disordered and Heterogeneous, Quasi-Brittle Granular Materials

Antoinette Tordesillas, Sanath Kahagalage, Charl Ras, Michal Nitka, Jacek Tejchman

Journal article  |  2020  |  FRONTIERS IN MATERIALS

A disordered and heterogeneous, quasi-brittle granular material can withstand certain levels of internal damage before global fail..

Degree bounded bottleneck spanning trees in three dimensions

Patrick J Andersen, Charl J Ras

Journal article  |  2020  |  JOURNAL OF COMBINATORIAL OPTIMIZATION

The geometric δ-minimum spanning tree problem (δ-MST) is the problem of finding a minimum spanning tree for a set of points in a n..

Fixed parameter tractability of a biconnected bottleneck Steiner network problem

Charl J Ras

Journal article  |  2020  |  NETWORKS

For a given set X of points in the plane, we consider the problem of constructing a 2-vertex-connected network spanning X and at m..

New pruning rules for the Steiner tree problem and 2-connected Steiner network problem

Marcus Brazil, Marcus Volz, Martin Zachariasen, Charl Ras, Doreen Thomas

Journal article  |  2019  |  COMPUTATIONAL GEOMETRY-THEORY AND APPLICATIONS

We introduce the concepts of k-lunes and k-lune inequalities, which form the basis for new geometric pruning rules for limiting th..

Algorithms for Euclidean Degree Bounded Spanning Tree Problems

PJ Andersen, CJ Ras

Journal article  |  2019  |  International Journal of Computational Geometry and Applications

Given a set of points in the Euclidean plane, the Euclidean d-minimum spanning tree (d-MST) problem is the problem of finding a sp..

Unsupervised Basis Function Adaptation for Reinforcement Learning

Edward Barker, Charl Ras

Journal article  |  2019  |  JOURNAL OF MACHINE LEARNING RESEARCH

When using reinforcement learning (RL) algorithms it is common, given a large state space, to introduce some form of approximation..